The book describe the synthesis of nanostructured conducting polyaniline using single and composite structure directing agents (SDA).The role of various structure directing agents on the nano dimension, morphology, optical and electrochemical switching properties of polyaniline has been illustrated. A method of insitu preparation of nanocomposite comprising of nano structured polyaniline, graphene and gold nano particles is described and electrodeposited film of the above composite in the development of bienzymatic cholesterol biosensor is also demonstrated.