金属-电介质复合结构实现荧光远场增强（英文）

本文提出一种大尺度的金属-电介质复合微纳结构(银-硅结构),用于提高荧光生物检测的灵敏度及解决荧光物质距离结构远场范围时荧光增强的近场局限。这种大尺度的金属-电介质复合微纳结构与之前的金属-电介质复合微纳结构不同,其通过光的散射和干涉实现了荧光物质距离结构远场范围时的荧光增强。在本文中,通过采用时域有限差分法,主要从荧光激发和荧光发射两个过程研究银-硅结构。结果表明,在激发过程中,银-硅结构的荧光强度高于玻璃结构且位于银-硅结构两柱之间的狭缝中的电场分布比金属结构(银结构)更均匀,因此在银-硅结构中可以实现荧光增强,而且分子运动行为的检测更准确。在发射过程中,当荧光纳米粒子距离结构远场范围内时,与玻璃相比,银-硅结构可以实现更好的荧光增强效果。利用银-硅结构实现荧光增强的机理是光的散射和干涉,荧光被银膜向上散射,同时,结构两侧的银/硅柱也散射一部分荧光,荧光相互干涉传播至远场实现荧光增强。此外,银-硅结构易于制备和集成。因此,其可以很好地应用于生物传感领域。     

电介质微球和金属平面纳米层增强荧光远场定向发射

本文提出了一种由电介质微球和金属平面纳米层组成的复合结构,用于增强荧光远场定向发射强度和提高荧光收集效率.通过时域有限差分法研究了位于电介质微球和金层之间量子点的激发和发射过程.量子点作为荧光材料涂敷于聚甲基丙烯酸甲酯中,用于控制和金层的距离从而调控荧光增强.该结构基于等离激元耦合、回音壁模式以及光子纳米射流之间的协同效应,使远场荧光强度增强230倍,荧光收集效率高达70%.与电介质微球和金球二聚体复合结构增强荧光相比,金球二聚体之间的间距不易控制,此外量子点要放在金球之间特定的位置.而本文提出的三维平面复合纳米结构相对更方便实现.以上结果在提高荧光生物检测灵敏度、成像质量以及发光器件效率等领域具有非常重要的应用意义.     

紧聚焦角向矢量光激发下硅环-开口金环纳米天线的单向散射

采用时域有限差分法,数值研究了紧聚焦角向矢量光激发下硅环-开口金环纳米天线的远场散射特性.结果表明:紧聚焦的角向矢量光可在硅纳米环和开口金纳米环中分别激发出不同峰宽的磁偶极模式;由于模式间的杂化效应,两种磁偶极模式会耦合形成硅环-开口金环纳米结构的反键和成键模式;在峰谷1064 nm波长处,反键和成键模式间的相消干涉在面内形成了单向远场散射.进一步,详细研究了几何参数对单向散射的影响,并且借助该纳米天线的单向散射特性,实现了偶极光源的定向发射.研究结果提供了一种纳米光子结构远场散射的灵活调控手段,并有望为纳米光源、光学传感器等的设计和研发提供有益的参考.     

电介质球复合纳米天线对荧光定向发射的增强

在纳米光子学中,提高荧光物质的定向发光强度是许多应用要解决的关键问题。为了优化电介质纳米天线的荧光增强能力,本文提出了一种由硅纳米球二聚体与TiO 2微球组成的电介质球复合纳米天线。通过时域有限差分法,本文分别从量子产率增强、荧光收集效率增强以及荧光激发率增强3个方面研究了该复合纳米天线对荧光的增强效果。结果表明,这种复合纳米天线不仅可以解决单个TiO 2微球增强荧光时量子产率较低的问题,还可以弥补单个硅纳米球二聚体增强荧光时荧光收集效率较差的不足。该复合纳米天线可使CdSe量子点的量子产率增强约4倍、荧光收集效率增强约2倍。此外,由于硅纳米球二聚体与TiO 2微球对荧光激发过程具有增强效果,该复合天线最终可以产生较高的荧光定向增强倍数。在量子点发光的中心波长523 nm处,荧光定向增强约为3064倍。     

若干新型微纳光子学器件研究

光子晶体和纳米光纤是两种重要的微纳光子学材料,各自具有非常独特的控制光子传输状态的功能,是研究微纳尺度下光与物质相互作用的重要平台,也是实现新型微纳光子学器件的重要基础.文章简要介绍了超快速低功率光子晶体全光开关、纳米光纤传感器、干涉器和介质-金属纳米线复合结构器件的研究进展.     

