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1.
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 相似文献
2.
M. Quinten 《Applied physics. B, Lasers and optics》2001,73(3):245-255
A refined discussion of the near-field scattering of spherical nanoparticles and the electromagnetic fields close to the particle
surface is given. New results for the dependence on the distance from the surface and the angular distribution of the scattered
light in the near-field are given. It will be shown that the radial component of the electric field leads to striking differences
in the phase functions in the near-field and the far-field. Exemplary computations are presented for Ag and Au particles with
different size. In a second part the discussion is extended to assemblies of spherical Ag and Au nanoparticles. It will be
shown that large near-fields at wavelengths commonly used in SERS experiments are obtained for aggregates. In the near-field
scattering intensity “hot spots” mark regions between particles in the aggregate where the near-field is particularly high.
Received: 4 May 2001 / Revised version: 20 July 2001 / Published online: 19 September 2001 相似文献
3.
We have successfully synthesized Au/Ag colloidal nano-alloys with a wide range of compositions by laser ablation of single metal targets in water and a re-irradiation of mixed colloidal suspensions. The optical extinction spectra have been obtained in the plasmon resonance region and their analysis by using the Mie-Gans approach has lead to a quantitative estimation of a number of different structural features for the sols. Some of the obtained results are supported by X-ray photoelectron data and transmission electron microscopy, while others are used to investigate the kinetics of formation of the nano-alloys under laser irradiation. 相似文献
4.
The results of the theoretical study of optical properties of composite nanoparticles consisting of a metal core (Ag, Au,
Cu, Al, Ni, Cr) and a J-aggregate shell of organic dye are presented. Light extinction, absorption, and scattering coefficients
in colloidal solutions were calculated within the model based on the Mie theory modified taking into account dimensional phenomena
and complemented by calculations of complex dielectric functions of the metal core and J-aggregate shell. The model adequately
explains the features observed in light absorption and scattering spectra by hybrid nanoparticles, associated with the plasmon
resonance in the metal core and with electronic excitation of the J-aggregate. The strong dependence of the results on geometrical
parameters of nanoparticles and dielectric constants of core and shell materials was demonstrated. Methods for controlling
the effects of the plasmon-exciton interaction in the system and optical properties of composite materials developed based
on nanoparticles under study are discussed. 相似文献
5.
K. V. Kozadaev 《Journal of Applied Spectroscopy》2011,78(5):692-697
Two-factor dependences of the maximum and half-width of a surface plasmon resonance band on both the average diameter of nanoparticles
and the scatter in their particle-size distributions were defined for colloidal silver and gold aqueous solutions based on
modeling the extinction effectiveness factor by Mie theory. The obtained three-dimensional surfaces determined the shape of
calibration curves used to define the average particle diameters and the scatter in their particle-size distributions from
measurements of the maximum and half-width of the surface plasmon resonance band in spectra of the silver and gold colloidal
solutions. The calibration curves were correlated with experimental samples of aqueous ultradispersed media containing silver
and gold nanoparticles. 相似文献
6.
M. Merschdorf W. Pfeiffer A. Thon S. Voll G. Gerber 《Applied Physics A: Materials Science & Processing》2000,71(5):547-552
Two-photon photoemission spectroscopy using femtosecond laser pulses is used to investigate the excitation and decay mechanisms
of the surface plasmon resonance in Ag nanoparticles grown on graphite. The resonant excitation of this collective excitation
leads to a two-orders-of-magnitude-enhanced two-photon photoemission yield from a graphite surface with Ag nanoparticles compared
to the yield from pure graphite. From the shape of the photoemission spectra, the polarization dependence of the photoemission
yield and the excitation probabilities for different excitation pathways we conclude that excitation with 400-nm femtosecond
laser pulses leads to the coherent multiple excitation of the surface plasmon in the Ag nanoparticles. This multiply excited
plasmon mode can decay via the coupling to a single-particle excitation leading to the emission of an electron if its final
state is located in the continuum. The surface plasmon in metallic nanoparticles is a model system to investigate collective
excitations in multiphoton processes.
Received: 26 June 2000 / Accepted: 2 September 2000 / Published online: 12 October 2000 相似文献
7.
We present extinction measurements on rectangular two-dimensional arrays of gold nanoparticles on a dielectric waveguide.
