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# Algorithms/Introduction
This book covers techniques for the design and analysis of algorithms.
The algorithmic techniques covered include: divide and conquer,
backtracking, dynamic programming, greedy algorithms, and hill-climbing.
Any solvable problem generally has at least one algorithm of each of the
following types:
1. the obvious way;
2. the methodical way;
3. the clever way; and
4. the miraculous way.
On the first and most basic level, the \"obvious\" solution might try to
exhaustively search for the answer. Intuitively, the obvious solution is
the one that comes easily if you\'re familiar with a programming
language and the basic problem solving techniques.
The second level is the methodical level and is the heart of this book:
after understanding the material presented here you should be able to
methodically turn most obvious algorithms into better performing
algorithms.
The third level, the clever level, requires more understanding of the
elements involved in the problem and their properties or even a
reformulation of the algorithm (e.g., numerical algorithms exploit
mathematical properties that are not obvious). A clever algorithm may be
hard to understand by being non-obvious that it is correct, or it may be
hard to understand that it actually runs faster than what it would seem
to require.
The fourth and final level of an algorithmic solution is the miraculous
level: this is reserved for the rare cases where a breakthrough results
in a highly non-intuitive solution.
Naturally, all of these four levels are relative, and some clever
algorithms are covered in this book as well, in addition to the
methodical techniques. Let\'s begin.
## Prerequisites
To understand the material presented in this book you need to know a
programming language well enough to translate the pseudocode in this
book into a working solution. You also need to know the basics about the
following data structures: arrays, stacks, queues, linked-lists, trees,
heaps (also called priority queues), disjoint sets, and graphs.
Additionally, you should know some basic algorithms like binary search,
a sorting algorithm (merge sort, heap sort, insertion sort, or others),
and breadth-first or depth-first search.
If you are unfamiliar with any of these prerequisites you should review
the material in the *Data
Structures* book first.
## When is Efficiency Important?
Not every problem requires the most efficient solution available. For
our purposes, the term efficient is concerned with the time and/or space
needed to perform the task. When either time or space is abundant and
cheap, it may not be worth it to pay a programmer to spend a day or so
working to make a program faster.
However, here are some cases where efficiency matters:
- When resources are limited, a change in algorithms could create
great savings and allow limited machines (like cell phones, embedded
systems, and sensor networks) to be stretched to the frontier of
possibility.
```{=html}
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```
- When the data is large a more efficient solution can mean the
difference between a task finishing in two days versus two weeks.
Examples include physics, genetics, web searches, massive online
stores, and network traffic analysis.
```{=html}
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```
- Real time applications: the term \"real time applications\" actually
refers to computations that give time guarantees, versus meaning
\"fast.\" However, the quality can be increased further by choosing
the appropriate algorithm.
```{=html}
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```
- Computationally expensive jobs, like fluid dynamics, partial
differential equations, VLSI design, and cryptanalysis can sometimes
only be considered when the solution is found efficiently enough.
```{=html}
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```
- When a subroutine is common and frequently used, time spent on a
more efficient implementation can result in benefits for every
application that uses the subroutine. Examples include sorting,
searching, pseudorandom number generation, kernel operations (not to
be confused with the operating system kernel), database queries, and
graphics.
In short, it\'s important to save time when you do not have any time to
spare.
When is efficiency unimportant? Examples of these cases include
prototypes that are used only a few times, cases where the input is
small, when simplicity and ease of maintenance is more important, when
the area concerned is not the bottle neck, or when there\'s another
process or area in the code that would benefit far more from efficient
design and attention to the algorithm(s).
## Inventing an Algorithm
Because we assume you have some knowledge of a programming language,
let\'s start with how we translate an idea into an algorithm. Suppose
you want to write a function that will take a string as input and output
the string in lowercase:
`// `*`tolower -- translates all alphabetic, uppercase characters in str to lowercase`*\
`function `**`tolower`**`(string `*`str`*`): string`
What first comes to your mind when you think about solving this problem?
Perhaps these two considerations crossed your mind:
1. Every character in *str* needs to be looked at
2. A routine for converting a single character to lower case is
required
The first point is \"obvious\" because a character that needs to be
converted might appear anywhere in the string. The second point follows
from the first because, once we consider each character, we need to do
something with it. There are many ways of writing the **tolower**
function for characters:
`function `**`tolower`**`(character `*`c`*`): character`
There are several ways to implement this function, including:
- look *c* up in a table---a character indexed array of characters
that holds the lowercase version of each character.
```{=html}
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```
- check if *c* is in the range \'A\' ≤ *c* ≤ \'Z\', and then add a
numerical offset to it.
These techniques depend upon the character encoding. (As an issue of
separation of concerns, perhaps the table solution is stronger because
it\'s clearer you only need to change one part of the code.)
However such a subroutine is implemented, once we have it, the
implementation of our original problem comes immediately:
`// `*`tolower -- translates all alphabetic, uppercase characters in str to lowercase`*\
`function `**`tolower`**`(string `*`str`*`): string`\
` let `*`result`*` := ""`\
` for-each `*`c`*` in `*`str`*`:`\
` `*`result`*`.append(`**`tolower`**`(`*`c`*`))`\
` repeat`\
` return `*`result`*\
`end`
The loop is the result of our ability to translate \"every character
needs to be looked at\" into our native programming language. It became
obvious that the **tolower** subroutine call should be in the loop\'s
body. The final step required to bring the high-level task into an
implementation was deciding how to build the resulting string. Here, we
chose to start with the empty string and append characters to the end of
it.
Now suppose you want to write a function for comparing two strings that
tests if they are equal, ignoring case:
`// `*`equal-ignore-case -- returns true if s and t are equal, ignoring case`*\
`function `**`equal-ignore-case`**`(string `*`s`*`, string `*`t`*`): boolean`
These ideas might come to mind:
1. Every character in strings *s* and *t* will have to be looked at
2. A single loop iterating through both might accomplish this
3. But such a loop should be careful that the strings are of equal
length first
4. If the strings aren\'t the same length, then they cannot be equal
because the consideration of ignoring case doesn\'t affect how long
the string is
5. A tolower subroutine for characters can be used again, and only the
lowercase versions will be compared
These ideas come from familiarity both with strings and with the looping
and conditional constructs in your language. The function you thought of
may have looked something like this:
`// `*`equal-ignore-case -- returns true if s or t are equal, ignoring case`*\
`function `**`equal-ignore-case`**`(string `*`s`*`[1..`*`n`*`], string `*`t`*`[1..`*`m`*`]): boolean`\
` if `*`n`*` != `*`m`*`:`\
` return false `*`\if they aren't the same length, they aren't equal\`*\
` fi`\
` `\
` for `*`i`*` := 1 to `*`n`*`:`\
` if `**`tolower`**`(`*`s`*`[`*`i`*`]) != `**`tolower`**`(`*`t`*`[`*`i`*`]):`\
` return false`\
` fi`\
` repeat`\
` return true`\
`end`
Or, if you thought of the problem in terms of functional decomposition
instead of iterations, you might have thought of a function more like
this:
`// `*`equal-ignore-case -- returns true if s or t are equal, ignoring case`*\
`function `**`equal-ignore-case`**`(string `*`s`*`, string `*`t`*`): boolean`\
` return `**`tolower`**`(`*`s`*`).equals(`**`tolower`**`(`*`t`*`))`\
`end`
Alternatively, you may feel neither of these solutions is efficient
enough, and you would prefer an algorithm that only ever made one pass
of *s* or *t*. The above two implementations each require two-passes:
the first version computes the lengths and then compares each character,
while the second version computes the lowercase versions of the string
and then compares the results to each other. (Note that for a pair of
strings, it is also possible to have the length precomputed to avoid the
second pass, but that can have its own drawbacks at times.) You could
imagine how similar routines can be written to test string equality that
not only ignore case, but also ignore accents.
Already you might be getting the spirit of the pseudocode in this book.
The pseudocode language is not meant to be a real programming language:
it abstracts away details that you would have to contend with in any
language. For example, the language doesn\'t assume generic types or
dynamic versus static types: the idea is that it should be clear what is
intended and it should not be too hard to convert it to your native
language. (However, in doing so, you might have to make some design
decisions that limit the implementation to one particular type or form
of data.)
There was nothing special about the techniques we used so far to solve
these simple string problems: such techniques are perhaps already in
your toolbox, and you may have found better or more elegant ways of
expressing the solutions in your programming language of choice. In this
book, we explore general algorithmic techniques to expand your toolbox
even further. Taking a naive algorithm and making it more efficient
might not come so immediately, but after understanding the material in
this book you should be able to methodically apply different solutions,
and, most importantly, you will be able to ask yourself more questions
about your programs. Asking questions can be just as important as
answering questions, because asking the right question can help you
reformulate the problem and think outside of the box.
## Understanding an Algorithm
Computer programmers need an excellent ability to reason with
multiple-layered abstractions. For example, consider the following code:
`function `**`foo`**`(integer `*`a`*`):`\
` if (`*`a`*` / 2) * 2 == `*`a`*`:`\
` print "The value " `*`a`*` " is even."`\
` fi`\
`end`
To understand this example, you need to know that integer division uses
truncation and therefore when the if-condition is true then the
least-significant bit in *a* is zero (which means that *a* must be
even). Additionally, the code uses a string printing API and is itself
the definition of a function to be used by different modules. Depending
on the programming task, you may think on the layer of hardware, on down
to the level of processor branch-prediction or the cache.
Often an understanding of binary is crucial, but many modern languages
have abstractions far enough away \"from the hardware\" that these
lower-levels are not necessary. Somewhere the abstraction stops: most
programmers don\'t need to think about logic gates, nor is the physics
of electronics necessary. Nevertheless, an essential part of programming
is multiple-layer thinking.
But stepping away from computer programs toward algorithms requires
another layer: mathematics. A program may exploit properties of binary
representations. An algorithm can exploit properties of set theory or
other mathematical constructs. Just as binary itself is not explicit in
a program, the mathematical properties used in an algorithm are not
explicit.
Typically, when an algorithm is introduced, a discussion (separate from
the code) is needed to explain the mathematics used by the algorithm.
For example, to really understand a greedy algorithm (such as
Dijkstra\'s algorithm) you should understand the mathematical properties
that show how the greedy strategy is valid for all cases. In a way, you
can think of the mathematics as its own kind of subroutine that the
algorithm invokes. But this \"subroutine\" is not present in the code
because there\'s nothing to call. As you read this book try to think
about mathematics as an implicit subroutine.
## Overview of the Techniques
The techniques this book covers are highlighted in the following
overview.
- **Divide and Conquer**: Many problems, particularly when the input
is given in an array, can be solved by cutting the problem into
smaller pieces (*divide*), solving the smaller parts recursively
(*conquer*), and then combining the solutions into a single result.
Examples include the merge sort and quicksort algorithms.
```{=html}
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```
- **Randomization**: Increasingly, randomization techniques are
important for many applications. This chapter presents some
classical algorithms that make use of random numbers.
```{=html}
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```
- **Backtracking**: Almost any problem can be cast in some form as a
backtracking algorithm. In backtracking, you consider all possible
choices to solve a problem and recursively solve subproblems under
the assumption that the choice is taken. The set of recursive calls
generates a tree in which each set of choices in the tree is
considered consecutively. Consequently, if a solution exists, it
will eventually be found.
Backtracking is generally an inefficient, brute-force technique, but
there are optimizations that can be performed to reduce both the depth
of the tree and the number of branches. The technique is called
backtracking because after one leaf of the tree is visited, the
algorithm will go back up the call stack (undoing choices that didn\'t
lead to success), and then proceed down some other branch. To be solved
with backtracking techniques, a problem needs to have some form of
\"self-similarity,\" that is, smaller instances of the problem (after a
choice has been made) must resemble the original problem. Usually,
problems can be generalized to become self-similar.
- **Dynamic Programming**: Dynamic programming is an optimization
technique for backtracking algorithms. When subproblems need to be
solved repeatedly (i.e., when there are many duplicate branches in
the backtracking algorithm) time can be saved by solving all of the
subproblems first (bottom-up, from smallest to largest) and storing
the solution to each subproblem in a table. Thus, each subproblem is
only visited and solved once instead of repeatedly. The
\"programming\" in this technique\'s name comes from programming in
the sense of writing things down in a table; for example, television
programming is making a table of what shows will be broadcast when.
```{=html}
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```
- **Greedy Algorithms**: A greedy algorithm can be useful when enough
information is known about possible choices that \"the best\" choice
can be determined without considering all possible choices.
Typically, greedy algorithms are not challenging to write, but they
are difficult to prove correct.
```{=html}
<!-- -->
```
- **Hill Climbing**: The final technique we explore is hill climbing.
The basic idea is to start with a poor solution to a problem, and
then repeatedly apply optimizations to that solution until it
becomes optimal or meets some other requirement. An important case
of hill climbing is network flow. Despite the name, network flow is
useful for many problems that describe relationships, so it\'s not
just for computer networks. Many matching problems can be solved
using network flow.
------------------------------------------------------------------------
## Algorithm and code example
### Level 1 (easiest)
1\. *Find maximum* With algorithm and
several different programming languages
2\. *Find minimum*With algorithm and
several different programming languages
3\. *Find average* With algorithm and
several different programming languages
4\. *Find mode* With algorithm and several
different programming languages
5\. *Find total* With algorithm and several
different programming languages
6\. *Counting* With algorithm and several
different programming languages
7\. *Find mean* With algorithm and several different programming
languages
### Level 2
1\. *Talking to computer Lv 1*
With algorithm and several different programming languages
2\. *Sorting-bubble sort* With
algorithm and several different programming languages
### Level 3
1\. *Talking to computer Lv 2*
With algorithm and several different programming languages
### Level 4
1\. *Talking to computer Lv 3*
With algorithm and several different programming languages
2\. *Find approximate maximum*
With algorithm and several different programming languages
### Level 5
1\. *Quicksort*
|
# Algorithms/Mathematical Background
Before we begin learning algorithmic techniques, we take a detour to
give ourselves some necessary mathematical tools. First, we cover
mathematical definitions of terms that are used later on in the book. By
expanding your mathematical vocabulary you can be more precise and you
can state or formulate problems more simply. Following that, we cover
techniques for analysing the running time of an algorithm. After each
major algorithm covered in this book we give an analysis of its running
time as well as a proof of its correctness
## Asymptotic Notation
In addition to correctness another important characteristic of a useful
algorithm is its time and memory consumption. Time and memory are both
valuable resources and there are important differences (even when both
are abundant) in how we can use them.
How can you measure resource consumption? One way is to create a
function that describes the usage in terms of some characteristic of the
input. One commonly used characteristic of an input dataset is its size.
For example, suppose an algorithm takes an input as an array of $n$
integers. We can describe the time this algorithm takes as a function
$f$ written in terms of $n$. For example, we might write:
$$f(n) = n^2 + 3n + 14$$
where the value of $f(n)$ is some unit of time (in this discussion the
main focus will be on time, but we could do the same for memory
consumption). Rarely are the units of time actually in seconds, because
that would depend on the machine itself, the system it\'s running, and
its load. Instead, the units of time typically used are in terms of the
number of some fundamental operation performed. For example, some
fundamental operations we might care about are: the number of additions
or multiplications needed; the number of element comparisons; the number
of memory-location swaps performed; or the raw number of machine
instructions executed. In general we might just refer to these
fundamental operations performed as steps taken.
Is this a good approach to determine an algorithm\'s resource
consumption? Yes and no. When two different algorithms are similar in
time consumption a precise function might help to determine which
algorithm is faster under given conditions. But in many cases it is
either difficult or impossible to calculate an analytical description of
the exact number of operations needed, especially when the algorithm
performs operations conditionally on the values of its input. Instead,
what really is important is not the precise time required to complete
the function, but rather the degree that resource consumption changes
depending on its inputs. Concretely, consider these two functions,
representing the computation time required for each size of input
dataset:
$$f(n) = n^3-12n^2+20n+110$$
$$g(n) = n^3+n^2+5n+5$$
They look quite different, but how do they behave? Let\'s look at a few
plots of the function ($f(n)$ is in red, $g(n)$ in blue):
+----------------------------------+----------------------------------+
| !Plot of f and g, in range 0 to | ![Plot of f and g, in range 0 to |
| 5 | t of f and g, in range 0 to 15") |
+----------------------------------+----------------------------------+
| !Plot of f and g, in range 0 to | ![Plot of f and g, in range 0 to |
| 100 | f f and g, in range 0 to 1000")\ |
+----------------------------------+----------------------------------+
In the first, very-limited plot the curves appear somewhat different. In
the second plot they start going in sort of the same way, in the third
there is only a very small difference, and at last they are virtually
identical. In fact, they approach $n^3$, the dominant term. As n gets
larger, the other terms become much less significant in comparison to
n^3^.
As you can see, modifying a polynomial-time algorithm\'s low-order
coefficients doesn\'t help much. What really matters is the
highest-order coefficient. This is why we\'ve adopted a notation for
this kind of analysis. We say that:
$$f(n) = n^3-12n^2+20n+110 = O(n^3)$$
We ignore the low-order terms. We can say that:
$$O(\log {n}) \le O(\sqrt{n}) \le O(n) \le O(n \log {n}) \le O(n^2) \le O(n^3) \le O(2^n)$$
This gives us a way to more easily compare algorithms with each other.
Running an insertion sort on $n$ elements takes steps on the order of
$O(n^2)$. Merge sort sorts in $O(n \log {n})$ steps. Therefore, once the
input dataset is large enough, merge sort is faster than insertion sort.
In general, we write
$$f(n) = O(g(n))$$
when
$$\exists c>0, \exists n_0> 0, \forall n\ge n_{0}: 0\le f(n)\le c\cdot g(n).$$
That is, $f(n) = O(g(n))$ holds if and only if there exists some
constants $c$ and $n_0$ such that for all $n>n_0$ $f(n)$ is positive and
less than or equal to $c g(n)$.
Note that the equal sign used in this notation describes a relationship
between $f(n)$ and $g(n)$ instead of reflecting a true equality. In
light of this, some define Big-O in terms of a set, stating that:
$$f(n)\in O(g(n))$$
when
$$f(n)\in \{f(n) : \exists c>0, \exists n_0> 0, \forall n\ge n_0: 0\le f(n)\le c\cdot g(n)\}.$$
Big-O notation is only an upper bound; these two are both true:
$$n^3 = O(n^4)$$
$$n^4 = O(n^4)$$
If we use the equal sign as an equality we can get very strange results,
such as:
$$n^3 = n^4$$
which is obviously nonsense. This is why the set-definition is handy.
You can avoid these things by thinking of the equal sign as a one-way
equality, i.e.:
$$n^3 = O(n^4)$$
does not imply
$$O(n^4) = n^3$$
Always keep the O on the right hand side.
### Big Omega
Sometimes, we want more than an upper bound on the behavior of a certain
function. Big Omega provides a lower bound. In general, we say that
$$f(n) = \Omega(g(n))$$
when
$$\exists c>0, \exists n_0> 0, \forall n\ge n_{0}: 0\le c\cdot g(n)\le f(n).$$
i.e. $f(n) = \Omega(g(n))$ if and only if there exist constants c and
n~0~ such that for all n\>n~0~ f(n) is positive and **greater** than or
equal to cg(n).
So, for example, we can say that
$$n^2-2n = \Omega(n^2)$$, (c=1/2, n~0~=4) or
$$n^2-2n = \Omega(n)$$, (c=1, n~0~=3),
but it is false to claim that
$$n^2-2n = \Omega(n^3).$$
### Big Theta
When a given function is both O(g(n)) and Ω(g(n)), we say it is Θ(g(n)),
and we have a tight bound on the function. A function f(n) is Θ(g(n))
when
$$\exists c_1>0, \exists c_2>0, \exists n_0> 0, \forall n\ge n_0 : 0\le c_1\cdot g(n)\le f(n)\le c_2\cdot g(n),$$
but most of the time, when we\'re trying to prove that a given
$f(n) = \Theta(g(n))$, instead of using this definition, we just show
that it is both O(g(n)) and Ω(g(n)).
### Little-O and Omega
When the asymptotic bound is not tight, we can express this by saying
that $f(n) = o(g(n))$ or $f(n) = \omega(g(n)).$ The definitions are:
: f(n) is o(g(n)) iff
$\forall c>0, \exists n_0> 0, \forall n\ge n_0: 0\le f(n) < c\cdot g(n)$
and
: f(n) is ω(g(n)) iff
$\forall c>0, \exists n_0> 0, \forall n\ge n_0: 0\le c\cdot g(n) < f(n).$
Note that a function f is in o(g(n)) when for any coefficient of g, g
eventually gets larger than f, while for O(g(n)), there only has to
exist a single coefficient for which g eventually gets at least as big
as f.
### Big-O with multiple variables
Given a functions with two parameters $f(n,m)$ and $g(n,m)$,
$f(n,m)=O(g(n,m))$ if and only if
$\exists c > 0, \exists n_0 > 0, \exists m_0 > 0, \forall n \geq n_0, \forall m \geq m_0 : 0 \leq f(n,m) \leq c \cdot g(n,m)$.
For example, $5n + 3m = O(n+m)$, and $n + 10m + 3nm = O(nm)$.
## Algorithm Analysis: Solving Recurrence Equations
Merge sort of n elements: $T(n) = 2*T(n/2) + c(n)$ This describes one
iteration of the merge sort: the problem space $n$ is reduced to two
halves ($2*T(n/2)$), and then merged back together at the end of all the
recursive calls ($c(n)$). This notation system is the bread and butter
of algorithm analysis, so get used to it.
There are some theorems you can use to estimate the big Oh time for a
function if its recurrence equation fits a certain pattern.
### Substitution method
Formulate a guess about the big Oh time of your equation. Then use proof
by induction to prove the guess is correct.
### Summations
### Draw the Tree and Table
This is really just a way of getting an intelligent guess. You still
have to go back to the substitution method in order to prove the big Oh
time.
### The Master Theorem
Consider a recurrence equation that fits the following formula:
$$T(n) = a T\left({\frac{n}{b}}\right) + O(n^k)$$
for *a* ≥ 1, *b* \> 1 and *k* ≥ 0. Here, *a* is the number of recursive
calls made per call to the function, *n* is the input size, *b* is how
much smaller the input gets, and *k* is the polynomial order of an
operation that occurs each time the function is called (except for the
base cases). For example, in the merge sort algorithm covered later, we
have
$$T(n) = 2 T\left({\frac{n}{2}}\right) + O(n)$$
because two subproblems are called for each non-base case iteration, and
the size of the array is divided in half each time. The $O(n)$ at the
end is the \"conquer\" part of this divide and conquer algorithm: it
takes linear time to merge the results from the two recursive calls into
the final result.
Thinking of the recursive calls of *T* as forming a tree, there are
three possible cases to determine where most of the algorithm is
spending its time (\"most\" in this sense is concerned with its
asymptotic behaviour):
1. the tree can be **top heavy**, and most time is spent during the
initial calls near the root;
2. the tree can have a **steady state**, where time is spread evenly;
or
3. the tree can be **bottom heavy**, and most time is spent in the
calls near the leaves
Depending upon which of these three states the tree is in *T* will have
different complexities:
```{=html}
<div style="background-color: #FFFFEE; border: solid 1px #FFC92E; padding: 1em; width: 80%;" valign=top>
```
**The Master Theorem**\
Given $T(n) = a T\left({\frac{n}{b}}\right) + O(n^k)$ for *a* ≥ 1, *b*
\> 1 and *k* ≥ 0:
- If $a < b^k$, then $T(n) = O(n^k)\$ (top heavy)
- If $a = b^k$, then $T(n) = O(n^k\cdot \log n)$ (steady state)
- If $a > b^k$, then $T(n) = O(n^{\log_b a})$ (bottom heavy)
```{=html}
</div>
```
For the merge sort example above, where
$$T(n) = 2 T\left({\frac{n}{2}}\right) + O(n)$$
we have
$$a=2, b=2, k=1\implies b^k = 2$$
thus, $a = b^k$ and so this is also in the \"steady state\": By the
master theorem, the complexity of merge sort is thus
$$T(n) = O(n^1\log n) = O(n \log n)$$.
## Amortized Analysis
\[Start with an adjacency list representation of a graph and show two
nested for loops: one for each node n, and nested inside that one loop
for each edge e. If there are n nodes and m edges, this could lead you
to say the loop takes O(nm) time. However, only once could the innerloop
take that long, and a tighter bound is O(n+m).\]
------------------------------------------------------------------------
|
# Algorithms/Divide and Conquer
The first major algorithmic technique we cover is **divide and
conquer**. Part of the trick of making a good divide and conquer
algorithm is determining how a given problem could be separated into two
or more similar, but smaller, subproblems. More generally, when we are
creating a divide and conquer algorithm we will take the following
steps:
+----------------------------------------------------------------------+
| **Divide and Conquer Methodology** |
| |
| 1. Given a problem, identify a small number of significantly |
| smaller subproblems of the same type |
| 2. Solve each subproblem recursively (the smallest possible size of |
| a subproblem is a base-case) |
| 3. Combine these solutions into a solution for the main problem |
+----------------------------------------------------------------------+
The first algorithm we\'ll present using this methodology is the merge
sort.
## Merge Sort
The problem that **merge sort** solves is general sorting: given an
unordered array of elements that have a total ordering, create an array
that has the same elements sorted. More precisely, for an array *a* with
indexes 1 through *n*, if the condition
: for all *i*, *j* such that 1 ≤ *i* \< *j* ≤ *n* then *a*\[*i*\] ≤
*a*\[*j*\]
holds, then *a* is said to be **sorted**. Here is the interface:
*`// sort -- returns a sorted copy of array a`*\
`function `**`sort`**`(array `*`a`*`): array`
Following the divide and conquer methodology, how can *a* be broken up
into smaller subproblems? Because *a* is an array of *n* elements, we
might want to start by breaking the array into two arrays of size *n*/2
elements. These smaller arrays will also be unsorted and it is
meaningful to sort these smaller problems; thus we can consider these
smaller arrays \"similar\". Ignoring the base case for a moment, this
reduces the problem into a different one: Given two sorted arrays, how
can they be combined to form a single sorted array that contains all the
elements of both given arrays:
`''// merge—given a and b (assumed to be sorted) returns a merged array that`\
`// preserves order`\
`function `**`merge`**`(array `*`a`*`, array `*`b`*`): array`
So far, following the methodology has led us to this point, but what
about the base case? The base case is the part of the algorithm
concerned with what happens when the problem cannot be broken into
smaller subproblems. Here, the base case is when the array only has one
element. The following is a sorting algorithm that faithfully sorts
arrays of only zero or one elements:
`''// base-sort -- given an array of one element (or empty), return a copy of the`\
`// array sorted''`\
`function `**`base-sort`**`(array `*`a`*`[1..`*`n`*`]): array`\
` assert (`*`n`*` <= 1)`\
` return `*`a`*`.copy()`\
`end`
Putting this together, here is what the methodology has told us to write
so far:
*`// sort -- returns a sorted copy of array a`*\
`function `**`sort`**`(array `*`a`*`[1..`*`n`*`]): array`\
` if `*`n`*` <= 1: return `*`a`*`.copy()`\
` else:`\
` let `*`sub_size`*` := `*`n`*` / 2`\
` let `*`first_half`*` := `**`sort`**`(`*`a`*`[1,..,`*`sub_size`*`])`\
` let `*`second_half`*` := `**`sort`**`(`*`a`*`[`*`sub_size`*` + 1,..,`*`n`*`])`\
` `\
` return `**`merge`**`(`*`first_half`*`, `*`second_half`*`)`\
` fi`\
`end`
And, other than the unimplemented merge subroutine, this sorting
algorithm is done! Before we cover how this algorithm works, here is how
merge can be written:
`''// merge -- given a and b (assumed to be sorted) returns a merged array that`\
`// preserves order''`\
`function `**`merge`**`(array `*`a`*`[1..`*`n`*`], array `*`b`*`[1..`*`m`*`]): array`\
` let `*`result`*` := new array[`*`n`*` + `*`m`*`]`\
` let `*`i`*`, `*`j`*` := 1`\
` `\
` for `*`k`*` := 1 to `*`n`*` + `*`m`*`:`\
` if `*`i`*` >= `*`n`*`: `*`result`*`[`*`k`*`] := `*`b`*`[`*`j`*`]; `*`j`*` += 1`\
` else-if `*`j`*` >= `*`m`*`: `*`result`*`[`*`k`*`] := `*`a`*`[`*`i`*`]; `*`i`*` += 1`\
` else:`\
` if `*`a`*`[`*`i`*`] < `*`b`*`[`*`j`*`]:`\
` `*`result`*`[`*`k`*`] := `*`a`*`[`*`i`*`]; `*`i`*` += 1`\
` else:`\
` `*`result`*`[`*`k`*`] := `*`b`*`[`*`j`*`]; `*`j`*` += 1`\
` fi`\
` fi`\
` repeat`\
`end`
\[TODO: how it works; including correctness proof\] This algorithm uses
the fact that, given two sorted arrays, the smallest element is always
in one of two places. It\'s either at the head of the first array, or
the head of the second.
### Analysis
Let $T(n)$ be the number of steps the algorithm takes to run on input of
size $n$.
Merging takes linear time and we recurse each time on two sub-problems
of half the original size, so
$$T(n) = 2\cdot T\left(\frac{n}{2}\right) + O(n).$$
By the master theorem, we see that this recurrence has a \"steady
state\" tree. Thus, the runtime is:
$$T(n) = O(n \cdot \log n).$$
This can be seen intuitively by asking how may times does n need to be
divided by 2 before the size of the array for sorting is 1? Why, m times
of course!
More directly, 2^m^ = n , equivalent to log 2^m^ = log n, equivalent to
m log~2~2 = log ~2~ n , and since log~2~ 2 = 1,
equivalent to m = log~2~n.
Since m is the number of halvings of an array before the array is
chopped up into bite sized pieces of 1-element arrays, and then it will
take m levels of merging a sub-array with its neighbor where the sum
size of sub-arrays will be n at each level, it will be exactly n
2 comparisons for merging at each level, with m
( log~2~n ) levels, thus O(n 2
log n ) \<=\> **O ( n log n).**
### Iterative Version
This merge sort algorithm can be turned into an iterative algorithm by
iteratively merging each subsequent pair, then each group of four, et
cetera. Due to a lack of function overhead, iterative algorithms tend to
be faster in practice. However, because the recursive version\'s call
tree is logarithmically deep, it does not require much run-time stack
space: Even sorting 4 gigs of items would only require 32 call entries
on the stack, a very modest amount considering if even each call
required 256 bytes on the stack, it would only require 8 kilobytes.
The iterative version of mergesort is a minor modification to the
recursive version - in fact we can reuse the earlier merging function.
The algorithm works by merging small, sorted subsections of the original
array to create larger subsections of the array which are sorted. To
accomplish this, we iterate through the array with successively larger
\"strides\".
*`// sort -- returns a sorted copy of array a`*\
`function `**`sort_iterative`**`(array `*`a`*`[1,.'n'']): array`\
` let `*`result`*` := `*`a`*`.copy()`\
` for `*`power`*` := 0 to log2(`*`n`*`-1)`\
` let `*`unit`*` := 2^power`\
` for `*`i`*` := 1 to `*`n`*` by `*`unit`*`*2`\
` if i+`*`unit`*`-1 < n: `\
` let `*`a1`*`[1..`*`unit`*`] := `*`result`*`[i..i+`*`unit`*`-1]`\
` let `*`a2`*`[1.`*`unit`*`] := `*`result`*`[i+`*`unit`*`..min(i+`*`unit`*`*2-1, `*`n`*`)]`\
` `*`result`*`[i..i+`*`unit`*`*2-1] := `**`merge`**`(`*`a1`*`,`*`a2`*`)`\
` fi`\
` repeat`\
` repeat`\
` `\
` return `*`result`*\
`end`
This works because each sublist of length 1 in the array is, by
definition, sorted. Each iteration through the array (using counting
variable *i*) doubles the size of sorted sublists by merging adjacent
sublists into sorted larger versions. The current size of sorted
sublists in the algorithm is represented by the *unit* variable.
### space inefficiency
Straight forward merge sort requires a space of 2
n , n to store the 2 sorted smaller arrays , and
n to store the final result of merging. But merge sort still lends
itself for batching of merging.
## Binary Search
Once an array is sorted, we can quickly locate items in the array by
doing a binary search. Binary search is different from other divide and
conquer algorithms in that it is mostly divide based (nothing needs to
be conquered). The concept behind binary search will be useful for
understanding the partition and quicksort algorithms, presented in the
randomization chapter.
Finding an item in an already sorted array is similar to finding a name
in a phonebook: you can start by flipping the book open toward the
middle. If the name you\'re looking for is on that page, you stop. If
you went too far, you can start the process again with the first half of
the book. If the name you\'re searching for appears later than the page,
you start from the second half of the book instead. You repeat this
process, narrowing down your search space by half each time, until you
find what you were looking for (or, alternatively, find where what you
were looking for would have been if it were present).
The following algorithm states this procedure precisely:
*`// binary-search -- returns the index of value in the given array, or`*\
*`// -1 if value cannot be found. Assumes array is sorted in ascending order`*\
`function `**`binary-search`**`(`*`value`*`, array `*`A`*`[1..`*`n`*`]): integer`\
` return `**`search-inner`**`(`*`value`*`, `*`A`*`, 1, `*`n`*` + 1)`\
`end`\
\
*`// search-inner -- search subparts of the array; end is one past the`*\
*`// last element`*\
`function `**`search-inner`**`(`*`value`*`, array `*`A`*`, `*`start`*`, `*`end`*`): integer`\
` if `*`start`*` == `*`end`*`: `\
` return -1 `*`// not found`*\
` fi`\
\
` let `*`length`*` := `*`end`*` - `*`start`*\
` if `*`length`*` == 1:`\
` if `*`value`*` == `*`A`*`[`*`start`*`]:`\
` return `*`start`*\
` else:`\
` return -1 `\
` fi`\
` fi`\
` `\
` let `*`mid`*` := `*`start`*` + (`*`length`*` / 2)`\
` if `*`value`*` == `*`A`*`[`*`mid`*`]:`\
` return `*`mid`*\
` else-if `*`value`*` > `*`A`*`[`*`mid`*`]:`\
` return `**`search-inner`**`(`*`value`*`, `*`A`*`, `*`mid`*` + 1, `*`end`*`)`\
` else:`\
` return `**`search-inner`**`(`*`value`*`, `*`A`*`, `*`start`*`, `*`mid`*`)`\
` fi`\
`end`
Note that all recursive calls made are tail-calls, and thus the
algorithm is iterative. We can explicitly remove the tail-calls if our
programming language does not do that for us already by turning the
argument values passed to the recursive call into assignments, and then
looping to the top of the function body again:
*`// binary-search -- returns the index of value in the given array, or`*\
*`// -1 if value cannot be found. Assumes array is sorted in ascending order`*\
`function `**`binary-search`**`(`*`value`*`, array `*`A`*`[1,..`*`n`*`]): integer`\
` let `*`start`*` := 1`\
` let `*`end`*` := `*`n`*` + 1`\
` `\
` loop:`\
` if `*`start`*` == `*`end`*`: return -1 fi `*`// not found`*\
` `\
` let `*`length`*` := `*`end`*` - `*`start`*\
` if `*`length`*` == 1:`\
` if `*`value`*` == `*`A`*`[`*`start`*`]: return `*`start`*\
` else: return -1 fi`\
` fi`\
` `\
` let `*`mid`*` := `*`start`*` + (`*`length`*` / 2)`\
` if `*`value`*` == `*`A`*`[`*`mid`*`]:`\
` return `*`mid`*\
` else-if `*`value`*` > `*`A`*`[`*`mid`*`]:`\
` `*`start`*` := `*`mid`*` + 1`\
` else:`\
` `*`end`*` := `*`mid`*\
` fi`\
` repeat`\
`end`
Even though we have an iterative algorithm, it\'s easier to reason about
the recursive version. If the number of steps the algorithm takes is
$T(n)$, then we have the following recurrence that defines $T(n)$:
$$T(n) = 1\cdot T\left(\frac{n}{2}\right) + O(1).$$ The size of each
recursive call made is on half of the input size ($n$), and there is a
constant amount of time spent outside of the recursion (i.e., computing
*length* and *mid* will take the same amount of time, regardless of how
many elements are in the array). By the master theorem, this recurrence
has values $a=1, b=2, k=0$, which is a \"steady state\" tree, and thus
we use the steady state case that tells us that
$$T(n) = \Theta(n^k\cdot\log n) = \Theta(\log n).$$ Thus, this algorithm
takes logarithmic time. Typically, even when *n* is large, it is safe to
let the stack grow by $\log n$ activation records through recursive
calls.
#### difficulty in initially correct binary search implementations
The article on wikipedia on Binary Search also mentions the difficulty
in writing a correct binary search algorithm: for instance, the java
Arrays.binarySearch(..) overloaded function implementation does an
iterative binary search which didn\'t work when large integers
overflowed a simple expression of mid calculation
`mid = ( end + start) / 2` i.e. `end + start > max_positive_integer`.
Hence the above algorithm is more correct in using a length = end -
start, and adding half length to start. The java binary Search algorithm
gave a return value useful for finding the position of the nearest key
greater than the search key, i.e. the position where the search key
could be inserted.
i.e. it returns *- (keypos+1)* , if the search key wasn\'t found
exactly, but an insertion point was needed for the search key (
insertion_point = *-return_value - 1*). Looking at boundary
values, an insertion point could be at the
front of the list ( ip = 0, return value = -1 ), to the position just
after the last element, ( ip = length(A), return value = *- length(A) -
1*) .
As an exercise, trying to implement this functionality on the above
iterative binary search can be useful for further comprehension.
## Integer Multiplication
If you want to perform arithmetic with small integers, you can simply
use the built-in arithmetic hardware of your machine. However, if you
wish to multiply integers larger than those that will fit into the
standard \"word\" integer size of your computer, you will have to
implement a multiplication algorithm in software or use a software
implementation written by someone else. For example, RSA encryption
needs to work with integers of very large size (that is, large relative
to the 64-bit word size of many machines) and utilizes special
multiplication algorithms.[^1]
### Grade School Multiplication
How do we represent a large, multi-word integer? We can have a binary
representation by using an array (or an allocated block of memory) of
words to represent the bits of the large integer. Suppose now that we
have two integers, $X$ and $Y$, and we want to multiply them together.
For simplicity, let\'s assume that both $X$ and $Y$ have $n$ bits each
(if one is shorter than the other, we can always pad on zeros at the
beginning). The most basic way to multiply the integers is to use the
grade school multiplication algorithm. This is even easier in binary,
because we only multiply by 1 or 0:
` x6 x5 x4 x3 x2 x1 x0`\
` × y6 y5 y4 y3 y2 y1 y0`\
` -----------------------`\
` x6 x5 x4 x3 x2 x1 x0 (when y0 is 1; 0 otherwise)`\
` x6 x5 x4 x3 x2 x1 x0 0 (when y1 is 1; 0 otherwise)`\
` x6 x5 x4 x3 x2 x1 x0 0 0 (when y2 is 1; 0 otherwise)`\
`x6 x5 x4 x3 x2 x1 x0 0 0 0 (when y3 is 1; 0 otherwise)`\
` ... et cetera`
As an algorithm, here\'s what multiplication would look like:
*`// multiply -- return the product of two binary integers, both of length n`*\
`function `**`multiply`**`(bitarray `*`x`*`[1,..`*`n`*`], bitarray `*`y`*`[1,..`*`n`*`]): bitarray`\
` bitarray `*`p`*` = 0`\
` for `*`i`*`:=1 to `*`n`*`:`\
` if `*`y`*`[`*`i`*`] == 1:`\
` `*`p`*` := `**`add`**`(`*`p`*`, `*`x`*`)`\
` fi`\
` `*`x`*` := `**`pad`**`(`*`x`*`, 0) `*`// add another zero to the end of x`*\
` repeat`\
` return `*`p`*\
`end`
The subroutine **add** adds two binary integers and returns the result,
and the subroutine **pad** adds an extra digit to the end of the number
(padding on a zero is the same thing as shifting the number to the left;
which is the same as multiplying it by two). Here, we loop *n* times,
and in the worst-case, we make *n* calls to **add**. The numbers given
to **add** will at most be of length $2n$. Further, we can expect that
the **add** subroutine can be done in linear time. Thus, if *n* calls to
a $O(n)$ subroutine are made, then the algorithm takes $O(n^2)$ time.
### Divide and Conquer Multiplication
As you may have figured, this isn\'t the end of the story. We\'ve
presented the \"obvious\" algorithm for multiplication; so let\'s see if
a divide and conquer strategy can give us something better. One route we
might want to try is breaking the integers up into two parts. For
example, the integer *x* could be divided into two parts, $x_{h}$ and
$x_{l}$, for the high-order and low-order halves of $x$. For example, if
$x$ has *n* bits, we have
$$x = x_{h}\cdot 2^{n/2} + x_{l}$$
We could do the same for $y$:
$$y = y_{h}\cdot 2^{n/2} + y_{l}$$
But from this division into smaller parts, it\'s not clear how we can
multiply these parts such that we can combine the results for the
solution to the main problem. First, let\'s write out $x\times y$ would
be in such a system:
$$x\times y = x_h\times y_h\cdot (2^{n/2})^2 + (x_h\times y_l + x_l\times y_h)\cdot (2^{n/2}) + x_l\times y_l$$
This comes from simply multiplying the new hi/lo representations of
and $y$ together. The multiplication of the
smaller pieces are marked by the \"$\times$\" symbol. Note that the
multiplies by $2^{n/2}$ and $(2^{n/2})^2 = 2^n$ does not require a real
multiplication: we can just pad on the right number of zeros instead.
This suggests the following divide and conquer algorithm:
*`// multiply -- return the product of two binary integers, both of length n`*\
`function `**`multiply`**`(bitarray `*`x`*`[1,..`*`n`*`], bitarray `*`y`*`[1,..`*`n`*`]): bitarray`\
` if `*`n`*` == 1: return `*`x`*`[1] * `*`y`*`[1] fi `*`// multiply single digits: O(1)`*\
` `\
` let `*`xh`*` := `*`x`*`[`*`n`*`/2 + 1, .., `*`n`*`] `*`// array slicing, O(n)`*\
` let `*`xl`*` := `*`x`*`[0, .., `*`n`*` / 2] `*`// array slicing, O(n)`*\
` let `*`yh`*` := `*`y`*`[`*`n`*`/2 + 1, .., `*`n`*`] `*`// array slicing, O(n)`*\
` let `*`yl`*` := `*`y`*`[0, .., `*`n`*` / 2] `*`// array slicing, O(n)`*\
` `\
` let `*`a`*` := `**`multiply`**`(`*`xh`*`, `*`yh`*`) `*`// recursive call; T(n/2)`*\
` let `*`b`*` := `**`multiply`**`(`*`xh`*`, `*`yl`*`) `*`// recursive call; T(n/2)`*\
` let `*`c`*` := `**`multiply`**`(`*`xl`*`, `*`yh`*`) `*`// recursive call; T(n/2)`*\
` let `*`d`*` := `**`multiply`**`(`*`xl`*`, `*`yl`*`) `*`// recursive call; T(n/2)`*\
` `\
` `*`b`*` := `**`add`**`(`*`b`*`, `*`c`*`) `*`// regular addition; O(n)`*\
` `*`a`*` := `**`shift`**`(`*`a`*`, `*`n`*`) `*`// pad on zeros; O(n)`*\
` `*`b`*` := `**`shift`**`(`*`b`*`, `*`n`*`/2) `*`// pad on zeros; O(n)`*\
` return `**`add`**`(`*`a`*`, `*`b`*`, `*`d`*`) `*`// regular addition; O(n)`*\
`end`
We can use the master theorem to analyze the running time of this
algorithm. Assuming that the algorithm\'s running time is $T(n)$, the
comments show how much time each step takes. Because there are four
recursive calls, each with an input of size $n/2$, we have:
$$T(n) = 4T(n/2) + O(n)$$
Here, $a=4, b=2, k=1$, and given that $4>2^1$ we are in the \"bottom
heavy\" case and thus plugging in these values into the bottom heavy
case of the master theorem gives us:
$$T(n)=O(n^{\log_2 4}) = O(n^2).$$
Thus, after all of that hard work, we\'re still no better off than the
grade school algorithm! Luckily, numbers and polynomials are a data set
we know additional information about. In fact, we can reduce the running
time by doing some mathematical tricks.
First, let\'s replace the $2^{n/2}$ with a variable, *z*:
$$x\times y = x_h*y_h z^2 + (x_h*y_l + x_l*y_h)z + x_l*y_l$$
This appears to be a quadratic formula, and we know that you only need
three co-efficients or points on a graph in order to uniquely describe a
quadratic formula. However, in our above algorithm we\'ve been using
four multiplications total. Let\'s try recasting
and $y$ as linear functions:
$$P_x(z) = x_h\cdot z + x_l$$
$$P_y(z) = y_h\cdot z + y_l$$
Now, for $x\times y$ we just need to compute $(P_x\cdot P_y)(2^{n/2})$.
We\'ll evaluate $P_x(z)$ and $P_y(z)$ at three points. Three convenient
points to evaluate the function will be at
$(P_x\cdot P_y)(1), (P_x\cdot P_y)(0), (P_x\cdot P_y)(-1)$:
\[TODO: show how to make the two-parts breaking more efficient; then
mention that the best multiplication uses the FFT, but don\'t actually
cover that topic (which is saved for the advanced book)\]
## Base Conversion
\[TODO: Convert numbers from decimal to binary quickly using DnC.\]
Along with the binary, the science of computers employs bases 8 and 16
for it\'s very easy to convert between the three while using bases 8 and
16 shortens considerably number representations.
To represent 8 first digits in the binary system we need 3 bits. Thus we
have, 0=000, 1=001, 2=010, 3=011, 4=100, 5=101, 6=110, 7=111. Assume
M=(2065)~8~. In order to obtain its binary representation, replace each
of the four digits with the corresponding triple of bits: 010 000 110
101. After removing the leading zeros, binary representation is
immediate: M=(10000110101)~2~. (For the hexadecimal system conversion is
quite similar, except that now one should use 4-bit representation of
numbers below 16.) This fact follows from the general conversion
algorithm and the observation that 8=$2^3$ (and, of course, 16=$2^4$).
Thus it appears that the shortest way to convert numbers into the binary
system is to first convert them into either octal or hexadecimal
representation. Now let see how to implement the general algorithm
programmatically.
For the sake of reference, representation of a number in a system with
base (radix) N may only consist of digits that are less than N.
More accurately, if
$$(1) M = a_kN^k+a_{k-1}N^{k-1}+...+a_1N^1+a_0$$
with $0 <= a_i < N$ we have a representation of M in base N system and
write
$$M = (a_ka_{k-1}...a_0)N$$ If we rewrite (1) as
$$(2) M = a_0+N*(a_1+N*(a_2+N*...))$$
the algorithm for obtaining coefficients ai becomes more obvious. For
example, $a_0=M\ modulo\ n$ and $a_1=(M/N)\ modulo\ n$, and so on.
### Recursive Implementation
Let\'s represent the algorithm mnemonically: (result is a string or
character variable where I shall accumulate the digits of the result one
at a time)
`result = "" `\
`if M < N, result = 'M' + result. Stop. `\
`S = M mod N, result = 'S' + result`\
`M = M/N `\
`goto 2 `
A few words of explanation.
\"\" is an empty string. You may remember it\'s a zero element for
string concatenation. Here we check whether the conversion procedure is
over. It\'s over if M is less than N in which case M is a digit (with
some qualification for N\>10) and no additional action is necessary.
Just prepend it in front of all other digits obtained previously. The
\'+\' plus sign stands for the string concatenation. If we got this far,
M is not less than N. First we extract its remainder of division by N,
prepend this digit to the result as described previously, and reassign M
to be M/N. This says that the whole process should be repeated starting
with step 2. I would like to have a function say called Conversion that
takes two arguments M and N and returns representation of the number M
in base N. The function might look like this
`1 String Conversion(int M, int N) // return string, accept two integers `\
`2 { `\
`3 if (M < N) // see if it's time to return `\
`4 return new String(""+M); // ""+M makes a string out of a digit `\
`5 else // the time is not yet ripe `\
`6 return Conversion(M/N, N) +`\
` new String(""+(M mod N)); // continue `\
`7 } `
This is virtually a working Java function and it would look very much
the same in C++ and require only a slight modification for C. As you
see, at some point the function calls itself with a different first
argument. One may say that the function is defined in terms of itself.
Such functions are called recursive. (The best known recursive function
is factorial: n!=n\*(n-1)!.) The function calls (applies) itself to its
arguments, and then (naturally) applies itself to its new arguments, and
then \... and so on. We can be sure that the process will eventually
stop because the sequence of arguments (the first ones) is decreasing.
Thus sooner or later the first argument will be less than the second and
the process will start emerging from the recursion, still a step at a
time.
### Iterative Implementation
Not all programming languages allow functions to call themselves
recursively. Recursive functions may also be undesirable if process
interruption might be expected for whatever reason. For example, in the
Tower of Hanoi puzzle, the user may want to interrupt the demonstration
being eager to test his or her understanding of the solution. There are
complications due to the manner in which computers execute programs when
one wishes to jump out of several levels of recursive calls.
Note however that the string produced by the conversion algorithm is
obtained in the wrong order: all digits are computed first and then
written into the string the last digit first. Recursive implementation
easily got around this difficulty. With each invocation of the
Conversion function, computer creates a new environment in which passed
values of M, N, and the newly computed S are stored. Completing the
function call, i.e. returning from the function we find the environment
as it was before the call. Recursive functions store a sequence of
computations implicitly. Eliminating recursive calls implies that we
must manage to store the computed digits explicitly and then retrieve
them in the reversed order.
In Computer Science such a mechanism is known as LIFO - Last In First
Out. It\'s best implemented with a stack data structure. Stack admits
only two operations: push and pop. Intuitively stack can be visualized
as indeed a stack of objects. Objects are stacked on top of each other
so that to retrieve an object one has to remove all the objects above
the needed one. Obviously the only object available for immediate
removal is the top one, i.e. the one that got on the stack last.
Then iterative implementation of the Conversion function might look as
the following.
` 1 String Conversion(int M, int N) // return string, accept two integers `\
` 2 { `\
` 3 Stack stack = new Stack(); // create a stack `\
` 4 while (M >= N) // now the repetitive loop is clearly seen `\
` 5 { `\
` 6 stack.push(M mod N); // store a digit `\
` 7 M = M/N; // find new M `\
` 8 } `\
` 9 // now it's time to collect the digits together `\
`10 String str = new String(""+M); // create a string with a single digit M `\
`11 while (stack.NotEmpty()) `\
`12 str = str+stack.pop() // get from the stack next digit `\
`13 return str; `\
`14 } `
The function is by far longer than its recursive counterpart; but, as I
said, sometimes it\'s the one you want to use, and sometimes it\'s the
only one you may actually use.
## Closest Pair of Points
For a set of points on a two-dimensional plane, if you want to find the
closest two points, you could compare all of them to each other, at
$O(n^2)$ time, or use a divide and conquer algorithm.
\[TODO: explain the algorithm, and show the n\^2 algorithm\]
\[TODO: write the algorithm, include intuition, proof of correctness,
and runtime analysis\]
Use this link for the original document.
<http://www.cs.mcgill.ca/~cs251/ClosestPair/ClosestPairDQ.html>
## Closest Pair: A Divide-and-Conquer Approach
### Introduction
The brute force approach to the closest pair problem (i.e. checking
every possible pair of points) takes quadratic time. We would now like
to introduce a faster divide-and-conquer algorithm for solving the
closest pair problem. Given a set of points in the plane S, our approach
will be to split the set into two roughly equal halves (S1 and S2) for
which we already have the solutions, and then to merge the halves in
linear time to yield an O(nlogn) algorithm. However, the actual solution
is far from obvious. It is possible that the desired pair might have one
point in S1 and one in S2, does this not force us once again to check
all possible pairs of points? The divide-and-conquer approach presented
here generalizes directly from the one dimensional algorithm we
presented in the previous section.
### Closest Pair in the Plane
Alright, we\'ll generalize our 1-D algorithm as directly as possible
(see figure 3.2). Given a set of points S in the plane, we partition it
into two subsets S1 and S2 by a vertical line l such that the points in
S1 are to the left of l and those in S2 are to the right of l.
We now recursively solve the problem on these two sets obtaining minimum
distances of d1 (for S1), and d2 (for S2). We let d be the minimum of
these.
Now, identical to the 1-D case, if the closes pair of the whole set
consists of one point from each subset, then these two points must be
within d of l. This area is represented as the two strips P1 and P2 on
either side of l
Up to now, we are completely in step with the 1-D case. At this point,
however, the extra dimension causes some problems. We wish to determine
if some point in say P1 is less than d away from another point in P2.
However, in the plane, we don\'t have the luxury that we had on the line
when we observed that only one point in each set can be within d of the
median. In fact, in two dimensions, all of the points could be in the
strip! This is disastrous, because we would have to compare n2 pairs of
points to merge the set, and hence our divide-and-conquer algorithm
wouldn\'t save us anything in terms of efficiency. Thankfully, we can
make another life saving observation at this point. For any particular
point p in one strip, only points that meet the following constraints in
the other strip need to be checked:
- those points within d of p in the direction of the other strip
- those within d of p in the positive and negative y directions
Simply because points outside of this bounding box cannot be less than d
units from p (see figure 3.3). It just so happens that because every
point in this box is at least d apart, there can be at most six points
within it.
Now we don\'t need to check all n2 points. All we have to do is sort the
points in the strip by their y-coordinates and scan the points in order,
checking each point against a maximum of 6 of its neighbors. This means
at most 6\*n comparisons are required to check all candidate pairs.
However, since we sorted the points in the strip by their y-coordinates
the process of merging our two subsets is not linear, but in fact takes
O(nlogn) time. Hence our full algorithm is not yet O(nlogn), but it is
still an improvement on the quadratic performance of the brute force
approach (as we shall see in the next section). In section 3.4, we will
demonstrate how to make this algorithm even more efficient by
strengthening our recursive sub-solution.
### Summary and Analysis of the 2-D Algorithm
We present here a step by step summary of the algorithm presented in the
previous section, followed by a performance analysis. The algorithm is
simply written in list form because I find pseudo-code to be burdensome
and unnecessary when trying to understand an algorithm. Note that we
pre-sort the points according to their x coordinates, and maintain
another structure which holds the points sorted by their y values(for
step 4), which in itself takes O(nlogn) time.
ClosestPair of a set of points:
1. Divide the set into two equal sized parts by the line l, and
recursively compute the minimal distance in each part.
2. Let d be the minimal of the two minimal distances.
3. Eliminate points that lie farther than d apart from l.
4. Consider the remaining points according to their y-coordinates,
which we have precomputed.
5. Scan the remaining points in the y order and compute the distances
of each point to all of its neighbors that are distanced no more
than d(that\'s why we need it sorted according to y). Note that
there are no more than 5(there is no figure 3.3 , so this 5 or 6
doesnt make sense without that figure . Please include it .) such
points(see previous section).
6. If any of these distances is less than d then update d.
Analysis:
- Let us note T(n) as the efficiency of out algorithm
- Step 1 takes 2T(n/2) (we apply our algorithm for both halves)
- Step 3 takes O(n) time
- Step 5 takes O(n) time (as we saw in the previous section)
so,
$T(n) = 2T(n/2) + O(n)$
which, according the Master Theorem, result
$T(n) \isin O(nlogn)$
Hence the merging of the sub-solutions is dominated by the sorting at
step 4, and hence takes O(nlogn) time.
This must be repeated once for each level of recursion in the
divide-and-conquer algorithm,
hence the whole of algorithm ClosestPair takes O(logn\*nlogn) =
O(nlog2n) time.
### Improving the Algorithm
We can improve on this algorithm slightly by reducing the time it takes
to achieve the y-coordinate sorting in Step 4. This is done by asking
that the recursive solution computed in Step 1 returns the points in
sorted order by their y coordinates. This will yield two sorted lists of
points which need only be merged (a linear time operation) in Step 4 in
order to yield a complete sorted list. Hence the revised algorithm
involves making the following changes: Step 1: Divide the set into\...,
and recursively compute the distance in each part, returning the points
in each set in sorted order by y-coordinate. Step 4: Merge the two
sorted lists into one sorted list in O(n) time. Hence the merging
process is now dominated by the linear time steps thereby yielding an
O(nlogn) algorithm for finding the closest pair of a set of points in
the plane.
## Towers Of Hanoi Problem
\[TODO: Write about the towers of hanoi algorithm and a program for it\]
There are n distinct sized discs and three pegs such that discs are
placed at the left peg in the order of their sizes. The smallest one is
at the top while the largest one is at the bottom. This game is to move
all the discs from the left peg
### Rules
1\) Only one disc can be moved in each step.
2\) Only the disc at the top can be moved.
3\) Any disc can only be placed on the top of a larger disc.
### Solution
#### Intuitive Idea
In order to move the largest disc from the left peg to the middle peg,
the smallest discs must be moved to the right peg first. After the
largest one is moved. The smaller discs are then moved from the right
peg to the middle peg.
#### Recurrence
Suppose n is the number of discs.
To move n discs from peg a to peg b,
1\) If n\>1 then move n-1 discs from peg a to peg c
2\) Move n-th disc from peg a to peg b
3\) If n\>1 then move n-1 discs from peg c to peg a
#### Pseudocode
`void hanoi(n,src,dst){`\
` if (n>1)`\
` hanoi(n-1,src,pegs-{src,dst});`\
` print "move n-th disc from src to dst";`\
` if (n>1)`\
` hanoi(n-1,pegs-{src,dst},dst);`\
`}`
#### Analysis
The analysis is trivial. $T(n) = 2T(n-1) + O(1) = O(2^n)$
------------------------------------------------------------------------
## Footnotes
[^1]: A (mathematical) integer larger than the largest \"int\" directly
supported by your computer\'s hardware is often called a \"BigInt\".
Working with such large numbers is often called \"multiple precision
arithmetic\". There are entire books on the various algorithms for
dealing with such numbers, such as:
- Modern Computer
Arithmetic,
Richard Brent and Paul Zimmermann, Cambridge University Press,
2010.
- Donald E. Knuth, The Art of Computer Programming , Volume 2:
Seminumerical Algorithms (3rd edition), 1997.
People who implement such algorithms may
- write a one-off implementation for one particular application
- write a library that you can use for many applications, such as
GMP, the GNU Multiple Precision Arithmetic
Library or McCutchen\'s Big Integer
Library or various libraries
1
2
3
4
5 used to demonstrate RSA encryption
- put those algorithms in the compiler of a programming language
that you can use (such as Python and Lisp) that automatically
switches from standard integers to BigInts when necessary
|
# Algorithms/Randomization
As deterministic algorithms are driven to their limits when one tries to
solve hard problems with them, a useful technique to speed up the
computation is **randomization**. In randomized algorithms, the
algorithm has access to a *random source*, which can be imagined as
tossing coins during the computation. Depending on the outcome of the
toss, the algorithm may split up its computation path.
There are two main types of randomized algorithms: Las Vegas algorithms
and Monte-Carlo algorithms. In Las Vegas algorithms, the algorithm may
use the randomness to speed up the computation, but the algorithm must
always return the correct answer to the input. Monte-Carlo algorithms do
not have the latter restriction, that is, they are allowed to give
*wrong* return values. However, returning a wrong return value must have
a *small probability*, otherwise that Monte-Carlo algorithm would not be
of any use.
Many approximation algorithms use randomization.
## Ordered Statistics
Before covering randomized techniques, we\'ll start with a deterministic
problem that leads to a problem that utilizes randomization. Suppose you
have an unsorted array of values and you want to find
- the maximum value,
- the minimum value, and
- the median value.
In the immortal words of one of our former computer science professors,
\"How can you do?\"
### find-max
First, it\'s relatively straightforward to find the largest element:
*`// find-max -- returns the maximum element`*\
`function `**`find-max`**`(array `*`vals`*`[1..`*`n`*`]): element`\
` let `*`result`*` := `*`vals[1]`*\
` for `*`i`*` from `*`2`*` to `*`n`*`:`\
` `*`result`*` := max(`*`result`*`, `*`vals[i]`*`)`\
` repeat`\
` `\
` return `*`result`*\
`end`
An initial assignment of $-\infty$ to *result* would work as well, but
this is a useless call to the max function since the first element
compared gets set to *result*. By initializing result as such the
function only requires *n-1* comparisons. (Moreover, in languages
capable of metaprogramming, the data type may not be strictly numerical
and there might be no good way of assigning $-\infty$; using vals\[1\]
is type-safe.)
A similar routine to find the minimum element can be done by calling the
min function instead of the max function.
### find-min-max
But now suppose you want to find the min and the max at the same time;
here\'s one solution:
*`// find-min-max -- returns the minimum and maximum element of the given array`*\
`function `**`find-min-max`**`(array `*`vals`*`): pair`\
` return pair {`**`find-min`**`(`*`vals`*`), `**`find-max`**`(`*`vals`*`)}`\
`end`
Because **find-max** and **find-min** both make *n-1* calls to the max
or min functions (when *vals* has *n* elements), the total number of
comparisons made in **find-min-max** is $2n-2$.
However, some redundant comparisons are being made. These redundancies
can be removed by \"weaving\" together the min and max functions:
*`// find-min-max -- returns the minimum and maximum element of the given array`*\
`function `**`find-min-max`**`(array `*`vals`*`[1..`*`n`*`]): pair`\
` let `*`min`*` := `$\infty$\
` let `*`max`*` := `$-\infty$\
` `\
` if `*`n`*` is odd:`\
` `*`min`*` := `*`max`*` := `*`vals`*`[1]`\
` `*`vals`*` := `*`vals`*`[2,..,`*`n`*`] `*`// we can now assume n is even`*\
` `*`n`*` := `*`n`*` - 1`\
` fi`\
` `\
` for `*`i`*`:=1 to `*`n`*` by 2: `*`// consider pairs of values in vals`*\
` if `*`vals`*`[`*`i`*`] < `*`vals`*`[`*`i`*` + 1]:`\
` let `*`a`*` := `*`vals`*`[`*`i`*`]`\
` let `*`b`*` := `*`vals`*`[`*`i`*` + 1]`\
` else:`\
` let `*`a`*` := `*`vals`*`[`*`i`*` + 1]`\
` let `*`b`*` := `*`vals`*`[`*`i`*`] `*`// invariant: a <= b`*\
` fi`\
` `\
` if `*`a`*` < `*`min`*`: `*`min`*` := `*`a`*` fi`\
` if `*`b`*` > `*`max`*`: `*`max`*` := `*`b`*` fi`\
` repeat`\
` `\
` return pair {`*`min`*`, `*`max`*`}`\
`end`
Here, we only loop $n/2$ times instead of *n* times, but for each
iteration we make three comparisons. Thus, the number of comparisons
made is $(3/2)n = 1.5n$, resulting in a $3/4$ speed up over the original
algorithm.
Only three comparisons need to be made instead of four because, by
construction, it\'s always the case that $a\le b$. (In the first part of
the \"if\", we actually know more specifically that $a < b$, but under
the else part, we can only conclude that $a\le b$.) This property is
utilized by noting that *a* doesn\'t need to be compared with the
current maximum, because *b* is already greater than or equal to *a*,
and similarly, *b* doesn\'t need to be compared with the current
minimum, because *a* is already less than or equal to *b*.
In software engineering, there is a struggle between using libraries
versus writing customized algorithms. In this case, the min and max
functions weren\'t used in order to get a faster **find-min-max**
routine. Such an operation would probably not be the bottleneck in a
real-life program: however, if testing reveals the routine should be
faster, such an approach should be taken. Typically, the solution that
reuses libraries is better overall than writing customized solutions.
Techniques such as open implementation and aspect-oriented programming
may help manage this contention to get the best of both worlds, but
regardless it\'s a useful distinction to recognize.
### find-median
Finally, we need to consider how to find the median value. One approach
is to sort the array then extract the median from the position
*`vals`*`[`*`n`*`/2]`:
*`// find-median -- returns the median element of vals`*\
`function `**`find-median`**`(array `*`vals`*`[1..`*`n`*`]): element`\
` assert (`*`n`*` > 0)`\
` `\
` sort(`*`vals`*`)`\
` return `*`vals`*`[`*`n`*` / 2]`\
`end`
If our values are not numbers close enough in value (or otherwise cannot
be sorted by a radix sort) the sort above is going to require
$O(n\log n)$ steps.
However, it is possible to extract the *n*th-ordered statistic in $O(n)$
time. The key is eliminating the sort: we don\'t actually require the
entire array to be sorted in order to find the median, so there is some
waste in sorting the entire array first. One technique we\'ll use to
accomplish this is randomness.
Before presenting a non-sorting **find-median** function, we introduce a
divide and conquer-style operation known as **partitioning**. What we
want is a routine that finds a random element in the array and then
partitions the array into three parts:
1. elements that are less than or equal to the random element;
2. elements that are equal to the random element; and
3. elements that are greater than or equal to the random element.
These three sections are denoted by two integers: *j* and *i*. The
partitioning is performed \"in place\" in the array:
*`// partition -- break the array three partitions based on a randomly picked element`*\
`function `**`partition`**`(array `*`vals`*`): pair{`*`j`*`, `*`i`*`}`
Note that when the random element picked is actually represented three
or more times in the array it\'s possible for entries in all three
partitions to have the same value as the random element. While this
operation may not sound very useful, it has a powerful property that can
be exploited: When the partition operation completes, the randomly
picked element will be in the same position in the array as it would be
if the array were fully sorted!
This property might not sound so powerful, but recall the optimization
for the **find-min-max** function: we noticed that by picking elements
from the array in pairs and comparing them to each other first we could
reduce the total number of comparisons needed (because the current min
and max values need to be compared with only one value each, and not
two). A similar concept is used here.
While the code for **partition** is not magical, it has some tricky
boundary cases:
*`// partition -- break the array into three ordered partitions from a random element`*\
`function `**`partition`**`(array `*`vals`*`): pair{`*`j`*`, `*`i`*`}`\
` let `*`m`*` := 0`\
` let `*`n`*` := `*`vals`*`.length - 2 // for an array vals, vals[vals.length-1] is the last element, which holds the partition, `\
` // so the last sort element is vals[vals.length-2]`\
` let `*`irand`*` := random(`*`m`*`, `*`n`*`) `*`// returns any value from m to n`*\
` let `*`x`*` := `*`vals`*`[`*`irand`*`]`\
` swap( `*`irand`*`,`*`n`*`+ 1 ) // n+1 = vals.length-1 , which is the right most element, and acts as store for partition element and sentinel for m`\
` // values in `*`vals`*`[`*`n`*`..] are greater than `*`x`*\
` // values in `*`vals`*`[0..`*`m`*`] are less than `*`x`*\
` while (m <= n ) // see explanation in quick sort why should be m <= n instead of m < n in the 2 element case, `\
` // vals.length -2 = 0 = n = m, but if the 2-element case is out-of-order vs. in-order, there must be a different action.`\
` // by implication, the different action occurs within this loop, so must process the m = n case before exiting.`\
` while `*`vals`*`[`*`m`*`] <= `*`x`*` // in the 2-element case, second element is partition, first element at m. If in-order, m will increment`\
` `*`m`*`++`\
` endwhile`\
` while `*`x`*` < `*`vals`*`[`*`n`*`] && `*`n`*` > 0 // stops if vals[n] belongs in left partition or hits start of array`\
` `*`n`*`—endwhile`\
` if ( m >= n) break;`\
` swap(`*`m`*`,`*`n`*`) // exchange `*`vals`*`[`*`n`*`] and `*`vals`*`[`*`m`*`]`\
` `*`m`*`++ // don't rescan swapped elements`\
` `*`n`*`—endwhile`\
` // partition: [0..`*`m`*`-1] [] [`*`n`*`+1..] note that `*`m`*`=`*`n`*`+1`\
` // if you need non empty sub-arrays:`\
` swap(`*`m`*`,`*`vals`*`.length - 1) // put the partition element in the between left and right partitions`\
` // in 2-element out-of-order case, m=0 (not incremented in loop), and the first and last(second) element will swap.`\
` // partition: [0..`*`n`*`-1] [`*`n`*`..`*`n`*`] [`*`n`*`+1..]`\
`end`
We can use **partition** as a subroutine for a general **find**
operation:
*`// find -- moves elements in vals such that location k holds the value it would when sorted`*\
`function `**`find`**`(array `*`vals`*`, integer `*`k`*`)`\
` assert (0 <= `*`k`*` < `*`vals`*`.length) `*`// k it must be a valid index`*\
` if `*`vals`*`.length <= 1:`\
` return`\
` fi`\
` `\
` let pair (`*`j`*`, `*`i`*`) := `**`partition`**`(`*`vals`*`)`\
` if `*`k`*` <= `*`i`*`:`\
` `**`find`**`(`*`a`*`[0,..,`*`i`*`], `*`k`*`)`\
` else-if `*`j`*` <= `*`k`*`:`\
` `**`find`**`(`*`a`*`[`*`j`*`,..,`*`n`*`], `*`k`*` - `*`j`*`)`\
` fi`\
` TODO: debug this!`\
`end`
Which leads us to the punch-line:
` `*`// find-median -- returns the median element of vals`*\
`function `**`find-median`**`(array `*`vals`*`): element`\
` assert (`*`vals`*`.length > 0)`\
` `\
` let `*`median_index`*` := `*`vals`*`.length / 2;`\
` `**`find`**`(`*`vals`*`, `*`median_index`*`)`\
` return `*`vals`*`[`*`median_index`*`]`\
`end`
One consideration that might cross your mind is \"is the random call
really necessary?\" For example, instead of picking a random pivot, we
could always pick the middle element instead. Given that our algorithm
works with all possible arrays, we could conclude that the running time
on average for *all of the possible inputs* is the same as our analysis
that used the random function. The reasoning here is that under the set
of all possible arrays, the middle element is going to be just as
\"random\" as picking anything else. But there\'s a pitfall in this
reasoning: Typically, the input to an algorithm in a program isn\'t
random at all. For example, the input has a higher probability of being
sorted than just by chance alone. Likewise, because it is real data from
real programs, the data might have other patterns in it that could lead
to suboptimal results.
To put this another way: for the randomized median finding algorithm,
there is a very small probability it will run suboptimally, independent
of what the input is; while for a deterministic algorithm that just
picks the middle element, there is a greater chance it will run poorly
on some of the most frequent input types it will receive. This leads us
to the following guideline:
```{=html}
<table WIDTH="80%" >
```
```{=html}
<tr>
```
```{=html}
<td style="background-color: #FFFFEE; border: solid 1px #FFC92E; padding: 1em;" valign=top>
```
**Randomization Guideline:**\
If your algorithm depends upon randomness, be sure you introduce the
randomness yourself instead of depending upon the data to be random.
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
Note that there are \"derandomization\" techniques that can take an
average-case fast algorithm and turn it into a fully deterministic
algorithm. Sometimes the overhead of derandomization is so much that it
requires very large datasets to get any gains. Nevertheless,
derandomization in itself has theoretical value.
The randomized **find** algorithm was invented by C. A. R. \"Tony\"
Hoare. While Hoare is an important figure in computer science, he may be
best known in general circles for his quicksort algorithm, which we
discuss in the next section.
## Quicksort
The median-finding partitioning algorithm in the previous section is
actually very close to the implementation of a full blown sorting
algorithm. Building a Quicksort Algorithm is left as an exercise for the
reader, and is recommended first, before reading the next section (
Quick sort is diabolical compared to Merge sort, which is a sort not
improved by a randomization step ) .
A key part of quick sort is choosing the right median. But to get it up
and running quickly, start with the assumption that the array is
unsorted, and the rightmost element of each array is as likely to be the
median as any other element, and that we are entirely optimistic that
the rightmost doesn\'t happen to be the largest key , which would mean
we would be removing one element only ( the partition element) at each
step, and having no right array to sort, and a n-1 left array to sort.
This is where **randomization** is important for quick sort, i.e.
*choosing the more optimal partition key*, which is pretty important for
quick sort to work efficiently.
Compare the number of comparisions that are required for quick sort vs.
insertion sort.
With insertion sort, the average number of comparisons for finding the
lowest first element in an ascending sort of a randomized array is n /2
.
The second element\'s average number of comparisons is (n-1)/2;
the third element ( n- 2) / 2.
The total number of comparisons is \[ n + (n - 1) + (n - 2) + (n - 3)
.. + (n - \[n-1\]) \] divided by 2, which is \[ n x n - (n-1)! \] /2 or
about O(n squared) .
In Quicksort, the number of comparisons will halve at each partition
step if the true median is chosen, since the left half partition
doesn\'t need to be compared with the right half partition, but at each
step , the number elements of all partitions created by the previously
level of partitioning will still be n.
The number of levels of comparing n elements is the number of steps of
dividing n by two , until n = 1. Or in reverse, 2 \^ m \~ n, so m =
log~2~ n.
So the total number of comparisons is n (elements) x m (levels of
scanning) or n x log~2~n ,
So the number of comparison is O(n x log ~2~(n) ) , which is smaller
than insertion sort\'s O(n\^2) or O( n x n ).
(Comparing O(n x log ~2~(n) ) with O( n x n ) , the common factor n can
be eliminated , and the comparison is log~2~(n) vs n , which is
exponentially different as n becomes larger. e.g. compare n = 2\^16 , or
16 vs 32768, or 32 vs 4 gig ).
To implement the partitioning in-place on a part of the array determined
by a previous recursive call, what is needed a scan from each end of the
part , swapping whenever the value of the left scan\'s current location
is greater than the partition value, and the value of the right scan\'s
current location is less than the partition value. So the initial step
is :-
` Assign the partition value to the right most element, swapping if necessary.`
So the partitioning step is :-
` increment the left scan pointer while the current value is less than the partition value.`\
` decrement the right scan pointer while the current value is more than the partition value , `\
` or the location is equal to or more than the left most location.`\
` exit if the pointers have crossed ( l >= r), `\
` OTHERWISE`\
` perform a swap where the left and right pointers have stopped ,`\
` on values where the left pointer's value is greater than the partition,`\
` and the right pointer's value is less than the partition.`\
\
` Finally, after exiting the loop because the left and right pointers have crossed,`\
` `*`swap the`*`rightmost'' partition value, `\
` with the last location of the `**`left`**` forward scan pointer '', `\
` and hence ends up between the left and right partitions. `
Make sure at this point , that after the final swap, the cases of a 2
element in-order array, and a 2 element out-of-order array , are handled
correctly, which should mean all cases are handled correctly. This is a
good debugging step for getting quick-sort to work.
**For the in-order two-element case**, the left pointer stops on the
partition or second element , as the partition value is found. The right
pointer , scanning backwards, starts on the first element before the
partition, and stops because it is in the leftmost position.
The pointers cross, and the loop exits before doing a loop swap. Outside
the loop, the contents of the left pointer at the rightmost position and
the partition , also at the right most position , are swapped, achieving
no change to the in-order two-element case.
**For the out-of-order two-element case**, The left pointer scans and
stops at the first element, because it is greater than the partition
(left scan value stops to swap values greater than the partition value).
The right pointer starts and stops at the first element because it has
reached the leftmost element.
The loop exits because left pointer and right pointer are equal at the
first position, and the contents of the left pointer at the first
position and the partition at the rightmost (other) position , are
swapped , putting previously out-of-order elements , into order.
Another implementation issue, is to how to move the pointers during
scanning. Moving them at the end of the outer loop seems logical.
`partition(a,l,r) {`\
` v = a[r];`\
` i = l;`\
` j = r -1;`\
` while ( i <= j ) { // need to also scan when i = j as well as i < j , `\
` // in the 2 in-order case, `\
` // so that i is incremented to the partition `\
` // and nothing happens in the final swap with the partition at r.`\
` while ( a[i] < v) ++i;`\
` while ( v <= a[j] && j > 0 ) --j;`\
` if ( i >= j) break;`\
` swap(a,i,j);`\
` ++i; --j;`\
` }`\
` swap(a, i, r);`\
` return i;`
With the pre-increment/decrement unary operators, scanning can be done
just before testing within the test condition of the while loops, but
this means the pointers should be offset -1 and +1 respectively at the
start : so the algorithm then looks like:-
`partition (a, l, r ) {`\
` v=a[r]; // v is partition value, at a[r]`\
` i=l-1;`\
` j=r;`\
` while(true) {`\
` while( a[++i] < v ); `\
` while( v <= a[--j] && j > l );`\
` if (i >= j) break;`\
` swap ( a, i, j);`\
` }`\
` swap (a,i,r);`\
` return i;`\
`}`
And the qsort algorithm is
`qsort( a, l, r) {`\
` if (l >= r) return ;`\
` p = partition(a, l, r)`\
` qsort(a , l, p-1)`\
` qsort( a, p+1, r)`
}
Finally, randomization of the partition element.
`random_partition (a,l,r) {`\
` p = random_int( r-l) + l;`\
` // median of a[l], a[p] , a[r]`\
` if (a[p] < a[l]) p =l;`\
` if ( a[r]< a[p]) p = r;`\
` swap(a, p, r);`\
`}`
this can be called just before calling partition in qsort().
## Shuffling an Array
` `**`This keeps data in during shuffle`**\
` temporaryArray = { }`\
` `**`This records if an item has been shuffled`**\
` usedItemArray = { }`\
` `**`Number of item in array`**\
` itemNum = 0`\
` while ( itemNum != lengthOf( inputArray) ){`\
` usedItemArray[ itemNum ] = false `**`None of the items have been shuffled`**\
` itemNum = itemNum + 1`\
` }`\
` itemNum = 0 `**`we'll use this again`**\
` itemPosition = randdomNumber( 0 --- (lengthOf(inputArray) - 1 ))`\
` while( itemNum != lengthOf( inputArray ) ){`\
` while( usedItemArray[ itemPosition ] != false ){`\
` itemPosition = randdomNumber( 0 --- (lengthOf(inputArray) - 1 ))`\
` }`\
` temporaryArray[ itemPosition ] = inputArray[ itemNum ]`\
` itemNum = itemNum + 1`\
` }`\
` inputArray = temporaryArray`
## Equal Multivariate Polynomials
\[TODO: as of now, there is no known deterministic polynomial time
solution, but there is a randomized polytime solution. The canonical
example used to be IsPrime, but a deterministic, polytime solution has
been found.\]
## Hash tables
Hashing relies on a hashcode function to randomly distribute keys to
available slots evenly. In java , this is done in a fairly straight
forward method of adding a moderate sized prime number (31 \* 17 ) to a
integer key , and then modulus by the size of the hash table. For string
keys, the initial hash number is obtained by adding the products of each
character\'s ordinal value multiplied by 31.
The wikibook Data Structures/Hash
Tables chapter covers the topic
well.
## Skip Lists
\[TODO: Talk about skips lists. The point is to show how randomization
can sometimes make a structure easier to understand, compared to the
complexity of balanced trees.\]
Dictionary or Map , is a general concept where a value is inserted under
some key, and retrieved by the key. For instance, in some languages ,
the dictionary concept is built-in (Python), in others , it is in core
libraries ( C++ S.T.L. , and Java standard collections library ). The
library providing languages usually lets the programmer choose between a
hash algorithm, or a balanced binary tree implementation (red-black
trees). Recently, skip lists have been offered, because they offer
advantages of being implemented to be highly concurrent for multiple
threaded applications.
Hashing is a technique that depends on the randomness of keys when
passed through a hash function, to find a hash value that corresponds to
an index into a linear table. Hashing works as fast as the hash
function, but works well only if the inserted keys spread out evenly in
the array, as any keys that hash to the same index , have to be deal
with as a hash collision problem e.g. by keeping a linked list for
collisions for each slot in the table, and iterating through the list to
compare the full key of each key-value pair vs the search key.
The disadvantage of hashing is that in-order traversal is not possible
with this data structure.
Binary trees can be used to represent dictionaries, and in-order
traversal of binary trees is possible by visiting of nodes ( visit left
child, visit current node, visit right child, recursively ). Binary
trees can suffer from poor search when they are \"unbalanced\" e.g. the
keys of key-value pairs that are inserted were inserted in ascending or
descending order, so they effectively look like *linked lists* with no
left child, and all right children. *self-balancing* binary trees can be
done probabilistically (using randomness) or deterministically ( using
child link coloring as red or black ) , through local 3-node tree
**rotation** operations. A rotation is simply swapping a parent with a
child node, but preserving order e.g. for a left child rotation, the
left child\'s right child becomes the parent\'s left child, and the
parent becomes the left child\'s right child.
**Red-black trees** can be understood more easily if corresponding
**2-3-4 trees** are examined. A 2-3-4 tree is a tree where nodes can
have 2 children, 3 children, or 4 children, with 3 children nodes having
2 keys between the 3 children, and 4 children-nodes having 3 keys
between the 4 children. 4-nodes are actively split into 3 single key 2
-nodes, and the middle 2-node passed up to be merged with the parent
node , which , if a one-key 2-node, becomes a two key 3-node; or if a
two key 3-node, becomes a 4-node, which will be later split (on the way
up). The act of splitting a three key 4-node is actually a re-balancing
operation, that prevents a string of 3 nodes of grandparent, parent ,
child occurring , without a balancing rotation happening. 2-3-4 trees
are a limited example of **B-trees**, which usually have enough nodes as
to fit a physical disk block, to facilitate caching of very large
indexes that can\'t fit in physical RAM ( which is much less common
nowadays).
A **red-black tree** is a binary tree representation of a 2-3-4 tree,
where 3-nodes are modeled by a parent with one red child, and 4 -nodes
modeled by a parent with two red children. Splitting of a 4-node is
represented by the parent with 2 red children, **flipping** the red
children to black, and itself into red. There is never a case where the
parent is already red, because there also occurs balancing operations
where if there is a grandparent with a red parent with a red child , the
grandparent is rotated to be a child of the parent, and parent is made
black and the grandparent is made red; this unifies with the previous
**flipping** scenario, of a 4-node represented by 2 red children.
Actually, it may be this standardization of 4-nodes with mandatory
rotation of skewed or zigzag 4-nodes that results in re-balancing of the
binary tree.
A newer optimization is to left rotate any single right red child to a
single left red child, so that only right rotation of left-skewed inline
4-nodes (3 red nodes inline ) would ever occur, simplifying the
re-balancing code.
**Skip lists** are modeled after single linked lists, except nodes are
multilevel. Tall nodes are rarer, but the insert operation ensures nodes
are connected at each level.
Implementation of skip lists requires creating randomly high multilevel
nodes, and then inserting them.
Nodes are created using iteration of a random function where high level
node occurs later in an iteration, and are rarer, because the iteration
has survived a number of random thresholds (e.g. 0.5, if the random is
between 0 and 1).
Insertion requires a temporary previous node array with the height of
the generated inserting node. It is used to store the last pointer for a
given level , which has a key less than the insertion key.
The scanning begins at the head of the skip list, at highest level of
the head node, and proceeds across until a node is found with a key
higher than the insertion key, and the previous pointer stored in the
temporary previous node array. Then the next lower level is scanned from
that node , and so on, walking zig-zag down, until the lowest level is
reached.
Then a list insertion is done at each level of the temporary previous
node array, so that the previous node\'s next node at each level is made
the next node for that level for the inserting node, and the inserting
node is made the previous node\'s next node.
Search involves iterating from the highest level of the head node to the
lowest level, and scanning along the next pointer for each level until a
node greater than the search key is found, moving down to the next level
, and proceeding with the scan, until the higher keyed node at the
lowest level has been found, or the search key found.
The creation of less frequent-when-taller , randomized height nodes, and
the process of linking in all nodes at every level, is what gives skip
lists their advantageous overall structure.
### a method of skip list implementation : implement lookahead single-linked linked list, then test , then transform to skip list implementation , then same test, then performance comparison
What follows is a implementation of skip lists in python. A single
linked list looking at next node as always the current node, is
implemented first, then the skip list implementation follows, attempting
minimal modification of the former, and comparison helps clarify
implementation.
``` python
#copyright SJT 2014, GNU
#start by implementing a one lookahead single-linked list :
#the head node has a next pointer to the start of the list, and the current node examined is the next node.
#This is much easier than having the head node one of the storage nodes.
class LN:
"a list node, so don't have to use dict objects as nodes"
def __init__(self):
self.k=None
self.v = None
self.next = None
class single_list2:
def __init__(self):
self.h = LN()
def insert(self, k, v):
prev = self.h
while not prev.next is None and k < prev.next.k :
prev = prev.next
n = LN()
n.k, n.v = k, v
n.next = prev.next
prev.next = n
def show(self):
prev = self.h
while not prev.next is None:
prev = prev.next
print prev.k, prev.v, ' '
def find (self,k):
prev = self.h
while not prev.next is None and k < prev.next.k:
prev = prev.next
if prev.next is None:
return None
return prev.next.k
#then after testing the single-linked list, model SkipList after it.
# The main conditions to remember when trying to transform single-linked code to skiplist code:
# * multi-level nodes are being inserted
# * the head node must be as tall as the node being inserted
# * walk backwards down levels from highest to lowest when inserting or searching,
# since this is the basis for algorithm efficiency, as taller nodes are less frequently and widely dispersed.
import random
class SkipList3:
def __init__(self):
self.h = LN()
self.h.next = [None]
def insert( self, k , v):
ht = 1
while random.randint(0,10) < 5:
ht +=1
if ht > len(self.h.next) :
self.h.next.extend( [None] * (ht - len(self.h.next) ) )
prev = self.h
prev_list = [self.h] * len(self.h.next)
# instead of just prev.next in the single linked list, each level i has a prev.next
for i in xrange( len(self.h.next)-1, -1, -1):
while not prev.next[i] is None and prev.next[i].k > k:
prev = prev.next[i]
#record the previous pointer for each level
prev_list[i] = prev
n = LN()
n.k,n.v = k,v
# create the next pointers to the height of the node for the current node.
n.next = [None] * ht
#print "prev list is ", prev_list
# instead of just linking in one node in the single-linked list , ie. n.next = prev.next, prev.next =n
# do it for each level of n.next using n.next[i] and prev_list[i].next[i]
# there may be a different prev node for each level, but the same level must be linked,
# therefore the [i] index occurs twice in prev_list[i].next[i].
for i in xrange(0, ht):
n.next[i] = prev_list[i].next[i]
prev_list[i].next[i] = n
#print "self.h ", self.h
def show(self):
#print self.h
prev = self.h
while not prev.next[0] is None:
print prev.next[0].k, prev.next[0].v
prev = prev.next[0]
def find(self, k):
prev = self.h
h = len(self.h.next)
#print "height ", h
for i in xrange( h-1, -1, -1):
while not prev.next[i] is None and prev.next[i].k > k:
prev = prev.next[i]
#if prev.next[i] <> None:
#print "i, k, prev.next[i].k and .v", i, k, prev.next[i].k, prev.next[i].v
if prev.next[i] <> None and prev.next[i].k == k:
return prev.next[i].v
if pref.next[i] is None:
return None
return prev.next[i].k
def clear(self):
self.h= LN()
self.h.next = [None]
#driver
if __name__ == "__main__":
#l = single_list2()
l = SkipList3()
test_dat = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
pairs = enumerate(test_dat)
m = [ (x,y) for x,y in pairs ]
while len(m) > 0:
i = random.randint(0,len(m)-1)
print "inserting ", m[i]
l.insert(m[i][0], m[i][1])
del m[i]
# l.insert( 3, 'C')
# l.insert(2, 'B')
# l.insert(4, 'D')
# l.insert(1, 'A')
l.show()
n = int(raw_input("How many elements to test?") )
if n <0: n = -n
l.clear()
import time
l2 = [ x for x in xrange(0, n)]
random.shuffle(l2)
for x in l2:
l.insert(x , x)
l.show()
print
print "finding.."
f = 0
t1 = time.time()
nf = []
for x in l2:
if l.find(x) == x:
f += 1
else:
nf.append(x)
t2 = time.time()
print "time", t2 - t1
td1 = t2 - t1
print "found ", f
print "didn't find", nf
dnf = []
for x in nf:
tu = (x,l.find(x))
dnf.append(tu)
print "find again ", dnf
sl = single_list2()
for x in l2:
sl.insert(x,x)
print "finding.."
f = 0
t1 = time.time()
for x in l2:
if sl.find(x) == x:
f += 1
t2 = time.time()
print "time", t2 - t1
print "found ", f
td2 = t2 - t1
print "factor difference time", td2/td1
```
### Role of Randomness
The idea of making higher nodes geometrically randomly less common,
means there are less keys to compare with the higher the level of
comparison, and since these are randomly selected, this should get rid
of problems of degenerate input that makes it necessary to do tree
balancing in tree algorithms. Since the higher level list have more
widely separated elements, but the search algorithm moves down a level
after each search terminates at a level, the higher levels help \"skip\"
over the need to search earlier elements on lower lists. Because there
are multiple levels of skipping, it becomes less likely that a meagre
skip at a higher level won\'t be compensated by better skips at lower
levels, and Pugh claims O(logN) performance overall.
Conceptually , is it easier to understand than balancing trees and hence
easier to implement ? The development of ideas from binary trees,
balanced binary trees, 2-3 trees, red-black trees, and B-trees make a
stronger conceptual network but is progressive in development, so
arguably, once red-black trees are understood, they have more conceptual
context to aid memory , or refresh of memory.
### concurrent access application
Apart from using randomization to enhance a basic memory structure of
linked lists, skip lists can also be extended as a global data structure
used in a multiprocessor application. See supplementary topic at the end
of the chapter.
### Idea for an exercise
Replace the Linux completely fair scheduler red-black tree
implementation with a skip list , and see how your brand of Linux runs
after recompiling.
## Treaps
A treap is a two keyed binary tree, that uses a second randomly
generated key and the previously discussed tree operation of
parent-child rotation to randomly rotate the tree so that overall, a
balanced tree is produced. Recall that binary trees work by having all
nodes in the left subtree small than a given node, and all nodes in a
right subtree greater. Also recall that node rotation does not break
this order ( some people call it an invariant), but changes the
relationship of parent and child, so that if the parent was smaller than
a right child, then the parent becomes the left child of the formerly
right child. The idea of a tree-heap or treap, is that a binary heap
relationship is maintained between parents and child, and that is a
parent node has higher priority than its children, which is not the same
as the left , right order of keys in a binary tree, and hence a recently
inserted leaf node in a binary tree which happens to have a high random
priority, can be rotated so it is relatively higher in the tree, having
no parent with a lower priority.
A treap is an alternative to both red-black trees, and skip lists, as a
self-balancing sorted storage structure.
### java example of treap implementation
``` java
// Treap example: 2014 SJT, copyleft GNU .
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Random;
public class Treap1<K extends Comparable<K>, V> {
public Treap1(boolean test) {
this.test = test;
}
public Treap1() {}
boolean test = false;
static Random random = new Random(System.currentTimeMillis());
class TreapNode {
int priority = 0;
K k;
V val;
TreapNode left, right;
public TreapNode() {
if (!test) {
priority = random.nextInt();
}
}
}
TreapNode root = null;
void insert(K k, V val) {
root = insert(k, val, root);
}
TreapNode insert(K k, V val, TreapNode node) {
TreapNode node2 = new TreapNode();
node2.k = k;
node2.val = val;
if (node == null) {
node = node2;
} else if (k.compareTo(node.k) < 0) {
node.left = insert(k, val, node.left);
} else {
node.right = insert(k, val, node.right);
}
if (node.left != null && node.left.priority > node.priority) {
// right rotate (rotate left node up, current node becomes right child )
TreapNode tmp = node.left;
node.left = node.left.right;
tmp.right = node;
node = tmp;
} else if (node.right != null && node.right.priority > node.priority) {
// left rotate (rotate right node up , current node becomes left child)
TreapNode tmp = node.right;
node.right = node.right.left;
tmp.left = node;
node = tmp;
}
return node;
}
V find(K k) {
return findNode(k, root);
}
private V findNode(K k, Treap1<K, V>.TreapNode node) {
// TODO Auto-generated method stub
if (node == null)
return null;
if (k.compareTo(node.k) < 0) {
return findNode(k, node.left);
} else if (k.compareTo(node.k) > 0) {
return findNode(k, node.right);
} else {
return node.val;
}
}
public static void main(String[] args) {
LinkedList<Integer> dat = new LinkedList<Integer>();
for (int i = 0; i < 15000; ++i) {
dat.add(i);
}
testNumbers(dat, true); // no random priority balancing
testNumbers(dat, false);
}
private static void testNumbers(LinkedList<Integer> dat,
boolean test) {
Treap1<Integer, Integer> tree= new Treap1<>(test);
for (Integer integer : dat) {
tree.insert(integer, integer);
}
long t1 = System.currentTimeMillis();
Iterator<Integer> iter = dat.iterator();
int found = 0;
while (iter.hasNext()) {
Integer j = desc.next();
Integer i = tree.find(j);
if (j.equals(i)) {
++found;
}
}
long t2 = System.currentTimeMillis();
System.out.println("found = " + found + " in " + (t2 - t1));
}
}
```
### Treaps compared and contrasted to Splay trees
*Splay trees* are similar to treaps in that rotation is used to bring a
higher priority node to the top without changing the main key order,
except instead of using a random key for priority, the last accessed
node is rotated to the root of the tree, so that more frequently
accessed nodes will be near the top. This means that in treaps, inserted
nodes will only rotate upto the priority given by their random priority
key, whereas in splay trees, the inserted node is rotated to the root,
and every search in a splay tree will result in a re-balancing, but not
so in a treap.
## Derandomization
\[TODO: Deterministic algorithms for Quicksort exist that perform as
well as quicksort in the average case and are guaranteed to perform at
least that well in all cases. Best of all, no randomization is needed.
Also in the discussion should be some perspective on using
randomization: some randomized algorithms give you better confidence
probabilities than the actual hardware itself! (e.g. sunspots can
randomly flip bits in hardware, causing failure, which is a risk we take
quite often)\]
\[Main idea: Look at all blocks of 5 elements, and pick the median (O(1)
to pick), put all medians into an array (O(n)), recursively pick the
medians of that array, repeat until you have \< 5 elements in the array.
This recursive median constructing of every five elements takes time
T(n)=T(n/5) + O(n), which by the master theorem is O(n). Thus, in O(n)
we can find the right pivot. Need to show that this pivot is
sufficiently good so that we\'re still O(n log n) no matter what the
input is. This version of quicksort doesn\'t need rand, and it never
performs poorly. Still need to show that element picked out is
sufficiently good for a pivot.\]
## Exercises
1. Write a **find-min** function and run it on several different inputs
to demonstrate its correctness.
## Supplementary Topic: skip lists and multiprocessor algorithms
Multiprocessor hardware provides CAS ( compare-and-set) or CMPEXCHG(
compare-and-exchange)(intel manual 253666.pdf, p 3-188) atomic
operations, where an expected value is loaded into the accumulator
register, which is compared to a target memory location\'s contents, and
if the same, a source memory location\'s contents is loaded into the
target memories contents, and the zero flag set, otherwise, if
different, the target memory\'s contents is returned in the accumulator,
and the zero flag is unset, signifying , for instance, a lock
contention. In the intel architecture, a LOCK instruction is issued
before CMPEXCHG , which either locks the cache from concurrent access if
the memory location is being cached, or locks a shared memory location
if not in the cache , for the next instruction.
The CMPEXCHG can be used to implement locking, where spinlocks , e.g.
retrying until the zero flag is set, are simplest in design.
Lockless design increases efficiency by avoiding spinning waiting for a
lock .
The java standard library has an implementation of non-blocking
concurrent skiplists, based on a paper titled \"a pragmatic
implementation of non-blocking single-linked lists\".
The skip list implementation is an extension of the lock-free
single-linked list , of which a description follows :-
The **insert** operation is : X -\> Y insert N , N -\> Y, X -\> N ;
expected result is X -\> N -\> Y .
A race condition is if M is inserting between X and Y and M completes
first , then N completes, so the situation is X -\> N -\> Y \<- M
M is not in the list. The CAS operation avoids this, because a copy of
-\> Y is checked before updating X -\> , against the current value of X
-\> .
If N gets to update X -\> first, then when M tries to update X -\> , its
copy of X -\> Y , which it got before doing M -\> Y , does not match X
-\> N , so CAS returns non-zero flag set (recall that CAS requires the
user to load the accumulator with the expected value, the target
location\'s current value, and then atomically updates the target
location with a source location if the target location still contains
the accumulator\'s value). The process that tried to insert M then can
retry the insertion after X, but now the CAS checks -\>N is X\'s next
pointer, so after retry, X-\>M-\>N-\>Y , and neither insertions are
lost.
If M updates X-\> first, N \'s copy of X-\>Y does not match X -\> M , so
the CAS will fail here too, and the above retry of the process inserting
N, would have the serialized result of X -\>N -\> M -\> Y .
The **delete** operation depends on a separate \'logical\' deletion
step, before \'physical\' deletion.
\'Logical\' deletion involves a CAS change of the next pointer into a
\'marked\' pointer. The java implementation substitutes with an atomic
insertion of a proxy marker node to the next node.
This prevents future insertions from inserting after a node which has a
next pointer \'marked\' , making the latter node \'logically\' deleted.
The **insert** operation relies on another function , *search* ,
returning _2_ **unmarked** , at the time of the
invocation, node pointers : the first pointing to a node , whose next
pointer is equal to the second.
The first node is the node before the insertion point.
The *insert* CAS operation checks that the current next pointer of the
first node, corresponds to the unmarked reference of the second, so will
fail \'logically\' if the first node\'s *next* pointer has become marked
*after* the call to the *search* function above, because the first node
has been concurrently logically deleted.
*This meets the aim to prevent a insertion occurring concurrently after
a node has been deleted.*
If the insert operation fails the CAS of the previous node\'s next
pointer, the search for the insertion point starts from the **start of
the entire list** again, since a new unmarked previous node needs to be
found, and there are no previous node pointers as the list nodes are
singly-linked.
{width="300"}
The **delete** operation outlined above, also relies on the *search*
operation returning two *unmarked* nodes, and the two CAS operations in
delete, one for logical deletion or marking of the second pointer\'s
next pointer, and the other for physical deletion by making the first
node\'s next pointer point to the second node\'s unmarked next pointer.
The first CAS of delete happens only after a check that the copy of the
original second nodes\' next pointer is unmarked, and ensures that only
one concurrent delete succeeds which reads the second node\'s current
next pointer as being unmarked as well.
The second CAS checks that the previous node hasn\'t been logically
deleted because its next pointer is not the same as the unmarked pointer
to the current second node returned by the search function, so only an
active previous node\'s next pointer is \'physically\' updated to a copy
of the original unmarked next pointer of the node being deleted ( whose
next pointer is already marked by the first CAS).
If the second CAS fails, then the previous node is logically deleted and
its next pointer is marked, and so is the current node\'s next pointer.
A call to *search* function again, tidies things up, because in
endeavouring to find the key of the current node and return adjacent
unmarked previous and current pointers, and while doing so, it truncates
strings of logically deleted nodes .
#### Lock-free programming issues
Starvation could be possible , as failed inserts have to restart from
the front of the list. Wait-freedom is a concept where the algorithm has
all threads safe from starvation.
The ABA problem exists, where a garbage collector recycles the pointer A
, but the address is loaded differently, and the pointer is re-added at
a point where a check is done for A by another thread that read A and is
doing a CAS to check A has not changed ; the address is the same and is
unmarked, but the contents of A has changed.
------------------------------------------------------------------------
|
# Algorithms/Backtracking
**Backtracking** is a general algorithmic technique that considers
searching every possible combination in order to solve an optimization
problem. Backtracking is also known as **depth-first search** or
**branch and bound**. By inserting more knowledge of the problem, the
search tree can be pruned to avoid considering cases that don\'t look
promising. While backtracking is useful for hard problems to which we do
not know more efficient solutions, it is a poor solution for the
everyday problems that other techniques are much better at solving.
However, dynamic programming and greedy algorithms can be thought of as
optimizations to backtracking, so the general technique behind
backtracking is useful for understanding these more advanced concepts.
Learning and understanding backtracking techniques first provides a good
stepping stone to these more advanced techniques because you won\'t have
to learn several new concepts all at once.
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```
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<tr>
```
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<td style="background-color: #FFFFEE; border: solid 1px #FFC92E; padding: 1em;" valign=top>
```
**Backtracking Methodology**
1. View picking a solution as a sequence of **choices**
2. For each choice, consider every **option** recursively
3. Return the best solution found
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</td>
```
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</tr>
```
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</table>
```
This methodology is generic enough that it can be applied to most
problems. However, even when taking care to improve a backtracking
algorithm, it will probably still take exponential time rather than
polynomial time. Additionally, exact time analysis of backtracking
algorithms can be extremely difficult: instead, simpler upperbounds that
may not be tight are given.
## Longest Common Subsequence (exhaustive version)
The LCS problem is similar to what the Unix \"diff\" program does. The
diff command in Unix takes two text files, *A* and *B*, as input and
outputs the differences line-by-line from *A* and *B*. For example, diff
can show you that lines missing from *A* have been added to *B*, and
lines present in *A* have been removed from *B*. The goal is to get a
list of additions and removals that could be used to transform *A* to
*B*. An overly conservative solution to the problem would say that all
lines from *A* were removed, and that all lines from *B* were added.
While this would solve the problem in a crude sense, we are concerned
with the minimal number of additions and removals to achieve a correct
transformation. Consider how you may implement a solution to this
problem yourself.
The LCS problem, instead of dealing with lines in text files, is
concerned with finding common items between two different arrays. For
example,
`let `*`a`*` := array {"The", "great", "square", "has", "no", "corners"}`\
`let `*`b`*` := array {"The", "great", "image", "has", "no", "form"}`
We want to find the longest subsequence possible of items that are found
in both *a* and *b* in the same order. The LCS of *a* and *b* is
: \"The\", \"great\", \"has\", \"no\"
Now consider two more sequences:
`let `*`c`*` := array {1, 2, 4, 8, 16, 32}`\
`let `*`d`*` := array {1, 2, 3, 32, 8}`
Here, there are two longest common subsequences of *c* and *d*:
: 1, 2, 32; and
: 1, 2, 8
Note that
: 1, 2, 32, 8
is *not* a common subsequence, because it is only a valid subsequence of
*d* and not *c* (because *c* has 8 before the 32). Thus, we can conclude
that for some cases, solutions to the LCS problem are not unique. If we
had more information about the sequences available we might prefer one
subsequence to another: for example, if the sequences were lines of text
in computer programs, we might choose the subsequences that would keep
function definitions or paired comment delimiters intact (instead of
choosing delimiters that were not paired in the syntax).
On the top level, our problem is to implement the following function
`// `*`lcs -- returns the longest common subsequence of a and b`*\
`function `**`lcs`**`(array `*`a`*`, array `*`b`*`): array`
which takes in two arrays as input and outputs the subsequence array.
How do you solve this problem? You could start by noticing that if the
two sequences start with the same word, then the longest common
subsequence always contains that word. You can automatically put that
word on your list, and you would have just reduced the problem to
finding the longest common subset of the rest of the two lists. Thus,
the problem was made smaller, which is good because it shows progress
was made.
But if the two lists do not begin with the same word, then one, or both,
of the first element in *a* or the first element in *b* do not belong in
the longest common subsequence. But yet, one of them might be. How do
you determine which one, if any, to add?
The solution can be thought in terms of the back tracking methodology:
Try it both ways and see! Either way, the two sub-problems are
manipulating smaller lists, so you know that the recursion will
eventually terminate. Whichever trial results in the longer common
subsequence is the winner.
Instead of \"throwing it away\" by deleting the item from the array we
use array slices. For example, the slice
: *a*\[1,..,5\]
represents the elements
: {*a*\[1\], *a*\[2\], *a*\[3\], *a*\[4\], *a*\[5\]}
of the array as an array itself. If your language doesn\'t support
slices you\'ll have to pass beginning and/or ending indices along with
the full array. Here, the slices are only of the form
: *a*\[1,..\]
which, when using 0 as the index to the first element in the array,
results in an array slice that doesn\'t have the 0th element. (Thus, a
non-sliced version of this algorithm would only need to pass the
beginning valid index around instead, and that value would have to be
subtracted from the complete array\'s length to get the pseudo-slice\'s
length.)
`// `*`lcs -- returns the longest common subsequence of a and b`*\
`function `**`lcs`**`(array `*`a`*`, array `*`b`*`): array`\
` if `*`a`*`.length == 0 OR `*`b`*`.length == 0:`\
` ''// if we're at the end of either list, then the lcs is empty`\
` `\
` return new array {}`\
` else-if `*`a`*`[0] == `*`b`*`[0]:`\
` `*`// if the start element is the same in both, then it is on the lcs,`*\
` `*`// so we just recurse on the remainder of both lists.`*\
` `\
` return append(new array {`*`a`*`[0]}, `**`lcs`**`(`*`a`*`[1,..], `*`b`*`[1,..]))`\
` else`\
` `*`// we don't know which list we should discard from. Try both ways,`*\
` `*`// pick whichever is better.`*\
` `\
` let `*`discard_a`*` := `**`lcs`**`(`*`a`*`[1,..], `*`b`*`)`\
` let `*`discard_b`*` := `**`lcs`**`(`*`a`*`, `*`b`*`[1,..])`\
` `\
` if `*`discard_a`*`.length > `*`discard_b`*`.length:`\
` let `*`result`*` := `*`discard_a`*\
` else`\
` let `*`result`*` := `*`discard_b`*\
` fi`\
` return `*`result`*\
` fi`\
`end`
## Shortest Path Problem (exhaustive version)
To be improved as Dijkstra\'s algorithm in a later section.
## Largest Independent Set
## Bounding Searches
If you\'ve already found something \"better\" and you\'re on a branch
that will never be as good as the one you already saw, you can terminate
that branch early. (Example to use: sum of numbers beginning with 1 2,
and then each number following is a sum of any of the numbers plus the
last number. Show performance improvements.)
## Constrained 3-Coloring
This problem doesn\'t have immediate self-similarity, so the problem
first needs to be generalized. Methodology: If there\'s no
self-similarity, try to generalize the problem until it has it.
## Traveling Salesperson Problem
Here, backtracking is one of the best solutions known.
------------------------------------------------------------------------
|
# Algorithms/Dynamic Programming
**Dynamic programming** can be thought of as an optimization technique
for particular classes of backtracking algorithms where subproblems are
repeatedly solved. Note that the term *dynamic* in dynamic programming
should not be confused with dynamic programming languages, like Scheme
or Lisp. Nor should the term *programming* be confused with the act of
writing computer programs. In the context of algorithms, dynamic
programming always refers to the technique of filling in a table with
values computed from other table values. (It\'s dynamic because the
values in the table are filled in by the algorithm based on other values
of the table, and it\'s programming in the sense of setting things in a
table, like how television programming is concerned with when to
broadcast what shows.)
## Fibonacci Numbers
Before presenting the dynamic programming technique, it will be useful
to first show a related technique, called **memoization**, on a toy
example: The Fibonacci numbers. What we want is a routine to compute the
*n*th Fibonacci number:
*`// fib -- compute Fibonacci(n)`*\
`function `**`fib`**`(integer `*`n`*`): integer`
By definition, the *n*th Fibonacci number, denoted $\textrm{F}_n$ is
$$\textrm{F}_0 = 0$$
$$\textrm{F}_1 = 1$$
$$\textrm{F}_n = \textrm{F}_{n-1} + \textrm{F}_{n-2}$$
How would one create a good algorithm for finding the nth
Fibonacci-number? Let\'s begin with the naive algorithm, which codes the
mathematical definition:
*`// fib -- compute Fibonacci(n)`*\
`function `**`fib`**`(integer `*`n`*`): integer`\
` assert (n >= 0)`\
` if `*`n`*` == 0: return 0 fi`\
` if `*`n`*` == 1: return 1 fi`\
` `\
` return `**`fib`**`(`*`n`*` - 1) + `**`fib`**`(`*`n`*` - 2)`\
`end`
Note that this is a toy example because there is already a
mathematically closed form for $\textrm{F}_n$:
$$F(n) = {\phi^n - (1 -\phi)^{n} \over \sqrt{5}}$$
where:
$$\phi = {1 + \sqrt{5} \over 2}$$
This latter equation is known as the Golden
Ratio. Thus, a program could efficiently
calculate $\textrm{F}_n$ for even very large *n*. However, it\'s
instructive to understand what\'s so inefficient about the current
algorithm.
To analyze the running time of `fib` we should look at a call tree for
something even as small as the sixth Fibonacci number:
Every leaf of the call tree has the value 0 or 1, and the sum of these
values is the final result. So, for any *n,* the number of leaves in the
call tree is actually $\textrm{F}_n$ itself! The closed form thus tells
us that the number of leaves in **`fib`**`(`*`n`*`)` is approximately
equal to
$$\left(\frac{1 + \sqrt{5}}{2}\right)^n\approx 1.618^n = 2^{\lg (1.618^n)} = 2^{n \lg (1.618)} \approx 2^{0.69 n}.$$
(Note the algebraic manipulation used above to make the base of the
exponent the number 2.) This means that there are far too many leaves,
particularly considering the repeated patterns found in the call tree
above.
One optimization we can make is to save a result in a table once it\'s
already been computed, so that the same result needs to be computed only
once. The optimization process is called memoization and conforms to the
following methodology:
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```
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<tr>
```
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<td style="background-color: #FFFFEE; border: solid 1px #FFC92E; padding: 1em;" valign=top>
```
**Memoization Methodology**
1. Start with a backtracking algorithm
2. Look up the problem in a table; if there\'s a valid entry for it,
return that value
3. Otherwise, compute the problem recursively, and then store the
result in the table before returning the value
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</td>
```
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</tr>
```
```{=html}
</table>
```
Consider the solution presented in the backtracking chapter for the
Longest Common Subsequence problem. In the execution of that algorithm,
many common subproblems were computed repeatedly. As an optimization, we
can compute these subproblems once and then store the result to read
back later. A recursive memoization algorithm can be turned
\"bottom-up\" into an iterative algorithm that fills in a table of
solutions to subproblems. Some of the subproblems solved might not be
needed by the end result (and that is where dynamic programming differs
from memoization), but dynamic programming can be very efficient because
the iterative version can better use the cache and have less call
overhead. Asymptotically, dynamic programming and memoization have the
same complexity.
So how would a fibonacci program using memoization work? Consider the
following program (*f*\[*n*\] contains the *n*th Fibonacci-number if has
been calculated, -1 otherwise):
`function `**`fib`**`(integer `*`n`*`): integer`\
` if `*`n`*` == 0 `**`or`**` n == 1:`\
` return `*`n`*\
` else-if `*`f`*`[`*`n`*`] != -1:`\
` return `*`f`*`[`*`n`*`]`\
` else`\
` `*`f`*`[`*`n`*`] = `**`fib`**`(`*`n`*` - 1) + `**`fib`**`(`*`n`*` - 2)`\
` return `*`f`*`[`*`n`*`]`\
` fi`\
`end`
The code should be pretty obvious. If the value of fib(n) already has
been calculated it\'s stored in f\[n\] and then returned instead of
calculating it again. That means all the copies of the sub-call trees
are removed from the calculation.
The values in the blue boxes are values that already have been
calculated and the calls can thus be skipped. It is thus a lot faster
than the straight-forward recursive algorithm. Since every value less
than n is calculated once, and only once, the first time you execute it,
the asymptotic running time is $O (n)$. Any other calls to it will take
$O (1)$ since the values have been precalculated (assuming each
subsequent call\'s argument is less than n).
The algorithm does consume a lot of memory. When we calculate fib(*n*),
the values fib(0) to fib(n) are stored in main memory. Can this be
improved? Yes it can, although the $O(1)$ running time of subsequent
calls are obviously lost since the values aren\'t stored. Since the
value of fib(*n*) only depends on fib(*n-1*) and fib(*n-2*) we can
discard the other values by going bottom-up. If we want to calculate
fib(*n*), we first calculate fib(2) = fib(0) + fib(1). Then we can
calculate fib(3) by adding fib(1) and fib(2). After that, fib(0) and
fib(1) can be discarded, since we don\'t need them to calculate any more
values. From fib(2) and fib(3) we calculate fib(4) and discard fib(2),
then we calculate fib(5) and discard fib(3), etc. etc. The code goes
something like this:
`function `**`fib`**`(integer `*`n`*`): integer`\
` if `*`n`*` == 0 `**`or`**` n == 1:`\
` return `*`n`*\
` fi`\
\
` let `*`u`*` := 0`\
` let `*`v`*` := 1`\
\
` for `*`i`*` := 2 to `*`n`*`:`\
` let `*`t`*` := `*`u`*` + `*`v`*\
` `*`u`*` := `*`v`*\
` `*`v`*` := `*`t`*\
` repeat`\
` `\
` return `*`v`*\
`end`
We can modify the code to store the values in an array for subsequent
calls, but the point is that we don\'t *have* to. This method is typical
for dynamic programming. First we identify what subproblems need to be
solved in order to solve the entire problem, and then we calculate the
values bottom-up using an iterative process.
## Longest Common Subsequence (DP version)
The problem of Longest Common Subsequence (LCS) involves comparing two
given sequences of characters, to find the longest subsequence common to
both the sequences.
Note that \'subsequence\' is not \'substring\' - the characters
appearing in the subsequence need not be consecutive in either of the
sequences; however, the individual characters do need to be in same
order as appearing in both sequences.
Given two sequences, namely,
: *X = {x~1~, x~2~, x~3~, \..., x~m~}* and *Y = {y~1~, y~2~, y~3~,
\..., y~n~}*
we defineː
: *Z = {z~1~, z~2~, z~3~, \..., z~k~}*
as a subsequence of *X*, if all the characters *z~1~, z~2~, z~3~, \...,
z~k~*, appear in *X*, and they appear in a strictly increasing sequence;
i.e. *z~1~* appears in *X* before *z~2~*, which in turn appears before
*z~3~*, and so on. Once again, it is not necessary for all the
characters *z~1~, z~2~, z~3~, \..., z~k~* to be consecutive; they must
only appear in the same order in *X* as they are in *Z*. And thus, we
can define *Z = {z~1~, z~2~, z~3~, \..., z~k~}* as a common subseqeunce
of *X* and *Y*, if *Z* appears as a subsequence in both *X* and *Y*.
The backtracking solution of LCS involves enumerating all possible
subsequences of *X*, and check each subsequence to see whether it is
also a subsequence of *Y*, keeping track of the longest subsequence we
find \see [ *Longest Common Subsequence (exhaustive
version)*\].
Since *X* has *m* characters in it, this leads to *2^m^* possible
combinations. This approach, thus, takes exponential time and is
impractical for long sequences.
## Matrix Chain Multiplication
Suppose that you need to multiply a series of $n$ matrices
$M_1,\ldots, M_n$ together to form a product matrix $P$:
$$P = M_1\cdot M_2 \cdots M_{n-1}\cdot M_n$$
This will require $n-1$ multiplications, but what is the fastest way we
can form this product? Matrix multiplication is associative, that is,
$$(A\cdot B)\cdot C = A\cdot (B\cdot C)$$ for any $A, B, C$, and so we
have some choice in what multiplication we perform first. (Note that
matrix multiplication is *not* commutative, that is, it does not hold in
general that $A\cdot B = B\cdot A$.)
Because you can only multiply two matrices at a time the product
$M_1\cdot M_2\cdot M_3\cdot M_4$ can be paranthesized in these ways:
$$((M_1 M_2) M_3) M_4$$
$$(M_1 (M_2 M_3)) M_4$$
$$M_1 ((M_2 M_3) M_4)$$
$$(M_1 M_2) (M_3 M_4)$$
$$M_1 (M_2 (M_3 M_4))$$
Two matrices $M_1$ and $M_2$ can be multiplied if the number of columns
in $M_1$ equals the number of rows in $M_2$. The number of rows in their
product will equal the number rows in $M_1$ and the number of columns
will equal the number of columns in $M_2$. That is, if the dimensions of
$M_1$ is $a \times b$ and $M_2$ has dimensions $b \times c$ their
product will have dimensions $a \times c$.
