Cyclic UV-Vis spectrovoltammetry of polyaniline

Polyaniline films deposited on indium-tin oxide (ITO) glass sheet electrodes were investigated by UV-Vis spectroelectrochemistry. A hysteresis in absorbance versus electrode potential profiles was found during cyclic potential sweeps for three characteristic absorbance bands of polyaniline. The hysteresis was shown to depend on the potential scan rate. Linear correlations were found between the electrode potential of absorbance half-intensity and the potential scan rate. From these relationships it is concluded that the growth rate of the absorbance of the main band in the red region of the spectrum during the anodic potential sweep is more sensitive to the potential scan rate than the decrease of the absorbance in the reverse cathodic scan. Thus, the coloration of polyaniline film proceeds slower during its anodic oxidation than its bleaching during the reverse cathodic reduction.