Hierarchically In2S3@In2O3 nanorods heterojunctions for enhanced NO2 sensing at lower operating temperature

Hierarchically structured In2S3@In2O3 nanorods were synthesized via a two-step hydrothermal method. Compared to single-component In2O3 based sensors, the as-developed In2S3@In2O3 nanorods based chemiresistive-type sensor exhibited significantly enhanced response and reduced operating temperature. The sensor displayed a response of approximately 51.2 to 3 ppm NO2 at 120 degrees C, with a response time and recovery time of 76 and 48 seconds, respectively, and a detection limit of NO2 concentration to 0.014 ppm. By constructing In2S3@In2O3 heterojunctions, the optimal operating temperature has been effectively lowered from 160 degrees C to 120 degrees C. The improved sensing performance is attributable to the nano-heterojunctions formed between In2S3 and In2O3, which increase the specific surface area to provide additional active adsorption sites, and as well, prevent the shielding effect of surface-adsorbed oxygen on NO2. Density functional theory (DFT) calculations demonstrated that the introduction of heterojunctions of In2S3@In2O3 enhances the adsorption energy and charge transfer between NO2 and the sensing material.