Template Electropolymerization of Polypyrrole Nanostructures on Highly Ordered Pyrolytic Graphite Step and Pit Defects

Abstract

Polypyrrole nanostructures with diameters ≤ 10 nm have been electropolymerized using step and pit defects on highly ordered pyrolytic graphite (HOPG) as templates for electropolymerization. Step defects were naturally occurring, and pits were formed via oxidation of freshly cleaved surfaces of an HOPG wafer by heating at ≃640°C. Underpotential deposition of approximately ≃80 mV caused polypyrrole to form only on the step and pit edges of HOPG at and not on the basal plane. The size of these nanostructures could be controlled by limiting the pyrrole polymerization time at anodic potentials. Recent modeling results allow the morphology of the deposition to be inferred, and we find the electrochemical data consistent with wire-shaped growth for up to 30 s at constant potential, after which the growth changes morphology. Scanning tunneling microscopy data confirm this result. Preliminary studies show that these polypyrrole nanostructures can be removed by sonication.