光散射中的anapole态：理论、结构以及应用

光散射中的anapole态是纳米光子学领域的一种独特的光学现象，可以用Mie理论以及多极展开理论进行分析。对于最常见的一阶电anapole态，其可以看做是由笛卡尔坐标系下电偶极矩和环偶极矩的干涉相消产生，具有典型的远场散射抑制和近场增强性能。本文首先对anapole态的基本概念和理论进行阐述，其次对激发anapole态的微纳结构进行总结，最后结合anapole态独特的光学特性，对其在近场增强、非线性光学、激光等方面潜在的光子学应用和最新研究进展进行了讨论和展望。     

微纳光子结构中光子和激子相互作用

微纳光子结构中超强的光场局域给光和物质相互作用带来了新的研究机遇.通过设计光学模式,微纳结构中的光子和激子可以实现可逆或者不可逆的能量交换作用.本文综述了我们近年来在微纳结构,尤其是表面等离激元及其复合结构中光子和激子在强弱耦合区域的系列研究工作,如高效可调谐及方向性的单光子发射,利用电磁真空构造增强光子和激子的耦合等.这些工作为微纳尺度上光和物质作用提供了新的物理内容,在芯片上量子信息过程及可扩展的量子网络构建中有潜在应用.     

基于严格耦合波理论的蝴蝶鳞翅分级结构光学特性研究

Morpho蝴蝶的颜色效应是由蝴蝶鳞翅上特殊的分级微纳结构与光发生干涉、衍射和散射等作用引起的,是一种典型的结构色.以严格耦合波理论(RCWA)为基础,借助光学衍射结构综合设计工具,建立了仿蝴蝶鳞翅分级结构的二维模型,系统分析了底层电介质单元横向周期占空比、纵向相邻电介质单元宽度差值、介质层纵向周期占空比以及脊柱与基底...     

金属-电介质-金属柔性结构增强荧光发射

增强荧光发射可以提高荧光检测灵敏度、提高LED的亮度,在提高发光器件性能方面具有重要意义。由于金属结构在增强局域场、增强荧光发射方面具有很好效果,而柔性电介质材料具有灵活的可弯曲性特性,本文提出一种由金属-电介质-金属（MDM）组成的柔性结构以增强荧光发射。利用时域有限差分方法系统研究了该结构对量子点定向发射增强的影响。理论计算表明柔性MDM结构局部起伏和弧度对荧光增强起促进作用,且可以使位于结构中心位置量子点的量子效率增强约7倍。此外,还可以改变电介质的折射率和厚度从而实现目标波长的可调谐性。实验结果表明该柔性MDM结构对荧光增强有一定的促进作用,这一发现对未来的显示技术和柔性发光器件都有很大的价值,对高效柔性器件的开发应用具有一定的指导意义。     

纳流通道-谐振腔耦合结构测量荧光物质微位移

本文提出了一种纳流通道-谐振腔耦合结构,用于实现对荧光物质微位移的检测.在本文中,首先,使用时域有限差分法,研究了量子点偏振态及结构参数对荧光与结构耦合效果的影响,进而对结构进行优化;然后,通过测量耦合结构输出光功率的变化,实现对荧光物质微位移的检测;最后,对影响传感灵敏度的因素进行研究.结果表明,相比传统方法,纳流通...     

纳米银与表面吸附荧光素的荧光性能的影响

研究了纳米银粒子对表面吸附荧光素(fluorescein,Fl)的荧光性能的影响。Fl溶液中加入纳米银粒子,Fl分子包覆在纳米银粒子表面形成Fl_n-Ag复合物使纳米银相互桥连形成类似网络的结构,且Fl分子吸收峰随着纳米银浓度的增加发生红移。纳米银通过产生的强局域场将能量传输给Fl发光中心,实现了Fl的荧光增强,荧光增强效率随着纳米银浓度的增加具有最大值。较大粒径的纳米银使Fl获得最大荧光增强效率所需浓度较低且最大荧光增强效率值较高。研究结果表明,纳米银与Fl间的能量传输主要由Fl分子附近局域电磁场增强和分子到金属表面无辐射跃迁能量转移过程所决定并与纳米银的浓度、尺寸密切相关。     