To multiply two matrices with each other we use a function called
matrix-multiply that takes two matrices and returns their product. We
will leave implementation of this function alone for the moment as it is
not the focus of this chapter (how to multiply two matrices in the
fastest way has been under intensive study for several years \[TODO:
propose this topic for the *Advanced* book\]). The time this function
takes to multiply two matrices of size $a \times b$ and $b \times c$ is
proportional to the number of scalar multiplications, which is
proportional to $a b c$. Thus, paranthezation matters: Say that we have
three matrices $M_1$, $M_2$ and $M_3$. $M_1$ has dimensions
$5 \times 100$, $M_2$ has dimensions $100 \times 100$ and $M_3$ has
dimensions $100 \times 50$. Let\'s paranthezise them in the two possible
ways and see which way requires the least amount of multiplications. The
two ways are
$$((M_1 M_2) M_3)$$, and
$$(M_1 (M_2 M_3))$$.
To form the product in the first way requires 75000 scalar
multiplications (5\*100\*100=50000 to form product $(M_1 M_2)$ and
another 5\*100\*50=25000 for the last multiplications.) This might seem
like a lot, but in comparison to the 525000 scalar multiplications
required by the second parenthesization (50\*100\*100=500000 plus
5\*50\*100=25000) it is miniscule! You can see why determining the
parenthesization is important: imagine what would happen if we needed to
multiply 50 matrices!
### Forming a Recursive Solution
Note that we concentrate on finding a how many scalar multiplications
are needed instead of the actual order. This is because once we have
found a working algorithm to find the amount it is trivial to create an
algorithm for the actual parenthesization. It will, however, be
discussed in the end.
So how would an algorithm for the optimum parenthesization look? By the
chapter title you might expect that a dynamic programming method is in
order (not to give the answer away or anything). So how would a dynamic
programming method work? Because dynamic programming algorithms are
based on optimal substructure, what would the optimal substructure in
this problem be?
Suppose that the optimal way to parenthesize
$$M_1 M_2 \dots M_n$$ splits the product at $k$:
$$(M_1 M_2 \dots M_k)(M_{k+1} M_{k+2} \dots M_n)$$. Then the optimal
solution contains the optimal solutions to the two subproblems
$$(M_1 \dots M_k)$$
$$(M_{k+1} \dots M_n)$$ That is, just in accordance with the fundamental
principle of dynamic programming, the solution to the problem depends on
the solution of smaller sub-problems.
Let\'s say that it takes $c(n)$ scalar multiplications to multiply
matrices $M_n$ and $M_{n+1}$, and $f(m,n)$ is the number of scalar
multiplications to be performed in an optimal parenthesization of the
matrices $M_m \dots M_n$. The definition of $f(m,n)$ is the first step
toward a solution.
When $n-m=1$, the formulation is trivial; it is just $c(m)$. But what is
it when the distance is larger? Using the observation above, we can
derive a formulation. Suppose an optimal solution to the problem divides
the matrices at matrices k and k+1 (i.e.
$(M_m \dots M_k)(M_{k+1} \dots M_n)$) then the number of scalar
multiplications are.
$$f(m,k) + f(k+1,n) + c(k)$$
That is, the amount of time to form the first product, the amount of
time it takes to form the second product, and the amount of time it
takes to multiply them together. But what is this optimal value k? The
answer is, of course, the value that makes the above formula assume its
minimum value. We can thus form the complete definition for the
function:
$$f(m,n) = \begin{cases} \min_{m \le k < n}f(m,k) + f(k+1,n) + c(k) & \mbox{if } n-m>1 \\ 0 & \mbox{if } n=m\end{cases}$$
A straight-forward recursive solution to this would look something like
this *(the language is
Wikicode)*:
`function `**`f`**`(`*`m`*`, `*`n`*`) {`\
\
` if `*`m`*` == `*`n`*\
` return 0`\
\
` let `*`minCost`*` := `$\infty$\
\
` for `*`k`*` := `*`m`*` to `*`n`*` - 1 {`\
` v := `**`f`**`(`*`m`*`, `*`k`*`) + `**`f`**`(`*`k`*` + 1, `*`n`*`) + `*`c`*`(`*`k`*`)`\
` if `*`v`*` < `*`minCost`*\
` `*`minCost`*` := `*`v`*\
` }`\
` return `*`minCost`*\
`}`
This rather simple solution is, unfortunately, not a very good one. It
spends mountains of time recomputing data and its running time is
exponential.
Using the same adaptation as above we get:
`function `**`f`**`(`*`m`*`, `*`n`*`) {`\
\
` if `*`m`*` == `*`n`*\
` return 0`\
\
` else-if `*`f`*`[`*`m,n`*`] != -1:`\
` return `*`f`*`[`*`m,n`*`]`\
` fi`\
\
` let `*`minCost`*` := `$\infty$\
\
` for `*`k`*` := `*`m`*` to `*`n`*` - 1 {`\
` v := `**`f`**`(`*`m`*`, `*`k`*`) + `**`f`**`(`*`k`*` + 1, `*`n`*`) + `*`c`*`(`*`k`*`)`\
` if `*`v`*` < `*`minCost`*\
` `*`minCost`*` := `*`v`*\
` }`\
` `*`f`*`[`*`m,n`*`]=minCost`\
` return `*`minCost`*\
`}`
## Parsing Any Context-Free Grammar
Note that special types of context-free grammars can be parsed much more
efficiently than this technique, but in terms of generality, the DP
method is the only way to go.
------------------------------------------------------------------------
|
# Algorithms/Greedy Algorithms
In the backtracking algorithms we looked at, we saw algorithms that
found decision points and recursed over all options from that decision
point. A **greedy algorithm** can be thought of as a backtracking
algorithm where at each decision point \"the best\" option is already
known and thus can be picked without having to recurse over any of the
alternative options.
The name \"greedy\" comes from the fact that the algorithms make
decisions based on a single criterion, instead of a global analysis that
would take into account the decision\'s effect on further steps. As we
will see, such a backtracking analysis will be unnecessary in the case
of greedy algorithms, so it is not greedy in the sense of causing harm
for only short-term gain.
Unlike backtracking algorithms, greedy algorithms can\'t be made for
every problem. Not every problem is \"solvable\" using greedy
algorithms. Viewing the finding solution to an optimization problem as a
hill climbing problem greedy algorithms can be used for only those hills
where at every point taking the steepest step would lead to the peak
always.
Greedy algorithms tend to be very efficient and can be implemented in a
relatively straightforward fashion. Many a times in O(n) complexity as
there would be a single choice at every point. However, most attempts at
creating a correct greedy algorithm fail unless a precise proof of the
algorithm\'s correctness is first demonstrated. When a greedy strategy
fails to produce optimal results on all inputs, we instead refer to it
as a heuristic instead of an algorithm. Heuristics can be useful when
speed is more important than exact results (for example, when \"good
enough\" results are sufficient).
## Event Scheduling Problem
The first problem we\'ll look at that can be solved with a greedy
algorithm is the event scheduling problem. We are given a set of events
that have a start time and finish time, and we need to produce a subset
of these events such that no events intersect each other (that is,
having overlapping times), and that we have the maximum number of events
scheduled as possible.
Here is a formal statement of the problem:
: *Input*: *events*: a set of intervals $(s_i, f_i)$ where $s_i$ is
the start time, and $f_i$ is the finish time.
: *Solution*: A subset *S* of *Events*.
: *Constraint*: No events can intersect (start time exclusive). That
is, for all intervals $i=(s_i, f_i), j=(s_j, f_j)$ where $s_i < s_j$
it holds that $f_i\le s_j$.
: *Objective*: Maximize the number of scheduled events, i.e. maximize
the size of the set *S*.
We first begin with a backtracking solution to the problem:
*`// event-schedule -- schedule as many non-conflicting events as possible`*\
`function `**`event-schedule`**`(`*`events`*` array of `*`s`*`[1..`*`n`*`], `*`j`*`[1..`*`n`*`]): set`\
` if `*`n`*` == 0: return `$\emptyset$` fi`\
` if `*`n`*` == 1: return {`*`events`*`[1]} fi`\
` let `*`event`*` := `*`events`*`[1]`\
` let `*`S1`*` := union(`**`event-schedule`**`(`*`events`*` - set of conflicting events), `*`event`*`)`\
` let `*`S2`*` := `**`event-schedule`**`(`*`events`*` - {`*`event`*`})`\
` if `*`S1`*`.size() >= `*`S2`*`.size():`\
` return `*`S1`*\
` else`\
` return `*`S2`*\
` fi`\
`end`
The above algorithm will faithfully find the largest set of
non-conflicting events. It brushes aside details of how the set
: *events* - set of conflicting events
is computed, but it would require $O(n)$ time. Because the algorithm
makes two recursive calls on itself, each with an argument of size
$n - 1$, and because removing conflicts takes linear time, a recurrence
for the time this algorithm takes is:
$$T(n) = 2\cdot T(n - 1) + O(n)$$
which is $O(2^{n})$.
But suppose instead of picking just the first element in the array we
used some other criterion. The aim is to just pick the \"right\" one so
that we wouldn\'t need two recursive calls. First, let\'s consider the
greedy strategy of picking the shortest events first, until we can add
no more events without conflicts. The idea here is that the shortest
events would likely interfere less than other events.
There are scenarios were picking the shortest event first produces the
optimal result. However, here\'s a scenario where that strategy is
sub-optimal:
Above, the optimal solution is to pick event A and C, instead of just B
alone. Perhaps instead of the shortest event we should pick the events
that have the least number of conflicts. This strategy seems more
direct, but it fails in this scenario:
Above, we can maximize the number of events by picking A, B, C, D, and
E. However, the events with the least conflicts are 6, 2 and 7, 3. But
picking one of 6, 2 and one of 7, 3 means that we cannot pick B, C and
D, which includes three events instead of just two.
==== Longest Path solution to critical path scheduling of jobs ===
Construction with dependency constraints but concurrency can use
critical path determination to find minimum time feasible, which is
equivalent to a longest path in a directed acyclic graph problem. By
using relaxation and breath first search, the shortest path can be the
longest path by negating weights(time constraint), finding solution,
then restoring the positive weights. (Relaxation is determining the
parent with least accumulated weight for each adjacent node being
scheduled to be visited)
## Dijkstra\'s Shortest Path Algorithm
With two (high-level, pseudocode) transformations, Dijsktra\'s algorithm
can be derived from the much less efficient backtracking algorithm. The
trick here is to prove the transformations maintain correctness, but
that\'s the whole insight into Dijkstra\'s algorithm anyway. \[TODO:
important to note the paradox that to solve this problem it\'s easier to
solve a more-general version. That is, shortest path from s to all
nodes, not just to t. Worthy of its own colored box.\]
To see the workings of Dijkstra\'s Shortest Path Algorithm, take an
example:
There is a start and end node, with 2 paths between them ; one path has
cost 30 on first hop, then 10 on last hop to the target node, with total
cost 40. Another path cost 10 on first hop, 10 on second hop, and 40 on
last hop, with total cost 60.
The start node is given distance zero so it can be at the front of a
shortest distance queue, all the other nodes are given infinity or a
large number e.g. 32767 .
This makes the start node the first current node in the queue.
With each iteration, the current node is the first node of a shortest
path queue. It looks at all nodes adjacent to the current node;
For the case of the start node, in the first path it will find a node of
distance 30, and in the second path, an adjacent node of distance 10.
The current nodes distance, which is zero at the beginning, is added to
distances of the adjacent nodes, and the distances from the start node
of each node are updated, so the nodes will be 30+0 = 30 in the 1st
path, and 10+0=10 in the 2nd path.
Importantly, also updated is a previous pointer attribute for each node,
so each node will point back to the current node, which is the start
node for these two nodes.
Each node\'s priority is updated in the priority queue using the new
distance.
That ends one iteration. The current node was removed from the queue
before examining its adjacent nodes.
In the next iteration, the front of the queue will be the node in the
second path of distance 10, and it has only one adjacent node of
distance 10, and that adjacent node will distance will be updated from
32767 to 10 (the current node distance) + 10 ( the distance from the
current node) = 20.
In the next iteration, the second path node of cost 20 will be examined,
and it has one adjacent hop of 40 to the target node, and the target
nodes distance is updated from 32767 to 20 + 40 = 60 . The target node
has its priority updated.
In the next iteration, the shortest path node will be the first path
node of cost 30, and the target node has not been yet removed from the
queue. It is also adjacent to the target node, with the total distance
cost of 30 + 10 = 40.
Since 40 is less than 60, the previous calculated distance of the target
node, the target node distance is updated to 40, and the previous
pointer of the target node is updated to the node on the first path.
In the final iteration, the shortest path node is the target node, and
the loop exits.
Looking at the previous pointers starting with the target node, a
shortest path can be reverse constructed as a list to the start node.
Given the above example, what kind of data structures are needed for the
nodes and the algorithm ?
``` python
# author, copyright under GFDL
class Node :
def __init__(self, label, distance = 32767 ):
# a bug in constructor, uses a shared map initializer
#, adjacency_distance_map = {} ):
self.label = label
self.adjacent = {} # this is an adjacency map, with keys nodes, and values the adjacent distance
self.distance = distance # this is the updated distance from the start node, used as the node's priority
# default distance is 32767
self.shortest_previous = None #this the last shortest distance adjacent node
# the logic is that the last adjacent distance added is recorded, for any distances of the same node added
def add_adjacent(self, local_distance, node):
self.adjacent[node]=local_distance
print "adjacency to ", self.label, " of ", self.adjacent[node], " to ", \
node.label
def get_adjacent(self) :
return self.adjacent.iteritems()
def update_shortest( self, node):
new_distance = node.adjacent[self] + node.distance
#DEBUG
print "for node ", node.label, " updating ", self.label, \
" with distance ", node.distance, \
" and adjacent distance ", node.adjacent[self]
updated = False
# node's adjacency map gives the adjacent distance for this node
# the new distance for the path to this (self)node is the adjacent distance plus the other node's distance
if new_distance < self.distance :
# if it is the shortest distance then record the distance, and make the previous node that node
self.distance = new_distance
self.shortest_previous= node
updated = True
return updated
MAX_IN_PQ = 100000
class PQ:
def __init__(self, sign = -1 ):
self.q = [None ] * MAX_IN_PQ # make the array preallocated
self.sign = sign # a negative sign is a minimum priority queue
self.end = 1 # this is the next slot of the array (self.q) to be used,
self.map = {}
def insert( self, priority, data):
self.q[self.end] = (priority, data)
# sift up after insert
p = self.end
self.end = self.end + 1
self.sift_up(p)
def sift_up(self, p):
# p is the current node's position
# q[p][0] is the priority, q[p][1] is the item or node
# while the parent exists ( p >= 1), and parent's priority is less than the current node's priority
while p / 2 != 0 and self.q[p/2][0]*self.sign < self.q[p][0]*self.sign:
# swap the parent and the current node, and make the current node's position the parent's position
tmp = self.q[p]
self.q[p] = self.q[p/2]
self.q[p/2] = tmp
self.map[self.q[p][1]] = p
p = p/2
# this map's the node to the position in the priority queue
self.map[self.q[p][1]] = p
return p
def remove_top(self):
if self.end == 1 :
return (-1, None)
(priority, node) = self.q[1]
# put the end of the heap at the top of the heap, and sift it down to adjust the heap
# after the heap's top has been removed. this takes log2(N) time, where N iis the size of the heap.
self.q[1] = self.q[self.end-1]
self.end = self.end - 1
self.sift_down(1)
return (priority, node)
def sift_down(self, p):
while 1:
l = p * 2
# if the left child's position is more than the size of the heap,
# then left and right children don't exist
if ( l > self.end) :
break
r= l + 1
# the selected child node should have the greatest priority
t = l
if r < self.end and self.q[r][0]*self.sign > self.q[l][0]*self.sign :
t = r
print "checking for sift down of ", self.q[p][1].label, self.q[p][0], " vs child ", self.q[t][1].label, self.q[t][0]
# if the selected child with the greatest priority has a higher priority than the current node
if self.q[t] [0] * self. sign > self.q [p] [0] * self.sign :
# swap the current node with that child, and update the mapping of the child node to its new position
tmp = self. q [ t ]
self. q [ t ] = self.q [ p ]
self. q [ p ] = tmp
self.map [ tmp [1 ] ] = p
p = t
else: break # end the swap if the greatest priority child has a lesser priority than the current node
# after the sift down, update the new position of the current node.
self.map [ self.q[p][1] ] = p
return p
def update_priority(self, priority, data ) :
p = self. map[ data ]
print "priority prior update", p, "for priority", priority, " previous priority", self.q[p][0]
if p is None :
return -1
self.q[p] = (priority, self.q[p][1])
p = self.sift_up(p)
p = self.sift_down(p)
print "updated ", self.q[p][1].label, p, "priority now ", self.q[p][0]
return p
class NoPathToTargetNode ( BaseException):
pass
def test_1() :
st = Node('start', 0)
p1a = Node('p1a')
p1b = Node('p1b')
p2a = Node('p2a')
p2b = Node('p2b')
p2c = Node('p2c')
p2d = Node('p2d')
targ = Node('target')
st.add_adjacent ( 30, p1a)
#st.add_adjacent ( 10, p2a)
st.add_adjacent ( 20, p2a)
#p1a.add_adjacent(10, targ)
p1a.add_adjacent(40, targ)
p1a.add_adjacent(10, p1b)
p1b.add_adjacent(10, targ)
# testing alternative
#p1b.add_adjacent(20, targ)
p2a.add_adjacent(10, p2b)
p2b.add_adjacent(5,p2c)
p2c.add_adjacent(5,p2d)
#p2d.add_adjacent(5,targ)
#chooses the alternate path
p2d.add_adjacent(15,targ)
pq = PQ()
# st.distance is 0, but the other's have default starting distance 32767
pq.insert( st.distance, st)
pq.insert( p1a.distance, p1a)
pq.insert( p2a.distance, p2a)
pq.insert( p2b.distance, p2b)
pq.insert(targ.distance, targ)
pq.insert( p2c.distance, p2c)
pq.insert( p2d.distance, p2d)
pq.insert(p1b.distance, p1b)
node = None
while node != targ :
(pr, node ) = pq.remove_top()
#debug
print "node ", node.label, " removed from top "
if node is None:
print "target node not in queue"
raise
elif pr == 32767:
print "max distance encountered so no further nodes updated. No path to target node."
raise NoPathToTargetNode
# update the distance to the start node using this node's distance to all of the nodes adjacent to it, and update its priority if
# a shorter distance was found for an adjacent node ( .update_shortest(..) returns true ).
# this is the greedy part of the dijsktra's algorithm, always greedy for the shortest distance using the priority queue.
for adj_node, dist in node.get_adjacent():
#debug
print "updating adjacency from ", node.label, " to ", adj_node.label
if adj_node.update_shortest( node ):
pq.update_priority( adj_node.distance, adj_node)
print "node and targ ", node, targ, node <> targ
print "length of path", targ.distance
print " shortest path"
#create a reverse list from the target node, through the shortes path nodes to the start node
node = targ
path = []
while node <> None :
path.append(node)
node = node. shortest_previous
for node in reversed(path): # new iterator version of list.reverse()
print node.label
if __name__ == "__main__":
test_1()
```
## Minimum spanning tree
Greedily looking for the minimum weight edges; this could be achieved
with sorting edges into a list in ascending weight. Two well known
algorithms are Prim\'s Algorithm and Kruskal\'s Algorithm. Kruskal
selects the next minimum weight edge that has the condition that no
cycle is formed in the resulting updated graph. Prim\'s algorithm
selects a minimum edge that has the condition that only one edge is
connected to the tree. For both the algorithms, it looks that most work
will be done verifying an examined edge fits the primary condition. In
Kruskal\'s, a search and mark technique would have to be done on the
candidate edge. This will result in a search of any connected edges
already selected, and if a marked edge is encountered, than a cycle has
been formed. In Prim\'s algorithm, the candidate edge would be compared
to the list of currently selected edges, which could be keyed on vertex
number in a symbol table, and if both end vertexes are found, then the
candidate edge is rejected.
## Maximum Flow in weighted graphs
In a flow graph, edges have a forward capacity, a direction, and a flow
quantity in the direction and less than or equal to the forward
capacity. Residual capacity is capacity minus flow in the direction of
the edge, and flow in the other direction.
Maxflow in Ford Fulkerson method requires a step to search for a viable
path from a source to a sink vertex, with non-zero residual capacities
at each step of the path. Then the minimum residual capacity determines
the maximum flow for this path. Multiple iterations of searches using
BFS can be done (the Edmond-Karp algorithm), until the sink vertex is
not marked when the last node is off the queue or stack. All marked
nodes in the last iteration are said to be in the minimum cut.
Here are 2 java examples of implementation of Ford Fulkerson method,
using BFS. The first uses maps to map vertices to input edges, whilst
the second avoids the Collections types Map and List, by counting edges
to a vertex and then allocating space for each edges array indexed by
vertex number, and by using a primitive list node class to implement the
queue for BFS.
For both programs, the input are lines of \"vertex_1, vertex_2,
capacity\", and the output are lines of \"vertex_1, vertex_2, capacity,
flow\", which describe the initial and final flow graph.
``` {.java .numberLines}
// copyright GFDL and CC-BY-SA
package test.ff;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
public class Main {
public static void main(String[] args) throws IOException {
System.err.print("Hello World\n");
final String filename = args[0];
BufferedReader br = new BufferedReader( new FileReader(filename));
String line;
ArrayList<String[]> lines = new ArrayList<>();
while ((line= br.readLine()) != null) {
String[] toks = line.split("\\s+");
if (toks.length == 3)
lines.add(toks);
for (String tok : toks) {
System.out.print(tok);
System.out.print("-");
}
System.out.println("");
}
int [][]edges = new int[lines.size()][4];
// edges, 0 is from-vertex, 1 is to-vertex, 2 is capacity, 3 is flow
for (int i = 0; i < edges.length; ++i)
for (int j =0; j < 3; ++j)
edges[i][j] = Integer.parseInt(lines.get(i)[j]);
Map<Integer, List<int[]>> edgeMap = new HashMap<>();
// add both ends into edge map for each edge
int last = -1;
for (int i = 0; i < edges.length; ++i)
for (int j = 0; j < 2; ++j) {
edgeMap.put(edges[i][j],
edgeMap.getOrDefault(edges[i][j],
new LinkedList<int[]>()) );
edgeMap.get(edges[i][j]).add(edges[i]);
// find the highest numbered vertex, which will be the sink.
if ( edges[i][j] > last )
last = edges[i][j];
}
while(true) {
boolean[] visited = new boolean[edgeMap.size()];
int[] previous = new int[edgeMap.size()];
int[][] edgeTo = new int[edgeMap.size()][];
LinkedList<Integer> q = new LinkedList<>();
q.addLast(0);
int v = 0;
while (!q.isEmpty()) {
v = q.removeFirst();
visited[v] = true;
if (v == last)
break;
int prevQsize = q.size();
for ( int[] edge: edgeMap.get(v)) {
if (v == edge[0] &&
!visited[edge[1]] &&
edge[2]-edge[3] > 0)
q.addLast(edge[1]);
else if( v == edge[1] &&
!visited[edge[0]] &&
edge[3] > 0 )
q.addLast(edge[0]);
else
continue;
edgeTo[q.getLast()] = edge;
}
for (int i = prevQsize; i < q.size(); ++i) {
previous[q.get(i)] = v;
}
}
if ( v == last) {
int a = v;
int b = v;
int smallest = Integer.MAX_VALUE;
while (a != 0) {
// get the path by following previous,
// also find the smallest forward capacity
a = previous[b];
int[] edge = edgeTo[b];
if ( a == edge[0] && edge[2]-edge[3] < smallest)
smallest = edge[2]-edge[3];
else if (a == edge[1] && edge[3] < smallest )
smallest = edge[3];
b = a;
}
// fill the capacity along the path to the smallest
b = last; a = last;
while ( a != 0) {
a = previous[b];
int[] edge = edgeTo[b];
if ( a == edge[0] )
edge[3] = edge[3] + smallest;
else
edge[3] = edge[3] - smallest;
b = a;
}
} else {
// v != last, so no path found
// max flow reached
break;
}
}
for ( int[] edge: edges) {
for ( int j = 0; j < 4; ++j)
System.out.printf("%d-",edge[j]);
System.out.println();
}
}
}
```
``` {.java .numberLines}
// copyright GFDL and CC-BY-SA
package test.ff2;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
public class MainFFArray {
static class Node {
public Node(int i) {
v = i;
}
int v;
Node next;
}
public static void main(String[] args) throws IOException {
System.err.print("Hello World\n");
final String filename = args[0];
BufferedReader br = new BufferedReader(new FileReader(filename));
String line;
ArrayList<String[]> lines = new ArrayList<>();
while ((line = br.readLine()) != null) {
String[] toks = line.split("\\s+");
if (toks.length == 3)
lines.add(toks);
for (String tok : toks) {
System.out.print(tok);
System.out.print("-");
}
System.out.println("");
}
int[][] edges = new int[lines.size()][4];
for (int i = 0; i < edges.length; ++i)
for (int j = 0; j < 3; ++j)
edges[i][j] = Integer.parseInt(lines.get(i)[j]);
int last = 0;
for (int[] edge : edges) {
for (int j = 0; j < 2; ++j)
if (edge[j] > last)
last = edge[j];
}
int[] ne = new int[last + 1];
for (int[] edge : edges)
for (int j = 0; j < 2; ++j)
++ne[edge[j]];
int[][][] edgeFrom = new int[last + 1][][];
for (int i = 0; i < last + 1; ++i)
edgeFrom[i] = new int[ne[i]][];
int[] ie = new int[last + 1];
for (int[] edge : edges)
for (int j = 0; j < 2; ++j)
edgeFrom[edge[j]][ie[edge[j]]++] = edge;
while (true) {
Node head = new Node(0);
Node tail = head;
int[] previous = new int[last + 1];
for (int i = 0; i < last + 1; ++i)
previous[i] = -1;
int[][] pathEdge = new int[last + 1][];
while (head != null ) {
int v = head.v;
if (v==last)break;
int[][] edgesFrom = edgeFrom[v];
for (int[] edge : edgesFrom) {
int nv = -1;
if (edge[0] == v && previous[edge[1]] == -1 && edge[2] - edge[3] > 0)
nv = edge[1];
else if (edge[1] == v && previous[edge[0]] == -1 && edge[3] > 0)
nv = edge[0];
else
continue;
Node node = new Node(nv);
previous[nv]=v;
pathEdge[nv]=edge;
tail.next = node;
tail = tail.next;
}
head = head.next;
}
if (head == null)
break;
int v = last;
int minCapacity = Integer.MAX_VALUE;
while (v != 0) {
int fv = previous[v];
int[] edge = pathEdge[v];
if (edge[0] == fv && minCapacity > edge[2] - edge[3])
minCapacity = edge[2] - edge[3];
else if (edge[1] == fv && minCapacity > edge[3])
minCapacity = edge[3];
v = fv;
}
v = last;
while (v != 0) {
int fv = previous[v];
int[] edge = pathEdge[v];
if (edge[0] == fv)
edge[3] += minCapacity;
else if (edge[1] == fv)
edge[3] -= minCapacity;
v = fv;
}
}
for (int[] edge : edges) {
for (int j = 0; j < 4; ++j)
System.out.printf("%d-", edge[j]);
System.out.println();
}
}
}
```
------------------------------------------------------------------------
|
# Algorithms/Hill Climbing
**Hill climbing** is a technique for certain classes of optimization
problems. The idea is to start with a sub-optimal solution to a problem
(i.e., *start at the base of a hill*) and then repeatedly improve the
solution (*walk up the hill*) until some condition is maximized (*the
top of the hill is reached*).
```{=html}
<table WIDTH="80%">
```
```{=html}
<tr>
```
```{=html}
<td style="background-color: #FFFFEE; border: solid 1px #FFC92E; padding: 1em;" valign=top>
```
**Hill-Climbing Methodology**
1. Construct a sub-optimal solution that meets the constraints of the
problem
2. Take the solution and make an improvement upon it
3. Repeatedly improve the solution until no more improvements are
necessary/possible
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
One of the most popular hill-climbing problems is the network flow
problem. Although network flow may sound somewhat specific it is
important because it has high expressive power: for example, many
algorithmic problems encountered in practice can actually be considered
special cases of network flow. After covering a simple example of the
hill-climbing approach for a numerical problem we cover network flow and
then present examples of applications of network flow.
## Newton\'s Root Finding Method
!An illustration of Newton\'s method: The zero of the *f(x)* function
is at *x*. We see that the guess *x~n+1~* is a better guess than *x~n~*
because it is closer to *x*. (*from
Wikipedia*) function is at x. We see that the guess xn+1 is a better guess than xn because it is closer to x. (from Wikipedia)"){width="300"}
Newton\'s Root Finding Method is a three-centuries-old algorithm for
finding numerical approximations to roots of a function (that is a point
$x$ where the function $f(x)$ becomes zero), starting from an initial
guess. You need to know the function $f(x)\,$ and its first derivative
$f'(x)\,$ for this algorithm. The idea is the following: In the vicinity
of the initial guess $x_0$ we can form the Taylor expansion of the
function
$$f(x)=f(x_0+\epsilon)\,$$$\approx f(x_0)+\epsilon f'(x_0)$$+\frac{\epsilon^2}{2} f''(x_0)+...$
which gives a good approximation to the function near $x_0$. Taking only
the first two terms on the right hand side, setting them equal to zero,
and solving for $\epsilon$, we obtain
$$\epsilon=-\frac{f(x_0)}{f'(x_0)}$$
which we can use to construct a better solution
$$x_1=x_0+\epsilon=x_0-\frac{f(x_0)}{f'(x_0)}.$$
This new solution can be the starting point for applying the same
procedure again. Thus, in general a better approximation can be
constructed by repeatedly applying
$$x_{n+1}=x_n-\frac{f(x_n)}{f'(x_n)}.$$
As shown in the illustration, this is nothing else but the construction
of the zero from the tangent at the initial guessing point. In general,
Newton\'s root finding method converges quadratically, except when the
first derivative of the solution $f'(x)=0\,$ vanishes at the root.
Coming back to the \"Hill climbing\" analogy, we could apply Newton\'s
root finding method not to the function $f(x)\,$, but to its first
derivative $f'(x)\,$, that is look for $x$ such that $f'(x)=0\,$. This
would give the extremal positions of the function, its maxima and
minima. Starting Newton\'s method close enough to a maximum this way, we
climb the hill.
#### Example application of Newton\'s method
The net present value function is a function of time, an interest rate,
and a series of cash flows. A related function is Internal Rate of
Return. The formula for each period is (CF~i~ x (1+ i/100) ^t^ , and
this will give a polynomial function which is the total cash flow, and
equals zero when the interest rate equals the IRR. In using Newton\'s
method, x is the interest rate, and y is the total cash flow, and the
method will use the derivative function of the polynomial to find the
slope of the graph at a given interest rate (x-value), which will give
the x~n+1~ , or a better interest rate to try in the next iteration to
find the target x where y ( the total returns) is zero.
Instead of regarding continuous functions, the hill-climbing method can
also be applied to discrete networks.
## Network Flow
Suppose you have a directed graph (possibly with cycles) with one vertex
labeled as the source and another vertex labeled as the destination or
the \"sink\". The source vertex only has edges coming out of it, with no
edges going into it. Similarly, the destination vertex only has edges
going into it, with no edges coming out of it. We can assume that the
graph is fully connected with no dead-ends; i.e., for every vertex
(except the source and the sink), there is at least one edge going into
the vertex and one edge going out of it.
We assign a \"capacity\" to each edge, and initially we\'ll consider
only integral-valued capacities. The following graph meets our
requirements, where \"s\" is the source and \"t\" is the destination:
We\'d like now to imagine that we have some series of inputs arriving at
the source that we want to carry on the edges over to the sink. The
number of units we can send on an edge at a time must be less than or
equal to the edge\'s capacity. You can think of the vertices as cities
and the edges as roads between the cities and we want to send as many
cars from the source city to the destination city as possible. The
constraint is that we cannot send more cars down a road than its
capacity can handle.
**The goal of network flow** is to send as much traffic from $s$ to $t$
as each street can bear.
To organize the traffic routes, we can build a list of different paths
from city $s$ to city $t$. Each path has a carrying capacity equal to
the smallest capacity value for any edge on the path; for example,
consider the following path $p$:
Even though the final edge of $p$ has a capacity of 8, that edge only
has one car traveling on it because the edge before it only has a
capacity of 1 (thus, that edge is at full capacity). After using this
path, we can compute the **residual graph** by subtracting 1 from the
capacity of each edge:
(We subtracted 1 from the capacity of each edge in $p$ because 1 was the
carrying capacity of $p$.) We can say that path $p$ has a flow of 1.
Formally, a **flow** is an assignment $f(e)$ of values to the set of
edges in the graph $G = (V, E)$ such that:
: 1\. $\forall e\in E: f(e)\in\R$
: 2\. $\forall (u,v)\in E: f((u,v)) = -f((v,u))$
: 3\. $\forall u\in V, u\ne s,t: \sum_{v\in V}f(u,v) = 0$
: 4\. $\forall e\in E: f(e)\le c(e)$
Where $s$ is the source node and $t$ is the sink node, and $c(e)\ge 0$
is the capacity of edge $e$. We define the value of a flow $f$ to be:
$$\textrm{Value}(f) = \sum_{v\in V} f((s, v))$$ The goal of network flow
is to find an $f$ such that $\textrm{Value}(f)$ is maximal. To be
maximal means that there is no other flow assignment that obeys the
constraints 1-4 that would have a higher value. The traffic example can
describe what the four flow constraints mean:
1. $\forall e\in E: f(e)\in\R$. This rule simply defines a flow to be a
function from edges in the graph to real numbers. The function is
defined for every edge in the graph. You could also consider the
\"function\" to simply be a mapping: Every edge can be an index into
an array and the value of the array at an edge is the value of the
flow function at that edge.
2. $\forall (u,v)\in E: f((u,v)) = -f((v,u))$. This rule says that if
there is some traffic flowing from node *u* to node *v* then there
should be considered negative that amount flowing from *v* to *u*.
For example, if two cars are flowing from city *u* to city *v*, then
negative two cars are going in the other direction. Similarly, if
three cars are going from city *u* to city *v* and two cars are
going city *v* to city *u* then the net effect is the same as if one
car was going from city *u* to city *v* and no cars are going from
city *v* to city *u*.
3. $\forall u\in V, u\ne s,t: \sum_{v\in V}f(u,v) = 0$. This rule says
that the net flow (except for the source and the destination) should
be neutral. That is, you won\'t ever have more cars going into a
city than you would have coming out of the city. New cars can only
come from the source, and cars can only be stored in the
destination. Similarly, whatever flows out of *s* must eventually
flow into *t*. Note that if a city has three cars coming into it, it
could send two cars to one city and the remaining car to a different
city. Also, a city might have cars coming into it from multiple
sources (although all are ultimately from city *s*).
4. $\forall e\in E: f(e)\le c(e)$.
## The Ford-Fulkerson Algorithm
The following algorithm computes the maximal flow for a given graph with
non-negative capacities. What the algorithm does can be easy to
understand, but it\'s non-trivial to show that it terminates and
provides an optimal solution.
`function `**`net-flow`**`(graph (`*`V`*`, `*`E`*`), node `*`s`*`, node `*`t`*`, cost `*`c`*`): flow`\
` initialize `*`f`*`(`*`e`*`) := 0 for all `*`e`*` in `*`E`*\
` loop while not `*`done`*\
` for all `*`e`*` in `*`E`*`: `*`// compute residual capacities`*\
` let `*`cf`*`(`*`e`*`) := `*`c`*`(`*`e`*`) - `*`f`*`(`*`e`*`)`\
` repeat`\
` `\
` let `*`Gf`*` := (`*`V`*`, {`*`e`*` : `*`e`*` in `*`E`*` and `*`cf`*`(`*`e`*`) > 0})`\
\
` find a path `*`p`*` from `*`s`*` to `*`t`*` in `*`Gf`*` `*`// e.g., use depth first search`*\
` if no path `*`p`*` exists: signal `*`done`*\
\
` let `*`path-capacities`*` := map(`*`p`*`, `*`cf`*`) `*`// a path is a set of edges`*\
` let `*`m`*` := min-val-of(`*`path-capacities`*`) `*`// smallest residual capacity of p`*\
` for all (`*`u`*`, `*`v`*`) in `*`p`*`: `*`// maintain flow constraints`*\
` `*`f`*`((`*`u`*`, `*`v`*`)) := `*`f`*`((`*`u`*`, `*`v`*`)) + `*`m`*\
` `*`f`*`((`*`v`*`, `*`u`*`)) := `*`f`*`((`*`v`*`, `*`u`*`)) - `*`m`*\
` repeat`\
` repeat`\
`end`
The Ford-Fulkerson algorithm uses repeated calls to Breadth-First Search
( use a queue to schedule the children of a node to become the current
node). Breadth-First Search increments the length of each path +1 so
that the first path to get to the destination, the shortest path, will
be the first off the queue. This is in contrast with using a Stack,
which is Depth-First Search, and will come up with \*any\* path to the
target, with the \"descendants\" of current node examined, but not
necessarily the shortest.
- In one search, a path from source to target is found. All nodes are
made unmarked at the beginning of a new search. Seen nodes are
\"marked\" , and not searched again if encountered again.
Eventually, all reachable nodes will have been scheduled on the
queue , and no more unmarked nodes can be reached off the last the
node on the queue.
- During the search, nodes scheduled have the finding \"edge\"
(consisting of the current node , the found node, a current flow,
and a total capacity in the direction first to second node),
recorded.
- This allows finding a reverse path from the target node once
reached, to the start node. Once a path is found, the edges are
examined to find the edge with the minimum remaining capacity, and
this becomes the flow that will result along this path , and this
quantity is removed from the remaining capacity of each edge along
the path. At the \"bottleneck\" edge with the minimum remaining
capacity, no more flow will be possible, in the forward direction,
but still possible in the backward direction.
- This process of BFS for a path to the target node, filling up the
path to the bottleneck edge\'s residual capacity, is repeated, until
BFS cannot find a path to the target node ( the node is not reached
because all sequences of edges leading to the target have had their
bottleneck edges filled). Hence memory of the side effects of
previous paths found, is recorded in the flows of the edges, and
affect the results of future searches.
- An important property of maximal flow is that flow can occur in the
backward direction of an edge, and the residual capacity in the
backward direction is the current flow in the foward direction.
Normally, the residual capacity in the forward direction of an edge
is the initial capacity less forward flow. Intuitively, this allows
more options for maximizing flow as earlier augmenting paths block
off shorter paths.
- On termination, the algorithm will retain the marked and unmarked
states of the results of the last BFS.
- the minimum cut state is the two sets of marked and unmarked nodes
formed from the last unsuccessful BFS starting from the start node,
and not marking the target the node. The start node belongs to one
side of the cut, and the target node belongs to the other.
Arbitrarily, being \"in Cut\" means being on the start side, or
being a marked node. Recall how are a node comes to be marked, given
an edge with a flow and a residual capacity.
#### Example application of Ford-Fulkerson maximum flow/ minimum cut
An example of application of Ford-Fulkerson is in baseball season
elimination. The question is whether the team can possibly win the whole
season by exceeding some combination of wins of the other teams.
The idea is that a flow graph is set up with teams not being able to
exceed the number of total wins which a target team can maximally win
for the entire season. There are game nodes whose edges represent the
number of remaining matches between two teams, and each game node
outflows to two team nodes, via edges that will not limit forward flow;
team nodes receive edges from all games they participate. Then outflow
edges with win limiting capacity flow to the virtual target node. In a
maximal flow state where the target node\'s total wins will exceed some
combination of wins of the other teams, the penultimate depth-first
search will cutoff the start node from the rest of the graph, because no
flow will be possible to any of the game nodes, as a result of the
penultimate depth-first search (recall what happens to the flow , in the
second part of the algorithm after finding the path). This is because in
seeking the maximal flow of each path, the game edges\' capacities will
be maximally drained by the win-limit edges further along the path, and
any residual game capacity means there are more games to be played that
will make at least one team overtake the target teams\' maximal wins. If
a team node is in the minimum cut, then there is an edge with residual
capacity leading to the team, which means what , given the previous
statements? What do the set of teams found in a minimum cut represent (
hint: consider the game node edge) ?
#### Example Maximum bipartite matching ( intern matching )
This matching problem doesn\'t include preference weightings. A set of
companies offers jobs which are made into one big set , and interns
apply to companies for specific jobs. The applications are edges with a
weight of 1. To convert the bipartite matching problem to a maximum flow
problem, virtual vertexes s and t are created , which have weighted 1
edges from s to all interns, and from all jobs to t. Then the
Ford-Fulkerson algorithm is used to sequentially saturate 1 capacity
edges from the graph, by augmenting found paths. It may happen that a
intermediate state is reached where left over interns and jobs are
unmatched, but backtracking along reverse edges which have residual
capacity = forward flow = 1, along longer paths that occur later during
breadth-first search, will negate previous suboptimal augmenting paths,
and provide further search options for matching, and will terminate only
when maximal flow or maximum matching is reached.
|
# Algorithms/Unweighted Graph Algorithms
Please edit and omit unweighted in title
## Representation of Graph
### Adjacency Matrix
The rows/columns are the source/target vertex, the matrix is a square
matrix with non-negative entries, 0 if there is no edge between the
vertices, *n* if there are *n* edges from the source to the target
vertex. This is efficient for dense multigraphs. For undirected graphs
you either extend the matrix as being symmetric or you only use it as a
triangular matrix.
### Adjacency List
A vector with entries the list of adjacent vertices. If you need to
represent a multigraph, then you need a vector of dictionaries where the
key is the target vector and the value the multiplicity of the edge.
This is efficient for sparse graphs. For undirected graphs you either
fix an order of the vertices on an edge or you enter each edge twice
(once at each vertex).
### Comparison
the list might work better with level 1 cache with adjacency objects
(which node, visited, inPath, pathWeight, fromWhere).
## Depth First Search
### Pseudocode
` dfs(vertex w)`\
` if w has already been marked visited`\
` return`\
` mark w as visited`\
` for each adjacent vertex v`\
` dfs(v)`
Non recursive DFS is more difficult. It requires that each node keep
memory of the last child visited, as it descends the current child. One
implementation uses a indexed array of iterators, so on visiting a node,
the node\'s number is an index into an array that stores the iterator
for the nodes child. Then the first iterator value is pushed onto the
job stack. Peek not pop is used to examine the current top of the stack,
and pop is only invoked when the iterator for the peeked node is
exhausted.
### Properties
### Classification of Edge
#### Tree Edge
#### Backward Edge
#### Forward Edge
#### Cross Edge
IT is good techniques from :Yogesh Jakhar
## Breadth First Search
### Pseudocode
` bfs ( x ): `\
` q insert x;`\
` while (q not empty )`\
` y = remove head q`\
` visit y`\
` mark y`\
` for each z adjacent y `\
` q add tail z`
### Example
### Correctness
### Analysis
### Usage
A breadth first search can be used to explore a database schema, in an
attempt to turn it into an xml schema. This is done by naming the root
table, and then doing a referential breadth first search . The search is
both done on the referring and referred ends, so if another table refers
to to the current node being searched, than that table has a one-to-many
relationship in the xml schema, otherwise it is many-to-one.
## Classical Graph Problems
### Directed graph cycle detection
In a directed graph, check is \*acyclic\* by having a second marker on
before dfs recursive call and off after, and checking for second marker
before original mark check in dfs adjacency traversal. If second marker
present, then cycle exists.
### Topological Sort of Directed Graph
1. check for cycle as in previous section.
2. dfs the acyclic graph. Reverse postorder by storing on stack instead
of queue after dfs calls on adjacent nodes.
The last node on stack must be there from first dfs call, and removing
the last node exposes the second node which can only have been reached
by last node. Use induction to show topological order.
### Strongly Connected Components in Directed Graphs
1. Strong connected components have cycles within and must by acyclic
between components ( the kernel directed acyclic graph).
2. Difference between dfs reverse postorder of original graph vs the
same on reverse graph is that first node is least dependent in
latter. Thus all non strong connected nodes will be removed first by
dfs on the original graph in the latter\'s order, and then dfs will
remove only strongly connected nodes by marking , one SC component
at each iteration over reverse postorder of reverse graph , visiting
unmarked nodes only. Each outgoing edge from a SC component being
traversed will go to an already marked node due to reverse postorder
on reverse graph.
### Articulation Vertex
### Bridge
### Diameter
------------------------------------------------------------------------
|
# Algorithms/Distance approximations
Calculating distances is common in spatial and other search algorithms,
as well as in computer game physics engines. However, the common
Euclidean distance requires calculating **square roots**, which is often
a relatively heavy operation on a CPU.
## You don\'t need a square root to *compare* distances
Given (x1, y1) and (x2, y2), which is closer to the origin by Euclidean
distance? You might be tempted to calculate the two Euclidean distances,
and compare them:
d1 = sqrt(x1^2 + y1^2)
d2 = sqrt(x2^2 + y2^2)
return d1 > d2
But those square roots are often heavy to compute, and what\'s more,
*you don\'t need to compute them at all*. Do this instead:
dd1 = x1^2 + y1^2
dd2 = x2^2 + y2^2
return dd1 > dd2
The result is exactly the same (because the positive square root is a
*strictly monotonic* function). This only works for *comparing*
distances though, not for calculating individual values, which is
sometimes what you need. So we look at approximations.
## Approximations of Euclidean distance
### Taxicab/Manhattan/L1
The w:taxicab distance is one of the
simplest to compute, so use it when you\'re very tight on resources:
Given two points (x1, y1) and (x2, y2),
: $dx = | x1 - x2 |$ (w:absolute value)
: $dy = | y1 - y2 |$
: $d = dx + dy$ (taxicab distance)
Note that you can also use it as a \"first pass\" since it\'s **never
lower** than the Euclidean distance. You could check if data points are
within a particular bounding box, as a first pass for checking if they
are within the bounding sphere that you\'re really interested in. In
fact, if you take this idea further, you end up with an efficient
spatial data structure such as a w:Kd-tree.
However, be warned that taxicab distance is **not
w:isotropic** - if you\'re in a Euclidean
space, taxicab distances change a lot depending on which way your
\"grid\" is aligned. This can lead to big discrepancies if you use it as
a drop-in replacement for Euclidean distance. Octagonal distance
approximations help to knock some of the problematic corners off, giving
better isotropy:
### Octagonal
A fast approximation of 2D distance based on an octagonal boundary can
be computed as follows.
Given two points $(p_x, p_y)$ and $(q_x, q_y)$, Let $dx = | p_x - q_x |$
(w:absolute value) and
$dy = | p_y - q_y|$. If $dy > dx$, approximated distance is
$0.41 dx + 0.941246 dy$.
: Some years ago I developed a similar distance approximation
algorithm using three terms, instead of just 2, which is much more
accurate, and because it uses power of 2 denominators for the
coefficients can be implemented without using division hardware. The
formula is: *1007/1024 max(\|x\|,\|y\|) + 441/1024
min(\|x\|,\|y\|) - if ( max(\|x\|.\|y\|)\<16min(\|x\|,\|y\|),
40/1024 max(\|x\|,\|y\|), 0 )*. Also it is possible to implement a
distance approximation without using either multiplication or
division when you have very limited hardware: *((( max \<\< 8 ) + (
max \<\< 3 ) - ( max \<\< 4 ) - ( max \<\< 1 ) + ( min \<\< 7 ) - (
min \<\< 5 ) + ( min \<\< 3 ) - ( min \<\< 1 )) \>\> 8 )*. This is
just like the 2 coefficient min max algorithm presented earlier, but
with the coefficients 123/128 and 51/128. I have an article about it
at
<http://web.oroboro.com:90/rafael/docserv.php/index/programming/article/distance>
\--Rafael
: (Apparently that article has moved to
<http://www.flipcode.com/archives/Fast_Approximate_Distance_Functions.shtml>
?)
(Source for this
section)
------------------------------------------------------------------------
|
# Using Wikibooks/Scripting and the MediaWiki API
While this section is most useful for administrators, any user can make
use of the MediaWiki API, and hence this section should benefit any
Wikibookian.
### The MediaWiki API
MediaWiki offers a powerful API tool that can allow you to perform
virtually any task that you can do on-wiki using API calls. Consider the
following example:
https://en.wikipedia.org/w/api.php?action=query&prop=revisions&titles=Pet_door&rvslots=\*&rvprop=content&formatversion=2
Try it on your web browser. You\'ll get a page that looks like this:
> MediaWiki API result
>
> This is the HTML representation of the JSON format. HTML is good for
> debugging, but is unsuitable for application use.
>
> Specify the `<var>`{=html}format`</var>`{=html} parameter to change
> the output format. To see the non-HTML representation of the JSON
> format, set format=json.
>
> See the complete documentation, or the API help for more information.
and a bunch of JSON text, which contains the content of the title \"Pet
door\".
How does this help? Well, if you want to get the details of 100
articles, you do not have to manually visit all of them! Just use a
simple bash script that would do this work for you.
### Scripting
Now, how does this apply to a Wikibooks administrator? Suppose you\'re
working on a large deletion request. If there are
500 of the pages, manually deleting each page is likely to take hours
and cause frustration to you! Instead, use a Python 3 script! The
MediaWiki API page on MediaWiki.org
contains a list of all such API calls, and contains helpful example code
from which the code in this page was derived from.
First, the script. Here it is. The annotations explain what\'s going on.
``` python
import requests # import the necessary modules
S = requests.Session()
URL = "https://en.wikibooks.org/w/api.php" # the API location for Wikibooks
file_object = open("pages_to_delete.txt", "r", encoding="utf-8") # open the file in utf-8 encoding (otherwise files with accents and non-Latin characters may not work)
f1 = file_object.readlines()
# Step 1: Retrieve a login token
PARAMS_1 = {
"action": "query",
"meta": "tokens",
"type": "login",
"format": "json"
}
R = S.get(url=URL, params=PARAMS_1)
DATA = R.json()
LOGIN_TOKEN = DATA['query']['tokens']['logintoken']
# Step 2: Send a post request to login.
# Obtain credentials for BOT_USERNAME & BOT_PASSWORDS via Special:BotPasswords
# (https://www.mediawiki.org/wiki/Special:BotPasswords)
# You will need to make sure that the bot username has the necessary rights to perform the requested task
PARAMS_2 = {
"action": "login",
"lgname": "BOT_USERNAME",
"lgpassword": "BOT_PASSWORD",
"lgtoken": LOGIN_TOKEN,
"format": "json"
}
R = S.post(URL, data=PARAMS_2)
# Step 3: While logged in, get an CSRF token
PARAMS_3 = {
"action": "query",
"meta": "tokens",
"format": "json"
}
R = S.get(url=URL, params=PARAMS_3)
DATA = R.json()
CSRF_TOKEN = DATA["query"]["tokens"]["csrftoken"]
# Step 4: Send a post request to delete each page
for x in f1:
# depends on what you're doing - you may need to tweak the script a bit
if ("Pinyin" not in x):
continue
# remove possible trailing spaces
if (x.isalnum() == False):
xx = x.rstrip(x[-1])
else:
xx = x
print(xx)
# tell Wikibooks to delete!
PARAMS_4 = {
'action':"delete",
'title':xx,
'token':CSRF_TOKEN,
'format':"json"
}
R = S.post(URL, data=PARAMS_4)
DATA = R.json()
print(DATA)
print("done")
```
So how do you use it? Put this in a Python file, put all the pages to
delete in `pages_to_delete.txt`, and run it. Watch the output - if there
are errors, MediaWiki will let you know. Common issues include
- cannot find the requests module - install it using `pip`
- not adapting the script. For instance, if you\'re performing
undeletions, you may want to put the new pages in a different
location from the old ones. Make sure that they work as expected!
You may want to perform a test run first.
If you\'re stuck at any point, just ask at WB:RR.
Now, this can be easily adapted. Suppose instead of deleting, you want
to undelete these pages. Then all that is needed is replace `PARAMS_4`
to
``` python
PARAMS_4 = {
"action": "undelete",
"format": "json",
"token": CSRF_TOKEN,
"title": xx,
"reason": "per [[WB:RFU]]"
}
```
Even non-admins can benefit from the use of the script. Suppose you\'re
trying to mass-move pages. In that case, `PARAMS_4` can be changed to
``` python
PARAMS_4 = {
"action": "move",
"format": "json",
"from": "Current title",
"to": "Page with new title",
"reason": "Typo",
"movetalk": "1", # move the corresponding talk page
"noredirect": "1", # suppress redirects when moving (only available to reviewers and higher)
"token": CSRF_TOKEN
}
```
While unlikely, it is possible to run into ratelimit issues when running
scripts such as these. In that case, if you\'re not yet a reviewer, the
best choice would be to become one.
|
# Nanotechnology/Perspective#
Navigate
---------------------------------------------------------
\<\< Prev: Introduction
\>\< Main: Nanotechnology
\>\> Next: Overviews
\_\_TOC\_\_
------------------------------------------------------------------------
# A perspective on Nanotechnology
**Nanotechnology in the Middle Ages?**
The Duke TIP eStudies Nanotechnology course will be adding more to this
section (this will be completed by 22 Jun 08)
One of the first uses of nanotechnology was in the Middle Ages. It was
done by using gold nanoparticles to make red pigments in stained glass
showing that nanotechnology has been around for centuries. The gold when
clumped together appears gold, but certain sized particles when spread
out appear different colors. Reference: The Nanotech Pioneers Where are
they taking us? By Steven A Edwards
In the year 1974 at the Tokyo Science University, Professor Norio
Taniigrichi came up with the term
nanotechnology.
Nanotechnology was first used to describe the extension of traditional
silicon machining down into regions smaller than one micron (one
millionth of a meter) by Tokyo Science University Professor Norio
Taniguchi in 1974. It is now commonly used to describe the engineering
and fabrication of objects with features smaller than 100 nanometers
(one tenth of a micron). [^1]
Nanotechnology has been used for thousands of years, although people did
not know what they were doing. For example, stained glass was the
product of nanofabrication of gold. Medieval forgers were the first
nanotecnologists in a sense, because they, by accident, found out a way
to make stained glass.
Reference Nanotechnology A GENTLE INTRODUCTION TO THE NEXT BIG IDEA By
Mark Ratner & Daniel Ratner
In 2001, the federal government announced the National Nanotechnology
Intiative to coordinate the work of different U.S. agencies and to
provide funds for research and accelerate development in nanotechnology.
This was spearheaded by Mahail Roco and supported by both president
Clinton and Bush.
References The Nanotech Pioneers Where are they taking us? By Steven A.
Edwards
<http://www.nano.gov/html/about/docs/20070521NNI_Industrial_Nano_Impact_NSTI_Carim.pdf>
**A Vision**
Richard Feynman was a man of great importance to the field of
nanotechnology. He was a man with a vision. He believed that with
research we could change things on a small scale. In his famous speech
There\'s Plenty of Room at the
Bottom in 1959, Richard
Feynman discussed the possibility of
manipulating and controlling things on a molecular scale in order to
achieve electronic and mechanical systems with atomic sized components.
He concluded that the development of technologies to construct such
small systems would be interdisciplinary, combining fields such as
physics, chemistry and biology, and would offer a new world of
possibilities that could radically change the technology around us.
**Miniaturization**
A few years later, in 1965, Moore
noted that the number of transistors on a chip had roughly doubled every
other year since 1959, and predicted that the trend was likely to hold
as each new generation of microsystems
would help to develop the next generation at lower prices and with
smaller components. To date, the semiconductor industry has been able to
fulfill Moore\'s Law, in part through the reduction of lateral feature
sizes on silicon chips from around 10 micrometers in 1965 to 45-65 nm in
2007 via changing from the use of optical contact lithography to deep
ultraviolet projection lithography.
In 1974 in Japan, Norio Taniguchi coined the word \"nano-technology\"
[^2] to describe semiconductor processes such as thin film deposition
and ion beam milling exhibiting characteristic control on the order of a
nanometer: \"'Nano-technology' mainly consists of the processing of
separation, consolidation, and deformation of materials by one atom or
one molecule.\"
Since Feynman\'s 1959 speech the arts of \"seeing\" and \"manipulation\"
at the nanoscale have progressed from transmission electron microscopy
(TEM) and scanning electron microscopy (SEM) to various forms of
scanning probe microscopy including scanning tunneling microscopy
(STM) developed by Binnig and Rohrer
at IBM Zurich and atomic force microscopy
(AFM) devloped by (Binnig and Quate?)
The STM, in particular, is capable of single-atom manipulation on
conducting surfaces and has been used to build \"quantum corrals\" of
atoms in which quantum mechanical wave function phenomena can be
discerned. These atomic-scale manipulation capabilities prompt thoughts
of building up complex atomic structures via manipulation rather than
traditional stochastic chemistry. (Note: this pragraph is still rough
and references are needed.)
Motivated by Feynman's beliefs building things nanoscale top-down, Eric
Drexler devoted much of his research to making a universal assembler.
The American engineer Eric Drexler has
speculated extensively about the laboratory synthesis of machines at the
molecular level via manipulation techniques, emulating biochemistry and
producing components much smaller than any microprocessor via techniques
which have been called molecular
nanotechnology or MNT. [^3] [^4]
[^5]
Successful realization of the
MNT dream would comprise a
collection of technologies which are not currently practical, and the
dream has resulted in considerable hyperbolic description of the
resulting capabilities. While realization of these capabilities would be
a vindication of the hype associated with MNT, concrete plans for
anything other than computer modeling of finished structures are scant.
Somehow, a means has to be found for MNT design evolution at the
nanoscale which mimics the process of biological evolution at the
molecular scale. Biological evolution proceeds by random variation in
ensemble averages of organisms combined with culling of the
less-successful variants and reproduction of the more-successful
variants, and macroscale engineering design also proceeds by a process
of design evolution from simplicity to complexity as set forth somewhat
satirically by John Gall: \"A
complex system that works is invariably found to have evolved from a
simple system that worked. . . . A complex system designed from scratch
never works and can not be patched up to make it work. You have to start
over, beginning with a system that works.\" \<ref name=\"JohnGall\>
Gall, John, (1986) Systemantics: How Systems Really Work and How They
Fail, 2nd ed. Ann Arbor, MI : The General Systemantics Press.
```{=html}
</ref>
```
A breakthrough in MNT is needed
which proceeds from the simple atomic ensembles which can be built with,
e.g., an STM to complex
MNT systems via a process of
design evolution. A handicap in this process is the difficulty of seeing
and manipulation at the nanoscale compared to the macroscale which makes
deterministic selection of successful trials difficult; in contrast
biological evolution proceeds via action of what Richard Dawkins has
called the \"blind watchmaker\" [^6] comprising random molecular
variation and deterministic survival/death.
**Technological development and limits**
The impact on society and our lives of the continuous downscaling of
systems is profound, and continues to open up new frontiers and
possibilities. However, no exponential growth can continue forever, and
the semiconductor industry will eventually reach the atomic limit for
downsizing the transistor. Atoms in solid matter are typically one or
two hundred picometers apart so nanotechnology involves manipulating
individual structures which are between ten and ten thousand atoms
across; for example, the gate length of a 45 nm transistor is about 180
silicon atoms long. Such very small structures are vulnerable to
molecular level damage by cosmic rays, thermal activity, and so forth.
The way in which they are assembled, designed and used is different from
prior microelectronics.
**New ways**
Today, as that limit still seems to be some 20 years in the future, the
growth is beginning to take new directions, indicating that the atomic
limit might not be the limiting factor for technological development in
the future, because systems are becoming more diverse and because new
effects appear when the systems become so small that quantum effects
dominate. The semiconductor devices show an increased diversification,
dividing for instance processors into very different systems such as
those for cheap disposable chips, low power consumption portable
devices, or high processing power devices. Microfabrication is also
merging with other branches of science to include for instance chemical
and optical micro systems. In addition, microbiology and biochemistry
are becoming important for applications of all the developing methods.
This diversity seems to be increasing on all levels in technology and
many of these cross-disciplinary developments are linked to
nanotechnology.
**Diversification**
As the components become so small that quantum effects become important,
the diversity will probably further increase as completely new devices
and possibilities begin to open up that are not possible with the bulk
materials of today\'s technology.
**The nanorevolution?**
The visions of Feynman are today shared by many others: when
nanotechnology is seen as a general cross disciplinary technology, it
has the potential to create a coming \"industrial\" revolution that will
have a major impact on society and everyday life, comparable to or
exceeding the impact of electricity and information technology.
# Nanocomponents, Tools, and Methods
**A positive spiral**
As an emerging technology, the methods and components of nanotechnology
are under continuous development and each generation is providing a
better foundation for the following generation.
**Seeing \'nano\'**
With regards to the methods, the Scanning tunneling microscope
(STM) and Atomic Force
Microscope (AFM) were developed
in the 1980s and opened up completely new ways to investigate nanoscale
materials. An important aspect was the novel possibility to directly
manipulate nanoscale objects. Transmission and scanning electron
microscopes (TEM and
SEM) had been available
since the 30s, and offered the possibility to image as well as create
nanodevices by electron beam
lithography.
**New nanomaterials**
Several unique nanoscale structures were also discovered around 1990:
the Carbon-60 molecule and later the carbon
nanotubes. In recent years, more complex
nanostructures such as semiconductor nanowire
heterostructures have also proven to be useful building blocks or
components in nanodevices.
**So what can I use this \'nano\' for?**
The applications of such nanocomponents span all aspects of technology:
Electronics, optics/photonics, medical, and
biochemical, as well as better and smarter materials. But to date few
real products are available with nanoscale components, apart from
traditional nanoscale products, such as paint with nanoparticles or
catalytic particles for chemical reactors.
Prototype devices have been created from individual nanocomponents, but
actual production is still on the verge. As when integrated electronics
were developed, nanotechnology is currently in the phase where component
production methods, characterization methods, tools for manipulation and
integration are evolving by mutual support and convergence.
**Difficult nanointegration**
A main problem is reliable integration of the nanoscale components into
microsystems, since the production methods
are often not compatible. For fabrication of devices with integrated
nanocomponents, the optimal manipulation technique is of course to have
the individual components self-assembling or growing into the required
complex systems. Self assembly of devices in liquids is an expanding
field within nanotechnology but usually requires the components to be
covered in various surfactants, which usually also influence the
component properties. To avoid surface treatments, nanotubes and
whiskers/wires can be grown on chips and
microsystems directly from pre-patterned
catalytic particles. Although promising for future large scale
production of devices, few working devices have been made by the method
to date.
The prevailing integration technique for nanowire/tube systems seems to
be electron beam lithography
(EBL) of metal structures onto
substrates with randomly positioned nanowires deposited from liquid
dispersions. By using flow alignment or electrical fields, the wire
deposition from liquids can be controlled to some extent. The EBL method
has allowed for systematic investigations of nanowires\' and tubes\'
electrical properties, and creation of high performance electronic
components such as field-effect transistors and chemical sensors. These
proof-of-principle devices are some of the few but important
demonstrations of devices nanotechnology might offer. In addition,
nanomechanical structures have also recently been demonstrated, such as
a rotational actuator with a carbon nanotube axis built by Fennimore et
al.
A more active approach to creating nanowire structures is to use
Scanning probe microscopy(SPM)
to push, slide and roll the nanostructures across surfaces. SPM
manipulation has been used to create and study nanotube junctions and
properties. The ability to manipulate individual nanoscale objects has
hence proven very useful for building proof-of-principle devices and
prototypes, as well as for characterizing and testing components.
**Top-down manufacturing** takes bulky products and shrinks them to the
nano scale, vs. bottom-up manufacturing is when individual molecules are
placed in a specific order to make a product.[^7] The **bottom-up
self-assembly** method may be important for future large scale
production as well as many of the different approaches to improve the
top-down lithographic processes. Such techniques could hence become
important factors in the self-sustaining development of nanotechnology.
# Hot and hyped
**Suddenly everything is \'nano\'**
There\'s no question that the field of nanotechnology has quite a sense
of hype to it - many universities have created new nanotech departments
and courses. But there is also a vision behind the hype and emerging
results - which are truly very few in industrial production, but
nevertheless hold promise for a bright future. In the hype, many things
that were once chemistry, microtechnology,
optics, mesoscopic or cluster physics, have been
reborn as nanotechnology.
**Nanotech is old**
You can find nanotechnology in the sunscreen you use in the summer, and
some paints and coatings can also be called nanotech since they all
contain nanoparticles with unique optical properties. In a way,
nanoparticles have been known in optics for
hundreds of years if you like to take a broad perspective on things,
since they have been used to stain and color
glasses, etc. since the middle ages.
Nano-size particles of gold were used to create red pigments.[^8]
Catalysis is a major industrial process,
without which not many of the materials we have around us today would be
possible to make, and catalysis is often highly dependent on nanoscale
catalytic particles. In this way thousands of tons of nanotechnology
have been used with great benefit for years.
Nanoscale wires and tubes have only recently really been given attention
with the advent of carbon nanotubes and
semiconductor nanowires, while nanoscale films are ever present in
antireflection coatings on your glasses and binoculars, and thin metal
films have been used for sensitive detection with surface
plasmons for decades. Surface
plasmons are excitations of the charges at a surface. Nanowires actually
were observed in the middle ages - well, they did not have the means to
observe them, but saw whiskers grow from melted metals.
The better control over the nanostructure of materials has led to
optimization of all these phenomena - and the emergence of many new
methods and possibilities.
**An example**
Take for instance nano-optics: The surface plasmons turn out to be very
efficient at enhancing local electrical fields and work as a local
amplifier for optical fields, making a laser seem much more powerful to
atoms in the vicinity of the surface plasmon. From this comes the
surface enhanced raman spectroscopy
which is increasingly used today because it makes it possible to do
sensitive raman spectroscopy on the large majority of samples that would
otherwise be impossible to make such spectra on. In addition, photonic
crystals, fancy new quantum light
sources that can make single photons on demand and other non-classical
photon states are being developed, based on nanotechnology.
**The future**
There are definitely future scientific applications and commercial
potential of all these new methods to handle light, use it for extremely
sensitive detection and control its interaction with matter - and so it
seems nanotechnology, being about making smaller versions of existing
technology as well as new technology, is worth a bit of hype.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: N. Taniguchi, \"On the Basic Concept of \'Nano-Technology\',\"
Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of
Precision Engineering, 1974.
[^3]: Steven A. Edwards, *The Nanotech Pioneers*, (WILEY-VCH, 2006)
[^4]: Eric Drexler, *Engines of Creation*, (New York: Anchor
Press/Doubleday, 1986).
[^5]: Eric Drexler, *Nanosystems: Molecular Machinery, Manufacturing and
Computation*, (New York: John Wiley, 1992).
[^6]: Richard Dawkins, The Blind Watchmaker: Why the Evidence of
Evolution Reveals a Universe Without Design, W. W. Norton; Reissue
edition (September 19, 1996)
[^7]: Eric Drexler, *Engines of Creation*
[^8]: Nanotech Pioneers, Steven A. Edwards (WILEY-VCH, 2006, Weinheim)
|
# Nanotechnology/Perspective#A perspective on Nanotechnology
Navigate
---------------------------------------------------------
\<\< Prev: Introduction
\>\< Main: Nanotechnology
\>\> Next: Overviews
\_\_TOC\_\_
------------------------------------------------------------------------
# A perspective on Nanotechnology
**Nanotechnology in the Middle Ages?**
The Duke TIP eStudies Nanotechnology course will be adding more to this
section (this will be completed by 22 Jun 08)
One of the first uses of nanotechnology was in the Middle Ages. It was
done by using gold nanoparticles to make red pigments in stained glass
showing that nanotechnology has been around for centuries. The gold when
clumped together appears gold, but certain sized particles when spread
out appear different colors. Reference: The Nanotech Pioneers Where are
they taking us? By Steven A Edwards
In the year 1974 at the Tokyo Science University, Professor Norio
Taniigrichi came up with the term
nanotechnology.
Nanotechnology was first used to describe the extension of traditional
silicon machining down into regions smaller than one micron (one
millionth of a meter) by Tokyo Science University Professor Norio
Taniguchi in 1974. It is now commonly used to describe the engineering
and fabrication of objects with features smaller than 100 nanometers
(one tenth of a micron). [^1]
Nanotechnology has been used for thousands of years, although people did
not know what they were doing. For example, stained glass was the
product of nanofabrication of gold. Medieval forgers were the first
nanotecnologists in a sense, because they, by accident, found out a way
to make stained glass.
Reference Nanotechnology A GENTLE INTRODUCTION TO THE NEXT BIG IDEA By
Mark Ratner & Daniel Ratner
In 2001, the federal government announced the National Nanotechnology
Intiative to coordinate the work of different U.S. agencies and to
provide funds for research and accelerate development in nanotechnology.
This was spearheaded by Mahail Roco and supported by both president
Clinton and Bush.
References The Nanotech Pioneers Where are they taking us? By Steven A.
Edwards
<http://www.nano.gov/html/about/docs/20070521NNI_Industrial_Nano_Impact_NSTI_Carim.pdf>
**A Vision**
Richard Feynman was a man of great importance to the field of
nanotechnology. He was a man with a vision. He believed that with
research we could change things on a small scale. In his famous speech
There\'s Plenty of Room at the
Bottom in 1959, Richard
Feynman discussed the possibility of
manipulating and controlling things on a molecular scale in order to
achieve electronic and mechanical systems with atomic sized components.
He concluded that the development of technologies to construct such
small systems would be interdisciplinary, combining fields such as
physics, chemistry and biology, and would offer a new world of
possibilities that could radically change the technology around us.
**Miniaturization**
A few years later, in 1965, Moore
noted that the number of transistors on a chip had roughly doubled every
other year since 1959, and predicted that the trend was likely to hold
as each new generation of microsystems
would help to develop the next generation at lower prices and with
smaller components. To date, the semiconductor industry has been able to
fulfill Moore\'s Law, in part through the reduction of lateral feature
sizes on silicon chips from around 10 micrometers in 1965 to 45-65 nm in
2007 via changing from the use of optical contact lithography to deep
ultraviolet projection lithography.
In 1974 in Japan, Norio Taniguchi coined the word \"nano-technology\"
[^2] to describe semiconductor processes such as thin film deposition
and ion beam milling exhibiting characteristic control on the order of a
nanometer: \"'Nano-technology' mainly consists of the processing of
separation, consolidation, and deformation of materials by one atom or
one molecule.\"
Since Feynman\'s 1959 speech the arts of \"seeing\" and \"manipulation\"
at the nanoscale have progressed from transmission electron microscopy
(TEM) and scanning electron microscopy (SEM) to various forms of
scanning probe microscopy including scanning tunneling microscopy
(STM) developed by Binnig and Rohrer
at IBM Zurich and atomic force microscopy
(AFM) devloped by (Binnig and Quate?)
The STM, in particular, is capable of single-atom manipulation on
conducting surfaces and has been used to build \"quantum corrals\" of
atoms in which quantum mechanical wave function phenomena can be
discerned. These atomic-scale manipulation capabilities prompt thoughts
of building up complex atomic structures via manipulation rather than
traditional stochastic chemistry. (Note: this pragraph is still rough
and references are needed.)
Motivated by Feynman's beliefs building things nanoscale top-down, Eric
Drexler devoted much of his research to making a universal assembler.
The American engineer Eric Drexler has
speculated extensively about the laboratory synthesis of machines at the
molecular level via manipulation techniques, emulating biochemistry and
producing components much smaller than any microprocessor via techniques
which have been called molecular
nanotechnology or MNT. [^3] [^4]
[^5]
Successful realization of the
MNT dream would comprise a
collection of technologies which are not currently practical, and the
dream has resulted in considerable hyperbolic description of the
resulting capabilities. While realization of these capabilities would be
a vindication of the hype associated with MNT, concrete plans for
anything other than computer modeling of finished structures are scant.
Somehow, a means has to be found for MNT design evolution at the
nanoscale which mimics the process of biological evolution at the
molecular scale. Biological evolution proceeds by random variation in
ensemble averages of organisms combined with culling of the
less-successful variants and reproduction of the more-successful
variants, and macroscale engineering design also proceeds by a process
of design evolution from simplicity to complexity as set forth somewhat
satirically by John Gall: \"A
complex system that works is invariably found to have evolved from a
simple system that worked. . . . A complex system designed from scratch
never works and can not be patched up to make it work. You have to start
over, beginning with a system that works.\" \<ref name=\"JohnGall\>
Gall, John, (1986) Systemantics: How Systems Really Work and How They
Fail, 2nd ed. Ann Arbor, MI : The General Systemantics Press.
```{=html}
</ref>
```
A breakthrough in MNT is needed
which proceeds from the simple atomic ensembles which can be built with,
e.g., an STM to complex
MNT systems via a process of
design evolution. A handicap in this process is the difficulty of seeing
and manipulation at the nanoscale compared to the macroscale which makes
deterministic selection of successful trials difficult; in contrast
biological evolution proceeds via action of what Richard Dawkins has
called the \"blind watchmaker\" [^6] comprising random molecular
variation and deterministic survival/death.
**Technological development and limits**
The impact on society and our lives of the continuous downscaling of
systems is profound, and continues to open up new frontiers and
possibilities. However, no exponential growth can continue forever, and
the semiconductor industry will eventually reach the atomic limit for
downsizing the transistor. Atoms in solid matter are typically one or
two hundred picometers apart so nanotechnology involves manipulating
individual structures which are between ten and ten thousand atoms
across; for example, the gate length of a 45 nm transistor is about 180
silicon atoms long. Such very small structures are vulnerable to
molecular level damage by cosmic rays, thermal activity, and so forth.
The way in which they are assembled, designed and used is different from
prior microelectronics.
**New ways**
Today, as that limit still seems to be some 20 years in the future, the
growth is beginning to take new directions, indicating that the atomic
limit might not be the limiting factor for technological development in
the future, because systems are becoming more diverse and because new
effects appear when the systems become so small that quantum effects
dominate. The semiconductor devices show an increased diversification,
dividing for instance processors into very different systems such as
those for cheap disposable chips, low power consumption portable
devices, or high processing power devices. Microfabrication is also
merging with other branches of science to include for instance chemical
and optical micro systems. In addition, microbiology and biochemistry
are becoming important for applications of all the developing methods.
This diversity seems to be increasing on all levels in technology and
many of these cross-disciplinary developments are linked to
nanotechnology.
**Diversification**
As the components become so small that quantum effects become important,
the diversity will probably further increase as completely new devices
and possibilities begin to open up that are not possible with the bulk
materials of today\'s technology.
**The nanorevolution?**
The visions of Feynman are today shared by many others: when
nanotechnology is seen as a general cross disciplinary technology, it
has the potential to create a coming \"industrial\" revolution that will
have a major impact on society and everyday life, comparable to or
exceeding the impact of electricity and information technology.
# Nanocomponents, Tools, and Methods
**A positive spiral**
As an emerging technology, the methods and components of nanotechnology
are under continuous development and each generation is providing a
better foundation for the following generation.
**Seeing \'nano\'**
With regards to the methods, the Scanning tunneling microscope
(STM) and Atomic Force
Microscope (AFM) were developed
in the 1980s and opened up completely new ways to investigate nanoscale
materials. An important aspect was the novel possibility to directly
manipulate nanoscale objects. Transmission and scanning electron
microscopes (TEM and
SEM) had been available
since the 30s, and offered the possibility to image as well as create
nanodevices by electron beam
lithography.
**New nanomaterials**
Several unique nanoscale structures were also discovered around 1990:
the Carbon-60 molecule and later the carbon
nanotubes. In recent years, more complex
nanostructures such as semiconductor nanowire
heterostructures have also proven to be useful building blocks or
components in nanodevices.
**So what can I use this \'nano\' for?**
The applications of such nanocomponents span all aspects of technology:
Electronics, optics/photonics, medical, and
biochemical, as well as better and smarter materials. But to date few
real products are available with nanoscale components, apart from
traditional nanoscale products, such as paint with nanoparticles or
catalytic particles for chemical reactors.
Prototype devices have been created from individual nanocomponents, but
actual production is still on the verge. As when integrated electronics
were developed, nanotechnology is currently in the phase where component
production methods, characterization methods, tools for manipulation and
integration are evolving by mutual support and convergence.
**Difficult nanointegration**
A main problem is reliable integration of the nanoscale components into
microsystems, since the production methods
are often not compatible. For fabrication of devices with integrated
nanocomponents, the optimal manipulation technique is of course to have
the individual components self-assembling or growing into the required
complex systems. Self assembly of devices in liquids is an expanding
field within nanotechnology but usually requires the components to be
covered in various surfactants, which usually also influence the
component properties. To avoid surface treatments, nanotubes and
whiskers/wires can be grown on chips and
microsystems directly from pre-patterned
catalytic particles. Although promising for future large scale
production of devices, few working devices have been made by the method
to date.
The prevailing integration technique for nanowire/tube systems seems to
be electron beam lithography
(EBL) of metal structures onto
substrates with randomly positioned nanowires deposited from liquid
dispersions. By using flow alignment or electrical fields, the wire
deposition from liquids can be controlled to some extent. The EBL method
has allowed for systematic investigations of nanowires\' and tubes\'
electrical properties, and creation of high performance electronic
components such as field-effect transistors and chemical sensors. These
proof-of-principle devices are some of the few but important
demonstrations of devices nanotechnology might offer. In addition,
nanomechanical structures have also recently been demonstrated, such as
a rotational actuator with a carbon nanotube axis built by Fennimore et
al.
A more active approach to creating nanowire structures is to use
Scanning probe microscopy(SPM)
to push, slide and roll the nanostructures across surfaces. SPM
manipulation has been used to create and study nanotube junctions and
properties. The ability to manipulate individual nanoscale objects has
hence proven very useful for building proof-of-principle devices and
prototypes, as well as for characterizing and testing components.
**Top-down manufacturing** takes bulky products and shrinks them to the
nano scale, vs. bottom-up manufacturing is when individual molecules are
placed in a specific order to make a product.[^7] The **bottom-up
self-assembly** method may be important for future large scale
production as well as many of the different approaches to improve the
top-down lithographic processes. Such techniques could hence become
important factors in the self-sustaining development of nanotechnology.
# Hot and hyped
**Suddenly everything is \'nano\'**
There\'s no question that the field of nanotechnology has quite a sense
of hype to it - many universities have created new nanotech departments
and courses. But there is also a vision behind the hype and emerging
results - which are truly very few in industrial production, but
nevertheless hold promise for a bright future. In the hype, many things
that were once chemistry, microtechnology,
optics, mesoscopic or cluster physics, have been
reborn as nanotechnology.
**Nanotech is old**
You can find nanotechnology in the sunscreen you use in the summer, and
some paints and coatings can also be called nanotech since they all
contain nanoparticles with unique optical properties. In a way,
nanoparticles have been known in optics for
hundreds of years if you like to take a broad perspective on things,
since they have been used to stain and color
glasses, etc. since the middle ages.
Nano-size particles of gold were used to create red pigments.[^8]
Catalysis is a major industrial process,
without which not many of the materials we have around us today would be
possible to make, and catalysis is often highly dependent on nanoscale
catalytic particles. In this way thousands of tons of nanotechnology
have been used with great benefit for years.
Nanoscale wires and tubes have only recently really been given attention
with the advent of carbon nanotubes and
semiconductor nanowires, while nanoscale films are ever present in
antireflection coatings on your glasses and binoculars, and thin metal
films have been used for sensitive detection with surface
plasmons for decades. Surface
plasmons are excitations of the charges at a surface. Nanowires actually
were observed in the middle ages - well, they did not have the means to
observe them, but saw whiskers grow from melted metals.
The better control over the nanostructure of materials has led to
optimization of all these phenomena - and the emergence of many new
methods and possibilities.
**An example**
Take for instance nano-optics: The surface plasmons turn out to be very
efficient at enhancing local electrical fields and work as a local
amplifier for optical fields, making a laser seem much more powerful to
atoms in the vicinity of the surface plasmon. From this comes the
surface enhanced raman spectroscopy
which is increasingly used today because it makes it possible to do
sensitive raman spectroscopy on the large majority of samples that would
otherwise be impossible to make such spectra on. In addition, photonic
crystals, fancy new quantum light
sources that can make single photons on demand and other non-classical
photon states are being developed, based on nanotechnology.
**The future**
There are definitely future scientific applications and commercial
potential of all these new methods to handle light, use it for extremely
sensitive detection and control its interaction with matter - and so it
seems nanotechnology, being about making smaller versions of existing
technology as well as new technology, is worth a bit of hype.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: N. Taniguchi, \"On the Basic Concept of \'Nano-Technology\',\"
Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of
Precision Engineering, 1974.
[^3]: Steven A. Edwards, *The Nanotech Pioneers*, (WILEY-VCH, 2006)
[^4]: Eric Drexler, *Engines of Creation*, (New York: Anchor
Press/Doubleday, 1986).
[^5]: Eric Drexler, *Nanosystems: Molecular Machinery, Manufacturing and
Computation*, (New York: John Wiley, 1992).
[^6]: Richard Dawkins, The Blind Watchmaker: Why the Evidence of
Evolution Reveals a Universe Without Design, W. W. Norton; Reissue
edition (September 19, 1996)
[^7]: Eric Drexler, *Engines of Creation*
[^8]: Nanotech Pioneers, Steven A. Edwards (WILEY-VCH, 2006, Weinheim)
|
# Nanotechnology/Perspective#Nanocomponents.2C Tools.2C and Methods
Navigate
---------------------------------------------------------
\<\< Prev: Introduction
\>\< Main: Nanotechnology
\>\> Next: Overviews
\_\_TOC\_\_
------------------------------------------------------------------------
# A perspective on Nanotechnology
**Nanotechnology in the Middle Ages?**
The Duke TIP eStudies Nanotechnology course will be adding more to this
section (this will be completed by 22 Jun 08)
One of the first uses of nanotechnology was in the Middle Ages. It was
done by using gold nanoparticles to make red pigments in stained glass
showing that nanotechnology has been around for centuries. The gold when
clumped together appears gold, but certain sized particles when spread
out appear different colors. Reference: The Nanotech Pioneers Where are
they taking us? By Steven A Edwards
In the year 1974 at the Tokyo Science University, Professor Norio
Taniigrichi came up with the term
nanotechnology.
Nanotechnology was first used to describe the extension of traditional
silicon machining down into regions smaller than one micron (one
millionth of a meter) by Tokyo Science University Professor Norio
Taniguchi in 1974. It is now commonly used to describe the engineering
and fabrication of objects with features smaller than 100 nanometers
(one tenth of a micron). [^1]
Nanotechnology has been used for thousands of years, although people did
not know what they were doing. For example, stained glass was the
product of nanofabrication of gold. Medieval forgers were the first
nanotecnologists in a sense, because they, by accident, found out a way
to make stained glass.
Reference Nanotechnology A GENTLE INTRODUCTION TO THE NEXT BIG IDEA By
Mark Ratner & Daniel Ratner
In 2001, the federal government announced the National Nanotechnology
Intiative to coordinate the work of different U.S. agencies and to
provide funds for research and accelerate development in nanotechnology.
This was spearheaded by Mahail Roco and supported by both president
Clinton and Bush.
References The Nanotech Pioneers Where are they taking us? By Steven A.
Edwards
<http://www.nano.gov/html/about/docs/20070521NNI_Industrial_Nano_Impact_NSTI_Carim.pdf>
**A Vision**
Richard Feynman was a man of great importance to the field of
nanotechnology. He was a man with a vision. He believed that with
research we could change things on a small scale. In his famous speech
There\'s Plenty of Room at the
Bottom in 1959, Richard
Feynman discussed the possibility of
manipulating and controlling things on a molecular scale in order to
achieve electronic and mechanical systems with atomic sized components.
He concluded that the development of technologies to construct such
small systems would be interdisciplinary, combining fields such as
physics, chemistry and biology, and would offer a new world of
possibilities that could radically change the technology around us.
**Miniaturization**
A few years later, in 1965, Moore
noted that the number of transistors on a chip had roughly doubled every
other year since 1959, and predicted that the trend was likely to hold
as each new generation of microsystems
would help to develop the next generation at lower prices and with
smaller components. To date, the semiconductor industry has been able to
fulfill Moore\'s Law, in part through the reduction of lateral feature
sizes on silicon chips from around 10 micrometers in 1965 to 45-65 nm in
2007 via changing from the use of optical contact lithography to deep
ultraviolet projection lithography.
In 1974 in Japan, Norio Taniguchi coined the word \"nano-technology\"
[^2] to describe semiconductor processes such as thin film deposition
and ion beam milling exhibiting characteristic control on the order of a
nanometer: \"'Nano-technology' mainly consists of the processing of
separation, consolidation, and deformation of materials by one atom or
one molecule.\"
Since Feynman\'s 1959 speech the arts of \"seeing\" and \"manipulation\"
at the nanoscale have progressed from transmission electron microscopy
(TEM) and scanning electron microscopy (SEM) to various forms of
scanning probe microscopy including scanning tunneling microscopy
(STM) developed by Binnig and Rohrer
at IBM Zurich and atomic force microscopy
(AFM) devloped by (Binnig and Quate?)
The STM, in particular, is capable of single-atom manipulation on
conducting surfaces and has been used to build \"quantum corrals\" of
atoms in which quantum mechanical wave function phenomena can be
discerned. These atomic-scale manipulation capabilities prompt thoughts
of building up complex atomic structures via manipulation rather than
traditional stochastic chemistry. (Note: this pragraph is still rough
and references are needed.)
Motivated by Feynman's beliefs building things nanoscale top-down, Eric
Drexler devoted much of his research to making a universal assembler.
The American engineer Eric Drexler has
speculated extensively about the laboratory synthesis of machines at the
molecular level via manipulation techniques, emulating biochemistry and
producing components much smaller than any microprocessor via techniques
which have been called molecular
nanotechnology or MNT. [^3] [^4]
[^5]
Successful realization of the
MNT dream would comprise a
collection of technologies which are not currently practical, and the
dream has resulted in considerable hyperbolic description of the
resulting capabilities. While realization of these capabilities would be
a vindication of the hype associated with MNT, concrete plans for
anything other than computer modeling of finished structures are scant.
Somehow, a means has to be found for MNT design evolution at the
nanoscale which mimics the process of biological evolution at the
molecular scale. Biological evolution proceeds by random variation in
ensemble averages of organisms combined with culling of the
less-successful variants and reproduction of the more-successful
variants, and macroscale engineering design also proceeds by a process
of design evolution from simplicity to complexity as set forth somewhat
satirically by John Gall: \"A
complex system that works is invariably found to have evolved from a
simple system that worked. . . . A complex system designed from scratch
never works and can not be patched up to make it work. You have to start
over, beginning with a system that works.\" \<ref name=\"JohnGall\>
Gall, John, (1986) Systemantics: How Systems Really Work and How They
Fail, 2nd ed. Ann Arbor, MI : The General Systemantics Press.
```{=html}
</ref>
```
A breakthrough in MNT is needed
which proceeds from the simple atomic ensembles which can be built with,
e.g., an STM to complex
MNT systems via a process of
design evolution. A handicap in this process is the difficulty of seeing
and manipulation at the nanoscale compared to the macroscale which makes
deterministic selection of successful trials difficult; in contrast
biological evolution proceeds via action of what Richard Dawkins has
called the \"blind watchmaker\" [^6] comprising random molecular
variation and deterministic survival/death.
**Technological development and limits**
The impact on society and our lives of the continuous downscaling of
systems is profound, and continues to open up new frontiers and
possibilities. However, no exponential growth can continue forever, and
the semiconductor industry will eventually reach the atomic limit for
downsizing the transistor. Atoms in solid matter are typically one or
two hundred picometers apart so nanotechnology involves manipulating
individual structures which are between ten and ten thousand atoms
across; for example, the gate length of a 45 nm transistor is about 180
silicon atoms long. Such very small structures are vulnerable to
molecular level damage by cosmic rays, thermal activity, and so forth.
The way in which they are assembled, designed and used is different from
prior microelectronics.
**New ways**
Today, as that limit still seems to be some 20 years in the future, the
growth is beginning to take new directions, indicating that the atomic
limit might not be the limiting factor for technological development in
the future, because systems are becoming more diverse and because new
effects appear when the systems become so small that quantum effects
dominate. The semiconductor devices show an increased diversification,
dividing for instance processors into very different systems such as
those for cheap disposable chips, low power consumption portable
devices, or high processing power devices. Microfabrication is also
merging with other branches of science to include for instance chemical
and optical micro systems. In addition, microbiology and biochemistry
are becoming important for applications of all the developing methods.
This diversity seems to be increasing on all levels in technology and
many of these cross-disciplinary developments are linked to
nanotechnology.
**Diversification**
As the components become so small that quantum effects become important,
the diversity will probably further increase as completely new devices
and possibilities begin to open up that are not possible with the bulk
materials of today\'s technology.
**The nanorevolution?**
The visions of Feynman are today shared by many others: when
nanotechnology is seen as a general cross disciplinary technology, it
has the potential to create a coming \"industrial\" revolution that will
have a major impact on society and everyday life, comparable to or
exceeding the impact of electricity and information technology.
# Nanocomponents, Tools, and Methods
**A positive spiral**
As an emerging technology, the methods and components of nanotechnology
are under continuous development and each generation is providing a
better foundation for the following generation.
**Seeing \'nano\'**
With regards to the methods, the Scanning tunneling microscope
(STM) and Atomic Force
Microscope (AFM) were developed
in the 1980s and opened up completely new ways to investigate nanoscale
materials. An important aspect was the novel possibility to directly
manipulate nanoscale objects. Transmission and scanning electron
microscopes (TEM and
SEM) had been available
since the 30s, and offered the possibility to image as well as create
nanodevices by electron beam
lithography.
**New nanomaterials**
Several unique nanoscale structures were also discovered around 1990:
the Carbon-60 molecule and later the carbon
nanotubes. In recent years, more complex
nanostructures such as semiconductor nanowire
heterostructures have also proven to be useful building blocks or
components in nanodevices.
**So what can I use this \'nano\' for?**
The applications of such nanocomponents span all aspects of technology:
Electronics, optics/photonics, medical, and
biochemical, as well as better and smarter materials. But to date few
real products are available with nanoscale components, apart from
traditional nanoscale products, such as paint with nanoparticles or
catalytic particles for chemical reactors.
Prototype devices have been created from individual nanocomponents, but
actual production is still on the verge. As when integrated electronics
were developed, nanotechnology is currently in the phase where component
production methods, characterization methods, tools for manipulation and
integration are evolving by mutual support and convergence.
**Difficult nanointegration**
A main problem is reliable integration of the nanoscale components into
microsystems, since the production methods
are often not compatible. For fabrication of devices with integrated
nanocomponents, the optimal manipulation technique is of course to have
the individual components self-assembling or growing into the required
complex systems. Self assembly of devices in liquids is an expanding
field within nanotechnology but usually requires the components to be
covered in various surfactants, which usually also influence the
component properties. To avoid surface treatments, nanotubes and
whiskers/wires can be grown on chips and
microsystems directly from pre-patterned
catalytic particles. Although promising for future large scale
production of devices, few working devices have been made by the method
to date.
The prevailing integration technique for nanowire/tube systems seems to
be electron beam lithography
(EBL) of metal structures onto
substrates with randomly positioned nanowires deposited from liquid
dispersions. By using flow alignment or electrical fields, the wire
deposition from liquids can be controlled to some extent. The EBL method
has allowed for systematic investigations of nanowires\' and tubes\'
electrical properties, and creation of high performance electronic
components such as field-effect transistors and chemical sensors. These
proof-of-principle devices are some of the few but important
demonstrations of devices nanotechnology might offer. In addition,
nanomechanical structures have also recently been demonstrated, such as
a rotational actuator with a carbon nanotube axis built by Fennimore et
al.
A more active approach to creating nanowire structures is to use
Scanning probe microscopy(SPM)
to push, slide and roll the nanostructures across surfaces. SPM
manipulation has been used to create and study nanotube junctions and
properties. The ability to manipulate individual nanoscale objects has
hence proven very useful for building proof-of-principle devices and
prototypes, as well as for characterizing and testing components.
**Top-down manufacturing** takes bulky products and shrinks them to the
nano scale, vs. bottom-up manufacturing is when individual molecules are
placed in a specific order to make a product.[^7] The **bottom-up
self-assembly** method may be important for future large scale
production as well as many of the different approaches to improve the
top-down lithographic processes. Such techniques could hence become
important factors in the self-sustaining development of nanotechnology.
# Hot and hyped
**Suddenly everything is \'nano\'**
There\'s no question that the field of nanotechnology has quite a sense
of hype to it - many universities have created new nanotech departments
and courses. But there is also a vision behind the hype and emerging
results - which are truly very few in industrial production, but
nevertheless hold promise for a bright future. In the hype, many things
that were once chemistry, microtechnology,
optics, mesoscopic or cluster physics, have been
reborn as nanotechnology.
**Nanotech is old**
You can find nanotechnology in the sunscreen you use in the summer, and
some paints and coatings can also be called nanotech since they all
contain nanoparticles with unique optical properties. In a way,
nanoparticles have been known in optics for
hundreds of years if you like to take a broad perspective on things,
since they have been used to stain and color
glasses, etc. since the middle ages.
Nano-size particles of gold were used to create red pigments.[^8]
Catalysis is a major industrial process,
without which not many of the materials we have around us today would be
possible to make, and catalysis is often highly dependent on nanoscale
catalytic particles. In this way thousands of tons of nanotechnology
have been used with great benefit for years.
Nanoscale wires and tubes have only recently really been given attention
with the advent of carbon nanotubes and
semiconductor nanowires, while nanoscale films are ever present in
antireflection coatings on your glasses and binoculars, and thin metal
films have been used for sensitive detection with surface
plasmons for decades. Surface
plasmons are excitations of the charges at a surface. Nanowires actually
were observed in the middle ages - well, they did not have the means to
observe them, but saw whiskers grow from melted metals.
The better control over the nanostructure of materials has led to
optimization of all these phenomena - and the emergence of many new
methods and possibilities.
**An example**
Take for instance nano-optics: The surface plasmons turn out to be very
efficient at enhancing local electrical fields and work as a local
amplifier for optical fields, making a laser seem much more powerful to
atoms in the vicinity of the surface plasmon. From this comes the
surface enhanced raman spectroscopy
which is increasingly used today because it makes it possible to do
sensitive raman spectroscopy on the large majority of samples that would
otherwise be impossible to make such spectra on. In addition, photonic
crystals, fancy new quantum light
sources that can make single photons on demand and other non-classical
photon states are being developed, based on nanotechnology.
**The future**
There are definitely future scientific applications and commercial
potential of all these new methods to handle light, use it for extremely
sensitive detection and control its interaction with matter - and so it
seems nanotechnology, being about making smaller versions of existing
technology as well as new technology, is worth a bit of hype.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: N. Taniguchi, \"On the Basic Concept of \'Nano-Technology\',\"
Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of
Precision Engineering, 1974.
[^3]: Steven A. Edwards, *The Nanotech Pioneers*, (WILEY-VCH, 2006)
[^4]: Eric Drexler, *Engines of Creation*, (New York: Anchor
Press/Doubleday, 1986).
[^5]: Eric Drexler, *Nanosystems: Molecular Machinery, Manufacturing and
Computation*, (New York: John Wiley, 1992).
[^6]: Richard Dawkins, The Blind Watchmaker: Why the Evidence of
Evolution Reveals a Universe Without Design, W. W. Norton; Reissue
edition (September 19, 1996)
[^7]: Eric Drexler, *Engines of Creation*
[^8]: Nanotech Pioneers, Steven A. Edwards (WILEY-VCH, 2006, Weinheim)
|
# Nanotechnology/Perspective#Hot and hyped
Navigate
---------------------------------------------------------
\<\< Prev: Introduction
\>\< Main: Nanotechnology
\>\> Next: Overviews
\_\_TOC\_\_
------------------------------------------------------------------------
# A perspective on Nanotechnology
**Nanotechnology in the Middle Ages?**
The Duke TIP eStudies Nanotechnology course will be adding more to this
section (this will be completed by 22 Jun 08)
One of the first uses of nanotechnology was in the Middle Ages. It was
done by using gold nanoparticles to make red pigments in stained glass
showing that nanotechnology has been around for centuries. The gold when
clumped together appears gold, but certain sized particles when spread
out appear different colors. Reference: The Nanotech Pioneers Where are
they taking us? By Steven A Edwards
In the year 1974 at the Tokyo Science University, Professor Norio
Taniigrichi came up with the term
nanotechnology.
Nanotechnology was first used to describe the extension of traditional
silicon machining down into regions smaller than one micron (one
millionth of a meter) by Tokyo Science University Professor Norio
Taniguchi in 1974. It is now commonly used to describe the engineering
and fabrication of objects with features smaller than 100 nanometers
(one tenth of a micron). [^1]
Nanotechnology has been used for thousands of years, although people did
not know what they were doing. For example, stained glass was the
product of nanofabrication of gold. Medieval forgers were the first
nanotecnologists in a sense, because they, by accident, found out a way
to make stained glass.
Reference Nanotechnology A GENTLE INTRODUCTION TO THE NEXT BIG IDEA By
Mark Ratner & Daniel Ratner
In 2001, the federal government announced the National Nanotechnology
Intiative to coordinate the work of different U.S. agencies and to
provide funds for research and accelerate development in nanotechnology.
This was spearheaded by Mahail Roco and supported by both president
Clinton and Bush.
References The Nanotech Pioneers Where are they taking us? By Steven A.
Edwards
<http://www.nano.gov/html/about/docs/20070521NNI_Industrial_Nano_Impact_NSTI_Carim.pdf>
**A Vision**
Richard Feynman was a man of great importance to the field of
nanotechnology. He was a man with a vision. He believed that with
research we could change things on a small scale. In his famous speech
There\'s Plenty of Room at the
Bottom in 1959, Richard
Feynman discussed the possibility of
manipulating and controlling things on a molecular scale in order to
achieve electronic and mechanical systems with atomic sized components.
He concluded that the development of technologies to construct such
small systems would be interdisciplinary, combining fields such as
physics, chemistry and biology, and would offer a new world of
possibilities that could radically change the technology around us.
**Miniaturization**
A few years later, in 1965, Moore
noted that the number of transistors on a chip had roughly doubled every
other year since 1959, and predicted that the trend was likely to hold
as each new generation of microsystems
would help to develop the next generation at lower prices and with
smaller components. To date, the semiconductor industry has been able to
fulfill Moore\'s Law, in part through the reduction of lateral feature
sizes on silicon chips from around 10 micrometers in 1965 to 45-65 nm in
2007 via changing from the use of optical contact lithography to deep
ultraviolet projection lithography.
In 1974 in Japan, Norio Taniguchi coined the word \"nano-technology\"
[^2] to describe semiconductor processes such as thin film deposition
and ion beam milling exhibiting characteristic control on the order of a
nanometer: \"'Nano-technology' mainly consists of the processing of
separation, consolidation, and deformation of materials by one atom or
one molecule.\"
Since Feynman\'s 1959 speech the arts of \"seeing\" and \"manipulation\"
at the nanoscale have progressed from transmission electron microscopy
(TEM) and scanning electron microscopy (SEM) to various forms of
scanning probe microscopy including scanning tunneling microscopy
(STM) developed by Binnig and Rohrer
at IBM Zurich and atomic force microscopy
(AFM) devloped by (Binnig and Quate?)
The STM, in particular, is capable of single-atom manipulation on
conducting surfaces and has been used to build \"quantum corrals\" of
atoms in which quantum mechanical wave function phenomena can be
discerned. These atomic-scale manipulation capabilities prompt thoughts
of building up complex atomic structures via manipulation rather than
traditional stochastic chemistry. (Note: this pragraph is still rough
and references are needed.)
Motivated by Feynman's beliefs building things nanoscale top-down, Eric
Drexler devoted much of his research to making a universal assembler.
The American engineer Eric Drexler has
speculated extensively about the laboratory synthesis of machines at the
molecular level via manipulation techniques, emulating biochemistry and
producing components much smaller than any microprocessor via techniques
which have been called molecular
nanotechnology or MNT. [^3] [^4]
[^5]
Successful realization of the
MNT dream would comprise a
collection of technologies which are not currently practical, and the
dream has resulted in considerable hyperbolic description of the
resulting capabilities. While realization of these capabilities would be
a vindication of the hype associated with MNT, concrete plans for
anything other than computer modeling of finished structures are scant.
Somehow, a means has to be found for MNT design evolution at the
nanoscale which mimics the process of biological evolution at the
molecular scale. Biological evolution proceeds by random variation in
ensemble averages of organisms combined with culling of the
less-successful variants and reproduction of the more-successful
variants, and macroscale engineering design also proceeds by a process
of design evolution from simplicity to complexity as set forth somewhat
satirically by John Gall: \"A
complex system that works is invariably found to have evolved from a
simple system that worked. . . . A complex system designed from scratch
never works and can not be patched up to make it work. You have to start
over, beginning with a system that works.\" \<ref name=\"JohnGall\>
Gall, John, (1986) Systemantics: How Systems Really Work and How They
Fail, 2nd ed. Ann Arbor, MI : The General Systemantics Press.
```{=html}
</ref>
```
A breakthrough in MNT is needed
which proceeds from the simple atomic ensembles which can be built with,
e.g., an STM to complex
MNT systems via a process of
design evolution. A handicap in this process is the difficulty of seeing
and manipulation at the nanoscale compared to the macroscale which makes
deterministic selection of successful trials difficult; in contrast
biological evolution proceeds via action of what Richard Dawkins has
called the \"blind watchmaker\" [^6] comprising random molecular
variation and deterministic survival/death.
**Technological development and limits**
The impact on society and our lives of the continuous downscaling of
systems is profound, and continues to open up new frontiers and
possibilities. However, no exponential growth can continue forever, and
the semiconductor industry will eventually reach the atomic limit for
downsizing the transistor. Atoms in solid matter are typically one or
two hundred picometers apart so nanotechnology involves manipulating
individual structures which are between ten and ten thousand atoms
across; for example, the gate length of a 45 nm transistor is about 180
silicon atoms long. Such very small structures are vulnerable to
molecular level damage by cosmic rays, thermal activity, and so forth.
The way in which they are assembled, designed and used is different from
prior microelectronics.
**New ways**
Today, as that limit still seems to be some 20 years in the future, the
growth is beginning to take new directions, indicating that the atomic
limit might not be the limiting factor for technological development in
the future, because systems are becoming more diverse and because new
effects appear when the systems become so small that quantum effects
dominate. The semiconductor devices show an increased diversification,
dividing for instance processors into very different systems such as
those for cheap disposable chips, low power consumption portable
devices, or high processing power devices. Microfabrication is also
merging with other branches of science to include for instance chemical
and optical micro systems. In addition, microbiology and biochemistry
are becoming important for applications of all the developing methods.
This diversity seems to be increasing on all levels in technology and
many of these cross-disciplinary developments are linked to
nanotechnology.
**Diversification**
As the components become so small that quantum effects become important,
the diversity will probably further increase as completely new devices
and possibilities begin to open up that are not possible with the bulk
materials of today\'s technology.
**The nanorevolution?**
The visions of Feynman are today shared by many others: when
nanotechnology is seen as a general cross disciplinary technology, it
has the potential to create a coming \"industrial\" revolution that will
have a major impact on society and everyday life, comparable to or
exceeding the impact of electricity and information technology.
# Nanocomponents, Tools, and Methods
**A positive spiral**
As an emerging technology, the methods and components of nanotechnology
are under continuous development and each generation is providing a
better foundation for the following generation.
**Seeing \'nano\'**
With regards to the methods, the Scanning tunneling microscope
(STM) and Atomic Force
Microscope (AFM) were developed
in the 1980s and opened up completely new ways to investigate nanoscale
materials. An important aspect was the novel possibility to directly
manipulate nanoscale objects. Transmission and scanning electron
microscopes (TEM and
SEM) had been available
since the 30s, and offered the possibility to image as well as create
nanodevices by electron beam
lithography.
**New nanomaterials**
Several unique nanoscale structures were also discovered around 1990:
the Carbon-60 molecule and later the carbon
nanotubes. In recent years, more complex
nanostructures such as semiconductor nanowire
heterostructures have also proven to be useful building blocks or
components in nanodevices.
**So what can I use this \'nano\' for?**
The applications of such nanocomponents span all aspects of technology:
Electronics, optics/photonics, medical, and
biochemical, as well as better and smarter materials. But to date few
real products are available with nanoscale components, apart from
traditional nanoscale products, such as paint with nanoparticles or
catalytic particles for chemical reactors.
Prototype devices have been created from individual nanocomponents, but
actual production is still on the verge. As when integrated electronics
were developed, nanotechnology is currently in the phase where component
production methods, characterization methods, tools for manipulation and
integration are evolving by mutual support and convergence.
**Difficult nanointegration**
A main problem is reliable integration of the nanoscale components into
microsystems, since the production methods
are often not compatible. For fabrication of devices with integrated
nanocomponents, the optimal manipulation technique is of course to have
the individual components self-assembling or growing into the required
complex systems. Self assembly of devices in liquids is an expanding
field within nanotechnology but usually requires the components to be
covered in various surfactants, which usually also influence the
component properties. To avoid surface treatments, nanotubes and
whiskers/wires can be grown on chips and
microsystems directly from pre-patterned
catalytic particles. Although promising for future large scale
production of devices, few working devices have been made by the method
to date.
The prevailing integration technique for nanowire/tube systems seems to
be electron beam lithography
(EBL) of metal structures onto
substrates with randomly positioned nanowires deposited from liquid
dispersions. By using flow alignment or electrical fields, the wire
deposition from liquids can be controlled to some extent. The EBL method
has allowed for systematic investigations of nanowires\' and tubes\'
electrical properties, and creation of high performance electronic
components such as field-effect transistors and chemical sensors. These
proof-of-principle devices are some of the few but important
demonstrations of devices nanotechnology might offer. In addition,
nanomechanical structures have also recently been demonstrated, such as
a rotational actuator with a carbon nanotube axis built by Fennimore et
al.
A more active approach to creating nanowire structures is to use
Scanning probe microscopy(SPM)
to push, slide and roll the nanostructures across surfaces. SPM
manipulation has been used to create and study nanotube junctions and
properties. The ability to manipulate individual nanoscale objects has
hence proven very useful for building proof-of-principle devices and
prototypes, as well as for characterizing and testing components.
**Top-down manufacturing** takes bulky products and shrinks them to the
nano scale, vs. bottom-up manufacturing is when individual molecules are
placed in a specific order to make a product.[^7] The **bottom-up
self-assembly** method may be important for future large scale
production as well as many of the different approaches to improve the
top-down lithographic processes. Such techniques could hence become
important factors in the self-sustaining development of nanotechnology.
# Hot and hyped
**Suddenly everything is \'nano\'**
There\'s no question that the field of nanotechnology has quite a sense
of hype to it - many universities have created new nanotech departments
and courses. But there is also a vision behind the hype and emerging
results - which are truly very few in industrial production, but
nevertheless hold promise for a bright future. In the hype, many things
that were once chemistry, microtechnology,
optics, mesoscopic or cluster physics, have been
reborn as nanotechnology.
**Nanotech is old**
You can find nanotechnology in the sunscreen you use in the summer, and
some paints and coatings can also be called nanotech since they all
contain nanoparticles with unique optical properties. In a way,
nanoparticles have been known in optics for
hundreds of years if you like to take a broad perspective on things,
since they have been used to stain and color
glasses, etc. since the middle ages.
Nano-size particles of gold were used to create red pigments.[^8]
Catalysis is a major industrial process,
without which not many of the materials we have around us today would be
possible to make, and catalysis is often highly dependent on nanoscale
catalytic particles. In this way thousands of tons of nanotechnology
have been used with great benefit for years.
Nanoscale wires and tubes have only recently really been given attention
with the advent of carbon nanotubes and
semiconductor nanowires, while nanoscale films are ever present in
antireflection coatings on your glasses and binoculars, and thin metal
films have been used for sensitive detection with surface
plasmons for decades. Surface
plasmons are excitations of the charges at a surface. Nanowires actually
were observed in the middle ages - well, they did not have the means to
observe them, but saw whiskers grow from melted metals.
The better control over the nanostructure of materials has led to
optimization of all these phenomena - and the emergence of many new
methods and possibilities.
**An example**
Take for instance nano-optics: The surface plasmons turn out to be very
efficient at enhancing local electrical fields and work as a local
amplifier for optical fields, making a laser seem much more powerful to
atoms in the vicinity of the surface plasmon. From this comes the
surface enhanced raman spectroscopy
which is increasingly used today because it makes it possible to do
sensitive raman spectroscopy on the large majority of samples that would
otherwise be impossible to make such spectra on. In addition, photonic
crystals, fancy new quantum light
sources that can make single photons on demand and other non-classical
photon states are being developed, based on nanotechnology.
**The future**
There are definitely future scientific applications and commercial
potential of all these new methods to handle light, use it for extremely
sensitive detection and control its interaction with matter - and so it
seems nanotechnology, being about making smaller versions of existing
technology as well as new technology, is worth a bit of hype.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: N. Taniguchi, \"On the Basic Concept of \'Nano-Technology\',\"
Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of
Precision Engineering, 1974.
[^3]: Steven A. Edwards, *The Nanotech Pioneers*, (WILEY-VCH, 2006)
[^4]: Eric Drexler, *Engines of Creation*, (New York: Anchor
Press/Doubleday, 1986).
[^5]: Eric Drexler, *Nanosystems: Molecular Machinery, Manufacturing and
Computation*, (New York: John Wiley, 1992).
[^6]: Richard Dawkins, The Blind Watchmaker: Why the Evidence of
Evolution Reveals a Universe Without Design, W. W. Norton; Reissue
edition (September 19, 1996)
[^7]: Eric Drexler, *Engines of Creation*
[^8]: Nanotech Pioneers, Steven A. Edwards (WILEY-VCH, 2006, Weinheim)
|
# Nanotechnology/Overviews#Peer reviewed Journals
Navigate
---------------------------------------------------------
\<\< Prev: Perspective
\>\< Main: Nanotechnology
\>\> Next: About
\_\_TOC\_\_
------------------------------------------------------------------------
# Internet Resources
## Handbooks and Encyclopedias
These are only accessible for subscribers (which is one reason this
Wikibook on Nanotechnology was started):
- Encyclopedia of Nanoscience and Nanotechnology, 10-Volume
Set
- Handbook of Theoretical and Computational Nanotechnology, 10-Volume
Set
- Springer Handbook of
Nanotechnology
## Websites and newsletters
- International Council on Nanotechnology
(ICON) a multi-stakeholder group dedicated to
the safe, responsible and beneficial development of nanotechnology.
ICON serves as an aggregator for news and research related to
nanotechnology environment, health and safety.
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety compiles papers in
peer-reviewed journals that address EHS issues in nanotechnology.
- Virtual journal of nanotechnology
compiles nano-related papers in peer reviewed journals that do not
specialize solely in nanotechnology.
- ACS Nanotation
- Nanotechweb.org
- Nanoforum
- Nanowerk
- nanoRISK
- Physorg.com
- Foresight Nanotech Institute
- Center for Responsible Nanotechnology
- A-Z of nanotechnology
- Google Directory -
Nanotechnology
(sourced from the Open Directory
Project)
- Scientific American Nanotechnology
Page
- NanoEd Resource Portal managed by the
National Center for Learning and Teaching in Nanoscale Science and
Engineering (NCLT)
- NanoHub.org
- UnderstandingNano
## Search engines
There are many ways to find information in scientific literature and
some that even specialize in nanotechnology. Apart from the free search
engines and useful tools such as Google
scholar and Google
Desktop, there are several more dedicated
commercial services:
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety (VJ-NanoEHS)
compiles papers in peer-reviewed journals that address EHS issues in
nanotechnology.
- ISI - Web of Science
Database contains peer
reviewed journals, their references and citations. It also has very
useful tools such as \'find related papers\' that searches for
papers sharing the same references as the entry you\'re looking at.
This is the database behind the compilation of the journal citation
factors.
- Knovel - Online Handbook Collection and
Database is an
extensive collection of handbooks and tables.
- PROLA - the Physical Review Online Archive
searches Physical Review journals.
- Rubber Bible Online is a physical
chemistry handbook which contains tables of physical and chemical
data.
- Spin AIP Scitation searches related
journals.
- Web of Science by ISI
generates the impact factors (see
journals below).
- Virtual Journal of Nanotechnology
collects nanotech related papers from non-nano specialized journals.
- Derwent Patent database
# Peer reviewed Journals
Overview of the nanotechnology related journals and their impact factors
(2007 values):
Name Web Impact Factor ISSN Comments
--------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------- ------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ACS Nano 1 N/A 1936-0851 general nanotech journal
Advanced Functional Materials 2 7.5 1616-301X ?
Advanced Materials 3 8.2 0935-9648 ?
American Journal of Physics (AJP) 4 0.9 0002-9505 ?
Applied Physics A: Materials Science & Processing 5 1.9 0947-8396 ?
Applied Physics Letters (APL) [](http://apl.aip.org/apl/top.jsp) 3.6 ? ?
AZojono - Journal of Nanotechnology Online 6 N/A ? Free access journal
Chemical Reviews 7 22.8 0009-2665 ?
Current Nanoscience 8 2.8 1573-4137 Reviews and original research reports
Fullerenes, Nanotubes, and Carbon Nanostructures 9 0.5 1536-383x all areas of fullerene research
IEEE Transactions on Nanotechnology 10 2.1 1536-125X physical basis and engineering applications of nanotechnology
International Journal of Nanomedicine 11 N/A 1176-9114 ?
International Journal of Nanoscience 12 N/A 0219-581X New nanotech journal (Feb 2002)
Japanese Journal of Applied Physics 13 1.2 1347-4065 ?
Journal of Applied Physics 14 2.2 ? ?
Journal of Biomedical Nanotechnology \[\] N/A ? JBN is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
Journal of Experimental Nanoscience 15 N/A 1745-8080 New nanotech journal(March 2006)
Journal Of Microlithography Microfabrication And Microsystems 16 N/A 1537-1646
Journal of Micromechanics and Microengineering 17 1.9 0960-1317 ?
Journal of Nano Research 18 N/A 1661-9897
Journal of Nanomaterials 19 N/A ? science and applications of nanoscale and nanostructured materials
Journal of Nanoparticle Research 20 2.3 1388-0764 ?
Journal of Nanoscience and Nanotechnology 21 2.0 ? JNN is a multidisciplinary peer-reviewed journal covering fundamental and applied research in all disciplines of science, engineering and medicine. JNN publishes all aspects of nanoscale science and technology dealing with materials synthesis, processing, nanofabrication, nanoprobes, spectroscopy, properties, biological systems, nanostructures, theory and computation, nanoelectronics, nano-optics, nano-mechanics, nanodevices, nanobiotechnology, nanomedicine, nanotoxicology.
Journal of Physical Chemistry A 22 2.9 ? ?
Journal of Physical Chemistry B 23 4.1 ? ?
Journal of Physical Chemistry C 24 N/A ? Nanomaterials and Interfaces, Nanoparticles and Nanostructures, Surfaces, Interfaces, Catalysis, Electron Transport, Optical and Electronic Devices, Energy Conversion and Storage
Journal of the American Chemical Society (JACS) 25 7.9 ? Multidisciplinary chemistry journal
Journal of Vacuum Science & Technology A (JVSTA) 26 1.3 ? Vacuum, Surfaces, Films
Journal of Vacuum Science & Technology B (JVSTB) 27 1.4 ? Microelectronics and Nanometer Structures: Processing, Measurement, and Phenomena
Langmuir 28 4.0 ? Research in the fields of colloids, surfaces, and interfaces
Micron 29 1.7 ? Journal for Microscopy
Materials Chemistry and Physics 30 1.9 0254-0584 materials science, including nanomaterials and opto electronics
Materials Science and Engineering: C 31 1.3 0928-4931 Biomimetic and Supramolecular Systems
Materials Science and Engineering: R: Reports 32 17.7 0927-796X Invited review papers covering the full spectrum of materials science and engineering
Materials Today 33 N/A 1369-7021 materials science and technology
Microfluidics and Nanofluidics 34 2.2 1613-4982 all aspects of microfluidics, nanofluidics, and lab-on-a-chip science and technology
Microscopy Research and Technique 35 1.6 ? ?
