Dissertations / Theses on the topic 'Silver'
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1
Di, Pietro Giovanna. "Silver mirroring on silver gelatin glass negatives /." [S.l.] : [s.n.], 2002. http://edoc.unibas.ch/diss/DissB_6232.
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Moncada, de la Rosa Jorge Daniel. "Winning Silver." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/52861.
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The search for mineral deposits is a time consuming, risky and very
expensive process. Applying new models and methods provides a competitive
advantage in the search for mineral deposits because an explorationist can
quickly evaluate potential targets and eliminate areas without good potential for
mineralization.
This dissertation presents a practical technique for prediction to finding
precious metal mineralization at Guanajauato mining district (GMD) base on
theoretical and experimental studies of fluids properties, mineral phase
equilibrium, physical and chemical mechanisms. Making the technique highly
transportable so that it can be applied in the field during an exploration program
base on petrographic characteristics of mineral textures produced during boiling
events in quartz, calcite and adularia, and fluid inclusions contained in these
phases. While this work was conducted in GMD, the results should be applicable
in exploration for epithermal deposits worldwide.
The GMD is one of the largest silver producing districts in the world. Ore
shoots are localized along three major northwest trending vein systems, the La
Luz, Veta Madre and Vetas de la Sierra. More than 1200 samples were collected
from surface outcrops, underground mine and historical and recent drill core.
Traverses perpendicular to veins in all system were also conducted. Most of the
samples (approximately 90%) were also assayed for Au, Ag, Cu, Pb, Zn, As, Sb.
Samples from the GMD show a wide range in silica textures are indicative
of rapid precipitation, such as occurs when fluids boil. Other mineral phases,
including illite, rhombic adularia and bladed calcite are also indicative of rapid
growth in a hydrothermal system and are characteristic of boiling systems.
Because boiling is an effective mechanism for precipitating gold and silver from
hydrothermal fluids, the presence of mineral textures indicative of boiling is a
desirable feature in exploration. In many samples, textural evidence for boiling is
supported by coexisting liquid-rich and vapor-rich fluid inclusions, or Fluid
Inclusion Assemblages consisting of only vapor-rich inclusions, suggesting
"flashing" of the hydrothermal fluids. Textural and fluid inclusion evidence for
boiling has been observed in the deepest levels of the GMD, suggesting that
additional precious metal resources may occur beneath these levels.Ph. D.
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Riley, David. "Silver Sands." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5870.
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Silver Sands is a thirty-minute documentary film and accompanying installation that traces the story of Marc Hampton, a gay, desert-dwelling Vietnam vet, former Playgirl model, and vintage car collector who lost two lovers to AIDS. Drawing on videotaped interviews, shots of his house and environs, and extensive use of his personal photographic archive, this work addresses evolving ideas of memory and representation within the queer community. The film is divided into various chapters which function as meditations on masculinity, aging, loss, spirituality and intergenerational relationships. Marc becomes an archetypal figure––the survivor––whose meandering recollections illustrate some of the complexities of gay experience in the past fifty years, and the difficulty of historicizing them. By emphasizing overlooked stories and forgotten spaces, exploring the tension between visibility and invisibility, and summoning the ghosts of the AIDS era, Silver Sands proposes remembering as a form of resistance.
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Talebpour, Cyrus. "A perovskite silver antimicrobial compound with diminished silver ion release." Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/66752.
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L'infection microbienne est une des causes des maladies menaçant la vie. Elle est conventionnellement traitée par des antibiotiques. Cette pratique a entraîné l'émergence de la résistance aux antimicrobiens (RAM), qui est associée à un taux de mortalité croissant. Afin de contrer le problème, les cellules microbiennes doivent être retirées de la zone de cible sans que l’agent microbienne libère des sous-produits. Les désinfectants, tels que l'eau de Javel et le chlore, tout en étant très efficace à large spectre antimicrobien, ne conviennent pas dans certaines circonstances. Ces composés sont chimiquement réactifs, ils peuvent donc corroder les surfaces en contact et laisser des composés toxiques. D'autre part, les antibiotiques conventionnels, bien qu'ils ne présentent pas ces propriétés indésirables de désinfectants, ont généralement un spectre d'action plus étroit et sont plus sujets au développement du RAM. Entre les désinfectants et les antibiotiques, il existe des composés à base d'argent qui, tout en ayant une activité antimicrobienne à large spectre, sont relativement sans danger pour les cellules de mammifères. Le mécanisme de l'action antimicrobienne des composés d’argent classiques est basé sur la libération d'ions argent dans le milieu. L'argent est un métal coûteux et se dégrade en libérant des ions. De plus, l'exposition à des niveaux élevés d'ions d'argent est un danger pour la santé et l'environnement et donc doit être évitée. Par conséquent, incorporer étroitement des atomes d'argent dans une structure moléculaire résistante à la corrosion, tout en gardant l'activité antimicrobienne, permettrait d'utiliser l'argent comme agent antimicrobien dans des applications exigeant un composé d'argent résistant à la corrosion avec de faibles niveaux de libération d'argent dans l'environnement. Pour atteindre cet objectif, un nouveau composé d'argent, AgNbO3, a été synthétisé et caractérisé en termes de taille, de morphologie, de comportement de sédimentation, de corrosion et d'activité antimicrobienne. Il a été démontré que tout en ayant un taux de libération d'argent diminué de plus de 150 fois par rapport aux particules Ag2O de référence, l'activité antimicrobienne des nanoparticules AgNbO3, quantifiée par la concentration minimale inhibitrice (MIC), était similaire dans le cas des milieux aqueux. L'étude du mécanisme d'action a indiqué que le composé exerce son action antimicrobienne par contact avec des cellules microbiennes.Microbial infections are the main causes of life threatening diseases and are conventionally treated by antibiotic agents. This practice has resulted in the emergence of antimicrobial resistance (AMR), which is associated with ever-increasing rate of mortality. In order to counter the issue, the microbial cells should be removed from targeted areas without releasing toxic byproducts behind. Disinfectants, such as bleach and chlorine, while being very effective broad-spectrum antimicrobial, are not suitable in some circumstances. These compounds are chemically reactive; thus, they can corrode the surfaces in contact and can leave behind toxic compounds particularly in reaction with organic matter. On the other hand, the conventional antibiotics, while not having these undesired properties of disinfectants, have generally narrower spectrum of action and are more prone to the development of AMR. In between of disinfectants and antibiotics there are silver-based compounds, which while having broad-spectrum antimicrobial activity, are relatively safe to mammalian cells. There are, however, some challenges associated with the usage of the conventional silver compounds as antimicrobial agent, arising from the mechanism of antimicrobial action through the release of silver ions to the medium. Silver is an expensive metal and degrades in while releasing ions. Moreover, exposure to high levels of silver ions is a health an environmental hazard and should be avoided. Therefore, tightly incorporating silver atoms in a corrosion-resistant molecular level structure with keeping the antimicrobial activity would enable feasibility of using silver as an antimicrobial agent in applications that require corrosion resistant silver compound with low levels of silver release to the environment. To achieve this goal, a new silver compound, AgNbO3, was synthesized and characterized in terms of its size, morphology, sedimentation behavior, corrosion, and antimicrobial activity. It was demonstrated that while having a diminished silver release rate of more than 150 fold compared to the reference Ag2O particles, the antimicrobial activity of AgNbO3 nanoparticles, quantified by minimum inhibitory concentration (MIC), was similar in the case of aqueous media. Investigating the mechanism of action indicated that the compound exerts its antimicrobial action via contact with microbial cells.
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Clavelli, Tony. "Your silver nose." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11084.
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Dale, Vukanovich Theodore Lawrence, Loza José Adrián Ponce, Morales Joel Omar Quintanilla, Bustamante Víctor Alberto Rodríguez, and Cabrera Raúl Fernando Saldaña. "Proyecto Ideo Silver." Master's thesis, Universidad del Pacífico, 2016. http://hdl.handle.net/11354/1696.
