共查询到20条相似文献,搜索用时 62 毫秒
1.
Sönnichsen C Franzl T Wilk T von Plessen G Feldmann J Wilson O Mulvaney P 《Physical review letters》2002,88(7):077402
The dephasing of particle plasmons is investigated using light-scattering spectroscopy on individual gold nanoparticles. We find a drastic reduction of the plasmon dephasing rate in nanorods as compared to small nanospheres due to a suppression of interband damping. The rods studied here also show very little radiation damping, due to their small volumes. These findings imply large local-field enhancement factors and relatively high light-scattering efficiencies, making metal nanorods extremely interesting for optical applications. Comparison with theory shows that pure dephasing and interface damping give negligible contributions to the total plasmon dephasing rate. 相似文献
2.
As demonstrated recently, persistent spectral hole burning in the optical spectra of metal nanoparticles makes possible the determination of the ultrafast dephasing time T2 of surface plasmon excitation. Here, the influence of the chemical environment on the dephasing process is investigated under ultrahigh vacuum conditions by depositing an adsorbate on the nanoparticles. By comparing the optical spectra and the widths of the generated holes of the nanoparticles with and without adsorbate coverage, the influence of chemical interface damping on the dephasing process is examined. The potential of the novel procedure is demonstrated for silver nanoparticles on sapphire and quartz substrates using SO2 as the adsorbate. A drastic decrease of T2 for the adsorbate-covered nanoparticles is observed and explained by dynamic charge transfer of electrons from the particles into and out of adsorbate states of the SO2 molecules. PACS 78.67.Bf; 61.46.+w; 71.45.Gm; 73.22.Lp; 68.43.-h 相似文献
3.
We report on a strong damping of the localized surface plasmon polariton resonance of gold nanoparticles. The ultra-fast dephasing
time of localized surface plasmon polariton resonances in gold nanoparticles was systematically studied as a function of the
particle size at a fixed photon energy of h
ν=1.85 eV. Dephasing times ranging from T2expT_{2}^{\mathrm{exp}} = 5.5 fs to 15.0 fs were extracted and an influence of the reduced dimensions was detected. We have identified two dominant
damping mechanisms: the well-known surface scattering and, for the first time, band structure changes. We have quantified
the influence of these band structure changes on the optical properties by determining the essential damping parameter A to be A
exp=0.32 nm/fs. 相似文献
4.
K. Kolwas A. Derkachova M. Shopa 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(14-16):1490-1501
The change of the scattering properties of sodium, gold and silver spherical particles with size is discussed in the context of surface multipolar plasmon resonances. The presented surface plasmon size characteristics are abstracted from the quantity which is observed and deliver multipolar plasmon resonance frequencies and plasmon damping rates in the form of a continuous function of particle radius. The performed analysis of the plasmon dispersion relation is analogous to the problem of surface plasmon localized at a semi-infinite, flat metal/dielectric interface.Correlation between the multipolar plasmon resonance parameters, and the spectroscopic optical properties of conductive nanoparticles appearing as peaks in the measurable light intensities is analyzed. We discuss the fact, that such peaks arise from interference of all the electromagnetic fields contributing to the measured intensity, and not solely to the fields due to surface plasmon multipolar modes.We describe the results of light scattering experiment in orthogonal polarization geometries with use of spontaneously growing sodium droplets. The polarization geometry of the experiment allows for distinct separation of resonant contribution of dipole and quadrupole plasmon TM mode contributions to the measured intensities as a function of size.Predictions concerning size characteristics for dipole and quadrupole plasmons are compared with the results of light scattering experiments using spherical sodium droplets (our results) and gold and silver particles in suspension [other authors: Sönnichsen C, Franzl T, Wilk T, von Plessen G, Feldmann J. Plasmon resonances in large noble-metal clusters. New J Phys 2002; 4:93.1–8; Haiss W, Thanh NTK, Aveyard J, Fernig DG. Determination of size and concentration of gold nanoparticles from UV–vis spectra. Anal Chem 2007; 79:4215–21; Njoki PN, Lim I-IS, Mott D, Park H-Y, Khan B, Mishra S, et al. Size correlation of optical and spectroscopic properties for gold nanoparticles. J Phys Chem C 2007; 111:14664–9; Mock JJ, Barbic M, Smith DR, Schultz DA, Schultz S. Shape effects in plasmon resonance of individual colloidal silver nanoparticles. J Chem Phys 2002; 116:6755–9]. 相似文献
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6.
