Dissertations / Theses on the topic 'Metallic silver'
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Botez, Cristian E. "Synchrotron x-ray scattering studies of metallic surfaces /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3052151.
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Lee, Myung-hyun. "Optoelectronic properties of small silver particles embedded in non-metallic matrices." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314890.
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Schaefer, Glen Allen. "Ultrathin metallic coatings for silver surfaces: Function and utilization in low Earth orbit." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060351586.
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Eccles, James William Lesile. "An electron energy loss spectroscopy study of metallic nanoparticles of gold and silver." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/an-electron-energy-loss-spectroscopy-study-of-metallic-nanoparticles-of-gold-and-silver(08669aaa-cdc8-4f5c-8428-4677dbc358cc).html.
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The application of gold and silver nanoparticles to areas such as medical research is based on unique optical properties exhibited by some metals. These properties are a direct consequence of localised excitations occurring at visible frequencies known as Surface Plasmon Resonances (SPRs). The exact frequency of an SPR induced in a nanoparticle can be 'tuned' in the optical range by, for example, changing the size of gold and silver nanoparticles, or by varying the relative concentrations of gold and silver within an alloy nanoparticle. Whatever the desired frequency, it is critical that the majority of nanoparticles exhibit the frequency within the resolution limit of the imaging system. The research presented here utilises the high resolution imaging and spectroscopy techniques of (Scanning) Transmission Electron Microscopy ((S)TEM) and Electron Energy Loss Spectroscopy (EELS). It is common practice to analyse the optical properties of alloy nanoparticles using techniques that acquire a single spectrum averaged over multiple particles such as Ultraviolet-Visible (UV-Vis) spectroscopy. However, this technique cannot detect any optical variation between the nanoparticles resulting from compositional change. In this research the author demonstrates through the use of EELS that the SPR can be determined for individual gold/silver alloy nanoparticles, for the purpose of determining the extent of their homogeneity. Importantly, the data presented here suggest dramatic variation in SPR frequency between particles and even within the same particle, indicative of large variations in alloy composition. This puts the assumption that alloying can be scaled down to the nanometre-scale to the test. In order to resolve and extract the SPR in both the pure gold and gold and silver alloy nanoparticles, the author has successfully applied multiple post acquisition techniques such as Richardson-Lucy deconvolution and Principle Component Analysis (PCA) to the EELS Spectrum Imaging (SI) acquisition method. Additionally, the valence band EELS data are supported by complementary electron microscopy techniques; Core loss EELS, Energy Dispersive X-Ray Spectroscopy (EDX) and High Angle Annular Dark Field (HAADF) imaging.
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Ha, Hung M. "Micro- and Nano-Scale Corrosion in Iron-Based Bulk Metallic Glass Sam 1651 and Silver-cored MP35N Lt Composite." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1260391940.
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Peterson, Sarah M. "Influence of scale, geometry, and microstructure on the electrical properties of chemically deposited thin silver films /." Connect to title online (ProQuest), 2007. http://proquest.umi.com/pqdweb?did=1453183211&sid=2&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-101). Also available online in ProQuest, free to University of Oregon users.
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Sennuga, Afolake Temitope. "Biological synthesis of metallic nanoparticles and their interactions with various biomedical targets." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1004069.
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The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology. In this study, a comparative biological synthesis, characterization and biomedical effects of metallic nanoparticles of platinum, gold and silver were investigated. Metallic nanoparticles were biologically synthesized using cage-like (apoferritin), barrel-like (GroEL) and non-caged (ribonuclease) proteins. Nanoparticles generated were characterized using common techniques such as UV-visible spectroscopy, scanning and transmission electron microscopy, inductively coupled optical emission spectroscopy, Fourier transform infra-red spectroscopy and energy dispersion analysis of X-rays (EDAX). Nanoparticles synthesised biologically using apoferritin, GroEL and RNase with exhibited similar chemical and physical properties as thoses nanoparticles generated chemically. In addition, the metallic nanoparticles fabricated within the cage-like and barrel-like cavities of apoferritin and GroEL respectively, resulted in nanoparticles with relatively uniform morphology as opposed to those obtained with the non-caged ribonuclease. The enzymatic (ferroxidase) activity of apoferritin was found to be greatly enhanced with platinum (9-fold), gold (7-fold) and silver (54-fold) nanoparticles. The ATPase activity of GroEL was inhibited by silver nanoparticles (64%), was moderately activated by gold nanoparticles (47%) and considerably enhanced by platinum nanoparticles (85%). The hydrolytic activity of RNase was however, lowered by these metallic nanoparticles (90% in Ag nanoparticles) and to a higher degree with platinum (95%) and gold nanoparticles (~100%). The effect of synthesized nanoparticles on the respective enzyme activities of these proteins was also investigated and the potential neurotoxic property of these particles was also determined by an in vitro interaction with acetylcholinesterase. Protein encapsulated nanoparticles with apoferrtin and GroEL showed a decreased inhibition of acetylcholinesterase (<50%) compared with nanoparticles attached to ribonuclease (>50%). Thus, it can be concluded that the cavities of apoferitin and GroEL acted as nanobiofactories for the synthesis and confinement of the size and shape of nanoparticles. Furthermore, the interior of these proteins provided a shielding effect for these nanoparticles and thus reduced/prevented their possible neurotoxic effect and confirmed safety in their method of production and application. The findings from this study would prove beneficial in the application of these nanoparticles as a potential drug/drug delivery vehicle for the prevention, treatment/management of diseases associated with these enzymes/proteins.
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MAGLIE, M. DE. "BIODISTRIBUTION AND TOXICITY OF METALLIC NANOPARTICLES:IN VIVO STUDIES IN MICE." Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/487404.
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In the last decade, nanotechnology has emerged as one of the fastest growing area of science. This is a highly promising field for the generation of new engineering applications, consumer products, medical healthcare and medicine. However, the increasing development of nanomaterials (NMs) is not supported by in vivo studies taking systematically into consideration nanoparticles (NPs) types, doses and period of treatment that would allow to forecast possible adverse outcomes that might occur upon human exposure.
In our studies, fully characterized silver nanoparticles (AgNPs) and iron oxide nanoparticles (IONP), designed for cancer treatment, were used to assess biodistribution and potential toxic effects after single intravenous and repeated oral administration in mice.
Unexpected histopathological findings, strictly related to the physicochemical properties, i.e. size and vehicle used for the NPs synthesis, were observed after intravenous administration. This confirms that a complete characterization of NPs is of the most importance for the identification of in vivo outcomes. NPs mainly localized in organs containing large number of specialized tissue-resident macrophages belonging to the mononuclear phagocyte system. The retention of NPs in these tissues raises concerns about the potential toxicity.
The 28 days repeated oral administration of AgNPs demonstrated that the brain is the organ where Ag accumulation takes place. In fact, Ag it is still detected in brain after the recovery period because of its low clearance. Morphological changes observed in the blood brain barrier (BBB), and the involvement of glial cells in response to AgNPs administration, suggested a perturbation of brain homeostasis that should be taken into consideration and further investigated.
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Geng, Xin. "Migration of metallic fission products through SiC or ZrC coating in TRISO coated fuel particles." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/migration-of-metallic-fission-products-through-sic-or-zrc-coating-in-triso-coated-fuel-particles(c4ff06cb-1adf-4748-87ff-247d29916ba2).html.
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Release of metallic fission products from fully intact tri-structural isotropic (TRISO) fuel particles raises serious concern on the safety of high temperature gas-cooled reactors (HTGRs). In TRISO particles, SiC and/or ZrC coating is considered as the major barrier for the migration of the fission products. This thesis focuses on the migration mechanism study of Ag in SiC and Pd in ZrC.The mechanism of the migration of Ag in SiC is a long-lasting mystery. None of the currently existing models could satisfactorily explain the reported experimental facts. In this work, a new mechanism, termed as the “reaction-recrystallization” model, is proposed to explain the Ag migration behavior through SiC. Designed SiC/Ag diffusion couple experiments were carried out, and the results indicate that Ag migrates in SiC by the following three steps. First, Ag reacts with SiC to form an Ag-Si alloy (reaction). Second, carbon precipitates as a second phase and subsequently reacts with the Ag-Si alloy to form new β-SiC (recrystallization). Third, the Ag-Si alloy penetrates through the SiC layer by wetting its grain boundaries (migration). The validity of the proposed model was supported by thermodynamic calculations. (Chapter 3) The finding that SiC could be recrystallized in the presence of Ag inspires the idea of Ag-assisted crack healing in SiC. Cracks were intentionally generated by indenting the bulk SiC by a Vickers indenter. After vacuum annealing with Ag powder, the indent impressions were healed by newly-formed β-SiC grains with a recovery ratio of~ 60%. Median cracks were fully healed by both newly formed SiC and Ag-Si nodules. TEM observation reveals that the newly formed β-SiC layer is presented between the Ag-Si nodule and pristine SiC crack surface and smooths the tortuous crack surface. The above result is in potential to solve the problem of brittleness of SiC as a structural material. (Chapter 4)ZrC is considered as a candidate to replace SiC in TRISO fuel particles. The migration behavior of Pd in ZrC was investigated by designed Pd/ZrC diffusion couple experiments. It is found that ZrC reacts with Pd at temperatures higher than 600 °C to form Pd3Zr and amorphous carbon. The reaction kinetics parameters, i.e., the activation energy and the reaction order, along with the inter-diffusion coefficients of Zr and Pd, were calculated based on established models. These results provide preliminary explanation to the Pd migration in ZrC (Chapter 5).
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Jarro, Sanabria Carlos Andrés. "METALLIC PATTERNING USING AN ATOMIC FORCE MICROSCOPE TIP AND LASER-INDUCED LIQUID DEPOSITION." UKnowledge, 2012. http://uknowledge.uky.edu/ece_etds/6.
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The development of nanoscale patterns has a vast variety of applications going from biology to solid state devices. In this research we present a new direct patterning technique in which laser photoreduction of silver from a liquid is controlled by a scanning atomic force microscope tip. While pursuing the formation of patterns using the plasmonic field enhancement of an electromagnetic wave incident on a metallic Atomic Force Microscope (AFM) tip, our group discovered that contrary to expectations, the tip suppresses, rather than enhances, deposition on the underlying substrate, and this suppression persists in the absence of the tip. Experiments presented here exclude three potential mechanisms: purely mechanical material removal, depletion of the silver precursor, and preferential photoreduction on existing deposits. An example of a nano-scaled pattern was generated to show the possibilities of this work. These results represent a first step toward direct, negative tone, tip-based patterning of functional materials.
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Liu, Jianfei. "Selective Deposition of Metallic and Semiconductor Materials onto DNA Templates for Nanofabrication." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3143.
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This work examines the selective deposition of metallic and semiconductor materials onto DNA templates for the fabrication of nanodevices. DNA origami provides a simple and robust method for folding DNA into a variety of shapes and patterns and makes it possible to create the complex templates needed for nanodevices, such as nanoelectronic circuits, plasmonics, and nanosensors. Metallization of DNA origami templates is essential for the fabrication of such nanodevices. In addition, selective deposition of semiconductor materials onto the DNA template is of importance for making many nanodevices such as nanocircuits. Metallization of DNA origami presents several challenges beyond those associated with the metallization of other DNA templates such as λ-DNA. All of these challenges were addressed in this study. DNA origami templates were seeded with Ag and then plated with Au via electroless deposition. Selective continuous metal deposition was achieved, with an average metallized height as small as 32 nm. The structure of T-shaped DNA origami was also retained after metallization. Following the metallization of complete origami, site-specific metallization of branched DNA origami was also demonstrated. To achieve this, staple strands at select locations on origami were replaced with staple strands modified with binding sites at the end. These binding sites then attached to thiolated DNA coated Au nanoparticles through base pairing. The continuous Au nanowires formed at designated sites on DNA origami after Au plating had an average width of 33 nm, with the smallest ones ~20 nm wide. The continuity of nanowires was verified by conductivity tests- the only tests of this nature of which I am aware. Moreover, predesigned sites on "circuit-shaped" DNA origami were successfully metallized. The selective deposition of a variety of materials onto DNA templates for the formation of continuous DNA-templated nanowires was also demonstrated. Specifically, an electroless Ni plating solution was developed to enable the fabrication of uniform and continuous DNA-templated Ni nanowires. Tests showed that these DNA-templated Ni nanowires were conductive. Moreover, continuous DNA-templated Bi2Te3 and/or Te nanowires have been fabricated through galvanic displacement of DNA-templated Ni and Cu nanowires. Altogether, these results represent important progress toward the realization of DNA-templated nanofabrication.
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Abtahi, Seyyed Mohammad Hossein. "Synthesis and characterization of metallic nanoparticles with photoactivated surface chemistries." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78081.
