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The fatty acid salts formed during production constitute the actual soap and are effective cleaners due to their surfactant properties. Using soap helps dissolve many water-insoluble substances, like fats and oils, making them washable with water.
In most cases, hard soaps or products based on them are used for handwashing because they exhibit an alkaline (pH value above 7) nature and can irritate the skin when in contact with mucous membranes. Hard soap has antiseptic qualities and can be used alongside warm water as a household remedy for paronychia. It's also used to shape dreadlocks.
In the realm of detergents, soaps are generally secondary due to the creation of soap scum. They are primarily utilized as defoamers.
Beyond cleaning, soaps also treat wood surfaces. They enhance the appearance of conifer woods, seal the wood's pores, minimize dirt accumulation, and prevent staining from fats or embedded dyes. For cleaning brushes, especially in oil painting, hard soap ensures extended durability of the bristles or hairs.
On occasion, water-based soap solutions are employed for pest control on cultivated plants, like against thrips and aphids. | 0 | Colloidal Chemistry |
Alivisatos is the founding editor of Nano Letters, a publication of the American Chemical Society. He formerly served on the Senior Editorial Board of Science. He has also served on the editorial advisory boards of ACS Nano, the Journal of Physical Chemistry, Chemical Physics, the Journal of Chemical Physics, and Advanced Materials. | 1 | Solid-state chemistry |
Europium(III) phosphide forms dark crystals which are stable in air and do not dissolve in water. Like sodium chloride, it crystallizes cubically in the space group Fm3m with cell parameter a = 575.5 nm with four formula units per unit cell. Europium(III) phosphide tends to form europium(II) oxide (EuO) in air, and pure EuP shows Van Vleck paramagnetism. The vapor pressure of EuP is 133-266.6 Pa at 1273 K.
Europium(III) phosphide actively reacts with nitric acid. | 1 | Solid-state chemistry |
Acute respiratory distress syndrome, respiratory syncytial virus infection, familial lung disease, and pneumocystis infection are examples of deficiencies in and issues with SP-B that are correlated with lung issues.
Because so many lung conditions are associated with issues around SP-B, synthetic replacements have been researched, created, and manufactured. It has been shown that 21 amino acid long peptides with positive charge and intermittent hydrophobic regions mimicking SP-B can minimize surface tension at the gas/fluid interface, and surfactant replacements for surfactant deficient patients has been used to save lives.
Once lung distress has occurred, SP-B has been shown to be effective as a biomarker in the blood stream. Higher levels of SP-B indicate some kind of lung distress, and can even indicate if the patient is currently a smoker. This may be useful in the future to predict atherosclerosis, a solidifying of vascular tissue that has negative effects on the heart. | 0 | Colloidal Chemistry |
Lead iodide is a precursor material in the fabrication of highly efficient Perovskite solar cell. Typically, a solution of in an organic solvent, such as dimethylformamide or dimethylsulfoxide, is applied over a titanium dioxide layer by spin coating. The layer is then treated with a solution of methylammonium iodide and annealed, turning it into the double salt methylammonium lead iodide , with a perovskite structure. The reaction changes the film's color from yellow to light brown.
is also used as a high-energy photon detector for gamma-rays and X-rays, due to its wide band gap which ensures low noise operation.
Lead iodide was formerly used as a paint pigment under the name "iodine yellow". It was described by Prosper Mérimée (1830) as "not yet much known in commerce, is as bright as orpiment or chromate of lead. It is thought to be more permanent; but time only can prove its pretension to so essential a quality. It is prepared by precipitating a solution of acetate or nitrate of lead, with potassium iodide: the nitrate produces a more brilliant yellow color." However, due to the toxicity and instability of the compound it is no longer used as such. It may still be used in art for bronzing and in gold-like mosaic tiles. | 1 | Solid-state chemistry |
Self-propagating high-temperature synthesis is a green synthesis technique that is highly energy efficient, using little if any toxic solvents. There have been environmental analysis conducted to show that SHS has a lesser environmental impact than traditional solution-phase processing techniques. The technique uses less energy for production of materials, and the energy cost savings increase as synthesis batch sizes increase.
SHS is not a suitable technique for production of nanoparticles. Typically, the high-temperature nature of the process leads to particle sintering during and after the reaction. The high-temperatures generated during synthesis also lead to problems with energy dissipation and suitable reaction vessels, however, some systems use this excess heat to drive other plant-processes. | 1 | Solid-state chemistry |
Caliche is used in construction worldwide. Its reserves in the Llano Estacado in Texas can be used in the manufacture of Portland cement; the caliche meets the chemical composition requirements and has been used as a principal raw material in Portland cement production.
The Great House at Casa Grande Ruins National Monument, Arizona, US, was built with walls of caliche. Caliche was also used in mortars used in of the Mayan buildings in the Yucatán Peninsula in Mexico. A dormitory in Ingram, Texas, and a demonstration building in Carrizo Springs, Texas, for the United States Department of Energy were also built using caliche as part of studies by the Center for Maximum Potential Building Systems.
In many areas, caliche is also used for road construction, either as a surfacing material, or more commonly, as base material. It is one of the most common road materials used in Southern Africa. Caliche is widely used as a base material when it is locally available and cheap. However, it does not hold up to moisture (rain), and is never used if a hard-rock base material, such as limestone, is available. | 1 | Solid-state chemistry |
Porous carbons (PCs) are versatile materials with a wide range of applications, including sensors, actuators, thermal insulation, and energy conversion. Some examples of PCs are graphene and carbon nanotube-based aerogel. Physical properties that make PCs unique are their low density, high conductivity, mechanical flexibility, and stability in extreme environments. | 0 | Colloidal Chemistry |
When both large colloidal particles and small depletants are in a suspension, there is a region which surrounds every large colloidal particle that is unavailable for the centers of the depletants to occupy. This steric restriction is due to the colloid-depletant hard-sphere potential. The volume of the excluded region is
where is the diameter of the large spheres and is the diameter of the small spheres.
When the large spheres get close enough, the excluded volumes surrounding the spheres intersect. The overlapping volumes result in a reduced excluded volume, that is, an increase in the total free volume available to small spheres. The reduced excluded volume, can be written
where is half the width of the lens-shaped region of overlap volume formed by spherical caps. The volume available for small spheres is the difference between the total volume of the system and the excluded volume. To determine the available volume for small spheres, there are two distinguishable cases: first, the separation of the large spheres is big enough so small spheres can penetrate in between them; second, the large spheres are close enough so that small spheres cannot penetrate between them. For each case, the available volume for small spheres is given by
In the latter case small spheres are depleted from the interparticle region between large spheres and a depletion force ensues. | 0 | Colloidal Chemistry |
Bocarslys publications include around 200 refereed journal papers, multiple patents, and the edited book Fuel Cells and Hydrogen Storage' (2011).
Bocarsly has published on catalysts for the reduction of carbon dioxide to organic products.
With Emily Barton Cole, he has worked on the selective conversion of carbon dioxide to methanol.
This interest in artificial photosynthesis led to the founding of the company Liquid Light in 2009. | 1 | Solid-state chemistry |
Moving-boundary electrophoresis was developed by Arne Tiselius in 1930. Tiselius was awarded the 1948 Nobel Prize in chemistry for his work on the separation of colloids through electrophoresis, the motion of charged particles through a stationary liquid under the influence of an electric field. | 0 | Colloidal Chemistry |
Tarascon was educated at the University of Bordeaux, where he was awarded a Diplôme d'études universitaires générales in physics and chemistry, a Master of Science degree in chemical engineering, and a PhD in solid-state chemistry in 1981. | 1 | Solid-state chemistry |
Block copolymers are a well-studied and versatile class of self-assembling materials characterized by
chemically distinct polymer blocks that are covalently bonded. This molecular architecture of the
covalent bond enhancement is what causes block copolymers to spontaneously form nanoscale
patterns. In block copolymers, covalent bonds frustrate the natural tendency of each individual polymer to remain separate (in general, different polymers, do not like to mix), so the material assembles into a nano-pattern instead. These copolymers offer the ability to self-assemble into uniform, nanosized micelles and accumulate in tumors via the enhanced permeability and retention effect. Polymer composition can be chosen to control the micelle size and compatibility with the drug of choice. The challenges of this application are the difficulty of reproducing or controlling the size of self-assembly nano micelle, preparing predictable size-distribution, and the stability of the micelle with high drug load content. | 0 | Colloidal Chemistry |
Cuprous oxide is commonly used as a pigment, a fungicide, and an antifouling agent for marine paints. Rectifier diodes based on this material have been used industrially as early as 1924, long before silicon became the standard. Copper(I) oxide is also responsible for the pink color in a positive Benedict's test.
In December 2021, Toshiba announced the creation of a transparent cuprous oxide (CuO) thin-film solar cell. The cell achieved an 8.4% energy conversion efficiency, the highest efficiency ever reported for any cell of this type as of 2021. The cells could be used for high-altitude platform station applications and electric vehicles. | 1 | Solid-state chemistry |
Lecithin contains dietary precursors to choline, an essential nutrient, which was formerly classified as a B vitamin (vitamin B). Lecithin is a mixture of fats that contains phospholipids, including phosphatidylcholine, and the human body can convert phosphatidylcholine into choline. The choline content in lecithin can vary, but it's found that phosphatidylcholine makes up about 25 to 35 percent of lecithin. Furthermore, only about 12 percent of phosphatidylcholine is actually choline. This adds up to a choline content of approximately 4 percent for lecithin. For example, 10 grams of lecithin has 2,500mg of phosphatidylcholine.
Phosphatidylcholine is approximately 13.7% choline; as such, about 342mg of choline is present per 10 grams of lecithin. Therefore, 10 grams of lecithin can be a source for the body to produce about the same amount of choline (342mg) as can be produced by the body from 2 egg yolks. The recommended intake of choline varies depending on age, sex, and physiological conditions, and is roughly 500 mg per day for adults.
Lecithin is generally recognized as safe (GRAS) by the FDA.
