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Highly Sensitive QCM Humidity Sensor Based on MOFs-Derived SnO2/Chitosan Hybrid Film

This paper demonstrated an accurate and reliable QCM humidity sensor based on metal–organic frameworks (MOFs)–derived SnO2/chitosan (CS) nanostructure. MOF-SnO2 nanoparticles with uniform size were derived from Sn-based MOFs. The morphologies and nanostructures of the MOF-SnO2/CS composite were characterized by multiple characterization techniques. The MOF-SnO2/CS composite based QCM humidity sensor exhibits high sensitivity (43.14 Hz/%RH), short response/recovery time (8 s/3 s), excellent selectivity, and fine long-term stability. Besides, the tests of finger approaching/sliding and human breathing based on MOF-SnO2/CS QCM humidity sensor were performed in this work, showing its potential applications in identifying humidity change and analyzing aspiration status. The resonant behavior of MOF-SnO2/CS QCM humidity sensor was analyzed by conductance spectrum. The adsorption and desorption processes of water molecules were analyzed by a bimodal exponential model, which reveals the adsorption and desorption dynamics of water molecules on the MOF-SnO2/CS composite.