Silver nanoplates: controlled preparation, self-assembly, and applications in surface-enhanced Raman scattering

Silver nanoplates were prepared in a dual reduction system with NaBH₄ and sodium citrate both as reducing agents. And then the as-prepared nanoplates could be growing up through multistage growth methodology. The average edge length of Ag nanoplates can be tailored from 40 nm to 260 nm without changing their shape, crystallinity, and the average thickness. Furthermore, the effectiveness of these silver nanoplates as substrates prepared by the silanization self-assembly method toward surface-enhanced Raman scattering (SERS) detection was evaluated by using 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) as probe molecules. It was found that the enhancement ability of the silver nanoplates film is remarkable lower than that of the spherical silver nanoparticle film. The reason is attributed to the electromagnetic mechanism and chemical mechanism. This work will be of great significance in understanding the SERS enhancement mechanism and in the fabrication of nanoparticle films for biosensing.     

Glass‐embedded silver nanoparticle patterns by masked ion‐exchange process for surface‐enhanced Raman scattering

Glass‐embedded silver nanoparticle patterns were fabricated by masked silver–sodium ion‐exchange process followed by etching to reveal the particles for surface‐enhanced Raman scattering (SERS). The intensity of the enhanced Raman signal is comparable to that of the fluorescence, and the detection limit of 1 nM for Rhodamine 6G has been achieved. Raman images at different etching depths and corresponding morphological images are compared to find optimal SERS signal. Our results demonstrate that silver nanoparticle patterns embedded in glass can be used as SERS‐active substrates. Nanoparticles can be formed in a glass of high optical quality and have potential to be integrated with optical waveguides for a sensor chip. Copyright © 2010 John Wiley & Sons, Ltd.     

Giant enhancement of two-photon fluorescence induced by resonant double grating waveguide structures

We report a 350-fold enhancement of ultra-short-pulse-excited two-photon fluorescence (TPF) using a resonant double grating waveguide structure (DGWS). These structures show vanishing transmission and maximum reflection under resonance conditions, i.e. specific wavelength, polarisation and angular orientation of the incident light. This guided mode phenomenon is characterised by a large field enhancement inducing an enormous TPF signal of fluorescent molecules at the waveguide surface, as compared to direct non-resonant excitation. We demonstrate that high spectral acceptance for ultra-short pulses with broad spectral bandwidths can be achieved by a specifically designed DGWS, and that neither beam focussing nor high laser power is necessary for TPF excitation. Due to the high enhancement of more than two orders of magnitude, DGWS can be considered as a powerful platform for TPF applications such as biosensing and microarray technology. PACS 42.62.Be; 42.79.Dj; 42.79.Gn     

一种用表面增强拉曼光谱进行免疫检测的方法

一种结合表面增强拉曼(SERS)技术和纳米粒子标记技术,通过银增强来实现免疫检测的方法。将p-巯基苯甲酸(MBA)作为探针,固定在免疫金溶胶粒子表面形成纳米标记,其与被基底捕获抗原分子发生免疫识别。通过银增强技术,在"三明治"结构对探针进行拉曼检测。     

Investigation of surface plasmon resonance using cylindrical dielectric-metal-dielectric (C-DMD) plasmonic configuration

In this paper we have proposed a technique based on image analysis of the surface plasmon excitation at the metal-dielectric interface of inside silver coated fused silica capillary glass tube. Chemical deposition technique has been used for the deposition of silver. Angular interrogation in Kretschmann-like configuration is realized by non-radial transverse illumination of this cylindrical dielectric-metal-dielectric (C-DMD) structure with a He–Ne laser source. Here the uniform film deposition of the inside surface of the capillary is not that crucial except within the transversely illuminated working area concerned. Moreover, the proposed technique has been validated experimentally for sensing different aqueous dielectric samples inserted inside the tube.     

