Polymer-modified electrodes as electrochromic material Part III. Formation of poly-N-vinylcarbazole films on transparent semiconductor ITO surfaces by electropolymerization of NVK in acetonitrile

Abstract

The electrochemical oxidation of N-vinylcarbazole (NVK) in CH3CN on a transparent indium tin oxide (ITO) electrode leads to the formation of poly-N-vinylcarbazole films the evolvement of which is followed in situ by parallel detection visible-UV absorption spectroscopy. The PNVK films obtained thereby are dark green (λmax=740 nm) resulting from the association of carbazolylium cation radicals with anions from the supporting electrolyte. For polarization at a constant potential (1.2 V/Ag), there is a linear relation between the absorbance and the amount of current consumed. In the presence of tetrabutylammonium perchlorate, this relation has a slope of 0.018 cm2 mC−1. The color of PNVK films can be bleached by electrochemical reduction. The contrast between the oxidized and reduced forms diminishes more or less rapidly according to the nature of the supporting salt in the course of polarization cycles with a linear variation of potential. Bleaching is more pronounced in the presence of tetrafluoroborate than in that of hexafluorophosphate or tetrabutylammonium perchlorate.