Potential-Averaged Surface-Enhanced Raman Spectroscopy

Abstract

This paper describes a novel technique called potential-averaged surface-enhanced Raman spectroscopy (PASERS) which has several advantages over SERS. A PASERS spectrum is acquired when the electrode is rapidly modulated between two potentials by applying a square-wave voltage. The potential-averaged SERS spectrum contains all the information on the surface species at the two modulated potentials, and each individual SERS spectrum can then be extracted by deconvolution. By properly choosing the two modulating potentials, one can obtain SERS spectra of surface species at electrode potentials where SERS-active sites are normally unstable. PASERS also leads to a unique way of studying complex interfacial kinetic processes by controlling the voltage pulse height, frequency, and shape. Moreover, the measurement of time-resolved spectra in the very low vibrational frequency region can be achieved by PASERS with the use of a conventional scanning spectrometer with a single-channel detector. In this paper, the main advantages of PASERS are illustrated by studying two typical SERS systems, i.e., thiocyanate ion and thiourea adsorbed at silver electrodes, respectively. It is shown that the potential-averaging method can be applied as a common method to many other existing spectroelectrochemical techniques.