Synthesis Of Water-soluble Quantum Dots And Their Application In Food Analysis

Quantum dots, as a new pattern of fluorescent probes, have a great deal ofadvantages such as broad excitation spectrum, narrow-band emission spectrum, highchemical stability compared to the traditional fluorescent dyes. Quantum dots showedbroad application prospects in the fields of life science, analytical chemistry, materialsscience and immunology in recent years. The work of predecessor was summarizedsuch as preparation, characterization and application in detection of food safety ofquantum dots.(1) The first chapter briefly introduced the basic characteristics, the synthesismethods and the surface modification methods of the quantum dots, and then gave abrief overview of the research progress and application prospects of quantum dots infood detection.(2) In this chapter, a simple and sensitive method based on the enhancement of thefluorescence intensity of thioglycolic acid-capped CdSe quantum dots is proposed forthe determination of Sudan I. That UV-visible spectrophotometer、 fluorescencespectroscopy and transmission electron microscopy(TEM) were used to characterize theQDs. With the increment of the concentration of Sudan I, it gives a calibration graphlinear in the range of3×10-7mol/L-8×10-6mol/L. The obtained tropics equation isF/F0=1.538C+2.689, with the correlation coefficient of0.9962and the detection limit of1×10-7mol/L. The measurement has been applied to the determination of Sudan I in hotchili powder, and the recovery was94.11%-104.86%.(3) On the basis of the second chapter, we synthesized of the core-shell CdSe/ZnSquantum dots. A novel method for determination of metronidazole has been developedbased on quenching of the fluorescence of CdSe/ZnS in aqueous solutions. Effects ofexperimental conditions were investigated such as the effect of buffer systems, theconcentration of CdSe/ZnS QDs, the pH values, and the incubation time. Under theoptimal conditions，a good linearity was obtained between the quenched fluorescenceintensity of CdTe/ZnS QDs and the concentration of metronidazole in the range of0.024~0.8μmol/L. The correlation coefficient is0.9987and the limit of detection was0.008μmol/L (3σ). The amounts of metronidazole in pill were determined by theproposed method and the results agreed with the claimed value.(4) The water-soluble CdTe/ZnS core-shell quantum dots (QDs) were synthesizedusing thioglycolic acid (TGA) as stabilizer．Fluorescence resonance energy transfer (FRET) system was constructed between CdTe/ZnS QDs (donor) and the MalachiteGreen (acceptor). Based on this FRET system, a sensitive method for the determinationof the Malachite Green (MG) was developed. Under the optimal conditions，a goodlinearity was obtained between the quenched fluorescence intensity of CdTe/ZnS QDsand the concentration of MG in the range of0.048～3.2μmol/L. The correlationcoefficient is0.9993and the limit of detection was0.0158μmol/L. The proposedmethod was successfully applied in the determination of MG in water samples with thespiked recovery of99.3-102%. Furthermore, the possible mechanism of interactionbetween CdTe/ZnS QDs and MG was discussed.