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1
Finnemore, Alexander. "On biomimetic nanostructured materials." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610543.
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Smith, Steven P. "Lanthanide-containing Nanostructured Materials." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145459.
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The research described in this Dissertation is concerned generally with the exploration of the potential use of lanthanide elements in nanostructured materials for the purpose of modification of the magnetic and optical properties. This is explored through a focus on the development of lanthanide-containing iron oxide nanosystems. Our objectives of producing lanthanide containing nanostructured materials with potentially useful optical and magnetic applications has been achieved through the development of lanthanide-doped Fe3O4 and -Fe2O3 nanoparticles, as well as a unique core-shell magnetic-upconverting nanoparticle system.Necessary background information on nanomaterials, rationale for the study of lanthanide-containing iron oxide nanosystems and context for discussion of the results obtained in each project is provided in the Introduction Chapter. The syntheses of Fe3O4 nanoparticles doped with Eu(III) and Sm(III) are discussed, along with structural characterization and magnetic property investigation of products In Chapter 2. The following Chapter expands the study of lanthanide doping to -Fe2O3, a closely related yet distinct magnetic nanoparticle system. A completely different synthesis is attempted, and comparisons between the two systems are made.The development of novel synthetic methodologies used to create such products has yielded high-quality lanthanide-containing materials and are evidenced by TEM images displaying nearly monodisperse particles in each of our efforts. The modifications to the magnetic properties resulting from lanthanide doping include theobservation of ferromagnetism in the Fe3O4 system and increased magnetic saturation of -Fe2O3 nanoparticles, and are characterized by VSM and the visual observation of magnetic alignment of products. Our efforts towards developing a novel methodology capable of producing high quality Fe3O4 nanoparticles, and subsequent characterization of products, were published in the Journal of the American Chemical Society.Optically active, magnetic, core-shell nanoparticles are investigated in Chapter 4 for the potential uses in diagnosis and treatment of cancer. This multifunctional system uses Fe3O4 as a magnetic core, shelled by upconverting lanthanide-containing nanomaterials, and is rendered biocompatible through encapsulation of the core-shell structure by a silica shell. Added functionality is achieved through amine functionalization of the silica surface, with the goal of coupling the inorganic nanoparticle with drug targeting groups. TEM results indicate successful formation of the core-shell nanoparticles, and expected magnetic and optical properties are shown by visual observation and luminescence spectroscopy, respectively.
3
Wang, Lingyan. "Design and fabrication of functional nanomaterials with tunable electrical, optical, and magnetic properties." Diss., Online access via UMI:, 2007.
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4
Akinyeye, Richard Odunayo. "Nanostructured polypyrrole impedimetric sensors for anthropogenic organic pollutants." Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5301_1248150815.
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The main aim of this study was to develop a novel strategy for harnessing the properties of electroconductive polymers in sensor technology by using polymeric nanostructured blends in the preparation of high performance sensor devices.
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Wiley, Benjamin J. "Synthesis of silver nanostructures with controlled shapes and properties /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9923.
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Kariuki, Nancy N. "Nanostructured materials for electroanalytical applications." Diss., Online access via UMI:, 2005.
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7
Assfour, Bassem. "Hydrogen Storage In Nanostructured Materials." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-65858.
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Hydrogen is an appealing energy carrier for clean energy use. However, storage of hydrogen is still the main bottleneck for the realization of an energy economy based on hydrogen. Many materials with outstanding properties have been synthesized with the aim to store enough amount of hydrogen under ambient conditions.
Such efforts need guidance from material science, which includes predictive theoretical tools.
Carbon nanotubes were considered as promising candidates for hydrogen storage applications, but later on it was found to be unable to store enough amounts of hydrogen under ambient conditions. New arrangements of carbon nanotubes were constructed and hydrogen sorption properties were investigated using state-of-the-art simulation methods. The simulations indicate outstanding total hydrogen uptake (up to 19.0 wt.% at 77 K and 5.52wt.% at 300 K), which makes these materials excellent candidates for storage applications. This reopens the carbon route to superior materials for a hydrogen-based economy.
Zeolite imidazolate frameworks are subclass of MOFs with an exceptional chemical and thermal stability. The hydrogen adsorption in ZIFs was investigated as a function of network geometry and organic linker exchange. Ab initio calculations performed at the MP2 level to obtain correct interaction energies between hydrogen molecules and the ZIF framework. Subsequently, GCMC simulations are carried out to obtain the hydrogen uptake of ZIFs at different thermodynamic conditions. The best of these materials (ZIF-8) is found to be able to store up to 5 wt.% at 77 K and high pressure.
We expected possible improvement of hydrogen capacity of ZIFs by substituting the metal atom (Zn 2+) in the structure by lighter elements such as B or Li. Therefore, we investigated the energy landscape of LiB(IM)4 polymorphs in detail and analyzed their hydrogen storage capacities. The structure with the fau topology was shown to be one of the best materials for hydrogen storage. Its total hydrogen uptake at 77 K and 100 bar amounts to 7.8 wt.% comparable to the total uptake reported of MOF-177 (10 wt.%), which is a benchmark material for high pressure and low temperature H2 adsorption.
