Papers by Keyword: Silver

Abstract: The temperature and concentration dependences of kinematic viscosity of alloys of Cu-Ag system with Ag content to 99 mass % in liquid state have been studied. It has been found that heating above certain critical temperatures leads to transform the melt to equilibrium state. The kinematic viscosity of the Cu-Ag melts are extremely depend from silver content in the alloy. The new regime of amorphous ribbon production is selected. Proposed regime leads to increasing of microhardness and weld strength on 10 % and corrosion resistivity on 15 %.

Abstract: The nanosized silica (SiO₂) with the size less than 100 nm have successfully been prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) via a modified Stöber method at room temperature. The experiment was conducted by controlling the amount of the catalyst used, i.e., ammonium hydroxide (NH₄OH). The morphology observation of the synthesized silica nanoparticles was conducted by using a transmission electron microscope (TEM). It was found that the size of the silica depending on the amount of the catalyst used, with homogenous size ranging from 10 to 360 nm. The doping of silver nanoparticles was done by mixing the synthesized silica with the silver ions (Ag⁺) solutions. Then the sample was annealed for 75 min which results in the nucleation of the silver nanoparticles less than 20 nm onto the silica surfaces, depending on the temperature used.

Abstract: A simple fluorescent iodide ion sensor was fabricated. Ag⁺ was found to specifically induce the aggregation of perylene–3, 4, 9, 10–tetracarboxylate tetrapotassium salt (PTK) in water, simultaneously, fluorescence of PTK was quenched. The resultant PTK–Ag⁺ aggregates showed a "turn–on" fluorescence response for halide ion, especially I^-, and excellent selectivity toward possible interfering anions, contain sulfide.

Abstract: In addition to the good electrochemical performance criteria in solid oxide fuel cell (SOFC) applications, cathode material must match thermal expansion with other SOFC components. Thus, effects of Ag on thermal mismatch, chemical reactions, and microstructure are investigated. Ag (1 wt% to 5 wt. %) was mixed with La₀.₆Sr₀.₄Co₀.₂Fe₀.₈O_3-δ (LSCF6428) and Sm-doped ceria carbonate (SDCC) composite cathode powder. LSCF6428-SDCC-Ag samples were sintered at 600 °C for 2 h. The thermal expansion coefficients (TECs), which were determined using a dilatometer, indicated relatively less TEC mismatch between LSCF-SDCC-Ag cathodes composite and SDCC electrolyte. The average TEC value obtained from 20 °C to 600 °C implied that LSCF-SDCC-A5 (5 wt. % Ag) showed better thermal matching (13.18×10⁻⁶ K⁻¹) with SDCC electrolyte (12.84×10⁻⁶ K⁻¹) and achieved better compatibility. The X-ray diffraction patterns indicated that the LSCF6428-SDCC-Ag peak increased with the increase in the amount of Ag. Scanning electron microscopy analysis showed that Ag was capable of maintaining the porosity that is required for cathodes (20%–40%). Results showed that Ag exhibited desirable thermal and chemical compatibility with LSCF-SDCC. Thus, LSCF6428-SDCC-Ag can be used as a composite cathode for low-temperature SOFCs.

Abstract: This paper discusses the effect of reaction time and temperature of silver-copper nanoparticles prepared by a polyol method. In this study, silver-copper nanoparticles were synthesized through the green approach of polyol method using ethylene glycol (EG) as green solvent and reductant, and polyoxyethylene-(80)-sorbitan monooleate (Tween 80) as a nontoxic stabilizer. The phase and morphology of silver-copper nanoparticles were characterized by X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM). The results XRD confirmed silver and copper nanoparticles to be phase-pure crystalline silver and copper with face-centered cubic (fcc) structure on the basis of XRD analyses. FESEM analysis confirmed the existence of Ag and Cu nanoparticles.

Abstract: Heterostructure of Ag/ZnO was synthesized by a reduction of Tollen’s reagent on ZnO powders. The photocatalytic activity of Ag/ZnO was investigated through the degradation of three different dye solutions (methylene blue, rhodamine B and reactive orange 16) under visible light using the fluorescent lamps with a 420 nm longpass filter. The efficiencies of dye degradations for all three dyes by Ag/ZnO are better than that of pure ZnO. Furthermore, the parameters including photocatalyst loadings and initial pHs of dye solutions were also studied. The photocatalytic degradations for all three dyes were increased with the increasing of catalyst loadings. The effect of pHs on photocatalytic activity of Ag/ZnO can be explained by the interaction between the charge on the surface of photocatalyst and the charge of dye ions.

