Hydrothermal synthesis of zinc oxide-reduced graphene oxide nanocomposites for an electrochemical hydrazine sensor

We report here a facile synthesis of different zinc oxide (ZnO) nanostructures on reduced graphene oxide (RGO) by an in situ hydrothermal reaction. ZnO nanostructures with different morphologies on the surface of RGO were successfully synthesized by adjusting the mass ratio of Zn2+ to RGO in this reaction system. It was found that ZnO nanostructures with nanoparticles, mixed nanoparticles and microspindles, and microspindles were formed on RGO by adjusting the mass ratio of Zn2+ to RGO. The synthesized ZnO–RGO nanocomposites with different structures were immobilized onto glassy carbon electrodes and applied to construct electrochemical hydrazine (N2H4) sensors. The results indicate that the ZnO–RGO nanocomposites created with the mass ratio of 4.4 : 1 present the best sensor performance. The fabricated N2H4 sensor exhibited a fast amperometric response to N2H4 with a linear detection range from 1.0 μM to 33.5 mM and a detection limit of 0.8 μM. The superior performance is ascribed to the unique structure of the synthesized ZnO and the excellent conductivity of RGO. In addition, we found that the synthesized ZnO–RGO composites exhibited improved electrochemical stability. Such novel ZnO–RGO hybrid materials represent promising nonenzymatic electrochemical N2H4 sensors with high sensitivity and selectivity, improved stability, and fast amperometric response.