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1
Coetzee, Karolien. "Gold complexes obtained from gold ylide preparations". Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/21206.
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Thesis (MSc)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: This investigation comprised the synthesis and characterisation of new Au(I) phosphonium ylide complexes and other compounds formed during coordination reactions. These complexes could exploit the synergism between two pharmacologically active substances (gold complex unit and phosphorus ylide) to furnish an even more active substance. Four phosphonium salts were prepared, [C6H5CH2PPh3]Br (1), [Ph3P(CH2)3PPh3]Br2 (2a), p-[{Ph3PCH2}2C6H4]Br2 (3a) and m- [{Ph3PCH2}2C6H4]Br2 (4a), by reacting PPh3 with the corresponding alkylbromides. The 13C and 1H NMR spectra of the compounds 1 – 4a indicated that many of the nuclei are magnetically inequivalent. The aromatic units in PPh3 are normally identical, but multiple, overlapping signals proved that the corresponding ortho, meta and para carbon and proton nuclei are in magnetically different environments from each other. Single crystal structures of salts 3a and 4a were determined. Different methods were followed to deprotonate the phosphonium salts to afford the corresponding ylides and to coordinate the ylides to gold precursor compounds. Most of the reactions yielded inseparable mixtures of products and pure compounds could not be isolated in large enough quantities for characterisation by all physical methods. Sufficient crystals for structure determination by X-ray diffraction were obtained. The product mixtures were characterised by 1H, 13C and 31P NMR spectroscopy and mass spectrometry. Characteristic downfield chemical shift changes after coordination of the ylides to Au(I) were observed for the carbon and phosphorus nuclei, while the protons displayed upfield shifts. Reaction of (C6F5)Au(tht) with the salts 1 – 4a, and subsequent deprotonation yielded the gold(I) ylide complexes [C6H5CH(AuC6F5)PPh3] (5), [{Ph3PCH(AuC6F5)}2CH2] (6), p-[{Ph3PCH(AuC6F5)}2C6H4] (8), and m- [{Ph3PCH(AuC6F5)}2C6H4] (9). The crystal and molecular structures of compounds 5 and 9 were determined. Deprotonation of 4a with n-BuLi, followed by reaction with (C6F5)Au(tht) yielded complexes 9 and [{Ph3PCH2}2C6H4][BrAuC6F5]2 (10). The crystal structure of compound 10 was determined. Two aurocyclic compounds, [μ- {(Ph3PCH)2CH2}2Au2][BF4]2 (12) and [μ–{(Ph3PCH)2C6H4}2Au2][BF4]2 (13) were synthesised by deprotonating salts 2b and 3b with n-BuLi and subsequently reacting the corresponding bisylides with ClAu(tht). Reaction procedures in which Ag2O was used as deprotonating agent for the phosphonium salts 2a, 3a and 4a, yielded mixtures of products. Single crystals of complexes m-[Ph3PCH(AuC6F5)C6H4CH3] (14), [C6F5Au(tht)] (15) and [(C6F5)2Au][(Ph3PCH2)2C6H4] (16) were isolated from the reaction mixtures and subjected to X-ray crystal structure determination. The molecular structure of 15 exhibited unusual aurophilic interactions and represents the first example of a linear gold chain in which the gold···gold distances systematically alternate between 3.13Å, 3.31Å and 3.20Å. Salt 2b was reacted with Ph3PAu(acac) to afford the desired compound, [{Ph3PCH(AuPPh3)}2CH2](BF4)2 (19), along with [CH3C(O)C(AuPPh3)2C(O)CH3] (17) and some byproducts. Compound 17 was characterised by single crystal Xray diffraction. The fluorobiphenylgold(I) complexes, 4,4’-[(AuPPh3)2C12F8] (21) and 2,2’- [(AuPPh3)2C12F8] (22) were synthesised by reaction of ClAuPPh3 with the lithiated 2,2’-dibromooctafluorobiphenyl and 4,4’-dibromooctafluorobiphenyl respectively. The molecular structure of 21 revealed that one of the C–Au–P bond angles deviates from linearity by 12.5°, probably as a result of π-stacking of the tetrafluorophenyl rings and steric requirements of the bulky PPh3 units. The other C–Au–P bond angle is linear [177.9(3)°].
AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van nuwe fosfoniumylied goud(I)-komplekse en ander verbindings wat gedurende koördinasiereaksies vorm. Sulke komplekse kan sinergisme tussen twee farmakologies-aktiewe entiteite (goud(I) en fosfoniumylied) om ʼn meer aktiewe verbinding te vorm meebring. Vier fosfoniumsoute is berei, [C6H5CH2PPh3]Br (1), [Ph3P(CH2)3PPh3]Br2 (2a), p- [{Ph3PCH2}2C6H4]Br2 (3a) en m-[{Ph3PCH2}2C6H4]Br2 (4a), deur PPh3 met die ooreenstemmende alkielbromiedes te reageer. Die 13C- en 1H- KMR-spektra van dié verbindings toon dat ʼn aantal kerne in aromatiese ringe magneties onekwivalent is. Normaalweg is die koolstowwe in PPh3-eenhede ekwivalent, maar meervoudige, oorvleuelende pieke het nou getoon dat die ooreenstemmende orto-, meta- en para-koolstof sowel as die ooreenstemmende protonkerne in verskillende magnetiese omgewings voorkom. Die kristalstrukture van die soute 3a en 4a hierbo is met behulp van X-straal tegnieke bepaal. Verskillende metodes is gevolg om die fosfoniumsoute te deprotoneer na die ooreenstemmende yliede en om die yliede dan aan goud-bevattende uitgangstowwe te probeer koördineer. Die meeste reaksies het nie-skeibare mengsels gevorm en enkelprodukte kon nie in groot genoeg konsentrasies geïsoleer word om hulle afsonderlik te karakteriseer nie. Kristalle vir X-straal kristalstruktuur bepalings is verkry. Die produkmengsels is gekarakteriseer met behulp van 1H-, 13C- en 31P- KMR-spektroskopie en massaspektrometrie. Karakteristieke veranderinge in chemiese verskuiwings na laer veldsterktes vir die koolstof en fosfor kerne is waargeneem na koördinasie van die yliede aan Au(I), terwyl die protone na höer veldsterktes verskuif het. Die reaksie tussen (C6F5)Au(tht) (tetrahidrotiofeen) en soute 1 – 4a gevolg deur deprotonering, vorm die goud-yliedkomplekse [C6H5CH(AuC6F5)PPh3] (5), [{Ph3PCH(AuC6F5)}2CH2] (6), p-[{Ph3PCH(AuC6F5)}2C6H4] (8), en m- [{Ph3PCH(AuC6F5)}2C6H4] (9). Die kristalstrukture van komplekse 5 en 9 het al die molekulêre interaksies daarin blootgelê. Deprotonering van 4a met n-BuLi, gevolg deur reaksie met (C6F5)Au(tht) lewer komplekse 9 en [{Ph3PCH2}2C6H4][BrAuC6F5]2 (10). Die kristal- en molekulêre struktuuur van kompleks 10 is bepaal. Twee aurosikliese verbindings, [μ- {(Ph3PCH)2CH2}2Au2][BF4]2 (12) en [μ–{(Ph3PCH)2C6H4}2Au2][BF4]2 (13) is gesintetiseer deur gedeprotoneerde bisyliede verkry van 2b en 3b met substitusie van tht aan die ClAu-eenheid te koördineer. Reaksieprosedures waarin Ag2O vir deprotonering van die fosfoniumsoute 2a, 3a en 4a gebruik is, het tot mengsels van produkte aanleiding gegee. Enkelkristalle van komplekse [Ph3PCH(AuC6F5)C6H4CH3] (14), [C6F5Au(tht)] (15) en [(C6F5)2Au][(Ph3PCH2)2C6H4] (16) is geïsoleer uit die reaksies en kristalstruktuurbepalings is uitgevoer. Die molekulere struktuur van 15 toon ongewone aurofiliese interaksies en verteenwoordig die eerste voorbeeld van ʼn linieêre goudketting; met goud···goud afstande wat sistematies varieër tussen 3.13Å, 3.31Å en 3.20Å. Sout 2b is met Ph3PAu(acac) gereageer om die gewenste produk, [{Ph3PCH(AuPPh3)}2CH2](BF4)2 (19), saam met [CH3C(O)C(AuPPh3)2C(O)CH3] (17) en ander byprodukte te vorm. Verbinding 17 is as enkelkristalle Xstraalkristallografies gekarakteriseer. Die fluorobifeniel goud(I)-komplekse, 4,4’-[(AuPPh3)2C12F8] (21) en 2,2’- [(AuPPh3)2C12F8] (22), is gesintetiseer deur koördinasie van AuPPh3 aan die gelitieërde 2,2’-dibromooktafluorobifeniel en 4,4’-dibromooktafluorobifeniel respektiewelik. Die molekulere struktuur van 21 het getoon dat een van die C-Au- P bindingshoeke met 12.5º afwyk van 180º, waarskynlik as gevolg van π- interaksie van die tetrafluorofenielringe en die steriese vereistes van die groot PPh3-eenhede. Die ander C-Au-P bindingshoek is linieêr [177.9(3)°].
