【作者】 邓楚芸；

【导师】 马万云；

【作者基本信息】 清华大学 ， 物理学， 2013， 博士

【摘要】 在单分子层次上对DNA分子进行研究，对深入理解复杂的生命机制具有重要意义。但是单分子的信号强度往往非常低，普通的仪器设备难以检测到如此弱的信号。贵金属纳米结构的表面增强效应可将表面附近分子的荧光与拉曼散射增强几个数量级，利用贵金属纳米结构基底有可能实现DNA的单分子检测。本论文研究了纳米结构的表面增强效应，并探索了纳米结构基底在DNA表面增强检测与拉直操纵中的应用。首先，制备出一种新型的银纳米芽结构，考察了基于银纳米芽结构表面增强基底的性能。银纳米芽结构由固态离子学方法制备，表面高度粗糙；在银纳米芽基底上检测到较低浓度的染料小分子Rhodamine6G的表面增强拉曼散射信号；比较了自然氧化与加热氧化对银纳米芽基底的影响，发现氧化会显著改变基底表面增强能力。其次，以银膜结构为对象研究了氧化对基底表面增强性质的影响。检测了不同氧化时间下Rhodamine6G在银膜基底上的表面增强光谱，观测到表面增强拉曼散射与表面增强荧光随着氧化时间增加而同步地振荡，氧化后的银膜基底表面增强拉曼性质优于未氧化的银膜基底；测量了氧化过程中银膜基底氧化层厚度与表面粗糙度的变化，从检测物分子与基底的距离和基底的表面结构两方面分析了氧化对基底表面增强性质的影响机制。最后，将纳米结构应用于λDNA的表面增强检测与拉直操纵。使用银纳米芽基底在单分子水平探测到λDNA的拉曼信号，与扫描拉曼光谱成像结合检测到结构更精细的λDNA拉曼光谱；在荧光成像检测中观察到银纳米芽基底氧化前后对λDNA分子荧光的淬灭与增强效应；利用亲水的超顺排碳纳米管阵列定向操纵λDNA分子，使其沿碳纳米管方向自动排列拉直；获得λDNA分子光断裂过程的实时荧光图像，并估算了在超顺排碳纳米管基底上拉直的λDNA分子的受力与光断裂后的弹性回缩速率。本论文的研究将有助于表面增强相关理论的完善和DNA单分子检测技术的进一步发展。更多还原

【Abstract】 Study of DNA molecules in single molecule level is of great importance to theunderstanding of complicated life mechanism. However, single molecule signal isusually very weak and hard to be detected by ordinary devices. The surfaceenhancement effect of noble metal nanostructures is able to enhance the fluorescenceand Raman scattering of molecules in the vicinity by several degrees of magnitude.Such significant enhancement provides a potential approach to single moleculedetection of DNA. For such purpose, this dissertation studied the surface enhancementeffect of nanostructures, and explored its application in surface enhanced detection andstretching manipulation of DNA molecules.Firstly, a novel silver nanobud structure was fabricated and the surface enhancingperformance of silver-nanobud-based substrates was investigated. The silver nanobudstructure with a highly rough surface was manufactured from a solid state ionics method.We managed to detect the surface enhanced Raman scattering signal of Rhodamine6Gon silver nanobud substrates in low concentration. Natural oxidation and heatedoxidation of silver nanobud substrates were also studied, and the surface enhancingability of silver nanobud substrates was found to be evidently altered by oxidationprocess.Secondly, details of how oxidation affects surface enhancement for silver filmsubstrates was examined. Surface enhanced spectra of Rhodamine6G on silver filmsubstrates for different oxidation time were detected. The surface enhanced Ramanscattering and surface enhanced fluorescence presented a synchronous oscillation withincreasing oxidation time. Besides, surface enhanced Raman scattering effect of oxydicsubstrates was better than that of newly-fabricated substrates. Surface roughness andsilver oxide layer thickness of the silver film substrate were measured through itsoxidation. The mechanism of oxidation affecting surface enhancement intensity wasanalyzed based on changes in molecular-substrate distance and surface properties.Finally, nanostructures were applied in surface enhanced detection andstretching manipulation of λDNA molecules. The Raman signal of λDNA insingle molecule level was detected with surface enhancement from silvernanobud substrates. Quenching and enhancement of fluorescence were observed in fluorescence imaging of λDNA molecules on silver nanobud substrates. Onthe other hand, hydrophilic super-aligned carbon nanotube arrays wereemployed to manipulate the stretching direction of λDNA molecules, andstretched λDNA molecules were arranged along the direction of carbonnanotubes automatically. Meanwhile, the real time fluorescence images ofλDNA-photocleavage were obtained. The stress on λDNA molecules fromsuper-aligned carbon nanotube substrates and the rebounding velocity of λDNAafter photocleavage were extimated.This dissertation could be helpful to surface enhancement theories andsingle molecule detection of DNA.更多还原