Ultrasensitive and low detection limit of nitrogen dioxide gas sensor based on flower-like ZnO hierarchical nanostructure modified by reduced graphene oxide

Hierarchical rGO/ZnO hybrids with a flower-like morphology of ZnO and flexible rGO sheets were synthesized by a facile solution-processed method. The structures and morphologies of the hybrids were investigated by different kinds of techniques, including X-ray diffraction, field-emission electron scanning microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The gas sensing properties of hierarchical rGO/ZnO hybrids toward nitrogen dioxide were studied via a static system. The response of rGO/ZnO hybrids to 50 ppb NO2 was 12, which was seven times higher than that of pristine ZnO at 100 °C. The limit of detection could be achieved as low as 5 ppb. The enhanced sensor response was attributed to the presence of local p-n heterojunctions between rGO sheets and hierarchical structure of ZnO.