Highly Sensitive and Spatially Homogeneous Surface-Enhanced Raman Scattering Substrate under Plasmon–Nanocavity Coupling
Xiaoqian Zang, Xu Shi, Tomoya Oshikiri, Kosei Ueno, Yuji Sunaba, Keiji Sasaki, Hiroaki Misawa
Abstract
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 ∼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 × 20 μm2 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.