There is no robust, scientifically validated clinical research investigating the safety and effectiveness of high-dose lecithin supplementation in lactating women and their infants. A meta-analysis found no evidence that high doses of lecithin improved milk flow in breast-feeding mothers or infants, though concluded that that "higher maternal choline intake was likely to be associated with better child neurocognition and neurodevelopment."
Soy lecithin does not contain enough allergenic proteins for most people allergic to soy, although the US FDA only exempts a few soy lecithin products from its mandatory requirements for allergenic source labeling. An alternative source of lecithin, derived from sunflowers, is available as a dietary supplement for those with concerns about soy-based foods.
A 2003 review of randomized trials found no benefit of lecithin in people with dementia. | 0 | Colloidal Chemistry |
In neutron activation, the probe is prepared directly from the sample material by converting very small part of one of the elements of the sample material into the desired PAC probe or its parent isotope by neutron capture. As with implantation, radiation damage must be healed. This method is limited to sample materials containing elements from which neutron capture PAC probes can be made. Furthermore, samples can be intentionally contaminated with those elements that are to be activated. For example, hafnium is excellently suited for activation because of its large capture cross section for neutrons. | 1 | Solid-state chemistry |
SP-B is a critical protein for lung function, and is found in the context of pulmonary surfactant. Understanding surfactant is important to gaining a full understanding of SP-B. Surfactant is a mixture of lipids and proteins that coats the inside of alveoli and is essential for life due to its key role in preventing alveolar collapse at low lung volumes. In the absence of surfactant, the surface tension at the gas/fluid interface prevents inhalation at standard pressure, but surfactant minimizes surface tension to values near zero and allows for normal breathing. It is also known to have a role in both the immune response and inflammation control.
Surfactant deficiency is a common cause of respiratory disease. Respiratory distress syndrome (RDS) is a particularly well-known instance of surfactant deficiency because it has a high mortality rate among preterm babies, a variety of other conditions are related to surfactant levels and composition.
Surfactant is composed of primarily lipids (90% by weight), and proteins make up only the remaining 10%. The following two sections will address the lipid and protein components respectively. | 0 | Colloidal Chemistry |
pH-dependent primary, secondary, or tertiary amines; primary and secondary amines become positively charged at pH < 10: octenidine dihydrochloride.
Permanently charged quaternary ammonium salts: cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), dimethyldioctadecylammonium chloride, and dioctadecyldimethylammonium bromide (DODAB). | 0 | Colloidal Chemistry |
Self-assembly is the most common term in use in the modern scientific community to describe the spontaneous aggregation of particles (atoms, molecules, colloids, micelles, etc.) without the influence of any external forces. Large groups of such particles are known to assemble themselves into thermodynamically stable, structurally well-defined arrays, quite reminiscent of one of the 7 crystal systems found in metallurgy and mineralogy (e.g. face-centered cubic, body-centered cubic, etc.). The fundamental difference in equilibrium structure is in the spatial scale of the unit cell (or lattice parameter) in each particular case.
Molecular self-assembly is found widely in biological systems and provides the basis of a wide variety of complex biological structures. This includes an emerging class of mechanically superior biomaterials based on microstructural features and designs found in nature. Thus, self-assembly is also emerging as a new strategy in chemical synthesis and nanotechnology. Molecular crystals, liquid crystals, colloids, micelles, emulsions, phase-separated polymers, thin films and self-assembled monolayers all represent examples of the types of highly ordered structures which are obtained using these techniques. The distinguishing feature of these methods is self-organization. | 0 | Colloidal Chemistry |
At ordinary temperatures, Na is solid and Br is liquid, so the enthalpy of vaporization of liquid bromine is added to the equation:
In the above equation, is the enthalpy of vaporization of Br at the temperature of interest (usually in kJ/mol). | 1 | Solid-state chemistry |
Being a multi-scale system involving many phenomena, and a versatile medium, foam can be studied using many different techniques. Considering the different scales, experimental techniques are diffraction ones, mainly light scattering techniques (DWS, see below, static and dynamic light scattering, X-rays and neutron scattering) at sub-micrometer scales, or microscopic ones. Considering the system as continuous, its bulk properties can be characterized by light transmittance but also conductimetry. The correlation between structure and bulk is evidenced more accurately by acoustics in particular. The organisation between bubbles has been studied numerically using sequential attempts of evolution of the minimum surface energy either at random (Potts model) or deterministic way (surface evolver). The evolution with time (i.e., the dynamics) can be simulated using these models, or the bubble model' (Durian), which considers the motion of individual bubbles.
Observations of the small-scale structure can be made by shining the foam with laser light or x-ray beams and measuring the reflectivity of the films between bubbles. Observations of the global structure can be done using neutron scattering.
A typical light scattering (or diffusion) optical technique, multiple light scattering coupled with vertical scanning, is the most widely used technique to monitor the dispersion state of a product, hence identifying and quantifying destabilization phenomena. It works on any concentrated dispersions without dilution, including foams. When light is sent through the sample, it is backscattered by the bubbles. The backscattering intensity is directly proportional to the size and volume fraction of the dispersed phase. Therefore, local changes in concentration (drainage, syneresis) and global changes in size (ripening, coalescence) are detected and monitored. | 0 | Colloidal Chemistry |
The lipophilic group is typically a large hydrocarbon moiety, such as a long chain of the form CH(CH), with n > 4.
The hydrophilic group falls into one of the following categories:
# charged groups
#* anionic. Examples, with the lipophilic part of the molecule represented by R, are:
#** carboxylates: RCO
#** sulfates: RSO
#** sulfonates: RSO
#** phosphates (the charged functional group in phospholipids)
#* cationic. Examples:
#** ammoniums: RNH
# polar, uncharged groups. Examples are alcohols with large R groups, such as diacyl glycerol (DAG), and oligo ethylene glycol with long alkyl chains.
Often, amphiphilic species have several lipophilic parts, several hydrophilic parts, or several of both. Proteins and some block copolymers are such examples.
Amphiphilic compounds have lipophilic (typically hydrocarbon) structures and hydrophilic polar functional groups (either ionic or uncharged).
As a result of having both lipophilic and hydrophilic portions, some amphiphilic compounds may dissolve in water and to some extent in non-polar organic solvents.
When placed in an immiscible biphasic system consisting of aqueous and organic solvents, the amphiphilic compound will partition the two phases. The extent of the hydrophobic and hydrophilic portions determines the extent of partitioning. | 0 | Colloidal Chemistry |
Dead Sea salt refers to salt and other mineral deposits extracted or taken from the Dead Sea. The composition of this material differs significantly from oceanic salt. | 1 | Solid-state chemistry |
Poole-Frenkel saturation occurs when all the trap sites become ionized, resulting in a maximum of the number of conduction carriers.
The corresponding saturation field is obtained from the expression describing the vanishing of the barrier:
where is the saturation field. Thus
The trap sites are now necessarily empty, being at the edge of the conduction band.
The fact that the Poole–Frenkel effect is described by an expression for the conductivity (and for the current) that diverges with increasing fields and does not experience a saturation, is attributable to the simplifying assumption that the trap population follows the Maxwell-Boltzmann statistics. An enhanced Poole-Frenkel model, comprehensive of a more accurate description of the trap statistics with the Fermi-Dirac formula, and capable to quantitatively represent the saturation, has been devised by Ongaro and Pillonnet. | 1 | Solid-state chemistry |
Atomic force microscopy (AFM) is commonly used to directly measure the magnitude of depletion forces. This method uses the deflection of a very small cantilever contacting a sample which is measured by a laser. The force required to cause a certain amount of beam deflection can be determined from the change in angle of the laser. The small scale of AFM allows for dispersion particles to be measured directly yielding a relatively accurate measurement of depletion forces. | 0 | Colloidal Chemistry |
Surface tension draws fluid from capillaries to the alveolar spaces. Surfactant reduces fluid accumulation and keeps the airways dry by reducing surface tension. | 0 | Colloidal Chemistry |
In 2022, it was found that levels of at least four perfluoroalkyl acids (PFAAs) in rainwater worldwide ubiquitously and often greatly exceeded the EPA's lifetime drinking water health advisories as well as comparable Danish, Dutch, and European Union safety standards, leading to the conclusion that "the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded". There are some moves to restrict and replace their use. | 0 | Colloidal Chemistry |
Silicone foam is a synthetic rubber product used in gasketing, sheets and firestops. It is available in solid, cured form as well as in individual liquid components for field installations. | 0 | Colloidal Chemistry |
Due to the lack of spatial inversion symmetry, odd-layer MoS2 is a promising material for valleytronics because both the CBM and VBM have two energy-degenerate valleys at the corners of the first Brillouin zone, providing an exciting opportunity to store the information of 0s and 1s at different discrete values of the crystal momentum. The Berry curvature is even under spatial inversion (P) and odd under time reversal (T), the valley Hall effect cannot survive when both P and T symmetries are present. To excite valley Hall effect in specific valleys, circularly polarized lights were used for breaking the T symmetry in atomically thin transition-metal dichalcogenides. In monolayer MoS2, the T and mirror symmetries lock the spin and valley indices of the sub-bands split by the spin-orbit couplings, both of which are flipped under T; the spin conservation suppresses the inter-valley scattering. Therefore, monolayer MoS2 have been deemed an ideal platform for realizing intrinsic valley Hall effect without extrinsic symmetry breaking. | 1 | Solid-state chemistry |
Currently, in many countries, such as Spain, Israel, Chile and Australia, the development of a rigorous environmental impact assessment process is required, both for the construction and operational phases. During its developent, the most important legal management tools are established within the local environmental regulation, to prevent and adopt mitigation measures that guarantee the sustainable development of desalination projects. This includes a series of administrative tools and periodic environmental monitoring, to adopt preventive, corrective and further monitoring measures of the state of the surrounding marine environment.
