【作者】 易早；

【导师】 易有根；

【作者基本信息】 中南大学 ， 物理学， 2014， 博士

【摘要】 由于具有表面等离子体共振(SPR)吸收特性,金、银纳米材料在艺术加工、生物医学、传感探测、表面增强活性基底、激光惯性约束聚变等领域具有重要的应用价值。本论文中,我们系统研究了金、银纳米材料的可控制备以及其光学特性。论文的主要内容如下：1.通过采用单宁酸作为还原剂和形貌控制剂,设计了一个绿色合成线路。该线路在室温的条件下,简单、一步、绿色合成大小可调的银纳米片。该合成过程是一个无种子过程,没有加入任何其他的表面活性剂和形貌控制剂,实现了纳米粒子的形貌控制生长。通过改变单宁酸的浓度以及溶液的PH值等实验参数,银纳米片的形貌以及SPR峰可以得到好的调控。并且该绿色合成法可以扩展到其他二维纳米粒子的制备。另外,我们采用双还原法,即NaBH4和H202体系,制备出三角形银纳米片,之后以此为种子,采用多轮生长法控制三角形银纳米片的生长。之后将银纳米片组装在石英玻璃基底上。采用紫外-可见吸收光谱研究了溶液相中以及基底上纳米粒子的吸收光谱。最后研究了银纳米片薄膜以及银纳米球状纳米粒子薄膜的拉曼增强效应。2.我们采用对环境友好的葡萄糖作为还原剂和形貌控制剂,在碱性的条件下利用水热法制备出银泡沫。通过改变葡萄糖的浓度,溶液的PH值和反应的温度等实验参数,得到银泡沫。据我们所知,这是国际上首次采用如此方法制备银泡沫。该方法有以下几个优点：方法简单,实验过程为一步；该实验为无种子过程,反应过程中不需要引入其他表面活性剂和形貌控制剂；该绿色法可以扩展到其他三维贵金属纳米材料的制备。我们之前制备出的银泡沫可以作为一种有效的SERS基底,其拉曼增强因子可达到3.5×1012。通过3D-FDTD模拟计算,我们可知链直径、链长、间距、链夹角以及针尖结构均能影响SERS增强因子。实验和理论工作表明银泡沫能够提供大量的“热点”,该材料是一种非常有效的SERS基底。3.通过热处理石英玻璃基底上的Ag+/PVA/PVP混合物薄膜,我们提出了一种简单且低成本的方法实现了大面积制备银纳米环。通过控制AgNO3/PVA/PVP混合物的摩尔比,薄膜是否还原以及混合物薄膜的旋涂次数,我们实现银纳米环的制备。并且通过实验测量与理论模拟,我们得到了银纳米环的耦合共振吸收峰以及四极矩共振吸收峰。采用R6G作为探针分子和FDTD SOLUTION作为计算软件,系统的研究了银纳米环的SERS特性。4.我们报道了采用二氧化硅小球为模板制备出单分散性好,Au、Ag原子含量可调的中空Au/Ag双金属纳米球。并且我们首次研究了该中空双金属纳米小球薄膜的SERS活性。我们发现中空双金属纳米小球薄膜的SERS活性非常好,并且稳定性高。研究表明该新型复合材料的SERS性能优异,它将在SERS领域具有广泛的应用前景。另外,我们提出采用一种简单且有效的多轮置换法制备树枝状Ag-Pd双金属纳米材料。相比于一步置换法,多轮置换法能更有效的控制合金的组分以及形态。通过控制置换反应的次数以及反应的温度能得到不同形貌以及不同组分的Ag-Pd双金属纳米材料。这些树枝状Ag-Pd双金属纳米材料能展示强的SERS活性,并且不同形貌的Ag-Pd双金属纳米材料展示着不同的SERS活性。5.我们通过一种简单的水热合成法,系统的改变水热温度、pH值和前驱体溶液中Zn源的初始浓度,在石英玻璃基底上制备出高均一性的ZnO纳米棒阵列。以此为基底,我们制备出ZnO纳米棒@Au纳米颗粒复合阵列的以及其对三聚氰胺的检测,分析了其复合结构的光致发光特性,并得到该结构对三聚氰胺的最低检测线。另外,我们提出了采用物理溅射的方法实现在ZnO纳米棒阵列表面溅射银纳米粒子,得到ZnO@Ag核壳纳米棒阵列。并且我们详细的研究了PATP有机分子在ZnO@Ag核壳纳米棒阵列上的SERS增强效应。重点研究了ZnO@Ag核壳纳米棒阵列体系中核ZnO对电荷转移诱导SERS增强效应的贡献。通过与银活性基底相比,复合体系中ZnO的引入有效的促进电荷从金属到有机分子的转移,从而引起更强的拉曼信号。更多还原

