SnO 2 -Based NO 2 Gas Sensor with Outstanding Sensing Performance at Room Temperature.

The controlled and efficient formation of oxygen vacancies on the surface of metal oxide semiconductors is required for their use in gas sensors. This work addresses the gas-sensing behaviour of tin oxide (SnO 2 ) nanoparticles for nitrogen oxide (NO 2 ), NH 3 , CO, and H 2 S detection at various temperatures. Synthesis of SnO 2 powder and deposition of SnO 2 film is conducted using sol-gel and spin-coating methods, respectively, as these methods are cost-effective and easy to handle. The structural, morphological, and optoelectrical properties of nanocrystalline SnO 2 films were studied using XRD, SEM, and UV-visible characterizations. The gas sensitivity of the film was tested by a two-probe resistivity measurement device, showing a better response for the NO 2 and outstanding low-concentration detection capacity (down to 0.5 ppm). The anomalous relationship between specific surface area and gas-sensing performance indicates the SnO 2 surface's higher oxygen vacancies. The sensor depicts a high sensitivity at 2 ppm for NO 2 with response and recovery times of 184 s and 432 s, respectively, at room temperature. The result demonstrates that oxygen vacancies can significantly improve the gas-sensing capability of metal oxide semiconductors.