Covalent organic frameworks are new class of nanoporous materials constructed solely from light elements (C, H, B, and O). The number of adsorption sites as well as the strength of adsorption are essential prerequisites for hydrogen storage in porous materials because they determine the storage capacity and the operational conditions. Currently, to the best of our knowledge, no experimental data are available on the position of preferential H2 adsorption sites in COFs. Molecular dynamics simulations were applied to determine the position of preferential hydrogen sites in COFs. Our results demonstrate that H2 molecule adsorbed at low temperature in seven different adsorption sites in COFs. The calculated adsorption energies are about 3 kJ/mol, comparable to that found for MOF systems. The gravimetric uptake for COF-108 reached 4.17 wt.% at room temperature and 100 bar, which makes this class of materials promising for hydrogen storage applications.
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Kubo, Shiori. "Nanostructured carbohydrate-derived carbonaceous materials." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5315/.
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Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 – 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity.
In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry.
As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers).
Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 % microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 % mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially “templated”, either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range.Nanoporöse kohlenstoffbasierte Materialien sind in der Industrie als Adsorbentien und Katalysatorträger weit verbreitet und gewinnen im aufstrebenden Bereich der Energiespeicherung/erzeugung und für Trennverfahren an wachsender Bedeutung. In der vorliegenden Arbeit wird gezeigt, dass die Kombination aus hydrothermaler Karbonisierung von Zuckern (HTC) mit Templatierungsstrategien einen effizienten Weg zu nanostrukturierten kohlenstoffbasierten Materialien darstellt. HTC ist ein in Wasser und bei niedrigen Temperaturen (130 - 200 °C) durchgeführter Karbonisierungsprozess, bei dem Zucker und deren Derivate einen einfachen Zugang zu hochfunktionalisierten Materialien erlauben. Obwohl diese sauerstoffhaltige Funktionalitäten auf der Oberfläche besitzen, an welche andere chemische Gruppen gebunden werden könnten, was die Verwendung für Trennverfahren und in der verzögerten Wirkstofffreisetzung ermöglichen sollte, ist die mittels HTC hergestellte Kohle für solche Anwendungen nicht porös genug. Das Ziel dieser Arbeit ist es daher, Methoden zu entwickeln, um wohldefinierte Poren in solchen Materialien zu erzeugen. Hierbei führte unter anderem der Einsatz von anorganischen formgebenden mesoporösen Silikapartikeln und makroporösen Aluminiumoxid-Membranen zum Erfolg. Durch Zugabe einer Kohlenstoffquelle (z. B. 2-Furfural), HTC und anschließender Entfernung des Templats konnten poröse kohlenstoffbasierte Partikel und röhrenförmige Nanostrukturen hergestellt werden. Gleichzeitig konnte durch eine zusätzliche Nachbehandlung bei hoher Temperatur (350-750 °C) auch noch die Oberflächenfunktionalität hin zu aromatischen Systemen verschoben werden. Analog zur Formgebung durch anorganische Template konnte mit sog. Soft-Templaten, z. B. PEO-PPO-PEO Blockcopolymeren, eine funktionelle poröse Struktur induziert werden. Hierbei machte man sich die Ausbildung geordneter Mizellen mit der Kohlenstoffquelle D-Fructose zu Nutze. Das erhaltene Material wies hochgeordnete Mikroporen mit einem Durchmesser von ca. 0,9 nm auf. Dieser konnte desweiteren durch Zugabe von Quell-Additiven (z. B. Trimethylbenzol) auf 4 nm in den mesoporösen Bereich vergrößert werden. Zusammenfassend lässt sich sagen, dass beide untersuchten Synthesewege nanostrukturierte kohlenstoffbasierte Materialien mit vielfältiger Oberflächenchemie liefern, und das mittels einer bei relativ niedriger Temperatur in Wasser ablaufenden Reaktion und einer billigen, nachhaltigen Kohlenstoffquelle. Die so hergestellten Produkte eröffnen vielseitige Anwendungsmöglichkeiten, z. B. zur Molekültrennung in der Flüssigchromatographie, in der Energiespeicherung als Anodenmaterial in Li-Ionen Akkus oder Superkondensatoren, oder als Trägermaterial für die gezielte Pharmakotherapie.
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Clavel, Guylhaine. "Magnetic impurities in nanostructured materials." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3210.
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Doutoramento em QuímicaOs resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”. O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.
The results presented here have been achieved under the PhD program entitled “Magnetic Impurities in Nanostructured Materials”. This study had as purpose the synthesis and characterization of oxidic semiconductor containing magnetic impurities. During this work we have developed non-aqueous sol-gel routes, leading to well controlled oxide nanomaterials, to the synthesis of transition-metal doped oxides (ZnO and ZrO2). Homogeneous doping is particularly important in the comprehensive study of diluted magnetic semiconductors (DMSs), and the main point of this study was to ascertain the oxidation state and local structure of the dopant, as well as to exclude the existence of secondary phase as the origin of ferromagnetism. To enlarge the field of research and fully explore the concept of “magnetic impurities in nanostructured materials” we have studied the magnetic properties of nanoparticles embedded in an oxide matrix. The nanoparticles (cobalt ferrite) were deposited as a film and coated by a semiconducting or dielectric metal oxide (ZnO, TiO2). These hetero-systems can be regarded as dispersion of magnetic impurities in oxides. The characterizations needed by these nanomaterials were performed at the University of Aveiro and University of Montpellier because of complementary available equipments.
10
Li, Guangru. "Nanostructured materials for optoelectronic devices." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/263671.
