Vanadium pentoxide decorated with gold as a reliable platform for surface-enhanced Raman spectroscopy

Although semiconductor materials such as vanadium pentoxide (V₂O₅) are promising non-plasmonic substrates for surface-enhanced Raman scattering (SERS) spectroscopy, their broader use is still hampered by their relatively low SERS enhancement. One strategy to overcome this limitation is to combine these materials with plasmonic noble metallic nanostructures. In this study, we investigate this approach for thin V₂O₅ nanostructural film decorated with Au (V₂O₅/Au) fabricated by sputter deposition and combined with thermal annealing. We found that SERS enhancement arises from both electromagnetic and chemical (charge-transfer) enhancement as well as it benefits from the morphology of the Au layer. The presence of the continuous Au film leads to a tremendous enhancement of the SERS signal of methylene blue (MB) as compared with Au-free V₂O₅ substrates. Under optimised conditions (an Au deposition time of 240 s), the SERS enhancement caused by the Au layer was found to be 1200-fold. Furthermore, spectral mapping across the V₂O₅/Au substrates shows that the relative standard deviation (RSD) of the SERS signal is less than 35 %, i.e., still sufficiently low for reliable detection. Finally, we successfully applied V₂O₅/Au substrates for sensitive detection of 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)porphine (TMPyP), and 2,2'-bipyridine (BPy).