Field-Applicable Quartz Crystal Microbalance Sensor Based on H-mTiO ₂ @mPDA Nanotubes for Highly Selective and Sensitive Monitoring of Listeria monocytogenes in Ready-to-Eat Foods

Listeria monocytogenes (LM) causes severe foodborne illness with 20-30% mortality, which demands novel and rapid detection methods. Crucially, 3-hydroxy-2-butanone (3H2B) comprises 32.2% of the LM-emitted volatiles, serving as a specific biomarker for indirect LM monitoring. Mesoporous polydopamine (mPDA)-functionalized hollow mesoporous TiO₂ nanotubes (H-mTiO₂@mPDA) are rationally engineered via cooperative assembly for constructing quartz crystal microbalance gas sensors to detect 3H2B. Optimized H-mTiO₂@mPDA-2 sensors demonstrate exceptional performance, including high sensitivity (6.8 Hz/ppm), rapid response/recovery (7:9 s), and outstanding selectivity. The comparative experiments against Escherichia coli and Staphylococcus aureus in ready-to-eat foods, along with practical assessments of ham and lettuce samples, illustrate the sensor's remarkable potential for LM evaluation. Moreover, morphology characterizations, Gaussian simulations, thermodynamic analysis coupled with the Clausius-Clapeyron equation, and in situ diffuse reflectance infrared Fourier-transform were synthetically utilized to study the gas sensing mechanism. It is revealed that the mesoporous structures on both TiO₂ and mPDA surfaces with radial channels facilitate rapid diffusion of 3H2B and provide abundant active sites, while the hydrogen bond adsorption and Schiff base reaction between mPDA and 3H2B enhance gas-sensing efficiency and selectivity. This work pioneers an in situ monitoring paradigm for LM through synergistic material design and mechanistic innovation. Meanwhile, the established gas detection technology system exhibits significant potential for extension into environmental science, public health, and medical diagnostics.