V2O5 nanoparticle films as a platform for plasmon-free surface-enhanced Raman spectroscopy

Metal-oxide nanomaterials represent a promising and inexpensive alternative to plasmonic metallic nanostructures currently used for surface-enhanced Raman scattering (SERS) spectroscopy. They profit from a chemical enhancing mechanism, i.e., charge transfer between the adsorbed molecule and the substrate. In this study, SERS-active nanostructured films based on vanadium pentoxide (V2O5) are produced by the combination of gas-phase synthesis of nanoparticles followed by their thermal annealing, i.e., using a fully solvent- and linker-free procedure. The SERS performance of V2O5 nanoparticle films was found to be strongly linked with porosity and the appropriate crystalline structure adjusted by annealing. A Raman spectroscopy and X-ray diffraction revealed that V2O5 crystalline nanoparticles are formed only after the annealing at temperatures equal to or higher than 300 °C. Such produced V2O5 nanoparticle films allow for sensitive and reproducible detection of organic dyes (methylene blue, rhodamine 6G and crystal violet), while their SERS enhancement (analytical enhancement factor close to 103) is significantly higher as compared with magnetron sputtered and annealed V2O5 thin films. Our study represents an important step in designing novel plasmon-free SERS-active platforms with the aim of improving their stability and spectral reproducibility compared to other non-plasmonic and plasmonic ones.