Hierarchical flower-like WO3 nanostructures and their gas sensing properties

Flower-like WO3 composed of nanosheets were successfully synthesized by calcining the acid-treated hydrothermal precursor. Field emission scanning electron microscopy and transmission electron microscopy results reveal that the flower-like WO3 are assembled by a number of irregular-shaped nanosheets, which are cross-linked in the interior of the microflower. A possible formation mechanism is proposed on the basis of the results of time-dependent experiments. Moreover, the gas sensing properties of the obtained flower-like nanostructured WO3 were investigated. It is found that the sensor based on the flower-like WO3 nanostructure exhibits good selectivity and high response to NO2, and the detection limit is about 2 ppb.