Au-Au2S复合纳米球壳微粒的空腔谐振及参量讨论

Au-Au2S复合纳米球壳微粒（金纳米球壳），是一种新型复合结构的纳米微粒，其结构为纳米级的Au2S介质球外包裹了一层几个纳米厚的黄金球壳。这种复合纳米球壳微粒可以被抽象为球型谐振腔。报道了它的空腔谐振吸收的实验结果，并且运用经典理论结合介观结构特征，讨论了有关Au-Au2S复合纳米球壳微粒空腔谐振吸收的一些重要参量，其中包括谐振吸收波长、品质因数、谐振能量等。另外，还讨论了金球壳的厚度对这些重要参量的影响。     

纳米 Au 球壳材料的制备及其近红外光热转换性质

报道了一种采用湿化学法,以Ag纳米球为模板合成纳米Au球壳水溶胶的新方法,并对这种材料的光热转换性质进行了研究。TEM分析表明,Au纳米颗粒呈球壳结构,粒径约为20nm,粒径分布比较均匀,无明显硬团聚体存在。随着氯金酸加入量的增加,Au球壳的吸收峰位置从可见区(-400nm)逐渐红移至近红外区(-800nm)。测量了不同浓度的Au球壳水溶胶经近红外激光照射后的温度变化。结果表明,经1．9W／mm^2的808nm近红外光照射10min,温度最高升高了5．5℃。由于800—1200nm是人体组织的透射窗口,肿瘤细胞在42℃左右即可被杀死,这种纳米Au球壳材料有望在利用光热转换的红外热疗中得到应用,并有可能利用光动力实现药物释放。     

利用时域有限差分法模拟金纳米球及球壳的光学特性

利用时域有限差分方法研究了金纳米球、金纳米球壳及多层球壳的消光特性及电场分布.结果表明:金纳米颗粒的几何参量对消光峰的位置有显著影响.随着SiO2核心半径的增大,金纳米壳的消光峰显著红移.随着金核心半径的增大,gold-silica-gold多层球壳消光谱的低能峰显著红移,而高能峰微弱蓝移.     

金纳米球壳对的局域表面等离激元共振特性分析

应用有限元方法, 研究金纳米球壳对的几何结构参数及物理参量对其表面等离激元共振的散射及消光光谱的影响, 并根据等离激元杂化理论进行了理论分析. 结果表明, 随着金壳厚度的增加, 金纳米球壳对的散射及消光共振峰先发生蓝移而后红移, 而随着金纳米球壳间隙的减小, 或者随着金纳米球壳的内核尺寸或内核介质折射率的增大, 散射及消光共振峰均发生红移; 随着金壳厚度或内核尺寸减小, 或者随着内核介质折射率增大, 金纳米球壳对的散射与消光共振强度减弱, 而随着金壳间隙的减小, 金纳米球壳对的散射共振强度先增强后减弱, 而消光共振强度逐渐增强, 数值模拟与理论分析一致.     

金纳米核壳局域表面等离子体激元的消光特性研究

采用离散偶极近似(Discrete Dipole Approximation,DDA)方法考察核壳比和外界介质折射率对ITO/Au、CdS/Au、Nb-Sn/Au纳米核壳粒子表面等离子体共振消光特性的影响,并利用杂化理论对其物理本质解释。仿真结果表明,ITO/Au和CdS/Au纳米核壳的ω-模式对应的共振峰峰位随核壳比的增加逐渐红移,而Nb-Sn/Au纳米核壳对应的共振峰峰位随核壳比的增加逐渐蓝移;ω+模式对应的四极共振峰峰位随核壳比的增大缓慢蓝移;集中在金壳两极点的振荡电荷对核壳球模式和腔模式的耦合作用以及电场分布有显著影响;相同尺寸纳米核壳的消光能力由强到弱依次是ITO/Au、Nb-Sn/Au、CdS/Au。     

消光式核壳二聚体传感器的设计与光谱特性分析

根据ITO/Au纳米核壳二聚体粒子在生物医学领域的应用合理性,设计了一种实时检测生物液体的核壳二聚体探针消光式传感器;由偶极子理论推导出输出波长与外界环境折射率关系;利用MATLAB设计ITO/Au纳米核壳二聚体粒子结构;采用软件DDSCAT7.3结合离散偶极近似法,利用二聚体有效半径模拟计算了300~950nm可见光到红外光波段不同核壳比、二聚体间距、以及不同介质折射率的消光光谱;根据传感芯片折射率与偶极共振、耦合八级共振的响应关系得出ITO/Au二聚体的折射率灵敏特性。与传统Ag/Au核壳纳米粒子相比,ITO/Au纳米核壳二聚体结构引入了可作为传感芯片灵敏性自参考参数的耦合八级共振峰,同时ITO/Au二聚体结构的折射率灵敏度可达到419nm/RIU。这些工作及其结果对制作消光式传感器具有重要的意义。     

