Contribution of the hydrostatic pressure to the shape of silver island particles

NASA Astrophysics Data System (ADS)

Anno, E.; Hoshino, R.

1984-09-01

We have investigated the shape change of silver island particles caused by the surface energy reduction. When the surface energy was reduced by the reaction with hydrogen sulfide, the flattening of the particles was observed. As is well known, the similar shape change takes place when the particle size increases. Therefore, the particle shape is considered to depend both on the surface energy and the particle size. From this consideration, we predict the contribution of the hydrostatic pressure P to the particle shape. As evidence of this contribution, we consider the existence of the critical size below which P is larger than the adhesive force FA between deposit and substrate surface. Investigating the influence of the flattening due to the surface energy reduction on the size distribution, the critical size is found and estimated to be about 80 Å in diameter. This value is comparable with that estimated from the condition P = FA.

Antimicrobial action of silver nitrate.

PubMed

Richards, R M

1981-01-01

Silver nitrate 3 mug/ml prevented the separation into two daughter cells of sensitive dividing cells of Pseudomonas aeruginosa growing in nutrient broth plus the chemical. Cell size of sensitive cells was increased and the cytoplasmic contents, cytoplasmic membrane and external cell envelope structures were all abnormal. P. aeruginosa cells grown in the presence of silver nitrate 9 mug/ml showed all these changes to a marked degree except inhibition of cell division was not observed. Silver nitrate (1.5 mug/ml) in distilled water inactivated bacteriophage T2 particles as determined by their infectivity to Escherichia coli B cultures. Lysozyme (50 mug/ml) reduced, and sodium chloride (0.9%) blocked this activity.

Extraction of three-dimensional silver nanostructures with supercritical fluid

NASA Astrophysics Data System (ADS)

Taguchi, Natsuo; Takeyasu, Nobuyuki; Kawata, Satoshi

2018-02-01

In a previous report, a self-growing approach was proposed for fabricating complex silver nanostructures, where silver dendrites were grown at silver nanoseeds in silver ion solution owing to plasmonic heating with ultraviolet light. Structures were deformed or destroyed when they were extracted with acetone and dried in air. In this Letter, we discuss the use of supercritical carbon dioxide fluid for the nondestructive extraction of nanostructures. We show the experimental results and discuss the laser power dependence of resultant structures. Another experiment was performed for nanostructure growth inside an agarose gel as a matrix. Silver nanostructures were immobilized without damage in an agarose skeleton network.

Leaf chemical composition of twenty-one Populus hybrid clones grown under intensive culture

Treesearch

Richard E. Dickson; Philip R. Larson

1976-01-01

Leaf material from 21 nursery-grown Populus hybrid clones was analyzed for three nitrogen fractions (total N, soluble protein, and soluble amino acids) and three carbhydrate fractions (reducing sugars, total soluble sugars, and total nonstructural carbohydrates-TNC). In addition, nursery-grown green ash and silver maple, field-grown bigtooth and trembling aspen, and...

Synthesis and characterization of bactericidal silver nanoparticles using cultural filtrate of simulated microgravity grown Klebsiella pneumoniae.

PubMed

Kalpana, Duraisamy; Lee, Yang Soo

2013-03-05

Silver nanoparticles were synthesized by biological method using cultural filtrate of Klebsiella pneumoniae cultured under simulated microgravity and silver nitrate solution as precursor. The nanoparticles exhibited typical plasmon absorption maximum of silver nanoparticles between 405 and 407 nm. Spherical silver nanoparticles were found to have size between 15 and 37 nm by TEM analysis. XRD pattern corresponding to planes (111), (200), (220) (311) revealed the crystalline nature of the biosynthesized silver nanoparticles. FTIR spectrum proposed stabilization of silver nanoparticles by the protein molecules present in the cultural filtrate. The silver nanoparticles exhibited high bactericidal activity against Salmonella enterica, Escherichia coli and moderate bactericidal activity against Streptococcus pyogenes. Copyright © 2012 Elsevier Inc. All rights reserved.

A possible oriented attachment growth mechanism for silver nanowire formation

DOE PAGES

Murph, Simona E. Hunyadi; Murphy, Catherine J.; Leach, Austin; ...

2015-04-06

Electron microscopy studies suggest that silver nanowires prepared by an approach reported earlier by us (Caswell, K. K., Bender, C. M., Murphy, C. J. Nano Lett.,2003, 3, 667–669) form through a coarsening process via an oriented attachment mechanism. Initially, silver nucleation centers were produced by chemical reduction of silver ions in boiling water, with sodium citrate and sodium hydroxide as additives in solution. These nucleation centers, with a twinned crystallographic orientation, ultimately merge into fully grown silver nanowires. This is a completely different mechanism from the seed-mediated growth approach, which has also been used to produce silver nanowires. Furthermore, companionmore » molecular dynamics performed with the embedded atom method are in agreement with our experimental data.« less

A possible oriented attachment growth mechanism for silver nanowire formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murph, Simona E. Hunyadi; Murphy, Catherine J.; Leach, Austin

Electron microscopy studies suggest that silver nanowires prepared by an approach reported earlier by us (Caswell, K. K., Bender, C. M., Murphy, C. J. Nano Lett.,2003, 3, 667–669) form through a coarsening process via an oriented attachment mechanism. Initially, silver nucleation centers were produced by chemical reduction of silver ions in boiling water, with sodium citrate and sodium hydroxide as additives in solution. These nucleation centers, with a twinned crystallographic orientation, ultimately merge into fully grown silver nanowires. This is a completely different mechanism from the seed-mediated growth approach, which has also been used to produce silver nanowires. Furthermore, companionmore » molecular dynamics performed with the embedded atom method are in agreement with our experimental data.« less

Frictional behavior of atomically thin sheets: hexagonal-shaped graphene islands grown on copper by chemical vapor deposition.

PubMed

Egberts, Philip; Han, Gang Hee; Liu, Xin Z; Johnson, A T Charlie; Carpick, Robert W

2014-05-27

Single asperity friction experiments using atomic force microscopy (AFM) have been conducted on chemical vapor deposited (CVD) graphene grown on polycrystalline copper foils. Graphene substantially lowers the friction force experienced by the sliding asperity of a silicon AFM tip compared to the surrounding oxidized copper surface by a factor ranging from 1.5 to 7 over loads from the adhesive minimum up to 80 nN. No damage to the graphene was observed over this range, showing that friction force microscopy serves as a facile, high contrast probe for identifying the presence of graphene on Cu. Consistent with studies of epitaxially grown, thermally grown, and mechanically exfoliated graphene films, the friction force measured between the tip and these CVD-prepared films depends on the number of layers of graphene present on the surface and reduces friction in comparison to the substrate. Friction results on graphene indicate that the layer-dependent friction properties result from puckering of the graphene sheet around the sliding tip. Substantial hysteresis in the normal force dependence of friction is observed with repeated scanning without breaking contact with a graphene-covered region. Because of the hysteresis, friction measured on graphene changes with time and maximum applied force, unless the tip slides over the edge of the graphene island or contact with the surface is broken. These results also indicate that relatively weak binding forces exist between the copper foil and these CVD-grown graphene sheets.

Island of Luzon, Philippines

NASA Technical Reports Server (NTRS)

1990-01-01

In this north to south view of the Island of Luzon, Philippines (13.0N, 120.0E), the prominent Cordillera Central mountain range where gold, copper and silver are mined. The several large rivers that drain this region normally carry a heavy silt load to the sea but the absence of sediment plumes in this view is evidence of hot dry weather and lack of recent rains. Manila, the capital city is just visible at the south end of the island.

Deposition of hermetic silver shells onto copper flakes.

PubMed

Njagi, John I; Netzband, Christopher M; Goia, Dan V

2017-02-15

Continuous silver shells were deposited on copper flakes using a two-stage precipitation process. A tightly packed layer of silver nanoparticles was first formed on the surface of the base metal by galvanic displacement. The size of the noble metal particles and their distribution on the substrate were controlled using complexing agents and dispersants. A continuous Ag deposit was subsequently grown by reducing slowly [Ag(NH 3 ) 2 ] + ions with glucose. The final shell thickness was controlled by varying the amount of metal deposited in the second step. The electrical properties of resulting silver coated copper flakes are comparable to those measured for silver flakes of similar size and aspect ratio. By preventing the oxidation of copper cores up to 400°C, the hermetic noble metal shell dramatically extends the temperature range in which Ag/Cu flakes can successfully replace pure silver. Copyright © 2016 Elsevier Inc. All rights reserved.

Decreasing photobleaching by silver island films: application to muscle⋆

PubMed Central

Muthu, P.; Gryczynski, I.; Gryczynski, Z.; Talent, J.; Akopova, I.; Jain, K.; Borejdo, J.

2007-01-01

Recently it has become possible to study interactions between proteins at the level of single molecules. This requires collecting data from an extremely small volume, small enough to contain one molecule—typically of the order of attoliters (10−18 L). Collection of data from such a small volume with sufficiently high signal-to-noise ratio requires that the rate of photon detection per molecule be high. This calls for a large illuminating light flux, which in turn leads to rapid photobleaching of the fluorophores that are labeling the proteins. To decrease photobleaching, we measured fluorescence from a sample placed on coverslips coated with silver island films (SIF). SIF reduce photobleaching because they enhance fluorescence brightness and significantly decrease fluorescence lifetime. Increase in the brightness effectively decreases photobleaching because illumination can be attenuated to obtain the same fluorescence intensity. Decrease of lifetime decreases photobleaching because short lifetime minimizes the probability of oxygen attack while the fluorophore is in the excited state. The decrease of photobleaching was demonstrated in skeletal muscle. Myofibrils were labeled lightly with rhodamine–phalloidin, placed on coverslips coated with SIF, illuminated by total internal reflection, and observed through a confocal aperture. We show that SIF causes the intensity of phalloidin fluorescence to increase 4- to 5- fold and its fluorescence lifetime to decrease on average 23-fold. As a consequence, the rate of photobleaching of four or five molecules of actin of a myofibril on Olympus coverslips coated with SIF decreased at least 30-fold in comparison with photobleaching on an uncoated coverslip. Significant decrease of photobleaching makes the measurement of signal from a single cross-bridge of contracting muscle feasible. PMID:17531183

Somatic mutation frequencies in the stamen hairs of Tradescantia grown in soil samples from the Bikini Island.

PubMed

Ichikawa, S; Ishii, C

1991-02-01

Somatic pink mutation frequencies in the stamen hairs of Tradescantia BNL 02 clone grown for 76 days in two soil samples taken from the Bikini Island (where a hydrogen bomb explosion test had been conducted in 1954) were investigated. A significantly high mutation frequency (2.58 +/- 0.17 pink mutant events per 10(3) hairs or 1.34 +/- 0.09 pink mutant events per 10(4) hair-cell divisions) was observed for the plant grown in one of the two Bikini soil samples, as compared to the control plants (1.70 +/- 0.14 or 0.88 +/- 0.07, respectively) grown in the field soil of Saitama University. The soil sample which caused the significant increase in mutation frequency contained 6,880 +/- 330 mBq/g 137Cs, 62.5 +/- 4.4 mBq/g 60Co, and some other nuclides; a 150 microR/hr exposure rate being measured on the surface of the soil sample. The effective cumulative external exposures measured for the inflorescences of the plant grown in this soil sample averaged at most 60.8 mR, being too small to explain the significant elevation in mutation frequency observed. On the other hand, internal exposure due to uptake of radioactive nuclides was estimated to be 125 mrad (1.25 mGy) as an accumulated effective dose, mainly based on a gamma-spectrometrical analysis. However, it seemed highly likely that this value of internal exposure was a considerable underestimate, and the internal exposure was considered to be more significant than the external exposure.

Optical properties of ultrarough silver films on silicon

NASA Astrophysics Data System (ADS)

Neff, H.; Henkel, S.; Sass, J. K.; Steinbeiss, E.; Ratz, P.; Müller, J.; Michalke, W.

1996-07-01

The optical properties of inhomogeneously grown rough silver films have been analyzed on the basis of reflectance measurements. Data have been recorded within the wave number range 50 cm-1<λ-1<50 000 cm-1. The results are compared with compact and fairly smooth films, made from the same metal. Rough films reveal very low reflectance and high absorptivity values of nearly 1, at wave numbers ≳200 cm-1. The reflectance of these films is peaking at the bulk plasma resonance hvp of silver at 3.87 eV. Smooth compact films, in contrast, show a pronounced minimum at the same energy. Based on an effective medium approach and available literature data, the dielectric function (DF) and absorption coefficient have been calculated. For rough films, the real part of the DF remains positive within the whole spectral range, but is negative for compact films below hvp, in agreement with published data. The calculated DF of the inhomogeneously grown films fully resembles the experimental observations.

High prevalence of Salmonella and IMP-4-producing Enterobacteriaceae in the silver gull on Five Islands, Australia.

PubMed

Dolejska, Monika; Masarikova, Martina; Dobiasova, Hana; Jamborova, Ivana; Karpiskova, Renata; Havlicek, Martin; Carlile, Nicholas; Priddel, David; Cizek, Alois; Literak, Ivan

2016-01-01

The objective of this study was to investigate the silver gull as an indicator of environmental contamination by salmonellae and carbapenemase-producing Enterobacteriaceae (CPE) in south-east Australia. A total of 504 cloacal samples were collected from gull chicks at three nesting colonies in New South Wales, Australia [White Bay (n = 144), Five Islands (n = 200) and Montague Island (n = 160)] and were examined for salmonellae and CPE. Isolates were tested for carbapenemase genes and susceptibility to 14 antibiotics. Clonality was determined by PFGE and MLST. Genetic context and conjugative transfer of the carbapenemase gene were determined. A total of 120 CPE of 10 species, mainly Escherichia coli (n = 85), carrying the gene blaIMP-4, blaIMP-38 or blaIMP-26 were obtained from 80 (40%) gulls from Five Islands. Thirty percent of birds from this colony were colonized by salmonellae. Most isolates contained the gene within a class 1 integron showing a blaIMP-4-qacG-aacA4-catB3 array. The blaIMP gene was carried by conjugative plasmids of variable sizes (80-400 kb) and diverse replicons, including HI2-N (n = 30), HI2 (11), A/C (17), A/C-Y (2), L/M (5), I1 (1) and non-typeable (6). Despite the overall high genetic variability, common clones and plasmid types were shared by different birds and bacterial isolates, respectively. Our data demonstrate a large-scale transmission of carbapenemase-producing bacteria into wildlife, likely as a result of the feeding habits of the birds at a local waste depot. The isolates from gulls showed significant similarities with clinical isolates from Australia, suggesting the human origin of the isolates. The sources of CPE for gulls on Five Islands should be explored and proper measures applied to stop the transmission into the environment. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.

Pyocyanin Production by Pseudomonas aeruginosa Confers Resistance to Ionic Silver

PubMed Central

Merrett, Neil D.

2014-01-01

Silver in its ionic form (Ag+), but not the bulk metal (Ag0), is toxic to microbial life forms and has been used for many years in the treatment of wound infections. The prevalence of bacterial resistance to silver is considered low due to the nonspecific nature of its toxicity. However, the recent increased use of silver as an antimicrobial agent for medical, consumer, and industrial products has raised concern that widespread silver resistance may emerge. Pseudomonas aeruginosa is a common pathogen that produces pyocyanin, a redox toxin and a reductant for molecular oxygen and ferric (Fe3+) ions. The objective of this study was to determine whether pyocyanin reduces Ag+ to Ag0, which may contribute to silver resistance due to lower bioavailability of the cation. Using surface plasmon resonance spectroscopy and scanning electron microscopy, pyocyanin was confirmed to be a reductant for Ag+, forming Ag0 nanoparticles and reducing the bioavailability of free Ag+ by >95% within minutes. Similarly, a pyocyanin-producing strain of P. aeruginosa (PA14) reduced Ag+ but not a pyocyanin-deficient (ΔphzM) strain of the bacterium. Challenge of each strain with Ag+ (as AgNO3) gave MICs of 20 and 5 μg/ml for the PA14 and ΔphzM strains, respectively. Removal of pyocyanin from the medium strain PA14 was grown in or its addition to the medium that ΔphzM mutant was grown in gave MICs of 5 and 20 μg/ml, respectively. Clinical isolates demonstrated similar pyocyanin-dependent resistance to Ag+. We conclude that pseudomonal silver resistance exists independently of previously recognized intracellular mechanisms and may be more prevalent than previously considered. PMID:25001302

Substrate decomposition in galvanic displacement reaction: Contrast between gold and silver nanoparticle formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Tapas; Satpati, Biswarup, E-mail: biswarup.satpati@saha.ac.in; Kabiraj, D.

We have investigated substrate decomposition during formation of silver and gold nanoparticles in galvanic displacement reaction on germanium surfaces. Silver and gold nanoparticles were synthesized by electroless deposition on sputter coated germanium thin film (∼ 200 nm) grown initially on silicon substrate. The nanoparticles formation and the substrate corrosion were studied using scanning transmission electron microscopy (STEM) and the energy dispersive X-ray (EDX) spectroscopy.

Sap sugar parameters of silver maple provenances and clones grown on upland and bottomland sites

Treesearch

J. J. Zaczek; A. D. Carver; K. W. J. Williard; J. K. Buchheit; J. E. Preece; J. C. Mangun

2003-01-01

Sap sugar concentration (SSC), sap volume, and stem diameter were measured for 49 different silver maple clones representing a range-wide collection of 13 provenances within replicated upland and bottomland plantations in southern Illinois during the winter of 2001. For comparison, 42 sugar maple trees were sampled in a local sugarbush. Silver maple SSC averaged 1.51...

Electroless growth of silver nanoparticles into mesostructured silica block copolymer films.

PubMed

Bois, Laurence; Chassagneux, Fernand; Desroches, Cédric; Battie, Yann; Destouches, Nathalie; Gilon, Nicole; Parola, Stéphane; Stéphan, Olivier

2010-06-01

Silver nanoparticles and silver nanowires have been grown inside mesostructured silica films obtained from block copolymers using two successive reduction steps: the first one involves a sodium borohydride reduction or a photoreduction of silver nitrate contained in the film, and the second one consists of a silver deposit on the primary nanoparticles, carried out by silver ion solution reduction with hydroxylamine chloride. We have demonstrated that the F127 block copolymer ((PEO)(106)(PPO)(70)(PEO)(106)), "F type", mesostructured silica film is a suitable "soft" template for the fabrication of spherical silver nanoparticles arrays. Silver spheres grow from 7 to 11 nm upon the second reduction step. As a consequence, a red shift of the surface plasmon resonance associated with metallic silver has been observed and attributed to plasmonic coupling between particles. Using a P123 block copolymer ((PEO)(20)(PPO)(70)(PEO)(20)), "P type", mesostructured silica film, we have obtained silver nanowires with typical dimension of 10 nm x 100 nm. The corresponding surface plasmon resonance is blue-shifted. The hydroxylamine chloride treatment appears to be efficient only when a previous chemical reduction is performed, assuming that the first sodium borohydride reduction induces a high concentration of silver nuclei in the first layer of the porous silica (film/air interface), which explains their reactivity for further growth.

Substrates coated with silver nanoparticles as a neuronal regenerative material

PubMed Central

Alon, Noa; Miroshnikov, Yana; Perkas, Nina; Nissan, Ifat; Gedanken, Aharon; Shefi, Orit

2014-01-01

Much effort has been devoted to the design of effective biomaterials for nerve regeneration. Here, we report the novel use of silver nanoparticles (AgNPs) as regenerative agents to promote neuronal growth. We grew neuroblastoma cells on surfaces coated with AgNPs and studied the effect on the development of the neurites during the initiation and the elongation growth phases. We find that the AgNPs function as favorable anchoring sites, and the growth on the AgNP-coated substrates leads to a significantly enhanced neurite outgrowth. Cells grown on substrates coated with AgNPs have initiated three times more neurites than cells grown on uncoated substrates, and two times more than cells grown on substrates sputtered with a plain homogenous layer of silver. The growth of neurites on AgNPs in the elongation phase was enhanced as well. A comparison with substrates coated with gold nanoparticles (AuNPs) and zinc oxide nanoparticles (ZnONPs) demonstrated a clear silver material-driven promoting effect, in addition to the nanotopography. The growth on substrates coated with AgNPs has led to a significantly higher number of initiating neurites when compared to substrates coated with AuNPs or ZnONPs. All nanoparticle-coated substrates affected and promoted the elongation of neurites, with a significant positive maximal effect for the AgNPs. Our results, combined with the well-known antibacterial effect of AgNPs, suggest the use of AgNPs as an attractive nanomaterial – with dual activity – for neuronal repair studies. PMID:24872701

Protein retention on plasma-treated hierarchical nanoscale gold-silver platform

PubMed Central

Fang, Jinghua; Levchenko, Igor; Mai-Prochnow, Anne; Keidar, Michael; Cvelbar, Uros; Filipic, Gregor; Han, Zhao Jun; Ostrikov, Kostya (Ken)

2015-01-01

Dense arrays of gold-supported silver nanowires of about 100 nm in diameter grown directly in the channels of nanoporous aluminium oxide membrane were fabricated and tested as a novel platform for the immobilization and retention of BSA proteins in the microbial-protective environments. Additional treatment of the silver nanowires using low-temperature plasmas in the inductively-coupled plasma reactor and an atmospheric-pressure plasma jet have demonstrated that the morphology of the nanowire array can be controlled and the amount of the retained protein may be increased due to the plasma effect. A combination of the neutral gold sublayer with the antimicrobial properties of silver nanowires could significantly enhance the efficiency of the platforms used in various biotechnological processes. PMID:26307515

Protein retention on plasma-treated hierarchical nanoscale gold-silver platform

NASA Astrophysics Data System (ADS)

Fang, Jinghua; Levchenko, Igor; Mai-Prochnow, Anne; Keidar, Michael; Cvelbar, Uros; Filipic, Gregor; Han, Zhao Jun; Ostrikov, Kostya (Ken)

2015-08-01

Dense arrays of gold-supported silver nanowires of about 100 nm in diameter grown directly in the channels of nanoporous aluminium oxide membrane were fabricated and tested as a novel platform for the immobilization and retention of BSA proteins in the microbial-protective environments. Additional treatment of the silver nanowires using low-temperature plasmas in the inductively-coupled plasma reactor and an atmospheric-pressure plasma jet have demonstrated that the morphology of the nanowire array can be controlled and the amount of the retained protein may be increased due to the plasma effect. A combination of the neutral gold sublayer with the antimicrobial properties of silver nanowires could significantly enhance the efficiency of the platforms used in various biotechnological processes.

The role of Ag buffer layer in Fe islands growth on Ge (111) surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw; Wu, Jia-Yuan; Jhou, Ming-Kuan

2015-05-07

Sub-monolayer iron atoms were deposited at room temperature on Ge (111)-c(2 × 8) substrates with and without Ag buffer layers. The behavior of Fe islands growth was investigated by using scanning tunneling microscope (STM) after different annealing temperatures. STM images show that iron atoms will cause defects and holes on substrates at room temperature. As the annealing temperature rises, iron atoms pull out germanium to form various kinds of alloyed islands. However, the silver layer can protect the Ag/Ge(111)-(√3×√3) reconstruction from forming defects. The phase diagram shows that ring, dot, and triangular defects were only found on Ge (111)-c(2 × 8) substrates. The kindsmore » of islands found in Fe/Ge system are similar to Fe/Ag/Ge system. It indicates that Ge atoms were pulled out to form islands at high annealing temperatures whether there was a Ag layer or not. But a few differences in big pyramidal or strip islands show that the silver layer affects the development of islands by changing the surface symmetry and diffusion coefficient. The structure characters of various islands are also discussed.« less

In vitro cytotoxity of silver: implication for clinical wound care.

PubMed

Poon, Vincent K M; Burd, Andrew

2004-03-01

In this study, we look at the cytotoxic effects of silver on keratinocytes and fibroblasts. We have assessed the viability of monolayer cultures using the MTT and BrdU assays. The composition of the culture medium and also the culture technique were modified to assess the effects of culture 'environment' on the susceptibility of the cells to the toxic action of silver. Further in vitro, experiments were performed using tissue culture models to allow cellular behavior in three dimensional planes which more closely simulated in vivo behavior. The silver source was both silver released from silver nitrate solution but also nanocrystalline silver released from a commercially available dressing. The results show that silver is highly toxic to both keratinocytes and fibroblasts in monolayer culture. When using optimized and individualized culture the fibroblasts appear to be more sensitive to silver than keratinocytes. However, when both cell types were grown in the same medium their viability was the same. Using tissue culture models again indicated an 'environmental effect' with decreased sensitivity of the cells to the cytotoxic effects of the silver. Nevertheless in these studies the toxic dose of skin cells ranging from 7 x 10(-4) to 55 x 10(-4)% was similar to that of bacteria. These results suggest that consideration of the cytotoxic effects of silver and silver-based products should be taken when deciding on dressings for specific wound care strategies. This is important when using keratinocyte culture, in situ, which is playing an increasing role in contemporary wound and burn care.

Bioconcentration factors (BCF) of silver in wild Agaricus campestris

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falandysz, J.; Danisiewicz, D.

Silver is an element naturally occurring in small concentrations in different environmental sites. However, many anthropogenic sources of silver led to contamination of this element in soil surfaces, pastures, and coastal marine areas in different parts of the world. Estimates are that 40% of the 1.15x10{sup 4}t of silver produced annually worldwide, will escape into the environment. Due to municipal waste discharge and/or industrial effluents with high silver concentrations, 100 x above the background level have been reported in invertebrate species from polluted marine areas. The meta-stabile radioisotope, {sup 110m}Ag, is a main component of the liquid effluents from nuclearmore » facilities under normal operating conditions. The presence of {sup 111}Ag and {sup 110m}Ag also has been widely found throughout Europe in the 1986 Chernobyl fallout. Silver ions are environmentally harmful. High toxic effects have been observed at low concentrations, especially in aquatic species. Species of lower fungi as well as the mushroom Agaricus bisporus are know to bioaccumulate high concentrations of silver when grown on an artificially enriched substrate. This study looks at the relationship between the silver content of soil and bioconcentration potential of wild Agaricus campestris from sites under different use and with different concentrations of heavy metals. 28 refs., 2 figs., 2 tabs.« less

Largely Enhanced Single-molecule Fluorescence in Plasmonic Nanogaps formed by Hybrid Silver Nanostructures

PubMed Central

Zhang, Jian; Lakowicz, Joseph R.

2013-01-01

It has been suggested that narrow gaps between metallic nanostructures can be practical for producing large field enhancement. We design a hybrid silver nanostructure geometry in which fluorescent emitters are sandwiched between silver nanoparticles and silver island film (SIF). A desired number of polyelectrolyte layers are deposited on the SIF surface before the self-assembly of a second silver nanoparticle layer. Layer-by-layer configuration provides a well-defined dye position. It allows us to study the photophyical behaviors of fluorophores in the resulting gap at the single molecule level. The enhancement factor of a fluorophore located in the gap is much higher than those on silver surfaces alone and on glass. These effects may be used for increased detectability of single molecules bound to surfaces which contain metallic structures for either biophysical studies or high sensitivity assays. PMID:23373787

Dendrochronology of strain-relaxed islands.

PubMed

Merdzhanova, T; Kiravittaya, S; Rastelli, A; Stoffel, M; Denker, U; Schmidt, O G

2006-06-09

We report on the observation and study of tree-ring structures below dislocated SiGe islands (superdomes) grown on Si(001) substrates. Analogous to the study of tree rings (dendrochronology), these footprints enable us to gain unambiguous information on the growth and evolution of superdomes and their neighboring islands. The temperature dependence of the critical volume for dislocation introduction is measured and related to the composition of the islands. We show clearly that island coalescence is the dominant pathway towards dislocation nucleation at low temperatures, while at higher temperatures anomalous coarsening is effective and leads to the formation of a depletion region around superdomes.

Colloidal silver: a novel treatment for Staphylococcus aureus biofilms?

PubMed

Goggin, Rachel; Jardeleza, Camille; Wormald, Peter-John; Vreugde, Sarah

2014-03-01

Colloidal silver is an alternative medicine consisting of silver particles suspended in water. After using this solution as a nasal spray, the symptoms of a previously recalcitrant Staphylococcus aureus (S. aureus)-infected chronic rhinosinusitis patient were observed to have improved markedly. The aim of this study was to determine whether colloidal silver has any direct bactericidal effects on these biofilms in vitro. S. aureus biofilms were grown from the ATCC 25923 reference strain on Minimum Biofilm Eradication Concentration (MBEC) device pegs, and treated with colloidal silver. Concentrations tested ranged from 10 to 150 μL colloidal silver diluted to 200 μL with sterile water in 50 μL cerebrospinal fluid (CSF) broth. Control pegs were exposed to equivalent volumes of CSF broth and sterile water. The sample size was 4 biomass values per treatment or control group. Confocal scanning laser microscopy and COMSTAT software were used to quantify biofilms 24 hours after treatment. Significant differences from control were found for all concentrations tested bar the lowest of 10 μL colloidal silver in 200 μL. At 20 μL colloidal silver, the reduction in biomass was 98.9% (mean difference between control and treatment = -4.0317 μm(3) /μm(2) , p < 0.0001). A maximum biomass reduction of 99.8% was reached at both 100 and 150 μL colloidal silver (mean differences = -4.0681 and -4.0675μm(3) /μm(2) , respectively, p < 0.0001). Colloidal silver directly attenuates in vitro S. aureus biofilms. © 2014 ARS-AAOA, LLC.

Photochemical Synthesis of Silver Nanodecahedrons and Related Nanostructures for Plasmonic Field Enhancement Applications

NASA Astrophysics Data System (ADS)

Lu, Haifei

excitation. These silver NDs acting as seeds can be re-grown into larger silver NDs with LSPR ranging from 490 nm to 590 nm, upon receiving LED irradiation with emission close to the LSPR of silver ND seeds, which are suspended in a precursor solution containing small silver nanoparticles. With the aid of centrifugation, silver NDs with high purity can be obtained. Furthermore, silver ND with a broad tuning range (LSPR 490 ~ 660 nm) can be synthesized from these seeds using irradiation from a 500 nm LED. Second, the optical properties of silver NDs and their SERS application for sensitive molecular detection are presented. Raman signal obtained from silver NDs show remarkable advantage over noble nanoparticles of other shaped, thus revealing their strong localized field enhancement. Experimental results demonstrate that average enhancement factor from individual silver ND may be as high as 106. In order to explore their application for biosensing and bioimaging, stable silica coated SERS tags based on silver ND producing high Raman intensity have been studied. Our experiment results indicate that 10-8 M 4-MBA in solution can be detected by silver NDs modified silicon chip through SERS. Simulation result on the geometry of silver ND/silica spacer/gold film/substrate shows that the Raman sensitivity of the NDs modified chip can be further improved with the insertion of a dielectric/conductor film between them. Finally, we present a photochemical method for the preparation of silver nanostructures preparation with the use of 633 nm laser. Silver nanostructures composed of silver nanoplates could be grown from small silver nanoparticles deposited on a glass substrate. The periodicity of the silver nanostructures is several micrometers, revealing that this photochemical method has the potential for "writing" silver pattern on a solid substrate. Raman spectroscopy has also been explored for real-time monitoring of silver nanostructure growth and SERS hotspots formation.

Fabrication and characterization of ZnS/ZnO core shell nanostructures on silver wires

NASA Astrophysics Data System (ADS)

Kao, Chyuan Haur; Su, Wei Ming; Li, Cheng Yuan; Weng, Wei Chih; Weng, Chen Yuan; Cheng, Chin-Chi; Lin, Yung-Sen; Lin, Chia Feng; Chen, Hsiang

2018-06-01

In this research, ZnS nanoparticles were synthesized on ZnO/silver wires to form ZnS/ZnO core shell structures. Various outward appearance and colors could be observed by different ZnO growth and sulfurization conditions. To evaluate the properties of these nanostructures, optical properties and chemical bindings were analyzed by photoluminescence, Raman analysis, and X-ray photoelectron spectroscopy. Furthermore, material characterizations including transmission electron microscopy and X-ray diffraction confirmed that cubic ZnS (311)/ZnO nanostructures were grown on silver wires for the first time. ZnS/ZnO core shell structures on silver wires are promising for future optoelectronic and biomedical applications.

In situ bioinspired synthesis of silver chloride nanocrystals on silk fibroin fibers

NASA Astrophysics Data System (ADS)

Su, Huilan; Han, Jie; Dong, Qun; Xu, Jia; Chen, Ying; Gu, Yu; Song, Weiqiang; Zhang, Di

2011-02-01

Silver chloride (AgCl) nanocrystals were formed and grown on silk fibroin fibers (SFFs) by a room-temperature process. Practically, the degummed SFFs were immersed into silver nitrate solution and sodium chloride solution in turn. The amino acids on the SFF surface were negatively charged in alkaline impregnant, providing locations to immobilize silver ions and form silver chloride seeds. AgCl nanocrystals can further grow into cubic AgCl nanocrystals with an edge of about 100 nm. The morphologies of the AgCl nanocrystals were mostly influenced by the concentration of sodium chloride solution and the special configurations of the SFFs. The target AgCl/SFF nanocomposites constructed by AgCl nanocrystals and substrate SFFs could be used as photocatalysts in water splitting and antibacterial agents. This work provides an important example in the introduction of natural biofibers to the synthesis of functional hybrid nanocomposites by a green and mild technique.

Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry.

PubMed

Battistel, Dario; Baldi, Franco; Gallo, Michele; Faleri, Claudia; Daniele, Salvatore

2015-01-01

Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface. Copyright © 2014 Elsevier B.V. All rights reserved.

Xylary pH and Reduction Potential Levels of Iron-stressed Silver Maple (Acer saccharinum L.) 1

PubMed Central

Morris, Robert L.; Swanson, Bert T.

1980-01-01

Xylary fluid pH and reduction potentials were measured on silver maple (Acer saccharinum L.) grown under Fe and pH stress. Although pH and reduction potential (millivolt/59.2) varied significantly in the nutrient solution, xylary pH and reduction potential remained constant. It was concluded that changes in the pH and reduction potential in the xylary fluid of silver maple are not responsible for iron chlorosis. PMID:16661196

Optimization of silver-dielectric-silver nanoshell for sensing applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirzaditabar, Farzad; Saliminasab, Maryam

2013-08-15

In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivitymore » of silver-dielectric-silver nanoshell.« less

X-ray diffraction analysis of LiCu2O2 crystals with additives of silver atoms

NASA Astrophysics Data System (ADS)

Sirotinkin, V. P.; Bush, A. A.; Kamentsev, K. E.; Dau, H. S.; Yakovlev, K. A.; Tishchenko, E. A.

2015-09-01

Silver-containing LiCu2O2 crystals up to 4 × 8 × 8 mm in size were grown by the crystallization of 80(1- x)CuO · 20 x AgNO3 · 20Li2CO3 (0 ≤ х ≤ 0.5) mixture melt. According to the X-ray spectral and Rietveld X-ray diffraction data, the maximum amount of silver incorporated in the LiCu2O2 structure is about 4 at % relative to the copper content. It was established that silver atoms occupy statistically crystallographic positions of lithium atoms. The incorporation of silver atoms is accompanied by a noticeable increase in parameter с of the LiCu2O2 rhombic unit cell, a slight increase in parameter а, and a slight decrease in parameter b.

Use of surfactants to control island size and density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merrell, Jason; Liu, Feng; Stringfellow, Gerald B.

Methods of controlling island size and density on an OMVPE growth film may comprise adding a surfactant at a critical concentration level, allowing a growth phase for a first period of time, and ending the growth phase when desired island size and density are achieved. For example, the island size and density of an OMVPE grown InGaN thin film may be controlled by adding an antimony surfactant at a critical concentration level.

Critical island size for Ag thin film growth on ZnO (0 0 0 1 bar)

NASA Astrophysics Data System (ADS)

Lloyd, Adam L.; Smith, Roger; Kenny, Steven D.

2017-02-01

Island growth of Ag on ZnO is investigated with the development of a new technique to approximate critical island sizes. Ag is shown to attach in one of three highly symmetric sites on the ZnO surface or initial monolayers of grown Ag. Due to this, a lattice based adaptive kinetic Monte Carlo (LatAKMC) method is used to investigate initial growth phases. As island formation is commonly reported in the literature, the critical island sizes of Ag islands on a perfect polar ZnO surface and a first monolayer of grown Ag on the ZnO surface are considered. A mean rate approach is used to calculate the average time for an Ag ad-atom to drop off an island and this is then compared to deposition rates on the same island. Results suggest that Ag on ZnO (0 0 0 1 bar) will exhibit Stranski-Krastanov (layer plus island) growth.

Pre-coalescence scaling of graphene island sizes

NASA Astrophysics Data System (ADS)

Das, Shantanu; Drucker, Jeff

2018-05-01

Graphene grown using cold-wall chemical vapor deposition on Cu surfaces follows a classical nucleation and growth mechanism. Following nucleation at the earliest growth stages, isolated crystallites grow, impinge, and coalesce to form a continuous layer. During the pre-coalescence growth regime, the size distributions of graphene crystallites exhibit scaling of the form N(s) = θ/⟨s⟩2 g(s/⟨s⟩), where s is the island area, θ is the graphene coverage, ⟨s⟩ is the average island area, N is the areal density, and g(x) is a scaling function. For graphene grown on Cu surfaces that have been annealed in a reducing Ar + H2 ambient, excellent data collapse onto a universal Avrami scaling function is observed irrespective of graphene coverage, surface roughness, or Cu grain size. This result is interpreted to indicate attachment-limited growth and desorption of diffusing C-containing species. Graphene grown on Cu surfaces that were annealed in a non-reducing environment exhibits a qualitatively different scaling function, indicating diffusion-limited growth with a lower attachment barrier combined with C detachment from the graphene edges.

Silver(II) Oxide or Silver(I,III) Oxide?

ERIC Educational Resources Information Center

Tudela, David

2008-01-01

The often called silver peroxide and silver(II) oxide, AgO or Ag[subscript 2]O[subscript 2], is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the "volume-based" thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide.…

Biomineralization of hydroxyapatite in silver ion-exchanged nanocrystalline ZSM-5 zeolite using simulated body fluid.

PubMed

Kaur, Balwinder; Srivastava, Rajendra; Satpati, Biswarup; Kondepudi, Kanthi Kiran; Bishnoi, Mahendra

2015-11-01

Silver ion-exchanged nanocrystalline zeolite (Ag-Nano-ZSM-5) and silver ion-exchanged conventional zeolite (Ag-ZSM-5) were synthesized. Zeolites were incubated in simulated body fluid at 310K for different time periods to grow hydroxyapatite in their matrixes. Significant large amount of hydroxyapatite was grown in Ag-Nano-ZSM-5 matrix after incubation in simulated body fluid when compared to Ag-ZSM-5. The resultant material was characterized using X-ray diffraction, N2-adsorption, scanning/transmission electron microscopy, energy dispersive X-ray, and inductively coupled plasma analysis. Mechanical properties such as compressive modulus, compressive strength, and strain at failure of the parent materials were evaluated. Biocompatibility assays suggested that Ag-Nano-ZSM-5 and hydroxyapatite grown in Ag-Nano-ZSM-5 were compatible and did not impose any toxicity to RAW 264.7 cells macrophase and Caco2 cells suggesting considerable potential for biomedical applications such as bone implants. Copyright © 2015 Elsevier B.V. All rights reserved.

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, G.A.

1985-03-05

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Method for the recovery of silver from silver zeolite

DOEpatents

Reimann, George A.

1986-01-01

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

75 FR 5898 - Cranberries Grown in the States of Massachusetts, Rhode Island, Connecticut, New Jersey...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-05

... Massachusetts, Rhode Island, Connecticut, New Jersey, Wisconsin, Michigan, Minnesota, Oregon, Washington, and Long Island in the State of New York; Changes to Reporting Dates AGENCY: Agricultural Marketing Service... States of Massachusetts, Rhode Island, Connecticut, New Jersey, Wisconsin, Michigan, Minnesota, Oregon...

Magnetite nano-islands on Graphene

NASA Astrophysics Data System (ADS)

Anderson, Nathaniel; Zhang, Qiang; Rosenberg, Richard; Vaknin, David

X-ray magnetic circular dichroism (XMCD) of ex-situ iron nano-islands grown on graphene reveals that iron oxidation spontaneously leads to the formation of magnetite nano-particles - i.e, the formation of the inverse spinel Fe3O4. Fe islands have been grown with two different heights (20 and 75 MLs) on epitaxial graphene and we have determined their magnetic behavior both as function of temperature and applied external field. Our XAS and XMCD at an applied magnetic field of B = 5 T show that the thin film (20 MLs) is totally converted to magnetite whereas the thicker film (75 MLs) exhibits magnetite properties but also those of pure metal iron. For both samples, temperature dependence of the XMCD shows clear transitions at ~120 K consistent with the Verwey transition of bulk magnetite. XMCD at low temperatures shows a weak hysteresis and provide the average spin and angular-momentum moments, the dipolar term, and the total moment . In addition, manipulation and comparison of the XMCD data from both samples allows us to extract information about the pure iron nano-islands from the thicker sample. Ames Laboratory is supported by the U.S. DOE, BES, MSE Contract No. DE-AC02-07CH11358. APS is supported by U.S. DOE Contract No. DE-AC02-06CH11357.

Silver electrodeposition on nanostructured gold: from nanodots to nanoripples.

PubMed

Dos Santos Claro, P C; Fonticelli, M; Benítez, G; Azzaroni, O; Schilardi, P L; Luque, N B; Leiva, E; Salvarezza, R C

2006-07-28

Silver nanodots and nanoripples have been grown on nanocavity-patterned polycrystalline Au templates by controlled electrodeposition. The initial step is the growth of a first continuous Ag monolayer followed by preferential deposition at nanocavities. The Ag-coated nanocavities act as preferred sites for instantaneous nucleation and growth of the three-dimensional metallic centres. By controlling the amount of deposited Ag, dots of approximately 50 nm average size and approximately 4 nm average height can be grown with spatial and size distributions dictated by the template. The dots are in a metastable state. Further Ag deposition drives the dot surface structure to nanoripple formation. Results show that electrodeposition on nanopatterned electrodes can be used to prepare a high density of nanostructures with a narrow size distribution and spatial order.

Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering.

PubMed

Ke, S Y; Yang, J; Qiu, F; Wang, Z Q; Wang, C; Yang, Y

2015-11-06

We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.

Antibacterial activity and toxicity of silver - nanosilver versus ionic silver

NASA Astrophysics Data System (ADS)

Kvitek, L.; Panacek, A.; Prucek, R.; Soukupova, J.; Vanickova, M.; Kolar, M.; Zboril, R.

2011-07-01

The in vitro study of antibacterial activity of silver nanoparticles (NPs), prepared via modified Tollens process, revealed high antibacterial activity even at very low concentrations around several units of mg/L. These concentrations are comparable with concentrations of ionic silver revealing same antibacterial effect. However, such low concentrations of silver NPs did not show acute cytotoxicity to mammalian cells - this occurs at concentrations higher than 60 mg/L of silver, while the cytotoxic level of ionic silver is much more lower (approx. 1 mg/L). Moreover, the silver NPs exhibit lower acute ecotoxicity against the eukaryotic organisms such as Paramecium caudatum, Monoraphidium sp. and D. melanogaster. The silver NPs are toxic to these organisms at the concentrations higher than 30 mg/L of silver. On contrary, ionic silver retains its cytoxicity and ecotoxicity even at the concentration equal to 1 mg/L. The performed experiments demonstrate significantly lower toxicity of silver NPs against the eukaryotic organisms than against the prokaryotic organisms.

X-ray diffraction analysis of LiCu{sub 2}O{sub 2} crystals with additives of silver atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sirotinkin, V. P., E-mail: irotinkin.vladimir@mail.ru; Bush, A. A.; Kamentsev, K. E.

2015-09-15

Silver-containing LiCu{sub 2}O{sub 2} crystals up to 4 × 8 × 8 mm in size were grown by the crystallization of 80(1-x)CuO · 20{sub x}AgNO{sub 3} · 20Li{sub 2}CO{sub 3} (0 ≤ x ≤ 0.5) mixture melt. According to the X-ray spectral and Rietveld X-ray diffraction data, the maximum amount of silver incorporated in the LiCu{sub 2}O{sub 2} structure is about 4 at % relative to the copper content. It was established that silver atoms occupy statistically crystallographic positions of lithium atoms. The incorporation of silver atoms is accompanied by a noticeable increase in parameter c of the LiCu{sub 2}O{submore » 2} rhombic unit cell, a slight increase in parameter a, and a slight decrease in parameter b.« less

Oral toxicity of silver ions, silver nanoparticles and colloidal silver--a review.

PubMed

Hadrup, Niels; Lam, Henrik R

2014-02-01

Orally administered silver has been described to be absorbed in a range of 0.4-18% in mammals with a human value of 18%. Based on findings in animals, silver seems to be distributed to all of the organs investigated, with the highest levels being observed in the intestine and stomach. In the skin, silver induces a blue-grey discoloration termed argyria. Excretion occurs via the bile and urine. The following dose-dependent animal toxicity findings have been reported: death, weight loss, hypoactivity, altered neurotransmitter levels, altered liver enzymes, altered blood values, enlarged hearts and immunological effects. Substantial evidence exists suggesting that the effects induced by particulate silver are mediated via silver ions that are released from the particle surface. With the current data regarding toxicity and average human dietary exposure, a Margin of Safety calculation indicates at least a factor of five before a level of concern to the general population is reached. Copyright © 2013 Elsevier Inc. All rights reserved.

Silver deposition and tissue staining associated with wound dressings containing silver.

PubMed

Walker, Michael; Cochrane, Christine A; Bowler, Philip G; Parsons, David; Bradshaw, Peter

2006-01-01

Argyria is the general term used to denote a clinical condition in which excessive administration and deposition of silver causes a permanent irreversible gray-blue discoloration of the skin or mucous membranes. The amount of discoloration usually depends on the route of silver delivery (ie, oral or topical administration) along with the body's ability to absorb and excrete the administered silver compound. Argyria is accepted as a rare dermatosis but once silver particles are deposited, they remain immobile and may accumulate during the aging process. Topical application of silver salts (eg, silver nitrate solution) may lead to transient skin staining. To investigate their potential to cause skin staining, two silver-containing dressings (Hydrofiber and nanocrystalline) were applied to human skin samples taken from electively amputated lower limbs. The potential for skin discoloration was assayed using atomic absorption spectroscopy. When the dressings were hydrated with water, a significantly higher amount of silver was released from the nanocrystalline dressing compared to the Hydrofiber dressing (P <0.005), which resulted in approximately 30 times more silver deposition. In contrast, when saline was used as the hydration medium, the release rates were low for both dressings and not significantly different (silver deposition was minimal). Controlling the amount of silver released from silver-containing dressings should help reduce excessive deposition of silver into wound tissue and minimize skin staining.

Versatile synthesis of PHMB-stabilized silver nanoparticles and their significant stimulating effect on fodder beet (Beta vulgaris L.).

PubMed

Gusev, Alexander А; Kudrinsky, Alexey A; Zakharova, Olga V; Klimov, Alexey I; Zherebin, Pavel M; Lisichkin, George V; Vasyukova, Inna A; Denisov, Albert N; Krutyakov, Yurii A

2016-05-01

Silver nanoparticles (AgNPs) are well-known bactericidal agents. However, information about the influence of AgNPs on the morphometric parameters and biochemical status of most important agricultural crops is limited. The present study reports the influence of AgNPs stabilized with cationic polymer polyhexamethylene biguanide hydrochloride (PHMB) on growth, development, and biochemical status of fodder beet Beta vulgaris L. under laboratory and greenhouse conditions. PHMB-stabilized AgNPs were obtained via sodium borohydride reduction of silver nitrate in an aqueous solution. The average diameter of thus prepared AgNPs was 10 nm. It appears that the results of experiments with laboratory-grown beets in the nanosilver-containing medium, where germination of seeds and growth of roots were suppressed, do not correlate with the results of greenhouse experiments. The observed growth-stimulating action of PHMB-stabilized AgNPs can be explained by the change of activity of oxidases and, consequently, by the change of auxins amount in plant tissues. In beets grown in the presence of PHMB-stabilized AgNPs no negative deviations of biological parameters from normal values were registered. Furthermore, the SEM/EDS examination revealed no presence of silver in the tissues of the studied plants. Copyright © 2016 Elsevier B.V. All rights reserved.

Copper vapor-assisted growth of hexagonal graphene domains on silica islands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jun; Que, Yande; Jiang, Lili

2016-07-11

Silica (SiO{sub 2}) islands with a dendritic structure were prepared on polycrystalline copper foil, using silane (SiH{sub 4}) as a precursor, by annealing at high temperature. Assisted by copper vapor from bare sections of the foil, single-layer hexagonal graphene domains were grown directly on the SiO{sub 2} islands by chemical vapor deposition. Scanning electron microscopy, atomic force microscopy, Raman spectra, and X-ray photoelectron spectroscopy confirm that hexagonal graphene domains, each measuring several microns, were synthesized on the silica islands.

Origins of Moiré Patterns in CVD-grown MoS2 Bilayer Structures at the Atomic Scales.

