Der geschichtliche Abbau des Silbers erfolgte bereits vor etwa 6000 Jahren. Silber wurde meistens zu Schmuck und Münzen verarbeitet. Es ist ein weiches Metall und l?sst sich daher leicht bearbeiten. In d
Der geschichtliche Abbau des Silbers erfolgte bereits vor etwa 6000 Jahren. Silber wurde meistens zu Schmuck und Münzen verarbeitet. Es ist ein weiches Metall und l?sst sich daher leicht bearbeiten. In diesem Beitrag wird haupts?chlich über die Silbergewinnung in ?gypten, Spanien, Deutschland, Südamerika und USA berichtet. Einer der bekanntesten Silberforscher war Justus von Liebig, der erstmalig Knallsilber beschrieb.
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Stable concentrated aqueous dispersions of silver nanoparticles of narrow size distribution were prepared by reducing silver nitrate solutions with ascorbic acid in the presence of Daxad 19 (sodium salt of a high-molecular-weight ...
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Stable concentrated aqueous dispersions of silver nanoparticles of narrow size distribution were prepared by reducing silver nitrate solutions with ascorbic acid in the presence of Daxad 19 (sodium salt of a high-molecular-weight naphthalene sulfonate formaldehyde condensate) as stabilizing agent. The latter has ecellent ability to preent the aggregation of nanosize silver at high ionic strength and high concentration of metal (up to 0.3 mol dm~(-3)). The presence of the dispersing agent on the surface of silver particles was confirmed by ATR-FTIR spectroscopy and electrokinetic measurements, explaining both the negative charge over the entire pH range and the electrosteric effect responsible for their long-term stawbility. The other experimental conditions, i.e., the pH of the reacting solutions, the concentration of the stabilizing agent, and the metal/dispersant ratio, also have a significant impact on the size and stability of these dispersions. The final nanosize silver can be obtained as drived powder, and can be fully redispersed in deionized water by sonication.
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A much studied oil-soluble surfactant, bis[2-ethylhexyljsulfosuccinate, sodium salt, was ion exchanged into the silver ion form and dissolved into microemulsionsof immiscible polyurethane step monomers. Coating andcuring of these ...
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A much studied oil-soluble surfactant, bis[2-ethylhexyljsulfosuccinate, sodium salt, was ion exchanged into the silver ion form and dissolved into microemulsionsof immiscible polyurethane step monomers. Coating andcuring of these microemulsions produced polyurethanecoatings that exhibit bactericidal activity against representative Gram negative bacteria. After 24 h exposure, 0.006-0.012% weight Ag relative to coating weight (0.0013-0.0025 mu mol Ag/cm~2) results in the three-log reduction in Escherichia coli. A slightly higher level of 0.031% weightAg relative to coating weight (0.006 mu mol Ag/cm~2) killedall of the E. coli after 12 h exposure. Similar results wereobtained for Pseudomonas aeruginosa. Since the doubletail surfactant anion promotes reverse micelle formation in many different kinds of oils and solvents, it appears anexcellent vector for incorporating low and effectiveamounts of silver ion into many industrial, hospital, andhousehold coating formulations.
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A simple, rapid, and environmentally friendly process using hydrogen peroxide, was developed for recovering high purity silver directly from industry and laboratory wastes. Silver ammine complex, [Ag(NH3)(2)]+CI-, derived from AgC...
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A simple, rapid, and environmentally friendly process using hydrogen peroxide, was developed for recovering high purity silver directly from industry and laboratory wastes. Silver ammine complex, [Ag(NH3)(2)]+CI-, derived from AgCI were generated and then directly reduced using H2O2 to reliably turn into high purity microcrystalline silver (99.99%) examined by EDS and XRD. Morphology of the recovered silver microcrystals could be selectively tuned by an addition of poly(vinyl pyrrolidone). The main parameters in the recovering process including pH, concentration of Ag+ and the mole ratio of H2O2:Ag+ were carefully optimized though the central composite design (CCD). The optimized condition was employed for a trial recovery of 50 L silver ammine complex prepared from a collection of silver-wastes during 3-year research on industrial nanoparticle production. The recovered silver microcrystals >700 g could be recovered with 91.27%. The remaining solution after filtering of the recovered silver micro crystals can be used repeatedly (at least 8 cycles) without losing recovery efficiency. Matrix interferences including Pb2+ and Cl play a minimal role in our silver recovery process. Furthermore, the direct usage of the recovered silver microcrystals was demonstrated by using as a raw material of silver clay for creating a set of wearable silver jewelries. (C) 2017 Elsevier Ltd. All rights reserved.
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Silver nanoparticles were produced with AgF as the starting Ag(I) salt, with pectin as the reductant and protecting agent. While the obtained nanoparticles (pAgNP-F) have the same dimensional and physicochemical properties as thos...
