Carbon dots@Cu metal-organic frameworks hybrids for ratiometric fluorescent determination of pesticide thiophanate-methyl.

A dual-emission fluorescent (FL) probe was constructed by coordinating Cu of copper metal-organic frameworks (Cu-MOFs) with - COO group of carbon dots (CDs) for pesticide thiophanate-methyl (TM) determination. TM was recognized by organic ligands (HBDC and HBDC-NH) of Cu-MOFs via π stacking. Due to the higher affinity of Cu to TM than ligands and CDs, TM chelated with Cu to form TM-Cu complex. Thus coordination of Cu-MOFs was damaged and the ligands were released resulting in the FL intensity increase of Cu-MOFs (F). And also CDs were released from CDs@Cu-MOFs hybrids and electron transfer from CDs to CuMOFs was inhibited, leading to the FL intensity increase of CDs (F). The FL intensity ratio (F/F) showed a good linear relationship with TM concentrations of 0.0307-0.769 μmol L with a limit of detection (LOD) of ~ 3.67 nmol L. The probe was successfully applied to detect TM in spiked food samples with satisfactory recoveries of 93.1-113%. Additionally, visual detection of TM was achieved according to the fluorescence color variation from blue to carmine, indicating promising application of CDs@Cu-MOFs probe.