The spectra exhibit spectrally narrow bands of suppressed extinction within the particle–plasmon resonance, resulting from
destructive interference between the incident light field and the excited waveguide modes. The dependence of the spectral
position of these high-transmission bands on different waveguide modes is investigated in detail.
Received: 3 July 2001 / Published online: 10 October 2001 相似文献
8.
For spherical Cu, Ag, and Au nanoparticles with a radius of 1–3 nm in copper phthalocyanine (CuPc), with allowance for internal
size effects, we calculate the scattering efficiency factor in the near zone, the extinction efficiency factor due to scattering
and absorption of incident radiation, and the efficiency of the increase in absorption by the matrix material. This occurs
in the CuPc absorption bands, as well as in the weak absorption region of CuPc, where, owing to surface plasmon resonance,
an additional absorption band arises for nanoparticles of all three materials. For Ag nanoparticles, the increase in absorption
is twice as high as for Cu and Au nanoparticles; for these it differs inconsiderably. 相似文献
9.
利用激光烧蚀方法在水中制备了金核银壳层纳米颗粒胶体,发现这种复合胶体的等离子体振动吸收峰频率会随着激光烧蚀时间的不同而发生改变。利用等离子杂化理论定性解释了共振吸收峰可调谐的物理机制. 相似文献
10.
R.M. Tilaki A. Iraji zad S.M. Mahdavi 《Applied Physics A: Materials Science & Processing》2007,88(2):415-419
Colloidal copper nanoparticles were prepared by pulsed Nd:YAG laser ablation in water and acetone. Size and optical properties
of the nanoparticles were characterized by transmission electron microscopy and UV–visible spectrophotometry, respectively.
The copper particles were rather spherical and their mean diameter in water was 30 nm, whereas in acetone much smaller particles
were produced with an average diameter of 3 nm. Optical extinction immediately after the ablation showed surface plasmon resonance
peaks at 626 and 575 nm for the colloidal copper in water and acetone, respectively. Time evaluation showed a blue shift of
the optical extinction maximum, which is related to the change of the particle size distribution. Copper nanoparticles in
acetone are yellowish and stable even after 10 months. In water, the color of the blue-green solution was changed to brown-black
and the nanoparticles precipitated completely after two weeks, which is assigned to oxidation of copper nanoparticles into
copper oxide (II) as was confirmed by the electron diffraction pattern and optical absorption measurements. We conclude that
the ablation of bulk copper in water and acetone is a physical and flexible method for synthesis of stable colloidal copper
and oxidized copper nanoparticles.
PACS 42.62.-b; 81.07.-b; 61.46.+w 相似文献
11.
C. Kennerknecht H. Hövel M. Merschdorf S. Voll W. Pfeiffer 《Applied physics. B, Lasers and optics》2001,73(4):425-429
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 相似文献
12.
Santanu Pyne Priyanka Sarkar Samita Basu Gobinda Prasad Sahoo Dipak Kumar Bhui Harekrishna Bar Ajay Misra 《Journal of nanoparticle research》2011,13(4):1759-1767
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. 相似文献
13.
We investigate the nanostructure, surface plasmon resonance (SPR) absorption and nonlinear enhancement of Au/Ag alloyed hollow nanoshells prepared by the replacement reaction of Ag nanoparticles in a HAuCI4 aqueous solution. As the volume of HAuCl4 increases from OmL to 0.S mL, the SPR band of the Au/Ag alloyed nanoshells is tuned from 430nm to 780nm, and the third-order nonlinear optical susceptibility is enhanced nearly by an order of magnitude, which indicates a large enhancement of local field in the Au/Ag alloyed hollow nanoshells with hole defects. 相似文献
14.
The effect of the temperature of a silver sol on its extinction spectra during formation of aggregates of plasmon resonance nanoparticles with varying degree of order and the effect exerted on these spectra by changes in the structure of a colloidal crystal during its heating, which lowers elastic properties of a polymer adsorption layer of particles are studied. 相似文献
15.
