Ionic liquid-assisted synthesis of In₂O₃ nanoparticles for ppb-level NO₂ sensing at low temperature

Highly sensitive detection of nitric dioxide (NO₂) has recently attracted much attention due to its harmful to the human health even at a low concentration of 0.1 parts per million (ppm). Herein, In₂O₃ nanoparticles (NPs) were prepared via a facile ionic liquid (IL) assisted solvothermal method with subsequent calcination and then were analyzed through the characterization of X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption techniques. Morphological characterization demonstrated that the resultant compounds were In₂O₃ NPs with a diameter ranging from 20 to 30 nm. The gas sensor based on the In₂O₃ NPs prepared with IL exhibited excellent NO₂-sensing properties in terms of fast response/recovery speed (26.6/10.0 s), high response (310.0), good repeatability and long-term stability to 10 ppm NO₂ gas at low working temperature of 92 °C. The gas-sensing mechanism of In₂O₃ NPs to NO₂ was represented to the surface adsorption control model and the possibilities relating to the improved NO₂ sensing performance of the In₂O₃ NPs synthesized with IL-assisted were also discussed in detail.