Indium tin oxide (ITO) coated slides and gold-coated slides were obtained from Sigma-Aldrich and NanoCS. p-phenylenediamine was recrystallized from boiling water containing decolorized carbon and dried in a dessicator containing anhydrous calcium chloride pellets. 18MΩ water from a central lab system was used in all applications requiring water. HPLC-grade acetonitrile and dichloromethane were stored over 4A molecular sieves. Unless otherwise stated, chemical reagents were obtained from Fisher Scientific and used as received.