Visible Light Driven Ultrasensitive and Selective NO 2 Detection in Tin Oxide Nanoparticles with Sulfur Doping Assisted by l-Cysteine.

In the pandemic era, the development of high-performance indoor air quality monitoring sensors has become more critical than ever. NO 2 is one of the most toxic gases in daily life, which induces severe respiratory diseases. Thus, the real-time monitoring of low concentrations of NO 2 is highly required. Herein, a visible light-driven ultrasensitive and selective chemoresistive NO 2 sensor is presented based on sulfur-doped SnO 2 nanoparticles. Sulfur-doped SnO 2 nanoparticles are synthesized by incorporating l-cysteine as a sulfur doping agent, which also increases the surface area. The cationic and anionic doping of sulfur induces the formation of intermediate states in the band gap, highly contributing to the substantial enhancement of gas sensing performance under visible light illumination. Extraordinary gas sensing performances such as the gas response of 418 to 5 ppm of NO 2 and a detection limit of 0.9 ppt are achieved under blue light illumination. Even under red light illumination, sulfur-doped SnO 2 nanoparticles exhibit stable gas sensing. The endurance to humidity and long-term stability of the sensor are outstanding, which amplify the capability as an indoor air quality monitoring sensor. Overall, this study suggests an innovative strategy for developing the next generation of electronic noses.