Enhanced NO2 sensing performance of ZnO nanowires functionalized with ultra-fine In2O3 nanoparticles

Structure and surface properties of the sensing materials have been recognized as the primary consideration for fabricating metal oxide semiconductor gas sensors. In this study, one-dimensional ZnO nanowires with large length-to-diameter ratio were firstly synthesized by a facile hydrothermal method. Then, different contents of ultra-fine In2O3 nanoparticles were directly grown on their surface. The structural characterization confirmed that the In2O3 nanoparticles were only 3–5 nm in diameter and well dispersed on the surface of ZnO nanowires. The gas sensing results showed that the ultra-fine In2O3 nanoparticles gave rise to a significant improvement in NO2 response at their optimal operating temperature of 150 °C. The highest response of 54.6 to 1 ppm NO2 was obtained for the sensor based on In2O3/ZnO composites with the In/Zn molar ratio of 5 %, which was about 8 times higher than that of pure ZnO nanowires. Importantly, a high response of 18.4 to a relatively low NO2 concentration of 250 ppb was also observed for In2O3-functionalized ZnO nanowires. The enhanced NO2 sensing mechanisms of ZnO nanowires functionalized with ultra-fine In2O3 nanoparticles were discussed.