Template-free one-step electrochemical formation of polypyrrole nanowire array

Oriented polypyrrole nanowire (nanorod) array readily forms using one-step pyrrole electropolymerization without using a template. These nanostructures having diameter in the range of 40-120 nm are obtained by electrogenerating polypyrrole in the presence of jointly non-acidic and weak-acidic anions. The latter are essential, their presence leads to the formation of an overoxidized polypyrrole thin layer that surrounds the polypyrrole nanostructure base. This simple and convenient method allows direct polymer nanowire array fabrication on various conductive substrates, the length of nanostructures being controlled by the polymerization time. Finally, a reaction mechanism involving oxidation of pyrrole and water and polypyrrole overoxidation is discussed. (C) 2008 Elsevier B.V. All rights reserved.