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This thesis is about new ways to experimentally realise materials with desired nano-structures for solution-processable optoelectronic devices such as solar cells and light-emitting diodes (LEDs), and examine structure-performance relationships in these devices. Short exciton diffusion length limits the efficiency of most exciton-based solar cells. By introducing nano-structured architectures to solar cells, excitons can be separated more effectively, leading to an enhancement of the cell’s power conversion efficiency. We use diblock copolymer lithography combined with solvent-vapour-assisted imprinting to fabricate nano-structures with 20-80 nm feature sizes. We demonstrate nanostructured solar cell incorporating the high-performance polymer PBDTTT-CT. Furthermore, we demonstrated the patterning of singlet fission materials, including a TIPS-pentacene solar cell based on ZnO nanopillars. Recently perovskites have emerged as a promising semiconductor for optoelectronic applications. We demonstrate a perovskite light-emitting diode that employs perovskite nanoparticles embedded in a dielectric polymer matrix as the emissive layer. The emissive layer is spin-coated from perovskite precursor/polymer blend solution. The resultant polymer-perovskite composites effectively block shunt pathways within the LED, thus leading to an external quantum efficiency of 1.2%, one order of magnitude higher than previous reports. We demonstrate formations of stably emissive perovskite nanoparticles in an alumina nanoparticle matrix. These nanoparticles have much higher photoluminescence quantum efficiency (25%) than bulk perovskite and the emission is found to be stable over several months. Finally, we demonstrate a new vapour-phase crosslinking method to construct full-colour perovskite nanocrystal LEDs. With detailed structural and compositional analysis we are able to pinpoint the aluminium-based crosslinker that resides between the nanocrystals, which enables remarkably high EQE of 5.7% in CsPbI3 LEDs.
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Zhu, Ronghua (Richard). "Atomistic Simulation of Nanostructured Materials." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164059775.
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Hartschuh, Ryan D. "Optical Spectroscopy of Nanostructured Materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1195016254.
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Malkovskiy, Andrey Victorovich. "Light Scattering of Nanostructured Materials." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1303760576.
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Qiu, Xiaofeng. "NANOSTRUCTURED MATERIALS FOR ENERGY CONVERSION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1207243913.
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Li, Yanguang. "Nanostructured Materials for Energy Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275610758.
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Clavel, Guylhaine. "Magnetic impurities in nanostructured materials." Doctoral thesis, Montpellier 2, 2009. http://www.theses.fr/2009MON20121.
Full textAbstract:
Doutoramento em QuímicaOs resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”. O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.
Les résultats présentés ici ont été réalisés dans le cadre du programme doctorat intitulé "impuretés magnétiques dans les matériaux nanostructurés". Cette étude avait comme objectif la synthèse et la caractérisation d'oxydes contenant des impuretés magnétiques. Durant ces travaux, nous avons développé des voies de synthèses par sol-gel non-aqueux pour la synthèse d'oxydes dopés par des métaux de transition (ZnO et ZrO2). Un dopage homogène est particulièrement important dans l'étude des semi-conducteurs magnétiques dilués (DMSs), et le point principal de cette étude était de vérifier l'état d'oxydation et l'environnement local du dopant, ainsi que d'exclure l'existence d'une phase secondaire, comme l'origine du ferromagnétisme. Pour élargir le champ de recherche et étudier pleinement la notion d' "impuretés magnétiques dans les matériaux nanostructurés" Nous avons étudié les propriétés magnétiques de nanoparticules dispersées dans une matrice d'oxyde. Les nanoparticules (ferrite de cobalt) ont été déposées sous forme de film et recouvertes d'un oxyde métallique semi-conducteur ou diélectrique (ZnO, TiO2). Ces hétéro-systèmes peut être considérés comme une dispersion d'impureté magnétique dans un oxyde. Les caractérisations requises par ces nanomatériaux ont été réalisées à l'Université d'Aveiro et l'Université de Montpellier en raison des équipements complémentaires disponibles
The results presented here have been achieved under the PhD program entitled “Magnetic Impurities in nanostructured materials”. This study had as purpose the synthesis and characterization of oxidic semiconductor containing magnetic impurities. During this work we have developed non-aqueous sol-gel routes, leading to well controlled oxide nanomaterials, to the synthesis of transition-metal doped oxides (ZnO and ZrO2). Homogeneous doping is particularly important in the comprehensive study of diluted magnetic semiconductors (DMSs), and the main point of this study was to ascertain the oxidation state and local structure of the dopant, as well as to exclude the existence of secondary phase as the origin of ferromagnetism. To enlarge the field of research and fully explore the concept of “Magnetic Impurities in Nanostructured Materials” we have studied the magnetic properties of nanoparticles embedded in an oxide matrix. The nanoparticles (cobalt ferrite) were deposited as a film and coated by a semiconducting or dielectric metal oxide (ZnO, TiO2). These hetero-systems can be regarded as dispersion of magnetic impurities in oxides. The characterization needed by these nanomaterials was performed at the University of Aveiro and University of Montpellier because of complementary available equipments
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Ye, Yueping. "Microstructure and properties of epoxy/halloysite nanocomposite /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20YE.
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Stolk, Jonathan Douglas. "Development of low thermal expansion, high conductivity nanocomposites /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Wahlberg, Sverker. "Nanostructured Tungsten Materials by Chemical Methods." Licentiate thesis, KTH, Funktionella material, FNM, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-42702.