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Mulley, Melinda Ann. "We hear nothing but gold, gold, gold : women and poverty in South Australia during the gold rushes 1850-1855 /". Title page, table of contents and introduction only, 2004. http://web4.library.adelaide.edu.au/theses/09AR/09arm9589.pdf.
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Wetzel, Mary S. "Sodek's Gold". Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc500390/.
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Sodek's Gold is a novel based on individuals the writer has known in the Caribbean who have been placed in fictitious circumstances. Included are social issues, conditions, and dialects found there. The main character, David Sodek, is an Englishman working in the Caribbean who discovers an ancient coin and becomes obsessed with finding more. Sodek's search is impeded by the strongarm Mostyn, but with the help of his friend Elbert he recovers an underwater cache of golden treasure. Elbert is killed. Sodek avenges Elbert's death but ultimately relinquishes the gold and himself to the sea. The theme of the work involves Sodek's obsessive personality as seen in his increasingly pedantic and destructive search, and in his unrealistic belief that money buys freedom. Included between chapters are vignettes comparing the characters and nature, and foreshadowing following events.
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Cotten, Nicole. "Fool's gold". Thesis, University of Iowa, 2018. https://ir.uiowa.edu/etd/6086.
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Fool’s Gold is a collection of handmade books that illustrate selected Grimms’ fairy tales and offer an unexpected interpretation of the actions of the heroes. Each book displays a unique cover decoration, inspired by medieval European treasure bindings. Treasure bindings incorporate dimensional decorative elements such as gems, gold or other metalwork and often depict Christ's suffering. In a similar way, Fool's Gold beautifies the suffering of the protagonists using gold leaf, glass beads and lush illustrations. A traditional hidden fore-edge painting technique is used to reveal more scenes from each story. When the pages are fanned opened, the fore-edge paintings display the gruesome revenge the perceived heroes take upon the villains.
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Warm, Julie J. Day Nancy E. "From good to gold: predicting nonprofit engagement in entrepreneurial activity /". Diss., UMK access, 2004.
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Thesis (Ph. D.)--Henry W. Bloch School of Business and Public Administration. University of Missouri--Kansas City, 2004."A dissertation in public affairs and administration and education." Advisor: Nancy Day. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 28, 2006. Includes bibliographical references (leaves 107-113). Online version of the print edition.
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Gottfried, Jörg Michael. "CO oxidation over gold adsorption and reaction of oxygen, carbon monoxide, and carbon dioxide on an Au(110)-(1x2) surface /". [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/133/index.html.
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Skelton, Helen Elisabeth. "Gold and gold-based nanoparticles for NOx reduction catalysis". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610182.
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Yang, Yi. "Gold(I) oxo, imido, hydrazido complexes and gold clusters /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9841362.
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Bartlett, Samuel Andrew. "God, Gold, or Glory: Norman Piety and the First Crusade". UNF Digital Commons, 2008. http://digitalcommons.unf.edu/etd/119.
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Recent trends in crusade historiography depict the Frankish participants of the First Crusade as acting out of piety, while their Norman counterparts remain as impious opportunists. This thesis challenges this prevailing point of view, arguing that the Norman crusaders met the same standard of piety as the Franks. To support my theory, I looked at four different facets on the question of Norman piety, dividing them up into chapters of my thesis. In the first chapter, there is a brief discussion of the current portrayal of the Normans in modem crusade historiography. In the next chapter, I established what piety meant and how it was demonstrated by Christians of the 11th and 12th centuries. This includes an examination of relevant monastic charters, which provide evidence that the Normans had strong ties to the Papacy prior to the expedition to the East. The third chapter is a short summary about the developments leading to the First Crusade, and the standard of piety set by Pope Urban II. In the fourth chapter I examine the chronicles of the First Crusade and their characterization of the crusaders, both Norman and Frank, to see if the crusaders met the pontiff's standard.
I conclude that the primary accounts depict the Normans as no different from their Frankish co-religionists, with both groups acting out of piety as well as ambition. The actions of a Norman knight, Bohemond, and a Frankish crusader, Raymond of Toulouse, exemplify this fact. The comparison of these two, as well as the rest of the crusade leaders, demonstrate that the Norman crusaders were driven by a complex and sometimes conflicting mix of pious and secular motivations, no different from their Frankish counterparts.
The armies of soldiers fighting in the First Crusade in response to Pope Urban II's call to retake Jerusalem were composed of a variety of cultural groups from Western Europe. The argument over what motivated these men to become armed pilgrims, to travel long distances to strange lands, to fight and most likely die, began with the accounts of the eyewitnesses and continues to the present day. Early on the distinction was made between the pious Franks and the materialist Normans. Some Medieval chroniclers portrayed the Norman crusaders as interested only in amassing land and power, rather than fulfilling their religious vow. Even in recent historiography, the traditional interpretation of the Norman role in the First Crusade is not one of piety, but rather of opportunism - to use the conflict as a springboard for expansion into Byzantine and Muslim lands. This depiction is in stark contrast to the ongoing reexamination of the Frankish crusaders, who some crusade historians see as having a deep religious motivation. The Normans remain as the standard bearer of the pre-revisionist interpretation of crusader motives - for gold and glory, but not for God. However, examination of the evidence does not bear this distinction out. Instead of greed, a pattern of pious acts emerges performed by the families of the prominent Norman crusaders or in the case of Bohemond of Taranto, the crusaders themselves. The Normans who took up the cause for crusade were as conventionally pious as the Franks and other Europeans, exposing the falsehood of their historical portrayal as impious opportunists.
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Jennings, Nicola. "Laser deposition of metallic gold using gold(I)-carbene complexes". Thesis, Keele University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436197.
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Gomes, Ricardo Cláudio. "Is gold a hedge? The relation between gold and shares". Master's thesis, Instituto Superior de Economia e Gestão, 2016. http://hdl.handle.net/10400.5/13080.
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Mestrado em FinançasNum período em que uma estratégia de investimento cuidadosa e diligente é cada vez mais necessária, o hedging é uma poderosa ferramenta que pode ser usada pelos investidores com o propósito de reduzir os riscos associados aos investimentos no mercado de ações. Este projecto tem como objectivo estudar a correlação entre os retornos do ouro e os retornos das ações, com o intuito de descobrir se o ouro pode ser considerado um hedge para as ações ou um safe haven. Os resultados do uso de um modelo econométrico, baseado em dados de alguns dos maiores índices a nível mundial e de um índice de rastreamento de referência para futuros de ouro, para o período de Janeiro de 1996 até Dezembro de 2015, sugerem que o ouro não é um hedge para qualquer dos mercados de ações analisados, ainda que aparente ser um forte safe haven sobre condições extremas de retornos negativos do mercado de ações. Ainda assim, é demonstrado que os resultados do modelo econométrico estão dependentes do período analisado.
In a period where careful and diligent investing is increasingly required, hedging is a powerful weapon that can be used by investors in order to reduce the risks associated with stock market investments. This project aims at studying the correlation between gold returns and stock returns, intending to find out if gold can be considered a hedge for stocks or a safe haven. The results of the use of an econometric model, based on data from some major worldwide stock indexes and a benchmark tracking index for gold futures, regarding the period from January of 1996 until December of 2015, suggest that gold is not a hedge for any of the stock markets under analysis but it appears to be a strong safe haven under extreme negative stock market conditions. However, it is shown that the results from the model are dependent on the period analysed.
