Fluorescence enhancement of acridine orange in a water solution by Au nanoparticles

The surface enhanced fluorescence effect of acridine orange fluorophore in the proximity of Au nanoparticles has been investigated experimentally in the system of aqueous solution.Significant enhancement of the fluorescence intensity was observed when the system was excited with 532 nm or 442 nm CW lasers.The influence of the distances between neighboring Au particles as well as that between the fluorophore molecules and the Au surface were explored experimentally.The results demonstrated that a compact distribution of metallic particles was able to produce stronger fluorescence enhancement.Proper separation between the fluorophore molecules and the metal surface was favorable for a better enhancement.     

Enhanced Fluorescence from Periodic Arrays of Silver Nanoparticles

Electron beam lithography was used to fabricate silver nanoparticle arrays and study the effects of geometrical properties of particles on metal-enhanced fluorescence. Nanoparticle size, shape, interparticle spacing, and nominal thickness were varied in a combinatorial pattern for investigation of the particle plasmon resonance effect on enhancement of fluorescence from three different fluorophores; Fluorescein, Cy3, and Cy5. A specific geometric property for optimal enhancement from each fluorophore was determined. For interparticle spacings greater or equal to 270 nm, the enhancement matched what is expected for a single-particle model. For those particles smaller than 210 nm, the enhancement was lower than for the larger spacing in the range studied. Triangular-shaped particles gave similar enhancement to those of square-shaped particles. This combinatorial pattern by e-beam lithography was found to be useful for studying how individual parameters enhance the fluorescence that are important for rational design of enhanced fluorescence sensors.     

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。     

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。     

银纳米颗粒对胆固醇荧光的增强效用研究

在传统荧光光谱技术的基础上,结合金属纳米颗粒的增强荧光技术,探索提高荧光光谱技术检测人全血溶液中胆固醇含量的精度和分辨率的方法。实验研究方面,采用波长为407 nm的激光作为激发光,照射加入一定量银纳米颗粒作为荧光增强剂的人全血溶液,研究了银纳米颗粒对人全血溶液在可见光波段的荧光增强作用。结果表明,胶体状态的银纳米颗粒可以显著增强低浓度的人全血溶液荧光光谱的强度,且不同位置荧光发射峰的荧光增强效率随银胶加入量的增加均呈现先增后减的趋势,但不同峰位置的最强增强效率对应的银胶加入量不同。理论分析方面,根据实验结果及胆固醇分子和银纳米颗粒在溶液中的分布情况,建立了分子间距模型,并根据模型计算得出胆固醇分子和银纳米粒子之间的最佳增强荧光效果间距在12.19～25 nm范围内,这个结果和其他文献中的理论值吻合较好。综上所述,使用银纳米颗粒可实现全血溶液荧光的增强,研究结果为提高检测血液中多种物质的灵敏度和精度提供了有价值的参考作用。     

Plasmonic Enhancement of Single-Molecule Fluorescence Near a Silver Nanoparticle

In this short paper, we reported the enhanced fluorescence from a single fluorophore bound to a 50nm silver nanoparticle. We found that on average the Cy5 molecules bound to metal nanoparticles are approximately 15-fold brighter than that of free dyes, and that single molecule lifetimes are shorter as compared to free fluorophores. The increased emission rate is primarily the result of local plasmon enhancement. These results demonstrate that the use of fluorophore-metal interactions can increase the brightness and photostability of fluorophores for single molecule detection.     

纳米银组装结构的表面增强荧光效应

采用表面自组装技术,在玻片表面构筑银纳米粒子二维组装结构.银纳米粒子组装结构的吸收光谱表明银粒子表面等离子体共振与粒子间电磁偶合密切相关,偶极子表面等离子体共振更为敏感而发生较大位移.在银纳米粒子组装结构上,荧光素分子的荧光得到极大增强,其表面增强效应强烈依赖于组装金属粒子的表面等离子体共振.     

Surface plasmon assisted photoemission from Au nanoparticles on graphite

The resonant multiple excitation of collective modes in metallic nanoparticles using ultrashort laser pulses leads to an enhanced multiphoton photoemission from the particles. This effect is here demonstrated for the surface-plasmon resonance of Au nanoparticles on graphite. The shape of the photoemission spectra is explained by multiphoton photo-assisted thermionic emission from the nanoparticles and resonant emission via the image-potential state on graphite. Tuning the photon energy between 1.7 eV and 3.2 eV allows the identification of an enhancement of the photoemission yield at 2.1±0.1-eV photon energy that is attributed to the resonant excitation of the surface plasmon in the Au nanoparticles. This identification of the surface-plasmon excitation in this energy range is also supported by electron energy loss spectroscopy. Received: 8 August 2001 / Revised version: 13 September 2001 / Published online: 10 October 2001     

Surface plasmons for fluorescence enhancement in Sm-doped borate glasses

Heat treatment of Sm-activated lithium and sodium borate glasses which are additionally doped with silver oxide leads to a reduction of the doped silver ions and to the formation of metallic silver nanoparticles indicated by a broad plasmon-related absorption band in the visible spectral range. The influence of the plasmon resonance field enhancement on the Sm³⁺ fluorescence excitation bands is too small to lead to enhanced fluorescence emission intensities.     

