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Active plasmonic nanostructures /Fatemeh Hosseini Alast.Hosseini Alast, Fatemeh 01 January 2017 (has links)
In principle, the surface plasmon polaritons, at the planar metal/dielectric interface, cannot be excited by incident light. However momentum transfer from incident light to Surface Plasmon Polaritons (SPPs) inside the light line can be achieved by adding a periodic structure at the interface. The lattice wave vector can compensate the difference between incident light and surface wave momentum and satisfy momentum matching requirement. Two methods are commonly used to achieve this goal: first, using prism and second, surface engineering using different array apertures at the metal/dielectric interfaces. In this thesis, the ruled grating pattern at the metal/dielectric interface using conventional photolithography technique was fabricated. The dimension of ruled grating pattern is proportional to expanding/collimating system in the interference set-up. In fact, a large area grating can be utilized for many optoelectronic applications with greater efficiency. In this work, large area grating pattern, 10×10 mm2, on top of the microcavity structure was integrated that permitting cavity mode-SPP coupling. Hence, Rabi-like splitting was observed from the hybrid plasmonic microcavity. The splitting was created from the coupling of cavity mode with the surface plasmon polariton mode; anti-crossing was observed alongside the modal conversional channel on the reflection light measurement. In following, it was experimentally explored the effect of using organic fluorescent molecules inside the hybrid plasmonic microcavity. Accordingly we integrated large area ruled metal grating onto photonic microcavity and assessed the cavity mode-SPP coupling with reflectivity measurement. We got much more grounded modal coupling in presence of florescent molecules within photonic cavity. The anti-crossing was detected with enormous Rabi-like splitting energy at 280 meV in the strong coupling regime. Besides we compared the coupling strength of plasmonic microcavities with various cavity lengths to explore the absorption impact.
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Synthèse électrochimique de nanofils de Bi2Te3 dans des matrices poreuses en polycarbonate / Electrochemical synthesis of Bi2Te3 nanowires in polycarbonate porous templatesFrantz, Cédric 10 November 2011 (has links)
Le tellurure de bismuth (Bi2Te3) est le matériau thermoélectrique de référence à température ambiante. De ses propriétés thermiques et électroniques se définit son facteur de mérite qui permet d’évaluer son efficacité. Parmi les voies récentes visant l’amélioration de ce facteur, la nanostructuration apparait comme une approche prometteuse. Des réseaux de nanofils de Bi2Te3 ont été élaborés par électrodéposition dans les pores de membranes en polycarbonate, de 30 μm de longueur et de 30 à 120 nm de diamètre. Le projet visant l’utilisation de membranes remplies comme éléments thermoélectriques, les travaux se sont focalisés sur trois aspects. Tout d’abord, le taux de remplissage des membranes a été amélioré via l’ajout de 50 % v/v DMSO dans l’électrolyte, permettant d’augmenter cette valeur de 40% à 80%. La seconde partie a concerné l’étude des systèmes électrochimiques et les pics voltammétriques ont été identifiés ; la présence de DMSO implique un décalage négatif des potentiels de déposition tandis que l’emploi des membranes entraîne un décalage positif. La connaissance de ces systèmes a permis de maîtriser la composition des dépôts. La morphologie, la microstructure et la composition des nanofils ont été étudiées par microscopie électronique en transmission. La composition est homogène sur la quasi-totalité des nanofils sauf à leurs deux extrémités. Toutefois, ces variations localisées peuvent être réduites en ajustant le potentiel de déposition. Les structures sont polycristallines et fortement orientées perpendiculairement aux plans (01.5). Finalement, des mesures thermoélectriques ont été réalisées sur des réseaux de nanofils et sur des nanofils isolés / Bismuth telluride (Bi2Te3) is the thermoelectric reference material at room temperature. Its figure of merit is defined from its thermal and electronic properties and allows estimating its efficiency. Among recent ways to improve this factor, nanostructuration appears to be a promising approach. Bi2Te3 nanowire arrays have been obtained by electrochemical deposition within the pores of polycarbonate membranes of 30 μm length and homogeneous diameter from 30 nm to 120 nm. The project aims the use of filled membranes as efficient thermoelectric elements and the studies were focused on three main aspects. First of all, the filling ratio of the porous volume has been improved by adding 50 % v/v of DMSO in the electrolyte, allowing raising this value from 40 % to 80 %. The second part concerned the electrochemical behavior indepth studies. The identified voltammetric peaks showed that the DMSO leads to a negative shift of the deposition potential whereas the membrane involves a positive shift. The understanding of electrochemical systems offered the opportunity to monitor the nanowire chemical composition. The nanowire morphology, microstructure and composition were mainly studied by Transmission Electron Microscopy. Calibrated Energy Dispersive X-ray Spectroscopy revealed a homogeneous composition along the nanowires excepted at both their extremities. However, these localized deviations can be partially inhibited by adjusting the deposition potential. Diffraction analyses revealed textured polycrystalline structures with strong orientation perpendicular to (01.5) planes. Finally, thermoelectric measurements were carried out for nanowire arrays and for individual nanowires
