Synthesis and Characterization of Zinc Oxide-Reduced Graphene Oxide Hybrid Materials and their Application for Nitrogen Dioxide Detection

Herein, we report a facile synthesis of zinc oxide-reduced graphene oxide (ZnO-rGO) hybrid materials by two-step method. Firstly, rGO was synthesized by using graphite powder mixed with sodium nitrate, sulfuric acid and potassium permanganate via Hummers method. Synthesized rGO were dispersed in ethanol by ultra-sonication for a designated time period. Then, zinc oxide (ZnO) powder was added into rGO-ethanol solution and transferred into Teflon-lined stainless steel autoclave. The ZnO-rGO was produced by hydrothermal method at 180 °C for 120 and 180 min (here after referred to as ZnO(120)-rGO and ZnO(180)-rGO, respectively). The morphological and crystalline structures of synthesized rGO and ZnO-rGO were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Synthesized ZnO-rGO was exposed to 100 parts per million (ppm) nitrogen dioxide (NO2) gas at room temperature, 50 °C and 75 °C for testing its sensing performance. The results show that ZnO(180)-rGO hybrid materials exhibit high response to NO2 gas at 50 °C and 75 °C. The electrical resistance of ZnO-rGO sensors decreased when the sensors responded to NO2 gas, indicating a p-type behavior. Moreover, the ZnO-rGO hybrid materials can detect 100 ppm NO2 gas with an operating temperature limit at 50 °C. The results imply that synthesized ZnO-rGO hybrid materials could be used as gas sensing device for ppm-level NO2 detection at low temperature and consume low power.