PubMed

Wang, Jin; Namburu, Raju; Dubey, Madan; Dongare, Avinash M

2018-06-21

The chemical vapor deposition (CVD)-grown two-dimensional molybdenum disulfide (MoS 2 ) structures comprise of flakes of few layers with different dimensions. The top layers are relatively smaller in size than the bottom layers, resulting in the formation of edges/steps across adjacent layers. The strain response of such few-layer terraced structures is therefore likely to be different from exfoliated few-layered structures with similar dimensions without any terraces. In this study, the strain response of CVD-grown few-layered MoS 2 terraced structures is investigated at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the strain relaxation of CVD-grown triangular terraced structures is observed in the vertical displacement of the atoms across the layers that results in the formation of Moiré patterns. The Moiré islands are observed to nucleate at the corners or edges of the few-layered structure and propagate inwards under both tensile and compressive strains. The nucleation of these islands is observed to happen at tensile strains of ~ 2% and at compressive strains of ~2.5%. The vertical displacements of the atoms and the dimensions of the Moiré islands predicted using the MD simulation are in excellent agreement with that observed experimentally.

Exposure-related health effects of silver and silver compounds: a review.

PubMed

Drake, Pamela L; Hazelwood, Kyle J

2005-10-01

A critical review of studies examining exposures to the various forms of silver was conducted to determine if some silver species are more toxic than others. The impetus behind conducting this review is that several occupational exposure limits and guidelines exist for silver, but the values for each depend on the form of silver as well as the individual agency making the recommendations. For instance, the American Conference of Governmental Industrial Hygienists has established separate threshold limit values for metallic silver (0.1 mg/m3) and soluble compounds of silver (0.01 mg/m3). On the other hand, the permissible exposure limit (PEL) recommended by the Occupational Safety and Health Administration and the Mine Safety and Health Administration and the recommended exposure limit set by the National Institute for Occupational Safety and Health is 0.01 mg/m3 for all forms of silver. The adverse effects of chronic exposure to silver are a permanent bluish-gray discoloration of the skin (argyria) or eyes (argyrosis). Most studies discuss cases of argyria and argyrosis that have resulted primarily from exposure to the soluble forms of silver. Besides argyria and argyrosis, exposure to soluble silver compounds may produce other toxic effects, including liver and kidney damage, irritation of the eyes, skin, respiratory, and intestinal tract, and changes in blood cells. Metallic silver appears to pose minimal risk to health. The current occupational exposure limits do not reflect the apparent difference in toxicities between soluble and metallic silver; thus, many researchers have recommended that separate PELs be established.

Effect of silver on the phase transition and wettability of titanium oxide films

PubMed Central

Mosquera, Adolfo A.; Albella, Jose M.; Navarro, Violeta; Bhattacharyya, Debabrata; Endrino, Jose L.

2016-01-01

The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO2 films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO2 matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO2 was evaluated to demonstrate its improved photocatalytic performance. PMID:27571937

Green synthesis of silver nanoparticles using Stevia leaves extracts

NASA Astrophysics Data System (ADS)

Laguta, Iryna; Stavinskaya, Oksana; Kazakova, Olga; Fesenko, Tetiana; Brychka, Sergey

2018-02-01

Three extracts of Stevia rebaudiana (Bertoni) were prepared using different types of raw materials: leaves of plants grown ex situ, leaves of plants grown in vitro, callus culture formed on damaged leaves. Composition of the extracts was studied by means of high-performance liquid chromatography and laser desorption/ionization mass spectrometry; total phenol content was estimated using Folin-Ciocalteau method. Flavonoids and hydroxycinnamic acids were found to be the main groups of phenol antioxidants available in the Stevia leaves, with the amount of these compounds in the extract being dependent on the type of raw material. The reducing properties of phenol compounds identified in the extracts were characterized using quantum chemical method; flavonoids and hydroxycinnamic acids were found to have similar redox parameters. Silver nanoparticles (AgNPs) colloids were synthesized using three Stevia extracts; AgNPs size distribution were characterized by means of scanning electron microscopy. All the extracts revealed significant activity in AgNPs synthesis; the nanoparticles of predominantly spherical shape with the average sizes of 16-25 nm were formed. The reducing properties of the extracts were found to correlate with total phenol content; the activity of extracts from the leaves of plants grown ex situ and from callus culture in Ag+ ions reduction was similar to each other and exceeded the activity of extract from the leaves of plants grown in vitro.

Engineered Escherichia coli Silver-Binding Periplasmic Protein That Promotes Silver Tolerance

PubMed Central

Hall Sedlak, Ruth; Hnilova, Marketa; Grosh, Carolynn; Fong, Hanson; Baneyx, Francois; Schwartz, Dan; Sarikaya, Mehmet; Tamerler, Candan

2012-01-01

Silver toxicity is a problem that microorganisms face in medical and environmental settings. Through exposure to silver compounds, some bacteria have adapted to growth in high concentrations of silver ions. Such adapted microbes may be dangerous as pathogens but, alternatively, could be potentially useful in nanomaterial-manufacturing applications. While naturally adapted isolates typically utilize efflux pumps to achieve metal resistance, we have engineered a silver-tolerant Escherichia coli strain by the use of a simple silver-binding peptide motif. A silver-binding peptide, AgBP2, was identified from a combinatorial display library and fused to the C terminus of the E. coli maltose-binding protein (MBP) to yield a silver-binding protein exhibiting nanomolar affinity for the metal. Growth experiments performed in the presence of silver nitrate showed that cells secreting MBP-AgBP2 into the periplasm exhibited silver tolerance in a batch culture, while those expressing a cytoplasmic version of the fusion protein or MBP alone did not. Transmission electron microscopy analysis of silver-tolerant cells revealed the presence of electron-dense silver nanoparticles. This is the first report of a specifically engineered metal-binding peptide exhibiting a strong in vivo phenotype, pointing toward a novel ability to manipulate bacterial interactions with heavy metals by the use of short and simple peptide motifs. Engineered metal-ion-tolerant microorganisms such as this E. coli strain could potentially be used in applications ranging from remediation to interrogation of biomolecule-metal interactions in vivo. PMID:22286990

Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Khaydarov, R. R.; Khaydarov, R. A.; Estrin, Y.; Evgrafova, S.; Scheper, T.; Endres, C.; Cho, S. Y.

The bactericidal effect of silver nanoparticles obtained by a novel electrochemical method on Escherichia coli, Staphylococcus aureus, Aspergillus niger and Penicillium phoeniceum cultures has been studied. The tests conducted have demonstrated that synthesized silver nanoparticles — when added to water paints or cotton fabrics — show a pronounced antibacterial/antifungal effect. It was shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. The paper also provides a review of scientific literature with regard to recent developments in the field of toxicity of silver nanoparticles and its effect on environment and human health.

From open to closed canopy: A century of change in Douglas-fir forest, Orcas Island, Washington

USGS Publications Warehouse

Peterson, D.L.; Hammer, R.D.

2001-01-01

During the past century, forest structure on south-facing slopes of Mount Constitution, Orcas Island, Washington, has changed from open-grown Douglas-fir (Pseudotsuga menziesii) mixed with prairie to primarily closed canopy forest. Density of open-grown Douglas-fir was approximately 7 stems/ha in the 19th century, while current density of trees in closed-canopy mature forest is 426 stems/ha. Trees occur at intermediate densities in areas of transition from savanna-like stands to closed canopy. Analysis of fire scars indicates that at least seven fires have occurred on Mount Constitution since 1736, but only one fire has occurred since 1893, which suggests that the recent increase in stem density has been caused primarily by fire exclusion. The high stem densities currently found in this landscape put the relict (120-350+ years old) Douglas-fir at risk from contemporary fires, which would likely be high-intensity crown fires. Given the transition of forests on Orcas Island during the 20th century to closed canopy structure, undisturbed open-grown coniferous forest is now extremely rare in the San Juan Islands.

The silver cation (Ag+): antistaphylococcal activity, mode of action and resistance studies.

PubMed

Randall, Christopher P; Oyama, Linda B; Bostock, Julieanne M; Chopra, Ian; O'Neill, Alex J

2013-01-01

To examine several poorly understood or contentious aspects of the antibacterial activity of silver (Ag(+)), including its cidality, mode of action, the prevalence of resistance amongst clinical staphylococcal isolates and the propensity for Staphylococcus aureus to develop Ag(+) resistance. The effects of Ag(+) on the viability, macromolecular synthesis and membrane integrity of S. aureus SH1000 were assessed using established methodology. Silver nitrate MICs were determined for a collection of staphylococcal isolates (n = 1006) collected from hospitals across Europe and Canada between 1997 and 2010. S. aureus biofilms were grown using the Calgary Biofilm Device. To examine the in vitro development of staphylococcal resistance to Ag(+), bacteria were subjected to continuous subculture in the presence of sub-MIC concentrations of Ag(+). Silver was bactericidal against S. aureus in buffered solution, but bacteriostatic in growth medium, and was unable to eradicate staphylococcal biofilms in vitro. Challenge of S. aureus with Ag(+) caused rapid loss of membrane integrity and inhibition of the major macromolecular synthetic pathways. All clinical staphylococcal isolates were susceptible to ≤ 16 mg/L silver nitrate and prolonged exposure (42 days) to Ag(+) in vitro failed to select resistant mutants. The rapid and extensive loss of membrane integrity observed upon challenge with Ag(+) suggests that the antibacterial activity results directly from damage to the bacterial membrane. The universal susceptibility of staphylococci to Ag(+), and failure to select for resistance to Ag(+), suggest that silver compounds remain a viable option for the prevention and treatment of topical staphylococcal infections.

Production of silver nanoparticles by the diatom Phaeodactylum tricornutum

NASA Astrophysics Data System (ADS)

Wishkerman, Asher; Arad (Malis), Shoshana

2017-05-01

Diatoms (Bacillariophyceae) are the most species-rich group of algae, they are single-celled characterized by a silicified cell wall called a frustule. Diatoms are diverse in shape with many distinct features like raphe and fultoportulae. The diatom cell wall morphology and its hierarchy structure make it a unique unicellular organism for nanotechnology research and applications. Diatom cells are a promising system for green synthesis of nanomaterials like metallic nanoparticles (NPs), nanostructured polymers and other nanomaterials. The production of NPs is achieved today by using methods like attrition or pyrolysis. The cost and the toxic substances often used in these common methods of NPs synthesis limit their applications. Therefore, NPs biosynthesis by diatom cultures, which can be done at ambient CO2 concentrations, temperature and pressure, offers a sustainable alternative solution. In this work, we examined the formation of silver NPs (AgNPs) by the diatom Phaeodactylum tricornutum cultivated at 25°C for a period of 8 days. Using this approach, diatom cultures were either grown throughout the duration of the experiment in an artificial seawater (ASW)-f/2 medium enriched with 1 ppm Ag+ or grown in an ASW-f/2 medium where similar silver ion concentrations were added on experimental day 4. We found that 1 ppm Ag+ reduces the P. tricornutum growth by up to 50% as compared with the control. Moreover, scanning electron microscopy (SEM) in combination with Energy-Dispersive X-ray (EDX) showed the presence of AgNPs nanoparticles with different sizes and chemical composition associated with the diatom frustules and extracellular polymeric substances.

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

PubMed Central

2011-01-01

Background The study investigated the distribution of silver after 28 days repeated oral administration of silver nanoparticles (AgNPs) and silver acetate (AgAc) to rats. Oral administration is a relevant route of exposure because of the use of silver nanoparticles in products related to food and food contact materials. Results AgNPs were synthesized with a size distribution of 14 ± 4 nm in diameter (90% of the nanoparticle volume) and stabilized in aqueous suspension by the polymer polyvinylpyrrolidone (PVP). The AgNPs remained stable throughout the duration of the 28-day oral toxicity study in rats. The organ distribution pattern of silver following administration of AgNPs and AgAc was similar. However the absolute silver concentrations in tissues were lower following oral exposure to AgNPs. This was in agreement with an indication of a higher fecal excretion following administration of AgNPs. Besides the intestinal system, the largest silver concentrations were detected in the liver and kidneys. Silver was also found in the lungs and brain. Autometallographic (AMG) staining revealed a similar cellular localization of silver in ileum, liver, and kidney tissue in rats exposed to AgNPs or AgAc. Using transmission electron microscopy (TEM), nanosized granules were detected in the ileum of animals exposed to AgNPs or AgAc and were mainly located in the basal lamina of the ileal epithelium and in lysosomes of macrophages within the lamina propria. Using energy dispersive x-ray spectroscopy it was shown that the granules in lysosomes consisted of silver, selenium, and sulfur for both AgNP and AgAc exposed rats. The diameter of the deposited granules was in the same size range as that of the administered AgNPs. No silver granules were detected by TEM in the liver. Conclusions The results of the present study demonstrate that the organ distribution of silver was similar when AgNPs or AgAc were administered orally to rats. The presence of silver granules containing

Leaching of Silver from Silver-Impregnated Food Storage Containers

ERIC Educational Resources Information Center

Hauri, James F.; Niece, Brian K.

2011-01-01

The use of silver in commercial products has proliferated in recent years owing to its antibacterial properties. Food containers impregnated with micro-sized silver promise long food life, but there is some concern because silver can leach out of the plastic and into the stored food. This laboratory experiment gives students the opportunity to…

Effect of nano silver and silver nitrate on seed yield of (Ocimum basilicum L.)

PubMed Central

2014-01-01

Background The aim of this study was to evaluate the effect of nano silver and silver nitrate on yield of seed in basil plant. The study was carried out in a randomized block design with three replications. Results Four levels of either silver nitrate (0, 100, 200 and 300 ppm) or nano silver (0, 20, 40, and 60 ppm) were sprayed on basil plant at seed growth stage. The results showed that there was no significant difference between 100 ppm of silver nitrate and 60 ppm concentration of nano silver on the shoot silver concentration. However, increasing the concentration of silver nitrate from 100 to 300 ppm caused a decrease in seed yield. In contrast, a raise in the concentration of nano silver from 20 to 60 ppm has led to an improvement in the seed yield. Additionally, the lowest amount of seed yield was found with control plants. Conclusions Finally, with increasing level of silver nitrate, the polyphenol compound content was raised but the enhancing level of nano silver resulting in the reduction of these components. In conclusion, nano silver can be used instead of other compounds of silver. PMID:25383311

Electrically Conductive Silver Paste Obtained by Use of Silver Neodecanoate as Precursor

NASA Astrophysics Data System (ADS)

Shen, Longguang; Liu, Jianguo; Zeng, Xiaoyan; Ren, Zhao

2015-02-01

An electrically conductive silver paste has been prepared from an organometallic compound, silver neodecanoate, as silver precursor. The precursor was highly soluble in organic solvents and decomposed into metallic silver at low sintering temperatures (<200°C). Thermogravimetric analysis showed the silver content of the paste was approximately 25 wt.%. Viscosity studies indicated the paste was a pseudoplastic liquid with viscosity in the range 6.5-9 Pa s. The paste was compatible with the micro-pen direct-writing process, enabling production of silver lines on a substrate. The electrical resistivity of the silver lines was 9 × 10-6 Ω cm after sintering at 115°C for 60 min, 5.8 × 10-6 Ω cm when sintered at 150°C for 60 min, and 3 × 10-6 Ω cm when sintered above 300°C, values which are similar to those of bulk silver. Hence, the prepared paste can be successfully used on flexible substrates such as polymers.

Bacterial transmission from lens storage cases to contact lenses-Effects of lens care solutions and silver impregnation of cases.

PubMed

Vermeltfoort, Pit B J; Hooymans, Johanna M M; Busscher, Henk J; van der Mei, Henny C

2008-10-01

The killing efficacies of multipurpose lens care solutions on planktonic and biofilm bacteria grown in polypropylene contact lens storage cases with and without silver impregnation and effects on bacterial transmission from storage cases to silicone hydrogel contact lenses were investigated. For transmission studies, biofilms of Staphylococcus aureus 835 or Pseudomonas aeruginosa no. 3 were grown on lens storage cases and incubated with a contact lens in different multipurpose lens care solutions (Opti-Free(R)Express(R), ReNu(R) MultiPlus(R), and SoloCare Aquatrade mark) or 0.9% NaCl. In addition, planktonic bacteria were directly suspended in multipurpose solutions and their killing efficacies were determined. The numbers of transmitted live and dead bacteria on the lenses were measured using a combination of plate counting and fluorescence microscopy. The highest killing efficacies were shown by Opti-Free(R) Express(R) for planktonic as well as for biofilm bacteria. Silver impregnation of lens cases in combination with the prescribed solution increased the killing efficacy for P. aeruginosa in biofilms, whereas effects for S. aureus were minor. Lowest numbers of live and dead bacteria were transmitted to a lens in Opti-Free(R) Express(R) multipurpose solution, with no significant differences between lens types and no effects of silver impregnation. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008. (c) 2008 Wiley Periodicals, Inc.

Fluorescence enhancement on silver nanostructures: studies of components of ribosomal translation in vitro

NASA Astrophysics Data System (ADS)

Mandecki, Wlodek; Bharill, Shashank; Borejdo, Julian; Cabral, Diana; Cooperman, Barry S.; Farrell, Ian; Fetter, Linus; Goldman, Emanuel; Gryczynski, Zygmunt; Jakubowski, Hieronim; Liu, Hanqing; Luchowski, Rafal; Matveeva, Evgenia; Pan, Dongli; Qin, Haiou; Tennant, Donald; Gryczynski, Ignacy

2008-02-01

Metallic particles, silver in particular, can significantly enhance the fluorescence of dye molecules in the immediate vicinity (5-20 nm) of the particle. This magnifying effect can be theoretically explained/predicted by considering the change of photonic mode density near the fluorophore due to coupling to the conducting surface. We are using this method to observe fluorescence from a single ribosomal particle in a project aimed at acquiring sequence information from the translating ribosome (NIH's $1000 Genome Initiative). Several quartz slides with silver nanostructures were made using electron beam lithography techniques. The structures were approximately 50 nm high silver tiles measuring 400-700 nm on the side, and were spaced differently over a total area of 1 mm x 1 mm on any given quartz slide. In a preliminary experiment, we coated this surface with the Alexa 647-labeled antibodies and collected single molecule images using the MicroTime 200 (PicoQuant) confocal system. We showed that the fluorescence intensity measured over the silver islands film was more than 100-fold higher than fluorescence from a comparable site on uncoated section of the quartz slide. No noticeable photobleaching was seen. The fluorescence lifetime was very short, about 200 ps or less (this is the resolution limit of the system). The method has great promise for investigations of biologically relevant single molecules.

Effect of nano-silver and boric acid on extending the vase life of cut rose (Rosa hybrida L.).

PubMed

Hashemabadi, Davood; Liavali, Mahbanoo Hoseinzadeh; Kaviani, Behzad; Mousavi, Meysam; Keyghobadi, Saghi; Zahiri, Samaneh

2014-09-01

Silver nano-particles (2-5 nm diam.), as antimicrobial agent and boric acid, as ethylene production inhibitor are used for enhancing the quality and vase life of cut flowers. In the present study the effects of a preservative solution containing nano-silver and boric acid on some traits of cut rose (Rosa hybrida L. cv. Yellow Island) including vase life, ethylene production, dry weight percentage, chlorophyll content, flower opening index, beta-carotene of petals and the number of basal stem end bacteria were investigated. The results showed that the effect of nano-silver and boric acid as either solitary or in combination with each other were significant (p < or = 0.01) on vase life, ethylene production and beta-carotene pigment. The effect of nano-silver on the number of bacteria on the end of stem was significant (p < or = 0.01). The highest cut flower longevity (9.69 day) was obtained in pulse-treated flowers with 100 mg l(-1) boric acid. The least ethylene production (0.59 nl(-1) g(-1) h(-1)) was observed in cut rose treated with 100 mg l(-1) boric acid along with 5 mg l(-1) nano-silver. The lowest number of bacteria in the end of stem was calculated in cut flowers treated with the highest concentrations of boric acid (300 mg l(-1)) and nano-silver (20 mg l(-1)).

Effect of Silver or Copper Nanoparticles-Dispersed Silane Coatings on Biofilm Formation in Cooling Water Systems

PubMed Central

Ogawa, Akiko; Kanematsu, Hideyuki; Sano, Katsuhiko; Sakai, Yoshiyuki; Ishida, Kunimitsu; Beech, Iwona B.; Suzuki, Osamu; Tanaka, Toshihiro

2016-01-01

Biofouling often occurs in cooling water systems, resulting in the reduction of heat exchange efficiency and corrosion of the cooling pipes, which raises the running costs. Therefore, controlling biofouling is very important. To regulate biofouling, we focus on the formation of biofilm, which is the early step of biofouling. In this study, we investigated whether silver or copper nanoparticles-dispersed silane coatings inhibited biofilm formation in cooling systems. We developed a closed laboratory biofilm reactor as a model of a cooling pipe and used seawater as a model for cooling water. Silver or copper nanoparticles-dispersed silane coating (Ag coating and Cu coating) coupons were soaked in seawater, and the seawater was circulated in the laboratory biofilm reactor for several days to create biofilms. Three-dimensional images of the surface showed that sea-island-like structures were formed on silane coatings and low concentration Cu coating, whereas nothing was formed on high concentration Cu coatings and low concentration Ag coating. The sea-island-like structures were analyzed by Raman spectroscopy to estimate the components of the biofilm. We found that both the Cu coating and Ag coating were effective methods to inhibit biofilm formation in cooling pipes. PMID:28773758

Facile and highly efficient approach for the fabrication of multifunctional silk nanofibers containing hydroxyapatite and silver nanoparticles.

PubMed

Sheikh, Faheem A; Ju, Hyung Woo; Moon, Bo Mi; Park, Hyun Jung; Kim, Jung-Ho; Lee, Ok Joo; Park, Chan Hum

2014-10-01

In this study, a good combination consisting of electrospun silk fibroin nanofibers incorporated with high-purity hydroxyapatite (HAp) nanoparticles (NPs) and silver NPs is introduced as antimicrobial for tissue engineering applications. The variable pressure field emission scanning electron microscope results confirmed randomly placed nanofibers are produced with highly dispersed HAp and silver NPs in nanofibers after electrospinning. The X-ray diffraction results demonstrated crystalline features of each of the three components used for electrospinning. Moreover, the TEM-EDS analysis confirmed the presence and chemical nature of each component over individual silk nanofiber. The FT-IR analyses was used confirm the different vibration modes caused due to functional groups present in silk fibroin, Hap, and silver NPs. The obtained nanofibers were checked for antimicrobial activity by using two model organisms Escherichia coli and Staphylococcus aureus. Subsequently, the antimicrobial tests have indicated that prepared nanofibers do possess good bactericidal activity. The ability of N,N-dimethylformamide and silk fibroin used to reduce silver nitrate into silver metal was evaluated using MTT assay. The nanofibers were grown in presence of NIH 3T3 fibroblasts, which revealed toxic behavior to fibroblasts at higher concentrations of silver nitrate used in this study. Furthermore, cell attachment studies on nanofibers for 3 and 12 days of incubation time were minutely observed and correlated with the results of MTT assay. The reported results confirmed the high amounts of silver nitrate can lead to toxic effects on viability of fibroblasts and had bad effect in cell attachment. © 2013 Wiley Periodicals, Inc.

In vitro percutaneous penetration and characterization of silver from silver-containing textiles

PubMed Central

Bianco, Carlotta; Kezic, Sanja; Crosera, Matteo; Svetličić, Vesna; Šegota, Suzana; Maina, Giovanni; Romano, Canzio; Larese, Francesca; Adami, Gianpiero

2015-01-01

The objective of this study was to determine the in vitro percutaneous penetration of silver and characterize the silver species released from textiles in different layers of full thickness human skin. For this purpose, two different wound dressings and a garment soaked in artificial sweat were placed in the donor compartments of Franz cells for 24 hours. The concentration of silver in the donor phase and in the skin was determined by an electrothermal atomic absorption spectrometer (ET-AAS) and by inductively coupled plasma mass spectrometer (ICP-MS). The characterization of silver species in the textiles and in the skin layers was made by scanning electron microscopy with integrated energy dispersive X-ray spectroscopy (SEM-EDX). Additionally, the size distribution of silver nanoparticles in the textiles was performed by atomic force microscopy (AFM). On the surface of all investigated materials, silver nanoparticles of different size and morphology were found. Released silver concentrations in the soaking solutions (ie, exposure concentration) ranged from 0.7 to 4.7 μg/mL (0.6–4.0 μg/cm2), fitting the bactericidal range. Silver and silver chloride aggregates at sizes of up to 1 μm were identified both in the epidermis and dermis. The large size of these particles suggests that the aggregation occurred in the skin. The formation of these aggregates likely slowed down the systemic absorption of silver. Conversely, these aggregates may form a reservoir enabling prolonged release of silver ions, which might lead to local effects. PMID:25792824

Electrochemical deposition of silver in room-temperature ionic liquids and its surface-enhanced Raman scattering effect.

PubMed

He, Ping; Liu, Hongtao; Li, Zhiying; Liu, Yang; Xu, Xiudong; Li, Jinghong

2004-11-09

The use of room-temperature ionic liquids (RTILs) as media for electrochemical application is very attractive. In this work, the electrochemical deposition of silver was investigated at a glassy carbon electrode in hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) RTILs and in KNO3 aqueous solution by cyclic voltammetric and potentiostatic transient techniques. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of silver from AgBF4 in both BMIMPF6 and BMIMBF(4), resembling the redox behavior of AgNO3 in KNO3 aqueous solution. A crossover loop was observed in all the cyclic voltammograms of these electrochemical systems, indicating a nucleation process. From the analysis of the experimental current transients, it was shown that the electrochemical deposition process of silver in these media was characteristic of 3D nucleation with diffusion-controlled hemispherical growth, and the silver nucleation closely followed the response predicted for progressive nucleation in BMIMPF6 and instantaneous nucleation in KNO3 aqueous solution, respectively. Compared with these two cases, the electrochemical deposition of silver in BMIMBF4 deviated from both the instantaneous and progressive nucleation models, which could be controlled by mixed kinetics and diffusion. On the basis of the experimental results, it was shown that parameters such as viscosity and water miscibility of RTILs would affect the electrodeposition behavior of silver. Atom force microscopy was employed to probe the surface morphology of the silver deposit, and it showed that the shining electrodeposit of silver was fairly dense and separate nanoclusters of <100 nm were in evidence, corresponding to an island growth model. The strongly enhanced Raman scattering from the monolayer film of 4-mercaptobenzoic acid demonstrated that as-prepared silver

Magnetite nano-islands on silicon-carbide with graphene

DOE PAGES

Anderson, Nathaniel A.; Zhang, Qiang; Hupalo, Myron; ...

2017-01-05

X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, Fe 3O 4). The Fe nano-islands (20 and 75 monolayers; MLs) are grown on epitaxial graphene formed by thermally annealing 6HSiC( 0001) and subsequently covered, in the growth chamber, with nominal 20 layers of Au. Our X-ray absorption spectroscopy and XMCD measurements at applied magnetic fields show that the thin film (20 ML) is totally converted to magnetite whereas the thickermore » lm (75 ML) exhibits properties of magnetite but also those of pure metallic iron. Temperature dependence of the XMCD signal (of both samples) shows a clear transition at T V ≈ 120 K consistent with the Verwey transition of bulk magnetite. These results have implications on the synthesis of magnetite nano-crystals and also on their regular arrangements on functional substrates such as graphene.« less

Magnetite nano-islands on silicon-carbide with graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Nathaniel A.; Zhang, Qiang; Hupalo, Myron

X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, Fe 3O 4). The Fe nano-islands (20 and 75 monolayers; MLs) are grown on epitaxial graphene formed by thermally annealing 6HSiC( 0001) and subsequently covered, in the growth chamber, with nominal 20 layers of Au. Our X-ray absorption spectroscopy and XMCD measurements at applied magnetic fields show that the thin film (20 ML) is totally converted to magnetite whereas the thickermore » lm (75 ML) exhibits properties of magnetite but also those of pure metallic iron. Temperature dependence of the XMCD signal (of both samples) shows a clear transition at T V ≈ 120 K consistent with the Verwey transition of bulk magnetite. These results have implications on the synthesis of magnetite nano-crystals and also on their regular arrangements on functional substrates such as graphene.« less

Photochemical Study of Silver Nanoparticles Formed from the Reduction of Silver Ions by Humic Acid

NASA Astrophysics Data System (ADS)

Leslie, Renee M.

This study focuses on the ability of silver ions and humic acid to form silver nanoparticles in the presence of UV and visible light. Silver nanoparticles have a number of industrial applications due primarily to their antimicrobial properties, but these properties pose an environmental threat. Silver nanoparticles can directly disrupt sensitive ecosystems by harming bacteria. Consumption of silver nanoparticles results in silver ions and silver nanoparticles entering waterways; the presence of silver ions raises the question of whether nanoparticles can reform in environmental waters. As our data show, silver nanoparticles can form from the reduction of silver ions by humic acid after irradiation with UV and visible light. In order to better understand the mechanism of these naturally synthesized silver nanoparticles, we investigated the effects of reactant concentration, experimental conditions and presence of ions/reactive species. We monitored silver nanoparticle growth with UV-visible spectroscopy. The evolution in time of nanoparticle size was monitored by dynamic light scattering (DLS).

Mineral commodity profiles: Silver

USGS Publications Warehouse

Butterman, W.C.; Hilliard, Henry E.

2005-01-01

Overview -- Silver is one of the eight precious, or noble, metals; the others are gold and the six platinum-group metals (PGM). World mine production in 2001 was 18,700 metric tons (t) and came from mines in 60 countries; the 10 leading producing countries accounted for 86 percent of the total. The largest producer was Mexico, followed by Peru, Australia, and the United States. About 25 percent of the silver mined in the world in 2001 came from silver ores; 15 percent, from gold ores and the remaining 60 percent, from copper, lead, and zinc ores. In the United States, 14 percent of the silver mined in 2001 came from silver ores; 39 percent, from gold ores; 10 percent, from copper and copper-molybdenum ores; and 37 percent, from lead, zinc, and lead-zinc ores. The precious metal ores (gold and silver) came from 30 lode mines and 10 placer mines; the base-metal ores (copper, lead, molybdenum, and zinc) came from 24 lode mines. Placer mines yielded less than 1 percent of the national silver production. Silver was mined in 12 States, of which Nevada was by far the largest producer; it accounted for nearly one-third of the national total. The production of silver at domestic mines generated employment for about 1,100 mine and mill workers. The value of mined domestic silver was estimated to be $290 million. Of the nearly 27,000 t of world silver that was fabricated in 2001, about one-third went into jewelry and silverware, one-fourth into the light-sensitive compounds used in photography, and nearly all the remainder went for industrial uses, of which there were 7 substantial uses and many other small-volume uses. By comparison, 85 percent of the silver used in the United States went to photography and industrial uses, 8 percent to jewelry and silverware, and 7 percent to coins and medals. The United States was the largest consumer of silver followed by India, Japan, and Italy; the 13 largest consuming countries accounted for nearly 90 percent of the world total. In the

Silver Flakes and Silver Dendrites for Hybrid Electrically Conductive Adhesives with Enhanced Conductivity

NASA Astrophysics Data System (ADS)

Ma, Hongru; Li, Zhuo; Tian, Xun; Yan, Shaocun; Li, Zhe; Guo, Xuhong; Ma, Yanqing; Ma, Lei

2018-03-01

Silver dendrites were prepared by a facile replacement reaction between silver nitrate and zinc microparticles of 20 μm in size. The influence of reactant molar ratio, reaction solution volume, silver nitrate concentration, and reaction time on the morphology of dendrites was investigated systematically. It was found that uniform tree-like silver structures are synthesized under the optimal conditions. Their structure can be described as a trunk, symmetrical branches, and leaves, which length scales of 5-10, 1-2 μm, and 100-300 nm, respectively. All features were systematically characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and x-ray powder diffraction. A hybrid fillers system using silver flakes and dendrites as electrically conductive adhesives (ECAs) exhibited excellent overall performance. This good conductivity can be attributed mainly to the synergy between the silver microflakes (5-20 μm sized irregular sheet structures) and dendrites, allowing more conductive pathways to be formed between the fillers. In order to further optimize the overall electrical conductivity, various mixtures of silver microflakes and silver dendrites were tested in ECAs, with results indicating that the highest conductivity was shown when the amounts of silver microflakes, silver dendrites and the polymer matrix were 69.4 wt.% (20.82 vol.%), 0.6 wt.% (0.18 vol.%), and 30.0 wt.% (79.00 vol.%), respectively. The corresponding mass ratio of silver flakes to silver dendrites was 347:3. The resistivity of ECAs reached as low as 1.7 × 10-4 Ω cm.

Colored and semitransparent silver nanoparticle layers deposited by spin coating of silver nanoink

NASA Astrophysics Data System (ADS)

Yoon, Hoi Jin; Jo, Yejin; Jeong, Sunho; Lim, Jung Wook; Lee, Seung-Yun

2018-05-01

In this letter, we report on the fabrication and characterization of colored and semitransparent silver nanoparticle layers. A spin coating of silver nanoink is used to deposit silver nanoparticle layers onto substrates. The transmittance and color of the silver nanoparticle layers are significantly dependent on the spin speed and nanoink concentration, owing to variations in the size and distribution of the nanoparticles. Both color variation and efficiency improvement are achieved with the application of silver nanoparticles to semitransparent Si thin-film solar cells, which is associated with the excitation of the dipole or quadruple plasmon modes of the silver nanoparticles.

Interpreting plasmonic response of epitaxial Ag/Si(100) island ensembles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Dexin; Jiang, Liying; Drucker, Jeff

Associating features in the experimentally measured optical response of epitaxial Ag islands grown on Si(100) with the localized surface plasmon resonances (LSPRs) hosted by the Ag islands is challenging due to the variation of the Si dielectric function over the energy range under consideration. However, it is possible to conclusively identify features in the experimental spectra with LSPR modes oscillating both parallel and perpendicular to the epitaxial interface by simulating the optical response. The Abeles matrix method is used to describe the composite layered system and the Ag islands are modeled using the thin island film model developed by Bedeauxmore » and Vlieger. By incorporating island morphology parameters determined by quantitative analysis of electron micrographs, the simulation faithfully reproduces the main features of the experimental spectra. Individually zeroing the dipoles associated with the LSPR modes enables conclusive identification of their contribution to the optical response of the composite system.« less

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors

NASA Astrophysics Data System (ADS)

Uznanski, Pawel; Zakrzewska, Joanna; Favier, Frederic; Kazmierski, Slawomir; Bryszewska, Ewa

2017-03-01

A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors.

PubMed

Uznanski, Pawel; Zakrzewska, Joanna; Favier, Frederic; Kazmierski, Slawomir; Bryszewska, Ewa

2017-01-01

A comparative study of amine and silver carboxylate adducts [R 1 COOAg-2(R 2 NH 2 )] (R 1  = 1, 7, 11; R 2  = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13 C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies ( 1 H and 13 C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism. Graphical abstractThe synthesis of a series (bis)alkylamine silver(I) carboxylate complexes in nonpolar solvents were carried out and fully characterized both in the solid and solution. Carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of

Similarities and Differences between Silver Ions and Silver in Nanoforms as Antibacterial Agents

PubMed Central

Kędziora, Anna; Speruda, Mateusz; Rybka, Jacek; Łukowiak, Anna; Bugla-Płoskońska, Gabriela

2018-01-01

Silver is considered as antibacterial agent with well-known mode of action and bacterial resistance against it is well described. The development of nanotechnology provided different methods for the modification of the chemical and physical structure of silver, which may increase its antibacterial potential. The physico-chemical properties of silver nanoparticles and their interaction with living cells differs substantially from those of silver ions. Moreover, the variety of the forms and characteristics of various silver nanoparticles are also responsible for differences in their antibacterial mode of action and probably bacterial mechanism of resistance. The paper discusses in details the aforementioned aspects of silver activity. PMID:29393866

Effect of fractal silver electrodes on charge collection and light distribution in semiconducting organic polymer films

DOE PAGES

Chamousis, Rachel L.; Chang, Lilian; Watterson, William J.; ...

2014-08-21

Living organisms use fractal structures to optimize material and energy transport across regions of differing size scales. Here we test the effect of fractal silver electrodes on light distribution and charge collection in organic semiconducting polymer films made of P3HT and PCBM. The semiconducting polymers were deposited onto electrochemically grown fractal silver structures (5000 nm × 500 nm; fractal dimension of 1.71) with PEDOT:PSS as hole-selective interlayer. The fractal silver electrodes appear black due to increased horizontal light scattering, which is shown to improve light absorption in the polymer. According to surface photovoltage spectroscopy, fractal silver electrodes outperform the flatmore » electrodes when the BHJ film thickness is large (>400 nm, 0.4 V photovoltage). Photocurrents of up to 200 microamperes cm -2 are generated from the bulk heterojunction (BHJ) photoelectrodes under 435 nm LED (10–20 mW cm -2) illumination in acetonitrile solution containing 0.005 M ferrocenium hexafluorophosphate as the electron acceptor. In conclusion, the low IPCE values (0.3–0.7%) are due to slow electron transfer to ferrocenium ion and due to shunting along the large metal–polymer interface. Overall, this work provides an initial assessment of the potential of fractal electrodes for organic photovoltaic cells.« less

Silver distribution and release from an antimicrobial denture base resin containing silver colloidal nanoparticles.

PubMed

Monteiro, Douglas Roberto; Gorup, Luiz Fernando; Takamiya, Aline Satie; de Camargo, Emerson Rodrigues; Filho, Adhemar Colla Ruvolo; Barbosa, Debora Barros

2012-01-01

The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods. A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers' instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37°C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy. Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens. Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers. © 2011 by the American College of Prosthodontists.

Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

NASA Astrophysics Data System (ADS)

Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

2012-10-01

Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

Self-ordering of a Ge island single layer induced by Si overgrowth.

PubMed

Capellini, G; De Seta, M; Evangelisti, F; Zinovyev, V A; Vastola, G; Montalenti, F; Miglio, Leo

2006-03-17

We provide a direct experimental proof and the related modeling of the role played by Si overgrowth in promoting the lateral ordering of Ge islands grown by chemical vapor deposition on Si(001). The deposition of silicon induces a shape transformation, from domes to truncated pyramids with a larger base, generating an array of closely spaced interacting islands. By modeling, we show that the resulting gradient in the chemical potential across the island should be the driving force for a selective flow of both Ge and Si atoms at the surface and, in turn, to a real motion of the dots, favoring the lateral order.

Plasmonic characterization of photo-induced silver nanoparticles extracted from silver halide based TEM film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

The plasmonic responses of silver nanoparticles extracted from silver halide based electron microscope film are investigated. Photo-reduction process is carried out to convert the silver halide grains into the metallic silver. The centrifuge technique is used for separating the silver nanoparticles from the residual solution. Morphological study performed by field emission scanning electron microscope (FESEM) shows that all the nanoparticles have an average diameter of ~120 nm with a high degree of mono dispersion in size. The localized surface plasmon resonance (LSPR) absorption peak at ~537 nm confirms the presence of large size silver nanoparticles.

Use of Silver in the Prevention and Treatment of Infections: Silver Review

PubMed Central

Campbell, Kristin T.; Rosenberger, Laura H.; Sawyer, Robert G.

2013-01-01

Abstract Background The use of silver for the treatment of various maladies or to prevent the transmission of infection dates back to at least 4000 b.c.e. Medical applications are documented in the literature throughout the 17th and 18th centuries. The bactericidal activity of silver is well established. Silver nitrate was used topically throughout the 1800s for the treatment of burns, ulcerations, and infected wounds, and although its use declined after World War II and the advent of antibiotics, Fox revitalized its use in the form of silver sulfadiazine in 1968. Method Review of the pertinent English-language literature. Results Since Fox's work, the use of topical silver to reduce bacterial burden and promote healing has been investigated in the setting of chronic wounds and ulcers, post-operative incision dressings, blood and urinary catheter designs, endotracheal tubes, orthopedic devices, vascular prostheses, and the sewing ring of prosthetic heart valves. The beneficial effects of silver in reducing or preventing infection have been seen in the topical treatment of burns and chronic wounds and in its use as a coating for many medical devices. However, silver has been unsuccessful in certain applications, such as the Silzone heart valve. In other settings, such as orthopedic hardware coatings, its benefit remains unproved. Conclusion Silver remains a reasonable addition to the armamentarium against infection and has relatively few side effects. However, one should weigh the benefits of silver-containing products against the known side effects and the other options available for the intended purpose when selecting the most appropriate therapy. PMID:23448590

Ethylene Receptor 1 (ETR1) Is Sufficient and Has the Predominant Role in Mediating Inhibition of Ethylene Responses by Silver in Arabidopsis thaliana*

PubMed Central

McDaniel, Brittany K.; Binder, Brad M.

2012-01-01

Ethylene influences many processes in Arabidopsis thaliana through the action of five receptor isoforms. All five isoforms use copper as a cofactor for binding ethylene. Previous research showed that silver can substitute for copper as a cofactor for ethylene binding activity in the ETR1 ethylene receptor yet also inhibit ethylene responses in plants. End-point and rapid kinetic analyses of dark-grown seedling growth revealed that the effects of silver are mostly dependent upon ETR1, and ETR1 alone is sufficient for the effects of silver. Ethylene responses in etr1-6 etr2-3 ein4-4 triple mutants were not blocked by silver. Transformation of these triple mutants with cDNA for each receptor isoform under the promoter control of ETR1 revealed that the cETR1 transgene completely rescued responses to silver while the cETR2 transgene failed to rescue these responses. The other three isoforms partially rescued responses to silver. Ethylene binding assays on the binding domains of the five receptor isoforms expressed in yeast showed that silver supports ethylene binding to ETR1 and ERS1 but not the other isoforms. Thus, silver may have an effect on ethylene signaling outside of the ethylene binding pocket of the receptors. Ethylene binding to ETR1 with silver was ∼30% of binding with copper. However, alterations in the Kd for ethylene binding to ETR1 and the half-time of ethylene dissociation from ETR1 do not underlie this lower binding. Thus, it is likely that the lower ethylene binding activity of ETR1 with silver is due to fewer ethylene binding sites generated with silver versus copper. PMID:22692214

High purity silver microcrystals recovered from silver wastes by eco-friendly process using hydrogen peroxide.

PubMed

Gatemala, Harnchana; Ekgasit, Sanong; Wongravee, Kanet

2017-07-01

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(NH 3 ) 2 ] + Cl - , derived from AgCl were generated and then directly reduced using H 2 O 2 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 H 2 O 2 :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 microcrystals can be used repeatedly (at least 8 cycles) without losing recovery efficiency. Matrix interferences including Pb 2+ 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. Copyright © 2017 Elsevier Ltd. All rights reserved.

Island of Hawaii, Hawaiian Archipelago

NASA Technical Reports Server (NTRS)

1983-01-01

This single photo covers almost all of the big island of Hawaii (19.5N, 155.5E) in the Hawaiian Archipelago. The active Kilauea Volcano and lava flow is under clouds and hardly visible at the lower right edge but the Mauna Loa volcano crater and its older lava flow is at the bottom center. The Kona Coast, that produces the only coffee grown in the United States, is to the left. Mauna Kea is the extinct volcano and lava flow in the right center.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

NASA Astrophysics Data System (ADS)

Liu, Suwen; Wehmschulte, Rudolf J.; Lian, Guoda; Burba, Christopher M.

2006-03-01

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 μm, some even more than 100 μm, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silver nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD).

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages

PubMed Central

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; Baer, Donald R.; Smith, Jordan N.; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D.; Chen, Shu; Porter, Alexandra E.; Ryan, Mary P.

2015-01-01

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies. PMID:26178265

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages.

PubMed

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H; Baer, Donald R; Smith, Jordan N; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D; Chen, Shu; Porter, Alexandra E; Ryan, Mary P

2015-09-15

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.

Room temperature direct band gap emission characteristics of surfactant mediated grown compressively strained Ge films

NASA Astrophysics Data System (ADS)

Katiyar, Ajit K.; Grimm, Andreas; Bar, R.; Schmidt, Jan; Wietler, Tobias; Joerg Osten, H.; Ray, Samit K.

2016-10-01

Compressively strained Ge films have been grown on relaxed Si0.45Ge0.55 virtual substrates using molecular beam epitaxy in the presence of Sb as a surfactant. Structural characterization has shown that films grown in the presence of surfactant exhibit very smooth surfaces with a relatively higher strain value in comparison to those grown without any surfactant. The variation of strain with increasing Ge layer thickness was analyzed using Raman spectroscopy. The strain is found to be reduced with increasing film thickness due to the onset of island nucleation following Stranski-Krastanov growth mechanism. No phonon assisted direct band gap photoluminescence from compressively strained Ge films grown on relaxed Si0.45Ge0.55 has been achieved up to room temperature. Excitation power and temperature dependent photoluminescence have been studied in details to investigate the origin of different emission sub-bands.

Polyimides Containing Silver Trifluoroacetylacetonate

NASA Technical Reports Server (NTRS)

Stoakley, Diane M.; St. Clair, Anne K.; Rancourt, James D.; Taylor, Larry T.; Caplan, Maggie L.

1994-01-01

Mechanically strong, flexible, thermally stable, electrically conductive films and coatings suitable for use in electronics industry made by incorporating silver trifluoroacetylacetonate into linear aromatic condensation polyimides. In experimental films, most successful combinations of flexibility and conductivity obtained by use of 1:1, 1:1.74, and 1:2 mole ratios of silver trifluoroacetylacetonate per polyimide repeat unit. Other concentrations of silver trifluoroacetylacetonate used with different heat-treatment schedules to obtain conductive silver-impregnated films.

Fractionation of silver isotopes in native silver explained by redox reactions

NASA Astrophysics Data System (ADS)

Mathur, Ryan; Arribas, Antonio; Megaw, Peter; Wilson, Marc; Stroup, Steven; Meyer-Arrivillaga, Danilo; Arribas, Isabel

2018-03-01

Scant data exist on the silver isotope composition of native silver specimens because of the relative newness of the technique. This study increases the published dataset by an order of magnitude and presents 80 silver new isotope analyses from native silver originating from a diverse set of worldwide deposits (8 deposit types, 33 mining districts in five continents). The measured isotopic range (defined as δ109Ag/107Ag in per mil units compared to NIST 978 Ag isotope standard) is +2.1 to -0.86‰ (2σ errors less than 0.015); with no apparent systematic correlations to date with deposit type or even within districts. Importantly, the data centering on 0‰ all come from high temperature hypogene/primary deposits whereas flanking and overlapping data represent secondary supergene deposits. To investigate the causes for the more fractionated values, several laboratory experiments involving oxidation of silver from natural specimens of Ag-rich sulfides and precipitation and adsorption of silver onto reagent grade MnO2 and FeOOH were conducted. Simple leach experiments demonstrate little Ag isotope fractionation occurred through oxidation of Ag from native Ag (Δsolution-native109Ag = 0.12‰). In contrast, significant fractionation occurred through precipitation of native Ag onto MnO2 (up to Δsolution-MnO2109Ag = 0.68‰, or 0.3amu). Adsorption of silver onto the MnO2 and FeOOH did not produce as large fractionation as precipitation (mean value of Δsolution-MnO2109Ag = 0.10‰). The most likely cause for the isotopic variations seen relates to redox effects such as the reduction of silver from Ag (I) to Ag° that occurs during precipitation onto the mineral surface. Since many Ag deposits have halos dominated by MnO2 and FeOOH phases, potential may exist for the silver isotope composition of ores and surrounding geochemical haloes to be used to better understand ore genesis and potential exploration applications. Aside from the Mn oxides, surface fluid silver

Production of silver ions from colloidal silver by nanoparticle iontophoresis system.

PubMed

Tseng, Kuo-Hsiung; Liao, Chih-Yu

2011-03-01

Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion release application. For medical purposes, conversion of colloidal silver into an ionic form is necessary, but not using silver salts (e.g., AgNO3, Ag2SO4), due to the fact that the counter-ion of silver salts may cause problems to the body as the silver ion (Ag+) is consumed. The goal of this research is to develop a silver nanoparticle iontophoresis system (NIS) which can provide a relatively safe bactericidal silver ion solution with a controllable electric field. In this study, ion-selective electrodes were used to identify and observe details of the system's activity. Both qualitative and quantitative data analyses were performed. The experimental results show that the ion releasing peak time (R(PT)) has an inversely proportional relationship with the applied current and voltage. The ion releasing maximum level (R(ML)) and dosage (R(D)) are proportional to the current density and inversely proportional to the voltage, respectively. These results reveal that the nanoparticle iontophoresis system (NIS) is an alternative method for the controlled release of a metal ion and the ion's concentration profile, by controlling the magnitude of current density (1 microA/cm2 equal to 1 ppm/hour) and applied voltage.

Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction▿ †

PubMed Central

Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.

2010-01-01

Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact. PMID:20660682

Process for making silver metal filaments

DOEpatents

Bamberger, Carlos E.

1997-01-01

A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Suwen; Wehmschulte, Rudolf J.; Lian Guoda

2006-03-15

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 {mu}m, some even more than 100 {mu}m, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silvermore » nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD)« less

A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles

PubMed Central

Bachler, Gerald; von Goetz, Natalie; Hungerbühler, Konrad

2013-01-01

Silver is a strong antibiotic that is increasingly incorporated into consumer products as a bulk, salt, or nanosilver, thus potentially causing side-effects related to human exposure. However, the fate and behavior of (nano)silver in the human body is presently not well understood. In order to aggregate the existing experimental information, a physiologically based pharmacokinetic model (PBPK) was developed in this study for ionic silver and nanosilver. The structure of the model was established on the basis of toxicokinetic data from intravenous studies. The number of calibrated parameters was minimized in order to enhance the predictive capability of the model. We validated the model structure for both silver forms by reproducing exposure conditions (dermal, oral, and inhalation) of in vivo experiments and comparing simulated and experimentally assessed organ concentrations. Therefore, the percutaneous, intestinal, or pulmonary absorption fraction was estimated based on the blood silver concentration of the respective experimental data set. In all of the cases examined, the model could successfully predict the biodistribution of ionic silver and 15–150 nm silver nanoparticles, which were not coated with substances designed to prolong the circulatory time (eg, polyethylene glycol). Furthermore, the results of our model indicate that: (1) within the application domain of our model, the particle size and coating had a minor influence on the biodistribution; (2) in vivo, it is more likely that silver nanoparticles are directly stored as insoluble salt particles than dissolve into Ag+; and (3) compartments of the mononuclear phagocytic system play a minor role in exposure levels that are relevant for human consumers. We also give an example of how the model can be used in exposure and risk assessments based on five different exposure scenarios, namely dietary intake, use of three separate consumer products, and occupational exposure. PMID:24039420

Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

NASA Astrophysics Data System (ADS)

Pal, Hemant; Sharma, Vimal

2014-11-01

The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young's modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young's modulus of the nanocomposites were increased by 30%-40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

Monitoring seasonal bat activity on a coastal barrier island in Maryland, USA.