Surface-enhanced optical third-harmonic generation in Ag island films

Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than 2 orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to a local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a two-dimensional random array of silver nanoparticles.     

金/银纳米颗粒对Eu掺杂薄膜发光特性影响的研究

本文将三种金属纳米颗粒(球形银纳米颗粒、三角形银纳米薄片和三角形金纳米薄片)分别置于Eu(TTFA)3掺杂的Su8薄膜上研究了它们对铕配合物薄膜发光的影响.结果显示,金属纳米颗粒的局域等离子体共振(LSPR)谱对薄膜发光有很好的调控作用.对于LSPR谱分别与铕配合物激发谱和辐射谱重叠较好的球形和三角形两种银颗粒,相比于未放置颗粒时薄膜的发光,放置有颗粒的发光有明显的增强,其中球形银颗粒的样品的发光增强效果更为明显.而对于LSPR谱与铕配合物激发谱和辐射谱都不重叠的三角形片状金颗粒,该颗粒对样品的发光则起到了猝灭作用.     

Broadening of resonances in yttrium nanoparticle optical spectra

The dielectric function of yttrium in the range between 0.2 μm and 2 μm is composed of a harmonic oscillator contribution due to a discrete interband transition and the contribution of free electrons. Hence, it is possible to discuss surface plasmon polaritons as well as other electronic resonances in the optical extinction spectra of yttrium nanoparticles. For the latter, we discuss the broadening of the resonance caused by the aggregation of particles. When particles are lumped into aggregates, the color of the particle system also changes. Aggregation also affects the surface plasmon resonance in yttrium nanoparticles in a way comparable to silver or gold nanoparticle aggregates. Comparison is made with the first experimental results on yttriumnanoparticles, showing that aggregation is the dominant effect for the broad resonance in the measured extinction spectra. Received: 2 July 2001 / Revised version: 10 September 2001 / Published online: 15 October 2001     

Advances in Surface-Enhanced Fluorescence

We report recent achievements in metal-enhanced fluorescence from our laboratory. Several fluorophore systems have been studied on metal particle-coated surfaces and in colloid suspensions. In particular, we describe a distance dependent enhancement on silver island films (SIFs), release of self-quenching of fluorescence near silver particles, and the applications of fluorescence enhancement near metalized surfaces to bioassays. We discuss a number of methods for various shaped silver particle deposition on surfaces.     

Using gold colloid nanoparticles to modulate the surface enhanced fluorescence of Rhodamine B

Enhanced fluorescence from Rhodamine B (RB) mixed with gold colloids has been observed under ultraviolet irradiation. Spectroscopic studies show that with the increasing gold colloids content, the fluorescence of RB at about 590 nm increases firstly and then decreases with slight red shift. These features observed in the experiment can be explained by the local electric field enhancement via surface plasmon resonance (SPR) of gold nanoparticles. Fluorescence enhancement is obtained when the emission frequency of RB lies within the bandwidth of local field enhancement from gold nanoparticles. Theoretical calculation results show that the local field band red shifts obviously with increase the thickness of dye shell which capped on gold particle, whereas the fluorescence band of RB is fixed around 590 nm. Therefore, the red shift and non-monotonic change of fluorescence intensity from RB is attributed to the dye shell dependent red shift of local field band of gold particles.     

银纳米粒子的SERS效应和SEF效应在微流控芯片光学检测中的应用

银纳米离子的SERS技术和SEF技术的信号检测灵敏度非常高,可以用在微流控芯片的定量分析中。为了提高微流控芯片光学检测技术的检测精度,提出一种在微通道中添加银纳米粒子来增强SYBR GreenⅠ拉曼和荧光信号的方法,并对该方法的原理和增强效果进行了研究。首先,利用准分子激光器在PMMA基板上直写刻蚀出宽200 μm、深68 μm的微通道,接着将制备的银前体溶液加入微通道,通过加热制备出表面增强拉曼（SERS）和表面增强荧光（SEF）基板,接下来对添加银纳米粒子前后的拉曼和荧光信号分别进行对比,进一步研究了微通道中不同浓度银纳米粒子对SYBR GREEN I的拉曼和荧光信号增强效果。添加银纳米粒子后,表面增强拉曼（SERS）实验的增强因子为3.5×10³,添加银纳米粒子的样品的荧光信号强度与不含银纳米粒子样品的荧光信号强度相比,约增加了1倍。结果表明,在微通道中检测SYBR Green I时通过增加银纳米粒子显著地增强了拉曼和荧光信号,这种方法可以用在以SYBR GreenⅠ做染料的微流控芯片检测技术中。     

