共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Dubiel S. Brunsch W. Seifert H. Hofmeister G.L. Tan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):229-232
Ag particles of 3.9 and 5.1 nm mean size in silicate glasses were produced by ion exchange and subsequent annealing at 480
and 600 °C. These thermal treatments may induce stresses in matrix and particles in addition to the well known effect of surface atoms
because of the thermal expansion mismatch of both materials. Structural characterisation of the particles by high-resolution
electron microscopy revealed a size-dependent lattice dilatation quite opposite to the so far observed lattice contraction
of similar metal/glass composites. This result, confirmed by X-ray absorption spectroscopy at the Ag K-edge, is discussed
in terms of an Ag-Ag bond length increase near the particle surface. The temperature-dependent EXAFS spectra (10-300 K) indicate
an increased thermal expansion coefficient of the particles with an increased mean particle size calculated on the basis of
an anharmonic Einstein model. With that the bond length increase can be explained. The results can be interpreted by a combination
of both the particle size effects and the influence of the surrounding matrix.
Received 30 November 2000 相似文献
2.
M. Gaudry J. Lermé E. Cottancin M. Pellarin B. Prével M. Treilleux P. Mélinon J.-L. Rousset M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):201-204
Optical properties of mixed clusters (AuxAg
1 - x
)
n
and (NixAg
1 - x
)
n
, produced by laser vaporization and embedded in an alumina matrix, are reported. The size effects are investigated for different
concentrations (x
= 0.25, 0.5 and 0.75) in the diameter range 2-4 nm. For alloyed clusters (AuxAg
1 - x
)
n
of a given size an almost linear evolution of the surface plasmon frequency ω
s
with the concentration is observed (between those of pure gold and pure silver clusters). Moreover the blue-shift and the
damping of the resonance with decreasing size is all the more important as the gold concentration in the particles increases.
Such results are in agreement with theoretical calculations carried out in the frame of the time-dependent local-density-approximation
(TDLDA) including an inner skin of ineffective screening and the porosity of the matrix. The optical response of (NixAg
1 - x
)
n
clusters exhibits a surface plasmon resonance in the same spectral range as the one observed for pure silver clusters, but
considerably damped and broadened. For a given mean cluster size 3.0 nm, a blue-shift of the resonance is observed when increasing
the nickel concentration (between x
= 0.25 and x
= 0.75). The results are in good qualitative agreement with classical predictions in the dipolar approximation, assuming a core-shell
geometry.
Received 21 November 2000 相似文献
3.
H. Portales L. Saviot E. Duval M. Gaudry E. Cottancin J. Lermé M. Pellarin M. Broyer B. Prével M. Treilleux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):197-200
Low-frequency Raman scattering experiments have been performed on thin films consisting of pure gold or gold-silver alloy
clusters embedded in alumina matrix. It is clearly shown that the quadrupolar vibrational modes are observed by Raman scattering
because of the effect of resonance with the excitation of the electronic surface dipolar plasmon. This is due to the strong
coupling between the collective electronic dipolar excitation and the quadrupolar vibrational modes. This effect of resonance
does not exist with the core electron excitations. The mixing of the conduction electron dipolar excitation (surface plasmon)
with the core electrons leads to the quenching of the resonant Raman scattering.
Received 16 November 2000 相似文献
4.
Preparation and characterization of nano-sized Ag/PVP composites for optical applications 总被引:2,自引:0,他引:2
G. Carotenuto G.P. Pepe L. Nicolais 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):11-17
A modification of the polyol process has enabled the direct synthesis of nm-sized Ag particles with narrow size distribution
and controlled average dimension embedded in a polymeric matrix. Dispersion of colloidal silver was obtained by reduction
of silver nitrate in ethylene-glycol in the presence of a polymeric protective agent (i.e., poly(N-vinylpyrrolidone)) and ultrasounds. The final particle size was controlled by removing the colloid from the reactive
mixture by addition of acetone. The very strong plasmon resonance peak at 410 nm and a feature at 350 nm in the UV-visible
spectra are a clear consequence of the nano-size of dilute Ag particles. The proposed process offers the possibility to effectively
use these synthesised materials for the production of colour filters for advanced optical devices.