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Nuestro proyecto ofrece microfranquicias de joyas de lujo (plata 960), cuyos diseños están orientados a las mujeres modernas de los niveles socioeconómicos B, C y D, entre 21 y 35 años de edad que radican en Lima Metropolitana. Asimismo, hemos definido como segmento de clientes franquiciados a los microempresarios con experiencia en productos y/o servicios relacionados con la moda. Nuestro concepto de negocio hacia el franquiciado se resume en “Sea joyero en un día, de manera formal y sostenible”, sobre la base de nuestro know-how, marca, mínima inversión, garantía de por vida de nuestros productos, innovación abierta y soporte integral mediante la tecnología web. Las joyas de plata que ofrecemos logran cubrir las expectativas que más valora nuestro segmento de cliente final, es decir: diseño, precio, seguridad, lujo y calidad, mediante las siguientes características de nuestros productos: Joyas de plata 960, garantía de por vida y hereditaria, precios bajos, acabado tipo “oro blanco”, diseños sobrios y estilos modernos. Adicionalmente, de manera innovadora estamos incluyendo la facilidad de que el cliente final pueda “renovar las joyas de marca Ideo Silver”. Nuestro modelo de negocio presenta importantes barreras de entrada, basados en el poco acceso a proveedores (materia prima, plata, especialmente para joyas de lujo), alta diferenciación (certificado internacional de autenticidad, renovación de joyas, know-how) y falta de experiencia en la industria (producción de joyas 960, que es el más alto nivel de pureza permitida para la plata). En resumen, nuestra misión es: “Promover el autoempleo a través de microfranquicias de joyas de plata peruana de alta pureza (960), a bajo precio y con diseños preferidos por la mujer moderna, generar desarrollo económico para los socios y contribuir con el desarrollo sostenido del país”.
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Gross, Shurice L. "Under Silver Ash." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1312397649.
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Paul, Anita N. "Silver-Polymer Nanocomposites." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3077.
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The objective of this research was the development of an efficient method for the preparation of silver-polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by thiolation with 2-aminoethanethiol. Amino-modified nanosilver was covalently bonded to polyacrylic acid, biodegradable polymers like acid terminated polylactic acid, ester terminated poly(DL-lactide-co-glycolide) and acid terminated poly(DL lactide-co-glycolide) in the presence of diisopropylcarbodiimide by carbodiimide method. Esterification of the carboxyl groups of Ag-polyacrylic acid by hydrochloric acid in methanol resulted in the formation of a stable colloidal dispersion of Ag nanoparticles in the polymer matrix. It was observed that not just acid terminated polymers but also ester terminated polymers could react with functionalized nanosilver. This unusual reaction was due to the aminolysis of the ester bond in the polymer chain by the surface amino groups. Silver-polymer nanocomposites obtained with acid terminated polylactic acid and poly(DL-lactide-co-glycolide) contained highly dispersed nanosilver in the polymer matrix in comparison with the ester terminated poly(DL-lactide-co-glycolide). Chemical and structural characteristics of the obtained materials were studied by instrumental methods. Attained biodegradable materials confirmed X-ray contrast and bactericidal properties, which could be eventually used for biomedical applications.
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Zhang, Li 1973. "Shockwave consolidation of nano silver powder into bulk nano structured silver." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100238.
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Bulk nanostructured silver components were fabricated from nano-sized powder using a shockwave consolidation technique. The grain size evolution during compaction, the mechanical properties of the bulk components, and the effect of surface finish on the mechanical behavior were studied. X-Ray diffraction, transmission electron microscopy (TEM), atomic force microscopy (AFM), microhardness, compression testing and shear punch testing at room temperature were used to characterize the materials. Upon consolidation, the average grain size calculated from image analysis of the TEM micrographs was 49+/-22 nm, showing the feasibility of maintaining a nanostructure upon dynamic consolidation. The hardness of the bulk nanostructured components was constant across the diameter with an average of 83+/-1 HV. Compression results showed strength about 390+/-10 MPa and ductility of 23+/-2%, which is well above strength level obtainable from strain hardened Ag components. The AFM results show that samples possessing a surface roughness of 267 nm exhibited a brittle behavior and a reduction in strength of 35% when compared to the smoother surfaces. Dimples were observed for the samples exhibiting plasticity, while an intergranular pattern was identified for the brittle materials. Fracture toughness of 0.2 MPa m was calculated, which confirms the strong relationship between fracture toughness and defects observed in nanomaterials.
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Khodaparast, Zahra. "Toxicity of silver nanoparticles and silver nitrate on Nassarius reticulatus larvae." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15327.
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Mestrado em Toxicologia e EcotoxicologiaProduction and utilization of silver nanoparticles (AgNPs) for various applications is growing rapidly, mainly due to their antibacterial activity. Their inclusion in many consumer products led to an increased release of AgNPs in the environment, especially in aquatic ecosystems. AgNPs reach both freshwater and marine environments from the effluents of the wastewater treatment plants, presenting differentiated behavior in these two environments potentially influencing its toxicity. The study of AgNPs toxicity to marine organisms is extremely important to the assessment of the potential risk of AgNPs in the environment. The toxicity of AgNPs on the living organisms is dependent on various environmental conditions. Regarding the toxicity of AgNPs in the marine environment, there is a lack of information on the toxic effects at different salinities. This study upsurges to fill this gap, being the first report on the effects of AgNPs on marine gastropods, using Nassarius reticulatus as a case study. N. reticulatus adults were collected from a reference population in Ria de Aveiro (NW Portugal, 40° 38' 33.24"N | 8° 44' 06.69’’W). Specimens were transported to the laboratory in local seawater and kept in aquaria to spawn. Egg capsules were maintained until veliger larva were noticed, which enclosure was induced by cesarean. These recently hatched larvae were then exposed to nominal concentrations of AgNPs and Ag+ (0.1, 1, 10, 100 μg Ag/L) for up to 96 h, either in the presence or absence of food. Larval mortality and swimming behavior –namely the velum beating arrest–were determined for each treatment. The median lethal concentration (LC50) of AgNPs was higher to that of ionic Ag (AgNO3). Results also revealed that the negative impact of AgNPs on N. reticulatus veligers swimming ability is higher when compared with the effect of ionic Ag (EC50-96 h 1.044 μg Ag/L). However, although the velum arrests have significantly decreased under Ag+ exposure, AgNPs did not show any effects. Additionally, the presence of the food proved to be an effective factor that can cause a significant drop in the mortality of the N. reticulatus larvae exposed to AgNPs.
