Biocompatible Anatase Single-Crystal Photocatalysts with Tunable Percentage of Reactive Facets

Biocompatible anatase TiO2 single-crystals with 27−50% chemically reactive {001} facets were obtained in 90 min by using a microwave-assisted method. The preparation involved an aqueous solution of titanium tetrafluoride and an ionic liquid (1-methyl-imidazolium tetrafluoroborate). The as-obtained TiO2 single-crystals exhibited a truncated tetragonal bipyramidal shape. By simply changing the concentration of the ionic liquid, the level of reactive {001} facets can be continuously tuned from 27 to 50%. The use of microwave heating is critical as it allows rapid and uniform heating of the reaction mixture. The TiO2 single-crystals were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra, and field emission scanning electron microscopy. The products exhibited excellent photocatalytic efficiency for both oxidation of nitric oxide in air and degradation of organic compounds in aqueous solution under UV light irradiation. The relationship between the physicochemical properties and the photocatalytic performance of the samples is discussed. The TiO2 single-crystals were found to be nontoxic using Zebrafish (Danio rerio) as a model.