| 초록 |
Recently, hybridization of metal oxide nanostructures with functional materials has been gaining a lot of attention for enhancing gas sensing performance. Especially, zeolitic imidazolate framework-8 (ZIF-8), a subclass of metal organic frameworks (MOF), is an adoptable material for integrating ZnO-based gas sensors owing to its high internal surface area, subnanometer-sized cavities, thermal stability, and chemical controllability. It is well-established that the hybridization of ZnO with ZIF-8 allows the improvement of gas selectivity owing to molecular sieving capability induced by well-defined porous structures (pore size = 3.4 Å). Here, we focused on the effects of preconcentration of ZIF-8 hybridized with ZnO nanowires in terms of NO2, NH3, and H2 gas sensitivity as well as gas selectivity. Hydrothermally-grown ZnO NWs are employed as a support material for the nucleation and growth of ZIF-8 nanocrystals, in which their morphological features were optimized by adjusting growth conditions including solution concentration, reaction time, and temperature. The thickness of encapsulated ZIF-8 can be effectively manipulated by the concentration of HmIM, which strongly affects to gas sensitivity of ZIF-8/ZnO NWs-based gas sensors because of a variation in gas diffusion path. For ZIF-8/ZnO NWs synthesized using 8 mM HmIM solution, NO2, NH3, H2 gas sensitivity was improved significantly compared to that of pristine ZnO NWs. Based on these results, two effects are anticipated to improve both gas sensitivity and selectivity after the hybridization of ZnO NWs with ZIF-8 nanocrystals. |
