【作者】 王志江；

【导师】 蔡伟；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2010， 博士

【摘要】 金纳米粒子具有优异的生物相容性以及独特的光学、电学和催化特性,在生物医学、传感器、光电器件和催化等诸多领域具有广阔的应用前景。金纳米粒子液相合成中的形核、长大规律和机理,特定尺寸和形貌的可控合成原理和方法以及多功能修饰和组装等是金纳米粒子研究与应用的重点和热点。本论文采用改进的Brust法制备了性能稳定的单分散Au₁₁纳米团簇和水溶性金纳米晶,以纳米粒子自组装的方式制备了金纳米粒子超晶格,研究了反应条件对纳米粒子形核、长大以及有序组装的影响规律和机理。并以金纳米粒子为基本组成单元,制备了多功能NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au和Fe₃O₄/Au纳米复合粒子,阐明了金纳米粒子及其复合材料微观结构与性能之间的内在联系。以巯基丙酸为配体,采用Brust双相法,通过控制Au³⁺与巯基丙酸的摩尔比值、还原剂添加速度以及反应温度,合成出具有良好稳定性的单分散Au₁₁（SCH₂CH₂COO-）₇（TOA⁺）₇纳米团簇。Au₁₁纳米团簇在355 nm光激发下产生蓝色荧光,最大荧光发射峰在417 nm处,荧光量子效率高达8.6%。Au₁₁纳米团簇具有高荧光量子效率的主要原因为:团簇尺寸的高度单分散性避免了其他粒径纳米粒子的干扰,同时类树枝状（SCH₂CH₂COO-）（TOA⁺）作为稳定配体阻止了溶剂的猝灭效应。以单分散Au₁₁纳米团簇为构筑单元,通过自组装制备出Au₁₁纳米团簇超晶格。超晶格也发射蓝色荧光,但与稀溶液中Au₁₁纳米团簇的荧光发射峰相比,其荧光发射峰红移了56 nm。系统研究了Brust单相法的合成条件及中间体的尺寸分布对金纳米晶单分散性的影响规律和机理,发现Au0均一形核和均匀生长是获得粒子尺寸单分散的必要条件。分别通过控制Au1+中间体尺寸分布和反应搅拌速度实现Au0均一形核和均匀生长。在此基础上,调节还原剂滴加速度制备出不同尺寸的单分散水溶性金纳米晶。在0.2 mol/L的浓度下,尺寸为6.6 nm的金纳米晶的X射线衰减值为1663 HU,明显高于目前临床使用的欧苏造影剂X射线衰减值（826 HU）。巯基丙酸作为稳定配体的金纳米晶具有优异的稳定性,以干粉存放14个月,其性质基本保持不变;分散于浓度为240 mmol/L的NaCl溶液中,依然保持良好的胶体稳定性。采用层层组装方法制备了NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au纳米复合粒子,纳米粒子具有上转换荧光性能、表面等离子共振效应和丰富的表面修饰途径。金纳米粒子的负载不改变NaYF₄:Yb³⁺/Ho³⁺纳米晶的上转换发光机制,但降低了上转换荧光强度,主要原因为NaYF₄:Yb³⁺/Ho³⁺纳米晶与Au纳米粒子发生了能量共振转移。利用Au与巯基之间强的化学键合作用,设计并合成出结合牢固的Fe₃O₄/Au纳米复合粒子。研究发现,随金负载量增加,⁵21 nm处的紫外-可见光吸收峰明显宽化和红移,饱和磁化强度降低。Fe₃O₄/Au纳米复合粒子在室温下具有超顺磁性和表面增强拉曼散射特性。用于水中的硝基苯检测,灵敏、快捷且具有选择性,检测限为10^-7 mol/L,低于现行国家规定的饮用水质标准限值。更多还原

