A SERS study of thiocyanate adsorption on Au-core Pd-shell nanoparticle film electrodes

We have systematically studied the adsorption of thiocyanate (SCN−) on gold-core palladium-shell nanoparticles (Au@Pd NPs) with different Pd shell thicknesses by surface-enhanced Raman scattering (SERS). When the Pd shell thickness is increased from one to ten atomic layers, the νCN stretching frequency increases 6 cm−1 for S-bound SCN− and 10 cm−1 for N-bound SCN−. It infers that the CN stretching frequency is quite sensitive to electronic properties of the NP surface, but even more so when bonding to Pd occurs through the N atom (at negative potentials) than when it occurs through the S atom (at positive potentials). Data for a second probe, p-aminothiophenol (PATP), was compared to that of SCN−; however, PATP was found to be less sensitive than SCN− to the surface electronic properties of Au@Pd NPs.