In situ investigations on the electrochemical polymerization and properties of polyaniline thin films by surface plasmon optical techniques

The combination of in situ surface plasmon resonance spectroscopy (SPS) and surface plasmon field-enhanced light scattering (SPLS) with an electrochemical method was used to simultaneously investigate the optical and electrochemical properties of polyaniline films on a planar gold electrode. First, the electropolymerization process of aniline and then the doping-dedoping process of the resulting polyaniline film were investigated using SPS and SPLS. The electropolymerization of aniline was achieved by applying a cycling potential known from cyclic voltammetry. Potential cycling resulted in distinct oscillations sensitively monitored with both techniques. Information was obtained on the change of the dielectric constant of the film and of the film thickness, corresponding to morphology transitions of the polyaniline film. The time-differential SPS kinetic reflectivity curve was correlated with cyclic voltammetry. SPLS was also applied in a reversed attenuated total reflection configuration to obtain more correlation with the electrochemical behavior and optical properties of the polyaniline film. Thus, this combination of experimental approaches allows for the simultaneous elucidation of optical and electrochemical properties of an ultrathin conducting polymer film.