The titanium dioxide (TiO2) nanostructures resulted by the pyrolysis of titanium tetrachloride (TiCl4) at a low temperature of 80 °C were found to be a mixture of amorphous TiO2 complexes and anatase nanostructures, whose ratio depends on the pH of the pyrolysis medium. At a low pH level, the resulting TiO2 nanostructures are predominantly anatase and gradually shift to amorphous TiO2 complexes as the pH level increases. Moreover, the amorphous TiO2 complexes can convert back to anatase nanostructures by a post-heating treatment, and can then transform to rutile with elevating temperature. Amongst the TiO2 nanostructures recovered from the amorphous TiO2 complexes, anatase appears to be the most effective photocatalyst in the decomposition of methylene blue.

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 that depends on the pH of the pyrolysis medium. Anatase nanostructure is predominant at low pH level and gradually converts to amorphous TiO2 complexes with increasing pH level. By means of heat treatment, the TiO2 nanostructures can be recovered from amorphous TiO2 complexes. Amongst of the TiO2 nanostructure recovered from amorphous TiO2 complexes, the anatase nanostructure shows to be the strongest photocatalyst in decomposition of methylene blue.