Temperature and acidity effects on WO3 nanostructures and gas-sensing properties of WO3 nanoplates

WO3 nanostructures were successfully synthesized by a facile hydrothermal method using Na2WO4·2H2O and HNO3 as raw materials. They are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The specific surface area was obtained from N2 adsorption–desorption isotherm. The effects of the amount of HNO3, hydrothermal temperature and reaction time on the crystal phases and morphologies of the WO3 nanostructures were investigated in detail, and the reaction mechanism was discussed. Large amount of acid is found for the first time to be helpful to the oriented growth of tungsten oxides, forming nanoplate-like products, while hydrothermal temperature has more influence on the crystal phase of the product. Gas-sensing properties of the series of as-prepared WO3 nanoplates were tested by means of acetone, ethanol, formaldehyde and ammonia. One of the WO3 nanoplates with high specific surface area and high crystallinity displays high sensitivity, fast response and distinct sensing selectivity to acetone gas.