Three-dimensional In2O3–CuO inverse opals: synthesis and improved gas sensing properties towards acetone

Abstract

Specific three-dimensional inverse opal (3DIO) In₂O₃–CuO architecture with additional via-holes was first prepared by a simple sacrificial template method. Such specific nanostructures enable fast transport of gas molecules to the entire thin-walled sensing layers, which is very helpful for improving the sensing performance. Moreover, the mole ratio of Cu/In was controlled, ranging from 0–38.1% to adjust the hetero-contact amounts in the In₂O₃–CuO composites. The gas sensing properties of the as-prepared 3DIO In₂O₃–CuO samples were evaluated toward trace acetone, which is an important biomarker of diabetes in exhaled breath. The response of the 3DIO In₂O₃–CuO gas sensor with the best performance (with a mole ratio of Cu/In = 16.4%) was ∼14 to 5 ppm acetone, and had a calculated low detection limit of ∼30 ppb at 370 °C when R_a/R_g ≥ 1.2 was used as the criterion for reliable gas sensing. Besides, it also showed good selectivity, fast response (τ_res) and recovery (τ_rec) times, and stability. The enhanced gas sensing performance could be attributed to the hetero-contact effects between the different components and the specific 3DIO structure with the via-holes which provided a larger effective surface area for gas adsorption. It is believed that the as-prepared 3DIO sensor can be a promising ppb-level acetone sensor in various areas.