In₂O₃ Nanoparticles Decorated ZnO Hierarchical Structures for n‑Butanol Sensor

In₂O₃ nanoparticles decorated ZnO hierarchical structures with excellent n-butanol-sensing performance were successfully fabricated by the one-pot sol–gel method. The formation process of the unique In₂O₃–ZnO hierarchical structure was investigated through experiments. The addition of indium was a crucial factor for the morphology and structure of the final product. The influence of the addition of indium on the sensor properties of the In₂O₃–ZnO hierarchical structure was examined systematically. The optimum indium–zinc ratio was 1:3. Sensor responses of the In₂O₃–ZnO (1:3) heterostructures toward 10 and 100 ppm n-butanol reached 18 and 218.3 at 260 °C. The response–recovery times toward 10 ppm n-butanol were 1 and 5 s. The gas-sensing mechanism was investigated based on the X-ray photoelectronic spectroscopy, photoluminescence spectroscopy, electron paramagnetic resonance spectroscopy, and UV–vis diffuser reflectance spectroscopy analyses. The improved gas-sensing performance of In₂O₃–ZnO was ascribed mainly to the unique microstructure and the surface decoration by In₂O₃ nanoparticles.