A comparative multiwavelength Raman spectroelectrochemical study of polyaniline: a review

A comparative Raman spectroelectrochemical study on polyaniline electrodeposited at a gold electrode was performed within the broad range of spectra excitation wavelengths from UV (325 nm) through blue (442 nm), green (532 nm), red (633 nm) to NIR (785 nm) laser lines. Two solutions of pH 2.0 and 8.0 were selected for protonated and deprotonated forms of polyaniline, and two limiting redox forms, a reduced (leucoemeraldine), and a fully oxidized one were taken into account. Raman spectra obtained and discussed reveal a strong enhancement of spectra for reduced form at a short wavelength excitation, and for oxidized form at red and NIR excitations. Raman features for all four polyaniline forms differing in protonation degree and redox state were analyzed and compared; excitation wavelength-dependent characteristic marker bands were suggested.