Received 10 November 1999 相似文献
5.
R.K. Roy S.K. Mandal A.K. Pal 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(1):109-114
Nanocrystalline Au and Ag in multilayer thin film form with Au/Ag/Au structure were prepared by high pressure (∼40 Pa) d.c.
sputtering techniques. The Ag concentrations in AgxAu1-x films were changed from x = 0 to 1. These multilayer films with varying Ag concentration showed significant changes in microstructures obtained from
TEM and XRD analyses. The optical absorption spectra of these multilayer films showed a single plasmon band confirming the
formation of Au-Ag alloy. We ascribe this alloying to the interfacial reactions in nanophase limited at the Au-Ag interface.
The red-shift and broadening of the plasmon bands with the increase in silver concentration could be associated to the increase
in size of the nanoparticles and its distribution. The observed red shift in the plasmon band may be associated with the change
in electronic structure at the Au-Ag interface due to configuration mixing of the atomic energy levels of Au and Ag.
Received 17 October 2002 / Received in final form 26 February 2003 Published online 23 May 2003
RID="a"
ID="a"e-mail: msakp@mahendra.iacs.res.in 相似文献
6.
The effect of oxidation on the structure of nickel nanoparticles 总被引:1,自引:0,他引:1
B. Rellinghaus S. Stappert E.F. Wassermann H. Sauer B. Spliethoff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):249-252
The structural properties of nickel nanoparticles which are prepared by means of DC sputtering in argon and subsequently oxidized
in ambient air are reported. Ex situ structural and chemical investigations utilizing (high resolution) transmission electron microscopy and electron energy loss
spectroscopy reveal that the particles consist of a metallic core surrounded by an oxide shell. The lattice constant of the
nickel core is found to increase significantly with decreasing particle size. This widening of the nickel lattice is attributed
to an interfacial stress that originates from the lattice mismatch between nickel and nickel oxide.
Received 21 December 2000 相似文献
7.
M. Kaempfe G. Seifert K.-J. Berg H. Hofmeister H. Graener 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):237-240
Glass containing spherical silver nanoparticles has been irradiated with single, intense, ultrashort laser pulses, with a
wavelength corresponding to the surface plasmon resonance of the particles. After irradiation with linear polarization, dichroism
is observed. Transmission electron microscopy studies reveal that these spectral changes are caused by deformation of the
particles to anisotropic (in the TEM projection approximately ellipsoidal) shapes with an additional halo of small silver
particles around the central one. The deformed particles are uniformly oriented with their longer axes perpendicular to the
laser polarization. Using laser pulses with circular polarization, again a halo is formed around the particles, but the central
particles remain spherical, and no dichroism was observed in the optical spectra.
Received 30 November 2000 相似文献
8.
S. Deki Hnin Yu Yu Ko T. Fujita K. Akamatsu M. Mizuhata A. Kajinami 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):325-328
Au nanoparticles dispersed SiO2-TiO2 composite films have been prepared by a novel wet process, Liquid Phase Deposition (LPD) method. The composite films were
characterized by XRD, XPS, TEM, ICP, SEM and UV-VIS absorption spectroscopy. The results showed that the SiO2-TiO2 composite films containing AuIII and AuI ionic species were co-deposited from a mixed solution of ammonium silicofluoride, ammonium hexafluorotitanate, boric acid
and tetrachloroauric acid. The heat treatment induced the reduction of Au ions and formation of Au nanoparticles in the film.
TEM observation revealed that the Au nanoparticles with 5-10 nm in diameter were found to be dispersed uniformly in the SiO2-TiO2 matrix. The optical absorption band due to the surface plasmon resonance of dispersed Au particles were observed at the wavelength
of 550 nm and shifted toward longer wavelength with increasing heat treatment temperature.
Received 28 November 2000 相似文献
9.