Abstract: Novel hybrids, comprised of a biologically active protein molecule core, coated with a thin outer layer of porous metallic silver, were developed in our lab. By the conjugation of silver reducing polymer to the surface of soluble, molecular, biologically active protein molecules and subsequent addition of silver salt, electroless silver deposition, culminating in thin porous metallic coating, was directed to the surface of the protein molecules. The silver-protein hybrids thus obtained, presenting novel nanoparticles several nanometers in size, retained their solubility and biological activity.The silver coating combined with the retained biological activity of its protein core, paved the way to a series of biomedical applications of these hybrids including "wiring" of the active site of oxido-reductase enzyme to electrodes, imaging of the presence of targeted ligands displayed on cancer cell surface and antimicrobial enzymatically attenuated release of silver ions.In this presentation we shall overview the technology of protein-silver hybrid's fabrication and analytical applications of silver-glucose oxidase and silver-Avidin hybrids, followed by feasibility demonstration of using silver-glucose oxidase hybrid as novel antibacterial and antifungal agent.

Abstract: Elimination of the residual microorganisms from an infectious bone defects and the prevention of subsequent re-infection are of importance for chronic osteomyelitis treatment. The application of bone repair materials with antibacterial properties in such a condition has advantages. The present study reported a novel method to fabricate nanohydroxyapatite/polyurethane (n-HA/PU) based antibacterial porous scaffolds through immobilization "core-shell" silver-based mesoporous silica particles (Ag@SiO₂), i.e., silver nanoparticle as core and mesoporous silica as shell, on the surface of n-HA/PU scaffold. The samples were characterized by Scanning Electron Microscope (SEM) and antibacterial tests. The results revealed that the Ag@SiO₂ nanoparticles distributed uniformly on the surface of n-HA/PU porous scaffold. The Ag@SiO₂ could been kept on the surface of n-HA/PU porous scaffold more than 2 weeks, resulting in long-lasting the release of silver ions and antibacterial ability. The porous n-HA/PU scaffolds with an antibacterial surface may hold promise to be used in infectious bone defects repair.

Abstract: Compared with the lithography and traditional technology, ink-jet printing technology has huge advantages such as reducing costs, improving production efficiency and reducing environment damage. The silver nanoparticles conductive ink used as core material in ink-jet printing technology has been greatly developed. At present, the conductive inks for printed circuit usually has high sintering temperature, low adhesion, poor mechanical properties, high cost, which limit the further industrial application. In this paper, nano silver pulp was prepared through liquid phase reduction method, and a self-made protective agent ensured that the particle size distribution of silver particles is about 5nm. The above silver pulp was dispersed in the organic resin to get conductive ink with 20% (wt%) silver content. Under 170°Csintering, the electrical conductivity of the ink layer was 1.15×104S/m.

Abstract: The use of bone substitutes for recovery of lost function is a constant search within the medical field. So biomaterials have received a very large attention from the scientific community, including the materials the basis of calcium phosphate. Hydroxyapatite (HA) has been studied as apart from representing the natural constitution of the mass of bones and teeth in 30 to 70 %, has properties of bioactivity and osteoconductivity, encouraging and assisting the growth of bone tissue. In contrast, bacterial infections can arise after implantation causing the loss of functionality in the short and medium term. Several alternatives are being tested, usually associated with the use of conventional antibiotics incorporated into biomaterials. An alternative to antibiotics would be use such metals that possess antibacterial properties. Silver (Ag) is known as a bactericidal metal and so gained a prominent place among the studies as an important ally in the control of post-surgical infections. This work aimed to synthesize, characterize and evaluate the antimicrobial effect of the addition of silver ions into hydroxyapatite. The hydroxyapatites containing silver were obtained by the precipitation method in aqueous solution containing AgNO₃ and by immersing the powder after the precipitation process in aqueous solutions containing AgNO₃. At this stage of the work, were analyzed and characterized the crystalline phases and the ionic groups present in HA, HA precipitates with Ag and immersed in a solution of Ag. X-ray diffraction (XRD) spectra showed that regardless of the method used, precipitation (room temperature or 90°C) or by immersion, the metallic Ag was present in the structure of HA. Additionally, it was observed that the peaks indicated in the XRD pattern for HA corresponding to the diffraction pattern of plugs JPCDS 09-0432 (Joint Committee on Powder Diffraction Standards). No peaks related to the phases being observed β-TCP and CaO, respectively, indicating that the conditions adopted for obtaining HA Ag, only HA phase is present and that methods, precipitation and immersion are efficient to occur doping of HA with Ag