PubMed

Johnson, Joshua B; Gates, J Edward; Zegre, Nicolas P

2011-02-01

Research on effects of wind turbines on bats has increased dramatically in recent years because of significant numbers of bats killed by rotating wind turbine blades. Whereas most research has focused on the Midwest and inland portions of eastern North America, bat activity and migration on the Atlantic Coast has largely been unexamined. We used three long-term acoustic monitoring stations to determine seasonal bat activity patterns on the Assateague Island National Seashore, a barrier island off the coast of Maryland, from 2005 to 2006. We recorded five species, including eastern red bats (Lasiurus borealis), big brown bats (Eptesicus fuscus), hoary bats (Lasiurus cinereus), tri-colored bats (Perimyotis subflavus), and silver-haired bats (Lasionycteris noctivagans). Seasonal bat activity (number of bat passes recorded) followed a cosine function and gradually increased beginning in April, peaked in August, and declined gradually until cessation in December. Based on autoregressive models, inter-night bat activity was autocorrelated for lags of seven nights or fewer but varied among acoustic monitoring stations. Higher nightly temperatures and lower wind speeds positively affected bat activity. When autoregressive model predictions were fitted to the observed nightly bat pass totals, model residuals>2 standard deviations from the mean existed only during migration periods, indicating that periodic increases in bat activity could not be accounted for by seasonal trends and weather variables alone. Rather, the additional bat passes were attributable to migrating bats. We conclude that bats, specifically eastern red, hoary, and silver-haired bats, use this barrier island during migration and that this phenomenon may have implications for the development of near and offshore wind energy.

Effects of Disinfectants in Water on Mir- and Earth-Grown Wheat

NASA Technical Reports Server (NTRS)

Campbell, William .F.; Bubenheim, D. L.; Bugbee, B.; Salisbury, F. B.; Bingham, G. E.; Levinskikh, M.; Sytchev, V. N.; Ivanova, I.; Chernova, L.; Podolsky, I.

2002-01-01

-based post-flight analyses, the levels of iodine- and/or silver fluoride-treated water used on Mir-grown plants onboard the Mir did not cause the poor growth and development of the wheat plants.

"Go local" island food network: using email networking to promote island foods for their health, biodiversity, and other "CHEEF" benefits.

PubMed

Englberger, L; Lorens, A; Pretrick, M E; Spegal, R; Falcam, I

2010-04-01

Dietary- and lifestyle-related diseases are problems of epidemic proportion in the Federated States of Micronesia (FSM). Public health resources to help prevent nutrition-related problems are limited. There is also concern about biodiversity, neglect of traditional staple foods, and threatened loss of traditional knowledge. A "Go Local" campaign was initiated to increase production and consumption of locally grown foods, for their Culture, Health, Environment, Economics, and Food security ("CHEEF") benefits. To provide updates and discuss local island food topics, the Island Food Community of Pohnpei launched an interagency email network in 2003. Interested members' email addresses were recorded in distribution lists, weekly/bi-weekly emails were sent and from these messages, a database was organized to record email topic details. An analysis of all emails up to July 2009 showed that membership had expanded to over 600 listed people from all FSM states, other Pacific Island countries and beyond. Information was shared on topics ranging from scientific findings of carotenoid content in local island food cultivars, to discussions on how daily habits related to island food use can be improved. Over 200 men and women, aged 22 to 80 years, contributed items, some indicating that they had shared emails to a further network at their workplace or community. In conclusion, this email network is a simple, cost-effective method to share information, create awareness, and mobilize island food promotion efforts with potential for providing health, biodiversity and other benefits of island foods to populations in the FSM and other countries.

Silver-halide gelatin holograms

NASA Astrophysics Data System (ADS)

Chang, B. J.; Winick, K.

1980-05-01

The use of a silver-halide gelatin for volume phase holograms having a wide spectral response and lower exposure requirements than alternatives and using commercially available silver salts, is proposed. The main difference between the dichromated gelatin and silver-halide processes is the creation of a hologram latent image, which is given in the form of a hardness differential between exposed and unexposed regions in the silver halide hologram; the differential is in turn created by the reaction products of either tanning development or tanning bleach, which harden the gelatin with link-bonds between molecules.

A perspective on the hemolytic activity of chemical and green-synthesized silver and silver oxide nanoparticles

NASA Astrophysics Data System (ADS)

Ashokraja, C.; Sakar, M.; Balakumar, S.

2017-10-01

We report the hemolysis properties of silver and silver oxide nanoparticles (NPs) prepared by chemical and green-synthesis methods. The prepared silver and silver oxide NPs were analyzed using UV-vis spectroscopy to confirm their formation by characterizing their surface plasmon resonance (SPR) and absorption band peaks respectively. The Fourier transmission infrared (FTIR) spectra of the materials showed the characteristic functional groups corresponding to the molecules present in leaf extracts, which is proposed to be acted as reducing and capping agents that are also found on the surface of silver and silver oxide nanoparticles that synthesized via green-synthesis method. Zeta potential analysis revealed the surface charge and stability of the prepared NPs. HRTEM images showed almost spherical shape nanoparticles with an average size of 15.2 and 31.5 nm for wet chemical synthesized silver and silver oxide nanoparticles respectively. In the case of green synthesized silver and silver oxide nanoparticles, it was observed to be 19.4 and 30.4 nm respectively. The order of hemolysis efficacy of the materials is found to be as follows: chemically synthesized Ag2O>  chemically synthesized Ag NPs followed by green-synthesized Ag2O and green-synthesized Ag NPs which showed almost similar hemolysis with respect to concentration. The relatively stable nature of the silver NPs could be attributed to their lower hemolysis efficacy, while the increased lysis properties of silver oxide could be attributed due to reductive/oxidative processes that give rise to the hemolysis through interfacial charge interactions with RBCs.

Geology of Unga Island and the northwestern part of Popof Island: Chapter 2 in A geological and geophysical study of the gold-silver vein system of Unga Island, Southwestern Alaska

USGS Publications Warehouse

Riehle, James R.; Wilson, Frederic H.; Shew, Nora B.; White, Willis H.

1999-01-01

The first geologic map of Unga Island was published by Atwood (1911; scale 1:250,000), who correctly inferred the middle Tertiary age of the volcanic rocks and made the important distinction between the lava flows and the intrusive domes. Although Burk's (1964) reconnaissance map of the Alaska Peninsula (scale 1:250,000) has been modified in some respects, it does correct Atwood's map by replacing the Kenai Formation on northwestern Unga Island with the Unga Conglomerate and by recognizing the older Stepovak Formation elsewhere on Unga and Popof Islands.U.S. Geological Survey (USGS) field studies that were focused on the mineral-resource potential of the Alaska Peninsula began in the late 1970's. These studies led to a geologic map of the Port Moller quadrangle--including Unga Island--at 1:250,000 scale (Wilson and others, 1995), as well as summaries of mineral occurrences and geochronological studies (Wilson and others, 1988, 1994) and a formal revision of the stratigraphic units of the Alaska Peninsula (Detterman and others, 1996). As follow-up to the regional studies, a detailed study of the vein systems on Unga Island was undertaken as a collaborative effort between USGS and private industry (White and Queen, 1989). The fieldwork leading to the present report and geologic map was started in 1978 (Riehle and others, 1982) and was completed as part of the vein study. The objective was a better understanding of the geologic setting of the vein systems: the geologic history of the host rocks, the structural controls on the veins, and the types of processes that likely caused the mineralization.

Effect of Silver Flakes in Silver Paste on the Joining Process and Properties of Sandwich Power Modules (IGBTs Chip/Silver Paste/Bare Cu)

NASA Astrophysics Data System (ADS)

Zhao, Su-Yan; Li, Xin; Mei, Yun-Hui; Lu, Guo-Quan

2016-11-01

In this study, a silver paste has been introduced for attaching chips onto bare Cu substrates (without coating) without applying pressure. Small nano-thickness Ag flakes, measuring 1 μm-5 μm length, were embedded uniformly in Ag nanoparticles for improving the density of the material. The presence of silver flakes in the silver paste affected the joining process and its microstructure. Microstructure characterization revealed that densification of the silver layer was affected by the presence of silver flakes as the flakes coarsened and formed reactive in situ nanoparticles, which facilitated the sintering between the flakes and the incorporated nanoparticles. Coarsening of silver flakes depended on the sintering temperature, time, and the atmosphere, which affected the decomposition and burning out of organics presented on the surface of the flakes. A high-density silver layer was obtained due to the presence of compact silver flakes. With an increase in the microstructure density, a higher bonding strength and a lower thermal impedance of the sintered joints were achieved. On performing pressureless sintering at 270°C for 30 min under 99.99% N2 or 4% H2/N2, the bonding strength and thermal impedance for 11 × 11 mm2 chips were excellent, measuring approximately 21.9 MPa and 0.077°C/W, respectively.

Characterization of Electrochemically Generated Silver

NASA Technical Reports Server (NTRS)

Adam, Niklas; Martinez, James; Carrier, Chris

2014-01-01

Silver biocide offers a potential advantage over iodine, the current state of the art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. Low concentrations of silver (<500 ppb) have been shown to kill bacteria in water systems and keep it safe for potability. Silver does not require hardware to remove it from a water system, and therefore can provide a simpler means for disinfecting water. The Russian segment of the International Space Station has utilized an electrochemically generated silver solution, which is colloidal in nature. To be able to reliably provide a silver biocide to drinking water by electrochemical means would reduce mass required for removing another biocide such as iodine from the water. This would also aid in crew time required to replace iodine removal cartridges. Future long term missions would benefit from electrochemically produced silver as the biocide could be produced on demand and requires only a small concentration to be effective. Since it can also be consumed safely, there is less mass in removal hardware and little consumables required for production. The goal of this project initially is to understand the nature of the electrochemically produced silver, the particle sizes produced by the electrochemical cell and the effect that voltage adjustment has on the particle size. In literature, it has been documented that dissolved oxygen and pH have an effect on the ionization of the electrochemical silver so those parameters would be measured and possibly adjusted to understand their effect on the silver.

Dosimetry using silver salts

DOEpatents

Warner, Benjamin P.

2003-06-24

The present invention provides a method for detecting ionizing radiation. Exposure of silver salt AgX to ionizing radiation results in the partial reduction of the salt to a mixture of silver salt and silver metal. The mixture is further reduced by a reducing agent, which causes the production of acid (HX) and the oxidized form of the reducing agent (R). Detection of HX indicates that the silver salt has been exposed to ionizing radiation. The oxidized form of the reducing agent (R) may also be detected. The invention also includes dosimeters employing the above method for detecting ionizing radiation.

Effect of preconditioning on silver leaching and bromide removal properties of silver-impregnated activated carbon (SIAC).

PubMed

Rajaeian, Babak; Allard, Sébastien; Joll, Cynthia; Heitz, Anna

2018-07-01

Silver impregnated activated carbon (SIAC) has been found to be effective in mitigating the formation of brominated-disinfection by products during drinking water treatment. However, there are still uncertainties regarding its silver leaching properties, and strategies for the prevention of silver leaching have remained elusive. This study focused on the evaluation of one type of commercially available SIAC for its ability to remove bromide while minimising silver leaching from the material. Both synthetic and real water matrices were tested. Depending on solution pH, it was found that changing the surface charge properties of SIAC, as measured by the point of zero charge pH, can result in additional bromide removal while minimising the extent of silver leaching. To better understand the mechanism of silver leaching from the SIAC, eight preconditioning environments, i.e. variable pH and ionic strength were tested for a fixed amount of SIAC and two preconditioning environments were selected for a more detailed investigation. Experiments carried out in synthetic water showed that preconditioning at pH 10.4 did not deteriorate the capacity of SIAC to remove bromide, but significantly decreased the release of silver in the form of ionic silver (Ag + ), silver bromide (AgBr) and silver chloride (AgCl) from 40% for the pristine to 3% for the treated SIAC. This was confirmed using a groundwater sample. These results suggest that preconditioned SIAC has the potential to be an effective method for bromide removal with minimised silver leaching in a long-term field application for drinking water production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ultralight Conductive Silver Nanowire Aerogels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Fang; Lan, Pui Ching; Freyman, Megan C.

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here in this work, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm 3 and an electrical conductivity up tomore » 51 000 S/m. Lastly, mechanical studies show that silver nanowire aerogels exhibit “elastic stiffening” behavior with a Young’s modulus up to 16 800 Pa.« less

Ultralight Conductive Silver Nanowire Aerogels

DOE PAGES

Qian, Fang; Lan, Pui Ching; Freyman, Megan C.; ...

2017-09-05

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here in this work, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm 3 and an electrical conductivity up tomore » 51 000 S/m. Lastly, mechanical studies show that silver nanowire aerogels exhibit “elastic stiffening” behavior with a Young’s modulus up to 16 800 Pa.« less

One-Pot Silver Nanoring Synthesis

NASA Astrophysics Data System (ADS)

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2010-03-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-pot silver nanoring synthesis.

PubMed

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2009-12-16

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-Pot Silver Nanoring Synthesis

PubMed Central

2010-01-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation. PMID:20672109

Bioinspired Hierarchical Nanofibrous Silver-Nanoparticle/Anatase-Rutile-Titania Composite as an Anode Material for Lithium-Ion Batteries.

PubMed

Luo, Yan; Li, Jiao; Huang, Jianguo

2016-11-29

A new bioinspired hierarchical nanofibrous silver-nanoparticle/anatase-rutile-titania (Ag-NP/A-R-titania) composite was fabricated by employing a natural cellulose substance (e.g., commercial laboratory cellulose filter paper) as the structural scaffold template, which was composed of anatase-phase titania (A-titania) nanotubes with rutile-phase titania (R-titania) nanoneedles grown on the surfaces and further silver nanoparticles (AgNPs) immobilized thereon. As it was employed as an anode material for lithium-ion batteries (LIBs), high reversible capacity, enhanced rate performance, and excellent cycling stability were achieved as compared with those of the corresponding cellulose-substance-derived nanotubular A-titania, R-titania, heterogeneous anatase/rutile titania (A-R-titania) composite, and commercial P25 powder. This benefited from its unique porous cross-linked three-dimensional structure inherited from the initial cellulose substance scaffold, which enhances the sufficient electrode/electrolyte contact, relieves the severe volume change upon cycling, and improves the amount of lithium-ion storage; moreover, the high loading content of the silver component in the composite improves the electrical conductivity of the electrode. The structural integrity of the composite was maintained upon long-term charge/discharge cycling, indicating its significant stability.

Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

NASA Astrophysics Data System (ADS)

Petala, M.; Tsiridis, V.; Mintsouli, I.; Pliatsikas, N.; Spanos, Th.; Rebeyre, P.; Darakas, E.; Patsalas, P.; Vourlias, G.; Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th.

2017-02-01

Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

Reflective Silvered Polyimide Films Via In Situ Thermal Reduction Silver (I) Complexes

NASA Technical Reports Server (NTRS)

Southward, Robin E. (Inventor); Thompson, David W. (Inventor); St.Clair, Anne K. (Inventor); Stoakley, Diane M. (Inventor)

2000-01-01

Self-metallizing. flexible polyimide films with highly reflective surfaces are prepared by an in situ self-metallization procedure involving thermally initiated reduction of polymer-soluble silver(I) complexes. Polyamic acid solutions are doped with silver(I) acetate and solubilizing agents. Thermally curing the silver(I) doped resins leads to flexible. metallized films which have reflectivities as high as 100%. abrasion-resistant surfaces. thermal stability and, in some cases, electrical conductivity, rendering them useful for space applications.

Indium Growth and Island Height Control on Si Submonolayer Phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jizhou

2009-01-01

length of 13.4 nm so it can curve on the surface of an sample to make structure as small as the order of 10 nm. however, lithograph usually causes permanent damages to the surface and in many cases the QDs are damaged during the lithograph and therefore result in high percentage of defects. Quantum size effect has attracted more and more interests in surface science due to many of its effects. One of its effects is the height preference in film growing and the resulting possibility of uniformly sized self-assemble nanostructure. The experiment of Pb islands on In 4x1 phase shows that both the height and the width can be controlled by proper growth conditions, which expands the growth dimensions from 1 to 2. This discover leads us to study the In/Pb interface. In Ch.3, we found that the Pb islands growing on In 4x1-Si(111) surface which have uniform height due to QSE and uniform width due to the constriction of In 4x1 lattice have unexpected stability. These islands are stable in even RT, unlike usual nanostructures on Pb/Si surface which are stable only at low temperature. Since similar structures are usually grown at low temperature, this discovery makes the grown structures closer to technological applications. It also shows the unusual of In/Pb interface. Then we studied the In islands grown on Pb-α-√3x√3-Si(111) phase in Ch.4. These islands have fcc structure in the first few layers, and then convert to bct structure. The In fcc islands have sharp height preference due to QSE like Pb islands. However, the preferred height is different (7 layer for Pb on Si 7x7 and 4 layer for Pb on In 4x1), due to the difference of interface. The In islands structure prefers to be bct than fcc with coverage increase. It is quantitatively supported by first-principle calculation. Unexpectedly, the In islands grown on various of In interfaces didn't show QSE effects and phase transition from fcc and bct structures as on the Pb-α interface (Ch.6). In g(s) curve there is no clear

Measurements of the optical properties of thin films of silver and silver oxide

NASA Technical Reports Server (NTRS)

Peters, Palmer N.; Sisk, Robert C.; Brown, Yolanda; Gregory, John C.; Nag, Pallob K.; Christl, Ligia

1995-01-01

The optical properties of silver films and their oxides are measured to better characterize such films for use as sensors for atomic oxygen. Good agreement between properties of measured pure silver films and reported optical constants is observed. Similar comparisons for silver oxide have not been possible because of a lack of reported constants, but self-consistencies and discrepancies in our measured results are described.

Quantification of metal loading to Silver Creek through the Silver Maple Claims area, Park City, Utah, May 2002

USGS Publications Warehouse

Kimball, Briant A.; Johnson, Kevin K.; Runkel, Robert L.; Steiger, Judy I.

2004-01-01

The Silver Maple Claims area along Silver Creek, near Park City, Utah, is administered by the Bureau of Land Management. To quantify possible sources of elevated zinc concentrations in Silver Creek that exceed water-quality standards, the U.S. Geological Survey conducted a mass-loading study in May 2002 along a 1,400-meter reach of Silver Creek that included the Silver Maple Claims area. Additional samples were collected upstream and downstream from the injection reach to investigate other possible sources of zinc and other metals to the stream. Many metals were investigated in the study, but zinc is of particular concern for water-quality standards. The total loading of zinc along the study reach from Park City to Wanship, Utah, was about 49 kilograms per day. The Silver Maple Claims area contributed about 38 percent of this load. The Silver Creek tailings discharge pipe, which empties just inside the Silver Maple Claims area, contributed more than half the load of the Silver Maple Claims area. Substantial zinc loads also were added to Silver Creek downstream from the Silver Maple Claims area. Ground-water discharge upstream from the waste-water treatment plant contributed 20 percent of the total zinc load, and another 17 percent was contributed near the waste-water treatment plant. By identifying the specific areas where zinc and other metal loads are contributed to Silver Creek, it is possible to assess the needs of a remediation plan. For example, removing the tailings from the Silver Maple Claims area could contribute to lowering the zinc concentration in Silver Creek, but without also addressing the loading from the Silver Creek tailings discharge pipe and the ground-water discharge farther downstream, the zinc concentration could not be lowered enough to meet water-quality standards. Additional existing sources of zinc loading downstream from the Silver Maple Claims area could complicate the process of lowering zinc concentration to meet water

Percutaneous penetration of silver from a silver containing garment in healthy volunteers and patients with atopic dermatitis.

PubMed

Pluut, Olivier A; Bianco, Carlotta; Jakasa, Ivone; Visser, Maaike J; Krystek, Petra; Larese-Filon, Francesca; Rustemeyer, Thomas; Kezic, Sanja

2015-06-01

Human data on dermal absorption of silver under "in use" scenario are scarce which hampers health risk assessment. The main objective of the present study was to determine percutaneous penetration of silver after dermal exposure to silver containing garment in healthy individuals and atopic dermatitis (AD) patients. Next to assess pro-inflammatory effect of silver in the skin. Healthy subjects (n=15) and patients with AD (n=15) wore a sleeve containing 3.6% (w/w) silver on their lower arms for 8h during 5 consecutive days. The percutaneous penetration parameters were deduced from the silver concentration-depth profiles in the stratum corneum (SC) collected by adhesive tapes. Furthermore, silver was measured in urine samples collected before and after exposure. Inflammatory response was assessed by measuring IL-1α and IL-1RA in the exposed and non-exposed skin sites. Dermal flux of silver in healthy subjects and AD patients was respectively 0.23 and 0.20 ng/cm(2)/h. The urine silver concentrations showed no increase after exposure. Furthermore, exposure to silver did not lead to the changes in the profiles of IL-1α and IL-1RA. Dermal absorption of silver under "real life scenario" was lower than the current reference dose. Furthermore, dermal exposure did not lead to altered expression of inflammatory IL-1 cytokines in the skin. Copyright © 2015. Published by Elsevier Ireland Ltd.

Green synthesis of colloid silver nanoparticles and resulting biodegradable starch/silver nanocomposites.

PubMed

Cheviron, Perrine; Gouanvé, Fabrice; Espuche, Eliane

2014-08-08

Environmentally friendly silver nanocomposite films were prepared by an ex situ method consisting firstly in the preparation of colloidal silver dispersions and secondly in the dispersion of the as-prepared nanoparticles in a potato starch/glycerol matrix, keeping a green chemistry process all along the synthesis steps. In the first step concerned with the preparation of the colloidal silver dispersions, water, glucose and soluble starch were used as solvent, reducing agent and stabilizing agent, respectively. The influences of the glucose amount and reaction time were investigated on the size and size distribution of the silver nanoparticles. Two distinct silver nanoparticle populations in size (diameter around 5 nm size for the first one and from 20 to 50 nm for the second one) were distinguished and still highlighted in the potato starch/glycerol based nanocomposite films. It was remarkable that lower nanoparticle mean sizes were evidenced by both TEM and UV-vis analyses in the nanocomposites in comparison to the respective colloidal silver dispersions. A dispersion mechanism based on the potential interactions developed between the nanoparticles and the polymer matrix and on the polymer chain lengths was proposed to explain this morphology. These nanocomposite film series can be viewed as a promising candidate for many applications in antimicrobial packaging, biomedicines and sensors. Copyright © 2014 Elsevier Ltd. All rights reserved.

Printing Silver Nanogrids on Glass

ERIC Educational Resources Information Center

Sanders, Wesley C.; Valcarce, Ron; Iles, Peter; Smith, James S.; Glass, Gabe; Gomez, Jesus; Johnson, Glen; Johnston, Dan; Morham, Maclaine; Befus, Elliot; Oz, Aimee; Tomaraei, Mohammad

2017-01-01

This manuscript describes a laboratory experiment that provides students with an opportunity to create conductive silver nanogrids using polymeric templates. A microcontact-printed polyvinylpyrrolidone grid directs the citrate-induced reduction of silver ions for the fabrication of silver nanogrids on glass substrates. In addition to…

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2011 CFR

2011-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2010 CFR

2010-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2013 CFR

2013-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2012 CFR

2012-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

Code of Federal Regulations, 2014 CFR

2014-04-01

... ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. 310...) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have... disease conditions. There are serious and complicating aspects to many of the diseases these silver...

Sponge-like silver obtained by decomposition of silver nitrate hexamethylenetetramine complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afanasiev, Pavel, E-mail: pavel.afanasiev@ircelyon.univ-lyon.fr

2016-07-15

Silver nitrate hexamethylenetetramine [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] coordination compound has been prepared via aqueous route and characterized by chemical analysis, XRD and electron microscopy. Decomposition of [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] under hydrogen and under inert has been studied by thermal analysis and mass spectrometry. Thermal decomposition of [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] proceeds in the range 200–250 °C as a self-propagating rapid redox process accompanied with the release of multiple gases. The decomposition leads to formation of sponge-like silver having hierarchical open pore system with pore size spanning from 10 µm to 10 nm. The as-obtained silver spongesmore » exhibited favorable activity toward H{sub 2}O{sub 2} electrochemical reduction, making them potentially interesting as non-enzyme hydrogen peroxide sensors. - Graphical abstract: Thermal decomposition of silver nitrate hexamethylenetetramine coordination compound [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] leads to sponge like silver that possesses open porous structure and demonstrates interesting properties as an electrochemical hydrogen peroxide sensor. Display Omitted - Highlights: • [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] orthorhombic phase prepared and characterized. • Decomposition of [Ag(NO{sub 3})·N{sub 4}(CH{sub 2}){sub 6}] leads to metallic silver sponge with opened porosity. • Ag sponge showed promising properties as a material for hydrogen peroxide sensors.« less

Selective recovery of silver from waste low-temperature co-fired ceramic and valorization through silver nanoparticle synthesis.

PubMed

Swain, Basudev; Shin, Dongyoon; Joo, So Yeong; Ahn, Nak Kyoon; Lee, Chan Gi; Yoon, Jin-Ho

2017-11-01

Considering the value of silver metal and silver nanoparticles, the waste generated during manufacturing of low temperature co-fired ceramic (LTCC) were recycled through the simple yet cost effective process by chemical-metallurgy. Followed by leaching optimization, silver was selectively recovered through precipitation. The precipitated silver chloride was valorized though silver nanoparticle synthesis by a simple one-pot greener synthesis route. Through leaching-precipitation optimization, quantitative selective recovery of silver chloride was achieved, followed by homogeneous pure silver nanoparticle about 100nm size were synthesized. The reported recycling process is a simple process, versatile, easy to implement, requires minimum facilities and no specialty chemicals, through which semiconductor manufacturing industry can treat the waste generated during manufacturing of LTCC and reutilize the valorized silver nanoparticles in manufacturing in a close loop process. Our reported process can address issues like; (i) waste disposal, as well as value-added silver recovery, (ii) brings back the material to production stream and address the circular economy, and (iii) can be part of lower the futuristic carbon economy and cradle-to-cradle technology management, simultaneously. Copyright © 2017 Elsevier Ltd. All rights reserved.

Formation of hybrid nanocomposites polymethylolacrylamide/silver

NASA Astrophysics Data System (ADS)

Kolzunova, L. G.; Shchitovskaya, E. V.; Rodzik, I. G.

2018-05-01

In this study, polymethylolacrylamide/silver composites have been formed by incorporating silver nanoparticles into the pre-electrosynthesized polymer film. The composites were formed in a two-step process involving the sorption of silver nitrate by a polymer matrix followed by chemical reduction of Ag-ions. The presence of crystalline silver phase in the polymer was confirmed by X-ray phase analysis (XRD), plasmon resonance and scanning electron microscopy (SEM). The small-angle X-ray scattering (SAXS) method has obtained the distribution functions of silver particles over radii. It is established that the content of silver in composites without chitosan is 10-15 times higher than with its additive. The dependences of cyclic voltammetry in pure phosphate buffer (pH 6.86) and in the presence of hydrogen peroxide were obtained. It has been shown that polymer/silver composites exhibit selectivity to hydrogen peroxide.

Absorbent silver (I) antimicrobial fabrics

USDA-ARS?s Scientific Manuscript database

In recent years, silver in form of silver ions, has been gaining importance in the wound management as an effective broad-spectrum antimicrobial agent. Silver has a long history as an antimicrobial agent, especially in the treatment of wounds. Alginates and carboxymethyl (CM) cotton contain carboxyl...

Silver Recovery and Power Generation from Ammonia Chelated Silver Solution in a Bio-Electrochemical Reactor

NASA Astrophysics Data System (ADS)

Ho, N. A. D.; Babel, S.

2017-06-01

Silver has valuable features and limited availability, and thus recovery from wastewater or aqueous solutions plays an important role in environmental protection and economic profits. In this study, silver recovery along with power generation and COD removal were investigated in a bio-electrochemical system (BES). The BES comprised of an anode and a cathode chamber which were separated by a cation exchange membrane to prevent the cross-over of electrolytes. During the biological oxidation of acetate as an electron donor in the anode chamber, the reduction of ammonia chelated silver ions as electron acceptors in the cathode side occurred spontaneously. Results showed that a silver recovery of 99% and COD removal efficiency of 60% were achieved at the initial silver concentration of 1,000 mg/L after 48 hours of operation. The power generation improved 4.66%, from 3,618 to 3,795 mW/m3, by adding NaNO3 of 850 mg/L to the catholyte containing 2,000 mg/L of silver ions. Deposits on the cathode surface were characterized using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Metallic silver with dendritic structures and high purity were detected. This study demonstrated that BES technology can be employed to recover silver from complex chelating solution, produce electricity, and treat wastewater.

The silver lining: towards the responsible and limited usage of silver.

PubMed

Naik, K; Kowshik, M

2017-11-01

Silver has attracted a lot of attention as a powerful, broad spectrum and natural antimicrobial agent since the ancient times because of its nontoxic nature to the human body at low concentrations. It has been used in treatment of various infections and ulcers, storage of water and prevention of bacterial growth on the surfaces and within materials. However, there are numerous medical and health benefits of colloidal or nanosilver apart from its microbicidal ability which as yet has not been fully embraced by the medical community. These include antiplatelet activity, antioxidant effect, anticancer activity, wound healing and bone regeneration, enhancement of immunity, and increase in antibiotic efficiency. Additionally silver also provides protection against alcohol toxicity, upper respiratory tract infections and stomach ailments. Although nanosilver has been proposed for various topical applications, its usage by ingestion and inhalation remains controversial due to the lack of detailed and precise toxicity information. These beneficial properties of silver can be utilized by using silver at very low concentrations which are not harmful to the human body and environment. The following review discusses the diverse medical applications of silver and further recommends human clinical studies for its in vivo usage. #x00A9; 2017 The Society for Applied Microbiology.

Antimicrobial activity of biogenic silver nanoparticles, and silver chloride nanoparticles: an overview and comments.

PubMed

Durán, Nelson; Nakazato, Gerson; Seabra, Amedea B

2016-08-01

The antimicrobial impact of biogenic-synthesized silver-based nanoparticles has been the focus of increasing interest. As the antimicrobial activity of nanoparticles is highly dependent on their size and surface, the complete and adequate characterization of the nanoparticle is important. This review discusses the characterization and antimicrobial activity of biogenic synthesized silver nanoparticles and silver chloride nanoparticles. By revising the literature, there is confusion in the characterization of these two silver-based nanoparticles, which consequently affects the conclusion regarding to their antimicrobial activities. This review critically analyzes recent publications on the synthesis of biogenic silver nanoparticles and silver chloride nanoparticles by attempting to correlate the characterization of the nanoparticles with their antimicrobial activity. It was difficult to correlate the size of biogenic nanoparticles with their antimicrobial activity, since different techniques are employed for the characterization. Biogenic synthesized silver-based nanoparticles are not completely characterized, particularly the nature of capped proteins covering the nanomaterials. Moreover, the antimicrobial activity of theses nanoparticles is assayed by using different protocols and strains, which difficult the comparison among the published papers. It is important to select some bacteria as standards, by following international foundations (Pharmaceutical Microbiology Manual) and use the minimal inhibitory concentration by broth microdilution assays from Clinical and Laboratory Standards Institute, which is the most common assay used in antibiotic ones. Therefore, we conclude that to have relevant results on antimicrobial effects of biogenic silver-based nanoparticles, it is necessary to have a complete and adequate characterization of these nanostructures, followed by standard methodology in microbiology protocols.

21 CFR 73.2500 - Silver.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Silver. 73.2500 Section 73.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2500 Silver. (a) Identity. (1) The color additive, silver...

21 CFR 73.2500 - Silver.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Silver. 73.2500 Section 73.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2500 Silver. (a) Identity. (1) The color additive, silver...

21 CFR 73.2500 - Silver.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Silver. 73.2500 Section 73.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2500 Silver. (a) Identity. (1) The color additive, silver...

21 CFR 73.2500 - Silver.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Silver. 73.2500 Section 73.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2500 Silver. (a) Identity. (1) The color additive, silver...

21 CFR 73.2500 - Silver.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Silver. 73.2500 Section 73.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2500 Silver. (a) Identity. (1) The color additive, silver...

Mineral resource of the month: silver

USGS Publications Warehouse

Brooks, William E.

2007-01-01

Silver has been used for thousands of years as ornaments and utensils, for trade and as the basis of many monetary systems. The metal has played an important part in world history. Silver from the mines at Laurion, Greece, for example, financed the Greek victory over the Persians in 480 B.C. Silver from Potosi, Bolivia, helped Spain become a world power in the 16th and 17th centuries. And silver from the gold-silver ores at the Comstock Lode in Virginia City, Nev., helped keep the Union solvent during the Civil War.

Vertically grown zinc oxide nanorods functionalized with ferric oxide for in vivo and non-enzymatic glucose detection

NASA Astrophysics Data System (ADS)

Marie, Mohammed; Manoharan, Anishkumar; Kuchuk, Andrian; Ang, Simon; Manasreh, M. O.

2018-03-01

An enzyme-free glucose sensor based on vertically grown zinc oxide nanorods (NRs) functionalized with ferric oxide (Fe2O3) is investigated. The well-aligned and high density ZnO NRs were synthesized on an FTO/glass substrate by a sol-gel and hydrothermal growth method. A dip-coating technique was utilized to modify the surface of the as-grown ZnO NRs with Fe2O3. The immobilized surface was coated with a layer of nafion membrane. The fabricated glucose sensor was characterized amperometrically at room temperature using three electrodes stationed in the phosphate buffer solution, where ZnO NRs/Fe2O3/nafion membrane was the sensing or working electrode, and platinum plate and silver/silver chloride were used as the counter and reference electrodes, respectively. The proposed non-enzymatic and modified glucose sensor exhibited a high sensitivity in the order of 0.052 μA cm-2 (mg/dL)-1, a lower detection limit of around 0.95 mmol L-1, a sharp and fast response time of ˜1 s, and a linear response to changes in glucose concentrations from 100-400 mg dL-1. The linear amperometric response of the sensor covers the physiological and clinical interest of glucose levels for diabetic patients. The device continues to function accurately after multiple measurements with a good reproducibility. The proposed glucose sensor is expected to be used clinically for in vivo monitoring of glucose.

Silver Clusters in Zeolites: From Self-Assembly to Ground-Breaking Luminescent Properties.

PubMed

Coutiño-Gonzalez, Eduardo; Baekelant, Wouter; Steele, Julian A; Kim, Cheol Woong; Roeffaers, Maarten B J; Hofkens, Johan

2017-09-19

Interest for functional silver clusters (Ag-CLs) has rapidly grown over years due to large advances in the field of nanoscale fabrication and materials science. The continuous development of strategies to fabricate small-scale silver clusters, together with their interesting physicochemical properties (molecule-like discrete energy levels, for example), make them very attractive for a wide variety of applied research fields, from biotechnology and the environmental sciences to fundamental chemistry and physics. Apart from useful catalytic properties, silver clusters (Ag n , n < 10) were recently shown to also exhibit exceptional optical properties. The optical properties and performance of Ag-CLs offer strong potential for their integration into appealing micro(nano)-optoelectronic devices. To date, however, the rational design and directed synthesis of Ag-CLs with specific functionalities has remained elusive. The inability for rational design stems mainly from a lack of understanding of their novel atomic-scale phenomena. This is because accurately studying silver cluster systems at such a scale is hindered by the perturbations introduced during exposure to various experimental probes. For instance, silver possesses a strong tendency to cluster and form ever-larger Ag aggregates while probed with high-energy electron beams and X-ray irradiation. As well, there exists a need to provide a stabilizing environment for which Ag n δ+ clusters can persist, setting up a complex interacting guest-host system, as isolated silver clusters are confined within a suitable hosting medium. Fundamental research into Ag n δ+ formation mechanisms and their important optical properties is paramount to establishing truly informed synthesis protocols. Over recent years, we have developed several protocols for the ship-in-a-bottle synthesis of highly luminescent Ag-CLs within the microporous interiors of zeolite frameworks. This approach has yielded materials displaying a wide

Isabela Island, Galapagos Islands

NASA Image and Video Library

1996-01-20

STS072-732-072 (11-20 Jan. 1996) --- Three of the nineteen Galapagos Islands are visible in this image, photographed from the Earth-orbiting Space Shuttle Endeavour. The Galapagos Islands are located 600 miles (1,000 kilometers) to the west of Ecuador. The largest of the islands, Isabela, is at center (north is toward the upper right corner). The numerous circular features on the island, highlighted by clouds, are volcanoes. The Galapagos Islands owe their existence to a hot spot, or persistent heat source in the mantle, which also is located over a rift, or place where plates are separating and new crust is being created. The rift is located between the Cocos and Nazca Plates. The dark linear features on the islands are lava flows from past eruptions. The island to the left of Isabela is Fernandina, while the island to the right is San Salvador. The Galapagos Islands were visited by the English naturalist Charles Darwin in 1835.

Preliminary flight prototype silver ion monitoring system

NASA Technical Reports Server (NTRS)

Brady, J.

1974-01-01

The design, fabrication, and testing of a preliminary flight prototype silver ion monitoring system based on potentiometric principles and utilizing a solid-state silver sulfide electrode paired with a pressurized double-junction reference electrode housing a replaceable electrolyte reservoir is described. The design provides automatic electronic calibration utilizing saturated silver bromide solution as a silver ion standard. The problem of loss of silver ion from recirculating fluid, its cause, and corrective procedures are reported. The instability of the silver sulfide electrode is discussed as well as difficulties met in implementing the autocalibration procedure.

Genetics Home Reference: Russell-Silver syndrome

MedlinePlus

... Facebook Twitter Home Health Conditions Russell-Silver syndrome Russell-Silver syndrome Printable PDF Open All Close All ... Javascript to view the expand/collapse boxes. Description Russell-Silver syndrome is a growth disorder characterized by ...

Nucleic acid nanomaterials: Silver-wired DNA

NASA Astrophysics Data System (ADS)

Auffinger, Pascal; Ennifar, Eric

2017-10-01

DNA double helical structures are supramolecular assemblies that are typically held together by classical Watson-Crick pairing. Now, nucleotide chelation of silver ions supports an extended silver-DNA hybrid duplex featuring an uninterrupted silver array.

MOD silver metallization for photovoltaics

NASA Technical Reports Server (NTRS)

Vest, G. M.; Vest, R. W.

1984-01-01

The development of flat plate solar arrays is reported. Photovoltaic cells require back side metallization and a collector grid system on the front surface. Metallo-organic decomposition (MOD) silver films can eliminate most of the present problems with silver conductors. The objectives are to: (1) identify and characterize suitable MO compounds; (2) develop generic synthesis procedures for the MO compounds; (3) develop generic fabrication procedures to screen printable MOD silver inks; (4) optimize processing conditions to produce grid patterns and photovoltaic cells; and (5) develop a model which describes the adhesion between the fired silver film and the silicon surface.

Speciation Matters: Bioavailability of Silver and Silver Sulfide Nanoparticles to Alfalfa (Medicago sativa).

PubMed

Stegemeier, John P; Schwab, Fabienne; Colman, Benjamin P; Webb, Samuel M; Newville, Matthew; Lanzirotti, Antonio; Winkler, Christopher; Wiesner, Mark R; Lowry, Gregory V

2015-07-21

Terrestrial crops are directly exposed to silver nanoparticles (Ag-NPs) and their environmentally transformed analog silver sulfide nanoparticles (Ag2S-NPs) when wastewater treatment biosolids are applied as fertilizer to agricultural soils. This leads to a need to understand their bioavailability to plants. In the present study, the mechanisms of uptake and distribution of silver in alfalfa (Medicago sativa) were quantified and visualized upon hydroponic exposure to Ag-NPs, Ag2S-NPs, and AgNO3 at 3 mg total Ag/L. Total silver uptake was measured in dried roots and shoots, and the spatial distribution of elements was investigated using transmission electron microscopy (TEM) and synchrotron-based X-ray imaging techniques. Despite large differences in release of Ag(+) ions from the particles, Ag-NPs, Ag2S-NPs, and Ag(+) became associated with plant roots to a similar degree, and exhibited similarly limited (<1%) amounts of translocation of silver into the shoot system. X-ray fluorescence (XRF) mapping revealed differences in the distribution of Ag into roots for each treatment. Silver nanoparticles mainly accumulated in the (columella) border cells and elongation zone, whereas Ag(+) accumulated more uniformly throughout the root. In contrast, Ag2S-NPs remained largely adhered to the root exterior, and the presence of cytoplasmic nano-SixOy aggregates was observed. Exclusively in roots exposed to particulate silver, NPs smaller than the originally dosed NPs were identified by TEM in the cell walls. The apparent accumulation of Ag in the root apoplast determined by XRF, and the presence of small NPs in root cell walls suggests uptake of partially dissolved NPs and translocation along the apoplast.

Daylighting with Fluorescent Concentrators and Highly Reflective Silver-Coated Plastic Films: A New Application for New Materials

NASA Astrophysics Data System (ADS)

Zastrow, Armin; Wittwer, Volker

1986-09-01

The interest in efficient daylighting systems has grown recently, due to their potential for saving a considerable amount of electrical energy used for lighting purposes. In this paper we discuss the properties of daylighting systems based on either fluorescent planar concentrators and transparent light guiding plates or light pipes coated with highly reflective silver coated plastic films. Finally we give first results from a demonstration project, daylighting systems in the students' living quarters in Stuttgart-Hohenheim, which is supported by the Commission of the European Communities.

Shape transition of endotaxial islands growth from kinetically constrained to equilibrium regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhi-Peng, E-mail: LI.Zhipeng@nims.go.jp; Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044; Tok, Engsoon

2013-09-01

Graphical abstract: - Highlights: • All Fe{sub 13}Ge{sub 8} islands will grow into Ge(0 0 1) substrate at temperatures from 350 to 675 °C. • Shape transition occurred from kinetically constrained to equilibrium regime. • All endotaxial islands can be clarified into two types. • The mechanisms of endotaxial growth and shape transition have been rationalized. - Abstract: A comprehensive study of Fe grown on Ge(0 0 1) substrates has been conducted at elevated temperatures, ranging from 350 to 675 °C. All iron germinide islands, with the same Fe{sub 13}Ge{sub 8} phase, grow into the Ge substrate with the samemore » epitaxial relationship. Shape transition occurs from small square islands (low temperatures), to elongated orthogonal islands or orthogonal nanowires (intermediate temperatures), and then finally to large square orthogonal islands (high temperatures). According to both transmission electron microscopy (TEM) and atomic force microscopy (AFM) investigations, all islands can be defined as either type-I or type-II. Type-I islands usually form at kinetically constrained growth regimes, like truncated pyramids. Type-II islands usually appear at equilibrium growth regimes forming a dome-like shape. Based on a simple semi-quantitative model, type-II islands have a lower total energy per volume than type-I, which is considered as the dominant mechanism for this type of shape transition. Moreover, this study not only elucidates details of endotaxial growth in the Fe–Ge system, but also suggests the possibility of controlled fabrication of temperature-dependent nanostructures, especially in materials with dissimilar crystal structures.« less

Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ringleb, F.; Eylers, K.; Teubner, Th.

2016-03-14

A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Basedmore » on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.« less

Fluorescent DNA-templated silver nanoclusters

NASA Astrophysics Data System (ADS)

Lin, Ruoqian

Because of the ultra-small size and biocompatibility of silver nanoclusters, they have attracted much research interest for their applications in biolabeling. Among the many ways of synthesizing silver nanoclusters, DNA templated method is particularly attractive---the high tunability of DNA sequences provides another degree of freedom for controlling the chemical and photophysical properties. However, systematic studies about how DNA sequences and concentrations are controlling the photophysical properties are still lacking. The aim of this thesis is to investigate the binding mechanisms of silver clusters binding and single stranded DNAs. Here in this thesis, we report synthesis and characterization of DNA-templated silver nanoclusters and provide a systematic interrogation of the effects of DNA concentrations and sequences, including lengths and secondary structures. We performed a series of syntheses utilizing five different sequences to explore the optimal synthesis condition. By characterizing samples with UV-vis and fluorescence spectroscopy, we achieved the most proper reactants ratio and synthesis conditions. Two of them were chosen for further concentration dependence studies and sequence dependence studies. We found that cytosine-rich sequences are more likely to produce silver nanoclusters with stronger fluorescence signals; however, sequences with hairpin secondary structures are more capable in stabilizing silver nanoclusters. In addition, the fluorescence peak emission intensities and wavelengths of the DNA templated silver clusters have sequence dependent fingerprints. This potentially can be applied to sequence sensing in the future. However all the current conclusions are not warranted; there is still difficulty in formulating general rules in DNA strand design and silver nanocluster production. Further investigation of more sequences could solve these questions in the future.

Synthesis and characterization of monodispersed silver nanoparticles

NASA Astrophysics Data System (ADS)

Jegatha Christy, A.; Umadevi, M.

2012-09-01

Synthesis of silver nanoparticles (NPs) has become a fascinating and important field of applied chemical research. In this paper silver NPs were prepared using silver nitrate (AgNO3), gelatin, and cetyl trimethyl ammonium bromide (CTAB). The prepared silver NPs were exposed under the laser ablation. In our photochemical procedure, gelatin acts as a biopolymer and CTAB acts as a reducing agent. The appearance of surface plasmon band around 410 nm indicates the formation of silver NPs. The nature of the prepared silver NPs in the face-centered cubic (fcc) structure are confirmed by the peaks in the x-ray diffraction (XRD) pattern corresponding to (111), (200), (220) and (311) planes. Monodispersed, stable, spherical silver NPs with diameter about 10 nm were obtained and confirmed by high-resolution transmission electron microscope (HRTEM).

Silver Ink For Jet Printing

NASA Technical Reports Server (NTRS)

Vest, R. W.; Singaram, Saraswathi

1989-01-01

Metallo-organic ink containing silver (with some bismuth as adhesion agent) applied to printed-circuit boards and pyrolized in air to form electrically conductive patterns. Ink contains no particles of silver, does not have to be mixed during use to maintain homogeneity, and applied to boards by ink-jet printing heads. Consists of silver neodecanoate and bismuth 2-ethylhexanoate dissolved in xylene and/or toluene.

Uptake and Distribution of Silver in the Aquatic Plant Landoltia punctata (Duckweed) Exposed to Silver and Silver Sulfide Nanoparticles.

PubMed

Stegemeier, John P; Colman, Benjamin P; Schwab, Fabienne; Wiesner, Mark R; Lowry, Gregory V

2017-05-02

Aquatic ecosystems are expected to receive Ag 0 and Ag 2 S nanoparticles (NPs) through anthropogenic waste streams. The speciation of silver in Ag-NPs affects their fate in ecosystems, but its influence on interactions with aquatic plants is still unclear. Here, the Ag speciation and distribution was measured in an aquatic plant, duckweed (Landoltia punctata), exposed to Ag 0 or Ag 2 S NPs, or to AgNO 3 . The silver distribution in duckweed roots was visualized using synchrotron-based micro X-ray fluorescence (XRF) mapping and Ag speciation was determined using extended X-ray absorption fine structure (EXAFS) spectroscopy. Duckweed exposed to Ag 2 S-NPs or Ag 0 -NPs accumulated similar Ag concentrations despite an order of magnitude smaller dissolved Ag fraction measured in the exposure medium for Ag 2 S-NPs compared to Ag 0 -NPs. By 24 h after exposure, all three forms of silver had accumulated on and partially in the roots regardless of the form of Ag exposed to the plants. Once associated with duckweed tissue, Ag 0 -NPs had transformed primarily into silver sulfide and silver thiol species. This suggests that plant defenses were active within or at the root surface. The Ag 2 S-NPs remained as Ag 2 S, while AgNO 3 exposure led to Ag 0 and sulfur-associated Ag species in plant tissue. Thus, regardless of initial speciation, Ag was readily available to duckweed.

Selective laser melting porous metallic implants with immobilized silver nanoparticles kill and prevent biofilm formation by methicillin-resistant Staphylococcus aureus.

PubMed

van Hengel, Ingmar A J; Riool, Martijn; Fratila-Apachitei, Lidy E; Witte-Bouma, Janneke; Farrell, Eric; Zadpoor, Amir A; Zaat, Sebastian A J; Apachitei, Iulian

2017-09-01

Implant-associated infection and limited longevity are two major challenges that orthopedic devices need to simultaneously address. Additively manufactured porous implants have recently shown tremendous promise in improving bone regeneration and osseointegration, but, as any conventional implant, are threatened by infection. In this study, we therefore used rational design and additive manufacturing in the form of selective laser melting (SLM) to fabricate porous titanium implants with interconnected pores, resulting in a 3.75 times larger surface area than corresponding solid implants. The SLM implants were biofunctionalized by embedding silver nanoparticles in an oxide surface layer grown using plasma electrolytic oxidation (PEO) in Ca/P-based electrolytes. The PEO layer of the SLM implants released silver ions for at least 28 days. X-ray diffraction analysis detected hydroxyapatite on the SLM PEO implants but not on the corresponding solid implants. In vitro and ex vivo assays showed strong antimicrobial activity of these novel SLM PEO silver-releasing implants, without any signs of cytotoxicity. The rationally designed SLM porous implants outperformed solid implants with similar dimensions undergoing the same biofunctionalization treatment. This included four times larger amount of released silver ions, two times larger zone of inhibition, and one additional order of magnitude of reduction in numbers of CFU in an ex vivo mouse infection model. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carboxylate and amino group coated silver nanoparticles as joining materials for copper-to-copper silver joints.