It has been shown over the last few years that the dynamics close to the glass transition is strongly heterogeneous, both
by measuring the diffusion coefficient of tagged particles or by NMR studies. Recent experiments have also demonstrated that
the glass transition temperature of thin polymer films can be shifted as compared to the same polymer in the bulk. We propose
here first a thermodynamical model for van der Waals liquids, which accounts for experimental results regarding the bulk modulus
of polymer melts and the evolution of the density with temperature. This model allows us to describe the density fluctuations
in such van der Waals liquids. Then, by considering the thermally induced density fluctuations in the bulk, we propose that
the 3D glass transition is controlled by the percolation of small domains of slow dynamics, which allows to explain the heterogeneous
dynamics close to T
g. We show then that these domains percolate at a lower temperature in the quasi-2D case of thin suspended polymer films and
we calculate the corresponding glass transition temperature reduction, in quantitative agreement with experimental results
of Jones and co-workers. In the case of strongly adsorbed films, we show that the strong adsorption amounts to enhance the
slow domains percolation. This effect leads to 1) a broadening of the glass transition and 2) an increase of T
g in quantitative agreement with experimental results. For both strongly and weakly adsorbed films, the shift in T
g is given by a power law, the exponent being the inverse of that of the correlation length of 3D percolation.
Received 21 March 2000 and Received in final form 4 December 2000 相似文献
10.
J. Lermé B. Palpant B. Prével E. Cottancin M. Pellarin M. Treilleux J.L. Vialle A. Perez M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):95-108
The optical response of free and matrix-embedded gold metal clusters AuN is investigated in the framework of the time-dependent local-density-approximation (TDLDA). The characteristics of the surface
plasmon resonance are carefully analyzed as a function of the model parameters and the particle radius. The strong influence
of the frequency-dependence of the 5d core-electron dielectric function in the vicinity of the interband threshold is emphasized. The size evolution of the Mie-frequency
in free gold clusters exhibits a noticeable blue-shift trend as the particle size decreases, much stronger than in silver
clusters. The width and shape of the resonance, essentially ruled by the decay via the interband transitions, are found closely correlated to the imaginary component of the core-electron dielectric function.
In presence of a surrounding matrix the blue-shift trend is largely rubbed out. Agreement with recent experimental results
on size-selected gold clusters embedded in an alumina matrix may be achieved by taking into account the porosity effects at
the metal/matrix interface. The comparison with the predictions of classical models is also provided.
Received: 9 March 1998 / Revised: 5 June 1998 / Accepted: 3 July 1998 相似文献
11.
E. Zhulina A.V. Dobrynin M. Rubinstein 《The European physical journal. E, Soft matter》2001,5(1):41-49
We develop a scaling theory for a single polyampholyte chain adsorbed on a charged spherical particle in a theta-solvent.
Adsorption of a polyampholyte molecule is due to its polarization in the electrostatic field of the particle. For large particles
with sizes exceeding the thickness of the adsorbed layer, the conformations of the chain are similar to the one found for
polyampholyte adsorption on charged planar surface. However, an adsorbed polyampholyte chain forms a self-similar flower-like
structure near the particles with sizes smaller than its Gaussian size. These self-similar structures result from the balance
of the polarization energy of loops and the excluded volume interactions between monomers. The structure of an adsorbed polyampholyte
in the flower-like conformation is similar to that of a neutral star polymer.
Received 3 March 2000 and Received in final form 5 July 2000 相似文献
12.
D. Zanghi A. Traverse J.-P. Dallas E. Snoeck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):171-179
Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combining several characterisation techniques
such as X-ray absorption spectroscopy, X-ray diffraction and high resolution transmission electron microscopy, we determined
the lattice parameter of the Ni clusters that display a fcc crystalline structure. The average size increases when the ion
fluence is increased or after a thermal treatment. Thanks to moiré fringes observed by high resolution transmission electron
microscopy and to satellite peaks seen on the diffraction patterns, we concluded that the annealed Ni clusters orientate their
(002) planes on the (101) of AlN. Moreover, the satellite positions allowed us to calculate Ni cluster average diameters,
that are in agreement with average sizes deduced by X-ray absorption spectroscopy.
