High-Response Room-Temperature NO 2 Sensor and Ultrafast Humidity Sensor Based on SnO 2 with Rich Oxygen Vacancy.

Oxygen vacancies determines the physical and chemical properties of metal oxides. SnO2 nanosheets with abundant vacancies (designated as SnO2-x) have been successfully prepared by annealing SnSe nanosheets in Ar. High-density SnO2-x nanoplates with the size of 5~10 nm are distributed on the surface of the amorphous carbon. After annealing, the acquired SnO2-x/amorphous carbon retain the square morphology. The stoichiometric ratio of Sn: O (1:1.55) confirmed that oxygen vacancies are abundant in nanosheets. The prepared SnO2-x exhibits excellent performance of sensing NO2 at room-temperature. The response of the SnO2-x-based sensor to 5 ppm NO2 is determined to be 16, which is superior to those of most reported room-temperature NO2 sensors based on SnO2 and other materials. The ultrafast humidity response (52 ms) and recovery (140 ms) are competitive compared with other state-of-art humidity sensors. According to the mechanistic study, the excellent sensing performance of SnO2-x is attributed to its special physicochemical properties.