PubMed

Oestreicher, A; Röhrich, T; Lerch, M

2012-12-01

Organic silver complexes are introduced where silver is linked either with a carboxyl group or with an amino group. Upon heating, nanoparticles are generated if the respective ligands are long enough to act as stabilizing agents in the nanoparticulate regime. With decomposition and volatilization of the organic material, the sintering of silver occurs. The thermal characteristics of the carboxylates silver-n-octanoate, silver-n-decanoate, and AgOOC(CH2OCH2)2CH2OCH3 are compared with silver-n-alkylamines (n = 8, 9, and 12), and their thermal behavior is discussed based on thermogravimetry (TG) measurements. The consecutive stages of a metallization process are addressed based on the properties of AgOOC(CH2OCH2)2CH2OCH3, and the usable effects of the individual phases of this metal organic compound are analyzed by cross-sectional scanning electron microscope (SEM) images of silver joints. Selection criteria are addressed based on the thermal behavior. A mechanism for the joining process is proposed, considering formation and sintering of the nanoparticles. It was found that the bulk material can be used for low-temperature joining processes. Strong adherence to copper as a basic material can be achieved.

Silver ion-mediated killing of a food pathogen: Melting curve analysis data of silver resistance genes and growth curve data.

PubMed

Gokulan, Kuppan; Williams, Katherine; Khare, Sangeeta

2017-04-01

Limited antibacterial activity of silver ions leached from silver-impregnated food contact materials could be due to: 1) the presence of silver resistance genes in tested bacteria ; or 2) lack of susceptibility to silver ion-mediated killing in the bacterial strain (K. Williams, L. Valencia, K. Gokulan, R. Trbojevich, S. Khare, 2016 [1]). This study contains data to address the specificity of silver resistance genes in Salmonella Typhimurium during the real time PCR using melting curve analysis and an assessment of the minimum inhibitory concentration of silver ions for Salmonella .

Rethinking Schools and the Power of Silver

ERIC Educational Resources Information Center

Sleeter, Christine

2011-01-01

This 25th anniversary of "Rethinking Schools" can be thought of as its silver anniversary. Silver itself must be considered through contrasting lenses. On the one hand, as lessons in "Rethinking Globalization" teach, silver and gold were the basis of Europe's horrendous exploitation of Latin America. On the other hand, silver is often associated…

Silver nanoparticles decorated lipase-sensitive polyurethane micelles for on-demand release of silver nanoparticles.

PubMed

Su, Yuling; Zhao, Lili; Meng, Fancui; Wang, Quanxin; Yao, Yongchao; Luo, Jianbin

2017-04-01

In order to improve the antibacterial activities while decrease the cytotoxity of silver nanoparticles, we prepared a novel nanocomposites composed of silver nanoparticles decorated lipase-sensitive polyurethane micelles (PUM-Ag) with MPEG brush on the surface. The nanocomposite was characterized by UV-vis, TEM and DLS. UV-vis and TEM demonstrated the formation of silver nanoparticles on PU micelles and the nanoassembly remained intact without the presence of lipase. The silver nanoparticles were protected by the polymer matrix and PEG brush which show good cytocompatibility to HUVEC cells and low hemolysis. Moreover, at the presence of lipase, the polymer matrix of nanocomposites is subject to degradation and the small silver nanoparticles were released as is shown by DLS and TEM. The MIC and MBC studies showed an enhanced toxicity of the nanocomposites to both gram negative and gram positive bacteria, i.e. E. coli and S. aureus, as the result of the degradation of polymer matrix by bacterial lipase. Therefore, the nanocomposites are biocompatible to mammalian cells cells which can also lead to activated smaller silver nanoparticles release at the presence of bacteria and subsequently enhanced inhibition of bacteria growth. The satisfactory selectivity for bacteria compared to HUVEC and RBCs make PUM-Ag a promising antibacterial nanomedicine in biomedical field. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of isothiocyanate yield from wasabi rhizome tissues grown in soil or water.

PubMed

Sultana, Tamanna; Porter, N G; Savage, G P; McNeil, D L

2003-06-04

The isothiocyanate (ITC) yield of wasabi, the Japanese horseradish (Wasabi japonica), was measured on its release from glucosinolates in the rhizomes of plants grown in two traditional ways. Mature plants of 18 months old were harvested from two different commercial farms located in the South Island of New Zealand. At one farm, the plants were grown in raised soil beds, while the plants at the other farm were grown in gravel irrigated by river water. Following harvest, the rhizomes from each growth medium were divided into five size groups based on the weight and length of the rhizomes. The different sized rhizomes were also subdivided into proximal, medial, and distal portions of the rhizomes and each portion was further subdivided into epidermis plus cortex, and vascular plus pith. The individual and total ITC contents of each portion (proximal, medial, and distal) of the rhizomes were measured using dichloromethane extraction followed by the GC-FPD. The total ITC content of the rhizomes grown in soil increased (13 times) linearly from 6 to 114 g of rhizome weight, while the mean ITC content of the water-grown wasabi increased (10 times) nonlinearly for similar sized rhizomes. Water-grown rhizomes in the weight range from 18 to 45 g gave significantly (P = 0.030) higher total ITC (1-2 times) than similarly sized soil-grown rhizomes. Analysis of the tissues showed that the total and the individual ITCs were found in significantly higher levels (73 and 64%, respectively) in the skin and cortex tissue compared to the vascular and pith tissues. Analysis of the ITC content of the different locations of the wasabi rhizome showed that the distal portion of the rhizome contained significantly higher levels of both total and individual ITCs compared to the medial and proximal portions of the rhizome.

Effect of silver nanoparticles on concentration of silver heavy element and growth indexes in cucumber ( Cucumis sativus L . negeen)

NASA Astrophysics Data System (ADS)

Shams, Gholamabbas; Ranjbar, Morteza; Amiri, Aliasghar

2013-05-01

The tremendous progress on nanoparticle research area has been made significant effects on the economy, society, and the environment. Silver nanoparticle is one of the most important particles in these categories. Silver nanoparticles can be converted to the heavy silver metal in water by oxidation. Moreover, in the high amounts of silver concentration, they will be accumulated in different parts of the plant. However, by changing the morphology of the plant, the production will be harmful for human consumptions. In this study, nano-powders with average 50 nm silver particles are mixed with deionized distilled water in a completely randomized design. Seven treatments with various concentrations of suspension silver nanoparticles were prepared and repeated in four different parts of the plant in a regular program of spraying. Samples were analyzed to study the growth indexes and concentration of silver in different parts of the plant. It was observed that with increasing concentration of silver nanoparticles on cucumber, the growth indexes (except pH fruit), and the concentration of silver heavy metal are increased significantly. The incremental concentration had the linear relationship with correlation coefficient 0.95 and an average of 0.617 PPM by increasing of each unit in one thousand concentration of nanosilver. Although, by increasing concentration of silver nanoparticles as spraying form, the plant morphological characteristics were improved, the concentration of silver heavy metal in various plant organs was increased. These results open a new pathway to consider the effect of nanoparticles on plant's productions for human consumptions.

Silver Dissolution and Release from Ceramic Water Filters.

PubMed

Mittelman, Anjuliee M; Lantagne, Daniele S; Rayner, Justine; Pennell, Kurt D

2015-07-21

Application of silver nanoparticles (nAg) or silver nitrate (AgNO3) has been shown to improve the microbiological efficacy of ceramic water filters used for household water treatment. Silver release, however, can lead to undesirable health effects and reduced filter effectiveness over time. The objectives of this study were to evaluate the contribution of nanoparticle detachment, dissolution, and cation exchange to silver elution, and to estimate silver retention under different influent water chemistries. Dissolved silver (Ag(+)) and nAg release from filter disks painted with 0.03 mg/g casein-coated nAg or AgNO3 were measured as a function of pH (5-9), ionic strength (1-50 mM), and cation species (Na(+), Ca(2+), Mg(2+)). Silver elution was controlled by dissolution as Ag(+) and subsequent cation exchange reactions regardless of the applied silver form. Effluent silver levels fell below the drinking water standard (0.1 mg/L) after flushing with 30-42 pore volumes of pH 7, 10 mM NaNO3 at pH 7. When the influent water was at pH 5, contained divalent cations or 50 mM NaNO3, silver concentrations were 5-10 times above the standard. Our findings support regular filter replacement and indicate that saline, hard, or acidic waters should be avoided to minimize effluent silver concentrations and preserve silver treatment integrity.

Monitoring of a Southern Giant Petrel Macronectes giganteus population on the Frazier Islands, Wilkes Land, Antarctica

USGS Publications Warehouse

Creuwels, J.C.S.; Stark, J.S.; Woehler, Eric J.; Van Franeker, J. A.; Ribic, C.A.

2005-01-01

Since 1956, Southern Giant Petrels on the Frazier Islands, East Antarctica, have been counted with different census techniques, sometimes varying within seasons and among islands, which hindered analysis of the data. Protective measures for the islands from 1986 onwards have increased the need for reliable long-term census data, but reduced the ways to collect these data. Published and unpublished data were re-examined, and population trends were reconstructed based on two relatively standardised techniques: the number of active chicks (AC) and the number of apparently occupied nests (AON) around hatching. AC-values from Nelly Island from 1959 to 1998 indicate substantial periodic fluctuations, but no consistent long-term change. Since the late 1970s, AC-values on the other two islands and AON-values suggest that the breeding population may have grown by 35%. This recent growth, however, is within the extent of periodic fluctuations observed in Southern Giant Petrel population that is stable over the long term. ?? Springer-Verlag 2004.

Crossed asymmetry in Russell-Silver syndrome.

PubMed Central

Qazi, Q H; Kassner, E G; Ganapathy, C

1977-01-01

Since the initial report by Silver et al (1953), more than 50 examples of the Russell-Silver syndrome have been reported. Unilateral congenital asymmetry of the extremities has been considered one of the major features of this disorder (Silver, 1964). We recently observed a child with otherwise typical features of the Russell-Silver syndrome who had enlargement of the right hand and of the left lower extremity. We know of no other recorded example of crossed asymmetry in this clinical entity. Images PMID:839508

Silver Recycling in the United States in 2000

USGS Publications Warehouse

Hilliard, Henry E.

2003-01-01

In 2000, the global silver supply deficit (the difference between mine and scrap supply and silver demand) was more than 3,000 metric tons. U.S. silver demand for photographic applications alone was nearly equal to annual U.S. silver production. Until 1968, the U.S. silver deficit was filled by withdrawals from the U.S. Treasury reserves. In 2000, the deficit was filled by destocking, imports, and recycling. Photographic wastes, spent catalysts, and electronic scrap are the major sources of materials for silver recycling. Nearly 1,800 tons of silver contained in these materials were available for recycling in 2000. Other recyclable silver-bearing materials include dental alloys, jewelry, and silverware. In 2000, an estimated 1,700 tons of silver were recovered from secondary sources in the United States. The U.S. recycling efficiency for old scrap was calculated to have been 97 percent in 2000; the recycling rate was estimated to be 32 percent.

Silver recycling in the United States in 2000

USGS Publications Warehouse

Hilliard, Henry E.

2003-01-01

In 2000, the global silver supply deficit (the difference between mine and scrap supply and silver demand) was more than 3,000 metric tons. U.S. silver demand for photographic applications alone was nearly equal to annual U.S. silver production. Until 1968, the U.S. silver deficit was filled by withdrawals from the U.S. Treasury reserves. In 2000, the deficit was filled by destocking, imports, and recycling. Photographic wastes, spent catalysts, and electronic scrap are the major sources of materials for silver recycling. Nearly 1,800 metric tons of silver contained in these materials were available for recycling in 2000. Other recyclable silver-bearing materials include dental alloys, jewelry, and silverware. In 2000, an estimated 1,700 tons of silver were recovered from secondary sources in the United States. The U.S. recycling efficiency for old scrap was calculated to have been 97 percent in 2000; the recycling rate was estimated to be 32 percent.

Separation of silver ions and starch modified silver nanoparticles using high performance liquid chromatography with ultraviolet and inductively coupled mass spectrometric detection

NASA Astrophysics Data System (ADS)

Hanley, Traci A.; Saadawi, Ryan; Zhang, Peng; Caruso, Joseph A.; Landero-Figueroa, Julio

2014-10-01

The production of commercially available products marketed to contain silver nanoparticles is rapidly increasing. Species-specific toxicity is a phenomenon associated with many elements, including silver, making it imperative to develop a method to identify and quantify the various forms of silver (namely, silver ions vs. silver nanoparticles) possibly present in these products. In this study a method was developed using high performance liquid chromatography (HPLC) with ultraviolet (UV-VIS) and inductively coupled mass spectrometric (ICP-MS) detection to separate starch stabilized silver nanoparticles (AgNPs) and silver ions (Ag+) by cation exchange chromatography with 0.5 M nitric acid mobile phase. The silver nanoparticles and ions were baseline resolved with an ICP-MS response linear over four orders of magnitude, 0.04 mg kg- 1 detection limit, and 90% chromatographic recovery for silver solutions containing ions and starch stabilized silver nanoparticles smaller than 100 nm.

A novel cetyltrimethyl ammonium silver bromide complex and silver bromide nanoparticles obtained by the surfactant counterion.

PubMed

Liu, Xian-Hao; Luo, Xiao-Hong; Lu, Shu-Xia; Zhang, Jing-Chang; Cao, Wei-Liang

2007-03-01

A novel cetyltrimethyl ammonium silver bromide (CTASB) complex has been prepared simply through the reaction of silver nitrate with cetyltrimethyl ammonium bromide (CTAB) in aqueous solution at room temperature by controlling the concentration of CTAB and the molar ratio of CTAB to silver nitrate in the reaction solution, in which halogen in CTAB is used as surfactant counterion. The structure and thermal behavior of cetyltrimethyl ammonium silver bromide have been investigated by using X-ray diffraction (XRD), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy, thermal analysis (TG-DTA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that the complex possesses a metastable layered structure. Upon heating the CTASB aqueous dispersion to above 80 degrees C, the structure change of the complex took place and CTAB-capped nanosized silver bromide particles further formed.

Step-reduced synthesis of starch-silver nanoparticles.

PubMed

Raghavendra, Gownolla Malegowd; Jung, Jeyoung; Kim, Dowan; Seo, Jongchul

2016-05-01

In the present process, silver nanoparticles were directly synthesized in a single step by microwave irradiation of a mixture of starch, silver nitrate, and deionized water. This is different from the commonly adopted procedure for starch-silver nanoparticle synthesis in which silver nanoparticles are synthesized by preparing a starch solution as a reaction medium first. Thus, the additional step associated with the preparation of the starch solution was eliminated. In addition, no additional reducing agent was utilized. The adopted method was facile and straight forward, affording spherical silver nanoparticles with diameter below 10nm that exhibited good antibacterial activity. Further, influence of starch on the size of the silver nanoparticles was noticed. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of silver nanoparticles at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Mini, E-mail: mishramini5@gmail.com; Chauhan, Pratima, E-mail: mangu167@yahoo.co.in

Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaksmore » of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.« less

In situ reduction of antibacterial silver ions to metallic silver nanoparticles on bioactive glasses functionalized with polyphenols

NASA Astrophysics Data System (ADS)

Ferraris, S.; Miola, M.; Cochis, A.; Azzimonti, B.; Rimondini, L.; Prenesti, E.; Vernè, E.

2017-02-01

The realization of surfaces with antibacterial properties due to silver nanoparticles loaded through a green approach is a promising research challenge of the biomaterial field. In this research work, two bioactive glasses have been doubly surface functionalized with polyphenols (gallic acid or natural polyphenols extracted from red grape skins and green tea leaves) and silver nanoparticles deposited by in situ reduction from a silver nitrate aqueous solution. The presence of biomolecules - showing reducing ability to directly obtain in situ metallic silver - and silver nanoparticles was investigated by means of UV-vis spectroscopy, X-Ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FESEM). The antibacterial activity of the modified surfaces was tested against a multidrug resistant Staphylococcus aureus bacterial strain.

Aligned Layers of Silver Nano-Fibers.

PubMed

Golovin, Andrii B; Stromer, Jeremy; Kreminska, Liubov

2012-02-01

We describe a new dichroic polarizers made by ordering silver nano-fibers to aligned layers. The aligned layers consist of nano-fibers and self-assembled molecular aggregates of lyotropic liquid crystals. Unidirectional alignment of the layers is achieved by means of mechanical shearing. Aligned layers of silver nano-fibers are partially transparent to a linearly polarized electromagnetic radiation. The unidirectional alignment and density of the silver nano-fibers determine degree of polarization of transmitted light. The aligned layers of silver nano-fibers might be used in optics, microwave applications, and organic electronics.

The Silver Bullet Syndrome.

ERIC Educational Resources Information Center

Dehne, George C.

1995-01-01

Many colleges address complex problems with a single "silver bullet" strategy. Because value shifts according to the consumer's situation or goal, private colleges should become more aware of their "situational value" and exploit it. This requires an understanding of how students choose colleges. In contrast, popular silver bullets target…

Low-Temperature Properties of Silver

PubMed Central

Smith, David R.; Fickett, F. R.

1995-01-01

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability. PMID:29151733

Argyria secondary to ingestion of homemade silver solution.

PubMed

Brandt, Douglas; Park, Betty; Hoang, Mai; Jacobe, Heidi T

2005-08-01

Argyria is a rare skin disease caused by cutaneous deposition of silver granules in the skin as a result of exposure to silver substrate or ingestion of silver salt. This report describes a patient with generalized argyria caused by ingestion of homemade colloidal silver solution. The patient learned about the uses of the silver solution and its preparation at a convention for "natural medicine."

Photosensitized synthesis of silver nanoparticles using Withania somnifera leaf powder and silver nitrate.

PubMed

Raut, Rajesh Warluji; Mendhulkar, Vijay Damodhar; Kashid, Sahebrao Balaso

2014-03-05

The metal nanoparticle synthesis is highly explored field of nanotechnology. The biological methods seem to be more effective; however, due to slow reduction rate and polydispersity of the resulting products, they are less preferred. In the present study, we report rapid and facile synthesis of silver nanoparticles at room temperature. The exposure of reaction mixtures containing silver nitrate and dried leaf powder of Withania somnifera Linn to direct sunlight resulted in reduction of metal ions within five minutes whereas, the dark exposure took almost 12h. Further studies using different light filters reveal the role of blue light in reduction of silver ions. The synthesized silver nanoparticles were characterized by UV-Vis, Infrared spectroscopy (IR), Transmission Electron Microscopy (TEM), X-ray Diffraction studies (XRD), Nanoparticle Tracking Analysis (NTA), Energy Dispersive Spectroscopy (EDS), and Cyclic Voltammetry (CV). The Antibacterial and antifungal studies showed significant activity as compared to their respective standards. Copyright © 2014 Elsevier B.V. All rights reserved.

Silver ions are responsible for memory impairment induced by oral administration of silver nanoparticles.

PubMed

Węsierska, M; Dziendzikowska, K; Gromadzka-Ostrowska, J; Dudek, J; Polkowska-Motrenko, H; Audinot, J N; Gutleb, A C; Lankoff, A; Kruszewski, M

2018-06-15

Increasing use of silver nanoparticles (AgNPs) results in increased human exposure. AgNPs are able to cross brain-blood barrier and are a risk factor for the brain. Thus, we hypothesized that AgNPs exposure might affect hippocampal dependent memory, which required cognitive coordination processes. To verify the assumption, in this study we evaluated the effects of orally administered bovine serum albumin (BSA)-coated AgNPs on spatial memory, which engage cognitive coordination processes for on-going stimuli segregation. Rats following 28 days of oral administration with 1 mg/kg (n = 10) or 30 mg/kg (n = 10) BSA-AgNPs or saline, a control groups (n = 10, n = 8), were tested with an active place avoidance task in the Carousel Maze test. The study revealed significant impairment of long- and short-term memory, irrespectively of dose of AgNPs, whereas non-cognitive activity was on a similar level. We found significantly higher content of silver in the hippocampus in comparison to the lateral cortex. No silver was found in the cerebellum and the frontal cortex. The nanoSIMS analysis reveal a weak signal of silver in the hippocampus of AgNPs treated animals that should be attributed to the presence of silver in ionic form rather than AgNPs. Our findings indicate that oral exposure to a low dose AgNPs induces detrimental effect on memory and cognitive coordination processes. The presence of silver ions rather than AgNPs in different brain regions, in particular the hippocampus, suggests crucial role of silver ions in AgNPs-induced impairment of the higher brain functions. Copyright © 2018 Elsevier B.V. All rights reserved.

Studying the morphological features of plasma treated silver and PEGylated silver nanoparticles: antibacterial activity

NASA Astrophysics Data System (ADS)

Waseem, M.; Awan, T.; Yasin, H. M.; Rehman, N. U.

2018-03-01

A strategy to treat the silver and PEGylated silver nanoparticles with plasma was being purposed. Oil in water (o/w) microemulsion method was used for the synthesis of Ag nanoparticles (AgNPs). Polyethylene glycol (PEG) having molecular weight 600 was used to coat the surface of AgNPs. Optical emission spectroscopy (OES) was used to characterize the plasma and it is noted that plasma treatment is useful to modify the structural characteristic of silver nanoparticles. The nanoparticles were treated with helium-oxygen mixture plasma, generated in plasma needle at atmospheric pressure. Both AgNPs and PEGylated AgNPs before and after plasma treatment were characterized by x-rays diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The crystallite size of silver nanoparticles after the treatment of plasma decreases from 71 nm to 27 nm. The SEM micrographs show that the size of Ag nanoparticles was nearly 118 nm whereas the thickness of the silver needle was around 135 nm. All the characteristics IR bands associated to the silver nanoparticles were detected. The FTIR spectrum also support the accumulation of OH radicals in the plasma treated samples. The samples before and after plasma treatment were screened against Gram positive (Bacillus Subtilis and Staphylococcus Aureus) and Gram negative (Escherichia Coli and Pseudomonas Aeruginosa) bacteria. The promising response was detected when plasma treated PEGylated AgNPs was tested against bacterial strains.

Testing nano-silver food packaging to evaluate silver migration and food spoilage bacteria on chicken meat.

PubMed

Gallocchio, Federica; Cibin, Veronica; Biancotto, Giancarlo; Roccato, Anna; Muzzolon, Orietta; Carmen, Losasso; Simone, Belluco; Manodori, Laura; Fabrizi, Alberto; Patuzzi, Ilaria; Ricci, Antonia

2016-06-01

Migration of nanomaterials from food containers into food is a matter of concern because of the potential risk for exposed consumers. The aims of this study were to evaluate silver migration from a commercially available food packaging containing silver nanoparticles into a real food matrix (chicken meat) under plausible domestic storage conditions and to test the contribution of such packaging to limit food spoilage bacteria proliferation. Chemical analysis revealed the absence of silver in chicken meatballs under the experimental conditions in compliance with current European Union legislation, which establishes a maximum level of 0.010 mg kg(-1) for the migration of non-authorised substances through a functional barrier (Commission Regulation (EU) No. 10/2011). On the other hand, microbiological tests (total microbial count, Pseudomonas spp. and Enterobacteriaceae) showed no relevant difference in the tested bacteria levels between meatballs stored in silver-nanoparticle plastic bags or control bags. This study shows the importance of testing food packaging not only to verify potential silver migration as an indicator of potential nanoparticle migration, but also to evaluate the benefits in terms of food preservation so as to avoid unjustified usage of silver nanoparticles and possible negative impacts on the environment.

Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

PubMed

Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

2014-01-01

The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

Ink composition for making a conductive silver structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Steven B.; Lewis, Jennifer A.

An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in themore » ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120.degree. C. or less.« less

Physicochemical properties of protein-modified silver nanoparticles in seawater

NASA Astrophysics Data System (ADS)

Zhong, Hangyue

2013-10-01

This study investigated the physicochemical properties of silver nanoparticles stabilized with casein protein in seawater. UV?vis spectrometry, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were applied to measure the stability of silver nanoparticles in seawater samples. The obtained results show an increased aggregation tendency of silver nanoparticles in seawater, which could be attributed its relatively high cation concentration that could neutralize the negatively charges adsorbed on the surface of silver nanoparticles and reduce the electrostatic repulsion forces between nanoparticles. Similarly, due to the surface charge screening process, the zeta potential of silver nanoparticles in seawater decreased. This observation further supported the aggregation behavior of silver nanoparticles. This study also investigated the dissolution of silver nanoparticles in seawater. Result shows that the silver nanoparticle dissolution in DI water is lower than in seawater, which is attributed to the high Cl? concentration present in seawater. As Cl? can react with silver and form soluble AgCl complex, dissolution of silver nanoparticles was enhanced. Finally, this study demonstrated that silver nanoparticles are destabilized in seawater condition. These results may be helpful in understanding the environmental risk of discharged silver nanoparticles in seawater conditions.

Potentiometric titration of thiols, cationic surfactants and halides using a solid-state silver-silver sulphide electrode.

PubMed

Pinzauti, S; Papeschi, G; La Porta, E

1983-01-01

A rugged, low resistance silver-silver sulphide solid-state electrode for determining pharmaceuticals as authentic samples or in dosage forms by potentiometric titration is described. Sodium tetraphenylborate, mercury(II) acetate and silver nitrate (0.01) M were employed as titrants in the analysis of cationic surfactants (cetylpyridinium chloride, benzethonium chloride, benzalkonium chloride and chlorhexidine salts), antithyroid drugs (methimazole and propylthiouracil) or sodium halides respectively.

In-Situ Silver Acetylide Silver Nitrate Explosive Deposition Measurements Using X-Ray Fluorescence.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Covert, Timothy Todd

2014-09-01

The Light Initiated High Explosive facility utilized a spray deposited coating of silver acetylide - silver nitrate explosive to impart a mechanical shock into targets of interest. A diagnostic was required to measure the explosive deposition in - situ. An X - ray fluorescence spectrometer was deployed at the facility. A measurement methodology was developed to measure the explosive quantity with sufficient accuracy. Through the use of a tin reference material under the silver based explosive, a field calibration relationship has been developed with a standard deviation of 3.2 % . The effect of the inserted tin material into themore » experiment configuration has been explored.« less

The Electrodeposition of Silver from Supercritical Carbon Dioxide/Acetonitrile

PubMed Central

Bartlett, Philip N; Perdjon-Abel, Magdalena; Cook, David; Reid, Gillian; Levason, William; Cheng, Fei; Zhang, Wenjian; George, Michael W; Ke, Jie; Beanland, Richard; Sloan, Jeremy

2014-01-01

Cyclic voltammetry of silver coordination complexes in acetonitrile and in a single-phase supercritical carbon dioxide/acetonitrile (scCO2/CH3CN) system is reported. Five silver precursors are investigated: (1,5-cyclooctadiene)(hexafluoroacetylacetonato) silver(I) [Ag(hfac)(COD)], (hexafluoroacetylacetonato)(triphenylphosphine) silver(I) [Ag(hfac)(PPh3)], (perfluorooctanoato)bis(triphenylphosphine) silver(I) [Ag(CF3(CF2)6CO2)(PPh3)2], tetrakis(triphenylphosphine) silver(I) tetrafluoroborate [Ag(PPh3)4][BF4] and tetrakis(acetonitrile) silver(I) tetrafluoroborate [Ag(CH3CN)4][BF4]. Of these, [Ag(CH3CN)4][BF4] is found to be the most suitable for electrodeposition of silver from scCO2/CH3CN.

The Myth of the Silver Surfer

ERIC Educational Resources Information Center

Gorard, Stephen; Selwyn, Neil

2008-01-01

In this article, the authors write about the myth of the "silver surfers"--those third-age learners adept at using the internet and other technologies for a mixture of formal and informal learning episodes. The notion of the silver surfer has endured since the latter half of the 1990s. It is sustained by the annual Silver Surfer week, media…

MOD silver metallization for photovoltaics

NASA Technical Reports Server (NTRS)

Vest, G. M.; Vest, R. W.

1985-01-01

The feasibility of utilizing metallo-organic decomposition (MOD) silver inks were investigated for front contact metallization of solar cells. Generic synthesis procedures were developed for all metallo-organic compounds investigated. Silver neodecanoate was found to be the most suitable silver metallo-organic compound for use in thick film inks, but the quality of the inks was found to be highly dependent on its purity. Although neither the process nor inks were completely optimized for solar cell front contact metallization, they show great promise for this application.

Rhizobia from Lanzarote, the Canary Islands, that nodulate Phaseolus vulgaris have characteristics in common with LMW RNA group II Sinorhizobium meliloti of Medicago, Melilotus and Trigonella from soils of mainland Spain

USDA-ARS?s Scientific Manuscript database

Several isolates from nodules of Phaseolus vulgaris grown in soil of Lanzarote, an island of the Canaries, had electrophoretic LMW RNA patterns identical with a less common pattern within S. meliloti (assigned as group II) obtained from nodules of alfalfa and alfalfa-related legumes grown in northe...

Large silver-cadmium technology program

NASA Technical Reports Server (NTRS)

Charlip, S.; Lerner, S.

1971-01-01

The effects of varying cell design on operation factors on the electrochemical performance of sealed, silver-cadmium cells were determined. A factorial experiment was conducted for all test cells constructed with organic separators. Three operating factors were evaluated: temperature, depth of discharge, and charge rate. The six construction factors considered were separator, absorber, electrolyte quantity, cadmium electrode type, cadmium-to-silver ratio, and auxiliary electrode. Test cells of 4 ampere-hour capacity were fabricated and cycled. The best performing cells, on a 94 minute orbit, at 40% depth of discharge, were those containing silver-treated fibrous sausage casings as the separator, and Teflon-ated, pressed cadmium electrodes. Cycling data of cells with inorganic separators (Astroset) are given. Best performance was shown by cells with nonwoven nylon absorbers. Rigid inorganic separators provided the best barrier to silver migration.

Evaluation of dose dependent antimicrobial activity of self-assembled chitosan, nano silver and chitosan-nano silver composite against several pathogens.

PubMed

Tareq, Foysal Kabir; Fayzunnesa, Mst; Kabir, Md Shahariar; Nuzat, Musrat

2018-01-01

The aim of this investigation to preparation of silver nanoparticles organized chitosan nano polymer, which effective against microbial and pathogens, when apply to liquid medium and edible food products surface, will rescue the growth of microbes. Self-assembly approach used to synthesis of silver nanoparticles and silver nanoparticles organized chitosan nano polymer. Silver nanoparticles and silver nanoparticles organized chitosan nano polymer and film characterized using Ultra-violate visible spectrometer (UV-vis), X-ray diffraction (X-ray), and Scanning electronic microscope (SEM). The crystalline structured protein capped nano silver successfully synthesized at range of 12 nm-29 nm and organized into chitosan nano polymer. Antimicrobial ingredient in liquid medium and food product surface provide to rescue oxidative change and growth of microorganism to provide higher safety. The silver nanoparticles organized chitosan nano polymer caused the death of microorganism. The materials in nano scale synthesized successfully using self-assembly method, which showed good antimicrobial properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Silver Complexes of Dihalogen Molecules.

PubMed

Malinowski, Przemysław J; Himmel, Daniel; Krossing, Ingo

2016-08-01

The perfluorohexane-soluble and donor-free silver compound Ag(A) (A=Al(OR(F) )4 ; R(F) =C(CF3 )3 ) prepared using a facile novel route has unprecedented capabilities to form unusual and weakly bound complexes. Here, we report on the three dihalogen-silver complexes Ag(Cl2 )A, Ag(Br2 )A, and Ag(I2 )A derived from the soluble silver compound Ag(A) (characterized by single-crystal/powder XRD, Raman spectra, and quantum-mechanical calculations). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toxicogenomic responses of nanotoxicity in Daphnia magna exposed to silver nitrate and coated silver nanoparticles

EPA Science Inventory

Applications for silver nanomaterials in consumer products are rapidly expanding, creating an urgent need for toxicological examination of the exposure potential and ecological effects of silver nanoparticles (AgNPs). The integration of genomic techniques into environmental toxic...

Intravenous Exposure of Pregnant Mice to Silver Nanoparticles: Silver Tissue Distribution and Effects in Maternal and Extra-Embryonic Tissues and Embryos

NASA Astrophysics Data System (ADS)

Austin, Carlye Anne

This research explores the tissue distribution of silver, as well as adverse effects in pregnant mice and embryos, following prenatal silver nanoparticle (AgNP) exposure. Chapter one of this dissertation is a survey of the published literature on the reproductive and/or developmental toxicity of AgNPs. The available data indicate that AgNPs adversely affect sperm count, viability, and/or motility both in vivo and in vitro, and cause apoptosis and necrosis in spermatogonial stem cells and testicular cells. Additionally, AgNP exposure results in mortality and morphological deformities in fish embryos, but produces no adverse effects in chicken embryos. The current published research on in vivo AgNP exposure to mammals during gestation consists of only three studies, one of which is described in chapter two of this dissertation. These studies report results that may suggest a potential for adverse effects on fetal development (e.g. , decreased viability and fetal and placental weights, increased incidence of developmentally young embryos), but additional research is needed. Chapter two of this dissertation investigates the distribution of silver in tissues of pregnant mice and gestation day (GD) 10 embryos following intravenous maternal exposure to 50 nm AgNPs during early organogenesis (GDs 7-9). Examinations of embryo morphology and histology were also performed. Results demonstrated the presence of silver in all organs and tissues examined. Silver concentrations were highest in liver, spleen, and visceral yolk sac, and lowest in embryos. Groups of mice were also treated with soluble silver nitrate, and the pattern of silver tissue distribution following silver nitrate exposure was similar to that which followed AgNP treatment. Transmission electron microscopy-energy dispersive x-ray spectroscopy (TEM-EDS) confirmed the presence of vesicle-bound nanoparticulate silver in visceral yolk sac endoderm, but not mesoderm. This finding, along with the high silver

Synthesis and Characterization of Composite Hydroxyapatite-Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Charlena; Nuzulia, N. A.; Handika

2017-03-01

Hydroxyapatite (HAp) is commonly used as bone implant coating recently; however, the material has disadvantage such as lack of antibacterial properties, that can cause an bacterial infection. Addition of silver nanoparticles is expected to be able to provide antibacterial properties. Silver nanoparticles was obtained by reduction of AgNO3 using glucose monohydrate with microwave heating at 100p for 4 minutes. The composite of hydroxyapatite-silver nanoparticles was synthesized using chemical methods by coprecipitation suspension of Ca(OH)2 with (NH4)HPO4, followed by adding silver nanoparticles solution. The size of the synthesized silver nanoparticles was 30-50 nm and exhibited good antibacterial activity. Nevertheless, when it was composited with HAp to form HAp-AgNPs, there was no antibacterial activity due to very low concentration of silver nanoparticles. This was indicated by the absence of silver nanoparticles diffraction patterns. Infrared spectra indicated the presence of chemical shift and the results of scanning electron microscope showed size of the HAp-AgNPs composite was smaller than that of the HAp. This showed the interaction between HAp and the silver nanoparticles.

Antibacterial Effect of Silver Diamine Fluoride on Cariogenic Organisms.

PubMed

Lou, Yali; Darvell, Brain W; Botelho, Michael G

2018-05-01

To screen the possible antimicrobial activity of a range of clinically used, silver-based compounds on cariogenic organisms: silver diamine fluoride (SDF), silver fluoride, and silver nitrate. Preliminary screening disk-diffusion susceptibility tests were conducted on Mueller-Hinton agar plates inoculated with Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii, organisms known to be cariogenic. In order to identify which component of the silver compounds was responsible for any antibacterial (AB) effect, and to provide controls, the following were also investigated at high and low concentrations: sodium fluoride, ammonium fluoride, ammonium chloride, sodium fluoride, sodium chloride, and sodium nitrate, as well as deionized water as control. A volume of 10 pL of a test solution was dispensed onto a paper disk resting on the inoculated agar surface, and the plate incubated anaerobically at 37°C for 48 hours. The zones of inhibition were then measured. Silver diamine fluoride, silver fluoride, silver nitrate, and ammonium fluoride had significant AB effect (p < 0.05) on all three test organisms, although ammonium fluoride had no effect at low concentration; the remaining other compounds had no effect. Silver ions appear to be the principal AB agent at both high and low concentration; fluoride ions only have an AB effect at high concentration, while ammonium, nitrate, chloride and sodium ions have none. The anticaries effect of topical silver solutions appears restricted to that of the silver ions. Silver compounds, such as SDF, silver fluoride, and silver nitrate have AB effect against cariogenic organisms and these may have clinical impact in arresting or preventing dental decay. Sodium fluoride did not have AB effect under the conditions tested.

Silver stain for electron microscopy

NASA Technical Reports Server (NTRS)

Corbett, R. L.

1972-01-01

Ammoniacal silver stain used for light microscopy was adapted advantageously for use with very thin biological sections required for electron microscopy. Silver stain can be performed in short time, has more contrast, and is especially useful for low power electron microscopy.

Glass frits coated with silver nanoparticles for silicon solar cells

NASA Astrophysics Data System (ADS)

Li, Yingfen; Gan, Weiping; Zhou, Jian; Li, Biyuan

2015-06-01

Glass frits coated with silver nanoparticles were prepared by electroless plating. Gum Arabic (GA) was used as the activating agent of glass frits without the assistance of stannous chloride or palladium chloride. The silver-coated glass frits prepared with different GA dosages were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The characterization results indicated that silver-coated glass frits had the structures of both glass and silver. Spherical silver nanoparticles were distributed on the glass frits evenly. The density and particle size of silver nanoparticles on the glass frits can be controlled by adjusting the GA dosage. The silver-coated glass frits were applied to silver pastes to act as both the densification promoter and silver crystallite formation aid in the silver electrodes. The prepared silver-coated glass frits can improve the photovoltaic performances of solar cells.

Silver nanocluster catalytic microreactors for water purification

NASA Astrophysics Data System (ADS)

Da Silva, B.; Habibi, M.; Ognier, S.; Schelcher, G.; Mostafavi-Amjad, J.; Khalesifard, H. R. M.; Tatoulian, M.; Bonn, D.

2016-07-01

A new method for the elaboration of a novel type of catalytic microsystem with a high specific area catalyst is developed. A silver nanocluster catalytic microreactor was elaborated by doping a soda-lime glass with a silver salt. By applying a high power laser beam to the glass, silver nanoclusters are obtained at one of the surfaces which were characterized by BET measurements and AFM. A microfluidic chip was obtained by sealing the silver coated glass with a NOA 81 microchannel. The catalytic activity of the silver nanoclusters was then tested for the efficiency of water purification by using catalytic ozonation to oxidize an organic pollutant. The silver nanoclusters were found to be very stable in the microreactor and efficiently oxidized the pollutant, in spite of the very short residence times in the microchannel. This opens the way to study catalytic reactions in microchannels without the need of introducing the catalyst as a powder or manufacturing complex packed bed microreactors.

Size Selective Green Synthesis of Silver and Gold Nanoparticles: Enhanced Antibacterial Efficacy of Resveratrol Capped Silver Sol.

PubMed

Shukla, Shashi P; Roy, Mainak; Mukherjee, Poulomi; Das, Laboni; Neogy, Suman; Srivastava, Dinesh; Adhikari, Soumyakanti

2016-03-01

In view of potential biomedical application of the noble metal nanoparticles, we report a size controlled yet simple and green synthesis of resveratrol stabilized silver and gold nanoparticles having low polydispersity of size. Here, resveratrol plays two simultaneous roles, reducing the metal ions and providing efficient capping of the small nanoparticles. This gives rise to specific size of silver and gold nanoparticles at specific ratios of metal to resveratrol. The particles have been characterized by XRD and transmission electron microscopy. The nanoparticle sols are stable for months. The UV Visible absorption spectra of the silver sol show the plasmon peak of spherical nanoparticles, presence of which is further reflected in the TEM images. Size of the silver particles obtained is in between 11 to 21 nm depending on the ratio of resveratrol to metal ion used. Resveratrol capped silver nanoparticles exhibit high antibacterial activity against Gram negative wild type E coli BW (25113). The minimum inhibitory concentration (MIC) of nano-silver against the bacterium has been estimated to be 6.48 μg/ml, which is significantly lower than that reported in some earlier as well as recent publications. Reaction of gold ions with resveratrol, on the other hand, produces gold nanoparticles of sizes varying from 7 to 29 nm at different ratios of resveratrol to the metal ions. Particles with higher size and aspect ratio are formed at lower concentration of the capping agent whereas particles with very small size and pseudo-spherical morphology are formed at higher capping concentration. Difference in the formation kinetics of silver and gold nanoparticles has been attributed to the different growth mechanisms in the two cases. Possible modes of anchorage of resveratrol to silver nanoparticles have been investigated using surface enhanced resonance Raman spectroscopy (SERS) which shows that the silver nanoparticles are capped by resveratrol molecule primarily through O

Adsorption mechanism of physiologically active L-phenylalanine phosphonodipeptide analogues: Comparison of colloidal silver and macroscopic silver substrates

NASA Astrophysics Data System (ADS)

Podstawka, E.; Kudelski, A.; Proniewicz, L. M.

2007-11-01

Here we present SERS spectra of several L-phenylalanine (Phe) phosphonodipeptides, i.e., L-Phe- L-Ala-PO 3H 2 ( MD1), L-Phe- L-Va L-PO 3H 2 ( MD2), L-Phe-β-Ala-CH(OH)-PO 3H 2 ( MD3), L-Phe- L-Ala-CH(OH)-PO 3H 2 ( MD4), L-Ala-(3,4-dimethoxy)- L-Phe-PO 3H 2 ( MD5), and L-Ala-(3,4-dimethoxy)-(des-CH 2)- L-Phe-PO 3H 2 ( MD6), immobilized on electrochemically roughened silver electrodes. These spectra are analyzed by theoretical calculations using density functional theory (DFT) at the B3LYP level with 6-31++G∗∗ basis set. In addition, these spectra are compared with SERS spectra of these species adsorbed on a colloidal silver surface. We showed that on the macroscopic silver substrate, the Phe aromatic ring of MD3 and MD4 is oriented vertically, while for MD1 it almost "stands up" on this surface. In the other three cases, the Phe ring adopts a tilted orientation in regard to the substrate. We also find that the phosphonate (-PO32-), methyl/methane, or dimethoxy groups of MD1, MD2, MD3, MD5, and MD6 are involved in the interaction of these phosphonodipeptides with the electrochemically roughened surface. This phenomenon is clearly seen for -CH 2-/-CH 3/-OCH 3 moieties as well as for the PO32- group that adsorbs on the macroscopic silver substrates mainly via the P dbnd O fragment. We also showed that MD4 binds to the macroscopic silver substrate through the hydroxyl, amine, and phosphonate groups, while the methylene/methane moieties are remote from this surface. We found that studied phosphonodipeptides often adsorb differently on the macroscopic silver substrate and on the colloidal silver nanoparticles. For example, MD1 adopts an almost vertical orientation on the electrochemically roughened silver substrate and is tilted or close to flat on the silver nanoparticles.

Transparent SiON/Ag/SiON multilayer passivation grown on a flexible polyethersulfone substrate using a continuous roll-to-roll sputtering system

PubMed Central

2012-01-01

We have investigated the characteristics of a silicon oxynitride/silver/silicon oxynitride [SiON/Ag/SiON] multilayer passivation grown using a specially designed roll-to-roll [R2R] sputtering system on a flexible polyethersulfone substrate. Optical, structural, and surface properties of the R2R grown SiON/Ag/SiON multilayer were investigated as a function of the SiON thickness at a constant Ag thickness of 12 nm. The flexible SiON/Ag/SiON multilayer has a high optical transmittance of 87.7% at optimized conditions due to the antireflection and surface plasmon effects in the oxide-metal-oxide structure. The water vapor transmission rate of the SiON/Ag/SiON multilayer is 0.031 g/m2 day at an optimized SiON thickness of 110 nm. This indicates that R2R grown SiON/Ag/SiON is a promising thin-film passivation for flexible organic light-emitting diodes and flexible organic photovoltaics due to its simple and low-temperature process. PMID:22221400

Realistic Silver Optical Constants for Plasmonics.

PubMed

Jiang, Yajie; Pillai, Supriya; Green, Martin A

2016-07-29

Silver remains the preferred conductor for optical and near-infrared plasmonics. Many high-profile studies focus exclusively on performance simulation in such applications. Almost invariably, these use silver optical data either from Palik's 1985 handbook or, more frequently, an earlier Johnson and Christy (J&C) tabulation. These data are inconsistent, making it difficult to ascertain the reliability of the simulations. The inconsistency stems from challenges in measuring representative properties of pristine silver, due to tarnishing on air exposure. We demonstrate techniques, including use of silicon-nitride membranes, to access the full capabilities of multiple-angle, spectrometric-ellipsometry to generate an improved data set, representative of overlayer-protected, freshly-deposited silver films on silicon-nitride and glass.

Synthesis of silver nanoparticle and its application.

PubMed

Pandian, A Muthu Kumara; Karthikeyan, C; Rajasimman, M; Dinesh, M G

2015-11-01

In this work, silver nanoparticles have been synthesized by wet chemical technique, green synthesis and microbial methods. Silver nitrate (10(-3)M) was used with aqueous extract to produce silver nanoparticles. From the results it was observed that the yield of nanoparticles was high in green synthesis. The size of the silver nanoparticles was determined from Scanning Electron Microscope analysis (SEM). Fourier Transform Infrared spectroscopy (FTIR) was carried out to determine the presence of biomolecules in them. Its cytotoxic effect was studied in cancerous cell line and normal cell line. MTT assay was done to test its optimal concentration and efficacy which gives valuable information for the use of silver nanoparticles for future cancer therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

Rapid Fabrication of Silver Nanowires through Photoreduction of Silver Nitrate from an Anodic-Aluminum-Oxide Template

NASA Astrophysics Data System (ADS)

Lin, Yu-Hsuan; Chen, Kun-Tso; Ho, Jeng-Rong

2011-06-01

A method for rapidly fabricating dense and high-aspect-ratio silver nanowires, with wire diameter of 200 nm and wire length more than 30 µm, is reported. The fabrication process simply involves filling the silver nitrate solution into the pores of an anodic-aluminum-oxide (AAO) membrane through capillary attraction and irradiating the dried template AAO membrane using a pulsed ArF excimer laser. Through varying the thickness and pore diameter of the employed AAO membrane, the primary dimensions of the targeted silver nanowires can be plainly specified; and, by amending the initial concentration of the silver nitrate solution and adjusting the laser operation parameters, laser fluence and number of laser pulses, the surface morphology and size of the resulting nanowires can be finely regulated. The wire formation mechanism is considered through two stages: the period of precipitation of silver particles from the dried silver nitrate film through the laser-induced photoreduction; and, the phase of clustering, merging and fusing of the reduced particles to form nanowires in the template pores by the thermal energy owing to photothermal effect. This approach is straightforward and takes the advantage that all the fabrication processes can be executed in an ambient environment and at room temperature. In addition, by the excellence in local processing that the laser possesses, this method is suitable for precisely growing nanowires.

Antimicrobial Activity of Silver Ions Released from Zeolites Immobilized on Cellulose Nanofiber Mats.

PubMed

Rieger, Katrina A; Cho, Hong Je; Yeung, Hiu Fai; Fan, Wei; Schiffman, Jessica D

2016-02-10

In this study, we exploit the high silver ion exchange capability of Linde Type A (LTA) zeolites and present, for the first time, electrospun nanofiber mats decorated with in-house synthesized silver (Ag(+)) ion exchanged zeolites that function as molecular delivery vehicles. LTA-Large zeolites with a particle size of 6.0 μm were grown on the surface of the cellulose nanofiber mats, whereas LTA-Small zeolites (0.2 μm) and three-dimensionally ordered mesoporous-imprinted (LTA-Meso) zeolites (0.5 μm) were attached to the surface of the cellulose nanofiber mats postsynthesis. After the three zeolite/nanofiber mat assemblies were ion-exchanged with Ag(+) ions, their ion release profiles and ability to inactivate Escherichia coli (E. coli) K12 were evaluated as a function of time. LTA-Large zeolites immobilized on the nanofiber mats displayed more than an 11 times greater E. coli K12 inactivation than the Ag-LTA-Large zeolites that were not immobilized on the nanofiber mats. This study demonstrates that by decorating nanometer to micrometer scale Ag(+) ion-exchanged zeolites on the surface of high porosity, hydrophilic cellulose nanofiber mats, we can achieve a tunable release of Ag(+) ions that inactivate bacteria faster and are more practical to use in applications over powder zeolites.

Synthesis of silver nanoparticles by silver salt reduction and its characterization

NASA Astrophysics Data System (ADS)

Muzamil, Muhammad; Khalid, Naveed; Danish Aziz, M.; Aun Abbas, S.