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Optical properties of chiral plasmonic nanoparticles and mesoporous silicon nanowiresLiu, Junjun 31 August 2017 (has links)
Structural engineering plays an essential role in controlling the optical properties of nanostructures, which are of fundamental and practical interest in nanoscience and technology. In this study, two kinds of nanostructural engineering were investigated systematically to enrich nano-optics research: structural helicity was imposed on plasmonic nanoparticles (NPs) with chiroptical activity engineerable in the ultraviolet (UV)-visible region, and porosification was imposed on silicon nanowires (SiNWs) to tune optical interaction and photoluminescence (PL).. The generation of helical metamaterials, which have strong, engineerable chiroptical activity in the UV-visible region, has attracted increasing attention due to the manipulation of the circular polarization state of light to develop diverse homochirality-associated bio-applications. Glancing-angle deposition with fast substrate rotation is performed to generate plasmonic helical NPs (PhNPs) with a helical pitch (P) of less than 10 nm, which is so much smaller than the wire diameter (d) that the PhNPs appear to be achiral NPs. The PhNPs exhibit chiroptical activity that originates intrinsically from hidden helicity, characterized by circular dichroism (CD). With an increase of P from 3 to 66 nm, the plasmonic CD signals barely shift but show a logarithmic amplification. PhNPs made of aluminum, silver, and copper exhibit a stable chiroptical response from the deep UV (~220 nm) region to the visible region. When an achiral plasmonic nanostructure guest is coated on a PhNP host (i.e., a chiral host@achiral guest nanostructure is created), the achiral guest becomes chiroptically active due to helicity transfer from the chiral host to the achiral guest. Such a helicity transfer can be generally adapted to diverse plasmonic metals to tailor the plasmonic chiroptical response flexibly in the UV-visible region. Furthermore, an amplification of the near-field optical chirality induced by the PhNPs would pave a novel way to performing asymmetric syntheses, for which investigations are currently lacking. Silver PhNPs are used to effectively mediate the enantioselective photocyclodimerization of 2-anthracenecarboxylate: left-handed silver PhNPs lead to a positive ee (enantiomeric excess) value, and right-handed silver PhNPs give rise to a negative ee value. The enantioselectivity is enhanced with a decreasing P. The PhNP-mediated enantioselective photocyclodimerization is ascribed to the synergistic contribution from chirally helical surface-induced enantioselective adsorption of 2-anthracenecarboxylate and chiroptically active nanoplasmon-enhanced optical chirality of near-field circularly polarized light.. Metal-assisted chemical etching (MACE) is carried out to generate mesoporous SiNWs (mp-SiNWs) with mesopores from 2 to 50 nm. The porosification imposes two prominent properties onto SiNWs: a high surface-to-volume ratio and quantum confinement ascribed to the shrinkage of silicon skeletons. Hence, engineering the porosity of SiNWs is of fundamental importance. Here, a new method is devised to reduce the porosity of mp-SiNWs without changes in the MACE conditions. After generating the mp-SiNWs with high porosity, the mp-SiNWs are removed from the mother Si wafers with sticky tape, followed by MACE under the same conditions to produce low-porosity mp-SiNWs. Less porous mp-SiNWs reduce optical scattering from the porous Si skeletons and vertically protrude on the wafer without aggregation to facilitate optical trapping. Consequently, low-porosity mp-SiNWs effectively reduce UV-visible reflection loss. Furthermore, optical applications require surface modification of mp-SiNWs with functional chemicals, which has a prerequisite to passivate mp-SiNWs with H-termination using 5% hydrogen fluoride. 40% NH4F, which has been widely used to passivate Si(111) wafers with H-termination, tends to unexpectedly etch mp-SiNWs attributed to surface F-termination caused by the nucleophilic attack of F− anions to Si atoms. It has been used to study systematically the NH4F-etching rate as a function of the doping levels of SiNWs, surface crystalline orientations, and porosity. At a modest temperature of 110°C, 1,4-diethynylbenzene (DEBZ) is grafted via monosilylation grafted on H-terminated mp-SiNWs. The modified mp-SiNWs with chemically active monolayers is facilely subjected to further chemical modification and surface functionalization. In addition, the monosilylation encodes mp-SiNWs with PL of DEBZ, opening a door to flexible engineering of PL of mp-SiNWs for optoelectronic and bio-detection applications.
