Ultrasensitive Room-Temperature NO<sub>2</sub> Detection Using SnS<sub>2</sub>/MWCNT Composites and Accelerated Recovery Kinetics by UV Activation
Imtej Singh Saggu, Sukhwinder Singh, Kaiwen Chen, Zhengxi Xuan, Mark T. Swihart, Sandeep Sharma
Abstract
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.