Polyaniline–DNA microsphere formation by simple electropolymerization

Abstract

Polyaniline (PANI) microspheres were prepared by electrochemical polymerization. To obtain PANI having novel micro- and nanostructures, by the potential scan technique, aniline was electropolymerized in the presence of DNA using four polymerizing solutions containing different acids: H2SO4, C6H5SO3H, HClO4, and CF3COOH. The growth rate of the PANI film on the electrode surface decreased by the presence of DNA, suggesting that DNA interacted with the growing PANI molecules during the electropolymerization. The growth rate also depended on the type of acid, i.e., the anion, in the polymerizing solution and was in the order of SO42− > C6H5SO3− > ClO4− > CF3COO−, which significantly coincided with the reverse order of the Hofmeister series representing the lyophilicity of the anion. When aniline was electropolymerized in the CF3COOH polymerizing solution containing DNA, PANI microspheres were obtained without any templates. This PANI showed a sufficient redox activity in the less acidic solution in which the ordinary PANI has a slight redox activity. On the other hand, the electronic state of the PANI differed from the ordinary ones; a new absorption band was evident at 620 nm. The difference in the redox activity and electronic state suggested that the DNA molecules were incorporated in the PANI and electronically interacted with the PANI molecules.