单晶金微米片的电磁场增强及伴随的SERS效应

我们通过SERS的方法研究了单个金微米片表面不同区域的电磁场增强。首次对单个金属粒子采用拉曼区域成像的方法为电磁场增强提供了直接的实验证据。用结晶紫作为探针分子,通过对金微米六边形及截断的金微米三角形的SERS研究,直接证明金属粒子的边和角比面的电磁场增强更强。排除分子吸附、杂质干扰、晶体缺陷、表面活性剂等因素的影响,最后得出金微米片上电磁场增强的强弱顺序是角#边#面。     

聚甲基丙烯酸甲酯间隔的金纳米立方体与金膜复合结构的表面增强拉曼散射研究

金属纳米颗粒与金属薄膜的复合结构由于其局域表面等离子体和传播表面等离子体间的强共振耦合作用,可作为表面增强拉曼散射(SERS)基底,显著增强吸附分子的拉曼信号.本文提出了一种聚甲基丙烯酸甲酯(PMMA)间隔的90 nm金纳米立方体与50 nm金膜复合结构的SERS基底,通过有限元方法数值模拟,得到PMMA的最优化厚度为15 nm.实验制备了PMMA间隔层厚度为14 nm的复合结构,利用罗丹明6G (R6G)为拉曼探针分子, 633 nm的氦氖激光器作为激发光源,研究了复合结构和单一金纳米立方体的SERS效应,发现复合结构可以使探针分子产生比单一结构更强的拉曼信号.在此基础上,研究了不同浓度金纳米立方体水溶液条件下复合结构中R6G的拉曼光谱.结果表明,当金纳米立方体水溶液浓度为5.625μg/mL的条件下复合结构中R6G的拉曼信号最强,且可测量R6G的最低浓度达10~(–11) mol/L.     

利用聚碳酸酯模板制备的金纳米棒的表面增强Raman散射效应研究

采用聚碳酸酯模板和电化学沉积法制备基于金纳米棒的Raman场增强衬底, 制备的金纳米棒直径大约36 nm, 长约1 μm, 测试结果显示其共振吸收峰的位置约为540 nm. 比较了谐振和非谐振条件下的场增强情况, 并确定了场增益系数, 结果显示谐振激光激发下的增益比非谐振情况下提高了7.36倍. 本研究相对于前人的工作取得了如下进展: 一是讨论了谐振模式与非谐振模式下的金纳米棒的场增益系数, 利用谐振波长的激光激发金纳米棒, 进一步提高了场增益; 二是消除了聚碳酸酯模板分子的荧光背底, 使其在表面增强 Raman 散射方面的应用进一步变得可行. 关键词： 金纳米棒 表面增强Raman散射 聚碳酸酯模板     

基于Klarite芯片的表面增强拉曼散射特性研究

本文介绍了一种商用的表面增强拉曼芯片(Klarite),并对其表面形貌、拉曼活性进行了表征和测试分析.Klarite芯片由于独特的倒金字塔形设计使得其具有较好的拉曼活性、稳定性和重现性,为生命科学和分析化学研究提供了有力的研究工具.此外,我们对Klarite芯片在外电磁场作用下的表面电场分布进行了模拟,发现一个结构单元...     

SERS enhancement of gold nanospheres of defined size

Monodisperse, citrate‐stabilized gold nanoparticles of sizes ranging from 15 to 40 nm were synthesized and characterized by small angle X‐ray scattering and UV‐vis experiments. Identical surface properties of nanoparticles of different sizes to avoid variation in the chemical surface‐enhanced Raman scattering (SERS) enhancement, as well as selection of experimental conditions so that no aggregation took place, enabled the investigation of enhancement of individual nanospheres. Enhancement factors (EFs) for SERS were determined using the dye crystal violet (CV). EFs for individual gold nanospheres ranged from 10² to 10³, in agreement with theoretical predictions. An increase of the EFs of individual spheres with size can be correlated to changes in the extinction spectra of nanoparticle solutions. This confirms that the increase in enhancement with increasing size results from an increase in electromagnetic enhancement. Beyond this dependence of EFs of isolated gold spheres on their size, EFs were shown to vary with analyte concentration as a result of analyte‐induced aggregation. This has implications for the application of nanoparticle solutions as SERS substrates in quantitative analytical tasks. Copyright © 2011 John Wiley & Sons, Ltd.     

