Ultrasensitive and low operating temperature NO2 gas sensor using nanosheets assembled hierarchical WO3 hollow microspheres

The nanosheets assembled hierarchical WO3 hollow microspheres were successfully synthesized by sintering acid-treated CaWO4 hollow microspheres precursor at 500 °C. The as-obtained sample was characterized with field emission scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption and desorption measurements. The results indicated that the as-prepared product was monoclinic tungsten oxide and the nanosheet was single crystal and had a large amount of surface defects. The as-obtained sample had porous structures with a wide range of pore size distributions from 1 nm to 170 nm. The sensor based on this hierarchical structures exhibited excellent sensing properties to nitrogen dioxide (NO2) at relatively low operating temperature, and the response to 40 ppb NO2 is about 16 at 75 °C. The nanosheets assembled hierarchical WO3 hollow microspheres might have potential application to fabricate highly sensitive and low power consumption NO2 gas sensor.