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.

► We found the shell-thickness dependent vibrational frequencies of thiocyanate adsorbed on Au@Pd Nanoparticles by using SERS. The CN stretching frequency is quite sensitive to electronic properties of the NP surface. The electronic structure is dependent on Pd shell thickness because of the ligand effects and geometrical effects. The N-bound thiocyanate is more sensitive to electronic structure than the S-bound.