UV Irradiation-Induced SERS Enhancement in Randomly Distributed Au Nanostructures.

Currently used platforms for surface-enhanced Raman scattering (SERS) sensors generally employ metallic nanostructures for enrichment of the plasmonic hotspots in order to provide higher Raman signals, but this procedure is still considered challenging for analyte-surface affinity. This study reports a UV irradiation-induced SERS enhancement that amplifies the interactions between the analytes and metallic surfaces. The UV light can play critical roles in the surface cleaning to improve the SERS signal by removing the impurities from the surfaces and the formation of the negatively charged adsorbed oxygen species on the Au surfaces to enhance the analyte-surface affinity. To evaluate this scenario, we prepared randomly distributed Au nanostructures via thermal annealing with a sputtered Au thin film. The UV light of central wavelength 254 nm was then irradiated on the Au nanostructures for 60 min. The SERS efficiency of the Au nanostructures was subsequently evaluated using rhodamine 6G molecules as the representative Raman probe material. The Raman signal of the Au nanostructures after UV treatment was enhanced by up to approximately 68.7% compared to that of those that did not receive the UV treatment. We expect that the proposed method has the potential to be applied to SERS enhancement with various plasmonic platforms.