Coupling real-time surface-enhanced raman spectroscopy with linear-sweep voltammetry : Application to elucidation of electrochemical mechanisms

The broad-based utilization of real-time surface-enhanced Raman spectra, obtained by using an intensified diode-array detector, to examine interfacial redox transformations under cyclic voltammetric conditions is exemplified for the oxidation at gold electrodes of irreversibly adsorbed benzidine and the reduction of adsorbed azoxybenzene. The first reaction, involving a pair of irreversible one-electron oxidation steps, enabled a quantitative comparison to be made between the extent of oxidation of the adsorbed layer during the potential sweep and the simultaneous spectral response. Although relatively slow (10–50 mV s^?1) sweeps are required in order to yield spectral sequences having a suitably narrow (?50 mV) potential interval, the spectral data acquisition requires only a single potential perturbation. This “single-shot” spectroelectrochemical approach, desirable for the examination of irreversible interfacial systems, differs from conventional time-resolved methods that involve signal integration over numerous repetitive perturbations.