Enhancing Surface-Enhanced Raman Scattering Intensity through Light Diffuse Reflection on Ag/ZnO Nanowire Arrays

In this study, we present a new strategy to enhance the intensity of surface-enhanced Raman scattering (SERS) signals by using three-dimensional aggregated silver nanoparticles (AgNPs) on the zinc oxide nanowire arrays (Ag/ZnO NWA). The ZnO NWA acts as a light-scattering substrate, providing multidirectional incident light and reflecting a portion of the Raman scattered light, resulting in an improved SERS signal intensity. The composite nanowire structure of the Ag/ZnO NWA was successfully fabricated, and 400 nm ZnO nanowires in the Ag/ZnO NWA exhibit optimal diffuse light reflection, resulting in a significant improvement of the SERS signal intensity. The SERS enhancement factor (EF) for the Ag/ZnO NWA was determined to be EF (ISERS/NSERS)/(IRaman/NRaman) = 3.5 × 106. This substrate generated a ∼7.9-fold increased SERS signal compared to the preaggregated AgNPs in the absence of the ZnO NWA. The detection limit of the Ag/ZnO NWA was estimated by measuring SERS spectra of rhodamine B, enabling discrimination down to 10–15 M. Our approach inducing multidirectional diffuse reflection light to SERS hot spots provides a simple and efficient strategy to enhance SERS signal intensity, with broad implications for other spectroscopic applications.