Enhanced NO₂ gas sensing performance of microwave irradiated SnO₂-ZnO nanocomposites prepared by a rotational hydrothermal method

In this work, we investigated the effects of microwave (MW) irradiation and the rotational hydrothermal method on SnO₂-ZnO nanocomposites for NO₂ gas detection by comparing commercial SnO₂ nanoparticles (NPs), SnO₂-ZnO nanocomposites, and MW-irradiated SnO₂-ZnO nanocomposites. Initially, a novel rotational hydrothermal method, involving exposure to temperatures of 180 °C for 24 h, was used to synthesize SnO₂-ZnO nanocomposites, which were then subjected to MW irradiation in 30 s intervals for a total of 10 cycles. The crystalline phase, morphology, chemical composition, physical effects of MW irradiation, and oxygen vacancies of the nanocomposite synthesized were thoroughly analyzed for the first time using MW irradiation and rotational hydrothermal methods. At 250 °C, the MW irradiated sensor recorded a response of 62.1 to 10 ppm NO₂ gas and response and recovery times of 257 s and 57 s, respectively. Furthermore, the sensor demonstrated high long-term stability and high selectivity to NO₂ gas. The improved NO₂ performance of the optimized sensor was related to the physical effects of MW irradiation and oxygen vacancies as well as the formation of ZnO-SnO₂ heterojunctions. We successfully presented a novel synthesis route for the preparation of nanocomposites and demonstrated the strong effect of MW irradiation on NO₂ sensing performance.