Synthesis Of Water-Soluble Quantum Dots And Its Application In Analysis

As a new class of fluorescent nanomaterial, quantum dots (QDs) have gained increasing attention, and sufficient progress has been made in the preparation and application of water-soluble QDs. However, some problems in the synthesis and application need to be further solved. Several works have mainly performed by taking QDs preparation and QDs application in the fields of pharmaceutical determination, protein analysis and metal ions detection. The main contents of this thesis are described as follows:(1) Mercaptopropionic acid (MPA)-capped CdTe QDs were prepared in an aqueous medium with CdCl2and TeO2as raw materials, and NaBH4as reductant. The influences of experimental variables, including pH value, MPA/Cd and Te/Cd molar ratios, on the emission peak and photoluminescence quantum yield of the obtained CdTe QDs were investigated, and the obtained QDs were characterized by transmission electron microscopy, X-ray powder diffraction, ultraviolet-visible spectroscopy and fluorescent spectroscopy, respectively. The results showed that the CdTe QDs were of zinc-blended crystal structure in a sphere-like shape. The fluorescence of CdTe QDs can be significantly quenched by copper ions. However, in the presence of tiopronin, copper ions were released from the QDs and thus restored the fluorescence of QDs. A new type of fluorescence turn-on assay for detection of tiopronin using QDs/copper ions ensemble is developed. Under the selected conditions, the response was linearly proportional to the concentration of tiopronin between1to10μg/mL, the limit of detection was0.039μg/mL. The developed method was successfully applied to the detection of tiopronin in real samples, and satisfactory results were achieved.(2) A novel technology has been developed for the synthesis of thioglycolic acid (TGA)-capped CdTe QDs in aqueous medium. The reaction was carried out in air atmosphere with one-pot by using Na2TeO3to replace Te or Al2Te3. The influences of various experimental variables, including refluxing time, pH value, Cd/Te and Cd/TGA molar ratios, on the luminescent properties of the obtained CdTe QDs have been systematically investigated. Furthermore, the obtained QDs were characterized by Fourier transform infrared spectra, X-ray powder diffraction and transmission electron microscopy, respectively. The results demonstrate that, under the optimized experimental conditions, the obtained CdTe QDs exhibited a narrow photoluminescence band (fwhm33-45nm) with reproducible room temperature quantum yields as high as28%, the emission color is tunable from green to orange with increasing diameter of QDs. A simple and rapid method for lysozyme determination was developed based on the interaction between CdTe QDs and lysozyme. Under the selected conditions, the linear range of resonance light scattering intensity versus the concentration of lysozyme was0.2-3.2mg/L. The linear equations was IRLs=46.815+319.12C, with a correlation coefficient of0.9987. The limit of detection of lysozyme of this method was0.08mg/L. The proposed method had the advantage of specificity. There was no interference to coexisting common amino acids. Finally, the proposed method was applied to the determination of lysozyme in real samples with satisfactory results.(3) CdSeTe QDs were synthesized by the reaction of CdCl2, Na2SeO3, Na2TeO3and N2H4·H2O in water in the presence of mercaptopropionic acid (MPA) as stabilizer. Compared with the CdTe QDs, the CdSeTe alloy QDs showed an obvious red-shifted emission with the color-tune capability to the near-infrared (NIR) wavelength. The fluorescence of the CdSeTe QDs could be markedly quenched by Cu2+ions. Based on this, a simple and rapid method for Cu2+ions determination was proposed using the NIR CdSeTe QDs as fluorescent probes. Under optimal conditions, the response was linearly proportional to the concentration of Cu2+ions between10to200μg/L, the limit of detection was1.13μg/L. The developed method was successfully applied to the determination of trace Cu in real samples with satisfactory results.