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Synthesis, characterization and applications of bottom-up metal complex nanosheetsLiu, Yurong 26 July 2018 (has links)
At the beginning, a brief overview of two-dimensional materials as well as an introduction of the organic metal complex nanosheets was presented in chapter 1. In this section, the attention was mainly focused on the concept of the 2D nanomaterial, including the design strategies, the categories, the synthetic approaches and the characterization methods. Also, the materials used as electrodes of batteries for energy storage were generally introduced. Those electroactive materials were classified according to their different functional mechanism. The opportunity and challenge of this kind of electroactive materials were then demonstrated. At last, the current development of the 2D materials as electrodes, including the typical structures and the superiority, was indicated.;A brand-new symmetric four-way terpyridine derivative (1,2,4,5-tetrakis(4-(2,2':6',2"-terpyridyl)phenyl)benzene) (L7) was then designed and coordinated with Co(II) ion to assemble a novel bottom-up multilayer nanosheet 7-Co in chapter 4. The generated nanosheet featured moderate mechanical strength and insolubility in both aqueous solution and organic solvent, which can facilitate the purification and collection of the product. By taking the advantages of the reversible and robust redox activity of Co2+/Co3+, a dual-ion battery cathode was achieved by employing the 7-Co and thus it reveals the possibility of this kind of metal organic complex nanosheet to be utilized in a battery.;1.7\xFinally, the findings, analysis results and future work were concluded in chapter 6. And the experimental details were described in chapter 7
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A parametric study of resin-gel synthesis to understand the formation mechanism of titanium-oxide nanoparticlesNarrandes, Ashvir Ashwin January 2018 (has links)
A thesis submitted to the Faculty of Science,
University of the Witwatersrand, Johannesburg,
in fulfilment of the requirements for the degree of
Doctor of Philosophy. Johannesburg, 29 May 2018. / The relatively unknown resin-gel synthesis technique has the potential to form multi-mode mixed metal oxide nanoparticles with differing stoichiometries. These oxides can be employed in a plethora of applications. In order to exploit these benefits, the mechanism of nanoparticle formation must be understood. To this end, this study embarked on a parametric investigation to gain insights on the formation of the less stable anatase and more stable rutile (titanium dioxide) using resin-gel synthesis. By adjusting parameters such as the type of polymer, solvent, acid, and metal ion precursor, and by varying other parameters such as the polymer chain length, polymer stoichiometry, and heating rate, a model for nanoparticle formation was developed and refined. This model considered the formation of hydroxylated metal ion species following the addition of a metal ion precursor to a hydroxyl-containing solvent. These species were protected and stabilised by the remaining fragments of solvent components. In addition, the size of the ligands attached to the metal ion precursor governed the amount of protection and stabilisation afforded to the hydroxylated species by the precursor. These complexes were coordinated to polymer chains that underwent degradation during the course of heating and ignition. Polymer degradation produced polymer reaction chambers. The formation, action, and interaction of these chambers with developing titania crystallites are a novel finding of this work. The sizes of these chambers were controlled largely by the quantity of polymer present in the reaction. The number of accessible oxygen sites on the precursor determined the degree of association between the metal ion complexes and the reaction chambers. If the association was intimate, the polymer reaction chambers served to stabilise and protect the newly nucleated anatase particles. If the combination of protection effects afforded by the solvent components, precursor ligands, and association of reaction chambers of appropriate sizes was insufficient to stabilise nucleated anatase, it readily converted into the rutile phase. Anisotropic growth along [0 0 1] then caused rutile to form nanorods. Rutile mesocrystals developed following sufficient polymer degradation. The association of nanoparticles with polymer fragments was viewed using TEM. Additionally, TEM investigations revealed the presence of polymer-derived superstructures containing reaction chambers. Reaction chambers presented with various morphologies and were composed of crystalline carbon. / LG2018
