Realizing Synergy between In₂O₃ Nanocubes and Nitrogen-Doped Reduced Graphene Oxide: An Excellent Nanocomposite for the Selective and Sensitive Detection of CO at Ambient Temperatures

Hierarchical mesoporous In 2 O 3 nanocubes and nitrogen-doped reduced graphene oxide–indium oxide nanocube (In NrGO ) composites were prepared for carbon monoxide (CO) sensing. The as-synthesized materials were systematically investigated by different characterization techniques such as field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetic analysis, X-ray photoelectron spectroscopy, micro-Raman, Fourier transform infrared spectroscopy, and photoluminesce analysis. The obtained results are consistent with each other. The CO-sensing characteristics of the In 2 O 3 nanocubes and In NrGO composites were examined at different operating temperatures (35 °C < T s < 300 °C) and CO concentrations (1–1000 ppm). Owing to their large surface-to-volume ratio and porosity, the In 2 O 3 nanocubes exhibited a superior sensitivity with a detection limit of 1 ppm at 250 °C. Furthermore, to enhance the sensing characteristics and reduce the operating temperature, a composite of NrGO and In 2 O 3 nanocubes was fabricated. The incorporation of NrGO drastically improved the sensing performance of the In 2 O 3 nanocubes, showing an excellent sensitivity ( S R ∼ 3.6–5 ppm of CO at ∼35 °C) with appreciably fast response (Γ RES ∼ 22 s) and recovery (Γ REC ∼ 32 s) times. The sensing studies supported by the structural and morphological material characteristics lead to the plausible sensing mechanism proposed.