SERS study of surface plasmon resonance induced carrier movement in Au@CuO core-shell nanoparticles.

A plasmon induced carrier movement enhanced mechanism of surface-enhanced Raman scattering (SERS) was investigated using a charge-transfer (CT) enhancement mechanism. Here, we designed a strategy to study SERS in Au@CuO nanoshell nanoparticles with different shell thicknesses. Among the plasmonically coupled nanostructures, Au spheres with CuO shells have been of special interest due to their ultrastrong electromagnetic fields and controllable carrier transfer properties, which are useful for SERS. Au@CuO nanoshell nanoparticles (NPs) with shell thicknesses of 48-56nm are synthesized that exhibit high SERS activity. This high activity originates from plasmonic-induced carrier transfer from Au@CuO to 4-mercaptobenzoic acid (MBA). The CT transition from the valence band (VB) of CuO to the second excited π-π* transition of MBA, and is of b electronic symmetry, which was enhanced significantly. The Herzberg-Teller selection rules were employed to predict the observed enhanced b symmetry modes. The system constructed in this study combines the long-range electromagnetic effect of Au NPs, localized surface plasmon resonance (LSPR) of the Au@CuO nanoshell, and the CT contribution to assist in understanding the SERS mechanism based on LSPR-induced carrier movement in metal/semiconductor nanocomposites.