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Tungsten based-materials are used in many different technical fields, particularly in applications requiring good temperature and/or erosion resistance. Nanostructuring of tungsten alloys and composites has the potential to dramatically improve the materials’ properties, enhancing the performance in present applications or enabling totally new possibilities. Nanostructured WC-Co composites have been the focus of researchers and industries for over two decades. New methods for powder fabrication and powder consolidation have been developed. However, the fabrication of true nanograined WC-Co materials is still a challenge. Nanostructured tungsten composites for applications as plasma facing materials in fusion reactors have in recent years attracted a growing interest. This Thesis summarizes work on the development of chemical methods for the fabrication of two different types of nanostructured tungsten based materials; WC-Co materials mainly aimed at cutting tools applications and W-ODS composites with rare earth oxide particles, intended as plasma facing materials in future fusion reactors. The approach has been to prepare powders in two steps: a) synthesis of uniform powder precursors containing ions of tungsten and the doping elements by co-precipitation from aqueous solutions, and b) further processing of the precursors into W or WC based nano-composite powders. Highly homogenous W and Co containing powder precursors for WC-Co composites were prepared via two different routes. Keggin-based precursors ((NH4)8[H2Co2W11O40]) with agglomerates of sizes up to 50 μm, were made from sodium tungstate or ammonium metatungstate and cobalt acetate. The powder composition corresponded to 5.2 % Co in the final WC-Co composites. In a second approach, paratungstate-based precursors (Cox(NH4)10-2x[H2W12O42]) were prepared from ammonium paratungstate (APT) and cobalt hydroxide with different compositions corresponding to 3.7 to 9.7 % Co in WC-Co. These particles had a plate-like morphology with sides of 5-20 μm and a thickness of less than 1 μm. Both precursors were processed and sintered into highly uniform microstructures with fine scale (<1μm). The processing of paratungstate-based precursors was also further investigated. Nanostructured WC-Co powders with grains size of less than 50 nm by decreasing processing temperatures and by applying gas phase carburization. W-ODS materials were fabricated starting from ammonium paratungstate and rare earth elements (Y or La). Paratungstate-based precursors were prepared with different homogeneity and particle sizes. The degree of the chemical uniformity varied with the particle size from ca 1 to 30 μm. Tungsten trioxide hydrate-based precursors made from APT and yttrium nitrate under acidic conditions had dramatically higher homogeneity and smaller particle size. The crystallite size was decreased to a few nanometers. These precursors were further processed to composite nanopowder and sintered to a nanostructured W-1.2%Y2O3 composite with 88% relative density. In summary, APT can be converted to highly homogenous powder precursors of different compositions. The transformations are carried out in aqueous suspensions as a solvent mediated process, in which the starting material dissolves and the precursor precipitates. Powders with fine scale morphologies are obtained, e.g. plate-like particles with thickness less than 1 μm or spherical particles with size of a few nanometers. These precursors were processed further in to nano-sized composite powders and sintered to highly uniform tungsten composites with fine microstructures.QC 20111013
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Mases, Mattias. "Nanostructured carbon materials under extreme conditions." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16837.
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Godkänd; 2012; 20111220 (matmas); LICENTIATSEMINARIUM Ämnesområde: Fysik/Physics Examinator: Professor Alexander Soldatov, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Alfonso San Miguel, Labor. of the physical properties of Nanomaterials, University Lyon 1, France Tid: Tisdag den 24 januari 2012 kl 10.00 Plats: E246 Studion, Luleå tekniska universitet
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Buchholt, Kristina. "Nanostructured materials for gas sensing applications." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69641.
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In this Thesis I have investigated the use of nanostructured films as sensing and contact layers for field effect gas sensors in order to achieve high sensitivity, selectivity, and long term stability of the devices in corrosive environments at elevated temperatures. Electrochemically synthesized Pd and Au nanoparticles deposited as sensing layers on capacitive field effect devices were found to give a significant response to NOx with small, or no responses to H2, NH3, and C3H6. Pt nanoparticles incorporated in a TiC matrix are catalytically active, but the agglomeration and migration of the Pt particles towards the substrate surface reduces the activity of the sensing layer. Magnetron sputtered epitaxial films from the Ti-Si-C and the Ti-Ge-C systems were grown on 4H-SiC substrates in order to explore their potential as high temperature stable ohmic contact materials to SiC based field effect gas sensors. Ti3SiC2 thin films deposited on 4H-SiC substrates were found to yield ohmic contacts to n-type SiC after a high temperature rapid thermal anneal at 950 ºC. Investigations on the growth mode of Ti3SiC2 thin films with varying Si content on 4H-SiC substrates showed the growth to be lateral step-flow with the propagation of steps with a height as small as half a unit cell. The amount of Si present during deposition leads to differences in surface faceting of the films and Si-supersaturation conditions gives growth of Ti3SiC2 films with the presence of TiSi2 crystallites. Current-voltage measurements of the as-deposited Ti3GeC2 films indicate that this material is also a promising candidate for achieving long term stable contact layers to 4H-SiC for operation at elevated temperatures in corrosive environments. Further investigations into the Ti-Ge-C system showed that the previously unreported solid solutions of (Ti,V)2GeC, (Ti,V)3GeC2 and (Ti,V)4GeC3 can be synthesized, and it was found that the growth of these films is affected by the nature of the substrate.
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Johansson, Anders. "Template-Based fabrication of Nanostructured Materials." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7364.
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Carew, Daniel B. "Self-assembly of soft nanostructured materials." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664972.
