Cathodic deposition of silver on silver bromide at microelectrodes

The cathodic deposition of silver metal on single crystalline silver bromide leads to deposits with different morphologies depending on the cathode geometry and the current density. The deposition at an extended planar electrode results in the growth of silver whiskers. The deposition at a point (micro-)electrode results in dendritic deposits on the surface of the solid electrolyte. The morphological development of the deposits is studied with microelectrodes of different diameters. A characteristic change from dendritic to whisker growth at microelectrodes upon time is always found. As the reason for the change of the growth mode from dendritic to whisker-type, the changing electric field distribution around a growing surface deposit is discussed.     

Extraction of silver from a refractory silver ore by sono-cyanidation

In this study, effect of ultrasound on silver extraction from a refractory silver ore containing both native silver and various silver sulphide minerals was investigated. Main effects and interaction effects of pulp density, ultrasonic frequency, cyanide concentration, air flow rate and agitation speed on the extraction rate of silver were studied by a two-level fractional factorial experimental design. A few additional cyanidation tests were also conducted to verify the findings of the designed experiments.It was found that the overall extraction yield was varied from 67% to 90% depending on the operating conditions used in the sono-cyanidation tests (48 h). However, it was varied from 63% to 80% by same operating conditions used in the direct cyanidation tests at the same cyanidation time. It was observed that an increase in the ultrasonic frequency has a negligible effect on the silver recovery. More importantly, it was determined that there were insignificant differences between the 24-h sono-cyanidation results and the 48-h direct cyanidation results for each cyanidation conditions. This finding, which is very important from the cyanidation practice standpoint, indicates that the cyanidation time can be reduced up to 50%, or the capacity of an operating silver extraction plant can be increased up to 100% by the sono-cyanidation by the refractory silver ores. In order to describe the rate of silver dissolution in the cyanide solutions, the experimental data were analysed using shrinking core models. It was found that there is a good fit between the experimental data and the models, indicating the rate of silver dissolution in cyanide can be described by a two-stage, porous layer diffusion controlled, shrinking core model.     

Corrosion processes of triangular silver nanoparticles compared to bulk silver

Excessive corrosion of silver nanoparticles is a significant impediment to their use in a variety of potential applications in the biosensing, plasmonic and antimicrobial fields. Here we examine the environmental degradation of triangular silver nanoparticles (AgNP) in laboratory air. In the early stages of corrosion, transmission electron microscopy shows that dissolution of the single-crystal, triangular, AgNP (side lengths 50–120 nm) is observed with the accompanying formation of smaller, polycrystalline Ag particles nearby. The new particles are then observed to corrode to Ag₂S and after 21 days nearly full corrosion has occurred, but some with minor Ag inclusions remaining. In contrast, a bulk Ag sheet, studied in cross section, showed an adherent corrosion layer of only around 20–50 nm in thickness after over a decade of being exposed to ambient air. The results have implications for antibacterial properties and ecotoxicology of AgNP during corrosion as the dissolution and reformation of Ag particles during corrosion will likely be accompanied by the release of Ag⁺ ions.     

On the formation of silver specks in silver halide crystals

This theoretical study summarizes ionic and electronic processes in AgBr crystals and the influence of its results on photographic process. It deals with the importance of surface generated interstitials which Gurney and Mott left untouched because of the non-availability of sufficient data at that time. The magnitude of various parameters,e.g., mean intra-electron-ion distance in a latent image site, the rate of neutralization of Ag⁺ ion with trapped electron and capture cross-section for combination of Ag⁺ ion with the trapped electron, etc. (as desired for understanding the theory of photographic process) are calculated at different temperatures. The results when used in our earlier papers (Singh and Sharma, 1974 and 1975, and Singh 1975) for calculating charged particle track characteristics theoretically were found to give good agreement with the published experimental data (Della Corteet al 1953 and Dyer and Hechman 1967). A model for the mechanism of latent image formation (silver speck) is discussed.     

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     

Formation of silver colloids in silver ion-exchanged soda-lime glasses during annealing

The structural and compositional changes of the soda-lime glasses during the formation of the silver colloids were analyzed by the X-ray Photoelectron Spectroscopy (XPS) in order to examine the silver colloid formation mechanism. The in situ behavior of silver and SiO₂ networks on the surfaces of silver ion-exchanged soda-lime glasses during heating and cooling processes in ultra-high vaccum was monitored. The results showed that silver diffuses toward the surface, precipitates, and crystallizes during heating and the total silver surface concentration is slowly increased during cooling. The concentration changes of oxidized and neutral Ag, a new non-bridging oxygen species (NBO^*), and a new silicon species (Si[a]) were applied to deduce a disappropriation reaction mechanism of Ag⁺ on the surface during annealing. The SiO₂ network is modified at temperatures below 350°C to accommodate more silver on the surface and to balance the extra charge carried by the Ag⁺. That the SiO₂ network polymerizes during annealing was deduced from the results of the higher binding energies of Si2p and O1s after annealing. This observation suggests that the reduction of the Gibbs free energies and the relaxation of tensile stress result in the formation of the silver colloids under thermal annealing.     

