Highly sensitive ZnO nanoparticles-loaded In2O3 hollow microsphere for detecting ppb-level NO2 at low working temperature

This paper presents a NO₂ sensor operating at low temperature, which was fabricated by ZnO nanoparticles-loaded In₂O₃ hollow microspheres composites. SEM, XRD, XPS and HRTEM were executed to determine the morphology and microstructure of ZnO–In₂O₃. The sensing performance of pure In₂O₃ and ZnO–In₂O₃ composite sensors was tested. The NO₂ sensing properties of the composite were greatly improved in contrast with the pure In₂O₃ sensor at the optimized operating temperature (75 °C). ZnO–In₂O₃ composite sensor exhibited an obviously higher response (805.2 for 100 ppb NO₂) than that of the pure In₂O₃ sensor (14 for 100 ppb NO₂). In particular, the response/recovery rate of ZnO–In₂O₃ composite sensor was greatly improved in contrast with the pure In₂O₃ sensor. The n-n heterojunctions created at ZnO–In₂O₃ interfaces improved the sensing performance.