Electrosorption of p-nitrobenzoic acid at a gold electrode in perchloric acid solutions studied by using cyclic voltammetry, EQCM, in situ FTIRS and Raman spectroscopy

Adsorption of p-nitrobenzoic acid (PNBA) at an Au electrode in 0.1 M HClO4 solutions has been studied by combining cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), in situ Fourier transform infrared spe ctroscopy (FTIRS) and surface enhanced Raman spectroscopy (SERS). The adsor ption of PNBA on Au electrode yields two current peaks appearing in the pot ential region between 0.3 and 1.0 V. A surface mass change of 74 ng cm(-2) has been determined by EQCM, corresponds to the adsorption, which associate s to a variation of surface concentration of 2.8 x 10(14) molecules cm(-2). The spectral features observed from studies of in situ FTIRS and SERS illu strated, at molecular level, the potential-dependence properties of PNBA ad sorption. The results demonstrated that the molecule of PNBA adsorbs in a R at mode at potentials below 0.3 V and that at higher potentials it trends t o adsorb in a vertical adsorption mode via its carboxylic group towards Au electrode surface. (C) 2000 Elsevier Science Ltd. All rights reserved.