Surface plasmon–exciton transition in ultra-thin silver and silver iodide films

Silver thin films in the thickness range 2–10 nm produced by thermal evaporation onto glass substrates were systematically iodized and carefully characterized by X-ray diffraction, atomic force microscopy (AFM) and optical absorption spectroscopy. While the uniodized films are X-ray amorphous in keeping with their quasi-continuous nature and 2D islanded structure, briefly iodized films showed characteristic beta AgI structure. Most interestingly, AFM of Ag films revealed uniform triangle-shaped embryos whose shape does not change appreciably upon iodization. Optical absorption spectra of uniodized Ag films show intense surface plasmon resonance (SPR) features with maxima at 440, 484 and 498 nm for the films of thicknesses 2, 5 and 10 nm, respectively, with 5 nm films showing properties characteristic of optimally matched dielectric and electronic properties of the substrate and sample, respectively. Finally, an interesting and unique SPR–exciton phase transition is observed as the ultra-thin films are progressively iodized. These Ag and AgI films could be promising candidates for plasmonic and nanophotonic applications. PACS 78.66.-w; 73.20.Mf; 71.35.Cc; 42.70; 68.37.Ps; 42.82.-m     

Transparent chromatic electrode using the mixture of silver nanowire and silver nanoprism

In this research, we studied a chromatic transparent silver nanowire (Ag NW) electrode using a silver nanoprism (Ag NP). Ag NW and Ag NP were produced using a chemical synthesis method (polyol method) and deposited on substrate via spray method.The Ag NW electrode showed a more than 80% transmittance and no or low conductivity without high temperature annealing process. In the case of applying an annealing process, a 13 Ω/□ sheet resistance was measured.The electrode, which consisted of a mixture of Ag NW and Ag NP, showed a reduced transmittance of about 70%. However, by applying Ag NPs to a conventional bare Ag NW electrode, we were able to add a chromatic characteristic to the transparent electrode; this addition was induced by the localized surface plasmon resonance (LSPR) and the low sheet resistance, even though no annealing process was applied.     

Friction of steel and silver on silver as a function of temperature

The peak frictional coefficient increases with the roughness of the surface, while it moves to lower temperature. The friction of silver on silver has a positive temperature coefficient.     

Luminescence of silver chlorides

It was found that single crystals of silver chloride without admixtures, prepared in the Institute of Physics of Charles University, exhibit a luminescent colour change at the temperature of liquid air. According to the change in luminescence the crystals can be divided into three groups —those with predominant red-orange, green-blue and blue-green luminescence.This paper briefly describes the factors influencing the colour changes in the luminescence of silver chloride. More details on the experiments and the connection between the changes in luminescence and the absorption will be given later.In conclusion the author thanks R. Kiradjieffová for her great help in the work.     

Stellate superhydrophobic silver particles

Stellate silver particles, which have from 24 to 56 arms with a length of 30–40 μm, have been synthesized for the first time. The synthesis has been performed by the chemical reduction of an aqueous solution of silver nitrate by a urea alkaline solution under illumination at room temperature. Stellate Ag particles are hydrophobic and have the relative density lower than the density of water. Varying pH and the relation between the concentrations of reagents, one can obtain superhydrophobic powders and films consisting of stellate Ag particles with different lengths of arms.     

Positronium formation from silver

Characterization of a positronium (Ps) gas target to be used for the charge conjugate reaction for antihydrogen formation [1], namely proton + Ps-atom → hydrogen + positron, has been performed [2–4]. In the above collision the Ps target utilised is produced efficiently on the transmission side of a hot thin (1900 Å) Ag(100) foil with 12% efficiency at 800 K foil temperature, with a mean velocity of thermally activated Ps of 1.2×10⁵ m/s and with a maximum kinetic energy of prompt emitted Ps of 1.5±0.2 eV.     

Self-diffusion in polycrystalline silver

An experimental study of self-diffusion in polycrystalline silver has been carried out using the radioisotope Ag-110. The electrolytic sectioning technique was used for measuring. This method made it possible to determine the temperature range in which the self-diffusion of silver is not influenced by grain-boundary diffusion. The temperature was found where the grain-diffusion predominates over the volume diffusion so that the grain-boundary diffusion coefficient can be estimated by Fischer's treatment. Finally, it was found that the temperature range of 619°C< <718°C is the transition region where the electrolytic sectioning technique does not permit the volume or grain-boundary diffusion coefficients to be determined.     

