Printed Chemiresistive In2O3 Nanoparticle-Based Sensors with ppb Detection of H2S Gas for Food Packaging

Cost-effective and disposable smart sensing technologies capable of monitoring packaged foods' degradation are necessary for human health and the growing processed-food industry. Herein, highly sensitive and selective hydrogen sulfide (H2S) gas sensors were fabricated from solution-printed nanocomposites comprising indium oxide nanoparticles (In2O3 NPs), graphite flakes (Gt), polystyrene (PS), and copper acetate monohydrate (CuAc). The standard In2O3 NP-based sensor (SS, without CuAc) showed H2S detection ≈100 ppb under ambient conditions. The presence of CuAc resulted in a highly sensitive nanocomposite layer enabling the detection of lower than 100 ppb (<100 ppb) concentrations of H2S gas levels, far superior to the standard In2O3 NP-based nanocomposite. Adding CuAc to the In2O3 NP-based nanocomposite as a modifying additive leads to copper sulfide (CuS) formation owing to its reaction with H2S gas. CuS significantly enhances the nanocomposite layer's conductivity and H2S reactions on the sensors' surface, resulting in a substantial reduction in electrical resistance for sensors. The modified In2O3 NP-based sensor presents remarkable enhancement in their selectivity toward H2S gas detection when evaluated against various hazardous vapors. Furthermore, the modified In2O3 NP-based sensors possess good anti-humid property under highly humid conditions (≈80% relative humidity).