Hydrogen Sulfide Adsorption Regulation on Indium Oxide Nanosheets via Defect Engineering for Meat Spoilage Detection

The limited sensitivity of indium oxide (In 2 O 3 ) gas-sensing materials for detection of hydrogen sulfide (H 2 S) restricts their application in identifying meat spoilage. In this study, two-dimensional indium oxide nanosheets (In 2 O 3 -NS) with intrinsic defects were synthesized using an “egg-box” structure, which was formed by the interaction between sodium alginate and metal cations, combined with an ice-templating method and annealing process. The resulting In 2 O 3 -NS sensor demonstrated a response of 950 to 5 ppm of H 2 S at its optimal operating temperature of 175 °C, with a detection limit as low as 100 ppb. Structural characterization and density functional theory calculations revealed that intrinsic defects in the In 2 O 3 -NS structure optimize the electron density distribution, providing additional adsorption sites for H 2 S and significantly enhancing gas sensitivity. Furthermore, a system utilizing In 2 O 3 -NS sensors was developed to evaluate meat freshness by detecting H 2 S emissions.