| Quantum dots (QDs) i. e. semiconductor nanocrystals (NCs) , with a diameter of 1-100 nanometers in size,as a specific kind of nanoparticles newly developed in recent years,provide an extremely good fluorescent signal and then can well be used for fluorescent labeling , also as an ideal bioconjugated fluorescent probe for bioanalysis,because of their unique optical and electronic properties,such as broad excitation spectrum,narrow emission spectrum, tunable emission and neglectable optical bleach phenomenon etc. Although its research and application has just been explored,QDs have attracted great attention from scientists in many fields. Their basic knowledge and characters,synthesis route,labeling approach,recent progress and prospect in potential application to life science,especially to immunoassay and rapid diagnostic analysis are reviewed in part 1 of chapter 1; the basic properties, synthesis, applications such as bioseparation of magnetic nanoparticles are reviewed in part 2 of chapter 1.In the chapter 2, a new aqueous route for synthesizing high-quality CdTe nanocrystals (NCs) is presented. Using both glutathione (GSH) and cysteine as stabilizers, high-quality CdTe NCs with controllable photoluminescence (PL) wavelength from 500 nm to 630 nm can be prepared within 4 hours. As-prepared CdTe NCs are shown to have higher photoluminescence quantum yields (PL QY) compared with CdTe NCs prepared with other aqueous methods, when the fluorescent emission peak appeared in orange-red window the PL QY reaches 70% or above at room temperature without any post-preparative treatment. To our best knowledge, this is one of the most successful methods which can directly prepare CdTe NCs in aqueous solution with high quality ( high PL QY, narrow FWHM and so on). In addition, as-prepared CdTe NCs can directly conjugate to biomolecules via functional groups (–NH2 or -COOH) for various research purposes, and certainly could be applied widely to optoelectronic devices in the near future due to their high quantum yields. The possible mechanism for such high PL QY is preliminarily deduced.In the chapter 3, with the above CdTe NCs as fluorephores, the NCs doped silica fluorescent nanoparticles were prepared using reverse microemulsion method. Results shows that more than one NCs could be embedded in one silica nanoparticle with as-prepared CdTe NCs and no other agents needed. So as-prepared NCs doped silica nanoparticles have much higher luminescence intensity and can be used in more and more fields.In the chapter 4, the above CdTe quantum dots (QDs) can be applied in the quantitive determination of copper (II) ions as probes based on fluorescence quenching mechanism. Through systematic study of the influencing factors on photoluminescent behavior of as-prepared CdTe QDs, the determination condition was optimized. In the phosphate buffer with pH value 6.2, when the concentration was 1.013×10-4mol/L, the fluorescence intensity of QDs decreased linearly with the copper (II) ions concentration in the range of 0-260μg/L. The detection limit was 0.15μg/L. Up to now, there is no report that can exceed our results in the case of such low detection limit and broad linear responding scope. Finally, the reason why this method can achieve better sensitivity and the fluorescence quenching mechanism were primarily deduced.In chapter 5, a novel method for preparing high efficiency fluorescence nanocrystals (NCs)-encoded microspheres with two steps was developed. First, a series of polystyrene (PS) microspheres from 1μm to 5μm in diameter were prepared by dispersion polymerization; then after a swelling step with CdSe NCs of different size the PS microspheres were encoded quantitatively. This method for fluorescence-encoding of microspheres was shown to have the following outstanding characteristics: (1) An emulsion containing CdSe NCs and swelling agents (chloroform ) are firstly used for introduction of NCs into microspheres. (2) The embedded nanocrystals remain their original properties and they are not simply absorbed onto the surface of the microspheres but being carried into the inner of microspheres and so the NCs cannot be released or leaked out easily. As-prepared fluorescence-encoded microspheres could conjugate with proteins by some further surface modification, so they have a great potential to be applied to such fields as biochemistry, molecular biology, cell biology, immunology, etc. In addition, this method can be operated easily and reproducibly.In chapter 6, with oleic acid functionalized Fe3O4 nanoparticles as the magnetic carriers, styrene and crylic acid as the monomers, and divinylbenzene (DVB) as cross linker, the magnetic polystyrene microspheres were prepared by disperse polymerization. A series of characterizations were carried out, these show that as-prepared magnetic polystyrene microspheres have narrower size distribution with smooth surface, fine morphology and structure. Even more, they are pretty superparamagnetic, the saturation magnetization of as-prepared microspheres reaches to 11.61emu/g at room temperature. Finally, after systematic study, the factors that affects the size of microspheres were discussed. |
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