Flake-like nanocrystalline V4O9 has been successfully synthesized by solvothermal process using V2O5 as vanadium source and phenolphthalein as a reducing agent and a structure-directing template. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-vis) spectroscopy have been used to characterize the structure, the morphology and the composition of the material. The photocatalytic activity of the material has been evaluated by the degradation of methylene blue under visible light irradiation. As a result, after the lapse of 150 min, around 93.54% bleaching was observed, with V4O9 nanoflakes yielding more photodegradation compared to that of bulk V2O5. This presents a degradation percentage of about 44.67%. (c) 2012 Elsevier Ltd. All rights reserved.