Synthesis of uniform WO3 square nanoplates via an organic acid-assisted hydrothermal process

Abstract Two kinds of tungsten oxide (WO 3 ) square nanoplates have been prepared by a simple hydrothermal method using l (+)-tartaric acid or citric acid as assistant agents. The products are characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). XRD, SEM and TEM images of the products illustrate that WO 3 square nanostructures prepared in the presence of l (+)-tartaric acid have a hexagonal phase, length of ∼ 200 nm and thickness of ∼ 100 nm, while WO 3 nanostructures synthesized in the presence of citric acid have an orthorhombic phase, length of ∼ 500 nm and thickness of ∼ 100 nm. Selected area electron diffraction (SAED) suggests that both of the as-prepared WO 3 square nanoplates are single crystalline. The plausible growth mechanism for the formation of WO 3 square nanostructures is also proposed.