2014-06-01

The wet chemical method route by metal salt reduction has been used to synthesize nanoparticles, using silver nitrate as an inorganic salt, aldehyde as a reducing agent and amino acid as a catalyst. During the reaction aldehyde oxidizes to carboxylic acid and encapsulates the silver nanoparticles to prevent agglomeration and provide barrier in the growth of particle. The existing work produces particles using lab grade chemical, here the presented work is by using industrial grade chemicals to make the process more cost & time effective. The nano silver powder has been studied for their formation, particle size, shape & compositional analysis using Scanning Electron Microscope (SEM) equipped with EDS. The particles size distributions were analyzed by Laser Particle Analyzer (LPA), structure & morphological analysis using x-ray diffraction (XRD) and Fourier-transform-infrared Spectroscopy (FTIR) confirmed the stabilization of particles by coating of carboxylic group. These studies infer that the particles are mostly spherical in shape and have an average size between 70 to 350 nm.

Electroless silver coating of rod-like glass particles.

PubMed

Moon, Jee Hyun; Kim, Kyung Hwan; Choi, Hyung Wook; Lee, Sang Wha; Park, Sang Joon

2008-09-01

An electroless silver coating of rod-like glass particles was performed and silver glass composite powders were prepared to impart electrical conductivity to these non-conducting glass particles. The low density Ag-coated glass particles may be utilized for manufacturing conducting inorganic materials for electromagnetic interference (EMI) shielding applications and the techniques for controlling the uniform thickness of silver coating can be employed in preparation of biosensor materials. For the surface pretreatment, Sn sensitization was performed and the coating powders were characterized by scanning electron microscopy (SEM), focused ion beam microscopy (FIB), and atomic force microscopy (AFM) along with the surface resistant measurements. In particular, the use of FIB technique for determining directly the Ag-coating thickness was very effective on obtaining the optimum conditions for coating. The surface sensitization and initial silver loading for electroless silver coating could be found and the uniform and smooth silver-coated layer with thickness of 46 nm was prepared at 2 mol/l of Sn and 20% silver loading.

Silver

Integrated Risk Information System (IRIS)

Silver ; CASRN 7440 - 22 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects )

Metal-support interactions during the adsorption of CO on thin layers and islands of epitaxial palladium

NASA Technical Reports Server (NTRS)

Park, C.; Poppa, H.; Soria, F.

1984-01-01

Islands and continuous layers of palladium were grown in an ultrahigh vacuum on substrates of Mo(110)c(14 x 7)-O, designated MoO(x), and of clean Mo(110). It was found that as-deposited islands and layers exhibited bulk palladium adsorption properties for CO when deposited at room temperature and for palladium thicknesses in excess of about 3 monolayers. CO adsorption was drastically reduced, however, on annealing. For islands, annealing temperatures of as low as 400 K led to some reduction in CO adsorption whereas more severe reductions were found to occur at 600 K for islands and at 800 K for continuous multilayers. The deactivation depended on the palladium thickness, the substrate species and the extent of thermal treatments. Auger electron spectroscopy, temperature-programmed desorption and Delta-Phi measurements were combined to interpret the deactivation behavior in terms of substrate-support interactions involving the diffusion of substrate species towards the palladium surface.

Effects of silver impurity on the structural, electrical, and optical properties of ZnO nanowires

PubMed Central

2011-01-01

1, 3, and 5 wt.% silver-doped ZnO (SZO) nanowires (NWs) are grown by hot-walled pulsed laser deposition. After silver-doping process, SZO NWs show some change behaviors, including structural, electrical, and optical properties. In case of structural property, the primary growth plane of SZO NWs is switched from (002) to (103) plane, and the electrical properties of SZO NWs are variously measured to be about 4.26 × 106, 1.34 × 106, and 3.04 × 105 Ω for 1, 3, and 5 SZO NWs, respectively. In other words, the electrical properties of SZO NWs depend on different Ag ratios resulting in controlling the carrier concentration. Finally, the optical properties of SZO NWs are investigated to confirm p-type semiconductor by observing the exciton bound to a neutral acceptor (A0X). Also, Ag presence in ZnO NWs is directly detected by both X-ray photoelectron spectroscopy and energy dispersive spectroscopy. These results imply that Ag doping facilitates the possibility of changing the properties in ZnO NWs by the atomic substitution of Ag with Zn in the lattice. PMID:21985620

Synthesis of silver-titanium dioxide nanocomposites for antimicrobial applications

NASA Astrophysics Data System (ADS)

Yang, X. H.; Fu, H. T.; Wang, X. C.; Yang, J. L.; Jiang, X. C.; Yu, A. B.

2014-08-01

Silver-titanium dioxide (Ag-TiO2) nanostructures have attracted increasing attention because of unique functional properties and potential applications in many areas such as photocatalysis, antibacterial, and self-cleaning coatings. In this study, Ag@TiO2 core-shell nanostructures and Ag-decorated TiO2 particles (TiO2@Ag) (the size of these two nanoparticles is ranging from 200-300 nm) have been synthesized by a developed facile but efficient method. These two types of hybrid nanostructures, characterized by various advanced techniques (TEM, XRD, BET and others), exhibit unique functional properties particularly in antibacterial toward Gram negative Escherichia coli, as a case study. Specifically: (i) the TiO2@Ag nanoparticles are superior in bacterial growth inhibition in standard culture conditions (37 °C incubator) to the Ag@TiO2 core-shell ones, in which silver may dominate the antibacterial performance; (ii) while after UV irradiation treatment, the Ag@TiO2 core-shell nanoparticles exhibit better performance in killing grown bacteria than the TiO2@Ag ones, probably because of the Ag cores facilitating charge separation for TiO2, and thus produce more hydroxyl radicals on the surface of the TiO2 particles; and (iii) without UV irradiation, both TiO2@Ag and Ag@TiO2 nanostructures show poor capabilities in killing mature bacteria. These findings would be useful for designing hybrid metal oxide nanocomposites with desirable functionalities in bioapplications in terms of sterilization, deodorization, and water purification.

Green synthesis of silver nanoparticle and silver based chitosan bionanocomposite using stem extract of Saccharum officinarum and assessment of its antibacterial activity

NASA Astrophysics Data System (ADS)

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Pavunraj, Manickam; Annadurai, Gurusamy

2017-09-01

Synthesis of nanoparticles and nanocomposites using green route is a major focus of modern nanotechnology. Herein we demonstrate the synthesis of silver nanoparticle and silver based chitosan bionanocomposite using the stem extract of Saccharum officinarum. The absorbance peak at 460 nm in the UV-Vis spectrum reveals the synthesis of silver nanoparticles using the stem extract of Saccharum officinarum. The size of the synthesized silver nanoparticle was in the range of 10-60 nm obtained from transmission electron microscope (TEM) analysis. The presence of silver nanoparticles on the chitosan suspension was identified by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). The presence of possible functional group involved in the reduction of silver metal ions into silver nanoparticles was identified by Fourier transform infrared spectroscopy (FTIR) analysis. The antibacterial activity of the synthesized silver based chitosan bionanocomposite was evaluated against Bacillus subtilis (MTCC 3053), Klebsiella planticola (MTCC 2277), Streptococcus faecalis (ATCC 8043), Pseudomonas aeruginosa (ATCC 9027) and Escherichia coli (ATCC 8739). The antibacterial activity of silver based chitosan bionanocomposite has remarkable scope in medicine, food packaging, textile and pharmaceuticals.

Green chemical synthesis of silver nanomaterials with maltodextrin.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tallant, David Robert; Lu, Ping; Lambert, Timothy N.

2010-11-01

Silver nanomaterials have significant application resulting from their optical properties related to surface enhanced Raman spectroscopy, high electrical conductivity, and anti-microbial impact. A 'green chemistry' synthetic approach for silver nanomaterials minimizes the environmental impact of silver synthesis, as well as lowers the toxicity of the reactive agents. Biopolymers have long been used for stabilization of silver nanomaterials during synthesis, and include gum Arabic, heparin, and common starch. Maltodextrin is a processed derivative of starch with lower molecular weight and an increase in the number of reactive reducing aldehyde groups, and serves as a suitable single reactant for the formation ofmore » metallic silver. Silver nanomaterials can be formed under either a thermal route at neutral pH in water or by reaction at room temperature under more alkaline conditions. Deposited silver materials are formed on substrates from near neutral pH solutions at low temperatures near 50 C. Experimental conditions based on material concentrations, pH and reaction time are investigated for development of deposited films. Deposit morphology and optical properties are characterized using SEM and UV-vis techniques. Silver nanoparticles are generated under alkaline conditions by a dissolution-reduction method from precipitated silver (II) oxide. Synthesis conditions were explored for the rapid development of stable silver nanoparticle dispersions. UV-vis absorption spectra, powder X-ray diffraction (PXRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques were used to characterize the nanoparticle formation kinetics and the influence of reaction conditions. The adsorbed content of the maltodextrin was characterized using thermogravimetric analysis (TGA).« less

The antifungal effect of silver nanoparticles on Trichosporon asahii.

PubMed

Xia, Zhi-Kuan; Ma, Qiu-Hua; Li, Shu-Yi; Zhang, De-Quan; Cong, Lin; Tian, Yan-Li; Yang, Rong-Ya

2016-04-01

Silver nanoparticles are receiving increasing attention in biomedical applications. This study aims at evaluating the antifungal properties of silver nanoparticles against the pathogenic fungus Trichosporon asahii. The growth of T. asahii on potato dextrose agar medium containing different concentrations of silver nanoparticles was examined and the antifungal effect was evaluated using minimum inhibitory concentration. Scanning and transmission electron microscopy were also used to investigate the antifungal effect of silver nanoparticles on T. asahii. Silver nanoparticles had a significant inhibitory effect on the growth of T. asahii. The minimum inhibitory concentration of silver nanoparticles against T. asahii was 0.5 μg/mL, which was lower than amphotericin B, 5-flucytosine, caspofungin, terbinafine, fluconazole, and itraconazole and higher than voriconazole. Silver nanoparticles obviously damaged the cell wall, cell membrane, mitochondria, chromatin, and ribosome. Our results demonstrate that silver nanoparticles have good antifungal activity against T. asahii. Based on our electron microscopy observations, silver nanoparticles may inhibit the growth of T. asahii by permeating the fungal cell and damaging the cell wall and cellular components. Copyright © 2014. Published by Elsevier B.V.

Interference of Steroidogenesis by Gold Nanorod Core/Silver Shell Nanostructures: Implications for Reproductive Toxicity of Silver Nanomaterials.

PubMed

Jiang, Xiumei; Wang, Liming; Ji, Yinglu; Tang, Jinglong; Tian, Xin; Cao, Mingjing; Li, Jingxuan; Bi, Shuying; Wu, Xiaochun; Chen, Chunying; Yin, Jun-Jie

2017-03-01

As a widely used nanomaterial in daily life, silver nanomaterials may cause great concern to female reproductive system as they are found to penetrate the blood-placental barrier and gain access to the ovary. However, it is largely unknown about how silver nanomaterials influence ovarian physiology and functions such as hormone production. This study performs in vitro toxicology study of silver nanomaterials, focusing especially on cytotoxicity and steroidogenesis and explores their underlying mechanisms. This study exposes primary rat granulosa cells to gold nanorod core/silver shell nanostructures (Au@Ag NRs), and compares outcomes with cells exposed to gold nanorods. The Au@Ag NRs generate more reactive oxygen species and reduce mitochondrial membrane potential and less production of adenosine triphosphate. Au@Ag NRs promote steroidogenesis, including progesterone and estradiol, in a time- and dose-dependent manner. Chemical reactivity and transformation of Au@Ag NRs are then studied by electron spin resonance spectroscopy and X-ray absorption near edge structure, which analyze the generation of free radical and intracellular silver species. Results suggest that both particle-specific activity and intracellular silver ion release of Au@Ag NR contribute to the toxic response of granulosa cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biomedical properties of laser prepared silver-doped hydroxyapatite

NASA Astrophysics Data System (ADS)

Jelínek, M.; Weiserová, M.; Kocourek, T.; Zezulová, M.; Strnad, J.

2011-07-01

Thin films of hydroxyapatite (HA) and silver-doped HA were synthesized using KrF excimer laser deposition. Material was ablated from one target composed from silver and HA segments. Layers properties as silver content, structure, color, FTIR spectra and antibacterial properties (Gram-positive Bacillus subtilis) were measured. Silver concentration in HA layers of 0.06, 0.3, 1.2, 4.4, 8.3, and 13.7 at % was detected. The antibacterial efficacy changed with silver dopation from 71.0 to 99.9%. The focus is on investigation of minimum Ag concentration needed to reach a high antibacterial efficacy.

Occurrence of silver minerals in a silver-rich pocket in the massive sulfide zinc-lead ores in the Edwards mine, New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serviss, C.R.; Grout, C.M.; Hagni, R.D.

1985-01-01

Ore microscopic examination of uncommon silver-rich ores from the Edwards mine has detected three silver minerals, native silver, freibergite, and argentite, that were previously unreported in the literature from the Balmat-Edwards district. The zinc-lead ore deposits of the Balmat-Edwards District in northern New York are composed of very coarse-grained massive sulfides, principally sphalerite, galena, and pyrite. The typical ores contain small amounts of silver in solid solution galena. Galena concentrates produced from those ores have contained an average of 15 ounces of silver per ton of 60% lead concentrates. In contrast to the typical ore a silver-rich pocket, that measuredmore » three feet by three feet on the vertical mine face and was the subject of this study, contained nearly 1% silver in a zinc ore. Ore microscopic study shows that this ore is especially characterized by abundant, relatively fine-grained chalcopyrite with anhedral pyrite inclusions. Fine-grained sphalerite, native silver, argentite, freibergite and arsenopyrite occur in association with the chalcopyrite and as fracture-fillings in gangue minerals. Geochemically anomalous amounts of tin, barium, chromium, and nickel also are present in the silver-rich pocket. The silver-rich pocket may mark the locus of an early feeder vent or alternatively it may record a hydrothermal event that was superimposed upon the event responsible for the metamorphic ore textures.« less

Differential Phytotoxic Impact of Plant Mediated Silver Nanoparticles (AgNPs) and Silver Nitrate (AgNO3) on Brassica sp.

PubMed Central

Vishwakarma, Kanchan; Shweta; Upadhyay, Neha; Singh, Jaspreet; Liu, Shiliang; Singh, Vijay P.; Prasad, Sheo M.; Chauhan, Devendra K.; Tripathi, Durgesh K.; Sharma, Shivesh

2017-01-01

Continuous formation and utilization of nanoparticles (NPs) have resulted into significant discharge of nanosized particles into the environment. NPs find applications in numerous products and agriculture sector, and gaining importance in recent years. In the present study, silver nanoparticles (AgNPs) were biosynthesized from silver nitrate (AgNO3) by green synthesis approach using Aloe vera extract. Mustard (Brassica sp.) seedlings were grown hydroponically and toxicity of both AgNP and AgNO3 (as ionic Ag+) was assessed at various concentrations (1 and 3 mM) by analyzing shoot and root length, fresh mass, protein content, photosynthetic pigments and performance, cell viability, oxidative damage, DNA degradation and enzyme activities. The results revealed that both AgNPs and AgNO3 declined growth of Brassica seedlings due to enhanced accumulation of AgNPs and AgNO3 that subsequently caused severe inhibition in photosynthesis. Further, the results showed that both AgNPs and AgNO3 induced oxidative stress as indicated by histochemical staining of superoxide radical and hydrogen peroxide that was manifested in terms of DNA degradation and cell death. Activities of antioxidants, i.e., ascorbate peroxidase (APX) and catalase (CAT) were inhibited by AgNPs and AgNO3. Interestingly, damaging impact of AgNPs was lesser than AgNO3 on Brassica seedlings which was due to lesser accumulation of AgNPs and better activities of APX and CAT, which resulted in lesser oxidative stress, DNA degradation and cell death. The results of the present study showed differential impact of AgNPs and AgNO3 on Brassica seedlings, their mode of action, and reasons for their differential impact. The results of the present study could be implied in toxicological research for designing strategies to reduce adverse impact of AgNPs and AgNO3 on crop plants. PMID:29075270

Nucleation sites of Ge nanoislands grown on pit-patterned Si substrate prepared by electron-beam lithography

NASA Astrophysics Data System (ADS)

Smagina, Zh. V.; Zinovyev, V. A.; Rudin, S. A.; Novikov, P. L.; Rodyakina, E. E.; Dvurechenskii, A. V.

2018-04-01

Regular pit-patterned Si(001) substrates were prepared by electron-beam lithography followed by plasma chemical etching. The geometry of the pits was controlled by varying the etching conditions and the electron-beam exposure duration. It was shown that the location of three-dimensional (3D) Ge nanoislands subsequently grown on the pit-patterned Si substrates depends on the shape of the pit bottom. In the case of pits having a sharp bottom, 3D Ge islands nucleate inside the pits. For pits with a wide flat bottom, the 3D Ge island nucleation takes place at the pit periphery. This effect is attributed to the strain relaxation depending not only on the initial pit shape, but also on its evolution during the Ge wetting layer deposition. It was shown by Monte Carlo simulations that in the case of a pit with a pointed bottom, the relaxation is most effective inside the pit, while for a pit with a wide bottom, the most relaxed area migrates during Ge deposition from the pit bottom to its edges, where 3D Ge islands nucleate.

Silver nanowires-templated metal oxide for broadband Schottky photodetector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong, E-mail: joonkim@inu.ac.kr

2016-04-04

Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W{sup −1}) and detectivity (2.75 × 10{sup 15} Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxidemore » devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.« less

Femtosecond laser structuring of silver-containing glass: Silver redistribution, selective etching, and surface topology engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desmoulin, Jean-Charles; Petit, Yannick; Cardinal, Thierry, E-mail: thierry.cardinal@icmcb.cnrs.fr

2015-12-07

Femtosecond direct laser writing in silver-containing phosphate glasses allows for the three-dimensional (3D) implementation of complex photonic structures. Sample translation along or perpendicular to the direction of the beam propagation has been performed, which led to the permanent formation of fluorescent structures, either corresponding to a tubular shape or to two parallel planes at the vicinity of the interaction voxel, respectively. These optical features are related to significant modifications of the local material chemistry. Indeed, silver depletion areas with a diameter below 200 nm were evidenced at the center of the photo-produced structures while photo-produced luminescence properties are attributed to themore » formation of silver clusters around the multiphoton interaction voxel. The laser-triggered oxidation-reduction processes and the associated photo-induced silver redistribution are proposed to be at the origin of the observed original 3D luminescent structures. Thanks to such material structuring, surface engineering has been also demonstrated. Selective surface chemical etching of the glass has been obtained subsequently to laser writing at the location of the photo-produced structures, revealing features with nanometric depth profiles and radial dimensions strongly related to the spatial distributions of the silver clusters.« less

Mechanism of Silver Sulfadiazine Action on Burn Wound Infections

PubMed Central

Fox, Charles L.; Modak, Shanta M.

1974-01-01

The role of silver and sulfadiazine in the mechanism of action of silver sulfadiazine on burn wound infections was investigated. Silver, but not sulfadiazine, was bound by bacteria. Sulfadiazine did not act as an antibacterial agent in low concentrations, but exhibited specific synergism in combination with subinhibitory levels of silver sulfadiazine. The efficacy of silver sulfadiazine is thought to result from its slow and steady reactions with serum and other sodium chloride-containing body fluids, which permits the slow and sustained delivery of silver ions into the wound environs. In this circumstance, a relatively minute amount of sulfadiazine appears active. PMID:15825409

Plasmonic particles of colloidal silver in high-resolution recording media

NASA Astrophysics Data System (ADS)

Andreeva, O. V.; Andreeva, N. V.; Kuzmina, T. B.

2017-01-01

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.

Oxygen isotope exchange with quartz during pyrolysis of silver sulfate and silver nitrate.

PubMed

Schauer, Andrew J; Kunasek, Shelley A; Sofen, Eric D; Erbland, Joseph; Savarino, Joel; Johnson, Ben W; Amos, Helen M; Shaheen, Robina; Abaunza, Mariana; Jackson, Terri L; Thiemens, Mark H; Alexander, Becky

2012-09-30

Triple oxygen isotopes of sulfate and nitrate are useful metrics for the chemistry of their formation. Existing measurement methods, however, do not account for oxygen atom exchange with quartz during the thermal decomposition of sulfate. We present evidence for oxygen atom exchange, a simple modification to prevent exchange, and a correction for previous measurements. Silver sulfates and silver nitrates with excess (17)O were thermally decomposed in quartz and gold (for sulfate) and quartz and silver (for nitrate) sample containers to O(2) and byproducts in a modified Temperature Conversion/Elemental Analyzer (TC/EA). Helium carries O(2) through purification for isotope-ratio analysis of the three isotopes of oxygen in a Finnigan MAT253 isotope ratio mass spectrometer. The Δ(17)O results show clear oxygen atom exchange from non-zero (17)O-excess reference materials to zero (17)O-excess quartz cup sample containers. Quartz sample containers lower the Δ(17)O values of designer sulfate reference materials and USGS35 nitrate by 15% relative to gold or silver sample containers for quantities of 2-10 µmol O(2). Previous Δ(17)O measurements of sulfate that rely on pyrolysis in a quartz cup have been affected by oxygen exchange. These previous results can be corrected using a simple linear equation (Δ(17)O(gold) = Δ(17)O(quartz) * 1.14 + 0.06). Future pyrolysis of silver sulfate should be conducted in gold capsules or corrected to data obtained from gold capsules to avoid obtaining oxygen isotope exchange-affected data. Copyright © 2012 John Wiley & Sons, Ltd.

[Design and application of silver needle-knife].

PubMed

Sun, Guodong; Shi, Bin; Zhang, Benwu; Xu, Haidong

2015-04-01

A silver needle-knife which has the dual function of silver needle and needle-knife is designed. The main components of this silver needle-knife are approximately 50% silver and approximately 50% nichrome. The silver needle-knife is composed of five parts, including needle-knife tail, spiral handle; steering handle, needle-knife body and needle-knife edge. It converges the advantages of needle-knife and silver needle, which can cut loose of diseased tissue and peel adhesion of lesions, but also be heated with moxa cone and thermal therapeutic instrument, and connect with electroacupuncture apparatus. It has the function of warming channel and removing coldness, dispelling wind and eliminating dampness, resolving spasm and relieving pain, dredging the channel and so on. Due to the spiral handle and the steering handle, the operation is easier, which reduces the blindness of cutting and increase the safety. It is mainly used for soft tissue injury, rheumatism and rheumatoid arthritis, as well as degenerative diseases of spine and joint, and it has obvious efficacy on some internal medical diseases.

Silver in medicine: a brief history BC 335 to present.

PubMed

Barillo, David J; Marx, David E

2014-12-01

Silver is a naturally occurring element. Similar to other metals, the ionized form of silver (Ag(+1)) has known antimicrobial properties. A number of wound dressings incorporating silver ion or silver compounds have recently been developed and marketed. In addition, the antimicrobial effects of silver are currently being promoted in consumer products such as clothing and household appliances. The present use of silver in medical and consumer products has prompted concerns for potential toxicity and ecological effects, including induction of microbial resistance to antibiotics. These concerns ignore the fact that silver has been used for medicinal purposes for several thousand years. A historical review of the uses of silver in medicine is presented.

Synthesis and characterization of colloidal fluorescent silver nanoclusters.

PubMed

Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

2012-06-19

Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryos.

PubMed

Guadagnolo, C M; Brauner, C J; Wood, C M

2001-03-01

Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl-, 1.3 mg/L dissolved organic matter. 12.3+/-0.1 degrees C) at nominal concentrations of 0.1, 1, and 10 microg/L (measured = 0.117+/-0.008, 1.22+/-0.16, and 13.51+/-1.58 microg/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 microg/L) were not significantly different from controls throughout embryonic development (days 1-32 postfertilization). Mortalities of embryos in the 13.5-microg/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-microg/L treatments reached the highest concentrations of 0.13 and 0.24 microg/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-microg/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout.

Synthesis of Silver Polymer Nanocomposites and Their Antibacterial Activity

NASA Astrophysics Data System (ADS)

Gavade, Chaitali; Shah, Sunil; Singh, N. L.

2011-07-01

PVA (Polyvinyl Alcohol) silver nanocomposites of different sizes were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and amine hydrazine as a reducing agent. The formation of the silver nanoparticles was noticed using UV- visible absorption spectroscopy. The UV-visible spectroscopy revealed the formation of silver nanoparticles by exhibiting the surface plasmon resonance. The bactericidal activity due to silver release from the surface was determined by the modification of conventional diffusion method. Salmonella typhimurium, Serratia sps and Shigella sps were used as test bacteria which are gram-negative type bacteria. Effect of the different sizes of silver nano particles on antibacterial efficiency was discussed. Zones of inhibition were measured after 24 hours of incubation at 37 °C which gave 20 mm radius for high concentration of silver nanoparticles.

Synthesis and Optical Properties of Silver Bicrystalline Nanowires

NASA Astrophysics Data System (ADS)

Sun, Yugang; Xia, Younan

2002-11-01

This paper describes a solution-phase route to the large-scale synthesis of silver nanowires with diameters in the range of 30-40 nm, and lengths up to ~50 μm. The initial step of this synthesis involved the formation of Pt nanoparticles by reducing PtCl2 with ethylene glycol (EG) refluxed at ~160 °C. These Pt nanoparticles could serve as seeds for the growth of silver (formed by reducing AgNO3 with EG) through heterogeneous nucleation process because their crystal structures and lattice constants matched closely. In the presence of poly(vinyl pyrrolidone) (PVP), the growth of silver could be led to a highly anisotropic mode with formation of uniform nanowires. UV-visible spectroscopy was used to track the growth process of silver nanowires because different silver nanostructures exhibited distinctive surface plasmon resonance peaks at different frequencies. SEM, TEM, XRD, and electron diffraction were used to characterize these silver nanowires, indicating the formation of a highly pure face-centered cubic phase, as well as uniform diameter and bicrystalline structure. The morphology of these silver nanostructures could be varied from particles and rods to long wires by tuning the reaction conditions, including reaction temperature, and the ratio of PVP to silver nitrate. These silver nanowires could be used as sacrificial templates to synthesize gold nanotubes via a template-engaged replacement reaction. The dispersion of gold nanotubes exhibited a strong extinction peak in the red regime, which was around 760 nm.

Preparation of silver-activated zinc sulfide thin films

NASA Technical Reports Server (NTRS)

Feldman, C.; Swindells, F. E.

1968-01-01

Silver improves luminescence and reduces contamination of zinc sulfide phosphors. The silver is added after the zinc sulfide phosphors are deposited in thin films by vapor evaporation, but before calcining, by immersion in a solution of silver salt.

Using sub-micron silver-nanoparticle based films to counter biofilm formation by Gram-negative bacteria

NASA Astrophysics Data System (ADS)

Gillett, A. R.; Baxter, S. N.; Hodgson, S. D.; Smith, G. C.; Thomas, P. J.

2018-06-01

Composite films comprised of silver nanoparticles (AgNPs) grown using a low-cost straightforward chemical bath based method have been deposited on glass microscope slides to investigate their potential as a sacrificial antibacterial coating. The as-deposited films have been characterised using scanning electron microscopy (SEM) and optical profilometry. These suggested that the films were relatively uniform in coverage. Chemical composition of the AgNP films has been studied by using X-ray photoelectron spectroscopy (XPS). The XPS analysis indicated that the Ag was in a metallic form able to sustain plasmon behaviour, and that low levels of residual nanoparticle precursors were present. Particle size was characterised using transmission electron microscopy (TEM) which showed an average particle size of 10.6 nm. The effectiveness of the films as an antibacterial coating was tested against Escherichia coli. The AgNP film was determined to be effective in the killing of E. coli cells over a 24 h period when compared to equivalent samples that contained no silver. Of particular note was that only minimal bacterial growth was detected over the first 12 h of testing, up to 78.6 times less than the control samples, suggesting the film is very efficient at slowing initial biofilm formation. The use of AgNP based films that have been synthesised using a novel low-cost, low-temperature and highly upscalable method is demonstrated as a promising solution for the deployment of silver as an effective sacrifical antimicrobial coating to counter the formation of potentially hazardous Gram negative biofilms.

Reinforced silver-embedded silica matrix from the cheap silica source for the controlled release of silver ions

NASA Astrophysics Data System (ADS)

Hilonga, A.; Kim, J. K.; Sarawade, P. B.; Kim, H. T.

2009-07-01

In this study, a reinforced silver-embedded silica matrix was designed by utilizing the interaction between the [AlO 4] - tetrahedral and the Ag + in sol-gel process using sodium silicate as a silica precursor. The Ag + mole ratio in each sample was significantly varied to examine the influence of silver concentration on the properties of the final product. Aluminium ions were added to reinforce and improve the chemical durability of silver-embedded silica. A templated sample at Al/Ag = 1 atomic ratio was also synthesized to attempt a possibility of controlling porosity of the final product. Also, a sample neither embedded with silver nor templated was synthesized and characterized to serve as reference. The material at Al/Ag = 1 was found to have a desirable properties, compared to its counterparts, before and even after calcination up to 1000 °C. The results demonstrate that materials with desirable properties can be obtained by this unprecedented method while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

Mechanism of Prophylaxis by Silver Compounds against Infection of Burns

PubMed Central

Ricketts, C. R.; Lowbury, E. J. L.; Lawrence, J. C.; Hall, M.; Wilkins, M. D.

1970-01-01

To clarify tthe mechanism by which local application of silver compounds protects burns against infection, an ion-specific electrode was used to measùre the concentration of silver ions in solutions. By this method it was shown that in burn dressings silver ions were reduced to a very low level by precipitation as silver chloride. The antibacterial effect was found to depend on the availability of silver ions from solution in contact with precipitate. Between 10-5 and 10-6 molar silver nitrate solution in water was rapidly bactericidal. The minimal amount of silver nitrate causing inhibition of respiration of skin in tissue culture was about 25 times the minimal concentration of silver nitrate that inhibited growth of Pseudomonas aeruginosa. PMID:4986877

Colloidal complexed silver and silver nanoparticles in extrapallial fluid of Mytilus edulis.

PubMed

Zuykov, Michael; Pelletier, Emilien; Demers, Serge

2011-02-01

Metal transport in mollusk extrapallial fluid (EPF) that acts as a "bridge" between soft tissues and shell has surprisingly received little attention until now. Using ultrafiltration and radiotracer techniques we determined silver concentrations and speciation in the EPF of the blue mussel Mytilus edulis after short-term uptake and depuration laboratory experiments. Radiolabelled silver ((¹¹⁰m)Ag) was used in dissolved or nanoparticulate phases (AgNPs < 40 nm), with a similar low Ag concentration (total radioactive and cold Ag ~0.7 μg/L) in a way that mussels could uptake radiotracers only from seawater. Our results indicated that silver nanoparticles were transported to the EPF of blue mussels at a level similar to the Ag ionic form. Bulk activity of radiolabelled silver in the EPF represented only up to 7% of the bulk activity measured in the whole mussels. The EPF extracted from mussels exposed to both treatments exhibited an Ag colloidal complexed form based on EPF ultrafiltration through a 3 kDa filter. This original study brings new insights to internal circulation of nanoparticles in living organisms and contributes to the international effort in studying the potential impacts of engineered nanomaterials on marine bivalves which play an essential role in coastal ecosystems, and are important contributors to human food supply from the sea. © 2010 Elsevier Ltd. All rights reserved.

The Empirical Formula of Silver Sulfide: An Experiment for Introductory Chemistry

ERIC Educational Resources Information Center

Trujillo, Carlos Alexander

2007-01-01

An experiment is described that allows students to experimentally determine an empirical formula for silver sulfide. At elevated temperatures, silver sulfide reacts in air to form silver, silver sulfate, and sulfur dioxide. At higher temperatures (960 [degree]C) silver sulfate decomposes to produce metallic silver. (Contains 1 figure and 1 table.)

Potential therapeutic activity of Phlogacanthus thyrsiformis Hardow (Mabb) flower extract and its biofabricated silver nanoparticles against chemically induced urolithiasis in male Wistar rats.

PubMed

Das, Poppy; Kumar, Kiran; Nambiraj, Arunai; Rajan, Reshma; Awasthi, Rajendra; Dua, Kamal; M, Himaja

2017-10-01

Urolithiasis is a painful disorder in which stones are formed in the kidney, bladder or urethra. There are no proper therapeutic treatments available for kidney stones and people suffering from larger stones have to undergo surgery which has many side effects. A natural remedy with therapeutic effects that can dissipate and remove even the larger stones would eliminate the need of a surgery and the risks associated with it. The flowers of Phlogacanthus thyrsiformis used in culinary recipes in the north eastern India are also widely used as a folklore medicine for the treatment of kidney stones and liver disorders. The aim of this study was to evaluate the prophylactic and therapeutic activity of the aqueous extract of P. thyrsiformis flowers and its biofabricated silver nanoparticles against struvite urinary stones and calcium oxalate kidney stones. A kidney stone inhibition study was carried out on struvite stones grown in gel medium and calcium oxalate stones in rat models using an aqueous extract of P. thyrsiformis flowers and its biofabricated silver nanoparticles. The aqueous extract of P. thyrsiformis flowers and their biofabricated silver nanoparticles, obtained by a green synthetic method, were used to treat struvite urinary stones in vitro and calcium oxalate kidney stones in vivo. Struvite stones were grown in tubes by gel diffusion technique and were treated with varying concentrations of the extract and its nanoparticles. The size of the struvite stones was monitored for 96h using a travelling microscope. Calcium oxalate stones were induced in male Wistar rats by feeding ethylene glycol-ammonium chloride mixture for 14days. Both, prophylactic and therapeutic activities were evaluated by analyzing the urine, serum and histopathological parameters of the rats. The qualitative screening of water extract unveiled the presence of flavonoids as a major constituent. Both, the extract and the nanoparticles effectively reduced the size of struvite stones in

Biopersistence of silver nanoparticles in tissues from Sprague–Dawley rats

PubMed Central

2013-01-01

Silver nanoparticles are known to be distributed in many tissues after oral or inhalation exposure. Thus, understanding the tissue clearance of such distributed nanoparticles is very important to understand the behavior of silver nanoparticles in vivo. For risk assessment purposes, easy clearance indicates a lower overall cumulative toxicity. Accordingly, to investigate the clearance of tissue silver concentrations following oral silver nanoparticle exposure, Sprague–Dawley rats were assigned to 3 groups: control, low dose (100 mg/kg body weight), and high dose (500 mg/kg body weight), and exposed to two different sizes of silver nanoparticles (average diameter 10 and 25 nm) over 28 days. Thereafter, the rats were allowed to recover for 4 months. Regardless of the silver nanoparticle size, the silver content in most tissues gradually decreased during the 4-month recovery period, indicating tissue clearance of the accumulated silver. The exceptions were the silver concentrations in the brain and testes, which did not clear well, even after the 4-month recovery period, indicating an obstruction in transporting the accumulated silver out of these tissues. Therefore, the results showed that the size of the silver nanoparticles did not affect their tissue distribution. Furthermore, biological barriers, such as the blood–brain barrier and blood-testis barrier, seemed to play an important role in the silver clearance from these tissues. PMID:24059869

Efficacy of some colloidal silver preparations and silver salts against Proteus bacteria, one possible cause of rheumatoid arthritis.

PubMed

Disaanayake, D M B T; Faoagali, Joan; Laroo, Hans; Hancock, Gerald; Whitehouse, Michael

2014-04-01

There has been increased interest in the role of anti-Proteus antibodies in the aetiology of rheumatoid arthritis (RA) and whether chemotherapeutic agents active against Proteus species might reduce the risk and/or exacerbations of RA. We examined the in vitro antibacterial effects of ten different silver preparations which were either ionic silver [Ag(I)] solutions or nanoparticulate silver (NPS) (Ag(0)) suspensions against ATCC and two wild (clinical) strains of Proteus. The data establish the low minimum inhibitory concentration and minimum bactericidal concentration of all the silver formulations tested against these four Proteus strains. In a pilot study, a potent NPS preparation ex vivo showed long-lasting anti-Proteus activity in a normal human volunteer.

Antimicrobial activity of silver nanoparticles impregnated wound dressing

NASA Astrophysics Data System (ADS)

Shinde, V. V.; Jadhav, P. R.; Patil, P. S.

2013-06-01

In this work, silver nanoparticles were synthesized by simple wet chemical reduction method. The silver nitrate was reduced by Sodium borohydride used as reducing agent and Poly (vinyl pyrrolidone) (PVP) as stabilizing agent. The formation of silver nanoparticles was evaluated by UV-visible spectroscope and transmission electron microscope (TEM). Absorption spectrum consist two plasmon peaks at 410 and 668 nm revels the formation of anisotropic nanoparticles confirmed by TEM. The formation of silver nanoparticles was also evidenced by dynamic light scattering (DLS) study. DLS showed polydisperse silver nanoparticles with hydrodynamic size 32 nm. Protecting mechanism of PVP was manifested by FT-Raman study. Silver nanoparticles were impregnated into wound dressing by sonochemical method. The Kirby-Bauer disc diffusion methods were used for antimicrobial susceptibility testing. The antimicrobial activity of the samples has been tested against gram-negative bacterium Escherichia coli and gram-positive bacterium Staphylococcus aureus.

Identification of a silver binding protein associated with the cytological silver staining of actively transcribing nucleolar regions.

PubMed

Hubbell, H R; Rothblum, L I; Hsu, T C

1979-10-01

Nucleoli isolated from Novikoff hepatoma cells were stained with AgNO3 to demonstrate the typical staining of active ribosomal cistrons. Pre-treatment of the nucleoli with 80 mM Tris-HCl (pH 7.5) -- 2.0 M NaCl did not interfere with silver staining. Treatment of the nucleoli with 80 mM Tris-HCl (pH 7.5) -- 0.15 M NaCl did, however, eliminate silver binding. Serial extraction of nucleoli with 2.0 M NaCl buffer followed by 0.15 M NaCl buffer also abolished silver staining. Analysis of the supernatant fraction of these extracts by polyacrylamide gel electrophoresis indicates that, although more than one nucleolar protein can bind silver, only one protein is associated with the staining of active ribosomal cistrons.

Enhanced Ge/Si(001) island areal density and self-organization due to P predeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, B.; Bareno, J.; Petrov, I.

The predeposition of P, with coverages {theta}{sub P} ranging from 0 to 1 ML, on Si(001) significantly increases both the areal density and spatial self-organization of Ge islands grown by gas-source molecular beam epitaxy from hydride precursors. The Ge island density {rho}{sub Ge} initially increases with {theta}{sub P}, reaching a maximum of 1.4 x 10{sup 10} cm{sup -2} at {theta}{sub P} = 0.7 ML, a factor of four times higher than on bare Si(001) under the same deposition conditions, before decreasing at higher P coverages. The increase in {rho}{sub Ge}({theta}{sub P}) is due to a corresponding decrease in Ge adatommore » mean free paths resulting from passivation of surface dangling bonds by adsorbed pentavalent P atoms which, in addition, leads to surface roughening and, therefore, higher Ge coverages at constant Ge{sub 2}H{sub 6} dose. As {theta}{sub P} (and hence, {rho}{sub Ge}) increases, so does the degree of Ge island ordering along <100> directions due to the anisotropic strain field surrounding individual islands. Similar results are obtained for Ge island growth on P-doped Si(001) layers where strong P surface segregation provides partial monolayer coverage prior to Ge deposition.« less

Analyzing silver concentration in soil using laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Prasetyo, S.; Isnaeni; Zaitun; Mitchell, K.; Suliyanti, M. M.; Herbani, Y.

2018-03-01

Determination of concentration of heavy metal ions in soil, such as silver, is very important to study soil pollution levels. Several techniques have been developed to determine silver ion concentration in soil. In this paper, we utilized laser-induced breakdown spectroscopy (LIBS) to study silver concentration in soil. We used four different data analysis methods to calculate silver concentration. In this case, we prepared soil samples with different silver ion concentrations from 400 ppm to 1000 ppm. Our analysis was focused on the 843.15 nm silver atomic absorption line. We found that plasma intensity increased as silver concentration increased. Our findings were based on our analysis using four different analysis methods. We believe that these analysis methods are able to calculate silver concentration in soil using LIBS.

Silver manganese oxide electrodes for lithium batteries

DOEpatents

Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

2006-05-09

This invention relates to electrodes for non-aqueous lithium cells and batteries with silver manganese oxide positive electrodes, denoted Ag_xMnO_y, in which x and y are such that the manganese ions in the charged or partially charged electrodes cells have an average oxidation state greater than 3.5. The silver manganese oxide electrodes optionally contain silver powder and/or silver foil to assist in current collection at the electrodes and to improve the power capability of the cells or batteries. The invention relates also to a method for preparing Ag_xMnO_y electrodes by decomposition of a permanganate salt, such as AgMnO₄, or by the decomposition of KMnO₄ or LiMnO₄ in the presence of a silver salt.

Properties of thin silver films with different thickness

NASA Astrophysics Data System (ADS)

Zhao, Pei; Su, Weitao; Wang, Reng; Xu, Xiaofeng; Zhang, Fengshan

2009-01-01

In order to investigate optical properties of silver films with different film thickness, multilayer composed of thin silver film sandwiched between ZnS films are sputtered on the float glass. The crystal structures, optical and electrical properties of films are characterized by various techniques, such as X-ray diffraction (XRD), spectrum analysis, etc. The optical constants of thin silver film are calculated by fitting the transmittance ( T) and reflectance ( R) spectrum of the multilayer. Electrical and optical properties of silver films thinner than 6.2 nm exhibit sharp change. However, variation becomes slow as film thickness is larger than 6.2 nm. The experimental results indicate that 6.2 nm is the optimum thickness for properties of silver.

Corrosion protection for silver reflectors

DOEpatents

Arendt, Paul N.; Scott, Marion L.

1991-12-31

A method of protecting silver reflectors from damage caused by contact with gaseous substances which are often present in the atmosphere and a silver reflector which is so protected. The inventive method comprises at least partially coating a reflector with a metal oxide such as aluminum oxide to a thickness of 15 .ANG. or less.

Selection of diet for culture of juvenile silver pomfret, Pampus argenteus

NASA Astrophysics Data System (ADS)

Peng, Shiming; Shi, Zhaohong; Yin, Fei; Sun, Peng; Wang, Jiangang

2012-03-01

Juvenile silver pomfret, Pampus argenteus, was grown in culture tanks for 9 weeks on four different diets, and their effects on fish growth, digestive enzyme activity, and body composition were assessed. The feeding regime was as follows: Diet 1: fish meat; Diet 2: fish meat+artificial feed; Diet 3: fish meat+artificial feed+Agamaki clam meat; Diet 4: fish meat+artificial feed+Agamaki clam+copepods. The greatest weight gain was associated with Diet 4, while the lowest weight gain was associated with Diet 1. No significant difference was observed in weight gain between fish receiving Diet 2 and Diet 3. Specific growth rate followed similar trends as weight gain. The feed conversion ratio (FCR) of fish fed Diet 1 was significantly higher than the other fish groups, but no significant differences were observed in FCRs of fish fed Diet 2, Diet 3 or Diet 4. There was also no significant difference in the hepatosomatic index (HSI) between the four diets. For fish that received Diets 2-4, containing artificial feed, higher protease activities were detected. A higher lipid content of the experimental diets also significantly increased lipase activities and body lipid content. No significant differences in amylase activity or body protein content were found between Diets 1-4. In conclusion, a variety of food components, including copepods and artificial feed, in the diet of silver pomfret significantly increased digestive enzyme activity and could improve growth performance.

Durable Corrosion and Ultraviolet-Resistant Silver Mirror

DOEpatents

Jorgensen, G. J.; Gee, R.

2006-01-24

A corrosion and ultra violet-resistant silver mirror for use in solar reflectors; the silver layer having a film-forming protective polymer bonded thereto, and a protective shield overlay comprising a transparent multipolymer film that incorporates a UV absorber. The corrosion and ultraviolet resistant silver mirror retains spectral hemispherical reflectance and high optical clarity throughout the UV and visible spectrum when used in solar reflectors.

Antibacterial properties and mechanisms of gold-silver nanocages

NASA Astrophysics Data System (ADS)

Wang, Yulan; Wan, Jiangshan; Miron, Richard J.; Zhao, Yanbin; Zhang, Yufeng

2016-05-01

Despite the number of antibiotics used in routine clinical practice, bacterial infections continue to be one of the most important challenges faced in humans. The main concerns arise from the continuing emergence of antibiotic-resistant bacteria and the difficulties faced with the pharmaceutical development of new antibiotics. Thus, advancements in the avenue of novel antibacterial agents are essential. In this study, gold (Au) was combined with silver (Ag), a well-known antibacterial material, to form silver nanoparticles producing a gold-silver alloy structure with hollow interiors and porous walls (gold-silver nanocage). This novel material was promising in antibacterial applications due to its better biocompatibility than Ag nanoparticles, potential in photothermal effects and drug delivery ability. The gold-silver nanocage was then tested for its antibacterial properties and the mechanism involved leading to its antibacterial properties. This study confirms that this novel gold-silver nanocage has broad-spectrum antibacterial properties exerting its effects through the destruction of the cell membrane, production of reactive oxygen species (ROS) and induction of cell apoptosis. Therefore, we introduce a novel gold-silver nanocage that serves as a potential nanocarrier for the future delivery of antibiotics.

Synthesis of silver nanoparticles in melts of amphiphilic polyesters

NASA Astrophysics Data System (ADS)

Vasylyev, S.; Damm, C.; Segets, D.; Hanisch, M.; Taccardi, N.; Wasserscheid, P.; Peukert, W.

2013-03-01

The current work presents a one-step procedure for the synthesis of amphiphilic silver nanoparticles suitable for production of silver-filled polymeric materials. This solvent free synthesis via reduction of Tollens’ reagent as silver precursor in melts of amphiphilic polyesters consisting of hydrophilic poly(ethylene glycol) blocks and hydrophobic alkyl chains allows the production of silver nanoparticles without any by-product formation. This makes them especially interesting for the production of medical devices with antimicrobial properties. In this article the influences of the chain length of the hydrophobic block in the amphiphilic polyesters and the process temperature on the particle size distribution (PSD) and the stability of the particles against agglomeration are discussed. According to the results of spectroscopic and viscosimetric investigations the silver precursor is reduced to elemental silver nanoparticles by a single electron transfer process from the poly(ethylene glycol) chain to the silver ion.

Durable silver coating for mirrors

DOEpatents

Wolfe, Jesse D.; Thomas, Norman L.

2000-01-01

A durable multilayer mirror includes reflective layers of aluminum and silver and has high reflectance over a broad spectral range from ultraviolet to visible to infrared. An adhesion layer of a nickel and/or chromium alloy or nitride is deposited on an aluminum surface, and a thin layer of silver is then deposited on the adhesion layer. The silver layer is protected by a passivation layer of a nickel and/or chromium alloy or nitride and by one or more durability layers made of metal oxides and typically a first layer of metal nitride. The durability layers may include a composite silicon aluminum nitride and an oxinitride transition layer to improve bonding between nitride and oxide layers.

Toward Interpreting Failure in Sintered-Silver Interconnection Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wereszczak, Andrew A; Waters, Shirley B

2016-01-01

The mechanical strength and subsequent reliability of a sintered-silver interconnection system is a function of numerous independent parameters. That system is still undergoing process development. Most of those parameters (e.g., choice of plating) are arguably and unfortunately taken for granted and are independent of the silver s cohesive strength. To explore such effects, shear strength testing and failure analyses were completed on a simple, mock sintered-silver interconnection system consisting of bonding two DBC ceramic substrates. Silver and gold platings were part of the test matrix, as was pre-drying strategies, and the consideration of stencil-printing vs. screen-printing. Shear strength of sintered-silvermore » interconnect systems was found to be was insensitive to the choice of plating, drying practice, and printing method provided careful and consistent processing of the sintered-silver are practiced. But if the service stress in sintered silver interconnect systems is anticipated to exceed ~ 60 MPa, then the system will likely fail.« less

The Effect of Silver Chloride Formation on the Kinetics of Silver Dissolution in Chloride Solution

PubMed Central

Ha, Hung; Payer, Joe

2011-01-01

The precipitation and growth of AgCl on silver in physiological NaCl solution were investigated. AgCl was found to form at bottom of scratches on the surface which may be the less effective sites for diffusion or the favorable sites for heterogeneous nucleation. Patches of silver chloride expanded laterally on the substrate until a continuous film formed. The ionic transport path through this newly formed continuous film was via spaces between AgCl patches. As the film grew, the spaces between AgCl patches closed and ion transport was primarily via micro-channels running through AgCl patches. The decrease of AgCl layer conductivity during film growth were attributed to the clogging of micro-channels or decrease in charge carrier concentration inside the micro-channels. Under thin AgCl layer, i.e. on the order of a micrometer, the dissolution of silver substrate was under mixed activation-Ohmic control. Under thick AgCl layer, i.e. on the order of tens of micrometers, the dissolution of silver substrate was mediated by the Ohmic resistance of AgCl layer. PMID:21516171

Development and Optimization of Silver Nanoparticle Formulation for Fabrication

DTIC Science & Technology

2015-08-14

Development and Optimization of Silver Nanoparticle Formulation for Fabrication Publication Type: DJournal/ Paper D Book Chapter ~ Tech Report D...leofPublicationorPresentation: Deve l opment and Optimization of Silver Nanoparticle Formulation for Fabrication 3. Author(s): (List authors starting...fabrication process of silver nanoparticl es could improve future silver containing products , which is i mpor tant to l owering toxicity and improving

21 CFR 524.802 - Enrofloxacin, silver sulfadiazine emulsion.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Enrofloxacin, silver sulfadiazine emulsion. 524... ANIMAL DRUGS § 524.802 Enrofloxacin, silver sulfadiazine emulsion. (a) Specifications. Each milliliter contains 5 milligrams (mg) enrofloxacin and 10 mg silver sulfadiazine. (b) Sponsor. See No. 000859 in § 510...