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Taurasi, Donatella <1984>. "Gold and the Stock Market: 3 Essays on Gold Investments". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5693/1/Taurasi_Donatella_Tesi.pdf.
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This thesis gives an overview of the history of gold per se, of gold as an investment good and offers some institutional details about gold and other precious metal markets. The goal of this study is to investigate the role of gold as a store of value and hedge against negative market movements in turbulent times. I investigate gold’s ability to act as a safe haven during periods of financial stress by employing instrumental variable techniques that allow for time varying conditional covariance. I find broad evidence supporting the view that gold acts as an anchor of stability during market downturns. During periods of high uncertainty and low stock market returns, gold tends to have higher than average excess returns. The effectiveness of gold as a safe haven is enhanced during periods of extreme crises: the largest peaks are observed during the global financial crises of 2007-2009 and, in particular, during the Lehman default (October 2008). A further goal of this thesis is to investigate whether gold provides protection from tail risk. I address the issue of asymmetric precious metal behavior conditioned to stock market performance and provide empirical evidence about the contribution of gold to a portfolio’s systematic skewness and kurtosis. I find that gold has positive coskewness with the market portfolio when the market is skewed to the left. Moreover, gold shows low cokurtosis with the market returns during volatile periods. I therefore show that gold is a desirable investment good to risk averse investors, since it tends to decrease the probability of experiencing extreme bad outcomes, and the magnitude of losses in case such events occur. Gold thus bears very important and under-researched characteristics as an asset class per se, which this thesis contributed to address and unveil.
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Taurasi, Donatella <1984>. "Gold and the Stock Market: 3 Essays on Gold Investments". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5693/.
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This thesis gives an overview of the history of gold per se, of gold as an investment good and offers some institutional details about gold and other precious metal markets. The goal of this study is to investigate the role of gold as a store of value and hedge against negative market movements in turbulent times. I investigate gold’s ability to act as a safe haven during periods of financial stress by employing instrumental variable techniques that allow for time varying conditional covariance. I find broad evidence supporting the view that gold acts as an anchor of stability during market downturns. During periods of high uncertainty and low stock market returns, gold tends to have higher than average excess returns. The effectiveness of gold as a safe haven is enhanced during periods of extreme crises: the largest peaks are observed during the global financial crises of 2007-2009 and, in particular, during the Lehman default (October 2008). A further goal of this thesis is to investigate whether gold provides protection from tail risk. I address the issue of asymmetric precious metal behavior conditioned to stock market performance and provide empirical evidence about the contribution of gold to a portfolio’s systematic skewness and kurtosis. I find that gold has positive coskewness with the market portfolio when the market is skewed to the left. Moreover, gold shows low cokurtosis with the market returns during volatile periods. I therefore show that gold is a desirable investment good to risk averse investors, since it tends to decrease the probability of experiencing extreme bad outcomes, and the magnitude of losses in case such events occur. Gold thus bears very important and under-researched characteristics as an asset class per se, which this thesis contributed to address and unveil.
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Ahmad, Khurram y Muhammad Azeem. "Gold Standard Website". Thesis, Växjö University, School of Mathematics and Systems Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-5520.
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The aim of this thesis is to design a web base system which provides functionality of comparison between two java files on the basis of point-to information (P2I). User will upload Java files and analysis of Java files called point-to analysis (P2A). System will store the files in the file system for reference and download in later time. System will extract the information called P2I from P2A and it will store that information in the database.
Database should be flexible to accommodate the changes in P2A file and system should be able to extract the P2I and store it in database with minimum support of system administrator.
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Smith, Jon Anthony. "Polyaniline Gold Nanocomposites". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4900.
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Polyaniline/Gold Nanocomposites
J. Anthony Smith
141 Pages
Directed by Dr. Ji and #345;?anata
The expectation that it is possible to create a range of new materials from two basic components, polyaniline fibers and gold particles is explored. Three synthetic methods were employed each of which created different materials and required different investigation techniques. The methods are: chemical, one step aniline oxidation / AuCl4- reduction; electrochemical/chemical, a two-step composite growth achieved by electrochemical polyaniline thin film growth followed by film immersion in AuCl4- solution and spontaneous reduction to gold particles; electrochemical, resulting in freestanding polyaniline thin film/Au nanoparticles carried out by electrochemical stripping of a polyaniline thin film grown over a sacrificial gold layer in the presence halide solutions. The incorporation of particles was shown to affect film morphology and electrical properties in all synthetic methods. The changes are in large part attributed to the development of a contact potential between the polyaniline and the gold particles. Applications for the composites include use as chemically sensitive layers, corrosion inhibition materials, and use as probes to evaluate nanoparticle substrate interactions.
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Tran, Dung Trung. "Gold-containing bimetallicnanoparticles". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1362/.
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This thesis describes computational studies, syntheses and characterization of Cu-Au, Pd-Au, and Pt-Au bimetallic nanoparticles. The computational methodology is a combination of a genetic algorithm coupled with an empirical potential and density functional theory, which is used to study theoretically the geometrical structure, chemical configuration, and electronic properties of 38 atom Cu-Au and 40-atom Pt-Au nanoparticles. Experimental Cu Au and Pt-Au nanoparticles are synthesized by wet-chemical methods: the two-phase method combined with a galvanic exchange procedure (dodecanethiol-stabilized Cu-Au nanoparticles), the polyol method (Polyvinylpyrrolidone stabilized Pt-Au nanoparticles), and the Turkevich-Frens method combined with a successive reduction procedure (citrate-stabilized Pt-Au nanoparticles). The Pd-Au nanoparticles which are characterized in our work were synthesized by a microbial method. The nanoparticles are characterized using transmission electron microscopy (TEM) and scanning TEM (STEM) combined with high angle annular dark field (HAADF) imaging, energy dispersive X-ray elemental mapping using a silicon drift detector (SDD), tomography, and electron energy loss spectroscopy (EELS). Sizes and shapes of the Cu-Au, Pd-Au, and Pt-Au nanoparticles are studied by TEM. Morphological evolution and aggregation of the Cu-Au nanoparticles are also observed under the TEM electron beam. SDD-EDX elemental mapping combined with HAADF contrast is used to study the chemical configuration of all the three systems. HAADF-STEM tomography is performed for the Pd-Au nanoparticles. Surface plasmon resonances of the Cu-Au and Pd-Au nanoparticles are studied using EELS. The structures and configurations of the theoretical bimetallic clusters and the experimental bimetallic nanoparticles are found to be composition-dependent.
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Ball, Liam Thomas. "Oxidative gold catalysis". Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.649363.
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The utility of aryltrimethylsilanes 1 as coupling partners in oxidative gold catalysis has been established through the development of first- and second-generation methodologies for alkene oxyarylation, and through the realisation of a protocol for the direct arylation of simple arenes. Oxidative oxyarylation of mono-substituted olefins 2 is achieved in the presence of a commercially-available precatalyst, Ph3P AuCl and a fluoronium oxidant, Selectfluor. The net addition of an O-nuc leophile and a silane-derived aryl moiety across the C=C double bond affords the conesponding homo benzylic alcohol derivative 3 with complete regioselectivity. Although diverse O-nucleophiles and arylating agents are tolerated, the substrate-scope is limited to alkenes bearing a single alkyl substituent due to the high reactivity of the oxidant. Relative to literature procedures employing arylboronic acids, the use of arylsilanes 1 significantly reduces the generation of symmetrical biaryls 4 via oxidative homocoupling of the arylating agent. Limitations imposed upon the first-generation protocol by Selectfluor prompted an extensive screen of reaction conditions that led to identification of l -hydroxy-I,2-benziodoxol-3-(lH)-one (IBA) as an efficient terminal oxidant for gold-catalysed oxyarylation. Use of IBA expands the substrate scope to include styrenes 5, thereby providing access to bibenzyls 6, and gem-disubstituted olefins 7, which afford tertiary homobenzylic alcohol derivatives 8. Whilst the range of suitable O-nucleophiles is largely resh'icted to methanol, sterically- and electronically-diverse arylsilanes 1 can be employed. Use of benzotrifluoride as the reaction solvent substantially reduces the generation of alylsilane homocoupling side-products 4.