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During recent decades metallic nanoparticles have been found very interesting due to their unique characteristics which make them suitable for different applications. In this research, for the very first time, we tried to perform selective surface photo activation chemistry on the targeted facets of nanoparticles while they are in suspension. This technique enabled us to form desired assemblies of nanoparticles. We focused on elongated shaped gold nanorod due to its unique surface plasmon resonance and probable biomedical applications. In this research we formed a dumbbell shape assembly of nanoparticles in suspension. A probable application for these assemblies can be in vivo imaging. Initially, we reproduced gold nanorods using existing techniques in prior papers and optimized them according to our research needs. A low rpm centrifugal separation technique was developed to efficiently separate synthesized gold nanorods from other shapes. Several characterization techniques were utilized to characterize nanoparticles at each step including UV-absorbance, zeta potential, and dynamic light scattering. Different generations of oligomers were synthesized to be used as gold nanorods coating, and each coating was tested and characterized using appropriate techniques. Our two-step coating replacement method using one of these photocleavable oligomers enabled us to achieve, for the very first time, selective UV photo activation of gold nanorod tips. The photo activated tips were then exposed to oppositely charged gold nanospheres to form dumbbell shape assemblies of gold nanorods and nanospheres. Furthermore, dumbbell shape assembly of nanoparticles was investigated and characterized.Master of Science
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Crisan, Diana [Verfasser]. "Anti-inflammatory effect of metallic silver and gold nanoparticles complexed with polyphenolic compounds in human chronic stationary plaque psoriasis / Diana Crisan." Ulm : Universität Ulm, 2016. http://d-nb.info/1101578319/34.
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Peterson, Sarah M. 1975. "Influence of scale, geometry, and microstructure on the electrical properties of chemically deposited thin silver films." Thesis, University of Oregon, 2007. http://hdl.handle.net/1794/8453.
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xv, 101 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries under the call number: KNIGHT QC176.84.E5 P47 2007Silver films with nanoscale to mesoscale thicknesses were produced by chemical reduction onto silica substrates and their physical and electrical properties were investigated and characterized. The method of silver deposition was developed in the context of this research and uses a single step reaction to produce consistent silver films on both flat silica coverslips and silica nanospheres of 250-1000 nm. Both the structure and the electrical properties of the silver films are found to differ significantly from those produced by vacuum deposition. Chemically deposited (CD) silver is not uniformly smooth, but rather is granular and porous with a network-like structure. By quantitatively accounting for the differences in scale, geometry, and microstructure of the CD films, it is found that the same models used to describe the resistivity of vacuum deposited films may be applied to CD films. A critical point in the analysis that allows this relation involves the definition of a geometric parameter, g, which replaces the thickness, t, as the critical length that influences the electrical properties of the film. The temperature dependent properties of electrical transport were also investigated and related to the microstructure of the CD films. A detailed characterization of CD silver as shells on silica spheres is also presented including physical and optical properties. In spite of the rough and porous morphology of the shells, the plasmon resonance of the core-shell structure is determined by the overall spherical shell structure and is tunable through variations in the shell thickness. Preliminary investigations into the electrical transport properties of aggregates of silver coated spheres suggest similarities in the influence scale, geometry, and microstructure to silver films on flat substrates. The aggregates of shells also exhibit pressure related resistance behavior due to the composite structure.
Adviser: Miriam Deutsch
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Lagrange, Mélanie. "Physical analysis of percolating silver nanowire networks used as transparent electrodes for flexible applications." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI075/document.
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Les électrodes transparentes (ET) sont présentes dans de nombreux dispositifs optoélectroniques. Par exemple, on peut les trouver au sein de cellules solaires, d'écrans tactiles, d'OLEDs ou encore de films chauffants transparents. Les propriétés physiques de ces électrodes influencent l'efficacité de ces dispositifs. Les ET sont fabriquées à partir de matériaux transparents conducteurs (TCM) dont le développement a débuté dans les années 1950 notamment avec les oxydes métalliques. Parmi ces oxydes transparents conducteurs (TCO), l'oxyde d'étain-indium (ITO) est celui le plus communément utilisé dans les cellules solaires et les écrans de télévision ou de smartphones. Cependant, de nouvelles exigences telles qu'une réduction des coûts, la flexibilité et la fabrication à faible température et/ou faible coût, ont orienté les recherches vers de nouveaux TCM, notamment à base de nanostructures. Parmi ces matériaux émergents, les réseaux de nanofils métalliques, en particulier de nanofils d'argent, présentent déjà des propriétés optiques et électriques approchant celles de l'ITO, c'est-à-dire une conductivité électrique et une transparence élevées. Ces deux propriétés sont cependant intrinsèquement liées à la densité de nanofils constituant le réseau, et lorsque la conductivité augmente, la transparence diminue. Des traitements post-dépôt existent et permettent d'augmenter la conductivité électrique des ET sans changer la densité du réseau. Plusieurs de ces méthodes d'optimisation ont été étudiées pendant ce travail de thèse, en particulier le recuit thermique, analysé minutieusement afin de comprendre les différents mécanismes de réduction de la conductivité électrique induits par la température. L'examen des effets thermiques a soulevé la question de l'instabilité des nanofils en température, qui est aussi abordée et discutée dans ce document. Le paramètre clé de la densité de nanofils optimale menant au meilleur compromis entre transparence et conductivité a été recherché pour des nanofils de différentes dimensions. La taille des nanofils a en effet un fort impact sur les propriétés du réseau. Ainsi, les propriétés électriques, dans le cadre de la théorie de la percolation, les propriétés optiques comme la transmittance et le facteur de haze, et même l'instabilité thermique ont été reliées aux dimensions des nanofils ainsi qu'à la densité du réseau en utilisant des modèles physiques simples. En ce qui concerne les applications de ces ET émergentes, des études ont été menées sur l'application des réseaux de nanofils d'argent comme film chauffant transparent, et les résultats sont rapportés à la fin de ce document. Les limitations soulevées par cette application, comme les limites de stabilités électrique et thermique ont aussi été abordées. Pour finir, des études préliminaires menées sur de nouvelles applications comme des antennes transparentes ou le blindage électromagnétique transparent utilisant les nanofils d'argent sont présentéesTransparent electrodes (TE) are used in a variety of optoelectrical devices. Among them, solar cells, flat panel displays, touch screens, OLEDs and transparent heaters can be cited. The physical properties of the TE influence the efficiency of the device as a whole. Such electrodes are fabricated from transparent conducting materials (TCM) that have been undergoing development since the 1950s, initially from metallic oxides. Among these transparent conducting oxides (TCO), indium tin oxide (ITO) is the most commonly used in solar cells, and television or smartphone screens. However requirements such as cost reduction, flexibility and low cost/temperature fabrication techniques have oriented the researches toward emerging TCM, mostly using nanostructures. Among them, metallic nanowire networks, and in particular silver nanowires (AgNW), already present optical and electrical properties approaching those of ITO, i.e. a high electrical conductivity and a high transparency. These two properties are intrinsically linked to the network density, therefore a tradeoff has to be considered knowing that when conductivity increases, transparency decreases. Some post-deposition treatments do exist, allowing an increase of the TE electrical conductivity without changing the network density. Several of these optimization methods have been thoroughly studied during this thesis work, especially thermal annealing. This method have been investigated in details to understand the different thermally-induced mechanisms of conductivity improvement. In addition, the investigation of thermal effects raised the question of thermal instability of the nanowires, which is also addressed and discussed in this document. The key issue of density optimization, allowing the best tradeoff between transparency and conductivity, has been investigated for nanowires with different dimensions. Nanowire size has a strong impact on the network properties. Thus, electrical properties, within the framework of percolation theory, optical properties such as transmittance or haziness, and even thermal instability have been linked to the nanowires' dimensions and the network density by using simple physical models. Regarding the application of these emerging TE, studies were conducted on the application of AgNWs as transparent heaters, and the results are reported at the end of the document. Limitations arising from this application, like thermal and electrical stabilities, have also been addressed. To finish, preliminary studies conducted on new applications such as transparent antennas and transparent electromagnetic shielding using AgNW are presented
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Ngema, Xolani Terrance. "Metallic nanoparticles with polymeric shell: A multifunctional platform for application to biosensor." University of the Western Cape, 2018. http://hdl.handle.net/11394/6330.
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Philosophiae Doctor - PhD (Chemistry)Tuberculosis (TB) is an airborne disease caused by Mycobacterium tuberculosis (MTB) that usually affects the lungs leading to severe coughing, fever and chest pains. It was estimated that over 9.6 million people worldwide developed TB and 1.5 million died from the infectious disease of which 12 % were co-infected with human immunodeficiency virus (HIV) in the year 2015. In 2016 the statistics increased to a total of 1.7 million people reportedly died from TB with an estimated 10.4 million new cases of TB diagnosed worldwide. The development of the efficient point-of-care systems that are ultra-sensitive, cheap and readily available is essential in order to address and control the spread of the tuberculosis (TB) disease and multidrugresistant tuberculosis.
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Young, Eleanor Dawn, and ellie@goldstreetstudios com au. "Mechanisms of Controlling Colour and Aesthetic Appearance of the Photographic Salt Print." RMIT University. Applied Science, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080901.142948.
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Abstract The salt print is an important part of photography, both in its historic value and in the tonal range it can provide. This tonal range is greater than any other photographic printing process available to date attributed to the inherent masking ability of the metallic silver. However the intrinsic production problems have made it a 'forgotten' process. There are five key problems. 1. The difficulties in achieving the potential extensive tonal range. 2. The varying colour of the print. 3. Staining that appears in the print, during and after processing. 4. Instability and longevity of the salt print. 5. Contradictory and inaccurate information in material published on the salt print. Although the emphasis of the research is on exploring and controlling the colour and tonal range, the staining problems and stability of the print are also addressed. The materials used for contact negatives today vary in both capture and output, from analogue film processed in the traditional wet darkroom to a variety of transparent film printed from digital files. Inadequate density and tonal range can affect all types of negatives. To provide sufficient exposure time for the salt prints extended tonal range adjustments to the negative were necessary. These long exposures then converted sufficient silver salts to the image making metallic silver, utilising the intrinsic self-masking process. Ultimately this research has uncovered ways to control colour and tonal range and certain aesthetic qualities of the salt print, while simultaneously resolving some of the conflicts in published information. Accurate and consistent methods of processing eliminate staining, providing some stability to the print. The activities and steps carried out to make a salt print are manual; precise duplication is therefore almost unattainable. Nevertheless, although tests on a densitometer may display numeric differences, visual differences are barely noticeable.
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Mayousse, Céline. "Élaboration d’électrodes transparentes souples à base de nanofils métalliques." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI085/document.
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Les matériaux conducteurs transparents font partie intégrante de très nombreux dispositifs optoélectroniques (de type cellule solaire, OLED, capteur tactile, etc.). Pour des raisons techniques et économiques (évolution des marchés vers les applications flexibles),d’importantes recherches sont mises en œuvre pour remplacer les couches minces d’oxydes métalliques (principalement en ITO) actuellement utilisées. En effet, de par sa faible résistance mécanique à la flexion et son coût d’élaboration élevé, l’ITO ne répond pas aux besoins de ces marchés émergents. L’utilisation de nanomatériaux en solution, et en particulier de nanofils métalliques, apparaît comme une alternative très prometteuse qui offre la possibilité d’utiliser des méthodes d’impression bas coût et grande surface. Ces travaux de thèse présentent les procédés de synthèse et purification de nanofils d’argent et de cuivre à forme facteur de forme. L’impression par spray de réseaux 2D percolants permet la réalisation d’électrodes flexibles démontrant d’excellentes propriétés optoélectroniques.Les nanofils d’Ag semblent toutefois être de meilleurs candidats que les nanofils de Cu (synthèse multi-grammes, impression grande surface, meilleure stabilité à l’air, etc.). Ainsi,après avoir identifié les principaux verrous technologiques ayant trait à l’utilisation des AgNF (rugosité, adhésion, travail de sortie, stabilités environnementales/électriques), différentes solutions ont été proposées dans le but d’améliorer les performances et de rendre les nanofils d’argent compatibles avec l’intégration en dispositif. Le potentiel des nanofils d’argent en tant que remplaçants de l’ITO a été confirmé grâce à l’intégration d’électrodes dans divers dispositifs fonctionnels (cellule solaire organique, capteur capacitif ou encore film chauffant)Transparent conductive thin films are widely used in technologies like solar cells, light-emitting diodes, and display technologies. The fabrication of transparent conductive films is currently realized with thin films of transparent conductive oxides (TCOs), and in particular indium tin oxide (ITO). The as-made ITO transparent conductors suffer from limitations like costly fabrication process and brittleness. The use of solution-processable nanomaterials, and especially metallic nanowires, appears as a promising alternative since it affords a large area, low-cost deposition method with high performances.This thesis report that by optimizing synthesis methods and printing methods, flexible electrodes demonstrating excellent opto-electronic properties were performed, either with the use of a percolating network of silver nanowires or copper nanowires. The silver nanowires, however, seem to be better candidates than the copper nanowires (synthesized substantial amount, printing large area, better stability in air, etc.). Thus, having identified the main technological barriers related to the use of Ag NW (roughness, adhesion, work function, electrical/environmental stabilities), different solutions have been proposed in order to make the silver nanowires compatible with as many devices for integration.The potential of silver nanowires as replacements for ITO was confirmed through the integration of electrodes in various functional devices (organic solar cell, capacitive touch sensor or the film heater)
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Sharma, Nipun. "Self-organization of silver nanoparticles with femtosecond laser in TiO2 matrix : Applications to plasmonic colours, multiple hidden images and Colour Image-Multiplexing." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSES032.
