Visible-light activated room temperature NO2 sensing of SnS2 nanosheets based chemiresistive sensors

The visible-light activated gas sensor has been successfully fabricated for detecting NO2 by using two dimensional (2D) structured SnS2 nanosheet as the chemiresistive sensing material. Under the light illumination, the SnS2 nanosheet based chemiresistive gas sensor exhibits a high response and excellent selectivity to NO2 at room temperature. Influences of light wavelength, light intensity, operating temperatures and humidity on the sensing characteristics are investigated in details. It suggests that photo-energy activation can effectively activate the SnS2 sensor and the green light is the most effective to achieve superior sensing property of the SnS2 sensor at room temperature in terms of the excellent sensitivity and a better response/recovery speeds. The sensor also demonstrated an excellent selectivity to NO2 over several possible interferants such as SO2, CO2, NH3, acetone, methanol, ethanol and formaldehyde, and a good stability for about six months activated by the green light. The sensing mechanism is intimately related to the extra photo-generated electrons which subsequently attract more NO2 at its 2D surface. A simple Langmuir - Hinshelwood dynamics model is proposed to explain the effect of the visible light irradiation on the absorption/desorption speed of gas molecules.