【作者】 李小灵；

【导师】 赵冰； 李伯符；

【作者基本信息】 吉林大学 ， 物理化学， 2004， 博士

【摘要】 当分子吸附到特定的金属表面时，其拉曼信号可以增加104~106倍，这就是所谓的表面增强拉曼散射（SERS）。SERS的发现引起了化学和物理学家们极大的兴趣，这方面的研究一直很活跃。SERS作为一种高灵敏光谱，在许多领域得到了广泛的应用，而SERS效应的应用范围的拓展有赖于SERS基底的发展，因而新型SERS基底的制备在SERS的进一步发展中起着重要的作用，是SERS研究领域的热点之一。另外，在SERS基底上按照人为设计去组装具有特殊功能的有机薄膜或超薄膜体系，可以为构造分子器件或超分子器件奠定一定的基础。对于有机薄膜来说，其性质取决于组装分子的性质和薄膜结构，而SERS作为一种极为灵敏的光谱研究手段，对薄膜结构与取向的研究具有独特的优势，因而利用光谱手段对自组装薄膜的研究能够让人们了解薄膜结构与性质之间的关系，对其关系的认识将进一步扩大这类薄膜在实际中的应用。基于以上这些考虑，本论文的主要研究工作包括以下几点：巯基乙酸包裹法制备SERS基底我们利用UV-vis和 TEM研究了银纳米粒子的形成过程。结果显示，在反应开始时球形和棒状的银粒子同时生成，然后随着反应时间的进行，棒状的银粒子逐渐转变为球形，在反应结束时，溶胶中含有少于3%的棒状粒子。最后形成的银纳米粒子形状较为均一，尺寸变化也较小。这种溶胶可以保持至少三周的活性。我们同时调查了Cl- 对溶胶光学性质的影响，发现Cl-　能加速溶胶粒子的聚集。 我们利用自组装技术将银粒子转移到固体基片上，发<WP=129>现银纳米粒子在转移过程中能够变大并且产生聚集。银溶胶和银基底都是SERS活性的。我们证实了SERS增强有赖于银粒子的尺寸和聚集，而且证实Cl-　有利于SERS信号的检出。自组装金属溶胶法制备SERS基底我们提出了两种制备SERS基底的新方法。两种方法都是利用静电作用将金属粒子从溶胶中转移到固体基片上。通过将纳米粒子从溶胶中转移到固体基片上避免了溶胶不稳定的缺点。用这两种方法制备的SERS基底既保留了银溶胶的优点又避免了它的缺点。方法一是先把碘化银粒子从溶胶中转移到固体基片上，然后在片子上再还原生成银粒子。方法二是在溶液中将碘化银还原为银，再把银粒子从溶胶中转移到固体基片上。我们通过控制转移次数的方法来控制基底的表面形态，使我们能更好地探索所捕获的溶胶粒子是如何地影响SERS增强能力和基底的光学性质。我们发现银膜的光学性质主要由孤立的银粒子所控制。我们以R6G为探针，比较了这两种基底的SERS活性。同时，证实了SERS增强与基底的表面形态和激发波长是密切相关的。银纳米粒子生长法制备SERS基底基于前面的工作，我们发展了一种具有更高增强能力的SERS基底的制备方法。用Silver Enhancer （银盐） and Initiator （引发剂）的混合溶液（以下简称为SEIM）浸泡带有银核的基底，得到活性更高的SERS基底，其增强能力可提高10倍。用紫外和原子力显微镜研究了这种新基底的光学性质和特性，发现被吸附物的SERS增强会随着基底放置时间的增加而增强，在45天左右时达到最大，这种新型基底至少可以保持90天的活性。我们把该基底SERS增强能力的变化归因为基底表面银纳米粒子的重组。该基底较好的稳定性和较高的SERS增强能力使它们在对痕量元素的超敏感分析和实际应用提供了很大的方便。我们还研究了不同浓度的BPENB分子吸附到这种新型基底上的紫外和SERS光谱。发现BPENB分子在不同浓度的溶液中呈现出<WP=130>不同的形态。盐酸羟胺络合法制备SERS基底我们利用盐酸羟胺络合银离子，先生成碘化银溶胶，然后再用硼氢化钠还原生成银溶胶，制备了一种形状均一的银纳米粒子溶胶。并用紫外-可见光谱和透射电镜研究了银纳米粒子的形成过程，形状及粒径分布。银粒子形成过程是：当还原剂加入碘化银溶胶后，立即形成了银粒子，开始时粒子粒径较小，小的粒子很快聚成较大的粒子。随着反应的进行，大的粒子逐渐碎裂，粒径分布也逐渐变窄，最后形成粒径分布较均匀的银纳米粒子，说明银纳米粒子的形成过程中存在着纳米粒子粒径均化的过程。 透射电镜的研究表明，我们得到了形状均一的球形银纳米粒子。将这种银纳米粒子转移到固体基片上得到了具有较高活性的SERS基底。5.　SERS研究基于轴向配位键结合的金属酞菁自组装膜我们选择两种典型的拉曼探针分子4-巯基吡啶（PySH）或BPENB作为轴向配体来组建包含酞菁分子的自组装膜，用紫外和SERS光谱研究了具有不同的共轭体系和分子长度的轴向配体对金属酞菁自组装膜结构和取向的影响。结果显示，RuPc 以近平行的取向被组装到 PySH或 BPENB修饰的银基底上，组装过程的驱动力是 Ru原子和配体吡啶基N原子之间形成了配位键。另外，两种组装膜的取向不同，在 RuPc-BPENB组装膜中，BPENB分子几乎是垂直于银表面的，而在 RuPc-PySH组装膜中， PySH分子是倾斜于银表面的。6.　SERS研究基于轴向配位键结合的金属卟啉自组装膜我们将两种金属卟啉同系物TbOH和 LuOH吸附到PySH修饰的银基底上，主要是调查中心金属对这种金属卟啉自组装膜结构和取向的影响。我们采用UV-vis、SERS和XPS来研究自组装膜的形成并且探索其结构和取向的变化。紫外和S更多还原

