Polydopamine-modified SnO₂ nanofiber composite coated QCM gas sensor for high-performance formaldehyde sensing

This paper introduces a quartz crystal microbalance sensor (QCM) based on SnO2 NFs/PDA composite with multi-layer stacked fiber nanostructure, which possesses high sensitivity and selectivity to formaldehyde gas. SnO2 NFs/PDA composite was synthesized via electrospinning and further oxidative polymerization. The morphology and chemical compositions of the as-prepared composite nanomaterials were confirmed by a series of material characterization technologies. The QCM sensor based on SnO2 NFs/PDA nanomaterials exhibited excellent sensing characteristics over a wide range of formaldehyde concentration (0.5 - 50 ppm), such as high sensitivity (12.2 Hz/ppm), short response/recovery times (25 s/38 s), high linearity and selectivity. The frequency shift characteristics and electrical parameters of the prepared sensors were confirmed by impedance analysis. The adsorption mechanism of formaldehyde gas could be attributed to hydrogen bonding and the combination of aldehyde ammonia Schiff base interactions. This work indicated that SnO2 NFs/PDA based QCM possessed great potential in actual formaldehyde sensing, which provided a feasible solution for designing highly sensitive and selective formaldehyde sensor.