Under the context of this environmental assessment process, numerous countries require compliance with an Environmental Monitoring Program (PVA), in order to evaluate the effectiveness of the preventive and corrective measures established during the environmental assessment process, and thus guarantee the operation of desalination plants without producing significant environmental impacts. The PVAs establishes a series of mandatory requirements that are mainly related to the monitoring of discharge, using a series of measurements and characterizations based on physical-chemical and biological information. In addition, the PVAs could also include different requirements related to monitoring the effects of seawater intake and those that may potentially be related to effects on the terrestrial environment. | 1 | Solid-state chemistry |
A potential challenge of aquasome-based drug delivery could be toxicity due to burst release of drugs if poorly absorbed on the carbohydrate coat. Aquasomes can also be expensive to formulate, particularly due to their step-by-step synthesis. Careful attention is needed during aquasome production to tune the thickness of each layer, and leaching and aggregation may occur during prolonged storage of aquasomes. A physiological challenge aquasomes present is that upon their entry into the bloodstream, they may be taken up nonspecifically, leading to opsonization and phagocytic clearance by the immune system. To prevent this, aquasome surfaces can be coated with polyethylene glycol (PEG) to block opsonin binding through steric hindrance; however, the effect of PEGylation on aquasome drug release has not been sufficiently explored to enable clinical applications. Polymer degradation in different physiological environments can change the stability and drug loading of aquasomes over time, as their surface properties directly impact drug release. Aquasomes may also be challenging to scale up and prepare as it is difficult to ensure consistent formulation quality. More research is needed to demonstrate both the efficiency and safety of aquasomes in clinical use. | 0 | Colloidal Chemistry |
Nanoclusters are agglomerates of nanoparticles with at least one dimension between 1 and 10 nanometers and a narrow size distribution. Nanopowders are agglomerates of ultrafine particles, nanoparticles, or nanoclusters. Nanometer-sized single crystals, or single-domain ultrafine particles, are often referred to as nanocrystals.
The terms colloid and nanoparticle are not interchangeable. A colloid is a mixture which has particles of one phase dispersed or suspended within an other phase. The term applies only if the particles are larger than atomic dimensions but small enough to exhibit Brownian motion, with the critical size range (or particle diameter) typically ranging from nanometers (10 m) to micrometers (10 m). Colloids can contain particles too large to be nanoparticles, and nanoparticles can exist in non-colloidal form, for examples as a powder or in a solid matrix. | 0 | Colloidal Chemistry |
Rheumatologic conditions can be treated in the balneotherapy of rheumatoid arthritis, psoriatic arthritis, and osteoarthritis. The minerals are absorbed while soaking, stimulating blood circulation. | 1 | Solid-state chemistry |
In 1999, Wu completed a dual B.S. in materials science and engineering and environmental science and engineering at Tsinghua University (THU). In 2001, she earned a M.S. in materials science and engineering at THU. She conducted her masters thesis, Structure Characterization and Performance of Porous Chemical Adsorbents for Indoor-Air Purification under advisor Feiyu Kang. Wu completed a Ph.D. in materials science and engineering at University of Pennsylvania in 2005. Her dissertation was titled Non-stoichiometric Ordered Perovskites for Microwave Applications. Wus doctoral advisor was Peter K. Davies. From 2005 to 2007, Wu conducted a postdoc as research associate in the National Institute of Standards and Technology Center for Neutron Research. Her postdoctoral advisor was Terrence J. Udovic. She researched the development and processing of novel metal hydride materials for hydrogen storage and hydrogen-storage materials using neutron scattering techniques. | 1 | Solid-state chemistry |
Characterization of crystalline g-CN can be carried out by identifying the triazine ring existing in the products by X-ray photoelectron spectroscopy (XPS) measurements, photoluminescence spectra and Fourier transform infrared spectroscopy (FTIR) spectrum (peaks at 800 cm, 1310 cm and 1610 cm). | 1 | Solid-state chemistry |
In chemistry, a dangling bond is an unsatisfied valence on an immobilized atom. An atom with a dangling bond is also referred to as an immobilized free radical or an immobilized radical, a reference to its structural and chemical similarity to a free radical.
When speaking of a dangling bond, one is generally referring to the state described above, containing one electron and thus leading to a neutrally charged atom. There are also dangling bond defects containing two or no electrons. These are negatively and positively charged respectively. Dangling bonds with two electrons have an energy close to the valence band of the material and those with none have an energy that is closer to the conduction band. | 1 | Solid-state chemistry |
The utilization of the difference between dielectrophoretic forces exerted on different particles in nonuniform electric fields is known as DEP separation. The exploitation of DEP forces has been classified into two groups: DEP migration and DEP retention. DEP migration uses DEP forces that exert opposite signs of force on different particle types to attract some of the particles and repel others. DEP retention uses the balance between DEP and fluid-flow forces. Particles experiencing repulsive and weak attractive DEP forces are eluted by fluid flow, whereas particles experiencing strong attractive DEP forces are trapped at electrode edges against flow drag.
Dielectrophoresis field-flow fractionation (DEP-FFF), introduced by Davis and Giddings, is a family of chromatographic-like separation methods. In DEP-FFF, DEP forces are combined with drag flow to fractionate a sample of different types of particles. Particles are injected into a carrier flow that passes through the separation chamber, with an external separating force (a DEP force) being applied perpendicular to the flow. By means of different factors, such as diffusion and steric, hydrodynamic, dielectric and other effects, or a combination thereof, particles (<1 μm in diameter) with different dielectric or diffusive properties attain different positions away from the chamber wall, which, in turn, exhibit different characteristic concentration profile. Particles that move further away from the wall reach higher positions in the parabolic velocity profile of the liquid flowing through the chamber and will be eluted from the chamber at a faster rate. | 0 | Colloidal Chemistry |
Viruses can be used to deliver genes for genetic engineering or gene therapy. Commonly used viruses include adenoviruses, retroviruses, and various bacteriophages. The surface of the viral particle can also be modified with ligands to increase targeting capabilities. While viral vectors can be used to great efficacy, one concern is that may cause off-target effects due to its natural tropism. This usually requires replacing the proteins causing virus-cell interactions with chimeric proteins.
In addition to using viruses, drug molecules can also be encapsulated in protein particles derived from the viral capsid, or virus-like particles (VLPs). VLPs are easier to manufacture than viruses, and their structural uniformity allows VLPs to be produced precisely in large amounts. VLPs also have easy-to-modify surfaces, allowing the possibility for targeted delivery. There are various methods of packaging the molecule into the capsid; most take advantage of the capsid's ability to self-assemble. One strategy is to alter the pH gradient outside the capsid to create pores on the capsid surface and trap the desired molecule. Other methods use aggregators such as leucine zippers or polymer-DNA amphiphiles to induce capsid formation and capture drug molecules. It is also possible to chemically conjugate of drugs directly onto the reactive sites on the capsid surface, often involving the formation of amide bonds.
After being introduced to the organism, VLPs often have broad tissue distribution, rapid clearance, and are generally non-toxic. It may, however, like viruses, invoke an immune response, so immune-masking agents may be necessary. | 0 | Colloidal Chemistry |
Europium(II) oxide is a violet compound as a bulk crystal and transparent blue in thin film form. It is unstable in humid atmosphere, slowly turning into the yellow europium(II) hydroxide hydrrate and then to white europium(III) hydroxide. EuO crystallizes in a cubic sodium chloride structure with a lattice parameter a = 0.5144nm. The compound is often non-stoichiometric, containing up to 4% Eu and small amounts of elemental europium. However, since 2008 high purity crystalline EuO films can be created in ultra high vacuum conditions. These films have a crystallite size of about 4 nm.
Europium(II) oxide is ferromagnetic with a Curie Temperature of 69.3 K. With the addition of about 5-7% elemental europium, this increases to 79 K. It also displays colossal magnetoresistance, with a dramatic increase in conductivity below the Curie temperature. One more way to increase the Curie temperature is doping with gadolinium, holmium, or lanthanum.
Europium(II) oxide is a semiconductor with a band gap of 1.12 eV. | 1 | Solid-state chemistry |
The currently largest PAC laboratory in the world is located at ISOLDE in CERN with about 10 PAC instruments, that receives its major funding form BMBF. Radioactive ion beams are produced at the ISOLDE by bombarding protons from the booster onto target materials (uranium carbide, liquid tin, etc.) and evaporating the spallation products at high temperatures (up to 2000 °C), then ionizing them and then accelerating them. With the subsequent mass separation usually very pure isotope beams can be produced, which can be implanted in PAC samples. Of particular interest to the PAC are short-lived isomeric probes such as: Cd, Hg, Pb, and various rare earth probes. | 1 | Solid-state chemistry |
In his career Fichtner worked on various topics, covering Theoretical Chemistry, Instrumental Analysis, Higher Administration, Chemical Engineering, Heterogeneous Catalysis, Hydrogen Storage, Electrochemistry and Battery Research.
Pioneering achievements were the first measurements of salts with Secondary Neutral Mass Spectrometry, the development of a depth-resolved speciation of beam sensitive salts, a microstructure reactor which could safely burn and transfer the heat from a stoichiometric hydrogen-oxygen mixture to a thermo oil, thus demonstrating the enormous capability of running dangerous reactions in microstructure reactors safely.
In the development of hydrogen storage materials, new complex hydride compounds were synthesized and investigated, the fasted charge and discharge of an aluminum hydride to date by a new Ti13 catalyst, first applied for that purpose by the Bogdanovig group of Max Planck Mülheim, was independently confirmed. Further work in this area was focused on elucidating nanoscale effects in energy materials and studies, based on pioneering work since the late 1990s by various groups from all over the world on hydrogen and the effects by nanostructures, of the change of thermodynamic properties of complex hydrides was conducted in his group.
In battery research, new synthesis methods were developed to stabilize conversion materials, new types of batteries based on anionic shuttles were presented and new electrolytes were developed for magnesium properties with outstanding voltage windows and non-nucleophilic properties, making reversible Mg-S cells possible. Moreover, a new class of cathode materials is being studied with the highest packing densities for Li ions to date, the so-called Li-excess disordered rocksalt materials (DRX), developed by the Gerbrand Ceder group. | 1 | Solid-state chemistry |
Silver ions have been shown to have potent antibacterial activity, and have been shown to affect the growth of Gram-positive and Gram-negative bacteria. This is due to their ability to form ligand complexes with proteins or enzymes in bacterial cells. Due to this unique property, these nanofoams create excellent air filters designed to filter out bacteria and other microorganisms, this level of filtration was shown to be more effective than tradition HCl analogues.
