Nanocrystalline TiO2 was prepared in the sol-gel method by hydrolysis of titanium (IV) isopropoxide (TIP) at the different pH: autogenic, pH = 10 (with ammonia solution) and pH = 3 (with acetic acid solution). The obtained materials were calcined at 400 degrees C. Time Resolved Microwave Conductivity (TRMC) analyses showed, that the highest lifetime of charge-carriers was obtained for sample prepared at pH = 10 calcined at 400 degrees C, which exhibited highly crystallised anatase phase and the lowest value of s potential. Preparation of TiO2 with an ammonia solution and its further calcination at 400 degrees C caused reduction of Ti4+ to Ti3+ in the bulk, narrowing of the band gap with formation of an extra band above the valence band of TiO2 assigned to formed NO22- species. Such prepared photocatalyst showed extended lifetime of free charges under UV irradiation in comparison with the other prepared samples and activity under visible light. (C) 2016 Elsevier Ltd. All rights reserved.