E. Almeida A. C. L. Moreira A. M. Brito-Silva A. Galembeck C. P. de Melo L. de S.?Menezes C. B. de Araújo 《Applied physics. B, Lasers and optics》2012,108(1):9-16
Localized surface plasmon dephasing times for aqueous colloidal silver nanoparticles (NPs) stabilized with three different capping agents (trisodium citrate??TSC, poly(vinylpyrrolidone)??PVP, and poly(vinylalcohol)?? PVA) were measured using the persistent spectral hole burning technique. The results obtained by fitting a theoretical curve to the experimental data show that the dephasing times are dependent on the chosen stabilizer (3.0, 2.3, and 1.8?fs for TSC, PVP, and PVA, respectively), and the differences are attributed to changes in the electronic density of states due to the interaction between the NPs and the capping agents. The results are supported by ab initio calculations for the chemisorbate and metallic cluster interaction. 相似文献
7.
Sarita Roy Soumen Basak Pulak Ray Anjan Kr. Dasgupta 《Photonics and Nanostructures》2012,10(4):506-515
Surface plasmon resonance (SPR) for spherical shaped silver nanoparticles showing double maxima at ~390 nm and ~520 nm respectively is reported. Self assembly of silver nanoparticles grown on tryptophan template leads to emergence of equal intensity double plasmon resonance (EIDPR). While for rod shaped nano-forms such double plasmon is explainable but for spherical shaped forms, such double plasmon can be explained on the basis of bidirectional formation of silver cluster in which attachment of silver at two nitrogen atom locations of tryptophan molecule seems to be obligatory. The absence of double resonance in case of silver nanoclusters formed with other amino acids or N-acetyl l-tryptophanamide (NATA), where bidirectional NH2 attachment is not possible, validates the proposed EIDPR mechanism. Electron micrograph of EIDPR particle indicates a bi-periodic fringe pattern indicating unusual crystalline property. Apart from sensing tryptophan, the double plasmon peaks are sensitive to temperature. Furthermore, the particle can be used as a smart killing agent showing bactericidal activity only upon exposure to low power laser. 相似文献
8.
Weiping Cai H. Hofmeister T. Rainer 《Physica E: Low-dimensional Systems and Nanostructures》2001,11(4)
The optical absorption has been investigated for silver and gold nanoparticles dispersed within the pores of monolithic mesoporous silica after annealing at different temperatures. It has been shown that with reduction of the particle size, the surface plasmon resonance position blue-shifts first and then red-shifts for silver/silica samples, but only red-shifts for gold/silica samples. This size evolution of the resonance is completely different from that previously reported for fully embedded particles. Based on the interaction of the particle surface with ambient air and the porosity at the particle/matrix interface, we present a multi-layer core/shell model and assume that the chemical adsorption of gas molecules from the air on the free surface of nanoparticles within the pores is mainly responsible for the observed size evolution of the resonance. 相似文献
9.
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
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12.
Absorbing and emitting optical properties of a spherical plasmonic nanoantenna are described in terms of the size dependent
resonance frequencies and damping rates of the multipolar surface plasmons (SP). We provide the plasmon size characteristics
for gold and silver spherical particles up to the large size retardation regime where the plasmon radiative damping is significant.
We underline the role of the radiation damping in comparison with the energy dissipation damping in formation of receiving
and transmitting properties of a plasmonic particle. The size dependence of both: the multipolar SP resonance frequencies
and corresponding damping rates can be a convenient tool in tailoring the characteristics of plasmonic nanoantennas for given
application. Such characteristics enable to control an operation frequency of a plasmonic nanoantenna and to change the operation
range from the spectrally broad to spectrally narrow and vice versa. It is also possible to switch between particle receiving
(enhanced absorption) and emitting (enhanced scattering) abilities. Changing the polarization geometry of observation it is
possible to effectively separate the dipole and the quadrupole plasmon radiation from all the non-plasmonic contributions
to the scattered light. 相似文献
13.
采用微乳液法合成了不同粒径的纳米银粒子,考察了环己烷和甲苯作为油相对制备纳米银的影响.对纳米银粒子的尺寸与结构进行了表征,观察到近球形多晶粒子,并有孪晶结构存在,对晶体结构的分析表明银粒子存在不同程度的点阵畸变,晶面间距增大.不同粒径的纳米银粒子氯仿体系可呈现荧光光谱,而纳米银甲苯体系则无荧光发射.结合紫外—可见吸收光谱和电子自旋共振谱对该体系的荧光发射机理进行了分析
关键词:
微乳液
纳米银粒子
纳米晶结构
荧光 相似文献
14.
