Non-destructive and ultra-sensitive detection of Listeria Monocytogenes in ready- to-eat foods based on hollow cauliflower-like PdAg/ZnO by surface modification engineering.

Listeria monocytogenes (LM) constitutes a considerable public health and environmental hazard, necessitating an urgent development of non-destructive and ultra-sensitive detection methods. In this study, a hollow cauliflower-like PdAg/ZnO was successfully fabricated via surface modified engineering strategies. The unique hierarchical hollow cauliflower-like structure, featuring abundant surface active sites and rapid gas transport channels, enhances the sensitivity of gas sensors for detecting the LM metabolic biomarker 3-hydroxy-2-butanone (3H2B). Meanwhile, the uniform loading of bimetallic PdAg further enhances the sensing performance of the sensor through modulation of surface reactivity. The optimized PdAg-1.5/ZnO sensor exhibited exceptional performance, characterized by reduced operating temperature from 240 °C to 180 °C, ultra-sensitive response (Ra/Rg = 157.5@50 ppm), remarkably rapid response/recovery speeds (9.0 s/5.4 s), and low detection limit (200 ppb), facilitating trace detection of LM. Mechanistic insights from in/ex-situ characterizations and density functional theory calculations reveal that the superior sensing performance stems from the PdAg synergistic effect strengthens 3H2B adsorption energy (Eads = -1.08 eV), promotes electron transfer and oxygen vacancy formation. Furthermore, supported by machine learning, the handheld sensor based on PdAg-1.5/ZnO achieved 98 % accuracy in detecting LM in salmon and sweet prawns. This advancement will promote the development of non-destructive detection technologies for food quality control and environmental safety assessment.