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L'auto-organisation de nanoparticules métalliques dans un support est un moyen efficace et peu coûteux de produire des systèmes plasmoniques pouvant être utilisés pour des applications d'affichage couleur actif, de codage d'image et de sécurité. De tels systèmes nanocomposites doivent être synthétisés sous forme de films stables qui pourraient être enduits sur tout type de surface pour un traitement laser. Cette thèse de doctorat porte sur l 'auto - organisation induite par laser de couches minces nanocomposites d' argent et d 'oxyde de titane mésoporeux.Dans ce travail, nous étudions d'abord la synthèse de couches minces mésoporeuses de TiO2 à l'aide d'un processus hydrolytique, facile à mettre en œuvre, pour fournir des films cristallisés à partir de 100 ° C. sont rapportés dans ce travail. En outre, les mécanismes de croissance des nanocristaux dans les films mésoporeux de TiO2 sont étudiés sous la forme de mesures ellipsométriques mettant en évidence son effet sur la porosité et la cristallinité du film avec la température de recuit.La deuxième étude démontre la fabrication de différentes structures nanocomposites à l'aide de la technique de balayage laser femtoseconde, déclenchant la croissance et l'auto-organisation de nanoparticules d'argent à l'intérieur d'une matrice de titane amorphe poreuse donnant lieu à des couleurs dichroïques plasmoniques. Une recherche plus approfondie sur l'étude paramétrique de ces nanocomposites donne lieu à différentes nanostructures à deux régimes de vitesse de balayage différents, qui se forment à la surface et sont noyées en dessous en raison de l'excitation de la surface et des modes guidés. La flexibilité de cette technologie de marquage laser permet également de fabriquer des nanostructures hybrides composées de différents types de nanostructures adjacentes, entrelacées pour couvrir de grandes surfaces. Une extension de cette étude est conclue sur des substrats plastiques / flexibles pour encoder des images imprimées diffractives. Ici, les nanostructures de surface (LIPSS) sont formées en utilisant le contrôle de la polarisation du laser et donc de l'orientation du réseau, qui est utilisé pour coder des images de niveau de gris qui peuvent être observées dans les modes de diffraction.De plus, cette étude se conclut en produisant trois multiplexages d'images qui peuvent être observés dans trois modes sélectionnés d'observation sous lumière blanche en réflexion avec lumière non polarisée et transmission entre polariseurs pour deux angles de polarisation différents. Cela est dû au fait que la biréfringence et le dichroïsme du film peuvent être contrôlés pour produire des gammes de couleurs sans précédent pour le multiplexage. Un tel traitement laser intelligent sur des films minces nanocomposites donne lieu à des applications artistiques et de sécurité en codant différentes images jusqu'à trois sous la même zoneSelf-organization of metallic nanoparticles in a medium is an efficient and a low-cost way to produce plasmonic systems that can be used for applications to active colour display, image encoding, and security. Such nanocomposite systems must be synthesized in form of stable films which could be coated on any kind of surface for laser processing. This doctoral thesis focuses on laser‐induced self‐organization of nanocomposite thin films of silver and mesoporous titania.In this work, we first investigate synthesizing mesoporous TiO2 thin films using hydrolytic process, which is easy to implement, to provide crystallized films starting at 100°C. First activation energies in mesoporous TiO2 films using Raman spectroscopy in combination with the phonon quantum confinement model are reported in this work. Further, growth mechanisms of nanocrystals in mesoporous TiO2 films are investigated in form of ellipsometric measurements highlighting its effect on film porosity and crystallinity with annealing temperature.The second study demonstrates fabrication of different nanocomposite structures using femtosecond laser scanning technique, triggering growth and self-organization of silver nanoparticles inside porous amorphous titania matrix giving rise to plasmonic dichroic colours. Further investigation on the parametric study of such nanocomposites gives rise to different nanostructures at two different scan speed regimes, which are formed at the surface and are embedded below due to excitation of surface and the guided modes. The flexibility of this laser-based marking technology also allows to fabricate hybrid nanostructures composed of different adjacent nanostructure types, interlaced to cover large areas. An extension of this study is concluded on plastic/flexible substrates to encode diffractive printed images. Here surface nanostructures (LIPSS) are formed by using the control of laser polarization and thus grating orientation, which is used to encode grey-level images that can be observed in diffraction modes.Further, this study is concluded by producing three image multiplexing which can be observed in three selected modes of observation under white light in reflection with non-polarized light and transmission between polarizers for two different polarization angles. This is due to the fact that the film birefringence and dichroism can be controlled to produce unprecedented colour gamuts for multiplexing. Such smart laser processing on nanocomposite thin films gives rise to artistic and security applications by encoding different images up to three under same area
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Wolf, Marcus. "Plasmaabscheidung von Metall-Polymer-Nanokompositen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-69923.
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Das Ziel der vorliegenden Arbeit war die Entwicklung eines neuartigen Abscheideverfahrens für Dünnschichten aus Polymer-Metall-Nanokompositen sowie die Charakterisierung sensorischer und antibakterieller Eigenschaften von ersten, mit diesem System abgeschiedenen Komposit-Schichten . Durch den Einbau eines rotierenden Probenhalters zwischen den beiden Plasmaquellen ist es möglich, Plasmapolymere und metallische Nanopartikel als Einzelschichten, Komposite oder Multischichten abzuscheiden. Mit der Gasflusssputterquelle werden Silber-Nanopartikel einer Größe von 1,8…20 nm mit einer Verteilungsbreite der gewichteten Normalverteilung von 0,1…2,7 nm durch Kathodenzerstäubung und anschließende Agglomeration der Cluster in der Gasphase generiert. Die Entladungsbedingungen, welche durch die Elektronentemperatur und -dichte charakterisiert werden, zeigen eine sprunghafte Änderung bei Drücken von 70…85 Pa und einer Spannung von 550 V. Ab einem Gasfluss von 3 slpm kehrt sich die Proportionalität zwischen zugeführter elektrischer Leistung und Elektronentemperatur um. Dies wird durch die vermehrte Emission von Sekundärelektronen erklärt. Die abgeschiedenen Partikel sind aus verschieden orientierten Clustern aufgebaut. Durch Kühlung des Substrates wurde nachgewiesen, dass eine Agglomeration auf dem Substrat nur bei Gasflüssen von 5 slpm stattfindet. Anhand der Auswertung von faktoriellen Versuchsplänen wurde gezeigt, dass der Gasfluss auf die Partikelgröße und Abscheiderate den größten Einfluss hat. Die Präkursoren Styrol, Methylmethacrylat und 3-Methyl-1,2-butadien wurden durch Plasmapolymerisation in einer 60 MHz-Linearquelle als dünne, homogene Schichten im nm-Bereich abgeschieden. Aus den Emissionsspektren von Argon konnten, unter Verwendung des Stoß-Strahlungs-Modells, Elektronendichten von 6*1010…1,5*1011 cm-3 und Elektronentemperaturen von 3…9 eV in Abhängigkeit von der Verweilzeit der Monomermoleküle im Plasma sowie des Energieeintrages berechnet werden. Die Elektronen haben bei Energieeinträgen oberhalb von 6*107 J/kg genügend Energie, um -Bindungen des Kohlenstoffs in der Gasphase zu spalten. Die freien Radikale initiieren Oxidationsreaktionen, was zur Bildung von Carbonylverbindungen in Schichten aus Styrol- und Isoprenplasmapolymeren führt. Die mit XPS-Messungen gefundenen hohen Sauerstoffgehalte der Plasmapolymer-Schichten konnten durch Kontaktwinkelmessungen bestätigt werden. Die Quellungsmessungen in organischen Lösungsmitteln (Aceton, Ethanol, Chloroform, Toluol) mit reflektometrischer Interferenzspektroskpie bestätigen die Tendenzen der Kontaktwinkelmessung im Fall von Styrol und Methylmethacrylat. Die Abscheiderate der Plasmapolymere wird besonders durch den Energieeintrag beeinflusst. Dabei zeigt sich nur bei Isopren eine deutliche Auswirkung der Abbaureaktionen.Die Härte der Isopren-Schichten korreliert ebenfalls mit der Elektronendichte. Die Perkolationsschwelle der Silber-Plasmapolymer-Nanokomposite liegt bei einem Füllgrad von 57 %, was typisch für Partikel mit geringem Aspektverhältnis ist. Die Schichten reagieren selektiv auf Dämpfe der Lösungsmittel. Bisher war die Langzeitstabilität von Membranen zur Trinkwasseraufbereitung durch Ultrafiltration durch das starke Wachstum von Mikroorganismen auf der Membranoberfläche eingeschränkt. Dies konnte durch die Beschichtung mit Silber-MMA-Kompositen verbessert werden. Durchflussmessungen an behandelten Membranen sowie elektronenmikroskopische Aufnahmen bestätigen die gute antibakterielle Wirkung der Beschichtung.
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ANZANO, MANUELA NADIA. "Research and development of new products and processes: reclamation of a manufacturing waste." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/14127.
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The aim of the research was the development of new products and processes from a manufacturing waste.
The manufacturing waste were produced by a metallurgic Italian company which produced thin silver metallic films. These films were used as coating and food decoration.
Thin films were produced by an hammering process. The starting material, silver laminate, had a thickness of 10 μm. During the hammering process films with various thickness were obtained. The final produced silver films had a thickness of about 300 nm which can be considered a submicrometric dimension, near to the nanometric range (≤100 nm). At the end the submicrometric films were cut, giving a square shape (10 cm x 10 cm) and inserted into boxes. The residues, produced during this step, named untreated flakes (UF), were used in the research.
Mainly we studied the possible use of UF as a catalyst in antimicrobial applications in aqueous medium.
After a thorough bibliographic research considering the various aspects of the use of silver as antimicrobial agent (chapter 2), the research was divided in various stages: to investigate the use of flakes as antimicrobial agent, at first we verified if they possessed antimicrobial capability. We conducted some antimicrobial tests using Escherichia coli (E. coli JM109) as Gram-negative microorganism model. We showed that the flakes (UF) didn’t present antimicrobial capability up to 24 h (chapter 3).
On the basis of these results we treated the UF with three activation processes:
1)Thermal activation in reducing atmosphere;
2)Thermal activation in air;
3)Chemical activation with H2O2.
Then we tested the antimicrobial activity of the new obtained products. We showed that the activation processes gave the flakes antimicrobial capability (chapter 3).
The antimicrobial agents are classified as bacteriostatic or bactericidal. Bacteriostatic agents cause only the growth inhibition of microorganisms while bactericidal agents cause the cells death. E. coli were observed at a fluorescence microscope and at a scanning electron microscope (SEM), after specific treatment processes. In this way we determined that activated flakes were bactericidal agents (chapter 4).
In the next two stages we investigated the possible mechanism of action of the flakes:
On the basis of literature knowledge we studied the relationship between the capability of flakes to release silver in aqueous medium and their antimicrobial activity. We showed that the presence of flakes was necessary to have E. coli decrease over time (chapter 5);
we characterised the morphology and chemical composition of the flakes surface by SEM and XPS to verify if the antimicrobial activity acquired by activated flakes could be affected by some morphological or chemical change. We concluded that the antimicrobial property was due to the presence of dissolved oxygen (chapter 6).
In the final stage we performed some experiments which simulated possible applications of activated silver flakes (chapter 7).
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Garuz, Richard. "Caractérisations optiques (LBIC, LBIV) et validation d’encres pour des cellules et des modules solaires photovoltaïques organiques." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0059/document.
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Les travaux de cette thèse sont en rapport avec la caractérisation de cellules solaires organiques et se déclinent suivant 3 axes :- Dans le cadre du projet IMPCELPHOTOR, nous avons développé un banc de caractérisation LBIC/LBIV permettant de cartographier des dispositifs OPV afin de visualiser et d’identifier les défauts de fonctionnement.- Dans le cadre du projet Européen SPrinTronics, nous avons travaillé sur l’amélioration des électrodes. Pour l’électrode collectrice d’électrons, nous avons sélectionné, testé et validé des encres métalliques à base de nanoparticules d’argent compatibles avec l’impression jet d’encre et permettant de réaliser des dispositifs OPV fonctionnels. Pour l’électrode collectrice de trous, nous avons testé des encres à base de nanofils d’argent et de nanotubes de carbone afin de remplacer l’ITO. Des résultats satisfaisants ont été obtenus avec une encre à base de nanofils d’argent. Cette dernière permet de réaliser des cellules semi-transparentes fonctionnelles sur verre et sur plastique. - Un travail sur l’aspect couleur d’un dispositif OPV a été mené au sein du projet PHASME. Nous avons mis en œuvre différentes techniques afin de modifier la couleur d’un dispositif OPV sans détruire ses performances photovoltaïques, le but étant de réaliser des modules polychromes. Nous avons développé simultanément un logiciel de colorimétrie permettant de contrôler et de prévoir le rendu de couleur dû à l’ajout de filtre coloré sur le dispositif OPVThe work of this thesis is related to the characterization of organic solar cells and is structured in three independant parts :- Within the IMPCELPHOTOR project, we developed an experimental bench based on LBIC/ LBIV mapping, in order to visualize and identify defects within OPV device and modules.- Within the European SPrinTronics project, we worked on the improvement of OPV electrodes. For the top electrode, we selected, tested, and validated metallic inks based on silver nanoparticles compatible with inkjet printing. For the bottom electrode, we tested silver nanowires and carbon nanotubes inks to replace ITO. Satisfactory results have been obtained with an ink based on silver nanowires, which allowed us to obtain functional semi-transparent cells on glass and plastic.- Within the PHASME project, we worked on the visual aspect of a coloured OPV device. We implemented various strategies to change the color of an OPV device without altering its photovoltaic performance, the aim being to achieve full color modules. Simultaneously, we developed a colorimetric software to control and predict the color rendering on the final device (OPV plus filter)
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Tambosi, Reem. "Stress and toxicity of metal in photosynthetic bacteria : multi-scale study of the effects and the targets of metal ions and nanoparticles Silver and Copper Acute Effects on Membrane Proteins and Impact on Photosynthetic and Respiratory Complexes in Bacteria Silver Effect on Bacterial Cell Membrane Structure Investigated by Atomic Force and Scanning Electron Microscopes Cadmium and Copper Cross-tolerance. Cu+ alleviates Cd2+ toxicity, and both cations target heme and chlorophyll biosynthesis pathway in Rubrivivax gelatinosus Additive effects of metal excess and superoxide, a highly toxic mixture in bacteria." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL070.
