Preparation Of Fluorescent Probes Based On CdTe Quantum Dots Coated With Molecularly Imprinted Polymers And Their Application In The Detection Of Malachite Green In Aquatic Products

Malachite green?MG?may result in teratogenic,carcinogenic,and mustagenic effect on human body.Current detection techniques for MG usually require expensive instruments and long detection period.In this dissertation,fluorescent probes based on CdTe quantum dots?QDs?coated with molecularly imprinted polymers?MIPs?were fabricated.The MIP-coated QDs were used for the determination of MG in water and fish samples by the strategy of fluorescence resonance energy transfer?FRET?.These fluorescent probes were successfully applied in the determination of MG with several advantages,such as specificity,accuracy and high detection speed.The dissertation mainly includes the following parts:Section 1,the probe of MIP-coated CdTe QDs for MG detection was synthesized through the precipitation polymerization.The optimum molar ratio of MG,monomer and cross-linker was chosen as 1:8:40,and the amount of CdTe QDs was 10 mg by optimizing the fluorescence intensities and quenching efficiencies of the MIP-coated CdTe QDs.The structure and morphology of the MIP-coated CdTe QDs were measured with transmission electron microscope?TEM?and Fourier transform infrared spectroscopy?FT-IR?.Core-shell structures were observed and the average diameter was around 290 nm.The MIP-coated CdTe QDs presented an adsorption capacity up to 150.2 mg g^-11 within 40 min.The quenching efficiencies of the MIP-coated CdTe QDs for MG were higher compared with those of MG analogues such as crystal violet?CV?and brilliant green?BG?,verifing that the particles possessed the specificity of binding to MG.The fluorescence intensities of the MIP-coated CdTe QDs were linearly quenched by MG at the concentrations from 0.1 to 20?mol L^-1with a detection limit of 0.059?mol L^-1.The spiked recoveries ranged from 94.8%to 106.2%for water and fish samples,indicating that the as-prepared MIP-coated CdTe QDs could be used as a fluorescent probe to rapidly detect MG in water and fish samples.Section 2,a fluorescent sensor for the detection of MG was fabricated by grafting MIPs onto the surface of CdTe QDs via a reverse microemulsion method.The optimum molar ratio of MG,functional monomer and cross-linker was 1:3:10,and the amount of CdTe QDs was 10 mg.TEM images showed that the particles were spherical with an average diameter of 49 nm.The MIP-coated CdTe QDs presented an adsorption capacity up to 31.4 mg g^-1and the adsorption equilibrium time was about 20 min.The fluorescence response of the MIP-coated CdTe QDs toward MG was much higher than its analogues including leuco malachite green,CV and BG.The as-synthesized MIP-coated CdTe QDs presented fluorescence quenching efficiencies for MG ranging from 0.08 to 20?mol L-1,the detedtion limit was 0.033?mol L-1.The spiked recoveries ranged from 94.3%to 109.5%.The measuring results were in accordance with those of HPLC mehod,which indicated that the MIP-coated CdTe QDs were able to detect MG rapidly and accurately in fish samples.Section 3,a magnetic fluorescent sensor?CdTe@MMIPs?was prepared based on the reverse microemulsion method using Fe3O4 nanoparticles and CdTe QDs as co-nucleus.With the specific adsorption and magnetic separation properties,the CdTe@MMIPs was used to realize the enrichment and detection of MG by repeating adsorption of low concentration MG samples.The TEM characterization demonstrated that the CdTe@MMIPs were well-shaped spherical particles with average diameter around 50 nm and the core-shell structures were formed with several Fe₃O₄ and CdTe QDs embedded in each of the polymer microsphere.Quick separation of CdTe@MMIPs from solutions could be realized with an external magnetic field,indicating that the CdTe@MMIPs presented excellent magnetic property.The microsphere particles possessed high selectivity of adsorption toward MG.The fluorescence quenching efficiencies of the CdTe@MMIPs were linearly quenched by MG at the concentrations from 0.025 to 1.5?mol L^-1.The detection limit was 0.014?mol L^-1.The recoveries of spiked MG in fish samples ranged from 102.7%to 108.6%.The result demonstrated that the as-prepared CdTe@MMIPs could be used for the detection of trace MG in fish samples.