Nano 36 N/A 1793-2920 New nanotech journal (July 2006)
Nano Letters 37 9.6 ? General nanotechnology journal
Nanomedicine 38 2.8 ? ?
Nanopages 39 N/A 1787-4033 Since sept 2006.
Nano Research 40 N/A ? First issue july 2008
Nano Research Letters 41 wait 1931-7573 articles with open access
Nanotechnology 42 3.3 ? Journal specializing in nanotechnology
NanoToday 43 N/A ? Is this peer reviewed or more a news/reviews journal?
Nature 44 31.434 ? One of the major journals in science
Nature Biotechnology 45 22.8 ? advances in life sciences
Nature Materials 46 19.8 ? covers a range of topics within materials science
Nature Methods 47 15.5 ? tried-and-tested techniques in the life sciences and related area of chemistry
Nature Nanotechnology 48 14.9 ? mix of news, reviews, and research papers
Nanotoxicology 49 N/A 1743-5404 Research relating to the potential for human and environmental exposure, hazard and risk associated with the use and development of nano-structured materials
Open Nanoscience Journal [](http://www.bentham.org/open/tonanoj) N/A 1874-1401 Open access journal with research articles, reviews and letters.
Physical Review Letters (PRL) [](http://scitation.aip.org/prl/help.jsp) 6.9 ? One of the top physics journals
PLoS Biology [](http://biology.plosjournals.org/) 13.5 1544-9173 Peer reviewed open access bio journal
PLoS ONE [](http://one.plosjournals.org/) N/A ? Peer reviewed open access science journal
Proceedings of the National Academy of Sciences(PNAS) [](http://www.pnas.org) 10.2 ? multidisciplinary scientific serial: biological, physical, and social sciences.
Recent Patents on Nanotechnology 50 N/A 1872-2105 ?
Science 51 26.4 ? One of the major journals in science
Solid-State Electronics 52 1.3 ? ?
Small Journal 53 6.4 1613-6810 New nanotech journal
Smart Materials and Structures 54 1.5 0964-1726 since 1992
Thin Solid Films 55 1.7 0040-6090 Thin-film synthesis, characterization, and applications.
Ultramicroscopy 56 2.0 ? Microscopy related research.
Virtual Journal of Nanotechnlogy 57 N/A 1553-9644 Collecting nanotech related papers from non-nano spcialized journals
: Nanotechnology Related Journals
- Impact factors are only guides to how much a papers is referenced in
the years just after publication.
- Please add comments about the journals and update impact factors!
- The Physics and Astronomy Classification Scheme
PACS2006 and
Nanoscale Science and Technology - Collection of Applicable Terms
from PACS 2006
# Conferences
- NSTI Nanotech 2008
- TNT - Trends in Nanotechnology
2007;2006
- MNE - Micro and Nanoengineering
2007;2008
- Virtual Conference on Nanoscale Science and
Technology
- Foresight Unconference Vision
Weekend
NanoBioInfoCognoSocioPhysical technologies
- 58
- International Microprocess and Nanotechnology Conference,
Japan
- Nanosafe 2008: International Conference on Safe production and use
of nanomaterials
# Nanotech Products
Please add more products, comments and more info about the products if
you have any!
See also the List of nanotechnology applications in
wikipedia
Woodrow Wilsom Center for International Scholars is starting a Project
on Emerging Nanotechnologies (website should be under construction at
www.nanoproject.org) that among other
things will try to map the available \'nano\'products and work to ensure
possible risks are minimized and benefits are realized.
### Emerging products
- 2008 MultiProbe's AFM Nanoprober is now qualified for 32nm
technology nodes. 59
- Intel will make products with 45 nm linewidth transistors available
from 2008
60
- Batteries are increasingly incorporating nanostructures.
- Flexible, cheaper, or more luminous Flat screen displays
- Pressure-sensitive mobile devices
61
### Available in 2006
- Surface coatings: TCnano,
Nanocover, Stay
clean.
### Available in 2005
- Molybdenum disulfide catalytic nanoparticles in Brimm
catalysts62
made by Haldor Topsøe
- Forbes top ten nanoproducts in
200563
- Apples IPod with sub 100nm elements in its memory chips
- Choleterol reducing nanoencapsulated oil,Shemen Industries
Canola Active.
- Nanocrystals improve the consistency of
chocolate64
- Zelen Fullerene C-60 Day Cream 65
- Easton Stealth CNT baseball bat
- Nanotex textiles once again
- ArcticShield polyester socks from ARC Outdoors with 19nm silver
particles that kill fungs to reduce odor.
- NanoGuard developed by Behr Process for improved paint hardness.
- Pilkingtons self-cleaning \'Activ Glass\'.
- NanoBreeze Air Purifier from NanoTwin Technologies, where the UV
light from a fluorescent tube cleans the air by photochemical
reactions in nanoparticles.
### Available in 2004
- Cold cathode carbon nanotube emitters for X-ray analysis by Oxford
instruments66\[\]
- Forbes has an overview in 2004 of what they consider the top ten
nanotech
products:
- Footwarmers with nanporous aerogel for 3-20 times lighter than
comparable insulating materials used in shoes (produced by Aspen
Aerogels).
- Matress covers with nanotex fibres that can be washed (Simmonos
bedding company).
- Better golf drivers with carbon nanotube enforced metal
composites (produced by Maruman & Co) and nanocomposite
containing golf balls (produced by NanoDynamics)
- The company \'Bionova\' apparently adds some nanoproducts to
their \'personalized product line\'.
- EnviroSystems make a nanoemulsive disinfectant cleaner, called
EcoTru, that is EPA Tox category 4 registered (meaning very safe
to use)
- EnviroSystems also make a spray-on version of this product.
- BASF makes a nanoparticle coating for building materials called
Mincor, that reduces their wettabililty.
- A nanostructured coating produced by Valley View, called Clarity
Defender, improves visibility through windscreens in rain.
Another company, Nano-Film, makes a similar coating on
sunglasses.
- w:Flex-Power makes a gel containing
nanoscale liposomes for soothing aching muscles
- 3M espe Dental adhesive with silica nanoparticle filler.
### Available in 2003
- NanoGuard Zink Oxide nanoparticles for sunscreens FDA
approved
- Forbes 2003 top ten nanoproduct
67
includes:
- High performance ski wax, Cerax Nanowax
68.
- Nanotex textiles in ski jackets from
Ziener69
- Nanotex textiles
- Plenitude Revitalift antiwrinkle cream by L\'Oréal contains
nanocapsules with vitamin A 70
- organic light-emitting diodes (OLEDs) in Sony camera flat screen
display
- Nanofilm coatings for ani-reflection and scratch resistance
71
- Zink oxide nanoparticles in Sunscreen by BASF
72
- carbon nanotube enforced tennis rackets
73 and nanopolymer enforced tennis
balls 74
### Available in 2000
Nanotex makes textiles where the clothing
fibres have been coating in nanoscale fibres to change the textile
wettability. This makes the textile much more stain resistant.
## Companies making nanotech research equipment
- MultiProbe Manufacturer of a 1-to-6 head
Atomic Force nanoprobing tool used in failure analysis, that
combines multi-scan fault isolation imaging with nanoprobing
electrical capabilities. For process technology node measurements of
32nm, 45nm, 65nm, 90nm or larger.
- Veeco AFM and related equipment
- Zyvex nanomanipulation equipment
- Nanofactory in-situ TEM manipulation
equipment
- SmarAct nanomanipulators
- Capres micro four point conductance measurement
probes
- ImageMetrology SPIP software for SPM
analysis
- QuantumWise software for simulating
nanosystems
- 75 AFM and related equipment
## Products that have been nanostructured for decades
- Catalysts
- Haldor Topsøe
- Computer processesors are increasingly made of nanoscale systems
- Intel
## Non-nanotech products and a warning
Not everything that says nano is nano - and given the hype surrounding
nanotechnology you will see an increasing number of \'nano\' products
that have nothing to do with it. It is worrying when sometimes problems
arise with non-nano products and this adds to the \'scare\' that is
present in the public, fuelled by the newspapers where they are just
waiting for a nice scandal\... an example was the product Magic Nano
from a German
company that
made a number of users sick when inhaling the aerosol cleaning product -
which in the end turned out to have nothing \'nano\' in it. There is
good reason to be very alert to such issues. Not all countries have
legislation in place to secure the consumers against the possible
dangers present in nanoparticles and some products could end being
marketed before having been tested well enough. Though this example
turned out to be \'non-nano\', we will probably meet new cases shortly
that are truly \'nano\'. On this background environmental and health
aspects will be an important part of this book.
# Suppliers
Nanomaterials
- Sigma-Aldrich
- Zyvex
- overview of companies making nanoparticles and related
equipment
Nanolithography
- NIL Technology sells stamps for nanoimprint
lithography (NIL) and provides imprint services.
Quantum Dots
- Evident technologies
# A nano-timeline
Overview of some important events in nanotechnology
See also History of Nanotechnology in
Wikipedia
Year Development
---------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Medieval Observation of metal whisker growth and nanoparticles used for staining glass
1900 Max Planck proposes energy quantization.
1905-30 Development of quantum mechanics
1927 Heisenberg formulated his uncertainty principle
1933 The first First electron microscope was built by Ernst Ruska
1952 First carbon nanotubes observation by Radushkevich and Lukyanovich
1953 DNA structure discovered by James D. Watson and Francis Crick
1959 Feynmanns talk There is plenty of room at the bottom
1965 Proposal of Moores Law
1981 Invention of STM by Gerd Binnig and Heinrich Rohrer
1985 Invention of AFM by Binnig, Quate and Gerber
1985 Buckyball discovery by Harry Kroto, Robert Curl, and Richard Smalley
1986 K. Eric Drexler publishes his book *Engines of Creation*, in which he discusses both the potential huge benefits and the potential dangers of nanotechnology. He talks about a future of nanotechnology defined by molecular manufacturing, where self-replicating nanobots/assemblers are engineered to carry out practical applications.
1989 Don Eigler pushed around xenon atoms to spell IBM
: A Nanotechnology Timeline
# A nano-scale overview
Just to get a sense of proportion
Scale typical elements
--------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 m 1 m is 1.000.000.000 nanometers ( 10\^9 nm )
200 µm About the size of the smallest letters you can write with a very very sharp pencil and a very very steady hand.
100 µm Typical thick hair
10-1000 µm Cells in living organisms can have many sizes, and neurons can be much longer. In frog embryos (Tadpoles) the initial embryo cells can be up to 1000µm.
8 µm Red blood cell
1 µm Bacteria
100 nm Virus
5-100 nm The range for nanotechnology systems built from atomic/molecular components (quantum dots, nanoparticles, diameter of nanotubes and nanowires, lipid membranes, nanopores\...).
10 nm Size of typical Antibody molecules in living organisms immune defence
6-10 nm Thickness of a cell membrane, and typical pore size in membrane.
2.5 nm The width of DNA (but it depends on the conditions)
1 nm The size of a C60 buckyball molecule or glucose molecule.
0.3 nm The size of a water molecule.
1 Å = 0.1 nm Roughly the size of hydrogen atom.
0.7 Å = 70 pm The best resolution in AFM achieved so far where they managed to image individual orbitals in an atom.
: A Nano-scale overview
- Distances between objects can be measured with sub Å precision with
STM, laser interferometry and its even done continuously in a
standard airbag acceleration sensor chip that costs a few dollars
and senses the vibrations of a micro-inertial mass element with
femtometer precision (10\^-15 m).
# Bibliography
- G. Ali Mansoori, *Principles of Nanotechnology*, Molecular-Based
Study of Condensed Matter in Small Systems, (New Jersey: World
Scientific, 2006).
- Monthioux, Marc; Kuznetsov, Vladimir L. (2006). \"Who should be
given the credit for the discovery of carbon nanotubes?\".
Carbon 44. <doi:10.1016/j.carbon.2006.03.019>. Retrieved on
2007-07-26.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
the nanotechnology pioneers by Steven A. Edwards
```{=html}
<references />
```
*Engines of Creation 2.0: The Coming Era of Nanotechnology* by K. Eric
Drexler
------------------------------------------------------------------------
|
# Nanotechnology/Overviews#Nanotech Products
Navigate
---------------------------------------------------------
\<\< Prev: Perspective
\>\< Main: Nanotechnology
\>\> Next: About
\_\_TOC\_\_
------------------------------------------------------------------------
# Internet Resources
## Handbooks and Encyclopedias
These are only accessible for subscribers (which is one reason this
Wikibook on Nanotechnology was started):
- Encyclopedia of Nanoscience and Nanotechnology, 10-Volume
Set
- Handbook of Theoretical and Computational Nanotechnology, 10-Volume
Set
- Springer Handbook of
Nanotechnology
## Websites and newsletters
- International Council on Nanotechnology
(ICON) a multi-stakeholder group dedicated to
the safe, responsible and beneficial development of nanotechnology.
ICON serves as an aggregator for news and research related to
nanotechnology environment, health and safety.
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety compiles papers in
peer-reviewed journals that address EHS issues in nanotechnology.
- Virtual journal of nanotechnology
compiles nano-related papers in peer reviewed journals that do not
specialize solely in nanotechnology.
- ACS Nanotation
- Nanotechweb.org
- Nanoforum
- Nanowerk
- nanoRISK
- Physorg.com
- Foresight Nanotech Institute
- Center for Responsible Nanotechnology
- A-Z of nanotechnology
- Google Directory -
Nanotechnology
(sourced from the Open Directory
Project)
- Scientific American Nanotechnology
Page
- NanoEd Resource Portal managed by the
National Center for Learning and Teaching in Nanoscale Science and
Engineering (NCLT)
- NanoHub.org
- UnderstandingNano
## Search engines
There are many ways to find information in scientific literature and
some that even specialize in nanotechnology. Apart from the free search
engines and useful tools such as Google
scholar and Google
Desktop, there are several more dedicated
commercial services:
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety (VJ-NanoEHS)
compiles papers in peer-reviewed journals that address EHS issues in
nanotechnology.
- ISI - Web of Science
Database contains peer
reviewed journals, their references and citations. It also has very
useful tools such as \'find related papers\' that searches for
papers sharing the same references as the entry you\'re looking at.
This is the database behind the compilation of the journal citation
factors.
- Knovel - Online Handbook Collection and
Database is an
extensive collection of handbooks and tables.
- PROLA - the Physical Review Online Archive
searches Physical Review journals.
- Rubber Bible Online is a physical
chemistry handbook which contains tables of physical and chemical
data.
- Spin AIP Scitation searches related
journals.
- Web of Science by ISI
generates the impact factors (see
journals below).
- Virtual Journal of Nanotechnology
collects nanotech related papers from non-nano specialized journals.
- Derwent Patent database
# Peer reviewed Journals
Overview of the nanotechnology related journals and their impact factors
(2007 values):
Name Web Impact Factor ISSN Comments
--------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------- ------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ACS Nano 1 N/A 1936-0851 general nanotech journal
Advanced Functional Materials 2 7.5 1616-301X ?
Advanced Materials 3 8.2 0935-9648 ?
American Journal of Physics (AJP) 4 0.9 0002-9505 ?
Applied Physics A: Materials Science & Processing 5 1.9 0947-8396 ?
Applied Physics Letters (APL) [](http://apl.aip.org/apl/top.jsp) 3.6 ? ?
AZojono - Journal of Nanotechnology Online 6 N/A ? Free access journal
Chemical Reviews 7 22.8 0009-2665 ?
Current Nanoscience 8 2.8 1573-4137 Reviews and original research reports
Fullerenes, Nanotubes, and Carbon Nanostructures 9 0.5 1536-383x all areas of fullerene research
IEEE Transactions on Nanotechnology 10 2.1 1536-125X physical basis and engineering applications of nanotechnology
International Journal of Nanomedicine 11 N/A 1176-9114 ?
International Journal of Nanoscience 12 N/A 0219-581X New nanotech journal (Feb 2002)
Japanese Journal of Applied Physics 13 1.2 1347-4065 ?
Journal of Applied Physics 14 2.2 ? ?
Journal of Biomedical Nanotechnology \[\] N/A ? JBN is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
Journal of Experimental Nanoscience 15 N/A 1745-8080 New nanotech journal(March 2006)
Journal Of Microlithography Microfabrication And Microsystems 16 N/A 1537-1646
Journal of Micromechanics and Microengineering 17 1.9 0960-1317 ?
Journal of Nano Research 18 N/A 1661-9897
Journal of Nanomaterials 19 N/A ? science and applications of nanoscale and nanostructured materials
Journal of Nanoparticle Research 20 2.3 1388-0764 ?
Journal of Nanoscience and Nanotechnology 21 2.0 ? JNN is a multidisciplinary peer-reviewed journal covering fundamental and applied research in all disciplines of science, engineering and medicine. JNN publishes all aspects of nanoscale science and technology dealing with materials synthesis, processing, nanofabrication, nanoprobes, spectroscopy, properties, biological systems, nanostructures, theory and computation, nanoelectronics, nano-optics, nano-mechanics, nanodevices, nanobiotechnology, nanomedicine, nanotoxicology.
Journal of Physical Chemistry A 22 2.9 ? ?
Journal of Physical Chemistry B 23 4.1 ? ?
Journal of Physical Chemistry C 24 N/A ? Nanomaterials and Interfaces, Nanoparticles and Nanostructures, Surfaces, Interfaces, Catalysis, Electron Transport, Optical and Electronic Devices, Energy Conversion and Storage
Journal of the American Chemical Society (JACS) 25 7.9 ? Multidisciplinary chemistry journal
Journal of Vacuum Science & Technology A (JVSTA) 26 1.3 ? Vacuum, Surfaces, Films
Journal of Vacuum Science & Technology B (JVSTB) 27 1.4 ? Microelectronics and Nanometer Structures: Processing, Measurement, and Phenomena
Langmuir 28 4.0 ? Research in the fields of colloids, surfaces, and interfaces
Micron 29 1.7 ? Journal for Microscopy
Materials Chemistry and Physics 30 1.9 0254-0584 materials science, including nanomaterials and opto electronics
Materials Science and Engineering: C 31 1.3 0928-4931 Biomimetic and Supramolecular Systems
Materials Science and Engineering: R: Reports 32 17.7 0927-796X Invited review papers covering the full spectrum of materials science and engineering
Materials Today 33 N/A 1369-7021 materials science and technology
Microfluidics and Nanofluidics 34 2.2 1613-4982 all aspects of microfluidics, nanofluidics, and lab-on-a-chip science and technology
Microscopy Research and Technique 35 1.6 ? ?
Nano 36 N/A 1793-2920 New nanotech journal (July 2006)
Nano Letters 37 9.6 ? General nanotechnology journal
Nanomedicine 38 2.8 ? ?
Nanopages 39 N/A 1787-4033 Since sept 2006.
Nano Research 40 N/A ? First issue july 2008
Nano Research Letters 41 wait 1931-7573 articles with open access
Nanotechnology 42 3.3 ? Journal specializing in nanotechnology
NanoToday 43 N/A ? Is this peer reviewed or more a news/reviews journal?
Nature 44 31.434 ? One of the major journals in science
Nature Biotechnology 45 22.8 ? advances in life sciences
Nature Materials 46 19.8 ? covers a range of topics within materials science
Nature Methods 47 15.5 ? tried-and-tested techniques in the life sciences and related area of chemistry
Nature Nanotechnology 48 14.9 ? mix of news, reviews, and research papers
Nanotoxicology 49 N/A 1743-5404 Research relating to the potential for human and environmental exposure, hazard and risk associated with the use and development of nano-structured materials
Open Nanoscience Journal [](http://www.bentham.org/open/tonanoj) N/A 1874-1401 Open access journal with research articles, reviews and letters.
Physical Review Letters (PRL) [](http://scitation.aip.org/prl/help.jsp) 6.9 ? One of the top physics journals
PLoS Biology [](http://biology.plosjournals.org/) 13.5 1544-9173 Peer reviewed open access bio journal
PLoS ONE [](http://one.plosjournals.org/) N/A ? Peer reviewed open access science journal
Proceedings of the National Academy of Sciences(PNAS) [](http://www.pnas.org) 10.2 ? multidisciplinary scientific serial: biological, physical, and social sciences.
Recent Patents on Nanotechnology 50 N/A 1872-2105 ?
Science 51 26.4 ? One of the major journals in science
Solid-State Electronics 52 1.3 ? ?
Small Journal 53 6.4 1613-6810 New nanotech journal
Smart Materials and Structures 54 1.5 0964-1726 since 1992
Thin Solid Films 55 1.7 0040-6090 Thin-film synthesis, characterization, and applications.
Ultramicroscopy 56 2.0 ? Microscopy related research.
Virtual Journal of Nanotechnlogy 57 N/A 1553-9644 Collecting nanotech related papers from non-nano spcialized journals
: Nanotechnology Related Journals
- Impact factors are only guides to how much a papers is referenced in
the years just after publication.
- Please add comments about the journals and update impact factors!
- The Physics and Astronomy Classification Scheme
PACS2006 and
Nanoscale Science and Technology - Collection of Applicable Terms
from PACS 2006
# Conferences
- NSTI Nanotech 2008
- TNT - Trends in Nanotechnology
2007;2006
- MNE - Micro and Nanoengineering
2007;2008
- Virtual Conference on Nanoscale Science and
Technology
- Foresight Unconference Vision
Weekend
NanoBioInfoCognoSocioPhysical technologies
- 58
- International Microprocess and Nanotechnology Conference,
Japan
- Nanosafe 2008: International Conference on Safe production and use
of nanomaterials
# Nanotech Products
Please add more products, comments and more info about the products if
you have any!
See also the List of nanotechnology applications in
wikipedia
Woodrow Wilsom Center for International Scholars is starting a Project
on Emerging Nanotechnologies (website should be under construction at
www.nanoproject.org) that among other
things will try to map the available \'nano\'products and work to ensure
possible risks are minimized and benefits are realized.
### Emerging products
- 2008 MultiProbe's AFM Nanoprober is now qualified for 32nm
technology nodes. 59
- Intel will make products with 45 nm linewidth transistors available
from 2008
60
- Batteries are increasingly incorporating nanostructures.
- Flexible, cheaper, or more luminous Flat screen displays
- Pressure-sensitive mobile devices
61
### Available in 2006
- Surface coatings: TCnano,
Nanocover, Stay
clean.
### Available in 2005
- Molybdenum disulfide catalytic nanoparticles in Brimm
catalysts62
made by Haldor Topsøe
- Forbes top ten nanoproducts in
200563
- Apples IPod with sub 100nm elements in its memory chips
- Choleterol reducing nanoencapsulated oil,Shemen Industries
Canola Active.
- Nanocrystals improve the consistency of
chocolate64
- Zelen Fullerene C-60 Day Cream 65
- Easton Stealth CNT baseball bat
- Nanotex textiles once again
- ArcticShield polyester socks from ARC Outdoors with 19nm silver
particles that kill fungs to reduce odor.
- NanoGuard developed by Behr Process for improved paint hardness.
- Pilkingtons self-cleaning \'Activ Glass\'.
- NanoBreeze Air Purifier from NanoTwin Technologies, where the UV
light from a fluorescent tube cleans the air by photochemical
reactions in nanoparticles.
### Available in 2004
- Cold cathode carbon nanotube emitters for X-ray analysis by Oxford
instruments66\[\]
- Forbes has an overview in 2004 of what they consider the top ten
nanotech
products:
- Footwarmers with nanporous aerogel for 3-20 times lighter than
comparable insulating materials used in shoes (produced by Aspen
Aerogels).
- Matress covers with nanotex fibres that can be washed (Simmonos
bedding company).
- Better golf drivers with carbon nanotube enforced metal
composites (produced by Maruman & Co) and nanocomposite
containing golf balls (produced by NanoDynamics)
- The company \'Bionova\' apparently adds some nanoproducts to
their \'personalized product line\'.
- EnviroSystems make a nanoemulsive disinfectant cleaner, called
EcoTru, that is EPA Tox category 4 registered (meaning very safe
to use)
- EnviroSystems also make a spray-on version of this product.
- BASF makes a nanoparticle coating for building materials called
Mincor, that reduces their wettabililty.
- A nanostructured coating produced by Valley View, called Clarity
Defender, improves visibility through windscreens in rain.
Another company, Nano-Film, makes a similar coating on
sunglasses.
- w:Flex-Power makes a gel containing
nanoscale liposomes for soothing aching muscles
- 3M espe Dental adhesive with silica nanoparticle filler.
### Available in 2003
- NanoGuard Zink Oxide nanoparticles for sunscreens FDA
approved
- Forbes 2003 top ten nanoproduct
67
includes:
- High performance ski wax, Cerax Nanowax
68.
- Nanotex textiles in ski jackets from
Ziener69
- Nanotex textiles
- Plenitude Revitalift antiwrinkle cream by L\'Oréal contains
nanocapsules with vitamin A 70
- organic light-emitting diodes (OLEDs) in Sony camera flat screen
display
- Nanofilm coatings for ani-reflection and scratch resistance
71
- Zink oxide nanoparticles in Sunscreen by BASF
72
- carbon nanotube enforced tennis rackets
73 and nanopolymer enforced tennis
balls 74
### Available in 2000
Nanotex makes textiles where the clothing
fibres have been coating in nanoscale fibres to change the textile
wettability. This makes the textile much more stain resistant.
## Companies making nanotech research equipment
- MultiProbe Manufacturer of a 1-to-6 head
Atomic Force nanoprobing tool used in failure analysis, that
combines multi-scan fault isolation imaging with nanoprobing
electrical capabilities. For process technology node measurements of
32nm, 45nm, 65nm, 90nm or larger.
- Veeco AFM and related equipment
- Zyvex nanomanipulation equipment
- Nanofactory in-situ TEM manipulation
equipment
- SmarAct nanomanipulators
- Capres micro four point conductance measurement
probes
- ImageMetrology SPIP software for SPM
analysis
- QuantumWise software for simulating
nanosystems
- 75 AFM and related equipment
## Products that have been nanostructured for decades
- Catalysts
- Haldor Topsøe
- Computer processesors are increasingly made of nanoscale systems
- Intel
## Non-nanotech products and a warning
Not everything that says nano is nano - and given the hype surrounding
nanotechnology you will see an increasing number of \'nano\' products
that have nothing to do with it. It is worrying when sometimes problems
arise with non-nano products and this adds to the \'scare\' that is
present in the public, fuelled by the newspapers where they are just
waiting for a nice scandal\... an example was the product Magic Nano
from a German
company that
made a number of users sick when inhaling the aerosol cleaning product -
which in the end turned out to have nothing \'nano\' in it. There is
good reason to be very alert to such issues. Not all countries have
legislation in place to secure the consumers against the possible
dangers present in nanoparticles and some products could end being
marketed before having been tested well enough. Though this example
turned out to be \'non-nano\', we will probably meet new cases shortly
that are truly \'nano\'. On this background environmental and health
aspects will be an important part of this book.
# Suppliers
Nanomaterials
- Sigma-Aldrich
- Zyvex
- overview of companies making nanoparticles and related
equipment
Nanolithography
- NIL Technology sells stamps for nanoimprint
lithography (NIL) and provides imprint services.
Quantum Dots
- Evident technologies
# A nano-timeline
Overview of some important events in nanotechnology
See also History of Nanotechnology in
Wikipedia
Year Development
---------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Medieval Observation of metal whisker growth and nanoparticles used for staining glass
1900 Max Planck proposes energy quantization.
1905-30 Development of quantum mechanics
1927 Heisenberg formulated his uncertainty principle
1933 The first First electron microscope was built by Ernst Ruska
1952 First carbon nanotubes observation by Radushkevich and Lukyanovich
1953 DNA structure discovered by James D. Watson and Francis Crick
1959 Feynmanns talk There is plenty of room at the bottom
1965 Proposal of Moores Law
1981 Invention of STM by Gerd Binnig and Heinrich Rohrer
1985 Invention of AFM by Binnig, Quate and Gerber
1985 Buckyball discovery by Harry Kroto, Robert Curl, and Richard Smalley
1986 K. Eric Drexler publishes his book *Engines of Creation*, in which he discusses both the potential huge benefits and the potential dangers of nanotechnology. He talks about a future of nanotechnology defined by molecular manufacturing, where self-replicating nanobots/assemblers are engineered to carry out practical applications.
1989 Don Eigler pushed around xenon atoms to spell IBM
: A Nanotechnology Timeline
# A nano-scale overview
Just to get a sense of proportion
Scale typical elements
--------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 m 1 m is 1.000.000.000 nanometers ( 10\^9 nm )
200 µm About the size of the smallest letters you can write with a very very sharp pencil and a very very steady hand.
100 µm Typical thick hair
10-1000 µm Cells in living organisms can have many sizes, and neurons can be much longer. In frog embryos (Tadpoles) the initial embryo cells can be up to 1000µm.
8 µm Red blood cell
1 µm Bacteria
100 nm Virus
5-100 nm The range for nanotechnology systems built from atomic/molecular components (quantum dots, nanoparticles, diameter of nanotubes and nanowires, lipid membranes, nanopores\...).
10 nm Size of typical Antibody molecules in living organisms immune defence
6-10 nm Thickness of a cell membrane, and typical pore size in membrane.
2.5 nm The width of DNA (but it depends on the conditions)
1 nm The size of a C60 buckyball molecule or glucose molecule.
0.3 nm The size of a water molecule.
1 Å = 0.1 nm Roughly the size of hydrogen atom.
0.7 Å = 70 pm The best resolution in AFM achieved so far where they managed to image individual orbitals in an atom.
: A Nano-scale overview
- Distances between objects can be measured with sub Å precision with
STM, laser interferometry and its even done continuously in a
standard airbag acceleration sensor chip that costs a few dollars
and senses the vibrations of a micro-inertial mass element with
femtometer precision (10\^-15 m).
# Bibliography
- G. Ali Mansoori, *Principles of Nanotechnology*, Molecular-Based
Study of Condensed Matter in Small Systems, (New Jersey: World
Scientific, 2006).
- Monthioux, Marc; Kuznetsov, Vladimir L. (2006). \"Who should be
given the credit for the discovery of carbon nanotubes?\".
Carbon 44. <doi:10.1016/j.carbon.2006.03.019>. Retrieved on
2007-07-26.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
the nanotechnology pioneers by Steven A. Edwards
```{=html}
<references />
```
*Engines of Creation 2.0: The Coming Era of Nanotechnology* by K. Eric
Drexler
------------------------------------------------------------------------
|
# Nanotechnology/Overviews#A nano-timeline
Navigate
---------------------------------------------------------
\<\< Prev: Perspective
\>\< Main: Nanotechnology
\>\> Next: About
\_\_TOC\_\_
------------------------------------------------------------------------
# Internet Resources
## Handbooks and Encyclopedias
These are only accessible for subscribers (which is one reason this
Wikibook on Nanotechnology was started):
- Encyclopedia of Nanoscience and Nanotechnology, 10-Volume
Set
- Handbook of Theoretical and Computational Nanotechnology, 10-Volume
Set
- Springer Handbook of
Nanotechnology
## Websites and newsletters
- International Council on Nanotechnology
(ICON) a multi-stakeholder group dedicated to
the safe, responsible and beneficial development of nanotechnology.
ICON serves as an aggregator for news and research related to
nanotechnology environment, health and safety.
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety compiles papers in
peer-reviewed journals that address EHS issues in nanotechnology.
- Virtual journal of nanotechnology
compiles nano-related papers in peer reviewed journals that do not
specialize solely in nanotechnology.
- ACS Nanotation
- Nanotechweb.org
- Nanoforum
- Nanowerk
- nanoRISK
- Physorg.com
- Foresight Nanotech Institute
- Center for Responsible Nanotechnology
- A-Z of nanotechnology
- Google Directory -
Nanotechnology
(sourced from the Open Directory
Project)
- Scientific American Nanotechnology
Page
- NanoEd Resource Portal managed by the
National Center for Learning and Teaching in Nanoscale Science and
Engineering (NCLT)
- NanoHub.org
- UnderstandingNano
## Search engines
There are many ways to find information in scientific literature and
some that even specialize in nanotechnology. Apart from the free search
engines and useful tools such as Google
scholar and Google
Desktop, there are several more dedicated
commercial services:
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety (VJ-NanoEHS)
compiles papers in peer-reviewed journals that address EHS issues in
nanotechnology.
- ISI - Web of Science
Database contains peer
reviewed journals, their references and citations. It also has very
useful tools such as \'find related papers\' that searches for
papers sharing the same references as the entry you\'re looking at.
This is the database behind the compilation of the journal citation
factors.
- Knovel - Online Handbook Collection and
Database is an
extensive collection of handbooks and tables.
- PROLA - the Physical Review Online Archive
searches Physical Review journals.
- Rubber Bible Online is a physical
chemistry handbook which contains tables of physical and chemical
data.
- Spin AIP Scitation searches related
journals.
- Web of Science by ISI
generates the impact factors (see
journals below).
- Virtual Journal of Nanotechnology
collects nanotech related papers from non-nano specialized journals.
- Derwent Patent database
# Peer reviewed Journals
Overview of the nanotechnology related journals and their impact factors
(2007 values):
Name Web Impact Factor ISSN Comments
--------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------- ------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ACS Nano 1 N/A 1936-0851 general nanotech journal
Advanced Functional Materials 2 7.5 1616-301X ?
Advanced Materials 3 8.2 0935-9648 ?
American Journal of Physics (AJP) 4 0.9 0002-9505 ?
Applied Physics A: Materials Science & Processing 5 1.9 0947-8396 ?
Applied Physics Letters (APL) [](http://apl.aip.org/apl/top.jsp) 3.6 ? ?
AZojono - Journal of Nanotechnology Online 6 N/A ? Free access journal
Chemical Reviews 7 22.8 0009-2665 ?
Current Nanoscience 8 2.8 1573-4137 Reviews and original research reports
Fullerenes, Nanotubes, and Carbon Nanostructures 9 0.5 1536-383x all areas of fullerene research
IEEE Transactions on Nanotechnology 10 2.1 1536-125X physical basis and engineering applications of nanotechnology
International Journal of Nanomedicine 11 N/A 1176-9114 ?
International Journal of Nanoscience 12 N/A 0219-581X New nanotech journal (Feb 2002)
Japanese Journal of Applied Physics 13 1.2 1347-4065 ?
Journal of Applied Physics 14 2.2 ? ?
Journal of Biomedical Nanotechnology \[\] N/A ? JBN is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
Journal of Experimental Nanoscience 15 N/A 1745-8080 New nanotech journal(March 2006)
Journal Of Microlithography Microfabrication And Microsystems 16 N/A 1537-1646
Journal of Micromechanics and Microengineering 17 1.9 0960-1317 ?
Journal of Nano Research 18 N/A 1661-9897
Journal of Nanomaterials 19 N/A ? science and applications of nanoscale and nanostructured materials
Journal of Nanoparticle Research 20 2.3 1388-0764 ?
Journal of Nanoscience and Nanotechnology 21 2.0 ? JNN is a multidisciplinary peer-reviewed journal covering fundamental and applied research in all disciplines of science, engineering and medicine. JNN publishes all aspects of nanoscale science and technology dealing with materials synthesis, processing, nanofabrication, nanoprobes, spectroscopy, properties, biological systems, nanostructures, theory and computation, nanoelectronics, nano-optics, nano-mechanics, nanodevices, nanobiotechnology, nanomedicine, nanotoxicology.
Journal of Physical Chemistry A 22 2.9 ? ?
Journal of Physical Chemistry B 23 4.1 ? ?
Journal of Physical Chemistry C 24 N/A ? Nanomaterials and Interfaces, Nanoparticles and Nanostructures, Surfaces, Interfaces, Catalysis, Electron Transport, Optical and Electronic Devices, Energy Conversion and Storage
Journal of the American Chemical Society (JACS) 25 7.9 ? Multidisciplinary chemistry journal
Journal of Vacuum Science & Technology A (JVSTA) 26 1.3 ? Vacuum, Surfaces, Films
Journal of Vacuum Science & Technology B (JVSTB) 27 1.4 ? Microelectronics and Nanometer Structures: Processing, Measurement, and Phenomena
Langmuir 28 4.0 ? Research in the fields of colloids, surfaces, and interfaces
Micron 29 1.7 ? Journal for Microscopy
Materials Chemistry and Physics 30 1.9 0254-0584 materials science, including nanomaterials and opto electronics
Materials Science and Engineering: C 31 1.3 0928-4931 Biomimetic and Supramolecular Systems
Materials Science and Engineering: R: Reports 32 17.7 0927-796X Invited review papers covering the full spectrum of materials science and engineering
Materials Today 33 N/A 1369-7021 materials science and technology
Microfluidics and Nanofluidics 34 2.2 1613-4982 all aspects of microfluidics, nanofluidics, and lab-on-a-chip science and technology
Microscopy Research and Technique 35 1.6 ? ?
Nano 36 N/A 1793-2920 New nanotech journal (July 2006)
Nano Letters 37 9.6 ? General nanotechnology journal
Nanomedicine 38 2.8 ? ?
Nanopages 39 N/A 1787-4033 Since sept 2006.
Nano Research 40 N/A ? First issue july 2008
Nano Research Letters 41 wait 1931-7573 articles with open access
Nanotechnology 42 3.3 ? Journal specializing in nanotechnology
NanoToday 43 N/A ? Is this peer reviewed or more a news/reviews journal?
Nature 44 31.434 ? One of the major journals in science
Nature Biotechnology 45 22.8 ? advances in life sciences
Nature Materials 46 19.8 ? covers a range of topics within materials science
Nature Methods 47 15.5 ? tried-and-tested techniques in the life sciences and related area of chemistry
Nature Nanotechnology 48 14.9 ? mix of news, reviews, and research papers
Nanotoxicology 49 N/A 1743-5404 Research relating to the potential for human and environmental exposure, hazard and risk associated with the use and development of nano-structured materials
Open Nanoscience Journal [](http://www.bentham.org/open/tonanoj) N/A 1874-1401 Open access journal with research articles, reviews and letters.
Physical Review Letters (PRL) [](http://scitation.aip.org/prl/help.jsp) 6.9 ? One of the top physics journals
PLoS Biology [](http://biology.plosjournals.org/) 13.5 1544-9173 Peer reviewed open access bio journal
PLoS ONE [](http://one.plosjournals.org/) N/A ? Peer reviewed open access science journal
Proceedings of the National Academy of Sciences(PNAS) [](http://www.pnas.org) 10.2 ? multidisciplinary scientific serial: biological, physical, and social sciences.
Recent Patents on Nanotechnology 50 N/A 1872-2105 ?
Science 51 26.4 ? One of the major journals in science
Solid-State Electronics 52 1.3 ? ?
Small Journal 53 6.4 1613-6810 New nanotech journal
Smart Materials and Structures 54 1.5 0964-1726 since 1992
Thin Solid Films 55 1.7 0040-6090 Thin-film synthesis, characterization, and applications.
Ultramicroscopy 56 2.0 ? Microscopy related research.
Virtual Journal of Nanotechnlogy 57 N/A 1553-9644 Collecting nanotech related papers from non-nano spcialized journals
: Nanotechnology Related Journals
- Impact factors are only guides to how much a papers is referenced in
the years just after publication.
- Please add comments about the journals and update impact factors!
- The Physics and Astronomy Classification Scheme
PACS2006 and
Nanoscale Science and Technology - Collection of Applicable Terms
from PACS 2006
# Conferences
- NSTI Nanotech 2008
- TNT - Trends in Nanotechnology
2007;2006
- MNE - Micro and Nanoengineering
2007;2008
- Virtual Conference on Nanoscale Science and
Technology
- Foresight Unconference Vision
Weekend
NanoBioInfoCognoSocioPhysical technologies
- 58
- International Microprocess and Nanotechnology Conference,
Japan
- Nanosafe 2008: International Conference on Safe production and use
of nanomaterials
# Nanotech Products
Please add more products, comments and more info about the products if
you have any!
See also the List of nanotechnology applications in
wikipedia
Woodrow Wilsom Center for International Scholars is starting a Project
on Emerging Nanotechnologies (website should be under construction at
www.nanoproject.org) that among other
things will try to map the available \'nano\'products and work to ensure
possible risks are minimized and benefits are realized.
### Emerging products
- 2008 MultiProbe's AFM Nanoprober is now qualified for 32nm
technology nodes. 59
- Intel will make products with 45 nm linewidth transistors available
from 2008
60
- Batteries are increasingly incorporating nanostructures.
- Flexible, cheaper, or more luminous Flat screen displays
- Pressure-sensitive mobile devices
61
### Available in 2006
- Surface coatings: TCnano,
Nanocover, Stay
clean.
### Available in 2005
- Molybdenum disulfide catalytic nanoparticles in Brimm
catalysts62
made by Haldor Topsøe
- Forbes top ten nanoproducts in
200563
- Apples IPod with sub 100nm elements in its memory chips
- Choleterol reducing nanoencapsulated oil,Shemen Industries
Canola Active.
- Nanocrystals improve the consistency of
chocolate64
- Zelen Fullerene C-60 Day Cream 65
- Easton Stealth CNT baseball bat
- Nanotex textiles once again
- ArcticShield polyester socks from ARC Outdoors with 19nm silver
particles that kill fungs to reduce odor.
- NanoGuard developed by Behr Process for improved paint hardness.
- Pilkingtons self-cleaning \'Activ Glass\'.
- NanoBreeze Air Purifier from NanoTwin Technologies, where the UV
light from a fluorescent tube cleans the air by photochemical
reactions in nanoparticles.
### Available in 2004
- Cold cathode carbon nanotube emitters for X-ray analysis by Oxford
instruments66\[\]
- Forbes has an overview in 2004 of what they consider the top ten
nanotech
products:
- Footwarmers with nanporous aerogel for 3-20 times lighter than
comparable insulating materials used in shoes (produced by Aspen
Aerogels).
- Matress covers with nanotex fibres that can be washed (Simmonos
bedding company).
- Better golf drivers with carbon nanotube enforced metal
composites (produced by Maruman & Co) and nanocomposite
containing golf balls (produced by NanoDynamics)
- The company \'Bionova\' apparently adds some nanoproducts to
their \'personalized product line\'.
- EnviroSystems make a nanoemulsive disinfectant cleaner, called
EcoTru, that is EPA Tox category 4 registered (meaning very safe
to use)
- EnviroSystems also make a spray-on version of this product.
- BASF makes a nanoparticle coating for building materials called
Mincor, that reduces their wettabililty.
- A nanostructured coating produced by Valley View, called Clarity
Defender, improves visibility through windscreens in rain.
Another company, Nano-Film, makes a similar coating on
sunglasses.
- w:Flex-Power makes a gel containing
nanoscale liposomes for soothing aching muscles
- 3M espe Dental adhesive with silica nanoparticle filler.
### Available in 2003
- NanoGuard Zink Oxide nanoparticles for sunscreens FDA
approved
- Forbes 2003 top ten nanoproduct
67
includes:
- High performance ski wax, Cerax Nanowax
68.
- Nanotex textiles in ski jackets from
Ziener69
- Nanotex textiles
- Plenitude Revitalift antiwrinkle cream by L\'Oréal contains
nanocapsules with vitamin A 70
- organic light-emitting diodes (OLEDs) in Sony camera flat screen
display
- Nanofilm coatings for ani-reflection and scratch resistance
71
- Zink oxide nanoparticles in Sunscreen by BASF
72
- carbon nanotube enforced tennis rackets
73 and nanopolymer enforced tennis
balls 74
### Available in 2000
Nanotex makes textiles where the clothing
fibres have been coating in nanoscale fibres to change the textile
wettability. This makes the textile much more stain resistant.
## Companies making nanotech research equipment
- MultiProbe Manufacturer of a 1-to-6 head
Atomic Force nanoprobing tool used in failure analysis, that
combines multi-scan fault isolation imaging with nanoprobing
electrical capabilities. For process technology node measurements of
32nm, 45nm, 65nm, 90nm or larger.
- Veeco AFM and related equipment
- Zyvex nanomanipulation equipment
- Nanofactory in-situ TEM manipulation
equipment
- SmarAct nanomanipulators
- Capres micro four point conductance measurement
probes
- ImageMetrology SPIP software for SPM
analysis
- QuantumWise software for simulating
nanosystems
- 75 AFM and related equipment
## Products that have been nanostructured for decades
- Catalysts
- Haldor Topsøe
- Computer processesors are increasingly made of nanoscale systems
- Intel
## Non-nanotech products and a warning
Not everything that says nano is nano - and given the hype surrounding
nanotechnology you will see an increasing number of \'nano\' products
that have nothing to do with it. It is worrying when sometimes problems
arise with non-nano products and this adds to the \'scare\' that is
present in the public, fuelled by the newspapers where they are just
waiting for a nice scandal\... an example was the product Magic Nano
from a German
company that
made a number of users sick when inhaling the aerosol cleaning product -
which in the end turned out to have nothing \'nano\' in it. There is
good reason to be very alert to such issues. Not all countries have
legislation in place to secure the consumers against the possible
dangers present in nanoparticles and some products could end being
marketed before having been tested well enough. Though this example
turned out to be \'non-nano\', we will probably meet new cases shortly
that are truly \'nano\'. On this background environmental and health
aspects will be an important part of this book.
# Suppliers
Nanomaterials
- Sigma-Aldrich
- Zyvex
- overview of companies making nanoparticles and related
equipment
Nanolithography
- NIL Technology sells stamps for nanoimprint
lithography (NIL) and provides imprint services.
Quantum Dots
- Evident technologies
# A nano-timeline
Overview of some important events in nanotechnology
See also History of Nanotechnology in
Wikipedia
Year Development
---------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Medieval Observation of metal whisker growth and nanoparticles used for staining glass
1900 Max Planck proposes energy quantization.
1905-30 Development of quantum mechanics
1927 Heisenberg formulated his uncertainty principle
1933 The first First electron microscope was built by Ernst Ruska
1952 First carbon nanotubes observation by Radushkevich and Lukyanovich
1953 DNA structure discovered by James D. Watson and Francis Crick
1959 Feynmanns talk There is plenty of room at the bottom
1965 Proposal of Moores Law
1981 Invention of STM by Gerd Binnig and Heinrich Rohrer
1985 Invention of AFM by Binnig, Quate and Gerber
1985 Buckyball discovery by Harry Kroto, Robert Curl, and Richard Smalley
1986 K. Eric Drexler publishes his book *Engines of Creation*, in which he discusses both the potential huge benefits and the potential dangers of nanotechnology. He talks about a future of nanotechnology defined by molecular manufacturing, where self-replicating nanobots/assemblers are engineered to carry out practical applications.
1989 Don Eigler pushed around xenon atoms to spell IBM
: A Nanotechnology Timeline
# A nano-scale overview
Just to get a sense of proportion
Scale typical elements
--------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 m 1 m is 1.000.000.000 nanometers ( 10\^9 nm )
200 µm About the size of the smallest letters you can write with a very very sharp pencil and a very very steady hand.
100 µm Typical thick hair
10-1000 µm Cells in living organisms can have many sizes, and neurons can be much longer. In frog embryos (Tadpoles) the initial embryo cells can be up to 1000µm.
8 µm Red blood cell
1 µm Bacteria
100 nm Virus
5-100 nm The range for nanotechnology systems built from atomic/molecular components (quantum dots, nanoparticles, diameter of nanotubes and nanowires, lipid membranes, nanopores\...).
10 nm Size of typical Antibody molecules in living organisms immune defence
6-10 nm Thickness of a cell membrane, and typical pore size in membrane.
2.5 nm The width of DNA (but it depends on the conditions)
1 nm The size of a C60 buckyball molecule or glucose molecule.
0.3 nm The size of a water molecule.
1 Å = 0.1 nm Roughly the size of hydrogen atom.
0.7 Å = 70 pm The best resolution in AFM achieved so far where they managed to image individual orbitals in an atom.
: A Nano-scale overview
- Distances between objects can be measured with sub Å precision with
STM, laser interferometry and its even done continuously in a
standard airbag acceleration sensor chip that costs a few dollars
and senses the vibrations of a micro-inertial mass element with
femtometer precision (10\^-15 m).
# Bibliography
- G. Ali Mansoori, *Principles of Nanotechnology*, Molecular-Based
Study of Condensed Matter in Small Systems, (New Jersey: World
Scientific, 2006).
- Monthioux, Marc; Kuznetsov, Vladimir L. (2006). \"Who should be
given the credit for the discovery of carbon nanotubes?\".
Carbon 44. <doi:10.1016/j.carbon.2006.03.019>. Retrieved on
2007-07-26.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
the nanotechnology pioneers by Steven A. Edwards
```{=html}
<references />
```
*Engines of Creation 2.0: The Coming Era of Nanotechnology* by K. Eric
Drexler
------------------------------------------------------------------------
|
# Nanotechnology/Overviews#A nano-scale overview
Navigate
---------------------------------------------------------
\<\< Prev: Perspective
\>\< Main: Nanotechnology
\>\> Next: About
\_\_TOC\_\_
------------------------------------------------------------------------
# Internet Resources
## Handbooks and Encyclopedias
These are only accessible for subscribers (which is one reason this
Wikibook on Nanotechnology was started):
- Encyclopedia of Nanoscience and Nanotechnology, 10-Volume
Set
- Handbook of Theoretical and Computational Nanotechnology, 10-Volume
Set
- Springer Handbook of
Nanotechnology
## Websites and newsletters
- International Council on Nanotechnology
(ICON) a multi-stakeholder group dedicated to
the safe, responsible and beneficial development of nanotechnology.
ICON serves as an aggregator for news and research related to
nanotechnology environment, health and safety.
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety compiles papers in
peer-reviewed journals that address EHS issues in nanotechnology.
- Virtual journal of nanotechnology
compiles nano-related papers in peer reviewed journals that do not
specialize solely in nanotechnology.
- ACS Nanotation
- Nanotechweb.org
- Nanoforum
- Nanowerk
- nanoRISK
- Physorg.com
- Foresight Nanotech Institute
- Center for Responsible Nanotechnology
- A-Z of nanotechnology
- Google Directory -
Nanotechnology
(sourced from the Open Directory
Project)
- Scientific American Nanotechnology
Page
- NanoEd Resource Portal managed by the
National Center for Learning and Teaching in Nanoscale Science and
Engineering (NCLT)
- NanoHub.org
- UnderstandingNano
## Search engines
There are many ways to find information in scientific literature and
some that even specialize in nanotechnology. Apart from the free search
engines and useful tools such as Google
scholar and Google
Desktop, there are several more dedicated
commercial services:
- ICON Virtual Journal of Nanotechnology Environment, Health and
Safety (VJ-NanoEHS)
compiles papers in peer-reviewed journals that address EHS issues in
nanotechnology.
- ISI - Web of Science
Database contains peer
reviewed journals, their references and citations. It also has very
useful tools such as \'find related papers\' that searches for
papers sharing the same references as the entry you\'re looking at.
This is the database behind the compilation of the journal citation
factors.
- Knovel - Online Handbook Collection and
Database is an
extensive collection of handbooks and tables.
- PROLA - the Physical Review Online Archive
searches Physical Review journals.
- Rubber Bible Online is a physical
chemistry handbook which contains tables of physical and chemical
data.
- Spin AIP Scitation searches related
journals.
- Web of Science by ISI
generates the impact factors (see
journals below).
- Virtual Journal of Nanotechnology
collects nanotech related papers from non-nano specialized journals.
- Derwent Patent database
# Peer reviewed Journals
Overview of the nanotechnology related journals and their impact factors
(2007 values):
Name Web Impact Factor ISSN Comments
--------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------- ------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ACS Nano 1 N/A 1936-0851 general nanotech journal
Advanced Functional Materials 2 7.5 1616-301X ?
Advanced Materials 3 8.2 0935-9648 ?
American Journal of Physics (AJP) 4 0.9 0002-9505 ?
Applied Physics A: Materials Science & Processing 5 1.9 0947-8396 ?
Applied Physics Letters (APL) [](http://apl.aip.org/apl/top.jsp) 3.6 ? ?
AZojono - Journal of Nanotechnology Online 6 N/A ? Free access journal
Chemical Reviews 7 22.8 0009-2665 ?
Current Nanoscience 8 2.8 1573-4137 Reviews and original research reports
Fullerenes, Nanotubes, and Carbon Nanostructures 9 0.5 1536-383x all areas of fullerene research
IEEE Transactions on Nanotechnology 10 2.1 1536-125X physical basis and engineering applications of nanotechnology
International Journal of Nanomedicine 11 N/A 1176-9114 ?
International Journal of Nanoscience 12 N/A 0219-581X New nanotech journal (Feb 2002)
Japanese Journal of Applied Physics 13 1.2 1347-4065 ?
Journal of Applied Physics 14 2.2 ? ?
Journal of Biomedical Nanotechnology \[\] N/A ? JBN is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
Journal of Experimental Nanoscience 15 N/A 1745-8080 New nanotech journal(March 2006)
Journal Of Microlithography Microfabrication And Microsystems 16 N/A 1537-1646
Journal of Micromechanics and Microengineering 17 1.9 0960-1317 ?
Journal of Nano Research 18 N/A 1661-9897
Journal of Nanomaterials 19 N/A ? science and applications of nanoscale and nanostructured materials
Journal of Nanoparticle Research 20 2.3 1388-0764 ?
Journal of Nanoscience and Nanotechnology 21 2.0 ? JNN is a multidisciplinary peer-reviewed journal covering fundamental and applied research in all disciplines of science, engineering and medicine. JNN publishes all aspects of nanoscale science and technology dealing with materials synthesis, processing, nanofabrication, nanoprobes, spectroscopy, properties, biological systems, nanostructures, theory and computation, nanoelectronics, nano-optics, nano-mechanics, nanodevices, nanobiotechnology, nanomedicine, nanotoxicology.
Journal of Physical Chemistry A 22 2.9 ? ?
Journal of Physical Chemistry B 23 4.1 ? ?
Journal of Physical Chemistry C 24 N/A ? Nanomaterials and Interfaces, Nanoparticles and Nanostructures, Surfaces, Interfaces, Catalysis, Electron Transport, Optical and Electronic Devices, Energy Conversion and Storage
Journal of the American Chemical Society (JACS) 25 7.9 ? Multidisciplinary chemistry journal
Journal of Vacuum Science & Technology A (JVSTA) 26 1.3 ? Vacuum, Surfaces, Films
Journal of Vacuum Science & Technology B (JVSTB) 27 1.4 ? Microelectronics and Nanometer Structures: Processing, Measurement, and Phenomena
Langmuir 28 4.0 ? Research in the fields of colloids, surfaces, and interfaces
Micron 29 1.7 ? Journal for Microscopy
Materials Chemistry and Physics 30 1.9 0254-0584 materials science, including nanomaterials and opto electronics
Materials Science and Engineering: C 31 1.3 0928-4931 Biomimetic and Supramolecular Systems
Materials Science and Engineering: R: Reports 32 17.7 0927-796X Invited review papers covering the full spectrum of materials science and engineering
Materials Today 33 N/A 1369-7021 materials science and technology
Microfluidics and Nanofluidics 34 2.2 1613-4982 all aspects of microfluidics, nanofluidics, and lab-on-a-chip science and technology
Microscopy Research and Technique 35 1.6 ? ?
Nano 36 N/A 1793-2920 New nanotech journal (July 2006)
Nano Letters 37 9.6 ? General nanotechnology journal
Nanomedicine 38 2.8 ? ?
Nanopages 39 N/A 1787-4033 Since sept 2006.
Nano Research 40 N/A ? First issue july 2008
Nano Research Letters 41 wait 1931-7573 articles with open access
Nanotechnology 42 3.3 ? Journal specializing in nanotechnology
NanoToday 43 N/A ? Is this peer reviewed or more a news/reviews journal?
Nature 44 31.434 ? One of the major journals in science
Nature Biotechnology 45 22.8 ? advances in life sciences
Nature Materials 46 19.8 ? covers a range of topics within materials science
Nature Methods 47 15.5 ? tried-and-tested techniques in the life sciences and related area of chemistry
Nature Nanotechnology 48 14.9 ? mix of news, reviews, and research papers
Nanotoxicology 49 N/A 1743-5404 Research relating to the potential for human and environmental exposure, hazard and risk associated with the use and development of nano-structured materials
Open Nanoscience Journal [](http://www.bentham.org/open/tonanoj) N/A 1874-1401 Open access journal with research articles, reviews and letters.
Physical Review Letters (PRL) [](http://scitation.aip.org/prl/help.jsp) 6.9 ? One of the top physics journals
PLoS Biology [](http://biology.plosjournals.org/) 13.5 1544-9173 Peer reviewed open access bio journal
PLoS ONE [](http://one.plosjournals.org/) N/A ? Peer reviewed open access science journal
Proceedings of the National Academy of Sciences(PNAS) [](http://www.pnas.org) 10.2 ? multidisciplinary scientific serial: biological, physical, and social sciences.
Recent Patents on Nanotechnology 50 N/A 1872-2105 ?
Science 51 26.4 ? One of the major journals in science
Solid-State Electronics 52 1.3 ? ?
Small Journal 53 6.4 1613-6810 New nanotech journal
Smart Materials and Structures 54 1.5 0964-1726 since 1992
Thin Solid Films 55 1.7 0040-6090 Thin-film synthesis, characterization, and applications.
Ultramicroscopy 56 2.0 ? Microscopy related research.
Virtual Journal of Nanotechnlogy 57 N/A 1553-9644 Collecting nanotech related papers from non-nano spcialized journals
: Nanotechnology Related Journals
- Impact factors are only guides to how much a papers is referenced in
the years just after publication.
- Please add comments about the journals and update impact factors!
- The Physics and Astronomy Classification Scheme
PACS2006 and
Nanoscale Science and Technology - Collection of Applicable Terms
from PACS 2006
# Conferences
- NSTI Nanotech 2008
- TNT - Trends in Nanotechnology
2007;2006
- MNE - Micro and Nanoengineering
2007;2008
- Virtual Conference on Nanoscale Science and
Technology
- Foresight Unconference Vision
Weekend
NanoBioInfoCognoSocioPhysical technologies
- 58
- International Microprocess and Nanotechnology Conference,
Japan
- Nanosafe 2008: International Conference on Safe production and use
of nanomaterials
# Nanotech Products
Please add more products, comments and more info about the products if
you have any!
See also the List of nanotechnology applications in
wikipedia
Woodrow Wilsom Center for International Scholars is starting a Project
on Emerging Nanotechnologies (website should be under construction at
www.nanoproject.org) that among other
things will try to map the available \'nano\'products and work to ensure
possible risks are minimized and benefits are realized.
### Emerging products
- 2008 MultiProbe's AFM Nanoprober is now qualified for 32nm
technology nodes. 59
- Intel will make products with 45 nm linewidth transistors available
from 2008
60
- Batteries are increasingly incorporating nanostructures.
- Flexible, cheaper, or more luminous Flat screen displays
- Pressure-sensitive mobile devices
61
### Available in 2006
- Surface coatings: TCnano,
Nanocover, Stay
clean.
### Available in 2005
- Molybdenum disulfide catalytic nanoparticles in Brimm
catalysts62
made by Haldor Topsøe
- Forbes top ten nanoproducts in
200563
- Apples IPod with sub 100nm elements in its memory chips
- Choleterol reducing nanoencapsulated oil,Shemen Industries
Canola Active.
- Nanocrystals improve the consistency of
chocolate64
- Zelen Fullerene C-60 Day Cream 65
- Easton Stealth CNT baseball bat
- Nanotex textiles once again
- ArcticShield polyester socks from ARC Outdoors with 19nm silver
particles that kill fungs to reduce odor.
- NanoGuard developed by Behr Process for improved paint hardness.
- Pilkingtons self-cleaning \'Activ Glass\'.
- NanoBreeze Air Purifier from NanoTwin Technologies, where the UV
light from a fluorescent tube cleans the air by photochemical
reactions in nanoparticles.
### Available in 2004
- Cold cathode carbon nanotube emitters for X-ray analysis by Oxford
instruments66\[\]
- Forbes has an overview in 2004 of what they consider the top ten
nanotech
products:
- Footwarmers with nanporous aerogel for 3-20 times lighter than
comparable insulating materials used in shoes (produced by Aspen
Aerogels).
- Matress covers with nanotex fibres that can be washed (Simmonos
bedding company).
- Better golf drivers with carbon nanotube enforced metal
composites (produced by Maruman & Co) and nanocomposite
containing golf balls (produced by NanoDynamics)
- The company \'Bionova\' apparently adds some nanoproducts to
their \'personalized product line\'.
- EnviroSystems make a nanoemulsive disinfectant cleaner, called
EcoTru, that is EPA Tox category 4 registered (meaning very safe
to use)
- EnviroSystems also make a spray-on version of this product.
- BASF makes a nanoparticle coating for building materials called
Mincor, that reduces their wettabililty.
- A nanostructured coating produced by Valley View, called Clarity
Defender, improves visibility through windscreens in rain.
Another company, Nano-Film, makes a similar coating on
sunglasses.
- w:Flex-Power makes a gel containing
nanoscale liposomes for soothing aching muscles
- 3M espe Dental adhesive with silica nanoparticle filler.
### Available in 2003
- NanoGuard Zink Oxide nanoparticles for sunscreens FDA
approved
- Forbes 2003 top ten nanoproduct
67
includes:
- High performance ski wax, Cerax Nanowax
68.
- Nanotex textiles in ski jackets from
Ziener69
- Nanotex textiles
- Plenitude Revitalift antiwrinkle cream by L\'Oréal contains
nanocapsules with vitamin A 70
- organic light-emitting diodes (OLEDs) in Sony camera flat screen
display
- Nanofilm coatings for ani-reflection and scratch resistance
71
- Zink oxide nanoparticles in Sunscreen by BASF
72
- carbon nanotube enforced tennis rackets
73 and nanopolymer enforced tennis
balls 74
### Available in 2000
Nanotex makes textiles where the clothing
fibres have been coating in nanoscale fibres to change the textile
wettability. This makes the textile much more stain resistant.
## Companies making nanotech research equipment
- MultiProbe Manufacturer of a 1-to-6 head
Atomic Force nanoprobing tool used in failure analysis, that
combines multi-scan fault isolation imaging with nanoprobing
electrical capabilities. For process technology node measurements of
32nm, 45nm, 65nm, 90nm or larger.
- Veeco AFM and related equipment
- Zyvex nanomanipulation equipment
- Nanofactory in-situ TEM manipulation
equipment
- SmarAct nanomanipulators
- Capres micro four point conductance measurement
probes
- ImageMetrology SPIP software for SPM
analysis
- QuantumWise software for simulating
nanosystems
- 75 AFM and related equipment
## Products that have been nanostructured for decades
- Catalysts
- Haldor Topsøe
- Computer processesors are increasingly made of nanoscale systems
- Intel
## Non-nanotech products and a warning
Not everything that says nano is nano - and given the hype surrounding
nanotechnology you will see an increasing number of \'nano\' products
that have nothing to do with it. It is worrying when sometimes problems
arise with non-nano products and this adds to the \'scare\' that is
present in the public, fuelled by the newspapers where they are just
waiting for a nice scandal\... an example was the product Magic Nano
from a German
company that
made a number of users sick when inhaling the aerosol cleaning product -
which in the end turned out to have nothing \'nano\' in it. There is
good reason to be very alert to such issues. Not all countries have
legislation in place to secure the consumers against the possible
dangers present in nanoparticles and some products could end being
marketed before having been tested well enough. Though this example
turned out to be \'non-nano\', we will probably meet new cases shortly
that are truly \'nano\'. On this background environmental and health
aspects will be an important part of this book.
# Suppliers
Nanomaterials
- Sigma-Aldrich
- Zyvex
- overview of companies making nanoparticles and related
equipment
Nanolithography
- NIL Technology sells stamps for nanoimprint
lithography (NIL) and provides imprint services.
Quantum Dots
- Evident technologies
# A nano-timeline
Overview of some important events in nanotechnology
See also History of Nanotechnology in
Wikipedia
Year Development
---------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Medieval Observation of metal whisker growth and nanoparticles used for staining glass
1900 Max Planck proposes energy quantization.
1905-30 Development of quantum mechanics
1927 Heisenberg formulated his uncertainty principle
1933 The first First electron microscope was built by Ernst Ruska
1952 First carbon nanotubes observation by Radushkevich and Lukyanovich
1953 DNA structure discovered by James D. Watson and Francis Crick
1959 Feynmanns talk There is plenty of room at the bottom
1965 Proposal of Moores Law
1981 Invention of STM by Gerd Binnig and Heinrich Rohrer
1985 Invention of AFM by Binnig, Quate and Gerber
1985 Buckyball discovery by Harry Kroto, Robert Curl, and Richard Smalley
1986 K. Eric Drexler publishes his book *Engines of Creation*, in which he discusses both the potential huge benefits and the potential dangers of nanotechnology. He talks about a future of nanotechnology defined by molecular manufacturing, where self-replicating nanobots/assemblers are engineered to carry out practical applications.
1989 Don Eigler pushed around xenon atoms to spell IBM
: A Nanotechnology Timeline
# A nano-scale overview
Just to get a sense of proportion
Scale typical elements
--------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1 m 1 m is 1.000.000.000 nanometers ( 10\^9 nm )
200 µm About the size of the smallest letters you can write with a very very sharp pencil and a very very steady hand.
100 µm Typical thick hair
10-1000 µm Cells in living organisms can have many sizes, and neurons can be much longer. In frog embryos (Tadpoles) the initial embryo cells can be up to 1000µm.
8 µm Red blood cell
1 µm Bacteria
100 nm Virus
5-100 nm The range for nanotechnology systems built from atomic/molecular components (quantum dots, nanoparticles, diameter of nanotubes and nanowires, lipid membranes, nanopores\...).
10 nm Size of typical Antibody molecules in living organisms immune defence
6-10 nm Thickness of a cell membrane, and typical pore size in membrane.
2.5 nm The width of DNA (but it depends on the conditions)
1 nm The size of a C60 buckyball molecule or glucose molecule.
0.3 nm The size of a water molecule.
1 Å = 0.1 nm Roughly the size of hydrogen atom.
0.7 Å = 70 pm The best resolution in AFM achieved so far where they managed to image individual orbitals in an atom.
: A Nano-scale overview
- Distances between objects can be measured with sub Å precision with
STM, laser interferometry and its even done continuously in a
standard airbag acceleration sensor chip that costs a few dollars
and senses the vibrations of a micro-inertial mass element with
femtometer precision (10\^-15 m).
# Bibliography
- G. Ali Mansoori, *Principles of Nanotechnology*, Molecular-Based
Study of Condensed Matter in Small Systems, (New Jersey: World
Scientific, 2006).
- Monthioux, Marc; Kuznetsov, Vladimir L. (2006). \"Who should be
given the credit for the discovery of carbon nanotubes?\".
Carbon 44. <doi:10.1016/j.carbon.2006.03.019>. Retrieved on
2007-07-26.
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
the nanotechnology pioneers by Steven A. Edwards
```{=html}
<references />
```
*Engines of Creation 2.0: The Coming Era of Nanotechnology* by K. Eric
Drexler
------------------------------------------------------------------------
|
# Nanotechnology/About#Vision
Navigate
---------------------------------------------------------
\<\< Prev: Overviews
\>\< Main: Nanotechnology
\>\> Next: Reaching Out
\_\_TOC\_\_
------------------------------------------------------------------------
## Vision
We hope to use the Wikibooks format to make an Open Source Handbook on
Nanoscience and Nanotechnology, freely accessible for everyone, that can
be updated continuously.
Wikipedia is growing fast and one of the most visited websites on the
net -- a valuable resource of information we all use.
In science and technology we often need more detailed information than
what can be presented in a brief encyclopedic article -- and here
wikibooks.org, a sister project to Wikipedia, can help us with this
newly started handbook.
Though the book is still in its infancy, it has been elected book of the
month December 2006, and we hope this will provide PR and more people
contributing to the project!
The plan to create the book:
1: First to create smaller articles to 'cover' the entire area of
nanotechnology and achieve a well defined structure the book (some parts
could be revised thoroughly in this process,for instance the materials
chapter).
2: Once the structure is reasonably well defined, to begin refining the
articles with in-depth material so we reach lecture-note level material.
3: Since everybody can contribute, a continuous contribution of material
is expected and a backing group of editors is needed to maintain a
trustworthy level of information.
An voluntary editorial board is being put together to oversee the book,
support, contribute and follow its development.
Discussion about the content of the book can be found on the main talk
page talk:Nanotechnology
As with Wikipedia, we hope to see a solid information resource
continuously updated with open source material available for everyone!
## Editing hints
### References in Wikibooks
Add references whenever possible, with reference lists at the end of
each page. Please try to make links to the articles with the DOI
(digital object identifier) because that gives a uniform and structured
access for everyone to the papers.
All papers get a DOI - a unique number like a bar code in a supermarket.
All DOIs are registered by www.doi.org and in
the reference list you can add links like
<https://doi.org/10.1039/b504435a>
so people will be able to find it no matter how the homepage of the
journal or their own library changes.
The References section has an example
reference.
Add links to the Wikipedia whenever possible - and for the beginning I
will rely extensively on Wikipedia\'s pages on the subjects, simply
referring to these. This textbook could be simply a gathering of
Wikipedia pages, but an encyclopedia entry is brief, and for a handbook
it is preferable to have more in-depth material with examples and the
necessary formulas. So, some information in this textbook will be very
much like the Wikipedia entries and we might not need to write it in the
book but can simply refer to Wikipedia, but the hope is that this will
be more a text book as is the intention with Wikibooks.
Multiple references, see w:Help:Footnotes
### Links
There\'s a shorthand way to make links to Wikipedia from Wikibooks:
\[\[w:Quantum_tunneling\|Wikipedia on Quantum Tunneling\]\] gives the
link Wikipedia on Quantum Tunneling.
### Media
## History
The book was started by Kristian
Molhave(wiki user
page) 13. Apr. 2006. Initially it was
named *Nanowiki*, and later changed to
Nanotechnology. Kristian is currently
slowly uploading material to the book and looking for people who would
like to contribute that can and substantial material to specific
sections under the GNU license. I hope we can make an \'editorial
panel\' of people each keeping an eye on and updating specific sections.
The Summer 2008 Duke Talent Identification Program (TIP) eStudies
Nanotechnology students will be adding to the content of this Wikibook.
From June-Aug 2008 there will be content additions with references that
will add to this great resource.
## Authors and Editors
- The Opensource Handbook on Nanoscience and Nanotechnology was
started by Kristian Molhave(wiki user
page)
### Editors
- An editorial board is currently being organized.
## Support and Acknowledgments
Starting this book is supported by the Danish Agency for Science,
Technology and
Innovation
through Kristian Mølhave\'s talent project
'NAMIC' No. 26-04-0258.
## How to Reference this Book
I am not currently sure how work on wikibooks or wikipedia can be
referenced reliably in published literature.
Three suggestions:
1\) Reference the references from the wikibook. Wikibooks are not
intended to be the publication channel for new results, but should be
based on published and accepted information with references and these
references can be used. But this of course does not give credit to the
book, so I recommend then adding an acknowledgement about the book to
give it PR and credit.
2\) Reference the book with a specific page and date - the previous
versions of the pages are all available in the history pane and can
easily be accessed by future users. You can also hit \"permanent
version\" on the left side of the webpage (it is under \"toolbox\").
That sends you specifically to the selected version of the wikipage with
a link to it that will never change.
3\) Reference the PDF version and its version number. Once the book
achieves a reasonable level, PDF versions will become available for
download and they will have a unique version number and can be
retrieved.
Other suggestions are most welcome!
Edwards, Steven A.,The Nanotech Pioneers Christiana, USA: Wiley-VCH
2006, pg 2
|
# Nanotechnology/About#History
Navigate
---------------------------------------------------------
\<\< Prev: Overviews
\>\< Main: Nanotechnology
\>\> Next: Reaching Out
\_\_TOC\_\_
------------------------------------------------------------------------
## Vision
We hope to use the Wikibooks format to make an Open Source Handbook on
Nanoscience and Nanotechnology, freely accessible for everyone, that can
be updated continuously.
Wikipedia is growing fast and one of the most visited websites on the
net -- a valuable resource of information we all use.
In science and technology we often need more detailed information than
what can be presented in a brief encyclopedic article -- and here
wikibooks.org, a sister project to Wikipedia, can help us with this
newly started handbook.
Though the book is still in its infancy, it has been elected book of the
month December 2006, and we hope this will provide PR and more people
contributing to the project!
The plan to create the book:
1: First to create smaller articles to 'cover' the entire area of
nanotechnology and achieve a well defined structure the book (some parts
could be revised thoroughly in this process,for instance the materials
chapter).
2: Once the structure is reasonably well defined, to begin refining the
articles with in-depth material so we reach lecture-note level material.
3: Since everybody can contribute, a continuous contribution of material
is expected and a backing group of editors is needed to maintain a
trustworthy level of information.
An voluntary editorial board is being put together to oversee the book,
support, contribute and follow its development.
Discussion about the content of the book can be found on the main talk
page talk:Nanotechnology
As with Wikipedia, we hope to see a solid information resource
continuously updated with open source material available for everyone!
## Editing hints
### References in Wikibooks
Add references whenever possible, with reference lists at the end of
each page. Please try to make links to the articles with the DOI
(digital object identifier) because that gives a uniform and structured
access for everyone to the papers.
All papers get a DOI - a unique number like a bar code in a supermarket.
All DOIs are registered by www.doi.org and in
the reference list you can add links like
<https://doi.org/10.1039/b504435a>
so people will be able to find it no matter how the homepage of the
journal or their own library changes.
The References section has an example
reference.
Add links to the Wikipedia whenever possible - and for the beginning I
will rely extensively on Wikipedia\'s pages on the subjects, simply
referring to these. This textbook could be simply a gathering of
Wikipedia pages, but an encyclopedia entry is brief, and for a handbook
it is preferable to have more in-depth material with examples and the
necessary formulas. So, some information in this textbook will be very
much like the Wikipedia entries and we might not need to write it in the
book but can simply refer to Wikipedia, but the hope is that this will
be more a text book as is the intention with Wikibooks.
Multiple references, see w:Help:Footnotes
### Links
There\'s a shorthand way to make links to Wikipedia from Wikibooks:
\[\[w:Quantum_tunneling\|Wikipedia on Quantum Tunneling\]\] gives the
link Wikipedia on Quantum Tunneling.
### Media
## History
The book was started by Kristian
Molhave(wiki user
page) 13. Apr. 2006. Initially it was
named *Nanowiki*, and later changed to
Nanotechnology. Kristian is currently
slowly uploading material to the book and looking for people who would
like to contribute that can and substantial material to specific
sections under the GNU license. I hope we can make an \'editorial
panel\' of people each keeping an eye on and updating specific sections.
The Summer 2008 Duke Talent Identification Program (TIP) eStudies
Nanotechnology students will be adding to the content of this Wikibook.
From June-Aug 2008 there will be content additions with references that
will add to this great resource.
## Authors and Editors
- The Opensource Handbook on Nanoscience and Nanotechnology was
started by Kristian Molhave(wiki user
page)
### Editors
- An editorial board is currently being organized.
## Support and Acknowledgments
Starting this book is supported by the Danish Agency for Science,
Technology and
Innovation
through Kristian Mølhave\'s talent project
'NAMIC' No. 26-04-0258.
## How to Reference this Book
I am not currently sure how work on wikibooks or wikipedia can be
referenced reliably in published literature.
Three suggestions:
1\) Reference the references from the wikibook. Wikibooks are not
intended to be the publication channel for new results, but should be
based on published and accepted information with references and these
references can be used. But this of course does not give credit to the
book, so I recommend then adding an acknowledgement about the book to
give it PR and credit.
2\) Reference the book with a specific page and date - the previous
versions of the pages are all available in the history pane and can
easily be accessed by future users. You can also hit \"permanent
version\" on the left side of the webpage (it is under \"toolbox\").
That sends you specifically to the selected version of the wikipage with
a link to it that will never change.
3\) Reference the PDF version and its version number. Once the book
achieves a reasonable level, PDF versions will become available for
download and they will have a unique version number and can be
retrieved.
Other suggestions are most welcome!
Edwards, Steven A.,The Nanotech Pioneers Christiana, USA: Wiley-VCH
2006, pg 2
|
# Nanotechnology/About#Support and Acknowledgments
Navigate
---------------------------------------------------------
\<\< Prev: Overviews
\>\< Main: Nanotechnology
\>\> Next: Reaching Out
\_\_TOC\_\_
------------------------------------------------------------------------
## Vision
We hope to use the Wikibooks format to make an Open Source Handbook on
Nanoscience and Nanotechnology, freely accessible for everyone, that can
be updated continuously.
Wikipedia is growing fast and one of the most visited websites on the
net -- a valuable resource of information we all use.
In science and technology we often need more detailed information than
what can be presented in a brief encyclopedic article -- and here
wikibooks.org, a sister project to Wikipedia, can help us with this
newly started handbook.
Though the book is still in its infancy, it has been elected book of the
month December 2006, and we hope this will provide PR and more people
contributing to the project!
The plan to create the book:
1: First to create smaller articles to 'cover' the entire area of
nanotechnology and achieve a well defined structure the book (some parts
could be revised thoroughly in this process,for instance the materials
chapter).
2: Once the structure is reasonably well defined, to begin refining the
articles with in-depth material so we reach lecture-note level material.
3: Since everybody can contribute, a continuous contribution of material
is expected and a backing group of editors is needed to maintain a
trustworthy level of information.
An voluntary editorial board is being put together to oversee the book,
support, contribute and follow its development.
Discussion about the content of the book can be found on the main talk
page talk:Nanotechnology
As with Wikipedia, we hope to see a solid information resource
continuously updated with open source material available for everyone!
## Editing hints
### References in Wikibooks
Add references whenever possible, with reference lists at the end of
each page. Please try to make links to the articles with the DOI
(digital object identifier) because that gives a uniform and structured
access for everyone to the papers.
All papers get a DOI - a unique number like a bar code in a supermarket.
All DOIs are registered by www.doi.org and in
the reference list you can add links like
<https://doi.org/10.1039/b504435a>
so people will be able to find it no matter how the homepage of the
journal or their own library changes.
The References section has an example
reference.
Add links to the Wikipedia whenever possible - and for the beginning I
will rely extensively on Wikipedia\'s pages on the subjects, simply
referring to these. This textbook could be simply a gathering of
Wikipedia pages, but an encyclopedia entry is brief, and for a handbook
it is preferable to have more in-depth material with examples and the
necessary formulas. So, some information in this textbook will be very
much like the Wikipedia entries and we might not need to write it in the
book but can simply refer to Wikipedia, but the hope is that this will
be more a text book as is the intention with Wikibooks.
Multiple references, see w:Help:Footnotes
### Links
There\'s a shorthand way to make links to Wikipedia from Wikibooks:
\[\[w:Quantum_tunneling\|Wikipedia on Quantum Tunneling\]\] gives the
link Wikipedia on Quantum Tunneling.
### Media
## History
The book was started by Kristian
Molhave(wiki user
page) 13. Apr. 2006. Initially it was
named *Nanowiki*, and later changed to
Nanotechnology. Kristian is currently
slowly uploading material to the book and looking for people who would
like to contribute that can and substantial material to specific
sections under the GNU license. I hope we can make an \'editorial
panel\' of people each keeping an eye on and updating specific sections.
The Summer 2008 Duke Talent Identification Program (TIP) eStudies
Nanotechnology students will be adding to the content of this Wikibook.
From June-Aug 2008 there will be content additions with references that
will add to this great resource.
## Authors and Editors
- The Opensource Handbook on Nanoscience and Nanotechnology was
started by Kristian Molhave(wiki user
page)
### Editors
- An editorial board is currently being organized.
## Support and Acknowledgments
Starting this book is supported by the Danish Agency for Science,
Technology and
Innovation
through Kristian Mølhave\'s talent project
'NAMIC' No. 26-04-0258.
## How to Reference this Book
I am not currently sure how work on wikibooks or wikipedia can be
referenced reliably in published literature.
Three suggestions:
1\) Reference the references from the wikibook. Wikibooks are not
intended to be the publication channel for new results, but should be
based on published and accepted information with references and these
references can be used. But this of course does not give credit to the
book, so I recommend then adding an acknowledgement about the book to
give it PR and credit.
2\) Reference the book with a specific page and date - the previous
versions of the pages are all available in the history pane and can
easily be accessed by future users. You can also hit \"permanent
version\" on the left side of the webpage (it is under \"toolbox\").
That sends you specifically to the selected version of the wikipage with
a link to it that will never change.
3\) Reference the PDF version and its version number. Once the book
achieves a reasonable level, PDF versions will become available for
download and they will have a unique version number and can be
retrieved.
Other suggestions are most welcome!
Edwards, Steven A.,The Nanotech Pioneers Christiana, USA: Wiley-VCH
2006, pg 2
|
# Nanotechnology/About#How to Reference this Book
Navigate
---------------------------------------------------------
\<\< Prev: Overviews
\>\< Main: Nanotechnology
\>\> Next: Reaching Out
\_\_TOC\_\_
------------------------------------------------------------------------
## Vision
We hope to use the Wikibooks format to make an Open Source Handbook on
Nanoscience and Nanotechnology, freely accessible for everyone, that can
be updated continuously.
Wikipedia is growing fast and one of the most visited websites on the
net -- a valuable resource of information we all use.
In science and technology we often need more detailed information than
what can be presented in a brief encyclopedic article -- and here
wikibooks.org, a sister project to Wikipedia, can help us with this
newly started handbook.
Though the book is still in its infancy, it has been elected book of the
month December 2006, and we hope this will provide PR and more people
contributing to the project!
The plan to create the book:
1: First to create smaller articles to 'cover' the entire area of
nanotechnology and achieve a well defined structure the book (some parts
could be revised thoroughly in this process,for instance the materials
chapter).
2: Once the structure is reasonably well defined, to begin refining the
articles with in-depth material so we reach lecture-note level material.
3: Since everybody can contribute, a continuous contribution of material
is expected and a backing group of editors is needed to maintain a
trustworthy level of information.
An voluntary editorial board is being put together to oversee the book,
support, contribute and follow its development.
Discussion about the content of the book can be found on the main talk
page talk:Nanotechnology
As with Wikipedia, we hope to see a solid information resource
continuously updated with open source material available for everyone!
## Editing hints
### References in Wikibooks
Add references whenever possible, with reference lists at the end of
each page. Please try to make links to the articles with the DOI
(digital object identifier) because that gives a uniform and structured
access for everyone to the papers.
All papers get a DOI - a unique number like a bar code in a supermarket.
All DOIs are registered by www.doi.org and in
the reference list you can add links like
<https://doi.org/10.1039/b504435a>
so people will be able to find it no matter how the homepage of the
journal or their own library changes.
The References section has an example
reference.
Add links to the Wikipedia whenever possible - and for the beginning I
will rely extensively on Wikipedia\'s pages on the subjects, simply
referring to these. This textbook could be simply a gathering of
Wikipedia pages, but an encyclopedia entry is brief, and for a handbook
it is preferable to have more in-depth material with examples and the
necessary formulas. So, some information in this textbook will be very
much like the Wikipedia entries and we might not need to write it in the
book but can simply refer to Wikipedia, but the hope is that this will
be more a text book as is the intention with Wikibooks.
Multiple references, see w:Help:Footnotes
### Links
There\'s a shorthand way to make links to Wikipedia from Wikibooks:
\[\[w:Quantum_tunneling\|Wikipedia on Quantum Tunneling\]\] gives the
link Wikipedia on Quantum Tunneling.
### Media
## History
The book was started by Kristian
Molhave(wiki user
page) 13. Apr. 2006. Initially it was
named *Nanowiki*, and later changed to
Nanotechnology. Kristian is currently
slowly uploading material to the book and looking for people who would
like to contribute that can and substantial material to specific
sections under the GNU license. I hope we can make an \'editorial
panel\' of people each keeping an eye on and updating specific sections.
The Summer 2008 Duke Talent Identification Program (TIP) eStudies
Nanotechnology students will be adding to the content of this Wikibook.
From June-Aug 2008 there will be content additions with references that
will add to this great resource.
## Authors and Editors
- The Opensource Handbook on Nanoscience and Nanotechnology was
started by Kristian Molhave(wiki user
page)
### Editors
- An editorial board is currently being organized.
## Support and Acknowledgments
Starting this book is supported by the Danish Agency for Science,
Technology and
Innovation
through Kristian Mølhave\'s talent project
'NAMIC' No. 26-04-0258.
## How to Reference this Book
I am not currently sure how work on wikibooks or wikipedia can be
referenced reliably in published literature.
Three suggestions:
1\) Reference the references from the wikibook. Wikibooks are not
intended to be the publication channel for new results, but should be
based on published and accepted information with references and these
references can be used. But this of course does not give credit to the
book, so I recommend then adding an acknowledgement about the book to
give it PR and credit.
2\) Reference the book with a specific page and date - the previous
versions of the pages are all available in the history pane and can
easily be accessed by future users. You can also hit \"permanent
version\" on the left side of the webpage (it is under \"toolbox\").
That sends you specifically to the selected version of the wikipage with
a link to it that will never change.
3\) Reference the PDF version and its version number. Once the book
achieves a reasonable level, PDF versions will become available for
download and they will have a unique version number and can be
retrieved.
Other suggestions are most welcome!
Edwards, Steven A.,The Nanotech Pioneers Christiana, USA: Wiley-VCH
2006, pg 2
|
# Nanotechnology/Reaching Out#Teaching Nanotechnology
Navigate
---------------------------------------------------------
\<\< Prev: About
\>\< Main: Nanotechnology
\>\> Next: Seeing Nano
\_\_TOC\_\_
------------------------------------------------------------------------
# Teaching Nanotechnology
Teachers\' Toolbox is a Wikibook on
teaching methods and ways to improve teaching. The toolbox is intended
to give you an overview of methods you can use when teaching in general.
If you know of places that have teaching material available on the net,
please add a link to the list below:
- Nanotechnology
- Nano-to-Macro Transport Processes, Fall
2004
- nanostructured materials and
interfaces
# Outreach projects
There are several nanotechnology related outreach projects. Here are
some examples to give ideas:
- Nanoscale Science
Education
- Citizens school of
nanotechnology
- Webcast outreach
lecture
- Exploring the nanoworld
- K-14
outreach
- Cornell
Museum
# Demonstration experiments
There is a dedicated section for
nanotechnology in the
Wikiboook on Science Show, which is a cross
disciplinary collection of demonstration experiments. The Danish
version is growing steadily and we will
begin to add to the English version soon. Please add to these books with
any demonstration experiments and ideas you have!
There are others available on the net:
- Nano-Tex: Testing New Nano
Fabrics
- Nano kits and for
instance the exercise moving a
wall
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
|
# Nanotechnology/Reaching Out#Outreach projects
Navigate
---------------------------------------------------------
\<\< Prev: About
\>\< Main: Nanotechnology
\>\> Next: Seeing Nano
\_\_TOC\_\_
------------------------------------------------------------------------
# Teaching Nanotechnology
Teachers\' Toolbox is a Wikibook on
teaching methods and ways to improve teaching. The toolbox is intended
to give you an overview of methods you can use when teaching in general.
If you know of places that have teaching material available on the net,
please add a link to the list below:
- Nanotechnology
- Nano-to-Macro Transport Processes, Fall
2004
- nanostructured materials and
interfaces
# Outreach projects
There are several nanotechnology related outreach projects. Here are
some examples to give ideas:
- Nanoscale Science
Education
- Citizens school of
nanotechnology
- Webcast outreach
lecture
- Exploring the nanoworld
- K-14
outreach
- Cornell
Museum
# Demonstration experiments
There is a dedicated section for
nanotechnology in the
Wikiboook on Science Show, which is a cross
disciplinary collection of demonstration experiments. The Danish
version is growing steadily and we will
begin to add to the English version soon. Please add to these books with
any demonstration experiments and ideas you have!
There are others available on the net:
- Nano-Tex: Testing New Nano
Fabrics
- Nano kits and for
instance the exercise moving a
wall
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
|
# Nanotechnology/Reaching Out#Demonstration experiments
Navigate
---------------------------------------------------------
\<\< Prev: About
\>\< Main: Nanotechnology
\>\> Next: Seeing Nano
\_\_TOC\_\_
------------------------------------------------------------------------
# Teaching Nanotechnology
Teachers\' Toolbox is a Wikibook on
teaching methods and ways to improve teaching. The toolbox is intended
to give you an overview of methods you can use when teaching in general.
If you know of places that have teaching material available on the net,
please add a link to the list below:
- Nanotechnology
- Nano-to-Macro Transport Processes, Fall
2004
- nanostructured materials and
interfaces
# Outreach projects
There are several nanotechnology related outreach projects. Here are
some examples to give ideas:
- Nanoscale Science
Education
- Citizens school of
nanotechnology
- Webcast outreach
lecture
- Exploring the nanoworld
- K-14
outreach
- Cornell
Museum
# Demonstration experiments
There is a dedicated section for
nanotechnology in the
Wikiboook on Science Show, which is a cross
disciplinary collection of demonstration experiments. The Danish
version is growing steadily and we will
begin to add to the English version soon. Please add to these books with
any demonstration experiments and ideas you have!
There are others available on the net:
- Nano-Tex: Testing New Nano
Fabrics
- Nano kits and for
instance the exercise moving a
wall
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
|
# Nanotechnology/Optical Methods#Optical Microscopy
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Optical Methods#STED Microscopy
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Optical Methods#Laser Scanning Confocal Microscopy .28LSCM.29
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Optical Methods#X-ray microscopy
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Optical Methods#UV.2FVIS spectrometry
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Optical Methods#Raman Spectroscopy
Navigate
-----------------------------------------------------------------------
\<\< Prev: Seeing Nano
\>\< Main: Nanotechnology
\>\> Next: Electron Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Optical Microscopy
## The Abbe diffraction limit
Observation of sub-wavelength structures with microscopes is difficult
because of the Abbe diffraction
limit.
Ernst Abbe found in 1873 that light with wavelength λ,travelling in a
medium with refractive index n and converging to a spot with angle φ
will make a spot with radius
$$d=\frac{0.61 \lambda}{n sin \phi}$$
The denominator nsinφ is called the numerical aperture (NA) and can
reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
With green light around 500nm the Abbe limit is 250nm which is large
compared to most nanostructures or biological cells with sizes on the
order of 1μm and their internal organelles being much smaller. To
increase the resolution, shorter wavelengths can be used such as UV and
X-ray microscopes. These techniques offer splendid resolution but are
expensive, suffer from lack of contrast in biological samples, and also
tend to damage the sample.
## Resources
- Microscope
optics
- Microscopy
Primer
- Olympus Interactive Java Tutorials on
Microscopy
- Nikon MicroscopyU with interactive tutorials on microscopy
techniques
## The optical microscope
!Sketch of an optical
microscope{width="300"}
### Bright Field
The light is sent to the sample in the same directions as you are
looking - most things will look bright unless they absorb the light.
### Dark Field
Light is sent towards the sample at an angle to your viewing direction
and you only see light that is scattered. This makes most images appear
dark and only edges and curved surfaces will light up.
### Polarized Light
### DIC vs H
# Laser Scanning Confocal Microscopy (LSCM)
Confocal laser scanning
microscopy is a
technique that allows a much better resolution from optical microscopes
and three dimensional imaging. A review can be found in Paddock,
Biotechniques
1999
Using a high NA objective also gives a very shallow depth of focus and
hence the image will be blurred by structures above or below the focus
point in a classical microscope. A way to circumvent this problem is the
confocal microscope, or even better the Laser Scanning Confocal
Microscope (LSCM). Using a laser as the light source gives better
control of the illumintaion, especially when using fluorescent markers
in the sample. The theoretical resolution using a 1.4 NA objective can
reach 140nm laterally and 230nm vertically [^1] while the resolution
quoted in ref [^2] is 0.5×0.5×1μm. The image in the LSCM is made by
scanning the sample in 2D or 3D and recordning the signal for each point
in space on a PC which then generates the image.
# X-ray microscopy
X-ray microscopy uses X-rays to image
with much shorter wavelength than optical light, and hence can provide
much higher spatial resolution and use different contrast mechanisms.
X-ray microscopy allows the characterization of materials with submicron
resolution approaching the 10\'s of nanometers. X-ray microscopes can
use both laboratory x-ray sources and synchrotron radiation from
electron accelerators. X-ray microscopes using synchrotron radiation
provide the greatest sensitivity and power, but are unfortunately rather
large and expensive. X-ray microscopy is usually divided into two
overlapping ranges, referred to as soft x-ray microscopy (100eV - 2keV)
and hard x-ray microscopy (1keV-40keV). All x-rays penetrate materials,
more for higher energy x-rays. Hence, soft x-ray microscopy provides the
best contrast for small samples. Hard x-rays do have the ability to pass
nearly unhindered through objects like your body, and hence also give
rather poor contrast in many of the biological samples you would like to
observe with the x-ray microscope. Nevertheless, hard x-ray microscopy
allows imaging by phase contrast, or using scanning probe x-ray
microscopy, by using detection of fluorescent or scattered x-rays.
Despite its limitations, X-ray microscopy is a powerful technique and in
some cases can provide characterization of materials or samples that
cannot be done by any other means.
# UV/VIS spectrometry
# Infrared spectrometry (FTIR)
vIdentification of the functional groups present in a nanomaterial is a
frequent requirement in nanoscience and nanotechnology research. Among
other tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.Identification of
the functional groups present in a nanomaterial is a frequent
requirement in nanoscience and nanotechnology research. Among other
tools, FT-IR has found much popularity among researches due to its
versatility, relative ease of use and ability to use as a quantification
tool.
Atoms in a chemical bonds constantly vibrate. This vibration can be
analogue to a system with two masses attached to a spring. The vibration
frequency depend upon the weight of the masses and the spring constant
of the connecting spring. In the same way, depending on the masses of
the atoms that contributes to a bond and cohesiveness of the bond,
frequency differ. Since bonds have atoms with different shapes and sizes
and different strength, each combination of atoms in an each type of
bond has a unique harmonic frequency. This natural frequency lies in the
range of infrared region and therefore a spectroscopic method that use
IR can be devised to analyze bond vibrations.
When the IR radiation with the same harmonic frequency of the bond
shines upon the bond. The bond vibration is amplified by increased
transfer of energy from the IR radiation. When range of IR frequencies
given to the material, it only absorb IR frequencies that corresponds to
the natural frequencies of the bonds that exist in the sample. Others
are not absorbed and can be analyzed using an Infrared spectrometer,
which tells you the frequencies that are absorbed by the sample. This
provides important information about the functional groups present in
the sample. This is exactly what FT-IR does.
As FT-IR can be used to get information about functional groups present
in nanomaterials. This is particularly useful in cases such as when one
attempts to surface modify nanomaterials to increase affinity,
reactivity or compatibility. Analyzing the FT-IR of a nanomaterial would
tell you what groups present and then appropriate surface modification
strategy be decided based on the groups present. Further, it can also be
useful in characterizing the surface modification has taken place, as
new groups should emerge if the reaction is successful.
# Terahertz Spectroscopy
# Raman Spectroscopy
- Raman scattering
- Resonance Raman
spectroscopy
## Surface Enhanced Raman Spectroscopy (SERS)
- Surface Enhanced Raman Spectroscopy
(SERS)
- Surface-enhanced Raman spectroscopy: a brief
retrospective
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Confocal laser scanning microscopy, Paddock SW, Biotechniques ,
vol. 27 (5): 992 NOV 1999
[^2]: A new UV-visible confocal laser scanning microspectrofluorometer
designed for spectral cellular imaging, Favard C, Valisa P,
Egret-Charlier M, Sharonov S, Herben C, Manfait M, Da Silva E, Vigny
P, Biospectroscopy , vol. 5 (2): 101-115 1999
|
# Nanotechnology/Electron microscopy#The Electron Optical System
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Optical Methods
\>\< Main: Nanotechnology
\>\> Next: Scanning Probe Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Electron microscopy
An overview:
Electron microscopes uses electrons instead of photons, because
electrons have a much shorter wavelength than photons and so allows you
to observe matter with atomic resolution.
There are two general types of electron microscopes: the Scanning
Electron Microscope (SEM) that scans an electron beam over the surface
of an object and measures how many electrons are scattered back, and the
Transmission Electron Microscope (TEM) that shoots electrons through the
sample and measures how the electron beam changes because it is
scattered in the sample.
! A very simple sketch of a Transmission Electron Microscope (TEM) and
Scanning Electron Microscope (SEM) compared to an optical transmission
microscope and a cathode ray tube (CRT) TV screen - both systems have
many things on common with the electron microscope. The optical
microscope uses lenses to control the lights pathway through the system
and is in many ways built up like a TEM - only the TEM uses
electromagnetic lenses to direct the beam of electrons. The CRT uses
electromagnetic lenses as the TEM and SEM to control the electron beam,
and generates an image for the viewer by scanning the beam over a
fluorescent screen - in the same way the a SEM generates an image by
scanning the electron beam over a small
sample. and Scanning Electron Microscope (SEM) compared to an optical transmission microscope and a cathode ray tube (CRT) TV screen - both systems have many things on common with the electron microscope. The optical microscope uses lenses to control the lights pathway through the system and is in many ways built up like a TEM - only the TEM uses electromagnetic lenses to direct the beam of electrons. The CRT uses electromagnetic lenses as the TEM and SEM to control the electron beam, and generates an image for the viewer by scanning the beam over a fluorescent screen - in the same way the a SEM generates an image by scanning the electron beam over a small sample."){width="300"}
Using electron beams however requires working in a vacuum environment,
and this makes the instruments considerably larger and expensive. All
electron microscope work under at least low pressures and usually in
high vacuum chambers to avoid scattering the electrons in the gas. In
environmental electron microscopes, differential pumping systems are
used to actually have gasses present by the sample together with the
electron beam.
## Introduction to Electron Microscopy
For imaging of nanoscale objects, optical microscopy has limited
resolution since the objects are often much smaller than the wavelength
of light. The achievable resolution for a wavelength $\lambda$ is often
given by the diffraction limit $d$ as
$$d=0.61 \frac {\lambda}{(NA)}$$ *(r.g., diffraction limit)*
with numerical aperture $NA$, which can be approximated by the largest
angle of incidence $\alpha$ of the wavefront towards the sample,
$NA \approx \alpha$.
Since $\alpha \ll 1$ for the present purposes, we can approximate
$\sin(\alpha)\approx \tan(\alpha)\approx \alpha$ and hence
$NA \approx \alpha \approx r_{a}/r_{wd}$ where $r_{a}$ is the radius of
the objective lens aperture and $r_{wd}$ the working distance.
Optical microscopes can often reach a resolution of about $d=200$ nm.
For nanoscale resolution this is unfortunately not sufficient to
distinguish for instance a single nanotube from two adhering to each
other, since they have diameters of less than 100 nm.
The figure below gives an overview typical magnifications achievable by
the different electron microscopes compared to a light microscope.
!The different methods for microscopy cover a range of magnification
roughly indicated by the bars in the figure. The resolution of optical
microscopy is limited to about 200 nm. a) SEM image of the head of an
ant facing a microfabricated chip with a pair of microfabricated
grippers. The grippers are barely visibly at the tip of the arrow. b)
SEM image of a gripper approaching a large bundle of carbon nanotubes.
c) Closeup in SEM of the gripper and nanotubes. d) TEM image of a carbon
nanotube suspended between two grippers. e) TEM closeup of the shells of
carbon atoms in a carbon nanotube. On the nanometer scale this
particular carbon nanotube does not show a well defined carbon shell
structure. SEM image of the head of an ant facing a microfabricated chip with a pair of microfabricated grippers. The grippers are barely visibly at the tip of the arrow. b) SEM image of a gripper approaching a large bundle of carbon nanotubes. c) Closeup in SEM of the gripper and nanotubes. d) TEM image of a carbon nanotube suspended between two grippers. e) TEM closeup of the shells of carbon atoms in a carbon nanotube. On the nanometer scale this particular carbon nanotube does not show a well defined carbon shell structure."){width="400"}
Electron optical systems use electrical and magnetic fields to control
the electron beam. Although the law of refraction in optics is exchanged
with the Lorentz force in electrodynamics, the electron optical system
has similar diffraction limits as optical systems, since they depend on
the wave nature of the electron beam.
One can achieve a considerable improvement in resolution with
instruments such as the transmission electron microscope and the
scanning electron microscope that use electrons with De Broglie
wavelength much smaller than that of visible light. The De Broglie
wavelength λ of an electron with momentum p is
$$\lambda = \frac{h}{p} = \frac {h}{\sqrt{2m_{e}E_{b}}},$$ *(Eq. De
Broglie wavelength)*
where $h$ is Plancks constant. The electron has rest mass $m_{e}$ and
energy $E_{e}=m_{e}c^2=511 keV$.
If an electron with charge $q_{e}$ is accelerated from rest by an
electrical potential $U$, to the electron beam energy $E_{b}=q_{e}U$, it
will have a wavelength of 1 nm at 1 eV decreasing to 1 pm at 100 keV
where it will be travelling with 50% the speed of light.
This chapter will briefly review fundamental issues for electron
microscopy that are similar for SEM and TEM: the limitations imposed by
the electron optical beam system in the microscope column; the
interaction of the electron beam with the sample; the standard image
formation method in SEM and TEM. These issues are essential to
understand the results and limitations reached in SEM and TEM
microscopy.
For further details, please refer to reviews of electron microscopes and
their applications, such as Goldstein et al. [^1] that contains a
thorough review of SEM, while Goodhew and Humphreys [^2] is a more
general introduction to both SEM and TEM.
# The Electron Optical System
For high resolution imaging, a well focused beam is required, just as in
optical microscopy. Due to the short wavelength of electron beams with
keV energies, as given by the #Eq de Broglie
wavelength, the properties of the
electron optical system and the electron emitter mainly defines the
limits on the achievable beam diameter. The current density in the
electron beam can be approximated by a Gaussian distribution of current
density j \[A/m²\] as function of radius, r, from the beam center
$$j(r)=j_0 e^{- \frac{r^2}{r_{0}^2}},$$
with radius determined by $r_0$, giving a the full width half maximum
$FWHM=2v(ln2)r0$. Integrating $I_{b}=\int \int j(r)rdrd\theta$ gives the
total beam current
$$I_{b}=j_0 \pi r_{0}^2.$$
The electron optics impose a limit on the achievable beam current
density and radius by the brightness of the electron emitter
$\beta_{e}$, which is conserved throughout the system [^3].
Brightness, ß, is a measure of the current per area normal to the beam
direction and per element of solid angle [^4]. At the center of the
Gaussian beam,
\<div id=\"eq SEM current density\>
```{=html}
</div>
```
```{=html}
<div id="eq beam brightness">
```
```{=html}
</div>
```
$$\beta=\frac{j_0}{\pi \alpha^2}$$
and the brightness is related to the current density in eq SEM Gaussian
beam profile. The emitter brightness $\beta_{e}$ is determined by the
type of electron emitter and the beam energy $E_{b}$ [^5]
$\beta_{e}=\frac{j_{e}E_{b}}{\pi \Delta E}$
with emission current density for W-filament sources about $j_{e}$\~3
A/cm², for LaB6 sources about 100 A/cm², while field emission guns (FEG)
can reach 10^5^A/cm². The energy spread of the electrons from the
sources are about ΔE\~1 eV and slightly lower for FEGs. Due to
conservation of the brightness in the system, the beam diameter depends
on current as
```{=html}
<div id="eq SEM beam diameter">
```
```{=html}
</div>
```
$r_{0}=\frac{1}{\pi}\frac{r_{wd}}{r_{a}}\sqrt{\frac{I_{b}}{\beta_{e}}}.$
The ideal beam probe size determined by the conservation of brightness
cannot be obtained in a real system. Effects such as aberration will
make the minimum achievable beam diameter larger. Equation #eq SEM beam
diameter however seem to adequately
describe the beam diameter for the present discussion. Apart from the
additional beam widening contributions, the image detection method
imposes limits on useful values for the parameters in Eq. SEM beam
diameter which differ for SEM and TEM.
# Electron Range
The electron optical system sets limitations to the achievable primary
beam current and radius. The expected image resolution set by the
primary beam cannot be reached if the signal detected for imaging is
caused by electrons scattered far in the sample. The trajectory of an
electron penetrating a bulk solid is a complex trajectory due to
multiple elastic and inelastic collision events. As the primary electron
(PE) penetrates into the sample it will gradually change direction and
loose energy in collisions. The mean free path due to elastic and
inelastic collisions, $\lambda_{mfp}$, depends on the atomic number of
the material and the PE energy. At 100 keV $\lambda_{mfp}=150 nm$ for
carbon and 5 nm for gold [^6]. For samples thinner than $\lambda_{mfp}$
the main part of the PE will pass relatively unaffected through the
sample, which is the basis for TEM.
!Overview of electron electron scattering processes in bulk and
tip-shaped specimens. The PE are scattered within the interaction
volume, defined the electron range in the material. The range is longer
than the mean free path $\lambda_{mfp}$. The SE have a very short range,
and only those created within that range from the surface can escape the
material. This defines the SE escape
depth.{width="300"}
SEM can be used for thicker specimens. The electrons that escape from
the sample in a new direction compared to the PE due to elastic
collisions are called backscattered electrons (BSE).
For samples thicker than $\lambda_{mfp}$, the volume interacting with
the scattered PE defines the range of the electrons in the material, and
this is considerably larger than the minimum achievable primary beam
diameters.
The electron range is about 1 µm at 10 keV for carbon, decreasing with
higher atomic number for the material. Both the high energy PE and BSE
generate secondary electrons (SE) by inelastic scattering events. The SE
are generally defined as having energy below 50 eV while the BSE have
energies up to the PE energy. The range of SE is typically 1 nm for
metals and about 10 nm for insulators [^7].
The short range of the SE make the yield of SE highly dependent on the
energy lost by the PE within the SE range from the surface, and this
makes high Z substances efficient generators of SE. The main emission of
SE takes place in the region where the PE strikes the surface and within
the SE escape depth from this region.
!The electron range increases with beam energy. The internal structure
of the EEBD deposits can be examined at high electron beam energies in
SEM. At 5 kV with shallow penetration depth, the surface of the tips is
clearly visible while at higher energies a core of more dense material
becomes increasingly visible. At 100 keV and above, TEM images can
achieve atomic resolution where the lattice planes in nanocrystals such
as the gold nanocrystal in (c). The gold crystal is embedded in
amorphous carbon with no clear lattice
pattern.. The gold crystal is embedded in amorphous carbon with no clear lattice pattern."){width="300"}
# Scanning electron microscopy (SEM)
- Wikipedia: Scanning electron microscopy
(SEM)
In a scanning electron microscope a beam is scanned over the sample
surface in a raster pattern while a signal is recorded from electron
detectors for SE or BSE. The PE energy is kept relatively low (1-30 keV)
to limit the interaction volume in the specimen that will contribute to
the detected signal. Especially low energy PE will provide high
sensitivity to surface composition as they cannot penetrate far into the
sample.
The figure above showed the effect of PE penetration depth of a
carbonaceous nanostructure with a gold core, where only the surface is
visible at low PE energies, while the carbon becomes increasingly
transparent and the core visible at high PE energies.
The low energy SE can easily be attracted and collected by a positively
charged detector and are hence an efficient source for an image signal.
The standard SE detector is an Everhart-Thornley (ET) detector where a
positively charged grid attracts the SE and accelerates them to
sufficiently high energies to create a light pulse when striking a
scintillator. The light pulse is then amplified by a photomultiplier.
Despite the complex construction, the ET detector is remarkably
efficient, but requires large $r_{wd}$ for effective collection of the
SE by the charged grid.
Another SEM detector is the in-lens detector, where SE passing through
the column aperture are accelerated towards a solid state detector. The
in-lens detector complements the ET by being more efficient at short
$r_{wd}$.
## Environmental SEM (ESEM)
!Simple sketch of an Environmental Scanning Electron Microscope (ESEM),
where a differential pumping system with two pressure limiting apertures
between the ultra high vacuum SEM column and the low vacuum sample
chamber allows high pressures up to 10 hPa around the sample. This is
enough to have liquid water at moderate cooling of 5 deg.
C., where a differential pumping system with two pressure limiting apertures between the ultra high vacuum SEM column and the low vacuum sample chamber allows high pressures up to 10 hPa around the sample. This is enough to have liquid water at moderate cooling of 5 deg. C."){width="300"}
The ESEM makes it possible to use various gasses in the sample chamber
of the microscope since there are narrow apertures between the sample
chamber and the gun column, and a region in between that is connected to
a differential pumping system. Pressures up to about 10 Torr are
normally possible in the sample chamber.
The standard Everly-Thornhart SE detector would not work under such
conditions since it would create a discharge in the low pressure gas.
Instead a \"gaseous secondary electron detector (GSD)\" is used, as
shown in the figure below. The GSD measures the current of a weak
cascade discharge in the gas, which is seeded by the emission of
electrons from the sample.
! Two examples of images from an ESEM. Taken with a Philips XL-30 FEG.
The first shows a electron beam deposited nanowire between two
microelectrodes that has burnt after sustaining a high bias current. The
other shows a multiwall carbon nanotube sample. Shorter working
distances often improves image quality and so does a low beam current
but it also increases the image acquisition
time{width="300"}
In the ESEM one can work with for instance water vapour or argon as the
environmental gas, and it is possible to have liquid samples in the
chamber if the sample stage is cooled sufficiently to condense water.
# Transmission electron microscopy (TEM)
- Transmission electron microscopy
(TEM)
- High Resolution Transmission electron microscopy
(HRTEM)
! A Philips EM 430
TEM{width="100"}
When the specimen thickness is about the mean free path,
$\lambda_{mfp}$, TEM can be used to achieve high resolution images such
as the image above where the atomic lattice of a gold nanocrystal is
visible. Since the detected electrons are transmitted PE where the
energy can be in the 100 keV range, the resolution is not limited by the
issues regarding secondary electrons. The electron beam optics can be
optimized for higher current densities (Eq. #eq SEM current
density) at higher energies
compared to SEM.
To achieve optimal imaging conditions for the thin TEM samples, the
working distance has been made short. In most TEMs, the space for the
sample holder is only about (5 mm)³ between the two objective lenses for
the incoming and transmitted beam. Before reaching a CCD camera, the
transmitted beam is sent through several magnification lenses to achieve
the high magnification (500.000X is not unusual).
The image formation in TEM can be based on several principles, but
practically all images used in this work were made by phase contrast
imaging, here called High Resolution TEM or HRTEM. At sufficiently high
brightness, electron sources can produce coherent electron beams due to
the point-like emitter surface area and small energy spread [^8]. The
coherent electron beam can be considered as a spherical wave propagating
from the emitter and out through the electron optical system, much like
a laser beam would propagate through an optical system.
The HRTEM images are often based on the interference of the electron
wavefront after it has passed through the sample and reaches a CCD
detector to give a phase contrast image of the sample. The image will
have a resolution determined of course by the wavelength of the
electrons (Eq. #eq SEM de broglie
wavelength) but mainly by the
imperfections of the electron optics which also perturbs the wavefront.
The optimal imaging condition is for a sample thickness about
$\lambda_{mfp}$, where the wavefront is only slightly perturbed by
passing through the sample. TEM instruments are normally easily capable
of resolving individual shells of a carbon nanotubes. The fine-tuning of
the electron optical system to the required resolution can be achieved
in about 30 min for many microscopes.
!TEM images of the same nanostructure using standard \'bright field\'
TEM vs HAADF STEM. The sample is a gold nanoparticle containing
environmental electron beam deposited rod.
{width="300"}
# Electron Holography
In special TEM microscopes, the diffracted beam can be combined with a
part of the original electron beam from the electron gun, and the image
that is recorded is an interference pattern that depends on how much the
phase of the diffracted beam was changed. By recording such images, one
can measure how the electron wave function changes as it passes through
or nearby a nanostructure - and this allows you to measure the electric
and magnetic fields surrounding nanostructures.
# Electron Tomography
By recording numerous TEM images of an object at many different angles,
these images can in a computer be combined to create a three-dimensional
model of the object. The technique is time consuming but allows you to
see nanostructures in 3D.
## References
[^1]: J. Goldstein, D. Newbury, P. Echlin, D. C. Joy, A. D. Romig, C. E.
Lyman, C. Fiori, and E. Lifshin. Scanning Electron Microscopy and
X-Ray Microanalysis, 2nd Ed. Plenum Press, 1992.
[^2]: P. J. Goodhew and F. J. Humphreys. Electron Microscopy and
Analysis, 2rd Ed. Taylor and Francis, 1988.
[^3]: S. Humphries. Charged Particle Beams. John Wiley and Sons, 1990.
PDF version available at <http://www.fieldp.com/cpb/cpb.html>.
[^4]: P. W. Hawkes and E. Kasper. Principles Of Electron Optics.
Academic Press, 1989.
[^5]: L. Reimer. Transmission electron microscopy: Physics of image
formation and microanalysis, 3rd Ed. Springer-Verlag, 1993.
[^6]: P. J. Goodhew and F. J. Humphreys. Electron Microscopy and
Analysis, 2rd Ed. Taylor and Francis, 1988.
[^7]: J. Goldstein, D. Newbury, P. Echlin, D. C. Joy, A. D. Romig, C. E.
Lyman, C. Fiori, and E. Lifshin. Scanning Electron Microscopy and
X-Ray Microanalysis, 2nd Ed. Plenum Press, 1992.
[^8]: P. W. Milonni and J. H. Eberly. Lasers. John Wiley & Sons, Inc.,
1988.
|
# Nanotechnology/Electron microscopy#Electron Range
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Optical Methods
\>\< Main: Nanotechnology
\>\> Next: Scanning Probe Microscopy
\_\_TOC\_\_
------------------------------------------------------------------------
# Electron microscopy
An overview:
Electron microscopes uses electrons instead of photons, because
electrons have a much shorter wavelength than photons and so allows you
to observe matter with atomic resolution.
There are two general types of electron microscopes: the Scanning
Electron Microscope (SEM) that scans an electron beam over the surface
of an object and measures how many electrons are scattered back, and the
Transmission Electron Microscope (TEM) that shoots electrons through the
sample and measures how the electron beam changes because it is
scattered in the sample.
! A very simple sketch of a Transmission Electron Microscope (TEM) and
Scanning Electron Microscope (SEM) compared to an optical transmission
microscope and a cathode ray tube (CRT) TV screen - both systems have
many things on common with the electron microscope. The optical
microscope uses lenses to control the lights pathway through the system
and is in many ways built up like a TEM - only the TEM uses
electromagnetic lenses to direct the beam of electrons. The CRT uses
electromagnetic lenses as the TEM and SEM to control the electron beam,
and generates an image for the viewer by scanning the beam over a
fluorescent screen - in the same way the a SEM generates an image by
scanning the electron beam over a small
sample. and Scanning Electron Microscope (SEM) compared to an optical transmission microscope and a cathode ray tube (CRT) TV screen - both systems have many things on common with the electron microscope. The optical microscope uses lenses to control the lights pathway through the system and is in many ways built up like a TEM - only the TEM uses electromagnetic lenses to direct the beam of electrons. The CRT uses electromagnetic lenses as the TEM and SEM to control the electron beam, and generates an image for the viewer by scanning the beam over a fluorescent screen - in the same way the a SEM generates an image by scanning the electron beam over a small sample."){width="300"}
Using electron beams however requires working in a vacuum environment,
and this makes the instruments considerably larger and expensive. All
electron microscope work under at least low pressures and usually in
high vacuum chambers to avoid scattering the electrons in the gas. In
environmental electron microscopes, differential pumping systems are
used to actually have gasses present by the sample together with the
electron beam.
