金纳米旋转椭球的折射率传感特性分析与优化

对于金纳米颗粒在化学和生物传感中的应用,找到具有高品质因子的金纳米颗粒形状是近年来的研究热点。基于T矩阵方法和介电函数的尺寸修正模型,本文从理论上定量研究了金纳米旋转椭球的尺寸对其折射率灵敏度、半峰宽以及品质因子的影响。为了获得最佳传感性能,对品质因子进行了优化,并得到了最优的颗粒尺寸参数。结果发现,短半轴为11 nm和长半轴为49 nm的金纳米旋转椭球具有最大品质因子6.76。优化后的金纳米旋转椭球可以作为理想的化学和生物传感器。本研究为金纳米旋转椭球在化学和生物传感的应用中提供重要的理论依据。     

Au-Ag合金纳米球壳的折射率传感特性分析与优化

基于Au纳米颗粒的稳定性、无毒性、生物相容性和Ag纳米颗粒优异的消光特性,Au-Ag合金纳米颗粒在生物传感中存在着潜在的应用价值.为了能找到传感性能更好的合金纳米颗粒,本文利用双层球M ie散射理论和介电函数尺寸修正模型定量研究了Au-Ag合金纳米球壳的尺寸参数对折射率灵敏度、半峰宽和品质因子的影响,获得了最佳品质因子...     

金属纳米颗粒的热导率

本文使用统计模拟方法对金属纳米颗粒的电子平均自由程进行了计算,并考察了纳米颗粒的晶格比热和声子平均群速度,最后应用动力学理论对纳米颗粒的电子热导率和声子热导率分别进行了求解.研究结果表明:具有相同特征尺寸的方形、球形纳米颗粒的无量纲电子(或声子)平均自由程比较接近.金属纳米颗粒的电子热导率远大于声子热导率;电子、声子热导率随着直径减小呈现降低趋势,而电子热导率的颗粒尺度依赖性比声子热导率更为明显;随着颗粒直径进一步减小,声子热导率与电子热导率趋于同一数量级.当纳米颗粒特征尺寸大于4倍块材电子(或声子)平均自由程,其电子(或声子)热导率的颗粒尺度依赖性将减弱.     

利用Ag@SiO_2纳米粒子等离子体共振增强发光二极管辐射功率的数值研究

金属纳米粒子利用其局域表面等离子体共振效应(LSPR),可以增强附近荧光分子的自发辐射速率,因而在光学传感、光电器件等领域中具有潜在的应用价值.金属纳米粒子的LSPR与其自身的材料、形状、尺寸以及周围环境介质密切相关,这影响着纳米粒子在具体器件中的应用.本文利用三维时域有限差分法,研究了相同体积的球形、椭球形、立方形与三棱柱形银纳米粒子对薄膜发光二极管辐射功率的影响;计算了不同形状银纳米粒子对偶极子光源辐射功率和薄膜器件光出射强度的增强,并结合LSPR效应讨论了辐射功率变化的物理机理.研究结果表明:银纳米粒子自身形状尖锐程度的增加有利于提高LSPR的共振强度;同时纳米粒子的形状影响了LSPR共振电场与薄膜器件中偶极子辐射电场之间的耦合作用,其中立方形纳米粒子因为能实现最强的耦合作用而对器件的辐射功率增强最大.在此基础上进一步讨论了不同薄膜材料对LSPR共振及光源辐射功率的影响,发现较高的材料折射率有利于增强金属纳米粒子的LSPR与器件的耦合作用,从而改善发光二极管性能.     

金纳米粒子光学性质中的尺寸和形状效应

纳米尺度的金属及半导体呈现出特殊的光学、电学及磁学性质,采用近年发展起来的离散偶极近似(DDA)的方法,我们分析了金纳米粒子的尺寸及形状对其光学性质的影响。粒子周围介质的影响在文中亦作了分析。计算结果显示,金纳米粒子的等离子体吸收带同时受到粒子尺寸和形状的影响,但来自形状的影响更为明显。与米氏理论及扩展的甘氏理论相比较,DDA方法在粒子尺寸不再远小于入射光波长的时候更准确,并能应用于任何形状的纳米粒子。理论计算与实验结果能较好的吻合。     

三角形银纳米柱阵列传感乙醇气体方法

提出了一种基于金属纳米结构局域表面等离子体共振光谱的有机气体的传感方法.通过时域有限差分法设计了一种具有较高折射率灵敏度的三角形纳米柱阵列,并利用纳米球光刻法进行了制作.对乙醇蒸汽的传感实验结果证明,所制作的三角形银纳米柱对乙醇分子浓度非常敏感,其探测灵敏度达到24ppm/nm.该金属纳米结构传感有机气体的方法有望应用于环境监测等方面.     