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L’usage intensif des métaux et des ions métalliques dans l'industrie et l'agriculture représente une menace sérieuse pour l'environnement et pour tous les êtres vivants en raison de la toxicité aiguë de ces ions. Cependant, cela peut aussi être un outil prometteur. En effet, les ions comme les nanoparticules d'argent sont très utilisés dans diverses applications médicales, industrielles et sanitaires. L'effet antimicrobien de ces nanoparticules est en partie lié aux ions Ag⁺ libérés et à leur capacité à interagir avec les membranes bactériennes. L'objectif de ce projet est d'étudier l'interaction entre un objet biologique (les bactéries) et des objets physiques (métaux), pour comprendre l'impact des métaux sous différentes formes (ions, nanoparticules et nanostructures) sur les cellules bactériennes en utilisant différentes approches: de physiologie, biochimie, génétique et de biologie cellulaire. Nous avons utilisé comme modèles biologiques, principalement la bactérie photosynthétique pourpre Rubrivivax (R.) gelatinosus, mais aussi Escherichia coli; et pour les objets physiques, nous avons utilisé l'argent comme métal principal mais aussi d'autres métaux (cuivre, cadmium et nickel) à titre de comparaison. Les principaux objectifs de ce travail sont: 1- d'étudier l'impact et les mécanismes de toxicité de ces ions métalliques / NPs sur les métabolismes bactériens respiratoire et photosynthétique. 2- Identifier des gènes bactériens impliqués dans la réponse à un excès d'ions Ag⁺. 3- Etudier l'internalisation et l'interaction des ions métalliques et des NP au sein des membranes biologiques. Ainsi, nous avons pu identifier, à la fois in vitro et in vivo, des cibles spécifiques d'ions Ag⁺ et Cu²⁺ dans la membrane des bactéries. Cela inclut des complexes impliqués dans la photosynthèse, mais également des complexes de la chaine respiratoire. Il a été démontré que les ions Ag⁺ et Cu²⁺ ciblent spécifiquement une bactériochlorophylle exposée au solvant dans les antennes de collecte de lumière du photosystème de la bactérie. Ceci présente également, à notre connaissance, la première preuve directe de dommages induits par des ions Ag⁺ sur les protéines membranaires impliquées dans ces métabolismes. Par ailleurs, nous avons également réalisé une étude comparative par microscopie (AFM/ MEB) de l'effet de l'Ag⁺ en solution ou des Ag-NPs synthétisés dans notre laboratoire, sur la morphologie des cellules bactériennesThe extensive use of metal ions in industry and agriculture represents a serious threat to the environment and to all living being because of the acute toxicity of these ions. However, it can also be a promising tool, silver ions and nanoparticles are some of the most widely used metals in various industrial and health applications. The antimicrobial effect of these nanoparticles is in part related to the released Ag⁺ ions and their ability to interact with bacterial membranes. The goal of this project is to study the interaction between biological subject (the bacteria) and physical objects (metals), and more specifically to understand the impact of metals in different forms (ions, nanoparticles and nanostructures) on the growth of the bacterial cells using different approaches : physiology, biochemistry, genetics and cell biology. We used as biological models, principally the purple photosynthetic bacterium Rubrivivax (R.) gelatinosus, but also Escherichia coli; and for physical objects, we used silver as main metal but also other metals (copper, cadmium and nickel) for comparison. The main objectives are: 1- to study the impact and the mechanisms of toxicity of these metallic ions/NPs on the bacterial respiratory and photosynthesis metabolisms. 2- To identify the bacterial genes involved in response to excess silver. 3- To study the internalization and interaction of metals ions and NPs within biological membranes. The results showed that we were able to identify, both in vitro and in vivo, specific targets of Ag⁺ and Cu²⁺ ions within the membrane of bacteria. This include complexes involved in photosynthesis, but also complexes involved in respiration. Ag⁺ and Cu²⁺ were shown to specificaly target a solvent exposed bacteriochlorophyll in the light harvesting antennae of the photosystem. This also presents, in our knowledge, the first direct evidence of silver ions damages to membrane proteins involved in these metabolisms. We also carried out a microscopy (AFM/ SEM) comparative study of the effect of Ag⁺ ions or Ag-NPs synthesized in our laboratory, on the bacterial cell morphology
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Goldbach, Hanno. "Epitaktisches Wachstum von Metall- und Oxidschichten." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963203703.
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Wolde-Giorgis, Daniel. "Korngrenzsegregation in Silber-Nickel und Kupfer-Wismut Legierungen." Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/wolde-giorgis.
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Manandhar, Kedar Park Kenneth T. "Temperature-dependent structures of heteroepitaxial metallo-phthalocyanine (Mpc, M = Cu, Fe) thin films on silver." Waco, Tex. : Baylor University, 2007. http://hdl.handle.net/2104/5137.
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Aumer, Andreas. "Summenfrequenzerzeugungsspektroskopie an Metallen,Oxiden und oxidgeträgerten Metallpartikeln." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16158.
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Die vorliegende Arbeit widmet sich der Untersuchung von 4 Modellsystemen der Oberflächenforschung. Die verwendeten experimentellen Methoden sind Summenfrequenzerzeugungsspekroskopie (SFG), Thermische Desorptionsspektroskopie (TDS), Beugung niederenergetischer Elektronen (LEED), Augerelektronenspektroskopie (AES), Infrarotadsorptionsspektrokopie (IRAS) und Rastertunnelmikroskopie (STM). Durch die Verwendung von SFG waren Messungen bis zu 50 mbar möglich. Die untersuchten Systeme sind: CO auf Pt(111), Wasser auf Ag(001) und MgO/Ag(001), CO auf Au/MgO/Ag(001) und CO auf Au-Pd/MgO/Ag(001). Bei den Messungen von CO auf Pt(111) tritt unter bestimmten Druck- und Temperaturbedingungen eine bisher nicht näher untersuchte Doppelpeakstruktur auf, die genauer charakterisiert wurde. Die Untersuchungen von Wasser auf MgO/Ag(001) und Ag(001) zeigen, dass sich auf MgO/Ag(001) zuerst eine Monolage Wasser mit einer darauffolgenden Multilage ausbildet, wohingegen es auf Ag(001) von Beginn an in einer Multilagenschicht wächst. Die Monolage kann unter der Multilage gemessen werden und einige Resonanzen identifiziert werden. Für Au/MgO/Ag(001) zeigte sich mittels STM eine Abhängigkeit des Au-Wachstums von der Schichtdicke, die allerdings nicht spektroskopisch in Erscheinung tritt. Bei den Messungen an gemischten Au-Pd-Teilchen auf MgO/Ag(001) zeigen sich Unterschiede im Adsorptionsverhalten zwischen reinen Metallteilchen und gemischten Teilchen, die auf eine Wechselwirkung zwischen den beiden Metallen zurückzuführen ist. Nach Heizschritten auf 600 K reichern sich die Au-Atome im Mantel des Teilchens an, das Pd bildet den Kern. Die Ergebnisse aller Messungen werden unter Berücksichtigung neuer Veröffentlichungen diskutiert.This thesis focuses on 4 different model systems of surface science. The experimental techniques used for the measurements include sum frequency generation (SFG), thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), infrared adsorption spectrosocopy (IRAS) and scanning tunneling microscopy (STM). By using SFG, measurements could be performed up to a pressure of 50 mbar. The systems under investigation were: CO on Pt(111), water on Ag(001) and on MgO/Ag(001), CO on Au/MgO/Ag(001), and CO on Au-Pd/MgO/Ag(001). The system of CO on Pt(111) exhibits a two peak-pattern under certain pressure and temperature conditions which has not been studied so far. Various experiments helped to elucidate the origin of this distinct behaviour. The measurements of water on Ag(001) and MgO/Ag(001) show that on MgO, water first adsorbs as a monolayer with a following multilayer, whereas on Ag(001) it adsorbs as a multilayer from the beginning. The monolayer can be studied below the multilayer and some resonances can be identified. For the case of Au/MgO/Ag(001), STM shows that the growth mode of Au depends on the thickness of the supporting MgO film, which can not be seen with spectroscopic methods. For mixed Au-Pd particles on MgO/Ag(001) a clear difference in the adsorption behaviour between pure metal particles and mixed particles can be seen, which is explained by an interaction between these metals. Annealing the mixed particles to 600 K leads to a segregation of the metals, where the Au atoms diffuse to the shell and the Pd atoms make up the core. The results of all these measurements are discussed in the light of recent publications.
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Rauch, Nicole. "High temperature spreading kinetics of metals." [S.l. : s.n.], 2005. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-25946.
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Faraco, Thales Alves. "Estudo das propriedades térmicas, ópticas e estruturais de vidros fosfato de silício dopados com érbio e prata para aplicação em telecomunicação." Universidade Federal de Juiz de Fora (UFJF), 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/6141.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Vidros fosfatos são materiais tecnologicamente importantes, devido às suas propriedades físicas e químicas, podendo ser aplicados em sistemas ópticos, através da co-dopagem com íons terras raras e nanopartículas metálicas. São apresentados, neste trabalho, a produção pela técnica de fusão/resfriamento e a caracterização de vidros fosfato de silício dopados com trióxido de érbio 23 e/ou nitrato de prata 3, para a verificação da influência desses dopantes, quando adicionados à matriz hospedeira, nas propriedades térmica, ópticas e estruturais. As amostras foram submetidas a tratamento térmico e às técnicas de caracterização: Densidade, Índice de Refração Linear (IRL), Análise Térmica Diferencial (ATD), Absorção Óptica (AO), Fotoluminescência de Estado Estacionário (FL) e Fotoluminescência Resolvida no Tempo (FLRT); onde através delas e dos cálculos de Judd-Ofelt foi possível mapear características promissoras desses vidros para aplicações tecnológicas, com destaque em telecomunicação: transmissão de dados por fibras ópticas.
Phosphate glasses are technologically important materials due to their physical and chemical properties and can be applied in optical systems by co-doping with rare earth ions and metallic nanoparticles. In this work the production by melting and quenching technique and characterization of phosphate silica glasses doped with trioxide erbium and / or silver nitrate are shown, so that can checked the influence of these dopants, when added to the host matrix, in thermal, optical and structural properties. The samples were subjected to heat treatment and the characterization techniques: Density, Linear Refractive Index (LRI), Differential Thermal Analysis (DTA), optical absorption (OA), steady state photoluminescence (PL) and Time Resolved Photoluminescence (TRPL), where through them and Judd-Ofelt calculations, promising features of these glasses could be mapped for technological applications, especially in telecommunication: data transmission by optical fibers.
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Lombardi, Anna. "Linear and ultrafast response of individual multi-material nanoparticles." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10141.
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Les propriétés optiques et vibrationnelles de nanoparticules métalliques individuelles ont été étudiées par spectroscopie par modulation spatiale (SMS), avec une attention particulière aux effets de forme, composition, environnement local, ainsi que de couplage inter-particule. La réponse optique de nanoparticules (métalliques au cœur-couronne métal-diélectrique) allongées et des particules bimétalliques (hétérodimères or-argent) a été mesuré et en suite interprétée grâce à une corrélation avec la caractérisation morphologique de la même particule obtenue par microscopie à transmission électronique et avec des simulations par éléments finis prenants en compte la réelle géométrie du nano-objet et le substrat. Une technique pompe sonde résolue en temps a été en suite utilisée pour étudier le profil Fano dans l'absorption d'une particule d'or au sein d'un hétérodimères or-argent. Sur une échelle de temps des quelques dizaines de picosecondes, les vibrations acoustiques multimodales de nanobipyramides d'or individuelles ont été optiquement détectées et caractérisées par rapport à un modèle élastique classiqueOptical and vibrational properties of individual metal-based nanoparticles have been investigated by spatial modulation spectroscopy (SMS), focusing on their dependence on nano-object shape, composition, environment and inter-particle coupling. Quantitative investigations of the optical response, and in particular, the surface plasmon resonance (extinction cross-section amplitude, spectral position and linewidth) of elongated metal or metal-dielectric (gold nanorods, nanobipyramids with or without silica coating) and bimetallic (gold-silver heterodimers) nanoparticles deposited on a substrate have first been performed. The same nanoparticles were characterized by electron microscopy permitting quantitative interpretation of their optical response using finite element numerical simulations, taking into account the influence of the substrate. Combining SMS microscopy with a high sensitivity femtosecond two-color pump-probe setup, the ultrafast dynamics of single nano-objects has been investigated. The Fano absorption profile of a gold nanoparticle within a single gold-silver heterodimer, a parameter not accessible by linear spectroscopy, was directly measured. On a picosecond time-scale, multimodal acoustic vibrations of single gold nanobipyramids were optically lunched and detected, and their features compared to a model based on continuum elasticity
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Schubert, Gunnar. "Thick Film Metallisation of Crystalline Silicon Solar Cells Mechanisms, Models and Applications /." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-25592.
