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 degrees 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.