Engineering In₂O₃-based hybrid thin films with RGO and Fe₃O₄ for high-performance H₂S detection

Hydrogen sulfide (H₂S) is a hazardous gas relevant to environmental, industrial, and biomedical settings, creating a growing need for sensitive and low-temperature detection technologies. In this study, indium oxide (In₂O₃)–based thin-film nanocomposites were developed and evaluated for efficient H₂S sensing. Reduced graphene oxide (RGO) and iron oxide (Fe₃O₄) were selected as functional modifiers due to their reported conductivity enhancement, catalytic activity, and compatibility with green nanomaterial approaches. Binary (In₂O₃–RGO, In₂O₃–Fe₃O₄) and ternary (In₂O₃–RGO–Fe₃O₄) composites were synthesized to explore how synergistic structural and electronic effects influence sensing performance. The investigation proceeded by comparing pristine and modified In₂O₃, optimizing RGO loading, and subsequently adjusting Fe₃O₄ content to determine the most effective formulation. Pristine In₂O₃ displayed a maximum sensitivity of 21.2 % at 250 °C, whereas the In₂O₃–RGO binary composite reached 84.3 % at 150 °C—nearly a fourfold enhancement due to improved conductivity and heterojunction formation. Introducing Fe₃O₄ further accelerated adsorption–desorption kinetics, with the optimized 1:1:1 In₂O₃–RGO–Fe₃O₄ composite achieving sensitivities of 54.9 % at 150 °C and 70 % at 250 °C, along with a significantly reduced in the response time to 7.38 s. These quantitative improvements confirm the synergistic catalytic, electronic, and structural contributions of the ternary system, enabling a stable, low-temperature, and high-performance H₂S sensor that surpasses conventional metal-oxide designs. Structural analyses (SEM, TEM, AFM, BET) confirmed that enhanced porosity, surface roughness, and uniform nanoparticle distribution played key roles in the sensing mechanism. This study demonstrates an effective pathway for developing low-power, high-performance H₂S sensors using environmentally friendly nanomaterials. The synergistic morphological, electronic, and catalytic properties of the ternary composite position it as a strong candidate for next-generation gas-sensing applications in environmental, industrial, and biomedical fields.