Electropolymerization of Aniline onto Anodic WO3 Film: An Approach to Extend Polyaniline Electroactivity Beyond pH 7

Generally, the redox activity of polyaniline (PANI) can only be retained in acidic media at pH < 3. This high acidity requirement has been a large obstacle in many applications such as biosensor, marine antifouling, and anticorrosion. In this study, composite film systems of PANI and tungsten trioxide (WO 3 ) were fabricated by the electropolymerization of aniline onto anodic WO 3 film. For the first time, we found that the prepared PANI/WO 3 film possesses excellent electrochemical activity and cycling stability in neutral solutions. The morphology and composition of the PANI/WO 3 films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), whereas their electroactivity was evaluated by cyclic voltammetry. Particularly, the long-term stability of their electroactivity upon cycling was investigated in detail. The good electroactivity and high redox stability of the PANI/WO 3 films in neutral media can be ascribed to the intercalated H + ions into WO 3 film during electropolymerization of aniline. Moreover, the reduced electroactivity of the PANI/WO 3 films can be recovered readily by cyclic voltammetry in an acidic solution. This study provides a new method to tune the electroactivity of PANI beyond pH 7 and makes PANI a promising candidate for biosensors.