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This thesis describes the design and characterisation of self-assembled systems that employ Coulombic interactions as the primary means for driving assembly. Hierarchical self-assembly is sought in three different areas: mesoporous materials, two-dimensional polymers, and peptide fibres. Chapter 1 presents a general introduction to the rationale for using self-assembly to achieve nanotechnology, the basic principles of self-assembly, and an introduction to charge-based assembly, mesoporous materials, two dimensional polymers, and peptide fibres. Chapter 2 describes a new method to synthesise mesoporous membranes, which may contain silica, using ionic self-assembly. These materials result from combining polyelectrolytes with surfactants and inorganic precursors at liquid-liquid interfaces to give a columnar structure perpendicular to their surface. Chapter 3 describes the theoretical design requirements for a tecton that assembles to form a two-dimensional self-assembled polymer. Based on these rules a peptide-based building block is designed, synthesised, and characterised along with the resulting two-dimensional sheets. Chapter 4 continues the topic of 20 polymers with two next-generation systems for studying the assembly of two-dimensional peptide sheets. Chapter 5 describes research towards achieving hierarchical assembly with Self-Assembled Peptide Fibres using layer-by-layer self-assembly and electrophoretic deposition
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Krishnamurthy, Satheesh. "Synchrotron radiation studies of nanostructured materials." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430334.
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Choi, Jongwon Ph D. Massachusetts Institute of Technology. "Selective transport properties in nanostructured materials." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111322.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references.
Nanostructuring is an established method in engineering materials due to exciting new properties that manifest only in the nano-regime. When investigating nanomaterials, atom-scale simulations can be powerful tools. Through computational approach, one can 1) understand the underlying physics of a materials property, 2) propose new design principles for certain applications and 3) evaluate the performance of the material. In this thesis, we explore new materials and engineering approaches for various fields of application through a number of computational methods - molecular dynamics, density functional theory, semi-classical Boltzmann theory and Monte Carlo simulations. We first investigate the thermal and electrical transport properties of rippled graphene structures. Here we focus on the rippled textures formed by topological defects of graphene, namely Stone-Wales defects and graphene nanobuds. By exploring different configuration of Stone-Wales defects, the effect of rippling on the thermal conductivity is isolated. We also calculated the thermal and electrical transport properties of rippled graphene nanobuds and evaluate their thermoelectric efficiency. While looking into practical approaches to achieve two-dimensional materials with periodic nanostructures, our interest has extended to covalent organic frameworks (COFs) and their desalination properties. Through classical calculations, we show that COF membranes can achieve high salt rejection rate while enhancing the water permeability up to two to three orders of magnitude compared to conventional desalination membranes. The COF membrane was also shown to have decent mechanical properties although further modification may be needed to ensure its mechanical integrity in practical settings. Another type of self-assembled frameworks is the metal-organic frameworks (MOFs). Here the gas adsorption properties of MOF in defective and strained structures have been explored. We first look into water adsorption properties of MOF-801 and explore the role of defects. The defect sites contribute to preferential adsorptive behavior, which changes the water adsorption isotherm significantly. In addition, we look into strained UiO-66 structures and reveal that compressed, asymmetrical pores can affect the adsorptive behaviors of methane and carbon dioxide. This dissertation consists of five chapters. Chapter 1 first covers the general overview of the fields of application in concern: thermal and electrical properties of graphene-based systems, desalination, gas adsorption. Chapter 2 focuses on theoretical methods used for calculating thermal transport properties, electrical properties, desalination properties, and adsorption properties of materials of interest. Our results for the thermal and electrical transport properties of rippled graphene structure are presented in Chapter 3. In Chapter 4, we switch gears to calculate the desalination properties of two-dimensional covalent organic frameworks. Lastly, the gas adsorption of metal organic frameworks is discussed in Chapter 5.
by Jongwon Choi.
Ph. D.
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Sibanyoni, Johannes Mlandu. "Nanostructured light weight hydrogen storage materials." University of the Western Cape, 2012. http://hdl.handle.net/11394/4631.
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Philosophiae Doctor - PhDThe main objective of this study was to advance kinetic performances of formation and decomposition of magnesium hydride by design strategies which include high energy ball milling in hydrogen (HRBM), in combination with the introduction of catalytic/dopant additives. In this regard, the transformation of Mg → MgH2 by high energy reactive ball milling in hydrogen atmosphere (HRBM) of Mg with various additives to yield nanostructured composite hydrogen storage materials was studied using in situ pressure-temperature monitoring that allowed to get time-resolved results about hydrogenation behaviour during HRBM. The as-prepared and re-hydrogenated nanocomposites were characterized using XRD, high-resolution SEM and TEM, as well as measurements of the mean particle size. Dehydrogenation performances of the nanocomposites were studied by DSC / TGA and TDS; and the re-hydrogenation behaviour was investigated using Sieverts volumetric technique.
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Farghaly, Ahmed A. "Fabrication of Multifunctional Nanostructured Porous Materials." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4189.
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Nanostructured porous materials generally, and nanoporous noble metals specifically, have received considerable attention due to their superior chemical and physical properties over nanoparticles and bulk counterparts. This dissertation work aims to develop well-established strategies for the preparation of multifunctional nanostructured porous materials based on the combination of inorganic-chemistry, organic-chemistry and electrochemistry. The preparation strategies involved one or more of the following processes: sol-gel synthesis, co-electrodeposition, metal ions reduction, electropolymerization and dealloying or chemical etching. The study did not stop at the preparation limits but extended to investigate the reaction mechanism behind the formation of these multifunctional nanoporous structures in order to determine the different factors controlling the nanoporous structures formation. First, gold-silica nanocomposites were prepared and used as a building blocks for the fabrication of high surface area gold coral electrodes. Well-controlled surface area enhancement, film thickness and morphology were achieved. An enhancement in the electrode’s surface area up to 57 times relative to the geometric area was achieved. A critical sol-gel monomer concentration was also noted at which the deposited silica around the gold coral was able to stabilize the gold corals and below which the deposited coral structures are not stable. Second, free-standing and transferable strata-like 3D porous polypyrrole nanostructures were obtained from chemical etching of the electrodeposited polypyrrole-silica nanocomposite films. A new reaction mechanism was developed and a new structural directing factor has been discovered for the first time. Finally, silver-rich platinum alloys were prepared and dealloyed in acidic medium to produce 3D bicontinuous nanoporous platinum nanorods and films with a nanoporous gold-like structure. The 3D-BC-NP-Pt displayed high surface area, typical electrochemical sensing properties in an aqueous medium, and exceptional electrochemical sensing capability in a complex biofouling environment containing fibrinogen. The 3D-BC-NP-Pt displayed high catalytic activity toward the methanol electro-oxidation that is 30 times higher that of planar platinum and high volumetric capacitance of 400 F/cm3. These findings will pave the way toward the development of high performance and reliable electrodes for catalysis, sensing, high power outputs fuel cells, battery-like supercapacitors and miniaturized device applications.
