The photocatalytic activity of various proportions of nickel-chromium-molybdenum-phosphorous (NixCr1-xMoxP1-xO4) oxides in the oxidation of thymol blue at pH 8.001 under both UV and visible light has been examined. The nano-size different compositions of NixCr1-xMoxP1-xO4 (where x = 0.1, 0.2, 0.3 and 0.4) photocatalyst were prepared by chemical solution decomposition (CSD) method and characterized with X-ray diffraction (XRD), UV-vis spectroscopy, Transmission Electron microscopy (TEM), specific surface area (Brunauer-Emmett-Teller (BET)), X-ray photoelectron spectroscopy (XPS) and ICP analysis. The variations of phase separation temperature with respect to the amount of different constituents have been studied. The average particle size of NixCr1-xMoxP1-xO4 (x = 0.1) was found to be 55 +/- 10 nm measured from Transmission Electron microscopy (TEM) and specific surface area (BET) is found to be similar to 72.85 m(2)/g. (c) 2008 Elsevier B.V. All rights reserved.