A Smartphone-assisted Fluorescent Sensor Using Eu-MOF Nanorods for Visual and Sensitive Detection of Organophosphorus Pesticides

Organophosphorus pesticides (OPs) are extensively used for pest control in crops, yet their residues pose potential threats to food safety and human health. Therefore, this study developed a dual-ligand metal–organic framework with stable red fluorescence as a ratiometric fluorescent sensor for highly sensitive detection of omethoate (OMT). The sensor utilizes Eu 3 ⁺ as the metal node and employs 3,5-dicarboxyphenylboronic acid (BBDC) and 2-hydroxyterephthalic acid (BDC-OH) as mixed organic ligands. The introduction of OMT significantly quenches the red fluorescence of Eu-BBDC/BDC-OH through the inner filter effect (IFE), enabling the quantitative analysis of OMT. The sensor exhibits a good linear response within the ranges of 0.025–0.3 μg/mL and 0.3–0.9 μg/mL, with a detection limit of 7.35 ng/mL, and demonstrates excellent selectivity. Recoveries of OMT from strawberry and cucumber samples ranged from 95.74% to 101.1%, with relative standard deviations of 0.59%-5.91%, validating the reliability and practicality of the method. Moreover, a paper-based sensor integrated with smartphone RGB analysis was constructed, allowing rapid, real-time, and visual detection of OMT residues.