表面等离子体共振及其在探测金表面大分子方面的应用

论文摘要

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。

论文目录

• 摘要
• Abstract
• Résumé
• Acknowledgements
• Preamble
• Preparation of high performance gold layers and their characterization
• Preparation of SAMs and their characterization
• Adsorption of DNAs on SAMs and their characterization
• Developing a SPR enhanced second harmonic generation microscopy
• Conclusion
• 1 Introduction to Surface Plasmon Resonance
• 1.1 Fundamentals of SPs
• 1.1.1 Definitions of SPs
• 1.1.2 History and applications of SP techniques
• 1.1.2.1 Ultra-sensitive detectors
• 1.1.2.2 Plasmonics
• 1.1.3 Dispersion relation of SPR
• 1.1.4 Optical coupling methods
• 1.1.5 Various optical configurations to excite SPR
• 1.2 Description of our SPR experiment
• 1.2.1 Optical systems to generate SPR
• 1.2.2 Micro-fluid systems
• 1.2.3 Preparation of metal films
• 1.3 Computation of reflected and transmitted fields
• 1.3.1 Reflection and transmission of optical waves in isotropic layered media
• 1.3.1.1 Snell's law
• 1.3.1.2 Fresnel's formulae
• 1.3.1.3 Total internal reflection and critical angle
• 1.3.1.4 Evanescent wave and attenuated total reflection
• 1.3.2 Matrix formulation for isotropic layered media
• 1.3.2.1 Transmission and propagation matrices
• 1.3.2.2 Matrix formulation for a multilayer system
• 1.3.2.3 Application of matrix formulation on the modeling of SPR
• 1.3.2.4 The distribution of the transmitted and reflected fields
• 1.3.2.5 Influence of variation of refractive indices on SPR effect
• 1.3.2.6 Influence of excitation wavelength on SPR effect
• 1.3.2.7 Influence of the thickness of gold layer on SPR effect
• 1.4 Fine size effects
• 1.4.1 Focalization of the beam
• 1.4.2 Parallelism of the exciting beam
• 1.5 Conclusion
• 2 Effect of inhomogeneity of gold on SPR reflectivity curves
• 2.1 Methods of gold thermal vaporization
• 2.1.1 Slow thermal deposition
• 2.1.2 Fast thermal deposition
• 2.2 Set（A）of slow and fast gold vaporization
• 2.2.1 Experimental configuration for polarization
• 2.2.2 Slow gold vaporization
• 2.2.2.1 AFM characterization
• 2.2.2.2 SPR characterization
• 2.2.3 Reproducibility of the slow deposition
• 2.2.3.1 AFM characterization
• 2.2.3.2 SPR characterization
• 2.2.4 Fast gold vaporization
• 2.2.4.1 AFM characterization
• 2.2.4.2 SPR characterization
• 2.2.5 Aging of the gold layers
• 2.2.5.1 AFM characterization
• 2.2.5.2 SPR characterization
• 2.3 Set（B）of slow and fast gold vaporization
• 2.3.1 Experimental configuration for polarization
• 2.3.2 Slow gold vaporization
• 2.3.2.1 AFM characterization
• 2.3.2.2 SPR characterization
• 2.3.3 Fast gold vaporization
• 2.3.3.1 AFM characterization
• 2.3.3.2 SPR characterization
• 2.3.4 Reproducibility of the series（B）
• 2.3.5 Preliminary conclusions
• 2.4 Effective medium model for gold vaporized layers
• 2.4.1 Maxwell-Garnet and Bruggeman model
• 2.4.2 Roughness of gold surfaces modelling with an effective layer
• 2.4.2.1 Slow deposition mode
• 2.4.2.2 Fast deposition mode
• 2.4.3 Fitting slow and fast gold deposition with modified gold index values
• 2.4.3.1 Slow deposition mode
• 2.4.3.2 Fast deposition mode
• 2.4.4 Scanning Surface Plasmon Microscopy Images
• 2.4.5 AFM images of fast and "chopped" deposition gold surfaces
• 2.5 Conclusion
• 3 Self-Assembed Monolayers
• 3.1 Introduction to SAMs
• 3.1.1 Methods of preparing ultrathin layers