Received 25 August 1999 and Received in final form 8 February 2000 相似文献
13.
N. Pinçon B. Palpant D. Prot E. Charron S. Debrus 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):395-402
We report a study on the third-order nonlinear optical properties of nanocomposite thin films composed of gold particles embedded
in a silica host matrix. Samples of various metal volume fractions, ranging from 8 to 35%, are synthesized by the sputtering
technique. Some of them are annealed. Nonlinear optical measurements, which are performed by using the z-scan technique, reveal both a very large nonlinear absorption and a weak nonlinear refraction close to the surface plasmon
resonance frequency of the particles. We especially study the effect of the metal concentration and the influence of thermal
treatment on the real and imaginary components of the third-order nonlinear susceptibility. Our results reveal that, as the
metal concentration reaches a few percent, the mutual electromagnetic interactions between particles greatly enlarge the nonlinear
optical response of the material and can not be neglected in the theoretical analysis. Moreover, the thermal treatment leads,
for a given concentration, to a significant increase of the nonlinear response, which is ascribed to a modification of the
material morphology. We finally point out that the material nonlinear properties are very sensitive to the incident wavelength
through the local field enhancement phenomenon.
Received 12 December 2001 相似文献
14.
D. Hennig 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(3):419-425
We study localization in polymer chains modeled by the nonlinear discrete Schr?dinger equation (DNLS) with next-nearest-neighbor
(n-n-n) interaction extending beyond the usual nearest-neighbor exchange approximation. Modulational instability of plane
carrier waves is discussed and it is shown that localization gets amplified under the influence of an enhanced interaction
radius. Furthermore, we construct exact localized solitonlike solutions of the n-n-n interaction DNLS. To this end the stationary
lattice system is cast into a nonlinear map. The homoclinic orbits of unstable equilibria of this map are attributed to standing
solitonlike solutions of the lattice system. We note that in comparison with the standard next-neighbor interaction DNLS which
bears only one type of static soliton-like states (either staggering or unstaggering) the one with n-n-n interaction radius
can support unstaggering as well as staggering stationary localized states with frequencies lying above respectively below
the linear band. Generally, the stronger the n-n-n interaction on the DNLS lattice the smaller are the maximal amplitudes
of the standing solitonlike solutions and the less rapid are their exponential decays.
Received 4 October 2000 相似文献
15.
R.E. Benfield D. Grandjean J.C. Dore Z. Wu M. Kröll T. Sawitowski G. Schmid 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):399-402
The structure of nanowires of different metals grown within nanoporous alumina membranes has been studied by EXAFS, WAXS and
high energy X-ray diffraction. Nanowires of gold, silver, copper and iron adopt the lattice structure and bond distances of
the bulk metals. Cobalt nanowires on the other hand were composed of a mixture of hcp phase, stable at room temperature, and
fcc phase, which in bulk cobalt is normally stable only at high temperatures, in a ratio depending on the pore size. The nanowires
are non-continuous but are made of nanocrystallites whose shape and size was found to depend strongly on the metal. All the
metals except gold showed the presence of a preferred orientation which was slight in the case of Ag and Cu but much stronger
in the case of iron and cobalt nanowires.
Received 30 November 2000 相似文献
16.
A.M. Malvezzi M. Patrini A. Stella P. Tognini P. Cheyssac R. Kofman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):321-324
Ga nanoparticle monolayers formed by evaporation-condensation in ultrahigh vacuum and embedded in a transparent SiOx matrix generate second harmonic (SH) signals in transmission and reflection when illuminated by a 150 fs, 800 nm laser pulses.
The observed SH light exhibits a critical dependence on input and output polarizations, angle of incidence and azimuthal orientation
of the samples. The results lead to a consistent picture of shape and orientation of the nanoparticles. Linear transmittance
spectra in the visible range support these findings and the observed size dependence of the SH signal.
