The preparation of nano-sized TiO2 by titanium tetraisopropoxide (Ti(OiPr)4) via sol-gelmethod using acid as a catalyst is investigated and the optimized conditions concerning theproportional amount of acid, water, alcohol is established by XRD and SEM. The effect ofcalcination temperature on phase transformation of TiO2 (rutile, anatase and brookite) wasdetermined by XRD. The smallest grain size of TiO2 powder we have obtained is 25 nm foranatase at 400 ºC by controlling the acidity and the mole ratio of starting materials. Manuscript profile