【作者】 曾若生；

【导师】 邹炳锁；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2010， 博士

【摘要】 量子点是一种新型的无机半导体纳米材料。为改善发光性质,量子点通常为核壳结构,水相合成的新型核壳结构量子点由于其良好的光学性质和光化学稳定性,作为荧光探针在生物标记方面具有重要应用价值,相比有机相合成的量子点在生物标记方面有着独特的优势。另外,掺杂量子点更显出独特的发光性质,从而吸引许多研究者的目光。如何通过“绿色化学”方法,发展一种适合工业化生产的高效发光量子点的合成路线显得特别重要。本论文的主要工作是研究了新型核壳结构水相CdTe/CdSe量子点的合成方法,并作为荧光探针用于肿瘤细胞—HeLa的标记,以及用硒粉为硒源合成了高质量的Mn:ZnSe和Mn:CdSe量子点。系统研究了反应条件,优化了相关实验参数,并研究了其相关机理。希望能对以后量子点的研究等方面提供有益的借鉴。本论文的主要研究工作及研究成果如下：1.水性CdTe和Type-ⅡCdTe/CdSe(核壳)量子点的合成报道了通过一条新颖而简单的路线合成了水溶性高效发光的CdTe和type-ⅡCdTe/CdSe量子点。通过控制CdSe壳层厚度,CdTe/CdSe量子点的发光范围从510-640 nm连续可调。而且,具有最优化CdSe壳层厚度的CdTe/CdSe量子点量子效率可达40%以上。CdTe/CdSe量子点的结构和组成通过高分辨电子显微镜、x-射线粉末衍射仪和x光电子能谱进行了表征,对其形成机理进行了深入细致的讨论。2.叶酸介导的type-ⅡCdTe/CdSe量子点作为荧光探针标记肿瘤细胞采用稳定性和水溶性好、发光强度高的type-ⅡCdTe/CdSe量子点与叶酸偶联,利用叶酸与叶酸受体高度亲和的特性,使之成为一种高效的荧光探针来标记肿瘤细胞——HeLa细胞。通过荧光显微镜来观察在HeLa细胞里通过叶酸偶联的CdTe/CdSe量子点,结果表明叶酸偶联的CdTe/CdSe量子点有效地进入肿瘤细胞,在HeLa细胞内展现了良好的成像和示踪功能。这说明高质量量子点是细胞标记的一种很好的荧光探针,在生命科学领域有着重要的应用价值。3.高质量Mn:ZnSe量子点的合成及相关机理研究通过使用空气中稳定和易得原料,比如硬脂酸锌(锰)、相应的硬脂酸、硒粉、脂肪胺和十八烯,合成了高质量、纯杂质离子发光和量子效率高达40-60%的Mn掺杂的ZnSe量子点(Mn:ZnSe掺杂量子点)。在合成路线中,去除了易燃易爆、高毒性和价格昂贵的有机膦,因为脂肪胺的存在使得元素硒的反应活性增强,这也在很大程度上改变了反应的进程。对“成核掺杂”的两个关键步骤,即MnSe纳米簇的形成和ZnSe的包覆,进行了系统的讨论。通过前驱体“二次注射”模式调节了在掺杂量子点中的Mn离子“晶格扩散”的程度。获得的掺杂量子点为立方相晶体结构,具有优化的球形形貌,呈单分散分布以及可控的Mn:Zn比。4.Mn掺杂的CdSe量子点的合成及机理研究通过采用“成核掺杂”的路线将量子点成核过程和生长过程分离,采用硒粉为硒源,脂肪胺活化反应,合成了高质量的、纯杂质离子发光的Mn掺杂的CdSe量子点(Mn:CdSe)。系统研究了脂肪酸盐与脂肪酸的比例、壳层的包覆温度对Mn:CdSe掺杂量子点光学性质的影响；确定了Mn离子在CdSe量子点中“晶格扩散”的临界温度,提出了一种新的“晶格弹出”机理,对其他掺杂量子点的合成及机理研究具有重要的借鉴意义。更多还原

