Engineering SERS via absorption control in novel hybrid Ni/Au nanovoids

Nanoscale voids (or 'anti-nanoparticles') embedded in gold films possess plasmon modes with a strong field component at the cavity entrance, radically different to nanoparticle plasmon modes. By creating Ni/Au hybrid rim nanostructures we show how selective coupling to void plasmons provides strong electric field enhancements leading to large surface-enhanced Raman scattering (SERS) signals from molecules adsorbed on the nanovoid film. Since the rim plasmon modes are relatively independent of the supporting void material these results pave the way for hybrid nanovoid structures which combine plasmonic and catalytic properties of the constituent materials in a controllable and reproducible way.