ELECTROCHEMICAL-BEHAVIOR AND CHARACTERIZATION OF POLYPYRROLE COPPER PHTHALOCYANINE TETRASULFONATE THIN-FILM - CYCLIC VOLTAMMETRY AND INSITU RAMAN-SPECTROSCOPIC INVESTIGATION

Cyclic voltammetry has shown that polypyrrole thin films (200-5000 Å thick) doped with copper phthalocyanine tetrasulfonate (PPy-CuPcTs) are electrochemically conducting in the negative potential range where polypyrrole (PPy) in the PPy-CuPcTs film exists as a neutral form. In situ Raman spectroscopy showed that ion transport in the PPy-CuPcTs film was carried out by small cations from the supporting electrolytes during the redox reaction of the PPy. The majority of the CuPcTs of the original doping level still remains in the film after the reduction of the PPy. Large cations, such as tetrabutylammonium and methyl viologen, showed strong effects on shifting the redox potential of the PPy thin-film electrodes. A very strong resonance Raman band at 1556 cm-1, which is due to the symmetric stretching of the C=C bond in the neutral form of PPy, disappeared when a PPy thin-film electrode was oxidized. Redox potentials of several PPy thin films formed with different anions were calculated by monitoring the intensity change of the 1556-cm-1 Raman band when the electrode potential was changed. The redox potentials obtained by this method are very close to those obtained by cyclic voltammetry. In situ Raman spectroscopy also showed that the ring portion of CuPcTs in the thinner PPy-CuPcTs film (200-1000 Å thick) is reduced and reoxidized in the negative potential range. A huge anodic current observed at the PPy-CuPcTs thin-film electrode in the presence of methyl viologen (MV) in the NaClO4 solution is due to the catalytic oxidation of a methyl viologen polymer [or (MV)ClO4 film] by an oxidized form of PPy. © 1990, American Chemical Society. All rights reserved.