## Introduction to Electron Microscopy
For imaging of nanoscale objects, optical microscopy has limited
resolution since the objects are often much smaller than the wavelength
of light. The achievable resolution for a wavelength $\lambda$ is often
given by the diffraction limit $d$ as
$$d=0.61 \frac {\lambda}{(NA)}$$ *(r.g., diffraction limit)*
with numerical aperture $NA$, which can be approximated by the largest
angle of incidence $\alpha$ of the wavefront towards the sample,
$NA \approx \alpha$.
Since $\alpha \ll 1$ for the present purposes, we can approximate
$\sin(\alpha)\approx \tan(\alpha)\approx \alpha$ and hence
$NA \approx \alpha \approx r_{a}/r_{wd}$ where $r_{a}$ is the radius of
the objective lens aperture and $r_{wd}$ the working distance.
Optical microscopes can often reach a resolution of about $d=200$ nm.
For nanoscale resolution this is unfortunately not sufficient to
distinguish for instance a single nanotube from two adhering to each
other, since they have diameters of less than 100 nm.
The figure below gives an overview typical magnifications achievable by
the different electron microscopes compared to a light microscope.
!The different methods for microscopy cover a range of magnification
roughly indicated by the bars in the figure. The resolution of optical
microscopy is limited to about 200 nm. a) SEM image of the head of an
ant facing a microfabricated chip with a pair of microfabricated
grippers. The grippers are barely visibly at the tip of the arrow. b)
SEM image of a gripper approaching a large bundle of carbon nanotubes.
c) Closeup in SEM of the gripper and nanotubes. d) TEM image of a carbon
nanotube suspended between two grippers. e) TEM closeup of the shells of
carbon atoms in a carbon nanotube. On the nanometer scale this
particular carbon nanotube does not show a well defined carbon shell
structure. SEM image of the head of an ant facing a microfabricated chip with a pair of microfabricated grippers. The grippers are barely visibly at the tip of the arrow. b) SEM image of a gripper approaching a large bundle of carbon nanotubes. c) Closeup in SEM of the gripper and nanotubes. d) TEM image of a carbon nanotube suspended between two grippers. e) TEM closeup of the shells of carbon atoms in a carbon nanotube. On the nanometer scale this particular carbon nanotube does not show a well defined carbon shell structure."){width="400"}
Electron optical systems use electrical and magnetic fields to control
the electron beam. Although the law of refraction in optics is exchanged
with the Lorentz force in electrodynamics, the electron optical system
has similar diffraction limits as optical systems, since they depend on
the wave nature of the electron beam.
One can achieve a considerable improvement in resolution with
instruments such as the transmission electron microscope and the
scanning electron microscope that use electrons with De Broglie
wavelength much smaller than that of visible light. The De Broglie
wavelength λ of an electron with momentum p is
$$\lambda = \frac{h}{p} = \frac {h}{\sqrt{2m_{e}E_{b}}},$$ *(Eq. De
Broglie wavelength)*
where $h$ is Plancks constant. The electron has rest mass $m_{e}$ and
energy $E_{e}=m_{e}c^2=511 keV$.
If an electron with charge $q_{e}$ is accelerated from rest by an
electrical potential $U$, to the electron beam energy $E_{b}=q_{e}U$, it
will have a wavelength of 1 nm at 1 eV decreasing to 1 pm at 100 keV
where it will be travelling with 50% the speed of light.
This chapter will briefly review fundamental issues for electron
microscopy that are similar for SEM and TEM: the limitations imposed by
the electron optical beam system in the microscope column; the
interaction of the electron beam with the sample; the standard image
formation method in SEM and TEM. These issues are essential to
understand the results and limitations reached in SEM and TEM
microscopy.
For further details, please refer to reviews of electron microscopes and
their applications, such as Goldstein et al. [^1] that contains a
thorough review of SEM, while Goodhew and Humphreys [^2] is a more
general introduction to both SEM and TEM.
# The Electron Optical System
For high resolution imaging, a well focused beam is required, just as in
optical microscopy. Due to the short wavelength of electron beams with
keV energies, as given by the #Eq de Broglie
wavelength, the properties of the
electron optical system and the electron emitter mainly defines the
limits on the achievable beam diameter. The current density in the
electron beam can be approximated by a Gaussian distribution of current
density j \[A/m²\] as function of radius, r, from the beam center
$$j(r)=j_0 e^{- \frac{r^2}{r_{0}^2}},$$
with radius determined by $r_0$, giving a the full width half maximum
$FWHM=2v(ln2)r0$. Integrating $I_{b}=\int \int j(r)rdrd\theta$ gives the
total beam current
$$I_{b}=j_0 \pi r_{0}^2.$$
The electron optics impose a limit on the achievable beam current
density and radius by the brightness of the electron emitter
$\beta_{e}$, which is conserved throughout the system [^3].
Brightness, ß, is a measure of the current per area normal to the beam
direction and per element of solid angle [^4]. At the center of the
Gaussian beam,
\<div id=\"eq SEM current density\>
```{=html}
</div>
```
```{=html}
<div id="eq beam brightness">
```
```{=html}
</div>
```
$$\beta=\frac{j_0}{\pi \alpha^2}$$
and the brightness is related to the current density in eq SEM Gaussian
beam profile. The emitter brightness $\beta_{e}$ is determined by the
type of electron emitter and the beam energy $E_{b}$ [^5]
$\beta_{e}=\frac{j_{e}E_{b}}{\pi \Delta E}$
with emission current density for W-filament sources about $j_{e}$\~3
A/cm², for LaB6 sources about 100 A/cm², while field emission guns (FEG)
can reach 10^5^A/cm². The energy spread of the electrons from the
sources are about ΔE\~1 eV and slightly lower for FEGs. Due to
conservation of the brightness in the system, the beam diameter depends
on current as
```{=html}
<div id="eq SEM beam diameter">
```
```{=html}
</div>
```
$r_{0}=\frac{1}{\pi}\frac{r_{wd}}{r_{a}}\sqrt{\frac{I_{b}}{\beta_{e}}}.$
The ideal beam probe size determined by the conservation of brightness
cannot be obtained in a real system. Effects such as aberration will
make the minimum achievable beam diameter larger. Equation #eq SEM beam
diameter however seem to adequately
describe the beam diameter for the present discussion. Apart from the
additional beam widening contributions, the image detection method
imposes limits on useful values for the parameters in Eq. SEM beam
diameter which differ for SEM and TEM.
# Electron Range
The electron optical system sets limitations to the achievable primary
beam current and radius. The expected image resolution set by the
primary beam cannot be reached if the signal detected for imaging is
caused by electrons scattered far in the sample. The trajectory of an
electron penetrating a bulk solid is a complex trajectory due to
multiple elastic and inelastic collision events. As the primary electron
(PE) penetrates into the sample it will gradually change direction and
loose energy in collisions. The mean free path due to elastic and
inelastic collisions, $\lambda_{mfp}$, depends on the atomic number of
the material and the PE energy. At 100 keV $\lambda_{mfp}=150 nm$ for
carbon and 5 nm for gold [^6]. For samples thinner than $\lambda_{mfp}$
the main part of the PE will pass relatively unaffected through the
sample, which is the basis for TEM.
!Overview of electron electron scattering processes in bulk and
tip-shaped specimens. The PE are scattered within the interaction
volume, defined the electron range in the material. The range is longer
than the mean free path $\lambda_{mfp}$. The SE have a very short range,
and only those created within that range from the surface can escape the
material. This defines the SE escape
depth.{width="300"}
SEM can be used for thicker specimens. The electrons that escape from
the sample in a new direction compared to the PE due to elastic
collisions are called backscattered electrons (BSE).
For samples thicker than $\lambda_{mfp}$, the volume interacting with
the scattered PE defines the range of the electrons in the material, and
this is considerably larger than the minimum achievable primary beam
diameters.
The electron range is about 1 µm at 10 keV for carbon, decreasing with
higher atomic number for the material. Both the high energy PE and BSE
generate secondary electrons (SE) by inelastic scattering events. The SE
are generally defined as having energy below 50 eV while the BSE have
energies up to the PE energy. The range of SE is typically 1 nm for
metals and about 10 nm for insulators [^7].
The short range of the SE make the yield of SE highly dependent on the
energy lost by the PE within the SE range from the surface, and this
makes high Z substances efficient generators of SE. The main emission of
SE takes place in the region where the PE strikes the surface and within
the SE escape depth from this region.
!The electron range increases with beam energy. The internal structure
of the EEBD deposits can be examined at high electron beam energies in
SEM. At 5 kV with shallow penetration depth, the surface of the tips is
clearly visible while at higher energies a core of more dense material
becomes increasingly visible. At 100 keV and above, TEM images can
achieve atomic resolution where the lattice planes in nanocrystals such
as the gold nanocrystal in (c). The gold crystal is embedded in
amorphous carbon with no clear lattice
pattern.. The gold crystal is embedded in amorphous carbon with no clear lattice pattern."){width="300"}
# Scanning electron microscopy (SEM)
- Wikipedia: Scanning electron microscopy
(SEM)
In a scanning electron microscope a beam is scanned over the sample
surface in a raster pattern while a signal is recorded from electron
detectors for SE or BSE. The PE energy is kept relatively low (1-30 keV)
to limit the interaction volume in the specimen that will contribute to
the detected signal. Especially low energy PE will provide high
sensitivity to surface composition as they cannot penetrate far into the
sample.
The figure above showed the effect of PE penetration depth of a
carbonaceous nanostructure with a gold core, where only the surface is
visible at low PE energies, while the carbon becomes increasingly
transparent and the core visible at high PE energies.
The low energy SE can easily be attracted and collected by a positively
charged detector and are hence an efficient source for an image signal.
The standard SE detector is an Everhart-Thornley (ET) detector where a
positively charged grid attracts the SE and accelerates them to
sufficiently high energies to create a light pulse when striking a
scintillator. The light pulse is then amplified by a photomultiplier.
Despite the complex construction, the ET detector is remarkably
efficient, but requires large $r_{wd}$ for effective collection of the
SE by the charged grid.
Another SEM detector is the in-lens detector, where SE passing through
the column aperture are accelerated towards a solid state detector. The
in-lens detector complements the ET by being more efficient at short
$r_{wd}$.
## Environmental SEM (ESEM)
!Simple sketch of an Environmental Scanning Electron Microscope (ESEM),
where a differential pumping system with two pressure limiting apertures
between the ultra high vacuum SEM column and the low vacuum sample
chamber allows high pressures up to 10 hPa around the sample. This is
enough to have liquid water at moderate cooling of 5 deg.
C., where a differential pumping system with two pressure limiting apertures between the ultra high vacuum SEM column and the low vacuum sample chamber allows high pressures up to 10 hPa around the sample. This is enough to have liquid water at moderate cooling of 5 deg. C."){width="300"}
The ESEM makes it possible to use various gasses in the sample chamber
of the microscope since there are narrow apertures between the sample
chamber and the gun column, and a region in between that is connected to
a differential pumping system. Pressures up to about 10 Torr are
normally possible in the sample chamber.
The standard Everly-Thornhart SE detector would not work under such
conditions since it would create a discharge in the low pressure gas.
Instead a \"gaseous secondary electron detector (GSD)\" is used, as
shown in the figure below. The GSD measures the current of a weak
cascade discharge in the gas, which is seeded by the emission of
electrons from the sample.
! Two examples of images from an ESEM. Taken with a Philips XL-30 FEG.
The first shows a electron beam deposited nanowire between two
microelectrodes that has burnt after sustaining a high bias current. The
other shows a multiwall carbon nanotube sample. Shorter working
distances often improves image quality and so does a low beam current
but it also increases the image acquisition
time{width="300"}
In the ESEM one can work with for instance water vapour or argon as the
environmental gas, and it is possible to have liquid samples in the
chamber if the sample stage is cooled sufficiently to condense water.
# Transmission electron microscopy (TEM)
- Transmission electron microscopy
(TEM)
- High Resolution Transmission electron microscopy
(HRTEM)
! A Philips EM 430
TEM{width="100"}
When the specimen thickness is about the mean free path,
$\lambda_{mfp}$, TEM can be used to achieve high resolution images such
as the image above where the atomic lattice of a gold nanocrystal is
visible. Since the detected electrons are transmitted PE where the
energy can be in the 100 keV range, the resolution is not limited by the
issues regarding secondary electrons. The electron beam optics can be
optimized for higher current densities (Eq. #eq SEM current
density) at higher energies
compared to SEM.
To achieve optimal imaging conditions for the thin TEM samples, the
working distance has been made short. In most TEMs, the space for the
sample holder is only about (5 mm)³ between the two objective lenses for
the incoming and transmitted beam. Before reaching a CCD camera, the
transmitted beam is sent through several magnification lenses to achieve
the high magnification (500.000X is not unusual).
The image formation in TEM can be based on several principles, but
practically all images used in this work were made by phase contrast
imaging, here called High Resolution TEM or HRTEM. At sufficiently high
brightness, electron sources can produce coherent electron beams due to
the point-like emitter surface area and small energy spread [^8]. The
coherent electron beam can be considered as a spherical wave propagating
from the emitter and out through the electron optical system, much like
a laser beam would propagate through an optical system.
The HRTEM images are often based on the interference of the electron
wavefront after it has passed through the sample and reaches a CCD
detector to give a phase contrast image of the sample. The image will
have a resolution determined of course by the wavelength of the
electrons (Eq. #eq SEM de broglie
wavelength) but mainly by the
imperfections of the electron optics which also perturbs the wavefront.
The optimal imaging condition is for a sample thickness about
$\lambda_{mfp}$, where the wavefront is only slightly perturbed by
passing through the sample. TEM instruments are normally easily capable
of resolving individual shells of a carbon nanotubes. The fine-tuning of
the electron optical system to the required resolution can be achieved
in about 30 min for many microscopes.
!TEM images of the same nanostructure using standard \'bright field\'
TEM vs HAADF STEM. The sample is a gold nanoparticle containing
environmental electron beam deposited rod.
{width="300"}
# Electron Holography
In special TEM microscopes, the diffracted beam can be combined with a
part of the original electron beam from the electron gun, and the image
that is recorded is an interference pattern that depends on how much the
phase of the diffracted beam was changed. By recording such images, one
can measure how the electron wave function changes as it passes through
or nearby a nanostructure - and this allows you to measure the electric
and magnetic fields surrounding nanostructures.
# Electron Tomography
By recording numerous TEM images of an object at many different angles,
these images can in a computer be combined to create a three-dimensional
model of the object. The technique is time consuming but allows you to
see nanostructures in 3D.
## References
[^1]: J. Goldstein, D. Newbury, P. Echlin, D. C. Joy, A. D. Romig, C. E.
Lyman, C. Fiori, and E. Lifshin. Scanning Electron Microscopy and
X-Ray Microanalysis, 2nd Ed. Plenum Press, 1992.
[^2]: P. J. Goodhew and F. J. Humphreys. Electron Microscopy and
Analysis, 2rd Ed. Taylor and Francis, 1988.
[^3]: S. Humphries. Charged Particle Beams. John Wiley and Sons, 1990.
PDF version available at <http://www.fieldp.com/cpb/cpb.html>.
[^4]: P. W. Hawkes and E. Kasper. Principles Of Electron Optics.
Academic Press, 1989.
[^5]: L. Reimer. Transmission electron microscopy: Physics of image
formation and microanalysis, 3rd Ed. Springer-Verlag, 1993.
[^6]: P. J. Goodhew and F. J. Humphreys. Electron Microscopy and
Analysis, 2rd Ed. Taylor and Francis, 1988.
[^7]: J. Goldstein, D. Newbury, P. Echlin, D. C. Joy, A. D. Romig, C. E.
Lyman, C. Fiori, and E. Lifshin. Scanning Electron Microscopy and
X-Ray Microanalysis, 2nd Ed. Plenum Press, 1992.
[^8]: P. W. Milonni and J. H. Eberly. Lasers. John Wiley & Sons, Inc.,
1988.
|
# Nanotechnology/Additional methods#Point-Projection Microscopes
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Scanning probe microscopy
\>\< Main: Nanotechnology
\>\> Next: Physics on the nanoscale
\_\_TOC\_\_
------------------------------------------------------------------------
# Point-Projection Microscopes
Point-Projection Microscopes are a type of field emission
microscope[^1], and consists of
three components: an electron source, the object to the imaged, and the
viewing screen[^2].
- Field emission microscope
- Field ion microscope
- Atom Probe
# Low energy electron diffraction (LEED)
LEED is a technique for imaging surfaces, and has two principle methods
of use: qualitative and quantitative. The qualitative method measures
relative size and geometric properties, whereas the quantitative method
looks at diffracted beams as a way of determining the position of atoms.
- Low energy electron diffraction
(LEED)
- LEED intro
# Reflection High Energy Electron diffraction
RHEED is similar to LEED but uses higher energies
and the electrons are directed to the be reflected on the surface at
almost grazing incidence. This way the high energy electrons only
penetrates a few atomic layers of the surface.
# X-ray Spectroscopy and Diffraction
X-ray Spectroscopy refers to a
collection of techniques including, but not limited to X-ray
Absorption Spectroscopy and
X-ray Photoelectron
Spectroscopy.
X-rays can be used for X-ray
crystallography.
# Auger electron spectroscopy (AES)
Auger Electron Spectroscopy
is a technique that takes advantage of the Auger Process to analyze the
surface layers of a sample[^3].
# Nuclear Magnetic Resonance (NMR)
- Nuclear Magnetic Resonance
(NMR) - in a magnetic
field the spin of the nuclei of molecules will precess and in strong
fields (several tesla) this happens with rf frequencies that can be
detected by receiving rf antennas and amplifiers. The precession
frequency of an individual nucleus will deviate slightly depending
on the its surrounding molecules\' electronic structure and hence
detecting a spectrum of the radiofrequency precession frequencies in
a sample will provide a finger print of the types of molecules in
that sample.
- Nuclear quadrupole
resonance is a related
technique, based on the internal electrical fields of the molecules
to cause a splitting of the nuclear magnetic moments energy levels.
The level splitting is detected by rf as in NMR. Its is used mainly
for experimental explosives detection.
# Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)
Electron Spin Resonance (ESR)
measures the microwave frequency of
paramagnetic ions or molecules[^4] .
# Mössbauer spectroscopy
Mössbauer spectroscopy detects
the hyperfine interactions between the nucleus of an atom, and the
ambient environment. The atom must be part of a solid matrix to reduce
the recoil affect of a gamma ray emission or absorption[^5].
# Non-contact Nanoscale Temperature Measurements
Heat radiation has infrared wavelengths much longer than 1 µm and hence
taking a photo of a nanostructure with e.g. a thermal camera will not
provide much information about the temperature distribution within the
nanostructure (or microstructure for that sake).
Temperatures can be measured locally by different non-contact methods:
- Spectroscopy on individual quantum dots
1.
- Spectra of laser dyes incorporated in the structure
- Raman microscopy (the temperature influences the ratio of stokes and
anti-stokes lines amplitude, the width of the lines and the position
of the lines.)
- Transmission electron microscopy can also give temperature
information by various techniques
2
- Special AFM probes with a temperature dependent resistor at the tip
can be used for mapping surface temperatures
- Infrared Near-field Microscopy [^6]
- Confocal raman microscopy can provide 3D thermal maps
3
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Rochow, Theodore George, and Paul Arthur Tucker. \"Emissions
Microscopies\". Introduction to Microscopy by Means of Light,
Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
[^2]: The Future of the SEM for Image and
Metrology
[^3]: Auger Electron
Microscopy
[^4]: What is EPR?
[^5]: Introduction to Mossbauer Spectroscopy: Part
1
[^6]: C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, \"Thermal
Imaging by Infrared Near-field Microscopy,\" Proceedings of IEEE
Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1,
November 1996, pp. 249-250
|
# Nanotechnology/Additional methods#X-ray Spectroscopy and Diffraction
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Scanning probe microscopy
\>\< Main: Nanotechnology
\>\> Next: Physics on the nanoscale
\_\_TOC\_\_
------------------------------------------------------------------------
# Point-Projection Microscopes
Point-Projection Microscopes are a type of field emission
microscope[^1], and consists of
three components: an electron source, the object to the imaged, and the
viewing screen[^2].
- Field emission microscope
- Field ion microscope
- Atom Probe
# Low energy electron diffraction (LEED)
LEED is a technique for imaging surfaces, and has two principle methods
of use: qualitative and quantitative. The qualitative method measures
relative size and geometric properties, whereas the quantitative method
looks at diffracted beams as a way of determining the position of atoms.
- Low energy electron diffraction
(LEED)
- LEED intro
# Reflection High Energy Electron diffraction
RHEED is similar to LEED but uses higher energies
and the electrons are directed to the be reflected on the surface at
almost grazing incidence. This way the high energy electrons only
penetrates a few atomic layers of the surface.
# X-ray Spectroscopy and Diffraction
X-ray Spectroscopy refers to a
collection of techniques including, but not limited to X-ray
Absorption Spectroscopy and
X-ray Photoelectron
Spectroscopy.
X-rays can be used for X-ray
crystallography.
# Auger electron spectroscopy (AES)
Auger Electron Spectroscopy
is a technique that takes advantage of the Auger Process to analyze the
surface layers of a sample[^3].
# Nuclear Magnetic Resonance (NMR)
- Nuclear Magnetic Resonance
(NMR) - in a magnetic
field the spin of the nuclei of molecules will precess and in strong
fields (several tesla) this happens with rf frequencies that can be
detected by receiving rf antennas and amplifiers. The precession
frequency of an individual nucleus will deviate slightly depending
on the its surrounding molecules\' electronic structure and hence
detecting a spectrum of the radiofrequency precession frequencies in
a sample will provide a finger print of the types of molecules in
that sample.
- Nuclear quadrupole
resonance is a related
technique, based on the internal electrical fields of the molecules
to cause a splitting of the nuclear magnetic moments energy levels.
The level splitting is detected by rf as in NMR. Its is used mainly
for experimental explosives detection.
# Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)
Electron Spin Resonance (ESR)
measures the microwave frequency of
paramagnetic ions or molecules[^4] .
# Mössbauer spectroscopy
Mössbauer spectroscopy detects
the hyperfine interactions between the nucleus of an atom, and the
ambient environment. The atom must be part of a solid matrix to reduce
the recoil affect of a gamma ray emission or absorption[^5].
# Non-contact Nanoscale Temperature Measurements
Heat radiation has infrared wavelengths much longer than 1 µm and hence
taking a photo of a nanostructure with e.g. a thermal camera will not
provide much information about the temperature distribution within the
nanostructure (or microstructure for that sake).
Temperatures can be measured locally by different non-contact methods:
- Spectroscopy on individual quantum dots
1.
- Spectra of laser dyes incorporated in the structure
- Raman microscopy (the temperature influences the ratio of stokes and
anti-stokes lines amplitude, the width of the lines and the position
of the lines.)
- Transmission electron microscopy can also give temperature
information by various techniques
2
- Special AFM probes with a temperature dependent resistor at the tip
can be used for mapping surface temperatures
- Infrared Near-field Microscopy [^6]
- Confocal raman microscopy can provide 3D thermal maps
3
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Rochow, Theodore George, and Paul Arthur Tucker. \"Emissions
Microscopies\". Introduction to Microscopy by Means of Light,
Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
[^2]: The Future of the SEM for Image and
Metrology
[^3]: Auger Electron
Microscopy
[^4]: What is EPR?
[^5]: Introduction to Mossbauer Spectroscopy: Part
1
[^6]: C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, \"Thermal
Imaging by Infrared Near-field Microscopy,\" Proceedings of IEEE
Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1,
November 1996, pp. 249-250
|
# Nanotechnology/Additional methods#Electron Paramagnetic Resonance .28EPR.29 or Electron Spin Resonance .28ESR.29
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Scanning probe microscopy
\>\< Main: Nanotechnology
\>\> Next: Physics on the nanoscale
\_\_TOC\_\_
------------------------------------------------------------------------
# Point-Projection Microscopes
Point-Projection Microscopes are a type of field emission
microscope[^1], and consists of
three components: an electron source, the object to the imaged, and the
viewing screen[^2].
- Field emission microscope
- Field ion microscope
- Atom Probe
# Low energy electron diffraction (LEED)
LEED is a technique for imaging surfaces, and has two principle methods
of use: qualitative and quantitative. The qualitative method measures
relative size and geometric properties, whereas the quantitative method
looks at diffracted beams as a way of determining the position of atoms.
- Low energy electron diffraction
(LEED)
- LEED intro
# Reflection High Energy Electron diffraction
RHEED is similar to LEED but uses higher energies
and the electrons are directed to the be reflected on the surface at
almost grazing incidence. This way the high energy electrons only
penetrates a few atomic layers of the surface.
# X-ray Spectroscopy and Diffraction
X-ray Spectroscopy refers to a
collection of techniques including, but not limited to X-ray
Absorption Spectroscopy and
X-ray Photoelectron
Spectroscopy.
X-rays can be used for X-ray
crystallography.
# Auger electron spectroscopy (AES)
Auger Electron Spectroscopy
is a technique that takes advantage of the Auger Process to analyze the
surface layers of a sample[^3].
# Nuclear Magnetic Resonance (NMR)
- Nuclear Magnetic Resonance
(NMR) - in a magnetic
field the spin of the nuclei of molecules will precess and in strong
fields (several tesla) this happens with rf frequencies that can be
detected by receiving rf antennas and amplifiers. The precession
frequency of an individual nucleus will deviate slightly depending
on the its surrounding molecules\' electronic structure and hence
detecting a spectrum of the radiofrequency precession frequencies in
a sample will provide a finger print of the types of molecules in
that sample.
- Nuclear quadrupole
resonance is a related
technique, based on the internal electrical fields of the molecules
to cause a splitting of the nuclear magnetic moments energy levels.
The level splitting is detected by rf as in NMR. Its is used mainly
for experimental explosives detection.
# Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)
Electron Spin Resonance (ESR)
measures the microwave frequency of
paramagnetic ions or molecules[^4] .
# Mössbauer spectroscopy
Mössbauer spectroscopy detects
the hyperfine interactions between the nucleus of an atom, and the
ambient environment. The atom must be part of a solid matrix to reduce
the recoil affect of a gamma ray emission or absorption[^5].
# Non-contact Nanoscale Temperature Measurements
Heat radiation has infrared wavelengths much longer than 1 µm and hence
taking a photo of a nanostructure with e.g. a thermal camera will not
provide much information about the temperature distribution within the
nanostructure (or microstructure for that sake).
Temperatures can be measured locally by different non-contact methods:
- Spectroscopy on individual quantum dots
1.
- Spectra of laser dyes incorporated in the structure
- Raman microscopy (the temperature influences the ratio of stokes and
anti-stokes lines amplitude, the width of the lines and the position
of the lines.)
- Transmission electron microscopy can also give temperature
information by various techniques
2
- Special AFM probes with a temperature dependent resistor at the tip
can be used for mapping surface temperatures
- Infrared Near-field Microscopy [^6]
- Confocal raman microscopy can provide 3D thermal maps
3
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Rochow, Theodore George, and Paul Arthur Tucker. \"Emissions
Microscopies\". Introduction to Microscopy by Means of Light,
Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
[^2]: The Future of the SEM for Image and
Metrology
[^3]: Auger Electron
Microscopy
[^4]: What is EPR?
[^5]: Introduction to Mossbauer Spectroscopy: Part
1
[^6]: C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, \"Thermal
Imaging by Infrared Near-field Microscopy,\" Proceedings of IEEE
Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1,
November 1996, pp. 249-250
|
# Nanotechnology/Additional methods#M.C3.B6ssbauer spectroscopy
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Scanning probe microscopy
\>\< Main: Nanotechnology
\>\> Next: Physics on the nanoscale
\_\_TOC\_\_
------------------------------------------------------------------------
# Point-Projection Microscopes
Point-Projection Microscopes are a type of field emission
microscope[^1], and consists of
three components: an electron source, the object to the imaged, and the
viewing screen[^2].
- Field emission microscope
- Field ion microscope
- Atom Probe
# Low energy electron diffraction (LEED)
LEED is a technique for imaging surfaces, and has two principle methods
of use: qualitative and quantitative. The qualitative method measures
relative size and geometric properties, whereas the quantitative method
looks at diffracted beams as a way of determining the position of atoms.
- Low energy electron diffraction
(LEED)
- LEED intro
# Reflection High Energy Electron diffraction
RHEED is similar to LEED but uses higher energies
and the electrons are directed to the be reflected on the surface at
almost grazing incidence. This way the high energy electrons only
penetrates a few atomic layers of the surface.
# X-ray Spectroscopy and Diffraction
X-ray Spectroscopy refers to a
collection of techniques including, but not limited to X-ray
Absorption Spectroscopy and
X-ray Photoelectron
Spectroscopy.
X-rays can be used for X-ray
crystallography.
# Auger electron spectroscopy (AES)
Auger Electron Spectroscopy
is a technique that takes advantage of the Auger Process to analyze the
surface layers of a sample[^3].
# Nuclear Magnetic Resonance (NMR)
- Nuclear Magnetic Resonance
(NMR) - in a magnetic
field the spin of the nuclei of molecules will precess and in strong
fields (several tesla) this happens with rf frequencies that can be
detected by receiving rf antennas and amplifiers. The precession
frequency of an individual nucleus will deviate slightly depending
on the its surrounding molecules\' electronic structure and hence
detecting a spectrum of the radiofrequency precession frequencies in
a sample will provide a finger print of the types of molecules in
that sample.
- Nuclear quadrupole
resonance is a related
technique, based on the internal electrical fields of the molecules
to cause a splitting of the nuclear magnetic moments energy levels.
The level splitting is detected by rf as in NMR. Its is used mainly
for experimental explosives detection.
# Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)
Electron Spin Resonance (ESR)
measures the microwave frequency of
paramagnetic ions or molecules[^4] .
# Mössbauer spectroscopy
Mössbauer spectroscopy detects
the hyperfine interactions between the nucleus of an atom, and the
ambient environment. The atom must be part of a solid matrix to reduce
the recoil affect of a gamma ray emission or absorption[^5].
# Non-contact Nanoscale Temperature Measurements
Heat radiation has infrared wavelengths much longer than 1 µm and hence
taking a photo of a nanostructure with e.g. a thermal camera will not
provide much information about the temperature distribution within the
nanostructure (or microstructure for that sake).
Temperatures can be measured locally by different non-contact methods:
- Spectroscopy on individual quantum dots
1.
- Spectra of laser dyes incorporated in the structure
- Raman microscopy (the temperature influences the ratio of stokes and
anti-stokes lines amplitude, the width of the lines and the position
of the lines.)
- Transmission electron microscopy can also give temperature
information by various techniques
2
- Special AFM probes with a temperature dependent resistor at the tip
can be used for mapping surface temperatures
- Infrared Near-field Microscopy [^6]
- Confocal raman microscopy can provide 3D thermal maps
3
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Rochow, Theodore George, and Paul Arthur Tucker. \"Emissions
Microscopies\". Introduction to Microscopy by Means of Light,
Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
[^2]: The Future of the SEM for Image and
Metrology
[^3]: Auger Electron
Microscopy
[^4]: What is EPR?
[^5]: Introduction to Mossbauer Spectroscopy: Part
1
[^6]: C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, \"Thermal
Imaging by Infrared Near-field Microscopy,\" Proceedings of IEEE
Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1,
November 1996, pp. 249-250
|
# Nanotechnology/Additional methods#Non-contact Nanoscale Temperature Measurements
Navigate
-----------------------------------------------------------------------------------
\<\< Prev: Scanning probe microscopy
\>\< Main: Nanotechnology
\>\> Next: Physics on the nanoscale
\_\_TOC\_\_
------------------------------------------------------------------------
# Point-Projection Microscopes
Point-Projection Microscopes are a type of field emission
microscope[^1], and consists of
three components: an electron source, the object to the imaged, and the
viewing screen[^2].
- Field emission microscope
- Field ion microscope
- Atom Probe
# Low energy electron diffraction (LEED)
LEED is a technique for imaging surfaces, and has two principle methods
of use: qualitative and quantitative. The qualitative method measures
relative size and geometric properties, whereas the quantitative method
looks at diffracted beams as a way of determining the position of atoms.
- Low energy electron diffraction
(LEED)
- LEED intro
# Reflection High Energy Electron diffraction
RHEED is similar to LEED but uses higher energies
and the electrons are directed to the be reflected on the surface at
almost grazing incidence. This way the high energy electrons only
penetrates a few atomic layers of the surface.
# X-ray Spectroscopy and Diffraction
X-ray Spectroscopy refers to a
collection of techniques including, but not limited to X-ray
Absorption Spectroscopy and
X-ray Photoelectron
Spectroscopy.
X-rays can be used for X-ray
crystallography.
# Auger electron spectroscopy (AES)
Auger Electron Spectroscopy
is a technique that takes advantage of the Auger Process to analyze the
surface layers of a sample[^3].
# Nuclear Magnetic Resonance (NMR)
- Nuclear Magnetic Resonance
(NMR) - in a magnetic
field the spin of the nuclei of molecules will precess and in strong
fields (several tesla) this happens with rf frequencies that can be
detected by receiving rf antennas and amplifiers. The precession
frequency of an individual nucleus will deviate slightly depending
on the its surrounding molecules\' electronic structure and hence
detecting a spectrum of the radiofrequency precession frequencies in
a sample will provide a finger print of the types of molecules in
that sample.
- Nuclear quadrupole
resonance is a related
technique, based on the internal electrical fields of the molecules
to cause a splitting of the nuclear magnetic moments energy levels.
The level splitting is detected by rf as in NMR. Its is used mainly
for experimental explosives detection.
# Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR)
Electron Spin Resonance (ESR)
measures the microwave frequency of
paramagnetic ions or molecules[^4] .
# Mössbauer spectroscopy
Mössbauer spectroscopy detects
the hyperfine interactions between the nucleus of an atom, and the
ambient environment. The atom must be part of a solid matrix to reduce
the recoil affect of a gamma ray emission or absorption[^5].
# Non-contact Nanoscale Temperature Measurements
Heat radiation has infrared wavelengths much longer than 1 µm and hence
taking a photo of a nanostructure with e.g. a thermal camera will not
provide much information about the temperature distribution within the
nanostructure (or microstructure for that sake).
Temperatures can be measured locally by different non-contact methods:
- Spectroscopy on individual quantum dots
1.
- Spectra of laser dyes incorporated in the structure
- Raman microscopy (the temperature influences the ratio of stokes and
anti-stokes lines amplitude, the width of the lines and the position
of the lines.)
- Transmission electron microscopy can also give temperature
information by various techniques
2
- Special AFM probes with a temperature dependent resistor at the tip
can be used for mapping surface temperatures
- Infrared Near-field Microscopy [^6]
- Confocal raman microscopy can provide 3D thermal maps
3
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Rochow, Theodore George, and Paul Arthur Tucker. \"Emissions
Microscopies\". Introduction to Microscopy by Means of Light,
Electrons, X-Rays, or Acoustics (Chapter 16, page 329) 1994.
[^2]: The Future of the SEM for Image and
Metrology
[^3]: Auger Electron
Microscopy
[^4]: What is EPR?
[^5]: Introduction to Mossbauer Spectroscopy: Part
1
[^6]: C. Feng, M. S. Ünlü, B. B. Goldberg, and W. D. Herzog, \"Thermal
Imaging by Infrared Near-field Microscopy,\" Proceedings of IEEE
Lasers and Electro-Optics Society 1996 Annual Meeting, Vol. 1,
November 1996, pp. 249-250
|
# Nanotechnology/Physics#Scaling laws
Navigate
---------------------------------------------------------------------------
\<\< Prev: Additional methods
\>\< Main: Nanotechnology
\>\> Next: Modelling Nanosystems
\_\_TOC\_\_
------------------------------------------------------------------------
Quantum mechanics and classical
mechanics are still valid on the nanoscale - but many assumptions we are
used to take for granted are no longer valid. This makes many
traditional systems difficult to make on the atomic scale -if for
instance you scale down a car the new relation between adhesion forces
and gravity or changes in heat conduction will very likely make it
perform very poorly if at all - but at the same time a wealth of other
new possibilities open up!
Scaling laws can be used to determine how
the physical properties vary as the dimensions are changed. At some
point the scaling law no longer can be applied because the assumptions
behind it become invalid at some large or small scale.
So, scaling is one thing - the end of scaling another, and surfaces a
third! For instance at some point the idealized classical point of view
on a system being downscaled will need quantum mechanics to describe
what\'s going on in a proper way, but as the scale is decreased the
system might also be very different because the interaction at the
surface becomes very significant compared to the bulk.
This part will try to give an overview of these effects.
# Scaling laws
Scaling laws can be used to describe how
the physical properties of a system change as the dimensions are
changed.
! The scaling properties of physical laws is an important effect to
consider when miniaturizing devices. On the nanoscale the mass and heat
capacity become very unimportant, whereas eg. surface forces scaling
with area become dominant.
{width="300"}
# Quantized Nano Systems
Quantum wires are examples of nanosystems
where the quantum effects become very important.
Break junctions is another example.
Resources
- Simple model of conduction -
the classical case
# Bulk matter and the end of bulk: surfaces
- Surface states are electronic states
on the surface of a material, which can have radically different
properties than the underlying bulk material. For instance, a
semiconductor can have superconducting surface states.
```{=html}
<!-- -->
```
- Surface reconstruction
The surface of a material can be very different from the bulk because
the surface atoms rearrange themselves to lower their energy rather than
stay in the bulk lattice and have dangling bonds extending into space
where there is no more material. Atoms from the surroundings will easily
bind to such surfaces and for example for silicon, more than 2000
surface reconstructions have been found, depending on what additional
atoms and conditions are present.
- Surface plasmons
Plasmons are collective oscillations of the
electrons in matter, and the electrons on the surfaces can also make
local plasmons that propagate on the surface.
# The Tyndall Effect
The Tyndall Effect is caused by reflection of light off of small
particles such as dust or mist. This is also seen off of dust when
sunlight comes through windows and clouds or when headlight beams go
through fog. The Tyndall Effect can only be seen through colloidal
suspensions. A colloid is a substance that consists of particles
dispersed throughout another substance, which are too small for
resolution with an ordinary light microscope but are incapable of
passing through a semi permeable membrane. The Tyndall Effect is most
easily visible through liquid using a laser pointer. The Tyndall Effect
is named after its discoverer, the 19th-century British physicist John
Tyndall.[^1][^2][^3][^4][^5][^6]
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: "Tyndall Effect." Silver Lighting. 1 June 2008.
<http://silver-lightning.com/tyndall/>
[^2]: Davies, Paul. The Tyndall Effect. 1 June 2008.
<http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html>
[^3]: SonneNebel. 1 July 2008.
<http://upload.wikimedia.org/wikipedia/commons/f/f6/SonneNebel.jpg>
[^4]: Bright Flashlight. 1 July 2008.
<http://www.geekologie.com/2008/02/04/bright-flashlight.jpg>
[^5]: "The Tyndall Effect."
`http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html`` `
[^6]: "Colloid." 3 June 2008.
<http://www.merriam-webster.com/dictionary/colloid>
|
# Nanotechnology/Physics#Quantized Nano Systems
Navigate
---------------------------------------------------------------------------
\<\< Prev: Additional methods
\>\< Main: Nanotechnology
\>\> Next: Modelling Nanosystems
\_\_TOC\_\_
------------------------------------------------------------------------
Quantum mechanics and classical
mechanics are still valid on the nanoscale - but many assumptions we are
used to take for granted are no longer valid. This makes many
traditional systems difficult to make on the atomic scale -if for
instance you scale down a car the new relation between adhesion forces
and gravity or changes in heat conduction will very likely make it
perform very poorly if at all - but at the same time a wealth of other
new possibilities open up!
Scaling laws can be used to determine how
the physical properties vary as the dimensions are changed. At some
point the scaling law no longer can be applied because the assumptions
behind it become invalid at some large or small scale.
So, scaling is one thing - the end of scaling another, and surfaces a
third! For instance at some point the idealized classical point of view
on a system being downscaled will need quantum mechanics to describe
what\'s going on in a proper way, but as the scale is decreased the
system might also be very different because the interaction at the
surface becomes very significant compared to the bulk.
This part will try to give an overview of these effects.
# Scaling laws
Scaling laws can be used to describe how
the physical properties of a system change as the dimensions are
changed.
! The scaling properties of physical laws is an important effect to
consider when miniaturizing devices. On the nanoscale the mass and heat
capacity become very unimportant, whereas eg. surface forces scaling
with area become dominant.
{width="300"}
# Quantized Nano Systems
Quantum wires are examples of nanosystems
where the quantum effects become very important.
Break junctions is another example.
Resources
- Simple model of conduction -
the classical case
# Bulk matter and the end of bulk: surfaces
- Surface states are electronic states
on the surface of a material, which can have radically different
properties than the underlying bulk material. For instance, a
semiconductor can have superconducting surface states.
```{=html}
<!-- -->
```
- Surface reconstruction
The surface of a material can be very different from the bulk because
the surface atoms rearrange themselves to lower their energy rather than
stay in the bulk lattice and have dangling bonds extending into space
where there is no more material. Atoms from the surroundings will easily
bind to such surfaces and for example for silicon, more than 2000
surface reconstructions have been found, depending on what additional
atoms and conditions are present.
- Surface plasmons
Plasmons are collective oscillations of the
electrons in matter, and the electrons on the surfaces can also make
local plasmons that propagate on the surface.
# The Tyndall Effect
The Tyndall Effect is caused by reflection of light off of small
particles such as dust or mist. This is also seen off of dust when
sunlight comes through windows and clouds or when headlight beams go
through fog. The Tyndall Effect can only be seen through colloidal
suspensions. A colloid is a substance that consists of particles
dispersed throughout another substance, which are too small for
resolution with an ordinary light microscope but are incapable of
passing through a semi permeable membrane. The Tyndall Effect is most
easily visible through liquid using a laser pointer. The Tyndall Effect
is named after its discoverer, the 19th-century British physicist John
Tyndall.[^1][^2][^3][^4][^5][^6]
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: "Tyndall Effect." Silver Lighting. 1 June 2008.
<http://silver-lightning.com/tyndall/>
[^2]: Davies, Paul. The Tyndall Effect. 1 June 2008.
<http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html>
[^3]: SonneNebel. 1 July 2008.
<http://upload.wikimedia.org/wikipedia/commons/f/f6/SonneNebel.jpg>
[^4]: Bright Flashlight. 1 July 2008.
<http://www.geekologie.com/2008/02/04/bright-flashlight.jpg>
[^5]: "The Tyndall Effect."
`http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html`` `
[^6]: "Colloid." 3 June 2008.
<http://www.merriam-webster.com/dictionary/colloid>
|
# Nanotechnology/Physics#Bulk matter and the end of bulk: surfaces
Navigate
---------------------------------------------------------------------------
\<\< Prev: Additional methods
\>\< Main: Nanotechnology
\>\> Next: Modelling Nanosystems
\_\_TOC\_\_
------------------------------------------------------------------------
Quantum mechanics and classical
mechanics are still valid on the nanoscale - but many assumptions we are
used to take for granted are no longer valid. This makes many
traditional systems difficult to make on the atomic scale -if for
instance you scale down a car the new relation between adhesion forces
and gravity or changes in heat conduction will very likely make it
perform very poorly if at all - but at the same time a wealth of other
new possibilities open up!
Scaling laws can be used to determine how
the physical properties vary as the dimensions are changed. At some
point the scaling law no longer can be applied because the assumptions
behind it become invalid at some large or small scale.
So, scaling is one thing - the end of scaling another, and surfaces a
third! For instance at some point the idealized classical point of view
on a system being downscaled will need quantum mechanics to describe
what\'s going on in a proper way, but as the scale is decreased the
system might also be very different because the interaction at the
surface becomes very significant compared to the bulk.
This part will try to give an overview of these effects.
# Scaling laws
Scaling laws can be used to describe how
the physical properties of a system change as the dimensions are
changed.
! The scaling properties of physical laws is an important effect to
consider when miniaturizing devices. On the nanoscale the mass and heat
capacity become very unimportant, whereas eg. surface forces scaling
with area become dominant.
{width="300"}
# Quantized Nano Systems
Quantum wires are examples of nanosystems
where the quantum effects become very important.
Break junctions is another example.
Resources
- Simple model of conduction -
the classical case
# Bulk matter and the end of bulk: surfaces
- Surface states are electronic states
on the surface of a material, which can have radically different
properties than the underlying bulk material. For instance, a
semiconductor can have superconducting surface states.
```{=html}
<!-- -->
```
- Surface reconstruction
The surface of a material can be very different from the bulk because
the surface atoms rearrange themselves to lower their energy rather than
stay in the bulk lattice and have dangling bonds extending into space
where there is no more material. Atoms from the surroundings will easily
bind to such surfaces and for example for silicon, more than 2000
surface reconstructions have been found, depending on what additional
atoms and conditions are present.
- Surface plasmons
Plasmons are collective oscillations of the
electrons in matter, and the electrons on the surfaces can also make
local plasmons that propagate on the surface.
# The Tyndall Effect
The Tyndall Effect is caused by reflection of light off of small
particles such as dust or mist. This is also seen off of dust when
sunlight comes through windows and clouds or when headlight beams go
through fog. The Tyndall Effect can only be seen through colloidal
suspensions. A colloid is a substance that consists of particles
dispersed throughout another substance, which are too small for
resolution with an ordinary light microscope but are incapable of
passing through a semi permeable membrane. The Tyndall Effect is most
easily visible through liquid using a laser pointer. The Tyndall Effect
is named after its discoverer, the 19th-century British physicist John
Tyndall.[^1][^2][^3][^4][^5][^6]
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: "Tyndall Effect." Silver Lighting. 1 June 2008.
<http://silver-lightning.com/tyndall/>
[^2]: Davies, Paul. The Tyndall Effect. 1 June 2008.
<http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html>
[^3]: SonneNebel. 1 July 2008.
<http://upload.wikimedia.org/wikipedia/commons/f/f6/SonneNebel.jpg>
[^4]: Bright Flashlight. 1 July 2008.
<http://www.geekologie.com/2008/02/04/bright-flashlight.jpg>
[^5]: "The Tyndall Effect."
`http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html`` `
[^6]: "Colloid." 3 June 2008.
<http://www.merriam-webster.com/dictionary/colloid>
|
# Nanotechnology/Physics#The Tyndall Effect
Navigate
---------------------------------------------------------------------------
\<\< Prev: Additional methods
\>\< Main: Nanotechnology
\>\> Next: Modelling Nanosystems
\_\_TOC\_\_
------------------------------------------------------------------------
Quantum mechanics and classical
mechanics are still valid on the nanoscale - but many assumptions we are
used to take for granted are no longer valid. This makes many
traditional systems difficult to make on the atomic scale -if for
instance you scale down a car the new relation between adhesion forces
and gravity or changes in heat conduction will very likely make it
perform very poorly if at all - but at the same time a wealth of other
new possibilities open up!
Scaling laws can be used to determine how
the physical properties vary as the dimensions are changed. At some
point the scaling law no longer can be applied because the assumptions
behind it become invalid at some large or small scale.
So, scaling is one thing - the end of scaling another, and surfaces a
third! For instance at some point the idealized classical point of view
on a system being downscaled will need quantum mechanics to describe
what\'s going on in a proper way, but as the scale is decreased the
system might also be very different because the interaction at the
surface becomes very significant compared to the bulk.
This part will try to give an overview of these effects.
# Scaling laws
Scaling laws can be used to describe how
the physical properties of a system change as the dimensions are
changed.
! The scaling properties of physical laws is an important effect to
consider when miniaturizing devices. On the nanoscale the mass and heat
capacity become very unimportant, whereas eg. surface forces scaling
with area become dominant.
{width="300"}
# Quantized Nano Systems
Quantum wires are examples of nanosystems
where the quantum effects become very important.
Break junctions is another example.
Resources
- Simple model of conduction -
the classical case
# Bulk matter and the end of bulk: surfaces
- Surface states are electronic states
on the surface of a material, which can have radically different
properties than the underlying bulk material. For instance, a
semiconductor can have superconducting surface states.
```{=html}
<!-- -->
```
- Surface reconstruction
The surface of a material can be very different from the bulk because
the surface atoms rearrange themselves to lower their energy rather than
stay in the bulk lattice and have dangling bonds extending into space
where there is no more material. Atoms from the surroundings will easily
bind to such surfaces and for example for silicon, more than 2000
surface reconstructions have been found, depending on what additional
atoms and conditions are present.
- Surface plasmons
Plasmons are collective oscillations of the
electrons in matter, and the electrons on the surfaces can also make
local plasmons that propagate on the surface.
# The Tyndall Effect
The Tyndall Effect is caused by reflection of light off of small
particles such as dust or mist. This is also seen off of dust when
sunlight comes through windows and clouds or when headlight beams go
through fog. The Tyndall Effect can only be seen through colloidal
suspensions. A colloid is a substance that consists of particles
dispersed throughout another substance, which are too small for
resolution with an ordinary light microscope but are incapable of
passing through a semi permeable membrane. The Tyndall Effect is most
easily visible through liquid using a laser pointer. The Tyndall Effect
is named after its discoverer, the 19th-century British physicist John
Tyndall.[^1][^2][^3][^4][^5][^6]
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: "Tyndall Effect." Silver Lighting. 1 June 2008.
<http://silver-lightning.com/tyndall/>
[^2]: Davies, Paul. The Tyndall Effect. 1 June 2008.
<http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html>
[^3]: SonneNebel. 1 July 2008.
<http://upload.wikimedia.org/wikipedia/commons/f/f6/SonneNebel.jpg>
[^4]: Bright Flashlight. 1 July 2008.
<http://www.geekologie.com/2008/02/04/bright-flashlight.jpg>
[^5]: "The Tyndall Effect."
`http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html`` `
[^6]: "Colloid." 3 June 2008.
<http://www.merriam-webster.com/dictionary/colloid>
|
# Nanotechnology/Modelling Nanosystems#The Schrödinger equation
Navigate
---------------------------------------------------------------------------------------------
\<\< Prev: Physics
\>\< Main: Nanotechnology
\>\> Next: Physical Chemistry of Surfaces
\_\_TOC\_\_
------------------------------------------------------------------------
# Modelling Nanosystems
# The Schrödinger equation
the Schrödinger equation
$$H(t)\left|\psi\left(t\right)\right\rangle = \mathrm{i}\hbar \frac{\partial}{\partial t} \left| \psi \left(t\right) \right\rangle$$
where $\mathrm{i}$ is the imaginary unit,
$t$ is time, $\partial / \partial t$ is the partial
derivative with respect to $t$,
$\hbar$ is the reduced Planck\'s
constant (Planck\'s constant divided by
$2\pi$), $\psi (t)$ is the wave function,
and $H\!\left(t\right)$ is the
Hamiltonian "wikilink") operator.
# Hartree-Fock (HF) or self-consistent field (SCF)
In computational physics and
chemistry, the **Hartree--Fock**
(**HF**) method is a method of approximation for the determination of
the wave function and the energy of a
quantum many-body system in a
stationary state.
The Hartree--Fock method often assumes that the exact, *N*-body wave
function of the system can be approximated by a single Slater
determinant (in the case where the
particles are fermions) or by a single
permanent (in the case of
bosons) of *N*
spin-orbitals. By invoking the
w:variational method, one can derive
a set of *N*-coupled equations for the *N* spin orbitals. A solution of
these equations yields the Hartree--Fock wave function and energy of the
system.
Especially in the older literature, the Hartree--Fock method is also
called the **self-consistent field method** (**SCF**). In deriving what
is now called the Hartree equation as
an approximate solution of the Schrödinger
equation,
Hartree required the final field as
computed from the charge distribution to be \"self-consistent\" with the
assumed initial field. Thus, self-consistency was a requirement of the
solution. The solutions to the non-linear Hartree--Fock equations also
behave as if each particle is subjected to the mean field created by all
other particles (see the Fock
operator below) and hence
the terminology continued. The equations are almost universally solved
by means of an iterative method,
although the fixed-point iteration
algorithm does not always converge.[^1] This solution scheme is not the
only one possible and is not an essential feature of the Hartree--Fock
method.
The Hartree--Fock method finds its typical application in the solution
of the Schrödinger equation for
atoms, molecules, nanostructures[^2] and solids but it has also found
widespread use in nuclear physics. (See
Hartree--Fock--Bogoliubov
method for a discussion of its
application in nuclear
structure
theory). In atomic structure theory,
calculations may be for a spectrum with many excited energy levels and
consequently the Hartree--Fock method for
atoms assumes the wave
function is a single configuration
state function with
well-defined quantum numbers and that
the energy level is not necessarily the ground
state.
For both atoms and molecules, the Hartree--Fock solution is the central
starting point for most methods that describe the many-electron system
more accurately.
The rest of this article will focus on applications in electronic
structure theory suitable for molecules with the atom as a special case.
The discussion here is only for the Restricted Hartree--Fock method,
where the atom or molecule is a closed-shell system with all orbitals
(atomic or molecular) doubly occupied.
Open-shell systems, where some of the
electrons are not paired, can be dealt with by one of two Hartree--Fock
methods:
- w:Restricted open-shell
Hartree--Fock
(ROHF)
- w:Unrestricted
Hartree--Fock (UHF)
## history
The origin of the Hartree--Fock method dates back to the end of the
1920s, soon after the discovery of the w:Schrödinger
equation in 1926. In 1927 D. R.
Hartree introduced a procedure, which he
called the self-consistent field method, to calculate approximate wave
functions and energies for atoms and ions. Hartree was guided by some
earlier, semi-empirical methods of the early 1920s (by E. Fues, R. B.
Lindsay, and himself) set in the
w:old quantum theory of Bohr.
In the w:Bohr model of the atom, the energy
of a state with w:principal quantum
number n is given in atomic
units as $E = -1 / n^2$. It was observed from atomic spectra that the
energy levels of many-electron atoms are well described by applying a
modified version of Bohr\'s formula. By introducing the w:quantum
defect *d* as an empirical parameter, the
energy levels of a generic atom were well approximated by the formula
$E = -1/(n+d)^2$, in the sense that one could reproduce fairly well the
observed transitions levels observed in the
w:X-ray region (for example, see the empirical
discussion and derivation in w:Moseley\'s
law). The existence of a non-zero quantum
defect was attributed to electron-electron repulsion, which clearly does
not exist in the isolated hydrogen atom. This repulsion resulted in
partial screening of the bare nuclear
charge. These early researchers later introduced other potentials
containing additional empirical parameters with the hope of better
reproducing the experimental data.
Hartree sought to do away with empirical parameters and solve the
many-body time-independent Schrödinger equation from fundamental
physical principles, i.e., ab
initio. His first
proposed method of solution became known as the **Hartree method**.
However, many of Hartree\'s contemporaries did not understand the
physical reasoning behind the Hartree method: it appeared to many people
to contain empirical elements, and its connection to the solution of the
many-body Schrödinger equation was unclear. However, in 1928 J. C.
Slater and J. A. Gaunt independently
showed that the Hartree method could be couched on a sounder theoretical
basis by applying the w:variational
principle to an
w:ansatz (trial wave function) as a product of
single-particle functions.
In 1930 Slater and V. A. Fock
independently pointed out that the Hartree method did not respect the
principle of antisymmetry of the wave
function. The Hartree method used the w:Pauli exclusion
principle in its older
formulation, forbidding the presence of two electrons in the same
quantum state. However, this was shown to be fundamentally incomplete in
its neglect of w:quantum statistics.
It was then shown that a w:Slater
determinant, a
w:determinant of one-particle orbitals first
used by Heisenberg and Dirac in 1926, trivially satisfies the
antisymmetric property of the exact
solution and hence is a suitable w:ansatz for
applying the w:variational
principle. The original Hartree
method can then be viewed as an approximation to the Hartree--Fock
method by neglecting exchange. Fock\'s
original method relied heavily on w:group
theory and was too abstract for contemporary
physicists to understand and implement. In 1935 Hartree reformulated the
method more suitably for the purposes of calculation.
The Hartree--Fock method, despite its physically more accurate picture,
was little used until the advent of electronic computers in the 1950s
due to the much greater computational demands over the early Hartree
method and empirical models. Initially, both the Hartree method and the
Hartree--Fock method were applied exclusively to atoms, where the
spherical symmetry of the system allowed one to greatly simplify the
problem. These approximate methods were (and are) often used together
with the w:central field
approximation, to impose that
electrons in the same shell have the same radial part, and to restrict
the variational solution to be a spin eigenfunction. Even so, solution
by hand of the Hartree--Fock equations for a medium sized atom were
laborious; small molecules required computational resources far beyond
what was available before 1950.
## Hartree--Fock algorithm
The Hartree--Fock method is typically used to solve the time-independent
Schrödinger equation for a multi-electron atom or molecule as described
in the w:Born--Oppenheimer
approximation. Since there
are no known solutions for many-electron systems (hydrogenic
atoms and the diatomic hydrogen cation
being notable one-electron exceptions), the problem is solved
numerically. Due to the nonlinearities introduced by the Hartree--Fock
approximation, the equations are solved using a nonlinear method such as
w:iteration, which gives rise to the name
\"self-consistent field method.\"
### Approximations
The Hartree--Fock method makes five major simplifications in order to
deal with this task:
- The w:Born--Oppenheimer
approximation is
inherently assumed. The full molecular wave function is actually a
function of the coordinates of each of the nuclei, in addition to
those of the electrons.
- Typically, relativistic effects
are completely neglected. The momentum
operator is assumed to be completely
non-relativistic.
- The variational solution is assumed to be a w:linear
combination of a finite number of
basis functions "wikilink"), which are
usually (but not always) chosen to be
w:orthogonal. The finite basis set is
assumed to be approximately
complete.
- Each w:energy eigenfunction is
assumed to be describable by a single w:Slater
determinant, an antisymmetrized
product of one-electron wave functions (i.e., orbitals).
- The mean field approximation is
implied. Effects arising from deviations from this assumption, known
as w:electron correlation, are
completely neglected for the electrons of opposite spin, but are
taken into account for electrons of parallel spin.[^3][^4] (Electron
correlation should not be confused with electron exchange, which is
fully accounted for in the Hartree--Fock method.)[^5]
Relaxation of the last two approximations give rise to many so-called
w:post-Hartree--Fock methods.
!Greatly simplified algorithmic flowchart illustrating the
Hartree--Fock
method{width="325"}
### Variational optimization of orbitals
The variational
theorem "wikilink") states
that for a time-independent Hamiltonian operator, any trial wave
function will have an energy w:expectation
value that is greater than or equal to
the true w:ground state wave function
corresponding to the given Hamiltonian. Because of this, the
Hartree--Fock energy is an upper bound to the true ground state energy
of a given molecule. In the context of the Hartree--Fock method, the
best possible solution is at the *Hartree--Fock limit*; i.e., the limit
of the Hartree--Fock energy as the basis set approaches
completeness.
(The other is the *full-CI limit*, where the last two approximations of
the Hartree--Fock theory as described above are completely undone. It is
only when both limits are attained that the exact solution, up to the
Born--Oppenheimer approximation, is obtained.) The Hartree--Fock energy
is the minimal energy for a single Slater determinant.
The starting point for the Hartree--Fock method is a set of approximate
one-electron wave functions known as
*w:spin-orbitals*. For an w:atomic
orbital calculation, these are typically
the orbitals for a hydrogenic atom (an atom with only one electron, but
the appropriate nuclear charge). For a w:molecular
orbital or crystalline calculation, the
initial approximate one-electron wave functions are typically a
w:linear combination of atomic
orbitals (LCAO).
The orbitals above only account for the presence of other electrons in
an average manner. In the Hartree--Fock method, the effect of other
electrons are accounted for in a w:mean-field
theory context. The orbitals are
optimized by requiring them to minimize the energy of the respective
Slater determinant. The resultant variational conditions on the orbitals
lead to a new one-electron operator, the w:Fock
operator. At the minimum, the occupied
orbitals are eigensolutions to the Fock operator via a w:unitary
transformation between themselves.
The Fock operator is an effective one-electron Hamiltonian operator
being the sum of two terms. The first is a sum of kinetic energy
operators for each electron, the internuclear repulsion energy, and a
sum of nuclear-electronic Coulombic
attraction terms. The second are Coulombic repulsion terms between
electrons in a mean-field theory description; a net repulsion energy for
each electron in the system, which is calculated by treating all of the
other electrons within the molecule as a smooth distribution of negative
charge. This is the major simplification inherent in the Hartree--Fock
method, and is equivalent to the fifth simplification in the above list.
Since the Fock operator depends on the orbitals used to construct the
corresponding w:Fock matrix, the
eigenfunctions of the Fock operator are in turn new orbitals which can
be used to construct a new Fock operator. In this way, the Hartree--Fock
orbitals are optimized iteratively until the change in total electronic
energy falls below a predefined threshold. In this way, a set of
self-consistent one-electron orbitals are calculated. The Hartree--Fock
electronic wave function is then the Slater determinant constructed out
of these orbitals. Following the basic postulates of quantum mechanics,
the Hartree--Fock wave function can then be used to compute any desired
chemical or physical property within the framework of the Hartree--Fock
method and the approximations employed.
## Mathematical formulation
### The Fock operator
Because the electron-electron repulsion term of the w:electronic
molecular Hamiltonian
involves the coordinates of two different electrons, it is necessary to
reformulate it in an approximate way. Under this approximation,
(outlined under Hartree--Fock
algorithm), all of
the terms of the exact Hamiltonian except the nuclear-nuclear repulsion
term are re-expressed as the sum of one-electron operators outlined
below, for closed-shell atoms or molecules (with two electrons in each
spatial orbital).[^6] The \"(1)\" following each operator symbol simply
indicates that the operator is 1-electron in nature.
$$\hat F\{\phi_j\} = \hat H^{\text{core}}(1)+\sum_{j=1}^{N/2}[2\hat J_j(1)-\hat K_j(1)]$$
where
$$\hat F\{\phi_j\}$$
is the one-electron Fock operator generated by the orbitals $\phi_j$,
and
$$\hat H^{\text{core}}(1)=-\frac{1}{2}\nabla^2_1 - \sum_{\alpha} \frac{Z_\alpha}{r_{1\alpha}}$$
is the one-electron core
Hamiltonian "wikilink"). Also
$$\hat J_j(1)$$
is the w:Coulomb operator, defining the
electron-electron repulsion energy due to each of the two electrons in
the *j*th orbital.[^7] Finally
$$\hat K_j(1)$$
is the w:exchange operator, defining
the electron exchange energy due to the antisymmetry of the total
n-electron wave function. [^8] This (so called) \"exchange energy\"
operator, K, is simply an artifact of the Slater determinant. Finding
the Hartree--Fock one-electron wave functions is now equivalent to
solving the eigenfunction equation:
$$\hat F(1)\phi_i(1)=\epsilon_i \phi_i(1)$$
where $\phi_i\;(1)$ are a set of one-electron wave functions, called the
Hartree--Fock molecular orbitals.
### Linear combination of atomic orbitals
Typically, in modern Hartree--Fock calculations, the one-electron wave
functions are approximated by a w:linear combination of atomic
orbitals. These
atomic orbitals are called w:Slater-type
orbitals. Furthermore, it is very
common for the \"atomic orbitals\" in use to actually be composed of a
linear combination of one or more Gaussian-type
orbitals, rather than Slater-type
orbitals, in the interests of saving large amounts of computation time.
Various basis sets "wikilink") are used in
practice, most of which are composed of Gaussian functions. In some
applications, an orthogonalization method such as the w:Gram--Schmidt
process is performed in order to
produce a set of orthogonal basis functions. This can in principle save
computational time when the computer is solving the Roothaan--Hall
equations by converting the w:overlap
matrix effectively to an w:identity
matrix. However, in most modern computer
programs for molecular Hartree--Fock calculations this procedure is not
followed due to the high numerical cost of orthogonalization and the
advent of more efficient, often sparse, algorithms for solving the
w:generalized eigenvalue
problem, of which the
Roothaan--Hall equations are an
example.
## Numerical stability
w:Numerical stability can be a
problem with this procedure and there are various ways of combating this
instability. One of the most basic and generally applicable is called
*F-mixing* or damping. With F-mixing, once a single electron wave
function is calculated it is not used directly. Instead, some
combination of that calculated wave function and the previous wave
functions for that electron is used---the most common being a simple
linear combination of the calculated and immediately preceding wave
function. A clever dodge, employed by Hartree, for atomic calculations
was to increase the nuclear charge, thus pulling all the electrons
closer together. As the system stabilised, this was gradually reduced to
the correct charge. In molecular calculations a similar approach is
sometimes used by first calculating the wave function for a positive ion
and then to use these orbitals as the starting point for the neutral
molecule. Modern molecular Hartree--Fock computer programs use a variety
of methods to ensure convergence of the Roothaan--Hall equations.
## Weaknesses, extensions, and alternatives
Of the five simplifications outlined in the section \"Hartree--Fock
algorithm\", the fifth is typically the most important. Neglecting
electron correlation can lead to large deviations from experimental
results. A number of approaches to this weakness, collectively called
w:post-Hartree--Fock methods, have
been devised to include electron correlation to the multi-electron wave
function. One of these approaches, w:Møller--Plesset perturbation
theory, treats
correlation as a perturbation of the
Fock operator. Others expand the true multi-electron wave function in
terms of a linear combination of Slater determinants---such as
w:multi-configurational self-consistent
field,
w:configuration interaction,
w:quadratic configuration
interaction, and
complete active space SCF
(CASSCF).
Still others (such as variational quantum Monte
Carlo) modify the Hartree--Fock
wave function by multiplying it by a correlation function (\"Jastrow\"
factor), a term which is explicitly a function of multiple electrons
that cannot be decomposed into independent single-particle functions.
An alternative to Hartree--Fock calculations used in some cases is
w:density functional theory,
which treats both exchange and correlation energies, albeit
approximately. Indeed, it is common to use calculations that are a
hybrid of the two methods---the popular B3LYP scheme is one such
w:hybrid functional method. Another
option is to use w:modern valence
bond methods.
## Software packages
For a list of software packages known to handle Hartree--Fock
calculations, particularly for molecules and solids, see the w:list of
quantum chemistry and solid state physics
software.
## Sources
-
-
-
## Slater determinant
### Two-particle case
The simplest way to approximate the wave function of a many-particle
system is to take the product of properly chosen
orthogonal "wikilink") wave
functions of the individual particles. For the two-particle case with
spatial coordinates $\mathbf{x}_1$ and $\mathbf{x}_2$, we have
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = \chi_1(\mathbf{x}_1)\chi_2(\mathbf{x}_2).$$
This expression is used in the w:Hartree--Fock
method as an
w:ansatz for the many-particle wave function and
is known as a w:Hartree product.
However, it is not satisfactory for w:fermions
because the wave function above is not antisymmetric, as it must be for
w:fermions from the w:Pauli exclusion
principle. An antisymmetric
wave function can be mathematically described as follows:
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = -\Psi(\mathbf{x}_2,\mathbf{x}_1)$$
which does not hold for the Hartree product. Therefore the Hartree
product does not satisfy the Pauli principle. This problem can be
overcome by taking a w:linear
combination of both Hartree products
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = \frac{1}{\sqrt{2}}\{\chi_1(\mathbf{x}_1)\chi_2(\mathbf{x}_2) - \chi_1(\mathbf{x}_2)\chi_2(\mathbf{x}_1)\}$$
$$= \frac{1}{\sqrt2}\begin{vmatrix} \chi_1(\mathbf{x}_1) & \chi_2(\mathbf{x}_1) \\ \chi_1(\mathbf{x}_2) & \chi_2(\mathbf{x}_2) \end{vmatrix}$$
where the coefficient is the w:normalization
factor. This wave function is now
antisymmetric and no longer distinguishes between fermions, that is: one
cannot indicate an ordinal number to a specific particle and the indices
given are interchangeable. Moreover, it also goes to zero if any two
wave functions of two fermions are the same. This is equivalent to
satisfying the Pauli exclusion principle.
### Generalizations
The expression can be generalised to any number of fermions by writing
it as a w:determinant. For an *N*-electron
system, the Slater determinant is defined as [^9]
$$\Psi(\mathbf{x}_1, \mathbf{x}_2, \ldots, \mathbf{x}_N) =
\frac{1}{\sqrt{N!}}
\left|
\begin{matrix} \chi_1(\mathbf{x}_1) & \chi_2(\mathbf{x}_1) & \cdots & \chi_N(\mathbf{x}_1) \\
\chi_1(\mathbf{x}_2) & \chi_2(\mathbf{x}_2) & \cdots & \chi_N(\mathbf{x}_2) \\
\vdots & \vdots & \ddots & \vdots \\
\chi_1(\mathbf{x}_N) & \chi_2(\mathbf{x}_N) & \cdots & \chi_N(\mathbf{x}_N)
\end{matrix} \right|\equiv \left| \begin{matrix}
\chi _1 & \chi _2 & \cdots & \chi _N \\
\end{matrix}
\right|,$$
where in the final expression, a compact notation is introduced: the
normalization constant and labels for the fermion coordinates are
understood -- only the wavefunctions are exhibited. The linear
combination of Hartree products for the two-particle case can clearly be
seen as identical with the Slater determinant for *N* = 2. It can be
seen that the use of Slater determinants ensures an antisymmetrized
function at the outset; symmetric functions are automatically rejected.
In the same way, the use of Slater determinants ensures conformity to
the w:Pauli principle. Indeed, the
Slater determinant vanishes if the set {χ~i~ } is w:linearly
dependent. In particular, this is the
case when two (or more) spin orbitals are the same. In chemistry one
expresses this fact by stating that no two electrons can occupy the same
spin orbital. In general the Slater determinant is evaluated by the
w:Laplace expansion. Mathematically, a
Slater determinant is an antisymmetric tensor, also known as a w:wedge
product.
A single Slater determinant is used as an approximation to the
electronic wavefunction in Hartree--Fock
theory. In more accurate theories
(such as w:configuration
interaction and
w:MCSCF), a linear combination of Slater
determinants is needed.
The word \"**detor**\" was proposed by S. F. Boys to describe the Slater
determinant of the general type,[^10] but this term is rarely used.
Unlike w:fermions that are subject to the Pauli
exclusion principle, two or more w:bosons can
occupy the same quantum state of a system. Wavefunctions describing
systems of identical w:bosons are symmetric under
the exchange of particles and can be expanded in terms of
w:permanents.
## Fock matrix
In the w:Hartree--Fock method of
w:quantum mechanics, the **Fock
matrix** is a matrix "wikilink") approximating
the single-electron w:energy operator of
a given quantum system in a given set
of basis vectors.[^11]
It is most often formed in w:computational
chemistry when attempting to
solve the w:Roothaan equations for an
atomic or molecular system. The Fock matrix is actually an approximation
to the true Hamiltonian "wikilink")
operator "wikilink") of the quantum system.
It includes the effects of electron-electron
repulsion only in an average way.
Importantly, because the Fock operator is a one-electron operator, it
does not include the w:electron
correlation energy.
The Fock matrix is defined by the *Fock operator*. For the restricted
case which assumes w:closed-shell
orbitals and single-determinantal
wavefunctions, the Fock operator for the *i*-th electron is given
by:[^12]
$$\hat F(i) = \hat h(i)+\sum_{ j=1 }^{n/2}[2 \hat J_j(i)-\hat
K_j(i)]$$
where:
$$\hat F(i)$$ is the Fock operator for the *i*-th electron in the
system,
$${\hat h}(i)$$ is the w:one-electron
hamiltonian for the *i*-th
electron,
$$n$$ is the number of electrons and $\frac{n}{2}$ is the number of
occupied orbitals in the closed-shell system,
$$\hat J_j(i)$$ is the w:Coulomb
operator, defining the repulsive force
between the *j*-th and *i*-th electrons in the system,
$$\hat K_j(i)$$ is the w:exchange
operator, defining the quantum effect
produced by exchanging two electrons.
The Coulomb operator is multiplied by two since there are two electrons
in each occupied orbital. The exchange operator is not multiplied by two
since it has a non-zero result only for electrons which have the same
spin as the *i*-th electron.
For systems with unpaired electrons there are many choices of Fock
matrices.
Hartree-Fock (HF) or self-consistent field
(SCF)
# Density Functional Theory
## Connection to quantum state symmetry
The Pauli exclusion principle with a single-valued many-particle
wavefunction is equivalent to requiring the wavefunction to be
antisymmetric. An antisymmetric two-particle state is represented as a
sum of states in which one
particle is in state $\scriptstyle |x \rangle$ and the other in state
$\scriptstyle |y\rangle$:
$$|\psi\rangle = \sum_{x,y} A(x,y) |x,y\rangle$$
and antisymmetry under exchange means that
.
This implies that ,
which is Pauli exclusion. It is true in any basis, since unitary changes
of basis keep antisymmetric matrices antisymmetric, although strictly
speaking, the quantity is
not a matrix but an antisymmetric rank-two
w:tensor.
Conversely, if the diagonal quantities
are zero *in every basis*,
then the wavefunction component:
$$A(x,y)=\langle \psi|x,y\rangle = \langle \psi | ( |x\rangle \otimes |y\rangle )$$
is necessarily antisymmetric. To prove it, consider the matrix element:
$$\langle\psi| ((|x\rangle + |y\rangle)\otimes(|x\rangle + |y\rangle))
\,$$
This is zero, because the two particles have zero probability to both be
in the superposition state $\scriptstyle |x\rangle + |y\rangle$. But
this is equal to
$$\langle \psi |x,x\rangle + \langle \psi |x,y\rangle + \langle \psi |y,x\rangle + \langle \psi | y,y \rangle
\,$$
The first and last terms on the right hand side are diagonal elements
and are zero, and the whole sum is equal to zero. So the wavefunction
matrix elements obey:
$$\langle \psi|x,y\rangle + \langle\psi |y,x\rangle = 0
\,$$.
or
$$A(x,y)=-A(y,x)
\,$$
### Pauli principle in advanced quantum theory
According to the w:spin-statistics
theorem, particles with integer
spin occupy symmetric quantum states, and particles with half-integer
spin occupy antisymmetric states; furthermore, only integer or
half-integer values of spin are allowed by the principles of quantum
mechanics. In relativistic w:quantum field
theory, the Pauli principle follows
from applying a rotation operator in imaginary time to particles of
half-integer spin. Since, nonrelativistically, particles can have any
statistics and any spin, there is no way to prove a spin-statistics
theorem in nonrelativistic quantum mechanics.
In one dimension, bosons, as well as fermions, can obey the exclusion
principle. A one-dimensional Bose gas with delta function repulsive
interactions of infinite strength is equivalent to a gas of free
fermions. The reason for this is that, in one dimension, exchange of
particles requires that they pass through each other; for infinitely
strong repulsion this cannot happen. This model is described by a
quantum w:nonlinear Schrödinger
equation. In momentum
space the exclusion principle is valid also for finite repulsion in a
Bose gas with delta function interactions,[^13] as well as for
interacting spins "wikilink") and
w:Hubbard model in one dimension, and for
other models solvable by w:Bethe ansatz.
The ground state in models solvable by
Bethe ansatz is a Fermi sphere.
Density Functional Theory
# References
See also notes on editing this book about how to add references
w:Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]:
[^3]:
[^4]:
[^5]:
[^6]: Levine, Ira N. (1991). Quantum Chemistry (4th ed.). Englewood
Cliffs, New Jersey: Prentice Hall. p. 403.
.
[^7]:
[^8]:
[^9]: Molecular Quantum Mechanics Parts I and II: An Introduction to
QUANTUM CHEMISTRY (Volume 1), P.W. Atkins, Oxford University Press,
1977,
[^10]: {{ cite journal\| title=Electronic wave functions I. A general
method of calculation for the stationary states of any molecular
system\|author-link=S. Francis Boys\|first=S. F.
\|last=Boys\|page=542\| volume=A200 \|year=1950\|journal=
Proceedings of the Royal Society}}
[^11]:
[^12]: Levine, I.N. (1991) *Quantum Chemistry* (4th ed., Prentice-Hall),
p.403
[^13]: A. Izergin and V. Korepin, Letter in Mathematical Physics vol 6,
page 283, 1982
|
# Nanotechnology/Modelling Nanosystems#Transport phenomena
Navigate
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------------------------------------------------------------------------
# Modelling Nanosystems
# The Schrödinger equation
the Schrödinger equation
$$H(t)\left|\psi\left(t\right)\right\rangle = \mathrm{i}\hbar \frac{\partial}{\partial t} \left| \psi \left(t\right) \right\rangle$$
where $\mathrm{i}$ is the imaginary unit,
$t$ is time, $\partial / \partial t$ is the partial
derivative with respect to $t$,
$\hbar$ is the reduced Planck\'s
constant (Planck\'s constant divided by
$2\pi$), $\psi (t)$ is the wave function,
and $H\!\left(t\right)$ is the
Hamiltonian "wikilink") operator.
# Hartree-Fock (HF) or self-consistent field (SCF)
In computational physics and
chemistry, the **Hartree--Fock**
(**HF**) method is a method of approximation for the determination of
the wave function and the energy of a
quantum many-body system in a
stationary state.
The Hartree--Fock method often assumes that the exact, *N*-body wave
function of the system can be approximated by a single Slater
determinant (in the case where the
particles are fermions) or by a single
permanent (in the case of
bosons) of *N*
spin-orbitals. By invoking the
w:variational method, one can derive
a set of *N*-coupled equations for the *N* spin orbitals. A solution of
these equations yields the Hartree--Fock wave function and energy of the
system.
Especially in the older literature, the Hartree--Fock method is also
called the **self-consistent field method** (**SCF**). In deriving what
is now called the Hartree equation as
an approximate solution of the Schrödinger
equation,
Hartree required the final field as
computed from the charge distribution to be \"self-consistent\" with the
assumed initial field. Thus, self-consistency was a requirement of the
solution. The solutions to the non-linear Hartree--Fock equations also
behave as if each particle is subjected to the mean field created by all
other particles (see the Fock
operator below) and hence
the terminology continued. The equations are almost universally solved
by means of an iterative method,
although the fixed-point iteration
algorithm does not always converge.[^1] This solution scheme is not the
only one possible and is not an essential feature of the Hartree--Fock
method.
The Hartree--Fock method finds its typical application in the solution
of the Schrödinger equation for
atoms, molecules, nanostructures[^2] and solids but it has also found
widespread use in nuclear physics. (See
Hartree--Fock--Bogoliubov
method for a discussion of its
application in nuclear
structure
theory). In atomic structure theory,
calculations may be for a spectrum with many excited energy levels and
consequently the Hartree--Fock method for
atoms assumes the wave
function is a single configuration
state function with
well-defined quantum numbers and that
the energy level is not necessarily the ground
state.
For both atoms and molecules, the Hartree--Fock solution is the central
starting point for most methods that describe the many-electron system
more accurately.
The rest of this article will focus on applications in electronic
structure theory suitable for molecules with the atom as a special case.
The discussion here is only for the Restricted Hartree--Fock method,
where the atom or molecule is a closed-shell system with all orbitals
(atomic or molecular) doubly occupied.
Open-shell systems, where some of the
electrons are not paired, can be dealt with by one of two Hartree--Fock
methods:
- w:Restricted open-shell
Hartree--Fock
(ROHF)
- w:Unrestricted
Hartree--Fock (UHF)
## history
The origin of the Hartree--Fock method dates back to the end of the
1920s, soon after the discovery of the w:Schrödinger
equation in 1926. In 1927 D. R.
Hartree introduced a procedure, which he
called the self-consistent field method, to calculate approximate wave
functions and energies for atoms and ions. Hartree was guided by some
earlier, semi-empirical methods of the early 1920s (by E. Fues, R. B.
Lindsay, and himself) set in the
w:old quantum theory of Bohr.
In the w:Bohr model of the atom, the energy
of a state with w:principal quantum
number n is given in atomic
units as $E = -1 / n^2$. It was observed from atomic spectra that the
energy levels of many-electron atoms are well described by applying a
modified version of Bohr\'s formula. By introducing the w:quantum
defect *d* as an empirical parameter, the
energy levels of a generic atom were well approximated by the formula
$E = -1/(n+d)^2$, in the sense that one could reproduce fairly well the
observed transitions levels observed in the
w:X-ray region (for example, see the empirical
discussion and derivation in w:Moseley\'s
law). The existence of a non-zero quantum
defect was attributed to electron-electron repulsion, which clearly does
not exist in the isolated hydrogen atom. This repulsion resulted in
partial screening of the bare nuclear
charge. These early researchers later introduced other potentials
containing additional empirical parameters with the hope of better
reproducing the experimental data.
Hartree sought to do away with empirical parameters and solve the
many-body time-independent Schrödinger equation from fundamental
physical principles, i.e., ab
initio. His first
proposed method of solution became known as the **Hartree method**.
However, many of Hartree\'s contemporaries did not understand the
physical reasoning behind the Hartree method: it appeared to many people
to contain empirical elements, and its connection to the solution of the
many-body Schrödinger equation was unclear. However, in 1928 J. C.
Slater and J. A. Gaunt independently
showed that the Hartree method could be couched on a sounder theoretical
basis by applying the w:variational
principle to an
w:ansatz (trial wave function) as a product of
single-particle functions.
In 1930 Slater and V. A. Fock
independently pointed out that the Hartree method did not respect the
principle of antisymmetry of the wave
function. The Hartree method used the w:Pauli exclusion
principle in its older
formulation, forbidding the presence of two electrons in the same
quantum state. However, this was shown to be fundamentally incomplete in
its neglect of w:quantum statistics.
It was then shown that a w:Slater
determinant, a
w:determinant of one-particle orbitals first
used by Heisenberg and Dirac in 1926, trivially satisfies the
antisymmetric property of the exact
solution and hence is a suitable w:ansatz for
applying the w:variational
principle. The original Hartree
method can then be viewed as an approximation to the Hartree--Fock
method by neglecting exchange. Fock\'s
original method relied heavily on w:group
theory and was too abstract for contemporary
physicists to understand and implement. In 1935 Hartree reformulated the
method more suitably for the purposes of calculation.
The Hartree--Fock method, despite its physically more accurate picture,
was little used until the advent of electronic computers in the 1950s
due to the much greater computational demands over the early Hartree
method and empirical models. Initially, both the Hartree method and the
Hartree--Fock method were applied exclusively to atoms, where the
spherical symmetry of the system allowed one to greatly simplify the
problem. These approximate methods were (and are) often used together
with the w:central field
approximation, to impose that
electrons in the same shell have the same radial part, and to restrict
the variational solution to be a spin eigenfunction. Even so, solution
by hand of the Hartree--Fock equations for a medium sized atom were
laborious; small molecules required computational resources far beyond
what was available before 1950.
## Hartree--Fock algorithm
The Hartree--Fock method is typically used to solve the time-independent
Schrödinger equation for a multi-electron atom or molecule as described
in the w:Born--Oppenheimer
approximation. Since there
are no known solutions for many-electron systems (hydrogenic
atoms and the diatomic hydrogen cation
being notable one-electron exceptions), the problem is solved
numerically. Due to the nonlinearities introduced by the Hartree--Fock
approximation, the equations are solved using a nonlinear method such as
w:iteration, which gives rise to the name
\"self-consistent field method.\"
### Approximations
The Hartree--Fock method makes five major simplifications in order to
deal with this task:
- The w:Born--Oppenheimer
approximation is
inherently assumed. The full molecular wave function is actually a
function of the coordinates of each of the nuclei, in addition to
those of the electrons.
- Typically, relativistic effects
are completely neglected. The momentum
operator is assumed to be completely
non-relativistic.
- The variational solution is assumed to be a w:linear
combination of a finite number of
basis functions "wikilink"), which are
usually (but not always) chosen to be
w:orthogonal. The finite basis set is
assumed to be approximately
complete.
- Each w:energy eigenfunction is
assumed to be describable by a single w:Slater
determinant, an antisymmetrized
product of one-electron wave functions (i.e., orbitals).
- The mean field approximation is
implied. Effects arising from deviations from this assumption, known
as w:electron correlation, are
completely neglected for the electrons of opposite spin, but are
taken into account for electrons of parallel spin.[^3][^4] (Electron
correlation should not be confused with electron exchange, which is
fully accounted for in the Hartree--Fock method.)[^5]
Relaxation of the last two approximations give rise to many so-called
w:post-Hartree--Fock methods.
!Greatly simplified algorithmic flowchart illustrating the
Hartree--Fock
method{width="325"}
### Variational optimization of orbitals
The variational
theorem "wikilink") states
that for a time-independent Hamiltonian operator, any trial wave
function will have an energy w:expectation
value that is greater than or equal to
the true w:ground state wave function
corresponding to the given Hamiltonian. Because of this, the
Hartree--Fock energy is an upper bound to the true ground state energy
of a given molecule. In the context of the Hartree--Fock method, the
best possible solution is at the *Hartree--Fock limit*; i.e., the limit
of the Hartree--Fock energy as the basis set approaches
completeness.
(The other is the *full-CI limit*, where the last two approximations of
the Hartree--Fock theory as described above are completely undone. It is
only when both limits are attained that the exact solution, up to the
Born--Oppenheimer approximation, is obtained.) The Hartree--Fock energy
is the minimal energy for a single Slater determinant.
The starting point for the Hartree--Fock method is a set of approximate
one-electron wave functions known as
*w:spin-orbitals*. For an w:atomic
orbital calculation, these are typically
the orbitals for a hydrogenic atom (an atom with only one electron, but
the appropriate nuclear charge). For a w:molecular
orbital or crystalline calculation, the
initial approximate one-electron wave functions are typically a
w:linear combination of atomic
orbitals (LCAO).
The orbitals above only account for the presence of other electrons in
an average manner. In the Hartree--Fock method, the effect of other
electrons are accounted for in a w:mean-field
theory context. The orbitals are
optimized by requiring them to minimize the energy of the respective
Slater determinant. The resultant variational conditions on the orbitals
lead to a new one-electron operator, the w:Fock
operator. At the minimum, the occupied
orbitals are eigensolutions to the Fock operator via a w:unitary
transformation between themselves.
The Fock operator is an effective one-electron Hamiltonian operator
being the sum of two terms. The first is a sum of kinetic energy
operators for each electron, the internuclear repulsion energy, and a
sum of nuclear-electronic Coulombic
attraction terms. The second are Coulombic repulsion terms between
electrons in a mean-field theory description; a net repulsion energy for
each electron in the system, which is calculated by treating all of the
other electrons within the molecule as a smooth distribution of negative
charge. This is the major simplification inherent in the Hartree--Fock
method, and is equivalent to the fifth simplification in the above list.
Since the Fock operator depends on the orbitals used to construct the
corresponding w:Fock matrix, the
eigenfunctions of the Fock operator are in turn new orbitals which can
be used to construct a new Fock operator. In this way, the Hartree--Fock
orbitals are optimized iteratively until the change in total electronic
energy falls below a predefined threshold. In this way, a set of
self-consistent one-electron orbitals are calculated. The Hartree--Fock
electronic wave function is then the Slater determinant constructed out
of these orbitals. Following the basic postulates of quantum mechanics,
the Hartree--Fock wave function can then be used to compute any desired
chemical or physical property within the framework of the Hartree--Fock
method and the approximations employed.
## Mathematical formulation
### The Fock operator
Because the electron-electron repulsion term of the w:electronic
molecular Hamiltonian
involves the coordinates of two different electrons, it is necessary to
reformulate it in an approximate way. Under this approximation,
(outlined under Hartree--Fock
algorithm), all of
the terms of the exact Hamiltonian except the nuclear-nuclear repulsion
term are re-expressed as the sum of one-electron operators outlined
below, for closed-shell atoms or molecules (with two electrons in each
spatial orbital).[^6] The \"(1)\" following each operator symbol simply
indicates that the operator is 1-electron in nature.
$$\hat F\{\phi_j\} = \hat H^{\text{core}}(1)+\sum_{j=1}^{N/2}[2\hat J_j(1)-\hat K_j(1)]$$
where
$$\hat F\{\phi_j\}$$
is the one-electron Fock operator generated by the orbitals $\phi_j$,
and
$$\hat H^{\text{core}}(1)=-\frac{1}{2}\nabla^2_1 - \sum_{\alpha} \frac{Z_\alpha}{r_{1\alpha}}$$
is the one-electron core
Hamiltonian "wikilink"). Also
$$\hat J_j(1)$$
is the w:Coulomb operator, defining the
electron-electron repulsion energy due to each of the two electrons in
the *j*th orbital.[^7] Finally
$$\hat K_j(1)$$
is the w:exchange operator, defining
the electron exchange energy due to the antisymmetry of the total
n-electron wave function. [^8] This (so called) \"exchange energy\"
operator, K, is simply an artifact of the Slater determinant. Finding
the Hartree--Fock one-electron wave functions is now equivalent to
solving the eigenfunction equation:
$$\hat F(1)\phi_i(1)=\epsilon_i \phi_i(1)$$
where $\phi_i\;(1)$ are a set of one-electron wave functions, called the
Hartree--Fock molecular orbitals.
### Linear combination of atomic orbitals
Typically, in modern Hartree--Fock calculations, the one-electron wave
functions are approximated by a w:linear combination of atomic
orbitals. These
atomic orbitals are called w:Slater-type
orbitals. Furthermore, it is very
common for the \"atomic orbitals\" in use to actually be composed of a
linear combination of one or more Gaussian-type
orbitals, rather than Slater-type
orbitals, in the interests of saving large amounts of computation time.
Various basis sets "wikilink") are used in
practice, most of which are composed of Gaussian functions. In some
applications, an orthogonalization method such as the w:Gram--Schmidt
process is performed in order to
produce a set of orthogonal basis functions. This can in principle save
computational time when the computer is solving the Roothaan--Hall
equations by converting the w:overlap
matrix effectively to an w:identity
matrix. However, in most modern computer
programs for molecular Hartree--Fock calculations this procedure is not
followed due to the high numerical cost of orthogonalization and the
advent of more efficient, often sparse, algorithms for solving the
w:generalized eigenvalue
problem, of which the
Roothaan--Hall equations are an
example.
## Numerical stability
w:Numerical stability can be a
problem with this procedure and there are various ways of combating this
instability. One of the most basic and generally applicable is called
*F-mixing* or damping. With F-mixing, once a single electron wave
function is calculated it is not used directly. Instead, some
combination of that calculated wave function and the previous wave
functions for that electron is used---the most common being a simple
linear combination of the calculated and immediately preceding wave
function. A clever dodge, employed by Hartree, for atomic calculations
was to increase the nuclear charge, thus pulling all the electrons
closer together. As the system stabilised, this was gradually reduced to
the correct charge. In molecular calculations a similar approach is
sometimes used by first calculating the wave function for a positive ion
and then to use these orbitals as the starting point for the neutral
molecule. Modern molecular Hartree--Fock computer programs use a variety
of methods to ensure convergence of the Roothaan--Hall equations.
## Weaknesses, extensions, and alternatives
Of the five simplifications outlined in the section \"Hartree--Fock
algorithm\", the fifth is typically the most important. Neglecting
electron correlation can lead to large deviations from experimental
results. A number of approaches to this weakness, collectively called
w:post-Hartree--Fock methods, have
been devised to include electron correlation to the multi-electron wave
function. One of these approaches, w:Møller--Plesset perturbation
theory, treats
correlation as a perturbation of the
Fock operator. Others expand the true multi-electron wave function in
terms of a linear combination of Slater determinants---such as
w:multi-configurational self-consistent
field,
w:configuration interaction,
w:quadratic configuration
interaction, and
complete active space SCF
(CASSCF).
Still others (such as variational quantum Monte
Carlo) modify the Hartree--Fock
wave function by multiplying it by a correlation function (\"Jastrow\"
factor), a term which is explicitly a function of multiple electrons
that cannot be decomposed into independent single-particle functions.
An alternative to Hartree--Fock calculations used in some cases is
w:density functional theory,
which treats both exchange and correlation energies, albeit
approximately. Indeed, it is common to use calculations that are a
hybrid of the two methods---the popular B3LYP scheme is one such
w:hybrid functional method. Another
option is to use w:modern valence
bond methods.
## Software packages
For a list of software packages known to handle Hartree--Fock
calculations, particularly for molecules and solids, see the w:list of
quantum chemistry and solid state physics
software.
## Sources
-
-
-
## Slater determinant
### Two-particle case
The simplest way to approximate the wave function of a many-particle
system is to take the product of properly chosen
orthogonal "wikilink") wave
functions of the individual particles. For the two-particle case with
spatial coordinates $\mathbf{x}_1$ and $\mathbf{x}_2$, we have
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = \chi_1(\mathbf{x}_1)\chi_2(\mathbf{x}_2).$$
This expression is used in the w:Hartree--Fock
method as an
w:ansatz for the many-particle wave function and
is known as a w:Hartree product.
However, it is not satisfactory for w:fermions
because the wave function above is not antisymmetric, as it must be for
w:fermions from the w:Pauli exclusion
principle. An antisymmetric
wave function can be mathematically described as follows:
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = -\Psi(\mathbf{x}_2,\mathbf{x}_1)$$
which does not hold for the Hartree product. Therefore the Hartree
product does not satisfy the Pauli principle. This problem can be
overcome by taking a w:linear
combination of both Hartree products
$$\Psi(\mathbf{x}_1,\mathbf{x}_2) = \frac{1}{\sqrt{2}}\{\chi_1(\mathbf{x}_1)\chi_2(\mathbf{x}_2) - \chi_1(\mathbf{x}_2)\chi_2(\mathbf{x}_1)\}$$
$$= \frac{1}{\sqrt2}\begin{vmatrix} \chi_1(\mathbf{x}_1) & \chi_2(\mathbf{x}_1) \\ \chi_1(\mathbf{x}_2) & \chi_2(\mathbf{x}_2) \end{vmatrix}$$
where the coefficient is the w:normalization
factor. This wave function is now
antisymmetric and no longer distinguishes between fermions, that is: one
cannot indicate an ordinal number to a specific particle and the indices
given are interchangeable. Moreover, it also goes to zero if any two
wave functions of two fermions are the same. This is equivalent to
satisfying the Pauli exclusion principle.
### Generalizations
The expression can be generalised to any number of fermions by writing
it as a w:determinant. For an *N*-electron
system, the Slater determinant is defined as [^9]
$$\Psi(\mathbf{x}_1, \mathbf{x}_2, \ldots, \mathbf{x}_N) =
\frac{1}{\sqrt{N!}}
\left|
\begin{matrix} \chi_1(\mathbf{x}_1) & \chi_2(\mathbf{x}_1) & \cdots & \chi_N(\mathbf{x}_1) \\
\chi_1(\mathbf{x}_2) & \chi_2(\mathbf{x}_2) & \cdots & \chi_N(\mathbf{x}_2) \\
\vdots & \vdots & \ddots & \vdots \\
\chi_1(\mathbf{x}_N) & \chi_2(\mathbf{x}_N) & \cdots & \chi_N(\mathbf{x}_N)
\end{matrix} \right|\equiv \left| \begin{matrix}
\chi _1 & \chi _2 & \cdots & \chi _N \\
\end{matrix}
\right|,$$
where in the final expression, a compact notation is introduced: the
normalization constant and labels for the fermion coordinates are
understood -- only the wavefunctions are exhibited. The linear
combination of Hartree products for the two-particle case can clearly be
seen as identical with the Slater determinant for *N* = 2. It can be
seen that the use of Slater determinants ensures an antisymmetrized
function at the outset; symmetric functions are automatically rejected.
In the same way, the use of Slater determinants ensures conformity to
the w:Pauli principle. Indeed, the
Slater determinant vanishes if the set {χ~i~ } is w:linearly
dependent. In particular, this is the
case when two (or more) spin orbitals are the same. In chemistry one
expresses this fact by stating that no two electrons can occupy the same
spin orbital. In general the Slater determinant is evaluated by the
w:Laplace expansion. Mathematically, a
Slater determinant is an antisymmetric tensor, also known as a w:wedge
product.
A single Slater determinant is used as an approximation to the
electronic wavefunction in Hartree--Fock
theory. In more accurate theories
(such as w:configuration
interaction and
w:MCSCF), a linear combination of Slater
determinants is needed.
The word \"**detor**\" was proposed by S. F. Boys to describe the Slater
determinant of the general type,[^10] but this term is rarely used.
Unlike w:fermions that are subject to the Pauli
exclusion principle, two or more w:bosons can
occupy the same quantum state of a system. Wavefunctions describing
systems of identical w:bosons are symmetric under
the exchange of particles and can be expanded in terms of
w:permanents.
## Fock matrix
In the w:Hartree--Fock method of
w:quantum mechanics, the **Fock
matrix** is a matrix "wikilink") approximating
the single-electron w:energy operator of
a given quantum system in a given set
of basis vectors.[^11]
It is most often formed in w:computational
chemistry when attempting to
solve the w:Roothaan equations for an
atomic or molecular system. The Fock matrix is actually an approximation
to the true Hamiltonian "wikilink")
operator "wikilink") of the quantum system.
It includes the effects of electron-electron
repulsion only in an average way.
Importantly, because the Fock operator is a one-electron operator, it
does not include the w:electron
correlation energy.
The Fock matrix is defined by the *Fock operator*. For the restricted
case which assumes w:closed-shell
orbitals and single-determinantal
wavefunctions, the Fock operator for the *i*-th electron is given
by:[^12]
$$\hat F(i) = \hat h(i)+\sum_{ j=1 }^{n/2}[2 \hat J_j(i)-\hat
K_j(i)]$$
where:
$$\hat F(i)$$ is the Fock operator for the *i*-th electron in the
system,
$${\hat h}(i)$$ is the w:one-electron
hamiltonian for the *i*-th
electron,
$$n$$ is the number of electrons and $\frac{n}{2}$ is the number of
occupied orbitals in the closed-shell system,
$$\hat J_j(i)$$ is the w:Coulomb
operator, defining the repulsive force
between the *j*-th and *i*-th electrons in the system,
$$\hat K_j(i)$$ is the w:exchange
operator, defining the quantum effect
produced by exchanging two electrons.
The Coulomb operator is multiplied by two since there are two electrons
in each occupied orbital. The exchange operator is not multiplied by two
since it has a non-zero result only for electrons which have the same
spin as the *i*-th electron.
For systems with unpaired electrons there are many choices of Fock
matrices.
Hartree-Fock (HF) or self-consistent field
(SCF)
# Density Functional Theory
## Connection to quantum state symmetry
The Pauli exclusion principle with a single-valued many-particle
wavefunction is equivalent to requiring the wavefunction to be
antisymmetric. An antisymmetric two-particle state is represented as a
sum of states in which one
particle is in state $\scriptstyle |x \rangle$ and the other in state
$\scriptstyle |y\rangle$:
$$|\psi\rangle = \sum_{x,y} A(x,y) |x,y\rangle$$
and antisymmetry under exchange means that
.
This implies that ,
which is Pauli exclusion. It is true in any basis, since unitary changes
of basis keep antisymmetric matrices antisymmetric, although strictly
speaking, the quantity is
not a matrix but an antisymmetric rank-two
w:tensor.
Conversely, if the diagonal quantities
are zero *in every basis*,
then the wavefunction component:
$$A(x,y)=\langle \psi|x,y\rangle = \langle \psi | ( |x\rangle \otimes |y\rangle )$$
is necessarily antisymmetric. To prove it, consider the matrix element:
$$\langle\psi| ((|x\rangle + |y\rangle)\otimes(|x\rangle + |y\rangle))
\,$$
This is zero, because the two particles have zero probability to both be
in the superposition state $\scriptstyle |x\rangle + |y\rangle$. But
this is equal to
$$\langle \psi |x,x\rangle + \langle \psi |x,y\rangle + \langle \psi |y,x\rangle + \langle \psi | y,y \rangle
\,$$
The first and last terms on the right hand side are diagonal elements
and are zero, and the whole sum is equal to zero. So the wavefunction
matrix elements obey:
$$\langle \psi|x,y\rangle + \langle\psi |y,x\rangle = 0
\,$$.
or
$$A(x,y)=-A(y,x)
\,$$
### Pauli principle in advanced quantum theory
According to the w:spin-statistics
theorem, particles with integer
spin occupy symmetric quantum states, and particles with half-integer
spin occupy antisymmetric states; furthermore, only integer or
half-integer values of spin are allowed by the principles of quantum
mechanics. In relativistic w:quantum field
theory, the Pauli principle follows
from applying a rotation operator in imaginary time to particles of
half-integer spin. Since, nonrelativistically, particles can have any
statistics and any spin, there is no way to prove a spin-statistics
theorem in nonrelativistic quantum mechanics.
In one dimension, bosons, as well as fermions, can obey the exclusion
principle. A one-dimensional Bose gas with delta function repulsive
interactions of infinite strength is equivalent to a gas of free
fermions. The reason for this is that, in one dimension, exchange of
particles requires that they pass through each other; for infinitely
strong repulsion this cannot happen. This model is described by a
quantum w:nonlinear Schrödinger
equation. In momentum
space the exclusion principle is valid also for finite repulsion in a
Bose gas with delta function interactions,[^13] as well as for
interacting spins "wikilink") and
w:Hubbard model in one dimension, and for
other models solvable by w:Bethe ansatz.
The ground state in models solvable by
Bethe ansatz is a Fermi sphere.
Density Functional Theory
# References
See also notes on editing this book about how to add references
w:Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]:
[^3]:
[^4]:
[^5]:
[^6]: Levine, Ira N. (1991). Quantum Chemistry (4th ed.). Englewood
Cliffs, New Jersey: Prentice Hall. p. 403.
.
[^7]:
[^8]:
[^9]: Molecular Quantum Mechanics Parts I and II: An Introduction to
QUANTUM CHEMISTRY (Volume 1), P.W. Atkins, Oxford University Press,
1977,
[^10]: {{ cite journal\| title=Electronic wave functions I. A general
method of calculation for the stationary states of any molecular
system\|author-link=S. Francis Boys\|first=S. F.
\|last=Boys\|page=542\| volume=A200 \|year=1950\|journal=
Proceedings of the Royal Society}}
[^11]:
[^12]: Levine, I.N. (1991) *Quantum Chemistry* (4th ed., Prentice-Hall),
p.403
[^13]: A. Izergin and V. Korepin, Letter in Mathematical Physics vol 6,
page 283, 1982
|
# Nanotechnology/Semiconducting Nanostructures#Carbon Nanotubes
Navigate
---------------------------------------------------------------------------------------------
\<\< Prev: Overview of Production methods
\>\< Main: Nanotechnology
\>\> Next: Metallic Nanostructures
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanotubes
Certain compounds are capable of forming nanotubes where the tube
consists of round shell of a single layer of atoms in a cylindrical
lattice. Carbon nanotubes is the most famous example, but also other
materials can form nanotubes such as Boron-nitride, Molybdenum sulfide
and others.
Nanotubes can also be made by etching the core out of an shell
structured rod, but such tubes will normally contain many atomic layers
in the wall and have crystal facets on the sides.
# Carbon Nanotubes
Carbon nanotubes are fascinating nanostructures. A sheet of graphene as
in common graphite, but rolled up in small tubes rather than planar
sheets.
Carbon nanotubes have unique mechanical properties such as high
strength, high stiffness, and low density [^1] and also interesting
electronic properties. A single-walled carbon nanotube can be either
metallic or semiconducting depending on the atomic arrangement [^2].
This section is a short introduction to carbon nanotubes. For a broader
overview the reader is referred to one of the numerous review articles
or books on carbon nanotubes
[^3] [^4] [^5]
## Geometric Structure
The simplest type of carbon nanotube consists of just one layer of
graphene rolled up in the form of a seamless cylinder, known as a
single-walled carbon nanotube (SWCNT) with a typical diameter of just a
few nanometers. Larger diameter nanotube structures are nanotube ropes,
consisting of many individual, parallel nanotubes closed-packed into a
hexagonal lattice, and multi-walled carbon nanotubes (MWCNTs) consisting
of several concentric cylinders nested within each other.
! Multiwall carbon nanotube (MWCNT) sample made by a CVD process using
iron containing catalystic particles. The MWCNT are adhering in
mats. sample made by a CVD process using iron containing catalystic particles. The MWCNT are adhering in mats."){width="300"}
### Single walled Carbon Nanotube
The basic configuration is thus the SWCNT. Its structure is most easily
illustrated as a cylindrical tube conceptually formed by the wrapping of
a single graphene sheet. The hexagonal structure of the 2-dimensional
graphene sheet is due to the $sp^{2}$ hybridization of the carbon atoms,
which causes three directional, in-plane $\sigma$ bonds separated by an
angle of 120 degrees.
The nanotube can be described by a chiral vector $C$ that can be
expressed in terms of the graphene unit vectors $\textbf{a}_{1}$ and
$\textbf{a}_{2}$ as $\textbf{C}=n\textbf{a}_{1}+m\textbf{a}_{2}$ with
the set of integers $(n,m)$ uniquely identifying the nanotube. This
chiral vector or \'roll-up\' vector describes the nanotube circumference
by connecting two crystallographically equivalent positions i.e. the
tube is formed by superimposing the two ends of $\textbf{C}$.
Based on the chiral angle SWCNTs are defined as zig-zag tubes
($\theta =0 deg \leftrightarrow m=0$), armchair tubes
($\theta =30 deg \leftrightarrow n=m$), or chiral tubes
($0 deg < \theta < 30 deg$).
### Multiwalled Carbon Nanotubes
MWCNTs are composed of a number of SWCNTs in a coaxial geometry. Each
nested shell has a diameter of
$d=\sqrt{3}a_{C-C}(m^{2}+n^{2}+mn)^{1/2}/\pi$ where $a_{C-C}$ is the
length of the carbon-carbon bond which is 1.42 Å. The difference in
diameters of the individual shell means that their chiralities are
different, and adjacent shell are therefore in general non-commensurate,
which causes only a weak intershell interaction.
The intershell spacing in MWCNTs is $\sim$ 0.34 nm - quite close to the
interlayer spacing in turbostratic graphite [^6]
## Electronic Structure
The electronic structure of a SWCNT is most easily described by again
considering a single graphene sheet. The 2-D, hexagonal-lattice graphene
sheet has a 2-D reciprocal space with a hexagonal Brillouin zone (BZ).
The $\sigma$ bonds are mainly responsible for the mechanical properties,
while the electronic properties are mainly determined by the $\pi$
bands. By a tight-binding approach the band structure of these $\pi$
bands can be calculated [^7]
Graphene is a zero-gap semiconductor with an occupied $\pi$ band and an
unoccupied $\pi^{*}$ band meeting at the Fermi level at six $K$ points
in the BZ, thus it behaves metallic, a so-called semimetal.
Upon forming the tube by conceptually wrapping the graphene sheet, a
periodic boundary condition is imposed that causes only certain
electronic states of those of the planar graphene sheet to be allowed.
These states are determined by the tube\'s geometric structure, i.e. by
the indices $(n,m)$ of the chiral vector. The wave vectors of the
allowed states fall on certain lines in the graphene BZ.
Based on this scheme it is possible to estimate whether a particular
tube will be metallic or semiconducting. When the allowed states include
the $K$ point, the system will to a first approximation behave metallic.
However, in the points where the $\pi$ and the $\pi^{*}$ bands meet but
are shifted slightly away from the $K$ point due to curvature effects,
which causes a slight band opening in some cases [^8]
This leads to a classification scheme that has three types of nanotubes:
- Metallic: These are the armchair tubes where the small shift of the
degenerate point away from the $K$ point does not cause a band
opening for symmetry reasons.
```{=html}
<!-- -->
```
- Small-bandgap semiconducting: These are characterized by $n-m = 3j$
with $j$ being an integer. Here, the wave vectors of the allowed
states cross the $K$ point, but due to the slight shift of the
degenerate point a small gap will be present, the size of which is
inversely proportional to the tube diameter squared with typical
values between a few and a few tens meV
[^9]
- Semiconducting: In this case $n-m \neq 3j$. This causes a larger
bandgap, the size of which is inversely proportional to the tube
diameter: $E_{g}=k/d$ with experimental investigations suggesting a
value of $k$ of 0.7-0.8 eV/nm
[^10]
Typically the bandgap of the type 2 nanotubes is so small that they can
be considered metallic at room temperature. Based on this it can be
inferred that 1/3 of all tubes should behave metallic whereas the
remaining 2/3 should be semiconducting. However, it should be noted that
due to the inverse proportionality between the bandgap and the diameter
of the semiconducting tubes, large-diameter tubes will tend to behave
metallic at room temperature. This is especially important in regards to
large-diameter MWCNTs.
From a electrical point of view a MWCNT can be seen as a complex
structure of many parallel conductors that are only weakly interacting.
Since probing the electrical properties typically involves electrodes
contacting the outermost shell, this shell will be dominating the
transport properties [^11] In a simplistic view, this can be compared to
a large-diameter SWCNT, which will therefore typically display metallic
behavior.
## Electrical and Electromechanical Properties
Many studies have focused on SWCNTs for exploring the fundamental
properties of nanotubes. Due to their essentially 1-D nature and
intriguing electronic structure, SWCNTs exhibit a range of interesting
quantum phenomena at low temperature [^12]
The discussion here will so far, however, primarily be limited to room
temperature properties.
The conductance $~G~$ of a 1-dimensional conductor such as a SWCNT is
given by the Landauer formula [^13]
$~G=G_{0}\sum_{i}T_{i}~$,
where $~G_{0}=2e^{2}/h = (12.9 \rm k\Omega)^{-1}$;\
$~1/G_{0}~$ is the conductance quantum;\
and $~T_{i}~$ is the transmission coefficient of the contributing
channel $~i~$.
## More information on nanotubes
- Wikipedia Carbon nanotubes
- The nanotube site
- Compiled overview of properties of carbon
nanotubes
## Commercial suppliers of carbon nanotubes and related products
- Nanoledge.com nanotubes and related
products - fibers, pellets, resins and dispersions\...
- Carbon Solution, Inc. Mainly
SWCNT.
- BuckyUSA Fullerens, SWCNT, MWCNT.
- CNI
HiPco Carbon nanotubes
- Carbolex SWCNT,sub-gram quantities are
sold via sigma aldric
- Sigma-Aldrich
SWCNT
## \"Buckyball\"
!C~60~ with isosurface of ground state electron density as calculated
with
DFT{width="160"}
!An w:association football is a
model of the Buckminsterfullerene
C~60~{width="160"}
**Buckminsterfullerene** (IUPAC name
**(C~60~-I~h~)\[5,6\]fullerene**) is the smallest fullerene molecule in
which no two pentagons share an edge (which can be destabilizing, as in
pentalene). It is also the most common in
terms of natural occurrence, as it can often be found in
soot.
The structure of C~60~ is a truncated (T = 3)
icosahedron, which resembles a
soccer ball#Association_football "wikilink") of the
type made of twenty hexagons and twelve pentagons, with a carbon atom at
the vertices of each polygon and a bond along each polygon edge.
The w:van der Waals diameter of a
C~60~ molecule is about 1 nanometer (nm). The
nucleus to nucleus diameter of a C~60~ molecule is about 0.7 nm.
The C~60~ molecule has two bond lengths. The 6:6 ring bonds (between two
hexagons) can be considered \"double bonds\"
and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
Its average bond length is 1.4 angstroms.
Silicon buckyballs have been created around metal ions.
### Boron buckyball
A new type of buckyball utilizing boron atoms
instead of the usual carbon has been predicted and described by
researchers at Rice University. The B-80 structure, with each atom
forming 5 or 6 bonds, is predicted to be more stable than the C-60
buckyball.[^14] One reason for this given by the researchers is that the
B-80 is actually more like the original geodesic dome structure
popularized by Buckminster Fuller which utilizes triangles rather than
hexagons. However, this work has been subject to much criticism by
quantum chemists[^15][^16] as it was concluded that the predicted Ih
symmetric structure was vibrationally unstable and the resulting cage
undergoes a spontaneous symmetry break yielding a puckered cage with
rare Th symmetry (symmetry of a
volleyball "wikilink"))[^17]. The number of six
atom rings in this molecule is 20 and number of five member rings is 12.
There is an additional atom in the center of each six member ring,
bonded to each atom surrounding it.
### Variations of buckyballs
Another fairly common buckminsterfullerene is C~70~,[^18] but fullerenes
with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained.
In mathematical terms, the structure of a
**fullerene** is a trivalent "wikilink") convex
polyhedron with pentagonal and hexagonal
faces. In graph theory, the term
**fullerene** refers to any 3-regular,
planar graph with all faces of size 5 or 6
(including the external face). It follows from Euler\'s polyhedron
formula, \|V\|-\|E\|+\|F\| = 2,
(where \|V\|, \|E\|, \|F\| indicate the number of vertices, edges, and
faces), that there are exactly 12 pentagons in a fullerene and
\|V\|/2-10 hexagons.
+----------------+----------------+----------------+----------------+
| ![] | ![] | ![] | ![] |
| (Graph_of_20-f | (Graph_of_26-f | (Graph_of_60-f | (Graph_of_70-f |
| ullerene_w-nod | ullerene_5-bas | ullerene_w-nod | ullerene_w-nod |
| es.svg "Graph_ | e_w-nodes.svg | es.svg "Graph_ | es.svg "Graph_ |
| of_20-fulleren | "Graph_of_26-f | of_60-fulleren | of_70-fulleren |
| e_w-nodes.svg" | ullerene_5-bas | e_w-nodes.svg" | e_w-nodes.svg" |
| ){width="200"} | e_w-nodes.svg" | ){width="200"} | ){width="200"} |
| | ){width="200"} | | |
+----------------+----------------+----------------+----------------+
| 20-fullerene\ | 26-fullerene | 60-fullerene\ | 70-fullerene |
| (dodecahedral | graph | (truncated | graph |
| graph) | | icosahedral | |
| | | graph) | |
+----------------+----------------+----------------+----------------+
The smallest fullerene is the
w:dodecahedron\--the unique C~20~. There
are no fullerenes with 22 vertices.[^19] The number of fullerenes C~2n~
grows with increasing n = 12,13,14\..., roughly in proportion to n^9^.
For instance, there are 1812 non-isomorphic fullerenes C~60~. Note that
only one form of C~60~, the buckminsterfullerene alias w:truncated
icosahedron, has no pair of
adjacent pentagons (the smallest such fullerene). To further illustrate
the growth, there are 214,127,713 non-isomorphic fullerenes C~200~,
15,655,672 of which have no adjacent pentagons.
w:Trimetasphere carbon nanomaterials were
discovered by researchers at w:Virginia
Tech and licensed exclusively to w:Luna
Innovations. This class of novel
molecules comprises 80 carbon atoms (C80) forming a sphere which
encloses a complex of three metal atoms and one nitrogen atom. These
fullerenes encapsulate metals which puts them in the subset referred to
as w:metallofullerenes. Trimetaspheres
have the potential for use in diagnostics (as safe imaging agents),
therapeutics and in organic solar
cells.
# Semiconducting nanowires
Semiconducting nanowires can be made from most semiconducting materials
and with different methods, mainly variations of a chemical vapor
deposition process (CVD).
There are many different semiconducting materials, and heterosrtuctures
can be made if the lattice constants are not too incompatible.
Heterostructures made from combinations of materials such as GaAs-GaP
can be used to make barriers and guides for electrons in electrical
systems.
Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant.
!Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant. Nanowire growth is catalyzed by various nanoparticles, which
are deposited on the substrate surface, typically gold nanoparticles
with a diameter of 20-100nm.
can be used to grow III-V nanowires epitaxially on suitable crystalline substrates, sucha s III-V materials or silicon with a reasonably matching lattice constant. Nanowire growth is catalyzed by various nanoparticles, which are deposited on the substrate surface, typically gold nanoparticles with a diameter of 20-100nm. "){width="300"}
Nanowire growth is catalyzed by various nanoparticles, which are
deposited on the substrate surface, typically gold nanoparticles with a
diameter of 20-100nm.
To grow for instance GaP wires, the sample is typically annealed at 650C
in the heated reactor chamber to form an eutectic with between the gold
catalyst and the underlying substrate.
