Plasmonic particles of colloidal silver in high-resolution recording media

The optical properties of colloidal silver particles formed photographically in high-resolution silver halide photographic materials have been considered. The conditions that allow one to obtain exposed and developed light-sensitive silver halide particles in the form of colloidal particles of metallic silver having the properties of localized plasmons have been described. The results of the studies of the developed silver particles in traditional photographic materials for image holography and in nanoporous silver halide photographic materials for volume holography have been presented. The perspectives of using plasmonic silver nanoparticles produced photographically have been discussed.     

Tuning of particle plasmon resonances in binary dielectric medium

Using light scattering spectroscopy, I demonstrate an approach to tune particle plasmon resonance in a binary dielectric media where silver nano-rods are embedded partially both in Anodic Aluminum Oxide (AAO) matrix and in air. A systematic experimental study under a controlled variation of the degree of embedding of nano-rods in AAO matrix has been presented. Experimental results have been interpreted based on the Drude model. Finite Difference Time Domain (FDTD) method has been employed to calculate the nature of the silver nano-rod resonance at the experimental conditions. Both the simulation results and theory corroborate the experimental findings.     

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。     

Fluorescent silver nanoparticles via exploding wire technique

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     

Emissive properties of silver particles at silver oxide surface defects

The absorption and fluorescence properties of pure silver and silver oxide model systems have been explored using ab initio linear response methods in context of the observed fluorescence by photoactivation of thin silver oxide films. Silver clusters interacting with F-center defects created from silver oxide surfaces as well as silver clusters interacting directly with the silver oxide surface are good candidates for emissive centers giving rise to fluorescence in the visible regime. These findings represent a starting point towards conceptual understanding of emissive silver cluster-support properties, which might be important for the development of optical storage media with large data capacities. PACS 31.15.Qg; 31.15.Ar     

Electronic Absorption Spectra of Neutral and Charged Silver Molecular Clusters

The structural, energy, and optical properties of charged and neutral molecular clusters (MCs) of silver Ag_n (n = 2–5) have been simulated within the density functional theory (DFT). It has been shown that the electronic absorption spectrum of neutral MCs is shifted toward lower energies compared to the charged ones. The strengths of the oscillators of neutral MCs are mainly larger than the ones of charged MCs. A comparison of the simulation results with the previously obtained experimental ones for glasses with silver MCs has been carried out.     

银纳米粒子自组装复合LB膜的结构与性质

纳米粒子的自组装和有序组装膜的结构与性质近年来受到了人们的广泛关注,纳米粒子的表面结构与性质对由其组装成的有序膜的结构与性质有直接的影响。文章报道了利用自组装技术制备的银纳米粒子与双亲有机分子的单层和多层复合LB膜,通过吸收光谱和表面增强拉曼光谱研究了银纳米粒子与吸附分子间的相互作用,探讨了复合膜的成膜特性及银纳米粒子的拉曼增强特性。十八胺/银粒子复合LB膜的吸收光谱及拉曼光谱显示,十八胺分子与银纳米粒子表面的活位通过NH₂中的氮原子以复合体的形式结合;同时,在激发光的作用下复合体可能存在光催化过程。根据银粒子复合LB膜的实验结果,十八胺和十八酸之间的反应产物在复合膜中起空间位阻作用,与银粒子表面的相互作用较弱。     

吸附于银岛膜上的染料的表面荧光

利用“四能级”模型,对吸附于金属岛膜上的染料分子的表现荧光增强因子随分子表面覆盖度和分子的荧光量子效率的变化进行了理论分析,同时测量了吸附于银岛膜上的荧光素钠分子和若丹明6G分子的表观荧光增强因子随分子荧光量于效率的变化。 关键词：     

The effect of concentration on the thermo-optical properties of colloidal silver nanoparticles