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Gates, Byron Daniel. "Self-assembly approaches to nanostructured materials /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/11533.
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Piotto, Chiara. "Nanostructured materials for hydrophobic drug delivery." Doctoral thesis, Università degli studi di Trento, 2019. https://hdl.handle.net/11572/367644.
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Porous silicon (Psi) and nanocellulose (NC) hydrogels are nanostructured materials with several properties that make them promising for drug delivery applications. In this work, β-carotene (BC) and clofazimine (CFZ) are used as model molecules to investigate the physical and chemical processes governing the interactions of hydrophobic molecules with both inorganic (Psi) and organic (NC) nanostructured carriers. Despite the large number of advantages, Psi does not perform well as carrier for BC, since it stimulates the molecule degradation even if its surface is carefully passivated. Furthermore, during the release experiments, BC tends to nucleate on Psi surface forming aggregates whose dissolution is much slower than the BC molecules release, thus they negatively impact on the control over the drug release. On the other hand NC hydrogels do not pose heavy issues to the release of lipophilic drugs, provided that a suitable surfactant (either Tween-20 or Tween-80) mediates the molecule solvation and its subsequent release into aqueous media. Moreover, NC gels protect BC from degradation much better than its storage in freezer or in organic solvent, making these carriers interesting for DD.
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Piotto, Chiara. "Nanostructured materials for hydrophobic drug delivery." Doctoral thesis, University of Trento, 2019. http://eprints-phd.biblio.unitn.it/3575/2/Piotto_thesis.pdf.
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Porous silicon (Psi) and nanocellulose (NC) hydrogels are nanostructured materials with several properties that make them promising for drug delivery applications. In this work, β-carotene (BC) and clofazimine (CFZ) are used as model molecules to investigate the physical and chemical processes governing the interactions of hydrophobic molecules with both inorganic (Psi) and organic (NC) nanostructured carriers. Despite the large number of advantages, Psi does not perform well as carrier for BC, since it stimulates the molecule degradation even if its surface is carefully passivated. Furthermore, during the release experiments, BC tends to nucleate on Psi surface forming aggregates whose dissolution is much slower than the BC molecules release, thus they negatively impact on the control over the drug release. On the other hand NC hydrogels do not pose heavy issues to the release of lipophilic drugs, provided that a suitable surfactant (either Tween-20 or Tween-80) mediates the molecule solvation and its subsequent release into aqueous media. Moreover, NC gels protect BC from degradation much better than its storage in freezer or in organic solvent, making these carriers interesting for DD.
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Latini, Alessandro. "Inorganic Nanostructured Materials for Technological Applications." Doctoral thesis, La Sapienza, 2006. http://hdl.handle.net/11573/917353.
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Baruah, Arabinda. "Smart nanostructured materials for water purification." Thesis, IIT Delhi, 2016. http://localhost:8080/iit/handle/2074/7002.
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Gerlach, Ingmar. "Preparation of unique nanostructured materials using mesoporous materials as nanoreactors." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136274.
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Musselman, Kevin Philip Duncan. "Nanostructured solar cells." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609003.
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Jin, Kewang. "Fabrication and characterization of 1D oxide nanostructures /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202005%20JIN.
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Yiu, Wing-ching James. "Synthesis of one-dimensional tungsten oxide nano-structures by thermal evaporation." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32047770.
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Marceau, Ross K. W. "Design in light alloys by understanding solute clustering processes during the early stages of age hardening in Al-Cu-Mg alloys." Connect to full text, 2008. http://ses.library.usyd.edu.au/handle/2123/4008.
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Thesis (Ph. D.)--University of Sydney, 2008.Title from title screen (viewed Jan 07, 2009). Includes two published articles co-authored with others. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Australina Key Centre for Microscopy and Microanalysis, Electron Microscope Unit, Faculty of Science. Includes bibliographical references. Also available in print form.
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Maye, Mathew M. "Design, synthesis, and assembly of functional nanoarchitectures." Online access via UMI:, 2005.
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Xie, Xinfeng. "Production and Characterization of Carbon Structures Derived from Wood." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/XieX2008.pdf.
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Chan, Wing Kin. "Intrinsic and extrinsic effects on Young's modulus of nanowire measured in nanobridge tests /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20CHANW.
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Dinda, Guru Prasad. "Nonequilibrium processing of amorphous and nanostructured materials." Karlsruhe FZKA, 2006. http://nbn-resolving.de/urn:nbn:de:0005-072055.