Raman of indigo on a silver surface. Raman and theoretical characterization of indigo deposited on silicon dioxide-coated and uncoated silver nanoparticles

Raman, surface-enhanced Raman scattering, and shell isolated nanoparticles-enhanced Raman scattering techniques were used to study the indigo–nanoparticle interaction nature. Silver nanoparticles were employed with and without a silicon dioxide spacer inert layer. The SERS spectral profile, obtained using silver nanoparticles, is different from the Raman one, which led to the proposition that the indigo–silver interaction is in the range of intermolecular interactions. SERS spectral reproducibility suggests identical organization and orientation of the analyte on the metal surface. The shell isolated nanoparticles enhanced Raman scattering spectrum of indigo, obtained by using silicon dioxide coated silver nanoparticles resulted similar to its Raman spectrum. This result indicates that the indigo structure is chemically unmodified by the silicon dioxide-coated silver surface. From the shell-isolated nanoparticles-enhanced Raman scattering experiments, the electromagnetic mechanism is proposed as the reason for the spectral enhancement. Theoretical calculations allow one to infer both the indigo–silver surface interaction nature and the orientation of indigo on the surface.     

Enhancement of Raman scattering of light by ultramarine microcrystals in presence of silver nanoparticles

Approximately 10²‐fold enhancement of Raman scattering by ultramarine microcrystals is reported by means of interaction with silver nanoparticles in films and powders. Theoretical modeling predicts the maximal 10¹⁰‐fold enhancement in close vicinity of a silver spherical nanoparticle (0.24 nm) with rapid decay of enhancement factor to 1 in the range of approximately 50 nm. Experimental enhancement factor is treated as overall effect within the small portion of every microcrystal in the close vicinity of silver nanoparticle(s). The results are considered as an important extension of traditional surface enhanced molecular Raman spectroscopy towards bigger inorganic probes. Copyright © 2012 John Wiley & Sons, Ltd.     

纳米银组装结构上罗丹明B的表面增强荧光效应

采用表面自组装技术,在玻璃表面构筑银纳米粒子的二维组装结构。银纳米粒子组装结构的表面等离子共振光谱中偶极子表面等离子体共振对组装结构更为敏感而表现出较大位移。组装银纳米粒子可极大增强罗丹明B的荧光。荧光的表面增强效应主要来自银纳米粒子对荧光分子所处区域的局部电磁场增强,银纳米粒子的表面分子修饰对其表面增强效应有较大的影响。     

具有双共振吸收峰的Au纳米粒子制备及其拉曼表征

表面增强拉曼散射(SERS)很大程度的弥补了拉曼散射强度弱的缺点,迅速成为科研工作者们的研究热点,在食品安全、环境污染、毒品以及爆炸物检测等领域应用广泛。纳米技术的发展使得目前对于SERS的研究主要集中于金属纳米颗粒基底的制备,金属纳米粒子的种类、尺寸及形貌对SERS增强和吸收峰峰位均有影响,要获得好的增强效果,需要对金属纳米结构进行工艺优化。特别是,需要结合金属纳米粒子的结构和激励光波长,以期获得更好的增强效果。为了研究SERS增强和吸收峰之间的关系,开展了具有双共振吸收峰的金属纳米粒子的研究。首先利用FDTD Solutions仿真建模,主要针对金纳米颗粒直径、金纳米棒长径比及分布状态对共振吸收峰进行仿真,得到金纳米球理论直径在50 nm左右,金纳米棒理论长径比在3.5~4.5左右时,吸收峰分别分布在532及785 nm附近,符合多波段激励光拉曼增强条件;对于激励光偏振方向,其沿金纳米棒长轴方向偏振时吸收峰位于785 nm附近,沿金纳米球短轴方向偏振时吸收峰位于532 nm附近。然后采用种子生长法,制备了可用于多种波长激励光的双吸收峰表面增强拉曼散射基底。通过改变硝酸银用量(5,10,20,30和40 μL)、盐酸用量(0.1和0.2 mL)以及其生长时间(15,17,21和23 h)等多种工艺参数来控制金纳米棒含量,得到了同时含有金纳米球及金纳米棒的双吸收共振峰金纳米粒子。最后用该样品作为基底,罗丹明6G(R6G)作为探针分子,分别测试其在532,633和785 nm激励光入射时的SERS表征,对分析物R6G最低检测浓度均达到了10-7 mol·L-1,增强因子达到了~105,满足了多波段SERS检测的需要。