Then growth is done at a lower temperature around 500C in the presence
of the precursor gasses trimethyl gallium and phosphine. By changing the
precursor gasses during growth, nanowire heterostructures with varying
composition can be made
!SEM image of epitaxial nanowire heterostructures grown from catalytic
gold
nanoparticles{width="400"}
## Resources
- wikipedia Semiconducting nanowires
- IOFFE semiconductor physical
properties
# Nanoparticles
- Nanoparticles
- Quantum dots
## Catalytic particles
- Catalyst
- Catalysis
- Haber process
## Commercial suppliers of nanoparticles
- Reade has a wide selection of
nanoparticles
- sigma-aldrich
has dispersions of
nanoparticles
- nanophase
# Contributors and Acknowledgements
- Jakob Kjelstrup Hansen
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: qian2002
[^2]: hamada1992
[^3]: avouris2003
[^4]: dresselhaus2001
[^5]: saito1998
[^6]: dresselhaus2001
[^7]: saito1998
[^8]: hamada1992.
[^9]: zhou2000
[^10]: wildoer1998,odom1998
[^11]: frank1998
[^12]: nygard1999,dresselhaus2001
[^13]: datta1995
[^14]: *Bucky\'s brother \-- The boron buckyball makes its début* Jade
Boyd April **2007**
eurekalert.orgLink
[^15]: *The boron buckyball has an unexpected Th symmetry* G. Gopakumar,
Nguyen, M. T., Ceulemans, Arnout, Chem. Phys. lett. 450, 175,
2008.1&_cdi=5231&_sort=d&_docanchor=&view=c&_ct=53&_acct=C000024498&_version=1&_urlVersion=0&_userid=4466739&md5=2e8f3b9eacbc9a4b9a3dbd42fdbf2826)
[^16]: \"Stuffing improves the stability of fullerenelike boron
clusters\" Prasad, DLVK; Jemmis, E. D.; Phys. Rev. Lett. 100,
165504,
2008.2
[^17]:
[^18]: Buckminsterfullerene: Molecule of the
Month
[^19]: Goldberg Variations Challenge: Juris Meija, Anal. Bioanal. Chem.
2006 (385)
6-7
|
# Nanotechnology/Semiconducting Nanostructures#.22Buckyball.22
Navigate
---------------------------------------------------------------------------------------------
\<\< Prev: Overview of Production methods
\>\< Main: Nanotechnology
\>\> Next: Metallic Nanostructures
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanotubes
Certain compounds are capable of forming nanotubes where the tube
consists of round shell of a single layer of atoms in a cylindrical
lattice. Carbon nanotubes is the most famous example, but also other
materials can form nanotubes such as Boron-nitride, Molybdenum sulfide
and others.
Nanotubes can also be made by etching the core out of an shell
structured rod, but such tubes will normally contain many atomic layers
in the wall and have crystal facets on the sides.
# Carbon Nanotubes
Carbon nanotubes are fascinating nanostructures. A sheet of graphene as
in common graphite, but rolled up in small tubes rather than planar
sheets.
Carbon nanotubes have unique mechanical properties such as high
strength, high stiffness, and low density [^1] and also interesting
electronic properties. A single-walled carbon nanotube can be either
metallic or semiconducting depending on the atomic arrangement [^2].
This section is a short introduction to carbon nanotubes. For a broader
overview the reader is referred to one of the numerous review articles
or books on carbon nanotubes
[^3] [^4] [^5]
## Geometric Structure
The simplest type of carbon nanotube consists of just one layer of
graphene rolled up in the form of a seamless cylinder, known as a
single-walled carbon nanotube (SWCNT) with a typical diameter of just a
few nanometers. Larger diameter nanotube structures are nanotube ropes,
consisting of many individual, parallel nanotubes closed-packed into a
hexagonal lattice, and multi-walled carbon nanotubes (MWCNTs) consisting
of several concentric cylinders nested within each other.
! Multiwall carbon nanotube (MWCNT) sample made by a CVD process using
iron containing catalystic particles. The MWCNT are adhering in
mats. sample made by a CVD process using iron containing catalystic particles. The MWCNT are adhering in mats."){width="300"}
### Single walled Carbon Nanotube
The basic configuration is thus the SWCNT. Its structure is most easily
illustrated as a cylindrical tube conceptually formed by the wrapping of
a single graphene sheet. The hexagonal structure of the 2-dimensional
graphene sheet is due to the $sp^{2}$ hybridization of the carbon atoms,
which causes three directional, in-plane $\sigma$ bonds separated by an
angle of 120 degrees.
The nanotube can be described by a chiral vector $C$ that can be
expressed in terms of the graphene unit vectors $\textbf{a}_{1}$ and
$\textbf{a}_{2}$ as $\textbf{C}=n\textbf{a}_{1}+m\textbf{a}_{2}$ with
the set of integers $(n,m)$ uniquely identifying the nanotube. This
chiral vector or \'roll-up\' vector describes the nanotube circumference
by connecting two crystallographically equivalent positions i.e. the
tube is formed by superimposing the two ends of $\textbf{C}$.
Based on the chiral angle SWCNTs are defined as zig-zag tubes
($\theta =0 deg \leftrightarrow m=0$), armchair tubes
($\theta =30 deg \leftrightarrow n=m$), or chiral tubes
($0 deg < \theta < 30 deg$).
### Multiwalled Carbon Nanotubes
MWCNTs are composed of a number of SWCNTs in a coaxial geometry. Each
nested shell has a diameter of
$d=\sqrt{3}a_{C-C}(m^{2}+n^{2}+mn)^{1/2}/\pi$ where $a_{C-C}$ is the
length of the carbon-carbon bond which is 1.42 Å. The difference in
diameters of the individual shell means that their chiralities are
different, and adjacent shell are therefore in general non-commensurate,
which causes only a weak intershell interaction.
The intershell spacing in MWCNTs is $\sim$ 0.34 nm - quite close to the
interlayer spacing in turbostratic graphite [^6]
## Electronic Structure
The electronic structure of a SWCNT is most easily described by again
considering a single graphene sheet. The 2-D, hexagonal-lattice graphene
sheet has a 2-D reciprocal space with a hexagonal Brillouin zone (BZ).
The $\sigma$ bonds are mainly responsible for the mechanical properties,
while the electronic properties are mainly determined by the $\pi$
bands. By a tight-binding approach the band structure of these $\pi$
bands can be calculated [^7]
Graphene is a zero-gap semiconductor with an occupied $\pi$ band and an
unoccupied $\pi^{*}$ band meeting at the Fermi level at six $K$ points
in the BZ, thus it behaves metallic, a so-called semimetal.
Upon forming the tube by conceptually wrapping the graphene sheet, a
periodic boundary condition is imposed that causes only certain
electronic states of those of the planar graphene sheet to be allowed.
These states are determined by the tube\'s geometric structure, i.e. by
the indices $(n,m)$ of the chiral vector. The wave vectors of the
allowed states fall on certain lines in the graphene BZ.
Based on this scheme it is possible to estimate whether a particular
tube will be metallic or semiconducting. When the allowed states include
the $K$ point, the system will to a first approximation behave metallic.
However, in the points where the $\pi$ and the $\pi^{*}$ bands meet but
are shifted slightly away from the $K$ point due to curvature effects,
which causes a slight band opening in some cases [^8]
This leads to a classification scheme that has three types of nanotubes:
- Metallic: These are the armchair tubes where the small shift of the
degenerate point away from the $K$ point does not cause a band
opening for symmetry reasons.
```{=html}
<!-- -->
```
- Small-bandgap semiconducting: These are characterized by $n-m = 3j$
with $j$ being an integer. Here, the wave vectors of the allowed
states cross the $K$ point, but due to the slight shift of the
degenerate point a small gap will be present, the size of which is
inversely proportional to the tube diameter squared with typical
values between a few and a few tens meV
[^9]
- Semiconducting: In this case $n-m \neq 3j$. This causes a larger
bandgap, the size of which is inversely proportional to the tube
diameter: $E_{g}=k/d$ with experimental investigations suggesting a
value of $k$ of 0.7-0.8 eV/nm
[^10]
Typically the bandgap of the type 2 nanotubes is so small that they can
be considered metallic at room temperature. Based on this it can be
inferred that 1/3 of all tubes should behave metallic whereas the
remaining 2/3 should be semiconducting. However, it should be noted that
due to the inverse proportionality between the bandgap and the diameter
of the semiconducting tubes, large-diameter tubes will tend to behave
metallic at room temperature. This is especially important in regards to
large-diameter MWCNTs.
From a electrical point of view a MWCNT can be seen as a complex
structure of many parallel conductors that are only weakly interacting.
Since probing the electrical properties typically involves electrodes
contacting the outermost shell, this shell will be dominating the
transport properties [^11] In a simplistic view, this can be compared to
a large-diameter SWCNT, which will therefore typically display metallic
behavior.
## Electrical and Electromechanical Properties
Many studies have focused on SWCNTs for exploring the fundamental
properties of nanotubes. Due to their essentially 1-D nature and
intriguing electronic structure, SWCNTs exhibit a range of interesting
quantum phenomena at low temperature [^12]
The discussion here will so far, however, primarily be limited to room
temperature properties.
The conductance $~G~$ of a 1-dimensional conductor such as a SWCNT is
given by the Landauer formula [^13]
$~G=G_{0}\sum_{i}T_{i}~$,
where $~G_{0}=2e^{2}/h = (12.9 \rm k\Omega)^{-1}$;\
$~1/G_{0}~$ is the conductance quantum;\
and $~T_{i}~$ is the transmission coefficient of the contributing
channel $~i~$.
## More information on nanotubes
- Wikipedia Carbon nanotubes
- The nanotube site
- Compiled overview of properties of carbon
nanotubes
## Commercial suppliers of carbon nanotubes and related products
- Nanoledge.com nanotubes and related
products - fibers, pellets, resins and dispersions\...
- Carbon Solution, Inc. Mainly
SWCNT.
- BuckyUSA Fullerens, SWCNT, MWCNT.
- CNI
HiPco Carbon nanotubes
- Carbolex SWCNT,sub-gram quantities are
sold via sigma aldric
- Sigma-Aldrich
SWCNT
## \"Buckyball\"
!C~60~ with isosurface of ground state electron density as calculated
with
DFT{width="160"}
!An w:association football is a
model of the Buckminsterfullerene
C~60~{width="160"}
**Buckminsterfullerene** (IUPAC name
**(C~60~-I~h~)\[5,6\]fullerene**) is the smallest fullerene molecule in
which no two pentagons share an edge (which can be destabilizing, as in
pentalene). It is also the most common in
terms of natural occurrence, as it can often be found in
soot.
The structure of C~60~ is a truncated (T = 3)
icosahedron, which resembles a
soccer ball#Association_football "wikilink") of the
type made of twenty hexagons and twelve pentagons, with a carbon atom at
the vertices of each polygon and a bond along each polygon edge.
The w:van der Waals diameter of a
C~60~ molecule is about 1 nanometer (nm). The
nucleus to nucleus diameter of a C~60~ molecule is about 0.7 nm.
The C~60~ molecule has two bond lengths. The 6:6 ring bonds (between two
hexagons) can be considered \"double bonds\"
and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
Its average bond length is 1.4 angstroms.
Silicon buckyballs have been created around metal ions.
### Boron buckyball
A new type of buckyball utilizing boron atoms
instead of the usual carbon has been predicted and described by
researchers at Rice University. The B-80 structure, with each atom
forming 5 or 6 bonds, is predicted to be more stable than the C-60
buckyball.[^14] One reason for this given by the researchers is that the
B-80 is actually more like the original geodesic dome structure
popularized by Buckminster Fuller which utilizes triangles rather than
hexagons. However, this work has been subject to much criticism by
quantum chemists[^15][^16] as it was concluded that the predicted Ih
symmetric structure was vibrationally unstable and the resulting cage
undergoes a spontaneous symmetry break yielding a puckered cage with
rare Th symmetry (symmetry of a
volleyball "wikilink"))[^17]. The number of six
atom rings in this molecule is 20 and number of five member rings is 12.
There is an additional atom in the center of each six member ring,
bonded to each atom surrounding it.
### Variations of buckyballs
Another fairly common buckminsterfullerene is C~70~,[^18] but fullerenes
with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained.
In mathematical terms, the structure of a
**fullerene** is a trivalent "wikilink") convex
polyhedron with pentagonal and hexagonal
faces. In graph theory, the term
**fullerene** refers to any 3-regular,
planar graph with all faces of size 5 or 6
(including the external face). It follows from Euler\'s polyhedron
formula, \|V\|-\|E\|+\|F\| = 2,
(where \|V\|, \|E\|, \|F\| indicate the number of vertices, edges, and
faces), that there are exactly 12 pentagons in a fullerene and
\|V\|/2-10 hexagons.
+----------------+----------------+----------------+----------------+
| ![] | ![] | ![] | ![] |
| (Graph_of_20-f | (Graph_of_26-f | (Graph_of_60-f | (Graph_of_70-f |
| ullerene_w-nod | ullerene_5-bas | ullerene_w-nod | ullerene_w-nod |
| es.svg "Graph_ | e_w-nodes.svg | es.svg "Graph_ | es.svg "Graph_ |
| of_20-fulleren | "Graph_of_26-f | of_60-fulleren | of_70-fulleren |
| e_w-nodes.svg" | ullerene_5-bas | e_w-nodes.svg" | e_w-nodes.svg" |
| ){width="200"} | e_w-nodes.svg" | ){width="200"} | ){width="200"} |
| | ){width="200"} | | |
+----------------+----------------+----------------+----------------+
| 20-fullerene\ | 26-fullerene | 60-fullerene\ | 70-fullerene |
| (dodecahedral | graph | (truncated | graph |
| graph) | | icosahedral | |
| | | graph) | |
+----------------+----------------+----------------+----------------+
The smallest fullerene is the
w:dodecahedron\--the unique C~20~. There
are no fullerenes with 22 vertices.[^19] The number of fullerenes C~2n~
grows with increasing n = 12,13,14\..., roughly in proportion to n^9^.
For instance, there are 1812 non-isomorphic fullerenes C~60~. Note that
only one form of C~60~, the buckminsterfullerene alias w:truncated
icosahedron, has no pair of
adjacent pentagons (the smallest such fullerene). To further illustrate
the growth, there are 214,127,713 non-isomorphic fullerenes C~200~,
15,655,672 of which have no adjacent pentagons.
w:Trimetasphere carbon nanomaterials were
discovered by researchers at w:Virginia
Tech and licensed exclusively to w:Luna
Innovations. This class of novel
molecules comprises 80 carbon atoms (C80) forming a sphere which
encloses a complex of three metal atoms and one nitrogen atom. These
fullerenes encapsulate metals which puts them in the subset referred to
as w:metallofullerenes. Trimetaspheres
have the potential for use in diagnostics (as safe imaging agents),
therapeutics and in organic solar
cells.
# Semiconducting nanowires
Semiconducting nanowires can be made from most semiconducting materials
and with different methods, mainly variations of a chemical vapor
deposition process (CVD).
There are many different semiconducting materials, and heterosrtuctures
can be made if the lattice constants are not too incompatible.
Heterostructures made from combinations of materials such as GaAs-GaP
can be used to make barriers and guides for electrons in electrical
systems.
Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant.
!Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant. Nanowire growth is catalyzed by various nanoparticles, which
are deposited on the substrate surface, typically gold nanoparticles
with a diameter of 20-100nm.
can be used to grow III-V nanowires epitaxially on suitable crystalline substrates, sucha s III-V materials or silicon with a reasonably matching lattice constant. Nanowire growth is catalyzed by various nanoparticles, which are deposited on the substrate surface, typically gold nanoparticles with a diameter of 20-100nm. "){width="300"}
Nanowire growth is catalyzed by various nanoparticles, which are
deposited on the substrate surface, typically gold nanoparticles with a
diameter of 20-100nm.
To grow for instance GaP wires, the sample is typically annealed at 650C
in the heated reactor chamber to form an eutectic with between the gold
catalyst and the underlying substrate.
Then growth is done at a lower temperature around 500C in the presence
of the precursor gasses trimethyl gallium and phosphine. By changing the
precursor gasses during growth, nanowire heterostructures with varying
composition can be made
!SEM image of epitaxial nanowire heterostructures grown from catalytic
gold
nanoparticles{width="400"}
## Resources
- wikipedia Semiconducting nanowires
- IOFFE semiconductor physical
properties
# Nanoparticles
- Nanoparticles
- Quantum dots
## Catalytic particles
- Catalyst
- Catalysis
- Haber process
## Commercial suppliers of nanoparticles
- Reade has a wide selection of
nanoparticles
- sigma-aldrich
has dispersions of
nanoparticles
- nanophase
# Contributors and Acknowledgements
- Jakob Kjelstrup Hansen
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: qian2002
[^2]: hamada1992
[^3]: avouris2003
[^4]: dresselhaus2001
[^5]: saito1998
[^6]: dresselhaus2001
[^7]: saito1998
[^8]: hamada1992.
[^9]: zhou2000
[^10]: wildoer1998,odom1998
[^11]: frank1998
[^12]: nygard1999,dresselhaus2001
[^13]: datta1995
[^14]: *Bucky\'s brother \-- The boron buckyball makes its début* Jade
Boyd April **2007**
eurekalert.orgLink
[^15]: *The boron buckyball has an unexpected Th symmetry* G. Gopakumar,
Nguyen, M. T., Ceulemans, Arnout, Chem. Phys. lett. 450, 175,
2008.1&_cdi=5231&_sort=d&_docanchor=&view=c&_ct=53&_acct=C000024498&_version=1&_urlVersion=0&_userid=4466739&md5=2e8f3b9eacbc9a4b9a3dbd42fdbf2826)
[^16]: \"Stuffing improves the stability of fullerenelike boron
clusters\" Prasad, DLVK; Jemmis, E. D.; Phys. Rev. Lett. 100,
165504,
2008.2
[^17]:
[^18]: Buckminsterfullerene: Molecule of the
Month
[^19]: Goldberg Variations Challenge: Juris Meija, Anal. Bioanal. Chem.
2006 (385)
6-7
|
# Nanotechnology/Semiconducting Nanostructures#Semiconducting nanowires
Navigate
---------------------------------------------------------------------------------------------
\<\< Prev: Overview of Production methods
\>\< Main: Nanotechnology
\>\> Next: Metallic Nanostructures
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanotubes
Certain compounds are capable of forming nanotubes where the tube
consists of round shell of a single layer of atoms in a cylindrical
lattice. Carbon nanotubes is the most famous example, but also other
materials can form nanotubes such as Boron-nitride, Molybdenum sulfide
and others.
Nanotubes can also be made by etching the core out of an shell
structured rod, but such tubes will normally contain many atomic layers
in the wall and have crystal facets on the sides.
# Carbon Nanotubes
Carbon nanotubes are fascinating nanostructures. A sheet of graphene as
in common graphite, but rolled up in small tubes rather than planar
sheets.
Carbon nanotubes have unique mechanical properties such as high
strength, high stiffness, and low density [^1] and also interesting
electronic properties. A single-walled carbon nanotube can be either
metallic or semiconducting depending on the atomic arrangement [^2].
This section is a short introduction to carbon nanotubes. For a broader
overview the reader is referred to one of the numerous review articles
or books on carbon nanotubes
[^3] [^4] [^5]
## Geometric Structure
The simplest type of carbon nanotube consists of just one layer of
graphene rolled up in the form of a seamless cylinder, known as a
single-walled carbon nanotube (SWCNT) with a typical diameter of just a
few nanometers. Larger diameter nanotube structures are nanotube ropes,
consisting of many individual, parallel nanotubes closed-packed into a
hexagonal lattice, and multi-walled carbon nanotubes (MWCNTs) consisting
of several concentric cylinders nested within each other.
! Multiwall carbon nanotube (MWCNT) sample made by a CVD process using
iron containing catalystic particles. The MWCNT are adhering in
mats. sample made by a CVD process using iron containing catalystic particles. The MWCNT are adhering in mats."){width="300"}
### Single walled Carbon Nanotube
The basic configuration is thus the SWCNT. Its structure is most easily
illustrated as a cylindrical tube conceptually formed by the wrapping of
a single graphene sheet. The hexagonal structure of the 2-dimensional
graphene sheet is due to the $sp^{2}$ hybridization of the carbon atoms,
which causes three directional, in-plane $\sigma$ bonds separated by an
angle of 120 degrees.
The nanotube can be described by a chiral vector $C$ that can be
expressed in terms of the graphene unit vectors $\textbf{a}_{1}$ and
$\textbf{a}_{2}$ as $\textbf{C}=n\textbf{a}_{1}+m\textbf{a}_{2}$ with
the set of integers $(n,m)$ uniquely identifying the nanotube. This
chiral vector or \'roll-up\' vector describes the nanotube circumference
by connecting two crystallographically equivalent positions i.e. the
tube is formed by superimposing the two ends of $\textbf{C}$.
Based on the chiral angle SWCNTs are defined as zig-zag tubes
($\theta =0 deg \leftrightarrow m=0$), armchair tubes
($\theta =30 deg \leftrightarrow n=m$), or chiral tubes
($0 deg < \theta < 30 deg$).
### Multiwalled Carbon Nanotubes
MWCNTs are composed of a number of SWCNTs in a coaxial geometry. Each
nested shell has a diameter of
$d=\sqrt{3}a_{C-C}(m^{2}+n^{2}+mn)^{1/2}/\pi$ where $a_{C-C}$ is the
length of the carbon-carbon bond which is 1.42 Å. The difference in
diameters of the individual shell means that their chiralities are
different, and adjacent shell are therefore in general non-commensurate,
which causes only a weak intershell interaction.
The intershell spacing in MWCNTs is $\sim$ 0.34 nm - quite close to the
interlayer spacing in turbostratic graphite [^6]
## Electronic Structure
The electronic structure of a SWCNT is most easily described by again
considering a single graphene sheet. The 2-D, hexagonal-lattice graphene
sheet has a 2-D reciprocal space with a hexagonal Brillouin zone (BZ).
The $\sigma$ bonds are mainly responsible for the mechanical properties,
while the electronic properties are mainly determined by the $\pi$
bands. By a tight-binding approach the band structure of these $\pi$
bands can be calculated [^7]
Graphene is a zero-gap semiconductor with an occupied $\pi$ band and an
unoccupied $\pi^{*}$ band meeting at the Fermi level at six $K$ points
in the BZ, thus it behaves metallic, a so-called semimetal.
Upon forming the tube by conceptually wrapping the graphene sheet, a
periodic boundary condition is imposed that causes only certain
electronic states of those of the planar graphene sheet to be allowed.
These states are determined by the tube\'s geometric structure, i.e. by
the indices $(n,m)$ of the chiral vector. The wave vectors of the
allowed states fall on certain lines in the graphene BZ.
Based on this scheme it is possible to estimate whether a particular
tube will be metallic or semiconducting. When the allowed states include
the $K$ point, the system will to a first approximation behave metallic.
However, in the points where the $\pi$ and the $\pi^{*}$ bands meet but
are shifted slightly away from the $K$ point due to curvature effects,
which causes a slight band opening in some cases [^8]
This leads to a classification scheme that has three types of nanotubes:
- Metallic: These are the armchair tubes where the small shift of the
degenerate point away from the $K$ point does not cause a band
opening for symmetry reasons.
```{=html}
<!-- -->
```
- Small-bandgap semiconducting: These are characterized by $n-m = 3j$
with $j$ being an integer. Here, the wave vectors of the allowed
states cross the $K$ point, but due to the slight shift of the
degenerate point a small gap will be present, the size of which is
inversely proportional to the tube diameter squared with typical
values between a few and a few tens meV
[^9]
- Semiconducting: In this case $n-m \neq 3j$. This causes a larger
bandgap, the size of which is inversely proportional to the tube
diameter: $E_{g}=k/d$ with experimental investigations suggesting a
value of $k$ of 0.7-0.8 eV/nm
[^10]
Typically the bandgap of the type 2 nanotubes is so small that they can
be considered metallic at room temperature. Based on this it can be
inferred that 1/3 of all tubes should behave metallic whereas the
remaining 2/3 should be semiconducting. However, it should be noted that
due to the inverse proportionality between the bandgap and the diameter
of the semiconducting tubes, large-diameter tubes will tend to behave
metallic at room temperature. This is especially important in regards to
large-diameter MWCNTs.
From a electrical point of view a MWCNT can be seen as a complex
structure of many parallel conductors that are only weakly interacting.
Since probing the electrical properties typically involves electrodes
contacting the outermost shell, this shell will be dominating the
transport properties [^11] In a simplistic view, this can be compared to
a large-diameter SWCNT, which will therefore typically display metallic
behavior.
## Electrical and Electromechanical Properties
Many studies have focused on SWCNTs for exploring the fundamental
properties of nanotubes. Due to their essentially 1-D nature and
intriguing electronic structure, SWCNTs exhibit a range of interesting
quantum phenomena at low temperature [^12]
The discussion here will so far, however, primarily be limited to room
temperature properties.
The conductance $~G~$ of a 1-dimensional conductor such as a SWCNT is
given by the Landauer formula [^13]
$~G=G_{0}\sum_{i}T_{i}~$,
where $~G_{0}=2e^{2}/h = (12.9 \rm k\Omega)^{-1}$;\
$~1/G_{0}~$ is the conductance quantum;\
and $~T_{i}~$ is the transmission coefficient of the contributing
channel $~i~$.
## More information on nanotubes
- Wikipedia Carbon nanotubes
- The nanotube site
- Compiled overview of properties of carbon
nanotubes
## Commercial suppliers of carbon nanotubes and related products
- Nanoledge.com nanotubes and related
products - fibers, pellets, resins and dispersions\...
- Carbon Solution, Inc. Mainly
SWCNT.
- BuckyUSA Fullerens, SWCNT, MWCNT.
- CNI
HiPco Carbon nanotubes
- Carbolex SWCNT,sub-gram quantities are
sold via sigma aldric
- Sigma-Aldrich
SWCNT
## \"Buckyball\"
!C~60~ with isosurface of ground state electron density as calculated
with
DFT{width="160"}
!An w:association football is a
model of the Buckminsterfullerene
C~60~{width="160"}
**Buckminsterfullerene** (IUPAC name
**(C~60~-I~h~)\[5,6\]fullerene**) is the smallest fullerene molecule in
which no two pentagons share an edge (which can be destabilizing, as in
pentalene). It is also the most common in
terms of natural occurrence, as it can often be found in
soot.
The structure of C~60~ is a truncated (T = 3)
icosahedron, which resembles a
soccer ball#Association_football "wikilink") of the
type made of twenty hexagons and twelve pentagons, with a carbon atom at
the vertices of each polygon and a bond along each polygon edge.
The w:van der Waals diameter of a
C~60~ molecule is about 1 nanometer (nm). The
nucleus to nucleus diameter of a C~60~ molecule is about 0.7 nm.
The C~60~ molecule has two bond lengths. The 6:6 ring bonds (between two
hexagons) can be considered \"double bonds\"
and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
Its average bond length is 1.4 angstroms.
Silicon buckyballs have been created around metal ions.
### Boron buckyball
A new type of buckyball utilizing boron atoms
instead of the usual carbon has been predicted and described by
researchers at Rice University. The B-80 structure, with each atom
forming 5 or 6 bonds, is predicted to be more stable than the C-60
buckyball.[^14] One reason for this given by the researchers is that the
B-80 is actually more like the original geodesic dome structure
popularized by Buckminster Fuller which utilizes triangles rather than
hexagons. However, this work has been subject to much criticism by
quantum chemists[^15][^16] as it was concluded that the predicted Ih
symmetric structure was vibrationally unstable and the resulting cage
undergoes a spontaneous symmetry break yielding a puckered cage with
rare Th symmetry (symmetry of a
volleyball "wikilink"))[^17]. The number of six
atom rings in this molecule is 20 and number of five member rings is 12.
There is an additional atom in the center of each six member ring,
bonded to each atom surrounding it.
### Variations of buckyballs
Another fairly common buckminsterfullerene is C~70~,[^18] but fullerenes
with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained.
In mathematical terms, the structure of a
**fullerene** is a trivalent "wikilink") convex
polyhedron with pentagonal and hexagonal
faces. In graph theory, the term
**fullerene** refers to any 3-regular,
planar graph with all faces of size 5 or 6
(including the external face). It follows from Euler\'s polyhedron
formula, \|V\|-\|E\|+\|F\| = 2,
(where \|V\|, \|E\|, \|F\| indicate the number of vertices, edges, and
faces), that there are exactly 12 pentagons in a fullerene and
\|V\|/2-10 hexagons.
+----------------+----------------+----------------+----------------+
| ![] | ![] | ![] | ![] |
| (Graph_of_20-f | (Graph_of_26-f | (Graph_of_60-f | (Graph_of_70-f |
| ullerene_w-nod | ullerene_5-bas | ullerene_w-nod | ullerene_w-nod |
| es.svg "Graph_ | e_w-nodes.svg | es.svg "Graph_ | es.svg "Graph_ |
| of_20-fulleren | "Graph_of_26-f | of_60-fulleren | of_70-fulleren |
| e_w-nodes.svg" | ullerene_5-bas | e_w-nodes.svg" | e_w-nodes.svg" |
| ){width="200"} | e_w-nodes.svg" | ){width="200"} | ){width="200"} |
| | ){width="200"} | | |
+----------------+----------------+----------------+----------------+
| 20-fullerene\ | 26-fullerene | 60-fullerene\ | 70-fullerene |
| (dodecahedral | graph | (truncated | graph |
| graph) | | icosahedral | |
| | | graph) | |
+----------------+----------------+----------------+----------------+
The smallest fullerene is the
w:dodecahedron\--the unique C~20~. There
are no fullerenes with 22 vertices.[^19] The number of fullerenes C~2n~
grows with increasing n = 12,13,14\..., roughly in proportion to n^9^.
For instance, there are 1812 non-isomorphic fullerenes C~60~. Note that
only one form of C~60~, the buckminsterfullerene alias w:truncated
icosahedron, has no pair of
adjacent pentagons (the smallest such fullerene). To further illustrate
the growth, there are 214,127,713 non-isomorphic fullerenes C~200~,
15,655,672 of which have no adjacent pentagons.
w:Trimetasphere carbon nanomaterials were
discovered by researchers at w:Virginia
Tech and licensed exclusively to w:Luna
Innovations. This class of novel
molecules comprises 80 carbon atoms (C80) forming a sphere which
encloses a complex of three metal atoms and one nitrogen atom. These
fullerenes encapsulate metals which puts them in the subset referred to
as w:metallofullerenes. Trimetaspheres
have the potential for use in diagnostics (as safe imaging agents),
therapeutics and in organic solar
cells.
# Semiconducting nanowires
Semiconducting nanowires can be made from most semiconducting materials
and with different methods, mainly variations of a chemical vapor
deposition process (CVD).
There are many different semiconducting materials, and heterosrtuctures
can be made if the lattice constants are not too incompatible.
Heterostructures made from combinations of materials such as GaAs-GaP
can be used to make barriers and guides for electrons in electrical
systems.
Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant.
!Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant. Nanowire growth is catalyzed by various nanoparticles, which
are deposited on the substrate surface, typically gold nanoparticles
with a diameter of 20-100nm.
can be used to grow III-V nanowires epitaxially on suitable crystalline substrates, sucha s III-V materials or silicon with a reasonably matching lattice constant. Nanowire growth is catalyzed by various nanoparticles, which are deposited on the substrate surface, typically gold nanoparticles with a diameter of 20-100nm. "){width="300"}
Nanowire growth is catalyzed by various nanoparticles, which are
deposited on the substrate surface, typically gold nanoparticles with a
diameter of 20-100nm.
To grow for instance GaP wires, the sample is typically annealed at 650C
in the heated reactor chamber to form an eutectic with between the gold
catalyst and the underlying substrate.
Then growth is done at a lower temperature around 500C in the presence
of the precursor gasses trimethyl gallium and phosphine. By changing the
precursor gasses during growth, nanowire heterostructures with varying
composition can be made
!SEM image of epitaxial nanowire heterostructures grown from catalytic
gold
nanoparticles{width="400"}
## Resources
- wikipedia Semiconducting nanowires
- IOFFE semiconductor physical
properties
# Nanoparticles
- Nanoparticles
- Quantum dots
## Catalytic particles
- Catalyst
- Catalysis
- Haber process
## Commercial suppliers of nanoparticles
- Reade has a wide selection of
nanoparticles
- sigma-aldrich
has dispersions of
nanoparticles
- nanophase
# Contributors and Acknowledgements
- Jakob Kjelstrup Hansen
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: qian2002
[^2]: hamada1992
[^3]: avouris2003
[^4]: dresselhaus2001
[^5]: saito1998
[^6]: dresselhaus2001
[^7]: saito1998
[^8]: hamada1992.
[^9]: zhou2000
[^10]: wildoer1998,odom1998
[^11]: frank1998
[^12]: nygard1999,dresselhaus2001
[^13]: datta1995
[^14]: *Bucky\'s brother \-- The boron buckyball makes its début* Jade
Boyd April **2007**
eurekalert.orgLink
[^15]: *The boron buckyball has an unexpected Th symmetry* G. Gopakumar,
Nguyen, M. T., Ceulemans, Arnout, Chem. Phys. lett. 450, 175,
2008.1&_cdi=5231&_sort=d&_docanchor=&view=c&_ct=53&_acct=C000024498&_version=1&_urlVersion=0&_userid=4466739&md5=2e8f3b9eacbc9a4b9a3dbd42fdbf2826)
[^16]: \"Stuffing improves the stability of fullerenelike boron
clusters\" Prasad, DLVK; Jemmis, E. D.; Phys. Rev. Lett. 100,
165504,
2008.2
[^17]:
[^18]: Buckminsterfullerene: Molecule of the
Month
[^19]: Goldberg Variations Challenge: Juris Meija, Anal. Bioanal. Chem.
2006 (385)
6-7
|
# Nanotechnology/Semiconducting Nanostructures#Nanoparticles
Navigate
---------------------------------------------------------------------------------------------
\<\< Prev: Overview of Production methods
\>\< Main: Nanotechnology
\>\> Next: Metallic Nanostructures
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanotubes
Certain compounds are capable of forming nanotubes where the tube
consists of round shell of a single layer of atoms in a cylindrical
lattice. Carbon nanotubes is the most famous example, but also other
materials can form nanotubes such as Boron-nitride, Molybdenum sulfide
and others.
Nanotubes can also be made by etching the core out of an shell
structured rod, but such tubes will normally contain many atomic layers
in the wall and have crystal facets on the sides.
# Carbon Nanotubes
Carbon nanotubes are fascinating nanostructures. A sheet of graphene as
in common graphite, but rolled up in small tubes rather than planar
sheets.
Carbon nanotubes have unique mechanical properties such as high
strength, high stiffness, and low density [^1] and also interesting
electronic properties. A single-walled carbon nanotube can be either
metallic or semiconducting depending on the atomic arrangement [^2].
This section is a short introduction to carbon nanotubes. For a broader
overview the reader is referred to one of the numerous review articles
or books on carbon nanotubes
[^3] [^4] [^5]
## Geometric Structure
The simplest type of carbon nanotube consists of just one layer of
graphene rolled up in the form of a seamless cylinder, known as a
single-walled carbon nanotube (SWCNT) with a typical diameter of just a
few nanometers. Larger diameter nanotube structures are nanotube ropes,
consisting of many individual, parallel nanotubes closed-packed into a
hexagonal lattice, and multi-walled carbon nanotubes (MWCNTs) consisting
of several concentric cylinders nested within each other.
! Multiwall carbon nanotube (MWCNT) sample made by a CVD process using
iron containing catalystic particles. The MWCNT are adhering in
mats. sample made by a CVD process using iron containing catalystic particles. The MWCNT are adhering in mats."){width="300"}
### Single walled Carbon Nanotube
The basic configuration is thus the SWCNT. Its structure is most easily
illustrated as a cylindrical tube conceptually formed by the wrapping of
a single graphene sheet. The hexagonal structure of the 2-dimensional
graphene sheet is due to the $sp^{2}$ hybridization of the carbon atoms,
which causes three directional, in-plane $\sigma$ bonds separated by an
angle of 120 degrees.
The nanotube can be described by a chiral vector $C$ that can be
expressed in terms of the graphene unit vectors $\textbf{a}_{1}$ and
$\textbf{a}_{2}$ as $\textbf{C}=n\textbf{a}_{1}+m\textbf{a}_{2}$ with
the set of integers $(n,m)$ uniquely identifying the nanotube. This
chiral vector or \'roll-up\' vector describes the nanotube circumference
by connecting two crystallographically equivalent positions i.e. the
tube is formed by superimposing the two ends of $\textbf{C}$.
Based on the chiral angle SWCNTs are defined as zig-zag tubes
($\theta =0 deg \leftrightarrow m=0$), armchair tubes
($\theta =30 deg \leftrightarrow n=m$), or chiral tubes
($0 deg < \theta < 30 deg$).
### Multiwalled Carbon Nanotubes
MWCNTs are composed of a number of SWCNTs in a coaxial geometry. Each
nested shell has a diameter of
$d=\sqrt{3}a_{C-C}(m^{2}+n^{2}+mn)^{1/2}/\pi$ where $a_{C-C}$ is the
length of the carbon-carbon bond which is 1.42 Å. The difference in
diameters of the individual shell means that their chiralities are
different, and adjacent shell are therefore in general non-commensurate,
which causes only a weak intershell interaction.
The intershell spacing in MWCNTs is $\sim$ 0.34 nm - quite close to the
interlayer spacing in turbostratic graphite [^6]
## Electronic Structure
The electronic structure of a SWCNT is most easily described by again
considering a single graphene sheet. The 2-D, hexagonal-lattice graphene
sheet has a 2-D reciprocal space with a hexagonal Brillouin zone (BZ).
The $\sigma$ bonds are mainly responsible for the mechanical properties,
while the electronic properties are mainly determined by the $\pi$
bands. By a tight-binding approach the band structure of these $\pi$
bands can be calculated [^7]
Graphene is a zero-gap semiconductor with an occupied $\pi$ band and an
unoccupied $\pi^{*}$ band meeting at the Fermi level at six $K$ points
in the BZ, thus it behaves metallic, a so-called semimetal.
Upon forming the tube by conceptually wrapping the graphene sheet, a
periodic boundary condition is imposed that causes only certain
electronic states of those of the planar graphene sheet to be allowed.
These states are determined by the tube\'s geometric structure, i.e. by
the indices $(n,m)$ of the chiral vector. The wave vectors of the
allowed states fall on certain lines in the graphene BZ.
Based on this scheme it is possible to estimate whether a particular
tube will be metallic or semiconducting. When the allowed states include
the $K$ point, the system will to a first approximation behave metallic.
However, in the points where the $\pi$ and the $\pi^{*}$ bands meet but
are shifted slightly away from the $K$ point due to curvature effects,
which causes a slight band opening in some cases [^8]
This leads to a classification scheme that has three types of nanotubes:
- Metallic: These are the armchair tubes where the small shift of the
degenerate point away from the $K$ point does not cause a band
opening for symmetry reasons.
```{=html}
<!-- -->
```
- Small-bandgap semiconducting: These are characterized by $n-m = 3j$
with $j$ being an integer. Here, the wave vectors of the allowed
states cross the $K$ point, but due to the slight shift of the
degenerate point a small gap will be present, the size of which is
inversely proportional to the tube diameter squared with typical
values between a few and a few tens meV
[^9]
- Semiconducting: In this case $n-m \neq 3j$. This causes a larger
bandgap, the size of which is inversely proportional to the tube
diameter: $E_{g}=k/d$ with experimental investigations suggesting a
value of $k$ of 0.7-0.8 eV/nm
[^10]
Typically the bandgap of the type 2 nanotubes is so small that they can
be considered metallic at room temperature. Based on this it can be
inferred that 1/3 of all tubes should behave metallic whereas the
remaining 2/3 should be semiconducting. However, it should be noted that
due to the inverse proportionality between the bandgap and the diameter
of the semiconducting tubes, large-diameter tubes will tend to behave
metallic at room temperature. This is especially important in regards to
large-diameter MWCNTs.
From a electrical point of view a MWCNT can be seen as a complex
structure of many parallel conductors that are only weakly interacting.
Since probing the electrical properties typically involves electrodes
contacting the outermost shell, this shell will be dominating the
transport properties [^11] In a simplistic view, this can be compared to
a large-diameter SWCNT, which will therefore typically display metallic
behavior.
## Electrical and Electromechanical Properties
Many studies have focused on SWCNTs for exploring the fundamental
properties of nanotubes. Due to their essentially 1-D nature and
intriguing electronic structure, SWCNTs exhibit a range of interesting
quantum phenomena at low temperature [^12]
The discussion here will so far, however, primarily be limited to room
temperature properties.
The conductance $~G~$ of a 1-dimensional conductor such as a SWCNT is
given by the Landauer formula [^13]
$~G=G_{0}\sum_{i}T_{i}~$,
where $~G_{0}=2e^{2}/h = (12.9 \rm k\Omega)^{-1}$;\
$~1/G_{0}~$ is the conductance quantum;\
and $~T_{i}~$ is the transmission coefficient of the contributing
channel $~i~$.
## More information on nanotubes
- Wikipedia Carbon nanotubes
- The nanotube site
- Compiled overview of properties of carbon
nanotubes
## Commercial suppliers of carbon nanotubes and related products
- Nanoledge.com nanotubes and related
products - fibers, pellets, resins and dispersions\...
- Carbon Solution, Inc. Mainly
SWCNT.
- BuckyUSA Fullerens, SWCNT, MWCNT.
- CNI
HiPco Carbon nanotubes
- Carbolex SWCNT,sub-gram quantities are
sold via sigma aldric
- Sigma-Aldrich
SWCNT
## \"Buckyball\"
!C~60~ with isosurface of ground state electron density as calculated
with
DFT{width="160"}
!An w:association football is a
model of the Buckminsterfullerene
C~60~{width="160"}
**Buckminsterfullerene** (IUPAC name
**(C~60~-I~h~)\[5,6\]fullerene**) is the smallest fullerene molecule in
which no two pentagons share an edge (which can be destabilizing, as in
pentalene). It is also the most common in
terms of natural occurrence, as it can often be found in
soot.
The structure of C~60~ is a truncated (T = 3)
icosahedron, which resembles a
soccer ball#Association_football "wikilink") of the
type made of twenty hexagons and twelve pentagons, with a carbon atom at
the vertices of each polygon and a bond along each polygon edge.
The w:van der Waals diameter of a
C~60~ molecule is about 1 nanometer (nm). The
nucleus to nucleus diameter of a C~60~ molecule is about 0.7 nm.
The C~60~ molecule has two bond lengths. The 6:6 ring bonds (between two
hexagons) can be considered \"double bonds\"
and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
Its average bond length is 1.4 angstroms.
Silicon buckyballs have been created around metal ions.
### Boron buckyball
A new type of buckyball utilizing boron atoms
instead of the usual carbon has been predicted and described by
researchers at Rice University. The B-80 structure, with each atom
forming 5 or 6 bonds, is predicted to be more stable than the C-60
buckyball.[^14] One reason for this given by the researchers is that the
B-80 is actually more like the original geodesic dome structure
popularized by Buckminster Fuller which utilizes triangles rather than
hexagons. However, this work has been subject to much criticism by
quantum chemists[^15][^16] as it was concluded that the predicted Ih
symmetric structure was vibrationally unstable and the resulting cage
undergoes a spontaneous symmetry break yielding a puckered cage with
rare Th symmetry (symmetry of a
volleyball "wikilink"))[^17]. The number of six
atom rings in this molecule is 20 and number of five member rings is 12.
There is an additional atom in the center of each six member ring,
bonded to each atom surrounding it.
### Variations of buckyballs
Another fairly common buckminsterfullerene is C~70~,[^18] but fullerenes
with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained.
In mathematical terms, the structure of a
**fullerene** is a trivalent "wikilink") convex
polyhedron with pentagonal and hexagonal
faces. In graph theory, the term
**fullerene** refers to any 3-regular,
planar graph with all faces of size 5 or 6
(including the external face). It follows from Euler\'s polyhedron
formula, \|V\|-\|E\|+\|F\| = 2,
(where \|V\|, \|E\|, \|F\| indicate the number of vertices, edges, and
faces), that there are exactly 12 pentagons in a fullerene and
\|V\|/2-10 hexagons.
+----------------+----------------+----------------+----------------+
| ![] | ![] | ![] | ![] |
| (Graph_of_20-f | (Graph_of_26-f | (Graph_of_60-f | (Graph_of_70-f |
| ullerene_w-nod | ullerene_5-bas | ullerene_w-nod | ullerene_w-nod |
| es.svg "Graph_ | e_w-nodes.svg | es.svg "Graph_ | es.svg "Graph_ |
| of_20-fulleren | "Graph_of_26-f | of_60-fulleren | of_70-fulleren |
| e_w-nodes.svg" | ullerene_5-bas | e_w-nodes.svg" | e_w-nodes.svg" |
| ){width="200"} | e_w-nodes.svg" | ){width="200"} | ){width="200"} |
| | ){width="200"} | | |
+----------------+----------------+----------------+----------------+
| 20-fullerene\ | 26-fullerene | 60-fullerene\ | 70-fullerene |
| (dodecahedral | graph | (truncated | graph |
| graph) | | icosahedral | |
| | | graph) | |
+----------------+----------------+----------------+----------------+
The smallest fullerene is the
w:dodecahedron\--the unique C~20~. There
are no fullerenes with 22 vertices.[^19] The number of fullerenes C~2n~
grows with increasing n = 12,13,14\..., roughly in proportion to n^9^.
For instance, there are 1812 non-isomorphic fullerenes C~60~. Note that
only one form of C~60~, the buckminsterfullerene alias w:truncated
icosahedron, has no pair of
adjacent pentagons (the smallest such fullerene). To further illustrate
the growth, there are 214,127,713 non-isomorphic fullerenes C~200~,
15,655,672 of which have no adjacent pentagons.
w:Trimetasphere carbon nanomaterials were
discovered by researchers at w:Virginia
Tech and licensed exclusively to w:Luna
Innovations. This class of novel
molecules comprises 80 carbon atoms (C80) forming a sphere which
encloses a complex of three metal atoms and one nitrogen atom. These
fullerenes encapsulate metals which puts them in the subset referred to
as w:metallofullerenes. Trimetaspheres
have the potential for use in diagnostics (as safe imaging agents),
therapeutics and in organic solar
cells.
# Semiconducting nanowires
Semiconducting nanowires can be made from most semiconducting materials
and with different methods, mainly variations of a chemical vapor
deposition process (CVD).
There are many different semiconducting materials, and heterosrtuctures
can be made if the lattice constants are not too incompatible.
Heterostructures made from combinations of materials such as GaAs-GaP
can be used to make barriers and guides for electrons in electrical
systems.
Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant.
!Low pressure metal organic vapor phase epitaxy (MOVPE) can be used to
grow III-V nanowires epitaxially on suitable crystalline substrates,
sucha s III-V materials or silicon with a reasonably matching lattice
constant. Nanowire growth is catalyzed by various nanoparticles, which
are deposited on the substrate surface, typically gold nanoparticles
with a diameter of 20-100nm.
can be used to grow III-V nanowires epitaxially on suitable crystalline substrates, sucha s III-V materials or silicon with a reasonably matching lattice constant. Nanowire growth is catalyzed by various nanoparticles, which are deposited on the substrate surface, typically gold nanoparticles with a diameter of 20-100nm. "){width="300"}
Nanowire growth is catalyzed by various nanoparticles, which are
deposited on the substrate surface, typically gold nanoparticles with a
diameter of 20-100nm.
To grow for instance GaP wires, the sample is typically annealed at 650C
in the heated reactor chamber to form an eutectic with between the gold
catalyst and the underlying substrate.
Then growth is done at a lower temperature around 500C in the presence
of the precursor gasses trimethyl gallium and phosphine. By changing the
precursor gasses during growth, nanowire heterostructures with varying
composition can be made
!SEM image of epitaxial nanowire heterostructures grown from catalytic
gold
nanoparticles{width="400"}
## Resources
- wikipedia Semiconducting nanowires
- IOFFE semiconductor physical
properties
# Nanoparticles
- Nanoparticles
- Quantum dots
## Catalytic particles
- Catalyst
- Catalysis
- Haber process
## Commercial suppliers of nanoparticles
- Reade has a wide selection of
nanoparticles
- sigma-aldrich
has dispersions of
nanoparticles
- nanophase
# Contributors and Acknowledgements
- Jakob Kjelstrup Hansen
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: qian2002
[^2]: hamada1992
[^3]: avouris2003
[^4]: dresselhaus2001
[^5]: saito1998
[^6]: dresselhaus2001
[^7]: saito1998
[^8]: hamada1992.
[^9]: zhou2000
[^10]: wildoer1998,odom1998
[^11]: frank1998
[^12]: nygard1999,dresselhaus2001
[^13]: datta1995
[^14]: *Bucky\'s brother \-- The boron buckyball makes its début* Jade
Boyd April **2007**
eurekalert.orgLink
[^15]: *The boron buckyball has an unexpected Th symmetry* G. Gopakumar,
Nguyen, M. T., Ceulemans, Arnout, Chem. Phys. lett. 450, 175,
2008.1&_cdi=5231&_sort=d&_docanchor=&view=c&_ct=53&_acct=C000024498&_version=1&_urlVersion=0&_userid=4466739&md5=2e8f3b9eacbc9a4b9a3dbd42fdbf2826)
[^16]: \"Stuffing improves the stability of fullerenelike boron
clusters\" Prasad, DLVK; Jemmis, E. D.; Phys. Rev. Lett. 100,
165504,
2008.2
[^17]:
[^18]: Buckminsterfullerene: Molecule of the
Month
[^19]: Goldberg Variations Challenge: Juris Meija, Anal. Bioanal. Chem.
2006 (385)
6-7
|
# Nanotechnology/Nanomanipulation#AFM manipulation
Navigate
--------------------------------------------------------------------------
\<\< Prev: Lithography
\>\< Main: Nanotechnology
\>\> Next: Nano-bio Introduction
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanomanipulation
- Wikipedia Nanorobotics
- Nanorobotics
introduction
- Video clips of Nanomanipulation
on YouTube
- 1
Pick and Place of NW in SEM on YouTube
- Video of the manipulation of a nanowire for TEM observation on
YouTube
!A slip stick actuator that provides coarse and fine positionoing
modes. Coarse positioning provides long range but low precision, while
fine positioning provides high precision and short range. The slip stick
principle: Slow actuation of the piezo element leads to fine
positioning. A combination of rapid contraction and slow extension can
make the actuator move in coarse steps Δx because the force on the base
becomes larger than the static friction force between the base and base
plate. Reversing the direction is done by using slow contractions
instead.{width="300"}
# AFM manipulation
With AFM nanostructures such as nanotubes and nanowires lying on
surfaces can be manipulated to make electrical circuits and measure
their mechanical properties and the forces involved in manipulating
them.
# STM manipulation
Using an STM individual atoms can be manipulated on surface this was
first demonstrated by Eigler et al. Here Xe atoms were manipulated on Ni
to spell out IBM. This was then extended by Crommie et al., where Fe
atoms were moved to create quantum corals. Here the electron standing
waves created inside the corral are imaged by the STM tip. The probably
demonstrates the highest resolution nanomanipulation.
# In-situ SEM manipulation
To monitor a three-dimensional nanomanipulation process, in-situ SEM or
TEM manipulation seems preferable. AFM (or STM) does have the resolution
to image nanoscale objects, even down to the sub-atomic scale, but the
imaging frame rate is usually slow compared to SEM or TEM and the
structures will normally have to be planar. SEM offers the possibility
of high frame rates; almost nanometer resolution imaging of
three-dimensional objects; imaging over a large range of working
distances; and ample surrounding volume in the sample chamber for the
manipulation setup. TEM has a much more limited space available for the
sample and manipulation systems but can on the other hand provide atomic
resolution. For detailed studies of the nanowires\' structure, TEM is a
useful tool, but for the assembly of nanoscale components of a well
defined structure, such as batch fabricated nanowires and nanotubes, the
SEM resolution should be sufficient to complete the assembly task.
As the STM and AFM techniques opened up completely new fields of science
by allowing the investigator to interact with the sample rather than
just observe, development of nanomanipulation tools for SEM and TEM
could probably have a similar effect for three-dimensional manipulation.
Recently, commercial systems for such tasks have become available such
as the F100 Nanomanipulator System from Zyvex in October 2003. Several
research groups have also pursued developing such systems.
To date the tools used for in-situ SEM nanomanipulation have almost
exclusively been individual tips (AFM cantilever tips or etched tungsten
tips), sometimes tips used together with electron beam deposition have
been used to create nanowire devices. Despite the availability of
commercial microfabricated grippers in the last couple of years, little
has been reported on the use of such devices for handling
nanostructures. Some electrical measurements and manipulation tasks have
been performed in ambient conditions with carbon nanotube nanotweezers.
! A microfabricated electrostatic gripper inside a scanning electron
microscope where it has picked up some silicon
nanowires.{width="300"}
### Companies selling hardware
- Omniprobe
- Zyvex
- Imina Technologies
## The Optimal SEM Image for Nanomanipulation
As the typical SEM image is created from the secondary electrons
collected from the sample, compromises must always be made to obtain the
optimal imaging conditions regarding resolution and contrast. The
contrast in a SEM SE image depends on the variations in SE yield from
the different surface regions in the image and the signal to noise
level. The resolution depends on the beam diameter and is at least some
nm larger due to the SE range.
The optimal solution is always to use as good an emitter as possible
(high ß\_{e} in Eq.[^1]). This means using FEG sources. Working at short
r\_{wd} gives a narrow beam (Eq.[^2]), but will usually shield the
standard ET detectors from attracting sufficient secondary electrons.
Nanomanipulation often requires working with high resolution between two
large manipulator units which further limits the efficiency of signal
detection.
The manipulation equipment must be designed to make the end-effector and
samples meet at short r\_{wd}, and without obstructing the electron path
towards the detector. A short r\_{wd} also gives a short depth of focus,
which can be a help during nanomanipulation because it makes it possible
to judge the working distance to various objects by focussing on them.
The operator can use this to get an impression of the height of the
objects in the setup. Generally, for nanomanipulation, the above
considerations indicate an inlens detector often can be advantageous.
Reducing the beam current to narrow the electron beam necessarily limits
the number of detected electrons and make the signal-to-noise ratio low,
unless one makes very slow scans to increase the number of counts
`<footnote>`{=html}The signal to noise ratio S/N for Poisson distributed
count measurements n is S/N=vn and high counts are necessary to reduce
noise in the images. `</footnote>`{=html}.
When used for in-situ nanomanipulation one needs a fast scan rate to
follow the moving tools (preferably at rates approaching live video) and
this requires high beam currents. The acceleration voltage is also
important, and too high PE energy can make the sample transparent (such
as the carbon coating in Fig.[^3] b) while low energy usually make the
image susceptible to drift due to charging and similar effects.
# In-situ TEM manipulation
TEM offers atomic 3D resolution but the extreme requirements on
stability combined with very limited sample space makes the construction
of in-situ TEM manipulation equipment quite a task. With such systems,
people have observed freely suspended wires of individual atoms between
a gold tip and a gold surface; carbon nanotubes working as nanoscale
pipettes for metals and a wealth of other exotic phenomena.
Companies selling hardware
- Nanofactory
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How to
contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: eq SEM beam diameter
[^2]: eq SEM beam diameter
[^3]: fig INTRO 3 e depth
|
# Nanotechnology/Nanomanipulation#STM manipulation
Navigate
--------------------------------------------------------------------------
\<\< Prev: Lithography
\>\< Main: Nanotechnology
\>\> Next: Nano-bio Introduction
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanomanipulation
- Wikipedia Nanorobotics
- Nanorobotics
introduction
- Video clips of Nanomanipulation
on YouTube
- 1
Pick and Place of NW in SEM on YouTube
- Video of the manipulation of a nanowire for TEM observation on
YouTube
!A slip stick actuator that provides coarse and fine positionoing
modes. Coarse positioning provides long range but low precision, while
fine positioning provides high precision and short range. The slip stick
principle: Slow actuation of the piezo element leads to fine
positioning. A combination of rapid contraction and slow extension can
make the actuator move in coarse steps Δx because the force on the base
becomes larger than the static friction force between the base and base
plate. Reversing the direction is done by using slow contractions
instead.{width="300"}
# AFM manipulation
With AFM nanostructures such as nanotubes and nanowires lying on
surfaces can be manipulated to make electrical circuits and measure
their mechanical properties and the forces involved in manipulating
them.
# STM manipulation
Using an STM individual atoms can be manipulated on surface this was
first demonstrated by Eigler et al. Here Xe atoms were manipulated on Ni
to spell out IBM. This was then extended by Crommie et al., where Fe
atoms were moved to create quantum corals. Here the electron standing
waves created inside the corral are imaged by the STM tip. The probably
demonstrates the highest resolution nanomanipulation.
# In-situ SEM manipulation
To monitor a three-dimensional nanomanipulation process, in-situ SEM or
TEM manipulation seems preferable. AFM (or STM) does have the resolution
to image nanoscale objects, even down to the sub-atomic scale, but the
imaging frame rate is usually slow compared to SEM or TEM and the
structures will normally have to be planar. SEM offers the possibility
of high frame rates; almost nanometer resolution imaging of
three-dimensional objects; imaging over a large range of working
distances; and ample surrounding volume in the sample chamber for the
manipulation setup. TEM has a much more limited space available for the
sample and manipulation systems but can on the other hand provide atomic
resolution. For detailed studies of the nanowires\' structure, TEM is a
useful tool, but for the assembly of nanoscale components of a well
defined structure, such as batch fabricated nanowires and nanotubes, the
SEM resolution should be sufficient to complete the assembly task.
As the STM and AFM techniques opened up completely new fields of science
by allowing the investigator to interact with the sample rather than
just observe, development of nanomanipulation tools for SEM and TEM
could probably have a similar effect for three-dimensional manipulation.
Recently, commercial systems for such tasks have become available such
as the F100 Nanomanipulator System from Zyvex in October 2003. Several
research groups have also pursued developing such systems.
To date the tools used for in-situ SEM nanomanipulation have almost
exclusively been individual tips (AFM cantilever tips or etched tungsten
tips), sometimes tips used together with electron beam deposition have
been used to create nanowire devices. Despite the availability of
commercial microfabricated grippers in the last couple of years, little
has been reported on the use of such devices for handling
nanostructures. Some electrical measurements and manipulation tasks have
been performed in ambient conditions with carbon nanotube nanotweezers.
! A microfabricated electrostatic gripper inside a scanning electron
microscope where it has picked up some silicon
nanowires.{width="300"}
### Companies selling hardware
- Omniprobe
- Zyvex
- Imina Technologies
## The Optimal SEM Image for Nanomanipulation
As the typical SEM image is created from the secondary electrons
collected from the sample, compromises must always be made to obtain the
optimal imaging conditions regarding resolution and contrast. The
contrast in a SEM SE image depends on the variations in SE yield from
the different surface regions in the image and the signal to noise
level. The resolution depends on the beam diameter and is at least some
nm larger due to the SE range.
The optimal solution is always to use as good an emitter as possible
(high ß\_{e} in Eq.[^1]). This means using FEG sources. Working at short
r\_{wd} gives a narrow beam (Eq.[^2]), but will usually shield the
standard ET detectors from attracting sufficient secondary electrons.
Nanomanipulation often requires working with high resolution between two
large manipulator units which further limits the efficiency of signal
detection.
The manipulation equipment must be designed to make the end-effector and
samples meet at short r\_{wd}, and without obstructing the electron path
towards the detector. A short r\_{wd} also gives a short depth of focus,
which can be a help during nanomanipulation because it makes it possible
to judge the working distance to various objects by focussing on them.
The operator can use this to get an impression of the height of the
objects in the setup. Generally, for nanomanipulation, the above
considerations indicate an inlens detector often can be advantageous.
Reducing the beam current to narrow the electron beam necessarily limits
the number of detected electrons and make the signal-to-noise ratio low,
unless one makes very slow scans to increase the number of counts
`<footnote>`{=html}The signal to noise ratio S/N for Poisson distributed
count measurements n is S/N=vn and high counts are necessary to reduce
noise in the images. `</footnote>`{=html}.
When used for in-situ nanomanipulation one needs a fast scan rate to
follow the moving tools (preferably at rates approaching live video) and
this requires high beam currents. The acceleration voltage is also
important, and too high PE energy can make the sample transparent (such
as the carbon coating in Fig.[^3] b) while low energy usually make the
image susceptible to drift due to charging and similar effects.
# In-situ TEM manipulation
TEM offers atomic 3D resolution but the extreme requirements on
stability combined with very limited sample space makes the construction
of in-situ TEM manipulation equipment quite a task. With such systems,
people have observed freely suspended wires of individual atoms between
a gold tip and a gold surface; carbon nanotubes working as nanoscale
pipettes for metals and a wealth of other exotic phenomena.
Companies selling hardware
- Nanofactory
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How to
contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: eq SEM beam diameter
[^2]: eq SEM beam diameter
[^3]: fig INTRO 3 e depth
|
# Nanotechnology/Nanomanipulation#In-situ SEM manipulation
Navigate
--------------------------------------------------------------------------
\<\< Prev: Lithography
\>\< Main: Nanotechnology
\>\> Next: Nano-bio Introduction
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanomanipulation
- Wikipedia Nanorobotics
- Nanorobotics
introduction
- Video clips of Nanomanipulation
on YouTube
- 1
Pick and Place of NW in SEM on YouTube
- Video of the manipulation of a nanowire for TEM observation on
YouTube
!A slip stick actuator that provides coarse and fine positionoing
modes. Coarse positioning provides long range but low precision, while
fine positioning provides high precision and short range. The slip stick
principle: Slow actuation of the piezo element leads to fine
positioning. A combination of rapid contraction and slow extension can
make the actuator move in coarse steps Δx because the force on the base
becomes larger than the static friction force between the base and base
plate. Reversing the direction is done by using slow contractions
instead.{width="300"}
# AFM manipulation
With AFM nanostructures such as nanotubes and nanowires lying on
surfaces can be manipulated to make electrical circuits and measure
their mechanical properties and the forces involved in manipulating
them.
# STM manipulation
Using an STM individual atoms can be manipulated on surface this was
first demonstrated by Eigler et al. Here Xe atoms were manipulated on Ni
to spell out IBM. This was then extended by Crommie et al., where Fe
atoms were moved to create quantum corals. Here the electron standing
waves created inside the corral are imaged by the STM tip. The probably
demonstrates the highest resolution nanomanipulation.
# In-situ SEM manipulation
To monitor a three-dimensional nanomanipulation process, in-situ SEM or
TEM manipulation seems preferable. AFM (or STM) does have the resolution
to image nanoscale objects, even down to the sub-atomic scale, but the
imaging frame rate is usually slow compared to SEM or TEM and the
structures will normally have to be planar. SEM offers the possibility
of high frame rates; almost nanometer resolution imaging of
three-dimensional objects; imaging over a large range of working
distances; and ample surrounding volume in the sample chamber for the
manipulation setup. TEM has a much more limited space available for the
sample and manipulation systems but can on the other hand provide atomic
resolution. For detailed studies of the nanowires\' structure, TEM is a
useful tool, but for the assembly of nanoscale components of a well
defined structure, such as batch fabricated nanowires and nanotubes, the
SEM resolution should be sufficient to complete the assembly task.
As the STM and AFM techniques opened up completely new fields of science
by allowing the investigator to interact with the sample rather than
just observe, development of nanomanipulation tools for SEM and TEM
could probably have a similar effect for three-dimensional manipulation.
Recently, commercial systems for such tasks have become available such
as the F100 Nanomanipulator System from Zyvex in October 2003. Several
research groups have also pursued developing such systems.
To date the tools used for in-situ SEM nanomanipulation have almost
exclusively been individual tips (AFM cantilever tips or etched tungsten
tips), sometimes tips used together with electron beam deposition have
been used to create nanowire devices. Despite the availability of
commercial microfabricated grippers in the last couple of years, little
has been reported on the use of such devices for handling
nanostructures. Some electrical measurements and manipulation tasks have
been performed in ambient conditions with carbon nanotube nanotweezers.
! A microfabricated electrostatic gripper inside a scanning electron
microscope where it has picked up some silicon
nanowires.{width="300"}
### Companies selling hardware
- Omniprobe
- Zyvex
- Imina Technologies
## The Optimal SEM Image for Nanomanipulation
As the typical SEM image is created from the secondary electrons
collected from the sample, compromises must always be made to obtain the
optimal imaging conditions regarding resolution and contrast. The
contrast in a SEM SE image depends on the variations in SE yield from
the different surface regions in the image and the signal to noise
level. The resolution depends on the beam diameter and is at least some
nm larger due to the SE range.
The optimal solution is always to use as good an emitter as possible
(high ß\_{e} in Eq.[^1]). This means using FEG sources. Working at short
r\_{wd} gives a narrow beam (Eq.[^2]), but will usually shield the
standard ET detectors from attracting sufficient secondary electrons.
Nanomanipulation often requires working with high resolution between two
large manipulator units which further limits the efficiency of signal
detection.
The manipulation equipment must be designed to make the end-effector and
samples meet at short r\_{wd}, and without obstructing the electron path
towards the detector. A short r\_{wd} also gives a short depth of focus,
which can be a help during nanomanipulation because it makes it possible
to judge the working distance to various objects by focussing on them.
The operator can use this to get an impression of the height of the
objects in the setup. Generally, for nanomanipulation, the above
considerations indicate an inlens detector often can be advantageous.
Reducing the beam current to narrow the electron beam necessarily limits
the number of detected electrons and make the signal-to-noise ratio low,
unless one makes very slow scans to increase the number of counts
`<footnote>`{=html}The signal to noise ratio S/N for Poisson distributed
count measurements n is S/N=vn and high counts are necessary to reduce
noise in the images. `</footnote>`{=html}.
When used for in-situ nanomanipulation one needs a fast scan rate to
follow the moving tools (preferably at rates approaching live video) and
this requires high beam currents. The acceleration voltage is also
important, and too high PE energy can make the sample transparent (such
as the carbon coating in Fig.[^3] b) while low energy usually make the
image susceptible to drift due to charging and similar effects.
# In-situ TEM manipulation
TEM offers atomic 3D resolution but the extreme requirements on
stability combined with very limited sample space makes the construction
of in-situ TEM manipulation equipment quite a task. With such systems,
people have observed freely suspended wires of individual atoms between
a gold tip and a gold surface; carbon nanotubes working as nanoscale
pipettes for metals and a wealth of other exotic phenomena.
Companies selling hardware
- Nanofactory
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How to
contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: eq SEM beam diameter
[^2]: eq SEM beam diameter
[^3]: fig INTRO 3 e depth
|
# Nanotechnology/Nanomanipulation#In-situ TEM manipulation
Navigate
--------------------------------------------------------------------------
\<\< Prev: Lithography
\>\< Main: Nanotechnology
\>\> Next: Nano-bio Introduction
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanomanipulation
- Wikipedia Nanorobotics
- Nanorobotics
introduction
- Video clips of Nanomanipulation
on YouTube
- 1
Pick and Place of NW in SEM on YouTube
- Video of the manipulation of a nanowire for TEM observation on
YouTube
!A slip stick actuator that provides coarse and fine positionoing
modes. Coarse positioning provides long range but low precision, while
fine positioning provides high precision and short range. The slip stick
principle: Slow actuation of the piezo element leads to fine
positioning. A combination of rapid contraction and slow extension can
make the actuator move in coarse steps Δx because the force on the base
becomes larger than the static friction force between the base and base
plate. Reversing the direction is done by using slow contractions
instead.{width="300"}
# AFM manipulation
With AFM nanostructures such as nanotubes and nanowires lying on
surfaces can be manipulated to make electrical circuits and measure
their mechanical properties and the forces involved in manipulating
them.
# STM manipulation
Using an STM individual atoms can be manipulated on surface this was
first demonstrated by Eigler et al. Here Xe atoms were manipulated on Ni
to spell out IBM. This was then extended by Crommie et al., where Fe
atoms were moved to create quantum corals. Here the electron standing
waves created inside the corral are imaged by the STM tip. The probably
demonstrates the highest resolution nanomanipulation.
# In-situ SEM manipulation
To monitor a three-dimensional nanomanipulation process, in-situ SEM or
TEM manipulation seems preferable. AFM (or STM) does have the resolution
to image nanoscale objects, even down to the sub-atomic scale, but the
imaging frame rate is usually slow compared to SEM or TEM and the
structures will normally have to be planar. SEM offers the possibility
of high frame rates; almost nanometer resolution imaging of
three-dimensional objects; imaging over a large range of working
distances; and ample surrounding volume in the sample chamber for the
manipulation setup. TEM has a much more limited space available for the
sample and manipulation systems but can on the other hand provide atomic
resolution. For detailed studies of the nanowires\' structure, TEM is a
useful tool, but for the assembly of nanoscale components of a well
defined structure, such as batch fabricated nanowires and nanotubes, the
SEM resolution should be sufficient to complete the assembly task.
As the STM and AFM techniques opened up completely new fields of science
by allowing the investigator to interact with the sample rather than
just observe, development of nanomanipulation tools for SEM and TEM
could probably have a similar effect for three-dimensional manipulation.
Recently, commercial systems for such tasks have become available such
as the F100 Nanomanipulator System from Zyvex in October 2003. Several
research groups have also pursued developing such systems.
To date the tools used for in-situ SEM nanomanipulation have almost
exclusively been individual tips (AFM cantilever tips or etched tungsten
tips), sometimes tips used together with electron beam deposition have
been used to create nanowire devices. Despite the availability of
commercial microfabricated grippers in the last couple of years, little
has been reported on the use of such devices for handling
nanostructures. Some electrical measurements and manipulation tasks have
been performed in ambient conditions with carbon nanotube nanotweezers.
! A microfabricated electrostatic gripper inside a scanning electron
microscope where it has picked up some silicon
nanowires.{width="300"}
### Companies selling hardware
- Omniprobe
- Zyvex
- Imina Technologies
## The Optimal SEM Image for Nanomanipulation
As the typical SEM image is created from the secondary electrons
collected from the sample, compromises must always be made to obtain the
optimal imaging conditions regarding resolution and contrast. The
contrast in a SEM SE image depends on the variations in SE yield from
the different surface regions in the image and the signal to noise
level. The resolution depends on the beam diameter and is at least some
nm larger due to the SE range.
The optimal solution is always to use as good an emitter as possible
(high ß\_{e} in Eq.[^1]). This means using FEG sources. Working at short
r\_{wd} gives a narrow beam (Eq.[^2]), but will usually shield the
standard ET detectors from attracting sufficient secondary electrons.
Nanomanipulation often requires working with high resolution between two
large manipulator units which further limits the efficiency of signal
detection.
The manipulation equipment must be designed to make the end-effector and
samples meet at short r\_{wd}, and without obstructing the electron path
towards the detector. A short r\_{wd} also gives a short depth of focus,
which can be a help during nanomanipulation because it makes it possible
to judge the working distance to various objects by focussing on them.
The operator can use this to get an impression of the height of the
objects in the setup. Generally, for nanomanipulation, the above
considerations indicate an inlens detector often can be advantageous.
Reducing the beam current to narrow the electron beam necessarily limits
the number of detected electrons and make the signal-to-noise ratio low,
unless one makes very slow scans to increase the number of counts
`<footnote>`{=html}The signal to noise ratio S/N for Poisson distributed
count measurements n is S/N=vn and high counts are necessary to reduce
noise in the images. `</footnote>`{=html}.
When used for in-situ nanomanipulation one needs a fast scan rate to
follow the moving tools (preferably at rates approaching live video) and
this requires high beam currents. The acceleration voltage is also
important, and too high PE energy can make the sample transparent (such
as the carbon coating in Fig.[^3] b) while low energy usually make the
image susceptible to drift due to charging and similar effects.
# In-situ TEM manipulation
TEM offers atomic 3D resolution but the extreme requirements on
stability combined with very limited sample space makes the construction
of in-situ TEM manipulation equipment quite a task. With such systems,
people have observed freely suspended wires of individual atoms between
a gold tip and a gold surface; carbon nanotubes working as nanoscale
pipettes for metals and a wealth of other exotic phenomena.
Companies selling hardware
- Nanofactory
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How to
contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: eq SEM beam diameter
[^2]: eq SEM beam diameter
[^3]: fig INTRO 3 e depth
|
# Nanotechnology/Health effects of nanoparticles#Nanotoxicology: Health effects of nanotechnology
Navigate
--------------------------------------------------------------------------
\<\< Prev: Environmental Nanotechnology
\>\< Main: Nanotechnology
\>\> Next: Environmental Impact
\_\_TOC\_\_
------------------------------------------------------------------------
# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
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R.; Moussa, F. \[60\]Fullerene is a powerful antioxidant in vivo
with no acute or subacute toxicity. Nano Lett. 2005, 5 (12),
2578-2585.
[^116]: Bottini, M.; Bruckner, S.; Nika, K.; Bottini, N.; Bellucci, S.;
Magrini, A.; Bergamaschi, A.; Mustelin, T. Multi-walled carbon
nanotubes induce T lymphocyte apoptosis. Toxicology Letters 2006,
160 (2), 121-126.
[^117]: Sayes, C. M.; Fortner, J. D.; Guo, W.; Lyon, D.; Boyd, A. M.;
Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
water-soluble fullerenes. Nano Letters 2004, 4 (10), 1881-1887.
[^118]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^119]: Oberdorster, E. Manufactured nanomaterials (Fullerenes, C-60)
induce oxidative stress in the brain of juvenile largemouth bass.
Environmental Health Perspectives 2004, 112 (10), 1058-1062.
[^120]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^121]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^122]: Masciangioli, T.; Zhang, W. X. Environmental technologies at the
nanoscale. Environmental Science & Technology 2003, 37 (5),
102A-108A.
[^123]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^124]: Depledge, M.; Owen, R. Nanotechnology and the environment: risks
and rewards. Marine Pollution Bulletine 2005, 50, 609-612.
[^125]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^126]: European Commission Nanotechnologies: A Preliminary Risk
Analysis on the Basis of a Workshop Organized in Brussels on 1-2
March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Production and applications of nanotechnology
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
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The Royal Society: London, 04.
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induce oxidative stress in the brain of juvenile largemouth bass.
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Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
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Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
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[^123]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^124]: Depledge, M.; Owen, R. Nanotechnology and the environment: risks
and rewards. Marine Pollution Bulletine 2005, 50, 609-612.
[^125]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^126]: European Commission Nanotechnologies: A Preliminary Risk
Analysis on the Basis of a Workshop Organized in Brussels on 1-2
March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Exposure of environment and humans
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
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Nanosciences and nanotechnologies: opportunities and uncertainties;
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Analysis on the Basis of a Workshop Organized in Brussels on 1-2
March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Nanoecotoxicology 2
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
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and rewards. Marine Pollution Bulletine 2005, 50, 609-612.
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March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Identification of key hazard properties
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
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Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
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Environmental Health Perspectives 2004, 112 (10), 1058-1062.
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J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
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Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Hazard identification
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
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[^1]: Y. Gogotsi , How Safe are Nanotubes and Other Nanofilaments?, Mat.
Res. Innovat, 7, 192-194 (2003)
1\]
[^2]: Cristina Buzea, Ivan Pacheco, and Kevin Robbie \"Nanomaterials
and Nanoparticles: Sources and Toxicity\" Biointerphases 2 (1007)
MR17-MR71.
[^3]: Lam, C. W.; James, J. T.; McCluskey, R.; Hunter, R. L. Pulmonary
toxicity of single-wall carbon nanotubes in mice 7 and 90 days after
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|
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
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Degradation of C60 by light. Nature 1991, 351 (6324), 277.
[^107]: Zhu, S. Q.; Oberdorster, E.; Haasch, M. L. Toxicity of an
engineered nanoparticle (fullerene, C-60) in two aquatic species,
Daphnia and fathead minnow. Marine Environmental Research 2006, 62,
S5-S9.
[^108]: Scientific Committee on Emerging and Newly Identified Health
Risks Scientific Committee on Emerging and Newly Identified Health
Risks (SCENIHR) Opinion on The appropriateness of existing
methodologies to assess the potential risks associated with
engineered and adventitious products of nanotechnologies Adopted by
the SCENIHR during the 7th plenary meeting of 28-29 September
2005;SCENIHR/002/05; European Commission Health & Consumer
Protection Directorate-General: 05.
[^109]: Yamago, S.; Tokuyama, H.; Nakamura, E.; Kikuchi, K.; Kananishi,
S.; Sueki, K.; Nakahara, H.; Enomoto, S.; Ambe, F. In-Vivo
Biological Behavior of A Water-Miscible Fullerene - C-14 Labeling,
Absorption, Distribution, Excretion and Acute Toxicity. Chemistry &
Biology 1995, 2 (6), 385-389.
[^110]: Oberdorster, G.; Oberdorster, E.; Oberdorster, J.
Nanotoxicology: An emerging discipline evolving from studies of
ultrafine particles. Environmental Health Perspectives 2005, 113
(7), 823-839.
[^111]: Brumfiel, G. A little knowledge. Nature 2003, 424 (6946),
246-248.
[^112]: Brown, D. Nano Litterbugs? Experts see potential pollution
problems.
3
2002.
[^113]: Scientific Committee on Emerging and Newly Identified Health
Risks Scientific Committee on Emerging and Newly Identified Health
Risks (SCENIHR) Opinion on The appropriateness of existing
methodologies to assess the potential risks associated with
engineered and adventitious products of nanotechnologies Adopted by
the SCENIHR during the 7th plenary meeting of 28-29 September
2005;SCENIHR/002/05; European Commission Health & Consumer
Protection Directorate-General: 05.
[^114]: Sayes, C. M.; Fortner, J. D.; Guo, W.; Lyon, D.; Boyd, A. M.;
Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
water-soluble fullerenes. Nano Letters 2004, 4 (10), 1881-1887.
[^115]: Gharbi, N.; Pressac, M.; Hadchouel, M.; Szwarc, H.; Wilson, S.
R.; Moussa, F. \[60\]Fullerene is a powerful antioxidant in vivo
with no acute or subacute toxicity. Nano Lett. 2005, 5 (12),
2578-2585.
[^116]: Bottini, M.; Bruckner, S.; Nika, K.; Bottini, N.; Bellucci, S.;
Magrini, A.; Bergamaschi, A.; Mustelin, T. Multi-walled carbon
nanotubes induce T lymphocyte apoptosis. Toxicology Letters 2006,
160 (2), 121-126.
[^117]: Sayes, C. M.; Fortner, J. D.; Guo, W.; Lyon, D.; Boyd, A. M.;
Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
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[^118]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^119]: Oberdorster, E. Manufactured nanomaterials (Fullerenes, C-60)
induce oxidative stress in the brain of juvenile largemouth bass.
Environmental Health Perspectives 2004, 112 (10), 1058-1062.
[^120]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^121]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^122]: Masciangioli, T.; Zhang, W. X. Environmental technologies at the
nanoscale. Environmental Science & Technology 2003, 37 (5),
102A-108A.
[^123]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^124]: Depledge, M.; Owen, R. Nanotechnology and the environment: risks
and rewards. Marine Pollution Bulletine 2005, 50, 609-612.
[^125]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^126]: European Commission Nanotechnologies: A Preliminary Risk
Analysis on the Basis of a Workshop Organized in Brussels on 1-2
March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Interactions in the Environment
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
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2005, 39 (11), 4307-4316.
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B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
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The Royal Society: London, 04.
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Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
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Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
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[^123]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
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and rewards. Marine Pollution Bulletine 2005, 50, 609-612.
[^125]: The Royal Society & The Royal Academy of Engineering
Nanosciences and nanotechnologies: opportunities and uncertainties;
The Royal Society: London, 04.
[^126]: European Commission Nanotechnologies: A Preliminary Risk
Analysis on the Basis of a Workshop Organized in Brussels on 1-2
March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Health effects of nanoparticles#Conclusion
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# Nanotoxicology: Health effects of nanotechnology
The environmental impacts of nanotechnology have become an increasingly
active area of research.
Until recently the potential negative impacts of nanomaterials on human
health and the environment have been rather speculative and
unsubstantiated[^1].
However, within the past number of years several studies have indicated
that exposure to specific nanomaterials, e.g. nanoparticles, can lead to
a gamut of adverse effects in humans and animals [^2], [^3], [^4].
This has made some people very concerned drawing specific parallels to
past negative experiences with small particles [^5], [^6].
Some types of nanoparticles are expected to be benign and are FDA
approved and used for making paints and sunscreen lotion etc. However,
there are also dangerous nanosized particles and chemicals that are
known to accumulate in the food chain and have been known for many
years:
- Asbestos
- Diesel particulate matter
- ultra fine particles
- DDT
- lead
The problem is that it is difficult to extrapolate experience with bulk
materials to nanoparticles because their chemical properties can be
quite different. For instance, anti-bacterial silver nanoparticles
dissolve in acids that would not dissolve bulk silver, which indicates
their increased reactivity[^7].
An overview of some exposure cases for humans and the environment shown
in the table. For an overview of nanoproducts see the section Nanotech
Products in this
book.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
Product Examples Potential release and exposure
Cosmetics IV absorbing TiO~2~ or ZnO~2~ in sunscreen Directly applied to skin and late washed off. Disposal of containers
Fuel additives Cerium oxide additives in the EU Exhaust emission
Paints and coatings antibacterial silver nanoparticles coatings and hydrophobic nanocoatings wear and washing releases the particles or components such as Ag^+^.
Clothing antibacterial silver nanoparticles coatings and hydrophobic nanocoatings skin absorption; wear and washing releases the particles or components such as Ag^+^.
Electronics Carbon nanotubes are proposed for future use in commercial electronics disposal can lead to emission
Toys and utensils Sports gear such as golf clubs are beginning to be made from eg. carbon nanotubes Disposal can lead to emission
Combustion processes Ultrafine particles are the result of diesel combustion and many other processes can create nanoscale particles in large quantities. Emission with the exhaust
Soil regeneration Nanoparticles are being considered for soil regeneration (see later in this chapter) high local emission and exposure where it is used.
Nanoparticle production Production often produces by products that cannot be used (e.g. not all nanotubes are singlewall) If the production is not suitably planned, large quantities of nanoparticles could be emitted locally in wastewater and exhaust gasses.
------------------------- -------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------------------
: Ways nanoparticles can escape into the environment (adapted from
[^8])
The peer-reviewed journal
Nanotoxicology is
dedicated to Research relating to the potential for human and
environmental exposure, hazard and risk associated with the use and
development of nano-structured materials. Other journals also report on
the research, for see the full Nano-journal
list in
this book.
## Nanoecotoxicology
In response to the above concerns a new field of research has emergence
termed "nano(eco-)toxiciolgoy" defined
as the "science of engineered nanodevices and nanostructures that deals
with their effects in living organisms" [^9].
In the following we will first try to explain why some people are
concerned about nanomaterials and especially nanoparticles. This will
lead to a general presentation of what is known about the hazardous
properties of nanoparticles in the field of the environment and
nanoecotoxicology. This includes a discussion of the main areas of
uncertainty and gaps of knowledge.
## Human or ecotoxicology
The focus of this chapter is on the
ecotoxicological - and environmental
effects of nanomaterials, however references will be made to studies on
human toxicology where it is assumed that such analogies are warranted
or if studies have provided new insights that are relevant to the field
of nanoecotoxicology as well. As further investigations are made, more
knowledge will be gained about human toxicology of nanoparticles.
# Production and applications of nanotechnology
At present the global production of nanomaterials is hard to estimate
for three main reasons:
- Firstly, the definition of when something is "nanotechnology" is not
clear-cut.
- Secondly, nanomaterials are used in a great diversity of products
and industries and
- Thirdly, there is a general lack of information about what and how
much is being produced and by whom.
In 2001 the future global annual production of carbon-based
nanomaterials was estimated to be several hundred tons, but already in
2003 the global production of nanotubes alone was estimated to be around
900 tons distributed between 16 manufacturers [^10].
The Japanese company, Frontier Carbon Corp, plan to start an annual
production of 40 tons of C~60~ [^11].
It is estimated that the global annual production of nanotubes and fiber
was 65 tons equal to €144 million worth and it is expected to surpass €3
billion by 2010 representing an annual growth rate of well over 60%
[^12].
Even though the information about the production of carbon-based
nanomaterials is scarce, the annual production volumes of for instance
quantum dots, nano-metals, and materials with nanostructured surfaces
are completely unknown.
The development of nanotechnology is still in its infancy, and the
current production and use of nanomaterials is most likely not
representative for the future use and production. Some estimates for the
future manufacturing of nanomaterials have been made. For instance the
Royal Society and the Royal Academy of Engineering [^13] estimated that
nanomaterials used in relation to environmental technology alone will
increase from 10 tons per year in 2004 to between 1000-10.000 tons per
year before 2020. However, the basis of many of these estimations is
often highly unclear and the future production will depend on a number
of things such as for instance:
1. Whether the use of nanomaterials indeed entails the promised
benefits in the long run;
2. which and how many different applications and products will
eventually be developed and implemented;
3. And on how nanotechnology is perceived and embraced by the public?
With that said, the expectations are enormous. It is estimated that the
global market value of nano-related products will be U.S. \$1 trillion
in 2015 and that potentially 7 million jobs will be created globally
[^14] , [^15]
# Exposure of environment and humans
Exposure of nanomaterials to workers, consumers, and the environment
seems inevitable with the increasing production volumes and the
increasing number of commercially available products containing
nanomaterials or based on nanotechnology [^16].
Exposure is a key element in risk assessment of nanomaterials since it
is a precondition for the potential toxicological and ecotoxicological
effects to take place. If there is no exposure -- there is no risk.
Nanoparticles are already being used in various products and the
exposure can happen through multiple routes.
Human routes of exposure are:
- dermal (for instance through the use of cosmetics containing
nanoparticles);
- inhalation (of nanoparticles for instance in the workplace);
- ingestion (of for instance food products containing nanoparticles);
- and injection (of for instance medicine based on nanotechnology).
Although there are many different kinds of nanomaterials, concerns have
mainly been raised about free nanoparticles [^17], [^18].
Free nanoparticles could either get into the environment through direct
outlet to the environment or through the degradation of nanomaterials
(such as surface bound nanoparticles or nanosized coatings).
Environmental routes of exposure are multiple.
One route is via the wastewater system. At the moment research
laboratories and manufacturing companies must be assumed to be the main
contributor of carbon-based nanoparticles to the wastewater outlet.
For other kinds of nanoparticles for instance titanium dioxide and
silver, consumer products such as cosmetics, crèmes and detergents, is a
key source already and discharges must be assumed to increase with the
development of nanotechnology.
However, as development and applications of these materials increases
this exposure pattern must be assumed to change dramatically. Traces of
drugs and medicine based on nanoparticles can also be disposed of
through the wastewater system into the environment.
Drugs are often coated, and studies have show that these coatings can be
degraded through either metabolism inside the human body or
transformation in environment due to UV-light [^19]. Which only
emphasises the need to studying the many possible process that will
alter the properties of nanoparticles once they are released in nature.
Another route of exposure to the into the environment is from wastewater
overflow or if there is an outlet from the wastewater treatment plant
where nanoparticles are not effectively held back or degraded.
Additional routes of environmental exposure are spills from production,
transport, and disposal of nanomaterials or products [^20].
While many of the potential routes of exposure are uncertain scenarios,
which need confirmation, the direct application of nanoparticles, such
as for instance nano zero valent iron for remediation of polluted areas
or groundwater, is one route of exposure that will certainly lead to
environmental exposure. Although, remediation with the help of free
nanoparticles is one of the most promising environmental
nanotechnologies, it might also be one the one raising the most
concerns. The Royal Society and The Royal Academy of Engineering [^21]
actually recommend that the use of free nanoparticles in environmental
applications such as remediation should be prohibited until it has been
shown that the benefits outweigh the risks.
The presence of manufactured nanomaterials in the environment is not
widespread yet, it is important to remember that the concentration of
xenobiotic organic chemicals in the environment in the past has
increased proportionally with the application of these [^22] -- meaning
that it is only a question of time before we will find nanomaterials
such as nanoparticles in the environment -- if we have the means to
detect them.
The size of nanoparticles and our current lack of metrological methods
to detect them is a huge potential problem in relation to identification
and remediation both in relation to their fate in the human body and in
the environment [^23].
Once there is a widespread environmental exposure human exposure through
the environment seems almost inevitable since water- and sediment living
organisms can take up nanoparticles from water or by ingestion of
nanoparticles sorbed to the vegetation or sediment and thereby making
transport of nanoparticles up through the food chain possible [^24].
# Nanoecotoxicology
Despite the widespread development of nanotechnology and nanomaterials
through the last 10-20 years, it is only recently that focus has been
turned onto the potential toxicological effects on humans, animals, and
the environment through the exposure of manufactured nanomaterials
[^25].
With that being said, it is a new development that potential negative
health and environmental impacts of a technology or a material is given
attention at the developing stage and not after years of application
[^26].
The term "nano(eco-)toxicology" has been developed on the request of a
number of scientists and is now seen as a separate scientific discipline
with the purpose of generating data and knowledge about nanomaterials
effects on humans and the environment [^27], [^28].
Toxicological information and data on nanomaterials is limited and
ecotoxicological data is even more limited. Some toxicological studies
have been done on biological systems with nanoparticles in the form of
metals, metal oxides, selenium and carbon [^29], however the majority of
toxicological studies have been done with carbon fullerenes [^30].
Only a very limited number of ecotoxicological studies have been
performed on the effects of nanoparticles on environmentally relevant
species, and, as for the toxicological studies, most of the studies have
been done on fullerenes. However, according to the European Scientific
Committee on Emerging and Newly Identified Health Risks [^31] results
from human toxicological studies on the cellular level can be assumed to
be applicable for organisms in the environment, even though this of
cause needs further verification. In the following a summary of the
early findings from studies done on bacteria, crustaceans, fish, and
plants will be given and discussed.
## Bacteria
The effect of nanoparticles on bacteria is very important since bacteria
constitute the lowest level and hence the entrance to the food chain in
many ecosystems [^32].
The effects of C~60~ aggregates on two common
soil bacteria E. coli (gram negative) and B. subtilis (gram positive)
was investigated by Fortner et al. [^33] on rich and minimal media,
respectively, under aerobe and anaerobe conditions. At concentrations
above 0.4 mg/L growth was completely inhibited in both cultures exposed
with and without oxygen and light. No inhibition was observed on rich
media in concentration up to 2.5 mg/L, which could be due to that
C~60~ precipitates or gets coated by proteins
in the media. The importance of surface chemistry is highlighted by the
observation that hydroxylated C~60~ did not
give any response, which is in agreement with the results obtained by
Sayes et al. [^34] who investigated the toxicity on human dermal- and
liver cells. The antibacterial effects of
C~60~ has furthermore been observed by
Oberdorster [^35] , who observed remarkably clearer water during
experiments with fish in the aquarium with 0.5 mg/L compared to control.
Lyon et al. [^36] explored the influence of four different preparation
methods of C~60~ (stirred
C~60~, THF-C~60~,
toluene-C~60~, and
PVP-C~60~) on Bacillus subtilis and found that
all four suspensions exhibited relatively strong antibacterial activity
ranging from 0.09 ± 0.01 mg/L- 0.7 ± 0.3 mg/L, and although fractions
containing smaller aggregates had greater antibacterial activity, the
increase in toxicity was disproportionately higher than the associated
increase in surface area.
Silver nanoparticles are increasingly used as antibacterial agent [^37]
## Crustacean
A number of studies have been performed with the freshwater crustacean
Daphnia magna, which is an important ecological important species that
furthermore is the most commonly used organisms in regulatory testing of
chemicals.
The organism can filter up to 16 ml an hour, which entails contact with
large amounts of water in its surroundings. Nanoparticles can be taken
up via the filtration and hence could lead to potential toxic effects
[^38].
Lovern and Klaper [^39], [^40] observed some mortality after 48 hours of
exposure to 35 mg/L C~60~ (produced by
stirring and also known as "nanoC~60~" or
"nC~60~"), however 50% mortality was not
achieved, and hence an LC50 could not be determined [^41].
A considerable higher toxicity of LC50 = 0.8 mg/L is obtained when using
nC~60~ put into solution via the solvent
tetrahydrofuran (THF) -- which might indicate that residues of THF is
bound to or within the C~60~-aggreggates,
however whether this is the case in unclear at the moment. The
solubility of C~60~ using sonication has also
been found to increase toxicity [^42], whereas unfiltered
C~60~ dissolved by sonication has been found
to cause less toxicity (LC50 = 8 mg/L). This is attributed to the
formation of aggregates, which causes a variation of the bioavailability
to the different concentrations. Besides mortality, deviating behavior
was observed in the exposed Daphnia magna in the form of repeated
collisions with the glass beakers and swimming in circles at the surface
of the water [^43]. Changes in the number of hops, heart rate, and
appendage movement after subtoxic levels of exposure to
C~60~ and other
C~60~-derivatives [^44]. However, Titanium
dioxide (TiO2) dissolved via THF has been observed to cause increased
mortality in Daphania magna within 48 hours (LC50= 5.5 mg/L), but to a
lesser extent than fullerenes, while unfiltered TiO2 dissolved by
sonication did not results in a increasing dose-response relationship,
but rather a variation response [^45]. Lovern and Klaper [^46] have
furthermore investigated whether THF contributed to the toxicity by
comparing TiO2 manufactured with and without THF and found no difference
in toxicity and hence concluded that THF did not contribute to neither
the toxicity of TiO2 or fullerenes.
Experiments with the marine species Acartia tonsa exposed to 22.5 mg/L
stirred nC~60~ have been found to cause up to
23% mortality after 96 hours, however mortality was not significantly
different from control25. And exposure of Hyella azteca by 7 mg/L
stirred nC~60~ in 96 hours did not lead to any
visible toxic effects -- not even by administration of
C~60~ through the feed [^47].
Only a limited number of studies have investigated long-term exposure of
nanoparticles to crustaceans. Chronic exposure of Daphnia magna with 2.5
mg/L stirred nC~60~ was observed to cause 40%
mortality besides causing sub-lethal effects in the form of reduced
reproducibility (fewer offspring) and delayed shift of shield [^48].
Templeton et al. [^49] observed an average cumulative life-cycle
mortality of 13 ± 4% in an Estuarine Meiobenthic Copepod Amphiascus
tenuiremis after being exposed to SWCNT, while mean life-cycle
mortalities of 12 ± 3, 19 ± 2, 21 ± 3, and 36 ± 11 % were observed for
0.58, 0.97, 1.6, and 10 mg/L.
Exposure to 10 mg/L showed:
1. significantly increased mortalities for the naupliar stage and
cumulative life-cycle;
2. a dramatically reduced development success to 51% for the nauplius
to copepodite window, 89% for the copepodite to adult window, and
34% overall for the nauplius to adult period;
3. a significantly depressed fertilization rate averaging only 64 ±
13%.
Templeton also observed that exposure to 1.6 mg/L caused a significantly
increase in development rate of 1 day faster, whereas a 6 day
significant delay was seen for 10 mg/L.
## Fish
A limited number of studies have been done with fish as test species. In
a highly cited study Oberdorster [^50] found that 0.5 mg/L
C~60~ dissolved in THF caused increased lipid
peroxidation in the brain of largemouth bass (Mikropterus salmoides).
Lipid peroxidation was found to be decreased in the gills and the liver,
which was attributed to reparation enzymes. No protein oxidation was
observed in any of the mentioned tissue, however a discharge of the
antioxidant glutathione occurred in the liver possibility due to large
amount of reactive oxygen molecules stemming from oxidative stress
caused by C~60~ [^51].
For Pimephales promelas exposured to 1 mg/L THF-dissolved
C~60~, 100 % mortality was obtained within 18
hours, whereas 1 mg/L C~60~ stirred in water
did not lead to any mortality within 96 hours. However, at this
concentration inhibition of a gene which regulates fat metabolism was
observed. No effect was observed in the species Oryzia latipes at 1 mg/L
stirred C~60~, which indicates different
inter-species sensitivity toward C~60~ [^52],
[^53].
Smith et al. [^54] observed a dose-dependent rise in ventilation rate,
gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus
secretion with SWCNT precipitation on the gill mucus in juvenile rainbow
trout.
Smith et al. also observed:
- dose-dependent changes in brain and gill Zn or Cu, partly attributed
to the solvent;
- a significant increases in Na+K+ATPase activity in the gills and
intestine;
- a significant dose-dependent decreases in TBARS especially in the
gill, brain and liver;
- and a significant increases in the total glutathione levels in the
gills (28 %) and livers (18 %), compared to the solvent control (15
mg/l SDS).
- Finally, they observed increasing aggressive behavior; possible
aneurisms or swellings on the ventral surface of the cerebellum in
the brain and apoptotic bodies and cells in abnormal nuclear
division in liver cells.
Recently Kashiwada [^55]29 reported observing 35.6% lethal effect in
embryos of the medaka Oryzias latipes (ST II strain) exposed to 39.4 nm
polystyrene nanoparticles at 30 mg/L, but no mortality was observed
during the exposure and postexposure to hatch periods at exposure to 1
mg/L. The lethal effect was observed to increase proportionally with the
salinity, and 100% complete lethality occurred at 5 time higher
concentrated embryo rearing medium. Kashwada also found that 474 nm
particles showed the highest bioavailability to eggs, and 39.4 nm
particles were confirmed to shift into the yolk and gallbladder along
with embryonic development. High levels of particles were found in the
gills and intestine for adult medaka exposed to 39.4 nm nanoparticles at
10 mg/L, and it is hypothesized that particles pass through the
membranes of the gills and/or intestine and enter the circulation.
## Plants
To our knowledge only one study has been performed on phytotoxicity, and
it indicates that aluminum nanoparticles become less toxic when coated
with phenatrene, which again underlines the importance to surface
treatments in relation to the toxicity of nanoparticles [^56].
# Identification of key hazard properties
Size is the general reason why nanoparticles have become a matter of
discussion and concern.
The very small dimensions of nanoparticles increases the specific
surface area in relation to mass, which again means that even small
amounts of nanoparticles have a great surface area on which reactions
could happen.
If a reaction with chemical or biological components of an organism
leads to a toxic response, this response would be enhanced for
nanoparticles. This enhancement of the inherent toxicity is seen as the
main reason why smaller particles are generally more biologically active
and toxic that larger particles of the same material [^57].
Size can cause specific toxic response if for instance nanoparticles
will bind to proteins and thereby change their form and activity,
leading to inhibition or change in one or more specific reactions in the
body [^58].
Besides the increased reactivity, the small size of the nanoparticles
also means that they can easier be taken up by cells and that they are
taken up and distributed faster in organism compared to their larger
counterparts [^59], [^60].
Due to physical and chemical surface properties all nanoparticles are
expected to absorb to larger molecules after uptake in an organism via a
given route of uptake [^61].
Some nanoparticles such as fullerene derivates are developed
specifically with the intention of pharmacological applications because
of their ability of being taken up and distributed fast in the human
body, even in areas which are normally hard to reach -- such as the
brain tissue [^62]. Fast uptake and distribution can also be interpreted
as a warning about possible toxicity, however this need not always be
the case [^63]. Some nanoparticles are developed with the intension of
being toxic for instance with the purpose of killing bacteria or cancer
cells [^64], and in such cases toxicity can unintentionally lead to
adverse effects on humans or the environment.
Due to the lack of knowledge and lack of studies, the toxicity of
nanoparticles is often discussed on the basis of ultra fine particles
(UFPs), asbestos, and quartz, which due to their size could in theory
fall under the definition of nanotechnology [^65], [^66].
An estimation of the toxicity of nanoparticles could also be made on the
basis of the chemical composition, which is done for instance in the
USA, where safety data sheets for the most nanomaterials report the
properties and precautions related to the bulk material [^67].
Within such an approach lies the assumption that it is either the
chemical composition or the size that is determining for the toxicity.
However, many scientific experts agree that that the toxicity of
nanoparticles cannot and should not be predicted on the basis of the
toxicity of the bulk material alone [^68], [^69].
The increased surface area-to-mass ratio means that nanoparticles could
potentially be more toxic per mass than larger particles (assuming that
we are talking about bulk material and not suspensions), which means
that the dose-response relationship will be different for nanoparticles
compared to their larger counterparts for the same material. This aspect
is especially problematic in connection with toxicological and
ecotoxicological experiments, since conventional toxicology correlates
effects with the given mass of a substance [^70], [^71].
Inhalation studies on rodents have found that ultrafine particles of
titanium dioxide causes larger lung damage in rodents compared to larger
fine particles for the same amount of the substance. However, it turned
out that ultra fine- and fine particles cause the same response, if the
dose was estimated as surface area instead of as mass [^72].
This indicates that surface area might be a better parameter for
estimating toxicity than concentration, when comparing different sizes
of nanoparticles with the same chemical composition5. Besides surface
area, the number of particles has been pointed out as a key parameter
that should be used instead of concentration [^73].
Although comparison of ultrafine particles, fine particles, and even
nanoparticles of the same substance in a laboratory setting might be
relevant, it is questionable whether or not general analogies can be
made between the toxicity of ultrafine particles from anthropogenic
sources (such as cooking, combustion, wood-burning stoves, etc.) and
nanoparticles, since the chemical composition and structure of ultrafine
particles is very heterogeneous when compared to nanoparticles which
will often consists of specific homogeneous particles [^74].
From a chemical viewpoint nanoparticles can consist of transition
metals, metal oxides, carbon structures and in principle any other
material, and hence the toxicity is bound to vary as a results of that,
which again makes in impossible to classify nanoparticles according to
their toxicity based on size alone [^75].
Finally, the structure of nanoparticles has been shown to have a
profound influence on the toxicity of nanoparticles. In a study
comparing the cytotoxicity of different kinds of carbon-based
nanomaterials concluded that single walled carbon nanotubes was more
toxic that multi walled carbon nanotubes which again was more toxic than
C~60~ [^76].
# Hazard identification
In order to complete a hazard identification of nanomaterials, the
following is ideally required
- ecotoxicological studies
- data about toxic effects
- information on physical-chemical properties
- Solubility
- Sorption
- biodegradability
- accumulation
- and all likely depending on the specific size and detailed
composition of the nanoparticles
In addition to the physical-chemical properties normally considered in
relation to chemical substances, the physical-chemical properties of
nanomaterials is dependent on a number of additional factors such as
size, structure, shape, and surface area. Opinions on, which of these
factors are important differ among scientists, and the identification of
key properties is a key gap of our current knowledge [^77], [^78],
[^79].
There is little doubt that the physical-chemical properties normally
required when doing a hazard identification of chemical substances are
not representative for nanomaterials, however there is at current no
alternative methods. In the following key issues in regards to
determining the destiny and distribution of nanoparticles in the
environment will be discussed, however the focus will primarily be on
fullerenes such as C~60~.
## Solubility
Solubility in water is a key factor in the estimation of the
environmental effects of a given substance since it is often via contact
with water that effects-, or transformation, and distribution processes
occur such as for instance bioaccumulation.
Solubility of a given substance can be estimated from its structure and
reactive groups. For instance, Fullerenes consist of carbon atoms, which
results in a very hydrophobic molecule, which cannot easily be dissolved
in water.
Fortner et al. [^80] have estimated the solubility of individual
C~60~ in polar solvents such as water to be
10-9 mg/L. When C~60~ gets in contact with
water, aggregates are formed in the size range between 5-500 nm with a
greater solubility of up to 100 mg/L, which is 11 orders of magnitude
greater than the estimated molecular solubility. This can, however, only
be obtained by fast and long-term stirring in up to two months.
Aggregates of C~60~ can be formed at pH
between 3.75 and 10.25 and hence also by pH-values relevant to the
environment [^81].
As mentioned the solubility is affected by the formation of
C~60~ aggregates, which can lead to changes in
toxicity [^82].
Aggregates form reactive free radicals, which can cause harm to cell
membranes, while free C~60~ kept from
aggregation by coatings do not form free radical [^83]. Gharbi et al.
[^84] point to the accessibility of double bonds in the
C~60~ molecule as an important precondition
for its interactions with other biological molecules.
The solubility of C~60~ is less in salt water,
and according to Zhu et al. [^85] only 22.5 mg/L can be dissolved in 35
‰ sea water. Fortner et al. [^86] have found that aggregate precipitates
from the solution in both salt water and groundwater with an ionic
strength above 0.1 I, but aggregates would be stable in surface- and
groundwater, which typically have an ionic strength below 0.5 I.
The solubility of C~60~ can be increased to
about 13,000-100,000 mg/L by chemically modifying the
C~60~--molecule with polar functional groups
such as hydroxyl [^87]. The solubility can furthermore be increased by
the use of sonication or the use of none-polar solvents.
C~60~ will neither behave as molecules nor as
colloids in aqueous systems, but rather as a mixture of the two [^88],
[^89].
The chemical properties of individual C~60~
such as the log octanol-water partitioning coefficient (log Kow) and
solubility are not appropriate in regard to estimating the behavior of
aggregates of C~60~. Instead properties such
as size and surface chemistry should be applied a key parameters
[^90]18.
Just as the number of nanomaterials and the number of nanoparticles
differ greatly so does the solubility of the nanoparticles. For instance
carbon nanotubes have been reported to completely insoluble in water
[^91]. It should be underlined that which method is used to solute
nanoparticles is vital when performing and interpreting environmental
and toxicological tests.
## Evaporation
Information about evaporation of C~60~ from
aqueous suspensions has so far not been reported in the literature and
since the same goes for vapor pressure and Henry's constant, evaporation
cannot be estimated for the time being. Fullerenes are not considered to
evaporate -- neither from aqueous suspension or solvents -- since the
suspension of C~60~ using solvents still
entails C~60~ after evaporation of the solvent
[^92], [^93].
## Sorption
According to Oberdorster et al. [^94] nanoparticles will have a tendency
to sorb to sediments and soil particles and hence be immobile because of
the great surface area when compared to mass. Size alone will
furthermore have the effect that the transport of nanoparticles will be
dominated by diffusion rather than van der Waal forces and London
forces, which increases transport to surfaces, but it is not always that
collision with surfaces will lead to sorption [^95].
For C~60~ and carbon nanotubes the chemical
structure will furthermore result in great sorption to organic matter
and hence little mobility since these substances consists of carbon.
However, a study by Lecoanet et al. [^96]45 found that both
C~60~ and carbon nanotubes are able to migrate
through porous medium analogous to a sandy groundwater aquifer and that
C~60~ in general is transported with lower
velocity when compared to single walled carbon nanotubes, fullerol, and
surface modified C~60~. The study further
illustrates that modification of C~60~ on the
way to - or after - the outlet into the environment can profoundly
influence mobility. Reactions with naturally occurring enzymes [^97],
electrolytes or humid acid can for instance bind to the surface and make
thereby increase mobility [^98], just as degradation by UV-light or
microorganisms could potentially results in modified
C~60~ with increased mobility [^99]45.
## Degradability
Most nanomaterials are likely to be inert [^100], which could be due to
the applications of nanomaterials and products, which is often
manufactured with the purpose of being durable and hard-wearing.
Investigations made so far have however showed that fullerene might be
biological degradable whereas carbon nanotubes are consider biologically
non-degradable [^101], [^102]. According to the structure of fullerenes,
which consists of carbon only, it is possible that microorganisms can
use carbon as an energy source, such as it happens for instance with
other carbonaceous substances.
Fullerenes have been found to inhibit the growth of commonly occurring
soil- and water bacteria [^103], [^104] , which indicates that toxicity
can hinder degradability. It is, however, possible that biodegradation
can be performed by microorganisms other than the tested microorganisms,
or that the microorganism adapt after long-term exposure. Besides that
C~60~ can be degraded by UV-light and O
[^105]. UV-radiation of C~60~ dissolved in
hexane, lead to a partly or complete split-up of the fullerene structure
depending on concentration [^106].
## Bioaccumulation
Carbon based nanoparticles are lipophilic which means that they can
react with and penetrate different kinds of cell membranes [^107].
Nanomaterials with low solubility (such as
C~60~) could potentially accumulate in
biological organisms [^108] , however to the best of our knowledge no
studies have been performed investigating this in the environment.
Biokinetic studies with C~60~ in rats result
in very little excretion which indicates an accumulation in the
organisms [^109]. Fortner et al. [^110] estimates that it is likely that
nanoparticles can move up through the food chain via sediment consuming
organisms, which is confirmed by unpublished studies performed at Rice
University, U.S. [^111] Uptake in bacteria, which form the basis for
many ecosystems, is also seen as a potential entrance to whole food
chains [^112].
# Surface chemistry and coatings
In addition to the physical and chemical composition of the
nanoparticles, it is important to consider any coatings or modifications
of a given nanoparticles [^113].
A study by Sayes et al. [^114] found that the cytotoxicity of different
kinds of C~60~-derivatives varied by seven
orders of magnitude, and that the toxicity decreased with increasing
number of hydroxyl- and carbonyl groups attached to the surface.
According to Gharbi et al. [^115], it is in contradiction to previous
studies, which is supported by Bottini et al. [^116] who found an
increased toxicity of oxidized carbon nanotubes in immune cells when
compared to pristine carbon nanotubes.
The chemical composition of the surface of a given nanoparticle
influences both the bioavailability and the surface charge of the
particle, both of which are important factors for toxicology and
ecotoxicology. The negative charge on the surface of
C~60~ is suspected to be able to explain these
particles ability to induce oxidative stress in cells [^117].
The chemical composition also influences properties such as
lipophilicity, which is important in relation to uptake through cells
membranes in addition to distribution and transport to tissue and organs
in the organisms5. Coatings can furthermore be designed so that they are
transported to specific organs or cells, which has great importance for
toxicity [^118].
It is unknown, however, for how long nanoparticles stay coated
especially inside the human body and/or in the environment, since the
surface can be affected by for instance light if they get into the
environment. Experiments with non-toxic coated nanoparticles, turned out
to be very cell toxic after 30 min. exposure to UV-light or oxygen in
air [^119].
# Interactions in the Environment
Nanoparticles can be used to enhance the bioavailability of other
chemical substances so that they are easily degradable or harmful
substances can be transported to vulnerable ecosystems [^120].
Besides the toxicity of the nanoparticles itself, it is furthermore
unclear whether nanoparticles increases the bioavailability or toxicity
of other xenobiotics in the environment or other substances in the human
body. Nanoparticles such as C~60~ have many
potential uses in for instance in medicine because of their ability to
transport drugs to parts of the body which are normally hard to reach.
However, this property is exactly what also may be the source to adverse
toxic effects [^121]. Furthermore research is being done into the
application of nanoparticles for spreading of contaminants already in
the environment. This is being pursued in order to increase the
bioavailability for degradation of microorganisms [^122]54, however it
may also lead to increase uptake and increased toxicity of contaminants
in plants and animals, but to the best of our knowledge, no scientific
information is available that supports this [^123], [^124].
# Conclusion
It is still too early to determine whether nanomaterials or
nanoparticles are harmful or not, however the effects observed lately
have made many public and governmental institutions aware of
1. the lack of knowledge concerning the properties of nanoparticles
2. the urgent need for a systematic evaluation of the potential adverse
effect of Nanotechnology
[^125], [^126].
Furthermore, some guidance is needed as to which precautionary measures
are warranted in order to encourage the development of "green
nanotechnologies" and other future innovative technologies, while at the
same time minimizing the potential for negative surprises in the form of
adverse effects on human health and/or the environment.
It is important to understand that there are many different
nanomaterials and that the risk they pose will differ substantially
depending on their properties. At the moment it is not possible to
identify which properties or combination of properties make some
nanomaterials harmful and which make them harmless, and properly it will
depend on the nanomaterial is question. This makes it is extremely
difficult to do risk assessments and life-cycle assessment of
nanomaterials because, in theory, you would have to do a risk assessment
for each of the specific variation of nanomaterial -- a daunting task!
# Contributors to this page
This material is based on notes by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Stig Irving Olsen, Institute of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book about how to add references
Nanotechnology/About#How_to_contribute.
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accordance with the Technical Guidance Documents for new and
existing substances for assessing the risks of nanomaterials;
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Risks (SCENIHR) Opinion on The appropriateness of existing
methodologies to assess the potential risks associated with
engineered and adventitious products of nanotechnologies Adopted by
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nanomaterials. Nature Biotechnology 2003, 21 (10), 1166-1170.
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An emerging discipline evolving from studies of ultrafine particles.
Environmental Health Perspectives 2005, 113 (7), 823-839.
[^77]: SCENIHR The appropriateness of the risk assessment methodology in
accordance with the Technical Guidance Documents for new and
existing substances for assessing the risks of nanomaterials;
European Commission: 07.
[^78]: Oberdorster, G.; Maynard, A.; Donaldson, K.; Castranova, V.;
Fitzpatrick, J.; Ausman, K. D.; Carter, J.; Karn, B.; Kreyling, W.
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[^80]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
formation and microbial response. Environmental Science & Technology
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[^84]: Gharbi, N.; Pressac, M.; Hadchouel, M.; Szwarc, H.; Wilson, S.
R.; Moussa, F. \[60\]Fullerene is a powerful antioxidant in vivo
with no acute or subacute toxicity. Nano Lett. 2005, 5 (12),
2578-2585.
[^85]: Zhu, S. Q.; Oberdorster, E.; Haasch, M. L. Toxicity of an
engineered nanoparticle (fullerene, C-60) in two aquatic species,
Daphnia and fathead minnow. Marine Environmental Research 2006, 62,
S5-S9.
[^86]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
formation and microbial response. Environmental Science & Technology
2005, 39 (11), 4307-4316.
[^87]: Sayes, C. M.; Fortner, J. D.; Guo, W.; Lyon, D.; Boyd, A. M.;
Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
water-soluble fullerenes. Nano Letters 2004, 4 (10), 1881-1887.
[^88]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
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reflectance and UV-Vis spectroscopy. Chemical Physics Letters 2002,
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[^90]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
formation and microbial response. Environmental Science & Technology
2005, 39 (11), 4307-4316.
[^91]: Health and Safety Executive Health effects of particles produced
for nanotechnologies;EH75/6; Health and Safety Executive: Dec, 04.
[^92]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
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2005, 39 (11), 4307-4316.
[^93]: Deguchi, S.; Alargova, R. G.; Tsujii, K. Stable Dispersions of
Fullerenes, C~60~ and C70, in Water.
Preparation and Characterization. Langmuir 2001, 17 (19), 6013-6017.
[^94]: Oberdorster, G.; Oberdorster, E.; Oberdorster, J. Nanotoxicology:
An emerging discipline evolving from studies of ultrafine particles.
Environmental Health Perspectives 2005, 113 (7), 823-839.
[^95]: Lecoanet, H. F.; Bottero, J. Y.; Wiesner, M. R. Laboratory
assessment of the mobility of nanomaterials in porous media.
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[^96]: Lecoanet, H. F.; Bottero, J. Y.; Wiesner, M. R. Laboratory
assessment of the mobility of nanomaterials in porous media.
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[^97]: European Commission Nanotechnologies: A Preliminary Risk Analysis
on the Basis of a Workshop Organized in Brussels on 1-2 March 2004
by the Health and Consumer Protection Directorate General of the
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assessment of the mobility of nanomaterials in porous media.
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[^102]: Health and Safety Executive Health effects of particles produced
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[^103]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
formation and microbial response. Environmental Science & Technology
2005, 39 (11), 4307-4316.
[^104]: Oberdorster, E. Manufactured nanomaterials (Fullerenes, C-60)
induce oxidative stress in the brain of juvenile largemouth bass.
Environmental Health Perspectives 2004, 112 (10), 1058-1062.
[^105]: Fortner, J. D.; Lyon, D. Y.; Sayes, C. M.; Boyd, A. M.; Falkner,
J. C.; Hotze, E. M.; Alemany, L. B.; Tao, Y. J.; Guo, W.; Ausman, K.
D.; Colvin, V. L.; Hughes, J. B. C-60 in water: Nanocrystal
formation and microbial response. Environmental Science & Technology
2005, 39 (11), 4307-4316.
