In the present paper, pure phase and well-dispersed divanadium pentoxide nanoparticles (V2O5 NPs) with a orthorhombic structure were synthesized via the reverse microemulsion process and using low-cost NH4VO3 as the starting material in the absence of any co-surfactant. The synthetic method is facile, fast, low reaction temperature, environmental friendly, and easy controlled preparation condition. The structure, morphology and optical properties of these particles were characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential temperature analysis (DTA), fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible absorption spectroscopy (UV-Vis), and photoluminescence (PL) spectroscopy. The synthesized NPs were found to be fully crystalline and spherical in shape with uniform distribution. The mean crystallite size of the V2O5 NPs was estimated by X-ray powder diffraction pattern, which was in close agreement with the particles size obtained by TEM analysis. Optical properties of the nano-structured V2O5 are also tested and discussed. The band gap value of the V2O5 NPs is about 2.93 eV calculated by UV-Vis spectroscopy. Considerable emissions due to oxygen vacancies and band transition of PL peaks were observed. In addition, the photocatalytic activities of these particles were evaluated by photodegradation of toluidine blue O (TBO) dye under visible light irradiation. (C) 2013 Elsevier B.V. All rights reserved.