A produção e utilização de nanopartículas de prata (AgNPs) em diversas aplicações têm crescido rapidamente, principalmente devido à sua atividade antibacteriana. A inclusão de AgNPs em muitos produtos de consumo conduziu a um aumento da sua libertação no meio ambiente, especialmente nos ecossistemas aquáticos. As AgNPs atingem tanto o ambiente marinho como o de água doce a partir da descarga de efluentes de estações de tratamento de águas residuais, apresentando comportamento diferenciado nestes dois meios, potencialmente influenciando a sua toxicidade. O estudo da toxicidade das AgNPs em organismos marinhos é extremamente importante na avaliação do potencial risco da presença de AgNPs no ambiente. A toxicidade de AgNPs emorganismos vivos é dependente de várias condições ambientais. No que se refere à toxicidade das AgNPs em ambiente marinho, verifica-se uma lacuna de informação relativamente aos efeitos tóxicos a diferentes salinidades. Este trabalho surge para preencher esta lacuna, sendo o primeiro relato do efeito de AgNPs em larvas de gastrópodes marinhos, usando Nassarius reticulatus como caso de estudo. Foram colhidos adultos de N. reticulatus de uma população de referência da Ria de Aveiro (NW Portugal, 40° 38' 33.24"N | 8° 44' 06.69’’W). Os espécimes foram transportados para o laboratório em água do local e aí mantidos em aquário até à postura de cápsulas ovígeras. As cápsulas foram mantidas até à observação de larvas velígeras no seu interior, cuja eclosão foi induzida por cesariana. Estas larvas recém-eclodidas foram então expostas a concentrações nominais de AgNPs e Ag+ (0,1, 1, 10, 100 ug de Ag / L), durante 96 h, na presença ou ausência de alimento. A mortalidade larvar e o comportamento de natação, nomeadamente a inibição do batimento do velum, foram determinados para cada um dos tratamentos. A concentração letal média (CL50) das AgNPs revelou-se superior à da Ag iónica (AgNO3). Os resultados também revelaram que o impacto negativo das AgNPs na natação das velígeras de N. reticulatus é superior (EC50-96 h 0.044 μg Ag/L) quando comparado com o efeito da Ag iónica (EC50-96 h 1.044 μg Ag/L). Contudo, embora a inibição da movimentação do velum das larvas ter diminuido significativamente na presença de Ag+, as AgNPs não mostraram quaisquer efeitos na inibição do batimento do velum. Adicionalmente, a presença de alimento revelou ser um fator importante, podendo causar uma redução significativa na mortalidade das larvas de N. reticulatus expostas a AgNPs.
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Grasmik, Viktoria [Verfasser], and Matthias [Akademischer Betreuer] Epple. "Silver-based nanoparticles : synthesis and characterization of bimetallic silver-platinum and silver-gold nanoparticles / Viktoria Grasmik ; Betreuer: Matthias Epple." Duisburg, 2018. http://d-nb.info/1167683110/34.
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Cabaj, Maciej. "Preparation, characterisation and catalytic activity of palladium, silver and silver-based nanoparticles." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648133.
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McLeod, Ian. "Epitaxial growth of lead and bismuth on silver and silver rich alloys." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/16213/.
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The growth of Bi on Ag(111) induces different surface structures, including(√3×√3)R30°surface alloy, Bi-(p×) overlayer and Bi(110) thin film as a function of increasing Bi coverage. These structures have been studied using low-temperature scanning tunneling microscopy, low-energy electron diffraction, ab initio calculations and photoemission spectroscopy from core-levels and valence bands at room temperature. At 1/3 of a monolayer of Bi on Ag(111) leads to the formation of BiAg2 surface alloy with a long range ordered (√3×√3)R30° superstructure. A detailed analysis of this structure using LEED I-V measurements together with DFT calculations is presented. The Bi atom is found to replace one top layer Ag atom in each unit cell, forming a substitutional BiAg2 surface alloy. This mode of accommodation of Bi was found to be energetically favourable based on ab initio total-energy calculations. Based on photoemission spectroscopy we find the sp-derived Shockley surface state on Ag(111) is rapidly quenched upon deposition of Bi, due to the strong variation of inplane surface potential in the Ag2Bi surface alloy. The core levels of Bi 4f of the (√3×√3)R30° Ag2Bi alloy and Bi(110) thin film are shifted to lower binding energy by ~0.6 eV and ~0.3 eV compared with the Bi bulk value, respectively. Mechanisms inducing the core level shifts are discussed as due to a complex superposition of several factors. At coverage above a critical value of 0.55 monolayers, the Ag2Bi alloy phase gradually converts into an ordered Bi (p × √3) overlayer structure supported on Ag(111). We postulate that the dealloying transition is likely driven by compressive strain induced by incorporation of large-size Bi atoms into Ag at a high coverage and the subsequent lack of miscibility of Ag and Bi bulk phases. After completion of the dealloying process, Bi(110) thin films can be grown epitaxially on top of Ag(111) with a chemically abrupt interface. The deposition of 1/3 of a monolayer of Pb on Ag(111) leads to the formation of Ag2Pb surface alloy with a long range ordered (√3x√3)R30° superstructure. A detailed analysis of this structure using LEED I-V and MEIS measurements together with DFT calculations is presented. Quasicrystals, materials with aperiodic long-range order, are usually formed by at least two elements with a specific chemical composition. In this study, we demonstrate that, a single element multilayer quasicrystal can be formed on a template. Using a hitherto unexplored quasicrystalline substrate, the icosahedral Ag-In-Yb quasicrystal, and various experimental techniques including scanning tunneling microscopy combined with theoretical calculations of adsorption energies, we identify the initial adsorption sites for Pb atoms on the substrate and hence deduce the multilayer structure of the Pb overlayer. We propose a mechanism for the growth of epitaxial materials on the quasicrystalline substrate.
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Corrigan, Lauren. "Ecotoxicity of silver nanoparticles." Connect to resource, 2010. http://hdl.handle.net/1811/45420.
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Quickenden, Kenneth. "Boulton and Fothergill silver." Thesis, Queen Mary, University of London, 1990. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1573.
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This thesis is about the silver business of Matthew Boulton and John Fothergill at their Soho Manufactory near Birmingham. Their partnership lasted from 1762 until 1782. A rounded discussion of the topic is attempted. Within the contexts of industry elsewhere and Soho's other activities, successive chapters cover the early development, marketing, production, design, and later decline of the partners' silver. Silver plate was prestigious and, untypically for Boulton, he concentrated on sales to the public rather than trade customers. To attract orders he made modest charges. This was viable where mainly machinery was used to make plate, even though sales were not high, since the expense of machinery was substantially covered by the larger sales of non-silver items. However, where Boulton relied to a greater degree upon hand methods, he lacked technical means to compensate for low profit-margins. Moreover, inefficiency and the firm's lack of capital which led to substantial bankers' interest charges on payment for bullion, particularly when customers paid late, caused losses. These problems applied particularly to silver plate and were mainly responsible for the decision to reduce production drastically; however, the manufacture of a large range of small items remained relatively consistent. The thesis includes appendices. Some contain new information about annual totals for the following aspects of the business: the volume of assay silver; each type of article; pieces sold on commission; and sterling silver supplies. Other appendices provide details about the partners' silversmiths and extracts from a Soho inventory. This thesis involves a more detailed use of sources than previous studies of the topic. Apart from the silver itself (which is selectively illustrated), the Matthew Boulton Papers and statistics derived from The Birmingham Assay office provide the main sources. Manuscripts covering silver production elsewhere provide contextual material for understanding the partners' silver business.
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Garrison, Jered C. "Silver N-Heterocyclic Carbenes." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1124128998.
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Toh, Her Shuang. "Electrochemistry of silver nanoparticles." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:7b9c8a2f-6599-446e-a0b3-cb33ca39e476.
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This thesis presents findings realising two main objectives. The first aim is to investigate the electrochemical detection of nanomaterials with an emphasis on silver nanoparticles. The second goal is to employ silver nanoparticles in electroanalysis to aid in the detection of other analytes. First, the detection of silver nanoparticles was demostrated through two different electrochemical methods, stripping voltammetry and 'nano-impacts'. For stripping voltammetry, the potential of metallic nanoparticles oxidation was quantified by various new analytical expressions for peak potential. For the novel method of 'nano-impacts', individual silver nanoparticles were successfully detected in an optically opaque suspension. Then, a comparison between the two techniques was achieved via the oxidation of silver nanoparticles with different capping agents. Strong capping agent effects was found for stripping voltammetry and one may markedly underestimate the amount of silver nanoparticle present on the electrode surface. The electrochemical sizing of nanoparticles via 'nano-impacts' remained unaffected by the capping agent effect. Amidst the study on the various types of capping agent, it was discovered that cetyltrimethylammonium bromide (CTAB) is electroactive due to the oxidation of its bromide content. This inspired the use of 'nano-impacts' to detect the presence of large CTAB micelles which self-assembled at concentrations above the critical micelle concentration. Next, various types of silver nanoparticles were applied to different electroanalytical systems to aid in the measurement of other analytes. (a) Small silver nuclei, remaining after the oxidative stripping of an electrode modified by silver nanoparticle suspension drop casting, allowed subsequent signal enhancement (at least a factor of three) in anodic stripping voltammetry of silver ions. (b) The thermodynamic favourable formation of silver halide complexes allowed the silver nanoparticle modified electrode to analyse the halide content of a solution. Hence, a proof-of-concept for an electrochemical sensor based on silver nanoparticle modified electrode for chloride ions was established. This might be applied to the pre-screening of cystic fibrosis, a genetic disease detrimental to many infants' lives. (c) Another key halide in human body, iodide ions, was also measured using a related concept. The level of iodide ions in synthetic human urine was determined. Last, the strong affinity of silver to thiol groups also warranted a study devoted to their interaction through electrochemical and spectroscopic measurements. It was found that there is no general mechanism for silver-thiol interaction and each thiol must be treated as a separate entity.
