Green synthesis of hexagonal-shaped WO₃ · 0.33H ₂O nanodiscs composed of nanosheets

A facile route for the preparation of WO₃·0.33H ₂O hexagonal-shaped nanodiscs composed of nanosheets via hydrothermal treatment of an aqueous peroxo-polytungstic acid solution has been demonstrated for the first time. The hexagonal-shaped nanodiscs obtained have an average diameter of 200 nm and a mean thickness of several tens of nanometers. The effects of the preparation conditions such as the hydrothermal temperature and precursor concentration on the crystalline phase and morphology of the products have been studied systematically. The WO₃ · 0.33H₂O nanodiscs with an orthorhombic structure and regular hexagonal morphology can be synthesized in a wide hydrothermal temperature range from 100 to 200 °C. However, in the absence of hydrogen peroxide, monoclinic tungsten oxide square nanoplates are obtained. The hexagonal-shaped nanodiscs morphology have been well explained based on the crystal structure of orthorhombic WO ₃·0.33H₂O. It is expected that this material with a well-defined and accessible crystal surface may find applications in catalysis, gas sensors, and other research areas.