These silver nanofoams have also been used as electrocatalysts for the reduction reaction of to CO. It was found that on average silver nanofoams can maintain over 90% FECO in a wide potential window (−0.5 to −1.2 VRHE), enabling the maximum CO selective current density of 33 mA cm−2 and the mass activity of 23.5 A gAg−1, which are the highest values among recently reported metal foam-based electrocatalysts. | 0 | Colloidal Chemistry |
Mycosubtilin has strong antifungal and hemolytic activities. It is active against fungi and yeasts such as Candida albicans, Candida tropicalis, Saccharomyces cerevisiae, Penicillium notatum, and Fusarium oxysporum.
Its antibacterial activity is quite limited to bacteria such as Micrococcus luteus. | 0 | Colloidal Chemistry |
All forms of have a layered structure, in which a plane of molybdenum atoms is sandwiched by planes of sulfide ions. These three strata form a monolayer of MoS. Bulk MoS consists of stacked monolayers, which are held together by weak van der Waals interactions.
Crystalline MoS exists in one of two phases, 2H-MoS and 3R-MoS, where the "H" and the "R" indicate hexagonal and rhombohedral symmetry, respectively. In both of these structures, each molybdenum atom exists at the center of a trigonal prismatic coordination sphere and is covalently bonded to six sulfide ions. Each sulfur atom has pyramidal coordination and is bonded to three molybdenum atoms. Both the 2H- and 3R-phases are semiconducting.
A third, metastable crystalline phase known as 1T-MoS was discovered by intercalating 2H-MoS with alkali metals. This phase has trigonal symmetry and is metallic. The 1T-phase can be stabilized through doping with electron donors such as rhenium, or converted back to the 2H-phase by microwave radiation. The 2H/1T-phase transition can be controlled via the incorporation of S vacancies. | 1 | Solid-state chemistry |
Molecular beams can be used to create nanocluster beams of virtually any element. They can be synthesized in high vacuum by with molecular beam techniques combined with a mass spectrometer for mass selection, separation and analysis. And finally detected with detectors. | 0 | Colloidal Chemistry |
Researchers are attempting to eliminate the problem of blinking nanocrystals. One common solution is to suppress nanocrystal ionization. This could be done, for example, by growing a very thick semiconductor shell around the nanocrystal core. However, blinking was reduced, not eliminated, because the fundamental processes responsible for blinking - the non-radiative Auger recombination- were still present. | 0 | Colloidal Chemistry |
Sodium ethyl xanthate is a pale yellow powder. Its aqueous solutions are stable at high pH if not heated. It rapidly hydrolyses at pH less than 9 at 25 °C. It is the conjugate base of the ethyl xanthic acid, a strong acid with pK of 1.6 and pK estimated as 12.4 for the conjugate base. Sodium ethyl xanthate easily adsorbs on the surface of many sulfide minerals, a key step in froth flotation.
Xanthates are susceptible to hydrolysis and oxidation at low pH:
Oxidation gives diethyl dixanthogen disulfide: | 1 | Solid-state chemistry |
In the bulk aqueous phase, surfactants form aggregates, such as micelles, where the hydrophobic tails form the core of the aggregate and the hydrophilic heads are in contact with the surrounding liquid. Other types of aggregates can also be formed, such as spherical or cylindrical micelles or lipid bilayers. The shape of the aggregates depends on the chemical structure of the surfactants, namely the balance in size between the hydrophilic head and hydrophobic tail. A measure of this is the hydrophilic-lipophilic balance (HLB). Surfactants reduce the surface tension of water by adsorbing at the liquid-air interface. The relation that links the surface tension and the surface excess is known as the Gibbs isotherm. | 0 | Colloidal Chemistry |
* 1991–1995 – Presidential Young Investigator Award;
* 1991 – Alfred P. Sloan Foundation fellowship;
* 1991 – ACS Exxon Solid State Chemistry Fellowship;
* 1994 – Coblentz Award for Advances in Molecular Spectroscopy;
* 1994 – Wilson Prize at Harvard;
* 1994 – Department of Energy Award for Outstanding Scientific Accomplishment in Materials Chemistry;
* 1995 – Materials Research Society Outstanding Young Investigator Award;
* 1997 – Department of Energy Award for Sustained Outstanding Research in Materials Chemistry;
* 2005 – Colloid and Surface Chemistry American Chemical Society Award;
* 2006 – E. O. Lawrence Award;
* 2006 – Eni Italgas prize for Energy and Environment;
* 2006 – The Rank Prize (Optoelectronics);
* 2006 – University of Chicago's Distinguished Alumni Award (Professional Achievement);
* 2008 – Kavli Distinguished Lectureship in Nanoscience, Materials Research Society;
* 2009 – Nanoscience Prize, International Society for Nanoscale Science, Computation & Engineering;
* 2010 – Medaglia teresiana, University of Pavia;
* 2011 – Linus Pauling Award;
* 2011 – Von Hippel Award, Materials Research Society;
* 2012 – Wolf Prize in Chemistry;
* 2014 – National Medal of Science;
* 2014 – ACS Award in the Chemistry of Materials;
* 2015 – Axion Award, Hellenic American Professional Society;
* 2015 – Spiers Memorial Award, Royal Society of Chemistry;
* 2016 – Dan David Prize for nanoscience research;
* 2017 – NAS Award in Chemical Sciences;
* 2019 – Welch Award in Chemistry;
* 2020 – BBVA Foundation Frontiers of Knowledge Award;
* 2021 – Priestley Medal;
In addition to those listed above, Alivisatos has held fellowships with the American Association for the Advancement of Science, the American Physical Society (1996), and the American Chemical Society. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. | 1 | Solid-state chemistry |
Surfactant immune function is primarily attributed to two proteins: SP-A and SP-D. These proteins can bind to sugars on the surface of pathogens and thereby opsonize them for uptake by phagocytes. It also regulates inflammatory responses and interacts with the adaptive immune response. Surfactant degradation or inactivation may contribute to enhanced susceptibility to lung inflammation and infection. | 0 | Colloidal Chemistry |
The three major units of aquasomes are fabricated together according to self-assembly, a thermodynamically driven process that organizes subunits of a system in a manner that results in the lowest Gibbs Free Energy available, known as ΔG. Self-assembly as a mixing process offers high accuracy and control over sizes on the nanometer scale, which is especially relevant for aquasomes, which exist on this size scale. The three layers of aquasomes can be synthesized differently using a variety of techniques depending on the intended functions or desired therapeutic effects. The general scheme of aquasome fabrication involves a sequential synthesis of a nanocrystalline core, followed by a polyhydroxy coating, and finished with integration of bioactive molecules. Throughout this process, several intermittent steps are included that involve selective filtering and purification to remove byproducts while isolating the desired products for further processing. | 0 | Colloidal Chemistry |
Multiple light scattering coupled with vertical scanning is the most widely used technique to monitor the dispersion state of a product, hence identifying and quantifying destabilization phenomena. It works on concentrated dispersions without dilution. When light is sent through the sample, it is back scattered by the particles. The backscattering intensity is directly proportional to the size and volume fraction of the dispersed phase. Therefore, local changes in concentration (sedimentation) and global changes in size (flocculation, aggregation) are detected and monitored. Of primary importance in the analysis of stability in particle suspensions is the value of the zeta potential exhibited by suspended solids. This parameter indicates the magnitude of interparticle electrostatic repulsion and is commonly analyzed to determine how the use of adsorbates and pH modification affect particle repulsion and suspension stabilization or destabilization. | 0 | Colloidal Chemistry |
In 1918 Born and Landé proposed that the lattice energy could be derived from the electric potential of the ionic lattice and a repulsive potential energy term.
where
:N is the Avogadro constant;
:M is the Madelung constant, relating to the geometry of the crystal;
:z is the charge number of the cation;
:z is the charge number of the anion;
:e is the elementary charge, equal to ;
:ε is the permittivity of free space, equal to ;
:r is the nearest-neighbor distance between ions; and
:n is the Born exponent (a number between 5 and 12, determined experimentally by measuring the compressibility of the solid, or derived theoretically).
The Born–Landé equation above shows that the lattice energy of a compound depends principally on two factors:
* as the charges on the ions increase, the lattice energy increases (becomes more negative),
* when ions are closer together the lattice energy increases (becomes more negative)
Barium oxide (BaO), for instance, which has the NaCl structure and therefore the same Madelung constant, has a bond radius of 275 picometers and a lattice energy of −3054 kJ/mol, while sodium chloride (NaCl) has a bond radius of 283 picometers and a lattice energy of −786 kJ/mol. The bond radii are similar but the charge numbers are not, with BaO having charge numbers of (+2,−2) and NaCl having (+1,−1); the Born–Landé equation predicts that the difference in charge numbers is the principal reason for the large difference in lattice energies.
Closely related to this widely used formula is the Kapustinskii equation, which can be used as a simpler way of estimating lattice energies where high precision is not required. | 1 | Solid-state chemistry |
The colloidal probe technique uses a standard AFM for the force measurements. But instead the AFM cantilever with an attached sharp tip one uses the colloidal probe. This colloidal probe is normally obtained by attaching a colloidal particle to a cantilever. By recording the deflection of the cantilever as a function of the vertical displacement of the AFM scanner one can extract the force acting between the probe and the surface as a function of the surface separation. This type of AFM operation is referred to as the force mode. With this probe, one can study interactions between various surfaces and probe particles in the sphere-plane geometry. It is also possible to study forces between colloidal particles by attaching another particle to the substrate and perform the measurement in the sphere-sphere geometry, see figure above.
The force mode used in the colloidal probe technique is illustrated in the figure on the left. The scanner is fabricated from piezoelectric crystals, which enable its positioning with a precision better than 0.1 nm. The scanner is lifted towards the probe and thereby one records the scanner displacement D. At the same time, the deflection of the cantilever ξ is monitored as well, typically with a comparable precision. One measures the deflection by focusing a light beam originating from a non-coherent laser diode to the back of the cantilever and detecting the reflected beam with a split photodiode. The lever signal S represents the difference in the photocurrents originating from the two halves of the diode. The lever signal is therefore proportional to the deflection ξ.
