Potential-Modulated Attenuated Total Reflectance Spectroscopy on Adsorbed Films on Indium Tin Oxide

Potential modulated attenuated total reflectance (PM-ATR) spectroscopy is a novel technique that makes it possible to sensitively monitor spectroscopic changes in an adsorbed molecular film as a function of applied potential. Here, PM-ATR was used to study charge transfer processes in Prussian blue (PB) and cytochrome c (cyt c) films deposited on indium tin oxide (ITO) electrodes.The electron transfer rate of PB films determined by PM-ATR was found to be in good agreement with the rate determined by conventional cyclic voltammetry, which validates the optical technique.The relationship between molecular orientation and electron transfer in adsorbed cyt c monolayers was investigated using PM-ATR. The electron transfer rate measured using TM polarized light was four-fold greater than that measured using TE polarized light. These data are the first to correlate a distribution of molecular orientations with a distribution of electron transfer rates in a redox-active molecular film