ELECTROCHEMICAL-BEHAVIOR OF POLYPYRROLE FILM POLYMERIZED IN INDIGO CARMINE SOLUTION

Electrochemical studies have been conducted to characterize polypyrrol e film prepared in indigo carmine solution, PPy(IC). The PPy(IC) film was found to be formed via an adsorbed layer of IC on the substrate el ectrode surface. No obvious nucleation process was observed during the film deposition. The electrochemical processes of PPy(IC) are mediate d by the entrapped IC in the film. It was found that the redox potenti al of the PPy(IC) film is dependent on the pH of the solution in the p H range of 0-9, and a stable cyclic voltammogram was obtained at pH va lues lower than 7. In an alkaline medium, however, the film loses its redox response quickly upon potential cycling resulting in a cation pe rmselective membrane. The PPy(IC) membrane with the bulky and multi-ch arged dopant was found to have cationic sensitivity but the film was n evertheless rather non-selective to cations.