During an approach-retraction cycle, one records the lever signal S as a function of the vertical displacement D of the scanner. Suppose for the moment that the probe and the substrate are hard and non-deformable objects and that no forces are acting between them when they are not in contact. In such a situation, one refers to a hard-core repulsion. The cantilever will thus not deform as long not being in contact with the substrate. When the cantilever touches the substrate, its deflection will be the same as the displacement of the substrate. This response is referred to as the constant compliance or contact region. The lever signal S as a function of the scanner displacement D is shown in the figure below. This graph consists of two straight lines resembling a hockey-stick. When the surfaces are not in contact, the lever signal will be denoted as S. This value corresponds to the non-deformed lever. In the constant compliance region, the lever signal is simply a linear function of the displacement, and can be represented as a straight line
: S = a D + b
The parameters a and b can be obtained from a least-squares fit of the constant compliance region. The inverse slope a is also referred to as the optical lever sensitivity. By inverting this relation for the lever signal S, which corresponds to the non-deformed lever, one can accurately obtain the contact point from D = (S − b)/a. Depending on the substrate, the precision in determining this contact point is between 0.5–2 nm. In the constant compliance region, the lever deformation is given by
: ξ = (S − S)/a
In this fashion, one can detect deflections of the cantilever with typical resolution of better than 0.1 nm.
Let us now consider the relevant situation where the probe and the substrate interact. Let us denote by F(h) the force between the probe and the substrate. This force depends on the surface separation h.
In equilibrium, this force is compensated by the restoring force of the spring, which is given by the Hooke's law
: F = k ξ
where k is the spring constant of the cantilever. Typical spring constants of AFM cantilevers are in the range of 0.1−10 N/m. Since the deflection is monitored with a precision better 0.1 nm, one typically obtains a force resolution of 1−100 pN. The separation distance can be obtained from the displacement of the scanner and the cantilever deflection
: h = ξ + D − D
Figure below illustrates how the cantilever responds to different force profiles. In the case of a soft repulsive force, the cantilever is repelled from the surface and only slowly approaches the constant compliance region. In such situations, it might be actually difficult to identify this region correctly. When the force is attractive, the cantilever is attracted to the surface and may become unstable. From stability considerations one finds that the cantilever will be unstable provided
: dF/dh > k
This instability is illustrated in the right panel of the figure on the right. As the cantilever approaches, the slope of the force curve increases. When the slope becomes larger than the spring constant of the cantilever, the cantilever jumps into contact when the slope of the force curve exceeds the force constant of the cantilever. Upon retraction, the same phenomenon happens, but the point where the cantilever jumps out is reached at a smaller separation. Upon approach and retraction, the system will show a hysteresis. In such situations, a part of the force profile cannot be probed. However, this problem can be avoided by using a stiffer cantilever, albeit at the expense of an inferior force resolution. | 0 | Colloidal Chemistry |
Understanding the behavior of nanoparticles at liquid interfaces is essential for integrating them into electronics, optics, sensing, and catalysis devices. Molecular arrangements at liquid/liquid interfaces are uniform. Often, they also provide a defect-correcting platform and thus, liquid/liquid interfaces are ideal for self-assembly. Upon self-assembly, the structural and spatial arrangements can be determined via X-ray diffraction and optical reflectance. The number of nanoparticles involved in self-assembly can be controlled by manipulating the concentration of the electrolyte, which can be in the aqueous or the organic phase. Higher electrolyte concentrations correspond to decreased spacing between the nanoparticles.
Pickering and Ramsden worked with oil/water (O/W) interfaces to portray this idea. Pickering and Ramsden explained the idea of pickering emulsions when experimenting with paraffin-water emulsions with solid particles like iron oxide and silicon dioxide. They observed that the micron-sized colloids generated a resistant film at the interface between the two immiscible phases, inhibiting the coalescence of the emulsion drops. These Pickering emulsions are formed from the self-assembly of colloidal particles in two-part liquid systems, such as oil-water systems. The desorption energy, which is directly related to the stability of emulsions depends on the particle size, particles interacting with each other, and particles interacting with oil and water molecules.
A decrease in total free energy was observed to be a result of the assembly of nanoparticles at an oil/water interface. When moving to the interface, particles reduce the unfavorable contact between the immiscible fluids and decrease the interfacial energy. The decrease in total free energy for microscopic particles is much larger than that of thermal energy, resulting in an effective confinement of large colloids to the interface. Nanoparticles are restricted to the interface by an energy reduction comparable to thermal energy. Thus, nanoparticles are easily displaced from the interface. A constant particle exchange then occurs at the interface at rates dependent on particle size.
For the equilibrium state of assembly, the total gain in free energy is smaller for smaller particles. Thus, large nanoparticle assemblies are more stable. The size dependence allows nanoparticles to self-assemble at the interface to attain its equilibrium structure. Micrometer- size colloids, on the other hand, may be confined in a non-equilibrium state. | 0 | Colloidal Chemistry |
Robert Nelson Smith (September 25, 1916 – December 23, 1983) was an American chemist who specialized in colloids. He taught at Pomona College in Claremont, California, from 1945 to 1982. He was chair of the college's chemistry department and was known for his practical jokes. | 0 | Colloidal Chemistry |
Nanoparticles of sufficiently uniform size may spontaneously settle into regular arrangements, forming a colloidal crystal. These arrangements may exhibit original physical properties, such as observed in photonic crystals. | 0 | Colloidal Chemistry |
The simplest theoretical model is that of a homogeneous sphere surrounded by a conducting dielectric medium. For a homogeneous sphere of radius and complex permittivity in a medium with complex permittivity the (time-averaged) DEP force is:
The factor in curly brackets is known as the complex Clausius-Mossotti function and contains all the frequency dependence of the DEP force. Where the particle consists of nested spheres – the most common example of which is the approximation of a spherical cell composed of an inner part (the cytoplasm) surrounded by an outer layer (the cell membrane) – then this can be represented by nested expressions for the shells and the way in which they interact, allowing the properties to be elucidated where there are sufficient parameters related to the number of unknowns being sought.
For a more general field-aligned ellipsoid of radius and length with complex dielectric constant in a medium with complex dielectric constant the time-dependent dielectrophoretic force is given by:
The complex dielectric constant is , where is the dielectric constant, is the electrical conductivity, is the field frequency, and is the imaginary unit. This expression has been useful for approximating the dielectrophoretic behavior of particles such as red blood cells (as oblate spheroids) or long thin tubes (as prolate ellipsoids) allowing the approximation of the dielectrophoretic response of carbon nanotubes or tobacco mosaic viruses in suspension.
These equations are accurate for particles when the electric field gradients are not very large (e.g., close to electrode edges) or when the particle is not moving along an axis in which the field gradient is zero (such as at the center of an axisymmetric electrode array), as the equations only take into account the dipole formed and not higher order polarization. When the electric field gradients are large, or when there is a field null running through the center of the particle, higher order terms become relevant, and result in higher forces.
To be precise, the time-dependent equation only applies to lossless particles, because loss creates a lag between the field and the induced dipole. When averaged, the effect cancels out and the equation holds true for lossy particles as well. An equivalent time-averaged equation can be easily obtained by replacing E with E, or, for sinusoidal voltages by dividing the right hand side by 2.
These models ignores the fact that cells have a complex internal structure and are heterogeneous. A multi-shell model in a low conducting medium can be used to obtain information of the membrane conductivity and the permittivity of the cytoplasm.
For a cell with a shell surrounding a homogeneous core with its surrounding medium considered as a layer, as seen in Figure 2, the overall dielectric response is obtained from a combination of the properties of the shell and core.
where 1 is the core (in cellular terms, the cytoplasm), 2 is the shell (in a cell, the membrane). r1 is the radius from the centre of the sphere to the inside of the shell, and r2 is the radius from the centre of the sphere to the outside of the shell. | 0 | Colloidal Chemistry |
If there are two spheres of radii and on the axis, and the spheres are distance apart, where is much smaller than and , then the force, , in the direction is
In this equation, , and is the normal force per unit area between two flat surfaces distance apart.
When the Derjaguin approximation is applied to depletion forces, and 0<h<2Rs, then the depletion force given by the Derjaguin approximation is
In this equation, is the geometrical factor, which is set to 1, and , the interfacial tension at the wall-fluid interface. | 0 | Colloidal Chemistry |
The highest temperatures at which BiSb, as a thin film of thicknesses 150–1350 Å, superconducts (the critical temperature T) is approximately 2 K. Single crystal BiSb can superconduct at slightly higher temperatures, and at 4.2 K, its critical magnetic field B (the maximum magnetic field that the superconductor can expel) of 1.6 T at 4.2 K. | 1 | Solid-state chemistry |
In solid state physics and physical chemistry, the fine electronic structure of a solid are the features of the electronic bands induced by intrinsic interactions between charge carriers. Valence and conduction bands split slightly compared to the difference between the various bands. Some mechanisms that allow it are angular momentum couplings, spin-orbit coupling, lattice distortions (Jahn–Teller effect), and other interactions described by crystal field theory.
The name comes from the fine structure of atoms, where energy levels suffer from a similar effect from the non-relativistic calculation due to effects like spin–orbit interaction, zitterbewegung, and corrections to the kinetic energy. | 1 | Solid-state chemistry |
Beractant, also known by the trade name of Survanta, is a modified bovine pulmonary surfactant containing bovine lung extract (phospholipids, neutral lipids,
fatty acids, and bovine surfactant proteins), to which synthetic DPPC, tripalmitin and palmitic acid are added. The composition provides 25 mg/mL phospholipids, 0.5 to 1.75 mg/mL triglycerides, 1.4 to 3.5 mg/mL free fatty acids, and <1.0 mg/mL total surfactant proteins. As an intratracheal suspension, it can be used for the prevention and treatment of neonatal respiratory distress syndrome. Survanta is manufactured by Abbvie. | 0 | Colloidal Chemistry |
James A. Ibers was the Charles E. and Emma H. Morrison Professor of Chemistry before becoming an emeritus professor of chemistry at Northwestern University upon retirement. He is recognized for contributions to inorganic chemistry, especially in the areas of coordination chemistry, bio-inorganic chemistry, solid state synthesis and X-ray crystallography. Ibers passed on December 14, 2021, at the age of 91. | 1 | Solid-state chemistry |
The chemical processing and synthesis of high-performance technological components for the private, industrial, and military sectors requires the use of high-purity ceramics (oxide ceramics, such as aluminium oxide or copper(II) oxide), polymers, glass-ceramics, and composite materials, as metal carbides (SiC), nitrides (Aluminum nitrides, Silicon nitride), metals (Al, Cu), non-metals (graphite, carbon nanotubes), and layered (Al + aluminium carbonate, Cu + C). In condensed bodies formed from fine powders, the irregular particle sizes and shapes in a typical powder often lead to non-uniform packing morphologies that result in packing density variations in the powder compact.
