TiO2 nanopowders have been synthesized from a peroxotitanium solution chemical bath route. The variation of H+ concentrations of the reaction solutions was measured during the course of the synthesis. X-ray diffraction analysis and transmission electron microscope observation showed that peroxotitanium concentration can affect the crystal type and morphology of the TiO2 nanopowders. The particle size of TiO2 nanopowders prepared from 0.1 mol L-1 peroxotitanium is 7.7 nm. The specific surface area of this nanopowder is 250 m(2) g(-1). Thermogravimetric analysis showed that the TiO2 nanopowder dried at 80 degrees C for 24h contains 11% water. (C) 2008 Elsevier B.V. All rights reserved.