Suggest some highly sensitive temperature sensor Currently I am using DHT11 in my project, but its not very sensitive, it is quite slow in detecting temperature changes. 

What sensor could I use that will be more sensitive?
You can use the LM35, is a Precision Centigrade Temperature Sensors with TO-92 package or SO-8 SMD package. 

Here is a tutorial of how to use.

Its very simple to use it.