Integral fluorescence enhancement by silver nanoparticles controlled via PMMA matrix

The metal-enhanced fluorescence is measured with different thickness of emission film. Silver nanoparticles are immobilized on glass slide by chemical self-assembly method. Rhodamine B molecules are dispersed in the polymer matrix of Poly(methyl methacrylate) (PMMA), then spin coated on prepared silver particles substrate with different thickness from 15 nm to 70 nm. The enhanced fluorescence is observed depending on the thickness of emission film since the average distance between rhodamine B molecules and silver nanoparticles is altered by the PMMA matrix. The 5-fold enhancement is attained. The experiment was explained qualitatively by an integral fluorescence enhancement.     

Nanosphere Templated Metallic Grating Assisted Enhanced Fluorescence

In this paper, enhanced fluorescence from a silver film coated nanosphere templated grating is presented. Initially, numerical simulation was performed to determine the plasmon resonance wavelength by varying the thickness of the silver film on top of a monolayer of 400 nm nanospheres. The simulation results are verified experimentally and tested for enhancing fluorescence from fluorescein isothiocyanate whose excitation wavelength closely matches with the plasmon resonance wavelength of the substrate with 100 nm silver film over nanosphere. The 12 times enhancement in the intensity is attributed to the local field enhancement in addition to the excitation of surface plasmon polaritons along the surface.     

Characterization of the Plasmonic Fluorescence Enhancement of Poly (3-hexylthiophene) for Organic Solar Cell Applications

The dependence of surface-enhanced fluorescence of the semiconducting polymer poly (3-hexylthiophene) on the diameter of silver nanoparticles was studied. Particle suspensions with a high degree of monodispersity, ranging in diameter from 15 to 153 nm, were synthesized. Polymer films were spin-cast onto substrates containing immobilized silver particles. Fluorescence enhancement factors ranged from 0.9 to 4.9 and generally improved with increasing particle size. Normalization of the fluorescence enhancement to the number of interrogated particles showed an 800-fold increase in enhancement between the smallest and largest particles.     

纳米银粒子对表面吸附罗丹明B的光谱学性质的影响及电解质效应研究

基于贵金属纳米粒子的局域场增强效应,利用透射电子显微镜、紫外-可见分光光度计和荧光分光光度计等分析手段研究了纳米银粒子对表面吸附罗丹明B的光谱学性质的影响以及罗丹明B-纳米银体系中加入电解质离子后,电解质离子与纳米银、染料分子间的相互关系和作用.研究结果表明,当罗丹明B溶液的浓度小于0.6 μmol·L－1时,微量纳米银可使其荧光强度略增加,继续增加纳米银浓度则造成荧光强度下降.当罗丹明B溶液的浓度高于0.6 μmol·L－1时,纳米银总是引起溶液的荧光强度下降.KNO3、KCl、Ca(NO3)2、MgCl2和CaCl2电解质可造成纳米银粒子不同程度的聚集和生长.引起的纳米银粒子的聚集程度关系为:CaCl2>MgCl2>KCl>Ca(NO3)2>KNO3.随着电解质加入量的增加,溶液的荧光强度先下降,而后又逐渐增强,直至达到定值.各电解质对罗丹明B-Ag溶液的荧光强度影响强弱关系为Ca(NO3)2>CaCl2>MgCl2>Cl>KNO3.     

Influence of the incorporation of metals on the optical properties of MCM-41

We studied the optical properties of mesoporous aluminosilica incorporated with metal nanoparticles, which can be used to efficiently enhance catalytic activity for CO oxidation. Analysis of the PL spectra indicated that the incorporation of Al greatly enhanced the generation of oxygen related defects. When Au nanoparticles were deposited onto Al-MCM-41, both the PL and PLE spectra suggested that the metal nanoparticles were strongly attracted by the electrostatic force induced by the charged oxygen defects. Electron spin resonance measurement provided further evidence, registering a spike in the intensity following incorporation of the metal particles, as the strong interaction between the F+ center and the metal particles induced electron transfer to the trapped O₂ molecule. These discoveries shed further light on the perplexing mechanism by which the Si/Al ratio and metal particles can give rise to dramatic enhancement of the catalytic activity for CO oxidation.