银团簇结构与特性的分子动力学研究

用分子动力学方法模拟了银团簇的结构与力能学。计算模拟中使用了一种基于第一性原理的原子间互作用多体势函数。通过分子动力学模拟确定了银徽团簇（原子个数3－13）的稳态结构;模拟了原子个数为13－141的银FCC晶体结构理想球形团簇的力能学,发现球形银簇形成三维紧密结构;计算了平均结合能,给出了结合能随团簇原子数N的变化图,发现随N增大团簇结合能逐渐接近块材的数值。     

表面增强的分子间能量转移效应

研究了粗糙金属银表面对分子间能量转移效应的影响，实验观察到吸附分子增强的敏化荧光，结合表面局域电磁理论分析表明，吸附于银表面的分子间非辐射能量转移率被增强１０＾２倍，证实了表面增强的分子间能量转移效应的存在。     

Fast ionic transport in Ag<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>TiS<Subscript>2</Subscript>

The enthalpy of the subsystem of silver ions in the intercalation compounds Ag _x TiS₂ has been calculated from the electrochemically measured thermodynamic functions of the silver subsystem. The ionic conductivity and the coupled chemical diffusion coefficients for silver in the intercalation compound have been measured. The activation energy for diffusion of silver ions is determined and the obtained value is interpreted from analyzing the concentration dependence of the enthalpy of the ionic subsystem. The conclusion has been drawn that the high diffusion mobility is associated with the competition between the covalent and elastic interactions, which decreases the activation energy for diffusion of ions.     

Femtosecond optical diagnostics of interlevel energy relaxation in the band gap of silver iodide nanocrystals

The kinetics of the relaxation processes in silver iodide nanocrystals synthesized in a nanoporous silicate glass matrix and excited by femtosecond laser pulses has been experimentally studied. A short-lived characteristic transmission band is found to be formed in the spectral range of exciton absorption of nanocrystals. The specific features of photoexcited-carrier relaxation, which are due to the energy redistribution of captured carriers over levels in the band gap of silver iodide nanocrystals, are considered. The energy transfer relaxation rates are estimated and possible mechanisms of the energy transfer are discussed.     

Preparation of triethylamine stabilized silver nanoparticles for low-temperature sintering

In this article, silver nanoparticles were synthesized by chemical reduction from silver nitrate using triethylamine as the protecting and reducing agents simultaneously. The average size of the silver nanoparticles was about 2.10–4.65 nm, which allowed low-temperature sintering of the metal. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and energy dispersive spectrometric (EDS) analysis results indicate that silver nitrate has been converted to silver nanoparticles completely. Using a 20 wt% silver nanoparticles suspension with thermal treatment at 150 °C, silver films with a resistivity of 8.09 × 10⁻⁵ Ω cm have been produced, which is close to the resistivity of bulk silver.     

Optical Properties of Planar Nanostructures Based on Semiconductor Quantum Dots and Plasmonic Metal Nanoparticles

The optical properties of a composite material consisting of a thin polymer film, which is activated by semiconductor CdSe/ZnS quantum dots (QDs) and silver nanoparticles, on a transparent dielectric substrate have been investigated. It is revealed that the presence of silver nanoparticles leads to an increase in the QD absorption (by a factor of 4) and in the fluorescence intensity (by a factor of 10), whereas the fluorescence time drops by a factor of about 10. Excitation of the composite medium by a pulsed laser is found to result in narrowing of the fluorescence band and a sublinear dependence of its intensity on the pulse energy. In the absence of silver nanoparticles, the fluorescence spectrum of QDs is independent of the excitation-pulse energy density, and the fluorescence intensity depends linearly on the pulse energy in the entire range of energy densities, up to 75 mJ/cm².     

纳米银与表面吸附荧光素的荧光性能的影响

研究了纳米银粒子对表面吸附荧光素(fluorescein,Fl)的荧光性能的影响。Fl溶液中加入纳米银粒子,Fl分子包覆在纳米银粒子表面形成Fl_n-Ag复合物使纳米银相互桥连形成类似网络的结构,且Fl分子吸收峰随着纳米银浓度的增加发生红移。纳米银通过产生的强局域场将能量传输给Fl发光中心,实现了Fl的荧光增强,荧光增强效率随着纳米银浓度的增加具有最大值。较大粒径的纳米银使Fl获得最大荧光增强效率所需浓度较低且最大荧光增强效率值较高。研究结果表明,纳米银与Fl间的能量传输主要由Fl分子附近局域电磁场增强和分子到金属表面无辐射跃迁能量转移过程所决定并与纳米银的浓度、尺寸密切相关。     

Synthesis of silver nanowires via electroplating technology and its surface enhanced Raman scattering effect

This very paper is focusing on the preparation of silver nanostructures and the surface enhanced Raman scattering effect of the silver nanostructures produced. Via electroplating technology, silver nanowires and nanoparticles were prepared on silicon wafers. Characterization was performed by X-ray diffraction, scanning electron microscope, transmission electron microscope equipped with X-ray energy dispersion spectroscope and selected area electron diffraction, which reveals that the formation of silver nanostructures depends on the over-potential. The produced silver nanowires are of crystalline FCC structure and grow in 〈0 1 1〉 direction. The growth mechanism has been further discussed. The surface enhanced Raman scattering effect is achieved with the silver nanostructures produced.     