Andreas Schwenke Philipp Wagener Stefan Nolte Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2011,104(1):77-82
The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied
during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary
liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed
nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser
wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease
of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental
wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without
plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by
Mie-scattering of dispersed nanoparticle clusters. 相似文献
15.
A novel theoretical approach to the dynamics analysis of excitation and dephasing of plasmon modes in nanoparticles is presented. This approach is based on the biorthogonal plasmon mode expansion, and it leads to the predictions of time dynamics of excitation of specific plasmon modes as well as their steady state amplitude and their decay. Temporal characteristics of plasmon modes in nanoparticles are expressed in terms of their shapes, permittivity dispersion relations, and excitation conditions. In the case of the Drude model, analytical expressions for time-dynamics of plasmon modes are obtained. 相似文献
16.
Multipolar plasmon optical excitations at spherical gold nanoparticles and their manifestations in the particle images formatted
in the particle surface proximity are studied. The multipolar plasmon size characteristic: plasmon resonance frequencies and
plasmon damping rates were obtained within rigorous size dependent modelling. The realistic, frequency dependent dielectric
function of a metal was used. The distribution of light intensity and of electric field radial component at the flat square
scanning plane scattered by a gold sphere of radius 95 nm was acquired. The images resulted from the spatial distribution
of the full mean Poynting vector including near-field radial components of the scattered electromagnetic field. Monochromatic
images at frequencies close to and equal to the plasmon dipole and quadrupole resonance frequencies are discussed. The changes
in images and radial components of the scattered electromagnetic field distribution at the scanning plane moved away from
the particle surface from near-field to far-field region are discussed. 相似文献
17.
J Harra J M?kitalo R Siikanen M Virkki G Genty T Kobayashi M Kauranen JM M?kel? 《Journal of nanoparticle research》2012,14(6):870
Aerosol techniques were used to synthesize spherical and monodisperse silver nanoparticles for plasmonic materials. The particles were generated with an evaporation-condensation technique followed by size selection and sintering with a differential mobility analyzer and a tube furnace, respectively. Finally, the nanoparticles were collected on a glass substrate with an electrostatic precipitator. The particle size distributions were measured with a scanning mobility particle sizer and verified with a transmission electron microscope. A spectrophotometer was used to measure the optical extinction spectra of the prepared samples, which contained particles with diameters of approximately 50, 90 and 130?nm. By controlling the particle size, the dipolar peak of the localized surface plasmon resonance was tuned between wavelengths of 398 and 448?nm. In addition, quadrupolar resonances were observed at shorter wavelengths as predicted by the simplified theoretical model used to characterize the measured spectra. 相似文献
18.
E. Jimnez Kamal Abderrafi Juan Martínez-Pastor Rafael Abargues Jos Luís Valds Rafael Ibez 《Superlattices and Microstructures》2008,43(5-6):487
Metal nanoparticles can be prepared by a novel technique that consists of the laser ablation of a solid target immersed in a water solution of a metal salt. Silicon was chosen as the most adequate target to synthesize silver and gold nanoparticles from a water solution of either AgNO3 or HAuCl4. The influence of both the silver nitrate concentrations and the irradiation time of the Si target on the optical properties of the Au and Ag nanoparticles have been investigated. The crystalline nature of the metal nanoparticles has been determined by X-ray diffraction (XRD). Average size and particle size distribution have been measured by means of TEM. The absorbance spectra show the characteristic band of the surface resonant plasmon of silver and gold nanoparticles. 相似文献
19.
Fluorescent silver nanoparticles via exploding wire technique 总被引:2,自引:0,他引:2
Aqueous solution containing spherical silver nanoparticles of 20–80 nm size have been generated using a newly developed novel
electro-exploding wire (EEW) technique where thin silver wires have been exploded in double distilled water. Structural properties
of the resulted nanoparticles have been studied by means of X-ray diffractometer (XRD) and transmission electron microscopy
(TEM). The absorption spectrum of the aqueous solution of silver nanoparticles showed the appearance of a broad surface plasmon
resonance (SPR) peak centered at a wavelength of 390 nm. The theoretically generated SPR peak seems to be in good agreement
with the experimental one. Strong green fluorescence emission was observed from the water-suspended silver nanoparticles excited
with light of wavelengths 340, 360 and 390 nm. The fluorescence of silver nanoparticles could be due to the excitation of
the surface plasmon coherent electronic motion with the small size effect and the surface effect considerations 相似文献