Optical characterization of polypyrrole-polytungstate anion composite films

The polypyrrole (PPy)-polytungstate anion (H2W12O406-, PW) composite film formed by electrochemical polymerization was studied by two in situ optical methods: absorption spectroscopy and Raman spectroscopy. The PPy doped by chloride anions was also studied as a comparison. The potential dependence of the absorption band and the Raman shift indicates that the PPy-Cl film reduces in turn from the bipolaron-loaded PPy to the polaron-loaded PPy, and further to the neutral PPy with decrease of potential. The PPy-PW film does not, however, reach the neutral PPy even at a relatively low potential, where the reduction of tungsten ions of W(V1) to W(V) in the PW preferentially takes place.