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Danna, Caroline Silva [UNESP]. "Utilização de membranas de borracha natural com nanopartículas de prata como métodos de separação de parasitas de Leishmania braziliensis." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99665.
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As membranas de BN foram obtidas do látex da seringueira Hevea Braziliensis, através da técnica de casting. Este trabalho apresenta as fases de obtenção e caracterização de membranas de borracha natural (BN) com incorporação coloidal de nanopartículas metálicas de prata (AgNPs) gerando compósitos de BN/Ag. A incorporação das partículas de prata na membrana de BN se deu através do método de reação in situ, no processo de redução química do sal de nitrato de prata (AgNO3), utilizando água como meio reacional, para diferentes tempos de redução. Os compósitos de Bn/Ag foram utilizados para aplicação no processo de separação dos parasitas infectantes de Leishmania braziliensis. Esta etapa é necessária na busca de uma vacina eficiente contra a leishmaniose causada pela espécie original do Brasil. A eficácia do processo foi verificada por meio dos estudos comparativos com o método de separação de protozoários utilizando a lã de vidro. Três testes biológicos foram realizados, sendo (i) a cinética de crescimento populacional in vitro das formas promastigotas e amastigotas: (ii) a síntese de óciso nítrico (NO) por macrófagos murinos e; (iii) infecção experimental de camundongos isogênicos BALB/c e C57BL6. A caracterização do compósito de BN/Ag foi realizada através das técnicas de Espectroscopia no Ultravioleta visível (UV-VIS), análises térmicas por calorimetria exploratório diferencial (DSC) termogravimetria (TG) e acoplamento de termogravimetria com infravermelho com infravermelho (TG/FT-IR). os resultados mostram a ocorrência da redução das nanopartículas de prata na membrana de Bn, em diferentes tempos, e que não interfere nas propriedades termomecânicas, nas temperaturas de transições de fase e na estabilidade térmica, quando comparado com a membrana de Bn pura. Os testes biológicos...
The natural rubber membranes (NR) were obtained from the latex Hevea braziliensis rubber tree, using the technique of casting. This work presents the stages of obtainment and characterization of NR membranes with colloidal incorporation silver metallic nanoparticles - AgNPs, producing composites of NR/Ag. The NR/Ag membranes were used for application into separation process of the Leishmania brasiliensis parasites. This stage is very important in the research for an effective vaccine against leishmaniasis, cuased by the original species in Brazil. The effectiveness of the process will be done through comparative studies across the methods of separation of protozoa, using the membranes NR/Ag and glass wool. There biological tests were accomplished: (i) the growth kinetics of population of promastigostas and amastigotes in vitro; (ii) the synthesis of nitric oxide NO by murine macrophages; and (iii) experimental infection of inbred mice BALB/c and C57BL6. The characterization of the composite NR/Ag was performed using the techniques of ultraviolet visible spectroscopy (UV-Vis), thermal analysis differential scanning calorimetry (DSC), thermogravimetry (TG) and thermogravimetry coupled with infrared (TG/FT-IR). The result show the occurrence of the reduction of silver nanoparticles in the membrane of NR in different reduction times and does not interfere in the thermomechanical property, at temperatures of phase transitions and thermal stability compared with the membrane of pure NR. The biological tests to maintain non-infectious phase without cell damage that the composite BN/Ag has the capacity to separate the two stage... (Complete abstract click electronic access below)
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Danna, Caroline Silva. "Utilização de membranas de borracha natural com nanopartículas de prata como métodos de separação de parasitas de Leishmania braziliensis /." Presidente Prudente : [s.n.], 2012. http://hdl.handle.net/11449/99665.
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Orientador: Aldo Eloizo JobBanca: Ana Maria Pires
Banca: Edgardo Alfonso Gomez Pineda
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: As membranas de BN foram obtidas do látex da seringueira Hevea Braziliensis, através da técnica de casting. Este trabalho apresenta as fases de obtenção e caracterização de membranas de borracha natural (BN) com incorporação coloidal de nanopartículas metálicas de prata (AgNPs) gerando compósitos de BN/Ag. A incorporação das partículas de prata na membrana de BN se deu através do método de reação in situ, no processo de redução química do sal de nitrato de prata (AgNO3), utilizando água como meio reacional, para diferentes tempos de redução. Os compósitos de Bn/Ag foram utilizados para aplicação no processo de separação dos parasitas infectantes de Leishmania braziliensis. Esta etapa é necessária na busca de uma vacina eficiente contra a leishmaniose causada pela espécie original do Brasil. A eficácia do processo foi verificada por meio dos estudos comparativos com o método de separação de protozoários utilizando a lã de vidro. Três testes biológicos foram realizados, sendo (i) a cinética de crescimento populacional in vitro das formas promastigotas e amastigotas: (ii) a síntese de óciso nítrico (NO) por macrófagos murinos e; (iii) infecção experimental de camundongos isogênicos BALB/c e C57BL6. A caracterização do compósito de BN/Ag foi realizada através das técnicas de Espectroscopia no Ultravioleta visível (UV-VIS), análises térmicas por calorimetria exploratório diferencial (DSC) termogravimetria (TG) e acoplamento de termogravimetria com infravermelho com infravermelho (TG/FT-IR). os resultados mostram a ocorrência da redução das nanopartículas de prata na membrana de Bn, em diferentes tempos, e que não interfere nas propriedades termomecânicas, nas temperaturas de transições de fase e na estabilidade térmica, quando comparado com a membrana de Bn pura. Os testes biológicos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The natural rubber membranes (NR) were obtained from the latex Hevea braziliensis rubber tree, using the technique of casting. This work presents the stages of obtainment and characterization of NR membranes with colloidal incorporation silver metallic nanoparticles - AgNPs, producing composites of NR/Ag. The NR/Ag membranes were used for application into separation process of the Leishmania brasiliensis parasites. This stage is very important in the research for an effective vaccine against leishmaniasis, cuased by the original species in Brazil. The effectiveness of the process will be done through comparative studies across the methods of separation of protozoa, using the membranes NR/Ag and glass wool. There biological tests were accomplished: (i) the growth kinetics of population of promastigostas and amastigotes in vitro; (ii) the synthesis of nitric oxide NO by murine macrophages; and (iii) experimental infection of inbred mice BALB/c and C57BL6. The characterization of the composite NR/Ag was performed using the techniques of ultraviolet visible spectroscopy (UV-Vis), thermal analysis differential scanning calorimetry (DSC), thermogravimetry (TG) and thermogravimetry coupled with infrared (TG/FT-IR). The result show the occurrence of the reduction of silver nanoparticles in the membrane of NR in different reduction times and does not interfere in the thermomechanical property, at temperatures of phase transitions and thermal stability compared with the membrane of pure NR. The biological tests to maintain non-infectious phase without cell damage that the composite BN/Ag has the capacity to separate the two stage... (Complete abstract click electronic access below)
Mestre
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Ider, Mina. "Elaboration et caractérisation des nanomatériaux à base de métaux nobles." Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1022/document.
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Dans ce travail de thèse, la synthèse de nanoparticules d'argent (Ag) est réalisée par une méthode simple, efficace et rapide basée sur la réduction du nitrate d'argent (AgNO3) dans un milieu organique (éthanol) sous chauffage par irradiation micro-ondes (MW) pendant quelques secondes en présence d'une émulsion aqueuse de copolymère latex. Les expériences ont été effectuées soit de manière séquentielle en faisant varier les paramètres expérimentaux les uns après les autres (approche classique) ou bien en moyennant la méthodologie des plans d'expérience qui sert à varier simultanément ces conditions expérimentales dans le but à la fois d'optimiser et d'évaluer l'impact de ces facteurs sur les propriétés physico-chimiques des particules produites. L'objectif est d'arriver à préparer un maximum de concentration en nanoparticules d'argent avec un minimum de concentration en copolymère latex et en AgNO3. Les nanoparticules préparées sont trouvées extrêmement stables en solution colloïdale avec des distributions de taille très étroites, ce qui confirme la qualité élevée et le diamètre uniforme des nanoparticules obtenues par l'approche de synthèse micro-ondes. Ceci pourrait être probablement dû à l'effet de stabilisation produit par les molécules du latex, qui est un bon environnement pour contrôler efficacement la croissance de nanoparticules métalliques d'argent. En tant que principal objectif d'une telle réalisation de la synthèse de nanoparticules d'argent par la méthode MW ouvre la voie à l'exploitation d'effets plasmoniques de surface dans des réactions photocatalytiques en utilisant des structures semi-conductrices bien définies (Bi2O3, In2O3, TiO2...)In this thesis work, the synthesis of silver nanoparticles (Ag) is carried out by a simple, efficient and fast method based on the reduction of silver nitrate (AgNO3) in an organic medium (ethanol) under heating by micro irradiation (MW) for a few seconds in the presence of an aqueous emulsion of latex copolymer. The experiments were performed either by varying the experimental parameters one after the other (classical approach) or by means of the experimental design methodology which serves to vary simultaneously these experimental conditions in order to both optimize and evaluate the impact of these factors on the physicochemical properties of the nanoparticles. The main goal is to prepare a maximum concentration of silver nanoparticles with a minimum concentration of latex copolymer and AgNO3. The prepared nanoparticles were found to be extremely stable in colloidal solution with very narrow size distributions, which confirms the high quality and the uniform diameter of the nanoparticles obtained by the microwave synthesis approach. This could possibly be due to the stabilizing effect produced by the latex molecules, which is a good environment for effectively controlling the growth of metallic silver nanoparticles. As the main objective of such realization of the silver nanoparticle synthesis by the MW method opens the way to the exploration of surface plasmonic effects in photocatalytic reactions using well-defined semiconducting structures (Bi2O3 , In2O3, TiO2 ...)
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Bellova, Petri [Verfasser], Manfred [Gutachter] Köller, and Andreas [Gutachter] David. "Antibakterielle Aktivität von Opferanodensystemen durch Kombination von Platingruppen-Metallen mit Silber / Petri Bellova ; Gutachter: Manfred Köller, Andreas David ; Medizinische Fakultät." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1163451924/34.
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Marks, Manuel [Verfasser], and Ulrich [Akademischer Betreuer] Höfer. "Über die Dynamik von Elektronen auf Silber-Einkristalloberflächen, an metall-organischen Grenzschichten und in PTCDA-Monolagen / Manuel Marks. Betreuer: Ulrich Höfer." Marburg : Philipps-Universität Marburg, 2013. http://d-nb.info/104241050X/34.
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Sanjosé, i. Llongueras Lourdes de. "L’obra de Llemotges i d’altres orígens: L’obra de metall als segles XII-XIII a Catalunya." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/377751.
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L’objectiu que ens hem proposat és el de respondre a la pregunta: hi ha un taller català del metall als segles XII i XIII? I, en cas afirmatiu, respondre a una segona doble qüestió: primerament, si va sorgir de forma espontània o va ser la continuació d’un taller precedent, i segonament, quina és la hipotètica relació de les seves obres amb les de l’Œuvre de Limoges / Taller de Llemotges?
La documentació dels segles XII i XIII que hem treballat ens ha fet percebre la magnitud dels registres de vasos litúrgics de metall preuat i metall de les esglésies catalanes d’època comtal i reial. Es tracta d’un cos extraordinari que presentem en forma de quadres. Aquesta ingent obra ens va plantejar ben aviat una pregunta relacionada amb els possibles orígens en els que poguéssim establir les bases del taller que anomenem taller català que treballa el metall d’època alt medieval. Des d’un primer moment vàrem intuir que era necessari recular la cronologia dels documents als segles IX-XI per poder fixar les bases del segles XII i XIII.
El tractament aprofundit de l’orfebreria medieval catalana dels segles XII i XIII ha donat com a resultat la definició que hem fet del taller català en una doble vessant. La primera que des dels precedents fins a final del segle XIII el denominem genèricament «taller català que treballa el metall» d’època alt medieval. La segona és el taller català que definim com el que treballa «a la manera de Llemotges», aquest taller s’inicià a finals del segle XII, fructificà al XIII i s’extingí al XIV.
En el nostre estudi ens hem basat tant en la documentació com en l’obra que en els segles XII i XIII han estat el nostre referent. El taller català que treballa el metall preuat, l’orfebreria, té molt poca obra representativa. El gran nombre d’obra litúrgica que hem extret de la documentació ens hauria aportat tota la riquesa d’aquest taller si s’hagués conservat. Per altra banda, és deixen vasos d’argent, anells, estris d’animals i d’altres objectes per a fer fondre per a una determinada obra, això indica que, en una contrada no massa llunyana, hi ha un taller que possibilita aquest procés.
Per altra banda, el taller català que treballa el metall (fosa) ha estat una gran sorpresa per la informació que ens ha aportat una de les tipologies, la de l’encenser amb un total de cinquanta cinc exemplars. Això ens ha permès classificar-los i agrupar-los per tal de donar-los-hi fonament dins cada grup que hem acotat. Aquest taller català del metall s’ha de reivindicar com un taller extraordinari per la durada en el temps, alhora que reafirmar-lo com un taller creador de repertoris i formes. Un taller que no treballa aïlladament sinó que té en compte, aplica o assumeix models coneguts per la il·lustració de manuscrits, per la pintura mural o de taula i l’escultura catalana sense descartar, per suposat, la influència que per via forana en tingui coneixença.