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Mie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和对应的优化尺寸。同时,本文研究了Au摩尔分数对最佳品质因子和优化尺寸的影响。结果发现,当Au摩尔分数x为0.5时,Au-Ag@SiO_2(Au-Ag@Vacuum)合金纳米球壳的最大品质因子为2.09(2.20),对应的内核半径和外壳厚度分别为22.3 nm(23.6 nm)和8.7 nm(6.9 nm)。当Au摩尔分数小于0.25时,Au-Ag合金纳米球壳的品质因子优于Au纳米球壳。随着Au摩尔分数的减小,品质因子增大,甚至是Au纳米球壳的2～3倍。此研究为Au-Ag合金纳米球壳在生物传感领域中的有效应用提供了理论指导。     

多层纳米Au/DPO薄膜的荧光特性

在低压直流溅射沉积的纳米Au薄膜表面喷涂有机固体晶体2,5-二苯基恶唑（DPO）,制成具有（Au+DPO）单元结构的多层纳米薄膜。利用XRD表征多层纳米薄膜的晶体结构,通过SEM表征各层薄膜的表面形貌,并测试了多层纳米薄膜的紫外荧光特性。与纯DPO薄膜相比,多层纳米薄膜的紫外荧光峰出现了5 nm的蓝移,而且DPO荧光峰形貌发生改变。在多层膜中,DPO薄膜的荧光强度与薄膜层数成反比关系,而纳米Au膜的荧光强度与薄膜层数成正比关系。SEM与XRD测试结果表明,多层薄膜中的DPO薄膜随着薄膜层数的增加逐渐成为无定型结构。DPO薄膜与纳米Au膜相互作用,导致其晶体结构异于单层薄膜,进而改变了其荧光特性。     

Ag核Au壳复合纳米粒子为标记溶胶免疫检测的SERS研究

以种子生长法合成Ag核Au壳复合纳米粒子,苯硫酚分子(TP)在其表面的SERS增强随Au摩尔比例的增加呈现先增强后减弱的趋势,其最大增强为相应Ag纳米粒子的10倍。将标记分子TP,羊抗小鼠抗体固定在Ag核Au壳复合纳米粒子表面形成标记免疫溶胶,其与被基底捕获抗原分子发生免疫识别,通过TP分子的SERS信号进行免疫检测。     

(Au)_核(Ag)_壳纳米微粒-火焰原子吸收光谱法测定过氧化氢

在90 ℃水浴条件下,以粒径为10 nm的纳米金做晶种,用柠檬酸三钠还原硝酸银,制备了平均粒径为30 nm的（Au）核（Ag）壳纳米微粒,用高速离心纯化除去过量的柠檬酸三钠获得了较纯的（Au）核（Ag）壳纳米微粒。在pH 3.8的HAc-NaAc缓冲溶液中,Fe2＋催化H2O2反应产生的羟基自由基可氧化（Au）核（Ag）壳纳米微粒生成银离子。离心后,离心液中的银离子可用火焰原子吸收光谱法在328.1 nm波长处测量。随着H2O2浓度增大,离心液中银离子浓度增加,其吸光度值增加。H2O2浓度在2.64～42.24 μmol·L-1范围内与上清液中银离子的原子吸收值ΔA呈良好的线性关系,回归方程为ΔA=0.014c-0.013 1, 相关系数为0.998 4,检出限为0.81 μmol·L-1 H2O2。当用于水样中H2O2的测定,获得了满意的结果。     

金属包裹纳米微粒的光学特性研究(英文)

金属包裹纳米粒子是一种纳米量级的介质球核外包裹薄金属层的纳米粒子.在本文中,Au包裹Au₂S纳米粒子被抽象成微型电磁谐振腔,其谐振波长决定于Au₂S介质球核的半径.运用经典电磁理论可以得到谐振波长和谐振能量.由于Au包层很薄(2nm),这种微型谐振腔的耦合方式是有别于传统方式的透射耦合,因此Au包层的厚度决定了谐振的能量以及谐振腔品质因子Q.此外,本文还讨论了吸收峰的线宽.     

Au/Cu2O core/shell nanostructures with efficient photoresponses

Metal/semiconductor nanoscale heterojunctions are of pronounced attention because of their specific structures and properties that vary in their individual counterparts and anticipated applications in photo-driven fields. A modified facile method is reported in this connection for the formation of cuprous-oxide coated gold (Au/Cu₂O) nanostructures including octahedral, cuboctahedral and flower-like structures using cubic and multi-faceted gold nanostructures as the core material. The well-organized shape growth of the Cu₂O-shell is accomplished via an adequate adjustment of the ratio H₂O:NH₂OH^·HCl in the solution. The effect of nanoparticle's shape and thickness of the shell on the optical properties of truncated-octahedra, cuboctahedra and flower-like Au/Cu₂O nanostructures (having sizes within 90–230 nm) shows a bathochromatic shift in the surface plasmon resonance (SPR) band of the Au-core with the increase of shell thickness. A comparative study to correlate the photoluminescence analyses of core/shell nanostructures with their photocatalytic activities shows that truncated-octahedra and nanoflowers, bounded by {111} facets, are photocatalytically more active. On the other hand, cuboctahedra with more {100} catalytically inactive sites reveal a comparatively sharp emission peak. These photoresposes are also appeared to be affected by SPR coupling between plasmonic metal-core and semiconducting-shell.     