An investigation of the electronic structure of silver azide by the photoemission method

The energy structure of silver azide was investigated by the photoemission method. The photoelectric work function for photons in the energy range 6.7–11.2 eV was determined from the electron energy distribution curves and the Einstein equation. The position of the Fermi level was determined from the difference in stopping potentials for silver metal and silver azide. The position of the acceptor levels is estimated and the structure of the valence band is discussed. A band scheme for silver azide is proposed.     

Messung der Energieverlustspektren von Aluminium- und Silberfolien mit hoher Auflösung

The energy loss spectra of polycrystalline aluminium and silver foils have been measured with high resolution. For the plasmon energy of aluminium 14.97 eV is obtained. The half width of the plasmon peak is 0.60 eV corresponding to a relaxation time τ=1.1×10^?15 sec in fair agreement with optical data. In silver films of certain thicknesses the surface plasmon peak and the plasmon peak can be separated in the energy loss spectrum. The values of the energy losses are 3.64 and 3.78 eV respectively.     

Agn-1Si（n=5-10）团簇结构与性质研究

采用密度泛函理论研究了Agn-1Si团簇（n = 5-10）的几何结构和物理性质。首先得到体系最低能量结构,其中Ag5Si 和 Ag7Si团簇的结构比之前研究中结构能量更低。通过分析相应结构的能隙,平均结合能,二阶能量差可以发现Si原子的加入可以加强团簇结构稳定性,使团簇更加紧凑。在团簇尺寸n = 5-10的范围里,拥有八个价电子的Ag4Si团簇在以上三个方面都显示出非常稳定的特点。通过分析Agn-1Si团簇 (n = 5-10)的差分电荷发现,电荷的转移主要发生在Si原子与其相邻的Ag原子之间, Si原子和附近的Ag原子之间产生了强烈的共价相互作用,是团簇稳定性增强的重要原因。     

纳米银粒子的量子尺寸效应

实验上采用吸收光谱发现两种不同粒度的纳米银粒子其吸收峰的位置随粒子尺寸的增加而红移,理论上采用简单的球形势阱模型得到了本征能量与粒子尺寸的解析关系,该理论较圆满地解释了实验现象。     

Superconducting proximity effect in Ag—Mn

The proximity effect was studied by measuring the thermal conductivity of double layers films made of a normal metal (Ag or Ag—Mn) and a superconductor (Pb–5% Bi), in the temperature range of 0.3–2 K.Thermal conductivity ratios have been used to estimate induced energy gap in silver and in dilute silver manganese alloys. No evidence for bound states in the presence of magnetic impurities was observed.     

Sono and electrochemical synthesis and characterization of copper core–silver shell nanoparticles

Cu–Ag core–shell nanopowders have been prepared by ultrasound-assisted electrochemistry followed by a displacement reaction. The composition of the particles has been determined by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The XRD patterns versus time displacement show that higher are the silver peaks intensities, weaker are the copper ones. That exhibits the progressive recovering of copper by silver. EDX results and quartz crystal microbalance results indicate that various reaction mechanisms are implied in this process. Transmission electron microscopy (TEM) points out variable nanometric diameter grain and some small agglomerates. Elemental mapping obtained by electron energy-loss spectroscopy (EELS) underlines the core–shell structure.     

Silver aggregates and twofold-coordinated tin centers in phosphate glass: A photoluminescence study

