Self-organized electropolymerization of aniline on au (111) electrode in hydrochloric acid

The chemical identity of supporting electrolyte can affect the rate of oxidative polymerization of aniline and the structure of the produced polyaniline (PAN). While PAN molecules deposited on ordered gold electrodes are linear in sulfuric and perchloric acids, the situation in hydrochloric acid is yet to be characterized by scanning tunneling microscopy (STM). Although aniline molecules were adsorbed in disarray between 0.1 and 0.8 V (vs. reversible hydrogen electrode) in 0.5 M HCl + 30 mM aniline, they drifted toward nuclei formed preferentially at steps on the Au(111) electrode and self-assembled into highly organized PAN molecules upon anodization at E > 0.9 V. Shifting the potential from 0.9 to 0.6 V converted PAN molecules from the pernigraniline to emeraldine state, and an increase of the film's corrugation height. On Pt(111), aniline molecules were also adsorbed in disarray at E < 0.9 V, but anodization yielded winding PAN molecules in 0.5 M HCl + 3 mM aniline.