Uncontrolled agglomeration of powders due to attractive van der Waals forces can also give rise to microstructural heterogeneity. Differential stresses that develop as a result of non-uniform drying shrinkage are directly related to the rate at which the solvent can be removed, and thus highly dependent upon the distribution of porosity. Such stresses have been associated with a plastic-to-brittle transition in consolidated bodies, and can yield to crack propagation in the unfired body if not relieved.
In addition, any fluctuations in packing density in the compact as it is prepared for the kiln are often amplified during the sintering process, yielding inhomogeneous densification. Some pores and other structural defects associated with density variations have been shown to play a detrimental role in the sintering process by growing and thus limiting end-point densities. Differential stresses arising from inhomogeneous densification have also been shown to result in the propagation of internal cracks, thus becoming the strength-controlling flaws.
Inert gas evaporation and inert gas deposition are free many of these defects due to the distillation (cf. purification) nature of the process and having enough time to form single crystal particles, however even their non-aggreated deposits have lognormal size distribution, which is typical with nanoparticles. The reason why modern gas evaporation techniques can produce a relatively narrow size distribution is that aggregation can be avoided. However, even in this case, random residence times in the growth zone, due to the combination of drift and diffusion, result in a size distribution appearing lognormal.
It would, therefore, appear desirable to process a material in such a way that it is physically uniform with regard to the distribution of components and porosity, rather than using particle size distributions that will maximize the green density. The containment of a uniformly dispersed assembly of strongly interacting particles in suspension requires total control over interparticle forces. Monodisperse nanoparticles and colloids provide this potential. | 0 | Colloidal Chemistry |
The pronunciation of the compound reflects its origin and first isolation from sugar beets (Beta vulgaris subsp. vulgaris), and does not derive from the Greek letter beta (β). It is commonly pronounced beta-INE or BEE-tayn. | 0 | Colloidal Chemistry |
The Janovski reaction is the reaction of 1,3-dinitrobenzene with an enolizable ketone to the Meisenheimer adduct. | 1 | Solid-state chemistry |
In 1999, Brock joined Wayne State University as an assistant professor in the department of chemistry and was promoted to full professor in 2009. Her research considers pnictide, pnictide oxides and chalcogenides. In particular, Brock is interested in the controlled growth of functional nanoparticles and nanostructures. She demonstrated that manganese arsenide nanoparticles have magnetic properties that depend on their dopant concentration, and offer hope for magnetic refrigeration.
Brock has also realised sol–gel processes that allow the formation of functional chalcogenide self-assemblies. The gel-like cadmium selenide (CdSe) and zinc sulfide (ZnS) nanoparticles are akin to a cross-linked polymer network, and can be supercritically dried to form porous aerogels. The aerogels have high surface areas and form a conductive network with the optical properties of the nanoparticles themselves.
Brock is responsible for the development of electron microscopy at Wayne State University. She serves as Deputy Editor of the American Chemical Society journal ACS Materials. | 1 | Solid-state chemistry |
Wüstite (FeO, sometimes also written as FeO) is a mineral form of mostly iron(II) oxide found with meteorites and native iron. It has a grey colour with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound.
Wüstite was named after Fritz Wüst (1860–1938), a German metallurgist and founding director of the Kaiser-Wilhelm-Institut für Eisenforschung (presently Max Planck Institute for Iron Research GmbH).
In addition to its type locality in Germany, it has been reported from Disko Island, Greenland; the Jharia coalfield, Jharkhand, India; and as inclusions in diamonds in a number of kimberlite pipes. It also is reported from deep sea manganese nodules.
Its presence indicates a highly reducing environment. | 1 | Solid-state chemistry |
The first market for nanolattices may be small-scale, small-lot components for biomedical, electrochemical, microfluidic, and aerospace applications, which require highly customizable and extreme combinations of properties. In the aerospace industry, the application of nanolattice could make the aircraft lighter and save lots of energy. | 0 | Colloidal Chemistry |
Sarma received the Sir J. C. Ghosh Medal in 1981 and the Young Scientist Medal from the Indian National Science Academy in 1983. UNESCO awarded him the Biennial Javed Hussain Prize in 1989 and a year later, in 1990, he received the medal of excellence from the Materials Research Society of India. The Government of India awarded him the Shanti Swarup Bhatnagar Prize in 1994 and he received the C. V. Raman Award in 2004. The year 2005 brought him three awards, the Hari Om Ashram Trust Award by the University Grants Commission, G. D. Birla Award and the Alumnus Award for Excellence in Research from the Indian Institute of Science. He received FICCI Award in 2006, TWAS Prize in Physics in 2007, the National Research Award in 2009 and H. K. Firodia Award in 2013. He was honored with the Knight of "The Order of the Star of Italy" in 2014, and an Honorary Doctorate from the Faculty of Science and Technology at Uppsala University in 2015.
Sarma, an elected Fellow of the Indian National Science Academy, delivered three INSA lectures in 2006, Dr. Jagdish Shankar Memorial Award Lecture, Professor R. P. Mitra Memorial Award Lecture and A. V. Rama Rao Foundation Lecture. Two years later, he delivered the INSA Kotcherlakota Rangadhama Rao Memorial Lecture in 2008. Some of the other lectures delivered by Das Sarma are CSIR Foundation Day Lecture, Distinguished Public Lecture, 8th Atma Ram Memorial Lecture and the Joy Kissen Memorial Lecture, CNR Rao Prize Lecture.
He is an elected Fellow of the American Physical Society, The Academy of Sciences for the Developing World, the National Academy of Sciences, India, and the Indian Academy of Sciences and holds the fellowship of the Asia-Pacific Academy of Materials (APAM). He is also a J. C. Bose National Fellow and Homi Bhabha Fellow. | 1 | Solid-state chemistry |
In those cases where salt layers do not have the conditions necessary to develop passive salt structures, the salt may still move into relatively low pressure areas around developing folds and faults. Such structures are described as reactive. | 1 | Solid-state chemistry |
1-Tridecanol is an alcohol with the formula CHOH. It is a colorless fatty alcohol that turns white when solid. 1-Tridecanol usually occurs as a mixture of different isomeric to compounds such as 2-tridecanol, 3-tridecanol, 4-tridecanol, 5-tridecanol, 6-tridecanol, and isotridecanol. | 0 | Colloidal Chemistry |
The high concentration of bromide and magnesium in the Dead Sea salt may help relieve allergic reactions of the skin by reducing inflammation. | 1 | Solid-state chemistry |
The US Environmental Protection Agency (EPA) has published water quality criteria for turbidity. These criteria are scientific assessments of the effects of turbidity, which are used by states to develop water quality standards for water bodies. (States may also publish their own criteria.) Some states have promulgated water quality standards for turbidity, including:
* Louisiana. 25, 50 or 150 NTU, or background plus 10 percent, depending on the water body.
* Vermont. 10 NTU or 25 NTU, depending on water body classification.
* Washington. 5 NTU over background (when background is 50 NTU or less), or 10 percent increase when background is over 50 NTU. | 0 | Colloidal Chemistry |
Mechanical coalescers, which are the more common type of coalescers, operate by physically altering a droplet by mechanical means. They are commonly applied in the global oil and gas industries for the removal of water or hydrocarbon condensate. While coalescers by definition function as a separation tool for liquids, they are also used, and mistakenly referred to, as filters.
In the area of compressed air purification, coalescing filters are used to separate liquid water and oil from compressed air using a coalescing effect. Coalescence (physics) shows how coalescing filters operating at lower temperatures and high pressures work better. These filters additionally remove particles. The most commonly used media in this case is borosilicate micro-fiber.
In the Oil and Gas, Petrochemical and Oil Refining industries, liquid-gas coalescers are widely used to remove water and hydrocarbon liquids to less than 0.011 mW (plus particulate matter to less than 0.3 µm in size) from natural gas to ensure natural gas quality and protect downstream equipment such as compressors, gas turbines, amine or glycol absorbers, molecular sieves, PSA's, metering stations, mercury guard beds, gas fired heaters or furnaces, heat exchangers or gas-gas purification membranes.
In the natural gas industry, gas/liquid coalescers are used for recovery of lube oil downstream of a compressor. All liquids will be removed but lube oil recovery is the primary reason for installing a coalescer on the outlet of a compressor. Liquids from upstream of the compressor, which may include aerosol particles, entrained liquids or large volumes of liquids called "slugs" and which may be water and/or a combination of hydrocarbon liquids should be removed by a filter/coalescing vessel located upstream of the compressor. Efficiencies of gas/liquid coalescers are typically 0.3 µm (0.3 micron) liquid particles, with efficiencies to 99.98%.
Liquid-liquid coalescers can also be used to separate hydrocarbons from water phases such as oil removal from produced water. They have been also used in pyrolysis gasoline (benzene) removal from quench water in ethylene plants, although in this application, the constant changing of cartridges can lead to operator exposure to BTX (benzene, toluene and xylene), as well as disposal issues and high operating costs from frequent replacement. | 0 | Colloidal Chemistry |
Suspensions of nanoparticles are possible since the interaction of the particle surface with the solvent is strong enough to overcome density differences, which otherwise usually result in a material either sinking or floating in a liquid. | 0 | Colloidal Chemistry |
In contradistinction with electrophoresis, motion of particle in homogeneous electric field only, electrodiffusiophoresis occurs in the areas of the dispersion that experience concentration polarization due to, for instance, electrochemical reactions, see electrochemistry. There are concentration gradients in such areas that affect particles motion strongly. First of all they create inhomogeneity in the electric field. Secondly, they cause diffusiophoresis. This peculiarities of the particles motion in the areas subjected to the concentration polarization justifies introduction of the special term for this electrokinetic effect - electrodiffusiophoresis.