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Davies, Scott. "Catalysis by gold". Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/100727/.
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The oxidation of benzyl alcohol over supported Au, Pd and AuPd catalysts on a range of metal oxide supports was investigated using a Radley’s Starfish Reactor. Reaction conditions such as temperature, solvent, support and metal loading were varied in order to obtain insight into benzyl alcohol oxidation. All catalysts were prepared using the sol immobilisation technique. It was discovered that AuPd bimetallic catalysts were most active for benzyl alcohol oxidation, in a ratio of 1:1 Au:Pd. Further, substituted benzyl alcohol compounds were oxidised using AuPd catalysts in order to investigate the mechanistic properties of benzyl alcohol oxidation. By conducting the Hammett methodology on a range of substituents, mechanistic insight into the reaction was possible due to the electronic effects substituent groups had on the parent benzyl alcohol molecule. The results from these experiments indicate that a transition state with a formal charge is being created as the reaction proceeds and electron donating groups such as MeO in the para- position was able to stabilise this transition state and promote the oxidation reaction, resulting in a higher rate of reaction. Lastly, cinnamyl alcohol was subjected to the same oxidation reactions as benzyl alcohol in order to assess how a structural variant of benzyl alcohol is affected by varying certain catalytic parameters such as temperature, support and solvent. It was found that cinnamyl alcohol undergoes similar reactions as benzyl alcohol and the major oxidation product is the corresponding cinnamaldehyde. Differing supports had different effects on the oxidation, with disproportionation being suppressed on certain supports. Higher temperature also promoted hydrogenation of cinnamyl alcohol.
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Kowalski, Steven Casimer. "Gray and Gold". Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1154351928.
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Amir, Juliana R. "Glass and Gold". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491472934550759.
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Ford, Sarah. "Fire and Gold". Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1559072363615141.
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Hamzić, Melissa. "Enantio- und Diastereoselektive gold-katalysierte Reaktionen und Aktivitäts-Untersuchungen von Phosphan-Gold-Komplexen in der homogenen Gold-Katalyse". Berlin Mensch-und-Buch-Verl, 2009. http://d-nb.info/995894736/04.
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Smirnova, Ekaterina. "Polynuclear Gold(I) Catalysts: When One Gold(I) is not Enough". Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/401744.
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La recerca del nostre grup es basa en la invenció de noves metodologies sintètiques utilitzant catalitzadors d’or electrofílics. Amb l’objectiu d’incrementar l’electrofilicitat dels complexos catiònics fosfina-or(I), es va decidir utilitzar fosfines que continguin bor com a lligands ambifílics. L’extracció de l’halogen del complex neutre, va permetre obtenir per primera vegada el clúster hexanuclear Au6(I), el qual va resultar ser catalíticament actiu en la ciclació d’enins.
Els estudis mecanistics, confirmats pels càlculs DFT, han demostrat que l’etapa limitant de la isomerització dels 1,6-enins catalitzada pel clúster és la substitució associativa del lligand.
Per tal d’entendre millor la influència de les propietats electròniques de la fosfina en la reactivitat del clúster, s’han preparat dos clústers hexanuclears que contenen anells ciclohexil i 2-furil com a substituents a l’àtom de fòsfor.
D’altra banda, amb el fi d’incrementar l’electrofilicitat dels centres d’or, s’han obtingut complexos d’or(I) polinuclears mitjançant l’ús del lligand 2,6-bis(difenilfosfino)piridina (DPPPY). Com a conseqüència, aquests complexos linear i tetranuclear d’or(I) no només catalitzen transformacions d’enins sinó que també activen l’acetona i les 1,3-dicetones per formar complexos tetranuclears d’enolat amb or(I). A més, també han resultat ser catalíticament actius en reaccions com la carbonilació d’amines primàries a urea (productes finals i intermedis en la síntesi de pesticides, fertilitzants, pigments i compostos farmacèutics).
Quan el complex tetranuclear linear d’or(I) va ser preparat sense la presència d’acetonitril, es va obtenir un complex Au8 amb una estructura mai descrita prèviament, formant un anell en el mateix pla. Aquest fet representa una idea trencadora en la química de l’or, obrint pas a la catàlisis en superfície a nivell molecular.
En el futur, les propietats catalítiques del nou i polimorf complex amb diversos nuclis d’or(I) seran investigades de manera més àmplia cap a la recerca d’una síntesi eficient de complexos, molècules biològicament actives i materials aromàtics policíclics.La investigación de nuestro grupo se centra en la invención de nuevos métodos sintéticos usando catalizadores de oro electrófilos. En un intento de aumentar la electrofilia de los complejos de oro(I) decidimos usar fosfinas orto-boronadas como ligandos ambifílicos. Tras la abstracción de halógeno del complejo neutro de oro(I) obtuvimos el primer clúster Au6(I) con ligandos aromáticos geminalmente diaurados, que muestran actividad catalítica en la ciclación de eninos. Dos clústeres adicionales con sustituyentes ciclohexil y 2-furil han sido sintetizados, con la idea de lograr un mayor entendimiento de la influencia de las propiedades electrónicas de la fosfina en la reactividad. Nuestro siguiente enfoque para aumentar la electrofilia de oro(I) fue la aplicación del ligando 2,6-bis(difenilfosfino)piridina como estrategia para obtener complejos polinucleares de oro(I) que presenten interacciones aurofílicas. Como resultado, se encontró que el complejo linear tetranuclear de oro(I) obtenido no solo catalizaba transformaciones de 1,6-eninos sino también activaba acetona y 1,3-dicetonas para formar complejos de oro(I) y enolatos con una geometría rectangular para los centros de oro(I). Además, en la ausencia de acetona o 1,3-dicetonas observamos hidrólisis de los grupos nitrilo que dieron lugar a la formación de nuevos complejos pentanucleares heterometálicos. Estos complejos mostraron una actividad catalítica excelente en la carbonilación de aminas primarias para formar ureas (intermedios en la síntesis de pesticidas, fertilizantes, tintes y complejos farmacéuticos) bajo condiciones suaves de reacción. Cuando la síntesis del complejo linear tetranuclear de oro(I) se realizó en la ausencia de acetonitrilo, se obtuvo un nuevo complejo de Au8 plano y con forma de anillo. Esto representa un importante descubrimiento en la química del oro, abriendo la posibilidad de entender catálisis en superficies de oro a nivel molecular. En el futuro, las propiedades catalíticas de los complejos de oro(I) polinucleares únicos y con diversas formas presentados aquí serán investigados en mayor detalle.
Research in our group focuses on the invention of new synthetic methods using electrophilic gold catalysts. In an attempt to enhance the electrophilicity of the cationic phosphine gold(I) complexes we decided to use ortho-boronatephosphines as ambiphilic ligands. After abstraction of the halogen from the neutral gold(I) complex we obtained the first hexaauriocluster Au6(I) with geminally diaurated aromatic ring ligands, which shows catalytic activity in the cyclization of enynes. Two additional hexanuclear gold clusters bearing cyclohexyl and 2-furyl substituents on the phosphorus atom have been synthesized, aiming for a better understanding of the influence of the phosphine’s electronic properties in the reactivity of the gold(I) clusters. Our next approach to enhance the electrophilicity of the gold(I) center was the application of the 2,6-bis(diphenylphosphino)pyridine as a strategy to obtain polynuclear gold(I) complexes featuring aurophilic interactions. As a result, linear tetranuclear gold(I) complex was found not only to catalyze different skeletal transformations of enynes but also to activate acetone and 1,3-diketones to form tetranuclear enolate gold(I) complexes with a rectangular geometry of the gold(I) centers in the presence of a mild base. Moreover, in the absence of acetone or 1,3-diketones we observed nitrile hydrolysis that lead to the formation of new pentanuclear heterometallic complexes in good yields. These complexes showed moderate to excellent catalytic activity in the carbonylation of primary amines to ureas (intermediates in the synthesis of pesticides, fertilizers, dyes and pharmaceutical compounds) under mild conditions. When the synthesis of linear tetranuclear gold(I) complex was performed in the absence of acetonitrile, an unprecedented planar ring-shaped Au8 complex was obtained. This represents an important breakthrough in gold chemistry, opening the possibility of understanding catalysis on gold surfaces at the molecular level. In the future, the catalytic properties of the unique and multi-shaped polynuclear gold(I) complexes presented herein will be further investigated.