Preparation and characterization of silver nanoparticles homogenous thin films

NASA Astrophysics Data System (ADS)

Hegazy, Maroof A.; Borham, E.

2018-06-01

The wet chemical method by metal salt reduction has been widely used to synthesize nanoparticles. Accordingly the silver nitrate used as silver precursor and sodium borohydrate as reduction agent. The silver nanoparticles were characterized by different characterization techniques including UV-VIS spectrometry, Transmission electron microscope (TEM), and Zeta potential technique. Thin films of the colloidal solution were fabricated using direct precipitation technique on ITO glass, silicon substrate and commercial glass substrate and characterized by imaging technique. The absorption peak of the silver nanoparticles colloidal solution was around 400 nm. The TEM images indicate that the silver nanoparticles had spherical shape and their sizes were from 10 to 17 nm. The particle size of the silver nanoparticles was confirmed by Zeta potential technique. The imaging technique indicated that the homogeneous distribution of the colloidal silver solution thin film on the silicon substrate was stronger than the ITO glass and inhomogeneous film was emerged on the commercial glass.

Biomimetics of silver nanoparticles by white rot fungus, Phaenerochaete chrysosporium.

PubMed

Vigneshwaran, Nadanathangam; Kathe, Arati A; Varadarajan, P V; Nachane, Rajan P; Balasubramanya, R H

2006-11-01

Extracellular synthesis of silver nanoparticles by a white rot fungus, Phaenerochaete chrysosporium is reported in this paper. Incubation of P. chrysosporium mycelium with silver nitrate solution produced silver nanoparticles in 24h. These silver nanoparticles were characterized by means of UV-vis spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The synthesized silver nanoparticles absorbed maximum at 470 nm in the visible region. XRD spectrum of the silver nanoparticles confirmed the formation of metallic silver. The SEM characterization of the fungus reacted on the Ag+ indicated that the protein might be responsible for the stabilization of silver nanoparticles. This result was further supported by the TEM examination. Though shape variation was noticed, majority of the nanoparticles were found to be of pyramidal shape as seen under TEM. Photoluminescence spectrum showed a broad emission peak of silver nanoparticles at 423 nm when excited at 350 nm. Apart from eco-friendliness, fungus as bio-manufacturing unit will give us an added advantage in ease of handling when compared to other classes of microorganisms.

Dermal exposure potential from textiles that contain silver nanoparticles

PubMed Central

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Abbas Virji, M

2014-01-01

Background: Factors that influence exposure to silver particles from the use of textiles are not well understood. Objectives: The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Methods: Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Results: Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated “use” and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0.51±0.04%) than the masterbatch process textile (0.21±0.01%); P<0.01. Conclusions: We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva. PMID:25000110

Dermal exposure potential from textiles that contain silver nanoparticles.

PubMed

Stefaniak, Aleksandr B; Duling, Mathew G; Lawrence, Robert B; Thomas, Treye A; LeBouf, Ryan F; Wade, Eleanor E; Virji, M Abbas

2014-01-01

Factors that influence exposure to silver particles from the use of textiles are not well understood. The aim of this study was to evaluate the influence of product treatment and physiological factors on silver release from two textiles. Atomic and absorbance spectroscopy, electron microscopy, and dynamic light scattering (DLS) were applied to characterize the chemical and physical properties of the textiles and evaluate silver release in artificial sweat and saliva under varying physiological conditions. One textile had silver incorporated into fiber threads (masterbatch process) and the other had silver nanoparticles coated on fiber surfaces (finishing process). Several complementary and confirmatory analytical techniques (spectroscopy, microscopy, etc.) were required to properly assess silver release. Silver released into artificial sweat or saliva was primarily in ionic form. In a simulated "use" and laundering experiment, the total cumulative amount of silver ion released was greater for the finishing process textile (0·51±0·04%) than the masterbatch process textile (0·21±0·01%); P<0·01. We found that the process (masterbatch vs finishing) used to treat textile fibers was a more influential exposure factor than physiological properties of artificial sweat or saliva.

Green synthesis of silver nanoparticles using tannins

NASA Astrophysics Data System (ADS)

Raja, Pandian Bothi; Rahim, Afidah Abdul; Qureshi, Ahmad Kaleem; Awang, Khalijah

2014-09-01

Colloidal silver nanoparticles were prepared by rapid green synthesis using different tannin sources as reducing agent viz. chestnut (CN), mangrove (MG) and quebracho (QB). The aqueous silver ions when exposed to CN, MG and QB tannins were reduced which resulted in formation of silver nanoparticles. The resultant silver nanoparticles were characterized using UV-Visible, X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and transmission electron microscopy (TEM) techniques. Furthermore, the possible mechanism of nanoparticles synthesis was also derived using FT-IR analysis. Spectroscopy analysis revealed that the synthesized nanoparticles were within 30 to 75 nm in size, while XRD results showed that nanoparticles formed were crystalline with face centered cubic geometry.

Synthesis and applications of novel silver nanoparticle structures

NASA Astrophysics Data System (ADS)

Dukes, Kyle

The field of nanotechnology is rapidly expanding across disciplines as each new development is realized. New exciting technologies are being driven by advances in the application of nanotechnology; including biochemical, optical, and semiconductors research. This thesis will focus on the use of silver nanoparticles as optical labels on cells, methods of forming different small structures of silver nanoparticles, as well as the use of silver nanoparticles in the development of a photovoltaic cell. Silver nanoparticles have been modified with self-assembled monolayers of hydroxyl-terminated long chain thiols and encapsulated with a silica shell. The resulting core-shell nanoparticles were used as optical labels for cell analysis using flow cytometry and microscopy. The excitation of plasmon resonances in nanoparticles results in strong depolarized scattering of visible light permitting detection at the single nanoparticle level. The nanoparticles were modified with neutravidin via epoxide-azide coupling chemistry and biotinylated antibodies targeting cell surface receptors were bound to the nanoparticle surface. The nanoparticle labels exhibited long-term stability under physiological conditions without aggregation or silver ion leaching. Labeled cells exhibited two orders of magnitude enhancement of the scattering intensity compared to unlabeled cells. Dimers of silver nanoparticles have been fabricated by first immobilizing a monolayer of single silver nanoparticles onto poly(4-vinylpyridine) covered glass slides. The monolayer was then exposed to adenine, which has two amines which will bind to silver. The nanoparticle monolayer, now modified with adenine, is exposed to a second suspension of nanoparticles which will bind with the amine modified monolayer. Finally, a thin silica shell is formed about the structure via solgel chemistry to prevent dissolution or aggregation upon sonication/striping. Circular arrays of silver nanoparticels are developed using a

Sintered silver joints via controlled topography of electronic packaging subcomponents

DOEpatents

Wereszczak, Andrew A.

2014-09-02

Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

PREDICTING THE TOXICITY OF SEDIMENTS SPIKED WITH SILVER

EPA Science Inventory

Previous experiments conducted with freshwater sediments spiked with silver have shown that, when expressed on a dry weight basis, the toxicity of silver is sediment-specific and dependent on the form of silver added (e.g., AgNO3, Ag2S). This study was conducted to assess the use...

Silver Ion Biocide Delivery System for Water Disinfection

NASA Technical Reports Server (NTRS)

Slote, Benjamin M.; Salley, Edward; Carr, Daniel; Kimble, Michael C.; Adam, Niklas

2016-01-01

U.S. space exploration missions have long considered returning to the Moon and exploration of Mars that challenge life support systems. For these long duration missions, there is interest in replacing the iodine water treatment system with ionic silver, a proven biocide. For long duration exploration missions, it is imperative that an effective biocide be used that prevents microbial growth, biofilm formation, and microbially induced corrosion in the water storage and distribution systems while minimizing logistical supply requirements associated with the biocide delivery system. Two biocide delivery systems have been developed that electrochemically produce silver ions for disinfecting water throughout the water storage and distribution system. One system uses a newly developed hybrid micro-filtration and ion-exchange membrane to produce an abundance of silver ions at the 1000 ppb level upstream in the water distribution system to prevent biofilm growth. This is followed by a downstream collection module that electrochemically removes these silver ions before the water is discharged. Another approach uses a membraneless reactor to produce a 1000 ppb silver ion concentration level that also has a mechanically driven electrode cleaning mechanism that removes oxide films ensuring long life operation. By maintaining a sufficiently high level of silver ions throughout the water storage and distribution system, biofilm formation is suppressed. This approach overcomes present concerns where spurious silver deposition occurs on the container and flow line surfaces thus lowering the silver ion concentration to unsatisfactory disinfection levels.

A silver ion water sterilization system

NASA Technical Reports Server (NTRS)

Parry, E. P.

1971-01-01

Small amounts of silver are incorporated in mixture of ion exchange resins, and water passing through this mixture is thus exposed to silver ion concentration. System is useful in self-contained water systems except city water systems where residual chlorine level is stipulated.

Silver Nanoparticle Storage Stability in Aqueous and Biological Media

DTIC Science & Technology

2015-06-22

silver nanoparticle stability from the point of synthesis to the point of testing. The recommended conditions of water storage at 4°C protected from... silver nanoparticle formulation for fabrication. (Report No. 2014-73). 13 Métraux, G. S. & Mirkin, C. A. Rapid thermal synthesis of silver ...NAVAL MEDICAL RESEARCH UNIT SAN ANTONIO SILVER NANOPARTICLE STORAGE STABILITY IN AQUEOUS AND BIOLOGICAL MEDIA NATALIE A

Acoustical deterrence of Silver Carp (Hypophthalmichthys molitrix)

USGS Publications Warehouse

Brooke J. Vetter,; Cupp, Aaron R.; Fredricks, Kim T.; Gaikowski, Mark P.; Allen F. Mensinger,

2015-01-01

The invasive Silver Carp (Hypophthalmichthys molitrix) dominate large regions of the Mississippi River drainage and continue to expand their range northward threatening the Laurentian Great Lakes. This study found that complex broadband sound (0–10 kHz) is effective in altering the behavior of Silver Carp with implications for deterrent barriers or potential control measures (e.g., herding fish into nets). The phonotaxic response of Silver Carp was investigated using controlled experiments in outdoor concrete ponds (10 × 4.9 × 1.2 m). Pure tones (500–2000 Hz) and complex sound (underwater field recordings of outboard motors) were broadcast using underwater speakers. Silver Carp always reacted to the complex sounds by exhibiting negative phonotaxis to the sound source and by alternating speaker location, Silver Carp could be directed consistently, up to 37 consecutive times, to opposite ends of the large outdoor pond. However, fish habituated quickly to pure tones, reacting to only approximately 5 % of these presentations and never showed more than two consecutive responses. Previous studies have demonstrated the success of sound barriers in preventing Silver Carp movement using pure tones and this research suggests that a complex sound stimulus would be an even more effective deterrent.

Giant spin Hall effect in graphene grown by chemical vapour deposition

NASA Astrophysics Data System (ADS)

Balakrishnan, Jayakumar; Koon, Gavin Kok Wai; Avsar, Ahmet; Ho, Yuda; Lee, Jong Hak; Jaiswal, Manu; Baeck, Seung-Jae; Ahn, Jong-Hyun; Ferreira, Aires; Cazalilla, Miguel A.; Neto, Antonio H. Castro; Özyilmaz, Barbaros

2014-09-01

Advances in large-area graphene synthesis via chemical vapour deposition on metals like copper were instrumental in the demonstration of graphene-based novel, wafer-scale electronic circuits and proof-of-concept applications such as flexible touch panels. Here, we show that graphene grown by chemical vapour deposition on copper is equally promising for spintronics applications. In contrast to natural graphene, our experiments demonstrate that chemically synthesized graphene has a strong spin-orbit coupling as high as 20 meV giving rise to a giant spin Hall effect. The exceptionally large spin Hall angle ~0.2 provides an important step towards graphene-based spintronics devices within existing complementary metal-oxide-semiconductor technology. Our microscopic model shows that unavoidable residual copper adatom clusters act as local spin-orbit scatterers and, in the resonant scattering limit, induce transverse spin currents with enhanced skew-scattering contribution. Our findings are confirmed independently by introducing metallic adatoms-copper, silver and gold on exfoliated graphene samples.

Paper-based piezoelectric touch pads with hydrothermally grown zinc oxide nanowires.

PubMed

Li, Xiao; Wang, Yu-Hsuan; Zhao, Chen; Liu, Xinyu

2014-12-24

This paper describes a new type of paper-based piezoelectric touch pad integrating zinc oxide nanowires (ZnO NWs), which can serve as user interfaces in paper-based electronics. The sensing functionality of these touch pads is enabled by the piezoelectric property of ZnO NWs grown on paper using a simple, cost-efficient hydrothermal method. A piece of ZnO-NW paper with two screen-printed silver electrodes forms a touch button, and touch-induced electric charges from the button are converted into a voltage output using a charge amplifier circuit. A touch pad consisting of an array of buttons can be readily integrated into paper-based electronic devices, allowing user input of information for various purposes such as programming, identification checking, and gaming. This novel design features ease of fabrication, low cost, ultrathin structure, and good compatibility with techniques in printed electronics, and further enriches the available technologies of paper-based electronics.

Quantitatively in Situ Imaging Silver Nanowire Hollowing Kinetics

DOE PAGES

Yu, Le; Yan, Zhongying; Cai, Zhonghou; ...

2016-09-28

We report the in-situ investigation of the morphological evolution of silver nanowires to hollow silver oxide nanotubes using transmission x-ray microscopy (TXM). Complex silver diffusion kinetics and hollowing process via the Kirkendall effect have been captured in real time. Further quantitative x-ray absorption analysis reveals the difference between the longitudinal and radial diffusions. In conclusion, the diffusion coefficient of silver in its oxide nanoshell is, for the first time, calculated to be 1.2 × 10 -13 cm 2/s from the geometrical parameters extracted from the TXM images.

Crystal structure and optical properties of silver nanorings

NASA Astrophysics Data System (ADS)

Zhou, Li; Fu, Xiao-Feng; Yu, Liao; Zhang, Xian; Yu, Xue-Feng; Hao, Zhong-Hua

2009-04-01

We report the polyol synthesis and crystal structure characterization of silver nanorings, which have perfect circular shape, smooth surface, and elliptical wire cross-section. The characterization results show that the silver nanorings have well-defined crystal of singly twinned along the whole ring. The spatial distribution of the scattering of a silver nanoring with slanted incidence reveals the unique focus effect of the nanoring, and the focus scattering varies with the incident wavelength. The silver nanorings with perfect geometry and well-defined crystal have potential applications in nanoscaled photonics, plasmonic devices, and optical manipulation.

Geology of the Barite Hill gold-silver deposit in the southern Carolina slate belt

USGS Publications Warehouse

Clark, S.H.B.; Gray, K.J.; Back, J.M.

1999-01-01

Barite Hill is a stratiform gold-silver deposit associated with base metal sulfides and barite in greenschist facies rocks. The deposit, southernmost of four recently mined gold deposits in the Carolina slate belt, is located in the Lincolnton-McCormick district of Georgia and South Carolina, which includes several known gold-silver and base metal deposits in a Kuroko-type geological setting along with deposits of kyanite and manganese. Approximately 1,835,000 g of gold was produced mainly from oxidized ores in the Main and Rainsford pits from 1990 until their closing in 1994. Ore is hosted by sericitically altered felsic metavolcanic and metasedimentary rocks of the Late Proterozoic Persimmon Fork Formation. The deposit is stratigraphically below an overturned contact between upper and lower pyroclastic units, which overlie the Lincolnton metarhyolite, an intrusive unit. Gold-silver-rich zones in the Main pit are partly coincident with lenses of siliceous barite rock, but not confined to them, and occur more commonly in pyrite-quartz-altered fragmental rock. The Main pit ore is stratigraphically overlain by a zone of base metal and barite enrichment, which is, in turn, overlain by a talc-tremolite alteration zone locally. Siliceous barite zones are absent in the Rainsford pit, and gold-silver minerals are associated with silicified rocks and chert. The Barite Hill deposit is interpreted to be the result of Kuroko-type, volcanogenic, base metal sulfide mineralization, followed by gold-silver mineralization under epithermal conditions with the following stages of evolution: (1) massive sulfides, barite, and fine-grained siliceous exhalites were deposited during Late Proterozoic to Cambrian submarine volcanism, which was related to plate convergence and subduction in a microcontinental or island-arc setting distant from the North American continental plate; (2) Au-Ag-Te and base and precious metal Te-Se-Bi minerals were deposited either during waning stages of

Precise micropatterning of silver nanoparticles on plastic substrates

NASA Astrophysics Data System (ADS)

Ammosova, Lena; Jiang, Yu; Suvanto, Mika; Pakkanen, Tapani A.

2017-04-01

Conventional fabrication methods to obtain metal patterns on polymer substrates are restricted by high operating temperature and complex preparation steps. The present study demonstrates a simple yet versatile method for preparation of silver nanoparticle micropatterns on polymer substrates with various surface geometry. With the microworking robot technique, we were able not only to directly structure the surface, but also precisely deposit silver nanoparticle ink on the desired surface location with the minimum usage of ink material. The prepared silver nanoparticle ink, containing silver cations and polyethylene glycol (PEG) as a reducing agent, yields silver nanoparticle micropatterns on plastic substrates at low sintering temperature without any contamination. The influence of the ink behaviour was studied, such as substrate wettability, ink volume, and sintering temperature. The ultraviolet visible (UV-vis), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) measurements revealed the formation of micropatterns with uniformly distributed silver nanoparticles. The prepared patterns are expected to have a broad range of applications in optics, medicine, and sensor devices owing to the unique properties of silver. Furthermore, the deposition of a chemical compound, which is different from the substrate material, not only adds a fourth dimension to the prestructured three-dimensional (3D) surfaces, but also opens new application areas to the conventional surface structures.

Non-Arrhenius temperature dependence of the island density of one-dimensional Al chains on Si(100): A kinetic Monte Carlo study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albia, Jason R.; Albao, Marvin A., E-mail: maalbao@uplb.edu.ph

Classical nucleation theory predicts that the evolution of mean island density with temperature during growth in one-dimensional systems obeys the Arrhenius relation. In this study, kinetic Monte Carlo simulations of a suitable atomistic lattice-gas model were performed to investigate the experimentally observed non-Arrhenius scaling behavior of island density in the case of one-dimensional Al islands grown on Si(100). Previously, it was proposed that adatom desorption resulted in a transition temperature signaling the departure from classical predictions. Here, the authors demonstrate that desorption above the transition temperature is not possible. Instead, the authors posit that the existence of a transition temperaturemore » is due to a combination of factors such as reversibility of island growth, presence of C-defects, adatom diffusion rates, as well as detachment rates at island ends. In addition, the authors show that the anomalous non-Arrhenius behavior vanishes when adatom binds irreversibly with C-defects as observed in In on Si(100) studies.« less

Synthesis and optical properties of silver nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Jaiveer; Kaurav, Netram, E-mail: netramkaurav@yahoo.co.uk; Choudhary, K. K.

The preparation of stable, uniform silver nanoparticles by reduction of silver acetate by ethylene glycol (EG) is reported in the present paper. It is a simple process of recent interest for obtaining silver nanoparticles. The samples were characterized by X-Ray diffraction (XRD), which reveals an average particle size (D) of 38 nm. The UV/Vis spectra show that an absorption peak, occurring due to surface plasmon resonance (SPR), exists at 319 nm.

Hydrophobicity of silver surfaces with microparticle geometry

NASA Astrophysics Data System (ADS)

Macko, Ján; Oriňaková, Renáta; Oriňak, Andrej; Kovaľ, Karol; Kupková, Miriam; Erdélyi, Branislav; Kostecká, Zuzana; Smith, Roger M.

2016-11-01

The effect of the duration of the current deposition cycle and the number of current pulses on the geometry of silver microstructured surfaces and on the free surface energy, polarizability, hydrophobicity and thus adhesion force of the silver surfaces has been investigated. The changes in surface hydrophobicity were entirely dependent on the size and density of the microparticles on the surface. The results showed that formation of the silver microparticles was related to number of current pulses, while the duration of one current pulse played only a minor effect on the final surface microparticle geometry and thus on the surface tension and hydrophobicity. The conventional geometry of the silver particles has been transformed to the fractal dimension D. The surface hydrophobicity depended predominantly on the length of the dendrites not on their width. The highest silver surface hydrophobicity was observed on a surface prepared by 30 current pulses with a pulse duration of 1 s, the lowest one when deposition was performed by 10 current pulses with a duration of 0.1 s. The partial surface tension coefficients γDS and polarizability kS of the silver surfaces were calculated. Both parameters can be applied in future applications in living cells adhesion prediction and spectral method selection. Silver films with microparticle geometry showed a lower variability in final surface hydrophobicity when compared to nanostructured surfaces. The comparisons could be used to modify surfaces and to modulate human cells and bacterial adhesion on body implants, surgery instruments and clean surfaces.

Factors influencing the preparation of silver-coated glass frit with polyvinyl-pyrrolidone

NASA Astrophysics Data System (ADS)

Xiang, Feng; Gan, Weiping

2018-01-01

In this work, a new electroless silver plating method for the synthesis of silver-coated glass frit composite powders with good morphology has been proposed and the polyvinyl-pyrrolidone (PVP) was used the activating agent. It was found that the weight ratio of PVP to glass frit affected the distribution and number of silver nanoparticles. Moreover, the loading capacity of the glass frit, the pH value and reaction temperature could influence the size of the silver nanoparticles and morphology of silver on the surface of glass frit. The as-prepared silver-coated glass frit was used to prepare a silver paste using an optimized process to form silver nanoparticles with uniform size and high density. The silver paste with silver-coated glass frit increased the photovoltaic conversion efficiency of silicon solar cells by 0.271% compared with the silver paste prepared with pure glass frit. The silver nanoparticles can promoted the precipitation of Ag crystallites on the silicon wafer. Therefore, the silver-coated glass frit can further optimize and enhance the electrical performance of solar cells.

Bactericidal properties of silver films on intramedullary implants

NASA Astrophysics Data System (ADS)

Gallagher, C.; Walker, C.; Cortes, E.; Hettinger, Jeffrey; Krchnavek, R.; Caputo, G. A.; Ostrum, R.

2011-03-01

We report on investigations of silver films on titanium and stainless steel substrates as anti-bacterial coatings for intramedullary nails used in orthopedic trauma. Silver films are deposited using a magnetron sputtering technique from a single elemental target. The deposition parameter (energy, pressure, and temperature) dependence of the silver film microstructure and adhesion will be presented. Preliminary measurements of the effectiveness of the silver films as a bactericide on S. aureus bacteria demonstrate that the films are effective destroying the bacteria. The process of this investigation will be presented. Preliminary transmission electron microscopy measurements will also presented which image healthy and damaged bacteria helping to identify the fundamental mechanism leading to the effectiveness of silver as an anti-bacterial coating. We acknowledge the support of Rowan University, College of Liberal Arts and Sciences.

Utilization of hydroxypropyl carboxymethyl cellulose in synthesis of silver nanoparticles.

PubMed

Abdel-Halim, E S; Alanazi, Humaid H; Al-Deyab, Salem S

2015-04-01

Hydroxypropyl carboxymethyl cellulose samples having varying degrees of substitution and varying degrees of polymerization were used to reduce silver nitrate to silver nanoparticles. UV spectral analysis of silver nanoparticles colloidal solution reveal that increasing the pH of the reduction solution leads to improvement in the intensity of the absorption band for silver nanoparticles, to be maximum at pH 11. The absorption peak intensity also enhanced upon prolonging the reaction duration up to 60 min. The conversion of silver ions to metallic silver nanoparticles was found to be temperature-dependent and maximum transformation occurs at 60 °C. The reduction efficiency of hydroxypropyl carboxymethyl cellulose was found to be affected by its degree of polymerization. Colloidal solutions of silver nanoparticles having concentration up to 1000 ppm can be prepared upon fixing the ratio between silver nitrate and hydroxypropyl carboxymethyl cellulose at 0.017-0.3g per each 100ml of the reduction solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparative toxicity of silver nanoparticles and silver ions to Escherichia coli.

PubMed

Choi, Yoojin; Kim, Hyun-A; Kim, Kyoung-Woong; Lee, Byung-Tae

2018-04-01

With the increase in silver (Ag)-based products in our lives, it is essential to test the potential toxicity of silver nanoparticles (AgNPs) and silver ions (Ag ions) on living organisms under various conditions. Here, we investigated the toxicity of AgNPs with Ag ions to Escherichia coli K-12 strain under various conditions. We observed that both AgNPs and Ag ions display antibacterial activities, and that Ag ions had higher toxicity to E. coli K-12 strain than AgNPs under the same concentrations. To understand the toxicity of AgNPs at a cellular level, reactive oxygen species (ROS) enzymes were detected for use as antioxidant enzymatic biomarkers. We have also studied the toxicity of AgNPs and Ag ions under various coexistence conditions including: fixed total concentration, with a varied the ratio of AgNPs to Ag ions; fixed the AgNPs concentration and then increased the Ag ions concentration; fixed Ag ions concentration and then increasing the AgNPs concentration. Exposure to AgNPs and Ag ions clearly had synergistic toxicity; however, decreased toxicity (for a fixed AgNPs concentration of 5mg/L, after increasing the Ag ions concentration) to E. coli K-12 strain. AgNPs and Ag ions in the presence of L-cysteine accelerated the bacterial cell growth rate, thereby reducing the bioavailability of Ag ions released from AgNPs under the single and coexistence conditions. Further works are needed to consider this potential for AgNPs and Ag ions toxicity across a range of environmental conditions. As silver nanoparticles (AgNPs)-based products are being broadly used in commercial industries, an ecotoxicological understanding of the AgNPs being released into the environment should be further considered. Here, we investigate the comparative toxicity of AgNPs and silver ions (Ag ions) to Escherichia coli K-12 strain, a representative ecotoxicological bioreporter. This study showed that toxicities of AgNPs and Ag ions to E. coli K-12 strain display different relationships

Silver-silver sulfate reference electrodes for use in lead-acid batteries

NASA Astrophysics Data System (ADS)

Ruetschi, Paul

Electrochemical properties of silver-silver sulfate reference electrodes for lead-acid batteries are described, and the following possible applications discussed: Determination of individual capacities of positive and negative plates. Monitoring individual electrode behavior during deep discharge and cell reversal. Optimization charge or discharge parameters, by controlling the current such that pre-determined limits of positive or negative half-cell potential are respected. Observation of acid concentration differences, for example due to acid stratification, by measuring diffusion potentials (concentration-cell voltages). Detection of defective cells, and defective plate sets, in a string of cells, at the end of their service life. Silver-silver sulfate reference electrodes, permanently installed in lead-acid cells, may be a means to improve battery management, and therewith to improve reliability and service life. In vented batteries, reference electrodes may be used to limit positive plate polarization during charge, or float-charge. Limiting the positive half-cell potential to an upper, pre-set value would permit to keep anodic corrosion as low as possible. During cycling, discharge could be terminated when the half-cell potential of the positive electrode has dropped to a pre-set limit. This would prevent excessive discharge of the positive electrodes, which could result in an improvement of cycle life. In valve-regulated batteries, reference electrodes may be used to adjust float-charge conditions such as to assure sufficient cathodic polarization of the negative electrodes, in order to avoid sulfation. The use of such reference electrodes could be beneficial particularly in multi-cell batteries, with overall voltages above 12 V, operated in a partial-state-of-charge.

Rate Dependency of Silver Vanadium Phosphorous Oxide Reduction

NASA Astrophysics Data System (ADS)

Cheng, Po-Jen

2011-12-01

The silver vanadium phosphorus oxide (Ag2VO2PO 4) is a high-capacity and good-compatibility material for the cathode in the battery. Due to their innovative properties, they are used as cathode in lithium batteries. Therefore, when the lithium batteries begin to discharge, the anodes of the cell perform an electrochemical oxidation and release electrons. In the mean time, the cathodes in the cells perform the electrochemical reduction and catch the electrons. For reduction of Ag2VO2PO 4, two silver ions (Ag+) catch two electrons to form silver particles, and the vanadium ions (V5+) catch two electrons to form V3+. It means that four electrons will be released by lithium anode. We call this four electrons discharge as 100% discharge. In my most of the projects, the Ag2VO2PO4 material is tested by differential scanning calorimetry (DSC) to check purity. My study is based on the discharge of batteries, and I focus on the morphology and the intensity of silver particles on the cathode after discharge. Depending on different adjustment of factors, such as discharge time, discharge rate, storage time, storage temperature, I try to investigate the silver intensity, conductivity as a function of DOD (Depth of Discharge). The silver particles could be examined by optical microscope, and scanning electron microscope (SEM). Moreover, I do some x-ray diffraction analysis to quantify the silver particles after discharge. Also, I perform magnetic susceptibility measurement to check the mechanism of the reduction of vanadium ions. Under the research on silver ions and vanadium ions, I will know a big frame of reduction process on silver vanadium phosphorous oxide and the time effect on this cathode material.

Antibacterial effect of gallium and silver on Pseudomonas aeruginosa treated with gallium-silver-phosphate-based glasses.

PubMed

Valappil, Sabeel P; Higham, Susan M

2014-01-01

Gallium and silver incorporated phosphate-based glasses were evaluated for antibacterial effect on the growth of Pseudomonas aeruginosa, which is a leading cause of opportunistic infections. The glasses were produced by conventional melt quenching methods at 1100°C for 1 h. Glass degradation studies were conducted by weight loss method. Disc diffusion assay and cell viability assay displayed statistically significant (p ≤ 0.0005) effect on P. aeruginosa growth which increased with decreasing calcium content in the glasses. The gallium ion release rates (1.83, 0.69 and 0.48 ppm·h(-1)) and silver ion release rates (2.97, 2.84 and 2.47 ppm·h(-1)) were found to account for this variation. Constant depth film fermentor was used to evaluate the anti-biofilm properties of the glasses. Both gallium and silver in the glass contributed to biofilm growth inhibitory effect on P. aeruginosa (up to 2.68 reduction in log 10 values of the viable counts compared with controls). The glasses were found to deliver gallium and silver in a controlled way and exerted cumulative antibacterial action on planktonic and biofilm growth of P. aeruginosa. The antibacterial, especially anti-biofilm, properties of the gallium and silver incorporated phosphate-based glasses make them a potential candidate to combat infections caused by P. aeruginosa.

Capsaicin-capped silver nanoparticles: its kinetics, characterization and biocompatibility assay

NASA Astrophysics Data System (ADS)

Amruthraj, Nagoth Joseph; Preetam Raj, John Poonga; Lebel, Antoine

2015-04-01

Capsaicin was used as a bio-reductant for the reduction of silver nitrate to form silver nanoparticles. The formation of the silver nanoparticles was initially confirmed by color change and Tyndall effect of light scattering. It was characterized with UV-visible spectroscopy, FTIR and TEM. Hemagglutination (H) test and H-inhibition assay were performed in the presence of AgNPs-capsaicin conjugates. The silver colloid solution after complete reduction turned into pale gray color. The characteristic surface plasmon resonance of silver nanoparticles (SNPs) was observed at 450 nm. Time taken for complete bio-reduction of silver nitrate and capping was found to be 16 hours. The amount of capsaicin required to reduce 20 ml of 1 mM silver nitrate solution was found to be 40 μg approximately. The FTIR results confirmed the capping of capsaicin on the silver metal. The particle size was within the range of 20-30 nm. The hemagglutination and H-inhibition test was negative for all the blood groups. The capsaicin-capped silver nanoparticles were compatible with blood cells in hemagglutination test implying biocompatibility as future therapeutic drug.

The sorption of silver by poorly crystallized manganese oxides

USGS Publications Warehouse

Anderson, B.J.; Jenne, E.A.; Chao, T.T.

1973-01-01

The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

Recovery of Silver and Gold from Copper Anode Slimes

NASA Astrophysics Data System (ADS)

Chen, Ailiang; Peng, Zhiwei; Hwang, Jiann-Yang; Ma, Yutian; Liu, Xuheng; Chen, Xingyu

2015-02-01

Copper anode slimes, produced from copper electrolytic refining, are important industrial by-products containing several valuable metals, particularly silver and gold. This article provides a comprehensive overview of the development of the extraction processes for recovering silver and gold from conventional copper anode slimes. Existing processes, namely pyrometallurgical processes, hydrometallurgical processes, and hybrid processes involving the combination of pyrometallurgical and hydrometallurgical technologies, are discussed based in part on a review of the form and characteristics of silver and gold in copper anode slimes. The recovery of silver and gold in pyrometallurgical processes is influenced in part by the slag and matte/metal chemistry and related characteristics, whereas the extraction of these metals in hydrometallurgical processes depends on the leaching reagents used to break the structure of the silver- and gold-bearing phases, such as selenides. By taking advantage of both pyrometallurgical and hydrometallurgical techniques, high extraction yields of silver and gold can be obtained using such combined approaches that appear promising for efficient extraction of silver and gold from copper anode slimes.

Silver nanoparticles-coated glass frits for silicon solar cells

NASA Astrophysics Data System (ADS)

Li, Yingfen; Gan, Weiping; Li, Biyuan

2016-04-01

Silver nanoparticles-coated glass frit composite powders for silicon solar cells were prepared by electroless plating. Silver colloids were used as the activating agent of glass frits. The products were characterized by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry. The characterization results indicated that silver nanoparticles with the melting temperature of 838 °C were uniformly deposited on glass frit surface. The particle size of silver nanoparticles could be controlled by adjusting the [Ag(NH3)2]NO3 concentration. The as-prepared composite powders were applied in the front side metallization of silicon solar cells. Compared with those based on pure glass frits, the solar cells containing the composite powders had the denser silver electrodes and the better silver-silicon ohmic contacts. Furthermore, the photovoltaic performances of solar cells were improved after the electroless plating.

Silver nasal sprays: misleading Internet marketing.

PubMed

Gaslin, Michael T; Rubin, Cory; Pribitkin, Edmund A

2008-04-01

Long-term use of silver-containing products is associated with a permanent bluish-gray discoloration of the skin known as argyria, but they remain widely available despite several measures by the FDA to regulate them. Several recent case reports have described the occurrence of argyria as a result of using these "natural" products. We used the five most common Internet search engines to find Web sites providing information on silver-containing nasal sprays. Of 49 Web sites analyzed, only 2 (4%) mentioned argyria as a possible complication, although 30 (61%) did caution against long-term use. Eight sites (16%) made specific claims about the health benefits of the product. All 49 sites (100%) provided direct or indirect links to buy silver-containing nasal sprays. We conclude that information about silver-containing nasal sprays on the Internet is misleading and inaccurate. Therefore, otolaryngologists should be aware of the misinformation their patients may be receiving about these products.

Antimicrobial silver: An unprecedented anion effect

PubMed Central

Swathy, J. R.; Sankar, M. Udhaya; Chaudhary, Amrita; Aigal, Sahaja; Anshup; Pradeep, T.

2014-01-01

Silver is an indispensable metal but its use has to be minimised for sustainable growth. Much of the silver lost during use is unrecoverable; an example being its use as an antimicrobial agent, a property known since ages. While developing methods to create an affordable drinking water purifier especially for the developing world, we discovered that 50 parts per billion (ppb) of Ag+ released continuously from silver nanoparticles confined in nanoscale cages is enough to cause antimicrobial activity in conditions of normal water. Here we show that the antibacterial and antiviral activities of Ag+ can be enhanced ~1,000 fold, selectively, in presence of carbonate ions whose concentration was maintained below the drinking water norms. The protective layers of the organisms were affected during the carbonate-assisted antimicrobial activity. It is estimated that ~1,300 tons of silver can be saved annually using this new way to enhance its antimicrobial activity. PMID:25418185

Fabrication and testing of silver-hydrogen cells

NASA Technical Reports Server (NTRS)

Debicarri, D. J.; Charkey, A.

1978-01-01

Silver electrodes containing various additives were fabricated and tested in single electrode cells in order to improve the electrochemical utilization of sintered silver cathodes in Ag-H2 aerospace batteries. A standard stack arrangement was used which featured a NASA-developed organic-inorganic separator. All cells were cycled in a regime designed to remove 75% of the cells nominal capacity based on 3.3 gms/AHr Ag utilization. In cases where performance degradation was observed, the main feature mode appeared to be corrosion of either the expanded silver current collector or the connection between the silver electrode and the electrode tab. Promising silver electrodes from single electrode studies were used in the construction of 35 AHr Ag-H2 cells. Two such cells were constructed and installed in heavy walled pressure vessels for testing. Based on the data obtained from all cells tested during the program, four lightweight 35 AHr cells were fabricated. During acceptance testing these cells yielded an average gravimetric energy density of 30 WHr/1b.

Silver nanoparticles: Synthesis methods, bio-applications and properties.

PubMed

Abbasi, Elham; Milani, Morteza; Fekri Aval, Sedigheh; Kouhi, Mohammad; Akbarzadeh, Abolfazl; Tayefi Nasrabadi, Hamid; Nikasa, Parisa; Joo, San Woo; Hanifehpour, Younes; Nejati-Koshki, Kazem; Samiei, Mohammad

2016-01-01

Silver nanoparticles size makes wide range of new applications in various fields of industry. Synthesis of noble metal nanoparticles for applications such as catalysis, electronics, optics, environmental and biotechnology is an area of constant interest. Two main methods for Silver nanoparticles are the physical and chemical methods. The problem with these methods is absorption of toxic substances onto them. Green synthesis approaches overcome this limitation. Silver nanoparticles size makes wide range of new applications in various fields of industry. This article summarizes exclusively scalable techniques and focuses on strengths, respectively, limitations with respect to the biomedical applicability and regulatory requirements concerning silver nanoparticles.

Facile chemical routes to mesoporous silver substrates for SERS analysis

PubMed Central

Tastekova, Elina A; Polyakov, Alexander Yu; Goldt, Anastasia E; Sidorov, Alexander V; Oshmyanskaya, Alexandra A; Sukhorukova, Irina V; Shtansky, Dmitry V; Grünert, Wolgang

2018-01-01

Mesoporous silver nanoparticles were easily synthesized through the bulk reduction of crystalline silver(I) oxide and used for the preparation of highly porous surface-enhanced Raman scattering (SERS)-active substrates. An analogous procedure was successfully performed for the production of mesoporous silver films by chemical reduction of oxidized silver films. The sponge-like silver blocks with high surface area and the in-situ-prepared mesoporous silver films are efficient as both analyte adsorbents and Raman signal enhancement mediators. The efficiency of silver reduction was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The developed substrates were applied for SERS detection of rhodamine 6G (enhancement factor of about 1–5 × 105) and an anti-ischemic mildronate drug (meldonium; enhancement factor of ≈102) that is known for its ability to increase the endurance performance of athletes. PMID:29600149

The dual role of silver during silicon etching in HF solution.

PubMed

Abouda-Lachiheb, Manel; Nafie, Nesma; Bouaicha, Mongi

2012-08-13

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope.

The dual role of silver during silicon etching in HF solution

PubMed Central

2012-01-01

It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope. PMID:22888998

Ober's Island: The Mallard Ober's Island, One of the ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Ober's Island: The Mallard - Ober's Island, One of the Review Islands on Rainy Lake, bounded on the south by The Hawk Island and on the north by The Crow Island. These islands are located seven miles east of Ranier, Minnesota, three miles west of Voyageur National Park, and one mile south of the international border of the United States of America and Canada. The legal description of Mallard Island is Lot 6, Section 19, T-17-N, R-22-W, Koochiching County, Minnesota, Ranier, Koochiching County, MN

Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles

PubMed Central

Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

2015-01-01

In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antmicrobial efficacy of well-known commercial antibiotics. PMID:25848272

Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles.

PubMed

Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

2015-01-01

In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antimicrobial efficacy of well-known commercial antibiotics.

Silver-induced reconstruction of an adeninate-based metal-organic framework for encapsulation of luminescent adenine-stabilized silver clusters.

PubMed

Jonckheere, Dries; Coutino-Gonzalez, Eduardo; Baekelant, Wouter; Bueken, Bart; Reinsch, Helge; Stassen, Ivo; Fenwick, Oliver; Richard, Fanny; Samorì, Paolo; Ameloot, Rob; Hofkens, Johan; Roeffaers, Maarten B J; De Vos, Dirk E

2016-05-21

Bright luminescent silver-adenine species were successfully stabilized in the pores of the MOF-69A (zinc biphenyldicarboxylate) metal-organic framework, starting from the intrinsically blue luminescent bio-MOF-1 (zinc adeninate 4,4'-biphenyldicarboxylate). Bio-MOF-1 is transformed to the MOF-69A framework by selectively leaching structural adenine linkers from the original framework using silver nitrate solutions in aqueous ethanol. Simultaneously, bright blue-green luminescent silver-adenine clusters are formed inside the pores of the recrystallized MOF-69A matrix in high local concentrations. The structural transition and concurrent changes in optical properties were characterized using a range of structural, physicochemical and spectroscopic techniques (steady-state and time-resolved luminescence, quantum yield determination, fluorescence microscopy). The presented results open new avenues for exploring the use of MOFs containing luminescent silver clusters for solid-state lighting and sensor applications.

Island Formation: Constructing a Coral Island

ERIC Educational Resources Information Center

Austin, Heather; Edd, Amelia

2009-01-01

The process of coral island formation is often difficult for middle school students to comprehend. Coral island formation is a dynamic process, and students should have the opportunity to experience this process in a synergistic context. The authors provide instructional guidelines for constructing a coral island. Students play an interactive role…

Silver nanoparticles: A new view on mechanistic aspects on antimicrobial activity.

PubMed

Durán, Nelson; Durán, Marcela; de Jesus, Marcelo Bispo; Seabra, Amedea B; Fávaro, Wagner J; Nakazato, Gerson

2016-04-01

Silver nanoparticles are well known potent antimicrobial agents. Although significant progresses have been achieved on the elucidation of antimicrobial mechanism of silver nanoparticles, the exact mechanism of action is still not completely known. This overview incorporates a retrospective of previous reviews published and recent original contributions on the progress of research on antimicrobial mechanisms of silver nanoparticles. The main topics discussed include release of silver nanoparticles and silver ions, cell membrane damage, DNA interaction, free radical generation, bacterial resistance and the relationship of resistance to silver ions versus resistance to silver nanoparticles. The focus of the overview is to summarize the current knowledge in the field of antibacterial activity of silver nanoparticles. The possibility that pathogenic microbes may develop resistance to silver nanoparticles is also discussed. Antibacterial effect of nanoscopic silver generated a lot of interest both in research projects and in practical applications. However, the exact mechanism is still will have to be elucidated. This overview incorporates a retrospective of previous reviews published from 2007 to 2013 and recent original contributions on the progress of research on antimicrobial mechanisms to summarize our current knowledge in the field of antibacterial activity of silver nanoparticles. Copyright © 2015 Elsevier Inc. All rights reserved.

Status of SAFT silver hydrogen cell development

NASA Technical Reports Server (NTRS)

Goualard, B. J.

1983-01-01

Nickel-hydrogen cells appear to be an improvement over the nickel-cadmium in applications requiring longer lifetime and reduced weight. An even more efficient couple, the silver-hydrogen couple, is also considered. After a theoretical study first performed by the Battelle Institute of Geneva under ESA (European Space Agency) contract, SAFT has undertaken more detailed analyses of the silver-hydrogen degradation mechanisms. ESA and the French Department of Defense contracted with SAFT for a full-development program of the silver-hydrogen technology.

Recent development in deciphering the structure of luminescent silver nanodots

NASA Astrophysics Data System (ADS)

Choi, Sungmoon; Yu, Junhua

2017-05-01

Matrix-stabilized silver clusters and stable luminescent few-atom silver clusters, referred to as silver nanodots, show notable difference in their photophysical properties. We present recent research on deciphering the nature of silver clusters and nanodots and understanding the factors that lead to variations in luminescent mechanisms. Due to their relatively simple structure, the matrix-stabilized clusters have been well studied. However, the single-stranded DNA (ssDNA)-stabilized silver nanodots that show the most diverse emission wavelengths and the best photophysical properties remain mysterious species. It is clear that their photophysical properties highly depend on their protection scaffolds. Analyses from combinations of high-performance liquid chromatography, inductively coupled plasma-atomic emission spectroscopy, electrophoresis, and mass spectrometry indicate that about 10 to 20 silver atoms form emissive complexes with ssDNA. However, it is possible that not all of the silver atoms in the complex form effective emission centers. Investigation of the nanodot structure will help us understand why luminescent silver nanodots are stable in aqueous solution and how to further improve their chemical and photophysical properties.

Silver recovery aqueous techniques from diverse sources: Hydrometallurgy in recycling.

PubMed

Syed, S

2016-04-01

The demand of silver is ever increasing with the advance of the industrialized world, whereas worldwide reserves of high grade silver ores are retreating. However, there exist large stashes of low and lean grade silver ores that are yet to be exploited. The main impression of this work was to draw attention to the most advance technologies in silver recovery and recycling from various sources. The state of the art in recovery of silver from different sources by hydrometallurgical and bio-metallurgical processing and varieties of leaching, cementing, reducing agents, peeling, electro-coagulants, adsorbents, electro-dialysis, solvent extraction, ion exchange resins and bio sorbents are highlighted in this article. It is shown that the major economic driver for recycling of depleted sources is for the recovery of silver. In order to develop an nature-friendly technique for the recovery of silver from diverse sources, a critical comparison of existing technologies is analyzed for both economic viability and environmental impact was made in this amendment and silver ion toxicity is highlighted. Copyright © 2016 Elsevier Ltd. All rights reserved.

New Capabilities With Dry Silver Recording Materials

NASA Astrophysics Data System (ADS)

Morgan, David A.

1987-04-01

Dry Silver technology was discovered at 3M and introduced into various imaging applications in the mid-sixties. In the early 1980's, quality films and papers with extended spectral responses, greater dynamic ranges, and improved sensitivity and edge acuity were introduced into sophisticated imaging systems. These products also have improved shelf life at elevated storage temperatures, and improved print stability. At the present time, 3M is developing a full-color dry silver product. This product has the same rapid-access, easy-to-use characteristics as the black and white dry silver recording materials. It has high resolution, long gray scale, and adequate sensitivity for CRT's and other electronically addressable exposure devices. The product can be processed in the same processors used for the black and white dry silver products.

Comparative activity of silver based antimicrobial composites for urinary catheters.

PubMed

Thokala, Nikhil; Kealey, Carmel; Kennedy, James; Brady, Damien B; Farrell, Joseph

2018-04-04

Biomedical polymers are an integral component in a wide range of medical device designs due to their range of desirable properties. However, extensive use of polymer materials in medical devices have also been associated with an increasing incidence of patient infections. Efforts to address this issue have included the incorporation of antimicrobial additives for developing novel antimicrobial polymeric materials. Silver with its high toxicity towards bacteria, oligodynamic effect and good thermal stability has been employed as an additive for polymeric medical devices. In the present study, commercially available elemental (Biogate) and ionic (Ultrafresh 16) silver additives were incorporated into a Polyamide 11 (PA 11) matrix using a compression press. These polymer composites were evaluated for their antimicrobial and ion release properties. Elemental silver composites were determined to retain their antimicrobial properties for extended periods and actively release silver ions for 84 days; whereas the ionic silver composites lost their ion release activity and therefore antibacterial activity after 56 days. Bacterial log reduction units of 3.87 for ionic silver and 2.41 for elemental silver was identified within 24 hr, when tested in accordance with ISO 22196 test standard; indicating that ionic silver is more efficient for short-term applications compared to elemental silver. Copyright © 2018 Elsevier Ltd. All rights reserved.

Method for Reduction of Silver Biocide Plating on Metal Surfaces

NASA Technical Reports Server (NTRS)

Steele, John; Nalette, Timothy; Beringer, Durwood

2013-01-01

Silver ions in aqueous solutions (0.05 to 1 ppm) are used for microbial control in water systems. The silver ions remain in solution when stored in plastic containers, but the concentration rapidly decreases to non-biocidal levels when stored in metal containers. The silver deposits onto the surface and is reduced to non-biocidal silver metal when it contacts less noble metal surfaces, including stainless steel, titanium, and nickel-based alloys. Five methods of treatment of contact metal surfaces to deter silver deposition and reduction are proposed: (1) High-temperature oxidation of the metal surface; (2) High-concentration silver solution pre-treatment; (3) Silver plating; (4) Teflon coat by vapor deposition (titanium only); and (5) A combination of methods (1) and (2), which proved to be the best method for the nickel-based alloy application. The mechanism associated with surface treatments (1), (2), and (5) is thought to be the development of a less active oxide layer that deters ionic silver deposition. Mechanism (3) is an attempt to develop an equilibrium ionic silver concentration via dissolution of metallic silver. Mechanism (4) provides a non-reactive barrier to deter ionic silver plating. Development testing has shown that ionic silver in aqueous solution was maintained at essentially the same level of addition (0.4 ppm) for up to 15 months with method (5) (a combination of methods (1) and (2)), before the test was discontinued for nickel-based alloys. Method (1) resulted in the maintenance of a biocidal level (approximately 0.05 ppm) for up to 10 months before that test was discontinued for nickel-based alloys. Methods (1) and (2) used separately were able to maintain ionic silver in aqueous solution at essentially the same level of addition (0.4 ppm) for up to 10 months before the test was discontinued for stainless steel alloys. Method (3) was only utilized for titanium alloys, and was successful at maintaining ionic silver in aqueous solution at

Silver Sodalites Novel Optically Responsive Nanocomposites

DTIC Science & Technology

1988-01-01

writing mechanim employed. The sodalite may be in the form of a self -suprting pressed disk, suspended in another material (e.g. glass or polymer), or...present study of silver sodalitas one can deduce that: i) silver sodalites can be synthesized with a variety of ptoraiac resposes ; ii) the distribution

Habitat and environment of islands: primary and supplemental island sets

USGS Publications Warehouse

Matalas, Nicholas C.; Grossling, Bernardo F.

