Hydrothermal growth of nanometer- to micrometer-size anatase single crystals with exposed (0Â 0Â 1) facets and their ability to assist photodegradation of rhodamine B in water

Anatase single crystals with exposed (0 0 1) facets have been the focus of many researches in recent years. This paper reports the hydrothermal synthesis of (0 0 1)-exposed anatase single crystals through reactions of Ti plates in aqueous HF solutions with mass concentrations of 0.15-0.80%, in an autoclave at 180 °C for 2-12 h. The size of the achieved anatase single crystals varied from 0.4 to 13.6 μm, exposing 15-49% (0 0 1) facets. The crystal size and the (0 0 1) fraction increased with increasing HF concentrations. For a prolonged reaction time, anatase crystals with larger sizes and reduced fractions of (0 0 1) facets were achieved. The activity of the anatase crystals to assist photodegradation of rhodamine B in water increased with decreasing sizes and increasing fractions of (0 0 1) facets. Selective erosion of the anatase single crystals along the high-energy (0 0 1) facets was noted, for the first time, which resulted in cone-shaped walls with a thickness ranging from several to hundreds of nanometers. The selective erosion contributed to the photocatalytic activity of the (0 0 1)-exposed anatase single crystals.