Portable iron-organic frameworks hydrogel for glyphosate detection based on competitive coordination with iron

The detection techniques for glyphosate residues have garnered attention due to the potential toxicity associated. Herein, we introduced a fluorescent "turn-on" strategy, leveraging competitive coordination with iron, for glyphosate detection. We synthesized iron-based metal-organic frameworks (Fe-MOFs) at room temperature. Among them, 2,5-dihydroxyterephthalic acid (DOBDC) acted as a ligand to produce strong fluorescence, and iron ions acted as a quencher to quench the fluorescence of DOBDC. Another ligand, 2-nitroterephthalic acid, contained nitro quenching of the fluorescence, giving it a lower background. Glyphosate competed with the ligands for ions, weakening the interaction between ions and the ligands. This disruption restored the fluorescence emission at 535 nm, enabling glyphosate detection. To facilitate field application, Fe-MOFs were encapsulated within agarose to create a functional hydrogel. Glyphosate penetrated the hydrogel and resulting in fluorescence "turn-on". Remarkably, this method facilitated visual detection through smartphone photography coupled with RGB (red/green/blue) analysis, offering a user-friendly and portable solution.