共查询到20条相似文献,搜索用时 15 毫秒
1.
T. Orii M. Hirasawa T. Seto N. Aya S. Onari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):119-122
The temperature dependence of photoluminescence (PL) from
mono-dispersed Si nanoparticles was studied from 4 to 300 K. Si
nanoparticles produced by pulsed laser ablation in He background
gas were sorted into the 6 nm size range by a differential
mobility analyzer (DMA). The spread of the size distribution was
narrowed to a geometrical standard deviation
g = 1.05. On decreasing the temperature
from 300 to 4 K, the intensity of the PL spectra increased
gradually, peaked at about 60 K, and then decreased rapidly. The
temperature dependences of the intensity and the full width at
half maximum (FWHM) on the PL spectra are discussed in terms of
radiative and nonradiative decay rates. 相似文献
2.
Bozanić DK Djoković V Blanusa J Nair PS Georges MK Radhakrishnan T 《The European physical journal. E, Soft matter》2007,22(1):51-59
Silver (Ag) and silver sulfide (Ag2S) nanoparticles were synthesized in a sago starch matrix. The resulting nanocomposites were investigated using structural,
optical and thermal methods. XRD spectra of the nanocomposites confirmed the presence of nanostructured silver (cubic phase)
and silver sulfide (monoclinic phase) in the matrix. TEM micrographs showed that the nanoparticles are mostly spherical in
shape. Analyzes of the optical properties of the silver nanocomposite aqueous dispersions/solutions of various concentrations
were carried out. The results and the theoretical considerations suggested that at high concentrations there is a release
of silver nanoparticles from the composite in the water environment. Further dilution produces homogeneous solution in which
silver nanoparticles are capped with starch macromolecules. TGA analysis revealed reduced thermal stability of the nanocomposites
with respect to pure starch matrix. 相似文献
3.
《Solid State Communications》2003,128(11):407-411
We report the optical and structural properties of PbS nanoparticles in zeolite A. The samples were obtained by sulfidation of the Pb2+ ion-exchanged zeolite in a thiourea solution at 50 °C. The optical properties of the samples were studied by diffuse reflectance spectroscopy. Their crystalline structure and morphology were studied by electron diffraction and by transmission and scanning electron microscopy. The results show that the nanoparticles are not inside the zeolite cages but outside, embedded in the zeolite matrix. Exciton absorption peaks at much higher energy than the fundamental absorption edge of bulk PbS indicate quantum confinement effects in the spherical shape nanoparticles as a consequence of their small size. 相似文献
4.
V. Lozovski G. Strilchuk 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):297-302
The luminescence spectra of CdS particles obtained by sedimentation method
are studied. The comparison of measured and calculated photoluminescence
spectra was used as the base of the method defining the shape distribution
of the particles. For this purpose one can use the symmetry rule for
absorption and luminescence spectra. Absorption spectra were calculated via
dissipative function in terms of local field theory. The experimental
spectra of the photoluminescence were measured during the process of
sedimentation in the CdS nano-composite powder. The modification of
luminescence spectra detected during sedimentation time is associated with
changing the dimension and shape distributions of CdS suspension. As a
result, the particles shape distribution was estimated for sizes less then 1 μm. 相似文献
5.
P. Andersson C. Steinbach U. Buck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):53-56
The structure of large water clusters of known size
distributions 〈n〉 = 20-2000
is investigated by vibrational spectroscopy of the OH stretch
mode. The water clusters are predissociated by a pulsed tunable
infrared optical parametrical oscillator (OPO) in the frequency
range 2800-3800 cm-1. Their fragments
are detected off-axis by electron impact ionization and mass
analyzed by a quadrupole mass spectrometer. The largest ion
signal stems from the neutral water hexamer fragment. The ion
yield is investigated at certain wavelengths while the size of
the clusters is varied, and for certain sizes complete
absorption spectra of the OH stretch motion are measured.
Fingerprints of the different coordination types of the water
molecules in the clusters are found and it turns out that our
method is especially sensitive to amorphous structures with
frequencies shifting in the range of 3300-3400
cm-1. 相似文献
6.
M. Han J.F. Zhou F. Q. Song C. R. Yin M. D. Liu J. G. Wan G. H. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):269-272
Free beam of silicon oxide nanoclusters is produced by a
gas aggregation source from SiO precursor. Due to the
disproportionation reaction during the condensation of SiO vapor
the generated clusters are Si-riched. The clusters are
collimated to be a fine beam and deposited on the substrate at
room temperature. The microstructures of the cluster-based
nanofilm are characterized by TEM. It is shown that with
appropriate impacting parameters, Si-riched oxide nanofilms
assembled from uniformly distributed isolated clusters can be
obtained. And the clusters can self-organize into partially
densely ordered packing within local domains. XPS spectra are
taken to analyze the chemical components of the nanofilms.
