LAUSR

Controlling the crystal phase of a material using solution-based method is a challenging task and has significant consequence to the material’s properties. Herein we report the phase and size-controlled synthesis of tungsten oxide hydrates at room temperature via a simple precipitation method. In the absence and presence of oxalic acid, orthorhombic WO3·H2O and monoclinic WO3·2H2O nanoplates of size in the range of 200–600 (thickness <50 nm) and 40–200 nm (thickness <20 nm) were respectively synthesized. Oxalic acid is found to play the central role in the phase transition due to its chelating nature that facilitates bonding of oxalate ions to tungsten cations leading to formation of WO3·2H2O. Upon annealing at 400 °C for 2 h under air, both WO3·H2O and WO3·2H2O nanoplates were converted to monoclinic WO3 nanoplates. These nanoplates were demonstrated to be highly efficient for the photocatalytic detoxification of toxic Cr(VI) in the acidic pH under the visible light irradiation. The best Cr(VI) reduction...