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951.
Zhuomin Gu Shu Tian Qun Zhou Wenjuan Wei Lili Zhao Xiaowei Li Junwei Zheng 《Journal of Raman spectroscopy : JRS》2013,44(12):1682-1688
We presented a controlled particles‐in‐cavity (PIC) pattern for surface‐enhanced Raman scattering (SERS) detection. The periodic gold cavity array was fabricated by electrodeposition using highly ordered polystyrene spheres as a template. The as‐prepared gold cavities can be used as a SERS active substrate with significant spectral enhancement and reproducibility, which was evaluated by SERS signals using 4‐mercaptobenzoic acid (4‐MBA) as probe molecules. The surface of these gold cavities was further functionalized with cetyltrimethylammonium bromide molecules, which may immobilize the 4‐MBA‐modified silver nanoparticles in the gold cavity to form a PIC structure via the electrostatic interaction. We have demonstrated that there exists a pH window for the immobilization of the nanoparticles inside cavities. Therefore, the silver nanoparticles can be selectively immobilized into the functionalized gold cavities under the optimized pH value of the media. Further enhancement of the Raman scattering of the labeled molecules can be achieved due to the interconnection between the silver nanoparticles and gold cavity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
952.
Nano silica powders were synthesized from rice husk ash, the most silica-rich raw material, using alkaline extraction followed by acid precipitation. The phase transformation during sintering, the influence of sintering temperature and pH on the particle size and anti-reflective properties of nano silica were investigated. The results showed that the amorphous SiO2 sintered at 600°C were transformed to a cristobalite structures completely during the sintering process at 800°C and 1100°C. With the increasing sintering temperature and pH, the particle size distributions (d50) were increased respectively in the range of 62–84, 192–240, and 283–329?nm at sintering temperatures of 600°C, 800°C, and 1100°C. When the sintering temperatures were increased at 1100°C, 98.15% and 96.84% of transmittances were obtained respectively at the highest and lowest points of the anti-reflection band and could be used for anti-reflective applications. 相似文献
953.
Cheng-Gang Li Jin-Hai Gao Jie Zhang Wan-Ting Song Shui-Qing Liu Si-Zhuo Gao 《Molecular physics》2013,111(4):382-394
The structures, stabilities and electronic properties of neutral and anionic B3Sin (n?=?1–17) clusters have been systemically investigated on the basis of density functional theory at the B3LYP/6-311?+?G(d) level and CALYPSO structure prediction method. The structural searches show that three boron atoms tend to form B3 triangle encapsulated into Sin cages with the increasing number of silicon atoms. Most of the lowest energy structures can be derived by using the squashed pentagonal bipyramid structure of B3Si4 and B3Si4? as the major building unit. The relative stabilities are studied based on the calculated binding energies, second-order difference of energies and HOMO–LUMO gaps of the lowest energy structures. In addition, Hirshfeld, natural population analysis, Bader approaches and natural electronic configuration are performed to explore the charge transfer. At last, molecular orbital, magnetic properties, IR, Raman and UV–vis spectra are also, respectively, analysed for providing strong support for essential theoretical and experimental research. 相似文献
954.
AZ91镁合金及其Al2O3纤维-石墨颗粒混杂增强复合材料的滑动摩擦磨损性能研究 总被引:9,自引:0,他引:9
利用挤压铸造法制备了单-A12O3短纤维增强及A12O3短纤维一石墨(Gr)颗粒混杂增强AZ91镁合金复合材料,考察了镁合金及其复合材料的滑动摩擦磨损性能.结果表明,复合材料的耐磨性能优于基体合金,其中单一A12O3短纤维增强复合材料的耐磨性能更优,而混杂Gr颗粒的复合材料在磨损表面不能形成自润滑薄膜,故不能改善镁基复合材料在滑动干摩擦条件下的摩擦磨损性能.基体合金和单一A12O3短纤维增强复合材料的主要磨损机制为犁削磨损,而A12O3-Gr颗粒混杂增强复合材料的主要磨损机制为犁削和剥层破坏. 相似文献
955.
M. Csanád T. Csörgő A. Ster B. Lörstad N. N. Ajitanand J. M. Alexander P. Chung W. G. Holzmann M. Issah R. A. Lacey 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):363-368
Recent PHOBOS measurements of the excitation function for the pseudo-rapidity dependence of the elliptic flow in Au + Au collisions
at RHIC have posed a significant theoretical challenge. Here we show that these differential measurements, as well as the
RHIC measurements on transverse momentum satisfy a universal scaling relation predicted by the Buda-Lund model, based on exact
solutions of perfect fluid hydrodynamics. We also show that the recently found transverse kinetic energy scaling of the elliptic
flow is a special case of this universal scaling. 相似文献
956.