金纳米棒的飞秒激光组装研究

金属纳米粒子对于研究表面等离子体共振具有非常重要的意义,其自组装形成的功能组装体能够展现出更加优异的整体协同性能.本文通过飞秒激光加工对金纳米棒直接进行组装,不引入其它的修饰剂,过程简单、快速(约1 min),不仅保留了金纳米棒表面等离子特性,且可以实现金纳米棒的任意精细图案化.将组装的微纳结构用于微流控芯片表面增强拉曼散射探测,可以得到很好的增强效果,为等离子体器件的制备提供了新的方法.     

界面自组装的金/氧化石墨烯复合材料的表面增强拉曼散射行为研究

采用Frens法制备金纳米粒子溶胶,通过界面自组装技术在掺磷的非晶碳衬底表面构筑三维的金/氧化石墨烯/金复合结构.以罗丹明B为探针分子,考察金/氧化石墨烯/金复合材料的表面增强拉曼散射活性.结果表明,由于氧化石墨烯的化学增强和金纳米粒子的电磁场增强的协同作用,在该三维复合材料上获得了很强的罗丹明B拉曼信号.所设计的三维金/氧化石墨烯/金复合材料在生物分析、环境监测、疾病防控、食品安全等领域具有潜在的应用价值.     

阴极金属微凸起电场增强因子数值模拟

利用有限元方法对无穷大平板二极管中阴极表面金属微凸起的微观电场增强因子进行了计算研究,给出了微凸起微观电场增强因子随凸起参数的变化规律,拟合得到了微观电场增强因子的简单实用的经验表达式,并与文献中的近似公式进行了比较。模拟的结果表明,对锥状球头微凸起的电场增强因子,文献给出的近似公式误差较大,应避免使用。     

椭圆截面金纳米管近场增强特性的研究

本文基于时域有限差分方法(finite difference time domain, FDTD)研究了入射光波长、入射光偏振方向、纳米管几何形状、 管壁厚度及内核和包埋介质的变化对椭圆截面金纳米管近场分布特征的影响. 研究发现, 入射光波长为纳米管等离激元共振波长时, 纳米管近场增强最大; 入射光偏振方向与椭圆长轴夹角的增加会导致管内的场强迅速增大; 椭圆管半短轴变大可以调节纳米管场强分布从两端高、中间低变化为均匀分布; 内核和包埋介质介电常数的增大均会使得纳米管内部及周围场强逐渐减弱.     

Metal‐nanoparticle‐coating‐induced enhancement and weakening of resonant Raman scattering in ZnO: effect of surface electric field

Effects of Ag and Ti nanoparticle coatings on resonant Raman scattering in various ZnO thin films are presented. The longitudinal optical (LO) phonons, irrespective of the ZnO quality, exhibit an enhancement and a weakening by the Ag and Ti nanoparticle coatings, respectively. The enhancement (weakening) is always accompanied by a reduced (an increased) intensity ratio of the second to first‐order LO phonons, which can be associated with changes in the electron‐phonon coupling strength in the probed area of ZnO. Angle‐resolved X‐ray photoelectron spectroscopy provides evidence for the bending of the surface energy bands and their changes induced by the metal coatings. The effect of metal nanoparticle coatings on the Raman scattering of ZnO is thus attributed to the changes in the surface electric field. Copyright © 2011 John Wiley & Sons, Ltd.     

Nanoporous gold thin films synthesised via de-alloying of Au-based nanoglass for highly active SERS substrates

Nanoporous gold thin films have been fabricated through chemical de-alloying of Au-based nanoglass with a nanocolumnar structure, with composition Au₄₀Cu₂₈Ag₇Pd₅Si₂₀ (at.%), that had previously been deposited by magnetron sputtering. By varying the de-alloying conditions, gold ligaments ranging from 20 to 100?nm were obtained. The microstructure and chemical composition of the as-prepared films were characterised by various techniques. Surface-enhanced Raman scattering (SERS) of thin films was investigated using rhodamine 6G. The results indicate that the main microstructural features with interconnected ligaments and defects of nanoporous gold result in significant SERS enhancement.     

对碳纳米管阵列的场发射电场增强因子以及最佳阵列密度的研究

研究了外电场、碳纳米管自身线度、尤其管的阵列密度对碳纳米管的场发射性能的影响,从理论上深入探索碳纳米管阵列的电场增强因子并提出改善其场发射电子性能的有效途径.研究结果表明,碳纳米管阵列的电场增强因子的数量级一般为102—103,并对任何长径比的碳纳米管阵列,都对应着一个最佳阵列密度,当碳纳米管阵列密度取此最佳密度值时,其电场增强因子明显提高.这里的理论研究对弄清碳纳米管的场发射机理及实验合成高发射性能的碳纳米管阵列有一定的意义 关键词： 碳纳米管阵列 最佳阵列密度 电场增强因子 长径比     

