Realizing Synergy between In₂O₃ Nanocubes and Nitrogen-Doped Reduced Graphene Oxide: An Excellent Nanocomposite for...

Hierarchical mesoporous In₂O₃ 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 In₂O₃ 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 In₂O₃ 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 In₂O₃ nanocubes was fabricated. The incorporation of NrGO drastically improved the sensing performance of the In₂O₃ 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.