Strong Core@Shell Dependence in Surface-Enhanced Raman Scattering of Pyridine on Stable 13-Atom Silver-Caged Bimetallic Clusters

On the basis of calculations using time-dependent density functional theory, we conducted detailed analyses of the surface-enhanced Raman scattering (SERS) of pyridine adsorbed on 13-atom icosahedral M@Au12 and M@Ag12 (M = Mo, W) clusters in this article. Surprisingly, we find that, although the SERS enhancements for all complexes can reach the order of 104, the signals of pyridine on M@Ag12 at charge transfer (CT) transition excitations are twice as much as that of pyridine on M@Au12, and the corresponding energies used for SERS excitations are significantly different in the low-energy region of 1.63–2.10 eV. The interactive modulation between the core and shell can produce varying strong CT transitions from metal clusters to pyridine, which tunes the SERS enhancements with altered optical properties. The complexes of pyridine on silver-caged clusters are more easily influenced by the tunability of the core than that of pyridine on gold-caged clusters. Our analyses are expected to provide a theoretical basis for experimentally synthesizing multicomponent SERS substrates and exploring the dependence of SERS enhancement on the synergies between the different components in core@shell binary metal clusters.