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Molecular Level Assessment of Thermal Transport and Thermoelectricity in Materials: From Bulk Alloys to NanostructuresKinaci, Alper 03 October 2013 (has links)
The ability to manipulate material response to dynamical processes depends on the extent of understanding of transport properties and their variation with chemical and structural features in materials. In this perspective, current work focuses on the thermal and electronic transport behavior of technologically important bulk and nanomaterials. Strontium titanate is a potential thermoelectric material due to its large Seebeck coefficient. Here, first principles electronic band structure and Boltzmann transport calculations are employed in studying the thermoelectric properties of this material in doped and deformed states. The calculations verified that excessive carrier concentrations are needed for this material to be used in thermoelectric applications. Carbon- and boron nitride-based nanomaterials also offer new opportunities in many applications from thermoelectrics to fast heat removers. For these materials, molecular dynamics calculations are used to evaluate lattice thermal transport. To do this, first, an energy moment term is reformulated for periodic boundary conditions and tested to calculate thermal conductivity from Einstein relation in various systems. The influences of the structural details (size, dimensionality) and defects (vacancies, Stone-Wales defects, edge roughness, isotopic disorder) on the thermal conductivity of C and BN nanostructures are explored. It is observed that single vacancies scatter phonons stronger than other type of defects due to unsatisfied bonds in their structure. In pristine states, BN nanostructures have 4-6 times lower thermal conductivity compared to C counterparts. The reason of this observation is investigated on the basis of phonon group velocities, life times and heat capacities. The calculations show that both phonon group velocities and life times are smaller in BN systems. Quantum corrections are also discussed for these classical simulations. The chemical and structural diversity that could be attained by mixing hexagonal boron nitride and graphene provide further avenues for tuning thermal and electronic properties. In this work, the thermal conductivity of hybrid graphene/hexagonal-BN structures: stripe superlattices and BN (graphene) dots embedded in graphene (BN) are studied. The largest reduction in thermal conductivity is observed at 50% chemical mixture in dot superlattices. The dot radius appears to have little effect on the magnitude of reduction around large concentrations while smaller dots are more influential at dilute systems.
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Analyses morphologiques et dimensionnelles de nanostructures organisées par diffusion centrale des rayons X / Morphological and dimensional analyses of organized nanostructures by small angle X-Rays scatteringFreychet, Guillaume 20 October 2016 (has links)
L'industrie des semi-conducteurs fait aujourd'hui face à des challenges importants en termes de caractérisation. En effet, la diminution des tailles et des distances inter-objets a poussé les techniques, jusqu’alors utilisées sur les lignes de production, la microscopie (SEM) et l’ellipsométrie (OCD) ont montré plusieurs limites.. Ainsi, afin de répondre aux demandes de l’industrie, soit un contrôle précis de l’uniformité et des défauts en cours de production, des besoins en termes de métrologie sont apparus.Dans ce contexte, des techniques utilisant les rayons X ont commencé à être évaluée. Ainsi, le SAXS (Small Angle X-Ray Scattering) est une technique de diffusion des rayons X aux petits angles (angles d’incidences compris entre 0.1 et 10°) permettant l’étude d’objets de taille comprise entre 1 et 100 nm. Cette technique consiste à bombarder un échantillon avec des rayons X et à collecter grâce à un détecteur les photons traversant l’échantillon (étude en transmission). Elle est sensible au contraste de densité électronique à l’intérieur de l’échantillon. C’est une technique complémentaire aux techniques de caractérisation locale telles que les microscopies, car elle permet d’obtenir une information moyennée sur une grande surface (plusieurs mm2). Une seconde technique, le GISAXS (Grazing-Incidence SAXS) est également en plein développement. C’est une technique analogue au SAXS cependant, le faisceau de rayons X ne traverse plus l’échantillon mais est réfléchi par celui-ci. Ce qui