El segon aspecte del taller català és el que fructificà a partir de l’arribada de les obres del Taller de Llemotges, obres que l’influïren decisivament i de les que va sorgir, un «taller català a la manera de Llemotges». No va ser un taller creador sinó més aviat seguidor (de Llemotges).
L’obra més significativa quant a la creació d’aquest taller és el copó; però no es menys cert que els esmalts que s’apliquen al copó no sorgeixen per generació espontània, sinó que és un procés llarg, treballat i experimentat des de finals del segle XII fins al XIV. Aquest taller va produir obra que considerem d’ús local.The vast body of documentation we have studied from the twelfth and thirteenth centuries have helped us understand the magnitude of the existing records on liturgical vessels in precious metals (gold and silver) and other metals (bronze, copper, tin, etc.) of the Catalan churches.Their study has enabled us to define the Catalan workshop in two ways, based on the types of pieces it worked on.First, we call it generically “Catalan metal workshop" (c. X-XIII). In defining it as such, we have based our analysis on the documentation, the remaining works and the artistic comparison. The Catalan workshop that worked on precious metals has little representative work. Had it been preserved, the large number of liturgical pieces that we found referenced in the documentation would have represented a huge wealth. In some documentation references silver vessels and other objects left to melt for a silver piece, indicates that there must have been a workshop close in distance that allowed the process.Discovering the Catalan metal workshop has been extremely helpful in that it has provided information on one of the types of works, the censer. A workshop that does not work in isolation but takes into account known models of the Catalan illustration of manuscripts, mural or table painting, or sculpture without discarding, of course, the influence of foreign styles.Second, we have also defined a Catalan workshop as working "the Limoges way" (c. XII-XIV). This workshop developed at the end of the twelfth century and lasted until the fourteenth century and bore fruit after the arrival of the works of the L’Œuvre de Limoges. These works had a decisive influence on the Catalan workshop from which developed, "a Catalan workshop in the way of Limoges." This workshop was less creative as it followed the Limoges style but had its one personality.
La documentación de los siglos XII y XIII que hemos trabajado nos ha hecho percibir la magnitud de registros de vasos litúrgicos de metal noble y metal de las iglesias catalanas de época condal y real. Su estudio ha permitido la definición que hemos hecho del taller catalán en un doble sentido. Por un lado, lo denominamos genéricamente «taller catalán que trabaja el metal» (s. X-XIII). Para ello nos hemos basado en la documentación, en la obra conservada y en la comparativa. El taller catalán que trabaja el metal noble, la orfebrería, tiene escasa obra representativa. El gran número de obra litúrgica que hemos extraído de la documentación nos habría aportado toda la riqueza de este taller en caso de conservarse.Se legan objetos de plata para fundirlos y destinarlos a nuevas obras (litúrgicas) lo que indica que en un lugar no excesivamente lejano hay un taller que lo posibilita.El taller catalán que trabaja el metal nos ha sorprendido por la información que ha aportado una de las tipologías, la del incensario. Hay que reivindicar este taller como un taller extraordinario, un taller que no trabaja aisladamente sino que tiene en cuenta modelos conocidos por la ilustración de manuscritos, la pintura mural o de tabla así como la escultura catalana, sin descartar, por supuesto, la influencia foránea de la que pudiera tener conocimiento.Por otro lado, el taller catalán que definimos como el que «trabaja a la manera de Limoges», este taller se inició a finales del siglo XII, fructificó en el XIII y se extinguió en el XIV; fue a partir de la llegada de l’Œuvre de Limoges, obra que influyó decisivamente en este taller que no fue un taller creador sino más bien seguidor, con rasgos específicos que lo caracterizan.
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Hiredal, Sandra. "spår." Thesis, Konstfack, Ädellab, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-7415.
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In a place that has been abandoned I have collected the human-made traces. Preserving the perishability of places and people. Saving the small memory. To hold close and pass on to the next. Placing them in a jewelry context where we may care for them more tenderly. To approach the people through adornment and wearing. I don't want to physically mark anyone, but I still want to come close. A piercing of the clothes: brooches. You who left it. I who collected. Next one to wear. Where all of us become involved and equally important. With the traces taken from the place, I add my own imprint in the craftsmanship of the jewelry. Each brooch fragile and where the next one, the wearer, will become part of our traces and history. Each brooch with a part of us and in transformation. Traces can be left, and memories preserved. They can be passed on through the visible, the tangible, the sound and the anecdotes. They can be experienced or relived when we feel, listen and see. Therefore, I needed to pass on the traces in several ways. Through the brooches and through film. For more people to take part of. Where the next one can see, hear and feel a place; its traces, stories and the imagination created in the experience.
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Yen-RuChao and 趙彥儒. "The Developing Research of Silver Metallic Glaze." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58366000552478929901.
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碩士國立成功大學
資源工程學系碩博士班
100
The metallic glaze with silver luster was developed in this study. The trinary formulation was used to find the formula which can present silver metallic luster and well surface. The additions of feldspar and alkaline earth flux were adjusted to improve the luster, and then the optimal parameters were tested. The better ratio was obtained by the trinary formulation which contains FePO4 of 31wt%, feldspar of 36 wt%, and alkaline earth flux of 19 wt%. The silver metallic luster on sample surface is described by the hematite crystalline. The micro-particles caused by phase separation were observed by SEM after sample was etching by aqua regia. In the test of Na/K feldspar addition, the glaze surfaces on samples all presented silver metallic luster. When the ratio of Na-feldspar to K-feldspar is 3:1, the better luster value is obtained. In the test of alkaline earth flux addition, the hematite shows better crystalline in samples with high CaO addition. In the optimal test, the milling time of glaze, thickness of glaze, firing process and temperature were found. The hue figure of finished sample was located in silver region, and its gloss value is 47.7. A matte-like surface appears on the glaze, and whole appearance and flatness of glaze surface were improved.
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Ling, Tsung-Kai, and 凌崇凱. "Metallic nanoparticle over silver film for Surface Enhanced Raman Scattering." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/ucg29d.
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碩士國立臺灣海洋大學
光電科學研究所
102
The primary research of this paper is use atomic layer deposition (ALD) to deposit 1nm aluminium oxide on silver film ,and then we take gold ,silver and unique star-shaped gold nanoparticles to cover on glass substrate and aluminium oxide layer. Finally ,we can fabricate Surface Enhanced Raman Scattering (SERS) substrate. We know that different metal nanoparticles have various shape and absorbtion band. Thus their optical properties is different. First,we used simple chemistry method to synthesize metal nanoparticles, then we can get you want nanoparticle size and shape through by change concentration and formula in solution. We can also fabricate metal nanoparticle dimers and trimers by mixing gold nanoparticles with sodium chloride solution[1]. Next,we take these substate to measure transmission and Reflection spectrum. We can get Absorption spectrum by calculation. In 5-2 section we used COMSOL(Finite element analysis software) to simulate that we fabricated structures. First thing, we found that the thickness of aluminium oxide layer will affect localized electric field coupling effect. Second , we can compare the simulation result with measurement. We can observe interaction of substrate composition of different nanoparticles. In addition immersion method of the above , this part we use centrifugal method to arrange nanoparticles on our substrate. This method have high uniformity and good dispersion that can measure easily. Last, we take these substrate to measure raman spectrum with different excitation wavelength, including 532nm and 1064nm. We can observe metal nanoparticles will generate resonance in different excitation wavelength. In addition, we can use image j software to calculate numbers of nanoparticles in SEM image. Then, we take numbers of nanoparticles that can compare with raman spectrum.In the same density, we found that star-shaped gold nanoparticle’s signal is greater then gold,silver nanoparticles under 1064nm raman spectrum. Experiment result can get that we fabricated substrate by ALD, metal nanoparticle interact with silver film and aluminium oxide layer that localized electric field is certainty greater than glass substrate. The reason is localized surface plasmon enhanced electric field intensity.
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Lin, Ching-Yi, and 林晉毅. "Metallic Wire Patterning on Glass Substrate by Laser Reduction of Silver Ions." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/59bcg5.
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碩士國立中央大學
光電科學與工程學系
105
In this thesis, continuous silver micro-wires were fabricated by femtosecond laser direct writing (FLDW) of polyvinylpyrrolidone (PVP) films containing silver ions. The minimum line width achieved by FLDW is 1.5 μm. Using a solution with relatively higher concentration of silver nitrate, the resistivity of continuous silver wires can be further lowered down to 1.8×10-5 Ω•m. Attempt of producing silver micro-wires on the flexible substrates was conducted. Although the result shows silver can be reduced on the substrate, the poor heat resistance and surface adherence of the flexible substrate hinder the production of continuous silver wires. Future area of work for improving the production process where surface roughening in combination of smaller silver particle size might lower the manufacturing temperature on flexible substrate effectively.
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Huang, Kuo-Cheng, and 黃國政. "The Chemical Synthesis and Application of Nanosized Metallic Materials (Nickel, Iron and Silver)." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/02946202635347197841.
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博士國立清華大學
化學工程學系
95
In this study, chemical reduction method was adopted to produce ultrafine metallic materials including iron nanoparticles and nickel fibers in aqueous solution from their respective metal salt precursors. Related applications of these metallic materials were also investigated. Nickel fibers were reduced from nickel chloride by hydrazine in the presence of magnetic field. It was found that nickel fibers were composed of nickel particles connected linearly under the effect of the magnetic field. This work showed the morphology of nickel fibers was mainly affected by two factors: nucleation rate and growth rate. In the fast nucleation case, thinner nickel fibers would be obtained, and on the contrary, thicker fibers would be obtained in the slow nucleation case. When the growth rate was fast, the nickel fibers would be loose and weak, and when the growth rate was slow, the nickel fibers would be tight and strong. In the application as electromagnetic interference (EMI) shielding materials, nickel fibers showed a better effectiveness than nickel particles with the same diameter, this is benefited from the high aspect ratio of nickel fibers in the composite materials. Iron nanoparticles can be synthesized by using sodium borohydride as the reducing agent and iron chloride as the precursor in the aqueous solution. In was found that the water-soluble polymer PAA (polyacrylic acid) is beneficial to the dispersion of iron nanoparticles, hence stopping the agglomeration of iron nanoparticles. In order to decrease the diameter of iron nanoparticles, palladium iron considered as the nucleation promoter can be added to increase the nucleation sites. In addition, it was also found that the pH of the solution affected the iron nanoparticle size noticeably, which directly caused from the dispersing capability of dispersing agent under different pH values. When the pH was high, the dispersing capability of PAA increased and the nucleation sites were well-dispersed. The numerous nucleation sites therefore subsequently led to the small iron nanoparticles. On the contrary, when the pH was low, the dispersing capability of PAA decreased and the nucleation sites were agglomerated. Consequently, the loss of nucleation sites led to the large iron nanoparticles. The iron nanoparticle electrode showed the capacity as high as 510 mAh/g-Fe with the discharge current of over 200 mAh/g-Fe. This result indicated the utilization ratio of iron was indeed improved by the decrease of iron nanoparticle size as well as the discharge current was enhanced by the large surface area of iron nanoparticles. The silver nanoparticles could be dispersed on a substrate by the spin-coating method. By controlling the silver colloid concentration, the distribution of silver nanoparticles on the substrate could be varied from dispersed separation to mono-layered close packing, eventually to multi-layered close packing. After heat treatment at different temperatures, the multi-layered silver nanoparticles structure started to exhibit conductivity after 100℃ treatment. The resistivity initially decreased with temperature and then increased to become finally insulated again. On the SEM observation, the silver nanoparticle structure exhibited sintering effect at the increase of temperature and became conductive. But when the temperature continuously increased, the silver nanoparticles structure shrank into large particles and became insulated again.
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Lin, Pei-syuan, and 林沛萱. "Low Temperature Cu-to-Cu Bonding Using Silver Nanoparticle and Copper Formate Metallic Paste." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/8r6ebq.
Full textAbstract:
碩士國立中山大學
化學系研究所
102
Low temperature Cu-to-Cu bonding by sintering of metal nanoparticles is a promising lead-free bonding technique used in electronic packaging industry. The novelty of this study is based on silver nanoparticles, we use copper formate as an additive to promote the interconnection between joint and copper substrate. The Cu-to-Cu bonding was carried out under a force of 10 MPa at various temperature and nitrogen. After bonding process, the shear strength and interface structure of joint were investigated. The microstructure of interface between the joint and copper substrate was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We found that the average shear strength is about 41.44 MPa by using silver nanoparticle mixed with copper formate metallic paste under sintering temperature at 250 oC.
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"Crystalline and amorphous metallic membranes for hydrogen separation." Doctoral diss., 2015. http://hdl.handle.net/2286/R.I.36038.