【Abstract】 When molecules are adsorbed on special metal surface, their Raman intensities can be increased by a factor of 104~106 compared with their normal spectra observed. This phenomenon is generally known as surface-enhanced Raman scattering (SERS). A number of chemists and physical scientists are very interested with the study on SERS which have been an active research field. However, the evolution of SERS-active substrates is the key role to initiate and /or broaden novel SERS applications. To make SERS become a usual analytical tool, developing stable and reproducibly prepared substrates with high enhancement become important. Therefore, the methods of preparing SERS substrates have long been a matter of great concerns and have become a crucial role in the development of SERS.Additionally, the study on ultrathin organic molecular films can not only help people to understand the fabrication of organic molecules in organism, but also help people to fabricate organic thin films with special functions. Consequently, people can construct molecular devices or supermolecular devices. For thin organic molecular film, its properties depend on its molecular structure and character. As a sensitive analytic tool, SERS have unique advantages in studying the structure and orientation of thin films. Thus, study on the self-assembled films by using spectroscopy can make people understand the relationship between the structure and properties of the thin films, which can help <WP=133>spread the application of such films in practice.Based on the above facts, our study is outlined as follows: 1. Mercaptoacetic Acid-Capped Silver Nanoparticles Colloid --- Formation, Morphology and SERS ActivityWe discuss the formation, morphology and SERS activity of the mercaptoacetic acid-capped silver nanoparticles colloid. The formation process of the silver nanoparticles was investigated by UV-vis spectroscopy and TEM. The results show that the spherical and rodlike particles were formed at the beginning of the reaction, and then the rodlike particles were gradually converted into spherical particles with the reaction continuing. Finally, the content of the rodlike particles was less than 3% in the silver colloid. Thus, the final obtained silver nanoparticles were uniform in their shapes and showed little variation in their sizes. This silver colloid can remain stable for several weeks, which makes it convenient for use in practice. We also investigated the effect of Cl- on the rate of changes in the optical properties of the silver colloid by UV-vis absorption. The results indicate that Cl- accelerates the aggregation of the colloidal particles by effectively screening the repulsive electrostatic interactions between the negatively charged silver particles. We used the self-assembled technique to transfer the silver nanoparticles onto solid substrates from the colloid with and without Cl- in the solution. The UV-vis spectra show that the absorption band red shifts and a new band appears at a longer wavelength when the silver nanoparticles are transferred onto the substrate from the colloid with Cl- in the solution, indicating that the silver nanoparticles can grow and aggregate on the substrate. This was further confirmed by the atomic force microscopy measurements. Both the silver colloid and the substrates prepared by transferring <WP=134>the silver nanoparticles from the silver colloidal solution onto the quartz slides can serve as SERS-active substrates. It was found that the SERS enhancement depends on the size and aggregation of the silver particles, and the addition of Cl- generates much stronger SERS signals.2. Self-Assembled Metal Colloid Films: Two Approaches for Preparing New SERS Active SubstratesWe report the two new approaches for preparing SERS-active substrates. In the first approach (Method 1) one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (Method 2) deox更多还原