Multiwavelength Raman spectroelectrochemical study of poly(N-methylaniline): An overview

Raman spectroscopic study of poly(N-methylaniline) as a thin layer deposited at a electrode was performed in an electrochemical system. A broad range of Raman excitation wavelengths from UV (325 nm) through blue (442 nm) and red (633 nm) to NIR (785 nm) were used. Two limiting redox forms, a reduced (leucoemeraldine) and a fully oxidized one, were considered as obtained at controlled electrochemical potential conditions, and two solution pH of 2.0 and 8.0 were selected to ensure the existence of protonated and deprotonated forms. The Raman spectra obtained and discussed show a strong enhancement for the reduced form at UV and blue laser line excitations, whereas the Raman enhancement for an oxidized form was observed for red and NIR laser line excitations. The main Raman features for the combinations of the reduced and oxidized, and protonated or deprotonated states of poly(N-methylaniline) were analyzed and compared.