Full textAbstract:
abstract: In the United States, 95% of the industrially produced hydrogen is from natural gas reforming. Membrane-based techniques offer great potential for energy efficient hydrogen separations. Pd77Ag23 is the bench-mark metallic membrane material for hydrogen separation at high temperatures. However, the high cost of palladium limits widespread application. Amorphous metals with lower cost elements are one alternative to replace palladium-based membranes. The overall aim of this thesis is to investigate the potential of binary and ternary amorphous metallic membranes for hydrogen separation. First, as a benchmark, the influence of surface state of Pd77Ag23 crystalline metallic membranes on the hydrogen permeability was investigated. Second, the hydrogen permeability, thermal stability and mechanical properties of Cu-Zr and Ni60Nb35M5 (M=Sn, Ti and Zr) amorphous metallic membranes was evaluated.
Different heat treatments were applied to commercial Pd77Ag23 membranes to promote surface segregation. X-ray photoelectron spectroscopy (XPS) analysis indicates that the membrane surface composition changed after heat treatment. The surface area of all membranes increased after heat treatment. The higher the surface Pd/(Pd+Ag) ratio, the higher the hydrogen permeability. Surface carbon removal and surface area increase cannot explain the observed permeability differences.
Previous computational modeling predicted that Cu54Zr46 would have high hydrogen permeability. Amorphous metallic Cu-Zr (Zr=37, 54, 60 at. %) membranes were synthesized and investigated. The surface oxides may result in the lower experimental hydrogen permeability lower than that predicted by the simulations. The permeability decrease indicates that the Cu-Zr alloys crystallized in less than two hours during the test (performed at 300 °C) at temperatures below the glass transition temperature. This original experimental results show that thermal stability of amorphous metallic membranes is critical for hydrogen separation applications.
The hydrogen permeability of Ni60Nb35M5 (M=Sn, Ti and Zr) amorphous metallic membranes was investigated. Nanoindentation shows that the Young’s modulus and hardness increased after hydrogen permeability test. The structure is maintained amorphous after 24 hours of hydrogen permeability testing at 400°C. The maximum hydrogen permeability of three alloys is 10-10 mol m-1 s-1 Pa-0.5. Though these alloys exhibited a slight hydrogen permeability decreased during the test, the amorphous metallic membranes were thermally stable and did not crystalize.Dissertation/Thesis
Doctoral Dissertation Materials Science and Engineering 2015
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Wu, Zong-Han, and 吳宗翰. "Extraction, concentration and detection of metallic pollutants in environmental samples: (1) silver nanoparticles; (2) mercury ion." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41744949872269018226.
Full textAbstract:
碩士國立中山大學
化學系研究所
99
I. Combined cloud point extraction and Tween 20-stabilized gold nanoparticles for colorimetric assay of silver nanoparticles in environmental water This study investigated a simple, sensitive and selective method for the colorimetric assay of silver nanoparticles (AgNPs) using Triton X-114-based cloud point extraction (CPE) as a preconcentration step and Tween 20-stabilized gold nanoparticles (Tween-AuNPs) as a colorimetric probe. After heating beyond the cloud point temperature of Triton X-114, a solution containing Triton X-114 micelles and AgNPs separated into a surfactant-rich phase (small volume) and a dilute aqueous phase. AgNPs partitioned into a Triton X-114-rich phase through a hydrophobic interaction between Triton X-114 micelles and AgNPs. After phase separation, the concentrated AgNPs oxidized to form Ag+ upon adding H2O2. The generated Ag+ triggered the aggregation of Tween 20-AuNPs in a high-ionic-strength solution because the reduction of Ag+ on the AuNP surface enabled Tween 20 (stabilizer) to be removed from the NP surface. The efficiency of Triton X-114-based CPE of the AgNPs was found to be iv insensitive to their size and coating type. Under optimal extraction and detection conditions, the selectivity of this method for AgNPs was considerably higher than for other nanomaterials. The minimum detectable concentrations for 7, 22, and 54 nm AgNPs were measured to be 0.1, 420, and 600 ng/mL, respectively. This method was successfully applied to the analysis of 7 nm AgNPs in drinking water, tap water and seawater. Keyword: silver nanoparticles, gold nanoparticles, cloud point extraction, Tween-20, colorimetric assay II. Functionalized silver nanoparticles as an extracting and preconcentrating agent for detection of mercury ions In this research we provided highly sensitive and selective for fluorescence assay of combined polythymine oligonucleotide (PolyT) with silver nanoparticles (AgNPs) as an extracting agent to detect mercury ion in environmental water. According to previous researches, PolyT will form a hairpin structure in the presence of Hg2+, this structure provide several 3-D grooves that the fluorescent dye can inlay with it. SYBR Green I (SG) is a staining dye for DNA, when binding with single strand DNA, it shows low fluorescence. On the contrast, SG inlay with grooves of hairpin structure, it shows v 11-fold of fluorescence signal. Hence, we used SG as a fluorescence probe for Hg2+. We modified thiol group at the 5’ of PolyT DNA, because of forming silver sulfur bond, PolyT will able to modified on the surface of AgNPs. PolyT33SH-AgNPs are the extracting and concentrating agent in Hg2+ solution, by the centrifugation, we collected the PolyT33SH-AgNPs. For the purpose of releasing PolyT from AgNPs’ surface, we adding H2O2 to oxidize the AgNPs into Ag+. By mixing buffer and SG into previous solution, mercury ion could be detected. In this study, we successfully detecting Hg2+ in the aqueous solution contained drinking water and tap water. The detection limit in drinking water is 20 pM, which is below Environmental Protection Agency limit for Hg2+ in drinkable water (10 nM), the linear range is from 50-600 pM. On the other hand, the detection limit in tap water is 50 pM, linear range is from 100-700 pM. Keyword: silver nanoparticles, mercury ion, PolyT, SYBR Green I, thymine
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Sanders, Charlotte E. "Tailoring nanoscale metallic heterostructures with novel quantum properties." Thesis, 2013. http://hdl.handle.net/2152/21355.
Full textAbstract:
Silver (Ag) is an ideal low-loss platform for plasmonic applications, but from a materials standpoint it presents challenges. Development of plasmonic devices based on Ag thin film has been hindered both by the dificulty of fabricating such film and by its fragility out of vacuum. Silver is non-wetting on semiconducting and insulating substrates, but on certain semiconductors and insulators can adopt a metastable atomically at epitaxial film morphology if it is deposited using the "two-step" growth method. This method consists of deposition at low temperature and annealing to room temperature. However, epitaxial Ag is metastable, and dewets out of vacuum. The mechanisms of dewetting in this system remain little understood. The fragility of Ag film presents a particular problem for the engineering of plasmonic devices, which are predicted to have important industrial applications if robust low-loss platforms can be developed. This dissertation presents two sets of experiments. In the first set, scanning probe techniques and low energy electron microscopy have been used to characterize Ag(111) growth and dewetting on two orientations of silicon (Si), Si(111) and Si(100). These studies reveal that multiple mechanisms contribute to Ag film dewetting. Film stability is observed to increase with thickness, and thickness to play a decisive role in determining dewetting processes. A method has been developed to cap Ag film with germanium (Ge) to stabilize it against dewetting. The second set of experiments consists of optical studies that focus on the plasmonic properties of epitaxial Ag film. Because of the problems posed until now by epitaxial Ag growth and stabilization, research and development in the area of plasmonics has been limited to devices based on rough, thermally evaporated Ag film, which is robust and simple to produce. However, plasmonic damping in such film is higher than in epitaxial film. The optical studies presented here establish that Ag film can now be stabilized sufficiently to allow optical probing and device applications out of vacuum. Furthermore, they demonstrate the superiority of epitaxial Ag film relative to thermally evaporated film as a low-loss platform for plasmonic devices spanning the visible and infrared regimes.text
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Gondikas, Andreas Panagiotis. "The Role of Sulfhydryl-Containing Low Molecular Weight Ligands for the Environmental Fate of Zinc Sulfide and Metallic Silver Nanoparticles." Diss., 2012. http://hdl.handle.net/10161/5408.
Full textAbstract:
Nanomaterials often exhibit enhanced reactivity relative to their larger colloidal counterparts because of the high specific surface area and number of imperfections on the crystal lattice at the nanoscale. Management of ecosystems, remediation of contaminated waters, and assessment of the potential risks from the industrial use on nanomaterials requires an understanding of the environmental factors that control the reactivity and bioavailability of natural and manufactured nanomaterials. Dissolved organic matter (DOM) acts as a moderator of reactivity and bioavailability for dissolved and particulate moieties in natural waters. DOM consists of a range of low and high molecular weight species that are complex and heterogeneous. It has been historically categorized based on operational definitions, rather than physical properties. In order to understand the effect of DOM on nanomaterials, there is an urgent need for information regarding specific properties of DOM, such as ligand groups.
The goal of this research was to study how cysteine, a low molecular weight metal-binding ligand, affects the composition and reactivity of nanoparticulate zinc sulfide and metallic silver. Zinc sulfide was used as a representative of nanoparticulate metal sulfide which occurs naturally in sulfidic environments. Metallic silver nanoparticles were also studied because of its wide use in consumer products. Both types of nanomaterials contain metal constituents (zinc and silver) that are expected to strongly bind to sulfhydryl-containing ligands (such as cysteine) in the environment. Serine is structurally similar to cysteine, with the only difference of a hydroxyl group in the place of the sulfhydryl group of cysteine. Therefore, serine was used for comparison as a hydroxyl-containing analogue to cysteine.
The aggregation kinetics of zinc and other metal sulfide nanoparticles in the presence of cysteine and serine were investigated using dynamic light scattering. Cysteine decreased aggregation rates of the particles, while serine had no effect on their aggregation behavior. Further experiments revealed that the mechanism of stabilization occurred through the adsorption of cysteine on zinc sulfide, which induced electrostatic charge on the particles surface. A direct link was established between the amount of cysteine sorbed and attachment efficiency, an indicator of the tendency of particles to aggregate. These results shed light on discrepancies in the literature between metal sulfide precipitation experiments conducted in our lab and work on the formation and aggregation of zinc sulfide nanoparticles on biofilms of sulfate reducing bacteria.
The early-stage growth and aggregation kinetics of zinc sulfide nanoclusters in the presence of cysteine was studied in detail using a suite of complementary techniques. Growth and aggregation experiments have been traditionally difficult to conduct due to instrumental precision issues, but newly developed analytical tools and software products have made it possible to study the early-stage formation of nanoclusters. Experiments with small angle X-ray scattering, X-ray diffraction, dynamic light scattering, and X-ray absorption spectroscopy at the extended fine structure range showed that cysteine controlled the growth and aggregation of zinc sulfide nanoclusters. The molar ratio between zinc, sulfide, and cysteine was a determining factor in the precipitation process. When zinc and sulfide were in equimolar concentrations with cysteine, very small nanoclusters of about 2.5 nm formed within 12 hours and aggregated to structures with hydrodynamic diameter larger than 100 nm. When cysteine was in excess of zinc and sulfide, aggregation was held to a minimum, but monomer nanoclusters were able to grow to about 5 nm in 12 hours. Overall, these results indicate the importance of thiol ligands on the monomer size, extent of aggregation, and aggregate structure of zinc sulfides.
The effect of metal ligands on metal bearing particle surfaces is of particular interest for manufactured nanoparticles, because they are typically coated with an organic coating during the production process. These coatings are sorbed on the particles surface and are likely to interfere between the metallic surface and the ligand. Dissolution experiments using citrate and polyvinylpyrrolidone (PVP) coated zero valent silver nanoparticles in the presence of cysteine and serine showed that cysteine dissolved both types of particles, while serine did not. Dissolution rates depended on the aggregation state of the particles exposed to cysteine. As indicated by zeta potential and adsorption measurements, cysteine replaced the coating on the particles surface and altered their aggregation pattern. X-ray absorption spectroscopy near the absorption edge showed partial oxidation of silver and formation of Ag(+I)-sulfur bonds, indicating that the thiol group in cysteine formed chemical bonds with oxidized surface silver atoms. A comparison between the two coatings showed that citrate coated particles dissolved approximately three times faster than PVP coated particles. Overall, these results show that metal binding ligands can drastically change the fate of manufactured silver nanoparticles in the environment and that this effect is moderated by surface coatings.
The results of this study suggest that cysteine, a metal binding ligand was able to induce and control transformations, such as growth, aggregation, dissolution, and surface reactivity of zinc sulfide and metallic silver nanoparticles. Cysteine adsorbed on metal sites on both ZnS and Ag particles, inducing changes on their surface charge. Aggregation of ZnS particles was slowed because of a net decrease in zeta potential compared to the bare particles. On the contrary, cysteine enhanced the aggregation of Ag particles, by replacing the citrate and PVP coatings on the particles surface. Finally, the cysteine-Ag(+I) bonds caused strong polarization on the particles surface and lead to the oxidative dissolution of the particles.
Overall, this research provides a better understanding of the fate of natural and manufactured nanoparticles in anaerobic waters, where thiols are present in significant amounts. It may also be used for risk assessment of manufactured nanomaterials and the production of safer and environmentally responsible materials.
Dissertation
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Banerjee, Ipshita. "Formation of Porous Metallic Nanostructures Electrocatalytic Studies on Self-Assembled Au@Pt Nanoparticulate Films, and SERS Activity of Inkjet Printed Silver Substrates." Thesis, 2013. http://etd.iisc.ernet.in/2005/3453.
Full textAbstract:
Porous, conductive metallic nanostructures are required in several fields, such as energy conversion, low-cost sensors etc. This thesis reports on the development of an electrocatalytically active and conductive membrane for use in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and fabrication of low-cost substrates for Surface Enhanced Raman Spectroscopy (SERS).
