Mesoporous three-dimensional network of crystalline WO3 nanowires for gas sensing application

Mesoporous three-dimensional (3D) network of crystalline WO3 nanowires was prepared by nanocasting method using 3D SBA-15 silica with hexagonally ordered mesopores as hard template. After impregnation, mineralization and template removal, a mesoporous 3D framework of ordered crystalline WO3 nanowires with high specific surface area and stable mesopore channels was formed through the randomly distributed bridging between the neighboring nanowires. The mesostructure of the product was confirmed by low-angle X-ray diffraction (XRD) and nitrogen physisorption measurements. High resolution transmission electron microscopy (HRTEM) images indicate the single crystal structure with different crystal orientation for mesoporous particles. The gas sensing properties of the mesoporous 3D WO3 nanowires replica were investigated at 50 °C up to 200 °C over NO2 concentration ranging from 15 to 500 ppb. The results indicate that the mesoporous 3D WO3 nanowires exhibits high response, good selectivity and fast response–recovery characteristics in the detection of sub-ppm and ppb level NO2 at the optimal operating temperature of 125 °C due to the stable mesopore channels, large surface area and perfect single-crystal structure.

► Mesoporous 3D network of WO3 nanowires was prepared by nanocasting method. ► The 3D WO3 nanowires exhibits excellent structural properties for gas-sensing. ► The 3D WO3 nanowires is responsive to NO2 gas at ppb level. ► High NO2 response, fast response and recovery and good selectivity are achieved.