Bifunctional metal-organic framework Nanozymes with flexibly tunable valence states for dual-mode detection of organophosphorus pesticides.

Pesticides play a crucial role in crop production. However, they also pose significant pollution and health risks. This study presents a novel dual-mode cascade strategy for detecting pesticide residues, addressing the growing demand for improved safety control. The proposed method utilizes a bifunctional metal-organic framework nanozyme (BMFN) with both fluorescence and biomimetic capabilities, enabling efficient analysis of pesticide residues. The bifunctionalities of BMFN is achieved by modulating Ce3+/Ce4+ valence states and adjusting reaction conditions. The dual functionality is activated by changing the solvent pH, and its mechanism is thoroughly validated. Exposure to methyl paraoxon (MP) triggers a cascade reaction that generates both fluorescence and colorimetric signals, with detection limits of 0.2 and 0.5 μM, respectively. The effectiveness of the dual-mode strategy is demonstrated in complex matrices. Overall, the integrated system highlights the exceptional performance of the bifunctional nanozyme in chemical sensing and demonstrates the success of dual-mode cascade analytical approaches.