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.