The optical properties of silver species in various oxidation and aggregation states and of tin centers in melt-quenched phosphate glasses have been assessed by optical absorption and photoluminescence (PL) spectroscopy. Glasses containing silver and tin, or either dopant, were studied. Emission and excitation spectra along with time-resolved and temperature-dependent PL measurements were employed in elucidating the different emitting centers observed and investigating on their interactions. In regard to silver, the data suggests the presence of luminescent single Ag⁺ ions, Ag⁺-Ag⁺ and Ag⁺-Ag⁰ pairs, and nonluminescent Ag nanoparticles (NPs), where Ag⁺-Ag⁰→Ag⁺-Ag⁺ energy transfer is indicated. Tin optical centers appear as twofold-coordinated Sn centers displaying PL around 400 nm ascribed to triplet-to-singlet electronic transitions. The optically active silver centers were observed in glasses where 8 mol% of both Ag₂O and SnO, and 4 mol% of Ag₂O were added. Heat treatment (HT) of the glass with the high concentration of silver and tin leads to chemical reduction of ionic silver species resulting in a large volume fraction of silver NPs and the vanishing of silver PL features. Further characterization of such heat-treated glass by transmission electron microscopy and X-ray photoelectron spectroscopy appears consistent with silver being present mainly in nonoxidized form after HT. On the other hand, HT of the glass containing only silver results in the quenching of Ag⁺-Ag⁰ pairs emission that is ascribed to nonradiative energy transfer to Ag NPs due to the positioning of the pairs near the surface of NPs during HT. In this context, an important finding is that a faster relaxation was observed for this nanocomposite in relation to a heat-treated glass containing both silver and tin (no silver pairs) as revealed by degenerate four-wave mixing spectroscopy. Such result is attributed to Ag NP→Ag⁺-Ag⁰ plasmon resonance energy transfer. The data thus indicates that energy transfer between Ag⁺-Ag⁰ pairs and NPs is bi-directional.     

Photoemission measurements of KCl on Ag(110); adsorption parameters

The computer evaluation of photoemission digital data is described and used to keep track of the adsorption-desorption processes during KCl interactions with silver (110). Photoelectric work function changes were examined at different temperatures of the silver crystal substrate and for different impinging fluxes of KCl molecules. Preliminary estimates of the isosteric heat of adsorption and of the desorption energy have been made.     

基于表面等离子体共振效应的椭圆柱银纳米线的光力研究

运用有限时域差分方法,研究了两椭圆柱银纳米线之间的光力及其物理机制,并且分析了椭圆柱银纳米线的尺寸以及相对位置对光力的影响.结果表明:椭圆柱银纳米线的尺寸以及相对位置等结构参量的变化导致两椭圆柱银纳米线之间光力的明显变化.由于局域耦合共振,Ag纳米颗粒间的内壁上存在电子的振荡行为,将微腔中光子的能量转化成电子集体振荡的动能,这使得微腔中的电磁场能量减小到负能态,从而产生收缩的负光力.因此,Ag纳米颗粒间相互吸引.     

Silver nanoclusters formation in ion-exchanged waveguides by annealing in hydrogen atmosphere

Light waveguides containing silver, introduced by ion-exchange process in soda-lime glass, has been annealed in hydrogen atmosphere at temperatures in the 120–250°C range. Annealings cause a near-surface precipitation of metallic silver to form nanometer-size clusters with good uniformity in size and spatial distribution. Hydrogen permeation and ion-exchange between hydrogen and sodium (which remains in the glass matrix after silver-for-sodium exchange) are steps of the annealing process. A further step is the diffusion of silver ions towards the surface, and its eventual precipitation, with an activation energy close to that measured for silver-sodium interdiffusion in glasses of comparable composition.     

基于表面等离子体共振效应的椭圆柱银纳米线的光力研究

运用有限时域差分方法,研究了两椭圆柱银纳米线之间的光力及其物理机制,并且分析了椭圆柱银纳米线的尺寸以及相对位置对光力的影响.结果表明:椭圆柱银纳米线的尺寸以及相对位置等结构参量的变化导致两椭圆柱银纳米线之间光力的明显变化.由于局域耦合共振,Ag纳米颗粒间的内壁上存在电子的振荡行为,将微腔中光子的能量转化成电子集体振荡的动能,这使得微腔中的电磁场能量减小到负能态,从而产生收缩的负光力.因此,Ag纳米颗粒间相互吸引.     

Investigation of the influence of silver and tin on the luminescence of trivalent europium ions in glass

Europium-doped aluminophosphate glasses prepared by the melt-quenching technique have been studied by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The effects of silver and tin doping, and of further thermal processing on Eu³⁺ ions luminescence have been assessed. For the glass system containing only europium, Eu³⁺ PL observed under UV excitation is suggested to occur through energy transfer from the excited glass host. After silver and tin doping, an enhanced UV excited Eu³⁺ PL has been indicated to occur essentially due to radiative energy transfer from isolated Ag⁺ ions and/or two fold-coordinated Sn centers. Since thermal processing of the material leads to a quenching effect on Eu³⁺ PL and Ag nanoparticles (NPs) formation due to reduction of silver ions by tin, XPS was employed in order to investigate the possibility for Eu³⁺→Eu²⁺ reduction during HT as a potential source of the PL decrease. The data points towards Ag NPs as main responsible for the observed weakening of Eu³⁺ PL.