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Alex, Asha Philips. "Determination of silver(I) in the presence of silver(0) using EDTA titration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21150.pdf.
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Janes, Joseph Robert. "Electronic processes in the silver halides, silver atoms and clusters : an ESR study." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/33756.
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During bandgap exposure, the initial steps of latent image formation in the silver halides are dominated by the shallow trapping of free carriers (electrons and holes). Electron Spin Resonance studies of irradiated silver halides in powder, single crystal and de-gelled emulsion formats revealed signals assigned to electrons shallowly trapped at intrinsic sites. These signals were only observed at temperatures below ca. 50K. Experiments were carried out to probe the nature of these sites which appeared to be concentrated at structural dislocations in the lattice. The shallowly trapped electron signal was detected in silver bromide, silver chloride and a range of binary halide silver halide powders. The observation of this signal was accompanied in many cases by the simultaneous observation of a Cyclotron Resonance transition of free conduction band electrons. In addition doping with divalent lead ions capable of acting as "extrinsic" shallow traps resulted in an enhancement of the lifetime of the trapped electron ESR signal. The radiolytic formation of silver atoms and charged clusters (dimers, trimers and tetramers) in frozen solutions of silver perchlorate in methanol, were studied by ESR, this work includes the probable identification of the novel pentameric unit, Ag54+. The formation and detection of clusters of this type in the silver halide matrix is also discussed, together with the detection of latent image centres at liquid helium temperatures, where ionic motion does not occur.
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Nielsen, Michele D. "Thermoelectric Exploration of Silver Antimony Telluride and Removal of Second Phase Silver Telluride." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282146316.
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Domingues, Vasco Filipe de Castro. "Toxicity of silver nanoparticles and silver nitrate to the freshwater planarian Dugesia tigrina." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17016.
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Mestrado em Toxicologia e EcotoxicologiaAtualmente, as nanopartículas de prata (AgNP) são bastante utilizadas em vários produtos devido às suas propriedades únicas e excecionais, nomeadamente a sua potente atividade antibacteriana. Algumas das suas aplicações comuns são em têxteis, produtos cosméticos e tintas. Deste modo, é esperada a presença de AgNP nos sistemas aquáticos. Tendo isto em consideração, o objetivo deste trabalho é descrever os efeitos tóxicos de AgNP de diferentes tamanhos, e comparar estes efeitos com os induzidos pela exposição a AgNO3 usando as características comportamentais das planárias da espécie Dugesia tigrina. Foram efetuados testes de exposição aguda (96 h) e testes de exposição crónica (8 dias) onde foram avaliados parâmetros como a sobrevivência, a locomoção, alimentação e regeneração cefálica. Foram selecionadas AgNP de diferentes tamanhos (AgNP de 10-25 nm e AgNP 3-8 nm) e comparados os efeitos com os da exposição a AgNO3, de modo a analisar se a toxicidade tem origem na libertação de iões Ag ou se é devida às propriedades das diferentes nanopartículas. Os resultados mostraram que os valores de LC50 para as 24, 48, 72 e 96 h não variaram ao longo do tempo para AgNP (10-25 nm) (76.62 μg L-1) e para AgNO3 (109.1 μg L-1). As planárias experienciaram nas primeiras 24 h várias alterações morfológicas na zona da cabeça como aurículas suprimidas e principalmente dissolução da cabeça. Estes efeitos notaram-se principalmente na AgNP (10-25 nm) e AgNO3. Em relação à exposição crónica, as planárias apresentaram uma redução significativa na locomoção e na alimentação na exposição a todas as nanopartículas estudadas, sendo estes parâmetros os mais sensíveis para D. tigrina. Relativamente à capacidade de regeneração não houve efeitos significativos à exposição a Ag. A fonte de toxicidade pode estar relacionada com as propriedades das AgNP que interferem com o sistema nervoso das planárias, causando a sua morte. Este estudo demonstrou que as planárias são um organismo adequado para estudos ecotoxicológicos comportamentais e devem ser considerados em metodologias de avaliação de risco ambiental.
Currently, silver nanoparticles (AgNP) are widely used in several products because of their unique and exceptional properties, particularly its potent antibacterial activity. Thus, AgNP are very often applied in textiles, cosmetics and paints. Under those circumstances, AgNP is expected to be present in aquatic systems. Taking this into consideration, the objective of the present work is to describe the toxicity of AgNP of different sizes and compare to the toxicity from AgNO3 exposure using behavioral endpoints of the planarian Dugesia tigrina. Acute exposure tests (96 h) and chronic exposure tests (8 days) were performed, in which parameters such as survival, locomotion, feeding and regeneration were evaluated. Therefore, AgNP of different sizes were selected (AgNP of 10-25 nm and AgNP 3-8 nm) and effects from exposure were compared to those from AgNO3, in order to analyze whether the source of toxicity was originated by release the ionic form of Ag or related to the inherent properties of nanoparticles. The results showed that LC50 values at 24, 48, 72 and 96 h were equal over time for AgNP (10-25 nm) (76.62 μg L-1) and for AgNO3 (109.1 μg L -1). In the first 24 h, planarians experienced several morphological alterations at the head region such as suppressed auricles and mainly head dissolution. These effects were noted mainly in AgNP (10-25 nm) and AgNO3 exposures. Regarding chronic exposure, planarians presented a significant reduction in locomotion and feeding activity upon both AgNP exposures. These endpoints revealed to be the most sensitive to D. tigrina. There were no significant effects on the regeneration test. The source of toxicity may be related to the properties of AgNP that interfere with nervous system of planarians consequently causing their death. This study demonstrated that planarians are an adequate organism for behavioural ecotoxicological studies and should be considered in environmental risk assessment methodologies.
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Evers, Florian. "Comparative study of silver nanoparticles and silver(111) by means of femtosecond laser pulses." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979485967.
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Maeng, Sung Kyu. "Effect of a silver-bearing photoprocessing wastewater and silver compounds on biological treatment processes." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19024.
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Albiston, John Nigel. "The activated sintering of silver-tungsten compacts, produced via the reduction of silver tungstate." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329591.
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Liang, Irene. "Evaluation of Immobilized Titanium Dioxide-Silver-Hydroxyapatite Nanoparticles and Colloidal Silver for Water Disinfection." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297687.
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Titanium dioxide nanoparticles combined with silver and hydroxyapatite (TiO₂-Ag-Hap) form a photocatalytic composite capable of oxidizing and mineralizing a wide spectrum of microbiological and chemical contaminants in water, while silver nanoparticles have long been employed for their antimicrobial properties. These materials were evaluated through an iterative series of experiments that evaluated microbial reduction, material formulation, method of application, surface-interface interactions, and reusability. The TiO₂ formulation was assessed as an antimicrobial film coated onto fabric and ceramic beads in three experimental designs: a gravity filtration column, a portable treatment capsule, and a static chamber. Colloidal floating Ag nanoparticles in solution were also assessed. Reduction of Escherichia coli, Klebsiella terrigena, MS2 bacteriophage, and Rotavirus was evaluated though standard culture-based methods. Significant microbial reduction was only observed in the static open pan design for the TiO₂-Ag-HAp materials. Colloidal silver was more effective and caused a 5 log reduction of K. terrigena, within 60 minutes, and a 5 and 4 log reduction of MS2 within 120 and 90 minutes respectively in initial trials. The anti-microbial properties of both materials were apparent, but further investigations are necessary to assess the potential of the materials for integration and development in water treatment technologies.