[^106]: Taylor, R.; Parsons, J. P.; Avent, A. G.; Rannard, S. P.;
Dennis, T. J.; Hare, J. P.; Kroto, H. W.; Walton, D. R. M.
Degradation of C60 by light. Nature 1991, 351 (6324), 277.
[^107]: Zhu, S. Q.; Oberdorster, E.; Haasch, M. L. Toxicity of an
engineered nanoparticle (fullerene, C-60) in two aquatic species,
Daphnia and fathead minnow. Marine Environmental Research 2006, 62,
S5-S9.
[^108]: Scientific Committee on Emerging and Newly Identified Health
Risks Scientific Committee on Emerging and Newly Identified Health
Risks (SCENIHR) Opinion on The appropriateness of existing
methodologies to assess the potential risks associated with
engineered and adventitious products of nanotechnologies Adopted by
the SCENIHR during the 7th plenary meeting of 28-29 September
2005;SCENIHR/002/05; European Commission Health & Consumer
Protection Directorate-General: 05.
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engineered and adventitious products of nanotechnologies Adopted by
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2005;SCENIHR/002/05; European Commission Health & Consumer
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Ausman, K. D.; Tao, Y. J.; Sitharaman, B.; Wilson, L. J.; Hughes, J.
B.; West, J. L.; Colvin, V. L. The differential cytotoxicity of
water-soluble fullerenes. Nano Letters 2004, 4 (10), 1881-1887.
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Nanosciences and nanotechnologies: opportunities and uncertainties;
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March 2004 by the Health and Consumer Protection Directorate General
of the European Commission; European Commission Community Health and
Consumer Protection: 04.
|
# Nanotechnology/Environmental Impact#Potential environmental impacts of nanotechnology
Navigate
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# Potential environmental impacts of nanotechnology
So far most of the focus has been on the potential health and
environmental risks of nanoparticles and only a few studies has been
made of the overall environmental impacts during the life cycle such as
ecological footprint (EF) or life
cycle analysis (LCA). The life cycle
of nanoproducts may involve both risks to human health and environment
as well as environmental impacts associated with the different stages.
The topics of understanding and assessing the environmental impacts and
benefits of nanotechnology throughout the life cycle from extraction of
raw materials to the final disposal have only been addressed in a couple
of studies. The U.S. EPA, NCER have sponsored a few projects to
investigate Life Cycle Assessment methodologies. Only one of these has
yet published results on automotive catalysts [^1] and nanocomposites in
automobiles [^2] , respectively, and one project was sponsored by the
German government [^3] .
A 2007 special issue of Journal of Cleaner Production puts focus on
sustainable development of nanotechnology and includes a recent LCA
study in Switzerland [^4] .
The potential environmental impact of nanomaterials could be more
far-reaching than the potential impact on personal health of free
nanoparticles. Numerous international and national organizations have
recommended that evaluations of nanomaterials be done in a life-cycle
perspective [^5] , [^6],
This is also one conclusion from a recent series of workshops in the US
on "green nanotechnology" (Schmidt, 2007)[^7] .
A workshop co-organised by US EPA/Woodrow Wilson Center and EU
Commission DG Research put focus on the topic of Life Cycle Assessments
of Nanotechnologies (Klöpffer et al., 2007) [^8] .
Heresome of the potential environmental impacts related to
nanotechnological products in their life cycle are discussed followed by
some recommendations to the further work on Life Cycle Assessment (LCA)
of nanotechnological products.
However, when relating to existing experience in micro-manufacturing
(which to a large extent resembles the top-down manufacturing of
nanomaterials) several environmental issues emerge that should be
addressed. There are indications that especially the manufacturing and
the disposal stages may imply considerable environmental impacts. The
toxicological risks to humans and the environment in all life cycle
stages of a nanomaterials have been addressed above. Therefore, the
potentially negative impacts on the environment that will be further
explored in the following are:
- Increased exploitation and loss of scarce resources;
- Higher requirement to materials and chemicals;
- Increased energy demand in production lines;
- Increased waste production in top down production;
- Rebound effects (horizontal technology);
- Increased use of disposable systems;
- Disassembly and recycling problems.
## Exploitation and loss of scarce resources
Exploitation and loss of scarce resources is a concern since economic
consideration is a primary obstacle to use precious or rare materials in
everyday products. When products get smaller and the components that
include the rare materials reach the nanoscale, economy is not the most
urgent issue since it will not significantly affect the price of the
product. Therefore, developers will be more prone to use materials that
have the exact properties they are searching. For example in the search
for suitable hydrogen storage medias Dillon et al. [^9] experimented
with the use of fullerenes doped with Scandium to increase the
reversible binding of Hydrogen. Other examples are the use of Gallium
and other rare metals in electronics. While an increased usage of such
materials may be foreseen due to the expected widespread use of
nanotechnological products, the recycling will be more difficult (will
be discussed more in detail later), resulting in non-recoverable
dissemination of scarce resources.
## Energy intensity of materials
An issue apart from the loss of resources is the fact that the
extraction of most rare materials uses more energy and generates more
waste than more abundant materials. Table 1 illustrates the energy
intensity of a range of materials. [^10]
------------- ---------------------------------------
Material Energy intensity of materials (MJ/kg)
Glass 15
Steel 59
Copper 94
Ferrite 59
Aluminium 214
Plastics 84
Epoxy resin 140
Tin 230
Lead 54
Nickel 340
Silver 1570
Gold 84000
------------- ---------------------------------------
# Life cycle assessment (LCA)
As mentioned there are not many studies on LCA of nanotechnology and
much information has to be understood from extrapolation of experiences
from MEMS and micro manufacturing.
In the micro world LCA has predominantly been used in the
Micro-Electro-Mechanical Systems (MEMS) sector. The rapid development of
technologies and limited availability of data makes full blown LCAs
difficult and rather quickly outdated. An example is the manufacture of
a PC for which the energy requirement in the late 1980's were app. 2150
kWh whereas in the late 90's efficiency were improved and only 535 kWh
were necessary [^11] .
Using old data could result in erroneous results. Looking at the overall
environmental impact this fourfold increase in efficiency has been
overcompensated by an increase in number of sold computers from app. 21
mio to more than 150 mio [^12] causing an overall increase in
environmental impact. This is often referred to as a rebound effect. For
the development of cell phones, the same authors conclude that life
cycle impacts vary significantly from one product generation to the
next; hence generic product life cycle data should incorporate a
"technology development factor" for main parameters.
A major trend is that shrinking product dimensions raise production
environment requirements to prevent polluting the product. It involves
energy intensive heating, ventilation and air conditioning systems.
Clean room of class 10.000 for example requires app. 2280 kWh/m2∙a
whereas a class 100 requires 8440 kWh/m2∙a. The same increase of
requirements is relevant for supply materials like chemicals and gases.
The demand for higher purity levels implies more technical effort for
chemical purification, e.g. additional energy consumption and possibly
more waste. Most purification technologies are highly energy intensive,
e.g. all distillation processes, which are often used in wet chemical
purification, account in total for about 7 % of energy consumption of
the U.S. chemical industry [^13] . Chemicals used in large volumes in
semiconductor industry are hydrofluoric acid (HF), hydrogen peroxide
(H2O2) and ammonium hydroxide (NH4OH). These materials are used in final
cleaning processes and require XLSI grades (0.1 ppb). Sulphuric acid is
also used in large amounts, but it is a less critical chemical and
mainly requires an SLSI level purity [^14] .
Micromanufacturing of other types of products also puts higher
requirements on the quality and purity of the materials, e.g. a smaller
grain size in metals because of the smaller dimensions of the final
product. Additionally, a considerable amount of waste is produced. For
example, up to 99% of the material used for microinjection moulding of a
component may be waste since big runner are necessary for handling and
assembly. However, recycling of this waste may not be possible due to
requirements to and reduction of the material strength [^15] .
Miniaturisation also cause new problems in electronics recycling.
Take-back will hardly be possible. If they are integrated into other
product they need to be compatible with the recycling of these products
(established recycling paths) [^16] .
The very small size and incorporation into many different types of
products including product with limited longevity suggests an increased
use of disposable systems is required.
## Life cycle assessment of nanotechnology
As mentioned previously only few LCA studies have until now been
performed for nanotechnological products. A two day workshop on LCA of
nanotechnological products concluded that the current ISO-standard on
LCA (14040) applies to nanotechnological products but also that some
development is necessary [^17] [^18]
The main issues are that:sometimes it cracks the nerve
- There is no generic LCA of nanomaterials, just as there is no
generic LCA of chemicals.
- The ISO-framework for LCA (ISO 14040:2006) is fully suitable to
nanomaterials and nanoproducts, even if data regarding the
elementary flows and impacts might be uncertain and scarce. Since
environmental impacts of nanoproducts can occur in any life cycle
stage, all stages of the life cycle of nanoproducts should be
assessed in an LCA study.
- While the ISO 14040 framework is appropriate, a number of
operational issues need to be addressed in more detail in the case
of nanomaterials and nanoproducts. The main problem with LCA of
nanomaterials and nanoproducts is the lack of data and understanding
in certain areas.
- While LCA brings major benefits and useful information, there are
certain limits to its application and use, in particular with
respect to the assessment of toxicity impacts and of large-scale
impacts.
- Within future research, major efforts are needed to fully assess
potential risks and environmental impacts of nanoproducts and
materials (not just those related to LCA). There is a need for
protocols and practical methodologies for toxicology studies, fate
and transport studies and scaling approaches.
- International cooperation between Europe and the United States,
together with other partners, is needed in order to address these
concerns.
- Further research is needed to gather missing relevant data and to
develop user-friendly eco-design screening tools, especially ones
suitable for use by small and medium sized enterprises.
Some of the concerns regarding the assessment of toxicological impacts
is closely linked to the risk assessment of nanoparticles and have to
await knowledge building in this area. However, the most striking is the
need for knowledge and cases where LCA are applied in order to increase
understanding of nanotechnological systems -- what are the potential
environmental impacts? How do they differ between different types of
nanotechnologies? Where should focus be put in order to prevent
environmental impacts? Etc.
## Additional resources
- Nanometer societal assessment of
nanotechnological applications prior to market release.
# Contributors to this page
This material is based on notes by
- Stig Irving Olsen, Department of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
and also by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Lloyd, S. M.; Lave, L. B.; Matthews, H. S. Life Cycle Benefits of
Using Nanotechnology To Stabilize Platinum-Group Metal Particles in
Automotive Catalysts. Environ. Sci. Technol. 2005, 39 (5),
1384-1392.
[^2]: Lloyd, S. M.; Lave, L. B. Life Cycle Economic and Environmental
Implications of Using Nanocomposites in Automobiles. Environ. Sci.
Technol. 2003, 37 (15), 3458-3466.
[^3]: Steinfeldt, M.; Petschow, U.; Haum, R.; von Gleich, A.
Nanotechnology and Sustainability. Discussion paper of the IÖW
65/04; IÖW: 04.
[^4]: Helland A, Kastenholz H, Development of nanotechnology in light of
sustainability, J Clean Prod (2007),
<doi:10.1016/j.jclepro.2007.04.006>
[^5]: The Royal Society & The Royal Academy of Engineering Nanoscience
and nanotechnologies: opportunities and uncertainties; The Royal
Society: London, Jul, 04
[^6]: U.S.EPA U.S. Environmental Protection Agency Nanotechnology White
Paper;EPA 100/B-07/001; Science Policy Council U.S. Environmental
Protection Agency: Washington, DC, Feb, 07.
[^7]: Schmidt, K.: Green Nanotechnology: It\'s easier than you think.
Woodrow Wilson International Center for Scholars. PEN 8 April 2007
[^8]: Klöpffer, W., Curran, MA., Frankl, P., Heijungs, R., Köhler, A.,
Olsen, SI.: Nanotechnology and Life Cycle Assessment. A Systems
Approach to Nanotechnology and the Environment. March 2007.
Synthesis of Results Obtained at a Workshop in Washington, DC 2--3
October 2006.
[^9]: Dillon AC, Nelson BP, Zhao Y, Kim Y-H, Tracy CE and Zhang SB:
Importance of Turning to Renewable Energy Resources with Hydrogen as
a Promising Candidate and on-board Storage a Critical Barrier.
Mater. Res. Soc. Symp. Proc. Vol. 895, 2006
[^10]: Kuehr, R.; Williams, E. Computers and the environment; Kluwer
Academic Publishers: Dordrecht, Boston, London, 2003.
[^11]: Schischke, K.; Griese, H. Is small green? Life Cycle Aspects of
Technology Trends in Microelectronicss and Microsystems.
<http://www>. lcacenter. org/InLCA2004/papers/Schischke_K\_paper.
pdf 2004
[^12]:
[^13]: Plepys, A. The environmental impacts of electronics. Going beyond
the walls of semiconductor fabs. IEEE: 2004; pp 159-165.
[^14]: Plepys, A. The environmental impacts of electronics. Going beyond
the walls of semiconductor fabs. IEEE: 2004; pp 159-165.
[^15]: Sarasua, J. R.; Pouyet, J. Recycling effects on microstructure
and mechanical behaviour of PEEK short carbon-fibre composites.
Journal of Materials Science 1997, 32, 533-536.
[^16]:
[^17]:
[^18]: Something funny is happening with ref klöpffer3b
|
# Nanotechnology/Environmental Impact#Energy intensity of materials
Navigate
-----------------------------------------------------------------------------------------------
\<\< Prev: Health effects of nanoparticles
\>\< Main: Nanotechnology
\>\> Next: Nano and Society
\_\_TOC\_\_
------------------------------------------------------------------------
# Potential environmental impacts of nanotechnology
So far most of the focus has been on the potential health and
environmental risks of nanoparticles and only a few studies has been
made of the overall environmental impacts during the life cycle such as
ecological footprint (EF) or life
cycle analysis (LCA). The life cycle
of nanoproducts may involve both risks to human health and environment
as well as environmental impacts associated with the different stages.
The topics of understanding and assessing the environmental impacts and
benefits of nanotechnology throughout the life cycle from extraction of
raw materials to the final disposal have only been addressed in a couple
of studies. The U.S. EPA, NCER have sponsored a few projects to
investigate Life Cycle Assessment methodologies. Only one of these has
yet published results on automotive catalysts [^1] and nanocomposites in
automobiles [^2] , respectively, and one project was sponsored by the
German government [^3] .
A 2007 special issue of Journal of Cleaner Production puts focus on
sustainable development of nanotechnology and includes a recent LCA
study in Switzerland [^4] .
The potential environmental impact of nanomaterials could be more
far-reaching than the potential impact on personal health of free
nanoparticles. Numerous international and national organizations have
recommended that evaluations of nanomaterials be done in a life-cycle
perspective [^5] , [^6],
This is also one conclusion from a recent series of workshops in the US
on "green nanotechnology" (Schmidt, 2007)[^7] .
A workshop co-organised by US EPA/Woodrow Wilson Center and EU
Commission DG Research put focus on the topic of Life Cycle Assessments
of Nanotechnologies (Klöpffer et al., 2007) [^8] .
Heresome of the potential environmental impacts related to
nanotechnological products in their life cycle are discussed followed by
some recommendations to the further work on Life Cycle Assessment (LCA)
of nanotechnological products.
However, when relating to existing experience in micro-manufacturing
(which to a large extent resembles the top-down manufacturing of
nanomaterials) several environmental issues emerge that should be
addressed. There are indications that especially the manufacturing and
the disposal stages may imply considerable environmental impacts. The
toxicological risks to humans and the environment in all life cycle
stages of a nanomaterials have been addressed above. Therefore, the
potentially negative impacts on the environment that will be further
explored in the following are:
- Increased exploitation and loss of scarce resources;
- Higher requirement to materials and chemicals;
- Increased energy demand in production lines;
- Increased waste production in top down production;
- Rebound effects (horizontal technology);
- Increased use of disposable systems;
- Disassembly and recycling problems.
## Exploitation and loss of scarce resources
Exploitation and loss of scarce resources is a concern since economic
consideration is a primary obstacle to use precious or rare materials in
everyday products. When products get smaller and the components that
include the rare materials reach the nanoscale, economy is not the most
urgent issue since it will not significantly affect the price of the
product. Therefore, developers will be more prone to use materials that
have the exact properties they are searching. For example in the search
for suitable hydrogen storage medias Dillon et al. [^9] experimented
with the use of fullerenes doped with Scandium to increase the
reversible binding of Hydrogen. Other examples are the use of Gallium
and other rare metals in electronics. While an increased usage of such
materials may be foreseen due to the expected widespread use of
nanotechnological products, the recycling will be more difficult (will
be discussed more in detail later), resulting in non-recoverable
dissemination of scarce resources.
## Energy intensity of materials
An issue apart from the loss of resources is the fact that the
extraction of most rare materials uses more energy and generates more
waste than more abundant materials. Table 1 illustrates the energy
intensity of a range of materials. [^10]
------------- ---------------------------------------
Material Energy intensity of materials (MJ/kg)
Glass 15
Steel 59
Copper 94
Ferrite 59
Aluminium 214
Plastics 84
Epoxy resin 140
Tin 230
Lead 54
Nickel 340
Silver 1570
Gold 84000
------------- ---------------------------------------
# Life cycle assessment (LCA)
As mentioned there are not many studies on LCA of nanotechnology and
much information has to be understood from extrapolation of experiences
from MEMS and micro manufacturing.
In the micro world LCA has predominantly been used in the
Micro-Electro-Mechanical Systems (MEMS) sector. The rapid development of
technologies and limited availability of data makes full blown LCAs
difficult and rather quickly outdated. An example is the manufacture of
a PC for which the energy requirement in the late 1980's were app. 2150
kWh whereas in the late 90's efficiency were improved and only 535 kWh
were necessary [^11] .
Using old data could result in erroneous results. Looking at the overall
environmental impact this fourfold increase in efficiency has been
overcompensated by an increase in number of sold computers from app. 21
mio to more than 150 mio [^12] causing an overall increase in
environmental impact. This is often referred to as a rebound effect. For
the development of cell phones, the same authors conclude that life
cycle impacts vary significantly from one product generation to the
next; hence generic product life cycle data should incorporate a
"technology development factor" for main parameters.
A major trend is that shrinking product dimensions raise production
environment requirements to prevent polluting the product. It involves
energy intensive heating, ventilation and air conditioning systems.
Clean room of class 10.000 for example requires app. 2280 kWh/m2∙a
whereas a class 100 requires 8440 kWh/m2∙a. The same increase of
requirements is relevant for supply materials like chemicals and gases.
The demand for higher purity levels implies more technical effort for
chemical purification, e.g. additional energy consumption and possibly
more waste. Most purification technologies are highly energy intensive,
e.g. all distillation processes, which are often used in wet chemical
purification, account in total for about 7 % of energy consumption of
the U.S. chemical industry [^13] . Chemicals used in large volumes in
semiconductor industry are hydrofluoric acid (HF), hydrogen peroxide
(H2O2) and ammonium hydroxide (NH4OH). These materials are used in final
cleaning processes and require XLSI grades (0.1 ppb). Sulphuric acid is
also used in large amounts, but it is a less critical chemical and
mainly requires an SLSI level purity [^14] .
Micromanufacturing of other types of products also puts higher
requirements on the quality and purity of the materials, e.g. a smaller
grain size in metals because of the smaller dimensions of the final
product. Additionally, a considerable amount of waste is produced. For
example, up to 99% of the material used for microinjection moulding of a
component may be waste since big runner are necessary for handling and
assembly. However, recycling of this waste may not be possible due to
requirements to and reduction of the material strength [^15] .
Miniaturisation also cause new problems in electronics recycling.
Take-back will hardly be possible. If they are integrated into other
product they need to be compatible with the recycling of these products
(established recycling paths) [^16] .
The very small size and incorporation into many different types of
products including product with limited longevity suggests an increased
use of disposable systems is required.
## Life cycle assessment of nanotechnology
As mentioned previously only few LCA studies have until now been
performed for nanotechnological products. A two day workshop on LCA of
nanotechnological products concluded that the current ISO-standard on
LCA (14040) applies to nanotechnological products but also that some
development is necessary [^17] [^18]
The main issues are that:sometimes it cracks the nerve
- There is no generic LCA of nanomaterials, just as there is no
generic LCA of chemicals.
- The ISO-framework for LCA (ISO 14040:2006) is fully suitable to
nanomaterials and nanoproducts, even if data regarding the
elementary flows and impacts might be uncertain and scarce. Since
environmental impacts of nanoproducts can occur in any life cycle
stage, all stages of the life cycle of nanoproducts should be
assessed in an LCA study.
- While the ISO 14040 framework is appropriate, a number of
operational issues need to be addressed in more detail in the case
of nanomaterials and nanoproducts. The main problem with LCA of
nanomaterials and nanoproducts is the lack of data and understanding
in certain areas.
- While LCA brings major benefits and useful information, there are
certain limits to its application and use, in particular with
respect to the assessment of toxicity impacts and of large-scale
impacts.
- Within future research, major efforts are needed to fully assess
potential risks and environmental impacts of nanoproducts and
materials (not just those related to LCA). There is a need for
protocols and practical methodologies for toxicology studies, fate
and transport studies and scaling approaches.
- International cooperation between Europe and the United States,
together with other partners, is needed in order to address these
concerns.
- Further research is needed to gather missing relevant data and to
develop user-friendly eco-design screening tools, especially ones
suitable for use by small and medium sized enterprises.
Some of the concerns regarding the assessment of toxicological impacts
is closely linked to the risk assessment of nanoparticles and have to
await knowledge building in this area. However, the most striking is the
need for knowledge and cases where LCA are applied in order to increase
understanding of nanotechnological systems -- what are the potential
environmental impacts? How do they differ between different types of
nanotechnologies? Where should focus be put in order to prevent
environmental impacts? Etc.
## Additional resources
- Nanometer societal assessment of
nanotechnological applications prior to market release.
# Contributors to this page
This material is based on notes by
- Stig Irving Olsen, Department of Manufacturing Engineering and
Management, Building 424, NanoDTU Environment, Technical University
of Denmark
and also by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen,
Anders Baun. Institute of Environment & Resources, Building 113,
NanoDTU Environment, Technical University of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU -
www.mic.dtu.dk
# References
See also notes on editing this book
Nanotechnology/About#How_to_contribute.
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]: Lloyd, S. M.; Lave, L. B.; Matthews, H. S. Life Cycle Benefits of
Using Nanotechnology To Stabilize Platinum-Group Metal Particles in
Automotive Catalysts. Environ. Sci. Technol. 2005, 39 (5),
1384-1392.
[^2]: Lloyd, S. M.; Lave, L. B. Life Cycle Economic and Environmental
Implications of Using Nanocomposites in Automobiles. Environ. Sci.
Technol. 2003, 37 (15), 3458-3466.
[^3]: Steinfeldt, M.; Petschow, U.; Haum, R.; von Gleich, A.
Nanotechnology and Sustainability. Discussion paper of the IÖW
65/04; IÖW: 04.
[^4]: Helland A, Kastenholz H, Development of nanotechnology in light of
sustainability, J Clean Prod (2007),
<doi:10.1016/j.jclepro.2007.04.006>
[^5]: The Royal Society & The Royal Academy of Engineering Nanoscience
and nanotechnologies: opportunities and uncertainties; The Royal
Society: London, Jul, 04
[^6]: U.S.EPA U.S. Environmental Protection Agency Nanotechnology White
Paper;EPA 100/B-07/001; Science Policy Council U.S. Environmental
Protection Agency: Washington, DC, Feb, 07.
[^7]: Schmidt, K.: Green Nanotechnology: It\'s easier than you think.
Woodrow Wilson International Center for Scholars. PEN 8 April 2007
[^8]: Klöpffer, W., Curran, MA., Frankl, P., Heijungs, R., Köhler, A.,
Olsen, SI.: Nanotechnology and Life Cycle Assessment. A Systems
Approach to Nanotechnology and the Environment. March 2007.
Synthesis of Results Obtained at a Workshop in Washington, DC 2--3
October 2006.
[^9]: Dillon AC, Nelson BP, Zhao Y, Kim Y-H, Tracy CE and Zhang SB:
Importance of Turning to Renewable Energy Resources with Hydrogen as
a Promising Candidate and on-board Storage a Critical Barrier.
Mater. Res. Soc. Symp. Proc. Vol. 895, 2006
[^10]: Kuehr, R.; Williams, E. Computers and the environment; Kluwer
Academic Publishers: Dordrecht, Boston, London, 2003.
[^11]: Schischke, K.; Griese, H. Is small green? Life Cycle Aspects of
Technology Trends in Microelectronicss and Microsystems.
<http://www>. lcacenter. org/InLCA2004/papers/Schischke_K\_paper.
pdf 2004
[^12]:
[^13]: Plepys, A. The environmental impacts of electronics. Going beyond
the walls of semiconductor fabs. IEEE: 2004; pp 159-165.
[^14]: Plepys, A. The environmental impacts of electronics. Going beyond
the walls of semiconductor fabs. IEEE: 2004; pp 159-165.
[^15]: Sarasua, J. R.; Pouyet, J. Recycling effects on microstructure
and mechanical behaviour of PEEK short carbon-fibre composites.
Journal of Materials Science 1997, 32, 533-536.
[^16]:
[^17]:
[^18]: Something funny is happening with ref klöpffer3b
|
# Nanotechnology/Nano and Society#Building Scenarios for the Plausible Implications of Nanotechnology
Navigate
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\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
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## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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```
- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
```{=html}
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```
- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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```
- A nanoethics university group 6
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```
- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
```{=html}
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```
- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
```{=html}
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```
- Might current systems (ala
MSDS10)
be modified to include this information?
```{=html}
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```
- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
```{=html}
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```
- Articles on the Lux report on
Nanotechnology
```{=html}
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```
- Lux 5'th report on
Nanotechnology
```{=html}
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```
- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
```{=html}
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```
- The World Nanotechnology Market (2006)
11
```{=html}
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```
- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
```{=html}
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```
- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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```
- Public funding (eg. National nano initiative)
```{=html}
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```
- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
```{=html}
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```
- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
```{=html}
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```
- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
```{=html}
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
```{=html}
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
```{=html}
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
```{=html}
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
```{=html}
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
```{=html}
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
<!-- -->
```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
<!-- -->
```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Anticipatory Symptoms
Navigate
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\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
------------------------------------------------------------------------
## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
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- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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- A nanoethics university group 6
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- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
```{=html}
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- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
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```
- Might current systems (ala
MSDS10)
be modified to include this information?
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- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
```{=html}
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```
- Articles on the Lux report on
Nanotechnology
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```
- Lux 5'th report on
Nanotechnology
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```
- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
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- The World Nanotechnology Market (2006)
11
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```
- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
```{=html}
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```
- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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- Public funding (eg. National nano initiative)
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- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
```{=html}
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```
- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
```{=html}
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```
- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
```{=html}
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
```{=html}
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
```{=html}
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
```{=html}
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
```{=html}
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
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```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
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```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
Navigate
----------------------------------------------------------------------------
\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
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## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
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- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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- A nanoethics university group 6
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```
- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
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```
- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
```{=html}
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```
- Might current systems (ala
MSDS10)
be modified to include this information?
```{=html}
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```
- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
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```
- Articles on the Lux report on
Nanotechnology
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```
- Lux 5'th report on
Nanotechnology
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```
- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
```{=html}
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```
- The World Nanotechnology Market (2006)
11
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```
- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
```{=html}
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```
- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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```
- Public funding (eg. National nano initiative)
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```
- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
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```
- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
```{=html}
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```
- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
```{=html}
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
```{=html}
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
```{=html}
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
```{=html}
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
```{=html}
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
```{=html}
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
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```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
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```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Impact of Nanotechnologies on developing countries
Navigate
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\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
------------------------------------------------------------------------
## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
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- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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- A nanoethics university group 6
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- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
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- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
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- Might current systems (ala
MSDS10)
be modified to include this information?
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- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
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- Articles on the Lux report on
Nanotechnology
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- Lux 5'th report on
Nanotechnology
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- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
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- The World Nanotechnology Market (2006)
11
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- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
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- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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- Public funding (eg. National nano initiative)
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- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
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- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
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- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
```{=html}
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
```{=html}
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
```{=html}
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
```{=html}
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
```{=html}
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
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```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
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```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Collective Open Source Design and the Navigation of Risky Technological Evolution
Navigate
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\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
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## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
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- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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- A nanoethics university group 6
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```
- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
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- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
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```
- Might current systems (ala
MSDS10)
be modified to include this information?
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```
- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
```{=html}
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```
- Articles on the Lux report on
Nanotechnology
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```
- Lux 5'th report on
Nanotechnology
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```
- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
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```
- The World Nanotechnology Market (2006)
11
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```
- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
```{=html}
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```
- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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- Public funding (eg. National nano initiative)
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```
- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
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```
- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
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```
- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
```{=html}
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
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```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
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```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Prisoner.27s Dilemma and Ethics
Navigate
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\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
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## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
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- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
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- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
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- A nanoethics university group 6
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- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
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- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
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- Might current systems (ala
MSDS10)
be modified to include this information?
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- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
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- Articles on the Lux report on
Nanotechnology
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- Lux 5'th report on
Nanotechnology
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- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
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- The World Nanotechnology Market (2006)
11
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- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
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- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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- Public funding (eg. National nano initiative)
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- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
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- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
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- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
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- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
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- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
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- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
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- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
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- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
```{=html}
<!-- -->
```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
```{=html}
<!-- -->
```
- The real challenges of these technologies are largely of an
educational and cultural nature.
```{=html}
<!-- -->
```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
```{=html}
<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Nanotechnology/Nano and Society#Application of Open Source to Nanotechnology
Navigate
----------------------------------------------------------------------------
\<\< Prev: Environmental Impact
\>\< Main: Nanotechnology
\>\> Next: The Nanotechnology Talk Page
\_\_TOC\_\_
------------------------------------------------------------------------
## Principles for the Revision and Development of this Chapter of the Wikibook
*Unless they are held together by book covers or hypertext links, ideas
will tend to split up as they travel. We need to develop and spread an
understanding of the future as a whole, as a system of interlocking
dangers and opportunities. This calls for the effort of many minds. The
incentive to study and spread the needed information will be strong
enough: the issues are fascinating and important, and many people will
want their friends, families, and colleagues to join in considering what
lies ahead. If we push in the right directions - learning, teaching,
arguing, shifting directions, and pushing further - then we may yet
steer the technology race toward a future with room enough for our
dreams.* -Eric Drexler, Engines of Creation,
1986
Our method for growing and revising this chapter devoted to
Nanotechnology & Society will emphasize an open source approach to
\"nanoethics\" - we welcome collaboration from all over the planet as we
turn our collective attention to revising and transforming the current
handbook. Nature abhors a vacuum, so we are lucky to begin not with
nothing but with a significant beginning begun by a Danish scientist,
Kristian Molhave.
You can read the correspondence for the
project.
Our principles for the revision and development of this section of the
wikibook will continue to develop and will be based on those of
wikibooks manual of
style
## Introduction
Nanotechnology is already a major vector in the rapid technological
development of the 21st century. While the wide ranging effects of the
financial
crisis on
the venture capital and research markets have yet to be understood, it
is clear from the example of the integrated circuit
industry
that nanotechnology and nanoscience promise to (sooner or later)
transform our IT
infrastructure.
Both the World Wide Web and peer-to-peer
technologies (as well as
wikipedia) demonstrate the radical potential of even minor shifts in our
IT infrastructure, so any discussion of nanotechnology and society can,
at the very least, inquire into the plausible effects of radical
increases in information processing and production. The effects of, for
example, distributed knowledge production, are hardly well understood,
as the recent Wikileaks events have demonstrated. The very existence of
distributed knowledge production irrevocably alters the global stage.
Given the history of DDT
and other highly promising chemical innovations, it is now part of our
technological common sense to seek to \"debug\" emerging technologies.
This debugging includes, but is not limited to, the effects of nanoscale
materials on our health and environment, which are often not fully
understood. The very aspects of nanotechnology and nanoscience that
excite us - the unusual physical properties of the nanoscale (e.g.
increase in surface
area) -
also pose problems for our capacity to predict and control nanoscale
phenomena, particularly in their connections to the larger scales - such
as ourselves! This wikibook assumes (in a purely heuristic fashion) that
to think effectively about the implications of nanotechnology and
emerging nanoscience, we must (at the very least) think in evolutionary
terms. Nanotechnology may be a significant development in the evolution
of human capacities. As with any other technology (nuclear, bio-, info),
it has a range of socio-economic impacts that influences and transforms
our context. While \"evolution\" often conjures images of ruthless
competition towards a \"survival of the fittest,\" so too should it
involve visions of collective symbiosis: According to Margulis and
Sagan,[^1] \"Life did not take over the globe by combat, but by
networking\" (i.e., by cooperation)[^2].
Perhaps in this wikibook chapter we can begin to grow a community of
feedback capable of such cooperative debugging. Here we will create a
place for sharing plausible implications of nanoscale science and
technology based on emerging peer reviewed science and technology. Like
all chapters of all wikibooks, this is offered both as an educational
resource and collective invitation to participate. Investigating the
effects of nanotechnology on society requires that we first and foremost
become informed participants, and definitions are a useful place to
begin.
Strictly speaking, nanotechnology is a discourse. As a dynamic field in
rapid development across multiple disciplines and nations, the
definition of nanotechnology is not always clear cut. Yet, it is still
useful to begin with some definitions. \"Nanotechnology\" is often used
with little qualification or explanation, proving ambiguous and
confusing to those trying to grow an awareness of such tiny scales. This
can be quite confusing when the term \"nano\" is used both as a nickname
for nanotechnology and a buzzword for consumer products that have no
incorporated nanotechnology (eg. \"nano\"-
car and
ipod). It is thus useful for the
student of nanoscale science to make distinctions between what is
\"branded\" as nanotechnology and what this word represents in a broader
sense. Molecular biologists could argue that since DNA is \~2.5 nm wide,
life itself is nanotechnological in nature \-- making the antibacterial
silver nanoparticles
often used in current products appear nano-primitive in comparison. SI
units, the global
standard for units of measurement, assigns the \"nano\" prefix for 10
^-9^ meters, yet in usage \"nano\" often extends to 100 times that size.
International standards based on SI units offer definitions and
terminology for clarity, so we will follow that example while
incorporating the flexibility and open-ended nature of a wiki
definition. Our emerging glossary of nano-related
terms will prove useful as we
explore the various discourses of nanotechnology.
## Imagining Nanotechnology
As a research site and active ecology of design, the discussions in all
of the many discourses of nanotechnology and nanoscience must imagine
beyond the products currently marketed or envisioned. It thus often
traffics in science fiction style scenarios, what psychologist Roland
Fischer called the \"as-if
true\" register of representation. Indeed, given the challenges of
representing these minuscule scales smaller than a wavelength of
light, \"speculative
ideas\" may be the most accurate and honest way of describing our
plausible collective imaginings of the implications of nanotechnology.
Some have proposed great advantages derived from utility fogs of flying
nanomachinery or
self replicating
nanomachines, while others
expressed fears that such technology could lead to the end of life as we
know it when self replicating nanites take over in a *hungry grey
goo* scenario. Currently there
is no theorized mechanism for creating such a situation, though the
outbreak of a synthesized organism may be a realistic concern with some
analogies to some of the feared scenarios. More profoundly, thanks to
historical experience we know that technological change alters our
planet in radical and unpredictable ways. Though speculative, such fears
and hopes can nevertheless influence public opinion considerably and
challenge our thinking thoroughly. Imaginative and informed criticism
and enthusiasm are gifts to the development of nanotechnology and must
be integrated into our visions of the plausible impacts on society and
the attitudes toward nanotechnology.
While fear leads to overzealous avoidance of a technology, the hype
suffusing nanotechnology can be equally misleading, and makes many
people brand products as \"nano\" despite there being nothing
particularly special about it at the nanoscale. Examples have even
included illnesses caused by a \"nano\" product that turned out to have
nothing \"nano\" in it.
Between the fear and the hype, efforts are made to map the plausible
future impact of nanotechnology. Hopefully this will guide us to a
framework for the development of nanotechnology, and avoidance of
excessive fear and hype in the broadcast
media. So far,
nanotechnology has probably been more disposed to hype, with much of the
public relatively uninformed about either risks or promises.
Nanotechnology may follow the trend of biotechnology, which saw early
fear
(Asilomar)
superseded by enthusiasm (The Human Genome
Project)
accompanied by widespread but narrowly focused fear (genetically
modified
organisms).
What pushes nano research between the fear and hype of markets and
institutions? Nanotechnology is driven by a market pull for better
products (sometimes a military pull to computationally \"own\"
battlespace), but also by a push from public
funding
of research hoping to open a bigger market as well as explore the
fundamental properties of matter
on the nanoscale. The push and pull factors also change our education,
particularly at universities where cross-disciplinary nano-studies are
increasingly available.
Finally, nanotechnology is a part of the evolution of not only our
technological abilities, but also of our knowledge and understanding.
The future is unknown, but it is certain to have a range of
socio-economic impacts, sculpting the ecosystem and society around us.
This chapter looks at these societal and environment aspects of the
emerging technology.
## Building Scenarios for the Plausible Implications of Nanotechnology
Scenario
building
requires scenario
planning.
## Technophobia and Technophilia Associated with Nanotechnology
### Technophobia
Technophobia exists presently as a societal reaction to the darker
aspects of modern technology. As it concerns the progress of
nanotechnology, technophobia is and will play a large role in the
broader cultural reaction. Largely since the industrial
revolution, many
different individuals and collectives of society have feared the
unintended consequences of technological progress. Moral, ethical, and
aesthetic issues propagating from emergent technologies are often at the
forefront discourse of said technologies. When society deviates from the
natural state, human conciseness tends to question the implications of a
new rationale. Historically, several groups have emerged from the swells
of technophobia, such as the
Luddites and the
Amish.
### Technophilia
It is interesting to contemplate the role that technophilia has played
in the development of nanotechnology. Early investigators such as
Drexler drew on the utopian traditions of science fiction in imagining a
Post Scarcity and even immortal future, a strand of nanotechnology and
nanotechnology that continues with the work of Kurzweil and, after a
different fashion, Joy. In more contemporary terms, it is the
technophilia of the market that seems to drive nanotechnology research:
faster and cheaper chips.
## Anticipatory Symptoms: The Foresight of Literature
*\...reengineering the computer of life using nanotechnology could
eliminate any remaining obstacles and create a level of durability and
flexibility that goes beyond the inherent capabilities of biology.*
\--Ray Kurzweil, The Singularity is
Near
*The principles of physics, as far as I can see, do not speak against
the possibility of maneuvering things atom by atom. It would be, in
principle, possible\...for a physicist to synthesize any chemical
substance that the chemist writes down..How? Put the atoms down where
the chemist says, and so you make the substance. The problems of
chemistry and biology can be greatly helped if our ability to see what
we are doing, and to do things on an atomic level, is ultimately
developed\--a development which I think cannot be avoided.* \--Richard
Feynman, There\'s Plenty of Room at the
Bottom
There is much horror, revulsion, and delight regarding the promise and
peril of nanotechnology explored in science fiction and popular
literature. When machinery can allegedly outstrip the capabilities of
biological machinery (See Kurzweil\'s
notion of transcending biology),
much room is provided for speculative scenarios to grow in this realm of
the \"as-if true\". The \"good nano/bad nano\" rhetoric is consistent in
nearly all scenarios posited by both trade science and sci-fi writers.
The \"grey goo\" scenario plays the role of the \"bad nano\", while
\"good nano\" is traffics in immortality schemes and a post scarcity
economy. The good scenario usual features a \"nanoassembler\", an as yet
unrealized machine run by physics and information\--a machine that can
create anything imagined from blankets to steel beams with a schematic
and the push of a button. Here \"good nano\" follows in the footsteps of
\"good biotech\", where life extension and radically increased health
beckoned from somewhere over the DNA rainbow. Reality, of course, has
proved more complicated
Grey goo, the fear that a self-replicating nanobot set to re-create
itself using a highly common atom such as carbon, has been played out by
many sources and is the great cliche of nanoparanoia. There are two
notable science fiction books dealing with the grey goo scenario. The
first, Aristoi "wikilink") by Walter John
Williams, describes the scenario
with little embellishment. In the book, Earth is quickly destroyed by a
goo dubbed \"Mataglap nano\" and a second Earth is created, along with a
very rigid hierarchy with the *Aristoi*\--or controllers of
nanotechnology\--at the top of the spectrum. The other, Chasm
City by Alastair
Reynolds, describes the scenario as a
virus called the *melding plague.* It converts pre-existing
nanotechnology devices to meld and operate in dramatically different
ways on a cellular level. This causes the namesake city of the novel to
turn into a large, mangled mess wildly distorted by a mass-scale
malfunctioning of nanobots.
The much more delightful (and more probable) scenario of a machine that
can create anything imagined with a schematic and raw materials is dealt
with extensively in The Diamond Age or
A Young Lady\'s Illustrated
Primer by Neil
Stephenson and The Singularity is
Near by Ray
Kurzweil. Essentially, the machine works by
combining nanobots that follow specific schematics and produces items on
an atomic level\--fairly quickly. The speculated version has *The Feed*,
a grid similar to today\'s electrical grid that delivers molecules
required to build its many tools.
Is the future of civilization safe with the fusion of
malcontent and
nanotechnology?
## Early Contexts and Precursors: Disruptive Technologies and the Implementation of the Unforeseeable
In 2004, a
study in
Switzerland was conducted on the management of nanotechnology as a
disruptive
technology.
In many organization R&D models, two general categories of technology
development are examined. "Sustainable technologies" are those new
technologies that improve existing product and market performance. Known
market conditions of existing technologies provide valuable
opportunities for the short-term success of additions and improvements
to those technologies. For example, the
iphone's entrance into the
cellular market was largely successfully due to the existence of a
pre-existing consumer cell phone market. On the other hand, "disruptive
technologies" (e.g. peer-to-peer
networks,
Twitter) often enter the market with little or
nothing to stand on - they are unprecedented in scale, often impossible
to contain and highly unpredictable in their effects. These technologies
often have few short-term benefits and can result in the failure of the
organizations that invest in such radical market introductions.
At least some nanotechnologies are likely to fit into this precarious
category of disruptive technologies. Corporations typically have little
experience with disruptive technologies, and as a result it is crucial
to include outside expertise and processes of dissensus as early as
possible in the monitoring of newly synthesized technologies. The
formation of a community of diverse minds, both inside and outside
cooperate jurisdiction, is fundamental to the process of planning a
foreseeable environment for the emergence of possible disruptive
technologies. Here, non-corporate modalities of governance (e.g.
standards organizations, open source projects, universities) may thrive
on disruptive technologies where corporations falter. Ideally in project
planning, university researchers, contributors, post-docs, and venture
capitalists should consult top-level management on a regular basis
throughout the disruptive technology evaluation process. This ensures a
broad and clear base of technological prediction and market violability
that will pave a constructive pathway for the implementation of the
unforeseeable.
A cooperative paradigm shift is more often than not needed when
evaluating disruptive technologies. Instead of responding to current
market conditions, the future market itself must be formulated. Taking
the next giant leap in corporate planning is risky and requires absolute
precision through maximum redundancy \"with a thousand pairs of eyes,
all bugs are shallow.\" Alongside consumer needs, governmental,
political, cultural, and societal values must be added into the equation
when dealing such high-stakes disruptive technologies such as
nanotechnology. Therefore, the dominant function of nanotech
introduction is not derived from a particular organization's nanotech
competence base, but from a future created by an inter-organizational
ecosystem of multiple institutions.
## Early Symptoms
### Global Standards
Global standards organizations have already worked on metrological
standards for nanotechnology,
making uniformity of measurement and terminology more likely. Global
organizations such as ISO,
IEC,
OASIS, and
BIPM would seem likely venues for standards in
*Nanotechnology & Society*.
IEC
has included environmental health and
safety
in its purview.
### Examples of Hype
Predicted revolutions tend to be difficult to make, and the
nanorevolution might turn in other directions than initially
anticipated. A lot of the exotic nanomaterials that have been presented
in the media have faded away and only remain in science fiction, perhaps
to be revisited by later researchers. Some examples of such materials
are artificial atoms or quantum
corrals, the
space elevator, and
nanites. Nano-hype exists
in our collective consciousness due to the many products with which
carry the nano-banner. The BBC demonstrated in 2008 the joy of
nano that we
currently embrace globally.
The energy required to fabricate nanomaterials and the resulting
ecological footprint might not make the nanoversion of an already
existing product worth using -- except in the beginning when it is an
exotic novelty. Carbon nanotubes in sports
gear
could be an example of such overreach. Also, a fear of the toxicity,
both biologically and ecologically speaking, from newly synthesized
nanotechnologies should be examined before *full throttle* is set on
said technologies. Heir apparent to the thrones of the Commonwealth
realms, Charles, Prince of
Wales, has made
his concerns about nano-implications known in a
statement he gave in
2004. Questions have been raised about the safety of zinc oxide
nanoparticles
in sunscreen, but the FDA has already approved of
its sale and usage. In order to expose the realities and complexities of
newly introduced nanotechnologies, and avoid another anti-biotech
movement,
nano-education
is the key.
## Surveys of Nanotechnology
Since 2000, there has been increasing focus on the health and
environmental impact of nanotechnology. This has resulted in several
reports and ongoing surveillance of nanotechnology. Nanoscience and
nanotechnologies: Opportunities and
Uncertainties is a report by
the UK Royal Society and the Royal Academy
of Engineering.
Nanorisk is a bi-monthly newsletter
published by Nanowerk LLC. Also, the
Woodrow Wilson Center for International
Scholars is starting a new project on
emerging nanotechnologies (website is under
construction) that among other things will try to map the available
nano-products and work to ensure possible risks are minimized and
benefits are realized.
## Nanoethics
Nanoethics, or the study of nanotechnology\'s ethical and social
implications, is a rising yet contentious field. Nanoethics is a
controversial field for many reasons. Some argue that it should not be
recognized as a proper area of study, suggesting that nanotechnology
itself is not a true category but rather an incorporation of other
sciences, such as chemistry, physics, biology and engineering. Critics
also claim that nanoethics does not discover new issues, but only
revisits familiar ones. Yet the scalar shift associated with engineering
tolerances at 10-9th suggests that this new mode of technology is
analogous to the introduction of entirely new \"surfaces\" to be
machined. Writing technologies or *external symbolic
storage*
(Merlin Donald) and the
wheel both opened up entirely new dimensions to technology -
consciousness and smoothed spaced respectively.
(Deleuze and
Guattari)
Outside the realms of industry, academia, and geek culture, many people
learn about nanotechnology through fictional works that hypothesize
necessarily speculative scenarios which scientists both reject and, in
the tradition of
gedankenexperiment,
rely upon. Perhaps the most successful
meme associated with nanotechnology
has ironically been Michael
Chrichton\'s treatment of
self-replicating *nanobots* running amok like a pandemic virus in his
2002 book,
Prey.
In the mainstream
media, reports
proliferate about the risks that nanotechnology poses to the
environment, health, and safety, with conflicting reports within the
growing nanotechnology industry and its trade press, both silicon and
print. To orient the ethical and social questions that arise within this
rapidly changing evolutionary dynamic, some scholars have tried to
define nanoscience and nanoethics in disciplinary terms, yet the success
of Chrichton\'s treatment may suggest that nanoethics is more likely to
be successful if it makes use of narrative as well as definitions.
Wherever possible, this wikibook will seek to use both well defined
terms and offer the framework of narrative to organize any investigation
of *nanoethics*. Nanoscience and Nanoethics: Definning The
Disciplines[^3] is an excellent
starting guide to the this newly emerging field.
Concern: scientists/engineers as
-Dr. Strangeloves? (intentional SES impact)
-Mr. Chances? (ignorant of SES impact)
- journal paper on
nanoethics1
```{=html}
<!-- -->
```
- Book on nanoethics 2
Take a look at their chapters for this section...
- Grey goo and radical
nanotechnology3
```{=html}
<!-- -->
```
- Chris Phoenix on nanoethics and a priests' article
4
and the original article
5
```{=html}
<!-- -->
```
- A nanoethics university group 6
```{=html}
<!-- -->
```
- Cordis Nanoethics project
7
Concern: Nanohazmat
- New nanomaterials are being introduced to the environment simply
through research. How many graduate students are currently washing
nanoparticles, nanowires, carbon nanotubes, functionalized
buckminsterfullerenes, and other novel synthetic nanostructures down
the drain? Might these also be biohazards? (issue: Disposal)
```{=html}
<!-- -->
```
- Oversight of nanowaste may lead to concern about other adulterants
in waste water: (issue: Contamination/propagation)
- estrogens/phytoestrogens8
- BPA9?
```{=html}
<!-- -->
```
- Might current systems (ala
MSDS10)
be modified to include this information?
```{=html}
<!-- -->
```
- What about a startup company to reprocess such materials, in the
event that some sort of legislative oversight demands qualified
disposal operations?
There may well be as many ethical issues connected with the uses of
nanotechnology as with biotechnology. [^4]
- Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*
[^5]
### Prisoner\'s Dilemma and Ethics
The prisoner\'s
dilemma constitutes a
problem in game theory. It
was originally framed by Merrill
Flood and Melvin
Dresher working at
RAND in 1950. Albert W.
Tucker formalized the
game with prison sentence payoffs and gave it the *prisoner\'s dilemma*
name
(Poundstone,
1992). In its classical form, the prisoner\'s dilemma (\"PD\") is
presented as follows:
> Two suspects are arrested by the police. The police have insufficient
> evidence for a conviction, and, having separated both prisoners, visit
> each of them to offer the same deal. If one testifies (defects from
> the other) for the prosecution against the other and the other remains
> silent (cooperates with the other), the betrayer goes free and the
> silent accomplice receives the full 10-year sentence. If both remain
> silent, both prisoners are sentenced to only six months in jail for a
> minor charge. If each betrays the other, each receives a five-year
> sentence. Each prisoner must choose to betray the other or to remain
> silent. Each one is assured that the other would not know about the
> betrayal before the end of the investigation. How should the prisoners
> act?
If we assume that each player cares only about minimizing his or her own
time in jail, then the prisoner\'s dilemma forms a non-zero-sum game in
which two players may each cooperate with or defect from (betray) the
other player. In this game, as in all game theory, the only concern of
each individual player (prisoner) is maximizing his or her own payoff,
without any concern for the other player\'s payoff. The unique
equilibrium for this game is a Pareto-suboptimal solution, that is,
rational choice leads the two players to both play defect, even though
each player\'s individual reward would be greater if they both played
cooperatively. In the classic form of this game, cooperating is strictly
dominated by defecting, so that the only possible equilibrium for the
game is for all players to defect. No matter what the other player does,
one player will always gain a greater payoff by playing defect. Since in
any situation playing defect is more beneficial than cooperating, all
rational players will play defect, all things being equal.
In the iterated prisoner\'s dilemma, the game is played repeatedly. Thus
each player has an opportunity to punish the other player for previous
non-cooperative play. If the number of steps is known by both players in
advance, economic theory says that the two players should defect again
and again, no matter how many times the game is played. Only when the
players play an indefinite or random number of times can cooperation be
an equilibrium. In this case, the incentive to defect can be overcome by
the threat of punishment. When the game is infinitely repeated,
cooperation may be a subgame perfect equilibrium, although both players
defecting always remains an equilibrium and there are many other
equilibrium outcomes. In casual usage, the label \"prisoner\'s dilemma\"
may be applied to situations not strictly matching the formal criteria
of the classic or iterative games, for instance, those in which two
entities could gain important benefits from cooperating or suffer from
the failure to do so, but find it merely difficult or expensive, not
necessarily impossible, to coordinate their activities to achieve
cooperation.
## The Nanotechnology Market and Research Environment
### Market
Value chain
- Overview of nanotech
products
```{=html}
<!-- -->
```
- Articles on the Lux report on
Nanotechnology
```{=html}
<!-- -->
```
- Lux 5'th report on
Nanotechnology
```{=html}
<!-- -->
```
- Lux nanotec index and
Article on Lux
See also notes on editing this book in About this
book.
The National Science Foundation has made predictions of the of
nanotechnology by 2015
- \$340 billion for nanostructured materials,
- \$600 billion for electronics and information-related equipment,
- \$180 billion in annual sales from nanopharmaceutircals
[^6] All in all about 1000 Billion USD.
"The National Science Foundation (a major source of funding for
nanotechnology in the United States) funded researcher David Berube to
study the field of nanotechnology. His findings are published in the
monograph "Nano-Hype: The Truth Behind the Nanotechnology Buzz\". This
published study (with a foreword by Mihail Roco, Senior Advisor for
Nanotechnology at the National Science Foundation) concludes that much
of what is sold as "nanotechnology" is in fact a recasting of
straightforward materials science, which is leading to a "nanotech
industry built solely on selling nanotubes, nanowires, and the like"
which will "end up with a few suppliers selling low margin products in
huge volumes.\"
Market analysis
- <http://www.businessweek.com/magazine/content/05_07/b3920001_mz001.htm>
```{=html}
<!-- -->
```
- The World Nanotechnology Market (2006)
11
```{=html}
<!-- -->
```
- nanotube ecology
<http://www.nanotechproject.org/file_download/files/Nanotube%20SFA%20Report_revised%20part2.pdf>
Some products have always been nanostructured:
- Carbon blac used to color the rubber black in tires is a \$4 billion
industry.
```{=html}
<!-- -->
```
- Silver used in traditional photographic films
According to Lux Research, \"only about \$13 billion worth of
manufactured goods will incorporate nanotechnology in 2005.\"
\"Toward the end of the decade, Lux predicts, nanotechnology will have
worked their way into a universe of products worth \$292 billion.\"
Three California companies are developing nanomaterial for improving
catalytic
converters:
Catalytic Solutions,
Nanostellar, and
QuantumSphere. QuantumSphere, Inc. is a
leading manufacturer of high-quality nano catalysts for applications in
portable power, renewable energy, electronics, and defense. These
nanopowders can
be used in batteries, fuel cells, air-breathing systems, and hydrogen
production cells. They are also a leading producer of *NanoNickel* and
*NanoSilve.*
Cyclics Corp adds nanoscale clays to it\'s
registered resin for higher termal stability, stiffiness, dimensional
stability, and barrier to solvent and gas penetration. *Cyclics resins
expand the use of
thermoplastics to make
plastics parts that cannot be made using thermoplastics today, and make
them better, less expensively and recyclable.*
Naturalnano is a nanomaterials company
developing applications that include industrial polymers, plastics, and
composites; and additives to cosmetics, agricultural, and household
products. Industrial Nanotech has
developed nansulate, a spray on coating
with remarkable insulating qualities claiming the highest quality
insulation on the planet with temperature ranges from -40 to 400 C. The
coating can be applied to:
Pipes-Tanks-Ducts-Boilers-Refineries-Ships-Trucks-Containers-Commercial-Industrial-Residential.
ApNano is a producer of
nanotubes and nanosphere
made from inorganic compounds. ApNano product,
Nanolub is a solid lubricant that
enhances the performance of moving parts, reduces fuel consumption, and
replaces other additives. Production will shift from the United States
and Japan to Korea and China by 2010, and the major supplier of the
nanotubes will be Korea. Nanosonic is
creating metal rubber that exhibits electrical conductivity. GE
Advanced Materials and
DOW Automotive have both
developed nanocomposite technologies for online painted vertical body
panels. Mercedes is
using a clear-cost finish that includes nanoparticle engineered to
cluster together where form a shell resistant to abrasion.
eMembrane is developing a nanoscale polymer
brush that *coats with molecules to capture and remove poisonous metal
proteins, and germs.*
A study by FTM Consulting reported
future chips that use nanotechnology are forecasted to grow in sales
from \$12.3 billion in 2009 to \$172 billion by 2014. According to one
Harvard researcher, *applied nanowires to glass substrates in solution
and then used standard photolithography techniques to create circuits*.
Nanomarkets predicts *the market for
nano-enabled electronics will reach \$10.8 billion in 2007 and \$82.5
billion in 2011.* IBM researchers created a
circuit capable of performing simple logic calculations via
self-assembled carbon nanotubes (Millipede) and Millipede will be able
to store forty times more information as current hard drives.
MRAM
will be inexpensive enough to replace
SRAM and
nanomarket predicts MRAM will rise to \$3.8 billion by 2008 and 12.9
billion by 2011. Cavendish
Kinetics store data using thousands
of electro-mechanical switches that are toggeled up or down to represent
either a one or a zero as a binary bit. Their devices use 100 times less
power and work up to a 1000 times faster. Currently, the most common
nanostorage devices are based on ferroelectric random access memory,
FRAM. Data are store
using electric fields inside a capacitor. Typically FRAM memory chips
are found in electronics devices for storing small amounts of
non-volatile data. A team from Case Western has
approached production issues by growing carbon nanotube bridges in its
lab that automatically attach themselves to other components with the
help of an applied electrical current. *You can grow building blocks of
ultra large scale integrated circuits by growing self-assembled and
self-welded carbon nanotubes.* Applied
Nanotech using an electron-beam
lithograph
carved switches from wafers made of single-crystal layers of silicon and
silicon oxide.
### Research Funding
//Michael can you tell me how much funding the EC goes to 'nano'?
How big a percentage of nano research funding is
- Corporate research funding (eg. Intel)
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- Public funding (eg. National nano initiative)
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- Military funding (public and corporate)
12
These may sum up to more than 100% since the groups overlap.
For the US 2007:
135 billion federal research
budget13
73 billion military Research, Development, Testing & Evaluation
The nanotechnology related part is a fraction of this budget amounting
to a couple of billions
14
15
(newer reference is needed)
## Open Source Nanotechnology
Common property
resource management
is critical to many areas of society. Public spaces such as forests and
rivers are natural commons that can generally be utilized by anyone.
With these natural spaces, resource management is in place to minimize
the impact of any single user. With the advent of intellectual
property, such as
publications, designs, artwork, and more recently, computer software,
the patent system seeks to
control the distribution of such information in order to secure the
livelihood of the developer. Open source is a development technique
whereby the design is decentralized and open to the community for
collaboration.
While patents reward knowledge generation by an individual or company,
the reward of open source is usually the rapid development of a quality
product. It is characterized by reliability and adaptability through
continual revisions. The most notable usage for open source is in the
software development community. The Linux operating
system is continually improved by a large
volunteer community, who desire to make robust software that can compete
with the profit-based software companies while making it freely
downloadable for users. The incentive for programmers is a highly
regarded reputation in the community and individual pride in their work.
Author Bryan Bruns believes that this open
source model can be applied to the development of nanotechnology.
Nanotechnology and the Commons - Implications of Open Source Abundance
in Millennial Quasi-Commons is
a thoroughly written paper concerning open source nanotechnology by
Bryan Bruns. The article describes roles
of the open source nanotechnology community based on the claim that the
technology for nanotechnology manufacturing will one day be ubiquitous.
Since his early work a more urgent call has been coming for
nanotechnology researchers to use open source methodologies to
development nanotechnology because a nanotechnology patent thicket is
slowing innovation.[^7] For example, a researcher argued in the journal
*Nature* the application of the open-source paradigm from software
development can both accelerate nanotechnology innovation and improve
the social return from public investment in nanotechnology research.[^8]
*Building equipment, food and other materials might become as easy, and
cheap, as printing on paper is now. Just as a laborious process of
handwriting texts was transformed first into an industrial technology
for mass production and then individualized in computer printers, so
also the manufacturing of equipment and other goods might also reach the
same level of customized production. If \"assemblers\" could fabricate
materials to order, then what would matter would not be the materials,
but the design, the knowledge lying behind manufacture. The most
important part of nanotechnology would be the software, the description
of how to assemble something. This design information would then be
quintessentially an information resource, software*. -Bryan
Bruns, Nanotechnology and the Commons -
Implications of Open Source Abundance in Millennial
Quasi-Commons
Several important elements of an open source nanotechnology community
will be:
- Establishment of standards - early adopters will have the task of
developing standards of nanotechnology design and production for
which the rest of the community will improve gradually.
- Development of containment strategies - built-in failsafes that will
prevent the unchecked reproduction and operation of
\"nanoassemblers\". One possible scheme is the design of specialized
inputs for nanoassemblers that are required for operation\--the
machine has to stop when the input runs out.
- Innovative nanotechnology design and modelling tools - software that
allows users to design and model technology produced in the
nanoscale before using time and materials to fabricate the
technology.
- Transparency to external monitoring - the ability to observe the
development of technology reduces the risk of \"unsafe\" or
\"unstable\" designs from being released into the public.
- Lowered cost - the price of managing an open source community is
insignificant compared to the cost of management to secure
intellectual property.
### Application of Open Source to Nanotechnology
There are many currently existing open source communities that can serve
as working models for an open source nanotechnology community. Internet
forums promote knowledge and community input. In addition, new forum
users are quickly exposed to a wealth of knowledge and experience. This
type of format is easily accessible and promotes widespread awareness of
the topic. One such community is:
\[H\]ard\|OCP (http://www.hardforum.com) \"\[H\]ard\|OCP (Hardware
Overclockers Comparison Page) is an online magazine that offers news,
reviews, and editorials that relate to computer hardware, software,
modding, overclockingcooling, owned and operated by Kyle Bennett, who
started the website in 1997\"\[1\]. Hardforum is a direct parallel to an
traditional open source software community. Members obtain recognition,
reputation, and respect by spending time and effort within the
community. Members can create and discuss diverse topics that are not
limited to just software. Projects focusing on case modding are of key
interest as a parallel example of what is possible for a nanotechnology
project. Within these case modding projects, specific steps,
documention, results, and pictures are all shared within the community
for both good and bad comments. The information is presented in a pure
and straight forward manor for the purpose of information sharing.
## Socioeconomic Impact of Nanotechnology
Predicting is difficult, especially about the future and nanotech is
likely not going to take us where we first anticipated.
### For a Perspective
- Nuclear technology was hailed the new era of humanity in the 60's,
but today is left with little future as a power source due to low
availability for long term Uranium
sources16
and evidence that utilization of nuclear power systems still
generates appreciable CO2
emissions[](http://www.energybulletin.net/node/15345). The
development of nuclear technology however has provided us with a
wide range of therapeutic tools in hospitals and taught us a
thorough lesson on assessing the potential environmental impact
before taking a new technology to a large scale.
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```
- DDT was once the cure-all for malaria and mosquito related diseases
as well as a general pesticide for agriculture. It turned out that
DDT accumulated in the food chain and was banned, leading to a rise
in the plagues it had almost eradicated. Today DDT is still
generally banned by slowly reintroduced to be used where it has a
high efficiency and will not be spread into nature and in minute
quantities compared to when it was lavishly sprayed onto buildings,
fields and wetlands in the 1950's.
17
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```
- I need references for this one:
Polymer technology was 'hot' in the early 90's but results were not
coming as fast as anticipated, leading to a rapid decline in funding.
But after the 'fall', the technology has matured and polymer composites
are now finding applications everywhere. One could say the technology
was actually very worthy of funding but expectations were too high
leading to disappointment. But time has been working for polymer
technology even without large scale funding and now it is reemerging
--often disguised as nanotechnology.
- Biotechnology, especially genemodified crops, were promised to
eradicate hunger and malnutritionreference
needed. Fears of the environmental
impact led to strict legislation limiting its use in practical
applications, and many cases have since proven the restrictions
sensible as new an unexpected paths for cross-breeding have been
discovered\[\[reference needed\]. However, the market pull for
cheaper products leads to increased GM production worldwide with a
wide range of socio-economic impacts such as poor farmers dependence
on expensive GM seeds, nutrition aspects and health
influence\[\[reference needed\].
These examples do not even include the military aspects of the
technologies or the spin-off to civil life from military research --
which is luckily quite large considering that in the US the military
research budget is about 40% of the annual research funding
18 reference needed and check
up on the
number!.
### Socioeconomic Impact
The examples in the previous section demonstrate clearly how difficult
it is to predict the impact of new technology society because of
contingency - the inability to know which trajectories today determine
the future.
Contingency stem from two main causes:
1\) Trends versus events
Events -Taking a non-linear dynamics and somewhat mathematical point of
view, Events (in nonlinear dynamics) are deterministic and so can be
described with a model but they are also unpredictable (i.e. the model
does not give point predictions when exactly they will occur)
Trends -- The trends we observe depend largely on the framing we have in
our perception of problems and their solutions. The framing is the
analytical lens through which we perceive evolution and it changes over
time.
### Impact of Nanotechnologies on Developing Countries
Many in developing countries suffer from very basic needs, like
malnutrition and lack of safe drinking water. Many have poor
infrastructure in private and public R&D., including small public
research budgets and virtually no venture capital.Even if they are
developing such infrastructures, they still have little experience in
technology governance, including the launch and conduct of research
programs, safety and environmental regulations, marketing and patenting
strategies, and so on. These are a couple of points to point out on the
effect of Nanoenabled cheap produced solar-cells on these counties:
- Whether a product is useful and its use is beneficial to a country
are difficult to assess in advance.
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```
- The Problem with many technologies is that scientific context often
( by definition) ignores the prevailing socioeconomic and cultural
factors of a technology, such as social acceptance, customs and
specific needs.
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```
- Expensive healthcare products only benefit the economic elite and
risk increasing the health divide between the poor and rich.
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```
- According to the NNI, nanotechnology will be the "next industrial
revolution". This can be a unique opportunity for developing
countries to quickly catch up with their economical development.
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```
- About two billion people worldwide have no access to electricity
(World Energy Council, 1999), especially in rural areas.
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```
- Nanotechnology seems to be a promising potential in increasing
efficiency and reducing cost of solar cells.
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```
- Solar technologies seem to be particularly promising for developing
countries in geographic areas with high solar radiation.
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```
- Many international organizations have promoted solar rural
electrification since the 1980's, such as UNESCO's summer schools on
Solar Electricity for Rural Areas and the Solar Village program.
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```
- The real challenges of these technologies are largely of an
educational and cultural nature.
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```
- Implementing open source into nanotechnology, cheap solar cells for
rural communities might be a possibility.
\[1\] \"Impact of nanotechnologies in the developing world\"[^9]
## Contributors
This page is largely based on contributions by Kristian
Mølhave and Richard
Doyle.
## Case Studies of Ongoing Research and Likely Implications
E SC 497H (EDSGN 497H STS 497H) is a course offered at Penn State
University entitled *Nanotransformations: The
Social, Human, and Ethical Implications of Nanotechnology.* Three case
studies from the Spring 2009 class offer new insight into three
different areas of current *Nano and Society* study: Nanotechnology and
Night
Vision;
Nanotechnology and Solar
Cells;
Practical
Nanotechnology.
A sample syllabus for courses focused on
nanotechnology\'s impact on society can prove helpful for other
researchers and academics who want to synthesize new *Nano and Society*
courses.
# References
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<references />
```
------------------------------------------------------------------------
[^1]:
[^2]: Witzany, G. (2006) The Serial Endosymbiotic Theory (SET): The
Biosemiotic Update. Acta Biotheoretica 54: 103-117
[^3]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
[^4]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^5]: Joachim Schummer and Davis Baird, *Nanotechnology Challenges,
Implications for Philosophy, Ethics and Society*, (New Jersey: World
Scientific, 2006).
[^6]: From a
review
of the book "Nano-Hype: The Truth Behind the Nanotechnology
Buzz"
[^7]: Usman Mushtaq and Joshua M. Pearce "Open Source Appropriate
Nanotechnology " Chapter 9 in editors Donald Maclurcan and Natalia
Radywyl,
\[<http://www.crcpress.com/product/isbn/9781439855768;jsessionid=JYgI1HHTCole4ja3j4h9zQ>\*\*
Nanotechnology and Global Sustainability\], CRC Press, pp. 191-213,
2012.
[^8]: Joshua M. Pearce \"Make nanotechnology research
open-source\", *Nature* **491**,
pp. 519--521(2012).
[^9]: Patrick Lin and Fritz Allhoff, Nanoethics: The Ethical and Social
Implications of Nanotechnology. Hoboken, New Jersey: John Wiley &
Sons, Inc., 2007.
|
# Fundamentals of Transportation/Introduction
!Transportation inputs and
outputs{width="500"}
Transport is the movement of humans,animals and goods from one location
to another.Transportation moves people and goods from one place to
another using a variety of vehicles across different infrastructure
systems. It does this using not only technology (namely vehicles,
energy, and infrastructure), but also people's time and effort; producing
not only the desired outputs of passenger trips and freight shipments,
but also adverse outcomes such as air pollution, noise, congestion,
crashes, injuries, and fatalities.If agriculture and industries are
supposed to be the body of country,transport may be said to be the
nerves and veins of the economy.
Figure 1 illustrates the inputs, outputs, and outcomes of
transportation. In the upper left are traditional inputs (infrastructure
including pavements, bridges, etc.), labor required to produce
transportation, land consumed by infrastructure, energy inputs, and
vehicles). Infrastructure is the traditional preserve of civil
engineering, while vehicles are anchored in mechanical engineering.
Energy, to the extent it is powering existing vehicles is a mechanical
engineering question, but the design of systems to reduce or minimize
energy consumption require thinking beyond traditional disciplinary
boundaries.
On the top of the figure are Information, Operations, and Management, and
Travelers' Time and Effort. Transportation systems serve people, and are
created by people, both the system owners and operators, who run,
manage, and maintain the system and travelers who use it. Travelers'
time depends both on freeflow time, which is a product of the
infrastructure design and on delay due to congestion, which is an
interaction of system capacity and its use. On the upper right side of
the figure are the adverse outcomes of transportation, in particular its
negative externalities:
- by polluting, systems consume health and increase morbidity and
mortality;
- by being dangerous, they consume safety and produce injuries and
fatalities;
- by being loud they consume quiet and produce noise (decreasing
quality of life and property values); and
- by emitting carbon and other pollutants, they harm the environment.
All of these factors are increasingly being recognized as costs of
transportation, but the most notable are the environmental effects,
particularly with concerns about global climate change. The bottom of
the figure shows the outputs of transportation. Transportation is central
to economic activity and to people's lives, it enables them to engage in
work, attend school, shop for food and other goods, and participate in
all of the activities that comprise human existence. More
transportation, by increasing accessibility to more destinations,
enables people to better meet their personal objectives, but entails
higher costs both individually and socially. While the "transportation
problem" is often posed in terms of congestion, that delay is but one
cost of a system that has many costs and even more benefits. Further, by
changing accessibility, transportation gives shape to the development of
land.
## Modalism and Intermodalism
Transportation is often divided into infrastructure modes: e.g. highway,
rail, water, pipeline and air. These can be further divided. Highways
include different vehicle types: cars, buses, trucks, motorcycles,
bicycles, and pedestrians. Transportation can be further separated into
freight and passenger, and urban and inter-city. Passenger
transportation is divided in public (or mass) transit (bus, rail,
commercial air) and private transportation (car, taxi, general
aviation).
These modes of course intersect and interconnect. At-grade crossings of
railroads and highways, inter-modal transfer facilities (ports,
airports, terminals, stations).
Different combinations of modes are often used on the same trip. I may
walk to my car, drive to a parking lot, walk to a shuttle bus, ride the
shuttle bus to a stop near my building, and walk into the building where
I take an elevator.
Transportation is usually considered to be between buildings (or from
one address to another), although many of the same concepts apply within
buildings. The operations of an elevator and bus have a lot in common,
as do a forklift in a warehouse and a crane at a port.
## Motivation
Transportation engineering is usually taken by undergraduate Civil
Engineering students. Not all aim to become transportation
professionals, though some do. Loosely, students in this course may
consider themselves in one of two categories: Students who intend to
specialize in transportation (or are considering it), and students who
don\'t. The remainder of civil engineering often divides into two
groups: \"Wet\" and \"Dry\". Wets include those studying water
resources, hydrology, and environmental engineering, Drys are those
involved in structures and geotechnical engineering.
### Transportation students
Transportation students have an obvious motivation in the course above
and beyond the fact that it is required for graduation. Transportation
Engineering is a pre-requisite to further study of Highway Design,
Traffic Engineering, Transportation Policy and Planning, and
Transportation Materials. It is our hope, that by the end of the
semester, many of you will consider yourselves Transportation Students.
However not all will.
### \"Wet Students\"
*I am studying Environmental Engineering or Water Resources, why should
I care about Transportation Engineering?*
Transportation systems have major environmental impacts (air, land,
water), both in their construction and utilization. By understanding how
transportation systems are designed and operate, those impacts can be
measured, managed, and mitigated.
### \"Dry Students\"
*I am studying Structures or Geomechanics, why should I care about
Transportation Engineering?*
Transportation systems are huge structures of themselves, with very
specialized needs and constraints. Only by understanding the systems can
the structures (bridges, footings, pavements) be properly designed.
Vehicle traffic is the dynamic structural load on these structures.
### Citizens and Taxpayers
Everyone participates in society and uses transportation systems. Almost
everyone complains about transportation systems. In developed countries
you seldom hear similar levels of complaints about water quality or
bridges falling down. Why do transportation systems engender such
complaints, why do they fail on a daily basis? Are transportation
engineers just incompetent? Or is something more fundamental going on?
By understanding the systems as citizens, you can work toward their
improvement. Or at least you can entertain your friends at parties.
## Goal
It is often said that the goal of Transportation Engineering is \"The
Safe and Efficient Movement of People and Goods.\"
But that goal (safe and efficient movement of people and goods) doesn't
answer:
Who, What, When, Where, How, Why?
## Overview
This wikibook is broken into 4 major units
- Transportation
Planning:
Forecasting, determining needs and standards.
- Transit:
Transit demand, service planning, and operations.
- Traffic Engineering
(Operations):
Queueing, Traffic Flow Highway Capacity and Level of Service (LOS)
- Highway Engineering
(Design): Vehicle
Performance/Human Factors, Geometric Design
## Thought Questions
- What constraints keeps us from achieving the goal of transportation
systems?
- What is the \"Transportation Problem\"?
## Sample Problem
- Identify a transportation problem (local, regional, national, or
global) and consider solutions. Research the efficacy of various
solutions. Write a one-page memo documenting the problem and
solutions, documenting your references.
## Abbreviations
- LOS - Level of Service
- ITE - Institute of Transportation Engineers
- TRB - Transportation Research Board
- TLA - Three letter abbreviation
## Key Terms
- Hierarchy of Roads
- Functional Classification
- Modes
- Vehicles
- Freight, Passenger
- Urban, Intercity
- Public, Private
## References
|
# Fundamentals of Transportation/Pricing
**Pricing**
## Rationales for Pricing
Roadway congestion, air pollution from cars, and the lack of resources
to finance new surface transportation options present challenges. Road
pricing, charging users a monetary toll in addition to the amount of
time spent traveling, has been suggested as a solution to these
problems. While tolls are common for certain expensive facilities such
as tunnels and bridges, they are less common on streets and highways. A
new generation of private toll roads are being deployed in the United
States and elsewhere. There have been a few trials of areawide pricing
schemes, such as in Singapore, London, and Stockholm, and many others
proposed but not implemented.
In short pricing can accomplish several objectives
- Revenue
- Congestion management - Traffic congestion is very common in large
cities and on major highways. It is time consuming and imposes a
significant amount of uncertainty and aggravation on passengers and
freight transportation. Most of the cost of traffic congestion
caused by travelers\' selfish behaviors (see discussion of Route
Choice),
because they impose delays on others and do not pay the full
marginal cost of their trips. In economic terms, a negative
externality is created. In order to solve this problem some
economist proposed that there should be a tax on congestion. In the
first edition of his textbook, *The Economics of Welfare*,
Pigou (1920) argued for a tax on congestion and thereby launched the
literature on congestion pricing. Most economists support congestion
pricing as a good way to relieve the dilemma, while many have been
concerned about the details of implementation. Congestion charges
allocate scarce road capacity in congested areas and peak times.
Electronic Toll Collection (ETC) and Automated Vehicle
Identification (AVI) technologies allow this to be done without
delaying travelers.
- Pavement management - Pavement damage depends on vehicle weight per
axle, not total vehicle weight - the damage power rises
exponentially to the third power with the load per axle (e.g., a
rear axle of a typical 13-ton van causes over 1000 times as much
damages that of a car). In order to reflect the pavement damage
costs more accurately, Small and Winston (1989) propose a
\"graduated per-mile tax based on axle weight\". This would give
truckers (truck manufactuers) an incentive to reduce axle weights by
shifting to trucks with more axles, extending pavement life and
reducing highway maintenance. The fuel tax currently in place
provides truckers with the opposite incentives: the tax rises with a
vehicle\'s axles, since trucks with more axles require larger
engines and get lower fuel economy. They pointed out that the
pavement thickness guidelines of the American Association of State
Highway and Transportation Officials (AASHTO) fails to incorporate
economic optimization into the design procedure. For example, by
increasing rigid concrete pavement thickness only by 2.6 inches from
currently 11.2 inches to 13.8 inches would more than double the life
of the pavement.
- Off-loading costs or reallocating costs (changing who bears
burden) - Highway cost allocation studies periodically attempt to
update the amount of burden for roads borne by cars and various
classes of trucks, but they only have two policy tools (gasoline and
diesel fuel taxes) to do the job. A more robust pricing strategy
could make charges far more directly proportional to source.
- Changing energy supply indicates declining gas tax revenue
- Encourage alternatives to driving
There are reasons that road pricing is not more widespread. Until
recently, technical issues were dominant, toll collection added
considerable delay and greatly reduced net revenue with the need for
humans sitting in toll booths. However, advances in automatic vehicle
identification and tolling have enabled toll collection, without human
operators, at full speed. Other issues are fundamentally political:
concerns over privacy, equity, and the perception of double taxation.
Privacy concerns, though political, may have a technical solution, with
the use of electronic money, which is not identified with its owner,
rather than credit or debit cards or automatic identification and
billing of vehicles. Equity issues, the belief that there will be
winners and losers from the new system, may not be entirely resolvable.
Though it can be shown that under certain circumstances road pricing has
a net benefit for society as a whole, unless a mechanism exists for
making a sufficient majority of road users and voters benefit, or
perceive benefit, this concern is a roadblock to implementation.
Similarly, people may believe that they have paid for roads already
through gas taxes and general revenue, and that charging for them is
akin to double taxation. Unless users can be convinced that the revenue
raised is for maintenance and expansion, or another convincing public
purpose, the political sell will be difficult. Widespread road pricing
may require changes in the general transportation financing structure
and a clear accounting of the benefits will need to be provided.
## Theory of Congestion Pricing
!Caption: Congestion Pricing Brings About Efficient
Equilibrium.{width="400"}
Whenever a scarce and valued good such as road use is free or under
priced, demand will outstrip supply. An illustration pertaining to road
use is evident by the queues and traffic jams that occur when the number
of motorists attempting to use a section of roadway at the same time
exceeds the road's capacity. Expanding capacity to meet peak demand
results in wasteful excess capacity during non-peak periods unless the
peak users are charged the full cost of the expansion. If we look at
long-distance telephone service, allocation is determined with a market
mechanism by charging a premium for a call during peak periods and by
offering a discount during off peak periods. Consumers appear to accept
a market-based system for allocating demand in long-distance telephone
service and the system suggests this policy works.
In the case of roads, demand is allocated by congestion. The excess
demand for road use during peak periods causes congestion. Economists
believe that travel behavior is directed by the out-of-pocket expense of
a trip plus the value of time that is required. Some motorists do shift
their time of travel when congestion gets bad enough, but not enough
motorists shift to entirely alleviate the congestion. The number of
motorists that do shift their time of travel will never be sufficient to
reduce congestion because -without some sort of pricing or rationing of
road use- motorists using the road during peak periods do not have to
pay for the delays they cause each other.
Making motorists pay for the delays they caused others by making their
trips rather than just their personal costs would lead some to make
other choices. Motorists may decide to change their time of travel,
carpool, or use public transportation. Congestion pricing would allow
motorists to make peak-period trips under less congested conditions, but
only if they are willing to pay for the delays they impose on each
other. The price would be set at a level that reduces congestion to its
most efficient level, which can be shown to be the full monetary and
time cost for using a segment of road capacity during the peak period.
Decisions made by road users about where and when to use their vehicles
are made by comparing the benefits they will receive from using the road
with the costs to themselves. These costs do not include the costs they
impose on other travelers or on society as a whole, such as congestion
and environmental damage. The results from this type of behavior are
trips being made in which benefits to the motorist are less than the
costs to society. There is more traffic than can be justified and is not
efficiently located in time and capacity. If people are charged for the
costs they impose on others because of their travel decisions, then that
pattern of travel which results in optimal efficiently will occur.
## Alternative Revenue Mechanisms
Road user charging may be more or less direct. Generally, indirect
methods of road charges are related to vehicle ownership and usage.
Examples would be fixed charges for owning a car -purchase tax for
buying a new vehicle and annual licensing renewals- and variable charges
on car usage -taxes on tires oil and fuel.
Indirect methods of road charging, such as fuel taxes, are the most
commonly used in today's society because of the high volume of usage and
ease of collection. However, revenue methods like fuel taxes rarely
channel funds directly into a road or transportation fund that is
specifically for highway maintenance or development. Where there is
congestion caused by multiple road users, drivers impose a marginal
social cost in terms of delay and higher operating costs on other uses,
for which they are not being charged.
Direct charging involves monitoring the actual time or distance of
vehicle travel and charging appropriately. There are many ways in which
to carry out direct charging. With the development of electronic
technology, both off-vehicle and now in-vehicle charging mechanisms can
be implemented. Off-vehicle mechanisms are devices like manual toll
collection booths, coin operated machines, and road side auto-scanners.
In-vehicle mechanisms are magnetic cards, smart cards, and transponders.
Congestion pricing could take several forms. The most straightforward
example would be to add an extra fee to an existing toll, or to add a
peak fee on an untolled route or bridge. The charge could be a simple
peak premium price or off-peak discount received, or the charge could
vary according to the demand imposed on a facility at a specific time.
In practice, congestion pricing could take six forms:
- Point pricing, In which a highway user passing a point at a specific
time is charged a fee for passing that point regardless of the
distance traveled on a specified route;
- Cordon pricing, in which users wishing to enter a congested area are
charged fees at each entry point;
- Zone pricing, in which users traveling within a cordoned area also
pay a fee;
- Higher charges for parking in congested areas, with particular
emphasis on parking during the most congested period;
- Congestion-specific charges, in which users would be charged for
both the amount of time spent and distance traveled.
The policies have different implications for demand. General taxes
cannot be expected to reduce demand for travel in particular.
Transportation specific taxes should reduce demand to a limited extent,
but will not reduce demand on targeted road links, such as congested
facilities. A cordon toll will reduce demand crossing the cordon, but by
its nature is less targeted than "perfect tolls". While different
finance mechanisms have different implications for how they affect
demand, they also have different costs of collection. It has
historically been true that the more targeted the mechanism, the more
costly. However, with the advent of wider use of electronic toll
collection, those historical truisms may be altered. Varying the level
of jurisdiction administering the policy changes the perception of
welfare. Local governments are responsible to local citizens - their
constituents, and tend not to concern themselves with the welfare of
non-local residents. Therefore the incentive structure facing different
layers of government needs to be distinguished. The welfare resulting
from implementation when roads are owned and operated by a state may
differ from the welfare if the same financing mechanism were implemented
by a regional metropolitan planning organization that owned and operated
the roads and could retain toll revenue. Similarly, the metropolitan
planning organization differs from the county. The key reasons for these
differences relate to who pays the tolls, and whether or not the (or to
what extent) toll-payers reside within the boundaries of the local
governmental agency. A county's concern for the economic welfare of
non-county residents is minimal, as is a metropolitan regions concern
for residents of other areas. Decentralization of decision making can
thus influence the chosen policy.
## Effects of Congestion Pricing
The evidence from past changes in bridge and turnpike tolls demonstrates
that motorists do respond to changes in price. In referring to the price
elasticity of individual demand for transportation, analyses suggest an
elasticity of approximately -0.10 to -0.15 as a lower limit and -0.3 to
-0.4 as an upper limit depending on the charge, the current costs of
travel, and the capacity of alternative roads and transit systems. There
will be a decline in demand following a price increase, but consumer
demand for road use is strong enough that the percentage decline in
demand will not be as large as the percentage increase in price.
There are many possible changes in travel choice, including:
- Route, changing from tolled to untolled routes or to faster tolled
routes.
- Time, changing to earlier or later departures to avoid tolls or
tolled periods.
- Mode, changing to or away from carpools, transit, or other modes.
- Destination, changing to a closer location for non-work activities.
- Location, moving home or workplace to reduce the commute.
- Sequence, linking trips by combining multiple errands on a single
trip.
- Frequency, reducing the number of less important trips
- Presence, conducting activities by telecommuting to decrease work
related trips.
- Ownership, Motorists may also forgo ownership of automobiles to
bypass toll charges.
Congestion pricing on highways would have broad effects on the entire
transportation system by shifting the demand for transportation services
away from peak period highway use by solo drivers. A reduction in the
incentives to drive during peak periods would shift some traffic to the
off-peak, which would increase the efficiency of the road system -
therefore, reduce the demand for additional capacity. Some motorists
would continue to drive during the peak but would elect to share rides
with others or change the destinations of their trips. Sharing rides
with others would also increase the efficiency in which the system is
used by increasing the number of people per vehicle during peak periods.
Some motorists would shift to transit. The improvement in traffic flows
that would result from congestion pricing would improve service
reliability and speed, therefore, making transit more attractive than
the automobile. The increase in use of transit would increase revenues.
These revenues could be put towards increasing service frequency or
route coverage. Congestion pricing would also reduce demand for new
highway development. This would decrease the demand for capital
expenditure on road development in response to growing population and
travel demand.
## Unpacking
{width="400"}
The top part of Figure 2 shows schematically the travel time to a driver
(short run average cost) at a bottleneck or on a capacitated link
resulting from various levels of approach flow. The travel time function
relates travel time (or delay) and approach traffic flow. The greater
the approach flow, the higher the travel time. At flows below capacity
(level of service A (SA) or B (SB)), traffic flows smoothly, while at
high approach flows, those above capacity, traffic is stop and start and
is classified as level of service E (SE) or F (SF).
The bottom part of Figure 2 shows schematically the implicit demand for
travel on a link as a function of the travel time. All else equal (for
instance the price charged to users), demand to travel on a link at
level of service A (DA) is higher than demand at level of service F
(DF). However the demand and the travel time on a link are not
independent, as shown in Figure 2(A).
So the implicit demand and revealed demand are not identical, rather the
revealed demand is formed by projecting the travel time at a given flow
onto the implicit demand curves. So for instance, when the price charged
users is high, the revealed demand coincides with the implicit demand at
level of service A (DA). As the prices are lowered, the revealed demand
crosses the implicit demand curve at level of service B (DB), then DC,
DD, DE and finally at a zero money price it crosses DF. While the actual
prices that generate specific demand levels vary from place to place
with local circumstances, demand preferences, and market conditions, the
general trend (higher prices gives lower approach flow gives better
level of service) is simply an application of the law of demand from
economics along with traffic flow theory.
In other words, the change in welfare with congestion pricing depends
not only on both the change in price and quantity, but also on the
change in reservation price. The reservation price is the amount
travelers would be willing to pay at a given level of service. And at
better levels of service, travelers (and potential travelers) have a
higher reservation price.
## Welfare Analysis
!
right\|thumb\|400px
The movement along the revealed demand curve follows the shape of the
curve shown above because of the relationship between traffic flow
(quantity demanded) and travel time. Assume for instance that each level
of service category represents a one-minute increase in travel time from
the immediately better travel time. So in the graph, let the level of
service for a one minute trip be denoted SA , and for a six minute trip,
SF. The amount of traffic necessary to move from 1 minute to 2 minutes
exceeds the amount to move from 2 to 3 minutes. In other words, there is
a rising average (and thus marginal) cost in terms of time.
The concepts in Figure 2 can be used to develop the welfare analysis
shown in Figure 3. There are several areas of interest in Figure 3. The
first is defined by the lower left triangle (the blue + green) (triangle
VOZ) which is the consumer surplus when the road is unpriced. The second
is the producer surplus (profit) to the road authority when the road is
priced, illustrated by the rectangle formed in the lower left (yellow +
green) (rectangle OVWY). The third is the consumer surplus when the road
is priced, shown in gray (triangle UVW). This consumer surplus
represents a higher reservation price than the other because the level
of service is better when flow is lower.
That first area needs to be compared to the sum of the second and third
areas. If the sum of the second and third areas (OUWY) is larger than
the first (OVZ), then pricing has higher welfare than remaining
unpriced. Similarly, two price levels can be compared. In other words,
the welfare gain from pricing is equal to the yellow + gray area (VUWX)
minus the blue area (XYZ). In this particular figure, consumer's surplus
is maximized when the good is free, but overall welfare (including
producer's surplus) is not. Whether consumer's surplus is in fact higher
in a given situation depends on the slopes of the various demand curves.
The greatest welfare is achieved by maximizing the sum of the producer's
surplus rectangle and the consumer's surplus "triangle" (it may not be a
true triangle). This must recognize that the consumers surplus
triangle's hypotenuse must follow an underlying demand curve, not the
revealed demand curve. Differentiating the level of service (for
instance, providing two different levels of service at two different
prices) may result in higher overall welfare (though not necessarily
higher welfare for each individual).
## Use of the Revenue
How welfare is measured and how it is perceived are two different
things. If the producer's surplus is not returned to the users of the
system somehow the users will perceive an overall welfare gain as a
personal loss because it would be acting as an additional tax. The money
can be returned through rebates of other taxes or reinvestment in
transportation. It should be noted that the entire argument can be made
in reverse, where consumer and producers surplus are measured in time
rather than money, and the level of service is the monetary cost of
travel. This however has less practical application.
## Pricing and Cost Recovery
In low volume situations, those that are uncongested, it is unlikely
that the revenue from marginal cost congestion pricing will recover long
term fixed costs. This is because the marginal impacts of an additional
car when volume is low is almost zero, so that additional revenue which
can be raised with marginal cost pricing is also zero. Imagine a road
with one car - the car's marginal impact is zero, a marginal cost price
would also be zero, its revenue would thus be zero, which is less than
the fixed costs.
Add a second car, and marginal impacts are still nearly zero - a
phenomenon which remains true until capacity is approached.
## Vickery's Types of Congestion
- Simple interaction - light traffic, one car blocked by another,
delay is proportional to Q\^2
- Multiple interaction - 0.5 \< V/C \< 0.9
$Z = t - t_{o} = 1/s - 1/s_{o} = ax^k$
t actual time, to freeflow time, K \~ 3-5
- Bottleneck see below
- Triggerneck - overflow affects other traffic
- Network and Control - Traffic control devices transfer delay
- General Density - high traffic level in general
## Marginal Cost Pricing
Transportation is a broad field, attracting individuals with backgrounds
in engineering, economics, and planning, among others who don't share a
common model or worldview about traffic congestion. Economists look for
received technological functions that can be analyzed, but risk
misinterpreting them. Engineers seek basic economic concepts to manage
traffic, which they view as their own purview. These two fields
intersect in the domain of congestion pricing. However many engineers
view pricing with suspicion, believing that many economists are
overstating its efficacy, while the economists are frustrated with
engineering intransigence, and consider engineers as lacking
understanding of basic market principles.
This section applies the microscopic model of traffic congestion that to
congestion pricing, and allows us to critique the plausibility of
several economic models of congestion that have appeared in the
literature.
This section uses the idea of queueing and bottlenecks to explain
congestion. If there were no bottlenecks (which can be physical and
permanent such as lane drops or steep grades, or variable such as a
traffic control device, or temporary due to a crash), there would be
very little congestion. Vehicles interacting on an uncongested road lead
to relatively minimal delays and are not further considered (Vickery
1969, Daganzo 1995) . We define congestion, or the congested period, to
be the time when there is queueing. This exceeds the time when arrivals
exceed departures, as every vehicle has to wait for all previous
vehicles to depart the front of the queue before it can.
A previous
section
developed the queueing model of congestion.
!Input output diagram at level of individual
vehicle{width="400"}
!Marginal delay at level of individual
vehicle{width="400"}
What is the implication of our queueing models for marginal cost
pricing?
First, the use of hourly average time vs. flow functions such as the
Bureau of Public Roads function, (which we introduced in the discussion
of route
choice (which
approximates the hourly average delay from a queueing model) ignores
that different vehicles within that hour have different travel times.
They are at best useful for coarse macroscopic analyses, but should
never be applied to the level of individual vehicles.
Second, travel time for a vehicle through a bottleneck depends on the
number of vehicles that have come before, but not on the number of
vehicles coming after. Similarly, the marginal delay that a vehicle
imposes is only imposed on vehicles that come after. This implies that
the first vehicle in the queue imposes the highest marginal delay, and
the last vehicles in the queue have the lowest marginal delay. A
marginal delay function that looks like figure on the right (bottom) is
generated from the typical input-output diagram shown on the figure on
the right (top). If marginal cost were equal to the marginal delay, then
our pricing function would be unusual, and perhaps unstable. The
instability might be tempered by making demand respond to price, rather
than assuming it fixed (Rafferty and Levinson 2003), and by recognizing
the stochastic nature of arrival and departure patterns, which would
flatten the arrival curve to more closely resemble the departure curve,
and thereby flatten the marginal delay curve.
However, the idea that the first vehicle \"causes\" the delay is a
controversial point. Economists will sometimes argue Coase's position
(1992) -- that it takes two to have a negative externality, that there
would be no congestion externality but for the arrival of the following
vehicles. Coase is, of course, correct. Moreover, they would note that
charging a toll to the following vehicle will discourage that vehicle
from coming and might also eliminate the congestion externality. This
may also be true. This would however be charging the sufferer of
congestion twice (once in terms of time, a second in terms of toll),
while the person with the faster trip (earlier in the queue) wouldn't
pay at all. Further, it is the followers who have already internalized
the congestion externality in their decision making, so tolling them is
charging them twice, in contrast to charging the leaders. Given that
charging either party could eliminate the externality, it would be more
reasonable to charge the delayer than the delayed, which is much like
the "polluter pays principle" advocated by environmentalists. It would
also be more equitable, in that total costs (congestion delay + toll)
would now be equalized across travelers. The disadvantage of this is
that the amount of the delay caused is unknown at the time that the
first traveler passes; at best it can be approximated.
Implicitly, this privileges the "right to uncongested travel" over the
"right to unpriced travel". That is a philosophical question, but given
that there is to be some mechanism to finance highways, we can eliminate
the notion of unpriced travel altogether, the remaining issue is how to
implement financing: with insensitive prices like gas taxes or flat
tolls or with time-dependent (or flow-dependent) congestion prices.
The marginal cost equals marginal delay formulation does ignore the
question of schedule delay. There are practical reasons for not
including schedule delay in a marginal cost price. Unlike delay,
schedule delay is not easily measured. While a road administrator can
tell you from traffic counts how much delay a traveler caused, the
administrator has no clue as to how much schedule delay was caused.
Second, if the late (early) penalty is large, then it dominates
scheduling. Travelers can decide whether they would rather endure
arriving early (without delay) or arriving on time, with some delay (or
some combination of the two), presumably minimizing their associated
costs. If they choose the delay, it is the lower cost alternative. That
lower cost is the one they suffer, and thus that serves as a lower bound
on the marginal cost to attribute to other travelers. If they choose
schedule delay (which then becomes the cost they face) and avoid the
delay, they are affected as well by other travelers, but in a way that
is unknown to pricing authorities. They are "priced out of the market",
which happens all the time. In short, endogenizing schedule delay would
be nice, but requires more information than is actually available.
## Profit Maximizing Pricing
A realistic network of highway links is not, in the economists\'
terminology, perfectly competitive. Because a link uniquely occupies
space, it attains some semblance of monopoly power. While in most cases
users can switch to alternative links and routes, those alternatives
will be more costly to the user in terms of travel time. Theory suggests
that excess profits will attract new entrants into a market, but the
cost of building a new link is high, indicating barriers to entry not
easily overcome.
Although roads are generally treated as public goods, they are both
rivalrous when congested and in many cases excludable. This indicates
that it is feasible to consider them for privatization. The advantages
often associated with privatization are several: increasing the
efficiency of the transportation system through road pricing, providing
incentives for the facility operator to improve service through
innovation and entrepreneurship, and reducing the time and cost of
building and expanding infrastructure.
An issue little addressed is implementation. Most trials of road pricing
suppose either tolls on a single facility, or area-wide control.
Theoretical studies often assume marginal cost pricing on links, and
don\'t discuss ownership structure. However, in other sectors of the
economy, central control of pricing either through government ownership
or regulation has proven itself less effective than decentralized
control for serving customer demands in rapidly changing environments.
Single prices system-wide don't provide as much information as
link-specific prices. Links which are priced only at marginal cost, the
optimal solution in a first-best, perfectly competitive environment,
constrain profit. While in the short-term, excess profit is not socially
optimal, over the longer term, it attracts capital and entrepreneurs to
that sector of the economy. New capital will both invest more in
existing technology to further deploy it and enter the sector as
competitors trying to gain from a spatial monopoly or oligopoly.
Furthermore, new capitalists may also innovate, and thereby change the
supply (and demand) curves in the industry.
By examining road pricing and privatization from a decentralized point
of view, the issues associated with a marketplace of roads can be more
fully explored, including short and long term distributional
consequences and overall social welfare. The main contribution of this
research will be to approach the problem from a theoretical and
conceptual level and through the conduct of simulation experiments. This
analysis will identify salient empirical factors and critical parameters
that determine system performance. To the extent that available data
from recent road pricing experiments becomes available, it may be used
to compare with the results of the model.
### Case 1. Simple Monopoly
` The simplest example is that of a monopoly link, `$I-J$
The link has elastic demand $Q_d$:
$Q_d =f (P)$
here given by a linear equation:
$Q_d = \beta_0 - \beta_1 P$ for all $\beta_0$ and $\beta_1 > 0$
The objective of the link is to maximize profit $\pi= P Q_d(P)$. Here
we assume no congestion effects. Profit is maximized when the first
derivative is set to zero and the second derivative is negative.
$\pi= P Q_d(P) = P (\beta_0 - \beta_1P) = \beta_0P - \beta_1P^2$ Giving
the following first order conditions (f.o.c.):
$\delta\pi/dP = \beta_0 - 2 \beta_1P = 0$
$P = \beta_0 / 2 \beta_1$
Checking second order conditions (s.o.c.), we find them to be less than
zero, as required for a maximum.
$\delta^2 \pi / \delta P^2 = - 2 \beta_1 < 0$
` For this example, if `$\beta_0 = 1000$` and `$\beta_1 = 1$`, `$P = 500$` gives `$Q_d(P)=500$`, and `$profit = 250,000$`. This situation clearly does not maximize social welfare, defined as the sum of profit and consumer surplus. Consumer surplus at `$P=500$` for this demand curve is 125,000, giving a social welfare (SW) of 375,000. Potential social welfare, maximized at `$P=0$` (when links are costless), would be `$500,000 > 375,000$`, all of which comes from consumer surplus.`
### Case 2. Monopolistic Perfect Complements
` In a second simple example, we imagine two autonomous links, `$I-J$` and `$J-K$`, which are pure monopolies and perfect complements, one cannot be consumed without consuming (driving on) the other. The links are in series.`
` In this case, demand depends on the price of both links, so we can illustrate by using the following general expression, and a linear example :`
$Q_d = f(P_{ij} , P_{kl})$
$Q_d = \beta_0 - \beta_1 (P_{ij}+P_{jk})$
Again we assume no congestion costs. When we profit maximize, we attain
a system which produces a Nash equilibrium that is both worse off for
the owners of the links, who face lower profits, and for the users of
the links, who face higher collective profits, than a monopoly. Simply
put, the links do not suffer the full extent of their own pricing policy
as they would in the case of a monopoly, where the pricing externality
is internalized.
$\pi_{ij} = P_{ij} Q_d(P) = P_{ij} (\beta_0 - \beta_1P_{ij} - \beta_1P_{jk}) = \beta_0P_{ij} - \beta_1P_{ij}^2 - \beta_1 P_{ij} P_{jk}$
$\pi_{jk} = P_{jk} Q_d(P) = P_{jk} (\beta_0 - \beta_1P_{ij} - \beta_1P_{jk}) = \beta_0P_{jk} - \beta_1P_{jk}^2 - \beta_1 P_{ij} P_{jk}$
f.o.c.
$\delta \pi / dP_{ij} = \beta_0 - 2 \beta_1P_{ij} - \beta_1P_{jk} = 0$
$P_{ij} = (\beta_0- \beta_1P_{jk}) / 2 \beta_1$
$\delta \pi / \delta P_{jk} = \beta_0 - 2 \beta_1P_{jk} - \beta_1P_{ij} = 0$
$P_{jk} = (\beta_0- \beta_1P_{ij}) / 2 \beta_1$
solving the f.o.c. simultaneously yields:
$P_{ij} = P_{jk} = \beta_0 (2 \beta_1-1) / ( 4 \beta_1^2 - \beta_1)$
checking the s.o.c.: $\delta^2 \pi / \delta P_{ij}^2 = - 2 \beta_1 < 0$
$\delta^2 \pi / \delta P_{jk}^2 = - 2 \beta_1 < 0$
` At `$\beta_0 = 1000$` and `$\beta_1 = 1$`, the solution is `$P_{ij} = P_{jk} = 333.33$`, which gives `$Q_d(P) = 333.33$`, `$\pi_{ij}=\pi_{jk}=111,111$`, which is less total profit than the case of the simple monopoly. This situation results in total profit to both firms of 222,222, and a consumer surplus of 55,555, or total social welfare of 277,000, which is less than the results from the case of a simple monopoly.`\
` Similar arguments apply to three (or more) perfect complements, which are more and more dysfunctional if operated autonomously. The general formula for N autonomous perfectly complementary links, with linear demand and `$\beta_1=1$`, is given by:`
$P = Q_d(P)= \beta_0/(N+1).$
### Case 3. Duopoly of Perfect Substitutes
` In a third example, we imagine two parallel autonomous links, `$I-J$` and `$K-L$`, which serve the same, homogenous market. They are perfect substitutes (operate in parallel).`
` The optimal pricing for this case depends upon assumptions about how users distribute themselves across suppliers and the relationships between the links. First, assume there are no congestion costs and time costs are otherwise equal and not a factor in the decision. Do users simply and deterministically choose the lowest cost link, or are there other factors which shape this choice, so that a minor reduction in price will not attract all users from the other link? For this example, we assume deterministic route choice, so demand chooses the lowest cost link, or splits between the links if they post the same price. Here, demand is defined as below:`\
` `
$Q_d = f(P_{ij},P_{kl})$
$Q_d = \beta_0 - \beta_1 min(P_{ij},P_{kl}).$
As before, let $\beta_0=1000$, $\beta_1=1$. Also assume that
competitive links can respond instantaneously. Assume each link can
serve the entire market, so that there are no capacity restrictions.
` Clearly there is a (welfare maximizing) stable equilibrium at `$P=0$` (assuming equal and zero costs for the links), the result for a competitive system. Demonstration: Suppose each link sets price 500, and had 250 users. If link IJ lowers its prices by one unit to 499, it attains all 501 users, and profits on link IJ increase to 249,999 from 125,000. However profits on link KL drop to 0. The most profitable decision for KL is to lower its price to 498, attain 502 users, and profits of 249,996. This price war can continue until profits are eliminated. At any point in the process raising prices by one link alone loses all demand.`\
` `\
` However it seems unlikely in the case of only two links. Therefore, if the links could coordinate their actions they would want to. Even in the absence of formal cartels, strategic gaming and various price signaling methods are possible. For instance, a far sighted link KL, seeing that a price war will ultimately hurt both firms, may only match the price cut rather than undercut in retaliation. If IJ did not follow with a price cut, a price will be maintained. It has been argued (Chamberlin 1933), that the duopoly would act as a monopoly, and both links would charge the monopoly price and split the demand evenly, because that is the best result for each since lowering prices will lead to a price war, with one link either matching or undercutting the other, in both cases resulting in smaller profits.`
### Case 4. Monopoly and Congestion
` The previous three cases did not exploit any special features of transportation systems. In this case travel time is introduced on the network used in Case 1. Here demand is a function of both Price (`$P$`) and Time (`$T$`):`\
` `
$Q_d = f(P,T)$
For this example is given by linear form:
$Q_d = \beta_0 - \beta_1P - \beta_2T$
where travel time is evaluated with the following expression
incorporating both distance effects and congestion (queuing at a
bottleneck over a fixed period with steady demand):
if $(Q_d/Q_o) < 1$
$T = T_{f}$
if $(Q_d/Q_o) \ge 1$
$T=T_f + (C/2)((Q_d/Q_o) - 1)$
where: $T_f$ = freeflow travel time,
` `$C$` = length of congested period, `\
` `$Q_o$` = maximum flow through bottleneck.`
` Because `$T_f$` is a constant, and we are dealing with only a single link, it can be combined with `$\beta_0$` for the analysis and won’t be considered further. By inspection, if `$Q_o$` is large, it too does not figure into the analysis. From Case 1, with the `$\beta$` as given, `$Q_o$` is only important if it is less than `$Q_d = 500$`. For this example then, we will set `$Q_o$` at a value less than 500, in this case assume `$Q_o = 250$`.`\
` `\
` As before, the objective of the link is to maximize profit `$\pi= P Q_d(P)$`. Profit is maximized when the first derivative is set to zero and the second derivative is negative.`\
` `
$\pi=PQ_d(P)=P(\beta_0-\beta_1P-\beta_2T)=\beta_0P-\beta_1P^2-\beta_2P(C/2)((Q_d/Q_o)-1)$
Giving the following first order conditions (f.o.c.):
$\delta\pi/dP=\beta_0-2\beta_1P-\beta_2(C/2)((Q_d/Q_o)-1)=0$
$P = (\beta_0-\beta_2(C/2)((Q_d/Q_o)-1))/(2\beta_1)$
Solving equations (4.2) and (4.6) simultaneously, at values:
$\beta_0= 1000$, $\beta_1= \beta_2 =1$, reflecting that the value of
time for all homogenous travelers is 1 in the chosen unit set,
$C=1800$, representing 1800 time units (such as seconds) of congestion,
we get the following answer: $P = Q_d = 339.3, T = 320.4$. It is thus
to the advantage of the monopoly in the short term, with capacity fixed,
to allow congestion (delay) to continue, rather than raising prices high
enough to eliminate it entirely. In the longer term, capacity expansion
(which reduces delay), will allow the monopoly to charge a higher price.
In this case,$\pi=115,600$, and $consumer surplus = 57,800$. There is
a large deadweight loss to congestion, as can be seen by comparing with
Case 1.
### Simulation
More complex networks are not easily analyzed in the above fashion.
Links serve as complements and substitutes at the same time.
Simulation models address the same questions posed in the analytic
model on more complex networks, that is, what are the performance
measures and market organization under different model parameters and
scenarios. Second, we can consider market organization within the model
framework, so that the question becomes: What market organization
emerges under alternative assumptions, and what are the social welfare
consequences of the organization?
Competing links restrict the price that an autonomous link can charge
and still maximize profits. Furthermore, it is likely that government
regulations will ultimately constrain prices, though the level of
regulation may provide great latitude to the owners. It is anticipated
that each link will have an objective function for profit maximization.
However, depending upon assumptions of whether the firm perfectly
knows market demand, and how the firm treats the actions of competitors,
the Nash equilibrium solution to the problem may not be unique, or even
exist.
Because the demand on a link depends on the price of both upstream and
downstream links, its complements, revenue sharing between complementary
links, and the concomitant coordination of prices, may better serve all
links, increasing their profits as well as increasing social welfare.
Vertical integration among highly complementary links is Pareto
efficient.
It is widely recognized that the roadway network is subject to economies
of density, at least up to a point. This means that as the flow of
traffic on a link increases, all else equal, the average cost of
operating the link declines. It is less clear if links are subject to
economies of scale, that it is cheaper per unit of output (for instance
per passenger kilometer traveled) to build and manage two links, a
longer link, or a wider link than it is to build and manage a single
link, a shorter link, or a narrower link. If there are such economies
of scale, then link cost functions should reflect this.
Different classes of users (rich or poor; or cars, buses, or trucks)
have different values of time. The amount of time spent on a link
depends upon flow on that link, which in turn depends on price. It may
thus be a viable strategy for some links to price high and serve fewer
customers with a high value of time, and others to price low and serve
more customers with a lower value of time. It is hypothesized that in a
sufficiently complex network, such distinct pricing strategies should
emerge from simple profit maximizing rules and limited amounts of
coordination.
There are a number of parameters and rules to be considered in such
simulation model, some are listed below.
#### Parameters
*Network Size and Shape*. The first issue that must be considered is
the size of network in terms of the number of links and nodes and how
those links connect, determined by the shape of the network (symmetric:
grid, radial; asymmetric). While the research will begin with a small
network, it is possible that the equilibrium conditions found on limited
networks may not emerge on more complex networks, giving cause for
considering a more realistic system.
*Demand Size and Shape*. A second issue is the number of
origin-destination markets served by the network, the level of demand,
and the number of user classes (each with a different value of time).
Again, while the research will begin with very simple assumptions, the
results under simple conditions may be very different from those under
slightly more complex circumstances.
#### Rules
*Profit Seeking*. How do autonomous links determine the profit
maximizing price in a dynamic situation? Underlying the decision of
each autonomous link is an objective function, profit maximization given
certain amounts of information, and a behavioral rule which dictates the
amount and direction of price changes depending on certain factors.
Once a link has found a toll which it can neither raise nor lower
without losing profit, it will be tempted to stick with it. However, a
more intelligent link may realize that while it may have found a local
maxima, because of the non-linearities comprising a complex network, it
may not be at a global maxima. Furthermore other links may not be so
firmly attached to their decision, and a periodic probing of the market
landscape by testing alternative prices is in order. This too requires
rules.
*Revenue Sharing*. It may be advantageous for complementary links to
form coalitions to coordinate their action to maximize their profit.
How do these coalition form? By the inclusion of a share of the
profits of other links in one link's objective function, that link can
price more appropriately. What level of revenue sharing, between 0 and
100 percent is best? These questions need to be tested with the model.
An interlink negotiation process will need to be developed.
*Cost Sharing*. Similar to revenue sharing is the sharing of certain
expenses that each link faces. Links face large expenses periodically,
such as resurfacing or snow clearance in winter, that have economies of
scale. These economies of scale may be realized either through single
ownership of a great many links or through the formation of economic
networks. Just as revenue sharing between links is a variable which can
be negotiated, so is cost sharing.
*Rule Evaluation and Propagation*. A final set of considerations is the
possibility of competition between rules. If we consider the rules to
be identified with the firms which own links or shares of links, and set
pricing policy, the rules can compete. Accumulated profits can be used
by more successful rules to buy shares from less successful rules. The
decision to sell will compare future expected profits under current
management with the lump sum payment by a competing firm. An open
market in the shares of links will need to be modeled to test these
issues. Similarly, it may be possible to model rules which learn, and
obtain greater intelligence iteration to iteration.
## Discussion
Just as airline networks seem to have evolved a hub and spoke hierarchy,
a specific geometry may be optimal in a private highway network.
Initial analysis indicates that there are advantages to both the
private and social welfare to vertical integration of highly
complementary links. However the degree of complementarity for which
integration serves both public and private interests remains to be
determined. Other issues that are to be examined include the influence
of substitutes and degree of competition on pricing policies through
cross-elasticity of demand, economies of scale in the provision of
infrastructure, multiple classes of users with different values of time,
"free" roads competing with toll roads, and the consequences of
regulatory constraints. Using the principles developed under the
analytic approach, a repeated game of road pricing by autonomous links
learning the behavior of the system through adaptive expectation will be
developed.
## Additional Problems
- Homework
## References
- Chamberlin, E (1933) \"Monopolistic competition\". Harvard
University Press
- Coase, Ronald (1992), \"The Problem of Social Cost, and Notes on the
Problem of Social Cost\", reprinted in *The Firm, The Market and the
Law*, Chicago: University of Chicago Press.
- Daganzo, Carlos. (1995). *An Informal Introduction To Traffic Flow
Theory*. University of California at Berkeley, Institute of
Transportation Studies. Berkeley, CA.
- Levinson, David and Peter Rafferty (2004) Delayer Pays Principle:
Examining Congestion Pricing with
Compensation.
*International Journal of Transport Economics* 31:3 295-311
- Vickrey, William (1969) Congestion Theory and Transport Investment.
*American Economic Review* 59, pp. 251--260.
|
# A-level Computing/AQA/The Computing Practical Project
***Please note, that the AQA Computing practical has since been updated,
the proportion of marks allocated to the technical solution has been
significantly increased to 42/75 (56%), compared to the 20/75 (27%) on
the old specification.***
As such anyone on the current specification will **not** need to do the
following documentation:
- i\. System Maintenance
- ii\. User Guide
The following subsections are also **no** longer required:
- i\. Analysis: Realistic appraisal of the feasibility of potential
solutions
- ii\. Analysis: Justification of chosen solution
- iii\. Design: Identification of storage media
- iv\. Design: Description of measures planned for security and
integrity of data
- v\. Design: Description of measures planned for system security
- vi\. Design: Overall test strategy
This chapter aims to give you the skills to complete your A2 Computing
project. Unlike the rest of the course this unit is entirely based on
coursework submitted in May. This is great because if you work hard
enough then you can make sure you get some really good marks, you have
access to the mark scheme after all!!The classic waterfall
model Your project
involves making a **complex programming project** that will likely
involve **data processing**, and then writing a report about it. You
have to make a program for a **real user**, this is very important, you
can\'t just make them up. It doesn\'t have to be incredibly complicated,
but you need a degree of complexity in order to write a good report. You
can write a computer game but they can be an awful lot of work (2--3
years with a team of 40+ people for the latest console games) and it\'s
often difficult to find a real life user and a real need.
Over the course of the project you will be creating a report. This is
really important and lots of people spend so much time coding that they
forget to complete the write up. The **write up is worth nearly 70% of
the mark** and will take you through a waterfall
model of system development. There are
many other forms of system
development out there and you might find yourself completing sections of
the course not necessarily in the order given, the important thing is
that you make it a cohesive whole and **complete everything**.
Please use the links below to get you started and note where all the
marks are awarded, you might create a brilliant bit of code but if you
don\'t complete your writeup your grade will suffer.
+-------------------------------------+-----------------+------------+
| Chapter | Marks | Percentage |
+=====================================+=================+============+
| |
# A-level Computing/AQA/Java
**Java** is currently one of the most popular languages in Computing
worldwide. It was created to meet the need of the Internet age, with
programs that could run on any computer architecture (type of
hardware-processor combination) without the need for the programmer to
separately compile the code for each architecture. Java was developed by
Sun Microsystems, now acquired by, and merged into, Oracle Corporation.
Java is open source under the GNU Public License, and its standards are
controlled by a community process. There is an independent version of
Java called the OpenJDK Runtime Environment
(IcedTea6 1.9.10). This has been gaining ground since Oracle took over
Sun but it uses the same API (Application Programming Interface). There
is a widely recognised set of library functions for Java that are
available on-line for free.
Oracle produce versions of Java for Windows, Mac and Linux that are free
to download and use. These include three major flavours:
- the Standard Edition comes with libraries for writing client
(desktop computer) software, not unlike the standard libraries of
many other programming languages. The Standard Edition is the one
commonly used for learning Java.
- the Enterprise Edition extends the Standard Edition by adding
powerful libraries and tools for writing sophisticated web server
applications. Most professional Java developers actually use the
Java EE, which is why you will see numerous references to it on
Oracle\'s Java web site and download pages.
- the Micro Edition can be installed alongside the Standard Edition to
give access to the cut down libraries used on many mobile phones.
The Java ME is rather long in the tooth, and most Java mobile
developers have shifted focus to Google\'s Android (which also uses
Java).
There are at least three excellent and free IDEs (Integrated Development
environments) for Java. *viz* BlueJ,
Eclipse "wikilink") and
NetBeans.
