Modulating electrochemical activity in polyaniline/titanium oxide hybrid nanostructured ultrathin films

Hybrid and nanostructured ultrathin films of polyaniline (PANI) were fabricated using combined layer-by-layer (LbL) and surface sol-gel (SSG) processing with titanium oxide (TiO_x) layers. This enabled modulation of the electrochemical and the doping-dedoping process of the electroactive conjugated polymer with respect to thickness, presence of another polyelectrolyte, and intercalation of the inorganic slabs. The structure, composition, and viscoelastic behavior were proven by UV-vis absorbance, FT-IR, XPS, and QCM-D measurements. Spectroelectrochemical behavior showed that the oxidative stability of the films brought about the nanostructure control of the LbL process. On the other hand, the presence of the inorganic layer resulted in preventing electron transfer based on quinoid to benzenoid, Q → B, transitions. Thus, pairing the LbL assembly and the SSG process yielded a highly ordered, tunable structure in which the electrochemical behavior was modulated and correlated with diffusion-related arguments (Cottrell equation) of a blocking effect of the sol-gel layer. Further studies will be made on evaluating possible applications in thin film battery and capacitor devices.