【作者】 沈建华；

【导师】 朱以华；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2014， 博士

【摘要】 对于金纳米粒子(Au NPs)的研究已经有很悠久的历史,由于其独特的化学、物理、生物性能,被研究应用于催化、传感器、生物医药、能量转换存储等领域。特别是在催化方面,金纳米粒子的比表面积大,使其具有更高的利用效率。但是纳米粒子的小尺寸和高比表面能通常极易团聚从而降低性能。为了解决这一问题,将Au NPs固定在一些载体上,使材料具有更好的稳定结构和性能。同时为了进一步实现材料的简单回收和重复利用,制备磁性壳核微球固载的Au NPs,实现简单的磁可控分离。所以本课题在国家自然科学基金重点项目(基金编号：21236003)、自然科学基金(基金编号：20976054)、上海市科技创新项目(基金编号：09ZZ58)等的资助下,针对不同Au纳米壳核结构材料的特点,研究催化、电子传递、生物传感、SERS等领域内材料结构对应用性能的影响及作用机制,并完成了以下五个方面的工作：1.制备了多功能磁性复合微球,其尺寸、各成分的形态、表面化学可以被精确地控制,并可以通过各层组装形成壳核结构。Fe3O4@SiO2-LBL-Au(0)复合微球具有TiO2保护的磁性Fe3O4颗粒,在TiO2层表面通过层层静电自组装形成聚电解质包覆层,并通过原位生长合成活性Au纳米颗粒(约4nm)。所制备的复合微球具有高的磁性能(23.9emu g-1)、均匀的球型结构(约500nm)、表面固载有稳定活性的Au NPs。制备的复合微球由于其活性Au NPs对还原4-硝基苯酚的反应显示出高的催化活性(12min内转化95%以上),同时具有方便的磁性分离、优异的稳定性和良好的可重复性。其独特的纳米结构也可以使微球作为一种新型稳定、高效催化剂用于其他工业催化过程。2.设计制备了三明治结构的Fe3O4/SiO2/Au/TiO2光催化剂,该光催化剂具有磁分离性、高效选择性吸附/光催化特性,在可见光和模拟太阳光照射下可以光催化分解有机染料。设计的光催化剂具有致密、均匀的AuNPs(约4nm,1.63wt%)。由于非金属元素掺杂和Au NPs的等离子体共振特性使该光催化剂具有高效率的可见光催化活性。此外,锐钛矿型TiO2纳米晶体的晶粒尺寸较小,可以增强光的捕获和电荷分离,从而降低空穴和电子的复合率。更重要的是,通过界面控制可以使TiO2纳米晶颗粒暴露高活性{001}面,并可以利用表面修饰使光催化剂具有选择性吸附/光催化降解的性能。这些三明治结构的光催化剂可应用于其它催化体系如染料脱色、水分解、制氢等等。3.由于石墨烯优异的导电性和良好的生物相容性,使石墨烯在生物传感器中的应用变得越来越吸引人。但一个关键的挑战是如何获得组织结构良好多级结构石墨烯材料,同时在纳米尺度上控制构建大的结构材料也是发展纳米技术的基础和关键。为了解决这些问题,设计了一种新的制备方法,在外加磁场下将还原的氧化石墨烯封装的多功能磁性复合微球(rGOE-Ms)组装排列形成各向异性导电膜(ACF)。精心设计制备的rGOE-MS同时具有磁性和良好的电子传输性能。由于定向排列的rGOE-MS存在,所制备的ACF凝胶膜在其垂直方向的电阻率是水平方向的15倍以上。因此,此ACF可以扩展到其他应用领域,如化学/生物传感器、纳米电子器件等。4.设计制备了一种新的过氧化氢酶生物传感器载体材料,其结构是由连续的金纳米壳和Si02纤维核形成的核-壳杂化纤维。通过静电纺丝先制备Si02纤维,随后在纤维表面原位合成Au NPs种子,最后利用界面生长进一步形成连续的金壳包覆层。制备的SiO2@Au纤维具有优异的化学稳定性、生物相容性和高效率的电子传递特性,并可以潜在地应用于高灵敏化学或生物传感器。利用循环伏安法(CV)来评估SiO2@Au纳米纤维在ITO电极上的电化学性能。制备的H202酶传感器对于滴加的H202会产生一个快速的电流响应,其检测限约为2.0μmol L-1,线性范围为5μmol L-1至1.0mmol L-1。复合纤维形成的完整三维网络结构和Au纳米壳层的优异生物相容性有利于负载生物酶分子,并充当电子导线实现电子从酶活性中心到电极表面的直接传递,具有优异的电化学特性,并有望在其他生物传感中得到应用。5.Au和Ag的纳米结构具有表面增强拉曼散射(SERS)的特性,这种特性可以增强吸附在金属表面物质的拉曼信号。同时Au载体在水溶液中具有大的接触电位和高的生物相容性,使其在光谱电化学领域具有广泛的研究。但是Ag却比Au具有更广泛的应用光谱范围和SERS增强性能。所以本文设计制备了具有磁性核和Ag/Au双重特性的SERS基底材料。制备的Fe3O4@Ag/SiO2/Au复合微球具有粗糙的Au壳层表面和Ag-SiO2-Au的长程等离子耦合共振,使这种结构具有最强的SERS增强活性,对于RdB达到10-9M的检测限,其增强因子EF为2.2×104。制备的纳米结构可以作为稳定、灵敏和可重复使用的SERS基底。此外,低的信号干扰使这种材料可潜在地用于SERS传感器等领域。更多还原

【Abstract】 Research in gold nanoparticles has been around for a long time, large number of Au nanoparticles exhibiting fantastic physical, chemical, and biological properties have been created and they demonstrate high potentials for biomedicine, catalysis, sensor, energy conversion, and so on. Especially, Au nanoparticles are attractive for catalysis because their large surface area-to-volume ratio allows effective utilization of expensive metals. In particular, gold nanoparticles are interesting because bulk gold is frequently an inactive catalyst, whereas gold nanoparticles are highly efficient catalytic. Moreover, variation of gold nanoparticle size sometimes allows control over catalytic activity. However, the high surface energy of nanoparticles with diameters in the low nanometer range often leads to aggregation and decreased catalytic activity. To overcome this problem, catalytic nanoparticles have been immobilized on solid supports, such as carbon, metal oxides, and zeolites, which also facilitates catalyst recycling. But these catalyst