Conducting Polymer Films: Effect of doping-dedoping by gas on their electroptical and sensing properties

N. Sarkar, A. Sarkar, R. Narizzano, S. Paddeu and C. Nicolini

Institute of Biophysics, University of Genova, Via Corso Europa 30, 16132 Genova, Italy.

Conducting polymers, polyaniline and poly-o-anisidine were synthesized by oxidative polymerization.^,1,2
Films of conducting polymers were fabricated by means of solution casting and the Langmuir-Blodgett techniques. The doping-dedoping of the films were done by HCl gas/ NH₃vapour and were investigated by UV-visible spectroscopy. The UV-visible spectra of doped polymer films showed the appearence of new peaks due to the formation of polarons in polymer system and original spectra was again achived after dedoping by NH₃. Therefore, the polymer films were readily obtained in doped-dedoped state and the conductivity of these films could be tuned by controlling gas exposure time. It was observed that the efficiency of doping on polymer films depend on their chemical structure and it was revealed that the efficiency of pure polyaniline film was less than that of poly-o-anisidine. From the conductivity study, it was observed that the I-V curve of POA casted film showed ohmic nature. Further, the LB film of POA was exposed to 0.1% v/v HCl gas (in nitrogen) to study its sensitivity and it was observed that the film responded to this lower concentration of gas within 5 minutes.

References:

1.	M.K. Ram, S. Carrara, S. Paddeu, E. Maccioni, C. Nicolini, Langmuir 1997, 13, 2760.
2.	S. Dogan, U. Akabulut, T. Yalcin, S. Suzer, L. Toppare. Synt. Met. 1999, 60, 27