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Dou, Rui. "The Strength and Deformation Mechanisms of Gold Nanowires and Nanoporous Gold". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508553.
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Matcheswala, Akil Mannan. "GOLD NANOSPHERES AND GOLD NANORODS AS LOCALIZED SURFACE PLASMON RESONANCE SENSORS". UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/60.
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A novel localized surface plasmon resonance (LSPR) sensor that differentiates between background refractive index changes and surface-binding of a target analyte (e.g. a target molecule, protein, or bacterium) is presented. Standard, single channel LSPR sensors cannot differentiate these two effects as their design allows only one mode to be coupled. This novel technique uses two surface plasmon modes to simultaneously measure surface binding and solution refractive index changes. This increases the sensitivity of the sensor.
Different channels or modes can be created in sensors with the introduction of gold nanospheres or gold nanorods that act as receptor mechanisms. Once immobilization was achieved on gold nanospheres, the technique was optimized to achieve the same immobilization for gold nanorods to get the expected dual mode spectrum. Intricate fabrication methods are illustrated with using chemically terminated self assembled monolayers. Then the fabrication process advances from chemically silanized nanoparticles, on to specific and systematic patterns generated with the use of Electron Beam Lithography.
Comparisons are made within the different methods used, and guidelines are set to create possible room for improvement. Some methods implemented failed, but there was a lot to learn from these unsuccessful outcomes. Finally, the applications of the dual mode sensor are introduced, and current venues where the sensors can be used in chemical and biological settings are discussed.
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Bouwer, Wendy. "An environmentally sound gold recovery process for small-scale gold mining". Thesis, Cape Technikon, 1999. http://hdl.handle.net/20.500.11838/869.
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Thesis(MTech (Chem.Eng.Technology))--//Cape Technikon, 1999The gold mining industry has mainly relied upon the use of a highly polluting chemicals, such as mercury and cyanide, to recover gold from its ores. As environmental legislation has become more stringent in all countries and environmental protection has become the focus of world-wide research, development of environmental sound processes has been favoured. The Coal Gold Agglomeration (CGA) process is such a process which was developed some years ago and has the advantage in that gold is recovered by a procedure which has little or no effect on the environment. The CGA process is based on the hydrophobic characteristics of coal, gold and oil. Gold particles which are substantially free become attached to the coal-oil agglomerates during collision, and eventually penetrate into the agglomerates. The resulting agglomerates are recycled to increase the gold loading, separated from the slurry, burnt, ashed and smelted to produce gold bullion. Laboratory scale batch tests were performed on an artificial/synthetic gold ore, containing fine gold powder. The slurry was contacted with a mixture of coal and oil. i.e. coal-oil agglomerates, after which both the agglomerates and ore were analysed for gold. Operating parameters, such as the mode of contact between the coal-oil phase and the gold containing slurry, contact time of the slurry and the coal-oil phase, means of separating the coal-oil gold agglomerates from the slurry, coal to ore, coal to oil and water to ore ratios, type of oil, effect of collectors and the mineralogy of the ore on the gold recovery were investigated. Results have shown that stirring the coal-oil phase and the slug yielded higher gold loadings than shaking and the traditional rolling bottle technique. BI increasing the time of contact between the coal-oil phase and the gold slurry. the final gold loading in the agglomerates increases, until an equilibrium value is reached. An increase in the amount of coal, together with a decrease in the amount of water used in the slurry, has shown to increase gold recoveries. Furthermore, by varying the concentration and volume of a collector. such as potassium amyl xanthate (PAX) enhanced the settling rate and enabled the effectiveness of separation. Moreover, it was found that the gold loading on the coal-oil phase increased after recycling it. Further tests were performed on a real ore sample and after X-ray Diffraction (XRD) analysis, it was found that certain minerals other than gold was transferred to the coal-oil phase. The theoretical foundation of the CGA process is based on the difference in free energy and was expressed as a function of the interfacial tensions and three-phase contact angles between gold, oil and water, together with the ratio of coal-oil agglomerate to gold particle radii, as the free energy is a measure of the thermodynamic stability and hence, partly a measure of gold recoveries, meaningful predictions as to gold recoveries were made by performing a sensitivity analysis on the variables connected to the free energy, It was, however, found that some operating parameters, which were linked to other factors, such as the maximum gold transfer into coal-oil phase and the separation efficiency of the agglomerates. were vital to be taken into account when predictions as to gold recoveries were made. Therefore, the gold recoveries were found to be a function of the thermodynamic stability as well as the maximum gold transfer into the coal-oil phase and the separation efficiency of the agglomerates, The meaningful information gained by performing the theoretical investigations were applied and linked to gold recoveries, thereby providing useful explanations as to the typical gold recoveries obtained during experimentation. A comparative study on mercury amalgamation was done to evaluate the performance of the CGA process. It was found that the CGA process yielded better gold recoveries than amalgamation, which makes it the better process both in terms of recoveries as well as environmental safety, A further application of the theoretical knowledge was, however, very useful to explain the tendency of the CGA process yielding the better results.
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Westberg, Fredrik. "Textural characterization of gold in the Björkdal gold deposit, northern Sweden". Thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82496.
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The Björkdal gold deposit is located in the eastern part of the Skellefte district, northern Sweden. Twenty thin sections from four production areas in the open pit and four drifts from the underground mine were analysed for mineral association and grain size distribution of gold. In addition, the texture of gold was investigated in order to find out how that affects the recovery of gold. The overall gold grain size distribution shows an interval from very fine-grained (2 μm) to coarse grained(856 μm) while the overall median size is 7 μm. Gold from the Quartz Mountain production area displays the smallest median size of 4 μm, whereas gold from the sampled drifts at 340m- and 385m- level has the largest median size of 14 μm. Gold at grain boundary is the dominant textural mode of gold from all sampled locations and varies from 62% to 92%. This is followed by intergrown which ranges between 8% and 29%. Of the sulfides, pyrite, chalcopyrite and pyrrhotite are the most common. Galena and was also present in the samples. Gold is significantly and positively correlated with tellurium (Appendix 10.1.1), and weakly positive correlated to silver and mercury. Gold show a close association to bismuth-tellurides in the samples. Apart from native gold, which is the dominant mineral phase of gold, two additional gold-bearing tellurium minerals were detected with SEM-EDS, a Au-Te-mineral and a Ag-Au-Te-mineral. One additional bismuth-telluride mineral aside from the most commonly occurring tsumoite (BiTe) was also detected with SEM, with a elemental composition of Bi-Te-S. Liberated gold in the tailings was optically identified in two thick sections, TB1-02feb-1 and TB1-07feb-1 (Fig. 32A and B), where the flotation circuit failed to float the free gold. One grain of gold was also identified intergrown with bismuth-telluride as an inclusion in silicate (Fig. 33), where the flotation properties of the larger silicate grain likely dominated in the flotation process. This thesis highlights the importance of further quantitative analysis utilizing SEM/QEMSCAN/MLA to retrieve representative mineralogical data to benefit the mineral processing of the ore from the active mine. Keywords: Björkdal gold deposit, gold, gold-telluride, SEM, mineral association, grain size,geometallurgy.
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Young, Michaela Nicole 1963. "Characteristics of Skarns Related to Gold Mineralization at Gold Acres, Nevada". Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/558216.
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Samaimongkol, Panupon. "Surface plasmon resonance study of the purple gold (AuAl2) intermetallic, pH-responsive fluorescence gold nanoparticles, and gold nanosphere assembly". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96549.