The thermo-optical properties of colloidal silver nanoparticles (AgNPs) are investigated under a low power laser irradiation at 532 nm. Colloidal AgNPs are synthesized by nanosecond pulsed laser ablation of a pure silver plate in distilled water. The morphology and size of the AgNPs are determined by transmission electron microscopy. Closed Z-scan measurements reveal that nonlocal thermo-optic process is responsible for the nonlinear refractive index of colloid containing different concentrations of silver nanoparticles. The Z-scan behavior of the nanoparticle samples has been investigated based on a nonlocal thermo-optic process and it is shown that the aberrant thermal lens model is in excellent agreement with the experimental results. Z-scan measurement fits have allowed the values of nonlinear refractive index (n₂) and thermo-optic coefficients (dn/dt) to be determined at different concentrations of silver nanoparticles. Large enhancement factors were measured for values of n₂ and dn/dt of the colloids at higher silver nanoparticle volume fraction. Our results suggest that nonlocal thermal nonlinear processes will play an important role in the development of photonic applications involving metal nanoparticle colloids.     

Infrared response of small silver particles in silicon matrix

The infrared properties of inhomogeneous composites with small silver particles embedded in a matrix of silicon are presented. Thin films of silver particles in silicon have been produced using co-deposition and tandem deposition methods. These composite films demonstrate high infrared absorption which can be accounted for with the effective medium approximation based on free electron Drude model. The two constituents, Ag and Si, are pure because of ignorable mutual solubility and thus silver remains a Drude metal. The effects of microstructures are investigated.     

Theoretical studies on the photoionization cross-sections of solid silver

An alternative expression for photoionization cross-section of atoms or molecules and a dielectric influence function （DIF） in a high-density system proposed recently are used to study the photoionization cross-sections of solid silver. It is suggested that a density turning point （DTP） of a photoionized system may be viewed as the critical point where the photoionization properties of atoms in a real system may have a notable change. The results show that the present theoretical photoionization cross-sections are in good agreement with the experimental results of a silver crystal both in structure and in magnitude.     

用天线共振子模型研究银镜的紫外可见吸收光谱

我们研究了具有不同表面粗糙度银镜的紫外可见吸收光谱,实验结果表明随着表面粗糙度的增加,银粒子的共振吸收峰发生红移。根据天线共振子模型,进行了吸收光谱的理论计算,计算结果与实验相当吻合。     

Plasmon-enhanced fluorescence near metallic nanostructures: biochemical applications

Amplification of fluorescence is a nanoscale phenomenon which is particularly pronounced in close proximity to metal nanostructures. Due to its sharp distance dependence, it is ideally suited to monitor biorecognition reactions. Using this effect we have been able to demonstrate ultrasensitive bioassays. Two types of metal nanostructures have been employed, nanometric silver islands deposited over an ultrathin metal mirror and silver fractal structures. For the first type, metal mirrors (aluminum, gold, or silver protected with a thin silica layer) were coated with SIFs and an immunoassay (model assay for rabbit IgG or myoglobin immunoassay) was performed on this surface using fluorescently labeled antibodies. Our results show that SIFs alone (on a glass surface not coated with metal) enhance the immunoassay signal approximately 3 to 10-fold. Using a metal mirror instead of glass as support for SIFs leads to up to 50-fold signal enhancement. The second type of metal nanostructures, silver fractals, were produced by electrochemical reduction of silver nitrate deposited on sapphire covered with a thin conductive film of indium tin oxide. These structures were used as a substrate for a model rabbit IgG bioassay. The fluorescence resulting from the binding of antibody labeled with Rhodamine was highly nonuniform with distinctive hot spots. These highly fluorescent regions were correlated with areas of higher Ag thickness and coverage. Such high values of fluorescence amplification in both types of nanostructures have been interpreted by using time-resolved fluorescence data and by considering the radiative properties of plasmons in the environments which promote plasmon coupling. PACS 87.64.Ni; 81.07.-b; 87.14.-g     

Optical Properties of Ag and Au Nanoparticles Dispersed within the Pores of Monolithic Mesoporous Silica

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.     

