Determination of leucomalachite green in fish using a novel MIP-coated QDs probe based on synchronous fluorescence quenching effect

A novel fluorescent probe based on CdTe QDs coated with molecularly imprinted polymers (MIP) was prepared for the determination of leucomalachite green (LMG) with the method of synchronous fluorescence quenching. When the wavelength interval of excitation and emission positions (Δl) was set as 340   nm, the strongest synchronous fluorescence emission of MIP-coated QDs was achieved at 260   nm, enabling the maximum fluorescent quenching of LMG because of the inner filter effect. According to this principle, a synchronous fluorescence quenching method for the rapid detection of LMG in fish was developed. MIP-coated QDs were synthesized using acrylamide (AM) and ethylene glycol dimethacrylate (EGDMA) as functional monomers and cross-linker, respectively. MIP-coated QDs with an average diameter around 67   nm were obtained at the optimum conditions (the molar ratio of 1:8:20 of LMG, AM and EGDMA, 60   mL of acetonitrile, 28   h of polymerization time). The synchronous fluorescence of MIP-coated QDs was linearly quenched by LMG at concentrations from 0.1 to 20   μmol   L −1 . Detection limit was 30   nmol   L −1 (3 σ , n   =   9) with spiked recoveries from 94.0% to 107.8% in fish samples. The results indicate that the method can be applied to the accurate and rapid detection of LMG residues in fish samples.