Fabrication of silver stabilization layer of coated conductor using organic silver complexes

Silver stabilizing layer of coated conductor has been prepared by dip coating method using organic silver complexes containing 10 wt.% silver as a starting material. Coated silver complex layer was dried in situ with hot air and converted to crystalline silver by post heat treatment in flowing oxygen atmosphere. A dense continuous silver layer with good surface coverage and proper thickness of 230 nm is obtained by multiple dip coatings and heat treatments. The film heat treated at 500 °C showed good mechanical adhesion and crystallographic property. The interface resistivity between superconducting YBCO layer and silver layer prepared by dip coating was measured as 0.67 × 10⁻¹³ Ω m².     

Lattice dynamics of silver

The phonon dispersion curves of silver have been measured in the main symmetry directions at room temperature by coherent inelastic scattering of thermal neutrons using a correlation technique. The experimental results have been analyzed with parametrized expressions which have been derived from interatomic model potentials. With the Born-von Karman force constant model thermodynamic properties of silver could be calculated in good agreement with experimental results. Through the use of electron-ion model potentials the lattice dynamics of silver was correlated with its electronic properties. The results for some of those properties are compared with corresponding experimental values.     

Kinetic aspects of the silver ion release from antimicrobial polyamide/silver nanocomposites

Spherical silver nanoparticles were grown in situ in different polyamides by a thermal reduction of silver acetate during melt processing of the polymers. Most of the particles have a diameter of about 20 nm. The absolute amount as well as the kinetics of the silver ion release from the various polyamide/silver nanocomposites differ strongly, although the filler content in all materials is the same (1.5 wt. %) and the morphologies of the silver particles are not very different. One result of the investigations was that the absolute amount of the long-term silver ion release increases exponentially with the maximum water absorption of the polymers used as matrix materials, because silver ions are formed from elemental silver particles in the presence of water, only. Moreover, it was also found that the long-term silver ion release increases with a growing diffusion coefficient of water in the polymer. The water absorption properties of the polymers govern the kinetics of the silver ion release, too: for strong hydrophilic polyamides like PA6 or PA6.6, which are plasticized by water, the silver ion release is a zero-order process. For nanocomposites with less hydrophilic polyamides like a cycloaliphatic polyamide or a P12 modified with polytetrahydrofurane (PA12-poly-THF), the silver ion release is governed by diffusion. As expected from the efficacy of the silver ion release, PA6, PA6.6, PA12 and PA12 modified with polytetrahydrofurane and a cycloaliphatic polyamide filled with 1.5 wt. % of silver nanoparticles are active against Escherichia coli. But, only nanocomposites with PA6, PA6.6 and P12-poly-THF as matrix materials are suitable as long-term biocidal materials. PACS 68.35.bm; 68.35.Fx; 68.37.Lp     

A new molecular silver precursor for the preparation of thin conductive silver films

The synthesis and characterization of a new molecular silver precursor is reported. The presented complex [Ag(DioxoNic)₂]NO₃ (DioxoNic=(2,2-Dimethyl-1,3-dioxolan-4-yl)methyl nicotinate) can be obtained by the reaction of silver(I) nitrate and (2,2-Dimethyl-1,3-dioxolan-4-yl)methyl nicotinate in ethanol. The product crystallizes in the monoclinic space group P21/c (No. 14). Concentrated ethanolic solutions allow the fabrication of thin films via dip coating. Using UV-irradiation and subsequent moderate temperature treatment compact films of elemental silver can be obtained. The resulting silver films show excellent electrical properties with sheet resistances down to 0.7 Ω/sq at a film thickness of 25 nm corresponding to a specific electrical resistance of 1.75×10⁻⁸ Ωm very close to the value of bulk silver. For the potential application in optoelectronic devices, the complex was tested as an ink in a soft printing process for the preparation of patterned silver films.     

Light induced silver and copper plating on silver screen-printed contacts of silicon solar cells

In this paper we present the results of solar cell’s screen printed contacts thickening by light induced plating (LIP) of Cu and Ag. Light-induced and light-assisted plating techniques are compared. Plating bath current versus illumination intensity, the potentials of metallic anode, front and back surfaces of the solar cell were measured and analyzed for all possible plating modes. The current-voltage behaviour of cells under illumination in a plating bath for the cases of electrically insulated and non-insulated back-surface of a cell is analyzed and discussed. Finally, the exact values of current/voltage/illumination intensity for optimal depositions and a general recipe for their determination for different plating materials are given.