【Abstract】 Quantum dots (QDs) are novel inorganic semiconductor nanocrystal materials. The new core-shell aqueous quantum dots own good optical characters and high optical and chemical stability, can be used to biolabeling as the fluorescence probe and have many relative advantages compared with bare quantum dots synthesized in organic solvents. Doped quantum dots developed new views of scientists on synthetic chemistry because doped quantum dots have many advantages compared with undoped semiconductor quantum dots. It is very important to use green chemistry routes to realize industry production of doped quantum dots. This dissertation focus on synthesis of novel core-shell aqueous quantum dots, labeling in tumor cells—HeLa as the fluorescence probe, and synthesis and investigation of mechanisms of doped quantum dots (Mn:ZnSe and Mn:CdSe QDs). We also investigated the reaction conditions, relative mechanism and optimized experiment parameters of quantum dot growth and hope that this research is useful to the investigation of quantum dots in the future.The valuable results of this dissertation are following:1. Aqueous synthesis of CdTe and type-ⅡCdTe/CdSe core-shell quantum dotsIn this chapter, we report a two-step aqueous synthesis of highly luminescent CdTe and CdTe/CdSe core/shell quantum dots via a simple method. The emission range of CdTe/CdSe Quantum dots can be tuned from 510 to 640 nm by controlling the thickness of CdSe shell. Accordingly, the photoluminescence quantum yield (PL QY) of CdTe/CdSe quantum dots with an optimized thickness of the CdSe shell can reach up to 40%. The structure and compositions of the core/shell quantum dots were characterized by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, and the formation mechanism of the core-shell structure was discussed in detail.2. Labeling of aqueous type-ⅡCdTe/CdSe quantum dots in tumor cells as fluorescence probewe successfully labeled tumor cells—HeLa using aqueous, high emissive, and folate conjugated type-ⅡCdTe/CdSe quantum dots as fluorescence probe which were assessed with a fluorescence microscope. The results showed that folate conjugated CdTe/CdSe quantum dots could enter tumor cells efficiently, which showed good tracing and labeling of quantum dots in HeLa cells. The results indicated that the type-ⅡCdTe/CdSe quantum dots are a excellent fluorescence probe and could be applied in biolabeling.3. Synthesis of highly emissive Mn-doped ZnSe quantum dots without pyrophoric reagentsManganese-doped zinc selenide quantum dots (Mn:ZnSe d-dots) with high optical quality, pure dopant emission with 40-60% photoluminescence quantum yield, were synthesized with air-stable and generic starting materials, namely zinc (manganese) fatty acid salts with corresponding free fatty acids, Se powder, fatty amine, and octadecene. The pyrophoric, highly toxic, and expensive organophospines were eliminated from the existing synthetic protocols for high quality Mn:ZnSe d-dots, which changed the reaction profile substantially, because of the enhanced reactivity of elemental Se with the presence of fatty amines. The reaction temperatures for two key processes involved in "nucleation-doping", namely, formation of MnSe nanoclusters and their overcoating by the host, were both reduced. Multiple injection techniques were employed to realize balanced diffusion of Mn ions in the doped quantum dots (d-dots). The resulting d-dots were found to be in zinc-blende crystal structure, with optimal spherical shape, nearly monodispersed, and controlled in their Mn:Zn ratio.4. Investigation of synthesis and doping mechanism of Mn doped CdSe quantum dotsIn this chapter, we used the "nucleation doping" route to combine dopants and host materials and synthesized high-quality Mn doped CdSe nanocrystal emitters with nearly pure Mn emission and efficient dopant photoluminescence using selenium power as selenium source and carboxylic amine as active reagent. We investigated the effect of the ratio of carboxylic acid salts to carboxylic acid and the overcoating temperature of shell on the optical property of Mn doped CdSe nanocrtstals. The critical temperature of "lattice diffusion" of Mn ions in CdSe lattice was defined and a new "lattice ejection" mechanism was proposed, which is very valuable and interesting to the investigation of synthesis and mechanism of other doped quantum dots.更多还原