【作者】 张三军；

【导师】 曾和平； Francoise ARGOUL；

【作者基本信息】 华东师范大学 ， 光学， 2008， 博士

【摘要】 表面等离子体共振(surface plasmon resonance)可以存在于金属和电介质的交界面上,它的局域电场放大效应使得它对表面的特性非常敏感。在本论文中表面等离子体共振技术被用来研究金表面的大分子自组装效应。我们首先进行了一些实验和理论的工作来提高表面等离子体共振探测器的性能。通过对表面等离子体共振系统用多层膜模型来模拟,并且用菲涅耳理论来处理它的反射,我们研究了实验结果和理论模拟之间差别的来源。我们发现这种差别主要并不是由金表面的粗糙引起的,而是由金膜的紧密度引起的。我们改进了金膜的制备方法来减小实验结果与理论计算之间的差别。通过高沉积速度制备的金膜具有更高的紧密性,并且它的表面更平整,因此更适合制备高性能的SPR探测器。自组装单层膜(self-assembed monolayers)被制备在金表面上用来帮助吸附DNA等大分子。我们成功的制备了几种不同的自组装单层膜,并且通过电化学阻抗谱(electrochemical impedance spectroscopy)测试了它们的特性。此外,我们还通过表面等离子体共振技术实时监测了自组装单层膜形成的动力学过程。我们证明了通过巯丙基三甲氧基硅烷((3-Mercaptopropyl)trimethoxysilane)和3-氨丙基三乙氧基硅烷(3-Aminopropyl-triethoxysilan)构造的双层自组装单层膜来吸附DNA分子是可行的,但是它的效率不高。我们通过电化学阻抗谱和表面等离子体共振详细研究了巯基十一烷醇(11-Mercaptoundecanol)和11-氨基-1-十一烷硫醇(11-Amino-1-undecanethiol)分子构成的混合自组装单层膜。因为在缓冲液中巯基十一烷醇分子是不带电的,但是11-氨基-1-十一烷硫醇分子可以带有正电荷,具有自组装单层膜的表面的电荷可以通过改变这两种分子的比例以及缓冲液的特性来调节。我们研究了他们与溶液离子力以及酸碱度的关系。这种巯基十一烷醇/11-氨基-1-十一烷硫醇的自组装单层膜具有很好的电流阻断特性。此外,我们还研究了它们对施加电压的反应,这些自组装单层膜在一个很小的电压范围内丧失这种好的电流阻断特性,这个范围相对于银/氯化银标准参考电极一般为[-100mV,0mV]。为了制备基于表面等离子体共振的DNA芯片,我们致力于研究DNA在这些巯基十一烷醇/11-氨基-1-十一烷硫醇的混合自组装单层膜表面的吸附。我们通过表面等离子体共振测量了DNA吸附在这些混合自组装单层膜上的动力学过程。研究的DNA有两种,一种为3000对基的环形质粒DNA,另外一种为200对基的直DNA。我们分别研究了DNA吸附对于溶液中DNA的浓度、表面电荷、溶液离子力的关系。吸附在金表面的DNA的拓扑图也用原子力显微镜进行了观察。通过这两种方法的结合,我们可以提取DNA吸附的很多信息。为了从DNA芯片上提取基因信息,我们提出利用表面等离子体共振的电场增强效应构建一种新的灵敏的表面二次谐波显微镜。数值模拟的结果表明这种表面等离子体共振增强二次谐波显微镜能够探测更多的表面二阶非线性极化系数。它还具有高分辨率表面成像和探测表面分子取向的潜力。更多还原

【Abstract】 Surface plasmon resonance (SPR) occurs at the interface of metal and dielectric, whose local field enhancement effect makes it very sensitive to the properties of the surface. This SPR technique is used to study the self-assembling of macromolecules on gold surfaces in this thesis.The research work reported here started from improving the performance of SPR sensors. Some theoretical and experimental works were firstly carried out to analyze the differences between experimental results and theoretical calculations. The SPR configuration is modeled by a multilayer system, its reflection is treated by Fresnel’s theory. The topology of gold layer surface is measured by atomic force microscopy (AFM), and the influences of the surface roughness is modeled by effective medium theories. It is found that the differences are not mainly caused by the surface roughness of gold layer, but rather by the inhomogeneity of gold layer. The process of gold deposition is improved to prepare gold films of higher compactness. Higher deposition speed are experimentally proved to result in more compact gold layer and flatter gold surfaces, therefore more favorable for making ideal SPR sensors.In order to control the adsorption of macromolecules on gold surface, special self-assembed monolayers (SAMs) need to be prepared on gold surface. Several kinds of SAMs are prepared successfully, and their properties are studied by electrochemical impedance spectroscopy (EIS). In addition, the dynamics of SAM formation are also characterized in real time by SPR microscopy. Double layer SAMs of 3-mercaptopropyl-trimethoxysilan (MPTS) and 3-Aminopropyl-triethoxysilan (APTES) are proved to be feasible but less effective for DNA adsorption. Since the MUO 11-Mercaptoundecanol (MUO) molecules are uncharged and 11-Amino-1-undecanethiol (AUT) may be positively charged in buffers, the surface charge of mixed MUO/AUO SAMs can be varied by changing the proportion of MUO/AUO molecules and the buffer conditions. The properties of mixed SAMs of various MUO/AUO proportion and their dependence on solution ionic strength and pH value are studied by EIS and SPR microscopy. Both measurements show that the MUO/AUT SAMs have good charge carrier blocker performance. In addition, their responses versus the electric potential of the gold film are also investigated. The SAMs loose charge carrier blocking behavior in a finite range of potential typically [-100 mV, 0 mV] versus Ag/AgCl standard reference. This method of sweeping in potential is very suitable to detect the defects in SAMs, which are less evident in general conditions. EIS measurements also indicate that defects in mixed SAMs may be more serious in pure SAMs.Arming at the preparation of SPR based DNA sensors, our first study concentrated on the preparation of DNA layers on MUO/AUT mixed SAMs. The dynamics of DNA adsorption on these mixed SAMs was followed in real time by SPR microscopy. Two kinds of DNAs were investigated, namely circular DNA plasmids of 3000 base pair (bp), and straight DNAs of 200 bp. The dependence of DNA adsorption on DNA concentration in solution, surface charge, and solution ionic strength are reported here. The topography of adsorbed DNAs are observed by atomic force microscopy ex-situ. Many information can be drawn from the combination of these two kinds of measurements.We propose to use the local field enhancement of SPR to construct a new sensitive surface second harmonic generation (SSHG) microscopy. Numerical simulations show that the SPR enhanced SSHG microscopy is suitable for detecting the components of the second order nonlinear susceptibility of the surface. It also opens the possibility of imaging the surface with higher resolution, and detecting the orientations of surface molecules.更多还原