Discrete simulation methods are efficient tools to investigate the behaviors of complex fluids such as dry granular materials
or dilute suspensions of hard particles. By contrast, materials made of soft and/or concentrated units (emulsions, foams,
vesicles, dense suspensions) can exhibit both significant elastic particle deflections (Hertz-like response) and strong viscous
forces (squeezed liquid). We point out that the gap between two particles is then not determined solely by the positions of
their centers, but rather exhibits its own dynamics. We provide the first ingredients of a new discrete numerical method,
named Soft Dynamics, to simulate the combined dynamics of particles and contacts. As an illustration, we present the results for the approach
of two particles. We recover the scaling behaviors expected in three limits: the Stokes limit for very large gaps, the Poiseuille-lubricated limit for small gaps and even smaller surface deflections, and the Hertz limit for significant surface deflections. We find that for each gap value, an optimal force achieves the fastest approach
velocity. The principle of larger-scale simulations with this new method is provided. They will consitute a promising tool
for investigating the collective behaviors of many complex materials. 相似文献
957.
958.
C. Schneider G. Czycholl 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):43-50
We study the (spinless) Falicov-Kimball model extended by a finite band width (hopping t
f
) of the localized (f-) electrons in infinite dimensions in the weak-coupling limit of a small local interband Coulomb correlation U for half filling. In the case of overlapping conduction- and f-bands different kinds of ordered solutions are possible, namely charge-density wave (CDW) order, electronic ferroelectricity
(EFE) and electronic antiferroelectricity (EAFE). The order parameters are calculated as a function of the model parameters
and of the temperature. There is a first-order phase transition from the CDW-phase to the EFE- or EAFE-phase. The total energy
is calculated to determine the thermodynamically stable solution. The quantum phase diagrams are calculated. 相似文献
959.
J. Kurzyk W. Wójcik J. Spałek 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):385-398
The method used earlier for analysis of correlated nanoscopic systems is extended to infinite (periodic) s-band-like systems
described by the Hubbard model. The optimized single-particle Wannier wave functions contained in the parameters of the extended
Hubbard model (in the nearest-neghbor hopping (-t), in the magnitude of the intraatomic interaction U, and in other parameters) are determined explicitly in the correlated state for the electronic systems of various symmetries
and dimensions: Hubbard chain, square and triangular planar lattices, and the three cubic lattices (SC, BCC, FCC). In effect,
the evolution of the electronic properties as a function of interatomic distance R is obtained. The model parameters in most
cases do not scale linearly with the lattice spacing and hence, their solution as a function of microscopic parameters reflects
only qualitatively the system evolution. Also, the atomic energy changes with R and therefore should be included in the model
analysis. The solutions in one dimension (D = 1) can be analyzed both rigorously (by making use of the Lieb–Wu solution) and compared with the approximate Gutzwiller
treatments. In higher dimensions (D = 2 and 3) only the latter approach is possible to implement within the scheme. The renormalized single particle wave functions
are almost independent of the choice of the scheme selected to diagonalize the Hamiltonian in the Fock space in D = 1 case.
For dimensions D > 1 the qualitative behavior is independent of the structure considered. The wave-function size increases
above the Mott-Hubbard localization threshold and gradually reaches the atomic limit value. The method can be extended to
other approximation schemes, as stressed at the end. 相似文献
960.
This paper compares the stabilization performances of three dithiocarbamate and three phosphate chemical stabilizing agents, selects the best agents from each group, combines them as a mixed heavy metal stabilizer for municipal solid‐waste incineration (MSWI) fly ash, and investigates the effectiveness of the mixed chelator in stabilizing heavy metals in MSWI fly ash from southwest China. The mechanism of stabilization is also analyzed. Results indicate that piperazine dithiocarbamate can stabilize Cd, Cu, and Ni effectively, while sodium dihydrogen phosphate can stabilize Pb better. With the addition of the mixed chelator (2% sodium dihydrogen phosphate and 1% piperazine dithiocarbamate), all the targeted heavy metal concentrations in the leachate were below the standards for pollution control on municipal solid waste landfill sites in China. The stabilizing agents combined with the heavy metals in fly ash could not generate insoluble crystals; however, the heavy metals could combine with the agents' effective groups, generating flocs in the pores or on the surfaces of the fly ash and offering significant densification. The mixed chelator could transfer heavy metals from unstable fractions to stable fractions, so the leaching of heavy metals from the fly ash was greatly decreased. 相似文献