Novel zinc nanoclusters based ratiometric fluorescence sensing strategy for sensitive detection of thiram

Thiram residue has drawn widespread attention due to its severe threat to the agricultural safety. Herein, a ratiometric fluorescence probe was designed for thiram detection based on glutathione capped zinc nanoclusters (GSH-ZnNCs) and o-phenylenediamine (OPD). OPD was oxidized by Ag⁺ to produce 2, 3-diaminophenazine (DAP), and the fluorescence of GSH-ZnNCs was quenched by DAP through fluorescence resonance energy transfer (FRET) effect. When exposed to thiram, Ag⁺ led to the cleavage of SS bond in thiram to form Ag⁺-dimethyl thiocarbamate complex, inhibiting the oxidation of OPD. Accordingly, specific thiram detection was constructed with GSH-ZnNCs. The ratiometric fluorescence value of lg(I₅₇₄/I₄₄₂) decreased linearly with increasing thiram concentration, and the limit of detection 0.116 μM was achieved. Moreover, the convenient sensing of thiram was achieved by combining with a smartphone. Both the fluorescence and portable sensing strategies were applied to real food sample analysis, showing potential in thiram sensing in agricultural areas.