噻菌灵在纳米银胶表面吸附的表面增强拉曼光谱研究

噻菌灵(TBZ)属苯并咪唑类杀菌剂,容易在水果、蔬菜及相应的果蔬饮品中形成有毒残留。基于密度泛函理论(DFT)的量子化学计算方法和表面增强拉曼光谱(SERS)技术,从理论和实验角度系统研究了噻菌灵在纳米银胶粒子表面的吸附行为和增强效应。采用柠檬酸钠还原法制备了具有表面增强拉曼散射活性的银纳米溶胶,并对水相的噻菌灵进行了SERS光谱研究。利用TBZ-Ag₄四种吸附模型对噻菌灵与银纳米溶胶的相互作用进行了理论分析。结合FT-Raman光谱和B3LYP/6-311G(d)理论计算的结果,借助Gaussian View5.0程序的图形化功能,对噻菌灵分子的振动模式、FT-Raman振动光谱和SERS光谱进行了系统的指认。研究结果表明：噻菌灵分子的所有原子在同一平面上,属于Cs对称性;其在银纳米溶胶表面具有十分显著的表面增强拉曼活性;分子中的S原子与银胶粒子发生吸附作用,并通过该分子的长轴方向垂直于银纳米银胶表面;可利用SERS光谱方法对痕量的噻菌灵进行快速检测。为研究噻菌灵的特性以及其快速检测提供了理论和实验依据。     

金膜与银膜光纤SPR传感器

不同的金属传感层对光纤SPR传感器的特性有着重要的影响.根据该传感器的理论公式,计算了金膜、银膜传感器的输出光谱,并与实验结果进行了比较.结果表明,银膜光纤SPR传感器的理论输出光谱和实验检测光谱吻合很好,而金膜吻合较差.分析了出现这种偏差的原因.     

Quantitativer Vergleich von berechneten und gemessenen Elektronen-Energieverlustspektren an Silber

Energy loss measurements on the plasma loss of silver have been carried out with monochromatic 51 keV electrons. The loss spectra were compared with calculated ones. If retardation is taken into account, the intensity formula describes the experimental results correctly. The experiments were extended to silver foils with extremely fine crystallites. These films have a dielectric constant with a higher imaginary part (?₂) than the usual silver foils. The calculated spectra are again in good agreement with the observed ones, if retardation is taken into account.     

On the Fluorescence of Luminol in a Silver Nanoparticles Complex

The photophysical properties of luminol in a silver nanoparticles complex have been studied by steady-state and time resolved fluorescence spectroscopy. The effect of the serum albumin on the luminol fluorescence in the silver nanoparticles has been also investigated. It was found that the fluorescence quantum yield value of luminol in a silver nanoparticles complex is ??=?0.00407. The decrease of the average fluorescence lifetime value of the luminol in the silver nanoparticles complex was found to be low, <τ>?=?1.712 ns. The luminol does not bind to the serum albumins in the presence of silver nanoparticles. The formation of a new species of luminol on silver nanoparticles is discussed. The results have influence regarding the use of luminol as an assay for bio-analytical applications.     

Theoretical and experimental conductivities of silver halide-silver sulfide ISE membranes

In a previous paper, the Smith-Anderson particulate conductivity model has been extended to particulate ISE membranes. In this paper, theoretically calculated results are compared with experimentally measured results for silver halide-silver sulfide ISE membranes. Calculated and experimental ionic conductivities are in very good agreement. Calculated and experimental electronic conductivities are in poor agreement. The possible reasons for the latter are discussed.     

Thermo optical response and optical limiting in Ag and Au nanocolloid prepared by laser ablation

Optical limiting of the gold and silver nanocolloids has been studied under CW illumination at 532 nm. Nonlinear and thermo optical properties of the samples were investigated using CW Z-scan experiments. Sign of nonlinear refraction coefficient of colloids are negative at this condition. Negative sign implying thermal self defocusing is the most important mechanism of nonlinearity in our experiments. Diffraction pattern and greater magnitude of nonlinearities shows that gold nanocolloid is a better optical limiter than silver nanocolloid in the same experimental condition. Also thermo optical coefficient and limiting threshold of the samples have been determined.