三角形银纳米柱阵列传感乙醇气体方法研究

提出了一种基于金属纳米结构局域表面等离子体共振光谱的有机气体的传感方法.通过时域有限差分法设计了一种具有较高折射率灵敏度的三角形纳米柱阵列,并利用纳米球光刻法进行了制作.对乙醇蒸汽的传感实验结果证明,所制作的三角形银纳米柱对乙醇分子浓度非常敏感,其探测灵敏度达到24ppm/nm.该金属纳米结构传感有机气体的方法有望应用于环境监测等方面.     

绝缘体中金属离子注入合成纳米颗粒的理论研究

理论上提出了利用离散电子态来计算绝缘体中金属纳米颗粒Fermi能级的方法,给出了金属纳米颗粒的能级结构,并得到了依据金属纳米颗粒等离子体共振峰计算金属纳米颗粒尺寸的新公式.该理论可解释相关现象,通过实验初步验证了该理论的正确性. 关键词： 离子注入 金属纳米颗粒 绝缘体 Fermi能级     

金属纳米颗粒对有机太阳能电池光吸收效率影响的研究

借助时域有限差分法,对几种常见金属纳米颗粒影响有机太阳能电池光吸收效率的因素及其内部物理机制进行了研究.首先对金属纳米颗粒激发局域表面等离子共振的场分布特点进行分析,对比其在电池不同功能层中对光吸收率的影响;其次基于米氏理论与电共振效应,得出金属纳米颗粒的结构参量对局域表面等离子共振位置及强度的影响规律,并以此进行优化设计.结果表明,具有高对称性形貌的金属纳米颗粒以小尺寸密堆积结构引入电池活性层,能够促进电池光吸收增强三倍以上.     

金属纳米颗粒对有机太阳能电池光吸收效率影响的研究

借助时域有限差分法,对几种常见金属纳米颗粒影响有机太阳能电池光吸收效率的因素及其内部物理机制进行了研究.首先对金属纳米颗粒激发局域表面等离子共振的场分布特点进行分析,对比其在电池不同功能层中对光吸收率的影响;其次基于米氏理论与电共振效应,得出金属纳米颗粒的结构参量对局域表面等离子共振位置及强度的影响规律,并以此进行优化设计.结果表明,具有高对称性形貌的金属纳米颗粒以小尺寸密堆积结构引入电池活性层,能够促进电池光吸收增强三倍以上.     

Study of electrical field distribution of gold-capped nanoparticle for excitation of localized surface plasmon resonance

The specific optical characteristics which can be observed from noble metal nanostructured materials such as nanoparticles and nanoislands have wide variety of applications such as biosensors, solar cells, and optical circuit. Because, these noble metal nanostructures induce the increment of light absorption efficiency by the enhancing effect of electrical field from localized surface plasmon resonance (LSPR) excitation. However, the enhancing effects of electrical field from LSPR using simple structured noble metal nanostructures for several applications are not satisfactory. To realize the more effective light absorption efficiency by the enhancing effect of electrical field, quite different noble metal nanostructures have been desired for applying to several applications using LSPR. In this study, to obtain the more effective enhancing effect of electrical field, conditions for LSPR excitation using a gold-capped nanoparticle layer substrate are computationally analyzed using finite-difference time-domain (FDTD) method. From the previous research, LSPR excitation using such gold-capped nanoparticle layer substrates has a great potential for application to high-sensitive label-free monitoring of biomolecular interactions. For understanding of detailed LSPR excitation mechanism, LSPR excitation conditions were investigated by analyzing the electrical field distribution using simulation software and comparing the results obtained with experimental results. As a result of computational analysis, LSPR excitation was found to depend on the particle alignment, interparticle distance, and excitation wavelength. Furthermore, the LSPR optical characteristics obtained from the simulation analysis were consistent with experimentally approximated LSPR optical characteristics. Using this gold-capped nanoparticle layer substrate, LSPR can be excited easily more than conventional noble metal nanoparticle-based LSPR excitation without noble metal nanoparticle synthesis. Hence, this structure is detectable a small change of refractive index such as biomolecular interactions for biosensing applications.     

金和银纳米粒子二维周期阵列的光学性质

本文利用离散点偶极子近似方法(DDA)研究了金和银纳米粒子二维周期阵列的光学性质。研究结果表明二维周期阵列的消光性质及其表面等离子共振(SPR)波长受到阵列内粒子组成材料、粒子形状尺寸、阵列周期和阵列排布方式等因素的影响。对于二维正方阵列,当周期较小时(一般小于300 nm),阵列的共振波长主要取决于粒子组成材料和形状尺寸;当周期与阵列单体的共振波长附近时,阵列的消光谱中会出现极窄且锐的SPR共振峰,峰位只与阵列的周期值相关。改变阵列在平行和垂直于入射光偏振方向的周期,可以方便地调节二维长方阵列的共振峰的峰位和峰宽。     

芯帽纳米颗粒的光热性质

贵金属纳米结构中的光热效应在肿瘤光热治疗、光热成像、纳米药物等领域具有重要的应用价值.各向异性的芯帽纳米结构以其丰富的可调结构参数和对激发光偏振态敏感的特性,可灵活地在近红外波段获得理想的光学吸收性质,从而可以实现温度的高效调节.本文基于有限元方法研究了颗粒物纳米结构参数对其光热效果的作用规律,数值结果表明:通过对结构参数的微量改变(包括金壳厚度、芯壳比、芯径、金属表面覆盖率等)可实现温度的显著调整;在偏振态的旋转范围(30?—70?)内可快速地产生大温变光热的准线性调整.其不弱于纳米芯壳和纳米棒结构的光热性能可为纳米光热生医研究提供一种新的选择.     