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Antoku, Yasuko. "Fluorescent Polycytosine-Encapsulated Silver Nanoclusters." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14568.
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Small silver nanoclusters are synthesized using polycytosines as matrices. Different size silver nanoclusters ranging from Ag1 to Ag7 exhibit bright emission maxima at blue (480nm), green (525nm), red (650nm), and IR (720nm) wavelengths with varying the excitation wavelengths. With electrophoresis, correlation of emission with mass spectra, the Ag cluster sizes are identified with blue emitters as Ag5, green emitters as Ag4, red emitters as Ag3, and IR emitters as Ag2. Ag4 and Ag5 appear to be partially oxidized while Ag2 and Ag3 are likely fully reduced.
Silver cluster stability and their dynamics are observed from silver clusters encapsulated by polycytosine (Cm:Agn). From length study of polycytosine, the longer the polycytosine is, the more stable the larger clusters such as Ag5 are. In time-dependent optical measurements, isosbestic points are observed from Cm:Agn by converting red and IR species into blue and green species, while in the case of temperature-dependent optical properties, with increasing temperature, the blue (oxidized Ag5) and green (oxidized Ag4) emitters convert into the red (Ag3) and IR (Ag2) emitters. NaCl-dependent optical measurements support the assignments of oxidized and fully reduced silver emitters. Circular dichroism (CD) is used to investigate conformational changes in Cm and Cm:Agn with varying conditions (time, temperature and NaCl) and the studies indicate that no conformational changes in Cm:Agn are observed from the time and temperature, while the conformational changes in Cm:Agn are observed from the NaCl studies. From pH-dependent emission study of Cm:Agn, the silver nanocluster dynamics slow down at high pH.
Using confocal microscopy technique, single molecules on IR species, C12:Ag2 are investigated and demonstrate that C12:Ag2 is brighter and more photostable than Cy5 which is known to be one of the best IR dyes. With low excitation power, molecules can be monitored for hours, giving bright blinking free, stable fluorescence. The photophysics of this new dye make it a promising candidate for single molecule studies in biological applications.
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Antoku, Yasuko. "Fluorescent polyctosine-encapsulated silver nanoclusters." Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-02152007-084843/.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.Dickson, Robert, Committee Chair ; Barry, Bridgette, Committee Member ; Fahrni, Christoph, Committee Member ; Fernandez, Facundo, Committee Member ; Srinivasarao, Mohan, Committee Member.
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Villegas, Ortega Eduardo. "Reactive precipitation of silver powders." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83940.
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The present research project is part of an overall study whose aim is to develop a process for the production of silver powders by the reduction of silver nitrate with hydrazine. This is an extremely fast reaction, which results in uncontrolled particle properties. The main objective was to develop conditions at which the rate of the reaction and hence the particle properties could be controlled; this was accomplished by carrying out the reaction under the presence of EDTA as a complexing agent. EDTA effectively slowed down the reaction still allowing it to take place at concentrations between 0.22 and 3.3 mM.The analytical methods did not differentiate silver nanoparticles, which could not be filtered, from unreacted silver ions. Therefore, the reactive solutions were seeded so that crystal growth was favored over nucleation. A concentration of seeds of 0.27 mM was enough to avoid the production of nanoparticles. The silver reduction rate was found to be of order 1.1, 0.72 and -1.11 with respect to the silver, hydrazine and EDTA concentrations respectively. Silver crystal sizes were also evaluated at different conditions.
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Dias, Renuka. "Epigenetics of Silver-Russell syndrome." Thesis, Queen Mary, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545985.
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Chen, Haoguo, and 陳浩國. "Silver catalyzed enyne cyclization reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841409.
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Phillips, Thomas William. "Flow synthesis of silver nanowires." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/64907.
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This thesis reports the development of a droplet-based flow synthesis of silver nanowires. Using traditional batch methods of production it can be difficult to achieve the consistent reaction conditions needed to obtain nanocrystals with the desired properties. Microfluidic reactors offer superior control over reaction conditions and enable the scalable and continuous production of consistent and monodisperse nanoparticles. Silver nanowires are typically synthesised using the polyol reaction, where silver nitrate is reduced in hot ethylene glycol. Previous reports describing the synthesis of silver nanowires have come to contradictory conclusions about the conditions needed for growth. In this thesis a hot-injection polyol synthesis was adapted to a straightforward heat-up procedure for the production of silver nanowires. The success of the reaction was found to be dependent on the batch of ethylene glycol used. The modified synthesis enabled the development of a flow process using a polytetrafluoroethylene tubing-based droplet-based flow reactor. The reactor produced consistent silver nanowires over an eight hour period with no sign of reactor fouling. The reactor was used to investigate the effect of varying the reaction temperature, residence time, and concentration of iron nitrate and sodium chloride additives on the length of the silver nanowires produced. This thesis finishes with the development of an inline liquid-liquid separator based on the selective wetting and permeation of a porous capillary by one of the liquids. Efficient separation of aqueous-organic, aqueous-fluorous, and organic-fluorous flows was achieved over a wide range of flow rates. The separator was successfully applied to the inline aqueous-organic extraction of the pH indicator 2,6-dichloroindophenol. The organic extract and aqueous raffinate were separated using a porous capillary. UV-visible absorption spectroscopy showed the concentration of indicator in the aqueous raffinate to be less than one percent of its original value, confirming the efficacy of the extraction and separation process.
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Wang, Yu. "Applications of silver ionic liquids." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676609.
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Motsoeneng, Khothatso Patricia. "The toxicity of silver nanoparticles." University of the Western Cape, 2012. http://hdl.handle.net/11394/4700.
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>Magister Scientiae - MScUnavailability and contamination of available water resources are major factors contributing to adverse health conditions worldwide. AgNPs present a potential strategy for water purification; however, their ability to accumulate in organs such as the kidneys, lungs and spleen is a possible source of toxicity. This study investigates the toxicity of AgNPs to Saccharomyces cerevisiae (S. cerevisiae). S. cerevisiae is an excellent model organism for assessing toxic compounds that affect eukaryotic organisms due to their ease of cultivation. AgNPs were prepared by photo-reduction of silver nitrate with OSRAM Vitalux lamp (300 W and 230 V) in the presence of stabilizing agents such as polyvinylpyrrolidone and citric acid, yielding AgNPs. The effects of varying the concentration of the stabilizing agent, time of exposure to the light source, and pH were investigated. The formation of AgNPs was analysed by ultra-violet spectroscopy (UV-Vis) and transmission electron microscope techniques. The results showed that the AgNPs absorbed ultra-violet radiation between 400 and 500 nm and TEM images showed the particles to be both spherical and needle-like in shape. The shapes of the AgNPs were largely dependent on the synthesis method applied. The toxicity of AgNPs was assessed using metabolic activity of yeast cells as biomarker andmonitored with of the chromogenic assay, XTT. S. cerevisiae was introduced into different concentrations of AgNPs and incubated at 37oC for 72 h. After the incubation, XTT assay was performed to assess the cell viability. The XTT results showed that high concentration of AgNPs (100 µg/mL) inhibited the growth of S. cerevisiae. The synthesis of AgNPs and theassessment of their toxicity on S. cerevisiae was thus undertaken and established in this work.
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Promtong, Pawika. "Determinants of silver nanoparticle toxicity." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/determinants-of-silver-nanoparticle-toxicity(5b09211a-35b6-4f8c-8677-a76f652494b3).html.