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In this dissertation, I have verified that the striking purple color of the intermetallic compound
AuAl2, also known as purple gold, originates from surface plasmons (SPs). This contrasts to a
previous assumption that this color is due to an interband absorption transition. The existence of
SPs was demonstrated by launching them in thin AuAl2 films in the Kretschmann configuration,
which enables us to measure the SP dispersion relation. I observed that the SP energy in thin films of purple gold is around 2.1 eV, comparable to previous work on the dielectric function of this
material. Furthermore, SP sensing using AuAl2 also shows the ability to measure the change in the refractive index of standard sucrose solution. AuAl2 in nanoparticle form is also discussed in terms of plasmonic applications, where Mie scattering theory predicts that the particle bears nearly
uniform absorption over the entire visible spectrum with an order magnitude higher than a lightabsorbing carbonaceous particle. The second topic of this dissertation focuses on plasmon enhanced fluorescence in gold nanoparticles (Au NPs). Here, I investigated the distance-dependent fluorescence emission of rhodamine green 110 fluorophores from Au NPs with tunable spacers. These spacers consist of polyelectrolyte multilayers (PEMs) consisting of poly(allylamine
hydrochloride) and poly(styrene sulfonate) assembled at pH 8.4. The distance between Au NPs and fluorophores was varied by changing the ambient pH from 3 to 10 and back, which causes the
swelling and deswelling of PEM spacer. Maximum fluorescence intensity with 4.0-fold enhancement was observed with 7-layer coated Au NPs at ambient pH 10 referenced to pH 3. The last topic of this dissertation examines a novel approach to assemble nanoparticles, in particular, dimers of gold nanospheres (NSs). 16 nm and 60 nm diameter NSs were connected using
photocleavable molecules as linkers. I showed that the orientation of the dimers can be controlled
with the polarization of UV illumination that cleaves the linkers, making dipolar patches. This type
of assembly provides a simple method with potential applications in multiple contexts, such as
biomedicine and nanorobotics.PHD
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Fuxen, Claus. "Adsorption, Struktur und Desorption von Organothiolaten auf Goldsubstraten". [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963053744.
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Valet, Oliver K. "Bildung und Eigenschaften von 2,3-Dimercaptopropansulfonat-Schichten auf Gold(111)". [S.l. : s.n.], 1999. http://www.diss.fu-berlin.de/2000/43/index.html.
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Brisbin, Daniel Ivan. "Geological setting of gold deposits in the Porcupine Gold Camp, Timmins, Ontario". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20554.pdf.
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Kadalbajoo, Mridula. "Synthesis and characterization of oligosaccharides tethered to gold films and gold nanoparticles". College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2136.
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Thesis (M.S.)--University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Bomm, Jana. "Von Gold Plasmonen und Exzitonen : Synthese, Charakterisierung und Applikationen von Gold Nanopartikeln". Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6640/.
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In dieser Arbeit wurden sphärische Gold Nanopartikel (NP) mit einem Durchmesser größer ~ 2 nm, Gold Quantenpunkte (QDs) mit einem Durchmesser kleiner ~ 2 nm sowie Gold Nanostäbchen (NRs) unterschiedlicher Länge hergestellt und optisch charakterisiert. Zudem wurden zwei neue Synthesevarianten für die Herstellung thermosensitiver Gold QDs entwickelt werden. Sphärische Gold NP zeigen eine Plasmonenbande bei ~ 520 nm, die auf die kollektive Oszillation von Elektronen zurückzuführen ist. Gold NRs weisen aufgrund ihrer anisotropen Form zwei Plasmonenbanden auf, eine transversale Plasmonenbande bei ~ 520 nm und eine longitudinale Plasmonenbande, die vom Länge-zu-Durchmesser-Verhältnis der Gold NRs abhängig ist. Gold QDs besitzen keine Plasmonenbande, da ihre Elektronen Quantenbeschränkungen unterliegen. Gold QDs zeigen jedoch aufgrund diskreter Energieniveaus und einer Bandlücke Photolumineszenz (PL). Die synthetisierten Gold QDs besitzen eine Breitbandlumineszenz im Bereich von ~ 500-800 nm, wobei die Lumineszenz-eigenschaften (Emissionspeak, Quantenausbeute, Lebenszeiten) stark von den Herstellungs-bedingungen und den Oberflächenliganden abhängen. Die PL in Gold QDs ist ein sehr komplexes Phänomen und rührt vermutlich von Singulett- und Triplett-Zuständen her. Gold NRs und Gold QDs konnten in verschiedene Polymere wie bspw. Cellulosetriacetat eingearbeitet werden. Polymernanokomposite mit Gold NRs wurden erstmals unter definierten Bedingungen mechanisch gezogen, um Filme mit optisch anisotropen (richtungsabhängigen) Eigenschaften zu erhalten. Zudem wurde das Temperaturverhalten von Gold NRs und Gold QDs untersucht. Es konnte gezeigt werden, dass eine lokale Variation der Größe und Form von Gold NRs in Polymernanokompositen durch Temperaturerhöhung auf 225-250 °C erzielt werden kann. Es zeigte sich, dass die PL der Gold QDs stark temperaturabhängig ist, wodurch die PL QY der Proben beim Abkühlen (-7 °C) auf knapp 30 % verdoppelt und beim Erhitzen auf 70 °C nahezu vollständig gelöscht werden konnte. Es konnte demonstriert werden, dass die Länge der Alkylkette des Oberflächenliganden einen Einfluss auf die Temperaturstabilität der Gold QDs hat. Zudem wurden verschiedene neuartige und optisch anisotrope Sicherheitslabels mit Gold NRs sowie thermosensitive Sicherheitslabel mit Gold QDs entwickelt. Ebenso scheinen Gold NRs und QDs für die und die Optoelektronik (bspw. Datenspeicherung) und die Medizin (bspw. Krebsdiagnostik bzw. -therapie) von großem Interesse zu sein.In this thesis, the synthesis and optical characterization of spherical gold nanoparticles (NP) with diameters larger than ~ 2 nm, gold quantum dots (QDs) with diameters smaller than ~ 2 nm and gold nanorods (NRs) with different lengths are presented. In addition, a novel one-pot synthesis for the preparation of thermosensitive gold QDs is introduced. Gold NP solutions appear red colored due to their strong absorption in the visible range at ~ 520 nm. This absorption band is a result of surface plasmon resonance, which is caused by the coherent oscillation of conduction band electrons induced by an electromagnetic field. In contrast to spherical gold NPs, gold NRs show two surface plasmon bands due to their anisotropic shape, a transverse plasmon band at ~ 520 nm and a longitudinal plasmon band depending on the aspect ratio (length-to-width-ratio) of the gold NRs. If the size of the gold NPs decreases to values below ~ 2 nm, quantum-size confinement occurs and the surface plasmon band disappears. Additionally, the overlap between conduction band and valence band disappears, discrete electronic levels arise and a band gap is created. As a consequence of quantum confinement, the gold QDs show photoluminescence (PL) upon UV-irradiation. The gold QDs synthesized via the one-pot synthesis exhibit a broadband luminescence between 500 nm and 800 nm. The luminescence properties (emission peak, quantum yield, lifetime) strongly depend on the synthetic parameters like reaction temperature, stoichiometry and the surface ligand. Gold NRs and gold QDs were incoroporated into different polymers (e.g. cellulose triacetate). Polymer nanocomposite films showing optical anisotropy are obtainded by stretching polymer films containing gold NRs uniaxial in a tensile test machine. In addition to the optical characterization of gold NRs and QDs, their thermal behavior in solution as well as in different nanocomposites is studied. A shortening of the gold NRs or a transformation into spherical gold NP is observed, if the polymer nanocomposites containing gold NRs are heated above a temperature of 200 °C. The PL of the synthesized gold QDs strongly depends on the ambient temperature. An increase of PL quantum yield (QY) and PL lifetime occur, if the solutions are cooled. The best PL QY of 16.6 % was observed for octadecyl mercaptan capped gold QDs at room temperature, which could be improved to 28.6 % when cooling the solutions to -7 °C. Furthermore, optically anisotropic security labels containing gold NRs and thermosensitive security devices containing gold QDs are developed. Due to their unique optical properties, gold NRs and QDs are interesting candidates for optoelectronical as well as data storage devices and medical applications like biomedical imaging or cancer therapy.
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Urban, Scott Andrew. "Gold in the interwar monetary system : evolution of the gold-standard regime". Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.568412.
