Morphologically different TiO2 nanocrystals were prepared by oxidant-peroxo method (OPM) synthesis. Morphological characterization was performed with the use of field emission gun-scanning electron microscope, X-ray diffraction and low temperature N-2 adsorption. The photocatalytic behavior of synthesized TiO2 powders was studied in the reaction of Rhodamine B photodegradation in water. The trials showed that synthesis performed at pH value around 8 generated materials with higher photoactivities than at other pH values. Zeta potential, Fourier transform infrared spectroscopy. X-ray absorption near edge structure part of the absorption spectra, photoluminescence spectroscopy and high resolution-transmission electron microscopy measurements were performed to investigate why the materials had different photoactivities. Two dominant particle characteristics, which came from synthesis environment, interfered in the photoactivity of materials. These characteristics were surface hydroxylation, which had a positive effect on photocatalysis, and crystalline defects due to crystal growth, which had a deleterious effect on photocatalysis. Both characteristics increased with an increase in synthesis pH value. Dye degradation mechanism in water, an oxidation by hydroxyl radicals, was used to explain the different photoactivities and the optimum synthesis pH. (C) 2011 Elsevier B.V. All rights reserved.