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Silver nanoparticles (AgNPs) containing consumer products have increasingly emerged in the market because of their potential antibacterial property, which might result in increased human exposure and environmental contamination. AgNPs are toxic to mammalian and other cells but the determinants of this toxicity remain to be fully characterised and the potential impact of DNA repair systems has been poorly explored. This study, therefore, examined to what extent the size and shape of synthesised AgNPs determined AgNP toxicity in DNA repair proficient and deficient (8-oxoguanine DNAglycosylase; WT and OGG1-/-, respectively) mouse embryonic fibroblasts (MEFs) as well as a well-known human cell line used in the toxicity testing, HepG2 cells. Citrate-stabilised spherical- and triangular-shaped AgNPs (S-AgNPs andT-AgNPs, respectively) were synthesised chemically from AgNO3 using combinations of NaBH4 and sodium citrate as a reducing and stabilising agent, respectively, and purified by dialysis. Three different sized S-AgNPs were prepared with diameters of 7.6 ± 1.2, 14.3 ± 4.2, and 52.5 ± 17.9 nm as measured using transmission electron microscope (TEM), and their zeta potentials were -36.1±2.7, -39.5±2.7 and -36.7±4.1 mV, respectively. T-AgNPs had an edge length and thickness of 71.4 ± 11.1 nm and 5.7 ± 0.8 nm, respectively. The size and zeta potential of the purified AgNPs were constant in distilled water for at least 6 months. The uptake of both S- and T-AgNPs by cells resulted in a time and dose-dependent increase in the number of cellular AgNPs and the amount of Ag+ released intracellularly. These increases were associated with a decrease in cell viability (as measured using the MTT assay) and cell survival (the clonogenic assay), and an induction in ROS generation (the DCF assay) and DNA damage(the alkaline Comet assay) for all three cell lines. AgNPs were observed in cells using TEM, suggesting the uptake of AgNPs via an endocytosis pathway. Results suggested that an increase in cellular AgNP level and intracellular released Ag+ content were associated with a time and dose-dependent toxicity. Interestingly, cellular AgNP level and intracellular released Ag+ content might play an important role in size-dependent AgNP toxicity, in which exposure to the smaller S-AgNP sizes (7nm and 14nm) resulted in higher levels of both cellular AgNPs and Ag+ released intracellularly, and then to increased toxicity when compared with the larger S-AgNP size (50nm). Moreover, different shaped AgNPs might induce toxicity by different mechanisms: ROS-mediated toxicity might be induced by both 70nm T-AgNPs and 50nm S-AgNPs and 70nm T-AgNPs might also induce cell membrane damage. AgNP-induced toxicity was different in different cell lines with HepG2 cells being more sensitive to AgNPs particularly using the clonogenic assay, and this toxicity was associated with higher DNA damage observed in HepG2 cells after 24 h. OGG1-/- MEFs were more sensitive to intracellular released Ag+, leading to higher ROS formation and DNA damage in OGG1-/- MEFs than that observed in WT MEFs. In summary, this study strongly suggests that AgNPs induce toxicity via a Trojan-horse type mechanism, and not only Ag+ released intracellularly but also cellular AgNPs take part in this toxicity, and will eventually result in the biological responses of the cells.
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Patel, Sandeep A. "Photophysics of fluorescent silver nanoclusters." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28110.
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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Dickson, Robert; Committee Member: Brown, Ken; Committee Member: Curtis, Jennifer; Committee Member: Payne, Christine; Committee Member: Perry, Joseph.
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Chen, Haoguo. "Silver catalyzed enyne cyclization reactions." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841409.
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Crowell-Hilde, Kaki D. "There is a silver lining." [Johnson City, Tenn. : East Tennessee State University], 2003. http://etd-submit.etsu.edu/etd/theses/available/etd-0701103-123004/unrestricted/Crowell-HildeK072203f.pdf.
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Thesis (M.F.A.)--East Tennessee State University, 2003.Title from electronic submission form. ETSU ETD database URN: etd-0701103-123004. Includes bibliographical references. Also available via Internet at the UMI web site.
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Babaahmadi, V., M. Ghanbarajjeh, T. Toliyat, and M. Montazer. "Photochemical reduction of silver nitrate to nano silver using stannous chloride, ctab and daylight irradiation." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20633.
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Silver nanoparticles (NPs) were synthesized and stabilized by a simple method in
aqueous solution, by the reduction of silver nitrate with stannous chloride (SnCl2.2H2O)
and cetyl trimethyl ammonium bromide (CTAB)through day light irradiation. Thereby,
the silver nanoparticles were colloidally stabilized by CTAB as a surfactant. The synthesis
of silver NPs with different size were possible by changing the reaction conditions
such as reagent ratio. The silver NPs were characterized by Dynamic Light Scattering
(DLS) and UV-visible spectroscopy. A very strong plasmon resonance peak at 400-500
nm in the UV-visible spectra is a clear consequence of the silver NPs production. The
synthesized silver NPs showed good stability by using CTAB.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20633
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Schutze, Joan. "An evaluation of the Silver Chain Grief Support Service." Thesis, Curtin University, 1997. http://hdl.handle.net/20.500.11937/181.
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Client satisfaction is recognized as an important indicator in performance monitoring and evaluation. The Silver Chain Grief Support Service was evaluated using client satisfaction as a performance indicator. Data were collected via mailed, telephone and personal interviews utilizing the Client Satisfaction Questionnarie-8, dimensions of the Evaluation Ranking Scale, and open-ended questions. Results indicate high levels of satisfaction with the service. Findings and limitations of the evaluation are discussed. Recommendations for improvement of the service are presented.
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Jakobsen, Carolin. "Relation of silver release and antimicrobial effect in-vitro of silver containing wound dressings." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54803.
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Silver was used for its antimicrobial effect by the ancient Greeks, long before the existence of microorganisms were first suspected. Nowadays a wide range of antimicrobial dressings containing silver, either incorporated within or applied on the dressings, are available for clinical use. This type of dressings is designed to provide the antimicrobial activity of silver in a more convenient application. The aim with this master thesis was to evaluate if silver release and antimicrobial effect of nine silver containing dressings are dependent on the test medium and if there is any relation between silver release and antimicrobial effect. Release of silver and antimicrobial effect was evaluated by using a 6-well co-culture system, with inoculated test medium in the wells and dressing pieces in the culture well inserts. Three different test media with increased complexity and nutrient value were inoculated with either Results show that release of silver depends on the test fluid used; for phosphate buffered saline (PBS), the silver concentration was as most 1.2 ppm, but for a complex media containing calf serum (SWF), it varied from 9 ppm to 134 ppm. The viable counts in PBS were reduced by at least 3 log units for all dressings and bacteria, whereas in SWF there were no reduction and instead growth was observed. In general, a high release resulted in less bacterial growth. Results also indicated that kinetics of silver release affect the antimicrobial effect. It is likely to assume that it is important for a dressing to release silver quickly. It has previously not been possible to correlate silver release of wound care dressings and antimicrobial effect, since the two factors have been measured in different test systems and in different media. Since both factors depend on test medium and method used, it is shown in the present study that it is important to use relevant test medium for in-vitro evaluation. When measuring silver release and antimicrobial effect in the same test system, a relation is found.
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Watson, Venroy George. "Decoration of Graphene Oxide with Silver Nanoparticles and Controlling the Silver Nanoparticle Loading on Graphene Oxide." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1396879714.
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Hanks, Nicole A. "Silver Nanoparticle and Silver Ion Water Contamination: Assessment of phytoremediation and point-of-use filtration media." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1446547022.
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Oku, Yoshiaki. "Properties and Functions of Ultrasmall Silver and Gold Clusters on AgBr Microcrystals for Silver Halide Imaging." Kyoto University, 1999. http://hdl.handle.net/2433/181791.