One of the most important differences of the electrodiffusioporesis from the electrophoresis is that exists as directed particles drift in the alternating electric field. Electrophoresis, in contrary, causes only particles oscillation on the same spot. This difference opens opportunities for important applications.
Electrodiffusiophoresis was theoretically predicted in 1980 - 82.
It was experimentally observed microscopically in 1982.
The first application of this effect was explanation of particles depositing at some distance from the surface of the ion selective membrane.
These earlier experiments and theory were described in the review published in 1990. This review presents also application of electrodiffusiophoresis for making bactericidal coatings.
This effect has attracted new attention in 2010 with regard to microfluidics. | 0 | Colloidal Chemistry |
Self-assembly is an equilibrium process, i.e. the individual and assembled components exist in equilibrium. In addition, the flexibility and the lower free energy conformation is usually a result of a weaker intermolecular force between self-assembled moieties and is essentially enthalpic in nature.
The thermodynamics of the self-assembly process can be represented by a simple Gibbs free energy equation:
where if is negative, self-assembly is a spontaneous process. is the enthalpy change of the process and is largely determined by the potential energy/intermolecular forces between the assembling entities. is the change in entropy associated with the formation of the ordered arrangement. In general, the organization is accompanied by a decrease in entropy and in order for the assembly to be spontaneous the enthalpy term must be negative and in excess of the entropy term. This equation shows that as the value of approaches the value of and above a critical temperature, the self-assembly process will become progressively less likely to occur and spontaneous self-assembly will not happen.
The self-assembly is governed by the normal processes of nucleation and growth. Small assemblies are formed because of their increased lifetime as the attractive interactions between the components lower the Gibbs free energy. As the assembly grows, the Gibbs free energy continues to decrease until the assembly becomes stable enough to last for a long period of time. The necessity of the self-assembly to be an equilibrium process is defined by the organization of the structure which requires non-ideal arrangements to be formed before the lowest energy configuration is found.
Kinetics
The ultimate driving force in self-assembly is energy minimization and the corresponding evolution towards equilibrium, but kinetic effects can also play a very strong role. These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome in, for example, the formation of block copolymers.
Amphiphile self-assembly is an essential bottom-up approach of fabricating advanced functional materials. Self-assembled materials with desired structures are often obtained through thermodynamic control. Here, we demonstrate that the selection of kinetic pathways can lead to drastically different self-assembled structures, underlining the significance of kinetic control in self-assembly. | 0 | Colloidal Chemistry |
Shannon has about 164 publications that, together, have received over 77 thousand citations. His work on ionic radii of ions has drawn particularly wide attention. In a 2014 Nature paper his 1976 work on the ionic radii of ions was recognized as the 22d most cited paper in all of science. It is also been cited as the highest formally-cited database of all time.
He has a number of patents on glass compositions, zeolite catalysts, noble-metal oxide, electrodes, and chemical compounds. | 1 | Solid-state chemistry |
Albert married Catherine Robson in Cambridge in 1940. They had two children: Naomi, born in 1944 and a son, William Neil, known as Neil. Naomi was killed in a car crash in the USA in 1966.
Catherine died of cancer 14 November 1963. Two years later, on 10 December 1965 Alexander married Gisela Gudrum Baker (née Zutavern, of Heidelberg), the widow of Kingsley Ferguson Baker, a Sydney industrial chemist, at the Presbyterian Church in Pymble. Stricken by a brain tumour in 1969 when serving as dean of science, he died at his Mosman home on 23 May 1970 and was cremated. His wife, and the son of his first marriage, survived him. The Pymble Church “was packed by friends, colleagues, and students on 26 May for a funeral service during which a moving panegyric was spoken by Professor I.G. Ross”.
One obituary summed up Alexander the man thus: | 0 | Colloidal Chemistry |
The figures, in high relief form a circle around the shaft of the elephant tusk, supporting the bowl at top used to hold the salt. The amount and type of decoration indicates that this piece was created in a Benin court. Two of the four male figures are from clearly of a higher rank, probably from a higher class. They are more elaborately carved and shown frontally, while the other two have less ornament and are shown in profile. The men on the front and on the back are dressed with elaborate clothes with a cross necklace, showing they are European Christians. In addition they are wearing hats and holding spears in their left hand.
The style used to carve the ivory piece may be intended to be somewhat grotesque. In Afro-Portuguese ivories there are three African elements that are fundamental to call a piece African art: a focus on the human figure, an enunciation of the parts and a preference for pure geometric forms. Individuals are presented as the main subject in African art usually depicting an important figure like royalty or a deity, this is shown in the ivory salt cellar and other Benin Bronzes. The faces of each man are bigger with their long beards and deep eyes than their body while keeping their proportions in check. The geometry of the pattern of the men's clothing, the socket of the spear is another example where this geometry is repeated. | 1 | Solid-state chemistry |
The Tobacco and Salt Museum (Japanese:たばこと塩の博物館) is located in Sumida-ku, Tokyo. It was established in 1978 and is run by Japan Tobacco. The museum was originally located in Shibuya but, in 2015, it was relocated to Sumida. The museum has about 38,000 artifacts that show the history of tobacco and salt both from Japan and overseas. It holds a 1.4 tonne block of rock salt from Poland along with other blocks of rock salts that have been brought from various parts of world. There is a replica of a Mayan shrine from South America to show where tobacco was first used.
The museum also has a workshop room, a reading room and a museum shop. | 1 | Solid-state chemistry |
The most commonly seen environmental sensitivity in hydrogels is a response to temperature. Many polymers/hydrogels exhibit a temperature dependent phase transition, which can be classified as either an upper critical solution temperature (UCST) or lower critical solution temperature (LCST). UCST polymers increase in their water-solubility at higher temperatures, which lead to UCST hydrogels transitioning from a gel (solid) to a solution (liquid) as the temperature is increased (similar to the melting point behavior of pure materials). This phenomenon also causes UCST hydrogels to expand (increase their swell ratio) as temperature increases while they are below their UCST. However, polymers with LCSTs display an inverse (or negative) temperature-dependence, where their water-solubility decreases at higher temperatures. LCST hydrogels transition from a liquid solution to a solid gel as the temperature is increased, and they also shrink (decrease their swell ratio) as the temperature increases while they are above their LCST.
Applications can dictate for diverse thermal responses. For example, in the biomedical field, LCST hydrogels are being investigated as drug delivery systems due to being injectable (liquid) at room temp and then solidifying into a rigid gel upon exposure to the higher temperatures of the human body. There are many other stimuli that hydrogels can be responsive to, including: pH, glucose, electrical signals, light, pressure, ions, antigens, and more. | 0 | Colloidal Chemistry |
Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is one of a family of chemical compounds and minerals with the approximate formula . Iron sulfides are often iron-deficient non-stoichiometric. All are black, water-insoluble solids. | 1 | Solid-state chemistry |
Nanoclusters are atomically precise, crystalline materials most often existing on the 0-2 nanometer scale. They are often considered kinetically stable intermediates that form during the synthesis of comparatively larger materials such as semiconductor and metallic nanocrystals. The majority of research conducted to study nanoclusters has focused on characterizing their crystal structures and understanding their role in the nucleation and growth mechanisms of larger materials.
Materials can be categorized into three different regimes, namely bulk, nanoparticles and nanoclusters. Bulk metals are electrical conductors and good optical reflectors and metal nanoparticles display intense colors due to surface plasmon resonance. However, when the size of metal nanoclusters is further reduced to form a nanocluster, the band structure becomes discontinuous and breaks down into discrete energy levels, somewhat similar to the energy levels of molecules. This gives nanoclusters similar qualities as a singular molecule and does not exhibit plasmonic behavior; nanoclusters are known as the bridging link between atoms and nanoparticles. Nanoclusters may also be referred to as molecular nanoparticles. | 0 | Colloidal Chemistry |
Sodium ethyl xanthate is used in the mining industry as flotation agent for recovery of metals, such as copper, nickel, silver or gold, as well as solid metal sulfides or oxides from ore slurries. This application was introduced by Cornelius H. Keller in 1925. Other applications include defoliant, herbicide, and an additive to rubber to protect it against oxygen and ozone.
In 2000, Australia produced up to 10,000 tonnes of sodium ethyl xanthate and imported about 6,000 tonnes, mostly from China. The material produced in Australia is the so-called liquid sodium ethyl xanthate that refers to a 40% aqueous solution of the solid. It is obtained by treating carbon disulfide with sodium hydroxide and ethanol. Its density is 1.2 g/cm and the freezing point is −6 °C. | 1 | Solid-state chemistry |
In the intermediate region between Stokes drag and Newtonian drag, there exists a transitional regime, where the analytical solution to the problem of a falling sphere becomes problematic. To solve this, empirical expressions are used to calculate drag in this region. One such empirical equation is that of Schiller and Naumann, and may be valid for : | 0 | Colloidal Chemistry |
After completion of his graduate studies, Rao returned to Bangalore in 1959 to take up a lecturing position, joining IISc and embarking on an independent research program. The facility at the time was so meagre that he described it, saying, "You would get string and sealing wax and thats about it." In 1963 he accepted a permanent position in the Department of Chemistry at the Indian Institute of Technology Kanpur. He was elected Fellow of the Indian Academy of Sciences in 1964. He returned to IISc in 1976 to establish a solid state and structural chemistry unit. and became director of the IISc from 1984 to 1994. At various points in his career Rao has taken appointments as a visiting professor at Purdue University, the University of Oxford, the University of Cambridge and University of California, Santa Barbara. He was the Jawaharlal Nehru Professor at the University of Cambridge and Professorial Fellow at the Kings College, Cambridge during 1983–1984.
