Highly Sensitive and Spatially Homogeneous Surface-Enhanced Raman Scattering Substrate under Plasmon-Nanocavity Coupling

We fabricated a plasmon-nanocavity coupling structure composed of Au nanoparticles (Au-NPs), titanium dioxide, and Au-film (ATA) as a highly sensitive and spatially homogeneous surface-enhanced Raman scattering (SERS) substrate. The SERS intensity of the ATA was similar to 11 times higher than that of the Au-NPs/TiO2 substrates without cavity enhancement. This SERS enhancement was attributed to the remarkable near-field enhancement of Au-NPs under coupling with cavity resonance. Under the present experimental conditions, crystal violet (CV) molecule decorated ATA prepared from a concentration as low as 10(-7) mol/L could be detected, which is 1 order of magnitude higher sensitivity than the samples without cavities. More importantly, a spatially homogeneous SERS signal distribution of Raman mapping on the ATA was demonstrated over a 20 x 20 mu m(2) area on the sample, attributed to the homogeneous near-field distribution over the Au-NPs under coherent coupling between plasmon resonance and cavity resonance. We envision that this plasmon-nanocavity coupling SERS structure with high sensitivity, repeatability, and spatial homogeneity can be practically used in chemical and biomolecule detection devices.