偶联分子对金纳米粒子在玻片上组装的影响

将金纳米粒子组装在用3-氨基丙基-三乙氧基硅烷(APES)修饰的普通玻片上,再分别用偶联分子对巯基苯胺、1,4-二巯基苯在该基底上再次组装金纳米粒子,结果表明用对巯基苯胺作为组装的偶联分子得到双层金纳米粒子结构,对巯基苯胺的表面增强拉曼光谱信号得到增强,而用1,4-二巯基苯作为组装的偶联分子得到单层金纳米粒子结构。     

高频强电场下的等离子体X光发射增强

本文报道GaAs和Zn激光等离子体在高频强电场击穿气体从而在靶周围形成一层电子云的条件下,使等离子体高阶电离离子的X射线发射增强现象。     

Effect of built-in electric field on electron Raman scattering in InGaN/GaN coupled quantum wells

Electron Raman scattering (ERS) in wurtzite In_xGaN_1−x/GaN coupled quantum wells (CQWs) is investigated by effective-mass approximation and second-perturbation approach, including a strong built-in electric field (BEF) effect due to the piezoelectricity and spontaneous polarization. The dependence of differential cross-section (DCS) on structural parameters of CQWs is studied. Our results show that the strong BEF gives rise to a remarkable reduction of the DCS, which is around three orders smaller than that of the CQWs without BEF. With the presence of the BEF, the emitted photon energy decreases about 10 times as a consequence of quantum-confined Stark effect.     

波导内场增强法测量微波气体击穿

提出并研究了波导内场增强法测量微波气体击穿的实验方案,在密闭波导内加金属针实现电场增强,通过调节微波源辐射功率及两针距离,使微波传输达到气体击穿的条件。介绍了实验原理及诊断方法,进行了频率2.86 GHz、脉宽180 ns的微波在0.1 MPa空气中的击穿实验,分析了实验中得到的典型波形。结果表明实验现象与设计吻合,验证了该方案研究微波气体击穿的可行性。     

A high‐throughput method for controlled hot‐spot fabrication in SERS‐active gold nanoparticle dimer arrays

We present a high‐throughput method for fabricating large arrays of surface‐enhanced Raman scattering (SERS) active gold dimers. Using a large‐area/low‐cost nanopatterning method in conjunction with a meniscus force deposition technique, we were able to create large arrays of uniformly spaced nanoclusters comprising two 60‐nm gold nanospheres. Raman measurements of a thiophenol monolayer deposited on smaller scale arrays of aligned dimers yielded enhancement factors as high as 10⁹. Polarization‐controlled measurements show spectral peak heights to be 10–100 times smaller when the incident beam is polarized perpendicularly to the dimer axis, confirming that the measured enhancements arise from the ‘hot spots’ between the two nanospheres. Copyright © 2009 John Wiley & Sons, Ltd.     

基于多尺度理论的电各向异性介质椭球内电场

 基于电磁场的多尺度变换理论,将一个各向异性介质椭球重构为一个各向同性介质椭球,进一步得到了新椭球的形体参数。利用各向同性椭球电磁场与各向异性椭球电磁场的多尺度关系,得出了各向异性介质椭球内电场的解析表达式,对所得结果进行了验证。计算了椭球内电场方向与外电场方向的夹角,仿真结果表明：外电场的方向对椭球内电场的影响不大,介电常数张量对椭球内电场的方向和大小有较大的影响。     

阴极金属微凸起电场增强因子数值模拟

 利用有限元方法对无穷大平板二极管中阴极表面金属微凸起的微观电场增强因子进行了计算研究,给出了微凸起微观电场增强因子随凸起参数的变化规律,拟合得到了微观电场增强因子的简单实用的经验表达式,并与文献中的近似公式进行了比较。模拟的结果表明,对锥状球头微凸起的电场增强因子,文献给出的近似公式误差较大,应避免使用。     

金纳米环双体尺寸和耦合效应对表面等离子体共振特性的影响

采用离散偶极子近似方法系统地研究了金纳米环双体的消光光谱及其电场分布. 计算结果表明, 金纳米环双体在耦合作用下的共振消光峰对应着不同振动模式, 改变金纳米环双体的排列方式、 间距和尺寸大小, 其表面等离子体共振消光峰发生红移或蓝移. 因此可以通过对金纳米环双体结构参数和排列方式的设定, 调节其表面等离子体共振消光峰的位置. 电场分布表明, 水平排列的金纳米环双体较单个金纳米环产生更强的局部表面增强电场. 适当的小间距, 较大的内外半径的金纳米环水平阵列更适合做表面增强拉曼散射的衬底, 在生物分子检测等领域具有潜在的应用.