A room-temperature and ppb-level NO2 sensor based on n-CdS/p-CuO heterojunction modified with rGO nanosheets

Abstract

In this work, novel mesoporous heterostructure of CdS/CuO/rGO composites was synthesized by a green and ultra-low-cost hydrothermal method. More importantly, the sensor shows significantly higher response of 12.46, which is about 5.3 times and 1.5 times of the CdS (2.36) and CdS/CuO (8.22) sensors, respectively. Besides, the fabricated sensors have ultra-low limit of detection (LOD) of 50 ppb, ensuring the ppb-level detection to NO2 gas in practical applications. Besides, the CdS/CuO/rGO sensor has excellent reversibility, good selectivity to NO2 gas against other gases (such as NH3, H2, CO and SO2), and reliable stability. The improvement of the gas sensing properties for CdS/CuO/rGO sensor is mainly ascribed to the existence of numerous active sites, which are able to enhance the adsorption capacity of target gas, improving the affinity for gas molecules. Furthermore, the heterojunction formed between CdS/CuO/rGO composites can provide conductive channel to accelerate carrier transfer to further improve the performance of the sensor. It is no doubt that our work will provide potential applications for improving gas sensing performance of a room-temperature NO2 sensor.