Morphology engineering, room-temperature photoluminescence behavior, and sunlight photocatalytic activity of V2O5 nanostructures

V2O5 nanostructures of nanoparticles (NPs), nanorods (NRs), nanowires (NWs), and nanospheres (NSs), were prepared by hydrothermal and chemical reaction methods. Their morphology, structures, oxidation states, room temperature photoluminescence (PL) properties, and photocatalytic activity were then investigated. The morphology measurements showed well-shape nanostructures, the X-ray diffraction (XRD) and Raman results revealed that all nanostructures had an alpha-V2O5 phase with an orthorhombic structure. A large increase of the V4+ oxidation state in NSs compared to the other nanostructures was observed by X-ray photoelectron spectroscopy (XPS) measurements and confirmed by Raman spectroscopy. The results show that a larger number of V4+ oxidation states of V2O5 NSs strongly enhanced PL intensity compared with other structures that showed weak PL. In particular, V2O5 NSs showed intense ultraviolet (UV) PL near 395 nm (3.14 eV) due to strong excitation by UV light, while this PL peak was not observed from other nanostructures. A large amount of charge separation in V2O5 NSs and the large surface contact area in V2O5 NPs result in more efficient photocatalytic activity from these nanoparticles than from V2O5 NRs and NWs.