• 3.1.1.1 Spin coating
• 3.1.1.2 Langmuir-Blodgett technique
• 3.1.1.3 Self assembled monolayer（SAM）
• 3.1.2 SAMs of alkanethiol molecules on Au
• 3.1.2.1 The reason of choosing on gold to prepare SAMs
• 3.1.2.2 Method of preparing SAMs
• 3.1.2.3 Structure of alkanethiol SAMs on Au
• 3.1.2.4 Other results
• 3.1.3 Methods of characterization of SAMs
• 3.1.3.1 AFM technique
• 3.1.3.2 EIS technique
• 3.2 Preparation of SAMs
• 3.2.1 Preparation of double SAMs of MPTS and APTES
• 3.2.2 Preparation of mixed SAMs of MUO and AUT in ethanol
• 3.2.3 Preparation of mixed SAMs of MUO and AUT in buffers
• 3.3 Results
• 3.3.1 AFM images of SAM surface
• 3.3.1.1 AFM images of Double SAMs of MPTS and APTES
• 3.3.1.2 AFM images of of mixed SAMs of MUO and AUT
• 3.3.2 Formation of SAMs studied by SPR
• 3.3.2.1 Description of experiments
• 3.3.2.2 Experimental results
• 3.3.3 Characterization of SAMs by EIS
• 3.3.3.1 Description of EIS experiments
• 3.3.3.2 Modelling the interracial impedance
• 3.3.3.3 Typical curves recorded during an EIS experiments
• 3.3.3.4 Modulation of the gold potential during an EIS experiment
• 3.3.3.5 Potential response of an uncharged MUO SAM
• 3.3.3.6 Potential response of a charged AUT SAM
• 3.3.3.7 Potential response of mixed SAMs
• 3.3.3.8 Conclusion of the EIS study of SAMs on gold
• 4 Characterization of DNA adsorption by SPR
• 4.1 The purpose of studying the adsorption of DNA
• 4.1.1 Introduction to the structure of DNA
• 4.1.1.1 Chemical composites of DNA
• 4.1.1.2 Physical structures of DNA
• 4.1.2 DNA chips
• 4.1.3 Dynamics of DNA
• 4.1.3.1 Spontaneous bending of DNA
• 4.1.3.2 Long range correlation in DNA
• 4.2 Adsorption of long chain DNA
• 4.2.1 Influence of DNA concentration on DNA adsorption
• 4.2.2 Influence of surface charges on DNA adsorption
• 4.2.3 Influence of the solution ionic strength on DNA adsorption
• 4.3 Adsorption of short DNA chain
• 4.3.1 Influence of MUO/AUT proportion on DNA adsorption
• 4.3.2 Comparison of the adsorption of long and short DNAs
• 5 SPR enhanced surface second harmonic generation
• 5.1 Introduction to SSHG
• 5.2 SPR enhanced SSHG
• 5.2.1 Dependence of field enhancement on gold layer thickness
• 5.2.2 Description of experiment and primary results
• 5.3 SPR enhanced SHG microscopy
• 5.3.1 Excitation of SPR enhanced SSHG by objective lens
• 5.3.2 Electromagnetic field near focus
• 5.3.2.1 Scalar diffraction theory
• 5.3.2.2 Vectorial field distribution in a stratified focal region
• 5.3.2.3 Transformation matrices
• 5.3.2.4 Expression of electric field near focus
• 5.3.3 Numeric simulation results of electric field near focus
• 5.3.3.1 Electric fields at gold/air and glass/air interfaces
• 5.3.3.2 Influence of focus position
• 5.3.3.3 SHG at focus
• 5.3.4 Description of SPR enhanced SHG microscopy
• 6 Conclusion and future work
• Appendix A Preparation of metal films by thermal evaporation
• Appendix B Optical constants
• B.1 Optical constants of glass
• Au'>B.2 Optical constant of gold:∈^Au
• CT'>B.3 Optical constant of chromium:∈^CT
• SPR'>Appendix C Extraction of θ_SPR
• Appendix D Phosphate solutions of given pH and ionic strength
• D.1 Conductivity of phosphate solutions of given pH and ionic strength
• Appendix E Matlab codes for the calculation of reflected fields
• Appendix F Abbreviations
• Publications
• List of figures
• List of tables
• Bibliography