materials are sometimes separated by complex methods, and the separation is not sufficient. As an important family of separable materials, magnetic microspheres with magnetically responsive core and catalytic shell have gained much attention due to their unique separable features which makes it possible to realize controllable on-off reactions and convenient recycling of catalyst materials. And these core-shell nanostructure hybrid materials also can be used in catalyst, electron transfer, biosensors, SERS and so on. Main completed researchs are shown as follows:1. Multifunctional magnetic composite microspheres which possess the precise control of the size, morphology, surface chemistry, and assembly process of each component have been successfully prepared. These functional nanocomposite microspheres possess a core of silica-protected magnetite particles and in situ growth active gold nanoparticles (ca.4nm) on the outer shell by layer-by-layer electrostatic self-assembly. The well-designed microspheres have high magnetization (23.9emu g-1), uniform sphere size (ca.500nm), and stably confined and active small Au nanoparticles. As a result, the very little composite microspheres show high performance in catalytic reduction of4-nitrophenol (with conversion of95%in12min), special convenient magnetic separability, long life, and good reusability. The unique nanostructure makes the microsphere a novel stable and highly efficient catalyst system for various catalytic industry processes. 2. We have demonstrated a sandwich-structured Fe3O4/SiO2/Au/TiO2photocatalyst, which shows magnetic separability, selective absorption and photocatalysis activity, and high efficiency, in catalyzing the decomposition of organic compounds under illumination of visible-light and simulated sunlight. The structural design of the photocatalyst takes advantage of the dense, homogeneous structure and the AuNPs content (ca.4nm,1.63wt%), which is prepared by a simple method. It possesses high efficiency visible-light photocatalytic activity due to the stable from nonmetal-doping and the plasmonic metal decoration, which enhances light harvesting and charge separation, and the small grain size of the anatase nanocrystals, which reduces the exciton recombination rate. More importantly, the catalyst is synthesized by a combination of plasmonic metal decoration of TiO2nanocrystals with exposed{001} face, and the selective adsorption and photocatalytic decomposition of azo dyes is accomplished by design of the surface chemistry. Additionally, these sandwich-structured photocatalysts can be applied to other catalytic system such as dye decoloration, water decomposition, hydrogen generation, and so on.3. Due to the fast electron transportation and good biocompatibility, the use of graphene in biosensors is becoming more and more appealing. But a key challenge is how to obtain well-organized2D or3D graphene structures to build larger objects, and the development of methods for controlling the organization of functional objects on a nanometre scale to build larger objects is of fundamental and technological interest. To overcome this problem, we demonstrate a novel strategy for the fabrication of the reduced