A Gas Sensor Based on Zif-8-Coated Coupled Resonators With Enhanced Sensitivity and Reversible Detection Ability

This paper develops a gas sensor with zeolitic imidazolate framework-8 (ZIF-8) coated coupled resonators. The porous ZIF-8 structure coats only one of the two coupled resonators and can adsorb specific gas molecules, resulting in mass differences between the two resonators. This mass change can be measured by either monitoring frequency shift or amplitude ratio variation. The gas sensing performance of the fabricated ZIF-8-coated coupled resonators was tested with ethanol vapour of different concentration levels. The sensitivity using amplitude ratios as output was 0.013/(P/P
0
) for lower ethanol vapour concentrations (1%-10%), which is one order of magnitude higher than that with conventional frequency shift as the output. For higher ethanol vapour concentrations (20%-80%), the sensitivity was 0.0022/(P/P
o
), which is twice than that with frequency shift as output. Additionally, it was shown that the reported gas sensor could be used for repeatable detection due to the reversible physisorption of ZIF-8 to ethanol vapour.