Ultrafast optical nonlinear properties of metal nanoparticles

The physical origin and the dynamics of the ultrafast optical nonlinear response of noble metal nanoparticles are analyzed around the surface plasmon resonance frequency using extension of the bulk metal electron kinetics and band structure models. The computed spectral and temporal responses are found to be in very good agreement with the measured ones in silver when taking into account the impact of electron excitation on both the interband absorption and electron optical scattering rate. A good reproduction of the strong excitation regime experimental results is also obtained in the case of gold, with a dominant contribution of the interband effect. Received: 4 July 2001 / Published online: 10 October 2001     

Using Solution-Phase Nanoparticles, Surface-Confined Nanoparticle Arrays and Single Nanoparticles as Biological Sensing Platforms

The intense colors of noble metal nanoparticles have inspired artists and fascinated scientists for hundreds of years. In this review, we describe three sensing platforms based on the tunability of the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles. Specifically, the color associated with solution-phase nanoparticles, surface-confined nanoparticle arrays, and single nanoparticles will be shown to be tunable and useful as platforms for biological sensing.     

Humidity sensor based on localized surface plasmon resonance of multilayer thin films of gold nanoparticles linked with myoglobin

Layer-by-layer self-assembled multilayer thin films of gold nanoparticles (GNPs) linked with myoglobin (Mb) show substantial sensitivity to humidity at room temperature according to measurements of localized surface plasmon resonance (LSPR) absorption that relies on the interparticle interaction present in the film. The sensor response is reversible, with response and recovery times as low as 5 s. The sensing mechanism is as follows: as the ambient humidity changes, Mb molecules change their size, making the GNP-to-GNP spacing and thereby the interparticle interaction change; the change in the interparticle interaction causes a change in the LSPR absorption of the multilayer thin film. We found that the LSPR band of the multilayer thin film was almost insensitive to both the surrounding refractive index and the adlayer thickness, rendering the multilayer-film-based humidity sensor highly immune to ambient disturbances.     

金属纳米结构对光谱响应及折射率灵敏度的影响

推导了任意形状金属纳米结构对复杂环境折射率的局域表面等离子体共振(LSPR)光谱响应的解析解,给出了体折射率和局部折射率灵敏度公式,并进行了详细的理论分析和数值验证。结果表明,金属纳米结构的光谱响应与被分析物厚度呈指数增长关系,并与被分析物的折射率、敏感层厚度、金属纳米结构的材料和形状等因素有关。被分析物折射率越高,光谱响应越大。敏感层越厚,局部折射率灵敏度越差。同时,尖锐的金属纳米结构形状可以获得更大的体折射率灵敏度。对金属纳米结构光谱响应及折射率灵敏度的研究对制作高灵敏度LSPR传感器具有重要的指导意义。     

Metal Nanoparticle Photocatalysts: Synthesis,Characterization, and Application

Metal nanoparticles (NPs) have emerged as a kind of new photocatalyst to drive various chemical reactions by visible‐light irradiation. A distinct advantage of metal NP photocatalysts is that their light absorption is not limited to a certain wavelength but instead they are able to utilize a broad range of wavelengths, constituting a large fraction of the solar spectrum. Metal NPs like gold, silver, and copper NPs can strongly absorb visible light due to the localized surface plasmon resonance (LSPR) effect. Recent developments have shown that the light absorption properties strongly depend on the shape, size, and particle–particle interactions of NPs, which directly influence their photocatalytic activities. In this review, an overview of the preparation of metal NPs photocatalysts with various morphologies is given along with a brief discussion of the relationship between the morphology/composition and optical properties. The latest photocatalytic applications of these morphologies are also presented, and some of the challenges for the development of metal NPs photocatalysts are provided.     

基于含时密度泛函理论的表面等离激元研究进展

纳米粒子的局域表面等离激元(LSP)由于其新颖的光学特性成为目前国内外研究的热点之一. 本文利用含时密度泛函理论(TDDFT)对金属团簇及石墨烯纳米结构中的等离激元激发及调制的物理本质进行了研究. 和宏观大小的材料相比, 由于纳米结构的尺寸和量子受限效应, 纳米结构的等离激元具有一些不同的特征. 在低能共振区, 光谱线发生展宽, 并且发生劈裂. 由于纳米单体间的电磁耦合作用, 使聚合的纳米结构表现出了与单体不同的光学性质. 这些结果为等离激元的调控提供了坚实的理论指导.