采用纳米球刻蚀技术中漂移法在玻璃基片上制备较大 面积不同直径的聚苯乙烯小球掩模板, 采用磁控溅射技术在掩模板上沉积不同厚度的金薄膜, 去除聚苯乙烯小球后, 通过扫描电子显微镜观察到周期排列的三角状金纳米颗粒点阵. 通过紫外-可见分光光度计测试所制备样品的光吸收特性, 发现表面等离子体共振峰随粒径增大发生红移, 随金纳米颗粒高度增加发生蓝移. 基于Mie理论, 利用Matlab软件编程对不同粒径的金阵列光吸收特性进行理论模拟, 并与实验结果进行对比.
关键词:
纳米球刻蚀
金纳米颗粒阵列
表面等离子体共振 相似文献
16.
The effect of the temperature of a silver sol on its extinction spectra during formation of aggregates of plasmon resonance
nanoparticles with varying degree of order and the effect exerted on these spectra by changes in the structure of a colloidal
crystal during its heating, which lowers elastic properties of a polymer adsorption layer of particles are studied. 相似文献
17.
Optical Properties of Plasmon Resonances with Ag/SiO2/Ag Multi-Layer Composite Nanoparticles 下载免费PDF全文
Optical properties of plasmon resonance with Ag/SiO2/Ag multi-layer nanoparticles are studied by numerical simulation based on Green's function theory. The results show that compared with single-layer Ag nanoparticles, the multi-layer nanoparticles exhibit several distinctive optical properties, e.g. with increasing the numbers of the multi-layer nanoparticles, the scattering efficiency red shiRs, and the intensity of scattering enhances accordingly. It is interesting to find out that slicing an Ag-layer into multi-layers leads to stronger scattering intensity and more "hot spots" or regions of stronger field enhancement. This property of plasmon resonance of surface Raman scattering has greatly broadened the application scope of Raman spectroscopy. The study of metal surface plasmon resonance characteristics is critical to the further understanding of surface enhanced Raman scattering as well as its applications. 相似文献
18.
Individual Au@PNIPAM/Ag composite has been designed and fabricated as surface‐enhanced Raman scattering (SERS) substrate in this paper. Because of the high porosity of the polymer shell and the driving force of the Au core to Ag+(H2O)n (n = 1–4) in aqueous solution, chemical reactions can be carried out while aggregation is completely avoided. Also, this makes the formation of vast and monodisperse Ag nanoparticles within PNIPAM and increases the colloidal stability. The Au cores with different sizes and the vast Ag nanoparticles then form core–satellite structures that can generate plasmon resonance. Moreover, this kind of individual Au@PNIPAM/Ag composite can be seen directly through Raman optical microscope, and uncertain effects on SERS signals resulting from variability of the configurations are minimized because these individual composite particles are relatively uniform. Importantly, the gaps between the Au and Ag nanoparticles can decrease because the PNIPAM shrinks from swollen to collapse state, so the substrate can also be used for inspecting pesticide residues accurately and rapidly. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
Large area fabrication of metal alloy nanoparticles with tunable surface plasmon resonances on low-cost substrates is reported. A UV excimer laser was used to anneal 5 nm thick Ag Au bilayer films deposited with different composition ratios to create alloy nanoparticles. These engineered surfaces are used to investigate how the wavelength of the surface plasmon resonance affects the optical detection capability of chemical species by surface-enhanced Raman spectroscopy. 相似文献
20.
Ana Menéndez-Manjón Andreas Schwenke Timo Steinke Matthias Meyer Ulrich Giese Philipp Wagener Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2013,110(2):343-350
Polymer matrix nanocomposites filled with metallic and alloy nanoparticles add functionality in various applications such as optical devices and in the energy sector. However, matrix coupling agents or nanoparticle ligands may be unwanted additives, potentially inhibiting the resulting nanocomposite to be processed by injection molding. The generation of stabilizer-free Au, Ag, and AuAg alloy nanoparticle acrylate composites is achieved by picosecond-pulsed laser ablation of the respective metal target in the liquid monomer. Complementary to laser ablation of the solid alloy, we have alloyed nanoparticles by post-irradiation of Au and Ag colloids in the liquid monomer. The optical properties of the colloidal nanoparticles are successfully transferred to the solid poly(methyl methacrylate) matrix and characterized by their plasmon resonance that can be easily tuned between 400 and 600 nm by laser alloying in the liquid monomer. 相似文献