A room temperature sub-ppm NO2 gas sensor based on WO3 hollow spheres

Owing to the advantages of low power consumption, convenient design and simple preparation, room temperature (RT) gas sensors have been widely studied in recent years. In this study, we fabricated a gas sensor of WO3 hollow spheres obtained using a facile hydrothermal method, which exhibited an obvious room-temperature sensing response to sub-ppm NO2 without any other assistance. Multiple techniques were utilized to characterize the structures and morphologies of the WO3 materials and a series of gas sensors was fabricated and tested for exploring the potential application of the materials. It was found that the pH values in the hydrothermal reactions played an important role in both the morphologies and the gas sensing properties for the WO3 materials. The hollow spheres prepared at a pH of 0.7 exhibited good sensing properties to sub-ppm NO2 at RT, namely a high response, low detection limit, good selectivity and repeatability. Besides, the gas sensing mechanism was also discussed briefly.