Polymorphism of nanocrystalline TiO2 prepared in a stagnation flame: formation of the TiO2-II phase.
Royal Society of Chemistry (RSC)
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Manuputty, M. Y., Dreyer, J., Sheng, Y., Bringley, E., Botero, M. L., Akroyd, J., & Kraft, M. (2019). Polymorphism of nanocrystalline TiO2 prepared in a stagnation flame: formation of the TiO2-II phase.. Chem Sci, 10 (5), 1342-1350. https://doi.org/10.1039/c8sc02969e
A metastable "high-pressure" phase known as α-PbO2-type TiO2 or TiO2-II is prepared via a single-step synthesis using a laminar premixed stagnation flame. Three other TiO2 polymorphs, namely anatase, rutile and TiO2-B phases, can also be obtained by tuning the oxygen/fuel ratio. TiO2-II is observed as a mixture with rutile under oxygen-lean flame conditions. To the best of our knowledge, this is the first time that this phase has been identified in flame-synthesised TiO2. The formation of TiO2-II in an atmospheric pressure flame cannot be explained thermodynamically and is hypothesised to be kinetically driven through the oxidation and solid-state transformation of a sub-oxide TiO2-x intermediate. In this scenario, rutile is nucleated from the metastable TiO2-II phase instead of directly from a molten/amorphous state. Mixtures containing three-phase heterojunctions of anatase, rutile, and TiO2-II nanoparticles as prepared here in slightly oxygen-lean flames might be important in photocatalysis due to enhanced electron-hole separation.
National Research Foundation Singapore (via Cambridge Centre for Advanced Research and Education in Singapore (CARES)) (unknown)
External DOI: https://doi.org/10.1039/c8sc02969e
This record's URL: https://www.repository.cam.ac.uk/handle/1810/288522