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 degrees 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.