Hydrogen Sulfide Gas Detection in ppb Levels at Room Temperature with a Printed, Flexible, Disposable In2O3 NPs‐Based Sensor for IoT Food Packaging Applications

Abstract Flexible printed sensors are essential components for modern Internet of Things applications. They may twist and bend to fit any shape or surface. New potential applications emerge as these sensors’ sophistication and sensing efficiency improve. In this study, a printed sensor is prepared from indium oxide nanoparticles (In 2 O 3 NPs)‐based nanocomposite for hydrogen sulfide (H 2 S) gas detection at ambient conditions. The as‐fabricated sensor has excellent capabilities, including sensitivity and selectivity to low gas concentrations than 100 ppb (<100 ppb), anti‐humid property up to relative humidity (RH) ≈ 100%, high chemical stability in severe environments, good mechanical flexibility up to 50 bending cycles at 30° bending angle, and good thermomechanical stability between ‐40 °C ‐ 40 °C. Moreover, the sensor detects the low concentrations of H 2 S gas produced during the spoilage of organosulfur‐rich food (beef and fish) while remaining insensitive to humidity changes up to RH ≈ 100%, resulting in the fist‐of‐its‐type chemiresistive sensor for food packaging application. The sensors’ response to H 2 S gas is based on the contribution of the physical and chemical sensing mechanisms, which rely on the H 2 S molecules’ reactions on the sensor's surface with the adsorbed oxygen molecules and the sensing materials (copper acetate (CuAc) and In 2 O 3 NPs), respectively.