If you are starting out then the author of this page would strongly
advise that you initially compile and run a few programs with the
command line and then start with BlueJ, advantages being:
1. BlueJ does not add extra code to what you have written on
compilations. A common theme with sophisticated IDEs that many users
find that very confusing when they start out.
2. it is very well supported by a couple of Universities.
3. there is a huge tutorial
site with examples
maintained by Oracle.
## Java Myths
1. *Java is slower than C++*. This was true when Java started out but
for many years the JRE has used a \"Hotspot\" compiler which
compiles all the frequent areas of code into machine code for the
host architecture. You would be hard put to see a difference in all
but special cases designed to show off C++
2. *Java is for the web*. No Java is not for the web, it just happens
that you can easily write Java Applets for the web. Since Java is
not Architecture dependent it will run on any platform for which
there is a JRE and within most web browsers. In other words nearly
everywhere.
3. *Java is related to JavaScript*. No - JavaScript was a web scripting
language written by the Netscape people and they called it
Javascript to tag on to the coat tails of the Java Brand.
## Why Java?
- Users of many platforms can download free-of-charge Java compilers,
libraries and runtime environments, so students can easily pursue
their interest at home, work or at a computer club.
- Java has static typing, also known as strong typing, recommended by
some computer scientists to enforce contracts between modules at
compile time.
- As of 2012, Java is the standard application language for
Android "wikilink") phones and
tablets, and one of the two main languages that Google offers,
alongside Python, for its customer
APIs.
## Why not Java?
- The syntax for Java is probably more difficult for beginners than
VB or Pascal.
- Writing simple programs can take a lot more typing than python or VB
equivalents
## Getting Started
To get going you need to install a Java SDK (Software Development Kit):
the most popular is the Oracle JDK. You probably already have the JRE
(Java Runtime Environment). If you haven\'t, you get one with the JDK
anyway.
There are various versions of the JDK. The Standard Edition (Java SE)
gives you everything you need to compile programs to run on your own
computer, as well as database support. As of version 6, the Java SE SDK
come with Java DB (aka Apache Derby), a lightweight embedded database
originally developed by IBM.
To get access to something like a mysql database you will need the EE
version of the SDK (Enterprise version) and the mysql database
connector.
### SDK
- The Oracle Java
SDK
PC/Linux/Mac
- Users of Linux and Unix may find a version of the Oracle JDK or the
IcedTea6 SDK in their distribution\'s official source repository.
IcedTea6 is designed to be compatible with Oracle\'s JDK 6 and the
Java 1.6 published standards.[^1]
### IDEs
- BlueJ PC/Linux/Mac
- Eclipse PC/Linux/Mac (use the
drop down to select)
- netbeans PC/Linux/Mac
(use the drop down to select)
- IntelliJ IDEA − the open
source *Community* edition supports Standard Edition.[^2]
### Portable
Portableapps maintain a version of
eclipse that can be used from a memory stick on any windows machine
## COMP4
Java is the main language used for developing android applications. You
can download a plugin for the Eclipse IDE and there are many free
resources out there to get you started.
## Online resources
Java Programming and other Java books at
Wikibooks are listed under Java programming
language.
## Books
Useful printed books are as follows:
Title ISBN Suitable for
-------------------------------------------------------------------- ---------------- --------------
Sams Teach Yourself Java in 24 Hours (covering Java 7 and Android) 978-0672335754
Android Books:
Title ISBN Suitable for
------------------------------------------------------------------- ---------------- ----------------------------
Sams Teach Yourself Android Application Development in 24 Hours 978-0321673350 Simple android development
Hello, Android: Introducing Google\'s Mobile Development Platform 978-1934356562 Simple android development
## Notes
```{=html}
<references />
```
[^1]: In Fedora, `sudo yum install java-1.6.0-openjdk`. See also
`/usr/share/doc/system-switch-java-1.1.5/README` in the
`system-switch-java` package. In Ubuntu
`sudo aptitude install default-jdk,`
[^2]: The proprietary commercial *Ultimate* edition supports Enterprise
Edition and includes scripts to automate
refactoring.
|
# A-level Computing/AQA/Pascal
Pascal is a structured language specially designed by Niklaus Wirth for
learning programming and computer science.
## Why Pascal?
Pascal is accessible to beginners, its use of English-like syntax and
avoidance of curly brackets and other arcane symbols being similar to
Python and VB. Modern versions such as Delphi and Lazarus are very
flexible and powerful, enabling creation of console programs for AS as
well as very easy and rapid development of Graphical User Interfaces for
A2 projects. They also provide full support for Object-Oriented
Programming as required for A2. Pascal is the only language on the AQA
list which enables practical experience of pointer programming.
The open-source Free Pascal/Lazarus project provides a free, high
quality compiler and development environments for Windows, Linux and Mac
OSX.
The AQA textbook and exam papers use Pascal or Pascal-like pseudocode to
describe alogorithms.
## Why not Pascal?
The use of Pascal as a teaching language in universities peaked in the
1980\'s and is now probably extinct in the UK and US.
Pascal was never intended as a language for commercial development
though Delphi is used by some software companies especially in Eastern
Europe.
## Delphi or Free Pascal?
Lazarus/Free Pascal is
open-source, multi-platform and free!
Delphi runs only on Windows and costs
money (£23 per concurrent licence for educational use). However the
Development Environment is more polished, the compiler is much faster
and database connectivity is easier and more powerful.
## Getting Started
Download Lazarus from <http://sourceforge.net/projects/lazarus/files/>
## COMP1
Pascal fits the AQA specification very closely:
- it\'s very easy to create console programs using a purely procedural
approach (no objects or classes needed)
- the use of value and reference parameters matches that described in
the specification
- it supports static arrays, records and sets as native data types
- procedures and functions are distinguished and named as in the
specification
- traditional text files and typed files are supported
Pascal enforces strong typing and explicit variable declaration which
encourages students to think about data types before they code
## COMP3
Modern Pascal compilers provide full support for Object-Oriented
programming with a structure and syntax similar to that used in textbook
and exam questions.
The ability to use pointers explicitly, although indicative of Pascal\'s
1970\'s origins, does make it easy to teach some of the more difficult
data structure topics: linked lists, trees, use of the heap.
## COMP4
Delphi and Lazarus excel at the rapid development of graphical user
interfaces, allowing the student to spend much more time on the
underlying algorithms in their project. Only Microsoft Visual Studio
competes with this.
## Online resources
- Delphi Basics a very clear and
accesible reference, suitable for beginners
- PP4S Pascal Programming for Schools,
includes introductions to Lazarus and Delphi Object Pascal
environments
- Pascal Programming at Wikibooks
- Delphi For Fun full of excellent example
programs, including complex algorithms relevant to A2
- About Delphi includes a very good course
on connecting to databases
### Development environments
- Embarcadero Delphi
commercial and proprietary Object Pascal compiler and IDE
- Delphi via AQA
(PDF)
- Lazarus/Free Pascal open
source Object Pascal compiler and Lazarus IDE
## Books
Pascal\'s long history in universities and industry mean that it is
thoroughly documented. Useful printed books are as follows:
Title ISBN Suitable for
------------------------------------------ ------------ --------------------------------------------------
Learning to Program in Pascal and Delphi 1904467296 specially written for A Level students
Delphi in a Nutshell 1565926595 reference guide for more experienced programmers
Discover Pascal in Delphi 0201709198 beginners
|
# A-level Computing/AQA/Python
Python is a free multiplatform programming
language. Its original purpose and strengths were as a scripting
language to automate the administration of Unix systems. Both the core
language and the standard library have since been extended for many
other purposes, including web, database, interactive and graphical
applications.
## Why Python?
The reference implementation of Python, CPython,
runs almost everywhere, and is well supported for Linux, Unix, Mac OS X
and Windows. Many free text editors offer syntax highlighting, code
completion, class navigation, debugger integration and other tools.
Therefore students can pursue their interest easily at home, work or at
computer clubs.
The main implementations (CPython, Jython and
IronPython) are open source and
free-of-charge. CPython is included as standard in most Linux
distributions.
As of 2012, Python is one of the two main languages that Google offers,
alongside Java, for its customer
APIs. Though not as
popular in industry as Java and VB, it has been
adopted in various fields of employment.
Python is interpreted, so trial-and-error experimentation and debugging
can be fast. The standard runtime also includes an interactive console
with access to the executing program image.
Python has a wide range of data types, both built-in and in its standard
library, though there can be some quirks and inconsistencies among them.
For example, some types are mutable and
others are immutable.
Python\'s significant whitespace makes incorrect nesting of block
structured statements "wikilink") easy to spot.
## Why not Python?
CPython\'s virtual machine is a bytecode interpreter and execution of
Python can be much slower than say, execution of Java on its HotSpot
virtual machine with just-in-time compilation.
Python\'s significant whitespace can make it easy to break a working
method with the space bar or tab key.
Python uses variables without declaring datatypes, this can be confusing
when trying to teach them.
When using classes, python doesn\'t use the keywords public and private
to specify access to attributes and methods. They are
possible,
but may confuse students.
## 2.7 or 3.x?
When you read about python you will probably learn that there are two
different versions out there. AQA allows you to use either but which one
is most suitable for you? A quick summary:
2.7 is stable, end-of-life, no further updates, but solid and widely
deployed, with a vast array of libraries and learning resources.
3.x is the future - handles multi-lingual text correctly, many
improvements, but some libraries not yet converted.
Some tutorials written for python 2.7 won\'t work in python 3.x as there
are small changes in the language such as the `print` statement in
Python 2.x being replaced with the `print` function in Python 3.x:
``` python
print "hello world" #python 2.7
print("hello world") #python 3.x
```
You can install both and they\'ll play nicely together, but when
choosing what language to pick you might be wise to check out the
resources that you have available to your students.
## Getting Started
You can get a portable version of
python that can be run directly from a USB, available in 2.7 and 3.x
versions.
If you want to use Microsoft Visual Studio you can get
IronPython which is
free and integrates python 2.7. Alternatively
you can get Python Tools for Visual
Studio which is
free and works with existing
installations of Python 2.x and/or 3.x. This gives you syntax
highlighting, Intellisense, debugging, code folding, type hints, and
more in much the same way as Visual Studio works for other languages.
Python comes pre installed on the Raspberry
Pi with development tools and lots of
supporting learning resources.
## COMP1
### Arrays
Although some users encourage learners to use Python\'s built-in
`list` as an
array, the standard library includes the `array`
module which some teachers
may prefer. See, for example,
- <http://www.brpreiss.com/books/opus7/html/page83.html> and
- <http://stackoverflow.com/questions/176011/python-list-vs-array-when-to-use>
**Check which array the examiners prefer.**
## COMP3
### Object Orientation
Since Python doesn\'t have the concept of explicit declarations, or
PRIVATE and PUBLIC keywords, the syntax for defining classes differs
quite a lot from the generally accepted AQA syntax, e.g., the VB.NET
class\
``` vbnet
Class MediaFile
Public
Sub PlayFile
...
End Sub
Function GetTitle As String
Return Title
End Function
Function GetDuration As Single
Return Duration
End Function
Private
Dim Title As String
Dim Duration As Single
End
```
is a reasonable match to the June 2010 COMP3 question:
``` vbnet
MediaFile = Class
Public
Procedure PlayFile
Function GetTitle
Function GetDuration
Private
Title : String
Duration : Real
End
```
The Python version looks something like this:
``` python
class MediaFile
def __init__(self):
self.Title = ""
self.Duration = 0.0
def PlayFile:
...
def GetTitle(self):
return self.Title
def GetDuration(self):
return self.Duration
```
## COMP4
Python can be used to build anything from websites to games using
pygame (v2.7).
Blender "wikilink") has a python scripting engine
(3.x) meaning that it is possible to create
projects involving 3D
animation. Python also has a decent RAD (Rapid - Application -
Development) tool in the form of Glade and
PyGTK. Python\'s origins as a scripting
language mean that it can be used to glue together Unix programs to make
an application.
Open source library code can be imported, as teaching examples or to
extend the practical project, from PyPI <http://pypi.python.org/pypi> ,
with package management tools built into Python.
To ease the generation of some documentation, students may be introduced
to the `docstring`, a form of embedded documentation supported by Python
source code. A number of tools are available for generating readable
documents from source code containing docstrings, including
`pydoc` (in the standard
library), `Epydoc`,
`doxygen` and
`Sphinx` "wikilink").
For website creation, Python is one of the alternative \'P\'s in
LAMP. (Like Perl
and PHP, Python integrates well with Linux,
Unix, Apache HTTP Server and
MySQL.)
## Online resources
If you\'re already proficient in another programming language, the
official tutorial will get you up to speed at speed. Even if you\'re not
a programmer, this fast-paced, no-frills introduction will get you
programming in Python quickly, with a reasonable degree of mental pain!
- Official 3.2
tutorial
- Official 2.7 tutorial
- <http://mit.edu/6.01/mercurial/spring12/www/handouts/readings.pdf> A
free handout for an MIT first year undergraduate CS course based on
Python.
- <http://people.csail.mit.edu/pgbovine/python/> Online Python Tutor,
free graphical visualisation of step-by-step program execution.
Other Python books at Wikibooks are listed under Python programming
language.
## Books
Useful printed books are as follows:
+----------------------+----------------------+----------------------+
| Title | ISBN | Suitable for |
+======================+======================+======================+
| Python Programming | 978-1435455009 | Applications and |
| for the Absolute | | Games |
| Beginner (3.1) | | |
+----------------------+----------------------+----------------------+
| More Python | 978-1435459809 | Applications and |
| Programming for the | | Games |
| Absolute Beginner | | |
| (2.7) | | |
+----------------------+----------------------+----------------------+
| Dive Into Python | 978-1590593561\ | Websites |
| (2.7) | available for free | |
| | online | |
+----------------------+----------------------+----------------------+
| Python for Software | 978-0521725965\ | Algorithms and CS |
| Design: How to Think | available for free | thinking |
| Like a Computer | onlin | |
| Scientist (2.7) | e | |
+----------------------+----------------------+----------------------+
| Invent Your Own | 978-0982106013\ | Games |
| Computer Games with | available for free | |
| Python (3.2) | online | |
+----------------------+----------------------+----------------------+
|
# A-level Computing/AQA/VB
## Why VB?
VB.NET is an industry standard development platform. It offers a simple
syntax that is easy to learn by beginners, yet offering the latest
programming constructs and functionality.
- The Visual Studio
IDE provides a
supportive platform for new programmers, flagging up errors before
code execution, allowing for easy debugging and
predicting code snippets. By predicting
code snippets a new programmer can easily discover new program
features that they probably otherwise wouldn\'t stumble across.
- Visual Basic is not as strict as other languages and can normally
handle you declaring a variable with a capital letter and using it
with a lower case letter (some people might say that this is a bad
point!).
- Visual basic is also weakly typed,
meaning that it won\'t cause new programmer so many issues when
combining data types.
- For the second year project VB.NET allows for quick creations of
database links and forms.
- Visual Basic .NET is currently the most popular language for A-Level
Computing and wikibooks currently only supports VB.NET in its
examples. (The official textbook supports all the languages)
- VB.NET is compatible with Mono, which is an open-source project by
Xamarin (Previously Novell); an implementation of the .NET framework
which is compatible with many other operating systems. This means
your programs can be ported over with minimal effort. There is also
a compatible IDE (Integrated Development Environment) previously
named \'MonoDevelop\', now named \'Xamarin Studio\', which although
is no longer open-source, there is a free version available. Mono is
also compatible with MonoGame, which can lead on to game programming
for both PC/Mac/Linux and mobile devices.
- VB.NET is a \'gateway\' programming language which is easier to get
to grips with the concepts of programming. VB.NET easily leads on to
more powerful and advanced programming languages like C# .NET which
are more commonly used in the industry.
### VB.NET or VB 6.0
VB 6.0 has a long history and lots of
support in terms of teaching resources and available code. There are
also Development Environments freely available. However, as of March
2008 VB6 has entered Microsoft\'s \"non-supported phase\" and no further
development is being made on the language or the official development
environment. VB 6.0 is largely looked down upon within Universities and
thought by many not be be a good way to introduce programming.
VBA is a variant of VB 6.0
and is commonly used in Microsoft Office applications; especially Excel.
This can be useful for automating tasks and creating programs/games
within Excel.
VB.NET is a fairly new language built
upon the .NET framework. This means it offers interoperability with
languages such as C# "wikilink") and
F# "wikilink"). The Development
Platforms, Microsoft Visual
Studio (Windows only) and
Mono "wikilink") (cross platform), are being
actively developed and the language is fully supported by Microsoft.
VB.NET allows for easy Object Orientation and tools to create websites,
console applications and phone applications. Many academics look down
upon VB.NET, but it is unclear whether this might be a hang-over from
their hatred of VB 6.0.
The code written for each is not compatible with the other. Microsoft
provides a converter from VB 6.0 to VB.NET but it is not perfect.
Visual Basic.NET is currently the most popular language amongst centres
running AQA A-Level Computing and all code in this wikibook is provided
in VB.NET (there are plans to add python soon).
## Why not VB?
- Due to VB.NET being a young language that isn\'t used much in
universities there are fewer learning resources than you\'ll find
with the other three languages. There is very little in the way of
extension materials for learning the command line code required for
Unit 1.
- Students who don\'t have MS Windows at home might struggle to
install the Mono development environment.
- There is no \'portable\' version of the language
- VB.NET is used less by industry than Java and Python (though you
should be teaching concepts and not syntax!)
- VB.NET is very much confined to Microsoft operating systems, and it
is harder to port software over to GNU/Linux, OSX, BSD/other
operating systems, due to its use of the Microsoft .NET Framework.
## Getting started
A free version of Visual Basic 2010
Express is available from
Microsoft.
The multi-platform
Mono project
## COMP1
COMP1 requires the student to sit an exam based around a command line
program published by AQA. There are very few command line tutorials for
VB.NET and the best currently available are:
- studyvb.com
- The Nelson Thornes AQA accredited
textbook
- This wikibook has a tutorial matched to the
specification
Another way to start learning VB.NET is by starting with Microsoft Small
Basic as it is a simplified version of VB.NET: both these compilers are
available free. I would recommended that only a few weeks are spent
using this since there a number of differences, e.g., Visual Basic.NET
uses *Console* where Small Basic uses *TextWindow*.
Small Basic comes with a Tutorial
(PDF)
which is an introduction to programming and the language. Reference
Documentation is also available and
displays all the built-in Objects with their Properties and Operations.
Microsoft has also written a comprehensive
curriculum. It has the
feature to graduate to the full version and converts any Small Basic
programs in the process. One of the language\'s most useful features is
that it can publish any program online at a click of a button, providing
a shortened URL, but Silverlight is needed for this. Silverlight is
proprietary software and only officially works with Windows and OSX.
SmallBasic is not available for Linux and there are no open-source
alternatives (Like Mono and Xamarin Studio) and this may cause problems
with students who do not use a Microsoft based system.
## COMP3
To complete the COMP3 theory exam students should have experience of
programming many of the algorithms described. VB.NET allows for object
orientation with a few minor quirks.
## COMP4
The COMP4 project requires that students undertake a project of their
own. VB.NET offers the ability for students to build console apps,
forms, websites or phone apps. Students should not use Visual Basic for
Applications.
Microsoft has made video tutorials available on its Beginner Developer
Learning Center
which increase in complexity through three tiers. The first
tier introduces
the Visual Studio programming environment. The second
tier focuses on
the key features of the language through forms. Finally the third
tier follows
the development of an RSS reader, this can be useful for COMP4 projects.
They also have an
\[<http://msdn.microsoft.com/en-gb/library/bb330924(VS.80>).aspx
introduction document\] in the MSDN Library.
Home and Learn also offers useful tutorials on building a forms
application, Visual Basic .NET Programming for
Beginners.
The general wikibooks VB.NET article may
also be useful.
## Books
Useful printed books are as follows:
Title ISBN Suitable for
------------------------------------------------------------------------- ---------------- ----------------------------
Sams Teach Yourself Visual Basic 2010 in 24 Hours: Complete Starter Kit 978-0672331138 Applications and databases
Visual Basic Game Programming for Teens (3rd edition) 978-1435458109 Games and Graphics
Sams Teach Yourself ASP.NET 4 in 24 Hours: Complete Starter Kit 978-0672333057 Websites
(no known command line books)
|
# A-level Computing/AQA/CSharp
C# (pronounced \"C-sharp\") is an object-oriented programming language
from Microsoft that aims to combine the computing power of C++ with the
programming ease of Visual Basic. C# is based on C++ and contains
features similar to those of Java.
C# is designed to work with Microsoft\'s .Net platform. Microsoft\'s aim
is to facilitate the exchange of information and services over the Web,
and to enable developers to build highly portable applications. C#
simplifies programming through its use of Extensible Markup Language
(XML) and Simple Object Access Protocol (SOAP) which allow access to a
programming object or method without requiring the programmer to write
additional code for each step. Because programmers can build on existing
code, rather than repeatedly duplicating it, C# is expected to make it
faster and less expensive to get new products and services to market.
|
# Organic Chemistry/Cover
```{=html}
<div style="text-align: center;">
```
Welcome to the world\'s foremost open content\
`<big>`{=html}`<big>`{=html}`<big>`{=html}**Organic Chemistry
Textbook**`</big>`{=html}`</big>`{=html}`</big>`{=html}\
on the web!
```{=html}
</div>
```
------------------------------------------------------------------------------------------------------------------------------ ---------------------------------- -------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------ ---------------------------------- -------------------------------------------------------------------------------------------------
## The Study of Organic Chemistry
Organic chemistry is primarily devoted to the unique properties of the
carbon atom and its compounds. These compounds play a critical role in
biology and ecology, Earth sciences and geology, physics, industry,
medicine and --- of course --- chemistry. At first glance, the new
material that organic chemistry brings to the table may seem complicated
and daunting, but all it takes is concentration and perseverance.
Millions of students before you have successfully passed this course and
you can too!
This field of chemistry is based less on formulas and more on reactions
between various molecules under different conditions. Whereas a typical
general chemistry question may ask a student to compute an answer with
an equation from the chapter that they memorized, a more typical organic
chemistry question is along the lines of \"what product will form when
substance X is treated with solution Y and bombarded by light\". The key
to learning organic chemistry is to *understand* it rather than cram it
in the night before a test. It is all well and good to memorize the
mechanism of Michael addition, but a superior accomplishment would be
the ability to explain *why* such a reaction would take place.
As in all things, it is easier to build up a body of new knowledge on a
foundation of solid prior knowledge. Students will be well served by
much of the knowledge brought to this subject from the subject of
General Chemistry. Concepts with
particular importance to organic chemists are covalent bonding,
Molecular Orbit theory, VSEPR Modeling, understanding acid/base
chemistry vis-a-vis pKa values, and even trends of the periodic table.
This is by no means a comprehensive list of the knowledge you should
have gained already in order to fully understand the subject of organic
chemistry, but it should give you some idea of the things you need to
know to succeed in an organic chemistry test or course.
Organic Chemistry is one of the subjects which are very useful and close
to our daily life. We always try to figure out some of the unknown
mysteries of our daily life through our factious thinking habit, which
generates superstitions. Through the help of chemistry we can help
ourselves to get out of this kind of superstition. We always try to find
the ultimate truth through our own convenience. In the ancient past we
had struggled to make things to go as per our need. In that context we
have found fire, house, food, transportation, etc\...
Now the burning question is: \"how can chemistry help our daily life?\"
To find the answer of this questions, we have to know the subject
thoroughly. Let us start it from now.
|
# Organic Chemistry/To-Do List
\_\_NOTOC\_\_ \_\_NEWSECTIONLINK\_\_
```{=html}
<div class="noprint">
```
## Overview
This section is not meant to be part of the printed book. It is simply a
place for people working on the text to organize their thoughts about
work they have pending, ideas they\'re tossing around, and so forth.
Simply add a section for your own name and then add whatever information
you want specific to your own needs. Please do not edit or comment on
other peoples\' sections without first discussing it in the discussion
section.
Besides acting as personal reminders, it also allows other people
working on the book to see who else is working on different sections and
what plans they have, as an aid to avoid duplicated efforts, stepping on
each others\' toes, and so forth.
Just hit the + icon at the top and add a section for yourself (try not
to edit the whole page or you\'ll update the automated Last Updated code
for everyone who\'s using it.)
## Pete Davis
- Need a clear index. Functional groups rather be the lesson 1 than
one appendix.
- Need to complete ToDo sections in
cycloalkanes
- Need to complete discussions of **E1** and **E2**
elimination
reactions.
- Need to finish fixing up functional
groups
chart stolen from wikipedia
- Glossary continues to need
new definitions.
- Haloalkanes needs a lot
of work. The stuff on S~N~1 and S~N~2 reactions needs to be merged
with the existing stuff on these reactions. The text also needs to
be written like a textbook, not a checklist of information.
- We need to discuss Torsional strain somewhere. I\'m mentioning it in
cycloalkanes, but I don\'t believe it\'s covered before then and it
should probably be discussed earlier than that, probably in either
Alkanes or in the stereochemistry section.
- Okay, more strange stuff. Ethers are at the end of the Alcohol
section. Ethers should probably be their own section\...
- McMurray has Ethers in a section called *Ethers and Epoxides; Thiols
and Sulfides*. We might want to put together a miscellaneous section
similar to that. On the other hand, Carey has *Alcohols, Diols, and
Thiols* together and then a separate chapter for *Ethers, Epoxides,
and Sulfides*. There\'s an argument to be made for placing Thiols
with alcohols.
- Before Ketones and Aldehydes, we might want to have a short section
discussing carbonyls in general, since they encompass aldehydes,
ketones, carboxylic acids, esters, amides, enones, acid chlorides,
and anhydrides. I think of those, we only cover the first 3 well and
have everything else summarized pretty briefly in Carboxylic Acid
Derivatives, which barely scratches the surface on any of the
remaining. Several of them, at least, deserve more than passing
attention.
- Add Kolbe\'s Electrolysis to Carboxylic Acids page. Radical reaction
to create alkanes by decarboxylation and dimerisation of R groups of
carboxylic acids.
- Need to finish writing about bond polarities and dipole moment in
the Bonding section. And then need to discuss Molecular
Electrostatic Potential maps in Visualization.
## Up for Grabs
The items listed below need to be done, but nobody has claimed them yet.
If you want to claim one, add it to your list.
- End of chapter problems. Every chapter should have problems for the
reader to work. Instead of having them on the main chapter page,
there should be a link to the problem page and a separate link to
the answers page. We should try to come up with about 50 problems
per chapter, eventually.
```{=html}
</div>
```
## Dharav Solanki
I will start contributing to this wikibook within about two months. I
already have concise notes of the subject ready, so that gives me an
impression that a better TO-DO list exists offline for me!
I would be concentrating on other side projects as well, So I request
the other contributors to chisel out the rough works that I submit. I
believe that starting from scratch is a tad too difficult and hence I
would advocate a layered editing rather than submission of already
edited work, because otherwise, the contributions are too scarce.
- Grabbed - End Of Chapter Problems as well as Intext exercises.
```{=html}
<!-- -->
```
- A lot of editing has to be done in the works already submitted. The
text at many places is loose, in the sense that those having free
access to a library or a good tutor do not have anything to reap
from this book, while at the same time they have to stress
themselves a lot in understanding the latter two.
```{=html}
<!-- -->
```
- I feel I\'d edit the text as DIY format at places possible, so that
some of the newer logic is more like an interactive session rather
than a dull article.
\--Thewinster
(talk) 08:54, 12 February 2008 (UTC)
i think there HAS to be a individual topics such as amides rather than a
tiny tiny thing thats part of carboxylic acid derivatives. There is alot
of information missing.
|
# Organic Chemistry/Chirality
## Introduction
**Chirality** (pronounced kie-RAL-it-tee) is the property of
*handedness*. If you attempt to superimpose your right hand on top of
your left, the two do not match up in the sense that your right hand\'s
thumb overlays your left hand\'s pinky finger. Your two hands cannot be
superimposed identically, despite the fact that your fingers of each
hand are connected in the same way. Any object can have this property,
including molecules.
An object that is **chiral** is an object that can not be superimposed
on its mirror image. Chiral objects don\'t have a *plane of symmetry*.
An achiral object has a plane of symmetry or a rotation-reflection axis,
i.e. reflection gives a rotated version.
**Optical isomers** or **enantiomers** are stereoisomers which exhibit
chirality. Optical isomerism is of interest because of its application
in inorganic chemistry, organic chemistry, physical chemistry,
pharmacology and biochemistry.
They are often formed when asymmetric centers are present, for example,
a carbon with four different groups bonded to it. Every stereocenter in
one enantiomer has the opposite configuration in the other.
When a molecule has more than one source of asymmetry, two optical
isomers may be neither perfect reflections of each other nor
superimposeable: some but not all stereocenters are inverted. These
molecules are an example of **diastereomers**: They are not enantiomers.
Diastereomers seldom have the same physical properties. Sometimes, the
stereocentres are themselves symmetrical. This causes the
counterintuitive situation where two chiral centres may be present but
no isomers result. Such compounds are called **meso compounds**.
!Chiral
relationship.{width="300"}
A mixture of equal amounts of both enantiomers is said to be a **racemic
mixture**.
It is the symmetry of a molecule (or any other object) that determines
whether it is chiral or not. Technically, a molecule is achiral (not
chiral) if and only if it has an axis of improper rotation; that is, an
n-fold rotation (rotation by 360°/n) followed by a reflection in the
plane perpendicular to this axis which maps the molecule onto itself. A
chiral molecule is not necessarily dissymmetric (completely devoid of
symmetry) as it can have, e.g., rotational symmetry. A simplified rule
applies to tetrahedrally-bonded carbon, as shown in the illustration: if
all four substituents are different, the molecule is chiral.
It is important to keep in mind that molecules which are dissolved in
solution or are in the gas phase usually have considerable flexibility
and thus may adopt a variety of different conformations. These various
conformations are themselves almost always chiral. However, when
assessing chirality, one must use a structural picture of the molecule
which corresponds to just one chemical conformation -- the one of lowest
energy.
## Chiral Compounds With Stereocenters
Most commonly, chiral molecules have point chirality, centering around a
single atom, usually carbon, which has four different substituents. The
two enantiomers of such compounds are said to have different absolute
configurations at this center. This center is thus stereogenic (i.e., a
grouping within a molecular entity that may be considered a focus of
stereoisomerism), and is exemplified by the α-carbon of amino acids.
The special nature of carbon, its ability to form four bonds to
different substituents, means that a mirror
image of the carbon with four different bonds will not be the same as
the original compound, no matter how you try to rotate it. Understanding
this is vital because the goal of organic chemistry is understanding how
to use tools to synthesize a compound with the desired chirality,
because a different arrangement may have no effect, or even an undesired
one.
A carbon atom is chiral if it has four different items bonded to it at
the same time. Most often this refers to a carbon with three heteroatoms
and a hydrogen, or two heteroatoms plus a bond to another carbon plus a
bond to a hydrogen atom. It can also refer to a nitrogen atom bonded to
four different types of molecules, if the nitrogen atom is utilizing its
lone pair as a nucleophile. If the nitrogen has only three bonds it is
**not** chiral, because the lone pair of electrons can flip from one
side of the atom to the other spontaneously.
*Any atom in an organic molecule that is bonded to four different types
of atoms or chains of atoms can be considered \"chiral\".*
If a carbon atom (or other type of atom) has four different
substituents, that carbon atom forms a *chiral center* (also known as a
*stereocenter*). Chiral molecules often have one or more stereocenters.
When drawing molecules, stereocenters are usually indicated with an
asterisk near the carbon.
**Example:**
**Left**: The carbon atom has a Cl, a Br, and 2 CH~3~. That\'s only 3
different substituents, which means this is not a stereocenter.\
**Center**: The carbon atom has one ethyl group (CH~2~CH~3~), one methyl
group (CH~3~) and 2 H. This is not a stereocenter.\
**Right**: The carbon atom has a Cl and 1 H. Then you must look around
the ring. Since one side has a double bond and the other doesn\'t, it
means the substituents off that carbon are different. The 4 different
substituents make this carbon a stereocenter and makes the molecule
chiral.
A molecule can have multiple chiral centers without being chiral
overall: It is then called a meso compound. This occurs if there is a
symmetry element (a mirror plane or inversion center) which relates the
chiral centers.
### Fischer projections
Fischer projections (after the German chemist Hermann Emil
Fischer) are an ingenious means for
representing configurations of carbon atoms. Considering the carbon atom
as the center, the bonds which extend towards the viewer are placed
horizontally. Those extending away from the viewer are drawn vertically.
This process, when using the common dash and wedge representations of
bonds, yields what is sometimes referred to as the \"bowtie\" drawing
due to its characteristic shape. This representation is then further
shorthanded as two lines: the horizontal (forward) and the vertical
(back), as showed in the figure below:
!**Principle of Fischer
projection**
#### Operations on Fischer projections
- *in a Fischer projection, exchange two substituent positions results
in the inversion of the stereocenter*
- *rotation by 90° of the Fischer projection results in inversion*
- *rotation by 180° of the Fischer projection preserves the
configuration*
## Naming conventions
There are three main systems for describing configuration: the oldest,
the *relative* whose use is now deprecated, and the current, or
*absolute*. The relative configuration description is still used mainly
in glycochemistry. Configuration can also be assigned on the purely
empirical basis of the optical activity.
### By optical activity: (+)- and (-)-
An optical isomer can be named by the direction in which it rotates the
plane of polarized light. If an isomer rotates the plane clockwise as
seen by a viewer towards whom the light is traveling, that isomer is
labeled (+). Its counterpart is labeled (-). The (+) and (-) isomers
have also been termed d- and l-, respectively (for dextrorotatory and
levorotatory). This labeling is easy to confuse with D- and L- and is
therefore not encouraged by IUPAC.
The fact that an enantiomer can rotate polarised light clockwise (*d*-
or *+*- enantiomer) does not relate with the relative configuration (D-
or L-) of it.
### By relative configuration: D- and L-
Fischer, whose research interest was in carbohydrate chemistry, took
glyceraldehyde (the simplest sugar, systematic name
2,3-dihydroxypropanal) as a template chiral molecule and denoted the two
possible configurations with D- and L-, which rotated polarised light
clockwise and counterclockwise, respectively.
!Glycerladehyde, the starting molecule for *relative configuration*
assignent
{width="450"}
All other molecules are assigned the D- or L- configuration if the
chiral centre can be formally obtained from glyceraldehyde by
substitution. For this reason the D- or L- naming scheme is called
*relative configuration*.
+----------------------------------------------------------------------+
| --------------------------------------- |
| ------------------------------------------------ ------------------- |
| -------------------------------------------------------------------- |
| |
| D-glyceraldehyde |
| L-glyceraldehyde |
| !D-glyceraldehyde{width="80"} !L-glyceraldehy |
| de{width="100"} |
| !D-glyceraldehyde{width="150"} !L-glyceraldehyd |
| e{width="150"} |
| !D-glyceraldehyde{width="150"} !L-glyceralde |
| hyde{width="150"} |
| --------------------------------------- |
| ------------------------------------------------ ------------------- |
| -------------------------------------------------------------------- |
+----------------------------------------------------------------------+
An optical isomer can be named by the spatial configuration of its
atoms. The D/L system does this by relating the molecule to
glyceraldehyde. Glyceraldehyde is chiral itself, and its two isomers are
labeled D and L. Certain chemical manipulations can be performed on
glyceraldehyde without affecting its configuration, and its historical
use for this purpose (possibly combined with its convenience as one of
the smallest commonly-used chiral molecules) has resulted in its use for
nomenclature. In this system, compounds are named by analogy to
glyceraldehyde, which generally produces unambiguous designations, but
is easiest to see in the small biomolecules similar to glyceraldehyde.
!Optical isomers{width="300"} One
example is the amino acid alanine: alanine has two optical isomers, and
they are labeled according to which isomer of glyceraldehyde they come
from. Glycine, the amino acid derived from glyceraldehyde, incidentally,
does not retain its optical activity, since its central carbon is not
chiral. Alanine, however, is essentially methylated glycine and shows
optical activity.
The D/L labeling is unrelated to (+)/(-); it does not indicate which
enantiomer is dextrorotatory and which is levorotatory. Rather, it says
that the compound\'s stereochemistry is related to that of the
dextrorotatory or levorotatory enantiomer of glyceraldehyde. Nine of the
nineteen L-amino acids commonly found in proteins are dextrorotatory (at
a wavelength of 589 nm), and D-fructose is also referred to as levulose
because it is levorotatory.
The dextrorotatory isomer of glyceraldehyde is in fact the D isomer, but
this was a lucky guess. At the time this system was established, there
was no way to tell which configuration was dextrorotatory. (If the guess
had turned out wrong, the labeling situation would now be even more
confusing.)
A rule of thumb for determining the D/L isomeric form of an amino acid
is the \"CORN\" rule. The groups:
: COOH, R, NH2 and H (where R is an unnamed carbon chain)
are arranged around the chiral center carbon atom. If these groups are
arranged clockwise around the carbon atom, then it is the L-form. If
counter-clockwise, it is the D-form.This rule only holds when the
hydrogen atom is pointing out of the page.[^1]
### By absolute configuration: R- and S-
Main article: R-S
System
The absolute configuration system stems from the Cahn-Ingold-Prelog
priority rules,
which allow a precise description of a stereocenter without using any
reference compound. In fact the basis is now the atomic number of the
stereocenter substituents.
The R/S system is another way to name an optical isomer by its
configuration, without involving a reference molecule such as
glyceraldehyde. It labels each chiral center R or S according to a
system by which its ligands are each assigned a priority, according to
the Cahn Ingold Prelog priority rules, based on atomic number.
This system labels each chiral center in a molecule (and also has an
extension to chiral molecules not involving chiral centers). It thus has
greater generality than the D/L system, and can label, for example, an
(R,R) isomer versus an (R,S) --- diastereomers.
The R/S system has no fixed relation to the (+)/(-) system. An R isomer
can be either dextrorotatory or levorotatory, depending on its exact
ligands.
The R/S system also has no fixed relation to the D/L system. For
example, one of glyceraldehyde\'s ligands is a hydroxy group, -OH. If a
thiol group, -SH, were swapped in for it, the D/L labeling would, by its
definition, not be affected by the substitution. But this substitution
would invert the molecule\'s R/S labeling, due to the fact that
sulfur\'s atomic number is higher than carbon\'s, whereas oxygen\'s is
lower. \[Note: This seems incorrect. Oxygen has a higher atomic number
than carbon. Sulfur has a higher atomic number than oxygen. The reason
the assignment priorities change in this example is because the CH2SH
group gets a higher priority than the CHO, whereas in glyceraldehyde the
CHO takes priority over the CH2OH.\]
For this reason, the D/L system remains in common use in certain areas,
such as amino acid and carbohydrate chemistry. It is convenient to have
all of the common amino acids of higher organisms labeled the same way.
In D/L, they are all L. In R/S, they are not, conversely, all S --- most
are, but cysteine, for example, is R, again because of sulfur\'s higher
atomic number.
The word "racemic" is derived from the Latin word for grape; the term
having its origins in the work of Louis Pasteur who isolated racemic
tartaric acid from wine.
## Chiral Compounds Without Stereocenters
It is also possible for a molecule to be chiral without having actual
point chirality (stereocenters). Commonly encountered examples include
1,1\'-bi-2-naphthol (BINOL) and 1,3-dichloro-allene which have axial
chirality, and (E)-cyclooctene which has planar chirality.
For example, the isomers which are shown by the following figure are
different. The two isomers cannot convert from one to another
spontaneously because of restriction of rotation of double bonds.\
\
Other types of chiral compounds without stereocenters (like restriction
of rotation of a single bond because of steric hindrance) also exist.
Consider the following example of the R and S binol molecules:
-_and_(S)-BINOL.svg "(R)-_and_(S)-BINOL.svg"){width="200"}
{width="150"}
*The biphenyl C-C bond cannot rotate if the X and Y groups cause steric
hindrance.*
{width="200"}
*This compound exhibits spiral chirality.*
## Properties of optical isomers
Enantiomers have -- *when present in a symmetric environment* --
identical chemical and physical properties except for their ability to
rotate plane-polarized light by equal amounts but in opposite
directions. A solution of equal parts of an optically-active isomer and
its enantiomer is known as a racemic solution and has a net rotation of
plane-polarized light of zero.
Enantiomers differ in how they interact with different optical isomers
of other compounds. In nature, most biological compounds (such as amino
acids) occur as single enantiomers. As a result, different enantiomers
of a compound may have substantially different biological effects.
Different enantiomers of the same chiral drug can have very different
pharmological effects, mainly because the proteins they bind to are also
chiral.
For example, spearmint leaves and caraway seeds respectively contain
L-carvone and D-carvone -- enantiomers of carvone. These smell different
to most people because our taste receptors also contain chiral molecules
which behave differently in the presence of different enantiomers.
!Limonene enantiomers have different
smells.{width="300"}
D-form Amino acids tend to taste sweet, whereas L-forms are usually
tasteless. This is again due to our chiral taste molecules. The smells
of oranges and lemons are examples of the D and L enantiomers.
Penicillin\'s activity is stereoselective. The antibiotic only works on
peptide links of D-alanine which occur in the cell walls of bacteria --
but not in humans. The antibiotic can kill only the bacteria, and not
us, because we don\'t have these D-amino acids.
The electric and magnetic fields of polarized light oscillate in a
geometric plane. An axis normal to this plane gives the direction of
energy propagation. Optically active isomers rotate the plane that the
fields oscillate in. The polarized light is actually rotated in a
racemic mixture as well, but it is rotated to the left by one of the two
enantiomers, and to the right by the other, which cancel out to zero net
rotation.
## Chirality in biology
Many biologically-active molecules are chiral, including the
naturally-occurring amino acids (the building blocks of proteins), and
sugars. Interestingly, in biological systems most of these compounds are
of the same chirality: most amino acids are L and sugars are D. The
origin of this homochirality in biology is the subject of much debate.
!Enantiomers of amino
acids.
Chiral objects have different interactions with the two enantiomers of
other chiral objects. Enzymes, which are chiral, often distinguish
between the two enantiomers of a chiral substrate. Imagine an enzyme as
having a glove-like cavity which binds a substrate. If this glove is
right handed, then one enantiomer will fit inside and be bound while the
other enantiomer will have a poor fit and is unlikely to bind.
## Chirality in inorganic chemistry
![\[Ru(2,2\'-bipyridine)~3~\]^2+^](Delta-ruthenium-tris(bipyridine)-cation-3D-balls.png "[Ru(2,2'-bipyridine)3]2+")
Many coordination compounds are chiral; for example the well-known
\[Ru(2,2\'-bipyridine)~3~\]^2+^ complex in which the three bipyridine
ligands adopt a chiral propeller-like arrangement \[7\]. In this case,
the Ru atom may be regarded as a stereogenic centre, with the complex
having point chirality. The two enantiomers of complexes such as
\[Ru(2,2\'-bipyridine)3\]2+ may be designated as Λ (left-handed twist of
the propeller described by the ligands) and Δ (right-handed twist).
Hexol is a chiral cobalt compound.
## More definitions
- Any non-racemic chiral substance is called **scalemic**
- A chiral substance is **enantiopure** or **homochiral** when only
one of two possible enantiomers is present.
- A chiral substance is **enantioenriched** or **heterochiral** when
an excess of one enantiomer is present but not to the exclusion of
the other.
- **Enantiomeric excess** or **ee** is a measure for how much of one
enantiomer is present compared to the other. For example, in a
sample with 40% ee in R, the remaining 60% is racemic with 30% of R
and 30% of S, so that the total amount of R is 70%.
## Enantiopure preparations
Several strategies exist for the preparation of enantiopure compounds.
The first method is the separation of a racemic mixture into its
isomers. Louis Pasteur in his pioneering work was able to isolate the
isomers of tartaric acid because they crystallize from solution as
crystals with differing symmetry. A less common and more recently
discovered method is by enantiomer self-disproportionation, which is an
advanced technique involving the separation of a primarily racemic
fraction from a nearly enantiopure fraction via column chromatography.
In a non-symmetric environment (such as a biological environment)
enantiomers may react at different speeds with other substances. This is
the basis for *chiral synthesis*, which preserves a molecule\'s desired
chirality by reacting it with or catalyzing it with chiral molecules
capable of maintaining the product\'s chirality in the desired
conformation (using certain chiral molecules to help it keep its
configuration). Other methods also exist and are used by organic
chemists to synthesize only (or maybe only *mostly*) the desired
enantiomer in a given reaction.
## Enantiopure medications
Advances in industrial chemical processes have allowed pharmaceutical
manufacturers to take drugs that were originally marketed in racemic
form and divide them into individual enantiomers, each of which may have
unique properties. For some drugs, such as zopiclone, only one
enantiomer (eszopiclone) is active; the FDA has allowed such
once-generic drugs to be patented and marketed under another name. In
other cases, such as ibuprofen, both enantiomers produce the same
effects. Steroid receptor sites also show stereoisomer specificity.
Examples of racemic mixtures and enantiomers that have been marketed
include:
- **Ofloxacin** (Floxin) and **Levofloxacin** (Levaquin)
- **Bupivacaine** (Marcaine) and **Ropivacaine** (Naropin)
- **Methylphenidate** (Ritalin) and **Dexmethylphenidate** (Focalin)
- **Cetirizine** (Zyrtec) and **Levocetirizine** (Xyzal)
- **Albuterol** (Ventolin) and **Levalbuterol** (Xopenex)
- **Omeprazole** (Prilosec) and **Esomeprazole** (Nexium)
- **Citalopram** (Celexa / Cipramil) and **Escitalopram** (Lexapro /
Cipralex)
- **Zopiclone** (Imovane) and **Eszopiclone** (Lunesta)
- **Modafinil** (Provigil) and **Armodafinil** (Nuvigil) --- sulfur is
the chiral center in modafinil, instead of carbon.
Many chiral drugs must be made with high enantiomeric purity due to
potential side-effects of the other enantiomer. (The other enantiomer
may also merely be inactive.)
Consider a racemic sample of thalidomide. One enantiomer was thought to
be effective against morning sickness while the other is now known to be
teratogenic. Unfortunately, in this case administering just one of the
enantiomers to a pregnant patient would still be very dangerous as the
two enantiomers are readily interconverted *in vivo*. Thus, if a person
is given either enantiomer, both the D and L isomers will eventually be
present in the patient\'s serum and so chemical processes may not be
used to mitigate its toxicity.
!Thalidomide
enantiomers.{width="300"}
## See also
Optical
activity
------------------------------------------------------------------------
\<\< Haloalkanes \|
Stereochemistry \| Alcohols
[^1]: <http://www.chemguide.co.uk/organicprops/aminoacids/background.html>
|
# Organic Chemistry/Foundational concepts of organic chemistry
The purpose of this section is to review topics from freshman
chemistry and build the foundation for
further studies in organic chemistry.
1. History of organic
chemistry
2. Atomic
structure
3. Electronegativity
4. Bonding
5. Electron dot
structures
6. Visualization
7. Resonance
8. Acids and
bases
9. Nomenclature
------------------------------------------------------------------------
\| Alkanes \>\>
|
# Organic Chemistry/Alkanes
Alkanes are the simplest organic molecules, consisting solely of
singly-bonded carbon and hydrogen atoms. Alkanes are used as the basis
for naming the majority of organic compounds (their **nomenclature**).
Alkanes have the general formula C~n~H~2n+2~. Although their
reactivities are often rather uninteresting, they provide an excellent
basis for understanding bonding, conformation, and other important
concepts which can be generalized to more \"useful\" molecules.
# Introduction
thumb\|2,2-dimethylpropane or neopentane.\
An example of an alkane Alkanes
are the simplest and the least reactive
hydrocarbon species containing only carbons
and hydrogens. They are commercially very important, for being the
principal constituent of gasoline and lubricating oils and are
extensively employed in organic chemistry; though the role of pure
alkanes (such as hexanes) is delegated mostly to solvents.
The distinguishing feature of an alkane, making it distinct from other
compounds that also exclusively contain carbon and hydrogen, is its lack
of unsaturation. That is to say, it
contains no double or triple bonds, which are highly reactive in organic
chemistry.
Though not totally devoid of reactivity, their lack of reactivity under
most laboratory conditions makes them a relatively uninteresting, though
very important component of organic chemistry. As you will learn about
later, the energy confined within the carbon-carbon bond and the
carbon-hydrogen bond is quite high and their rapid oxidation produces a
large amount of heat, typically in the form of fire.
As said it is important, not considered very important component in the
chemistry.
## Introductory Definitions
**Organic compounds** contain **carbon** and **hydrogen** by definition
and usually other elements (e.g. **nitrogen** and **oxygen**) as well.
(CO~2~ is not an organic compound because it has no hydrogen).
**Hydrocarbons** are organic compounds that contain carbon and hydrogen
only.
**Alkanes** are hydrocarbons or organic compounds made up of only
carbon-carbon single bonds.Hence they are saturated. (as opposed to
double and triple bonds). The simplest alkane is
**methane.**
## Methane
```{=html}
<div class="noprint" style="border:1px solid gold; background:cornsilk; padding: 4px; text-align: center; float: right;">
```
`<small>`{=html} *On WP:*\
Alkanes `</small>`{=html}
```{=html}
</div>
```
Methane, (CH~4~, one carbon bonded to four hydrogens) is the simplest
organic molecule. It is a gas at standard temperature and pressure
(STP).
-------------------------------------------------------------------------
{width="150"}
Methane
-------------------------------------------------------------------------
This is a flattened, two-dimensional representation of methane that you
will see commonly. The true three-dimensional form of methane does not
have any 90 degree angles between bonded hydrogens. The bonds point to
the four corners of a tetrahedron, forming
cos^-1^(-1/3) ≈ 109.5 degree bond angles. !3D rendering of methane, a
regular tetrahedral
shape.
## Ethane
Two carbons singly bonded to each other with six hydrogens is called
**ethane**.
{width="80"}
Ethane is the second simplest hydrocarbon molecule. It can be thought of
as two methane molecules attached to each other, but with two fewer
hydrogen atoms. Note that, if we were simply to create a new bond
between the carbon centers of two methane molecules, this would violate
the octet rule for the involved atoms.
There are several common methods to draw organic molecules. They are
often used interchangeably, although some methods work better for one
situation or another. It is important to be familiar with the common
methods, as these are the \"languages\" organic chemists can use to
discuss structure with one another.
# Drawing alkanes
When writing out the alkane structures, you can use different levels of
the shorthand depending on the needs at hand in hand. For example,
pentane can be written out. Its formula is C~5~H~12~.
{width="150"},
or CH~3~--CH~2~--CH~2~--CH~2~--CH~3~,
or CH~3~(CH~2~)~3~CH~3~,
or minimized to
{width="100"}
## Line drawing shorthand
Although non-cyclic alkanes are called straight-chain alkanes they are
technically made of linked chains. This is reflected in the line-drawing
method. Each ending point and bend in the line represents one carbon
atom and each short line represents one single carbon-carbon bond. Every
carbon is assumed to be surrounded with a maximum number of hydrogen
atoms unless shown otherwise.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
{width="60"} {width="85"} {width="100"}
*Propane, butane, pentane*
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Structures drawn without explicitly showing all carbon atoms are often
called \"skeletal\" structures, since they represent the skeleton or the
backbone of the molecule. In organic chemistry, carbon is very
frequently used, so chemists know that there is a carbon atom at the
endpoints of every line that is not specifically labeled.
# Conformations
**Conformers**, also called **conformational isomers**, or **rotational
isomers**,or**rotomers** are arrangements of the same molecule made
transiently different by the rotation in space about one or more single
bonds.
Other types of isomer can only be converted from one form to another by
*breaking* bonds, but conformational isomers can be made simply by
*rotating* bonds.
## Newman projections
Newman projections are drawings used to represent different positions of
parts of molecules relative to each other in space. Remember that single
bonds can rotate in space if not impeded. Newman projections represent
different positions of rotating molecule parts.
+----------------------------------+----------------------------------+
| Conformers interconvert readily, |  |
| second as parts of molecules | |
| spin. | |
+----------------------------------+----------------------------------+
| In the following drawings, | ```{=html} |
| methyl groups are on the front | <div align=center> |
| and back ends of the molecule | ``` |
| and a circle represents all that | `<small>`{=html} |
| | *Note: This is how methyl groups |
| | are represented in Newman |
| | projections* `</small>`{=html} |
| | |
| | ```{=html} |
| | </div> |
| | ``` |
+----------------------------------+----------------------------------+
```{=html}
<center>
```
+----------------------------------+----------------------------------+
| ```{=html} | ```{=html} |
| <center> | <center> |
| ``` | ``` |
| ! | ! |
| "Staggerednewmanprojection.png") | |
| | ```{=html} |
| ```{=html} | </center> |
| </center> | ``` |
| ``` | |
+----------------------------------+----------------------------------+
| ```{=html} | ```{=html} |
| <center> | <center> |
| ``` | ``` |
| **Staggered conformation** | **Eclipsed conformation**\ |
| | (front end overlaps the back and |
| ```{=html} | also unstable) |
| </center> | |
| ``` | ```{=html} |
| | </center> |
| | ``` |
+----------------------------------+----------------------------------+
```{=html}
</center>
```
## Conformations and energy
Different conformations have different potential energies. The staggered
conformation is at a lower potential energy than the eclipsed
conformation, and is favored. In ethane, the barrier to rotation is
approximately 25 kJ/mol, indicating that each pair of eclipsed hydrogens
raises the energy by about 8 kJ/mol. This number also applies to other
organic compounds which have hydrogen atoms at similar distances from
each other. At very low temperatures all conformations revert to the
stabler( due to minimized vibration of atoms at it\'s mean position) ,
lower energy staggered conformation.
## Steric effects
Steric effects have to do with size. Two bulky objects run into each
other and invade each others space. If we replace one or more hydrogen
atoms on the above Newman projections with a methyl or other group, the
potential energy goes up especially for the eclipsed conformations.
Lets look at a Newman projection of butane as it rotates
counterclockwise around its axes.
```{=html}
<center>
```
+---------+---------+---------+---------+---------+---------+---------+
| ``` | ![{widt | ``` | "){widt | ``` | "){widt | ``` |
| ! | h="50"} | ! | h="50"} | ! | h="50"} | ! |
| [](Newm | | [](Newm | | [](Newm | | [](Newm |
| anproje | | anproje | | anproje | | anproje |
| ction1. | | ction2. | | ction3. | | ction4. |
| png "Ne | | png "Ne | | png "Ne | | png "Ne |
| wmanpro | | wmanpro | | wmanpro | | wmanpro |
| jection | | jection | | jection | | jection |
| 1.png") | | 2.png") | | 3.png") | | 4.png") |
| | | | | | | |
| ``` | | ``` | | ``` | | ``` |
| {=html} | | {=html} | | {=html} | | {=html} |
| </ | | </ | | </ | | </ |
| center> | | center> | | center> | | center> |
| ``` | | ``` | | ``` | | ``` |
+---------+---------+---------+---------+---------+---------+---------+
| ``` | | ``` | | ``` | | ``` |
| {=html} | | {=html} | | {=html} | | {=html} |
| < | | < | | < | | < |
| center> | | center> | | center> | | center> |
| ``` | | ``` | | ``` | | ``` |
| Anti | | E | | Gauche | | E |
| | | clipsed | | | | clipsed |
| ``` | | | | ``` | | |
| {=html} | | ``` | | {=html} | | ``` |
| </ | | {=html} | | </ | | {=html} |
| center> | | </ | | center> | | </ |
| ``` | | center> | | ``` | | center> |
| | | ``` | | | | ``` |
+---------+---------+---------+---------+---------+---------+---------+
```{=html}
</center>
```
When the larger groups overlap they repel each other more strongly than
do hydrogen, and the potential energy goes up.
## Entropy
Entropy, represented as a **ΔS**, is a mathematical construct that
represents disorder or probability. Natural systems want to find the
lowest energy or organization possible, which translates to the highest
entropy.
*A note about potential energy: If you are rusty on this, remember the
analogy of a big rock pushed to the top of a hill. At the top it has a
maximum of potential energy. When you push it and allow it to roll down
the hill the potential energy stored in it is transformed into kinetic
energy that can be used to generate heat or smash something.*
Notice that statistically, the ethane molecule has twice as many
opportunities to be in the gauche conformation as in the anti
conformation. However, because the Gauche configuration brings the
methyl groups closer together in space, this generates high energy
steric interactions and do not occur without the input of energy. Thus,
the butane molecules shown will almost never be found in such
unfavorable conformations.
# Preparation of Alkanes
### Wurtz reaction
Wurtz reaction is coupling of haloalkanes using sodium metal in solvent
like dry ether
`<B>`{=html} 2R-X + 2Na → R-R + 2Na^+^X^−^`</B>`{=html}
##### Mechanism
The reaction consists of a halogen-metal exchange involving the free
radical species R• (in a similar fashion to the formation of a Grignard
reagent and then the carbon-carbon bond formation in a nucleophilic
substitution reaction.)
One electron from the metal is transferred to the halogen to produce a
metal halide and an alkyl radical.
: R-X + M → R• + M^+^X^−^
The alkyl radical then accepts an electron from another metal atom to
form an alkyl anion and the metal becomes cationic. This intermediate
has been isolated in a several cases.
: R• + M → R^−^M^+^
The nucleophilic carbon of the alkyl anion then displaces the halide in
an S~N~2 reaction, forming a new carbon-carbon covalent bond.
: R^−^M^+^ + R-X → R-R + M^+^X^−^
: **COREY-HOUSE reactioN**
: \[Also called as \'coupling of alkyl halides with organo metallic
compounds\'\]
: It is a better method than wurtz reaction. An alkyl halides and a
lithium dialkyl copper are reacted to give a higher hydrocarbon
: R\'-X + R~2~CuLi\-\-\--\>R-R\' + R-Cu + LiX
: (R and R\' may be same or different)
: It
### Clemmensen reduction
Clemmensen reduction is a reduction of ketones (or aldehydes) to alkanes
using zinc amalgam and hydrochloric acid !The Clemmensen
reduction{width="300"}
The Clemmensen reduction is particularly effective at reducing
aryl-alkyl ketones. With aliphatic or cyclic ketones, zinc metal
reduction is much more effective
The substrate must be stable in the strongly acidic conditions of the
Clemmensen reduction. Acid sensitive substrates should be reacted in the
Wolff-Kishner reduction, which utilizes strongly basic conditions; a
further, milder method is the Mozingo reduction. As a result of
Clemmensen Reduction, the carbon of the carbonyl group involved is
converted from sp^2^ hybridisation to sp^3^ hybridisation. The oxygen
atom is lost in the form of one molecule of water.
### Wolff-Kishner reduction
!The Wolff-Kishner
reduction{width="400"}
The Wolff--Kishner reduction is a chemical reaction that fully reduces a
ketone (or aldehyde) to an alkane. Condensation of the carbonyl compound
with hydrazine forms the hydrazone, and treatment with base induces the
reduction of the carbon coupled with oxidation of the hydrazine to
gaseous nitrogen, to yield the corresponding alkane.
##### Mechanism
!The mechanism of Wolff-Kishner
reduction{width="600"}
The mechanism first involves the formation of the hydrazone in a
mechanism that is probably analogous to the formation of an imine.
Successive deprotonations eventually result in the evolution of
nitrogen. The mechanism can be justified by the evolution of nitrogen as
the thermodynamic driving force. This reaction is also used to
distinguish between aldehydes and ketones.
### Mozingo Reduction
A thioketal is first produced by reaction of the ketone with an
appropriate thiol. The product is then hydrogenolyzed to the alkane,
using Raney nickel
{width="600"}
# Properties of Alkanes
```{=html}
<div class="noprint" style="border:1px solid gold; background:cornsilk; padding: 4px; text-align: center; float: right;">
```
`<small>`{=html} *On WP:*\
Alkane properties `</small>`{=html}
```{=html}
</div>
```
Alkanes are **not very reactive** when compared with other chemical
species. This is because the backbone carbon atoms in alkanes have
attained their octet of electrons through forming four covalent bonds
(the maximum allowed number of bonds under the octet rule; which is why
carbon\'s valence number is 4). These four bonds formed by carbon in
alkanes are sigma bonds, which are more stable than other types of bond
because of the greater overlap of carbon\'s atomic orbitals with
neighboring atoms\' atomic orbitals. To make alkanes react, the input of
additional energy is needed; either through heat or radiation.
Gasoline is a mixture of the alkanes and unlike many chemicals, can be
stored for long periods and transported without problem. It is only when
ignited that it has enough energy to continue reacting. This property
makes it difficult for alkanes to be converted into other types of
organic molecules. (There are only a few ways to do this). Alkanes are
also **less dense than water**, as one can observe, oil, an alkane,
floats on water.
Alkanes are **non-polar solvents**. Since only C and H atoms are
present, alkanes are nonpolar. Alkanes are
immiscible in water but freely miscible in
other non-polar solvents. Alkanes consisting of weak dipole dipole bonds
can not break the strong hydrogen bond between water molecules hence it
is not miscible in water. The same character is also shown by alkenes.
Because alkanes contain only carbon and hydrogen, combustion produces
compounds that contain only carbon, hydrogen, and/or oxygen. Like other
hydrocarbons, combustion under most circumstances produces mainly carbon
dioxide and water. However, alkanes require more heat to combust and do
not release as much heat when they combust as other classes of
hydrocarbons. Therefore, combustion of alkanes produces higher
concentrations of organic compounds containing oxygen, such as aldehydes
and ketones, when combusting at the same temperature as other
hydrocarbons.
The general formula for alkanes is C~N~H~2N+2~; the simplest possible
alkane is therefore methane, CH~4~. The next simplest is ethane,
C~2~H~6~; the series continues indefinitely. Each carbon atom in an
alkane has sp³ hybridization.
Alkanes are also known as paraffins, or collectively as the paraffin
series. These terms are also used for alkanes whose carbon atoms form a
single, unbranched chain. Branched-chain alkanes are called
isoparaffins.
**Methane** through **Butane** are very flammable gases at standard
temperature and pressure (STP). **Pentane** is an extremely flammable
liquid boiling at 36 °C and boiling points and melting points steadily
increase from there; octadecane is the first alkane which is solid at
room temperature. Longer alkanes are waxy solids; candle wax generally
has between C~20~ and C~25~ chains. As chain length increases ultimately
we reach polyethylene, which consists of carbon chains of indefinite
length, which is generally a hard white solid.
## Chemical properties
Alkanes react only very poorly with ionic or other polar substances. The
pKa values of all alkanes are above 50, and so they are practically
inert to acids and bases. This inertness is the source of the term
paraffins (Latin para + affinis, with the meaning here of \"lacking
affinity\"). In crude oil the alkane molecules have remained chemically
unchanged for millions of years.
However redox reactions of alkanes, in particular with oxygen and the
halogens, are possible as the carbon atoms are in a strongly reduced
condition; in the case of methane, the lowest possible oxidation state
for carbon (−4) is reached. Reaction with oxygen leads to combustion
without any smoke; with halogens, substitution. In addition, alkanes
have been shown to interact with, and bind to, certain transition metal
complexes.
Free radicals, molecules with unpaired electrons, play a large role in
most reactions of alkanes, such as cracking and reformation where
long-chain alkanes are converted into shorter-chain alkanes and
straight-chain alkanes into branched-chain isomers.
In highly branched alkanes and cycloalkanes, the bond angles may differ
significantly from the optimal value (109.5°) in order to allow the
different groups sufficient space. This causes a tension in the
molecule, known as steric hinderance, and can substantially increase the
reactivity. The same is preferred for alkenes too.
# Introduction to Nomenclature
Before we can understand reactions in organic chemistry, we must begin
with a basic knowledge of naming the compounds. The
IUPAC nomenclature
is a system on which most organic chemists have agreed to provide
guidelines to allow them to learn from each others\' works.
Nomenclature, in other words, provides a foundation of language for
organic chemistry.
The names of all alkanes end with *-ane*. Whether or not the carbons are
linked together end-to-end in a ring (called *cyclic alkanes* or
*cycloalkanes*) or whether they contain side chains and branches, the
name of every carbon-hydrogen chain that lacks any double bonds or
functional groups will end with the suffix *-ane*.
Alkanes with unbranched carbon chains are simply named by the number of
carbons in the chain. The first four members of the series (in terms of
number of carbon atoms) are named as follows:
1. CH~4~ = **methane** = one hydrogen-saturated carbon
2. C~2~H~6~ = **ethane** = two hydrogen-saturated carbons
3. C~3~H~8~ = **propane** = three hydrogen-saturated carbons
4. C~4~H~10~ = **butane** = four hydrogen-saturated carbons
Alkanes with five or more carbon atoms are named by adding the suffix
*-ane* to the appropriate numerical multiplier, except the terminal *-a*
is removed from the basic numerical term. Hence, C~5~H~12~ is called
*pentane*, C~6~H~14~ is called *hexane*, C~7~H~16~ is called *heptane*
and so forth.
Straight-chain alkanes are sometimes indicated by the prefix *n-* (for
normal) to distinguish them from branched-chain alkanes having the same
number of carbon atoms. Although this is not strictly necessary, the
usage is still common in cases where there is an important difference in
properties between the straight-chain and branched-chain isomers: e.g.
*n-hexane* is a neurotoxin while its branched-chain isomers are not.
## Number of hydrogens to carbons
This equation describes the relationship between the number of hydrogen
and carbon atoms in alkanes:
: **H = 2C + 2**
where \"C\" and \"H\" are used to represent the number of carbon and
hydrogen atoms present in one molecule. If C = 2, then H = 6.
Many textbooks put this in the following format:
: **C~n~H~2n+2~**
where \"C~n~\" and \"H~2n+2~\" represent the number of carbon and
hydrogen atoms present in one molecule. If C~n~ = 3, then H~2n+2~ =
2(3) + 2 = 8. (For this formula look to the \"n\" for the number, the
\"C\" and the \"H\" letters themselves do not change.)
Progressively longer hydrocarbon chains can be made and are named
systematically, depending on the number of carbons in the longest chain.
## Naming carbon chains up to twelve
- methane (1 carbon)
- ethane (2 carbons)
- propane (3 carbons)
- butane (4 carbons)
- pentane (5 carbons)
- hexane (6 carbons)
- heptane (7 carbons)
- octane (8 carbons)
- nonane (9 carbons)
- decane (10 carbons)
- undecane (11 carbons)
- dodecane (12 carbons)
The prefixes of the first three are the contribution of a German
Chemist, August Wilhelm Hoffman, who also suggested the name quartane
for 4 carbons in 1866. However, the but- prefix had already been in use
since the 1820s and the name quartane never caught on. He also
recommended the endings to use the vowels, a, e, i (or y), o, and u, or
-ane, -ene, -ine or -yne, -one, and -une. Again, only the first three
caught on for single, double, and triple bonds and -one was already in
use for ketones. Pent, hex, hept, oct, and dec all come from the ancient
Greek numbers (penta, hex, hepta, octa, deka) and oddly, non, from the
Latin novem. For longer-chained alkanes we use the special IUPAC
multiplying affixes. For example, pentadecane signifies an alkane with
5+10 = 15 carbon atoms. For chains of length 30, 40, 50, and so on the
basic prefix is added to -contane. For example, C~57~H~116~ is named as
heptapentacontane. When the chain contains 20-29 atoms we have an
exception. C~20~H~42~ is known as icosane, and then we have, e.g.
tetracosane (eliding the \"i\" when necessary). For the length 100 we
have \"hecta\" but for 200, 300 \... 900 we have \"dicta\", \"tricta\",
and so on, eliding the \"i\" on \"icta\" when necessary; for 1000 we
have \"kilia\" but for 2000 and so on, \"dilia\", \"trilia\", and so on,
eliding the \"i\" on \"ilia\" when necessary.
We then put all of the prefixes together in reverse order. The alkane
with 9236 carbon atoms is then hexatridinoniliane.
## Isomerism
The atoms in alkanes with more than three carbon atoms can be arranged
in many ways, leading to a large number of potential different
configurations (isomers). So-called \"normal\" alkanes have a linear,
unbranched configuration, but the *n-* isomer of any given alkane is
only one of potentially hundreds or even possibly millions of
configurations for that number of carbon and hydrogen atoms in some sort
of chain arrangement.\
Isomerism is defined as the compound having same moleculer formula the
formula which present the different moleculer formula arrangement are
called as Isomerism.\
e.g.- The molecular formula for butane is C~4~H~10~.
The number of isomers increases rapidly with the number of carbon atoms
in a given alkane molecule; for alkanes with as few as 12 carbon atoms,
there are over three hundred and fifty-five possible forms the molecule
can take!
: {\| class=\"wikitable\"
\|- ! \# Carbon Atoms !! \# Isomers of Alkane \|- \| 1 \| 1 \|- \| 2 \|
1 \|- \| 3 \| 1 \|- \| 4 \| 2 \|- \| 5 \| 3 \|- \| 6 \| 5 \|- \| 7 \| 9
\|- \| 8 \| 18 \|- \| 9 \| 35 \|- \| 10 \| 75 \|- \| 11 \| 159 \|- \| 12
\| 355 \|}
## Branched chains
Carbon is able to bond in all four directions and easily forms strong
bonds with other carbon atoms. When one carbon is bonded to more than
two other carbons it forms a branch.
------------------------------------------------------------------ ------------------------------------------------------------
!Isobutane{width="200"} !Neopentane{width="200"}
------------------------------------------------------------------ ------------------------------------------------------------
Above you see a carbon bonded to three and four other carbons.
: Note: a methane group is called a **methyl** group when it is bonded
to another carbon instead of a fourth hydrogen. --CH~3~
The common system has naming convention for carbon chains as they relate
to branching.
: **n-alkanes** are linear
: **iso-alkanes** have one branch R~2~CH---
: **neo-alkanes** have two branches R~3~C---
*Note: \"R\" in organic chemistry is a placeholder that can represent
any carbon group.*
## Constitutional isomers
One of the most important characteristics of carbon is its ability to
form **several relatively strong bonds** per atom. It is for this reason
that many scientists believe that carbon is the only element that could
be the basis for the many complicated molecules needed to support a
living being.
One carbon atom can have attached to it not just the one or two other
carbons needed to form a single chain but can bond to up to four other
carbons. It is this ability to bond multiply that allows isomerism.
**Isomers** are two molecules with the same molecular formula but
different physical arrangements. **Constitutional isomers** have their
atoms arranged in a different order. A constitutional isomer of butane
has a main chain that is forked at the end and one carbon shorter in its
main chain than butane.
------------------------------------- ----------------------------------------------------------------------------------------------
!Butane !Isobutane (2-methyl-propane)"){width="100"}
------------------------------------- ----------------------------------------------------------------------------------------------
## Naming Alkanes
There are several ways or systems for the **nomenclature**, or naming,
of organic molecules, but just two main ones.
1. The traditional, non-systematic names. Many of these linger on,
especially for simpler or more common molecules.
2. The systematic **IUPAC**
(*eye-YOU-pack (International Union of Pure And Applied Chemistry)*)
names.
The IUPAC system is necessary for complicated organic compounds. It
gives a series of unified rules for naming a large compound by
conceptually dividing it up into smaller, more manageable nameable
units.
Many traditional (non-IUPAC) names are still commonly used in industry,
especially for simpler and more common chemicals, as the traditional
names were already entrenched.
## IUPAC naming rules
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`<small>`{=html} *On WP:*\
IUPAC naming
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1. Find the longest carbon chain, identify the end near which the most
substituents are located, and
number the carbons sequentially from that end. This will be the
parent chain.
2. Consider all other carbon groups as substituents.
3. Alphabetize the substituents.
4. Number the substituents according to the carbon to which they are
attached. If numbering can be done in more than one way, use the
numbering system that results in the smallest numbers.
Substituents are named like a parent, and replacing the *-ane* ending
with *-yl*.
### Numbering
The above molecule is numbered as follows:
2,3,7-Trimethyloctane
**Not** 2,6,7-Trimethyloctane. Remember, number so as to give the
smallest numbers to the substituents.
### Alphabetizing
3-Ethyl-3-methylpentane
*Ethyl* is listed before *methyl* for alphabetizing purposes.
## Branched Substituents
### Naming branched substituents
-2,4-dimet.png "3-(1-methylethyl)-2,4-dimet.png")
3-(1-methylethyl)-2,4-dimethylpentane
The main chain in the drawing is numbered 1-5. The main part of the
branched substituent, an ethyl group, is numbered 1\' and 2\'. The
methyl substituent off of the ethyl substituent is not numbered in the
drawing.
To name the compound, put the whole branched substituent name in
parentheses and then number and alphabetize as if a simple substituent.
## Common system
Some prefixes from the common system are accepted in the IUPAC system.
For alphabetization purposes, **iso-** and **neo-** are considered part
of the name, and alphabetized. **Sec-** and **tert-** are not considered
an alphabetizable part of the name.
(In the following images, the **R-** represents any carbon structure.)
### Iso-
**Iso-** can be used for substituents that branch at the second-to-last
carbon and end with two methyls. An isobutyl has four carbons total:
 *Isobutyl*
### Sec-
**Sec-** can be used for substituents that branch at the first carbon .
### Neo-
**Neo-** refers to a substituent whose second-to-last carbon of the
chain is trisubstituted (has three methyl groups attached to it). A
neo-pentyl has five carbons total.
 *Neopentyl*
### Tert-
**Tert-** is short for **tertiary** and refers to a substituent whose
first carbon has three other carbon groups attached to it.
# See also
1. Cycloalkanes
------------------------------------------------------------------------
\|\| \<\< Foundational
concepts
\| Alkanes \| Stereochemistry
\>\>
pl:Chemia_organiczna/Alkany
|
# Organic Chemistry/Stereochemistry
Organic Chemistry table of contents \>
# Stereoisomerism
**Stereoisomers** are compounds that have the same connectivity
(constitution) and the same chemical formula, but are isomers because
they differ in the spacial arrangement of the atoms attached to the
stereocenters (chirality centers) throughout the molecule. All
stereoisomers are unique and possess their own physical, chemical and
biological properties (with the exception of meso compounds).
!Two enantiomers of the common psychoactive drug
methamphetamine{width="450"}
To illustrate the importance of stereoisomerism in organic chemistry,
let\'s consider the well-known substance methamphetamine, which has two
enantiomers: (R)-N-methyl-1-phenylpropan-2-amine and
(S)-N-methyl-1-phenylpropan-2-amine. The S enantiomer, commonly called
D-methamphetamine is a controlled substance in most countries worldwide.
It is highly psychoactive, giving users an intense rush of euphoria when
ingested. Use of D-methamphetamine often leads to severe drug dependence
and even death in chronic users. By contrast, the R enantiomer of
methamphetamine, commonly called L-methamphetamine is a non-psychoactive
substance that is legal to possess in most jurisdictions. While not very
psychoactive, L-methamphetamine is an excellent sympathomimetic
vasoconstrictor and can be found in some OTC medications used to relieve
nasal congestion caused by the common cold or allergic sinusitis, often
under the name \"levmetamfetamine\".
\
## Types of Stereoisomers
**Enantiomers** are chiral molecules with non-superimposable mirror
images. When comparing stereoisomers, the enantiomer is always the
isomer without any internal planes of symmetry and that has had each of
its stereogenic centers flipped. In other words, each stereocenter has
gone from an R-configuration to an S-configuration.
!Two enantiomers of
3-chloro-1-ethylcyclohexane{width="225"}\
In this example, the two molecules are enantiomers of one another
because (1) this molecule lacks any internal plane of symmetry and (2)
all of its stereocenters have been flipped. The molecule on the right is
(1S,3S)-3-chloro-1-ethylcyclohexane, while the molecule on the left is
(1R,3R)-3-chloro-1-ethylcyclohexane.
\
**Diastereomers** are also chiral molecules, but differ from enantiomers
in that they are not mirror images of each other due to some **but not
all** of the chirality centers being flipped.
!Two diastereomers of
3-chloro-1-ethylcyclohexane{width="225"}\
The following two molecules are diastereomers of one another because (1)
they are not mirror images, and (2) only one of the stereocenters has
been flipped. The molecule on the left is
(1R,3S)-3-chloro-1-ethylcyclohaxane while the molecule on the right is
(1S,3R)-3-chloro-1-ethylcyclohexane.
\
**Meso compunds** are achiral molecules that contain stereogenic
centers. They are achiral molecules because their mirror images are
superimposable onto each other as they possess an internal plane of
symmetry, meaning that meso compounds are identical molecules with
identical properties.
!The meso compound
(1R\*,2S\*)-1,3-dichlorohexane.-1,3-dichlorohexane."){width="300"}\
A common mistake is thinking that these two molecules are enantiomeric
due to both stereogenic centers having been flipped. However, upon
closer inspection these two molecules are not enantiomeric because by
manipulating this molecule in space it could be superimposed on top of
its mirror image due to it possessing an internal plane of symmetry.
\
------------------------------------------------------------------------
- Configurations
- Enantiomers
: Optical
activity
: R-S notational
system
: Meso
compounds
- Diastereomers
------------------------------------------------------------------------
\<\< Alkanes and cycloalkanes \|
Stereochemistry \| Haloalkanes
|
# Organic Chemistry/Cycloalkanes
## Overview
A *cycloalkane* is a regular alkane with a ring or loop. An example is
cyclohexane, which is a ring of 6 carbon atoms, each bonded to 2
hydrogen atoms (C~6~H~12~).
We briefly discussed cycloalkanes in the
alkanes unit of this book, but
in this unit, we\'ll be going into much greater detail about
cycloalkanes as well as cycloalkenes. There are a number of properties
that are unique to these structures and thus they deserve special
attention.
Because of their cyclical nature, cycloalkanes do not have the freedom
of rotation that regular alkanes possess. Stereochemistry plays a very
important role in both the limitations of movements, but also, in some
instances the limitations of reactions that can take place. Often these
limitations are due less to the cyclical nature itself so much as the
lack of freedom of rotation found in such alkanes.
A good example is the restrictions placed on
**E2**
elimination reactions, which we\'ll cover later in the book.
## Drawing Cycloalkanes
!First four simple
cycloalkanes{width="400"}
The above image of the first four simple cycloalkanes shows that each
carbon has 2 hydrogens attached. As you can see, the other 2 bonds are
to adjacent carbons. While the shapes show the basic 2-dimensionaly,
top-down shape, only cyclopropane and cyclobutane have all of their
carbons on a plane. Cylcopentane and cyclohexane, as well as higher
cycloalkanes, all have a 3-dimensional geometry. Cyclohexane is
particularly important and it will be discussed separately.
!Cyclopentane and cyclohexane without atoms
labeled
More often, cycloalkanes, like many other organic structures, are drawn
such that their carbons and hydrogens aren\'t labeled. Cyclopentane and
cyclohexane (see above) are generally drawn as a pentagon and a hexagon,
respectively.
## Naming of Cycloalkanes
Naming of cycloalkanes is similar to alkanes. The smallest cycloalkane
is \"Cyclopropane\", so as you might imagine, this is a ring of 3
carbons. If the number of carbons on the cycloalkane is higher than the
number of carbons on any of its substituents (that is, carbon chains
attached to carbons on the cycloalkane), then the base name is prefixed
with \"cyclo\" and the rest of the name the same as an alkane with the
same number of carbons.
!3-cyclopentylhexane
If, as in the above image, the cycloalkane has fewer carbons than a
carbon chain it\'s connected to, then the longest carbon chain is the
primary and the cyclic portion receives the substituent \"-yl\" ending
and prefixes the primary name. Thus the name 1-ethylbutylcyclopentane,
while technically an accurate description, is not the correct name.
!3-chloro-1,1-dimethylcyclohexane and
2-bromo-3-chloro-1,1-dimethylcyclohexane
Numbering of carbons in substituted cycloalkanes is fairly
straight-forward. If there is only one substituent, it is the 1-carbon.
If there are more than one, then numbering proceeds, clockwise or
counter-clockwise, such that the lowest number after 1 goes to the least
(or a least) substituted carbon. I know that sounds tricky, so we\'ll
look at the example on the left, 3-chloro-1,1-dimethylcyclohexane. the
carbon with the chlorine bond is the least substituted carbon, so it
gets the lowest number after 1 and 1 goes to the nearest carbon with
more than 1 substituent. So, the 1 is applied to the methyls.
Substituents are still placed in alphabetic order, as you can see from
the second example,
2-**b**romo-3-**c**hloro-1,1-di**m**ethylcyclohexane.
## Ring Strain in Cycloalkanes
Carbons with 4 single bonds want the bonds to be at a tetrahedral angle
of 109.5°. In 1885, Adolf von Baeyer proposed that since carbons prefer
this angle, that only rings of 5 and 6 members should be possible.
Baeyer made the mistake of thinking in 2-dimensions and assuming that
all rings are planar. In fact, only cyclopropane and cyclobutane are
flat, resulting in their bond angles of 60° and 90°, respectively. But
for some time, it was believed that these smaller cycloalkanes could not
be created and that ones of more than 6 carbons would have strain
because their angles would be too far in excess of the 109.5° preferred
angle.
!First four simple cycloalkanes in 3-dimensional stick
representation
In the above figure, the first four simple cycloalkanes are again
represented, but this time the 3 dimensional representations are shown.
Notice how cyclopentane has 4 carbons on a plane and the 5th is slightly
off the plane, giving it the shape of an open envelope.
In fact, rings larger than 3 carbons have 3 dimensional shapes that
relieve this bond strain, but it\'s important to note that bond strain
does affect stability. For cyclopropane and cyclobutane, the strain
energy is about 110 kJ/mol. Cyclobutane can enter a \"puckered\"
formation that slightly relieves some torsional strain. Cyclopentane,
which is non-planar can remove some of the strain and has only about 25
kJ/mol of strain. Cyclohexane, because of its chair conformation, can
maintain perfect tetrahedral angles, resulting in no strain. As the ring
size goes up further, angle strain can be avoided at the cost of
introducing some eclipsing strain, and *vice versa*, so that some strain
exists, but the most strained of these, cyclononane, has only about 50
kJ/mol of strain. Ring strain pervades for ring sizes up to 13 members.
After that, there are enough carbons that ring strain is removed
completely.
!Cyclopentane in a 3-dimensional stick
representation
But angle strain isn\'t the only issue involved in ring strain.
Torsional strain is also a factor. When the hydrogen bonds in a ring
eclipse each other, this creates additional strain. In the case of
cyclopropane the hydrogens eclipse each other, greatly adding to the
strain. In fact, this is the cause of most of the strain found in
cyclopentane. Cyclopentane has bond angles very close to 109.5°, but
because 4 of its carbons are planar, there it has torsional strain that
makes it less stable. Looking at the cyclopentane along 2 of the bonds
on the plane, with the non-planar carbon closest to us, in the figure
above, one can see that the bend in the bonds allows the hydrogens to
move slightly out eclipse, reducing the torsional strain somewhat.
Cyclohexane is the lowest membered ring that\'s able to have both 109.5°
bond angles and maintain a staggered conformation, allowing it to be
strain free.
## Conformations of Cyclohexane
There are 3 main conformations of Cyclohexane, the chair, the reverse
chair and the boat. The chair conformations have no angular, torsional
or steric strain. However the boat conformation does have steric strain,
as the hydrogens at the high points on the front and back of the boat
are slightly overlapping.
## Conformations of Mono- and Di-substituted Cyclohexane
**TO DO**
## The Effect of Conformation on Reactions with Cyclohexane
Different conformations of cyclohexane can react differently for certain
reactions. For example, the **E2** elimination
reaction,
which we\'ll cover later in this book, requires that a halogen atom and
a hydrogen atom be on adjacent carbons and coplanar from each other, or
180° (anti). In cyclohexanes with multiple substituents attached to its
carbons, it\'s possible for that the hydrogen and halogen can be on
adjacent carbons, but never be coplanar, thus preventing the reaction
from occurring.
In other reactions, steric interference from adjacent substituents, for
example, a large alkyl group on an adjacent carbon, can prevent a
nucleophile from attacking a desired location. For these, and other
reasons, it\'s important to understand the 3-dimensional geometry and
structure of the reactants as well as the mechanisms of the reactions
that are taking place.
## Large Ring Systems
**TO DO**
## Polycyclic Ring Systems
In some compounds, two or more rings are fused together in the same
molecule. This can occur in both aliphatic and aromatic compounds.
If the two rings meet at a single carbon atom, where that carbon atom is
part of both rings, the compound is called a spiro
compound. The two rings are roughly (but
not exactly) perpendicular to each other because of the usual
tetrahedral bonding of four ligands around carbon.
If the two rings are bridged at two or more carbon atoms, the carbon
atoms form part of a bridge, and the compound is a bicycloalkane (for
two rings) or a polycycloalkane (for three or more rings).
An aromatic bicyclic compound is naphthalene
(C~10~H~8~), which is a pair of benzene rings fused across a
carbon-carbon bond. An aliphatic (non-aromatic) bicyclic compound is
decalin (C~10~H~18~), formally known as
decahydronaphthalene, which is a pair of cyclohexane rings fused across
a C-C bond.
### Naming conventions for bicyclic rings
A bicyclic alkane ring system is composed of three parts:
1. The longer carbon chain (**a**)
2. The shorter carbon chain (**b**)
3. The carbon-carbon bridge (**c**)
Note that $a >= b >= c$ always.
A bicyclic ring is named according to the **total number of carbons** in
the following form:
: **bicyclo\[a.b.c\]alkane**
In this formula, substitute \[a.b.c\] with the lengths of the carbon
chains, and substitute \"alkane\" with the total number of carbons
(heptane, octane, nonane, etc.).
A famous example of a bicyclic compound is
norbornane (see image below). The formal name
for norbornane is bicyclo\[2.2.1\]heptane. There are two carbons to the
left of the bridge, two carbons to the right of the bridge, and one
carbon on the bridge itself. Therefore, the numbers in the brackets are
\[2.2.1\]. Note that the two carbons at the base of the bridge are not
counted in the brackets.
!Norbornane.{width="300"}
## Introduction to Heterocyclic Compounds
!A sampling of single-ring heterocylic
compounds
Heterocyclic compounds are cyclic compounds that contain atoms other
than carbon in their ring. The figure above shows just a few single-ring
heterocyclic compounds. The ones shown are simply 5 and 6 membered
rings. There are smaller and larger rings and there are also multiple
ring heterocycles.
Heterocyclic compounds play a big role in organic chemistry and because
they have different electron configurations from carbon, they react
differently from carbon rings and differently from each other. Later in
this book we will discuss several specific heterocyclic compounds that
are very commonly used in organic chemistry and we\'ll discuss their
individual characteristics.
For now, it\'s simply important to know what a heterocyclic compound is.
------------------------------------------------------------------------
\|\| \<\< Haloalkanes \|
Alkanes \| Alcohols \>\>
|
# Organic Chemistry/Alkynes
The triple carbon bonds is formed in alkynes, due to the absence of
hydrogens, thus allowing carbon bonds to become stronger, due to the
nucleus central force which pulls in nearby atoms
\<\< Alkenes \|**Alkynes**\|
Dienes \>\>
{width="250"} **Alkynes**
are hydrocarbons containing carbon-carbon triple bond. They exhibit
neither geometric nor optical isomerism. The simplest alkyne is ethyne
(HCCH), commonly known as acetylene, as shown at right.
# Multiple Bonds Between Carbon Atoms
As you know from studying alkenes, atoms do not always bond with only
one pair of electrons. In alkenes (as well in other organic and
inorganic molecules) pairs of atoms can share between themselves more
than just a single pair of electrons. Alkynes take this sharing a step
further than alkenes, sharing three electron pairs between carbons
instead of just two.
### Two π Bonds
As you should know already, carbon is generally found in a *tetravalent*
state - it forms four covalent bonds with other atoms. As you know from
the section on alkenes, all four bonds are not necessarily to
*different* atoms, because carbon atoms can double-bond to one another.
What this does is create the appearance of only being bound to three
other atoms, but in actuality four bonds exist.
Alkenes are molecules that consist of carbon and hydrogen atoms where
one or more pairs of carbon atoms participate in a double bond, which
consists of one sigma (σ) and one pi (π) bond. Alkynes are also
molecules consisting of carbon and hydrogen atoms, but instead of
forming a double bond with only one sigma (σ) and one pi (π) bond, the
alkyne has at least one pair of carbon atoms who have a σ and **two** π
bonds \-- a *triple bond*.
The carbon-carbon triple bond, then, is a bond in which the carbon atoms
share an *s* and two *p* orbitals to form just one σ and two π bonds
between them. This results in a linear molecule with a bond angle of
about 180ﾟ. Since we know that double bonds are shorter than single
covalent bonds, it would be logical to predict that the triple bond
would be shorter still, and this is, in fact, the case. The triple
bond's length, 1.20Ǎ, is shorter than that of ethane and ethene's 1.54
and 1.34 angstroms, respectively, but the difference between the triple
and double bonds is slightly less than the difference between the single
and double bonds.
The chemistry is very similar to alkenes in that both are formed by
elimination reactions, and the major chemical reactions that alkynes
undergo are addition type reactions.
### Index Of Hydrogen Deficiency
If we compare the general molecular formulas for the Alkane, Alkene, and
Alkyne families as well as the Cycloalkane and cycloalkene families we
see the following relationship:
Family Molecular Formula
------------- -------------------
Alkane C~n~H~2n+2~
Alkene C~n~H~2n~
Cycloalkane C~n~H~2n~
Alkyne C~n~H~2n-2~
Cycloalkene C~n~H~2n-2~
We see that for a ring structure or a double bond there is a difference
of two hydrogens compared to the alkane structure with the same number
of carbons. If there is a ring + double bond (cycloalkene) or a triple
bond (alkyne) then the difference is four hydrogens compared to the
alkane with the same number of carbons. We say that the Index of
Hydrogen Deficiency is equal to the number of pairs of Hydrogens that
must be taken away from the alkane to get the same molecular formula of
the compound under investigation. Every π-bond in the molecule increases
the index by one. Any ring structure increases the index by one. Here is
a list of possibilities:
Per molecule Index of Hydrogen Deficiency
------------------------------- ------------------------------
One double bond 1
1 ring 1
1 double bond and 1 ring 2
2 double bonds 2
1 triple bond 2
1 triple bond + 1 double bond 3
3 double bonds 3
2 double bonds + 1 ring 3
2 triple bonds 4
4 double bonds 4
Just remember that double bonds have 1 π bond, triple bonds have 2 π
bonds and each π bond is an index of 1. We can use the index and the
molecular formula to identify possibilities as to the exact nature of
the molecule. For example, determine the molecular formula and speculate
on what kind of Pi bonding and/or ring structure the molecules would
have if the Index was given to be 3 and it is a 6 carbon hydrocarbon.
Identify the Alkane molecular formula for six carbons. For n = 6 we
would have C~n~H~2n+2~. That would be C~6~H~14~.
Since an index of 3 means that there are 3 pairs(2) of hydrogen atoms
less in the compound compared with the alkane we determined in step 1,
then we would have C~6~H~14-6~ or C~6~H~8~.
In speculating as to what the bonding and structure could be with an
index of 3 that could mean:
- - Three double bonds in a non-cyclic structure like hexatriene
- Two double bonds in a ring structure like a cyclohexadiene
- One triple bond and one double bond in a non-cyclic structure
Clearly the answer cannot be determined from the formula alone, but the
formula will give important clues as to a molecule\'s structure.
# Cycloalkynes
Cycloalkynes are seldom encountered, and are not stable in small rings
due to angle strain. Cyclooctyne has been isolated, but is very
reactive, and will polymerize with itself quickly. Cyclononyne is the
smallest stable cycloalkyne.
Benzyne is another cycloalkyne that has been proposed as an intermediate
for elimination-addition
reactions of benzene.
# Preparation
In order to synthesize alkynes, one generally starts with a vicinal or
geminal dihalide (an alkane with two halogen atoms attached either next
to one another or across from one another). Adding sodium amide
(NaNH~2~) removes the halogens with regiochemistry subject to Zaitsev\'s
Rule, resulting in a carbon-carbon triple bond due to the loss of both
halogens as well as two hydrogen atoms from the starting molecule. This
is called a double dehydrohalogenation.
## Dehydrogenation of an alkane or alkene
`R-R -(H^2)⇒ CH^2=CH^2`
## Dehalogenation of a tetrahaloalkane
Dehalogenation of tetrahalides in the presence of Zn yields Alkynes.
When the vapors of tetrahalides are passed over heated Zinc. However
this reaction is not so much useful for the preparation of Alkynes.
Because tetrahalides required for this reaction are prepared from
alkynes. So, this reaction can be used as a purification for the
alkynes.
## Dehydrohalogenation of a dihaloalkane
## Through Kolbe\'s Electrolysis
The starting compound is a salt already containing a carbon-carbon
double bond. One such compound is maleic acid. Mechanism is similar to
that of formation of ethane using kolbe\'s electrolysis.\
`CH-COONa`\
`|| (sodium maleate) (maleic acid)`\
`CH-COONa`\
\
`At Anode: At cathode:`\
`CH-COO`^`-`^` 2Na`^`+`^` + 2e`^`-`^` -> 2Na`\
`||`\
`CH-COO`^`-`^` 2Na + H`~`2`~`O -> 2NaOH + H`~`2`~\
\
`-2e`^`-`^` ->`\
\
`CH-COO* CH* CH`\
`|| -> -2CO`~`2`~` -> || -> |||`\
`CH-COO* CH* CH`\
`(free radical formation)`
In this manner, alkyne is obtained at anode, while NaOH is formed at
cathode and hydrogen gas is liberated.
Vicinal dihalides may be converted into alkynes by using extreme
conditions such as sodium amide NaNH2 typically at 150°C or molten/fused
potassium hydroxide KOH typically at 200°C.
## From Calcium carbide
Calcium carbide is the compound CaC~2~, which consists of calcium ions
(Ca^2+^) and acetylide ions, C~2~^2-^. It is synthesized from lime and
coke in the following reaction:
CaO + 3C → CaC~2~ + CO
This reaction is very endothermic and requires a temperature of 2000^o^
C. For this reason it is produced in an electrical arc furnace.
Calcium carbide may formally be considered a derivative of acetylene, an
extremely weak acid (though not as weak as ammonia). The double
deprotonation means that the carbide ion has very high energy. Instant
hydrolysis occurs when water is added to calcium carbide, yielding
acetylene gas.
CaC~2~ + 2H~2~O → Ca(OH)~2~ + C~2~H~2~
## From alkyl or aryl halides
# Properties
## Physical properties
Most alkynes are **less dense than water** (they float on top of water),
but there are a few exceptions.
## Chemical properties
Liquid alkynes are **non-polar solvents**, immiscible with water.
Alkynes are, however, more polar than alkanes or alkenes, as a result of
the electron density near the triple bond.
Alkynes with a low ratio of hydrogen atoms to carbon atoms are **highly
combustible**. Carbon-carbon triple bonds are highly reactive and easily
broken or converted to double or single bonds. Triple bonds store large
amounts of chemical energy and thus are highly exothermic when broken.
The heat released can cause rapid expansion, so care must be taken when
working with alkynes such as acetylene.
One synthetically important property of **terminal alkynes** is the
acidity of their protons. Whereas the protons in alkanes have p*K*~a~\'s
around 60 and alkene protons have p*K*~a~\'s in the mid-40\'s, terminal
alkynes have p*K*~a~\'s of about 25. Substitution of the alkyne can
reduce the p*K*~a~ of the alkyne even further; for example, PhCCH has a
p*K*~a~ around 23, and Me~3~SiCCH has a p*K*~a~ around 19. The acidity
of alkynes allows them easily to be deprotonated by sufficiently strong
bases, such as butyllithium BuLi or the amide ion NH~2~^-^. More acidic
alkynes such as PhCCH can even be deprotonated by alkoxide bases under
the right conditions.
# Reactions
Alkynes can be hydrated into either a ketone or an aldehyde form. A
(Markovnikov) ketone can be created from an alkyne using a solution of
aqueous sulfuric acid (H~2~O/H~2~SO~4~) and HgSO~4~, whereas the
anti-Markovnikov aldehyde product requires different reagents and is a
multi-step process.
## Oxidative Cleavage of Alkynes
## Hydrohalogenation of Alkynes
Alkynes react very quickly and to completion with hydrogen halides.
Addition is anti, and follows the Markovnikov
Rule.
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```
```{=html}
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```
```{=html}
<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
RCCH + H-Br (1 equiv) \--\> RCBr=CH~2~\
RCCH + H-Br (2 equivs) \--\> RCBr~2~CH~3~
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```
Adding a halide acid such as HCl or HBr to an alkyne can create a
geminal dihalide via a Markovnikov process, but adding HBr in the
presence of peroxides results in the Anti-Markovnikov alkenyl bromide
product.
## Halogenation of Alkynes
Adding diatomic halogen molecules such as Br~2~ or Cl~2~ results in
1,2-dihaloalkene, or, if the halogen is added in excess, a
1,1,2,2-tetrahaloalkane.
Adding H~2~O along with the diatomic halide results in a halohydrin
addition and an α-halo ketone.
## Combustion
Alkynes burn in air with a sooty, yellow flame, like alkanes. Alkenes
also burn yellow, while alkanes burn with blue flames. Acetylene burns
with large amounts of heat, and is used in oxyacetylene torches for
welding metals together, for example, in the superstructures of
skyscrapers.
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<tr>
```
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<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
2 C~2~H~2~ + 5 O~2~ \--\> 4 CO~2~ + 2 H~2~O
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
## Reduction
Alkynes can be hydrogenated by adding H~2~ with a metallic catalyst,
such as palladium-carbon or platinum or nickel, which results in both of
the alkyne carbons becoming fully saturated. If Lindlar\'s catalyst is
used instead, the alkyne hydrogenates to a Z enantiomer alkene, and if
an alkali metal in an ammonia solution is used for hydrogenating the
alkyne, an E enantiomer alkene is the result.
### Complete Hydrogenation of Alkynes
As mentioned above, alkynes are reduced to alkanes in the presence of an
active metal catalyst, such as Pt, Pd, Rh, or Ni in the presence of heat
and pressure.
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```
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<tr>
```
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<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
RCCR\' + 2 H~2~ (Pt cat.)\--\> RCH~2~CH~2~R\'
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
### Syn-Hydrogenation of an Alkyne
There are two kinds of addition type reactions where a π-bond is broken
and atoms are added to the molecule. If the atoms are added on the same
side of the molecule then the addition is said to be a \"syn\" addition.
If the added atoms are added on opposite sides of the molecule then the
addition is said to be an \"anti\" addition. Hydrogen atoms can be added
to an alkyne on a one mole to one mole ratio to get an alkene where the
hydrogen atoms have been added on the same side of the molecule.
Isotopic identification allows chemists to determine when this
syn-hydrogenation has occurred.
As mentioned above, alkynes can be reduced to *cis-*alkenes by hydrogen
in the presence of Lindlar Pd, i.e. palladium doped with CaSO~4~ or
BaSO~4~.
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<table WIDTH="75%">
```
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<tr>
```
```{=html}
<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
RCCR + H~2~ *cis-*RCH=CHR
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
### Anti-Hydrogenation of an Alkyne
In regards to the syn-hydrogenation, anti is hydrogenation when one
hydrogen is added from the top of the pi bond and the other is added
from the bottom. *Anti*-hydrogenation of an alkyne can be done via
metallic reduction, using sodium in liquid ammonia.
## Anion formation
Because of the acidity of the protons of terminal alkynes, they are
easily converted into alkynyl anions in high yield by strong bases.
**Examples**
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```
```{=html}
<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
RCCH + NaNH~2~ -\> RCCNa + NH~3~ C~4~H~9~Li + RCCH -\> C~4~H~10~ +RCCLi
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
Alkynes are stronger bases than water, and acetylene (ethyne) is
produced in a science classroom reaction of calcium carbide with water.
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```
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<tr>
```
```{=html}
<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
CaC~2~ + 2 H~2~O \--\> Ca(OH)~2~ + C~2~H~2~
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
Alkynyl anions are useful in lengthening carbon chains. They react by
nucleophilic substitution with
alkyl halides.
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```
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<tr>
```
```{=html}
<td style="background-color: #F3F3FF; border: solid 1px #E7E7FF; padding: 1em;" valign=top>
```
R-Cl + R\'CCNa \--\> RCCR\' + NaCl
```{=html}
</td>
```
```{=html}
</tr>
```
```{=html}
</table>
```
The product of this reaction can be reduced to an alkane with hydrogen
and a platinum or rhodium catalyst, or an alkene with Lindlar palladium.
# References
- IIT Chemistry by Dr.O.P.Agrawal and Avinash Agrawal
\<\< Alkenes \| Alkynes \|
Dienes \>\>
|
# Organic Chemistry/Overview of Functional Groups
## Introduction
The number of known organic compounds is quite large. In fact, there are
many times more organic compounds known than all the other (inorganic)
compounds discovered so far, about 7 million organic compounds in total.
Fortunately, organic chemicals consist of a relatively few similar
parts, combined in different ways, that allow us to predict how a
compound we have never seen before may react, by comparing how other
molecules containing the same types of parts are known to react.
These parts of organic molecules are called **functional groups**. The
identification of functional groups and the ability to predict
reactivity based on functional group properties is one of the
cornerstones of organic chemistry.
Functional groups are **specific atoms, ions, or groups of atoms**
having consistent properties. A functional group makes up part of a
larger molecule.
For example, **-OH**, the hydroxyl group that characterizes alcohols, is
an oxygen with a hydrogen attached. It could be found on any number of
different molecules.
Just as elements have distinctive properties, functional groups have
**characteristic chemistries**. An **-OH** group on one molecule will
tend to react similarly, although perhaps not identically, to an **-OH**
on another molecule.
**Organic reactions usually take place at the functional group**, so
learning about the reactivities of functional groups will prepare you to
understand many other things about organic chemistry.
## Memorizing Functional Groups
Don\'t assume that you can simply skim over the functional groups and
move on. As you proceed through the text, the writing will be in terms
of functional groups. It will be assumed that the student is familiar
with most of the ones in the tables below. It\'s simply impossible to
discuss chemistry without knowing the \"lingo\". It\'s like trying to
learn French without first learning the meaning of some of the words.
One of the easiest ways to learn functional groups is by making flash
cards. Get a pack of index cards and write the name of the functional
group on one side, and draw its chemical representation on the other.
For now, a list of the most important ones you should know is provided
here. Your initial set of cards should include, at the very least:
Alkene, Alkyne, Alkyl halide (or Haloalkane), Alcohol, Aldehyde, Ketone,
Carboxylic Acid, Acyl Chloride (or Acid Chloride), Ester, Ether, Amine,
Sulfide, and Thiol. After you\'ve learned all these, add a couple more
cards and learn those. Then add a few more and learn those. Every
functional group below is eventually discussed at one point or another
in the book. But the above list will give you what you need to continue
on.
And don\'t just look at the cards. Say and write the names and draw the
structures. To test yourself, try going through your cards and looking
at the names and then drawing their structure on a sheet of paper. Then
try going through and looking at the structures and naming them. Writing
is a good technique to help you memorize, because it is more active than
simply reading. Once you have the minimal list above memorized backwards
and forwards, you\'re ready to move on. But don\'t stop learning the
groups. If you choose to move on without learning the \"lingo\", then
you\'re not going to understand the language of the chapters to come.
Again, using the French analogy, it\'s like trying to ignore learning
the vocabulary and then picking up a novel in French and expecting to be
able to read it.
### Functional groups containing \...
In organic chemistry **functional
groups** are submolecular structural motifs, characterized by specific
elemental composition and connectivity, that confer reactivity upon the
molecule that contains them.
Common functional groups include:
+-------+-------+-------+-------+-------+-------+-------+-------+
| Sr | Che | Group | Fo | Grap | P | S | Ex |
| No. | mical | | rmula | hical | refix | uffix | ample |
| | class | | | Fo | | | |
| | | | | rmula | | | |
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| | hal | ormyl | | [Acyl | alofo | h | cetyl |
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| | | | | | | | 75"}\ |
| | | | | | | | A |
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| | | | | | | | chlor |
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| | | | | | | | *(Eth |
| | | | | | | | anoyl |
| | | | | | | | chlor |
| | | | | | | | ide)* |
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| | hol-s | | | "met |
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+-------+-------+-------+-------+-------+-------+-------+-------+
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| | Aldeh | Aldeh | | [Alde | | | talde |
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| | | | | g "Al | | | "){wi |
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| | | | | idth= | | | :A |
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| | | | | | | | dehyd |
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| | | | | | | | * |
| | | | | | | | (Etha |
| | | | | | | | nal)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 4 | Alk | [Alky | RH~n~ | ![A | a | -ane | ! |
| | ane | | neral | | | ne-2D |
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| | | | | | | | |
| | | | | | | | Metha |
| | | | | | | | ne |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 5 | Alk | [Alke | R | ![Al | alk | -ene | ![eth |
| | ene{w | | | "){wi |
| | ink") | ink") | | idth= | | | dth=" |
| | | | | "75"} | | | 75"}\ |
| | | | | | | | Eth |
| | | | | | | | ylene |
| | | | | | | | \ |
| | | | | | | | *(Eth |
| | | | | | | | ene)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
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| | yne{wi | | | lene" |
| | ink") | ink") | | dth=" | | | ){wid |
| | | | | 100"} | | | th="1 |
| | | | | | | | 00"}\ |
| | | | | | | | [ |
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| | | | | | | | lene] |
| | | | | | | | (w:Ac |
| | | | | | | | etyle |
| | | | | | | | ne "w |
| | | | | | | | ikili |
| | | | | | | | nk")\ |
| | | | | | | | *(Eth |
| | | | | | | | yne)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 7 | Am | [C | RCO | ![Am | ca | - | ! |
| | ide-ske | | | e_ske |
| | ossar | wikil | | letal | | | letal |
| | y#A " | ink") | | .png | | | .svg |
| | wikil | | | "Amid | | | "acet |
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| | | | | | | | [ |
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| | | | | | | | *(Et |
| | | | | | | | hanam |
| | | | | | | | ide)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 8 | Ami | [Pr | R | ![Pr | a | - | ! |
| | nes | y#A " | | amin | | | amine |
| | | wikil | | e"){w | | | "){wi |
| | | ink") | | idth= | | | dth=" |
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| | | | | | | | Meth |
| | | | | | | | ylami |
| | | | | | | | ne\ |
| | | | | | | | *(Met |
| | | | | | | | hanam |
| | | | | | | | ine)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
| Seco | R | ! | a | - | ![ | | |
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| am | | ndary | | | hylam | | |
| ine | | | D.png | | |
| ossar | | .png | | | "dim | | |
| y#A " | | "Seco | | | ethyl | | |
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| | | "75"} | | | Di | | |
| | | | | | methy | | |
| | | | | | lamin | | |
| | | | | | e | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
| Ter | R~3~N | ![Ter | a | - | ! | | |
| tiary | | tiary | mino- | amine | [trim | | |
| am | | am | | | ethyl | | |
| ine.png | | | e_che | | |
| ossar | | "Ter | | | mical | | |
| y#A " | | tiary | | | _stru | | |
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| | | | | | Trim | | |
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| | | | | | amine | | |
| | | | | | | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
| [4° | R~4 | ![ | amm | -amm | ![Cho | | |
| amm | ~N^+^ | Quate | onio- | onium | line] | | |
| onium | | rnary | | | (Chol | | |
| ion | | amm | | | ine-s | | |
| ](Qua | | onium | | | kelet | | |
| terna | | catio | | | al.sv | | |
| ry_am | | n](Qu | | | g "Ch | | |
| moniu | | atern | | | oline | | |
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+-------+-------+-------+-------+-------+-------+-------+-------+
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| | compo | (Diim | 2~R\' | o.png | | azene | ethyl |
| | und] | | l](Az | | | orang |
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| | ry/Gl | wikil | | o.png | | | e-ske |
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| | | | | | | | *(1 |
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+-------+-------+-------+-------+-------+-------+-------+-------+
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| | arbon | onate | OCOOR | [Carb | | **c | |
| | ate | | l.svg | | | |
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| | | | | idth= | | | |
| | | | | "75"} | | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 12 | Car | [C | RC | ![Car | car | -oate | ![S |
| | boxyl | arbox | OO^−^ | boxyl | boxy- | | odium |
| | ate | | e-hyb | | | D-ske |
| | y#C " | | | rid.p | | | letal |
| | wikil | | | ng "C | | | .png |
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| | | | | \ |
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| | | | | "75"} | | | thano |
| | | | | | | | ate)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
| 13 | | [ | RCOOH | ![ | car | -oic | ![A |
| | Carbo | Carbo | | Carbo | boxy- | acid | cetic |
| | xylic | xyl | | c-aci | | | d-2D- |
| | emist | | | d-ske | | | skele |
| | ry/Gl | | | letal | | | tal.s |
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| | | | | | | | anoic |
| | | | | | | | a |
| | | | | | | | cid)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
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| | Cyana | nate] | | Cyan | nato- | * | |
| | tes | | oup.p | | | |
| | ry/Gl | | | ng "C | | | |
| | ossar | | | yanat | | | |
| | y#C " | | | e"){w | | | |
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| | ink") | | | "75"} | | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
| Thi | RSCN | ![T | th | alkyl | | | |
| ocyan | | hiocy | iocya | **thi | | | |
| ate | | e"){w | | | | | |
| | | idth= | | | | | |
| | | "75"} | | | | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
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| | | | | | | | 75"}\ |
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| | | | | | | | \ |
| | | | | | | | * |
| | | | | | | | (Etho |
| | | | | | | | xyeth |
| | | | | | | | ane)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
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| | ossar | | | al.pn | | | yrate |
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| | | | | | | | dth=" |
| | | | | | | | 75"}\ |
| | | | | | | | [ |
| | | | | | | | Ethyl |
| | | | | | | | buty |
| | | | | | | | rate] |
| | | | | | | | (w:Et |
| | | | | | | | hyl_b |
| | | | | | | | utyra |
| | | | | | | | te "w |
| | | | | | | | ikili |
| | | | | | | | nk")\ |
| | | | | | | | *( |
| | | | | | | | Ethyl |
| | | | | | | | b |
| | | | | | | | utano |
| | | | | | | | ate)* |
+-------+-------+-------+-------+-------+-------+-------+-------+
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+-------+-------+-------+-------+-------+-------+-------+-------+
| 26 | | P | ROOR | cyclohexane.svg "(Dibromomethyl)cyclohexane.svg"){width="75"} (Dibromomethyl)cyclohexane
 Equatorial (Dibromomethyl)cyclohexane
 1,6-Dichloro-2,5-dimethylhexane
!50 px 1,1-Dichloro-3-methylcyclobutane
---------------------------------------------------------------------------------- --------------------------------------- ----------------------
## Physical properties
**R-X bond polarity:** C---F \> C---Cl \> C---Br \> C---I
------------- -------------------------- ----------------------------------
**atom** \| **electronegativity** \| **difference from C** (= 2.5) \|
F 4.0 1.5
Cl 3.0 0.5
Br 2.8 0.3
I 2.5 0.0
------------- -------------------------- ----------------------------------
The difference in electronegativity of the carbon-halogen bonds range
from 1.5 in C-F to almost 0 in C-I. This means that the C-F bond is
extremely polar, though not ionic, and the C-I bond is almost nonpolar.
**Physical appearance:** Haloalkanes are colourless when pure. However
bromo and iodo alkanes develop colour when exposed to light. Many
volatile halogen compounds have sweet smell.
**Boiling point:** Haloalkanes are generally liquids at room
temperature. Haloalkanes generally have a boiling point that is higher
than the alkane they are derived from. This is due to the increased
molecular weight due to the large halogen atoms and the increased
intermolecular forces due to the polar bonds, and the increasing
polarizabilty of the halogen.
For the same alkyl group, the boiling point of haloalkanes decreases in
the order RI \> RBr \> RCl \> RF.This is due to the increase in van der
Waals forces when the size and mass
of the halogen atom increases.
For isomeric haloalkanes, the boiling point decrease with increase in
branching. But boiling points of dihalobenzenes are nearly same; however
the para-isomers have higher melting points as it fits into the crystal
lattice better when compared to ortho- and meta-isomers.
**Density:** Haloalkanes are generally more dense than the alkane they
are derived from and usually more dense than water. Density increases
with the number of carbon and halogen atom. It also increases with the
increase in mass of halogen atom.
**Solubility:** The haloalkanes are only very slightly soluble in water,
but dissolves in organic solvents. This is because for dissolving
haloalkanes in water the strong hydrogen bonds present in the latter has
to be broken. When dissolved in organic (non polar) solvents, the
intermolecular attractions are almost same as that being broken.
**Bond Length:** C---F \< C---Cl \< C---Br \< C---I
---------- -----------------
**bond** **length** (pm)
C-F 138
C-Cl 177
C-Br 193
C-I 214
---------- -----------------
Larger atoms means larger bond lengths, as the orbitals on the halogen
is larger the heavier the halogen is. In F, the orbitals used to make
the bonds is 2s and 2p, in Cl, it\'s 3s and 3p, in Br, 4s and 4p, and in
I, 5s and 5p. The larger the principal quantum number, the bigger the
orbital. This is somewhat offset by the larger effective nuclear charge,
but not enough to reverse the order.
## Chemical properties
**Bond strength:** C---F \> C---Cl \> C---Br \> C---I
---------- ---------------------------
**bond** **strength** (kJ mol^-1^)
C-F 484
C-Cl 338
C-Br 276
C-I 238
---------- ---------------------------
The orbitals C uses to make bonds are 2s and 2p. The overlap integral is
larger the closer the principal quantum number of the orbitals is, so
the overlap is larger in the bonds to lighter halogens, making the bond
formation energetically favorable.
**Bond reactivity:** C---F \< C---Cl \< C---Br \< C---I
Stronger bonds are more difficult to break, making them less reactive.
In addition, the reactivity can also be determined by the stability of
the corresponding anion formed in solution. One of the many trends on
the periodic table states that the largest atoms are located on the
bottom right corner, implying that iodine is the largest and fluorine
being the smallest. When fluorine leaves as fluoride (if it does) in the
reaction, it is not so stable compared to iodide. Because there are no
resonance forms and inductive stabilizing effects on these individual
atoms, the atoms must utilize their own inherent abilities to stabilize
themselves. Iodide has the greatest surface area out of these four
elements, which gives it the ability to better distribute its negative
charge that it has obtained. Fluorine, having the least surface area, is
much more difficult to stabilize. This is the reason why iodine is the
best leaving group out of the four halogens discussed.
# Reactions
**Determination of Haloalkanes:** A famous test used to determine if a
compound is a haloalkane is the Beilstein test, in which the compound
tested is burned in a loop of copper wire. The compound will burn green
if it is a haloalkane. The numbers of fluorine, chlorine, bromine and
iodine atoms present in each molecule can be determined using the sodium
fusion reaction, in which the compound is subjected to the action of
liquid sodium, an exceptionally strong reducing agent, which causes the
formation of sodium halide salts. Qualitative analysis can be used to
discover which halogens were present in the original compound;
quantitative analysis is used to find the quantities.
## Substitution reactions of haloalkanes
R-X bonds are very commonly used throughout organic chemistry because
their polar bonds make them reasonably reactive. In a **substitution
reaction**, the halogen (X) is replaced by another substituent (Y). The
alkyl group (R) is not changed.
------------------------------------------------------------------------------
The \"**:**\" in a chemical equation represents a pair of unbound electrons.
------------------------------------------------------------------------------
+-------------------------------------+
| **A general substitution reaction** |
| |
| Y: + R---X → R---Y + X: |
+-------------------------------------+
Substitutions involving haloalkanes involve a type of substition called
**Nucleophilic substitution**, in which the substituent Y is a
**nucleophile**. A nucleophile is an electron pair donor. The
nucleophile replaces the halogen, an *electrophile*, which becomes a
**leaving group**. The leaving group is an electron pair acceptor.
Nuclephilic substition reactions are abbreviated as S~N~ reactions.
------------------------------------------
\"Nu\" represents a generic nucleophile.
