Preparation Of Molecular Imprinting-fluorescence Quantum Dot Double Function Composite Microspheres For Detection Of Pesticide Residues

In order to improve the economic benefit and prevent diseases and weeds growth, the crops, fruit trees and vegetables spray with pesticides. However, these pesticides have long half-life and slow degradation. They eventually converge to the rivers with the rain. Therefore, residual pesticides gather to accumulate in human body through the food chain and pose a great threat to human health.The composite material is prepared by the quantum dots with fluorescence characteristic combined with molecularly imprinted polymers with high selectivity. It is used to detect pesticides residues in water samples. And the main contents were as follows:The Mn:ZnS QDs was prepared and modified by oleic acid. The QDs@MIPs was successfully fabricated by using modified Mn:ZnS QDs as fluorescent component, chlorpyrifos as template molecule, acrylamide as functional monomer, ethylene glycol dimethacrylate as cross-linker and azoisobutyronitrile as initiator in ethanol reaction solvent. The polymers were characterized by structure and surface morphology characterizations. The adsorption and selective properties of the QDs@MIPs was studied by fluorescence spectrophotometer. The method has been used to detect chlorpyrifos in water samples. The recoveries and relative standard deviations at different concentrations were 87.1%-94.5%and 2.9%-6.5%, respectively.The Mn:ZnS QDs was modified by silane coupling agent KH550. The QDs@MIPs was successfully prepared by using modified Mn:ZnS QDs as fluorescent component and cyphenothrin as template molecule. The polymers were characterized by fluorescence spectrophotometer, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), dynamic light scattering (DLS) and X-ray powder diffraction (XRD). The fluorescence quenching was studied between the QDs@MIPs and cyphenothrin. The type of fluorescence quenching was investigated by UV-vis and fluorescence spectroscopy. The specific adsorption capacity of polymers to cyphenothrin was studied with satisfactory results. And it can detect down to 9.0 nmol L1 of cyphenothrin and the concentration range of 0.1-80.0 μmol L-1.The Mn:ZnS QDs was modified by L-cysteine. The QDs@MIPs was successfully constructed by using mercapto-modified Mn:ZnS QDs as fluorescent component and nicosulfuron as template molecule. The polymers were characterized by a series of characterizations. Some experiment conditions were studied:absorption and emission wavelength, pH value and incubation time, et al. The fluorescence analysis can get good results at the pH 9 and the binding time of more than 10 min. The non-imprinted polymers were compared to QDs@MIPs and the imprinted factor 4.0 was obtained. It showed good adsorption performance. And the different quantity of nicosulfuron was also added in water samples. The recoveries were in the range from 89.6%to 96.5%and the relative standard deviations were in the range of 2.5%-5.7%.