Dielectric Constant Controlled Solvothermal Synthesis of a TiO2 Photocatalyst with Tunable Crystallinity: A Strategy for Solvent Selection

Phase-pure anatase TiO2 nanocrystals with a tunable crystallinity have been prepared by a one-step solvothermal method in the absence of any templates or additives. The crystallinity can be successfully controlled by varying the dielectric constant of the reaction solvent. 2-Propanol, which has the lowest dielectric constant of those studied, favors the crystallization of TiO2 nanocrystals with the best crystallinity, in other words nano-TiO2 crystals with the largest crystallite size (14.8 nm), lowest lattice strain (7.27 x 10(-3)), and highest photocatalytic efficiency (almost six times that obtained in methanol). The effect of the dielectric constant on the solubility of the precursor and subsequent nucleation and crystal growth is discussed in detail. These discussions shed some light on solvent selection for the designed synthesis of nano-TiO2 with different crystallinity. The photocatalytic activity of the as-prepared samples has also been investigated with respect to their crystallinity. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)