2002-01-01

The original intent of the study was to develop a first-order synopsis of island hydrology with an integrated geologic basis on a global scale. As the study progressed, the aim was broadened to provide a framework for subsequent assessments on large regional or global scales of island resources and impacts on those resources that are derived from global changes. Fundamental to the study was the development of a comprehensive framework?a wide range of parameters that describe a set of 'saltwater' islands sufficiently large to Characterize the spatial distribution of the world?s islands; Account for all major archipelagos; Account for almost all oceanically isolated islands, and Account collectively for a very large proportion of the total area of the world?s islands whereby additional islands would only marginally contribute to the representativeness and accountability of the island set. The comprehensive framework, which is referred to as the ?Primary Island Set,? is built on 122 parameters that describe 1,000 islands. To complement the investigations based on the Primary Island Set, two supplemental island sets, Set A?Other Islands (not in the Primary Island Set) and Set B?Lagoonal Atolls, are included in the study. The Primary Island Set, together with the Supplemental Island Sets A and B, provides a framework that can be used in various scientific disciplines for their island-based studies on broad regional or global scales. The study uses an informal, coherent, geophysical organization of the islands that belong to the three island sets. The organization is in the form of a global island chain, which is a particular sequential ordering of the islands referred to as the 'Alisida.' The Alisida was developed through a trial-and-error procedure by seeking to strike a balance between 'minimizing the length of the global chain' and 'maximizing the chain?s geophysical coherence.' The fact that an objective function cannot be minimized and maximized simultaneously

Cytotoxicity and antimicrobial activities of green synthesized silver nanoparticles.

PubMed

Lokina, S; Stephen, A; Kaviyarasan, V; Arulvasu, C; Narayanan, V

2014-04-09

Bio-inspired silver nanoparticles are synthesized using Malus domestica (apple) extract. Polyphenols present in the apple extract act as a reducing and capping agent to produce the silver nanoparticles. UV-Visible analysis shows the surface plasmon resonance (SPR) absorption at 420 nm. The FTIR analysis was used to identify the functional groups responsible for the bio-reduction of silver ion. The XRD and HRTEM images confirm the formation of silver nanoparticles. The minimal inhibitory concentration (MIC) of silver nanoparticles was recorded against most of the bacteria and fungus. Further, MCF-7 human breast adenocarcinoma cancer cell line was employed to observe the efficacy of cancer cell killing. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Antibacterial potency of V.A.C. GranuFoam Silver(®) Dressing.

PubMed

Sachsenmaier, Saskia; Peschel, Andreas; Ipach, Ingmar; Kluba, Torsten

2013-10-01

V.A.C.(®) GranuFoam™ therapy is regularly used in the surgical therapy of infected wounds and soft tissue injuries. Silver nanoparticles can destroy bacterial cell walls and inhibit enzymes for cell replication. Silver dressings are therefore successfully used for many indications in wound therapy. In this study, we investigated the antimicrobial potency of ionic silver released from the silver-coated V.A.C.(®) GranuFoam™ during vacuum therapy. Silver dressing was exposed to agar plates populated with bacteria to measure silver release. A total of 15 agar plates colonised with either Staphylococcus aureus populations or with Staphylococcus epidermidis, were loaded with V.A.C. GranuFoam Silver(®) Dressing polyurethane foam (KCI, San Antonio, Texas). Each of 13 pieces of silver-coated foam was applied to an agar plate. Two plates were loaded with conventional black foam without any coating. After connecting to a vacuum pump, the vacuum therapy of the 15 plates lasted 5 days. The zone of inhibition of bacterial growth around the foam was measured daily. Silver release was also determined as a function of time. At each time point, there was evidence of silver in the agar independent of bacterial colonisation. The S. aureus agar showed a consecutive increase in silver concentration from baseline upon 48 h after exposure to the negative pressure of V.A.C. therapy. An increasing mean silver level after 48, 72 and 96 h was measured under V.A.C. therapy with a peak value after 120 h. In contrast, the results from the S. epidermidis plates did not follow a linear pattern. At the beginning of vacuum therapy, we documented a rise in silver concentration. After 48-96h, the silver levels fluctuated. A maximum zone of inhibition in both bacterial colonised plates (S. aureus and S. epidermidis) was found 39 h after the start of the V.A.C. GranuFoam Silver(®) therapy. From our results, we confirmed the antimicrobial effect of the silver ions against S. aureus and S

Extracellular biosynthesis of silver nanoparticles using the fungus Fusarium semitectum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basavaraja, S.; Balaji, S.D.; Department of Chemistry, Gulbarga University, Gulbarga 585106, Karnataka

2008-05-06

Development of environmental friendly procedures for the synthesis of metal nanoparticles through biological processes is evolving into an important branch of nanobiotechnology. In this paper, we report on the use of fungus 'Fusarium semitectum' for the extracellular synthesis of silver nanoparticles from silver nitrate solution (i.e. through the reduction of Ag{sup +} to Ag{sup 0}). Highly stable and crystalline silver nanoparticles are produced in solution by treating the filtrate of the fungus F. semitectum with the aqueous silver nitrate solution. The formations of nanoparticles are understood from the UV-vis and X-ray diffraction studies. Transmission electron microscopy of the silver particlesmore » indicated that they ranged in size from 10 to 60 nm and are mostly spherical in shape. Interestingly the colloidal suspensions of silver nanoparticles are stable for many weeks. Possible medicinal applications of these silver nanoparticles are envisaged.« less

Silver indium diphosphate, AgInP(2)O(7).

PubMed

Zouihri, Hafid; Saadi, Mohamed; Jaber, Boujemaa; El Ammari, Lehcen

2010-12-18

Polycrystalline material of the title compound, AgInP(2)O(7), was synthesized by traditional high-temperature solid-state methods and single crystals were grown from the melt of a mixture of AgInP(2)O(7) and B(2)O(3) as flux in a platinium crucible. The structure consists of InO(6) octa-hedra, which are corner-shared to PO(4) tetra-hedra into a three-dimensional network with hexa-gonal channels running parallel to the c axis. The silver cation, located in the channel, is bonded to seven O atoms of the [InP(2)O(7)] framework with Ag-O distances ranging from 2.370 (2) to 3.015 (2) Å. The P(2)O(7) diphosphate anion is characterized by a P-O-P angle of 137.27 (9) and a nearly eclipsed conformation. AgInP(2)O(7) is isotypic with the M(I)FeP(2)O(7) (M(I) = Na, K, Rb, Cs and Ag) diphosphate family.

Detection of colloidal silver chloride near solubility limit

NASA Astrophysics Data System (ADS)

Putri, K. Y.; Adawiah, R.

2018-03-01

Detection of nanoparticles in solution has been made possible by several means; one of them is laser-induced breakdown detection (LIBD). LIBD is able to distinguish colloids of various sizes and concentrations. This technique has been used in several solubility studies. In this study, the formation of colloids in a mixed system of silver nitrate and sodium chloride was observed by acoustic LIBD. Silver chloride has low solubility limit, therefore LIBD measurement is appropriate. Silver and chloride solutions with equal concentrations, set at below and above the solubility of silver chloride as the expected solid product, were mixed and the resulting colloids were observed. The result of LIBD measurement showed that larger particles were present as more silver and chloride introduced. However, once the concentrations exceeded the solubility limit of silver chloride, the detected particle size seemed to be decreasing, hence suggested the occurrence of coprecipitation process. This phenomenon indicated that the ability of LIBD to detect even small changes in colloid amounts might be a useful tool in study on formation and stability of colloids, i.e. to confirm whether nanoparticles synthesis has been successfully performed and whether the system is stable or not.

Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle-nanowires

NASA Astrophysics Data System (ADS)

Muhammed Ajmal, C.; Mol Menamparambath, Mini; Ryeol Choi, Hyouk; Baik, Seunghyun

2016-06-01

Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle-nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle-nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle-nanowires provided a greater maximum conductivity (54 390 S cm-1) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle-nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration.

XPS characterization of silver exchanged ETS-10 and mordenite molecular sieves.

PubMed

Anson, A; Maham, Y; Lin, C C H; Kuznicki, T M; Kuznicki, S M

2009-05-01

Silver exchanged molecular sieves ETS-10 (Ag-ETS-10) and mordenite (Ag-mordenite) were dehydrated under vacuum at temperatures between 100 degrees C-350 degrees C. Changes in the state of the silver were studied using X-ray photoelectron spectroscopy (XPS). Silver cations in titanosilicate Ag-ETS-10 are fully reduced to Ag(0) at temperatures as low as 150 degrees C. The characteristic features of the XPS spectrum of silver in this Ag-ETS-10 species correspond to only metallic silver. The signal for metallic silver is not observed in the XPS spectrum of aluminosilicate Ag-mordenite, indicating that silver cations are not reduced, even after heating to 350 degrees C.

Heat Islands

EPA Pesticide Factsheets

EPA's Heat Island Effect Site provides information on heat islands, their impacts, mitigation strategies, related research, a directory of heat island reduction initiatives in U.S. communities, and EPA's Heat Island Reduction Program.

Toxicity of Silver Nanoparticles at the Air-Liquid Interface

PubMed Central

Holder, Amara L.; Marr, Linsey C.

2013-01-01

Silver nanoparticles are one of the most prevalent nanomaterials in consumer products. Some of these products are likely to be aerosolized, making silver nanoparticles a high priority for inhalation toxicity assessment. To study the inhalation toxicity of silver nanoparticles, we have exposed cultured lung cells to them at the air-liquid interface. Cells were exposed to suspensions of silver or nickel oxide (positive control) nanoparticles at concentrations of 2.6, 6.6, and 13.2 μg cm−2 (volume concentrations of 10, 25, and 50 μg ml−1) and to 0.7 μg cm−2 silver or 2.1 μg cm−2 nickel oxide aerosol at the air-liquid interface. Unlike a number of in vitro studies employing suspensions of silver nanoparticles, which have shown strong toxic effects, both suspensions and aerosolized nanoparticles caused negligible cytotoxicity and only a mild inflammatory response, in agreement with animal exposures. Additionally, we have developed a novel method using a differential mobility analyzer to select aerosolized nanoparticles of a single diameter to assess the size-dependent toxicity of silver nanoparticles. PMID:23484109

[Silver-Russell syndrome with panhypopituitarism (author's transl)].

PubMed

Stögmann, W; Borkenstein, M; Grubbauer, H M

1978-11-01

This is a report on a 14 years old boy suffering from the unusual combination of Silver-Russell syndrome with panhypopituitarism. The Silver-Russell syndrome is a special form of primordial dwarfism characterised by congenital asymmetry, craniofacial dysmorphy and other anomalies. Its cause is unknown, intrauterine noxes and genetical factors are discussed. In the most cases results of hormone determinations are normal, but also cases with elevated or very low hormone levels were published. This is the first report about a Silver-Russell syndrome combined with panhypopituitarism.

Silver plating ensures reliable diffusion bonding of dissimilar metals

NASA Technical Reports Server (NTRS)

1967-01-01

Dissimilar metals are reliably joined by diffusion bonding when the surfaces are electroplated with silver. The process involves cleaning and etching, anodization, silver striking, and silver plating with a conventional plating bath. It minimizes the formation of detrimental intermetallic phases and provides greater tolerance of processing parameters.

Preparation of starch-stabilized silver nanoparticles from amylose-sodium palmitate inclusion complexes

USDA-ARS?s Scientific Manuscript database

Starch-stabilized silver nanoparticles were prepared from amylose-sodium palmitate complexes by first converting sodium palmitate to silver palmitate by reaction with silver nitrate and then reducing the silver ion to metallic silver. This process produced water solutions that could be dried and the...

Reducing Environmental Toxicity of Silver Nanoparticles through Shape Control.

PubMed

Gorka, Danielle E; Osterberg, Joshua S; Gwin, Carley A; Colman, Benjamin P; Meyer, Joel N; Bernhardt, Emily S; Gunsch, Claudia K; DiGulio, Richard T; Liu, Jie

2015-08-18

The use of antibacterial silver nanomaterials in consumer products ranging from textiles to toys has given rise to concerns over their environmental toxicity. These materials, primarily nanoparticles, have been shown to be toxic to a wide range of organisms; thus methods and materials that reduce their environmental toxicity while retaining their useful antibacterial properties can potentially solve this problem. Here we demonstrate that silver nanocubes display a lower toxicity toward the model plant species Lolium multiflorum while showing similar toxicity toward other environmentally relevant and model organisms (Danio rerio and Caenorhabditis elegans) and bacterial species (Esherichia coli, Bacillus cereus, and Pseudomonas aeruginosa) compared to quasi-spherical silver nanoparticles and silver nanowires. More specifically, in the L. multiflorum experiments, the roots of silver nanocube treated plants were 5.3% shorter than the control, while silver nanoparticle treated plant roots were 39.6% shorter than the control. The findings here could assist in the future development of new antibacterial products that cause less environmental toxicity after their intended use.

New complexes of silver (I) with N-hydroxy-succinimide

NASA Astrophysics Data System (ADS)

Sibiescu, Doina; Mîţǎ, Carmen; Vizitiu, Mihaela; Crudu, Andra Manuela

2016-12-01

Over the last period of time silver was considerably studied due to its lower resistivity. In the field of materials science, silver was used in applications such as: microelectronics components of high - temperature superconductiviting materials, bactericidal coatings and others domains. This study presents the process of obtaining and characterization the new complexes of silver (I) with Nhydroxy- succinimide. In the process of obtaining the new complex compounds in aqous solution, first we have to look at conductometry and UV-Vis absorbtion spectroscopy in order to determine the molar ratio silver : N-hydroxysuccinimide and the stability constants. The obtained solid coordination compounds were characterized by elemental analysis, IR spectroscopy and also was investigated of their thermostability. The X-ray powder diffraction reflects that the complexes compounds of silver (I) with N-hydroxysuccinimide are amorphous. In our further studies we want to determine if the new synthetized compounds will present the same or improuved properties as in the above mentioned silver characteristics.

Uniform height island growth on Pb/Si(111) at low temperatures and QSE

NASA Astrophysics Data System (ADS)

Tringides, Michael C.

2002-03-01

Highly uniform height Pb(111) islands (which can differ by bilayer height increments) of flat tops and steep edges can be grown on Pb/Si(111) at low temperatures 120Kislands are observed with SPA-LEED and variable temperature STM[2]. The formation of these unusual island structures is most likely related to Quantum Size Effects (QSE) i.e the dependence of the energy of the confined electrons on island height because of energy level quantization. We will review experiments carried out to identify the factors which determine the selected island heights: (i) the growth parameters (i.e. temperature T, coverage q) and kinetic pathway (i.e. growth vs annealing experiments).(ii) the role of the electronic structure of the initial substrate phase (i.e. whether the initial phase is Si(111)-(7x7) or Si(111)-Pb-(sq3xsq3)) and charge transfer at the interface[3]. Such experiments demonstrate that experimental control of the selected height can be attained in an easy and reproducible way. 1. K. Budde et al Phys. Rev. B61 Rap. Com. 10602 (2000) 2. M. Hupalo et al Surf. Sci. 493 526 (2001) 3. V. Yeh et al. Phys. Rev.Lett. 85, 5158 (2000) Work supported by Ames Laboratory-DOE in collaboration with M.Hupalo, K.Budde, E. Abram,V. Yeh, S. Kremmer, L.Berbil-Bautista, C. Z. Wang, K.M.Ho.

Thermal expansion of silver iodide-silver molybdate glasses at low temperatures

NASA Astrophysics Data System (ADS)

Mandanici, A.; Raimondo, A.; Cutroni, M.; Ramos, M. A.; Rodrigo, J. G.; Vieira, S.; Armellini, C.; Rocca, F.

2009-05-01

Ionic glasses obtained combining silver iodide and silver molybdate are characterized by quite low values of the glass transition temperature Tg around 320-350 K, by high values of the dc ionic conductivity even at room temperature and by a peculiar behavior of the mechanical response at ultrasonic frequencies. In fact, at temperatures well below their glass transition temperature, these glasses exhibit an intense peak of acoustic attenuation well described by two different and almost overlapping relaxational contributions. Considering also that negative thermal expansion has been reported for some molybdate crystalline compounds, we have investigated in this work the thermal expansion of two silver iodomolybdate glasses (AgI)1-x(Ag2MoO4)x for x =0.25 and x =0.33 in a wide temperature range (4.2-300 K) from cryogenic temperatures up to some 20 K below Tg using a precision capacitance dilatometer aiming to understand whether the expansivity shows some possible fingerprint corresponding to the above-mentioned mechanical response. Two different measuring methods, a quasiadiabatic and a continuous one, have been used for the thermal expansion measurements. The results are discussed in comparison with the information obtained from previous investigations based on the extended x-ray absorption fine structure (EXAFS) technique and with the behavior of other ionic glasses.

Silver enhances antibiotic activity against gram-negative bacteria.

PubMed

Morones-Ramirez, J Ruben; Winkler, Jonathan A; Spina, Catherine S; Collins, James J

2013-06-19

A declining pipeline of clinically useful antibiotics has made it imperative to develop more effective antimicrobial therapies, particularly against difficult-to-treat Gram-negative pathogens. Silver has been used as an antimicrobial since antiquity, yet its mechanism of action remains unclear. We show that silver disrupts multiple bacterial cellular processes, including disulfide bond formation, metabolism, and iron homeostasis. These changes lead to increased production of reactive oxygen species and increased membrane permeability of Gram-negative bacteria that can potentiate the activity of a broad range of antibiotics against Gram-negative bacteria in different metabolic states, as well as restore antibiotic susceptibility to a resistant bacterial strain. We show both in vitro and in a mouse model of urinary tract infection that the ability of silver to induce oxidative stress can be harnessed to potentiate antibiotic activity. Additionally, we demonstrate in vitro and in two different mouse models of peritonitis that silver sensitizes Gram-negative bacteria to the Gram-positive-specific antibiotic vancomycin, thereby expanding the antibacterial spectrum of this drug. Finally, we used silver and antibiotic combinations in vitro to eradicate bacterial persister cells, and show both in vitro and in a mouse biofilm infection model that silver can enhance antibacterial action against bacteria that produce biofilms. This work shows that silver can be used to enhance the action of existing antibiotics against Gram-negative bacteria, thus strengthening the antibiotic arsenal for fighting bacterial infections.

Benzoate-Induced High-Nuclearity Silver Thiolate Clusters.

PubMed

Su, Yan-Min; Liu, Wei; Wang, Zhi; Wang, Shu-Ao; Li, Yan-An; Yu, Fei; Zhao, Quan-Qin; Wang, Xing-Po; Tung, Chen-Ho; Sun, Di

2018-04-03

Compared with the well-known anion-templated effects in shaping silver thiolate clusters, the influence from the organic ligands in the outer shell is still poorly understood. Herein, three new benzoate-functionalized high-nuclearity silver(I) thiolate clusters are isolated and characterized for the first time in the presence of diverse anion templates such as S 2- , α-[Mo 5 O 18 ] 6- , and MoO 4 2- . Single-crystal X-ray analysis reveals that the nuclearities of the three silver clusters (SD/Ag28, SD/Ag29, SD/Ag30) vary from 32 to 38 to 78 with co-capped tBuS - and benzoate ligands on the surface. SD/Ag28 is a turtle-like cluster comprising a Ag 29 shell caging a Ag 3 S 3 trigon in the center, whereas SD/Ag29 is a prolate Ag 38 sphere templated by the α-[Mo 5 O 18 ] 6- anion. Upon changing from benzoate to methoxyl-substituted benzoate, SD/Ag30 is isolated as a very complicated core-shell spherical cluster composed of a Ag 57 shell and a vase-like Ag 21 S 13 core. Four MoO 4 2- anions are arranged in a supertetrahedron and located in the interstice between the core and shell. Introduction of the bulky benzoate changes elaborately the nuclearity and arrangements of silver polygons on the shell of silver clusters, which is exemplified by comparing SD/Ag28 and a known similar silver thiolate cluster. The three new clusters emit luminescence in the near-infrared (NIR) region and show different thermochromic luminescence properties. This work presents a flexible approach to synthetic studies of high-nuclearity silver clusters decorated by different benzoates, and structural modulations are also achieved. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Melanin-templated rapid synthesis of silver nanostructures

PubMed Central

2014-01-01

Background As a potent antimicrobial agent, silver nanostructures have been used in nanosensors and nanomaterial-based assays for the detection of food relevant analytes such as organic molecules, aroma, chemical contaminants, gases and food borne pathogens. In addition silver based nanocomposites act as an antimicrobial for food packaging materials. In this prospective, the food grade melanin pigment extracted from sponge associated actinobacterium Nocardiopsis alba MSA10 and melanin mediated synthesis of silver nanostructures were studied. Based on the present findings, antimicrobial nanostructures can be developed against food pathogens for food industrial applications. Results Briefly, the sponge associated actinobacterium N. alba MSA10 was screened and fermentation conditions were optimized for the production of melanin pigment. The Plackett-Burman design followed by a Box-Behnken design was developed to optimize the concentration of most significant factors for improved melanin yield. The antioxidant potential, reductive capabilities and physiochemical properties of Nocardiopsis melanin was characterized. The optimum production of melanin was attained with pH 7.5, temperature 35°C, salinity 2.5%, sucrose 25 g/L and tyrosine 12.5 g/L under submerged fermentation conditions. A highest melanin production of 3.4 mg/ml was reached with the optimization using Box-Behnken design. The purified melanin showed rapid reduction and stabilization of silver nanostructures. The melanin mediated process produced uniform and stable silver nanostructures with broad spectrum antimicrobial activity against food pathogens. Conclusions The melanin pigment produced by N. alba MSA10 can be used for environmentally benign synthesis of silver nanostructures and can be useful for food packaging materials. The characteristics of broad spectrum of activity against food pathogens of silver nanostructures gives an insight for their potential applicability in incorporation of food

Silver cyanide

Integrated Risk Information System (IRIS)

Silver cyanide ; CASRN 506 - 64 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

White-tailed deer ecology and management on Fire Island

USGS Publications Warehouse

Underwood, H.B.

2005-01-01

Deer populations have grown dramatically on Fire Island National Seashore (FIlS) since 1983. Trend data reveal a dichotomy in deer dynamics. In the eastern half of the island, deer density appears to have stabilized between 25-35 deer/km2. In the western half of the island, deer densities are 3-4 times as high in residential communities. Concomitant with that increase has been a general decline in physical stature of some animals, visible impacts on island vegetation, especially in the Sunken Forest, and a perceived increase in the frequency of human and deer interactions. Intensive research on FIlS has shown that deer occupy relatively predictable home ranges throughout the year, but can and do move up and down the island. Impacts of deer on vegetation are most dramatic in the Sunken Forest. Most obvious are the effects of browsing on the herb layer of the Sunken Forest. The least obvious, but perhaps more significant impact is the stark lack of regeneration of canopy tree species since about 1970, which coincides with the initiation of the deer population irruption. A number of herbs and shrubs have been greatly reduced in the understory, and their propagules from the soil. Deer do not readily transmit the bacterium that causes Lyme disease to other organisms, but deer are important hosts for adult ticks which underscores their importance in the transmission pathway of the disease to humans. Deer on FIlS, while occasionally docile, are still wild animals and should be treated as such. Some animals are relatively unafraid of humans due to the absence of predation and a lack of harassment. This in turn has contributed to a longstanding tradition of feeding deer by many residents and visitors, particularly in western portions of the island. Feeding affects both the behavior and population dynamics of deer inhabiting Fire Island. Recent efforts to reduce deer feeding by visitors and residents have been very effective. Ongoing experiments with Porcine Zona Pellucida

Governing factors affecting the impacts of silver nanoparticles on wastewater treatment.

PubMed

Zhang, Chiqian; Hu, Zhiqiang; Li, Ping; Gajaraj, Shashikanth

2016-12-01

Silver nanoparticles (nanosilver or AgNPs) enter municipal wastewater from various sources, raising concerns about their potential adverse effects on wastewater treatment processes. We argue that the biological effects of silver nanoparticles at environmentally realistic concentrations (μgL -1 or lower) on the performance of a full-scale municipal water resource recovery facility (WRRF) are minimal. Reactor configuration is a critical factor that reduces or even mutes the toxicity of silver nanoparticles towards wastewater microbes in a full-scale WRRF. Municipal sewage collection networks transform silver nanoparticles into silver(I)-complexes/precipitates with low ecotoxicity, and preliminary/primary treatment processes in front of biological treatment utilities partially remove silver nanoparticles to sludge. Microbial functional redundancy and microbial adaptability to silver nanoparticles also greatly alleviate the adverse effects of silver nanoparticles on the performance of a full-scale WRRF. Silver nanoparticles in a lab-scale bioreactor without a sewage collection system and/or a preliminary/primary treatment process, in contrast to being in a full scale system, may deteriorate the reactor performance at relatively high concentrations (e.g., mgL -1 levels or higher). However, in many cases, silver nanoparticles have minimal impacts on lab-scale bioreactors, such as sequencing batch bioreactors (SBRs), especially when at relatively low concentrations (e.g., less than 1mgL -1 ). The susceptibility of wastewater microbes to silver nanoparticles is species-specific. In general, silver nanoparticles have higher toxicity towards nitrifying bacteria than heterotrophic bacteria. Copyright © 2016 Elsevier B.V. All rights reserved.

Preliminary experimental research for silver recovery from radiographic films

NASA Astrophysics Data System (ADS)

Cânda, L. R.; Ardelean, E.

2017-01-01

Global demand for silver remains steadily to about 1,000 million ounces (28349500 kg), of which around 600 million ounces (17009700 kg) are used in industrial applications. Extraction of silver from the ore is expensive and harmful to the environment and low efficiency. X-ray films represent an important worldwide consumer as research on recovery of silver from exposed radiographic films must be oriented to achieve a maximum recovery and a high purity silver, with methods through the by-products will be less polluting for the environment. The paper presents some laboratory tests referring to the recovery of silver from radiographic films by leaching with sodium hydroxide. Two series of experiments were performed with different amounts of used X-ray film.

Silver oxysalts promote cutaneous wound healing independent of infection.

PubMed

Thomason, Helen A; Lovett, Jodie M; Spina, Carla J; Stephenson, Christian; McBain, Andrew J; Hardman, Matthew J

2018-03-12

Chronic wounds often exist in a heightened state of inflammation whereby excessive inflammatory cells release high levels of proteases and reactive oxygen species (ROS). While low levels of ROS play a fundamental role in the regulation of normal wound healing, their levels need to be tightly regulated to prevent a hostile wound environment resulting from excessive levels of ROS. Infection amplifies the inflammatory response, augmenting levels of ROS which creates additional tissue damage that supports microbial growth. Antimicrobial dressings are used to combat infection; however, the effects of these dressing on the wound environment and healing independent of infection are rarely assessed. Cytotoxic or adverse effects on healing may exacerbate the hostile wound environment and prolong healing. Here we assessed the effect on healing independent of infection of silver oxysalts which produce higher oxidative states of silver (Ag 2+ /Ag 3+ ). Silver oxysalts had no adverse effect on fibroblast scratch wound closure whilst significantly promoting closure of keratinocyte scratch wounds (34% increase compared with control). Furthermore, dressings containing silver oxysalts accelerated healing of full-thickness incisional wounds in wild-type mice, reducing wound area, promoting reepithelialization, and dampening inflammation. We explored the mechanisms by which silver oxysalts promote healing and found that unlike other silver dressings tested, silver oxysalt dressings catalyze the breakdown of hydrogen peroxide to water and oxygen. In addition, we found that silver oxysalts directly released oxygen when exposed to water. Collectively, these data provide the first indication that silver oxysalts promote healing independent of infection and may regulate oxidative stress within a wound through catalysis of hydrogen peroxide. © 2018 by the Wound Healing Society.

The lifecycle of silver in the United States in 2009

USGS Publications Warehouse

Goonan, Thomas G.

2014-01-01

Because silver is highly sought after for its properties, which make it eminently suitable for new technology applications, a clear understanding of the flow of materials in the economy, the historical context, and trends for the future can help project the future of silver in the economy of the United States. Silver has many properties that are desired in today’s economy. It has superior electrical and heat conductivity, chemical stability, high-temperature strength, malleability, and other characteristics that make it important in high-tech electronic and other industrial applications. Because it is relatively scarce as a natural resource and is easily coined, silver historically has been an important monetary metal. As knowledge of silver chemistry has increased, many industrial end uses have been developed. This study reviews the flows of silver into various end uses and examines the nature of the end use with respect to the silver properties desired and the ability of the end use to produce recyclable end-of-life materials. For the most part, silver can be profitably recycled, but the recycling activity is helped by tipping fees (fees imposed on scrap generators by scrap collectors for taking the material) for materials that might otherwise be regulated as hazardous wastes. New high-technology applications use silver in nanolevel amounts, leading to a potential for dissipative loss and reduced recycling capability.

Silver Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

USGS Publications Warehouse

Eisler, R.

1996-01-01

Ecological and toxicological aspects of silver (Ag) in the environment are briefly summarized with an emphasis on natural resources. Elevated silver concentrations in biota occur in the vicinities of sewage outfalls, electroplating plants, mine waste sites, and silver-iodide seeded areas; in the United States, the photography industry is the major source of anthropogenic silver discharges into the biosphere. Silver and its compounds are not known to be mutagenic, teratogenic, or carcinogenic. Under normal routes of exposure, silver does not pose serious environmental health problems to humans at less than 50.0 ug total Ag/L drinking water or 10.0 ug per cubic meter air. Free silver ion, however, was lethal to representative species of sensitive aquatic plants, invertebrates, and teleosts at nominal water concentrations of 1.2 to 4.9 ug/L; sublethal effects were significant between 0.17 and 0.6 ug/L. Silver was harmful to poultry at concentrations as low as 1.8 mg total Ag/kg whole egg fresh weight by way of injection, 100.0 mg total Ag/L in drinking water, or 200.0 mg total Ag/kg in diets; sensitive mammals were adversely affected at total silver concentrations as low as 250.0 ug/L in drinking water, 6.0 mg/kg in diets, or 13.9 mg/kg whole body.

How does solar ultraviolet-B radiation improve drought tolerance of silver birch (Betula pendula Roth.) seedlings?

PubMed

Robson, T Matthew; Hartikainen, Saara M; Aphalo, Pedro J

2015-05-01

We hypothesized that solar ultraviolet (UV) radiation would protect silver birch seedlings from the detrimental effects of water stress through a coordinated suite of trait responses, including morphological acclimation, improved control of water loss through gas exchange and hydraulic sufficiency. To better understand how this synergetic interaction works, plants were grown in an experiment under nine treatment combinations attenuating ultraviolet-A and ultraviolet-B (UVB) from solar radiation together with differential watering to create water-deficit conditions. In seedlings under water deficit, UV attenuation reduced height growth, leaf production and leaf length compared with seedlings receiving the full spectrum of solar radiation, whereas the growth and morphology of well-watered seedlings was largely unaffected by UV attenuation. There was an interactive effect of the treatment combination on water relations, which was more apparent as a change in the water potential at which leaves wilted or plants died than through differences in gas exchange. This suggests that changes occur in the cell wall elastic modulus or accumulation of osmolites in cells under UVB. Overall, the strong negative effects of water deficit are partially ameliorated by solar UV radiation, whereas well-watered silver birch seedlings are slightly disadvantaged by the solar UV radiation they receive. © 2014 John Wiley & Sons Ltd.

Aleutian Islands

NASA Image and Video Library

2014-05-21

Remote, rugged and extraordinarily beautiful, Alaska’s Aleutian Islands are best known for wildlife reserves, military bases, fishing, furs and fog. The sprawling volcanic archipelago was brought into the spotlight by the Russian-supported expedition of Alexey Chirikov and Vitus Bering in 1741, and soon became controlled by the Russian-American Fur Company. In 1867 the United States purchased Alaska, including the Aleutian Islands, from Russia. By 1900 the port in Unalaska was well established as a shipping port for Alaska gold. The archipelago sweeps about 1,200 miles (1,800 km) from the tip of the Alaskan Peninsula to Attu, the most westward island. Four major island groups hold 14 large islands, about 55 smaller islands, and a large number of islets, adding up to roughly 150 islands/islets in total. This chain separates the Bering Sea (north) from the Pacific Ocean (south) and the islands are connected by the Marine Highway Ferry – at least as far as Unalaska. For the most remote islands, such as birding paradise of Attu, the western-most Aleutian Island, travel becomes trickier and relies primarily on custom charter. The Moderate Resolution Imaging Spectroradiometer (MODIS) flew over the region and captured this spectacular true-color image of the eastern Aleutian Islands on May 15, 2014. In this image, the Alaskan Peninsula protrudes from the mainland and sweeps to the southwest. The first set of islands are called the Fox Island group. Unalaska Island is part of this group and can be identified, with some imagination, as an island formed in the shape of a flying cherub, with two arms (peninsulas) outstretched towards the northeast, seemingly reaching for the round “balls” of Akutan and Akun Islands. The smallest islands in the west of the image belong to the group known as the Islands of Four Mountains. The Aleutians continue far to the west of this image. Fog surrounds the Aleutians, stretching from just off the southwestern Alaska mainland to the

Silver nanostructures synthesis via optically induced electrochemical deposition

NASA Astrophysics Data System (ADS)

Li, Pan; Liu, Na; Yu, Haibo; Wang, Feifei; Liu, Lianqing; Lee, Gwo-Bin; Wang, Yuechao; Li, Wen Jung

2016-06-01

We present a new digitally controlled, optically induced electrochemical deposition (OED) method for fabricating silver nanostructures. Projected light patterns were used to induce an electrochemical reaction in a specialized sandwich-like microfluidic device composed of one indium tin oxide (ITO) glass electrode and an optically sensitive-layer-covered ITO electrode. Silver polyhedral nanoparticles, triangular and hexagonal nanoplates, and nanobelts were controllably synthesized in specific positions at which projected light was illuminated. The silver nanobelts had rectangular cross-sections with an average width of 300 nm and an average thickness of 100 nm. By controlling the applied voltage, frequency, and time, different silver nanostructure morphologies were obtained. Based on the classic electric double-layer theory, a dynamic process of reduction and crystallization can be described in terms of three phases. Because it is template- and surfactant-free, the digitally controlled OED method facilitates the easy, low cost, efficient, and flexible synthesis of functional silver nanostructures, especially quasi-one-dimensional nanobelts.

Tenarife Island, Canary Island Archipelago, Atlantic Ocean

NASA Technical Reports Server (NTRS)

1991-01-01

Tenarife Island is one of the most volcanically active of the Canary Island archipelago, Atlantic Ocean, just off the NW coast of Africa, (28.5N, 16.5W). The old central caldera, nearly filled in by successive volcanic activity culminating in two stratocones. From those two peaks, a line of smaller cinder cones extend to the point of the island. Extensive gullies dissect the west side of the island and some forests still remain on the east side.

Tenarife Island, Canary Island Archipelago, Atlantic Ocean

NASA Image and Video Library

1991-08-11

Tenarife Island is one of the most volcanically active of the Canary Island archipelago, Atlantic Ocean, just off the NW coast of Africa, (28.5N, 16.5W). The old central caldera, nearly filled in by successive volcanic activity culminating in two stratocones. From those two peaks, a line of smaller cinder cones extend to the point of the island. Extensive gullies dissect the west side of the island and some forests still remain on the east side.

Comparison of cross-sectional transmission electron microscope studies of thin germanium epilayers grown on differently oriented silicon wafers.

PubMed

Norris, D J; Myronov, M; Leadley, D R; Walther, T

2017-12-01

We compare transmission electron microscopical analyses of the onset of islanding in the germanium-on-silicon (Ge/Si) system for three different Si substrate orientations: (001), (11¯0) and (11¯1)Si. The Ge was deposited by reduced pressure chemical vapour deposition and forms islands on the surface of all Si wafers; however, the morphology (aspect ratio) of the deposited islands is different for each type of wafer. Moreover, the mechanism for strain relaxation is different for each type of wafer owing to the different orientation of the (111) slip planes with the growth surface. Ge grown on (001)Si is initially pseudomorphically strained, yielding small, almost symmetrical islands of high aspect ratio (clusters or domes) on top interdiffused SiGe pedestals, without any evidence of plastic relaxation by dislocations, which would nucleate later-on when the islands might have coalesced and then the Matthews-Blakeslee limit is reached. For (11¯0)Si, islands are flatter and more asymmetric, and this is correlated with plastic relaxation of some islands by dislocations. In the case of growth on (11¯1)Si wafers, there is evidence of immediate strain relaxation taking place by numerous dislocations and also twinning. In the case of untwined film/substrate interfaces, Burgers circuits drawn around certain (amorphous-like) regions show a nonclosure with an edge-type a/4[1¯12] Burgers vector component visible in projection along [110]. Microtwins of multiples of half unit cells in thickness have been observed which occur at the growth interface between the Si(11¯1) buffer layer and the overlying Ge material. Models of the growth mechanisms to explain the interfacial configurations of each type of wafer are suggested. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Silver ion bactericide system. [for Space Shuttle Orbiter potable water

NASA Technical Reports Server (NTRS)

Jasionowski, W. J.; Allen, E. T.

1974-01-01

Description of a preliminary flight prototype system which uses silver ions as the bactericide to preserve sterility of the water used for human consumption and hygiene in the Space Shuttle Orbiter. The performance of silver halide columns for passively dosing fuel cell water with silver ions is evaluated. Tests under simulated Orbiter mission conditions show that silver ion doses of 0.05 ppm are bactericidal for Pseudomonas aeruginosa and Type IIIa, the two bacteria found in Apollo potable water systems. The design of the Advance Prototype Silver Ion Water Bactericide System now under development is discussed.

Silver Trees: Chemistry on a TEM Grid

EPA Science Inventory

The copper/carbon substrate of a TEM grid reacted with aqueous silver nitrate solution within minutes to yield spectacular tree-like silver dendrites, without using any added capping or reducing reagents. These results demonstrate a facile, aqueous, room temperature synthesis of...

Silver disinfection in water distribution systems

NASA Astrophysics Data System (ADS)

Silvestry Rodriguez, Nadia

Silver was evaluated as disinfectant to maintain water quality in water distribution system. It was used to inhibit growth of two opportunistic bacteria in planktonik form and in biofilm formation in Robbins devices with stainless steel and PVC surfaces. The results of this work show that silver is a potential secondary disinfectant to be used in water distribution systems.

Direct patterning of silver particles on porous silicon by inkjet printing of a silver salt via in-situ reduction

PubMed Central

2012-01-01

We have developed a method for obtaining a direct pattern of silver nanoparticles (NPs) on porous silicon (p-Si) by means of inkjet printing (IjP) of a silver salt. Silver NPs were obtained by p-Si mediated in-situ reduction of Ag+ cations using solutions based on AgNO3 which were directly printed on p-Si according to specific geometries and process parameters. The main difference with respect to existing literature is that normally, inkjet printing is applied to silver (metal) NP suspensions, while in our experiment the NPs are formed after jetting the solution on the reactive substrate. We performed both optical and scanning electron microscopes on the NPs traces, correlating the morphology features with the IjP parameters, giving an insight on the synthesis kinetics. The patterned NPs show good performances as SERS substrates. PMID:22953722

Bacterial growth on a superhydrophobic surface containing silver nanoparticles

NASA Astrophysics Data System (ADS)

Heinonen, S.; Nikkanen, J.-P.; Laakso, J.; Raulio, M.; Priha, O.; Levänen, E.

2013-12-01

The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.

Hydroxyapatite-silver nanoparticles coatings on porous polyurethane scaffold.

PubMed

Ciobanu, Gabriela; Ilisei, Simona; Luca, Constantin

2014-02-01

The present paper is focused on a study regarding the possibility of obtaining hydroxyapatite-silver nanoparticle coatings on porous polyurethane scaffold. The method applied is based on a combined strategy involving hydroxyapatite biomimetic deposition on polyurethane surface using a Supersaturated Calcification Solution (SCS), combined with silver ions reduction and in-situ crystallization processes on hydroxyapatite-polyurethane surface by sample immersing in AgNO3 solution. The morphology, composition and phase structure of the prepared samples were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. The data obtained show that a layer of hydroxyapatite was deposited on porous polyurethane support and the silver nanoparticles (average size 34.71 nm) were dispersed among and even on the hydroxyapatite crystals. Hydroxyapatite/polyurethane surface acts as a reducer and a stabilizing agent for silver ions. The surface plasmon resonance peak in UV-Vis absorption spectra showed an absorption maximum at 415 nm, indicating formation of silver nanoparticles. The hydroxyapatite-silver polyurethane scaffolds were tested against Staphylococcus aureus and Escherichia coli and the obtained data were indicative of good antibacterial properties of the materials. © 2013.

25 CFR 304.7 - Eligibility of silver meeting standards.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 25 Indians 2 2010-04-01 2010-04-01 false Eligibility of silver meeting standards. 304.7 Section 304.7 Indians INDIAN ARTS AND CRAFTS BOARD, DEPARTMENT OF THE INTERIOR NAVAJO, PUEBLO, AND HOPI SILVER... currently made in compliance with the standards of the Indian Arts and Crafts Board, other silver products...

Powerful colloidal silver nanoparticles for the prevention of gastrointestinal bacterial infections

NASA Astrophysics Data System (ADS)

Le, Anh-Tuan; Tam Le, Thi; Quy Nguyen, Van; Hoang Tran, Huy; Dang, Duc Anh; Tran, Quang Huy; Vu, Dinh Lam

2012-12-01

In this work we have demonstrated a powerful disinfectant ability of colloidal silver nanoparticles (NPs) for the prevention of gastrointestinal bacterial infections. The silver NPs colloid was synthesized by a UV-enhanced chemical precipitation. Two gastrointestinal bacterial strains of Escherichia coli (ATCC 43888-O157:k-:H7) and Vibrio cholerae (O1) were used to verify the antibacterial activity of the as-prepared silver NPs colloid by means of surface disinfection assay in agar plates and turbidity assay in liquid media. Transmission electron microscopy was also employed to analyze the ultrastructural changes of bacterial cells caused by silver NPs. Noticeably, our silver NPs colloid displayed a highly effective bactericidal effect against two tested gastrointestinal bacterial strains at a silver concentration as low as ˜3 mg l-1. More importantly, the silver NPs colloid showed an enhancement of antibacterial activity and long-lasting disinfectant effect as compared to conventional chloramin B (5%) disinfection agent. These advantages of the as-prepared colloidal silver NPs make them very promising for environmental treatments contaminated with gastrointestinal bacteria and other infectious pathogens. Moreover, the powerful disinfectant activity of silver-containing materials can also help in controlling and preventing further outbreak of diseases.

Hyaluronan- and heparin-reduced silver nanoparticles with antimicrobial properties

PubMed Central

Kemp, Melissa M; Kumar, Ashavani; Clement, Dylan; Ajayan, Pulickel; Mousa, Shaker

2009-01-01

Aims Silver nanoparticles exhibit unique antibacterial properties that make these ideal candidates for biological and medical applications. We utilized a clean method involving a single synthetic step to prepare silver nanoparticles that exhibit antimicrobial activity. Materials & methods These nanoparticles were prepared by reducing silver nitrate with diaminopyridinylated heparin (DAPHP) and hyaluronan (HA) polysaccharides and tested for their efficacy in inhibiting microbial growth. Results & discussion The resulting silver nanoparticles exhibit potent antimicrobial activity against Staphylococcus aureus and modest activity against Escherichia coli. Silver–HA showed greater antimicrobial activity than silver–DAPHP, while silver–glucose nanoparticles exhibited very weak antimicrobial activity. Neither HA nor DAPHP showed activity against S. aureus or E. coli. Conclusion These results suggest that DAPHP and HA silver nanoparticles have potential in antimicrobial therapeutic applications. PMID:19505245

Canary Islands

NASA Technical Reports Server (NTRS)

1992-01-01

This easterly looking view shows the seven major volcanic islands of the Canary Island chain (28.0N, 16.5W) and offers a unique view of the islands that have become a frequent vacation spot for Europeans. The northwest coastline of Africa, (Morocco and Western Sahara), is visible in the background. Frequently, these islands create an impact on local weather (cloud formations) and ocean currents (island wakes) as seen in this photo.

Recent Developments in Silver/Zinc Rechargeable Cell Studies

NASA Technical Reports Server (NTRS)

Lewis, Harlan L.

2001-01-01

This viewgraph presentation discusses silver/zinc cell casing configurations and test results examining discharge capacity and silver migration comparisons. The following recommendations were proposed: 1) Use silver-treated cellophane instead of clear cellophane; 2) Use split wrap for cellophane whenever possible; and 3) Strongly consider use of sausage casing with PVA film in the following configuration: 1-mil (tubular) SC/1-mil PVA film/2.3-mil plain or 6-mil fiber-reinforced SC tubular.

The photoactivity of titanium dioxide coatings with silver nanoparticles prepared by sol-gel and reactive magnetron sputtering methods - comparative studies

NASA Astrophysics Data System (ADS)

Kądzioła, Kinga; Piwoński, Ireneusz; Kisielewska, Aneta; Szczukocki, Dominik; Krawczyk, Barbara; Sielski, Jan

2014-01-01

Titanium dioxide coatings were deposited on silicon substrates using two different methods: sol-gel dip-coating (SG) and reactive magnetron sputtering (MS). In order to obtain anatase phase, as-prepared coatings were calcined at 500 °C in air. Subsequently, silver nanoparticles (AgNPs) were grown on the surface of TiO2 coatings by photoreduction of silver ions, initiated by illumination of the UV lamp operated at λ = 365 nm. The concentrations of silver ions were 0.1 mmol dm-3 and 1.0 mmol dm-3. Coatings immersed in these solutions were illuminated during 5 min and 30 min. The coating thicknesses, evaluated by ellipsometry, were 118 nm and 147 nm for SG and MS methods, respectively. Atomic force microscopy (AFM) imaging revealed that the surface roughness of TiO2 coating prepared by MS is about 6 times larger as compared to coatings prepared by SG method. The size of AgNPs deposited on SG and MS coatings were in the range of 17-132 nm and 54-103 nm respectively. The photoactivity of AgNPs/TiO2 coatings was determined by the measurement of the decomposition rate of bisphenol A (BPA). The concentration of BPA before and after illumination under UV light (λ = 365 nm) was monitored by high-performance liquid chromatography (HPLC). It was found that AgNPs enhance the photoactivity of the TiO2 coatings.

Photocatalytic silver enhancement reaction for gravimetric immunosensors.

PubMed

Seo, Hyejung; Joo, Jinmyoung; Ko, Wooree; Jung, Namchul; Jeon, Sangmin

2010-12-17

A novel microgravimetric immunosensor has been developed using TiO(2) nanoparticle-modified immunoassay and silver enhancement reaction. An antibody-conjugated TiO(2) nanoparticle is bound to the AFP antigen immobilized on a quartz resonator. When the nanoparticles are exposed to UV light in a silver nitrate solution, the photocatalytic reduction of silver ions results in the formation of metallic silver onto the nanoparticles and induces a decrease in the resonance frequency. The frequency change by this photocatalytic reduction reaction is three orders of magnitude larger than the change by antigen binding alone. The efficiency of the photocatalytic reaction has been found to increase with the fraction of anatase crystallites in the nanoparticles and the concentration of the AgNO(3) solution. The results highlight the potential of the photocatalytic nanoparticles for the detection of low concentrations of target molecules using gravimetric sensors.

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

33 CFR 13.01-10 - Gold and silver bars.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Gold and silver bars. 13.01-10... DECORATIONS, MEDALS, RIBBONS AND SIMILAR DEVICES Gold and Silver Lifesaving Medals, Bars, and Miniatures § 13.01-10 Gold and silver bars. No person shall receive more than one Gold Lifesaving Medal and one...

Feasibility of the silver-UV process for drinking water disinfection.

PubMed

Butkus, Michael A; Talbot, Mark; Labare, Michael P

2005-12-01

A synergistic effect between cationic silver and UV radiation (silver-UV disinfection) has been observed that can appreciably enhance inactivation of viruses. The purpose of this work was to assess the feasibility of this technique for drinking water disinfection and evaluate the effects of selected impurities, found in fresh water, and common parameters on inactivation of the coliphage MS-2 with the silver-UV process. Turbidity (kaolin), calcium hardness, carbonate alkalinity, and pH did not significantly degrade inactivation. Inactivation was reduced in the presence of chloride, at concentrations greater than 30 mg/L, and in water samples with UV-254 absorbance values greater than ca. 0.1 cm(-1). Inactivation of MS-2 with silver-UV disinfection was also reduced at high phosphate concentrations (above ca. 5 mM). Silver-UV inactivation of MS-2 increased with increases in temperature between 10 and 20 degrees C. Silver-UV inactivation of MS-2 was increased by greater than 1-log over UV alone, in two untreated fresh water sources, which indicates that silver-UV may be a viable treatment technology. An assessment of operation and management costs suggests that an increase in inactivation of MS-2 with silver-UV disinfection could be economically beneficial.

Determination of silver nanoparticle release from antibacterial fabrics into artificial sweat

PubMed Central

2010-01-01

Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles. PMID:20359338

Reduction in Wound Bioburden using a Silver-Loaded Dissolvable Microfilm Construct

PubMed Central

Herron, Maggie; Agarwal, Ankit; Kierski, Patricia R.; Calderon, Diego F.; Teixeira, Leandro B. C.; Schurr, Michael J.; Murphy, Christopher J.

