Construction of ZnO@ZIF-CoZn bimetallic core-shell nanospheres for enhanced ethanol sensing performance

In order to achieve highly sensitive, stable and preferential monitoring of ethanol, a new core-shell structure of ZnO@ZIF-CoZn (zeolite imidazole framework-CoZn) was hydrothermally synthesized to meet actual detection requirements. The micro-morphology, crystal phase and element composition of the synthesized materials were studied by SEM, TEM, XRD, XPS and other characterization methods. It was found that the porous ZIF-CoZn film (∼100 nm) was uniformly and densely coated on the surface of the ZnO nanospheres (∼400 nm), and a core-shell structure of ZnO@ZIF-CoZn was successfully synthesized. In the gas sensitivity test, the response of ZnO@ZIF-CoZn to 100 ppm ethanol reached 18.4 at 200 °C, which is almost 3.6 times than that of pure ZnO, and the optimal working temperature of ZnO@ZIF-CoZn was lower than that of pure ZnO (240 °C). In addition, ZnO@ZIF-CoZn exhibited excellent selectivity and stability to ethanol. A heterojunction model and surface sensing response are proposed to explain the enhanced sensing response. Therefore, based on the unique nanostructure, low cost, high sensitivity and excellent selectivity of ethanol sensing performance, ZnO@ZIF-CoZn is expected to become a promising candidate in the ethanol sensor market.