Rao has been working as the National Research Professor holding the positions Linus Pauling Research Professor and Honorary President of Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, which he founded in 1989. He had served as chair of the Scientific Advisory Council to the Indian Prime Minister for two terms, from 1985 to 1989 and from 2005 to 2014. He is also the director of the International Centre for Materials Science (ICMS), which he founded in 2010, and serves on the board of the Science Initiative Group. | 1 | Solid-state chemistry |
Their tendency to form host–guest complexes is key to the molecular machines recognized by the 2016 Nobel Prize in Chemistry.
Viologens are used in the negative electrolytes of some experimental flow batteries. Viologens have been modified to optimize their performance in such batteries, e.g. by incorporating them into redox-active polymers.
Viologen catalysts have been reported to have the potential to oxidize glucose and other carbohydrates catalytically in a mildly alkaline solution, which makes direct carbohydrate fuel cells possible. | 1 | Solid-state chemistry |
Titanium(II) oxide (TiO) is an inorganic chemical compound of titanium and oxygen. It can be prepared from titanium dioxide and titanium metal at 1500 °C. It is non-stoichiometric in a range TiO to TiO and this is caused by vacancies of either Ti or O in the defect rock salt structure. In pure TiO 15% of both Ti and O sites are vacant, as the vacancies allow metal-metal bonding between adjacent Ti centres. Careful annealing can cause ordering of the vacancies producing a monoclinic form which has 5 TiO units in the primitive cell that exhibits lower resistivity. A high temperature form with titanium atoms with trigonal prismatic coordination is also known. Acid solutions of TiO are stable for a short time then decompose to give hydrogen:
:2 Ti(aq) + 2 H(aq) → 2 Ti(aq) + H(g)
Gas-phase TiO shows strong bands in the optical spectra of cool (M-type) stars. In 2017, TiO was claimed to be detected in an exoplanet atmosphere for the first time; a result which is still debated in the literature. Additionally, evidence has been obtained for the presence of the diatomic molecule TiO in the interstellar medium. | 1 | Solid-state chemistry |
Eigencolloid is a term derived from the German language (eigen: own) and used to designate colloids made of pure phases. Also known as intrinsic colloids.
Eigencolloids are metal oxyhydroxide colloids on the nanometer scale formed by aggregation of hydrolyzed metal ions. They are characterized by a very large specific surface area (up to 2000 m/g) and a high reactivity. They hold promise for the development of new industrial catalysts.
Many such colloids are formed by the hydrolysis of heavy metals cations or radionuclides, such as, for example, Tc(OH), Th(OH), U(OH), Pu(OH), or Am(OH).
The term eigencolloid or intrinsic colloid, is often used in distinction to a pseudocolloid. A pseudocolloid is one in which elements (colloids or cations) become adsorbed onto pre-existing groundwater colloids due to their affinity to these colloids or to the hydrophobic properties of the dispersing medium.
In environmental chemistry, enhanced migration of heavy metal and radioactive metal contaminants in ground and surface waters is often facilitated by eigencolloid formation. | 0 | Colloidal Chemistry |
Nanoparticles were used by artisans since prehistory, albeit without knowledge of their nature. They were used by glassmakers and potters in Classical Antiquity, as exemplified by the Roman Lycurgus cup of dichroic glass (4th century CE) and the lusterware pottery of Mesopotamia (9th century CE). The latter is characterized by silver and copper nanoparticles dispersed in the glassy glaze. | 0 | Colloidal Chemistry |
Block copolymers are interesting because they can "microphase separate" to form periodic nanostructures,[13][14][15] Microphase separation is a situation similar to that of oil and water. Oil and water are immiscible - they phase separate. Due to incompatibility between the blocks, block copolymers undergo a similar phase separation. Because the blocks are covalently bonded to each other, they cannot demix macroscopically as water and oil. In "microphase separation" the blocks form nanometer-sized structures. | 0 | Colloidal Chemistry |
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed.
In industrial processes, foams pose serious problems. They cause defects on surface coatings and prevent the efficient filling of containers. A variety of chemical formulae are available to prevent formation of foams. | 0 | Colloidal Chemistry |
Nanoparticle tracking analysis (NTA) is a method for visualizing and analyzing particles in liquids that relates the rate of Brownian motion to particle size. The rate of movement is related only to the viscosity and temperature of the liquid; it is not influenced by particle density or refractive index. NTA allows the determination of a size distribution profile of small particles with a diameter of approximately 10–1000 nanometers (nm) in liquid suspension.
The technique is used in conjunction with an ultramicroscope and a laser illumination unit that together allow small particles in liquid suspension to be visualized moving under Brownian motion. The light scattered by the particles is captured using a CCD or EMCCD camera over multiple frames. Computer software is then used to track the motion of each particle from frame to frame. The rate of particle movement is related to a sphere equivalent hydrodynamic radius as calculated through the Stokes–Einstein equation. The technique calculates particle size on a particle-by particle basis, overcoming inherent weaknesses in ensemble techniques such as dynamic light scattering. Since video clips form the basis of the analysis, accurate characterization of real time events such as aggregation and dissolution is possible. Samples require minimal preparation, minimizing the time required to process each sample. Speculators suggest that eventually the analysis may be done in real-time with no preparation, e.g. when detecting the presence of airborne viruses or biological weapons.
NTA currently operates for particles from about 10 to 1000 nm in diameter, depending on particle type. Analysis of particles at the lowest end of this range is possible only for particles composed of materials with a high refractive index, such gold and silver. The upper size limit is restricted by the limited Brownian motion of large particles; because a large particle moves very slowly, accuracy is diminished. The viscosity of the solvent also influences the movement of particles, and it, too, plays a part in determining the upper size limit for a specific system. | 0 | Colloidal Chemistry |
* Materials Science and Engineering in the United States: Proceedings (1970, contributor), Pennsylvania State University Press, .
* Materials Science and Engineering Serving Society (1998, with others), Elsevier Science, .
* The Interdisciplinary Imperative: Interactive Research and Education, Still an Elusive Goal in Academia (2000), Writers Club Press, . | 1 | Solid-state chemistry |
Eigencolloid formation occurs readily in groundwater upon storage of radioactive waste. Colloid-facilitated transport is a mechanism responsible for the mobilisation of radionuclides into the wider environment, causing radioactive contamination. This is a public health concern, since elevated radioactivity in the environment is mutagenic and can lead to cancer.
Eigencolloids have been implicated in the long-range transport of plutonium on the Nevada Test Site. | 0 | Colloidal Chemistry |
Uranium dioxide is carbonized in contact with carbon, forming uranium carbide and carbon monoxide.
This process must be done under an inert gas as uranium carbide is easily oxidized back into uranium oxide. | 1 | Solid-state chemistry |
The JTE is usually stronger where the electron density associated with the degenerate orbitals is more concentrated. This effect therefore plays a large role in determining the structure of transition metal complexes with active internal 3d orbitals.
The most iconic and prominent of the JT systems in coordination chemistry is probably the case of Cu(II) octahedral complexes. While in perfectly equivalent coordination, like a CuF complex associated to a Cu(II) impurity in a cubic crystal like KMgF, perfect octahedral (O) symmetry is expected. In fact a lower tetragonal symmetry is usually found experimentally. The origin of this JTE distortion it revealed by examining the electronic configuration of the undistorted complex. For an octahedral geometry, the five 3d orbitals partition into t and e orbitals (see diagram). These orbitals are occupied by nine electrons corresponding to the electronic configuration of Cu(II). Thus, the t shell is filled, and the e shell contains 3 electrons. Overall the unpaired electron produces a E state, which is Jahn–Teller active. The third electron can occupy either of the orbitals comprising the e shell: the mainly orbital or the mainly orbital. If the electron occupies the mainly level, which antibonding orbital the final geometry of the complex would be elongated as the axial ligands will be pushed away to reduce the global energy of the system. On the other hand, if the electron went into the mainly antibonding orbital the complex would distort into a compressed geometry. Experimentally elongated geometries are overwhelmingly observed and this fact has been attributed both to metal-ligand anharmonic interactions and 3d-4s hybridisations. Given that all the directions containing a fourfold axis are equivalent the distortion is equally likely to happen in any of these orientations. From the electronic point of view this means that the and orbitals, that are degenerate and free to hybridise in the octahedral geometry, will mix to produce appropriate equivalent orbitals in each direction like or .
The JTE is not just restricted to Cu(II) octahedral complexes. There are many other configurations, involving changes both in the initial structure and electronic configuration of the metal that yield degenerate states and, thus, JTE. However, the amount of distortion and stabilisation energy of the effect is strongly dependent on the particular case. In octahedral Cu(II), the JTE is particularly strong because
# the degenerate orbitals display a strongly antibonding σ character
# Cu is a transition metal with a relatively strong electronegativity yielding more covalent bonds than other metals which allows to increase the JT linear coupling constant.
In other configurations involving π or δ bonding, like for example when the degenerate state is associated to the t orbitals of an octahedral configuration, the distortion and stabilisation energies are usually much smaller and the possibility of not observing the distortion due to dynamic JT effects is much higher. Similarly for rare-earth ions where covalency is very small, the distortions associated to the JTE are usually very weak.
Importantly, the JTE is associated with strict degeneracy in the electronic subsystem and so it cannot appear in systems without this property. For example, the JTE is often associated to cases like quasi-octahedral CuXY complexes where the distances to X and Y ligands are clearly different. However, the intrinsic symmetry of these complexes is already tetragonal and no degenerate e orbital exists, having split into a (mainly ) and b (mainly ) orbitals due to the different electronic interactions with axial X ligands and equatorial Y ligands. In this and other similar cases some remaining vibronic effects related to the JTE are still present but are quenched with respect to the case with degeneracy due to the splitting of the orbitals. | 1 | Solid-state chemistry |
Stephanie Lee Brock is an American chemist who is professor of inorganic chemistry at Wayne State University. Her research considers transition metal pnictides and chalcogenide nanomaterials. She is a Fellow of the American Association for the Advancement of Science and the American Chemical Society. | 1 | Solid-state chemistry |
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