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Li, Shanghua. "Fabrication of Nanostructured Materials for Energy Applications." Doctoral thesis, Kista : Division of Functional Materials, Department of Microelectronics and Applied Physics, School of Information and Communication Technology, Royal Institute o Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4807.
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Moffat, Jamie R. "Nanostructured polymers : using gels for materials synthesis." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495902.
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Ho, G. W. "Synthesis, characterisation and properties of nanostructured materials." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604107.
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Synthesis of controlled quality and quantity of nanostructured materials form the basis of future nanotechnology building blocks. The understanding of fundamental properties, creation of complex hierarchical nanostructured materials and development of nanotechnologies are research areas which follow closely after the synthesis of nanomaterials. First and foremost, the key growth parameters of vapour-phase synthesis were identified so as to control the growth of nanomaterials with desired physical dimensions and chemical compositions. The synthesized nanomaterials were characterised using various chemical and structural analysis techniques in a complementary fashion. In addition, various self-assembly growth techniques were used to engineer the growth of complex nanostructures. The use of lithography; photolithography and ion beam lithography to generate micro to nano dimension catalyst patterns proved to be a valuable guide for selective growth of nanowires, whilst the use of zinc oxide polyhedron crystals and grain-boundary textured Cu templates have successfully produced a variety of interesting hierarchical nanostructures. Essentially, the templates act as a structure directing medium to intercede the growth in a confined manner. Success in the growth of one-dimensional single-crystal nanowires is the focus of interest since they offer the potential to answer fundamental questions about the effect of dimensionality on physical properties and are expected to play a central role in applications ranging from molecular electronics to scanning microscopy probes. Finally, with the availability of nanostructures in desirable crystal structures and chemical compositions, studies on their physical properties and phenomena were performed. Interesting properties such as the wettability and electrical properties were investigated. In particular, silicon carbide nanowire flowers show remarkable surface hydrophobicity and elasticity attributed to the unconventional multi-directional assembly of nanowires. The zinc oxide nanowires, on the other hand, exhibit superior electrical conductivity due to their clean surfaces and perfect crystallinity nature.
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Sawangphruk, Montree. "Electrochemical deposition and properties, of nanostructured materials." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526445.
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Magnusson, Roger. "Mueller matrix ellipsometry studies of nanostructured materials." Doctoral thesis, Linköpings universitet, Tillämpad optik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-111947.
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Materials can be tailored on the nano-scale to show properties that cannot be found in bulk materials. Often these properties reveal themselves when electromagnetic radiation, e.g. light, interacts with the material. Numerous examples of such types of materials are found in nature. There are for example many insects and birds with exoskeletons or feathers that reflect light in special ways. Of special interest in this work is the scarab beetle Cetonia aurata which has served as inspiration to develop advanced nanostructures due to its ability to turn unpolarized light into almost completely circularly polarized light. The objectives of this thesis are to design and characterize bioinspired nanostructures and to develop optical methodology for their analysis. Mueller-matrix ellipsometry has been used to extract optical and structural properties of nanostructured materials. Mueller-matrix ellipsometry is an excellent tool for studying the interaction between nanostructures and light. It is a non-destructive method and provides a complete description of the polarizing properties of a sample and allows for determination of structural parameters. Three types of nanostructures have been studied. The rst is an array of carbon nanobers grown on a conducting substrate. Detailed information on physical symmetries and band structure of the material were determined. Furthermore, changes in its optical properties when the individual nanobers were electromechanically bent to alter the periodicity of the photonic crystal were studied. The second type of nanostructure studied is bioinspired lms with nanospirals of InxAl1–xN which reflect light with a high degree of circular polarization in a narrow spectral band. These nanostructures were grown under controlled conditions to form columnar structures with an internally graded refractive index responsible for the ability to reflect circularly polarized light. Finally, angle-dependent Mueller matrices were recorded of natural nanostructures in C. aurata with the objective to refine the methodology for structural analysis. A Cloude sum decomposition was applied and a more stable regression-based decomposition was developed for deepened analysis of these depolarizing Mueller matrices. It was found that reflection at near-normal incidence from C. aurata can be described as a sum reflection o a mirror and a left-handed circular polarizer. At oblique incidence the description becomes more complex and involves additional optical components.
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Chao, Yimin. "Electronic and optical properties of nanostructured materials." Thesis, University of Newcastle Upon Tyne, 2003. http://hdl.handle.net/10443/588.
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Three types of nanostructured materials have been investigated: C60 on InP (100), Indium clusters on InP (100) and luminescent alkylated-Si quantum dots. The growth model and electronic structureOf C60molecules adsorbed on InP (100) were studied by XPS and UPS as a function of coverage and annealing temperature. The C Is, P 2p, In 4d core levels and the valence band spectra point to the presence of a localized covalent bond between C60 molecules and the substrate. No filling of the lowest unoccupied molecular orbit derived bands was observed. The absence of any change in the surface components of In 4d core level upon C6o adsorption indicated that the chemisorption bond exists between the fullerene molecules and phosphorus atoms rather than between C60 molecules and indium atoms. This assertion is supported by the simultaneous desorption of bothC6o and P upon annealing to 640 K and above. The evolution of clean, In-terminated InP (100)-(2 x 4) surfaces is investigated by SRPES as a function of annealing temperature. As-prepared InP (100)-(2 x 4) surface are found to be free of metallic indium, and the In 4d core level shows two clear surface components. A third, indium-cluster-related component appears after annealing above 360 ± 10 OC, due to phosphorous desorption, and is accompanied by a corresponding reduction in intensity in the In-P surface component. Further annealing leads to a decrease in binding energy of the indium cluster related peak due to increased metallicity and hence core-hole screening in the clusters. The increasingly metallic nature of the indium clusters is also revealed by the appearance and growth of a Fermi edge in valence band spectra. During the course of illumination with 145 eV photons we have monitored the evolution of the Si 2p core level, and observed in real time a splitting and growth of a new Si 2p component assigned to the Si4+ ionic state of Si. This new peak is attributed to in situ oxidation of Si quantum dots caused by photo-induced reaction with water, multilayers of which are present on the surface of the as-introduced quantum dots. X-ray excited optical luminescence (XEOL) reveals that two bands are active upon soft X-ray photon excitation. Surprisingly the 390 nm band (blue light) is the most intense, which is quite different to the result for UV photoexcitation, where the 600-700 nm band is the most prominent one (orange light). The orange light originated from Si-Si bond, blue light from Si-C bond. The ageing phenomenon of photoluminescence is observed but it is reversible.
