V-doped TiO2 nanoparticles (NPs) were synthesized by the sol-gel hydrolysis method using titanium butoxide (Ti(OBu)(4)) and vanadyl acetylacetonate (VO(acac)(2)) as the precursor and dopant, respectively. The effects of different V:Ti ratios on the crystal structure, bandgap energy, and photocatalytic activity were investigated. The photocatalytic activity of V-doped TiO2 NPs was evaluated by UV-vis absorption spectroscopy through the degradation of a methylene blue (MB) solution under visible light irradiation. The Raman spectra and X-ray diffraction patterns show that V was doped effectively, and oxygen vacancies and various defects or Ti3+ centers were formed. The results of energy dispersive X-ray analysis and X-ray photoelectron spectroscopy indicated the presence of V in the TiO2. The bandgap energy of 0.45% V-doped TiO2 NPs was determined to be 2.34 eV with a distinct red shift from 3.25 eV confirmed by diffuse reflectance spectroscopy. The photocatalytic activity of V-doped TiO2 NPs exhibited 2 times higher enhanced visible-light-induced photocatalytic performance compared to the pristine TiO2 NPs. (C) 2018 Elsevier B.V. All rights reserved.