Photoluminescence from the Si-riched oxide nanofilms has also
been observed. 相似文献
7.
W. Vervisch C. Mottet J. Goniakowski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):311-314
Morphology and atomic structure of supported Pd clusters
on MgO(100) substrate are investigated theoretically using a
mixed approach: a semi-empirical potential for the metal bonding
within the cluster and a potential fitted to
ab initio calculations for
the metal-oxide interaction. We find that the clusters adopt a
truncated pyramidal morphology in agreement with experimental
results. The detailed study of the epitaxial relation as a
function of cluster size shows the existence of a critical size
around 3 nm where elastic strain due to the misfit between the
substrate and the deposit is released by the introduction of
interfacial dislocations. 相似文献
8.
M. Iwamoto K. Kuroda V. Zaporojtchenko S. Hayashi F. Faupel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):365-367
Recently, production methods of metal nanoparticles have
been investigated extensively, not only for a research use in
laboratory, but also for an industrial use. However, it is
difficult to obtain metal nanoparticles in high amounts and
concentrations with simple methods. In this study, a gold
nanoparticle-polymer composite was prepared with a simple
procedure using a gold salt and a melted polymer. The composite,
which is in a wax state at room temperature, was highly soluble
in water and lower alcohols, moreover the composite was melted
at about 50
°C. 相似文献
9.
Non-crystalline structures in the growth of silver nanoclusters 总被引:2,自引:0,他引:2
F. Baletto C. Mottet R. Ferrando 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):25-28
The growth of nanometer-size free Ag clusters is studied by Molecular Dynamics simulations. The morphology transition from
the icosahedron at the magic size of N = 55 atoms to the Marks truncated decahedron at N = 75 is analyzed in details, in order to single out kinetic trapping and entropic effects. At very low T, the cluster is kinetically trapped in an icosahedral structure. At intermediate T the transition takes place sharply at N≃ 65. At higher T, the transition is smeared out and finally, around 550 K no transition is found because the 75 decahedron is melted.
Received 28 November 2000 相似文献
10.
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
11.
H. Yanagimoto K. Akamatsu K. Goto S. Deki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):313-316
Small Copper (I) oxide, Cu2O, nanoparticles dispersed in diamine-terminated polyethyleneoxide (PEO-NH2) matrix have been successfully prepared by vacuum evaporation of copper onto the molten PEO-NH2. The obtained composite were characterized by TEM, electron diffraction, TG-DTA and FT-IR spectroscopy. The stable composite,
in which the Cu2O nanoparticles are stabilized through interaction between NH2 chain end groups of PEO molecules and Cu2O nanoparticles was obtained when the samples were heat-treated at 110
°
C. The mean size of the Cu2O nanoparticles increased from 2.5 to 3.5 nm in diameter upon increasing the amount of initial Cu deposition. The obtained
composite material having a waxy texture was soluble in many solvents without aggregation and can be handled as a simple chemical
compound for starting material in various applications.
Received 29 November 2000 相似文献
12.
S. A. Nepijko D. N. Ievlev W. Schulze 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):115-117
The plasmon energy of Ag clusters produced on an amorphous
carbon substrate by gas-aggregation technique has been measured.
It has been determined from the plasmon peak position in the
light emission spectrum obtained during bombardment of Ag
clusters by low-energy electrons. For Ag cluster films with
maximum of the cluster size distribution at 30, 8 and 2.5 nm,
the plasmon energy comprised 3.76, 4.13 and 4.28 eV (the
wavelength was 330, 300 and 290 nm), respectively. The blue
shift of the plasmon energy is probably related to the effect of
confounding of collective and single-particle excitations. 相似文献
13.
F. Baletto C. Mottet R. Ferrando 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):233-236
The possibility of obtaining core-shell nanoparticles by
depositing adatoms of a different element B above a cluster of
an element A (system B/A) is studied by Molecular Dynamics
simulations. We consider the four cases Ag/Cu, Cu/Ag, Ag/Pd and
Pd/Ag, which present very different behaviours, and investigate
whether it is possible to build up of well-defined core-shell
structures. 相似文献
14.
H. B. Liu Y. L. Li H. Y. Luo H. J. Fang H. M. Li S. Q. Xiao Z. Q. Shi S. X. Xiao D. B. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):405-408
We demonstrate a new, simple, inexpensive process and
systemic control over CdS nanowires using sulfur powders and
organic diamines without any catalysts, surfactants, and
templates under atmospheric benchtop conditions. By changing the
kinds of amines and reaction temperatures can result in control
of the shape and size of the nanocrystals, which are moderately
monodispered with unique forms. 相似文献
15.