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Silver nanoparticles were produced with AgF as the starting Ag(I) salt, with pectin as the reductant and protecting agent. While the obtained nanoparticles (pAgNP-F) have the same dimensional and physicochemical properties as those already described by us and obtained from AgNO3 and pectin (pAgNP-N), the silver nanoparticles from AgF display an increased antibacterial activity against E. coli PHL628 and Staphylococcus epidermidis RP62A (S. epidermidis RP62A), both as planktonic strains and as their biofilms with respect to pAgNP-N. In particular, a comparison of the antimicrobial and antibiofilm action of pAgNP-F has been carried out with pAgNP-N, pAgNP-N and added NaF, pure AgNO3, pure AgF, AgNO3 and added NaF and pure NaNO3 and NaF salts. By also measuring the concentration of the Ag+ cation released by pAgNP-F and pAgNP-N, we were able to unravel the separate contributions of each potential antibacterial agent, observing an evident synergy between p-AgNP and the F? anion: the F? anion increases the antibacterial power of the p-AgNP solutions even when F? is just 10 μM, a concentration at which F? alone (i.e., as its Na+ salt) is completely ineffective.
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Dentists used silver-containing solutions for deep cavity disinfection before restoration. This review aims to identify the silver-containing solutions reported in the literature for deep cavity disinfection and summarize their ef...
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Dentists used silver-containing solutions for deep cavity disinfection before restoration. This review aims to identify the silver-containing solutions reported in the literature for deep cavity disinfection and summarize their effects on dental pulp. An extensive search was performed using the search words "(silver) AND (dental pulp OR pulp)" in ProQuest, PubMed, SCOPUS, and Web of Science to identify English publications on silver-containing solutions for cavity conditioning. The pulpal response to the included silver-containing solutions was summarized. The initial search identified 4112 publications and 14 publications met the inclusion criteria. Silver fluoride, silver nitrate, silver diamine nitrate, silver diamine fluoride, and nano-silver fluoride were used in deep cavities for antimicrobial purposes. Indirect silver fluoride application induced pulp inflammation and reparative dentine in most cases, and pulp necrosis in some cases. Direct silver nitrate application caused blood clots and a wide inflammatory band in the pulp, whilst indirect silver nitrate application caused hypoplasia in shallow cavities and partial pulp necrosis in deep cavities. Direct silver diamine fluoride application induced pulp necrosis, while indirect silver diamine fluoride application induced a mild inflammatory response and reparative dentine formation. No evidence of the dental pulpal response to silver diamine nitrate or nano-silver fluoride was available in the literature.
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A series of experiments for obtaining modified with silver nanoparticles ultra-high molecular weight polyethylene (UHMWPE) is done. Optimal precursors are silver trifluoroacetate, silver nitrate and silver methanesulfonate. Three ...
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A series of experiments for obtaining modified with silver nanoparticles ultra-high molecular weight polyethylene (UHMWPE) is done. Optimal precursors are silver trifluoroacetate, silver nitrate and silver methanesulfonate. Three variants of UHMWPE modification is studied: 1) the polyol synthesis, 2) polymer processing silver nanoparticle colloid and 3) reduction of silver salt solution in the UHMWPE polymer matrix. It is found that the last method is optimal. The specific surface of obtained nanoparticles is 7.1-7.6 m~2/g and the size varies in the range of 60-110 nm. The antibacterial activity of the composite samples to ￡ Coli and S. Aureus is studied. Inhibition of bacterial growth occurs at the level 10~4 cfu/ml and 10~6 cfu/ml respectively.
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Levofloxacin is a third generation fluoroquinolone antibiotic with a broad-spectrum including both Gram positive bacteria and Gram negative bacteria, as well atypical bacteria. In order to extend the spectrum of activity and to ad...
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Levofloxacin is a third generation fluoroquinolone antibiotic with a broad-spectrum including both Gram positive bacteria and Gram negative bacteria, as well atypical bacteria. In order to extend the spectrum of activity and to add new biological effects, several metal complexes of levofloxacin have been obtained and reported recently. The aim of our study was to obtain new silver complexes with levofloxacin with potential broad spectrum antibacterial and antifungal activity. Therefore three new silver complexes of levofloxacin with the proposed chemical structures (levofloxacin)(2)Ag(NO3), (levofloxacin)(2)Ag(NO3)(CH3OH) and (leyofloxacin)Ag(C6H6O7)center dot 3H(2)O were synthesized. In order to characterize the obtained complexes elemental analysis, conductivity measurement, spectroscopic, and thermal methods were used. Optimized molecular structures were determined using DFT (density functional theory) analysis. The antibacterial activity against Gram negative and Gram positive bacteria and antifungal activity against Candida spp of the complexes was tested by determination of minimum inhibitory concentration through microtitre broth dilution method. (C) 2016 Elsevier B.V. All rights reserved.
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A mechanism based on electrochemical, spectrophotometric and scanning electron microscopy (SEM) data in alkaline media is proposed for the generation of Ag(III) in the form of Ag(OH)_4~-. The formation of Ag(III) from Ag~0 is a ra...
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A mechanism based on electrochemical, spectrophotometric and scanning electron microscopy (SEM) data in alkaline media is proposed for the generation of Ag(III) in the form of Ag(OH)_4~-. The formation of Ag(III) from Ag~0 is a rather complex multistep process that involves several steps. The presence of soluble Ag(I) species as Ag(OH)_2~- is of paramount importance for the production of soluble Ag(OH)_4~-, whose decomposition time is shown to exceed 8 h.
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