UV-enhanced room temperature NO2 sensor using ZnO nanorods modified with SnO2 nanoparticles

ZnO/SnO2 composite materials are synthesized by hydrolyzing SnCl2 on ZnO nanorods via the wet chemical method. The gas sensing studies revealed that ZnO/SnO2 exhibits a high response to NO2 at room temperature under UV light emitting diode illumination. The highest response to NO2 was achieved by the ZnO/SnO2 composite with Zn and Sn molar ratio of 1:1 (ZS3). The resistance of sensor based on ZS3 with UV light stimulation changed 1266-fold to 500 ppb NO2 gas at room temperature. Furthermore, the selectivity, as well as response and recovery properties, of the sensor was improved remarkably by UV light irradiation. The ZnO/SnO2 heterojunction model and the increased photo-generated electrons are proposed to elucidate the gas sensing mechanism.