Colloidal TiO2 nanocrystals prepared from peroxotitanium complex solutions: Phase evolution from different precursors

We report the preparation of nanocrystalline anatase and rutile TiO2 from aqueous peroxotitanium complex (PTC) solutions and their characterization by powder X-ray diffraction (XRD), infrared spectroscopy, and Raman spectroscopy. The phase evolution of TiO2 prepared using PTC derived from different precursors, i.e., TiCl4 and titanium tetraisopropoxide (TTIP), is related to the nature of the intermediate steps. Phase-pure nanoanatase was formed in PTC solution derived from TiCl4, while a mixture of minor anatase and dominant rutile were prepared from PTC when TTIP was used as precursor. On the other hand, in the case of calcining PTC powders in air, a pure anatase phase of TiO2 was obtained, regardless of the precursor used. Thus, the formation and attachment of hydrated TiO6 units or TiO2·xH2O under a different environment, especially pH, plays a critical role in determining the phase during the crystallization of TiO2.

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