Received 29 November 2000 相似文献
17.
The optical absorption of silver and gold nanoparticles dispersed within the pores of monolithic mesoporous silica upon annealing at elevated temperatures has been investigated. With decreasing particle size, the surface plasmon resonance position of the particles 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 position is completely different from that previously reported for fully embedded particles. We assume a local porosity at the particle/matrix interface, such that free surface of particles within the pores may be in contact with ambient air, and present a two-layer core/shell model to calculate the optical properties. These calculations also consider deviations from the optical constants of bulk matter to account for corresponding effects below about 10 nm particle size. From the good agreement between experimental results and model calculations, we conclude a peculiar particle/ambience interaction dominating the size evolution of the resonance. Because of the difference of core electron structure, the relative importance of the effects of local porosity and free surface, respectively, are different for silver and gold. For silver, the effect of the local porosity is stronger, but for gold the opposite is found. 相似文献
18.
R. Ramasamy V. Selvarajan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):229-235
A new approach to study the particle velocity in a thermal plasma in relation to input parameters (power, gas flow rate, injection
velocity of the particle and particle size) and nozzle dimensions (nozzle length and diameter) has been made. Injected particle's
temperature and thermal history were calculated for particles of three different materials (alumina, tungsten and graphite)
in argon plasma. Allowable powder feed rate was calculated for the particles. Heat transfer per particle injected in to the
plasma is reported. Liquid fraction of the particle after it reached the melting point is also reported. Particle velocity
is found to increase with increase in power, gas flow rate and injection velocity and decrease with increase in particle size,
nozzle length and nozzle diameter. Thermal histories of the particles in relation to the plasma temperature and particle diameter
are presented. Particle's residence time is found to increase with increase in diameter of the particle. Allowable powder
feed rate for complete melting of the particle is higher at higher percentage utilisation of the plasma power. Powder feed
rate is seen to decrease with increase in particle size and it is higher for tungsten and lower for graphite particle. Heat
transfer rate from plasma to particle is seen to decrease with increase in time and the same is higher for plasmas of higher
temperature and smaller sized particle.
Received 4 May 2000 and Received in final form 15 March 2001 相似文献
19.
M. Quinten 《Applied physics. B, Lasers and optics》2001,73(4):317-326
We discuss the dependence of the color of low-concentrated nanoparticle systems on particle size and mass concentration for
Ag, Au and TiN nanoparticles, which exhibit a surface plasmon polariton resonance in extinction spectra. Comparison is made
with color data obtained for Ag and Au colloidal suspensions.
When particles lump into aggregates, the splitting of the surface plasmon resonance into new resonances affects the extinction
of light and, hence, the color of the particle assembly. This is demonstrated for aggregated colloidal suspensions of Ag and
Au nanoparticles.
Finally, for highly concentrated assemblies such as pigment films, we discuss the dependence of the color in diffuse reflectance
and transmittance according to Kubelka and Munk (P. Kubelka, F. Munk: Z. Techn. Phys. 12, 593 (1931)), and extend this model by using optical properties of aggregates of spheres.
Received: 2 July 2001 / Published online: 10 October 2001 相似文献
20.
R.-P. Methling V. Senz E.-D. Klinkenberg Th. Diederich J. Tiggesbäumker G. Holzhüter J. Bansmann K.H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):173-176
We have investigated the magnetic properties of mass-selected iron clusters using the Magneto-Optical Kerr effect (MOKE) in
longitudinal geometry. For the production of these clusters, a newly developed continuous arc cluster ion source (ACIS) was
applied. The source is based on cathodic arc erosion in inert gas environment and subsequent expansion into high vacuum. Its
intensity and stability allows mass selection within a wide size range. The source efficiency is demonstrated in deposition
experiments and transmission electron microscopy. For mass-selected iron particles deposited into a silver matrix we could
observe a change in the magnetic behaviour from ferromagnetism to superparamagnetism around a size of 10 nm at room temperature.
Received 1st December 2000 相似文献