Understanding the gas sensing mechanism of MoSe₂ nanoroses and rGO composite-based chemiresistive sensors for room temperature NO₂ detection

This study presents the synthesis of single-phase 2H-MoSe₂ and one-pot synthesis of MoSe₂/rGO (MSR) composite used for the detection of environmental pollutants (NO₂, NH₃, H₂S CO₂, CO, CH₄ CH₃COCH₃) at ambient temperature (∼25 °C). The gas sensing devices were fabricated on Ti/Pt interdigitated electrodes with different compositions of MSR composite viz. 10 (MSR-10), 20 (MSR-20), and 30 (MSR-30) weight % of rGO. The sensitivity of the p-type MoSe₂, rGO and MSR-20 was calculated to be ∼29 %, ∼24 % & ∼38 %, respectively at 4 ppm concentration of NO₂. The respective response and recovery time were calculated to be 191/218 s, 225/412 s, and 110/128 s for MoSe₂, rGO, and MSR-20 composite at 4 ppm of NO₂ gas. The response curve at the lowest detection limit indicates stable performance of the device, which makes it suitable for its real-time application. The response time and recovery time of the composite device are 40 s and 65 s, respectively at 100 ppb concentration of NO₂ gas. The sensing device was subjected to 0.1 ppm to 4 ppm of NO₂ gas concentration, and the obtained device response was highly repeatable and stable after 60 days. The possible gas sensing mechanism based on charge transfer is proposed for fabricated devices using MSR composite material. The gas sensing device parameters, selectivity, repeatability, sensitivity, and stability show a great potential of MoSe₂-rGO composite material in gas sensing.