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Louch, Sharon. "Magnetism of Fe and Co nanostructured materials." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/30688.
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The main purpose of this work was to produce a material with a saturation magnetisation greater than 2.45 T, the highest known value, which occurs in the alloy Fe65Co35.;In situ XMCD measurements carried out on size selected Fe nanoclusters deposited onto HOPG substrates revealed an enhancement of the orbital and spin moments above the bulk values for these systems. The measurements also show that there is a further increase in the moments when the Fe clusters are coated with Co. These experiments took place on beamline ID12B at the ESRF in Grenoble.;Following on from the XMCD results, samples were made consisting of Fe nanoparticles embedded in a Co matrix, and also, of Co nanoparticles embedded in a Fe matrix. The average magnetic moment per atom in these novel nanostructured materials was obtained from magnetisation curves as measured by a VSM. The results are compared to the Slater-Pauling curve for conventional Fe-Co alloys, and show that the magnetic moment per atom in samples containing up to about 20 at.% Fe nanoclusters embedded in a Co matrix (80 at.%) is larger than in the corresponding conventional Fe-Co alloy. There is a sharp drop in the moment above this concentration. Similarly, for samples with up to 20 at.% Co clusters embedded in a Fe matrix the moment per atom is above the Slater-Pauling curve. However, in the case of the latter, the enhancement in the magnetisation is significantly above the peak of the Slater-Pauling curve.;In order to determine the atomic structure of the embedded clusters, EXAFS measurements were carried out on both types of sample described in the previous paragraph. These experiments were performed on beamline 7.1 at the SRS in Daresbury. Fe nanoclusters embedded in Co were found to have the bcc structure, as in bulk Fe. However, simulations of the EXAFS data for Co clusters embedded in Fe show that the Co clusters adopt a bcc structure, as compared to hcp in bulk Co.
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Hudson, Amanda Gayle. "Characterization of Intermolecular Interactions in Nanostructured Materials." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77855.
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Advanced analytical techniques were utilized to investigate the intermolecular forces in several nanostructured materials. Techniques including, but not limited to, isothermal titration calorimetry (ITC), variable temperature Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) thermal curves were used to study the fundamental interactions present in various nanomaterials, and to further probe the influence of these interactions on the overall behavior of the material. The areas of focus included self-assembly of surfactant micelles, polycation complexation of DNA, and temperature-dependent hydrogen bonding in polymeric systems.
ITC was successfully used to determine the low critical micelle concentration (CMC) for a novel gemini surfactant with limited water solubility. CMCs were measured at decreasing methanol molar fractions (xMeOH) in water and the resulting linear relationship between CMC and methanol concentration was used to mathematically extrapolate to a predicted CMC at xMeOH = 0. Using this technique, the CMC value for the novel gemini surfactant was predicted to be 0.037 ± 0.004 mM. This extrapolation technique was also validated with surfactant standards.
ITC was also used to investigate the binding thermodynamics of polyplex formation with polycations and DNA. The imidazolium-containing and trehalose-based polycations were both found to have endothermic, entropically driven binding with DNA, while the adenine-containing polycation exhibited exothermic DNA binding. In addition, ITC was also used to confirm the stoichiometric binding ratio of linear polyethylenimine and DNA polyplexes as determined by a novel NMR method. Dynamic light scattering (DLS) and zeta potential measurements were also performed to determine the size and surface charge of polyplexes. Circular dichroism (CD) and FTIR spectroscopies provided information regarding the structural changes that may occur in the DNA upon complexation with polymers. UV-Vis thermal curves indicated that polyplexes exhibit a greater thermal stability than DNA by itself.
Variable temperature FTIR spectroscopy was used to quantitatively compare the hydrogen bonding behavior of multi-walled carbon nanotube (MWCNT)-polyurethane composites. Spectra were collected from 35 to 185 deg C for samples containing various weight percent loadings of MWCNTs with different hydrogen bonding surface functionalities. Peak fitting analysis was performed in the carbonyl-stretching region for each sample, and the hydrogen-bonding index (Rindex) was reported. Rindex values were used to quantitatively compare all of the composite samples in regards to temperature effects, weight percent loadings of MWCNTs, and the different functionalizations. In general, higher weight percent loadings of the MWCNTs resulted in greater Rindex values and increased hydrogen bond dissociation temperatures. In addition, at 5 and 10 wt% loadings the initial Rindex values displayed a trend that tracked well with the increasing hydrogen bonding capacity of the various surface functionalities.Ph. D.
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Kijak, Anna M. "Analytical Preconcentration Systems Based on Nanostructured Materials." Miami University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=miami1049915571.
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