graphene oxide-encapsulated multifunctional magnetic composite microspheres (rGOEMs)-based anisotropic conductive film (ACF). The well-designed rGOE-Ms possess both magnetization and good electron transport properties. Magnetic properties can be detected by their movement in the gel film under an external magnet. Most interestingly, the prepared gel film has displayed the existence of rGOE-Ms alignment and anisotropy in the ACF, and the electrical resistivity of the vertical ACF was almost fifteen times higher than the horizontal. Therefore, the ACF can be extended to various advanced applications, such as chemical/biosensors, nanoelectronics, and so on.4. We describe the preparation and characterization of a novel type of core-shell hybrid material for application in a novel hydrogen peroxide biosensor, where the structure consists of a continuous gold shell that encapsulates the silica fiber. The SiO2@Au nanofibers had been synthesized by electrospinning silica sol, and then golden seeds were in situ grown on the fiber, lastly the gold-seeded silica fibers were further coated by continuous gold shells. The above nanocomposites had satisfactory chemical stability, excellent biocompatibility and efficient electron transfer property, which may have potential application for the highly sensitive chemical or biological sensors. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the SiO2@Au nanocomposites at indium tin oxide (ITO). The biosensor showed high sensitivity and fast response upon the addition of H2O2and the linear range to H2O2was from5×10-6to1.0×10-3M with a detection limit of2μM (S/N=3). The apparent Michaelis-Menten constant of the biosensor was1.11mmol L-1. These results indicated that SiO2@Au nanocomposites have potential for constructing of a variety of electrochemical biosensors.5. Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the Raman scattering cross sections are dramatically enhanced for the molecules adsorbed thereon. Due to their wide accessible potential range in aqueous solutions and the high biocompatibility, Au supports are preferred for spectro-electrochemical investigations. However, the optical range in SERS spectroscopy is restricted to excitation lines above600nm, which is shorter than the Ag supports. In addition, these SERS-activity materials are not easy to separate and reused. Herein, the present article reports the novel multifunctional Fe3O4@Ag/SiO2/Au core-shell microspheres that display long-range plasmon transfer of Ag to Au leading to enhanced Raman scattering. The well-designed microspheres have high magnetization and uniform sphere size. As a result, Fe3O4@Ag/SiO2/Au microspheres have the best enhancement effect in the Raman active research by using Rhodamine-b (RdB) as a probe molecule. The enhancement factor is estimated to be2.2x104for RdB from the long-range plasmon transfer of Ag to Au, corresponding to an attenuation of the enhancement by a factor of only0.672x104compared to RdB adsorbed directly on the Fe3O4@Ag microspheres. RdB can be detected down to10-9M even without the resonance SERS effect. The unique nanostructure makes the microspheres novel stable and a high-enhancement effect for Raman detection.更多还原