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This thesis is motivated by discrepancies between the modem account of currency policies in the 1930s and the policies described by a contemporary, Ragnar Nurkse. The former emphasises a newfound policy independence, the latter a continuance of gold-standard constraints. Main contributions are empirical results, application of existing methodologies to historical data, use of previously unpublished data, and new theoretical analysis. Paper One presents evidence of persistent monetary conservatism in the 1930s. Statutory obligations to limit the supply of base money to a multiple of international assets were eased with the loss of gold convertibility (circa Britain's 1931 devaluation) but eliminated only in Germany, Italy and Greece. A central hypothesis of this dissertation is that collateralization of 1930s central bank money was standard practice, as before WWI. Paper Two tests whether 1930s central banks were more willing to sterilize reserve losses compared to the gold standard. It finds the odds of sterilization indistinguishable except where banks enacted strict capital controls. A minority of 1930s central banks did so. Paper Three applies the modem methodology of exchange-rate regime classification to interwar currency regimes. Post-gold observations are compared with the gold standard and observations preceding it. The results suggest that 1930s currencies were pegged, whereas the modem literature describes these as managed-floating. The three papers provide support both for the modem literature and for Nurkse. They confirm the former's emphasis on a dysfunctional gold standard. Yet they modify this literature's description of the ensuing regimes; here they support Nurkse's criticism of 1930s central bankers' inability more aggressively to cast aside their golden fetters. This thesis suggests that such behaviour might reflect a contemporary reluctance to embrace more fully the concept of un-backed money, which if true might indicate an evolved practice of the gold standard.
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Seitkan, Ainur. "Environmental mineralogy of gold recovery from refractory gold-arsenic-bearing Bakyrchik concentrates". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273373.
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Arsenic contamination of groundwater associated with mining operations is a widespread problem across the globe. The release of arsenic (As) into the environment occurs naturally by oxidation of exposed sulfide minerals. In the case of gold ores, the mining and beneficiation may also produce As-bearing wastes and this can accelerate the natural mechanisms of As mobilization. The Bakyrchik is the largest gold deposit in Kazakhstan and one of the largest in the world. Gold (Au) is dispersed in pyrite and arsenopyrite in the form of microscopic inclusions. Despite the fact that only 10% of gold ore has been mined to date, it has left behind a dangerous As-containing legacy. Speciation of As has been determined for samples from Bakyrchik to understand the post-processing environment and the mobility of arsenic in the mining-influenced area. As(III) and As(V) have been detected in water samples using HPLC-ICP-MS. The variability of As species across the narrow pH and Eh range indicates that biogeochemical processes can play a role in the speciation of As in water at the study site. In order to understand processes controlling As mobilization in water, the solid phase speciation of As in Bakyrchik sediments, soil, and metallurgical processing products has been investigated using XRD and EPMA. This revealed arsenopyrite, As-bearing pyrite, and their alteration products containing up to 25% As, iron oxides and oxyhydroxides (with up to 2.5% As), haidingerite, and calcium arsenate in studied samples. Sequential extraction demonstrated that in soil and sediment samples As is associated mainly with Al and amorphous Fe oxyhydroxides. Results suggest that the main mechanisms controlling As mobility in Bakyrchik are dilution with regional waters, adsorption onto iron and aluminium oxyhydroxides, and co-precipitation of dissolved As with alteration products of sulfide minerals. Assessment of As bioaccessibility through inhalation demonstrates its strong dependence on the mineralogy rather than on total As content of the solid samples. Calculated cancer and non-cancer risks of inhalation exposure imply that all samples are highly hazardous for human health. With the depletion of the oxide lode ore deposits, gold extraction is moving towards the mining of technologically difficult ores, such as those found at Bakyrchik. A new method of Au recovery from double refractory Au-As-bearing concentrates has been developed, allowing recovery of 97% of Au, and the conversion of up to 95% As into iron-arsenic alloy. Fe-As alloy can contain up to 40% As, and do not require further solidification/stabilisation prior to disposal. The method has been published as a patent with the Patent Office of the Republic of Kazakhstan. Quantitative phase composition of the Fe-As alloy, has been determined by EPMA, QEMSCAN, X-ray and neutron diffraction. Toxicity and solubility of Fe-As alloy in aqueous solutions have been characterised. High-temperature structural behaviour of Fe-As alloy and Fe$_{2}$As in inert atmosphere has been determined by $\textit{in situ}$ synchrotron XRD. Results of the study support the development of the new method as an efficient alternative for processing double refractory Au-As-bearing concentrates.
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Mather, Diarmid John. "An approach to analyzing gold supply from the South African gold mines". Thesis, Rhodes University, 1995. http://hdl.handle.net/10962/d1002750.
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The gold mining fIrm in South Africa is viewed as a normal fIrm producing gold bearing ore but faced with a quality constraint (grade). Grade, however, is never uniformly distributed in a metalliferous deposit and because high grades are mined fIrst, the quality constraint becomes increasingly severe with cumulated production. The fIrm will continue to mine gold bearing ore until it reaches its mining limit where the marginal cost of recovering the gold is equal to the marginal revenue received from that gold and at that point the economic deposit becomes exhausted. Because the mining limit is determined by cost/technology and price, it is not fIxed and thus the point of economic exhaustion may change. When high grades are mined fIrst the relationship between the tonnage of gold ore and the grade describes the rate at which the grade is expected to fall with cumulated production. In this thesis, the grade for South African Witwatersrand gold producers is modelled to fall exponentially. The mining limit, determined by costs/technology and price, can be expressed in terms of grade. By predicting the decay in grade relative to the tonnage of gold ore and applying a mining limit, a life-time size of the economic deposit can be estimated. The remaining life of a producing gold mine can then be determined and the flow of gold predicted. An empirical treatment using the disk model of a gold deposit is undertaken for a gold mine, a goldfIeld and the total Witwatersrand gold deposit. A dynamic econometric analysis of expected mining costs and gold prices is not attempted; however certain examples are used to illustrate the applicability of the model and the influence of the South African gold mining tax formula on the life of the mine.
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Groen, John Corwyn. "Gold-enriched rims on placer gold grains: an evaluation of formational processes". Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/40977.
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Placer gold is frequently reported to assay at overall higher values of tineness than the gold in the rock from which it was liberated. A related phenomenon is the historical discovery of many extremely large gold nuggets (up to 28 lbs) in the southeastern United States that have no apparent source rock. Placer gold grains from the southeastem United States have been examined and found to frequently exhibit the development of nearly pure to pure gold rims around their borders. These gold rims are suggested as a possible cause of the high frneness placer deposits. Formation of very thick rims may also be the cause of the large nuggets. Formation of these gold-enriched rims by the often attributed mechanism of simple silver leaching is disputed on the basis of ineffective mechanisms for the removal of silver from the alloy. Diffusion of silver through the gold at low temperatures proceeds far too slowly to produce the chemical gradients observed in the placer gold grains. Comparison of the complexation capacities of 41 ligands with subsequent modelling of expected complex concentrations in natural stream and stream sediment waters indicates CN- and S2- as the most likely functional ligands for the transport and redeposition of supergene gold. Electrolytic refming of placer Auâ Ag grains is also a process for forming gold-enriched rims that can operate together with secondary enrichment to produce the observed phenomena.
Master of Science
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Morse, Kathryn Taylor. "The nature of gold : an environmental history of the Klondike gold rush /". Seattle : University of Washington Press, 2003. http://catalogue.bnf.fr/ark:/12148/cb390579433.
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Ji, Chunxin. "Synthesis, characterization and applications for gold-silver alloy and nanoporous gold nanowires". Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3080690.
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Wu, Yafei. "Gold Source and Deportment in the Daqiao Epizonal Orogenic Gold Deposit, China". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78110.
Texto completoResumen
Yafei Wu’s PhD project has explored different ore-forming aspects of a world-class Chinese orogenic gold deposit. The results show that orogenic gold could be sourced from either metamorphism or magmatism. Silica has an important role in gold transport. Gold zoning in pyrite records both fluid conditions and local kinetics. Gold significantly redistributes during pyrite replacement. The knowledge gained increases our understanding of the genesis of orogenic gold widely distributed in Australia, New Zealand and worldwide.
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Price, Ryan Cameron. "Nanocrystalline Gold Arylthiolate Molecules". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14051.