One of the main challenges facing large-scale deployment of PEMFCs currently is to fabricate a catalyst layer that minimizes platinum loading, maximizes eletrocatalytically active area, and maximizes tolerance to CO in the feed stream. Modeling the kinetics of platinum catalyzed half cell reactions occurring in a PEMFC using the kinetic theory of gases and incorporating appropriate sticking coefficients provides a revealing insight that there is scope for an order of magnitude increase in maximum current density achievable from PEMFCs. To accomplish this, losses due to concentration polarization in gas diffusion layers, which occur at high current densities, need to be eliminated. A novel catalyst design, based on a porous metallic nanostructure, which aims to overcome the limitations of concentration polarization as well as minimize the amount of platinum loading in PEMFCs is proposed. Fabrication steps involving controlled in-plane fusion of self-assembled arrays of core-shell gold-platinum nanoparticles (Au@Pt) is envisioned. The key steps involved being the development of a facile synthesis route to form Au@Pt nanoparticles with tunable platinum shell thicknesses in the 5 nm size range, the formation of large-scale 2D arrays of Au@Pt nanoparticles using guided self-assembly, and optimization of an RF plasma process to promote in-plane fusion of the nanoparticles to form porous, electrocatalytically active and electrically conductive membranes.
This thesis consists of seven chapters. The first chapter provides an introduction into the topic of PEMFCs, some perspective on the current status of research and development of PEMFCs, and an outline of the thesis. The second chapter provides an overview on the methods used, characterization techniques employed and protocols followed for sample preparation. The third chapter describes the modelling of a PEMFC using the Kinetic theory of gases to arrive at an estimate of the maximum feasible current density, based on the kinetics of the electrocatalytic reactions. The fourth chapter presents the development of a simple protocol for synthesizing Au@Pt nanoparticles with control over platinum shell thicknesses from the sub monolayer coverage onwards. The results of spectroscopic and microscopic characterization establish the uniformity of coating and the absence of secondary nucleation. Chapter five describes the formation of a nanoporous, electrocatalytically active membrane by self-assembly to form bilayers of 2D arrays of Au@Pt nanoparticles and subsequent fusion using an RF plasma based process. The evolution of the electrocatalytic activity and electrical conductivity as a function of the duration of RF plasma treatment is monitored for Au@Pt nanoparticles with various extent of platinum coating. Spectroscopic, microscopic, electrical and cyclic voltammetry characterization of the samples at various stages were used to understand the structural evolution with RF plasma treatment duration and discussed. Next durability studies were carried out on the nanoporous, Au@Pt bilayer nanoparticle array with an optimum composition of Pt/Au atomic ratio of 0.88 treated to 16 minutes of argon plasma exposure. After this the novel catalyst membrane design of PEM fuel cell is revisited. Two different techniques are proposed so that the thin, nanoporous, metallic catalyst membrane achieves horizontal electronic resistance equivalent to that of the conventional gas diffusion layer with catalyst layer. The first technique proposes the introduction of gold coated polymeric mesh in between the thin, nanoporous, metallic catalyst membrane and bipolar plate and discusses the advantages. Later the gold coated polymeric mesh is introduced in a conventional membrane electrode assembly and efficiency of the polarization curves probed with and without the introduction of gold coated polymeric mesh. The second technique describes the results of fabrication of a nanoporous metallic membrane using multiple layers of 2D Au@Pt nanoparticle arrays at an optimum composition of Pt/Au atomic ratio of 0.88 to reduce the horizontal electronic resistance. Preliminary studies on the permeability of water through such membranes supported on a porous polycarbonate filter membrane are also presented.
In chapter six, a simple reactive inkjet printing process for fabricating SERS active silver nanostructures on paper is presented. The process adapts a simple room temperature protocol, using tannic acid as the reducing agent, developed earlier in our group to fabricate porous silver nanostructures on paper using a commercial office inkjet printer. The results of SERS characterization, spectroscopic and microscopic characterizations of the samples and the comparison of the substrate’s long-term performance with respect to a substrate fabricated using sodium borohydride as the reducing agent is discussed. Preliminary findings on attempts to fabricate a conductive silver network using RF plasma induced fusion area also presented. Chapter seven provides a summary of the results, draws conclusions and a perspective on work required to accomplish the goals of incorporating the porous metallic nanostructures into PEMFCs.
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Singh, Amrita. "Probing Magnetic And Structural Properties Of Metallic Nanowires Using Resistivity Noise." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/2132.
Full textAbstract:
The main focus of this thesis work has been the study of domain wall (DW) dynamics in disordered cylindrical nanomagnets. The study attempts to accurately quantify the stochasticity associated with driven (temperature/magnetic field/spin-torque) DW kinetics. Our results as summarized below, are particularly relevant with regard to the technological advancement of DW based magnetoelectronic devices.
1. Temperature dependent noise measurements showed an exponential increase in noise mag-nitude, which was explained in terms of thermally activated DW depinning within the Neel-Brown framework. The frequency-dependence of noise also indicated a crossover from nondiffusive kinetics to long-range diffusion of DWs at higher temperatures. We also observed strong collective depinning, which must be considered when implementing these nanowires in magnetoelectronic devices.
2. Our noise measurements were sensitive enough to detect not only the stochasticity in DW propagation (diffusive random walk) but also their nucleation in the presence of magnetic field down to a single DW unit inside an isolated single Ni nanowire. Controlled injection and detection of individual DWs is critical in designing DW based memory devices.
3. The spectral slope of noise was observed to be sensitive to DWkinetics that reveals a creep-like behavior of the DWs at the depinning threshold, and diffusive DW motion at higher spin torque drive. Different regimes of DW kinetics were characterized by universal kinetic exponents. Noise measurements also revealed that the critical current density and DW pinning energy can be significantly reduced in a magnetically coupled vertical ensemble of nanowires. This was attributed to strong dipolar interaction between the nanowires. Our results are particularly important in view of recent proposals for low power consumption magnetic storage devices that rely on DW motion.
In all our experiments, the critical magnetic field/current density, required to set the DWs in duffusive kinetics, were found to be much smaller than the reported values for nanostrips. This could be attributed to the circular cross section of nanowires, where massless DWs results in the absence of Walker breakdown and hence in zero critical current density. At present the contribution from the non-adiabaticity, which acts as an effective field and can reduce the crit- ical current density, can not be denied. The main di±culty in quantifying the non-adiabatic spin-torque is that not only does it contain contributions due to non-adiabatic transport but also due to spin-relaxation provided by magnetic impurities or the sources for spin-orbit scattering. Fortunately, in cylindrical nanomagnet, non-adiabaticity does not affect the DW motion. There- fore, cylindrical NWs may be promising candidate for future magnetic storage devices. However, a systematic experimental study of DW dynamics in cylindrical nanomagnets is lacking.
In chapter 7, silver nanowires (AgNWs) are shown to be stabilized in fcc or hcp crystal structure, depending on the electrochemical growth conditions. The AgNWs stabilized in hcp crystal structure are shown to exhibit exotic structural properties i.e. ultra low noise level, thermally driven unconventional structural phase transformation, and time dependent structural relaxation. Ultra noise level makes hcp AgNWs suitable for application in nanoelectronics and the structural transformation may be exploited for use in smart materials. Though time resolved transmission electron microscopy and noise measurements provide some understanding of the hcp AgNWs formation, the precise growth mechanism is still not clear.
Future scope of the work
The results in this thesis provide the groundwork for a good understanding of stochastic DW kinetics in isolated as well as ensemble of magnetic nanocylinders. Some extensions to this work that would help expand and strengthen the results, are listed below;
1. In all the nanocylinders used for our experiments the source of stochasticity in DWkinetics were randomly distributed structural defects. For a controlled injection and detection of DWs between the voltage probes, it would be of great importance to fabricate artificial notches (pinning centers) in the NW. These notches can be fabricated either by using nano-indentation or by a focussed ion beam.
2. To investigate whether DWs in different parts of the nanowire exhibit spatio-temporal correlation, a simultaneous detection of DWkinetics (through noise measurement) between different volage probes needs to be done. If the propagation time of DWs scales with the distance between the voltage probes, we can be confident of our velocity measurement. Then, by recording the DWvelocity as function of eld/current for nanowire (or nanostrip) absence (or presence) of the Walker breakdown can be probed. This would be a significant result for future spintronic devices. With an accurate determination of velocity even non- adiabaticity parameter may be calculated and one can see its effect on DW dynamics.
3. A complete understanding of sustained avalanches at finite magnetic fields, characterized by a high spectral exponent (a>¸ 2:5) in an ensemble of nanowires is still lacking. Per- forming a controlled experiment on a single nanowire, by varying the number of nanowires in the alumina matrix, one can study the chaotic dynamics of DWs in the ensemble in very accurate manner.
All the experiments on AgNWs were performed on ensembles. The large change in a as well as noise magnitude in hcp AgNWs could arise from stress relaxation due to the presence of an insulating matrix or structural relaxation, determined by the nanowire growth kinetics. To resolve this issue, time and temperature dependent noise measurements should be performed on single nanowire stabilized in both hcp and fcc crystal structure.
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Kundu, Paromita. "Controlled Nucleation, Growth And Directed Assembly Of Nanocrystals With Engineered Interfaces For Applications." Thesis, 2011. http://hdl.handle.net/2005/2406.
Full textAbstract:
Controlling the morphology of nanocrystals provides provides a possible pathway to tune properties and hence has been explored in depth. However, to obtain a wider spectrum of properties or for multi-functionality. Other strategies need to be devised. Combining different functional nanostructures to obtain a functional hybrid is one such strategy that holds promise for a wide range of applications. While this is simple in principle, there are no simple and general protocols for synthesis of such functional heterostructure. The challenge lies in producing a hybrid with good control over the structure and chemistry of the interfaces in the system. The use of molecular linkers or physical forces to form the hybrid has several drawbacks in terms of interface quality and stability.
In this dissertation, a rational basis is developed for the evolution of symmetry forbidden FCC nanocrystals via wet chemical route which relies on appropriate choice of
reagents and the reaction conditions for nucleation and growth. The concept is extended to devise general synthetic strategies for functional nanoheterostrcutres in solution via economic, facile and environment friendly routes. Electron microscopy and X-ray photoelectron spectroscopy has been used as the major tools for structural characterization of the materials and to investigates the reaction/formation mechanism. The properties of the synthesized materials are investigated primarily targeting the nanoelectronic and catalytic applications.
The entire study reported in the thesis is organized as follow:
chapter I leads to a general introduction of nanocrystals and role in different fields of application. It describes the motivation behind controlling the shape of nanocrystals and combining two or more nanostructures to obtain a functional heterostructure. The existing methodologies to achieve shape control and nanoscale hybrid/heterostructure with active interfaces are elaborated while indicating the role of morphology, interfaces and composition for enhanced activity/performance. The information on the chemical used for synthesis, routers adopted for synthesizing and the basic techniques utilized to characterize the materials in study are detailed in the respective chapters.
Chapter 2 provides a study by which one can easily select an appropriate reductant for a metal couple to achieve the desired morphology. Moreover, the role of kinetics and the factors driving the kinetics in obtaining the symmetry breaking shapes like 2-D and I-D for Ag and Au nanocrystals is discussed in detail and validated by experiments.
Chapter 3 describes the methodology to attach ultrafine Au nanowires to different nanosubstrates ranging from oxides to carbon (CNT/graphene) where the key step is heteronucleation of the Au (I) precursor on the substrate.
Chapter 4 deals with the growth of ultrafine Au nanowires on various substrates and between pre-defined contacts to fabricate nanodevices. The mechanistic investigation directs to the controlled heterogeneous nucleation of the building units (Au nanoparticles) on substrate as the key step followed by its subsequent growth into wires in presence of Au nanoparticles in the medium. Kinetic control of the nucleation and growth step enabled precise control over the population and length of the wires. This is of immense importance for application like catalysis, sensors and nanoelectronics. Moreover, the method enabled the first time electrical transport studies on these wires which revealed an insulating behavior in such metallic wires on progressive lowering of temperature down to few kelvins.
The concept of heterogeneous nucleation is extended to design nanoscale heterogeneous in the following three chapters where primarily a precursor coating is formed on a nanosubstrate, viz. ZnO nanorods and graphene, and converted to the phase of interest in a controlled manner to obtain the desired morphology. In each of the chapters the mechanisms of formation of the heterostructure are discussed in detail.
Chapter 5 deals with formation of semiconductor based heterostructure like ZnO/CdS in solution by aqueous route. The material has been demonstrated as a potential visible light catalyst for dye degradation with enhanced activity. The interfacial chemistry could be tuned appropriately to achieve high activity in the catalyst by simple wet chemical route.
In chapter 6, an ultrafast, facile, green route to obtain oxide supported metal catalyst has been demonstrated. ZnO/Au heterostructures were designed with well defined morphology and studied for low temperature CO oxidation reaction. Detail investigation reveals the surface doping of ZnO with Au the nucleation process leading to active ionic sites for CO oxidation.
Chapter 7 demonstrate a rapid and economically viable route to graphene based pt catalysts where a synergistic co-reduction mechanism operates between the metal precursor and the graphic oxide to from the heterostructure. The obtained G-Pt heterostructure exhibits high catalytic activity for methanol oxidation reaction and hydrogen convention at ambient conditions.
Finally a conclusion is drawn, highlighting the possibilities and prospects that the study leads to.