| Semiconductor quantum dots (QDs), representing one of the most important types of nanomaterials, show unique narrow size-dependent fluorescence, broad excitation ranges and excellent robustness against photobleaching, therefore, attracting considerable attentions in a wide variety of scientific fields. Due to the relatively high luminescence quantum yields and biocompatibility, CdTe quantum dots as the representative of semiconductor QDs directly synthesized in aqueous solutions has become a hot topic of fluorescent semiconductor QDs for many investigations. It is well known that the photoluminescence quantum yields play a significant role in the application of semiconductor QDs. but undoubtedly the stability is also a crucial point for implementing the integration of CdTe with other functional materials and need to be carefully studied. With the stable QDs, the QDs-biomolecule conjugates light up the research and development of bioimaging and specific bioanalysis. In addition, the QDs-silica nanocomposites improve the stability of QDs and make them easily be modified. Thus, it is of great value to fully tap potentials of QDs nanocomposites. In this thesis, we mainly focused on the stability of water-dispersed MPA-capped CdTe QDs and their integration with biomolecule and silica nanoparticles. The results were as follows:(1) CdTe QDs with different Cd-to-Te molar ratios were synthesized through hydrothermal method and then were put into three various ambience to investigate their stability. The first ambience was radical oxidation system with potassium persulfate (KPS), the second one was photooxidation environment and the third is high-temperature circumstance. The experiment datum showed that the CdTe QDs with high Cd-to-Te molar ratio (8:1or higher) owned superior photoluminescence stability and colloid stability under the three conditions mentioned above, while CdTe QDs with low Cd-to-Te molar ratio possessed weak stability. Taking the productivity into consideration, we chose the ratio of8:1that results in high productivity to study in depth. With the increasing size of CdTe QDs with the Cd-to-Te molar ratio of8:1. the surface displayed higher content of sulfur and the photoluminescence lifetime also increased. Moreover, the transition from multiexponential to monoexponential decay curves which was not detected in the CdTe QDs with the Cd-to-Te molar ratio of2:1was observed. (2) Based on the stable CdTe QDs in the first part, the QDs-BSA conjugates were fabricated via amide bond. As for the545nm-emitting CdTe QDs, the fluorescence intensity of the conjugates was higher than the initial QDs when the mass ratio of CdTe-to-BSA was1:5, in contrast, this ratio was1:1in the680nm-emitting CdTe QDs-BSA conjugates. The study of the the quenching of BSA’s fluorescence with QDs suggested that static and dynamic quenching might be occurring together. On the other hand, the TAG-72(CC49) monoclonal antibody was linked to the near-infrared CdTe QDs by the same technique. Their successful conjugation was confirmed by SDS-Polyacrylamide gel electrophoresis (SDS-PAGE) and Transmission Electron Microscopy (TEM) images. The high fluorescence intensity and immunoassays experiment verified their feasibility as immunofluorescence probes for Gastric tumor cells.(3) The CdTe@SiO2nanoparticles with particle size less than100nm were produced according to the method reported for incorporating anionic dyes into silica nanoparticles. The fluorescence intensity of CdTe@SiO2nanoparticles was28.6%of that of the original CdTe QDs. Then, we modified the synthesis process and effectively obtained CdTe@SiO2nanoparticles of10-20nm. Particularly, their fluorescence intensity was increased to69.3%of that of the original CdTe QDs. Besides, we preliminarily investigate the conjugation of CdTe QDs on the surface of mesoporous silica nanoparticles and got the spherical, monodispersed nanoparticles with good optical properties. |
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