An all-in-one Zn/Ce-MOF nanozyme: combining ratiometric sensing, oxidase-like activity, and apparent phosphoester hydrolase-like behavior for organophosphorus pesticide monitoring.

The widespread residue of highly toxic organophosphorus pesticides (OPs) poses a serious threat to food safety and human health, underscoring the need for sensitive screening methods. In this work, a ratiometric fluorescence sensor array was constructed based on a trifunctional Zn/Ce-MOF exhibiting intrinsic blue fluorescence, oxidase-like activity, and apparent phosphoester hydrolase-like behavior. LC-HRMS full-scan analysis further showed DDV signal depletion accompanied by a marked increase in a DMP-assigned signal after 90 min. Ce sites promoted o-phenylenediamine (OPD) oxidation to produce yellow-fluorescent 2,3-diaminophenazine (DAP), which attenuated the intrinsic fluorescence through the inner filter effect. Upon addition of OPs, the DAP-associated emission decreased while the intrinsic fluorescence of Zn/Ce-MOF recovered, resulting in a ratiometric response (F565/F440). Meanwhile, the fluorescence variation enabled visible color changes and smartphone-assisted signal acquisition based on red, green, and blue (RGB) analysis. The proposed sensor exhibited two linear response regions toward DDV over the final concentration ranges of 0-5 and 5-30 μg/mL, with a detection limit of 0.043 μg/mL. The sensing platform was preliminarily evaluated through post-extraction matrix-spike experiments for DDV in tenfold-diluted tomato and spinach extracts, yielding post-extraction matrix-spike recoveries of 93.5-121.5%. Multivariate analysis of F565/F440, G/B, and R/G signals revealed characteristic distribution, separation, and clustering patterns for five OP standards, including dichlorvos (DDV), dimethoate (DM), chlorpyrifos (CPF), methyl parathion (MP), and trichlorfon (TCF), in standard solutions. The study therefore provides a Zn/Ce-MOF-based strategy for smartphone-assisted DDV screening in tenfold-diluted tomato and spinach extracts and multichannel response-pattern analysis of five OP standards under controlled conditions. Further studies will evaluate the applicability of the multichannel response patterns to multiple OPs in complex food matrices.