ORIGINAL ABSTRACT

The widespread use of glyphosate in agriculture has raised concerns about environmental contamination and associated health risks, creating an urgent need for rapid, sensitive, and field-deployable analytical tools. In this work, Zr/Eu-metal-organic framework (Zr/Eu-MOFs) as an integrated bimetallic ratiometric fluorescent hydrogel sensor for fast and highly sensitive visual detection of glyphosate has been developed. By doping Eu3+ into a robust Zr-based MOF framework, Zr/Eu-MOFs exhibit dual-emission bands at 445 and 618 nm, enabling an intrinsic self-referenced signal without multicomponent assembly. Upon glyphosate addition, the sensor responds within 10 s. Zr/Eu-MOFs display a reliable ratiometric response over 0.05 - 10.0 mg/L with a low detection limit of 0.03 mg/L (0.2 μmol/L), which is far below the permissible maximum residue limit (MRL) for drinking water by the US EPA and China (4.1 μmol/L). Mechanistic evidence indicates that glyphosate forms P-O-Zr coordination linkages and interfacial interactions which modulate the ligand-to-metal charge transfer (LMCT) process, resulting in an enhanced ratiometric fluorescence response at 445 nm, while the Eu3+ emission at 618 nm remains essentially unchanged. Moreover, an agarose hydrogel format coupled with smartphone image analysis enables rapid visual detection. A spraying-enabled fluorescence imaging strategy further allows rapid screening of glyphosate contamination on leaves, apple surfaces, and soil-water matrices under UV illumination. Overall, this work provides a facile, integrated, and visually readable ratiometric platform for on-site glyphosate monitoring.