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This research focuses on generating, isolating, and characterizing nanophase gold clusters with diameters below two nanometers. In this size regime, the metal cores exhibit electronic and optical properties very different from those of colloidal and bulk gold, arising from quantum size confinement. The unoccupied molecular orbitals of the cores are known to accept electrons, analogous to a capacitor, but with discrete electrochemical potentials. This work describes the novel production of gold clusters with structurally rigid benzenethiolate bound to the surface, rather than typically used alkanethiolates.
The Aux(benzenethiolate)y clusters are anionic and charged balanced by tetraoctylammonium cations. They are enriched in ~1.5 nm diameter cores, compared to a dominance of 1.7 nm cores when alkanethiols are used during synthesis. The Aux(benzenethiolate)y clusters are more likely to form bulk crystals and possess enhanced electrochemistry relative to Aux(alkylthiolate)y clusters. They are characterized by x-ray diffraction, carbon and proton NMR, FTIR, optical spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis.
The etching of clusters in the presence of hydrogen peroxide and excess benzenethiol to yield smaller 1.1 nm clusters is reported for the first time in this work. These 1.1 nm clusters have a rich optical spectrum with clear electronic transitions at room temperature and orient spontaneously when deposited from solution. This oxidative etching process was applied to alkanethiolate clusters, converting ~2.0 nm polydisperse clusters into smaller clusters. This offers the potential to produce smaller gold clusters with more available charge states and may allow increase the types of thiols that can be bound to the surface of gold monolayer protected clusters (MPCs), known also as quantum dots.
The use of the bulky thiol, tert-butylmercaptan to produce 1.5 nm core gold clusters is also reported, indicating sterically hindered alkanethiols can play a role in limiting the size of Aux(alkylthiolate)y clusters. These clusters were characterized by x-ray diffraction, proton NMR, FTIR, optical spectroscopy, and mass spectrometry. The clusters are potentially useful for thiolate exchange reactions to produce new types of Aux(thiolate)y clusters.
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Trindade, Roberto de Barros Emery. "Catalysed cyanidation of gold". Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8601.
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Barbosa, Filho Olavo. "Thiocyanate leaching of gold". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46663.
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Espeland, Erlend. "Gold Nanostructures on Graphite". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22433.
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Gold nanoparticles supported on a graphite substrate are prepared by thermal evaporation, and subsequently studied by X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) of carbon monoxide and scanning electron microscopy (SEM).Increasing the amount of gold deposited leads to a shift of the desorption peak to higher temperatures, and the gold particles become larger.Depositing approximately the same amount of gold at different evaporation ratios does not seem to affect the desorption.Triangularly shaped gold particles appeared at higher evaporation rates.This is thought to be caused by diffusion effects dominating the formation of the particles.
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Sivasubramaniam, Prabalini. "Gold based electro catalysts". Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/193147/.
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Gold electrocatalysts have been of growing interest in recent years owing to their reactivity for a variety of important reactions such as the oxygen reduction reaction. This activity has been shown to be dependent on the size of the supported electrocatalyst nanoparticles. In this thesis the effects of Au nanoparticle size are explored for the oxygen reduction, ethanol oxidation and carbon monoxide oxidation reactions (Chapter four). The results show the oxygen reduction and ethanol oxidation reactions were favoured using larger particles, 6 nm in diameter, whilst the CO oxidation reaction was more facile on smaller particles, 3 nm in diameter. The effects of size are attributed to the size dependent strength of the Au-O (H) bond. Modified Au nanoparticles, in which the Au serves as a core for a Pt or Pd shell have also been of recent interest, as Au has been less expensive than Pt. These core-shell electrocatalysts thus affect both cost and activity advantages as the underlying Au core affect the properties of the shell. In this thesis the effects of the particle size of the Au core on the activity of Pt or Pd shells have been investigated (Chapter five). The results show that the oxygen reduction reaction is well again more facile when the core size is larger, whilst the ethanol oxidation reaction now is favoured with the small Au core size. The coverage of Pt or Pd on the Au core was also found to be dependent on the particle size, with smaller particles being covered by thinner shells. Thus, the size dependence of the oxygen reduction activity is once again attributed to O (H) coverage and bond strength, whilst the ethanol oxidation is attributed to either an electronic perturbation of the Pt or Pd by the Au core of an ensemble effect.
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Leeming, Prudence Mary. "Turbidite-hosted gold deposits". Thesis, Rhodes University, 1985. http://hdl.handle.net/10962/d1005939.
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Turbidite-hosted gold deposits contribute a significant proportion to world lode gold production and have also provided substantial gold to alluvial resources. Turbidity current deposits occur throughout geological time within Archaean greenstone belts, Proterozoic orogenic belts and rifted passive continental margins, and Palaeozoic geosynclines. Representing the end member of the sedimentary cycle, turbidites have the attribute of preservation not only on an individual bed basis but also due to below wave base accumulation in submarine deeps. Cyclic deposition according to the Bouma sequence punctuates turbidite deposition by a series of diastems. Accumulation of organic, pelagic and chemical sediments may concentrate gold to protore enrichment levels i n a primary sedimentary environment. Dewatering during diagenesis and low-grade metamorphism under reducing conditions may redistribute gold with transport as low energy organo- and thio-complexes. Gold may precipitate with diagenetic pyrite and silica near black shale and/or partially replace fine carbonate detritus. Gold solubility increases with high grade amphibolite facies metamorphism (T 400ºC) when efficient leaching of gold and transport by simple chloro- and hydroxychloro - complexes to lower greenschist regions takes place. Reduced permeability of turbidite strata induces hydrofracturing which focuses dewatering solutions. Gold is deposited due to pressure and temperature decrease or local changes in physico - chemico conditions caused by the reaction of fluids with wall rocks (reactive beds in turbidites are predominantly carbonaceous strata). The largest of turbidite - hosted goldfields are confined to back -arc or marginal sea basins with restricted oceanic circulation. The richest concentrations of gold occur proximal to the original source within the greenschist facies formations lowermost in a thick turbidite sequence and exhibit strong combined structural and lithological association. Turbidites represent important strata for the concentration and preservation of gold not only during sedimentation and diagenesis but also during later deformation and metamorphism.
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Mann, P. L. "Surficial placer gold deposits". Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1018245.
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This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
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Davidson, Raymond John. "Innovations in gold extraction". Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1004975.
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The thesis takes the form of a collection of publications and patents concerning gold extraction which were presented over a period of 18 years while employed at the Anglo American Research Laboratories.
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Rankine, Graham M. "Gold metallogeny of Australia". Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1004676.
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The gold metallogeny of Australia is predominantly confined to the Archaean and Palaeozoic Provinces. The Archaean gold occurrences are predominantly hosted in ultramafic-mafic dominated greenstone belts, with less associated tofelsic-volcanic and sedimentary sequences. Most gold occurrences are confined to shear zones or faults, and adjacent discoveries of economic laterite-hosted deposits, host rocks. Recent are presently under investigation and will supply a significant proportion of production in the future. The Proterozoic gold deposits of Australia , are confined to geosyncinal sequences, commonly turbidites (eg: Telfer), with other hydrothermal deposits associated directly to granites. An important feature of the North Australian Craton deposits, is the spatial association of most deposits to granite bodies, although a genetic link has not been established conclusively. The Roxby Downs deposit in South Australia is a unique occurrence of gold in association to copper, uranium and R.E.E. This deposit is tentatively related to intraplate alkaline-magmatism, with further work necessary. The most significant recent discovery of gold mineralization in Australia is in the Drummond Basin in Queensland. This epithermal is tentatively related to mineralization within the Georgetown Inlier. The latter mineralization is Permo-Carboniferous, in a Proterozoic (and possibly Archaean) sequence of schists. It is tentatively suggested that all the gold mineralization in northern Queensland may be related to single tectonic event, a feature which requires further study . Other mineralization in the Phanerozoic includes the turbidite-hosted metamorphogenic deposits of Victoria, the rift related deposits in New South Wales and magmatic related deposits in Queensland. The gold deposits in Australia may in the future be classified in a tectonogeological framework, similiar to the layout of this dissertation, particularly once further data becomes available on recent discoveries.