Highly-sensitive NO2 gas sensors based on three-dimensional nanotube graphene and ZnO nanospheres nanocomposite at room temperature

Abstract

NO2 sensing devices derived from three-dimensional (3D) nanotube graphene (NTG) and ZnO nanosphere nanocomposite are proposed for room temperature (RT) operation. The nickel nanowires were grown chemically, then graphene was grown onto the obtained nickel nanowires via chemical vapor deposition (CVD). The 3D NTG was then prepared through etching the nickel nanowires, while synthesis of the NTG/ZnO composite was achieved via the hydrothermal method. The sensing performance of these NTG and NTG/ZnO gas sensors to NO2 was systematically investigated. The NTG gas sensor responded with a 22.5% change upon being exposed to 50 ppm of NO2, while the response of the NTG/ZnO device reached 47.8% when exposed to the same NO2 concentration. Furthermore, these devices were also capable of detecting concentrations of NO2 as low as 100 ppb. In addition, NTG and NTG/ZnO gas sensors were found to have good selectivity and repeatability. According to the analysis of the sensing mechanism for the NTG/ZnO composite, the high response of the sensing device is attributed to the heterostructure between NTG and ZnO. When the device is exposed to air and NO2, the barrier changes significantly, thus causing a change of resistance.