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Torres, Urquidy Oscar Hernando. "Copper Resistant Bacteria Better Tolerate Commercially Available Antimicrobial Treatments Based in Silver and Silver-Copper Ions." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202734.
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In the current study, the antibacterial efficacy of zeolites containing silver or copper ions or a combination of these metals was assessed against several diverse copper resistant (CuR) and copper sensitive (CuS) strains of clinically relevant bacterial species. CuR Pseudomonas putida was significantly reduced in comparison to the unamended zeolite control. Unexpectedly, a CuS P. putida strain with no reported metal resistance appeared to be more resistant to the zeolite containing either Ag or Ag/Cu than the CuR strain. Contrary to expectations, after three and six hours of exposure, the CuS Escherichia coli displayed significantly more resistance to the Ag/Cu and Cu treatments than the reportedly CuR E. coli. All three reportedly CuR strains of Salmonella enterica exhibited resistance to Cu and Ag, as well as to the combination of the two metals after three and six hours of exposure. The reductions observed after 24 hours for all three CuR strains with Cu alone were still statistically significant compared to that of the CuS S. enterica strain. In addition, two of the CuR strains were more resistant to silver after 24 hours of exposure, suggesting a shared resistance mechanism such a copper efflux pump that also removes silver ions from the cell. Both the CuR and CuS strains of E. faecium were highly resistant to all of the treatments. In general, after comparison of all the resistances with all the treatments, E. faecium was the most resistant species, P. putida was the least resistant species, and the Salmonella strains were more resistant than E. coli in most cases.
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Steeg, Egon. "Investigations on growth and structure of silver and silver halide nanostructures formed on amphiphilic dye aggregates." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19577.
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Diese Arbeit beschäftigt sich mit dem Wachstumsmechanismus von Silberjodid Nanodrähten. Das Wachstum wurde über einen Zeitraum von Minuten bis hin zu Tagen untersucht. Im frühen Stadium bilden sich Silbernanopartikel innerhalb der Farbstoffröhren, welche als Keime für das weitere Wachstum von isolierten Drahtstücken dienen. Der Durchmesser dieser Drähte wird durch den Innendurchmesser der Röhren definiert. Im letzten Stadium wachsen diese Drahtstücke zusammen bis sie das gesamte Aggregat füllen. Dieser Wachstumsprozess impliziert einen Transport von Silber Ionen durch die Wand der Röhre. Das Wachstum der Drähte setzt sich weiter fort nachdem das Template gleichmäßig mit Drähten gefüllt ist und zerstört die Röhren in der Folge. Die Kristallstruktur der Drähte wurde sowohl mit hochauflösender Elektronenmikroskopie als auch Elektronenbeugung untersucht. Das Silberjodid konnte aufgrund seiner charakteristischen Wurtzite Struktur in der beta-Phase identifiziert werden. Da der Lösung nur Silbernitrat beigesetzt wurde, konnte die Quelle der Jod-Ionen als Verunreinigung im Farbstoffpulver ausgemacht werden. Das fragmentierte Wachstum der Drähte von verschiedenen Startpunkten aus führt zu Kristallen mit einkristallinen Domänen von mehr als 100 nm Länge. Eine bevorzugte Orientierung der Kristallstruktur relativ zur Aggregatachse wurde gefunden und durch die Molekülstruktur der Aggregate erklärt. Basierend auf diesen Ergebnissen wurde ein Model zum Wachstum von Silberjodid Nanodrähten im Inneren eines röhrenförmigen Molekülaggregats entwickelt. Es wurde angenommen, dass das Wachstum an Silberkeimen beginnt, die durch Photooxidation der bereits vorhandenen Jod Ionen mit Silber Ionen während der Belichtung der Probe gebildet werden. Diese Silberkeime ermöglichen die Bildung von stabilen Silberjodid Kristalliten und das nachfolgende Wachstum zu Drähten. Die Ergebnisse zeigen einen möglichen Weg zur Synthese von Metall-Halogenid Strukturen innerhalb von Farbstoffröhren.This thesis reports on the growth mechanism of silver iodide nanowires as revealed by conventional as well as cryogenic transmission electron microscopy. The growth, initiated by short illumination with UV light, has been observed over time scales ranging from minutes to days. In an early stage, within the tubular aggregates nanoparticles are formed which act as seeds for continuous growth of separate pieces of wires. The diameter of the wires is determined by the inner diameter of the tubes. In the final state, the pieces of wire totally fill the aggregate. The growth process indicates transport of at least silver ions through the tubular wall membrane. After homogeneously filling the template the wires grow onwards over the diameter of the nanotubes, destroying it in the process. The crystal structure of the wires was investigated by means of high resolution transmission electron microscopy and selected area electron diffraction. The silver iodide could be clearly identified in its beta-phase by its typical wurtzite structure. Since only silver nitrate was added to the solutions, the source of the iodide ions could be attributed to impurities within the dye powder itself. The fragmented growth of the wires from separate seeds leads to nanowires consisting of single crystalline domains exceeding 100 nm in length. A preferential orientation of the crystal lattice planes with respect to the aggregate axis was observed which is explained by the molecular structure of the aggregates. Based on these findings a model for the growth of silver iodide nanowires within the inner space of the tubular molecular aggregate is presented. The growth is assumed to start at silver seeds that are formed due to photo-oxidation of the already present iodide ions by the silver ions during the illumination of the sample. These silver seeds facilitate nucleation of silver iodide and subsequent growth into wires.
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Fridley, Brooke A. "Phytoformations of silver and gold nanoparticles." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4957.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xiii, 104 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 70-73).
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Leo, Bey Fen. "Stability and toxicity of silver nanomaterials." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/40887.
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Understanding the electrochemical stability or corrosion behaviour of metallic nanoparticles in aqueous environments is of central importance in the fields of catalysis, sensing and nano-electronics. The electrochemical stability of silver nanoparticles (AgNPs) was investigated as a function of applied potential, pH and particle size. The direct voltammetric measurements of the Ag oxidation potential indicate that the electrochemical stability of nanoparticles (NPs) is different from their bulk metal, suggesting that theoretically derived energy diagrams for a bulk material might not always be accurate for NPs. In order to understand interactions of nanomaterials (NMs) with biological systems, the cellular environment can be considered as an electrochemical cell, since metal ion release is a major pathway underlying their potential toxicity. NPs inhaled from the air into the deep lung first contact with the lung lining fluid where they have the potential to translocate into other organs like the brain, liver, spleen and heart via blood circulation. Here, this thesis specifically focuses on the impact of AgNMs on two major organs, the lung and brain. AgNMs as potential occupational and environmental hazards may raise health and safety concerns. For this reason, there is a need to assess the interaction of NMs with biological systems for early prediction of their cytotoxicity. The stability of AgNPs in dipalmitoylphosphatidylcholine (DPPC), the major component of lung surfactant, was investigated as a function of pH. TEM images revealed that the AgNPs were coated with a DPPC layer serving as a semi-permeable layer, improving their dispersion and delaying ions release in the lung. Furthermore, these studies suggested that size, stability and chemical composition of NP have to be taken into account in the evaluation of NP cytotoxicity. These observations have important implications for predicting the potential reactivity of AgNPs in the lung and the environment. In response to potential neurotoxicity, studies have shown that AgNPs can cross the blood brain barrier (BBB) via the systemic blood supply and then localise inside the brain, causing neurodegeneration, but much less is known about the distribution of AgNMs and their interaction with protein complexes inside the brain cells. Interaction of microglia with AgNMs, as well as their uptake, cytotoxicity and processing inside cells were investigated. The findings demonstrate that Ag2S formation acts as an ion trap for free Ag+, significantly limiting short term toxicity effects with important consequences for the neuro safety of AgNMs. In order to manipulate particular NPs features with favourable bio-availability and bio-distribution, not only NP uptake into cells, but also a fundamental understanding of the NPs-protein complex is necessary.
