Effect of pH on the Formation of Amorphous TiO<sub>2</sub> Complexes and TiO<sub>2</sub> Anatase during Pyrolysis of Aqueous TiCl<sub>4</sub> Solution

The TiO2 nanostructures resulted by pyrolysis of TiCl4 at low temperature of 80 oC are found to be a mixture of amorphous TiO2 complexes and anatase nanostructure whose ratio depends on the pH of the pyrolysis medium. At low pH level, the resulting TiO2 nanostructure is predominant anatase and gradually shifts to the amorphous TiO2 complexes with pH level increasing. By means of heat treatment, the amorphous TiO2 complexes can be converted back to the anatase nanostructure and then transform to rutile with the elevating temperature. Amongst of the TiO2 nanostructure recovered from amorphous TiO2 complexes, the anatase shows to be the most effective photocatalyst in decomposition of methylene blue.