Predictive mixed-gas detection using rGO/In₂O₃nanocomposite sensors assisted by machine learning

Selectivity towards specific analytes and detection at sub-ppm levels remain significant challenges for chemiresistive gas sensors. Hybrid materials, like reduced graphene oxide (rGO) combined with metal oxides, possess higher sensitivity at ultralow concentrations. In this work, rGO/In₂O₃ nanocomposite thin films were prepared by incorporating rGO synthesized via a modified Hummers' method into nanocrystalline In₂O₃, followed by spin coating and post-deposition annealing. Structural characterization confirmed the formation of phase-pure cubic bixbyite In₂O₃ with uniform rGO incorporation, providing abundant defect sites and efficient conductive pathways. The optimised rGO/In₂O₃ sensor exhibited good stability towards H₂S with a detection limit as low as 100 ppb. Nevertheless, accurate identification and concentration estimation of target gases in mixed environments remain challenging. To address this, a machine-intelligent framework was employed for simultaneous gas identification and concentration prediction using a single sensor. Features derived from the dynamic response curves allow the classifier to clearly distinguish gas clusters with 99.7% accuracy and correctly predict previously unseen H₂S, NH₃, and CO concentrations under interfering conditions. This combined platform opens the door to smart, ultra-low-level gas sensing in real-world, complicated environments, expanding environmental and health monitoring applications.