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Golder, Ryan. "Silver Complexes of Azobenzene and Derivatives." Thesis, University of Canterbury. Chemistry, 2012. http://hdl.handle.net/10092/9353.
Full textAbstract:
Thirty four silver(I) complexes of azobenzene and derivatives have been synthesised, only two of which have been previously published.
The azobenzene derivatives used are 2-bromo, 3-bromo, 4-bromo, 3,4’-dibromo, 2,4’-dibromo, 3-nitro, 4-dimethylamino, 4-methoxy, 2,6-dimethyl-4’-chloro, 2,6,2’,6’-tetramethyl and 2,2’-ethyleneazobenzene. 2,2’- and 4,4’-azobispyridine were also used along with diphenyltriazine. Six different silver(I) salts were used to make the complexes; they are tetrafluoroborate, hexafluorophosphate, perchlorate, nitrate, triflate and trifluoroacetate.
All of the complexes were analysed using X-ray crystallography.
In the complexes with azobenzene the anion was the most crucial factor in determining the resulting structure, as five different molecular topologies were seen with each change of anion. The 2-bromoazobenzene containing complexes continue this trend giving similar topologies to the azobenzene containing complexes. Once we come to the 3-bromo and 4-bromoazobenzene, we get a different molecular topology for the hexafluorophosphate containing complexes when compared to the original azobenzene containing complex, but we see a very similar structure for the perchlorate containing complexes. This would suggest that the coordinating anions give more predictable structures than the non-coordinating anions. The trend continues with both the 3,4’-dibromo and 2,4’-dibromoazobenzene complexes with triflate being structurally similar to the previous triflate containing complexes. The trend is reinforced further with 3-nitro and 4-methoxyazobenzene showing similar structures to the previously discussed complexes. The complex containing 4-dimethylaminoazobenzene can be disregarded, as the ligand has become protonated and therefore is unlike all the previously described results. When we come to the sterically hindered ligands 2,6-dimethyl-4’-chloroazobenzene the first three complexes show the same molecular topology of a silver atom bound to two ligands with a coordinating anion, however once we come to a tridentate coordinating anion triflate a 1-D metallopolymer is observed. This breaks the trend, as the structures are similar regardless of the change in anion. A similar effect is seen in 2,6,2’,6’-tetramethylazobenzene with both structures standing alone as no complexes with a similar molecular topology were observed. This effect is again noted in the complexes containing 2,2’-ethyleneazobenzene. The complexes all form a similar structure regardless of the anion used. As expected the 2,2’- and 4,4’-azobispyridine along with diphenyltriazine do not follow the trend observed earlier with the non-sterically hindered ligands as they can coordinate through additional nitrogen atoms in the aromatic ring or in the case of diphenyltriazine an additional nitrogen atom in the triazine group.
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Sütterlin, Susanne. "Aspects of Bacterial Resistance to Silver." Doctoral thesis, Uppsala universitet, Klinisk mikrobiologi och infektionsmedicin, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-247472.
Full textAbstract:
Bacterial resistance to antibiotics has increased rapidly within recent years, and it has become a serious threat to public health. Infections caused by multi-drug resistant bacteria entail higher morbidity, mortality, and a burden to health care systems. The use of biocides, including silver compounds, may affect the resistance to both biocides and antibiotics and, thereby, can be a driving factor in this development. The aim of the following thesis was to investigate the frequency of silver resistance and the effects of silver exposure on bacterial populations being of clinical significance and from geographically different parts of the world. Furthermore, it explored the genetic background of silver resistance, and if silver could select directly or indirectly for antibiotic resistance. By a range of methods, from culture in broth to whole genome sequencing, bacterial populations from humans, birds and from the environment were characterized. The studies showed that sil genes, encoding silver resistance, occurred at a high frequency. Sil genes were found in 48 % of Enterobacter spp., in 41 % of Klebsiella spp. and in 21 % of all human Escherichia coli isolates with production of certain types of extended-spectrum beta-lactamases (CTX-M-14 and CTX-M-15). In contrast, silver resistance was not found in bird isolates or in bacterial species, such as Pseudomonas aeruginosa and Legionella spp., with wet environments as their natural habitat. One silver-resistant Enterobacter cloacae strain was isolated from a chronic leg ulcer after only three weeks of treatment with silver-based dressings. The in-vivo effects of these dressings were limited, and they failed to eradicate both Gram-positive and Gram-negative bacteria. The activity of silver nitrate in vitro was bacteriostatic on Gram-positive species such as S. aureus and bactericidal on Gram-negative species. In Enterobacteriaceae, sil genes were associated with silver resistance phenotypes in all but one case. Using whole genome sequencing, single nucleotide polymorphisms in the silS gene were discovered after silver exposure in isolates with expressed silver resistance. This resistance could co-select for resistance to beta-lactams, co-trimoxazole and gentamicin. The findings of this thesis indicate that silver exposure may cause phenotypic silver resistance, and it may reduce the susceptibility to mainly beta-lactams and select for bacteria with resistance to clinically important antibiotics.
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Krusing, Cecilia. "Miljöbyggnad nivå Silver : Fallstudie brf Stenhuggaren." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-25161.
Full textAbstract:
De senaste decennierna har miljö och hållbarhet fått en större betydelse för bygg- och fastighetsbranschen. En rad miljöcertifieringar för byggnader har vuxit fram. Miljöbyggnad enligt Sweden Green Building Council (SGBC) är ett svenskt certifieringssystem för att certifiera byggnader inom Energi, Inomhusmiljö och Byggvaror. En certifierad byggnad enligt miljöbyggnad kan erhålla betyg guld, silver eller brons. Fallstudie har gjorts av brf Stenhuggaren, ett bostadsprojekt där 47 bostadsrätter ska byggas, där byggherren HSB Göta:s ambition är att certifiera byggnaden för Miljöklassning nivå Silver, som är ett led i att nå företagets övergripande klimatmiljömål. Arbetet har bestått av litteraturstudier, intervjuer med medverkande konsulter i projektet, studier av konsulternas resultat av projekteringen samt undersökning av vad entreprenören ska göra i det praktiska genomförandet av byggnationen för att säkerställa att uppställda mål nås. Manual 2.1 (utgåva 120101) Bedömningskriterier för nyproducerade byggnader, enligt SGBC, har utgjort en del av underlaget i denna rapport. En av slutsatserna som kommit fram i arbetet är att entreprenörens arbete i produktionen med miljöklassning inte har den betydelse som författaren antog inledningsvis, utan det huvudsakliga arbetet ligger i ett gediget arbete vid projektering. Att utveckla miljö-och hållbarhetsarbete i projektering kan skapa god förutsättning för att fler byggnader på sikt blir miljöklassade. Detta kan i ett längre perspektiv innebära kvalitativa och hållbara byggnader.In recent decades environment and sustainability have gained greater importance for construction and real estate. A number of environmental certifications have emerged. Green Building according to Sweden Green Building Council (SGBC), is a swedish system to certify buildings in energy, indoor environment and building materials. A certified building according to Green Building can obtain grade Gold, Silver or Bronze. A case study has been made on Stenhuggaren, a housing project with 47 condominiums, where the developer has the ambition to certify the building for grade Silver, in order to reach the companys overall climate targets. The case study consists of literature studies, interviews with participating consultants in the housing project. The author has studied the consultants results from project planning and examined what the contractor will do in practical implementation of construction to ensure that estimated goals will be reached. The Manual 2.1 (edition 120101) Evaluation criterias for new buildings, according to SGBC, has been part of data in this report. One of the conclusions that’s emerged from working with this report is that work by the contractor dont have the important significance for environmental classification, which the author assumed initially. The main work lies in thorough project planning. Developing environmental and sustainability work in project planning can create an opportunity for more buildings to be environmentally certified. In a longer perspective this provides an opportunity and possibility to obtain qualitative and sustainable buildings.