Comparison of the surface properties of the assembled silver nanoparticle electrode and roughened silver electrode

Surface properties of an assembled silver nanoparticle/ITO (AAgNP/ITO) electrode and an electrochemically roughened Ag electrode were studied by surface-enhanced Raman spectroscopy and electrochemical techniques. Methyl viologen (MV) and p-aminothiophenol (PATP) were used as the probing molecules. The electrochemical results show that MV can be strongly adsorbed on the surface of the roughened Ag electrode but not on the surface of the AAgNP/ITO electrode. The SERS spectra further indicate that the MV molecules are adsorbed with parallel orientation to the surface of the roughened Ag electrode. The fact that no SERS spectrum was observed on the AAgNP/ITO electrode may imply that there are no required active sites on the surface of the isolated Ag nanoparticle for the interaction between the ring plane of MV and Ag nanoparticle. On the other hand, the SERS spectra of PATP reveal that PATP molecules can be adsorbed on the surfaces of both electrodes, because of the perpendicular orientation of the adsorbed molecules relative to the surface of the Ag nanoparticle on the electrodes. Nevertheless, changes in relative intensities of several a(1) and b(2) modes also indicate that there are slight differences in the orientation of the adsorbed PATP and the chemical property of the electrode surfaces.