【Abstract】 Gold nanoparticles are one of the most promising nanomaterials for numerous applications in biomedicine, sensor, optoelectronic devices, and catalysis, due to their superior biocompatibility, special optical, electronic, and catalytic properties. The mechanism of nucleation and growth of gold nuclei in solution-based synthesis, the principle and routes of controllable synthesis of gold nanoparticles with well-defined size and morphology, as well as multifunctional modification and assembly are the focus and hot topics of gold nanoparticles. In this dissertation, stable monodisperse Au₁₁ nanoclusters and water-soluble gold nanocrystals have been successfully prepared via the modified Brust synthesis. The influence of the reaction parameters on the formation and growth of gold nuclei as well as the ordered assembly of nanoparticles has been investigated. Furthermore, using the prepared gold nanoparticles as building blocks, multifunctional NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au and Fe₃O₄/Au nanocomposites have been fabricated. The relationship between properties and microstructures of gold nanoparticles and their nanocomposites have been clarified.By employing 3-mercaptopropionic acid （MPA） as ligand and adjusting the mole ratio of Au3+ to MPA, the adding rate of NaBH4 and the reaction temperature, one-sized stable Au₁₁（SCH₂CH₂COO-）₇（TOA⁺）₇ nanoclusters are prepared by a modified Brust biphasic synthesis. The blue luminescence with excitation and emission maxima at 355 and 417 nm, respectively, is observed from the Au₁₁ nanoclusters. The luminescence quantum yield is determined to be as high as 8.6 %, which is attributed to the protection of nanoclusters from quenchers in the solution by the high-density （SCH₂CH₂COO-）（TOA⁺） ligands and one-sized nanoclusters prepared to eliminate the influence of other sized nanoclusters. By using the uniform Au₁₁ nanoclusters as building blocks, well-defined ordered Au₁₁ nanocluster superlattices have been fabricated. Compared to the emission maximum of diluted solutions of Au₁₁ nanoclusters, the superlattices exhibit a red-shift of 56 nm.The highly stable monodisperse water-soluble gold nanocrytals are prepared by a modified Brust single-phase method. It is found that the formation of homogeneous Au0 nuclei and uniform growth rate for every nucleus are key to obtain monodisperse gold nanocrystals. The homogeneous Au0 nuclei can be prepared by controlling the size distribution of Au1+ intermediates. The fast stirring speed can make every gold nuclei have a uniform growth rate. By tuning the adding rate of NaBH4, the different-sized gold nanocrystals can be obtained. The MPA-stabilized gold nanocrytals prepared exhibit a high X-ray attenuation and superior stability. When the concentration being 0.2 mol/L, 6.6nm-sized gold nanocrystals have an X-ray attenuation value of 1663 HU, while the commercial computed tomography iodinated contrast agent, Ousu, only has a value of 826 HU. The gold nanocrystals can be stored for as long as 14 months as a powder state and can keep stable in a solution containing NaCl, even with the concentration of NaCl being 240 mmol/L.A new type of bifunctional NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au nanocomposites is successfully fabricated by a layer-by-layer technology. The prepared nanocomposites possess upconversion （UC） luminescence, surface plasmonic resonance and easy modification. The gold nanoparticles loaded on the nanocomposites only decrease the intensity of UC luminescence, but have no influence on the UC mechanism. The main reason for the decrease of the intensity of UC luminescence is that NaYF₄:Yb³⁺/Ho³⁺ nanocrystals and gold nanoparticles constitute a fluorescence resonant energy transfer system.A novel and simple layer-by-layer assembly method is proposed to fabricate bifunctional Fe₃O₄/Au nanocomposites which are formed by a strong chemical Au-S bond linkage. With the increase of the gold content in the nanocomposite, the absorption peak is broadened and exhibits a red shift, and the magnetization decreases. The nanocomposites possess superparamagnetic property and exhibit high surface enhanced Raman scattering activity. When employing the nanocomposite as a probe to detect the nitrobenzene in water, the nanocomposites exhibit high selectivity of nitrobenzene and the process is facile with high sensitivity. The detection limit for nitrobenzene is 10-7 mol/L, which is lower than the maximum level of nitrobenzene in water permitted by the Chinese government.更多还原