Down to ppb level NO2 detection by ZnO/rGO heterojunction based chemiresistive sensors

In this work, we report parts per billion (ppb) NO₂ gas detection by utilizing zinc oxide/reduced graphene oxide (ZnO/rGO) heterostructure through a chemiresistive approach. The sensing material is carefully investigated through numerous characterization techniques. The experimental results indicated that the designed sensor shown good linearity in low ppb range of nitrogen dioxide (NO₂) gas. The sensor exhibited very high response of 33.11 at 2.5 ppm in 182 s with obtained detection limit down to ppb at relatively low optimal operating temperature of 110 °C. The remarkable performance of ZnO/rGO heterostructure towards NO₂ and negligible cross-response to other interfering gases along with high repeatability and long-term stability of the sensor is investigated. Due to many reactive sites and high transport capability of rGO along with high gas adsorption of ZnO nanospheres which attributes to the favorable charge transfer at ZnO/rGO interface under exposure of NO₂ gas which leads to modulate the energy band structure. This study shows that the simple, cost-effective synthesis method along with easy-fabricated and deployable sensor can be applied in many industrial and environmental applications.