Highly sensitive, selective, and ppb level detection of NO2 gas using SnSe2 micro-flower, SnO2/SnSe2, and Au-SnO2/SnSe2 heterojunctions

Transition metal dichalcogenides (TMDCs)-based materials have attracted considerable attention in gas sensing due to their mesmerizing chemical, electrical, optical, and physical properties. In this work, solvothermal synthesized SnSe₂ material is well-tuned by thermal treatment to obtain the series of materials such as SnO₂/SnSe₂, SnO₂, & Au-SnO₂/SnSe₂, and explored for NO₂ gas sensing. The SnSe₂-36 sensor exhibits a response (R_g/R_a) of 5.5 under 4 ppm NO₂ at 30 °C. The sensing performance is significantly enhanced for SnO₂/SnSe₂-1 heterojunction with a response of 15.07, response/recovery time of 63 s /122 s, and limit of detection (LOD) of 60.61 ppb to 4 ppm NO₂ at 90 °C. The remarkable sensing performance is observed for Au-SnO₂/SnSe₂-1 heterojunction with a response of 25.31, response/recovery time of 156 s/56 s, and LOD of 13.67 ppb to 4 ppm NO₂ at 80 °C. The improvement in the gas sensing properties of the materials is attributed to the good hoping of electron exchange between the depletion layer and NO₂ gas, increase in specific surface area at the interface, lower adsorption energy of NO₂ with heterojunction, and spill-over effect. The remarkable results could attract key attention in materials synthesis and its wide tunability towards gas sensing applications.