Probing the surface-enhanced Raman scattering properties of Au-Ag nanocages at two different excitation wavelengths.

The surface-enhanced Raman scattering (SERS) properties of bimetallic Au-Ag nanocages has been thoroughly investigated by changing the nanocage composition, localized surface plasmon resonance (LSPR) peak position and excitation wavelength. We found a significant dependency on excitation wavelength for the Au-Ag nanocages, independent of the underlying LSPR, which can be extended to other bimetallic SERS substrates. While it is well-understood that plasmon damping can occur for Au nanoparticles when their LSPR peaks are close to interband transition frequencies and thereby attenuate SERS intensities, this study probes an additional aspect and shows that SERS intensities are reduced when the excitation light source is near interband transition frequencies regardless of the LSPR location.