Graphene-Modified ZnO Nanostructures for Low-Temperature NO(2) Sensing

[Image: see text] This paper develops a novel ultrasonic spray-assisted solvothermal (USS) method to synthesize wrapped ZnO/reduced graphene oxide (rGO) nanocomposites with a Schottky junction for gas-sensing applications. The as-obtained ZnO/rGO-x samples with different graphene oxide (GO) contents (x = 0–1.5 wt %) are characterized by various techniques, and their gas-sensing properties for NO(2) and other VOC gases are also evaluated. The results show that the USS-derived ZnO/rGO samples exhibit high NO(2)-sensing property at low operating temperatures (e.g., 70–130 °C) because of their high specific surface area and porous structures when compared with the ZnO/rGO sample obtained by the traditional precipitation method. The content of rGO shows an obvious effect on their NO(2)-sensing properties, and the ZnO/rGO-0.5 sample has a high response of 62 operating at 130 °C, three times that of pure ZnO. The detection limit of the ZnO/rGO-0.5 sensor to NO(2) is as low as 10 ppb under the present test condition. In addition, the ZnO/rGO-0.5 sensor shows a highly selective response to NO(2) gas when compared with organic vapors and other inflammable or toxic gases. The theoretical and experimental analyses indicate that the enhancement in NO(2)-sensing performance of the ZnO/rGO sensor is attributed to the formation of wrapped ZnO/rGO Schottky junctions.