Highly Efficient SO 2 Sensing by Light-Assisted Ag/PANI/SnO 2 at Room Temperature and the Sensing Mechanism.

Sulfur dioxide (SO) is one of the most hazardous and common environmental pollutants. However, the development of room-temperature SO sensors is seriously lagging behind that of other toxic gas sensors due to their poor recovery properties. In this study, a light-assisted SO gas sensor based on polyaniline (PANI) and Ag nanoparticle-comodified tin dioxide nanostructures (Ag/PANI/SnO) was developed and exhibited remarkable SO sensitivity and excellent recovery properties. The response of the Ag/PANI/SnO sensor (20.1) to 50 ppm SO under 365 nm ultraviolet (UV) light illumination at 20 °C was almost 10 times higher than that of the pure SnO sensor. Significantly, the UV-assisted Ag/PANI/SnO sensor had a rapid response time (110 s) and recovery time (100 s) to 50 ppm SO, but in the absence of light, the sensors exhibited poor recovery performance or were even severely and irreversibly deactivated by SO. The UV-assisted Ag/PANI/SnO sensor also exhibited excellent selectivity, superior reproducibility, and satisfactory long-term stability at room temperature. The increased charge carrier density, improved charge-transfer capability, and the higher active surface of the Ag/PANI/SnO sensor were revealed by electrochemical measurements and endowed with high SO sensitivity. Moreover, the light-induced formation of hot electrons in a high-energy state in Ag/PANI/SnO significantly facilitated the recovery of SO by the gas sensor.