Multisignal Collaborative Detection of Thiram Based on Dual-Functional Iron-Based Metal Organic Frameworks

To address the thiram (Tr) residue risks to food safety and human health, a ratiometric fluorescence/colorimetric dual-mode detection method was developed using dual-functional iron-based metal organic frameworks (Fe-MOFs) with blue fluorescence and peroxidase-like activity. Fe-MOF catalyzed H 2 O 2 -mediated oxidation of o- p henylenediamine (OPD) to 2,3-diaminophenazine (DAP), quenching Fe-MOF’s fluorescence via the internal filtration effect (IFE). Tr inhibited the catalysis, enabling fluorescence recovery and reducing the absorbance of DAP. The dual-mode method achieved a detection limit of 0.18 μM, far below the allowable maximum residue level (MRL) of 21 μM. Simultaneously, on-site visualization analysis was realized via the RGB method based on the color changes under UV/sunlight. Applied to the detection of apple, cabbage, corn, bean sprout, and soil, the dual-mode/RGB methods showed consistent results, effectively avoiding false positives through cross-verification of multiple signals and enhancing detection accuracy.