Layer-by-layer films of enzymatically synthesized poly(aniline)/bacterial poly(γ-glutamic acid) for the construction of nanocapacitors

Poly(aniline) (PANi) and poly(γ-glutamic acid) (γ-PGA) have been synthesized by enzymatic catalysis and natural bacterial reactions, respectively. Layer-by-layer films have been prepared on glass or quartz slides by alternative immersions of the substrate in dilute solutions of γ-PGA and PANi, with several rinsing in between each deposition. UV–vis spectroscopy has been used to follow the evolution of the self-assembly process as well as to characterize the oxidative states of PANi. The linear dependence of the absorbance vs. the number of layers indicates a constant increase of thickness layer-by-layer. The morphology of the multilayer films, analyzed by atomic force microscopy, is granular type. Enzymatically synthesized PANi nanofilms present good electrical conductivity while γ-PGA acts as an insulating material. These differences in electrical properties and the possibility to obtain alternated multilayered films permit the construction of entirely “biological” nanocapacitors.