Crystalline and amorphous TiO2 particles have important potential applications in photocatalysis, structural ceramics, solar batteries and nanoglasses. Hence controlling the structure of TiO2 particles is of practical importance. Crystalline TiO2 particles are usually prepared by calcination of their amorphous precursor. Here a facile method was developed to control the structure of TiO2 particles at a low temperature. TiO2 particles were prepared by sal gel method; and it was found that during the washing process, the TiO2 particles washed with water are crystalline whereas the TiO2 particles washed with ethanol are amorphous. Further analyses indicate that ethanol washing may introduce an organic cover layer on the TiO2 particles which hinders the crystallization of amorphous TiO2 particles. Therefore, the structure of TiO2 particles, amorphous or crystalline (anatase), can be controlled just by changing the washing medium, water or ethanol. This method seems a common method for controlling the (amorphous or crystalline) structure of metal oxides and hydroxides and was verified in the preparation of ZrO2, FeO(OH), and Al(OH)(3) particles. (C) 2015 Elsevier B.V. All rights reserved.