------------------------------------------
+---------------------------------------------+
| ```{=html} |
| <H2> |
| ``` |
| General nucleophilic substitution reactions |
| |
| ```{=html} |
| </H2> |
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| Nu:^-^ + R---X → R---Nu + X:^-^\ |
| Nu: + R---X → R---Nu^+^ + X:^-^ |
+---------------------------------------------+
------------- ----------------- ---------------- -------------- -------------------
**Reagent** **Nucleophile** **Name** Product Product name
NaOH/KOH :O^-^H Hydroxide R---OH Alcohol
NaOR\' :O^-^R\' Alkoxide R---O---R\' Ether
:S^-^H Hydrosulfide R---SH Thiol
NH~3~ :NH~3~ Ammonia R---NH~3~^+^ Alkylammonium ion
KCN :C^-^N Cyanide R---CN Nitrile
AgCN Ag-CN: Silver cyanide R-NC isonitrile
:C^-^≡C---H Acetylide R-C≡C---H Alkyne
NaI :I^-^ Iodide R---I Alkyl Iodide
R\'^-^M^+^ :R\'^-^ Carbanion R-R\' Alkane
KNO~2~ O=N---O Nitrite R--O---N=O Alkyl nitrite
AgNO~2~ Ag---Ö---N=O Silver nitrite R---NO~2~ Nitroalkane
LiAlH~4~ H Hydrogen RH alkane
R\'COOAg R\'COO^-^ Alkanoate R\'COOR Ester
------------- ----------------- ---------------- -------------- -------------------
: **Common Nucleophiles**
**Example:** Suggest a reaction to produce the following molecule.
**Answer:**
`<span style="font-size:x-large;">`{=html}+`</span>`{=html}!Ethanolate{width="150"}
`<span style="font-size:x-large;">`{=html}OR`</span>`{=html}
`<span style="font-size:x-large;">`{=html}+`</span>`{=html}!Bromoethane{width="120"}
*Any halogen could be used instead of Br*
### Reaction mechanisms
Nucleophilic substitution can occur in two different ways. S~N~2
involves a **backside attack**. S~N~1 involves a **carbocation
intermediate**.
**S~N~2 mechanism** !Illustration of the Sn2 mechanism. First, the
electrons in the nucleophile attack the central carbon atom from the
side opposite the leaving group (in this case, a halogen). The electrons
forming the bond between the central carbon atom and the halogen move to
the halogen, causing the halogen to leave the
molecule.. The electrons forming the bond between the central carbon atom and the halogen move to the halogen, causing the halogen to leave the molecule.")
**S~N~1 mechanism** !Illustration of the Sn1 mechanism. First, in the
presence of a polar solvent, the C-X bond breaks, forming the
carbocation. This carbocation intermediate is highly reactive. In this
case, it reacts with water. Note that the water may attack from either
side.
### Comparison of S~N~1 and S~N~2 mechanism
**Stereochemistry:**\
S~N~2 - Configuration is inverted (i.e. R to S and vice-versa).\
S~N~1 - Product is a mixture of inversion and retention of orientation
because the carbocation can be attacked from either side. In theory the
products formed are usually racemic due to the 50% chance of attack from
the planar conformation. Interestingly, the amount of the inverted
product is often up to 20% greater than the amount of product with the
original orientation. Saul Winstein has proposed that this discrepancy
occurs through the leaving group forming an ion pair with the substrate,
which temporarily shields the carbocation from attack on the side with
the leaving group.\
**Rate of reaction:**\
S~N~2 - Rate depends on concentrations of both the haloalkane and the
nucleophile. S~N~2 reactions are fast.\
S~N~1 - Rate depends only on the concentration of the haloalkane. The
carbocation forms much slower than it reacts with other molecules. This
makes S~N~1 reactions slow.\
**Role of solvent:**\
S~N~2 - Polar aprotic solvents favored. Examples: Acetone, THF (an
ether), dimethyl sulfoxide, n,n-dimethylformamide,
hexamethylphosphoramide (HMPA).\
Nonpolar solvents will also work, such as carbon tetrachloride (CCl~4~)\
Protic solvents are the worst type for S~N~2 reactions because they
\"cage,\" or solvate, the nucleophile, making it much less reactive.\
S~N~1 - Polar protic solvents favored. Examples: H~2~O, Formic acid,
methanol.\
Aprotic solvents will work also, but protic solvents are better because
they will stabilize the leaving group, which is usually negatively
charged, by solvating it. Nonpolar solvents are the worst solvent for
S~N~1 reactions because they do nothing to stabilize the carbocation
intermediate.\
**Role of nucleophile:**\
S~N~2 - Good nucleophiles favored\
S~N~1 - Any nucleophile will work (since it has no effect on reaction
rate)\
**Carbocation stability:**\
3^°^ carbon - most stable = S~N~1 favored\
2^°^ carbon - less stable = either could be favored\
1^°^ carbon - seldom forms = S~N~2 favored\
CH~3~^+^ - never forms = S~N~2 favored\
The reason why the tertiary carbocation is most favored is due to the
inductive effect. In the carbocation intermediate, there is a resulting
formal charge of +1 on the carbon that possessed the haloalkane. The
positive charge will attract the electrons available. Because this is
tertiary, meaning that adjacent carbon atoms and substituents are
available, it will provide the most electron-density to stabilize this
charge.
### Example
Predict whether the following reactions will undergo S~N~2 or S~N~1 and
tell why.
1:
2:
3:
**Answers:**\
1) S~N~2. Good nucleophile, polar solvent.\
2) S~N~1. Tertiary carbon, polar solvent. Very slow reaction rate.\
3) S~N~2. Primary carbon, good nucleophile, nonpolar solvent.\
## Grignard reagents
Grignard reagents are created by reacting magnesium metal with a
haloalkane. The magnesium atom gets between the alkyl group and the
halogen atom with the general reaction as stated below:
R-Br + Mg → R-Mg-Br
Gringard reagents are very reactive and thus provide a means of organic
synthesis from haloalkanes. For example, adding water gives the alcohol
R-OH. Basic: R-X + Mg → R-Mg-X For example (X=Cl and R=CH3): CH3-Cl + Mg
→ CH3MgCl (methylmagnesiumchloride)
## Elimination reactions
With alcoholic potassium hydroxide, haloalkanes lose H-X and form the
corresponding alkene. Very strong bases such as KNH~2~/NH~3~ convert
vic-dihalides (haloalkanes with two halogen atoms on adjacent carbons)
into alkynes.
------------------------------------------------------------------------
\<\< Stereochemistry \|
Haloalkanes \| Alcohols \>\>
|
# Organic Chemistry/Alcohols
**Alcohols** are the family of compounds that contain one or more
**hydroxyl (-OH)** groups attached to a single bonded alkane. Alcohols
are represented by the general formula -OH. Alcohols are important in
organic chemistry because they can be converted to and from many other
types of compounds. Reactions with alcohols fall into two different
categories. Reactions can cleave the R-O bond or they can cleave the O-H
bond.
Ethanol (ethyl alcohol, or grain alcohol) is found in alcoholic
beverages, CH~3~CH~2~OH.
# Preparation
In the Alkenes section, we
already covered a few methods for synthesizing alcohols. One is the
hydroboration-oxidation of alkenes and the other is the
oxymercuration-reduction of alkenes. But there are a great many other
ways of creating alcohols as well.
A common source for producing alcohols is from carbonyl compounds. The
choice of carbonyl type (ketone, aldehyde, ester, etc.) and the type of
reaction (Grignard addition or Reduction), will determine the product(s)
you will get. Fortunately, there are a number of variations of
carbonyls, leading to a number of choices in product.
There are primarily two types of reactions used to create alcohols from
carbonyls: Grignard Addition reactions and Reduction reactions. We\'ll
look at each type of reaction for each type of carbonyl.
### Grignard Addition Reactions
As we learned previously, Grignard
reagents
are created by reacting magnesium metal with an alkyl halide (aka
haloalkanes). The magnesium
atom then gets between the alkyl group and the halogen atom with the
general reaction:
R-X + Mg → R-Mg-X
In our examples, we\'ll be using bromine in our Grignard reagents
because it\'s a common Grignard halogen and it will keep our examples a
little clearer without the need for X.
!Mechanism of Grignard reagent reacting with a
carbonyl{width="600"}
The general mechanism of a Grignard reagent reacting with a carbonyl
(except esters) involves the creation of a 6-membered ring transition
state. The pi bond of the oxygen attacks a neighboring magnesium bromide
which in turn, releases from its R group leaving a carbocation. At the
same time, the magnesium bromide ion from another Grignard molecule is
attacked by the carbocation and has its magnesium bromide ion stolen
(restoring it to its original state as a Grignard reagent). The second
molecule\'s carbocation is then free to attack the carbanion resulting
from the vacating pi bond, attaching the R group to the carbonyl.
According to youtube, see Grignard reagent, the carbanion (R:-) from the
R-MgBr attacks the partially positive carbonyl carbon, displacing the pi
electrons onto the O, which takes a proton, forming the alcohol.
At this point, there is a magnesium bromide on the oxygen of what was a
carbonyl. The proton from the acidic solvent easily displaces this
magnesium bromide ion and protonates the oxygen, creating a primary
alcohol with formaldehyde, a secondary alcohol with an aldehyde and a
tertiary alcohol with a ketone.
With esters, the mechanism is slightly different. Two moles of Grignard
are required for each mole of the ester. Initially, the pi bond on the
carbonyl oxygen attacks the magnesium bromide ion. This opens up the
carbon for attack from the R group of the Grignard. This part of the
reaction is slow because of the dual oxygens off of the carbon providing
some resonance stabilization. The oxygen\'s pi bond then re-forms,
expelling the O-R group of the ester which then joins with the magnesium
bromide, leaving R-O-MgBr and a ketone. The R-O-MgBr is quickly
protonated from the acidic solution and the ketone is then attacked by
Grignard reagent via the mechanism described earlier.
#### Synthesis from Formaldehyde
!Synthesis of alcohol from formaldehyde and Grignard
reagent{width="600"}
The image above shows the synthesis of an alcohol from formaldehyde
reacted with a Grignard reagent. When a formaldehyde is the target of
the Grignard\'s attack, the result is a primary alcohol.
#### Synthesis from an Aldehyde
!Synthesis of alcohol from an aldehyde and Grignard
reagent{width="600"}
The image above shows the synthesis of an alcohol from an aldehyde
reacted with a Grignard reagent. When an aldehyde is the target of the
Grignard\'s attack, the result is a secondary alcohol.
#### Synthesis from a Ketone
!Synthesis of alcohol from an ketone and Grignard
reagent{width="600"}
The image above shows the synthesis of an alcohol from a ketone reacted
with a Grignard reagent. When a ketone is the target of the Grignard\'s
attack, the result is a tertiary alcohol.
#### Synthesis from an Ester
!Synthesis of alcohol from an ester and Grignard
reagent{width="600"}
The image above shows the synthesis of an alcohol from an ester reacted
with a Grignard reagent. When an ester is the target of the Grignard\'s
attack, the result is a tertiary alcohol and a primary alcohol. The
primary alcohol is always from the -O-R portion of the ester and the
tertiary alcohol is the other R groups of the ester combined with the R
group from the Grignard reagent.
#### Synthesis from an Epoxide
!Synthesis of alcohol from an epoxide and Grignard
reagent{width="600"}
We will discuss reactions with Epoxides later when we cover epoxides,
but for now, we\'ll briefly discuss the synthesis of an alcohol from an
epoxide. The nature of the reaction is different than with the
carbonyls, as might be expected. The reaction of Grignard reagents with
epoxides is regioselective. The Grignard reagent attacks at the least
substituted side of the carbon-oxygen bonds, if there is one. In this
case, one carbon has 2 hydrogens and the other has 1, so the R group
attacks the carbon with 2 hydrogens, breaking the bond with oxygen which
is then protonated by the acidic solution. leaving a secondary alcohol
and a concatenated carbon chain. The R group can be alkyl or aryl.
#### Organolithium Alternative
As an alternative to Grignard reagents, organolithium reagents can be
used as well. Organolithium reagents are slightly more reactive, but
produce the same general results as Grignard reagents, including the
synthesis from epoxides. IT IS KNOWN AS Organolithium Alternative.
### Reduction
#### Synthesis from an Aldehyde
!Synthesis of alcohol from an aldehyde by
reduction.{width="600"}
The image above shows the synthesis of an alcohol from an aldehyde by
reduction.
#### Synthesis from a Ketone
!Synthesis of alcohol from an aldehyde by
reduction{width="600"}
The image above shows the synthesis of an alcohol from a ketone by
reduction.
#### Synthesis from an Ester
!Synthesis of alcohol from an ester by
reduction{width="600"}
The image above shows the synthesis of an alcohol from an ester by
reduction. Esters can be hydrolysed to form an alcohol and a carboxylic
acid.
#### Synthesis from a Carboxylic Acid
!Synthesis of alcohol from a carboxylic acid by
reduction{width="600"}
The image above shows the synthesis of an alcohol from a carboxylic acid
reacted by reduction.
# Properties
## Naming alcohols
Follow these rules to name alcohols the IUPAC way:
1. find the longest carbon chain containing at least one OH group, this
is the parent
1. if there are multiple OH groups, look for the chain with the
most of them, and the way to count as many carbons in that chain
2. name as an alcohol, alkane diol, triol, etc.
2. number the OH groups, giving each group the lowest number possible
when different numbering possibilities exist
3. treat all other groups as lower priority substituents (alcohol /
hydroxy groups are the highest priority group for naming)
### Example alcohols
IUPAC name Common name
--------------------------------------------------------------------------------- -------------------------------------------------- -------------------------------------------------------------------------------------------------
CH~3~CH~2~OH Ethanol Ethyl alcohol
CH~3~CH~2~CH~2~-OH 1-Propanol n-Propyl alcohol
(CH~3~)~2~CH-OH 2-Propanol Isopropyl alcohol (Note: Isopropanol would be incorrect. Cannot mix and match between systems.)
2-Ethylbutan-1-ol 2-Ethylbutanol
3-Methyl-3-pentanol
2,2-Dimethylcyclopropanol
Multiple OH functional groups
1,2-Ethanediol Ethylene glycol
1,1-Ethanediol Acetaldehyde hydrate
1,4-Cyclohexanediol
(form that body fat is stored as) 1,2,3-Propanetriol Glycerol
^-^OH can be named as a substituent hydroxyl group (hydroxyalkanes)
1,2-Di(hydroxymethyl)cyclohexane
2-(hydroxymethyl)-1,3-propanediol
Find the longest chain of carbons containing the maximum number of ^-^OH groups
1-(1-hydroxyethyl)-1-methylcyclopropane
2-(1-methylcyclopropyl)ethanol
2-(2-hydroxyethyl)-2-methylcyclopropanol
3-(2-hydroxyethyl)-3-methyl-1,2-cyclopropanediol
## Acidity
In an O-H bond, the O steals the H\'s electron due to its
electronegativity, and O can carry a negative charge (R-O^-^). This
leads to **deprotonation** in which the nucleus of the H, a proton,
leaves completely. This makes the -OH group (and alcohols) Bronsted
acids. Alcohols are weak acids, even weaker than water. Ethanol has a
pKa of 15.9 compared to water\'s pKa of 15.7. The larger the alcohol
molecule, the weaker an acid it is.
On the other hand, alcohols are also weakly basic. This may seem to be
contradictory\--how can a substance be both an acid and a base? However,
substances exist that can be an acid or a base depending on the
circumstances. Such a compound is said to be amphoteric or amphiprotic.
As a Bronsted base, the oxygen atom in the -OH group can accept a proton
(hydrogen ion.) This results in a positively-charged species known as an
oxonium ion. Oxonium ions have the general formula ROH~2~^+^, where R is
any alkyl group that is a carbon containing species that ranges from
-CH3.
## Alkoxides
When O becomes deprotonated, the result is an **alkoxide**. Alkoxides
are anions. The names of alkoxides are based on the original molecule.
(Ethanol=ethoxide, butanol=butoxide, etc.) Alkoxides are good
nucleophiles due to the negative charge on the oxygen atom.
### Producing an alkoxide
R-OH -\> H^+^ + R-O^-^
In this equation, R-O^-^ is the alkoxide produced and is the conjugate
base of R-OH
Alcohols can be converted into alkoxides by reaction with a strong base
(must be stronger than OH^-^) or reaction with metallic sodium or
potassium. Alkoxides themselves are basic. The larger an alkoxide
molecule is, the more basic it is.
# Reactions
## Conversion of alcohols to haloalkanes
Recall that haloalkanes can be converted to alcohols through
nucleophilic substitution.
+------------------------------------------+
| ```{=html} |
| <H2> |
| ``` |
| Conversion of a haloalkane to an alcohol |
| |
| ```{=html} |
| </H2> |
| ``` |
| R-X + OH^-^ → R-OH + X^-^ |
+------------------------------------------+
This reaction proceeds because X (a halogen) is a good leaving group and
OH^-^ is a good nucleophile. OH, however, is a poor leaving group. To
make the reverse reaction proceed, OH must become a good leaving group.
This is done by protonating the OH, turning it into H~2~O^+^, which is a
good leaving group. H^+^ must be present to do this. Therefore, the
compounds that can react with alcohols to form haloalkanes are HBr, HCl,
and HI. Just like the reverse reaction, this process can occur through
S~N~2 (backside attack) or S~N~1 (carbocation intermediate) mechanisms.
+--------------------------------------------------------+
| ```{=html} |
| <H2> |
| ``` |
| S~N~2 conversion of an alcohol to a haloalkane |
| |
| ```{=html} |
| </H2> |
| ``` |
| R-O-H + H^+^ + X^-^ → R-O^+^-H~2~ + X^-^ → R-X + H~2~O |
+--------------------------------------------------------+
+----------------------------------------------------------------------+
| ```{=html} |
| <H2> |
| ``` |
| S~N~1 conversion of an alcohol to a haloalkane |
| |
| ```{=html} |
| </H2> |
| ``` |
| R-O-H + H^+^ + X^-^ → R-O^+^-H~2~ + X^-^ → R^+^ + H~2~O + X^-^ → |
| R-X + H~2~O |
+----------------------------------------------------------------------+
As stated in the haloalkane chapter, the two mechanisms look similar but
the mechanism affects the rate of reaction and the stereochemistry of
the product.
## Oxidation of alcohols
Oxidation in organic chemistry always involves either the addition of
oxygen atoms (or other highly electronegative elements like sulphur or
nitrogen) or the removal of hydrogen atoms. Whenever a molecule is
oxidized, another molecule must be reduced. Therefore, these reactions
require a compound that can be reduced. These compounds are usually
inorganic. They are referred to as *oxidizing reagents*.
With regards to alcohol, oxidizing reagents can be strong or weak. Weak
reagents are able to oxidize a primary alcohol group into a aldehyde
group and a secondary alcohol into a ketone. Thus, the R-OH (alcohol)
functional group becomes R=O (carbonyl) after a hydrogen atom is
removed. Strong reagents will further oxidize the aldehyde into a
carboxylic acid (COOH). Tertiary alcohols cannot be oxidized.
An example of a strong oxidizing reagent is chromic acid (H~2~CrO~4~).
Some examples of a weak oxidizing reagents are pyridinium chlorochromate
(PCC) (C~5~H~6~NCrO~3~Cl) and pyridinium dichromate (PDC).
------------------------------------------------------------------------
\<\< Haloalkanes \| Alcohols
\| Alkenes \>\>
id:Kimia Organik/Alkohol
|
# Organic Chemistry/Ethers
# Ethers
Ethers can be derived from alcohols. The functional group of ethers is
**R-O-R** (instead of R-O-H in an alcohol). Ethers can be viewed as a
water molecule in which both H atoms are replaced with alkyl groups.
Ethers may exist in straight chain carbons (acyclic) or as part of a
carbon ring (cyclic).
!Example ethers. MTBE is acyclic. THF is
cyclic.
# Preparation of ethers
### Synthesis of acyclic ethers
Most acyclic ethers can be prepared using **Williamson\'s synthesis**.
This involves reacting an alkoxide with a haloalkane. As stated
previously, alkoxides are created by reacting an alcohol with metallic
sodium or potassium, or a metal hydride, such as sodium hydride (NaH).
To minimize steric hindrance and achieve a good yield, the haloalkane
must be a primary haloalkane. This is because the mechanism is S~N~2,
where the oxygen atom does a backside attack on the carbon atom with the
halogen atom, causing the halogen atom to leave with its electrons.
### Synthesis of cyclic ethers
You can also use the Williamson synthesis to produce cyclic ethers. You
need a molecule that has a hydroxyl group on one carbon and a halogen
atom attached to another carbon. This molecule will then undergo an
S~N~2 reaction with itself, creating a cyclic ether and a halogen anion.
# Properties of ethers
## Acyclic ethers
### Naming acyclic ethers
Name the two sides of the ether as substituents, then add the word
\"ether\" at the end. For example, CH~3~-O-CH~3~ is dimethyl ether.
CH~3~-O-C(CH~3~)~3~ can be called methyl *tert*-butyl ether (MTBE) or
*tert*-butyl methyl ether (TBME).
### Cleavage of acyclic ethers
Acyclic ethers can be cleaved by a strong acid, typically HI or HBr, but
not HCl. The acid breaks the ether apart into an alcohol and an alkyl
halide (a haloalkane.) Cleavage of ethers by an acid was first seen by
Alexander Butlerov in 1861, when he discovered that hydroiodic acid
causes 2-ethoxypropanoic acid to break apart into iodoethane (ethyl
iodide) and lactic acid (2-hydroxypropanoic acid.) The mechanism used in
acidic cleavage of ethers depends on whether they have primary,
secondary, or tertiary groups attached to oxygen. If one of the carbons
attached to the central oxygen atom is tertiary, benzylic (contains
benzene ring), or allylic (contains carbon-carbon double bond), then the
cleavage will occur via an S~N~1 or an E1 mechanism. The E1 mechanism
leads to an alcohol and an alkene instead of an alkyl halide. These
reactions often take place around 0 degrees C. On the other hand, if
both groups attached to the central oxygen atom are primary or
secondary, the reaction takes place via an S~N~2 mechanism. These
reactions are often conducted at 100 degrees C.
## Cyclic ethers
Two common cyclic ethers are epoxide, which has
two carbons each bonded to the oxygen atom; and
tetrahydrofuran, known by its
abbreviation THF, which has four carbons and an oxygen atom.
### Naming cyclic ethers
### Synthesis of cyclic ethers
### Cleavage of cyclic ethers
|
# Organic Chemistry/Dienes
\> Dienes
\<\< Alkynes \| Kinds of dienes
\>\>
In alkene chemistry, we
demonstrated that allylic carbon could maintain a cation charge because
the double bond could de-localize to support the charge. What of having
two double bonds separated by a single bond? What of having a compound
that alternates between double bond and single bond? In addition to
other concepts, this chapter will explore what a having a
conjugated system
means in terms of stability and reaction.
Dienes are simply hydrocarbons which contain two double bonds. Dienes
are intermediate between
alkenes and polyenes.
Dienes can divided into three classes:
- Unconjugated dienes have the double bonds separated by two or more
single bonds. These are also known as isolated dienes.
- Conjugated dienes have conjugated double bonds separated by one
single bond
- Cumulated dienes (cumulenes) have the
double bonds sharing a common atom as in a group of compounds called
*allenes*.
------------------------------------------------------------------------
1. Kinds of
dienes
2. Conjugation
3. Diene properties and
reactions
------------------------------------------------------------------------
\<\< Alkynes \| Dienes \|
Aromatics \>\>
|
# Organic Chemistry/Aromatics
\| Aromatics \| Aromatic
reactions\>\>
After understanding the usefulness of unsaturated compound, or
conjugated system, we hope to explore the unique structure of
aromatic compounds,
including why benzene should not be called 1,3,5-cyclohexatriene because
it is more stable than a typical triene, and seemingly unreactive.
Called \"aromatic\" initially because of its fragrance, aromaticity now
refers to the stability of compounds that are considered aromatic, not
only benzene. Any cyclic compound with 4n+2 pi electrons in the system
is aromatic. The stability of aromatic compounds arises because all
bonding orbitals are filled and low in energy.
# History of Aromatics
Early in the 19th century, advances in equipment, technique and
communications resulted in chemists discovering and experimenting with
novel chemical compounds. In the course of their investigations they
stumbled across a different kind of stable compound with the molecular
formula of C~6~H~6~. Unable to visualize what such a compound might look
like, the scientists invented all sorts of models for carbon-to-carbon
bonding \-- many of which were not entirely stable \-- in order to fit
what they had observed to what they expected the C~6~H~6~ compound to
look like.
Benzene (which is the name that was given to the aromatic compound
C~6~H~6~) is probably the most common and industrially important
aromatic compound in wide use today. It was discovered in 1825 by
Michael Faraday, and its commercial production from coal tar (and, later
on, other natural sources) began in earnest about twenty-five years
later. The structure of benzene emerged during the 1860s, the result of
contributions from several chemists, most famously that of
Kekulé.
Scientists of the time did not have the benefit of understanding that
electrons are capable of delocalization, so that all carbon atoms could
share the same π-bond electron configuration equally.
Huckel was the first to
apply the new theory of quantum mechanics to clearly separating σ and π
electrons. He went on to develop a theory of π electron bonding for
benzene, which was the first to explain the electronic origins of
aromaticity.
# Benzene Structure
Benzene is a hexagonal ring of six carbon atoms connected to each other
through one p-orbital per carbon. Its chemical formula is C~6~H~6~, and
its structure is a hexagonal ring of carbons sharing symmetrical bonds,
with all six hydrogen atoms protruding outwards from the carbon ring,
but in the same plane as the ring. The p-orbital system contains 6
electrons, and one way to distribute the electrons yields the following
structure:
: {width="45"}
However, another resonance form of benzene is possible, where the single
bonds of the first structure are replaced with double bonds, and the
double bonds with single bonds. These two resonance forms are
co-dominant in benzene. (Other forms, such as a structure with a π bond
connecting opposite carbons, are possible but negligible.) Thus, each
bond in benzene has been experimentally shown to be of equal length and
strength, and each is accounted as approximately a \"1.5\" bond instead
of either a single or double bond alone.
Electron density is shared between carbons, in effect yielding neither a
single nor a double bond, but a sort of one-and-a-half bond between each
of the six carbons. Benzene has a density of negative charge both above
and below the plane formed by the ring structure. Although benzene is
very stable and does not tend to react energetically with most
substances, electrophilic compounds may be attracted to this localized
electron density and such substances may form a bond with the aromatic
benzene ring.
An electron delocalisation ring can be used to show in a single picture
both dominant resonance forms of benzene:
: {width="45"}
## Benzene Properties
Benzene is a colorless, flammable liquid with a sweet aroma and
carcinogenic effects. The aromatic properties of benzene make it far
different from other alkenes in many ways.
### Benzene Reactions
: *Main article:* Aromatic
reactions
Unlike alkenes, aromatic compounds such as benzene undergo substitution
reactions instead of addition reactions. The most common reaction for
benzene to undergo is electrophilic aromatic substitution (EAS),
although in a few special cases, substituted benzenes can undergo
nucleophilic aromatic substitution.
## Benzene Health Effects
In the body, benzene is metabolized, and benzene exposure may have quite
serious health effects. Breathing in very high levels of benzene can
result in death, while somewhat lower (but still high) levels can cause
drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion,
and unconsciousness. Eating or drinking foods containing high levels of
benzene can cause vomiting, irritation of the stomach, dizziness,
sleepiness, convulsions, rapid heart rate, and even death.
The major effect of benzene from chronic (long-term) exposure is to the
blood. Benzene damages the bone marrow and can cause a decrease in red
blood cells, leading to anemia. It can also cause excessive bleeding and
depress the immune system, increasing the chance of infection. Some
women who breathed high levels of benzene for many months had irregular
menstrual periods and a decrease in the size of their ovaries. It is not
known whether benzene exposure affects the developing fetus in pregnant
women or fertility in men, however animal studies have shown low birth
weights, delayed bone formation, and bone marrow damage when pregnant
animals breathed benzene.
The US Department of Health and Human Services (DHHS) also classifies
benzene as a human carcinogen. Long-term exposure to high levels of
benzene in the air can cause leukemia, a potentially fatal cancer of the
blood-forming organs. In particular, Acute Myeloid Leukemia (AML) may be
caused by benzene.
# Aromaticity
Aromaticity in organic chemistry does not refer to whether or not a
molecule triggers a sensory response from olfactory organs (whether it
\"smells\"), but rather refers to the arrangement of electron bonds in a
cyclic molecule. Many molecules that have a strong odor (such as
diatomic chlorine Cl~2~) are not aromatic in structure \-- odor has
little to do with chemical aromaticity. It was the case, however, that
many of the earliest-known examples of aromatic compounds had
distinctively pleasant smells. This property led to the term
\"aromatic\" for this class of compounds, and hence the property of
having enhanced stability due to delocalized electrons came to be called
\"aromaticity\".
## Definition
Aromaticity is a chemical property in which a conjugated ring of
unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization
stronger than would be expected by the stabilization of conjugation
alone. It can also be considered a manifestation of cyclic
delocalization and of resonance.
This is usually considered to be because electrons are free to cycle
around circular arrangements of atoms, which are alternately single- and
double-bonded to one another. These bonds may be seen as a hybrid of a
single bond and a double bond, each bond in the ring identical to every
other. This commonly-seen model of aromatic rings was developed by
Kekulé. The model for benzene consists of two resonance forms, which
corresponds to the double and single bonds\' switching positions.
Benzene is a more stable molecule than would be expected of
cyclohexatriene, which is a theoretical molecule.
## Theory
By convention, the double-headed arrow indicates that two structures are
simply hypothetical, since neither can be said to be an accurate
representation of the actual compound. The actual molecule is best
represented by a hybrid (average) of most likely structures, called
resonance forms. A carbon-carbon double bond is shorter in length than a
carbon-carbon single bond, but aromatic compounds are perfectly
geometrical (that is, not lop-sided) because all the carbon-carbon bonds
have the same length. The actual distance between atoms inside an
aromatic molecule is intermediate between that of a single and that of a
double bond.
A better representation than Lewis drawings of double and single bonds
is that of the circular π bond (Armstrong\'s inner cycle), in which the
electron density is evenly distributed through a π bond above and below
the ring. This model more correctly represents the location of electron
density within the aromatic molecule\'s overall structure. The single
bonds are sigma (σ) bonds formed with electrons positioned \"in line\"
between the carbon atoms\' nuclei. Double bonds consist of one \"in
line\" σ bond and another non-linearly arranged bond \-- a π-bond. The
π-bonds are formed from the overlap of atomic p-orbitals simultaneously
above and below the plane of the ring formed by the \"in line\" σ-bonds.
Since they are out of the plane of the atoms, π orbitals can interact
with each other freely, and thereby they become delocalized. This means
that, instead of being tied to one particular atom of carbon, each
electron can be shared by all the carbon atoms in an aromatic ring.
Thus, there are not enough electrons to form double bonds on all the
carbon atoms, but the \"extra\" electrons strengthen all of the bonds of
the ring equally.
## Characteristics
An aromatic compound contains a set of covalently-bound atoms with
specific characteristics:
1. The molecule has to be cyclic
2. A delocalized conjugated pi system, most commonly an arrangement of
alternating single and double bonds (can sometimes include triple
bonds if the geometry of the molecule permits)
3. Coplanar structure, with all the contributing atoms in the same
plane
4. A number of pi delocalized electrons that is even, but not a
multiple of 4. (This is known as Hückel\'s (4n+2)Π rule, where,n=
0,1,2,3 and so on. Permissible numbers of π electrons include 2, 6,
10, 14, and so on)
5. Special reactivity in organic reactions such as electrophilic
aromatic substitution and nucleophilic aromatic substitution
Whereas benzene is aromatic (6 electrons, from 3 double bonds),
cyclobutadiene is not, since the number of π delocalized electrons is 4,
which is not satisfied by any n integer value. The cyclobutadienide (2−)
ion, however, is aromatic (6 electrons). An atom in an aromatic system
can have other electrons that are not part of the system, and are
therefore ignored for the 4n + 2 rule. In furan, the oxygen atom is
sp^2^ hybridized. One lone pair is in the π system and the other in the
plane of the ring (analogous to C-H bond on the other positions). There
are 6 π electrons, so furan is aromatic.
Aromatic molecules typically display enhanced chemical stability,
compared to similar non-aromatic molecules. The circulating (that is,
delocalized) π electrons in an aromatic molecule generate significant
local magnetic fields that can be detected by NMR techniques. NMR
experiments show that protons on the aromatic ring are shifted
substantially further down-field than those on aliphatic carbons. Planar
monocyclic molecules containing 4n π electrons are called anti-aromatic
and are, in general, destabilized. Molecules that could be anti-aromatic
will tend to alter their electronic or conformational structure to avoid
this situation, thereby becoming merely non-aromatic.
Aromatic molecules are able to interact with each other in so-called π-π
stacking: the π systems form two parallel rings overlap in a
\"face-to-face\" orientation. Aromatic molecules are also able to
interact with each other in an \"edge-to-face\" orientation: the slight
positive charge of the substituents on the ring atoms of one molecule
are attracted to the slight negative charge of the aromatic system on
another molecule.
# Monosubstituted Benzenes
Benzene is a very important basic structure which is useful for analysis
and synthesis in most aspects of organic chemistry. The benzene ring
itself is not the most interesting or useful feature of the molecule;
which substitutents and where they are placed on the ring can be
considered the most critical aspect of benzene chemistry in general.
## Effects of Different Substituents
Depending on the type of substituent, atoms or groups of atoms may serve
to make the benzene ring either more reactive or less reactive. If the
atom or group makes the ring more reactive, it is called **activating**,
and if less, then it is called **deactivating**.
Generally, the terms activating and deactivating are in terms of the
reactions that fall into the category of Electrophilic Aromatic
Substitution (EAS). These are the most common forms of reactions with
aromatic rings. Aromatic rings can undergo other types of reactions,
however, and in the case of Nucleophilic Aromatic Substitution, the
activating and deactivating nature of substituents on the rings is
reversed. In EAS, a hydroxyl groups is strongly activating, but in
Nucleophilic Aromatic Substitution, a hydroxyl group is strongly
deactivating. But since EAS is the most common reaction with aromatic
rings, when discussing activation and deactivation, it\'s normally done
in terms of the EAS.
In addition to activating or deactivating, all groups and/or substituent
atoms on a benzene ring are **directing**. An atom or group may
encourage additional atoms or groups to add or not to add to certain
other carbons in relation to the carbon connected to the directing
group. This concept will be further discussed in the next chapter, but
when memorizing the groups below it is helpful to also memorize whether
it is O (ortho), M (meta) or P (para)-directing.
Another factor that heavily influences direction, however, is steric
hindrance. If, for example, you have a tert-butyl substituent on the
ring, despite the fact that it is ortho/para directing, the ortho
positions will be largely blocked by the tert-butyl group and thus
nearly all the product would be para.
## Activating Substituents
Activating substituents make benzene either slightly more reactive or
very much more reactive, depending on the group or atom in question. In
general, if one of the major heteroatoms (nitrogen or oxygen) is
*directly* attached to the carbon ring then the result is probably
activation. This is merely a rule of thumb, and many exceptions exist,
so it is best to memorize the groups listed below instead of counting on
a quick and dirty rule of thumb.
```{=html}
<center>
```
----------------------- -------------- ---------------
**Group** **Strength** **Directing**
-NH~2~, -NHR, -NRR very strong ortho/para
-OH, -O^-^ very strong ortho/para
-NHCOCH~3~, -NHCOR strong ortho/para
-OCH~3~, -OR strong ortho/para
-CH~3~, -C~2~H~5~, -R weak ortho/para
-C~6~H~5~ very weak ortho/para
----------------------- -------------- ---------------
```{=html}
</center>
```
## Deactivating Substituents
A deactivating group is a functional group attached to a benzene
molecule that removes electron density from the benzene ring, making
electrophilic aromatic substitution reactions slower and more difficult
than they would be on benzene alone. As discussed above for activating
groups, deactivating groups may also determine the positions (relative
to themselves) on the benzene ring where substitutions take place, so
each deactivating group is listed below along with its directing
characteristic.
```{=html}
<center>
```
------------------ -------------- ---------------
**Group** **Strength** **Directing**
-NR~3~^+^ very strong meta
-NO~2~ very strong meta
-CF~3~, CCl~3~ very strong meta
-CN strong meta
-SO~3~H strong meta
-CO~2~H, -CO~2~R strong meta
-COH, -COR strong meta
-F weak ortho/para
-Cl weak ortho/para
-Br weak ortho/para
------------------ -------------- ---------------
```{=html}
</center>
```
## Activation vs. Deactivation and ortho/para vs. meta directing
So why are some substituents activating or deactivating? Why are some
meta directing and others ortho/para directing? From the above tables,
it seems pretty clear there\'s a relationship.
There are primarily two effects that substituents impart on the ring
that affect these features:
1. Resonance effects
2. Inductive effects
### Resonance Effects
Let\'s first look at resonance effects. Resonance effects are the
ability or inability of a substituent to provide electrons to the ring
and enhance its resonance stability. To see this, we must first get a
basic understanding of the mechanism of Electrophilic Aromatic
Subsitution. We\'ll discuss EAS in more detail in the next section, but
some basics are called for here.
!Basic Mechanism of Electrophilic Aromatic
Substitution
As you can see in the image above, the electrophile is attacked by pi
electrons in the ring. The same carbon is now bonded to both the
hydrogen that was bonded to it and the electrophile. This in turn
creates a carbocation on the adjacent carbon, making the ring
non-aromatic. But aromatic rings like to remain aromatic. The
nucleophile which was previously bonded to the electrophile now attacks
the hydrogen, abstracting it from the ring and allowing the pi-bond to
re-form and returning the ring to its aromatic nature.
As we\'ve seen before in some other reactions, when a carbocation is
created as an intermediate, stability of that carbocation is crucial to
the reaction. This is the case in Electrophilic Aromatic Subsitution as
well.
So what is the effect of substituents on the ring?
!Resonance Stability of ortho, para, and meta
attacks.
Let\'s look at the situation above. In this case we have Phenol, a
benzene ring with an -OH (hydroxyl) group attached. When we nitrate the
ring with nitric acid in sulfuric acid (a reaction we\'ll discuss in the
next section), a nitro group is attached to the benzene ring.
There are 3 possible places for the nitro group to attach: An ortho,
meta, or para position. To understand the stability of the carbocation,
we need to look at the resonance structures for a given attack and see
what the results are.
The first resonance structure of the ortho attack results in a positive
charge on the carbon with the hydroxyl group. This happens to be the
most stable of the 3 resonance structures for an ortho attack because
the two negative electron pairs in the oxygen act to stabilize the
positive charge on the carbon. The other two resonance forms leave a
carbon with a hydrogen attached, to hold the positive charge. Hydrogen
can do nothing to stabilize the charge and thus, these are less stable
forms.
In the para attack situation, notice that the second resonance form also
puts a positive charge on the carbon with the hydroxyl group. This
provides for stability just as it does in the case of an ortho attack
and thus, the middle resonance form is very stable.
Finally, in the meta attack situation, all of the resonance forms result
in a positive charge on a carbon with only a hydrogen attached. None of
these is stable, and thus, meta attack with a hydroxyl group attached,
is a very small percentage of the product.
So the electron pairs in the oxygen act to stabilize the ortho and para
attacks.
### Inductive Effects
Now let\'s look at the inductive effects of deactivating substituents.
Let\'s imagine that, instead of a hydroxyl group, we instead have a
carbonyl group attached to the ring in its place. When a carbonyl is
attached, the ring is bonded to a carbon which in turn, is double-bonded
to an oxygen, the double-bonded oxygen is withdrawing electrons and this
inductive effect is felt on the ring, strongly deactivating its pi-bond
nature and putting a positive dipole on the carbon. Looking at the
resonance structures, this carbon, which already has some positive
nature is now given the added resonance of a positive charge, in the
case of ortho and para attacks. Positive plus positive equals more
positive and thus, less stable. There\'s no negative charge or negative
electron pair to stabilize this positive charge.
So in this case, not only is the entire ring less activated, but the
ortho and para attacks result in much more unstable carbocation
resonance forms. Hence, meta is the preferred position, but the overall
reaction is less active than plain benzene.
### Halides as the Exception
Notice that in the list of activating vs. deactivating substituents, the
activating ones are all ortho/para directing. In the deactivating
substituents, all but the halides, are meta directing. Why are halides
an exception?
Because halides are more electronegative than carbon, they induce a
positive dipole on the attached carbon and a negative dipole on their
own atom(inductive effect), and in accordance to the previous logic of
activating/deactivating substituents, deactivate the ring. However,
halides also possess lone pair electrons in their outer shell to share
with the ring, allowing the resonance structures with favored ortho/para
attacks versus meta attacks due to their poor resonance forms. In
essence, although halides do deactivate the ring to some extent, they
provide major resonance contributors due to the availability of their
lone pairs. Resonance structures usually trump the inductive effect.
## Detailed Effects of Substituents
We\'ve discussed some generalities about the effects of substituents and
even some specifics about certain ones, but let\'s look more closely at
the substituents and try to understand the details of what makes them
activating vs. deactivating.
-NH~2~, -NHR, and -NRR are all very strongly activating. Though nitrogen
is more electronegative than carbon, its ability to share a pair of
electrons greatly outweighs its electron withdrawing effect.
-OH and -O^-^ is similar in that it is even more electronegative than
nitrogen, but it has two pairs of electrons to share, which also greatly
outweighs its electron withdrawing effect.
-NHCOCH~3~ and -NHCOR are also strongly activating, but the inductive
effect of the double-bonded oxygen acts to make the nitrogen more
electron withdrawing, so they\'re not quite as activating as the other
-N substituents above.
-OCH~3~ and -OR are also still strongly activating, but less so, because
the electron density is shared on both sides of the oxygen.
-CH~3~ and -R in general provide some electron density sharing, but not
nearly as much as a pair of electrons. Thus their effect is only weakly
felt.
For deactivating groups we have:
-NO~2~, or nitro and -NR~3~^+^. The nitro group is very strongly
deactivating because of its resonance structure. The nitro group has two
resonance forms: O=N^+^-O^-^ and O^-^-N^+^=O. Both of these forms leave
a full positive charge on the nitrogen making it completely unable to
help stabilize the positive carbocation intermediate. The same applies
to -NR~3~^+^.
-CF~3~ and -CCl~3~ both have an inductive electronegative effect of 3
halides, but with no electrons to share with the ring, leaving them also
very strongly deactivating.
-CN has a triple bond between the carbon and nitrogen with a resonance
form of a double bond between the carbon and nitrogen and a positive
charge on the carbon, meaning that between the electronegativity of the
nitrogen and positively charged carbon in the resonance form, it
destabilizes the carbocation and offer no electrons to the ring.
-SO~3~, -COR, -CO~2~R - all of these have electronegative oxygens giving
the carbon a positive partial charge and providing no electrons for
stability on the ring.
-F, -Cl, -Br, all have a similar effect. They are electronegative and
deactivate the ring, but have electrons to share that, to some degree,
makes up for it, allowing the ortho/para direction. But to understand
their effects better, you need to look at them in terms of their
placement on the periodic chart. Florine is the most electronegative
element and it\'s very small and thus very close to the carbon it\'s
bonded to. This gives its electromagnetic influence a stronger
deactivating character. Chlorine is less electronegative, but it\'s also
larger and thus further away from the carbon, making it harder for it to
share its electrons. And so on.
# Polysubstituted Benzenes
Unsubstituted benzene is seldom encountered in nature or in the
laboratory, and you will find in your studies that most often benzene
rings are found as parts of other, more complicated molecules. In order
for benzene to react in most situations, it gains or loses some
functionality dependent on which functional groups are attached.
Although the simplest case is to work with benzene that has only one
functional group, it is also essential to understand the interactions
and competitions between multiple functional groups attached to the same
benzene ring.
When there is more than one substituent present on a benzene ring the
spatial relationship between groups becomes important, which is why the
arene substitution patterns **ortho**, **meta** and **para** were
devised. For example three isomers exist for the molecule cresol because
the methyl group and the hydroxyl group can be placed either next to
each other (*ortho*), one position removed from each other (*meta*) or
two positions removed from each other (*para*). Where each group
attaches is most often a function of which order they were attached in,
due to the activating/deactivating and directing activities of
previously attached groups.
## Competition Between Functional Groups
When a ring has more than one functional group, the effects of the
groups are combined and their total effect must be taken into account.
In general, effects are summed. For example, toluene (methylbenzene) is
weakly activated. But p-nitrotoluene has both a methyl group and a nitro
group. The methyl group is weakly activating and the nitro is pretty
strongly deactivating, so overall, the group is very deactivated. In
terms of direction, however, both substitutents agree on the direction.
The methyl group is ortho/para directing. The nitro group occupies the
para position, so the methyl will now want just ortho direction. The
nitro group is meta directing. The positions meta to the nitro are also
ortho to the methyl, so this works out and further substituents will be
almost entirely in the positions ortho to the methyl group.
If two functional groups disagree on direction, the more activating
group is the one that controls direction. That is, if you had
m-nitrotoluene, most of your product would tend to be ortho/para to the
toluene and not meta to the nitro, despite the nitro having a stronger
influence on overall activation.
## Naming Conventions
When a benzene ring has more than one substituent group attached, the
location of all of the groups not directly attached to carbon number one
must be explicitly declared. This is done by listing the number of the
carbon atom where the group is attached, followed by a hyphen and the
group\'s name. The carbon atoms of the benzene ring should be numbered
in order of previously established precedence, i.e., a bromine would
take precedence over a nitro group, which itself would take precedence
over an alcohol or alkane group. The names of the groups should be
listed in alphabetical order, i.e. \"2-methyl-5-nitrobenzaldehyde.\"
------------------------------------------------------------------------
\<\< Dienes \| Aromatics \|
Aromatic
reactions\>\>
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# Organic Chemistry/Aromatic reactions
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\<\< Aromatics \| Aromatic
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The lack of reactivity of arenes is notable when compared to the
reactivities of typical compounds containing multiple conjugated double
bonds. For example, 1,3,5-hexatriene is much more reactive than hexane,
hexene, or any hexadiene. Benzene is much less reactive than any of
these. Any of the alkenes will be readily converted to alcohols in the
presence of a dilute aqueous solution of H~2~SO~4~, but benzene is
inert. Similarly, alkenes react readily with halogens and hydrogen
halides *by addition* to give alkyl halides, whereas halogens react with
benzene *by substitution* and only in the presence of a catalyst.
KMnO~4~ or chromic acid solutions (typically CrO~3~ or K~2~Cr~2~O~7~)
cleave the double bonds of alkenes, giving ketones or carboxylic acids,
but do not react at all with benzene. Because of the stability of
aromatic compounds, however, reactions involving these have extremely
high activation energies, for passage to the transition state
necessarily requires disruption of the aromatic system, resulting in a
temporary loss of aromatic stabilization energy. Instead of reacting by
addition and elimination, as nonaromatic compounds often do, benzene and
its derivatives usually react by electrophilic aromatic substitution.
# Redox
## Birch reduction
The **Birch reduction**[^1] is the reduction of aromatic compounds by
sodium in liquid ammonia. It is attributed to the chemist Arthur
Birch. The reaction product is a
1,4-cyclohexadiene. The metal can also be lithium or potassium and the
hydrogen atoms are supplied by an alcohol such as ethanol or
tert-butanol.
!Birch reduction of aromatic
rings
The first step of a Birch reduction is a one-electron reduction of the
aromatic ring to a radical anion. Sodium is oxidized to the sodium ion
Na^+^. This intermediate is able to dimerize to the dianion. In the
presence of an alcohol the second intermediate is a free radical which
takes up another electron to form the carbanion. This carbanion
abstracts a proton from the alcohol to form the cyclohexadiene.
center\|Birch reduction reaction
mechanism
In the presence of an alkyl halide, the carbanion can also engage in
nucleophilic substitution with carbon-carbon bond formation. In
substituted aromatics an electron withdrawing substituent such as a
carboxylic acid stabilizes a carbanion and the least-substituted alkene
is generated. With an electron donating substituent, the opposite effect
occurs. The non-conjugated 1,4-addition product is preferred over the
conjugated 1,3-diene which is explicable by the principle of least
motion. Experimental alkali
metal alternatives that are safer to handle, such as the M-SG reducing
agent, also exist.
## Oxidation of Benzene in the Human Body
Because benzene is nonpolar, it cannot be passed in urine, and will
remain in the body until oxidized. Benzene itself is not dangerous to
health, but in order to be passed, it is oxidized by cytochrome P-450 in
the liver. This produces benzene oxide, a highly teratogenic and
carcinogenic compound. Benzene has been replaced by toluene as an
industrial solvent, because toluene can be oxidized to benzoic acid,
which is mostly harmless to health, and is quickly passed. The
decomposition of benzoic acid into benzene and carbon dioxide in soda
pop has become an issue recently.
# Nucleophilic Aromatic Substitution
A nucleophilic substitution is a substitution reaction in organic
chemistry in which the nucleophile displaces a good leaving group, such
as a halide on an aromatic ring. In order to understand this type of
reaction, it is important to recognize which chemical groups are good
leaving groups and which are not.
## Leaving Groups
A leaving group can probably most simply be described as an atom or
molecule that detaches from an organic molecule. The ability for a
functional group to leave is called *lability*. Leaving groups affect
the intrinsic reactivity of the molecule as a whole, but only until,
quite naturally, they actually leave.
The lower the p*K*~a~ of the conjugate acid for a given leaving group,
the better that leaving group is at actually leaving. This is because
such groups can easily stabilize any developing negative charge and
without stabilization, a leaving group will actually become a
nucleophile causing the reaction to cycle pointlessly between attached
and detached forms. (This explains why a strong base is nearly always a
poor leaving group.)
In room temperature water, the sequence of lability is:
- *Less lability*
- amine/amide (NH~2~^-^)
- alkoxy/alkoxide (RO^-^)
- hydroxyl/hydroxide (HO^-^)
- carboxylate (RCOO^-^)
- fluoro/fluoride (F^-^)
- water (H~2~O)
- chloro/chloride (Cl^-^)
- bromo/bromide (Br^-^)
- iodo/iodide (I^-^)
- azide (N~3~^-^)
- thiocyanate (SCN^-^)
- nitro/nitrite (NO~2~)
- cyano/cyanide (CN^-^)
- *Greater Lability*
## Rate of Reaction
The better a leaving group, the faster a nucleophilic reaction will
occur. This is demonstrated by comparisons of the kinetics between
halogenalkanes, where the bromides dissociate more quickly than the
chlorides, but the iodides dissociate more rapidly than either of the
other two. This is because the bond between the halogen and its nearest
carbon must be broken at some point for a nucleophilic substitution to
take place. A bond between iodine and carbon is far more polarizable
than a bond between carbon and chlorine, for example, due to iodine\'s
relatively large size and relatively large number of ionizable
electrons. The fact that water is a far better leaving group than
hydroxide also has the important consequence that the rate of a reaction
in which hydroxide leaves is increased dramatically by the presence of
an acid, for hydroxide is then protonated to water, a much weaker
nucleophile.
## Types of Reactions
There are three nucleophilic substitution mechanisms commonly
encountered with aromatic systems, the SNAr (addition-elimination)
mechanism, the benzyne mechanism and the free radical SRN1 mechanism.
The most important of these is the SNAr mechanism, where electron
withdrawing groups activate the ring towards nucleophilic attack, for
example if there are nitro functional groups positioned ortho or para to
the halide leaving group. It is not generally necessary to discuss these
types in detail within the context of an introductory organic chemistry
course.
# Electrophilic Aromatic Substitution
**Electrophiles** are particles with a deficiency of electrons.
Therefore they are likely to react with substances that have excess
electrons. Aromatic compounds have increased electron density in the
form of delocalized π-orbitals.
## Step 1: Formation of a π-complex
At first, the electrophile interacts with the delocalized orbitals of
the aromatic ring and a π-complex is formed.
No chemical bonds are formed at this stage. Evidence of the formation of
a π-complex as an intermediate state has been found for some reactions,
but not for all, since the chemical interaction in π-complexes is very
weak.
## Step 2: Formation of a σ-complex
After the π-complex is formed, in the presence of an electron acceptor
another complex is formed - the σ-complex. It is a cationic species, an
intermediate that lacks aromatic properties, but its four π-electrons
are delocalized across the ring, which stabilizes the cation somewhat,
sometimes allowing its isolation. An example would be the salt mesityl
fluoroborate, which is stable at low temperatures, and is prepared by
the reaction of mesitylene (1,3,5-trimethylbenzene) with fluoroboric
acid (BF~3~/HF); the cation of this salt is protonated mesitylene.
σ-complexes are also known as *Wheland intermediates*.
## Step 3: Formation of a Substituted product
At the next stage the σ-complex decomposes, freeing a hydrogen cation
and forming the product of substitution.
### Electrophilic aromatic halogenation
!Electrophilic aromatic substitution of
benzene{width="450"}
Another important reaction of benzene is the electrophilic substitution
of halides, a specific type of electrophilic aromatic substitution.
These reactions are very useful for adding substituents to an aromatic
system. The rates of the reactions increase with the electrophilicity of
the halogen: hence, fluorination in this manner is too rapid and
exothermic to be practical, whereas iodine requires the most vigorous
conditions. Chlorination and bromination are the most often practiced in
the lab of the four possible halogenations. Halobenzenes are used for
pesticides, as well as the precursors to other products. Many COX-2
inhibitors contain halobenzene subunits.
Some highly activated aromatic compounds, such as phenol and aniline,
are reactive enough to undergo halogenation without a catalyst, but for
typical benzene derivatives (and benzene itself), the reactions are
extremely slow at room temperature in the absence of a catalyst.
Usually, Lewis acids are used as catalysts, which work by helping to
polarize the halogen-halogen bond, thus decreasing the electron density
around one halogen atom, making it more electrophilic. The most common
catalysts used are either Fe or Al, or their respective chlorides and
bromides (+3 oxidation state). Iron(III) bromide and iron(III) chloride
lose their catalytic activity if they are hydrolyzed by any moisture
present, including atmospheric water vapor. Therefore, they are
generated *in situ* by adding iron fillings to bromine or chlorine.
Iodination is carried out under different conditions: periodic acid is
often used as a catalyst. Under these conditions, the I^+^ ion is
formed, which is sufficiently electrophilic to attack the ring.
Iodination can also be accomplished using a diazonium reaction.
Fluorination is most often done using this technique, as the use of
fluorine gas is inconvenient and often fragments organic compounds.
Halogenation of aromatic compounds differs from the additions to alkenes
or the free-radical halogenations of alkanes, which do not require Lewis
acid catalysts. The formation of the arenium ion results in the
temporary loss of aromaticity, the overall result being that the
reaction\'s activation energy is higher than those of halogenations of
aliphatic compounds.
Halogenation of phenols is faster in polar solvents due to the
dissociation of phenol, because the phenoxide (-O^-^) group is more
strongly activating than hydroxyl itself.
### Electrophilic aromatic sulfonation
Aromatic sulfonation is an organic reaction in which a hydrogen atom on
an arene is replaced by a sulfonic acid functional group in an
electrophilic aromatic substitution.
The electrophile of such a reaction is sulfur trioxide (SO~3~), which
can be released from oleum (also known as fuming sulfuric acid),
essentially sulfuric acid in which gaseous sulfur trioxide has been
dissolved.
In contrast to aromatic nitration and other electrophilic aromatic
substitutions, aromatic sulfonation is reversible. Sulfonation takes
place in strongly acidic conditions, and desulfonation can occur on
heating with a trace of acid. This also means that thermodynamic, rather
than kinetic, control can be achieved at high temperatures. Hence,
directive effects are not expected to play a key role in determining the
proportions of isomeric products of high-temperature sulfonation.
Aromatic sulfonic acids can be intermediates in the preparation of dyes
and many pharmaceuticals. Sulfonation of aniline produces
p-aminobenzenesulfonic acid or sulfanilic acid, which is a zwitterionic
compound with an unusually high melting point. The amide of this
compound and related compounds form a large group of sulfa drugs (a type
of antibiotic).
Overall reaction: ArH + SO~3~ → ArSO~3~H
### Electrophilic aromatic nitration
Nitration occurs with aromatic organic compounds via an electrophilic
substitution mechanism involving the attack of the electron-rich benzene
ring by the nitronium (nitryl) ion. Benzene is commonly nitrated by
refluxing with a mixture of concentrated sulfuric acid and concentrated
nitric acid at 50°C. The sulfuric acid is regenerated and hence acts as
a catalyst.
Selectivity is always a challenge in nitrations. Fluorenone nitration is
selective and yields a tri-nitro compound or tetra-nitro compound by
tweaking reaction conditions just slightly. Another example of
trinitration can be found in the synthesis of phloroglucinol. Other
nitration reagents include nitronium tetrafluoroborate which is a true
nitronium salt. This compound can be prepared from hydrogen fluoride,
nitric acid and boron trifluoride. Aromatic nitro compounds are
important intermediates for anilines; the latter may be readily prepared
by action of a reducing agent.
Overall reaction: ArH + HNO~3~ → ArNO~2~ + H~2~O
### Friedel-Crafts alkylation
!Friedel-Crafts alkylation of benzene with methyl
chloride{width="400"}
The Friedel-Crafts reactions, discovered by French alkaloid chemist
Charles Friedel and his American partner, James Crafts, in 1877, is
either the alkylation or acylation of aromatic compounds catalyzed by a
Lewis acid. They are very useful in the lab for formation of
carbon-carbon bonds between an aromatic nucleus and a side chain.
#### Source of electrophile
Friedel-Crafts alkylation is an example of electrophilic substitution in
aromatic compounds. The electrophile is formed in the reaction of an
alkyl halide with a Lewis acid. The Lewis acid polarizes the alkyl
halide molecule, causing the hydrocarbon part of it to bear a positive
charge and thus become more electrophilic.
CH~3~---Cl + AlCl~3~ → CH~3~^+^ + AlCl~4~^−^
or
CH~3~Cl + AlCl~3~ → CH~3~^δ+^Cl^+^Al^−^Cl~3~
(The carbon atom has a slight excess of positive charge, as the
electronegative chlorine atom draws electron density towards itself. The
chlorine atom has a positive charge, as it has formed a sub-ordinate
bond with the aluminium atom. In effect, the Cl atom has lost an
electron, while the Al atom has gained an electron. Therefore, the Al
atom has a negative charge.)
#### Mechanism of alkylation
The polarized, electrophilic molecule then seeks to saturate its
electron deficiency and forms a π-complex with the aromatic compound
that is rich in π-electrons. Formation a π-complex does not lead to loss
of aromaticity. The aromaticity is lost however in the σ-complex that is
the next stage of reaction. The positive charge in the σ-complex is
evenly distributed across the benzene ring.
C~6~H~6~ + CH~3~^+^ → C~6~H~6~^+^Br → C~6~H~5~Br + H^+^
The σ-complex C~6~H~6~^+^Br can be separated (it is stable at low
temperatures), while the π-complex can not.
#### Restrictions
- Deactivating functional groups, such as nitro (-NO~2~), usually
prevent the reaction from occurring at any appreciable rate, so it
is possible to use solvents such as nitrobenzene for Friedel-Crafts
alkylation.
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- Primary and secondary carbocations are much less stable than
tertiary cations, so rearrangement typically occurs when one
attempts to introduce primary and secondary alkyl groups onto the
ring. Hence, Friedel-Crafts alkylation using n-butyl chloride
generates the n-butylium cation, which rearranges to the t-butyl
cation, which is far more stable, and the product is exclusively the
t-butyl derivative. This may, in some cases, be circumvented through
use of a weaker Lewis acid.
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- The Friedel-Crafts reaction can not be used to alkylate compounds
which are sensitive to acids, including many heterocycles.
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- Another factor that restricts the use of Friedel-Crafts alkylation
is polyalkylation. Since alkyl groups have an activating influence,
substituted aromatic compounds alkylate more easily than the
original compounds, so that the attempted methylation of benzene to
give toluene often gives significant amounts of xylene and
mesitylene. The usual workaround is to acylate first (see the
following sections) and then reduce the carbonyl group to an alkyl
group.
### Friedel-Crafts acylation
!Friedel-Crafts acylation of benzene by acetyl
chloride{width="300"}
Friedel-Crafts acylation, like Friedel-Crafts alkylation, is a classic
example of electrophilic substitution.
#### Source of electrophile
Reacting with Lewis acids, anhydrides and chloranhydrides of acids
become strongly polarized and often form acylium cations.
RCOCl + AlCl~3~ → RC^+^O + AlCl~4~^-^
#### Mechanism of acylation
The mechanism of acylation is very similar to that of alkylation.
C~6~H~6~ + RC^+^O → C~6~H~6~---CO---R + H^+^
The ketone that is formed then forms a complex with aluminum chloride,
reducing its catalytic activity.
C~6~H~6~---CO---R + AlCl~3~ → C~6~H~6~---C^+^(R)---O---Al^−^Cl~3~
Therefore, a much greater amount of catalyst is required for acylation
than for alkylation.
#### Restrictions
- Although no isomerisation of cations happens, due to the reasonance
stabilization provided by the acylium ion, certain cations may lose
CO and alkylation will occur instead of acylation. For example, an
attempt to add pivalyl (neopentanoyl) to an aromatic ring will
result in loss of CO from the cation, which then results in the
t-butyl derivative being formed.
- Acidophobic aromatic compounds, such as many heterocycles can\'t
exist in the presence of both Lewis acids and anhydrides.
- Formyl chloride is unstable and cannot be used to introduce the
formyl group onto a ring through Friedel-Crafts acylation. Instead,
the Gattermann-Koch reaction is often used.
#### Applications
Friedel-Crafts acylation is used, for example, in the synthesis of
anthraquinone from benzene and phtalic anhydride.
In laboratory synthesis Friedel-Crafts acylation is often used instead
of alkylation in cases where alkylation is difficult or impossible, such
as synthesis of monosubstituted alkylbenzenes.
# External links
- reduction of o-anisic acid to
2-heptyl-2-hexenone in Organic
Syntheses
Article
- reduction of naphthalene to
1,4,5,8-Tetrahydronaphthalene (isotetralin) in Organic
Syntheses
Article.
- reduction of o-xylene to
1,2-Dimethyl-1,4-cyclohexadiene in Organic
Syntheses
Article
- reduction of benzoic acid to
2,5-Cyclohexadiene-1-carboxylic acid in Organic
Syntheses
Article
# References
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[^1]: \* A. J. Birch, J. Chem. Soc. **1944**, 430.
|
# Organic Chemistry/Ketones and aldehydes
Aldehydes ({width="50"}) and ketones
({width="50"}) are both
carbonyl compounds. They are organic compounds in which the carbonyl
carbon is connected to conyl carbon satisfied by a H atom, while a
ketone has both its vacancies satisfied by carbon.
## Naming Aldehydes and Ketones
**Ketones** are named by replacing the**-e** in the alkane name with
**-one**. The **carbon chain** is numbered so that the ketone carbon,
called **the carbonyl group**, gets the lowest number. For example,
{width="50"}
would be named 2-butanone because the root structure is butane and the
ketone group is on the number two carbon.
Alternatively, functional class nomenclature of ketones is also
recognized by IUPAC, which is done by naming the substituents attached
to the carbonyl group in alphabetical order, ending with the word
ketone. The above example of 2-butanone can also be named ethyl methyl
ketone using this method.
If two ketone groups are on the same structure, the ending **-dione**
would be added to the alkane name, such as heptane-2,5-dione.
**Aldehydes** replace the**-e** ending of an alkane with **-al** for an
aldehyde. Since an aldehyde is always at the carbon that is numbered
one, a number designation is not needed. For example, the aldehyde of
pentane would simply be pentanal.
The **-CH=O group of aldehydes** is known as a formyl group. When a
formyl group is attached to a ring, the ring name is followed by the
suffix **\"carbaldehyde\"**. For example, a hexane ring with a formyl
group is named cyclohexanecarbaldehyde.
## Boiling Points and Bond Angles
**Aldehyde and ketone** polarity is characterized by the high dipole
moments of their carbonyl group, which makes them rather polar
molecules. They are more polar than alkenes and ethers, though because
they lack hydrogen, they cannot participate in hydrogen bonding like
alcohols, thus making their relative boiling points higher than alkenes
and ethers, yet lower than alcohols.
Typical bond angles between the carbonyl group and its substituents show
minor deviations from the trigonal planar angles of 120 degrees, with a
slightly higher bond angle between the O=C-R bond than the R-C-R bond on
the carbonyl carbon (with R being any substituent).
## Preparing Aldehydes and Ketones
### Preparing Aldehydes
#### Partial oxidation of primary alcohols to aldehydes
This reaction uses pyridinium chlorochromate (PCC) in the absence of
water (if water is present the alcohol will be oxidized further to a
carboxylic acid). 
#### From fatty acids
`<chem>`{=html}Ca(COOH)2 -\>\[\\Delta\] HCHO + CaCO3 `</chem>`{=html}
`<chem>`{=html}(CH3COO)2Ca -\>\[\\Delta\] CH3COCH3 +
CaCO3`</chem>`{=html}
`<chem>`{=html}(CH3COO)2Ca + (HCOO)2Ca -\> CH3CHO`</chem>`{=html}
#### Stephen reduction
`<chem>`{=html}R-CN + SnCl2 + HCl -\> R-CH=NH2+Cl- -\>\[H\^+/H_2O\]
R-CHO `</chem>`{=html}
Here sulfur is used as a poisoner so that aldehyde formed doesn\'t get
oxidised to the carboxylic acid. See the Wikipedia
article for more detail.
#### Rosenmund reaction
`<chem>`{=html}R-COCl + Pd + BaSO4 + S -\> R-CHO`</chem>`{=html}
(For solvent xylene is used)
### Preparing Ketones
#### From Grignard reagents
`<chem>`{=html}RCOOR\' + R\'MgX -\>RCOR + R\'OH`</chem>`{=html}
` R' R' OH `\
` | | |`
`<chem>`{=html}RC=O + R\'MgX -\> R-CO-MgX -\> R-C-OH +
Mg-X`</chem>`{=html}
`| | | `\
`O-R' OR' OR'`
#### From nitriles
RCN + R\'MgX \-\-\--\> RCOR\'(after hydrolysis) HCN does not react with
RMgX as HCN has acidic hydrogen which results in RH being formed.
#### From gem dihalides
RCCl~2~R + strong base \-\-\--\> RCOR
#### Oppenaur oxidation
Reagent is Aluminium tert. butoxide solvent is acetone
ROH + ACETONE \-\-\--\> Ketone + isopropyl alcohol this oxidation does
not affect double bonds in this oxidation ketone act as a oxidizing
agent this is exact opposite to merrwine pondroff reduction
#### Friedel-Crafts acylation of aromatic compounds
An aromatic ring reacts with a carboxylic acid chlorine (RCOCl) in the
presence of AlCl~3~ to form an aryl ketone of the form ArCOR.
#### Oxidation of secondary alcohols to ketones
A secondary alcohol can be oxidised into a ketone using acidified
potassium dichromate(VI) and heating under reflux.
The orange dichromate(VI) ion, Cr2O72-, is reduced to the green Cr3+(aq)
ion.
### Ozonolysis of alkenes
It is a reaction in which the double bond is completely broken and the
alkene molecule converted into two smaller molecules.
!A generalized scheme of
ozonolysis{width="350"}
Ozonolysis (cleavage \"by ozone) is carried out in two stages: first,
addition of ozone to the double bond to form an ozonide ; and second,
hydrolysis of the ozonide to yield the cleavage products.
Ozone gas is passed into a solution of the alkene in some inert solvent
like carbon tetrachloride; evaporation of the solvent leaves the ozonide
as a viscous oil. This unstable, explosive compound is not purified, but
is treated directly with water, generally in the presence of a reducing
agent. If oxidising reagent is used, aldehyde or ketone if oxidisable
can further oxidise into carboxylic acid which is not the case with
reducing agents
In the cleavage products a doubly-bonded oxygen is found attached to
each of the originally doubly-bonded carbons.
The function of the reducing agent, which is frequently zinc dust, is to
prevent formation of hydrogen peroxide, which would otherwise react with
the aldehydes and ketones. (Aldehydes, RCHO, are often converted into
acids,rCOOH, for ease of isolation.)
##### Mechanism
The alkene and ozone form an intermediate molozonide in a 1,3-dipolar
cycloaddition. Next, the molozonide reverts to its corresponding
carbonyl oxide (also called the Criegee intermediate or Criegee
zwitterion) and aldehyde or ketone in a retro-1,3-dipolar cycloaddition.
The oxide and aldehyde or ketone react again in a 1,3-dipolar
cycloaddition or produce a relatively stable ozonide intermediate (a
trioxolane) !The reaction mechanism of
ozonolysis.{width="600"}
### Hydration of alkynes
Water is added to an alkyne in a strong acid. The strong acid used is
sulfuric acid and mercuric acid.
## Keto-enol tautomerism
In the presence of an acid (H+) or a base (OH-), the aldehyde or ketone
will form an equilibrium with enols, in which the double bond of the
carbonyl group migrates to form double bond between the carbonyl and the
alpha (α) carbon.
In the presence of an acid, protonation of the oxygen group will occur,
and water will abstract an alpha (α) hydrogen.
In the presence of a base, deprotonation of the alpha hydrogen will
occur, and a hydrogen from water will be abstracted by the carbonyl
oxygen.
This is an important feature of ketone and aldehydes, and is known as
the *keto-enolic tautomery* or *keto-enol tautomerism*, i.e. the
equilibrium of carbonyl compounds between two forms.
It must be stressed that the *keto* and the *enol* forms are **two
distinct compounds**, not isomers. They are known as tautomers of each
other. The presence of α-hydrogen is necessary for this equilibrium:
those compounds not possessing it are called *non-enolizable* ketones.
!Mechanism of enol-keto
tautomerism
## Reactions of Aldehydes and Ketones
### Reactions with the carbonyl carbon
Since aldehydes and ketones contain a polar carbonyl group, the
partially positive carbon atom can act as an electrophile. Strong and
weak nucleophiles are able to attack this carbonyl carbon, resulting in
a net addition to the molecule.
#### Nucleophilic addition
With cyanide, nucleophilic addition occur to give a hydroxynitrile:
RR\'C=O + CN^-^ + H^+^ → RR\'COHCN
e.g. propanone → 2-hydroxymethylpropanonitrile
### Reactions with the carbonyl oxygen
The partially negative oxygen can act as a nucleophile, or be attacked
by electrophiles.
### Oxidation
Using a strong oxidizing agent such as the Tollens\' Reagent (Ag~2~O in
aqueous ammonia) acidified dichromate, Benedict\'s/Fehling\'s reagent
(essentially alkaline Cu^+2^); aldehydes but not ketones may be oxidized
into carboxylic acids. This is one way to test for the presence of an
aldehyde in a sample compound: an aldehyde will become a carboxylic acid
when reacted with Tollens\' reagent, but a ketone will not react. when
aldehydes react with fehling solution a red precipitate is obtained (due
to formation of Cu~2~O) .
## Inductive Effect and Greek letter assignment
The carbonyl group is very electron withdrawing, and adjacent carbons
are effected by induction. Using the carbonyl group as a reference,
adjacent carbons are named using Greek letters in order of closeness to
the carbonyl group. Alpha (α) carbons are directly attached to the
carbonyl group, beta (β) carbons are connected to alpha carbons, gamma
(γ) to beta (β), and so on.
Due to the inductive effect of the partial positive especially prone to
removal.
id:Kimia Organik/Keton dan
aldehida
|
# Organic Chemistry/Carboxylic acids
A carboxylic acid is characterized by the presence of the *carboxyl
group* -COOH. The chemical reactivity of carboxylic acids is dominated
by the very positive carbon, and the resonance stabilization that is
possible should the group lose a proton. These two factors contribute
both to acidity and to the group\'s dominant chemical reaction:
nucleophilic substitution.
# Preparation
1\) from alkenes
` R-CH=CHR + KMnO`~`4`~` + OH`^`-`^` + Heat----> 2RCOOH`\
` `
2\) from ROH
` RCH`~`2`~`OH + OXIDIZING AGENT ----> RCOOH`
Aliphatic carboxylic acids are formed from primary alcohols or aldehydes
by reflux with potassium dichromate (VI) acidified with sulphuric acid.
3\) from toluene etc.
` toluene + KMnO`~`4`~` ----> benzoic acid `
Alkyl benzenes (methyl benzene, ethyl benzene, etc) react with potassium
manganate (VII) to form benzoic acid. All alkyl benzenes give the same
product, because all but one alkyl carbon is lost.
No acidification is needed. The reaction is refluxed and generates KOH.
The benzoic acid is worked up by adding a proton source (such as HCl).
4\) from methyl ketones
` RCOCH`~`3`~` + NaOH + I-I ----> RCOO`^`-`^` + CHI`~`3`~
5\) from Grignard reagents
` RMgX + O=C=O ----> RCOOMgX `\
` RCOOMgX + HOH ----> RCOOH + MgX(OH)`
# Properties
## Nomenclature
The systematic IUPAC nomenclature for carboxylic acids requires the
longest carbon chain of the molecule to be identified and the -e of
alkane name to be replaced with -oic acid.
The traditional names of many carboxylic acids are still in common use.
formula IUPAC name traditional name
----------------- ------------------------ ------------------
HCOOH methanoic acid formic acid
CH~3~-COOH ethanoic acid acetic acid
CH~3~CH~2~-COOH propanoic acid propionic acid
CH~2~=CH-COOH propenoic acid acrylic acid
CF~3~-COOH trifluoroethanoic acid
: **Nomenclature of carboxylic acids**
The systematic approach for naming dicarboxylic acids (alkanes with
carboxylic acids on either end) is the same as for carboxylic acids,
except that the suffix is -dioic acid. Common name Nomenclature of
dicarboxylic acids is aided by the acronym OMSGAP (Om\'s Gap), where
each letter stands for the first letter of the first seven names for
each dicarboxylic acid, starting from the simplest.
formula IUPAC name traditional name
------------------------------------ ------------------- ------------------
HOOCCOOH Ethanedioic acid Oxalic acid
HOOCCH~2~-COOH propanedioic acid Malonic acid
HOOCCH~2~CH~2~-COOH butanedioic acid Succinic acid
HOOCCH~2~CH~2~CH~2~-COOH pentanedioic acid Glutaric acid
HOOCCH~2~CH~2~CH~2~CH~2~-COOH hexanedioic acid Adipic acid
HOOCCH~2~CH~2~CH~2~CH~2~CH~2~-COOH heptanedioic acid Pimelic acid
: **Nomenclature of dicarboxylic acids**
## Acidity
Most carboxylic acids are weak acids. To quantify the acidities we need
to know the pKa values: The pH above which the acids start showing
mostly acidic behaviour: Ethanoic acid: 4.8 Phenol: 10.0 Ethanol: 15.9
Water: 15.7
acid formula *pK*~a~
------------------------ ----------------- ---------
methanoic acid H-COOH 3.75
ethanoic acid CH~3~-COOH 4.75
propanoic acid CH~3~CH~2~-COOH 4.87
propenoic acid CH2=CH-COOH 4.25
benzoic acid C~6~H~5~-COOH 4.19
trifluoroethanoic acid CF~3~-COOH 0.3
phenol C~6~H~5~-OH 10.0
ethanol CH~3~CH~2~-OH 15.9
water H~2~O 15.7
: **Acidity of carboxylic acids in water**
Data from CRC Handbook of Chemistry & Physics, 64th edition, 1984
D-167-8 Except <http://en.wikipedia.org/wiki/Trifluoroacetic_acid>
Clearly, the carboxylic acids are remarkably acidic for organic
molecules. Somehow, the release of the H^+^ ion is favoured by the
structure. Two arguments: The O-H bond is polarised by the removal of
electrons to the carbonyl oxygen. The ion is stabilised by resonance:
the carbonyl oxygen can accept the charge from the other oxygen. The
acid strength of carboxylic acid are strongly modulated by the moiety
attached to the carboxyl. Electron-donor moiety decrease the acid
strength, whereas strong electron-withdrawing groups increase it.
# Reactions
## Acid Chloride Formation
Carboxylic acids are converted to acid chlorides by a range of reagents:
SOCl~2~, PCl~5~ or PCl~3~ are the usual reagents. Other products are HCl
& SO~2~, HCl & POCl~3~ and H~3~PO~3~ respectively. The conditions must
be dry, as water will hydrolyse the acid chloride in a vigorous
reaction. Hydrolysis forms the original carboxylic acid.
CH~3~COOH + SOCl~2~ → CH~3~COCl + HCl + SO~2~
C~6~H~5~COOH + PCl~5~ → C~6~H~5~COCl + HCl + POCl~3~
3 CH~3~CH~2~COOH + PCl~3~ → 3 CH~3~CH~2~COCl + H~3~PO~3~
## Esterification
Alcohols will react with acid chlorides or carboxylic acids to form
esters. This reaction is catalyzed by acidic or basic conditions. See
alcohol notes.
C~6~H~5~COCl + CH~3~CH~2~OH → C~6~H~5~COOCH~2~CH~3~ + HCl
With carboxylic acids, the condensation reaction is an unfavourable
equilibrium, promoted by using non-aqueous solvent (if any) and a
dehydrating agent such as sulfuric acid (non-nucleophilic), catalyzing
the reaction).
CH~3~COOH + CH~3~CH~2~CH~2~OH = CH~3~COOCH~2~CH~2~CH~3~ + H~2~O
!Ethanoic Acid reacts with Propanol to form Propyl
Ethanoate
Reversing the reaction is simply a matter of refluxing the ester with
plenty of aqueous acid. This hydrolysis produces the carboxylic acid and
the alcohol.
C~6~H~5~COOCH~3~ + H2O → C~6~H~5~COOH + CH~3~OH
Alternatively, the reflux is done with aqueous alkali. The salt of the
carboxylic acid is produced. This latter process is called
\'saponification\' because when fats are hydrolysed in this way, their
salts are useful as soap.
## Anhydrides
See acid anhydride.
## Amides
Conceptually, an amide is formed by reacting an acid (an
electrophile) with an amine
compound (a nucleophile),
releasing water.
RCOOH + H~2~NR\' → RCONHR\' + H~2~O
However, the acid-base reaction is much faster, which yields the
non-electrophilic carboxylate and the non-nucleophilic ammonium, and no
further reaction takes place.
RCOOH + H~2~NR\' → RCOO^-^ + H~3~NR\'^+^
To get around this, a variety of coupling reagents have been developed
that first react with the acid or carboxylate to form an active acyl
compound, which is basic enough to deprotonate an ammonium and
electrophilic enough to react with the free base of the amine. A common
coupling agent is
dicyclohexylcarbodiimide,
or DCC, which is very toxic.
## Acid Decarboxylation
On heating with sodalime (NaOH/CaO solid mix) carboxylic acids lose
their --COOH group and produce a small alkane plus sodium carbonate:
CH~3~CH~2~COOH + 2 NaOH →CH~3~CH~3~ + Na~2~CO~3~ + H~2~O
Note how a carbon is lost from the main chain. The product of the
reaction may be easier to identify than the original acid, helping us to
find the structure.
## Ethanoic anhydride
Industrially, ethanoic anhydride is used as a less costly and reactive
alternative to ethanoyl chloride. It forms esters and can be hydrolysed
in very similar ways, but yields a second ethanoic acid molecule, not
HCl The structure is formed from two ethanoic acid molecules...
## Polyester
Polyester can be made by reacting a diol (ethane-1,2-diol) with a
dicarboxylic acids (benzene-1,4-dicarboxylic acid). n HO-CH~2~CH~2~-OH +
n HOOC-C~6~H~4~-COOH → (-O-CH~2~CH~2~-O-OC-C~6~H~4~-CO-)n + n H~2~O
Polyester makes reasonable fibres, it is quite inflexible so it does not
crease easily; but for clothing it is usually combined with cotton for
comfort. The plastic is not light-sensitive, so it is often used for net
curtains. Film, bottles and other moulded products are made from
polyester.
## Distinguishing carboxylic acids from phenols
Although carboxylic acids are acidic, they can be distinguished from
phenol because: Only carboxylic acids will react with carbonates and
hydrogencarbonates to form CO2
2 CH~3~COOH + Na~2~CO~3~ → 2 CH~3~COONa + H~2~O + CO~2~
C~6~H~5~COOH + NaHCO~3~ → C~6~H~5~COONa + H~2~O + CO~2~
Some phenols react with FeCl~3~ solution, giving a characteristic purple
colour.
***Note***: Click on the following icon to go back to the contents page.
|
# Organic Chemistry/Carboxylic acid derivatives
The carboxyl group (abbreviated -CO~2~H or -COOH) is one of the most
widely occurring functional groups in chemistry as well as biochemistry.
The carboxyl group of a large family of related compounds called Acyl
compounds or **Carboxylic Acid Derivatives**.
All the reactions and compounds covered in this section will yield
Carboxylic Acids on hydrolysis, and thus are known as Carboxylic Acid
Derivatives. Hydrolysis is one example of *Nucleophilic Acyl
Substitution*, which is a very important two step mechanism that is
common in all reactions that will be covered here.
## Structure
This group of compounds also contains a carbonyl group, but now there is
an electronegative atom (oxygen, nitrogen, or a halogen) attached to the
carbonyl carbon. This difference in structure leads to a major change in
reactivity.
## Nomenclature
The systematic IUPAC nomenclature for carboxylic acid derivatives is
different for the various compounds which are in this vast category, but
each is based upon the name of the carboxylic acid closest to the
derivative in structure. Each type is discussed individually below.
### Acyl Groups
Acyl groups are named by stripping the *-ic acid* of the corresponding
carboxylic acid and replacing it with *-yl*.
> **EXAMPLE:**\
> CH~3~COOH = *acetic acid*\
> CH~3~CO-R = *acetyl-R*
### Acyl Halides
Simply add the name of the attached halide to the end of the acyl group.
> **EXAMPLE:**\
> CH~3~COOH = *acetic acid*\
> CH~3~COBr = *acetyl bromide*
### Carboxylic Acid Anhydrides
A carboxylic acid anhydride (\[RC=O\]O\[O=CR\]) is a carboxylic acid
(COOH) that has an acyl group (RC=O) attached to its oxygen instead of a
hydrogen. If both acyl groups are the same, then it is simply the name
of the carboxylic acid with the word *acid* replaced with *anhydride*.
If the acyl groups are different, then they are named in alphabetical
order in the same way, with *anhydride* replacing *acid*.
> **EXAMPLE:**\
> CH~3~COOH = *acetic acid*\
> CH~3~CO-O-OCCH~3~ = *Ethanoic Anhydride*
### Esters
Esters are created when the hydrogen on a carboxylic acid is replaced by
an alkyl group. Esters are known for their pleseant, fruity smell and
taste, and they are often found in both natural and artificial flavors.
Esters (RCOOR^1^) are named as *alkyl alkanoates*. The alkyl group
directly attached to the oxygen is named first, followed by the acyl
group, with *-ate* replacing *-yl* of the acyl group.
> **EXAMPLE:**\
> CH~3~COOH = *acetic acid*\
> CH~3~COOCH~2~CH~2~CH~2~CH~3~ = *acetyl butanoate*
> cooh 1 cooh 1 2-ethan oic acid
### Amides
Amides which have an amino group (-NH~2~) attached to a carbonyl group
(RC=O) are named by replacing the *-oic acid* or *-ic acid* of the
corresponding carboxylic acid with *-amide*.
> **EXAMPLE:**\
> CH~3~COOH = *acetic acid*\
> CH~3~CONH~2~ = *acetamide*
### Nitriles
Nitriles (RCN) can be viewed a nitrogen analogue of a carbonyl and are
known for their strong electron withdrawing nature and toxicity.
Nitriles are named by adding the suffix *-nitrile* to the longest
hydrocarbon chain (including the carbon of the cyano group). It can also
be named by replacing the *-ic acid* or *-oic acid* of their
corresponding carboxylic acids with *-onitrile*. Functional class IUPAC
nomenclature may also be used in the form of *alkyl cyanides*.
> **EXAMPLE:**\
> CH~3~CH~2~CH~2~CH~2~CN = *pentanenitrile* or *butyl cyanide*
## Structure and Reactivity
Stability and reactivity have an inverse relationship, which means that
the more stable a compound, generally the less reactive - and vice
versa. Since acyl halides are the least stable group listed above, it
makes sense that they can be chemically changed to the other types.
Since the amides are the most stable type listed above, it should
logically follow that they cannot easily changed into the other molecule
types, and this is indeed the case.
The stability of any type of carboxylic acid derivative is generally
determined by the ability of its functional group to donate electrons to
the rest of the molecule. In essence, the *more electronegative* the
atom or group attached to carbonyl group, the *less stable* the
molecule. This readily explains the fact that the acyl halides are the
most reactive, because halides are generally quite electronegative. It
also explains why acid anhydrides are unstable; with two carbonyl groups
so close together the oxygen in between them cannot stabilize both by
resonance - it can\'t *loan* electrons to both carbonyls.
The following derivative types are ordered in decreasing reactivity (the
first is the most reactive):
> Acyl Halides **(CO-X)** \> Acyl Anhydrides **(-CO-O-OCR)** \> Acyl
> Thioester **(-CO-SR)** \> Acyl Esters **(-CO-OR)** \> Acyl Amides
> **(-CO-NR~2~)**
As mentioned before, any substance in the preceding list can be readily
transformed into a substance to its right; that is, the more reactive
derivative types (acyl halides) can be directly transformed into less
reactive derivative types (esters and amides). Every type can be made
directly from carboxylic acid (hence the name of this subsection) but
carboxylic acid can also be made from any of these types.
## Reactions of Carboxylic Acids and Their Derivatives
### Carboxylic Acids
1\) As acids:
` RCO`~`2`~`H + NaOH ----> RCO`~`2`~^`-`^`Na`^`+`^` + H`~`2`~`O`\
` RCO`~`2`~`H + NaHCO`~`3`~` ----> RCO`~`2`~^`-`^`Na`^`+`^` + H`~`2`~`O + CO`~`2`~
2\) Reduction:
` RCO`~`2`~`H + LiAlH`~`4`~` --- (1) Et`~`2`~`O -- (2) H`~`2`~`O ----> RCH`~`2`~`OH`
2a) Fukyama reduction: Pd and Et3SiH COOH-\>CHO
3\) Conversion to acyl chlorides:
` RCO`~`2`~`H -----SOCl`~`2`~` or PCl`~`5`~` ----> RCOCl`
4\) Conversion to esters (Fischer esterfication):
` RCOOH + R'-OH <--- HA ---> RCOOR' + H`~`2`~`O`
5\) Conversion to amides:
` RCO`~`2`~`H -----SOCl`~`2`~` or PCl`~`5`~` ----> RCOCl + NH`~`3`~` <------> RCOO`^`-`^`NH`~`4`~^`+`^` --- heat ---> R-CONH`~`2`~` + H`~`2`~`O`
6\) Decarboxylation: (Note: you need a doubly-bonded oxygen (carbonyl)
two carbons away or two carboxylic acid groups attached to a same carbon
atom for this reaction to work)
` Note: Decarboxylation by heating can only occur for ẞ-keto acids or 1,1-dicarboxylic acids`\
` RCOCH`~`2`~`COOH --- heat ---> R-COCH`~`3`~` + CO`~`2`~\
` HOCOCH`~`2`~`COOH --- heat ---> CH`~`3`~`COOH + CO`~`2`~
7)R-COOH + R-OH \-\-\-\-\-\-\-\--R-COOR + H2O
### Acyl Chlorides
1\) Conversion to acids:
` R-COCl + H`~`2`~`O ----> R-COOH + HCl`
2\) Conversion to anhydrides:
` R-COCl + R'COO`^`-`^` ----> R-CO-O-COR' + Cl`^`-`^
3\) Conversion to esters:
` R-COCl + R'-OH --- pyridine ---> R-COOR' + Cl`^`-`^` + pyr-H`^`+`^
4\) Conversion to amides:
` R-COCl + R'NHR" (excess) ---> R-CONR'R" + R'NH`~`2`~`R"Cl`
R\' and/or R\" may be H
5\) Conversion to ketones:
Friedel-Crafts acylation
` R-COCl + C`~`6`~`H`~`6`~` --- AlCl`~`3`~` ---> C`~`6`~`H`~`5`~`-COR`
Reaction of Dialkylcuprates (also known as a Gilman reagent)
` R-COCl + R'`~`2`~`CuLi ----> R-CO-R'`
6\) Conversion to aldehydes:
` R-COCl + LiAlH[OC(CH`~`3`~`)`~`3`~`]`~`3`~` --- (1) Et`~`2`~`O (2) H`~`2`~`O ---> R-CHO`
### Acid Anhydrides
1\) Conversion to acids:
` (R-CO)`~`2`~`-O + H`~`2`~`O ----> 2 R-COOH`
2\) Conversion to esters:
` (R-CO)`~`2`~`-O + R'OH ----> R-COOR' + R-COOH`
3\) Conversion to amides:
` (R-CO)`~`2`~`-O + H-N-(R'R") ----> R-CON-(R'R") + R-COOH`
R\' and/or R\" may be H.
4\) Conversion to aryl ketones (Friedel-Crafts acylation):
` (R-CO)`~`2`~`-O + C`~`6`~`H`~`6`~` --- AlCl`~`3`~` C`~`6`~`H`~`5`~`-COR + R-COOH`
### Esters
1\) Hydrolysis:
` R-COOR' + H`~`2`~`O <--- HA ---> R-COOH + R'-OH`\
` R-COOR' + OH`^`-`^` ----> RCOO`^`-`^` + R'-OH`
2\) Transesterification (conversion to other esters):
` R-COOR' + R"-OH <--- HA ---> R-COO-R" + R'-OH`
3\) Conversion to amides:
` R-COOR' + HN-(R"R"') ----> R-CON-(R"R"') + R'-OH`
R\" and/or R\"\' may be H
4\) Reaction with Grignard reagents:
` R-COOR' + 2 R"MgX --- Et`~`2`~`O ---> R-C-R"`~`2`~`OMgX + R'OMgX ---> H`~`3`~`O`^`+`^` R-C-R"`~`2`~`OH`
The intermediate and final product is a tetrahedral carbon with two R\"
attached directly to the carbon along with R and OH/OMgX
X = halogen.
5\) Reduction:
` R-COOR' + LiAlH`~`4`~` --- (1) Et`~`2`~`O (2) H`~`2`~`O ---> R-CH`~`2`~`OH + R'-OH`
### Amides
1\) Hydrolysis:
` R-CON(R'R") + H`~`3`~`O`^`+`^` --- H`~`2`~`O ---> R-COOH + R'-N`^`+`^`H`~`2`~`R"`\
` R-CON(R'R") + OH`^`-`^` --- H`~`2`~`O ---> R-COO`^`-`^` + R'-NHR"`
R,R\' and/or R\" may be H.
2\) Dehydration (conversion to nitriles):
` R-CONH`~`2`~` --- P`~`4`~`O`~`10`~`, heat, (-H`~`2`~`O) ---> R-CN`
### Nitriles
1\) Hydrolysis:
` R-CN --- H`~`3`~`O`^`+`^`,heat ---> RCOOH`\
` R-CN --- OH`^`-`^`,H`~`2`~`O,heat ---> RCOO`^`-`^
2\) Reduction to aldehyde:
` R-CN --- (1) (`*`i`*`-Bu)`~`2`~`AlH (2) H`~`2`~`O ---> R-COH`
(*i*-Bu)~2~AlH = DIBAL-H
3\) Conversion to ketone (by Grignard or organolithium reagents):
` R-CN + R"-M --- (1) Et`~`2`~`O (2) H`~`3`~`O`^`+`^` ---> R-COR"`
M = MgBr (Grignard reagent) or Li (organolithium reagent)
### Mechanisms
A common motif in reactions dealing with carboxylic acid derivatives is
the tetrahedral intermediate. The carbonyl group is highly polar, with
the carbon having a low electron density, and the oxygen having a high
electron density. With an acid catalyst, a H+ is added to the oxygen of
the carbonyl group, increasing the positive charge at the carbon atom. A
nucleophile can then attack the carbonyl, creating a tetrahedral
intermediate.
For example, in Fischer esterification, the mechanism can be outlined
thus: 1) H+ is added to carbonyl oxygen 2) Oxygen atom of the alcohol
adds to the carbonyl carbon 3) Proton transfer from alcohol oxygen to
carboxyl oxygen 4) Water molecule ejected from tetrahedral intermediate,
double bond forms, recreating the carbonyl 5) H+ is removed from
carbonyl oxygen(very important for the base reduction of acids)
|
# Organic Chemistry/Questions and Discussions
Name the reagent used to distinguish the following pair Carboxylic and
ethanol Alkyne and alkene Butan-1-yne and Butan-2-yne
## Q1
**What is more acidic, cyclopentadiene or penta-1,4-diene? What is the
application of Huckel\'s rule here?**
### Discussion
In this context acidity is the ability to lose a proton.We will decide
the acidity on the basis of the stability of the resulting carbanion
\[Why did we emphasize the word \"context\" here? How else can a
molecule behave as an acid?\]\[Why is it that a carbanion is formed?\]
\[How did we relate stability of carbanion with acidity here?\]
Also, the number of carbons in both the compounds are same and are of a
similar structure.It is only now that we can compare the stability of
their conjugate bases \[What are they?\] \[carbanions we were talking
about in this case\...\]
So, first we decide what is the most acidic hydrogen in both the
molecules. In the straight chain carbon molecule, the two hydrogens
attached to the central carbon are more acidic than the rest of the
hydrogens. This is for a specific reason.Once any of the hydrogen is
extracted by a base, the central carbon should acquire a negative
charge.Instead,the molecule is represented by a resonance hybrid of two
degenerate \[equivalent\] resonance structures with a negative charge on
the terminal carbons and a third one with the negative charge on the
central carbon. This is a stabilizing factor of the carbanion. The
presence of this stabilizing factor makes the two hydrogens in the
original molecule acidic.
\[What exactly are we talking about here? What is the conjugate base
whose stability we discussed?\]
In the cyclic molecule, the same thing applies. We again have a molecule
which is represented by resonating structures.But the speciality is that
it has six pi electrons and is cyclic.In other words, by Huckel\'s rule
we find that the cyclopentadiene anion is aromatic. Aromaticity is a
better stabilizing factor than simple resonance. Hence the
cyclopentadiene molecule is the more acidic than the straight chain
molecule. Remember that the comparison could be made only because they
are similar molecules.
What is the smallest aromatic species? Is penta-1,4-diene hydrolyzed by
water? Is cyclopentadiene hydrolyzed by water? How do you relate these
observations to what we just discussed above?
### Additional Questions
#### Nucleophillicity and basicity
Proton is a lewis acid.It\'s also an electrophile. Consider hydroxide
ions- OH-(- indicates negative charge) They are nucleophiles. They are
Lewis bases as well.What property makes them nucleophiles and what
property makes them bases? Still another question: Give an example of a
strong base but a weak nucleophile. What gives the molecule these
characteristics?
#### A corrosive phenol
Which phenol has a boiling point of 132 to 134 degree Celsius and is
corrosive in nature? Dark orange in colour?
#### Answers
#### A little variation
What if the linear chain is hex-1,5-diene? Does aromaticity still
dominate?
#### Answers
If it\'s linear it cannot be aromatic, although it can still contain a
delocalised p-system.
|
# Organic Chemistry/Introduction to reactions
\> Introduction to reactions
------------------------------------------------------------------------
\> Introduction to reactions
------------------------------------------------------------------------
## Specific Reactions
1. Polar and radical
reactions
2. Redox
reactions
3. Carbocations
4. Hydroboration/oxidation
5. Free-radical
halogenation
6. Rearrangement
reactions
7. Pericyclic
reactions
8. Diels-Alder
reaction
------------------------------------------------------------------------
|
# Organic Chemistry/Glossary
\> Glossary
------------------------------------------------------------------------
## A
- Acetal - a molecule with two single bonded oxygens attached to the
same carbon atom
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```
- Acetyl - a functional group with chemical formula -COCH3
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```
- Achiral - a group containing atleast two identical substituents
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```
- Acid anhydride - hydrocarbon containing two carbonyl groups.Acyl
group attached with carboxylate group. eg RCOOCOR\'
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```
- Acid halide - acyl group with any halogen attached with carbon of
carbonyl group. eg RCO-X(X=F,Cl,Br,I).
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```
- Acidity constant K~a~ -
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```
- Activating group - any group which activates a molecule by
increasing positive or negative charge on a carbon atom. Mainly
towards neucleophilic or electrophilic substitution reactions.
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```
- Activation energy - the energy required for reactants to cross
energy barrier to undergo any chemical change; denoted by E~a~.
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```
- Acyl group - a group having an alkyl or aryl group with a carbonyl
group RCO-
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```
- Adam\'s catalyst - a catalyst for hydrogenation and hydrogenolysis
in organic synthesis. Also known as platinum dioxide
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```
- Addition
reaction -
a reaction where a product is created from the coming together of 2
reactants.
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```
- Alcohol - a saturated hydrocarbon chain with an -OH functional
group.
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```
- Aldehyde - a hydrocarbon containing at least one carbonyl group
having one hydrogen attached to it.(\>C=O)
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```
- Aldol reaction - a reaction of two aldehydes yielding a product with
both an aldehyde(\>C=O) and an alcohol() group.
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```
- Aliphatic - A non-cyclic, non-aromatic, hydrocarbon chain (e.g.
alkanes, alkenes, and alkynes)
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```
- Alkane - A hydrocarbon with all the carbon-carbon bonds are single
bonds.
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```
- Alkene - A hydrocarbon with at least one carbon-carbon bond is a
double-bond.
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```
- Alkoxide ion - The conjugate base of an alcohol without the terminal
H atom. For any alcohol R-OH, the corresponding alkoxide form is
R-O^-^.
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```
- Alkyl - A hydrocarbon having formula C~n~H~2n+1~
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```
- Alkylation - Addition of alkyl group in a compound.
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```
- Alkyne - An unsaturated hydrocarbon containog triple bond.and having
general formula C~n~H~2n-2~
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```
- Allyl - An alkene hydrocarbon group with the formula H2C=CH-CH2-
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```
- α Position - Carbon attached to a functional group is called
α-carbon and the position is known as α position.
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```
- α-carbon - Carbon attached to a functional group is called α-carbon
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```
- Amide - A hydrocarbon containing amine group attached to acyl group.
eg.- RCONH~2~
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```
- Amine - A simple hydrocarbon containing atleast one -NH~2~ group.
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```
- Amino Acid - A fundamental unit of polypeptides or proteins.having
general formula-COOHRCHNH~2~.eg.- glysine, alanine etc.
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```
- Anti conformation -
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```
- Anti periplaner -
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```
- Anti stereochemistry -
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```
- Anti bonding molecular orbital - Molecular orbitals having higher
energy than bonding molecular orbitals after combination of atomic
orbitals.denoted by an astric over Sigma or pi notations.
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<!-- -->
```
- Arene - Another name for an aromatic hydrocarbon.
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<!-- -->
```
- Aromaticity - A chemical property in which a conjugated ring of
unsaturated bonds, lone pairs, or empty orbitals exhibit a
stabilization stronger than would be expected by the stabilization
of conjugation alone.
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```
- Atomic mass - Total no of nucleon i.e. number of proton and number
of neutrons. Atomic mass is denoted by A.
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<!-- -->
```
- Atomic number - Total no. of protons is called the atomic number.
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```
- Axial bond - The bond parallel or antiparallel to axial coordinate
passing center of gravity.
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<!-- -->
```
- Azide synthesis - Dutt-Wormall reaction in which a diazonium salt
reacts with a sulfonamide first to a diazoaminosulfinate and then on
hydrolysis the azide and a sulfinic acid.
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```
- Azo compound - A compound containing -N=N group.
## B
- Benzoyl Group - The acyl of benzoic acid, with structure C6H5CO-
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```
- Benzyl Group - The radical or ion formed from the removal of one of
the methyl hydrogens of toluene (methylbenzene).
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```
- Benzylic -
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```
- β position -
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```
- β-carbon -
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```
- Bicylcoalkane - A compound containing two cyclic rings.
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```
- Bimolecular reaction - A second order reaction where the
concentration of two compounds determine the reaction rate.
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```
- Boat cyclohexane - A less-stable conformation of cyclohexane that
somewhat resembles a boat.
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```
- Bond - The attractive forces that create a link between atoms. Bonds
may be covalent or ionic.
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```
- Bond angle - The angle formed between three atoms across at least
two bonds.
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```
- Bond length - The average distance between the centers of two atoms
bonded together in any given molecule.
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```
- Bond strength - The degree to which each atom linked to a central
atom contributes to the valency of this central atom.
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```
- Bonding molecular orbital -
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```
- Bromonium ion -
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```
- Brønsted-Lowry
Acid
-
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```
- Brønsted-Lowry
Base
-
## C
- Cahn-Ingold-Prelog priorities - A rule for assigning priorities to
substituents off of carbon in a double-bond or in a chiral center.
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```
- Carbocation -
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```
- Carbonyl group - A functional group composed of a carbon atom
double-bonded to an oxygen atom: C=O.
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```
- Carboxylation - A chemical reaction in which a carboxylic acid group
is introduced in a substrate.
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```
- Carboxylic acid - An organic acid characterized by the presence of a
carboxyl group.
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```
- Chain reaction - A sequence of reactions where a reactive product or
by-product causes additional reactions to take place
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```
- Chair cyclohexane -
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```
- Chiral - A term used to describe an object that is non-superposable
on its mirror image
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```
- Chiral center - A carbon atom bonded to four different groups
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```
- Chromatography - The process of separating compounds such as a dye
into its constituents
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```
- Cis-trans isomers -
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```
- Claisen condensation reaction -
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```
- Claisen rearrangement reaction -
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```
- Concerted -
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```
- Configuration - the permanent geometry of a molecule that results
from the spatial arrangement of its bonds.
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```
- Conformation -
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```
- Conformer -
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```
- Conjugate acid -
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```
- Conjugate base -
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```
- Conjugation - A system of atoms covalently bonded with alternating
single and multiple (e.g. double) bonds (e.g., C=C-C=C-C).
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```
- Covalent bond - A form of chemical bonding that is characterized by
the sharing of pairs of electrons between atoms.
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```
- Cracking - The process whereby complex organic molecules such as
heavy hydrocarbons are broken down into simpler molecules (e.g.
light hydrocarbons) by the breaking of carbon-carbon bonds.
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```
- Cycloaddition reaction -
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```
- Cycloalkane - An alkane that has one or more rings of carbon atoms
in the chemical structure of its molecule.
## D
- Debye -
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- Decarboxylation -
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```
- Delocalization - The ability of electrons to spread out among pi
bonds to provide stabilization to electronically unstable areas of a
molecule.
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```
- Dextrorotatory -
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```
- Diastereomers - Two or more isomers of a molecule which are *not*
enantiomers of one another.
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```
- 1,3 Diaxial interaction - The steric intereaction between two methyl
or larger groups attached at the 1 and 3 cis positions of
cyclohexanes. The cyclohexane is in a higher energy state in the
ring flip conformation that results in both 1 and 3 positions being
axial due to steric strain between the 2 groups. This strain does
not exist when hydrogens are bonded at these positions.
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```
- Diels-Alder reaction -
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```
- Dienophile -
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```
- Dipolar -
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```
- Dipole moment -
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```
- Disulfide -
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```
- Downfield - A term used to describe the left direction on NMR
charts. A peak to the left of another peak is described as being
downfield from the peak.
## E
- E geometry -
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```
- E1 reaction -
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```
- E2 reaction -
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```
- Eclipsed conformation -
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```
- Eclipsing strain -
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```
- Electron - An elementary subatomic particle that carries a negative
electrical charge and occupies an electron shell outside the atomic
nucleus.
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<!-- -->
```
- Electron configuration - The arrangement of electrons in an atom or
molecule
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<!-- -->
```
- Electron-dot structure -
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```
- Electron shell - The orbit followed by electrons around an atomic
nucleus. The atom has a number of shells and they are normally
labelled K, L, M, N, O, P, and Q.
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<!-- -->
```
- Electronegativity - The ability of an atom to attract electrons
towards itself in a covalent bond.
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```
- Electrophile - Literally, electron lover. A positively or neutrally
charged reagent that forms bonds by accepting electrons from a
nucleophile. Elecrophiles are Lewis Acids.
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<!-- -->
```
- Electrophilic addition reaction -
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```
- Electrophilic aromatic substitution -
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```
- Elimination
reaction -
A reaction where atoms and/or functional groups are removed from a
reactant.
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<!-- -->
```
- Endergonic - In an endergonic process, work is done on the system,
and ΔG^0^ \> 0, so the process is nonspontaneous. An exergonic
process is the opposite: ΔG^0^ \< 0, so the process is spontaneous.
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```
- Endothermic - An endothermic reaction is a chemical reaction that
absorbs heat, and is the opposite of an exothermic reaction.
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```
- Enol - An alkene with a hydroxyl group affixed to one of the carbon
atoms composing the double bond.
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```
- Enolate ion -
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```
- Entgegen - German word meaning \"opposite\". Represented by E in the
E/Z naming system of alkenes.
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<!-- -->
```
- Enthalpy -
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<!-- -->
```
- Entropy -
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```
- Equatorial bond -
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```
- Ester - An inorganic or organic acid in which at least one -OH
(hydroxyl) group is replaced by an -O-alkyl (alkoxy) group.
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```
- Ether - An organic compound which contains an ether group --- an
oxygen atom connected to two (substituted) alkyl or aryl groups ---
of general formula R--O--R\'.
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```
- Exergonic -
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```
- Exothermic - An exothermic reaction is a chemical reaction that
releases heat, and is the opposite of an endothermic reaction.
## F
- Fingerprint region -
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```
- First order reaction - A reaction whose rate is determined by the
concentration of only one of its reactants leading to a reaction
rate equation of $Rate = k[X]$
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```
- Fischer projection -
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```
- Formal Charge -
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```
- Friedel-Crafts reaction -
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```
- Functional group - This is a specific group of atoms within a
molecule that is responsible for the characteristic chemical
reactions of that molecule. The same functional group will undergo
the same or similar chemical reaction(s) regardless of the size of
the molecule it is a part of.
## G
- Geminal -
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```
- Gibbs free energy -
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```
- Gilman reagent -
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```
- Glycol - A chemical compound containing two hydroxyl groups (-OH
groups). Also known as a Diol.
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<!-- -->
```
- Glycolysis - The metabolic pathway that converts glucose,
C~6~H~12~O~6~, into pyruvate, C~3~H~5~O~3~. This process usually
occurs outside the mitochondria of a cell to help produce energy.
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```
- Grignard reagent -
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<!-- -->
```
- Ground state - In electrons, the state where they have the least
energy. Electrons that gain energy get \"excited\" and leave the
ground state, now able to do more work. Moving electrons out of
their ground state is a key part of photosynthesis, where plants
create sugar from the sun, carbon dioxide, and water.
## H
- Halohydrin formation -
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```
- Hammond postulate -
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```
- Hemiacetal -
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```
- Hemiaminal -
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<!-- -->
```
- Heterocycle - A cyclic molecule with more than 2 types of atoms as
part of the ring. (e.g. Furan, a 5-membered ring with four carbons
and one oxygen, or a Pyran, a 6-membered ring with five carbons and
one oxygen)
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```
- HOMO - Acronym for Highest Occupied Molecular Orbital.
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```
- Homolytic cleavage - Where bond breaks leaving each atom with one of
the bonding electrons, producing two radicals.
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```
- Hybrid orbital -
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<!-- -->
```
- Hydration - A chemical reaction in which a hydroxyl group (OH-) and
a hydrogen cation (an acidic proton) are added to the two carbon
atoms bonded together in the carbon-carbon double bond which makes
up an alkene functional group.
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```
- Hybride shift -
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```
- Hydroboration - A reaction adding BH~3~ or B~2~H~6~ or an
alkylborane to an alkene to produce intermediate products consisting
of 3 alkyl groups attached to a boron atom. This molecule is then
used in other reactions, for example, to create an alcohol by
reacting it with H~2~O~2~ in a basic solution.
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```
- Hydrocarbon - A molecule consisting of hydrogens and carbons.
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```
- Hydrogen bond -
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```
- Hydrogenation - Addition of a hydrogen atoms to an alkene or alkane
to produce a saturated product.
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```
- Hydrophilic - literally, \"water loving\". In chemistry, these are
molecules that are soluble in water.
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```
- Hydrophobic - literally, \"water fearing\". In chemistry, molecules
that aren\'t soluble in water.
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<!-- -->
```
- Hydroxylation - A chemical process that introduces one or more
hydroxyl groups (-OH) into a compound (or radical) thereby oxidizing
it.
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<!-- -->
```
- Hyperconjugation -
## I
- Imide -
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```
- Imine -
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```
- Infrared spectroscopy -
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```
- Intermediate -
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```
- Isomer - Compounds with the same molecular formula but different
structural formulae. There are two main forms of isomerism:
structural isomerism and stereoisomerism.
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```
- Isotope - The different types of atoms of the same chemical element,
each having a different atomic mass (mass number). Isotopes of an
element have nuclei with the same number of protons (the same atomic
number) but different numbers of neutrons.
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```
- IUPAC - Acronym for International Union of Pure and Applied
Chemistry.
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<!-- -->
```
- IUPAC Nomenclature - The international standard set of rules for
naming molecules.
```{=html}
<div class="noprint">
```
(Available
Here)
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</div>
```
## K
- Kekulé structure -
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```
- Keto-enol tautomerism -
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```
- Ketone - The functional group characterized by a carbonyl group
(O=C) linked to two other carbon atoms, or a chemical compound that
contains a carbonyl group
## L
- Leaving group -
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```
- Levorotatory -
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```
- Lewis acid - A reagent that accepts a pair of electrons form a
covalent bond. *(see also Lewis Acids and
Bases)*
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```
- Lewis base - A reagent that forms covalent bonds by donating a pair
of electrons. *(see also Lewis Acids and
Bases)*
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```
- Lewis structure -
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```
- Lindlar catalyst -
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```
- Line-bond structure -
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```
- Lone pair electrons -
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```
- LUMO - Acronym for Lowest Unoccupied Molecular Orbital
## M
- Markovnikov\'s
rule -
States that \"when an unsymmetrical alkene reacts with a hydrogen
halide to give an alkyl halide, the hydrogen adds to the carbon of
the alkene that has the greater number of hydrogen substituents, and
the halogen to the carbon of the alkene with the fewer number of
hydrogen substituents.\"
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```
- Mass number - The total number of protons and neutrons (together
known as nucleons) in an atomic nucleus
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<!-- -->
```
- Mass spectrometry -
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<!-- -->
```
- Mechanism -
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```
- Meso compound -
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```
- Meta -
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```
- Methylene group -
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<!-- -->
```
- Molality - A measure of the concentration of a solute in a solvent
given by moles of solute per kg of solvent.
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<!-- -->
```
- Molarity - A measure of the concentration, given by moles of solute
per liter of *solution* (solute and solvent mixed).
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```
- Mole - A measure of a substance that is approximately Avogadro\'s
Number (6.022×10^23^) of molecules of the substance. More simply,
calculate the molecule\'s atomic mass and that many grams of the
substance is a mole.
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```
- Molecule -
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```
- Monomer - A small molecule that may become chemically bonded to
other monomers to form a polymer.
## N
- Nitrile - Any organic compound which has a -C≡N functional group.
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```
- NMR - See Nuclear magnetic resonance.
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<!-- -->
```
- Non-bonding electrons -
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```
- Normality -
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```
- Nuclear magnetic resonance -
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```
- Nucleophile - Literally, nucleus lover. A negatively or neutrally
charged reagent that forms a bond with an electrophile by donating
both bonding electrons. Nucleophiles are Lewis Bases.
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```
- Nucleophilic addition reaction -
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```
- Nucleophilic aromatic substitution reaction -
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```
- Nucleophilic substitution
reaction -
A reaction in which a halide is removed from a molecule and replaced
with a nucleophile.
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```
- Nucleophilicity -
## O
- Optical isomer -
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- Optical activity -
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- Orbital -
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- Ortho -
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- Oxidation -
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- Oxime -
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```
- Oxymercuration reduction reaction -
## P
- Para -
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- Pauli exclusion principle -
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```
- Pericyclic reaction -
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```
- Periplanar -
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- Peroxide -
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```
- Peroxyacid -
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```
- Phenol - A toxic, colourless crystalline solid with the chemical
formula C~6~H~5~OH and whose structure is that of a hydroxyl group
(-OH) bonded to a phenyl ring. It is also known as carbolic acid,
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```
- Phenyl - A functional group with the formula -C~6~H~5~
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```
- Pi bond -
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```
- Polar aprotic solvent -
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- Polar covalent bond -
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- Polar protic solvent -
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- Polar reaction -
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- Polarity -
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- Polarizability -
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```
- Polymer - A large molecule (macromolecule) composed of repeating
structural units (monomers) typically connected by covalent chemical
bonds.
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```
- Primary -
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```
- Prochiral -
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```
- Prochirality center -
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```
- Protic solvent -
## Q
## R
- R group -
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```
- R,S convention -
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```
- Racemic mixture -
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- Radical -
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- Radical reaction -
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- Rate constant -
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- Rate equation -
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- Rate-limiting step -
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- re face -
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- Reducation -
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```
- Regiochemistry -
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```
- Regioselectivity -
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```
- Resonance form -
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- Resonance hybrid -
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```
- Ring-flip -
## S
- Saponification - The hydrolysis of an ester under basic conditions
to form an alcohol and the salt of a carboxylic acid.
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```
- Saturated - Saturation in a general means possessing a maximal
quantity. A compound is commonly called saturated when it has no
double or triple bonds. Saturated can refer to a maximal amount of a
solute which can dissolve in a solution. Whether the context is
chemical bonding or solutions will determine which meaning is
appropriate.
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```
- Saytzeff\'s Rule - See Zaitsev\'s
rule
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```
- Second order reaction - A reaction whose rate is dependent on the
concentration of two reactants, leading to a reaction rate of
$Rate = k[X][Y]$
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```
- Secondary -
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```
- si face -
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```
- Side chain -
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```
- Sigma bond -
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```
- Simmons-Smith reaction -
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```
- S~N~1 reaction -
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```
- S~N~2 reaction -
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```
- Solvation -
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```
- Solvent -
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```
- sp orbital -
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```
- sp^2^ orbital -
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```
- sp^3^ orbital -
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```
- Spin-spin splitting -
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```
- Staggered conformation -
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```
- Stereochemistry -
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```
- Stereoisomer -
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```
- Steric hinderance -
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```
- Steric strain -
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```
- Substitution reaction - Reactions where one functional groups is
replaced with another functional group.
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```
- Symmetry plane -
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```
- Syn addition -
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```
- Syn periplanar -
## T
- Tautomers -
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```
- Tertiary - adjective describing a third occurrence or position
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```
- Thioester -
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```
- Thiol - A compound that contains the functional group composed of a
sulfur atom and a hydrogen atom (-SH).
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```
- Thiolate ion -
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```
- Torisional strain -
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```
- Tosylate -
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```
- Transition state -
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```
- Twist-boat conformation -
## U
- Ultraviolet spectroscopy -
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```
- Unsaturated - Unsaturated commonly describes a situation in which a
compound contains double or triple bonds.
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```
- Upfield - A term used to describe the right direction on NMR charts.
A peak to the right of another peak is described as being upfield
from the peak.
## V
- Valence bond theory -
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```
- Valence electrons -
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```
- Valence shell -
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```
- Van der Waals forces -
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```
- Vicinal -
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```
- Vinyl - An organic compound that contains a vinyl group (also called
ethenyl), −CH=CH2.
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```
- Vinylic -
## W, X, Y, Z
- Zaitsev\'s
rule -
In elimination
reactions,
the major reaction product is the alkene with the more highly
substituted double bond. This most-substituted alkene is also the
most stable.
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```
- Zussamen - German word meaning \"together\". Represented by Z in the
E/Z naming system of alkenes. Simple mnemonic, Z=Zame Zide (Same
Side).
|
Subsets and Splits