Solvent/Electrolyte Control of the Wall Thickness of Template-Synthesized Nanostructures

We study the morphology of polythiophene nanostructures synthesized by templated electrochemical oxidation of thiophene from different solvent/electrolyte systems. We find that the wall thickness of such nanostructures is greatly influenced by the choice of solvent/electrolyte. The role of solvent/electrolyte is related to the rate of polymerization. Solvent/electrolyte systems that increase the rate of thiophene polymerization yield solid nanowires, whereas systems that decrease the rate of polymerization yield thin-wall nanotubes. A solvent/electrolyte system that leads to an intermediate polymerization rate yields intermediate structures, namely thick wall nanotubes. These observations are explained by the thiophene electrochemical polymerization mechanism, which requires the loss of a proton, and thus the acidity or basicity of the solvent/electrolyte can be used to control the reaction rate.