Simultaneous detection of malachite & leucomalachite green based on dual template CdTe@MIP via normal and synchronous fluorescence quenching

Malachite green (MG) is an industrial dye, but has been once abused in aquaculture for disease treatment. Because MG and its metabolite, leucomalachite green (LMG), present great harm to human health, it is essential to rapidly and accurately detect MG and LMG residues in aquatic products. However, the simultaneous screening of MG and LMG is still a challenge to date. In this work, a dual-template molecularly imprinted polymer (MIP) coated CdTe QDs was developed and applied as a nano-probe to simultaneously detect MG and LMG in fish samples via normal and synchronous fluorescence quenching. The molar ratios of templates (MG and LMG) to monomer (APTES) and cross-linker (TEOS), and the amount of CdTe QDs in the probe preparation were optimized. A normal fluorescence emission at 600 nm could be linearly quenched by MG, while the synchronous fluorescence emission at the wavelength interval of 340 nm could be quenched by both LMG and MG. The detection limits of MG and LMG were 17 nmol L-1 and 28 nmol L-1 (3 sigma, n = 9), respectively. Based on the equations of Stem-Volmer, MG and LMG could be simultaneously detected without any conversion treatment. The recoveries of MG and LMG in fish samples ranged from 92% to 107% and from 91% to 108%, respectively. The results demonstrated that the as-prepared dual-template CdTe@MIP could be used as a fluorescent probe to rapidly and simultaneously detect MG and LMG in fish samples.