Humidity Detection Using Metal Organic Framework Coated on QCM
Quartz crystal microbalance (QCM) coated with poly 4 vinylpyridine (PVP) and metal organic framework HKUST 1 are investigated and compared for humidity sensing. Drop casting method is employed to coat the PVP and HKUST 1 solutions onto the surface of a quartz crystal microbalance. The resonance frequencies of these sensors with varying relative humidity (RH) from 22% RH to 69% RH are measured using impedance analysis method. The sensitivity, humidity hysteresis, response, and recovery times of these sensors are studied. The sensitivities of uncoated, PVP, and HKUST 1 coated QCM sensors are 7 Hz, 48 Hz, and 720 Hz, respectively, in the range of 22% RH 69% RH. The extraction of desorption rate and adsorption energy associated with the adsorption and desorption of water molecules on these surfaces reveals that HKUST 1 has better sensing properties than PVP and uncoated QCM sensors. In this work, the HKUST 1 coated QCM is shown to be a promising material for moisture detection.
J. Sensors