Dual Discrimination of Xylene and NO2 with UV-Boosted Recovery at Room Temperature Using SnSe2/MWCNT Composite-Based Sensors

Xylene and NO₂ are two prominent instances of indoor and outdoor pollutants, which directly affect human health. Detecting xylene at room temperature is difficult because of its nonpolar and less reactive nature. Tin diselenide (SnSe₂) has been determined to be a potential xylene and NO₂ sensor. But its room temperature conductivity results in poor sensitivity and slow recovery rates, which limits its practical application. To address this issue, we describe a low-cost, dual-sensitive and discriminant xylene and NO₂ gas sensor that employs tin diselenide/multiwalled carbon nanotube (SnSe₂/MWCNT) nanocomposite as the sensing element. The nanocomposite demonstrated substantially higher conductivity than that of pure SnSe₂. When exposed to xylene/NO₂, an oxidizing/reducing gas, the sensor shows an increase/decrease in resistance and exhibits overall p-type conduction, evaluated by independent Mott–Schottky measurements. At room temperature of 30 °C, the sensor device has a relative response of about ≈0.77% (0.18%) and 2.25% for 50 ppm (1 ppm) and 800 ppb of xylene and NO₂, respectively, with complete recovery in air (261 s) for xylene. In the case of NO₂, the complete recovery in ambient conditions required nearly 28 min, which significantly improves with ultraviolet (UV) activation to about ≈4 min. The theoretical lower limit (LOD) for xylene and NO₂ is estimated to be around 580 and 0.97 ppb, respectively. The proposed SnSe₂-MWCNT nanocomposite offers an effective sensing platform for the detection of these analytes. Its superior sensing qualities promote quick charge transfer, and dual discrimination along with exceptional repeatability, long-term stability, and reproducibility, thereby making it a viable alternative for monitoring pollutants.