Ultrasensitive Room-Temperature NO 2 Detection Using SnS 2 /MWCNT Composites and Accelerated Recovery Kinetics by UV Activation.

High performance with lower power consumption is one among the essential features of a sensing device. Minute traces of hazardous gases such as NO 2 are difficult to detect. Tin disulfide (SnS 2 ) nanosheets have emerged as a promising NO 2 sensor. However, their poor room-temperature conductivity gives rise to inferior sensitivity and sluggish recovery rates, thereby hindering their applications. To mitigate this problem, we present a low-cost ultrasensitive NO 2 gas sensor with tin disulfide/multiwalled carbon nanotube (SnS 2 /MWCNT) nanocomposites, prepared using a single-step hydrothermal method, as sensing elements. Relative to pure SnS 2 , the conductivity of nanocomposites improved significantly. The sensor displayed a decrease in resistance when exposed to NO 2 , an oxidizing gas, and exhibited p-type conduction, also confirmed in separate Mott-Schottky measurements. At a temperature of 20 °C, the sensor device has a relative response of about ≈5% (3%) for 25 ppb (1 ppb) of NO 2 with complete recovery in air (10 min) and excellent recovery rates with UV activation (0.3 min). A theoretical lower limit of detection (LOD) of 7 ppt implies greater sensitivity than all previously reported SnS 2 -based gas sensors, to the best of our knowledge. The improved sensing characteristics were attributed to the formation of nano p-n heterojunctions, which enhances the charge transport and gives rise to faster response. The composite sensor also demonstrated good NO 2 selectivity against a variety of oxidizing and reducing gases, as well as excellent stability and long-term durability. This work will provide a fresh perspective on SnS 2 -based composite materials for practical gas sensors.