Dispersion and alignment of carbon nanotubes in polycarbonate 总被引:2,自引:0,他引:2
M. Sennett E. Welsh J.B. Wright W.Z. Li J.G. Wen Z.F. Ren 《Applied Physics A: Materials Science & Processing》2003,76(1):111-113
Dispersion and alignment of carbon nanotubes in thermoplastic polymers such as polycarbonate have been studied. Dispersion
was accomplished by mixing in a conical twin-screw extruder and alignment was carried out using a fiber-spinning apparatus.
The effects of mixing time and fiber draw rates on dispersion and alignment were investigated. Uniform dispersions were produced
with relatively short residence times in the extruder. Excellent alignment of carbon nanotubes in nanocomposite filaments
was obtained when the fiber draw rate was greater than 70 m/min. The ability to closely control the dispersion and alignment
of carbon nanotubes in polymers is expected to lead to the development of nanocomposites with desirable electronic and structural
properties.
Received: 7 January 2002 / Accepted: 11 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-508/233-5521, E-mail: Michael.Sennett@natick.army.mil 相似文献
16.
Titania from nanoclusters to nanowires and nanoforks 总被引:1,自引:0,他引:1
G. Wang G. Li 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):355-360
A novel method - inverse microemulsion has been developed
not only for synthesizing low cost TiO2
nanoclusters but also for the first time preparing titania
nanowires and nanoforks with rutile structure of single crystal.
With two microemulsion systems, spherical
TiO2 nanoclusters of 5 nm in average
diameter are produced. These nanoclusters are amorphous and
turned into anatase at an annealing temperature lower than 750
°C, and changed into rutile when
annealed at higher temperature. When three microemulsions with
TiCl4, ammonia and NaCl as aqueous phase,
are used, the precursor powder containing
Ti(OH)4/NaCl with molar ratio of 1000 are
annealed at 750
°C and then
TiO2 rutile nanowires with 22 nm in
thickness and 4 m in length are formed. At the same time two
kinds of nanoforks with defined boundary structures are
constructed: one is a bent wire composed of two straight
whiskers related by twinning on a (101) plane with the angle of
114° between the two legs, and the
other by twinning on a (301) planes with the angle of
55° between the legs. Screw
dislocations and a periodic structure are found in (301) twin
boundary, while edge dislocations are observed in (101) twin
boundaries.The experiments demonstrate that the titania rutile
nanowires are formed through solid state phase transformation
and sodium chloride play an important role in the process. 相似文献
17.
18.
S.J. Lee S.W. Han H.J. Choi K. Kim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):293-296
We have investigated the structure and phase behavior of nonmolecularly layered silver stearate by means of temperature-dependent
diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Upon heating the sample, remarkable spectral changes
took place. The first phase transition took place that might be associated with a premelting event characterized by the formation
of gauche conformers at 390-420 K. A second phase transition took place in which silver nanoparticles with a size of ∼4 nm
were formed by thermal decomposition of silver stearate at 520-550 K. These silver nanoparticles, derivatized by stearate,
were readily spread as a monolayer at air/water interface, and could be packed in 3-D assemblies by the Langmuir-Blodgett
method.
Received 29 November 2000 相似文献
19.
H. Nabika S. Deki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):369-372
The effect of colloidal dispersion of silver on the
luminescent properties of Eu (III) complex with
pyridine-3,5-dicarboxylic acid (PyDC) was investigated. The
luminescence from Förster type europium complex was enhanced
several times with the presence of Ag colloid and the
enhancement factor showed Ag concentration dependence. The
observed enhancement effect was discussed in view of
surface-enhancement effect and optical absorption due to surface
plasmon resonance, both arising from excitation of surface
plasmon polariton. The coordination structure around Eu (III)
ion was also affected with the presence of Ag colloid, which
induced the change in the intensity ratio between two emission
bands of
5
D
0
7
F
1
and
5
D
0
7
F
2
transitions of Eu (III) ion. 相似文献
20.
Y. Chushak L.S. Bartell 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):43-46
A set of molten gold clusters, each with 1157 gold atoms, was studied by molecular dynamics simulations as the clusters underwent
freezing at three different temperatures. Most of the clusters attained an icosahedral structure upon freezing, a structure
found to be stable to mild annealing. Other structures observed were imperfect truncated decahedral, truncated octahedral
and hexagonal close packed structures. The role of kinetics in the process of cluster solidification is discussed.
Received 6 November 2000 相似文献