2014-01-01

Silver is a widely used antimicrobial agent, yet when impregnated in macroscopic dressings, it stains wounds, can lead to tissue toxicity and can inhibit healing. Recently, we reported that polymeric nanofilms containing silver nanoparticles exhibit antimicrobial activity at loadings and release rates of silver that are 100x lower than conventional dressings. Here we report fabrication of composite microfilm constructs that provide a facile way to transfer the silver-loaded polymeric nanofilms onto wounds in vivo. The construct is fabricated from a silver nanoparticle-loaded polymeric nanofilm that is laminated with a micrometer-thick soluble film of polyvinylalcohol (PVA). When placed on a moist wound, the PVA dissolves, leaving the silver-loaded nanofilm immobilized on the wound-bed. In vitro, the immobilized nanofilms release <1 μg cm−2/day of silver over 30 days from skin-dermis and they kill 5 log10 CFUs of Staphylococcus aureus in 24 h. In mice, wounds inoculated with 105 CFU S. aureus presented up to 3 log10 less bacterial burden when treated with silver/nanofilms for 3 days, as compared to unmodified wounds. In uncontaminated wounds, silver/nanofilms allow normal and complete wound closure by re-epithelialization. We conclude that dissolvable microfilm constructs may overcome key limitations associated with current uses of silver in wound healing. PMID:24523027

Indium hexagonal island as seed-layer to boost a-axis orientation of AlN thin films

NASA Astrophysics Data System (ADS)

Redjdal, N.; Salah, H.; Azzaz, M.; Menari, H.; Manseri, A.; Guedouar, B.; Garcia-Sanchez, A.; Chérif, S. M.

2018-06-01

Highly a-axis oriented aluminum nitride films have been grown on Indium coated (100) Si substrate by DC reactive magnetron sputtering. It is shown that In incorporated layer improve the extent of preferential growth along (100) axis and form dense AlN films with uniform surface and large grains, devoid of micro-cracks. As revealed by SEM cross section images, AlN structure consists of oriented columnar grains perpendicular to the Si surface, while AlN/In structure results in uniformely tilted column. SEM images also revealed the presence of In hexagonal islands persistent throughout the entire growth. Micro -Raman spectroscopy of the surface and the cross section of the AlN/In grown films evidenced their high degree of homogeneity and cristallinity.

Biosynthesis of Gold and Silver Nanoparticles Using Extracts of Callus Cultures of Pumpkin (Cucurbita maxima).

PubMed

Iyer, R Indira; Panda, Tapobrata

2018-08-01

The potential of callus cultures and field-grown organs of pumpkin (Cucurbita maxima) for the biosynthesis of nanoparticles of the noble metals gold and silver has been investigated. Biosynthesis of AuNPs (gold nanoparticles) and AgNPs (silver nanoparticles) was obtained with flowers of C. maxima but not with pulp and seeds. With callus cultures established in MS-based medium the biogenesis of both AuNPs and AgNPs could be obtained. At 65 °C the biogenesis of AuNPs and AgNPs by callus extracts was enhanced. The AuNPs and AgNPs have been characterized by UV-visible spectroscopy, TEM, DLS and XRD. Well-dispersed nanoparticles, which exhibited a remarkable diversity in size and shape, could be visualized by TEM. Gold nanoparticles were found to be of various shapes, viz., rods, triangles, star-shaped particles, spheres, hexagons, bipyramids, discoid particles, nanotrapezoids, prisms, cuboids. Silver nanoparticles were also of diverse shapes, viz., discoid, spherical, elliptical, triangle-like, belt-like, rod-shaped forms and cuboids. EDX analysis indicated that the AuNPs and AgNPs had a high degree of purity. The surface charges of the generated AuNPs and AgNPs were highly negative as indicated by zeta potential measurements. The AuNPs and AgNPs exhibited remarkable stability in solution for more than four months. FTIR studies indicated that biomolecules in the callus extracts were associated with the biosynthesis and stabilisation of the nanoparticles. The synthesized AgNPs could catalyse degradation of methylene blue and exhibited anti-bacterial activity against E. coli DH5α. There is no earlier report of the biosynthesis of nanoparticles by this plant species. Callus cultures of Cucurbita maxima are effective alternative resources of biomass for synthesis of nanoparticles.

The Alaska Mineral Resource Assessment Program; background information to accompany geologic and mineral-resource maps of the Cordova and Middleton Island quadrangles, southern Alaska

USGS Publications Warehouse

Winkler, Gary R.; Plafker, George; Goldfarb, R.J.; Case, J.E.

1992-01-01

report summarizes recent results of integrated geological, geochemical, and geophysical field and laboratory studies conducted by the U.S. Geological Survey in the Cordova and Middleton Island 1?x3 ? quadrangles of coastal southern Alaska. Published open-file reports and maps accompanied by descriptive and interpretative texts, tables, diagrams, and pertinent references provide background information for a mineral-resource assessment of the two quadrangles. Mines in the Cordova and Middleton Island quadrangles produced copper and byproduct gold and silver in the first three decades of the 20th century. The quadrangles may contain potentially significant undiscovered resources of precious and base metals (gold, silver, copper, zinc, and lead) in veins and massive sulfide deposits hosted by Cretaceous and Paleogene sedimentary and volcanic rocks. Resources of manganese also may be present in the Paleogene rocks; uranium resources may be present in Eocene granitic rocks; and placer gold may be present in beach sands near the mouth of the Copper River, in alluvial sands within the canyons of the Copper River, and in smaller alluvial deposits underlain by rocks of the Valdez Group. Significant coal resources are present in the Bering River area, but difficult access and structural complexities have discouraged development. Investigation of numerous oil and gas seeps near Katalla in the eastern part of the area led to the discovery of a small, shallow field from which oil was produced between 1902 and 1933. The field has been inactive since, and subsequent exploration and drilling onshore near Katalla in the 1960's and offshore near Middleton Island on the outer continental shelf in the 1970's and 1980's was not successful.

Island-Trapped Waves, Internal Waves, and Island Circulation

DTIC Science & Technology

2014-09-30

from the government of Palau to allow us to deliver some water and food to the officers. Governor Patris of Hatohobei State and the Coral Reef ...Island-trapped waves , internal waves , and island circulation T. M. Shaun Johnston Scripps Institution of Oceanography University of California...large islands (Godfrey, 1989; Firing et al., 1999); • Westward propagating eddies and/or Rossby waves encounter large islands and produce boundary

Chemical element accumulation in tree bark grown in volcanic soils of Cape Verde-a first biomonitoring of Fogo Island.

PubMed

Marques, Rosa; Prudêncio, Maria Isabel; Freitas, Maria do Carmo; Dias, Maria Isabel; Rocha, Fernando

2017-05-01

Barks from Prosopis juliflora (acacia) were collected in 12 sites of different geological contexts over the volcanic Fogo Island (Cape Verde). Elemental contents of Ba, Br, Co, Cr, Fe, K, Na, Zn and some rare earth elements (REE)-La, Ce, Sm, Eu, Tb, Yb, and Lu, were obtained for biological samples and topsoils by using k 0 -standardized and comparative method of instrumental neutron activation analysis (INAA), aiming the evaluation of chemical elements uptake by acacia bark. This first biomonitoring study of Fogo Island showed that, in general, significant accumulations of trace elements present in high amounts in these soils occur. This can be partially explained by the semi-arid climate with a consequent bioavailability of chemical elements when rain drops fall in this non-polluted environment. REE enrichment factors (EFs) increase with the decrease of ionic radius. Heavy REE (HREE) are significantly enriched in bark, which agrees with their release after the primary minerals breakdown and the formation of more soluble compounds than the other REE, and uptake by plants. Among the potential harmful chemical elements, Cr appears to be partially retained in nanoparticles of iron oxides. The high EFs found in tree barks of Fogo Island are certainly of geogenic origin rather than anthropogenic input since industry and the use of fertilizers is scarce.

Shell crosslinked nanoparticles carrying silver antimicrobials as therapeutics†

PubMed Central

Li, Yali; Hindi, Khadijah; Watts, Kristin M.; Taylor, Jane B.; Zhang, Ke; Li, Zicheng

2010-01-01

Amphiphilic polymer nanoparticles loaded with silver cations or/and N-heterocyclic carbene–silver complexes were assessed as antimicrobial agents against Gram-negative pathogens Escherichia coli and Pseudomonas aeruginosa. PMID:20024313

25 CFR 304.3 - Classifying and marking of silver.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Indians INDIAN ARTS AND CRAFTS BOARD, DEPARTMENT OF THE INTERIOR NAVAJO, PUEBLO, AND HOPI SILVER, USE OF GOVERNMENT MARK § 304.3 Classifying and marking of silver. For the present the Indian Arts and Crafts Board... Government mark. All such marking of silver shall, for the present, be done by an agent of the Indian Arts...

Autocatalytic Patterning with Silver Using Tin(II) Chloride Sensitizer

ERIC Educational Resources Information Center

Mbindyo, Jeremiah K. N.; Anna, Laura J.; Fell, B. Andrew; Patton, David A.

2011-01-01

A silver mirror can be deposited on many types of surfaces from the reduction of the silver-diammine complex by a reducing sugar as proposed by Kemp in this "Journal". Three extensions of Kemp's demonstration that highlight the role of SnCl[subscript 2] sensitizer in the deposition of a silver mirror on surfaces are presented. The demonstration…

Cytotoxicity and genotoxicity of biogenic silver nanoparticles

NASA Astrophysics Data System (ADS)

Lima, R.; Feitosa, L. O.; Ballottin, D.; Marcato, P. D.; Tasic, L.; Durán, N.

2013-04-01

Biogenic silver nanoparticles with 40.3 ± 3.5 nm size and negative surface charge (- 40 mV) were prepared with Fusarium oxysporum. The cytotoxicity of 3T3 cell and human lymphocyte were studied by a TaliTM image-based cytometer and the genotoxicity through Allium cepa and comet assay. The results of BioAg-w (washed) and BioAg-nw (unwashed) biogenic silver nanoparticles showed cytotoxicity exceeding 50 μg/mL with no significant differences of response in 5 and 10 μg/mL regarding viability. Results of genotoxicity at concentrations 5.0 and 10.0 ug/mL show some response, but at concentrations 0.5 and 1.0 μg/mL the washed and unwashed silver nanoparticles did not present any effect. This in an important result since in tests with different bacteria species and strains, including resistant, MIC (minimal inhibitory concentration) had good answers at concentrations less than 1.9 μg/mL. This work concludes that biogenic silver nanoparticles may be a promising option for antimicrobial use in the range where no cyto or genotoxic effect were observed. Furthermore, human cells were found to have a greater resistance to the toxic effects of silver nanoparticles in comparison with other cells.

Eco-geomorphic processes that maintain a small coral reef island: Ballast Island in the Ryukyu Islands, Japan

NASA Astrophysics Data System (ADS)

Kayanne, Hajime; Aoki, Kenji; Suzuki, Takuya; Hongo, Chuki; Yamano, Hiroya; Ide, Yoichi; Iwatsuka, Yuudai; Takahashi, Kenya; Katayama, Hiroyuki; Sekimoto, Tsunehiro; Isobe, Masahiko

2016-10-01

Landform changes in Ballast Island, a small coral reef island in the Ryukyu Islands, were investigated by remote sensing analysis and a field survey. The area of the island almost doubled after a mass coral bleaching event in 1998. Coral branches generated by the mass mortality and broken by waves were delivered and stocked on a reef flat and accumulated to expand the area of the island. In 2012 high waves generated by typhoons also changed the island's topography. Overall, the island moved in the downdrift direction of the higher waves. Waves impacting both sides of the island piled up a large volume of coral gravels above the high-tide level. Eco-geomorphic processes, including a supply of calcareous materials from the corals on the same reef especially during stormy wave conditions, were key factors in maintaining the dynamic topographic features of this small coral reef island.

Galapagos Islands

NASA Technical Reports Server (NTRS)

2002-01-01

This true-color image of the Galapagos Islands was acquired on March 12, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. The Galapagos Islands, which are part of Ecuador, sit in the Pacific Ocean about 1000 km (620 miles) west of South America. As the three craters on the largest island (Isabela Island) suggest, the archipelago was created by volcanic eruptions, which took place millions of years ago. Unlike most remote islands in the Pacific, the Galapagos have gone relatively untouched by humans over the past few millennia. As a result, many unique species have continued to thrive on the islands. Over 95 percent of the islands' reptile species and nearly three quarters of its land bird species cannot be found anywhere else in the world. Two of the more well known are the Galapagos giant tortoise and marine iguanas. The unhindered evolutionary development of the islands' species inspired Charles Darwin to begin The Origin of Species eight years after his visit there. To preserve the unique wildlife on the islands, the Ecuadorian government made the entire archipelago a national park in 1959. Each year roughly 60,000 tourists visit these islands to experience what Darwin did over a century and a half ago. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

31 CFR 56.1 - Conditions upon which silver will be sold.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Conditions upon which silver will be sold. 56.1 Section 56.1 Money and Finance: Treasury Regulations Relating to Money and Finance DOMESTIC GOLD AND SILVER OPERATIONS SALE OF SILVER § 56.1 Conditions upon which silver will be sold. The General...

Molecular beam epitaxially grown copper indium diselenide and copper gallium diselenide films

NASA Astrophysics Data System (ADS)

Yoon, Seokhyun

2005-12-01

To eliminate the influence of grain boundaries, CuInSe2 (CIS) and CuGaSe2 (CGS) films were grown on (100) GaAs wafers. The effects of Cu to III metal ratio and dosing with Na on the growth mode and defect properties were studied at two growth temperatures. The impact of post-annealing in Se on the defect structure of CGS film was also studied. Two-dimensional simulations were used to better understand the role of grain boundary on cell performance. For growth at 360°C, the In-rich CIS films were polycrystalline, whereas the Cu-rich CIS films were epitaxial exhibiting a Stranski-Krastanov (S-K) growth mode. It is proposed that a Cu-Se secondary phase enhances the mobility of adatoms, allowing epitaxial growth to a critical thickness, at which point segregation at the nucleation sites became faster the rate of growth. Island structures, embedded in a matrix region, were oriented along the [01-1] directed edges with surface undulations apparent on the matrix surface with dominant {112} crystal planes. At the higher growth temperature of 464°C, the CIS films grew epitaxially without the need of a Cu-Se phase. Both CIS films grown at low and high temperatures were nearly relaxed. The segregation of epitaxial Cu1.5Se was also observed in the Cu-rich, Na-dosed CIS film, which is attributed to a surfactant effect of Na. At a growth temperature of 438°C, CGS films showed a S-K growth mode and nearly pseudomorphic growth. Hemispherical islands with twins were observed in the Ga-rich CGS films and epitaxial Cu1.5Se phase were identified in the top region of the island structure. From the PL analysis of Cu-rich, Na-dosed CGS film after Se-annealing, a new defect level located 20 meV above the valence band edge was identified as NaGa acceptor state. Two-dimensional simulation of the impact of grain boundaries on device performance showed that the short circuit current decreases sharply along with the other device parameters below a critical grain size due to the complete

Green Synthesis of Silver Nanoparticles by using Eucalyptus Globulus Leaf Extract

NASA Astrophysics Data System (ADS)

Balamurugan, Madheswaran; Saravanan, Shanmugam

2017-12-01

A single step eco-friendly, energy efficient and economically scalable green method was employed to synthesize silver nanoparticles. In this work, the synthesis of silver nanoparticles using Eucalyptus globulus leaf extract as reducing and capping agent along with water as solvent at normal room temperature is described. Silver nanoparticles were prepared from aqueous silver nitrate solution by adding the leaf extract. The prepared nanoparticles were characterized by using UV-visible Spectrophotometer, X-ray diffractometer, High Resolution Transmission Electron Microscope (HR-TEM) and Fourier Transform Infrared Spectroscope (FTIS). X-ray diffraction studies brought to light the crystalline nature and the face centered cubic structure of the silver nanoparticles. Using HR-TEM. the nano sizes and morphology of the particles were studied. The mean sizes of the prepared silver nanoparticles ranged from 30 to 36 nm. The density of the particles was tuned by varying the molar ratio of silver nitrate. FTIS studies showed the functional group of organic molecules which were located on the surface of the silver nanoparticles. Originating from the leaf extracts, these organic molecules reduced and capped the particles.

Impact of chlorination on silver elution from ceramic water filters.

PubMed

Lyon-Marion, Bonnie A; Mittelman, Anjuliee M; Rayner, Justine; Lantagne, Daniele S; Pennell, Kurt D

2018-06-05

Applying silver nanoparticles (nAg) or silver nitrate (AgNO 3 ) to ceramic water filters improves microbiological efficacy, reduces biofilm formation, and protects stored water from recontamination. A challenge in ceramic filter production is adding sufficient silver to achieve these goals without exceeding the maximum recommended silver concentration in drinking water. Silver release is affected by silver type, application method, and influent water chemistry. Despite a lack of data, there is an assumption that chlorinated water should not be used as influent water because it may increase silver elution. Thus, the objective of this work was to systematically evaluate the impact of chlorinated water (0-4 mg/L free chlorine residual, FCR) on silver release from ceramic filter disks painted with casein-coated nAg, painted with AgNO 3 , or containing fired-in nAg over a range of ionic strength (IS = 0-10 mM as NaNO 3 ) in the presence or absence of natural organic matter (NOM). Influent deionized water containing chlorine increased silver release 2-5-fold compared to controls. However, this effect of chlorine was mitigated at higher IS (≥1 mM) or in the presence of NOM (3 mg C/L). For filter disks painted with nAg or AgNO 3 , silver release increased with increasing IS (with or without chlorine), and effluent concentrations remained above the World Health Organization (WHO) guideline of 0.1 mg/L even after 30 h (80 pore volumes, PVs) of flow with a background solution of 10 mM NaNO 3 . Silver speciation (nAg vs. Ag + ) was monitored in effluent samples from painted or fired-in nAg filter disks. Results indicated that in general, greater than 90% of the eluted silver was due to Ag + dissolution rather than nAg release. Additionally, a filter disk prepared with fired-in nAg exhibited a lower % released in the nanoparticle form (nAg = 5% of total Ag in effluent) compared to painted on nAg (nAg = 14% of total Ag in effluent). The findings of

Antibacterial and catalytic activities of green synthesized silver nanoparticles.

PubMed

Bindhu, M R; Umadevi, M

2015-01-25

The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis. The synthesized nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface plasmon resonance peak of synthesized nanoparticles was observed at 438 nm. As the concentration of beetroot extract increases, absorption spectra shows blue shift with decreasing particle size. The prepared silver nanoparticles were well dispersed, spherical in shape with the average particle size of 15 nm. The prepared silver nanoparticles are effective in inhibiting the growth of both gram positive and gram negative bacteria. The prepared silver nanoparticles reveal faster catalytic activity. This natural method for synthesis of silver nanoparticles offers a valuable contribution in the area of green synthesis and nanotechnology avoiding the presence of hazardous and toxic solvents and waste. Copyright © 2014 Elsevier B.V. All rights reserved.

Nonlinear Conductive Behaviour of Silver Nanowires/Silicone Rubber Composites

NASA Astrophysics Data System (ADS)

Lu, Pin; Qu, Zhaoming; Wang, Qingguo; Bai, Liyun; Zhao, Shiyang

2018-01-01

Silver nanowires with an average length of 10 μm and diameter of about 90 nm have been synthesized by polyol reduction of silver nitrate in the presence of polyvinylpyrrolidone(PVP). Silver nanowires (AgNWs)/silicone rubber (SR) composites have been made by mixing silver nanowires into silicone rubber. The nonlinear response of AgNWs/SR composites under high electric field is investigated. The nonlinear Conductive behavior of composites is considered as a competitive process of several effects. From the perspective of the microstructure of composites, the conductive path is established by the quantum tunnel effect between silver nanowires. The influence factors on the conductivity of composites are discussed and analyzed. The results show that the AgNWs/SR composites with nonlinear conductive properties are of great potential application in electromagnetic protection of electron device and system.

Sonochemical Synthesis of Silver Nanoparticles Using Starch: A Comparison

PubMed Central

Smita, Kumari; Cumbal, Luis; Debut, Alexis; Pathak, Ravinandan Nath

2014-01-01

A novel approach was applied to synthesize silver nanoparticles using starch under sonication. Colloidal silver nanoparticles solution exhibited an increase of absorption from 420 to 440 nm with increase starch quantity. Transmission electron microscopy followed by selected area electron diffraction pattern analysis indicated the formation of spherical, polydispersed, amorphous, silver nanoparticles of diameter ranging from 23 to 97 nm with mean particle size of 45.6 nm. Selected area electron diffraction (SAED) confirmed partial crystalline and amorphous nature of silver nanoparticles. Silver nanoparticles synthesized in this manner can be used for synthesis of 2-aryl substituted benzimidazoles which have numerous biomedical applications. The optimized reaction conditions include 10 ml of 1 mM AgNO3, 25 mg starch, 11 pH range, and sonication for 20 min at room temperature. PMID:24587771

Three-body wear of a hand-consolidated silver alternative to amalgam.

PubMed

Xu, H H; Eichmiller, F C; Giuseppetti, A A; Ives, L K; Parry, E E; Schumacher, G E

1999-09-01

Recent studies have investigated a mercury-free silver alternative to amalgam, but the silver powders required a relatively high compaction pressure to consolidate. The aim of the present study was to consolidate a precipitated silver powder into a cohesive solid using an air-driven pneumatic condenser fitted with an amalgam plugger at a clinically realistic load, and to study the mechanisms and rates of three-body wear of the consolidated silver in comparison with that of an amalgam. The silver powder was annealed, rinsed with a dilute acid, and consolidated either in a prepared tooth cavity or in a specimen mold at a load of 15 N. A four-station wear machine was used where each specimen was immersed in a slurry containing polymethyl methacrylate beads, then a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. The flexural strength in MPa (mean +/- SD; n = 10) was 86 +/- 20 for amalgam, 181 +/- 45 for silver with a polished surface, and 202 +/- 21 for silver with a burnished surface. After 4 x 10(5) wear cycles, the wear scar depth in microm was 134 +/- 54 for amalgam, 143 +/- 8 for polished silver, and 131 +/- 9 for burnished silver, which were not significantly different (Tukey's multiple comparison test; family confidence coefficient = 0.95). SEM examination revealed cracks and fracture pits in the worn surface of amalgam, in contrast to a smooth surface in silver. Wear and material removal in amalgam occurred by microfracture and dislodgement of cracked segments, while wear in the silver occurred by ductile deformation and flow of materials. To conclude, the consolidated silver possesses a three-body wear resistance similar to that of amalgam, and a higher resistance to wear-induced damage and cracking than amalgam. The mechanism of wear in amalgam is microfracture and material dislodgement, while that in consolidated silver is ductile deformation and flow of material.

Biological evaluation of silver nanoparticles incorporated into chitosan-based membranes.

PubMed

Shao, Jinlong; Yu, Na; Kolwijck, Eva; Wang, Bing; Tan, Ke Wei; Jansen, John A; Walboomers, X Frank; Yang, Fang

2017-11-01

To evaluate the antibacterial potential and biological performance of silver nanoparticles in chitosan-based membranes. Electrospun chitosan/poly(ethylene oxide) membranes with different amounts of silver nanoparticles were evaluated for antibacterial properties and cytotoxicity in vitro and for tissue response in a rabbit subcutaneous model. The nanoparticles displayed dose-dependent antibacterial properties against Porphyromonas gingivalis and Fusobacterium nucleatum, without showing noticeable cytotoxicity. The membranes with silver nanoparticles evoked a similar inflammatory response compared with the membranes without silver nanoparticles. The antibacterial effect, combined with the findings on cyto- and biocompatibility warrants further investigation to the usefulness of chitosan/poly(ethylene oxide) membranes with silver nanoparticles, for clinical applications like guided tissue regeneration.

The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes

PubMed Central

Seo, Tae Hoon; Lee, Seula; Min, Kyung Hyun; Chandramohan, S.; Park, Ah Hyun; Lee, Gun Hee; Park, Min; Suh, Eun-Kyung; Kim, Myung Jong

2016-01-01

This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs. PMID:27387274

The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes

NASA Astrophysics Data System (ADS)

Seo, Tae Hoon; Lee, Seula; Min, Kyung Hyun; Chandramohan, S.; Park, Ah Hyun; Lee, Gun Hee; Park, Min; Suh, Eun-Kyung; Kim, Myung Jong

2016-07-01

This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs.

One-step microwave-assisted colloidal synthesis of hybrid silver oxide/silver nanoparticles: characterization and catalytic study

NASA Astrophysics Data System (ADS)

Prakoso, S. P.; Taufik, A.; Saleh, R.

2017-04-01

This study reports the characterization and catalytic activities of silver-oxide/silver nanoparticles (Ag2O/Ag NPs) synthesized by microwave-assisted colloidal method in the presence of anionic sodium dodecyl sulfate (SDS) surfactant. To promote different contents of silver in silver oxide, the volume ratio (VR) of ethylene glycol (EG) was varied (VR: 10% to 14%) in relation to the total volume of distilled water solvent. The plasmonic resonance of Ag2O/Ag NPs could be detected around a wavelength of 350 nm, and it is suggested that Ag2O/Ag NPs were successfully formed in the colloid solution following exposure to microwaves. Additionally, the growth rate for each crystal phase within Ag2O and Ag was influenced by an increase of EG as revealed by x-ray diffraction patterns. The morphology, average diameter, and uniformity of Ag2O/Ag NPs were studied simultaneously by transmission electron microscopy. Infrared absorption measurement of Ag2O/Ag NPs confirmed the existence of SDS surfactant as a protective agent. Based on the characterization data, Ag2O/Ag NPs synthesized using this technique exhibited good properties, with high-yield production of NPs. The photocatalytic experiments demonstrate the key role of the crystal phase of Ag2O/Ag NPs in photocatalytic efficiency.

Understanding long-term silver release from surface modified porous titanium implants.

PubMed

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2017-08-01

Prevention of orthopedic device related infection (ODRI) using antibiotics has met with limited amount of success and is still a big concern during post-surgery. As an alternative, use of silver as an antibiotic treatment to prevent surgical infections is being used due to the well-established antimicrobial properties of silver. However, in most cases silver is used in particulate form with wound dressings or with short-term devices such as catheters but not with load-bearing implants. We hypothesize that strongly adherent silver to load-bearing implants can offer longer term solution to infection in vivo. Keeping that in mind, the focus of this study was to understand the long term release study of silver ions for a period of minimum 6months from silver coated surface modified porous titanium implants. Implants were fabricated using a LENS™ system, a powder based additive manufacturing technique, with at least 25% volume porosity, with and without TiO 2 nanotubes in phosphate buffer saline (pH 7.4) to see if the total release of silver ions is within the toxic limit for human cells. Considering the fact that infection sites may reduce the local pH, silver release was also studied in acetate buffer (pH 5.0) for a period of 4weeks. Along with that, the osseointegrative properties as well as cytotoxicity of porous titanium implants were assessed in vivo for a period of 12weeks using a rat distal femur model. In vivo results indicate that porous titanium implants with silver coating show comparable, if not better, biocompatibility and bonding at the bone-implant interface negating any concerns related to toxicity related to silver to normal cells. The current research is based on our recently patented technology, however focused on understanding longer-term silver release to mitigate infection related problems in load-bearing implants that can even arise several months after the surgery. Prevention of orthopedic device related infection using antibiotics has met

21 CFR 872.3840 - Endodontic silver point.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Endodontic silver point. 872.3840 Section 872.3840 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3840 Endodontic silver point. (a) Identification...

Ober's Island, One of the Review Islands on Rainy Lake, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Ober's Island, One of the Review Islands on Rainy Lake, bounded on the south by The Hawk Island and on the north by The Crow Island. These islands are located seven miles east of Ranier, Minnesota, three miles west of Voyageur National Park, and one mile south of the international border of the United States of America and Canada. The legal description of Mallard Island is Lot 6, Section 19, T-17-N, R-22-W, Koochiching County, Minnesota, Ranier, Koochiching County, MN

Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.

2017-10-01

Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

Antimicrobial activity of silver nanoparticles synthesized using honey and gamma radiation against silver-resistant bacteria from wounds and burns

NASA Astrophysics Data System (ADS)

Hosny, A. M. S.; Kashef, M. T.; Rasmy, S. A.; Aboul-Magd, D. S.; El-Bazza, Z. E.

2017-12-01

Silver nanoparticles (AgNPs) are promising antimicrobial agents for treatment of wounds and burns. We synthesized AgNPs using honey at different pH values or with different gamma irradiation doses. The resulting nanoparticles were characterized by UV-vis spectroscopy, TEM, DLS and FTIR. Their antimicrobial activity, against standard bacterial strains and silver-resistant clinical isolates from infected wounds and burns, was evaluated in vitro through determination of their minimum inhibitory concentration (MIC). AgNPs prepared using 30 g of honey exposed to 5 kGy gamma radiation had the best physical characters regarding stability and uniformity of particle size and shape. They recorded the lowest MIC values against both the standard and silver-resistant isolates. In conclusion, honey and gamma radiation can be used in synthesis of highly stable pure AgNPs, without affecting the physico-chemical and antimicrobial activity of honey. This offered an advantage in terms of inhibition of silver-resistant bacteria isolates.

Multidecadal shoreline changes of atoll islands in the Marshall Islands

NASA Astrophysics Data System (ADS)

Ford, M.

2012-12-01

Atoll islands are considered highly vulnerable to the impacts of continued sea level rise. One of the most commonly predicted outcomes of continued sea level rise is widespread and chronic shoreline erosion. Despite the widespread implications of predicted erosion, the decadal scale changes of atoll island shorelines are poorly resolved. The Marshall Islands is one of only four countries where the majority of inhabited land is comprised of reef and atoll islands. Consisting of 29 atolls and 5 mid-ocean reef islands, the Marshall Islands are considered highly vulnerable to the impacts of sea level rise. A detailed analysis of shoreline change on over 300 islands on 10 atolls was undertaken using historic aerial photos (1945-1978) and modern high resolution satellite imagery (2004-2012). Results highlight the complex and dynamic nature of atoll islands, with significant shifts in shoreline position observed over the period of analysis. Results suggest shoreline accretion is the dominant mode of change on the islands studied, often associated with a net increase in vegetated island area. However, considerable inter- and intra-atoll variability exists with regards to shoreline stability. Findings are discussed with respect to island morphodynamics and potential hazard mitigation and planning responses within atoll settings.

The electrodeposition of silver composites using deep eutectic solvents.

PubMed

Abbott, Andrew P; El Ttaib, Khalid; Frisch, Gero; Ryder, Karl S; Weston, David

2012-02-21

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.

State-Of-The-Science Review: Everything NanoSilver and More

EPA Science Inventory

Silver has been known to be a potent antibacterial, antifungal and antiviral agent, but in recent years, the use of silver as a biocide in solution, suspension, and especially in nano-particulate form has experienced a dramatic revival. Due to the properties of silver at the nano...

Silver plating technique seals leaks in thin wall tubing joints

NASA Technical Reports Server (NTRS)

Blenderman, W. H.

1966-01-01

Leaks in thin wall tubing joints are sealed by cleaning and silver plating the hot gas side of the joint in the leakage area. The pressure differential across the silver during hydrostatic test and subsequent use forces the ductile silver into the leak area and seals it.

Profiling and Imaging Ion Mobility-Mass Spectrometry Analysis of Cholesterol and 7-Dehydrocholesterol in Cells Via Sputtered Silver MALDI

PubMed Central

Xu, Libin; Kliman, Michal; Forsythe, Jay G.; Korade, Zeljka; Hmelo, Anthony B.; Porter, Ned A.; McLean, John A.

2015-01-01

Profiling and imaging of cholesterol and its precursors by mass spectrometry (MS) are important in a number of cholesterol biosynthesis disorders, such as in Smith-Lemli-Opitz syndrome (SLOS), where 7-dehydrocholesterol (7-DHC) is accumulated in affected individuals. SLOS is caused by defects in the enzyme that reduces 7-DHC to cholesterol. However, analysis of sterols is challenging because these hydrophobic olefins are difficult to ionize for MS detection. We report here sputtered silver matrix-assisted laser desorption/ionization (MALDI)-ion mobility-MS (IM-MS) analysis of cholesterol and 7-DHC. In comparison with liquid-based AgNO3 and colloidal Ag nanoparticle (AgNP), sputtered silver NP (10–25 nm) provided the lowest limits-of-detection based on the silver coordinated [cholesterol+Ag]+ and [7-DHC+Ag]+ signals while minimizing dehydrogenation products ([M+Ag-2H]+). When analyzing human fibroblasts that were directly grown on poly-L-lysine-coated ITO glass plates with this technique, in situ, the 7-DHC/cholesterol ratios for both control and SLOS human fibroblasts are readily obtained. The m/z of 491 (specific for [7-DHC+107Ag]+) and 495 (specific for [cholesterol+109Ag]+) were subsequently imaged using MALDI-IM-MS. MS images were co-registered with optical images of the cells for metabolic ratio determination. From these comparisons, ratios of 7-DHC/cholesterol for SLOS human fibroblasts are distinctly higher than in control human fibroblasts. Thus, this strategy demonstrates the utility for diagnosing/assaying the severity of cholesterol biosynthesis disorders in vitro. PMID:25822928

Profiling and Imaging Ion Mobility-Mass Spectrometry Analysis of Cholesterol and 7-Dehydrocholesterol in Cells Via Sputtered Silver MALDI

NASA Astrophysics Data System (ADS)

Xu, Libin; Kliman, Michal; Forsythe, Jay G.; Korade, Zeljka; Hmelo, Anthony B.; Porter, Ned A.; McLean, John A.

2015-06-01

Profiling and imaging of cholesterol and its precursors by mass spectrometry (MS) are important in a number of cholesterol biosynthesis disorders, such as in Smith-Lemli-Opitz syndrome (SLOS), where 7-dehydrocholesterol (7-DHC) is accumulated in affected individuals. SLOS is caused by defects in the enzyme that reduces 7-DHC to cholesterol. However, analysis of sterols is challenging because these hydrophobic olefins are difficult to ionize for MS detection. We report here sputtered silver matrix-assisted laser desorption/ionization (MALDI)-ion mobility-MS (IM-MS) analysis of cholesterol and 7-DHC. In comparison with liquid-based AgNO3 and colloidal Ag nanoparticle (AgNP), sputtered silver NP (10-25 nm) provided the lowest limits-of-detection based on the silver coordinated [cholesterol + Ag]+ and [7-DHC + Ag]+ signals while minimizing dehydrogenation products ([M + Ag-2H]+). When analyzing human fibroblasts that were directly grown on poly-L-lysine-coated ITO glass plates with this technique, in situ, the 7-DHC/cholesterol ratios for both control and SLOS human fibroblasts are readily obtained. The m/z of 491 (specific for [7-DHC + 107Ag]+) and 495 (specific for [cholesterol + 109Ag]+) were subsequently imaged using MALDI-IM-MS. MS images were co-registered with optical images of the cells for metabolic ratio determination. From these comparisons, ratios of 7-DHC/cholesterol for SLOS human fibroblasts are distinctly higher than in control human fibroblasts. Thus, this strategy demonstrates the utility for diagnosing/assaying the severity of cholesterol biosynthesis disorders in vitro.

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, Paul T.; Rejent, Jerome A.

1995-01-01

A lead-free solder alloy for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0silver composition to a desired level. Melting point ranges from about 218.degree. C. down to about 205.degree. C. depending an the amount of bismuth added to the eutectic tin-silver alloy as determined by DSC analysis, 10.degree. C./min. A preferred alloy composition is 91.84Sn-3.33Ag-4.83Bi (weight percent based on total alloy weight).

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, P.T.; Rejent, J.A.

1995-08-08

A lead-free solder alloy is disclosed for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0silver composition to a desired level. Melting point ranges from about 218 C down to about 205 C depending an the amount of bismuth added to the eutectic tin-silver alloy as determined by DSC analysis, 10 C/min. A preferred alloy composition is 91.84Sn-3.33Ag-4.83Bi (weight percent based on total alloy weight). 4 figs.

Sampling for silver nanoparticles in aqueous media using a rotating disk electrode: evidence for selective sampling of silver nanoparticles in the presence of ionic silver.

PubMed

Steinberg, Spencer; Hodge, Vernon; Schumacher, Brian; Sovocool, Wayne

2017-03-01

Amendment of a carbon paste electrode consisting of graphite and Nujol®, with a variety of organic and inorganic materials, allows direct adsorption of silver nanoparticles (AgNPs) from aqueous solution in either open or close circuit modes. The adsorbed AgNPs are detected by stripping voltammetry. Detection limits of less than 1 ppb Ag are achievable with a rotating disk system. More than one silver peak was apparent in many of the stripping voltammograms. The appearance of multiple peaks could be due to different species of silver formed upon stripping or variation in the state of aggregation or size of nanoparticles. With most of these packing materials, dissolved Ag + was also extracted from aqueous solution, but, with a packing material made with Fe(II,III) oxide nanoparticles, only AgNPs were extracted. Therefore, it is the best candidate for determination of metallic AgNPs in aqueous environmental samples without interference from Ag + .

Silver Film Surface Modification by Ion Bombardment Decreases Surface Plasmon Resonance Absorption.

PubMed

Fryauf, David M; Diaz Leon, Juan J; Phillips, Andrew C; Kobayashi, Nobuhiko P

2017-05-10

Silver thin films covered with dielectric films serving as protective coatings are desired for telescope mirrors, but durable coatings have proved elusive. As part of an effort to develop long-lived protected-silver mirrors, silver thin films were deposited by electron beam evaporation using a physical vapor deposition system at the University of California Observatories Astronomical Coatings Lab. The silver films were later covered with a stack of dielectric films utilizing silicon nitride and titanium dioxide deposited by ion-assisted electron beam evaporation to fabricate protected mirrors. In-situ argon ion bombardment was introduced after silver deposition and prior to the deposition of dielectric films to assess its effects on the performance of the mirrors. We found that ion bombardment of the silver influenced surface morphology and reflectivity, and these effects correlated with time between silver deposition and ion bombardment. The overall reflectivity at wavelengths in the range of 350-800 nm was found to improve due to ion bombardment, which was qualitatively interpreted as a result of decreased surface plasmon resonance coupling. We suggest that the observed decrease in coupling is caused by silver grain boundary pinning due to ion bombardment suppressing silver surface diffusion, forming smoother silver-dielectric interfaces.

[MAXIMUM SINGLE DOSE OF COLLOIDAL SILVER NEGATIVELY AFFECTS ERYTHROPOIESIS IN VITRO].

PubMed

Tishevskayal, N V; Zakharovl, Y M; Bolotovl, A A; Arkhipenko, Yu V; Sazontova, T G

2015-01-01

Erythroblastic islets (EI) of rat bone marrow were cultured for 24 h in the presence of silver nanoparticles (1.07 · 10(-4) mg/ml; 1.07 · 10(-3) mg/ml; and 1.07 · 10(-2) mg/mL). The colloidal silver at 1.07 · 10(-3) mg/ml concentration inhibited the formation of new Elby disrupting contacts of bone marrow macrophages with CFU-E (erythropoiesis de novo) by 65.3% (p < 0.05). Colloidal silver nanoparticles suppressed the reconstruction of erythropoiesis and inhibited the formation of new EI by disrupting contacts of CFU-E and central macrophages with matured erythroidal "crown" (erythropoiesis de repeto). The colloidal silver concentration of 1.07 · 10(-3) mg/ml in the culture medium also reduced the number of self-reconstructing EI by 67.5% (p <0.05), whereas 1.07 · 10(-2) mg/ml colloidal silver reduced this value by 93.7% (p < 0.05). Silver nanoparticles retarded maturation of erythroid cells at the stage of oxiphylic normoblast denucleation: 1.07 · 10(-3) mg/ml colloidal silver increased the number of mature El by 53% (p < 0.05). The retardation of erythropoiesis by colloidal silver in concentration equivalent to the maximum single dose is related to the effect of silver nanoparticles rather than glycerol present in the colloidal suspension.

Surface-independent antibacterial coating using silver nanoparticle-generating engineered mussel glue.

PubMed

Jo, Yun Kee; Seo, Jeong Hyun; Choi, Bong-Hyuk; Kim, Bum Jin; Shin, Hwa Hui; Hwang, Byeong Hee; Cha, Hyung Joon

2014-11-26

During implant surgeries, antibacterial agents are needed to prevent bacterial infections, which can cause the formation of biofilms between implanted materials and tissue. Mussel adhesive proteins (MAPs) derived from marine mussels are bioadhesives that show strong adhesion and coating ability on various surfaces even in wet environment. Here, we proposed a novel surface-independent antibacterial coating strategy based on the fusion of MAP to a silver-binding peptide, which can synthesize silver nanoparticles having broad antibacterial activity. This sticky recombinant fusion protein enabled the efficient coating on target surface and the easy generation of silver nanoparticles on the coated-surface under mild condition. The biosynthesized silver nanoparticles showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria and also revealed good cytocompatibility with mammalian cells. In this coating strategy, MAP-silver binding peptide fusion proteins provide hybrid environment incorporating inorganic silver nanoparticle and simultaneously mediate the interaction of silver nanoparticle with surroundings. Moreover, the silver nanoparticles were fully synthesized on various surfaces including metal, plastic, and glass by a simple, surface-independent coating manner, and they were also successfully synthesized on a nanofiber surface fabricated by electrospinning of the fusion protein. Thus, this facile surface-independent silver nanoparticle-generating antibacterial coating has great potential to be used for the prevention of bacterial infection in diverse biomedical fields.

Impact of moderate silver carp biomass gradient on zooplankton communities in a eutrophic reservoir. Consequences for the use of silver carp in biomanipulation.

PubMed

Domaizon, I; Dévaux, J

1999-07-01

We examined the impacts of moderate gradient silver carp biomass (five levels from 0 to 36 g.m-3, i.e. about 0-792 kg.ha-1) on zooplankton communities of the eutrophic Villerest reservoir (France). During our mesocosm experiment changes in zooplankton assemblages were dependent on silver carp biomass. In the fishless and low fish biomass treatments, zooplankton abundance increased through time, owing to a peak in cladoceran density, but decreased (mainly cladocerans) at highest fish biomass. Copepods and rotifers were less affected at the highest fish biomass and dominated zooplankton communities. We highlighted that the presence of high silver carp biomass could lead to changes in phytoplankton assemblage via the impact on herbivorous zooplankton. Since silver carp efficiently graze on particles > 20 microns, the suppression of herbivorous cladocerans could result in an increase in small size algae (< 20 microns) abundance since these species would be released from grazers as well as competitors (large algae grazed by silver carp) and nutrients levels would be enhanced by fish internal loading. Our results showed that the use of low silver carp biomass (< 200 kg.ha-1) would allow us to minimize these negative effects.

78 FR 41195 - Re-pricing of Several Silver Coin Products

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-09

... DEPARTMENT OF THE TREASURY United States Mint Re-pricing of Several Silver Coin Products AGENCY: United States Mint, Department of the Treasury. ACTION: Notice. SUMMARY: Because of the recent decrease in the market price of silver, the United States Mint is lowering the price of several silver coin...

Complex conductivity response to silver nanoparticles in ...

EPA Pesticide Factsheets

The increase in the use of nanoscale materials in consumer products has resulted in a growing concern of their potential hazard to ecosystems and public health from their accidental or intentional introduction to the environment. Key environmental, health, and safety research needs include knowledge and methods for their detection, characterization, fate, and transport. Specifically, techniques available for the direct detection and quantification of their fate and transport in the environment are limited. Their small size, high surface area to volume ratio, interfacial, and electrical properties make metallic nanoparticles, such as silver nanoparticles, good targets for detection using electrical geophysical techniques. Here we measured the complex conductivity response to silver nanoparticles in sand columns under varying moisture conditions (0–30%), nanoparticle concentrations (0–10 mg/g), lithology (presence of clay), pore water salinity (0.0275 and 0.1000 S/m), and particle size (35, 90–210 and 1500–2500 nm). Based on the Cole-Cole relaxation models we obtained the chargeability and the time constant. We demonstrate that complex conductivity can detect silver nanoparticles in porous media with the response enhanced by higher concentrations of silver nanoparticles, moisture content, ionic strength, clay content and particle diameter. Quantification of the volumetric silver nanoparticles content in the porous media can also be obtained from complex co

Surface-enhanced Raman scattering from silver nanostructures with different morphologies

NASA Astrophysics Data System (ADS)

Zhang, W. C.; Wu, X. L.; Kan, C. X.; Pan, F. M.; Chen, H. T.; Zhu, J.; Chu, Paul K.

2010-07-01

Scanning electron microscopy and X-ray diffraction reveal that four different types of crystalline silver nanostructures including nanoparticles, nanowires, nanocubes, and bipyramids are synthesized by a solvothermal method by reducing silver nitrate with ethylene glycol using poly(vinylpyrrolidone) as an adsorption agent and adding different quantities of sodium chloride to the solution. These nanostructures which exhibit different surface plasma resonance properties in the ultraviolet-visible region are shown to be good surface-enhanced Raman scattering (SERS) substrates using rhodamine 6G molecules. Our results demonstrate that the silver nanocubes, bipyramids with sharp corners and edges, and aggregated silver nanoparticles possess better SERS properties than the silver nanowires, indicating that they can serve as high-sensitivity substrates in SERS-based measurements.

Development of Technology for Enrichment of Silver Containing Ores

NASA Astrophysics Data System (ADS)

Shekiladze, Asmati; Kavtelashvili, Otari; Bagnashvili, Mamuka

2016-10-01

The progress of Georgian economics is substantially associated with a development of new deposits of mineral resources. Among them is the David-Gareji deposit where at present the intensive searching geological works are performed. The work goal involves the elaboration of the technology for processing of silver-containing quartz-barite ores. Without its development the mining of more valuable gold-polymetallic ores is impossible. Because of ore complexity silver and barite are considered in a common technological aspect. The investigations were carried out on the representative samples of quartz-barite ores containing 78-88 g/ton of silver and 27-29 % of silver is a nugget in the form of the simple sulphides and chlorides. The ore is characterized by fine coalescence of barite and ore-generating minerals. Non-ferrous metals haven't any industrial value because of their very low content. Therefore, for the processing of the ores under study the direct selective scheme of flotation enrichment was chosen and the formula of optimal reagent regime was elaborated. Potassium xanthogenate is used as a collector for flotation of silver minerals and pine oil- as a foaming agent. The effect of the pulp - pH and medium temperature on silver flotation was studied. It was established that the silver is actively floats in neutral medium. For barite flotation the various collectors were tested: sulfidezid cotton oil-soap stock, soaps of fatty acids and alkyl sulphates of C12 - C16 row, among the “Baritol” is the most efficient one. Depression of the barren rock was carried out by liquid glass in alkaline medium. The effect of pulp pH on barite flotation has been investigated. The best results were obtained at pH=8.5. The increase of the pulp alkalinity has no essential effect on the indexes of the barite enrichment. Conditional concentrate of the barite is obtained by two fold purification of the main flotation concentrate by the addition of the liquid glass to the re

Characterization of silver particles in the stratum corneum of healthy subjects and atopic dermatitis patients dermally exposed to a silver-containing garment

PubMed Central

Bianco, Carlotta; Visser, Maaike J.; Pluut, Olivier A.; Svetličić, Vesna; Pletikapić, Galja; Jakasa, Ivone; Riethmuller, Christoph; Adami, Gianpiero; Filon, Francesca Larese; Schwegler-Berry, Diane; Stefaniak, Aleksandr B.; Kezic, Sanja

2018-01-01

Silver is increasingly being used in garments to exploit its antibacterial properties. Information on the presence of silver nanoparticles (AgNPs) in garments and their in vivo penetration across healthy and impaired skin from use is limited. We investigated the presence of AgNPs in a silver containing garment and in the stratum corneum (SC) of healthy subjects (CTRLs) and individuals with atopic dermatitis (AD). Seven CTRLs and seven AD patients wore a silver sleeve (13% Ag w/w) 8 h/day for five days on a forearm and a placebo sleeve on the other forearm. After five days, the layers of the SC were collected by adhesive tapes. The silver particles in the garment and SC were characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and atomic force microscopy (AFM). AFM and SEM revealed the presence of sub-micrometre particles having a broad range of sizes (30–500 nm) on the surface of the garment that were identified as silver. On the SC tapes collected from different depths, aggregates with a wide range of sizes (150 nm−2 μm) and morphologies were found. Most aggregates contained primarily silver, although some also contained chlorine and sulfur. There was no clear difference in the number or size of the aggregates observed in SC between healthy and AD subjects. After use, AgNPs and their aggregates were present in the SC at different depths of both healthy subjects and AD patients. Their micrometre size suggests that aggregation likely occurred in the SC. PMID:27647219

Sunlight-assisted synthesis of colloidal silver nanoparticles using chitosan as reducing agent

NASA Astrophysics Data System (ADS)

Susilowati, E.; Maryani; Ashadi

2018-04-01

The present study we explore an environmentally friendly colloidal silver nanoparticles preparation using chitosan as reducing agent and stabilizer. It develops a new strategy on preparation of silver nanoparticles through the gel phase using sodium hydroxide (NaOH) as accelerator reagent. Sunlight irradiation was employed to assisted reducing process of silver ions to silver nanoparticles. Localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles was investigated using UV-Vis spectrophotometer. The shape and size of silver particles were analyzed using TEM. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 396.0–412.0 nm. The absorption peak of LSPR were affected by NaOH amount, time of sulight irradiation and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 5 to 8 nm as shown by TEM images. All colloidals were stable without any aggregation for 30 days after preparation.

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core.

PubMed

Richter, Alexander P; Brown, Joseph S; Bharti, Bhuvnesh; Wang, Amy; Gangwal, Sumit; Houck, Keith; Cohen Hubal, Elaine A; Paunov, Vesselin N; Stoyanov, Simeon D; Velev, Orlin D

2015-09-01

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.