MOF/PDMS Hybrid Nanofilm-based QCM for VOC Selective Virtual Sensing in High-Humidity Environments

As one of the most promising gravimetric gas sensors, the quartz crystal microbalance (QCM) sensor can effectively detect volatile organic compounds (VOCs) with high selectivity based on the virtual sensor array (VSA) technique. However, the susceptibility of the chemical sensing material to water molecules limits the applications in high-humidity environments such as urban underground pipeline galleries. Herein, we propose a novel QCM VOC sensor coated with a hydrophobic sensing layer of MOF/PDMS hybrid nanofilm. A modified selective virtual sensing (SVS) technique is also proposed to create high dimensional vectors by combining the resonant signal features and lumped parameters, which can be used to generate distinctive features under various concentrations of 5 different VOCs. Experimental results show that the sensitivity to relative humidity (RH) has been lowered to nearly 25% with the help of the few nanometer-thick PDMS coating. The presented work may enable qualitative and quantitative analysis of VOC compounds in the high RH environment.