In the present study, titanium dioxide nanoparticles were synthesized by sol-gel method, from various precursors in some solvents under different synthesis conditions such as solvent percent, water percent, reflux temperature, reflux time, sol drying method and calcination temperature. Structure, size, band gap and specific surface area of nanoparticles were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis reflectance spectroscopy (DRS) and BET analysis methods. The photocatalytic activity of TiO2 was evaluated in the photodegradation of C.I. Acid Red 27 as a model contaminant from textile industry under UV-C light irradiation. Results indicate that structure and photocatalytic activities are functions of precursor type, solvent type and other synthesis conditions. TiO2 nanoparticles synthesized in the presence of methanol as solvent and titanium (IV) isopropoxide as precursor under 3 h reflux at 80 degrees C with sol thermal drying and calcination temperature of 450 degrees C indicate high photocatalytic activity in comparison with TiO2-P25 (Degussa co.). (C) 2011 Elsevier B.V. All rights reserved.