Well-connected ZnO nanoparticle network fabricated by in-situ annealing of ZIF-8 for enhanced sensitivity in gas sensing application

Low-power microheater platforms are promising in lowering power consumption during gas sensing processes. However, the small amount of activated-material and poor electrical contact greatly affect the sensitivity. Here, via in-situ annealing of a porous metal organic framework (MOF), ZIF-8, using a miniature heater electrode with a fast ramp rate (ca. 60 °C/s), we demonstrate the formation of a well-connected nanoparticle network with high porosity. Nanoparticle networks prepared in-situ exhibit significantly enhanced response to ethanol, defined as the ratio of sensor's resistance before and after gas exposure, compared to ex-situ annealed counterparts (>10 times larger response) and to commercially available nanoparticles (∼4 times larger response) at a sensing temperature of 250 °C. The mechanism of the enhanced performance is studied using AC impedance spectroscopy. The results indicate that the large number of highly accessible and effective adsorption sites on the in-situ annealed material are responsible for the enhancement.