Light scattering calculations from Au and Au/SiO2 core/shell nanoparticles

Given the importance of the optical properties of Au and Au/SiO₂ core/shell nanoparticles, in this article we focus our attention on the light scattering properties of such systems and on a relative comparison. In particular, we report theoretical results of angle-dependent light scattering intensity and scattering efficiency for Au and Au/SiO₂ core/shell nanoparticles increasing the Au particle radius from 30 to 130 nm, and for Au/SiO₂ core/shell particles changing the core-to-shell sizes ratio. Finally, a comparison between the scattering efficiency of the Au and Au/SiO₂ core/shell nanoparticles is drawn. The results of this work can be used in the design of tunable efficiency light scattering devices (biological and molecular sensors, solar cells).     

Plasmonic effect of nanoshelled nanocavity on encapsulated emitter's spontaneous emission

The plasmonic enhancement of nanoshelled nanocavity (a silica core coated by Ag or Au shell) on the spontaneous emission of an encapsulated emitter (a molecule or quantum dot) is studied systematically by analyzing the excitation rate and the apparent quantum yield together. By averaging all possible locations and orientations of the emitter, the average enhancement factor (AEF) of the emitter randomly located in the core is calculated. Our results show that the AEF is weaker than that of the emitter located at the core center. In addition, Ag nanoshell (NS) is a narrowband enhancer. As the thickness of the shell becomes thinner, the surface plasmon resonance of NS is red-shifted and the peak of AEF increases. The specificity of Ag NS for enhancing a specific spontaneous emission is higher than Au NS. In addition, Ag NS with a smaller core has a larger AEF, while Au NS has an optimal radius of core (30 nm) to obtain the maximum AEF. Moreover, the AEF is reduced, as the Stokes shift increases.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

A novel method to prepare Au nanocage@SiO_2 nanoparticle

Gold （Au） nanocage@SiO2 nanoparticles are prepared by a novel approach. The silver （Ag） nanocube@SiO2 structure is synthetized firstly. Next, the method of etching a SiO2 shell by boiling water is adopted to change the penetration rate of AuCl4- through the SiO2 shell. AuCl4- can penetrate through silica shells of different thickness values to react with the Ag nanocube core by changing the incubation time. The surface plasma resonance （SPR） peak of synthetic Au nanocage@SiO2 can be easily tuned into the near-infrared region. Besides, CdTeS quantum dots （QDs） are successfully connected to the surface of Au nanocage@SiO2, which testifies that the incubation process does not change the property of silica.     

Optimization of ultrathin carbon film coated silver nanoshell for biomedical applications in vivo

The extinction spectroscopy and near-field enhancement of dielectric-silver nanoshell coated by tetrahedral amorphous carbon [ta-C] layer (DSC) have been calculated by using Mie theory. With decreasing the Ag layer thickness, the localized surface plasmon resonance (LSPR) of DSC nanoshell moves from the visible region into the near-infrared region and the corresponding local field factor (LFF) increases first and then decreases. In addition, the increase of ta-C shell thickness leads to red-shift of LSPR and the decrease of LFF in DSC nanoshell. We further find that the increase of the dielectric constant for the outer shell can induce a significant enhancement of near-field. Based on the simulation analysis, we show that the DSC nanoshell can provide strong near-field in near-infrared region and may be suitable for the biomedical applications in vivo.     

Fabrication of NIR‐Excitable SERS‐Active Composite Particles Composed of Densely Packed Au Nanoparticles on Polymer Microparticles

A simple fabrication method is demonstrated for surface‐enhanced Raman scattering (SERS)‐active plasmonic nanoballs, which consisted of Au nanoparticles (NPs) and core–shell polystyrene and amino‐terminated poly(butadiene) particles, by heterocoagulation and Au NP diffusion. The amount of Au NPs introduced into the core–shell particles increases with the concentration of Au NPs added to the aqueous dispersion of the core–shell particles. When the amount of Au NPs increases, closely packed, three‐dimensionally arranged and close‐packed Au NPs arrays are formed in the shells. Strong SERS signals from para‐mercaptophenol adsorbed onto composite particles with multilayered Au NPs arrays are obtained by near‐infrared (NIR) light illumination.     

Optical resonance of metal-coated nanoshell

Metal-coated nanoshell,the nanoparticle consisting of a nanometre-scale dielectric core coated with a thin metallic shell,exhibits three distinct optical resonant forms,the sphere cavity resonance(SCR),plasmon resonance(PR),and concentric dielectric sphere resonance(CDSR),The SCR,PR and CDSR of the metal-coated nanoshell reveal a geometric tunability controlled by the core radius and by the ratio of the core radius to the total radius,Classical electrodynamics and Mie scattering theory are used to treat the resonant forms and the transition state between the resonant forms.Based on previous experimental research,we present a group of resonant equations for all the resonant forms.which depend on the geometric structure of the metal-coated nanoshell.