【Abstract】 Noble metal nanostructures take on surface plasmon resonance (SPR) absorption under irradiation of incident light, thus show various potential applications in the fields of embellishment, biomedical sciences, sensing detection, Surface Enhanced Raman Scattering (SERS) substrates, laser induced inertial confinement fusion and so on. In this thesis, we have prepared the Au and Ag nanoparticles, and we have studied these properties such as optical, electrical and eatalytic properties. Some important results obtained are deseribed as follows:1. We describe a green protocol using tannic acid, a polyphenolic plant extract, as both the reducing and stabilizing agent. In this seedless process, the silver nanoplates have been prepared via the reduction of AgNO3by Tannic acid (TA) at room-temperature. This synthesis was a seedless process, without any other surfactant or capping agent to direct the anisotropic growth of the nanoparticles. The shape of the silver particles and the optical in-plane dipole plasmon resonance bands of these nanoplates could be controlled by varying the experimental parameters such as TA concentration and the pH of solution. Furthermore, this "green" method utilized in this thesis can be extended to fabricate other2D metal nanostructures. The double reduction system consisted of NaBH4and hydrogen peroxide which was used to prepare triangular silver nanoplates, and the as-prepared nanoplates were made to keep on growing through multi-stage growth of Ag ions by trisodium citrate. The UV-vis spectrum of the triangular silver nanoparticle self-assembled film (TSNF) is markedly different from that of the colloid of silver nanoparticles. It was found that the SERS enhancement ability of the TSNF is remarkable, and slightly lower than that of the spherical silver nanoparticle film (SSNF). Both electromagnetic mechanism (EM) and chemical mechanism (CM) were attributed as the reason for the difference in the SERS enhancement ability between the TSNF and the SSNF. 2. We describe a green protocol using glucose, as both the reducing and stabilizing agent. On the basis of the alkaline pH (10) of the glucose solution under solvothermal conditions, we can first synthesize stable silver NPs and then induce their linear welding into the nanowires leading to self-supporting3D silver spongelike networks. As we know, we have not been aware of reports on silver spongelike networks structured used such method. The advantages of the method are:(a) it is a simple route with just one step,(b) it is a seedless process, and does not need any other surfactant or capping agent to direct the growth of the silver spongelike frameworks,(c) this "green" method utilized in this thesis can be extended to fabricate other3D noble metals spongelike frameworks architectures. The electric field enhancement of the silver spongelike networks has been described to be a systematic investigation by using three-dimensional finite-difference time-domain (3D-FDTD) simulation. Surface enhanced Raman scattering (SERS) measurements have indicated that the junction regions, the hollow nanostructured and the sharp nanotips of the broken ligaments in the silver spongelike networks act as electromagnetic "hot-spots". The3D-FDTD calculations have indicated that the silver spongelike networks may exhibit a high quality SERS characteristic because of the Ag chain length, chain diameters, chains gap, chains angle and sharp nanotips. A maximum enhancement factor of3.5×1012can be obtained with the silver spongelike networks. As potential nanoantennas, silver spongelike networks can offer an effective method to optimize plasmon coupling for synthesizing devices.3. We provide a convenient and low cost way for the large-area self-organized synthesis of Ag nanorings through heat treatment of Ag+/PVA/PVP composite film on quartz glass. Because of templates and sophisticated apparatus are not necessary, the way provided here can be an important complement to existing methods for the fabrication of rings. In addition, the as-prepared special structural features with nanoparticle-attached Ag nanorings have been applied in SERS properties with Rhodamine6G (R6G) as the probe molecules. Using the3D-FDTD simulation, the theoretical examination of the local EM properties lets us to evaluate the contributions of nanoring and nanoparticle-attached Ag nanorings to the experimentally obtained SERS intensities. Via simulations, we provide that the weak enhancement can be remarkably improved through nanoparticle-attached Ag nanorings and availably utilizing transversely polarized light. In addition to we provide strong lateral coupling induced at the adjacent site between small Ag nanoparticles and nanoring.4. We report a facile silica colloidal templating method to synthesize Au/Ag bimetallic hollow nanospheres with fine monodispersity and controllable atom ratio of Ag and Au. As we know, we have not been aware of reports on Au/Ag bimetallic hollow nanospheres structured for SERS applications. The application of these Au/Ag bimetallic hollow nanospheres bimetallic structured films as SERS substrates is first investigated by using R6G as a probe molecule. We show that the as-prepared Au/Ag bimetallic hollow nanospheres structured films are extremely efficient SERS substrates in terms of high Raman intensity enhancement, excellent stability, and reproducibility. We report the preparation of Ag-Pd bimetallic dendrites by employing multi-stage galvanic replacement reaction (MGRR), which is a simple yet effective and versatile tool. Compared to one-stage reaction approach, multi-stage reaction is more favorable for compositional and modality control. We propose that these charged surface layers control galvanic charge transfer by controlling the stage of galvanic replacement reaction and reaction temperature at the deposition front. These bimetallic dendrites films exhibit high SERS activity and may have potential applications in investigation of "in situ" Pd catalytic reactions using SERS. This difference in the behaviors of the SERS activity is consistent with a strong influence of the changing morphology of the structures. The resulting nanostructures can be engineered to possess tailored, hierarchical morphologies and compositions that present new opportunities for systematically studying the optical catalytic properties of bimetallic NPs.5. We report a facile seed-assisted hydrothermal to synthesize ZnO nanorod arrays on quartz glass through changing the hydrothermal temperature, pH and initial concentration of Zn source in precursor solution. The large-scale arrays of vertically aligned ZnO-NRs decorated with Au-NPs were synthesized using ZnO nanorod arrays. This hybrid substrate manifests high SERS sensitivity to melamine and a detection limit as low as1.0×10-1010M (1.26μg L-1). A maximum enhancement factor of1.0×109can be obtained with the ZnO NF-Au film. The ZnO@Ag core-shell nanorods arrays were synthesized through physical sputtering method. We have studied the SERS enhancement effect of the ZnO@Ag core-shell nanorods array using PATP organic molecules as probe molecule. The result demonstrates for the first time that directional charge transfer between nanoscale metal and semiconductor tunneling through the interconnecting molecules may be examined by SERS.更多还原