permet l’étude de films minces ou de nanoobjets déposés sur des surfaces. Ces deux techniques sont non destructives. L’objectif de cette thèse a été d’implanter ces deux techniques au sein de la plateforme de nanocaractérisation du CEA-LETI et de montrer le leurs pertinences et leurs capacités à répondre aux demandes de l’industrie de la micro-électronique. Pour se faire la thèse se divise en deux thématiques.Dans un premier temps, des études de Contrôle-Dimensionnel SAXS (CD-SAXS) ont été réalisées sur des réseaux d’objets tridimensionnels, tels que des réseaux de lignes ou d’empilement multicouches avec des applications autour de la lithographie. Nous avons ainsi pu mettre en évidence la capacité du CD-SAXS à extraire la période et la largeur de lignes ainsi que leurs profils (hauteur de lignes et angles de parois notamment) avec une précision sub-nanométrique. De plus, la caractérisation de rugosité le long des lignes a également été étudiée. Les résultats autour du CD-SAXS sont prometteurs et permettent aujourd’hui d’envisager des approches multi-techniques afin de combiner par exemples les informations locales obtenues par microscopie et les informations statistiques obtenues par SAXS.Dans un second temps, des études GISAXS sur des films de copolymères à blocs ont été réalisées, avec pour objectifs l’utilisation de ces films comme masques pour la lithographie. Tour d’abord le système classique PS-b-PMMA a été étudié à haute énergie, et plus précisément le retrait d’un des deux blocs de polymères uniquement. Puis des mesures au seuil du carbone ont également été réalisées afin de montrer la capacité des rayons X à différencier deux espèces très proches chimiquement. De nouveaux systèmes de copolymères dit "high chi" (avec une plus grande répulsion entre bloc) ayant pour objectifs la génération d’objets plus petits ont également été étudiés. Pour finir l’approche développée au CEA nommée contact hole shrink a également été suivie par GISAXS et comparé avec les résultats obtenus par CD-SAXS. / The semiconductor industry now faces significant challenges in terms of characterization. Indeed, the size and inter-object distances reduction pushed the techniques previously used, such as microscopy (SEM) and ellipsometry (OCD) to their limitations. So in order to cope with demand of the industry (a precise control of the uniformity and defects) some needs in terms of metrology appeared.In this context, X-ray techniques were evaluated. Therefore, X-ray scattering at small angle (SAXS), using incident angles comprise between 0.1 and 10° to detect 1-100 nm objects, was studied. This technique consists on sending X-ray on a sample and to collect thanks to a 2D detector the photon going through the sample (study in transmission). This technique will detect the electronic density contrast in the sample and is nondestructive. Moreover, the statistical information over a large area (several mm2) obtained from SAXS is complementary with the local and direct information obtained from microscopies. A second technique called GISAXS (Grazing-incidence SAXS) was also tested. The X-ray beam is no more transmitted through the sample but reflected on the substrate. GISAXS is more adapted for the study of thin films and nano-objects deposited on substrate. The aim of this thesis was the implementation of SAXS and GISAXS techniques on the nanocharacterization platform of the CEA-LETI and the demonstration of the ability of such techniques to control the dimension and morphologies of samples coming from the micro-electronics industry. This thesis was divided in two parts.The first one deals with critical-dimension SAXS. The control of profiles and size of 3D arrays, such as line gratings or multilayer samples, were performed on samples related to lithographic applications. We showed the capability of CD-SAXS to extract the period, the line width and the line profile (height and sidewall angle) with a sub-nanometer resolution of line gratings. Therefore, line roughness was also studied, showing promising results on periodic roughness with sub-nanometer amplitudes. Results around CD-SAXS led to new possibilities such as the multi-scale approaches, with several techniques to control in the same time the local structure, with microscopes, and the statistical structures with CD-SAXS.Secondly, GISAXS studies were performed on block copolymer films used as masks for lithography. First, the conventional system PS-b-PMMA was studied at high energy and more precisely, the removal of the PMMA bloc only. Then measurements at the carbon were also carried out to demonstrate the ability of X-rays to differentiate between two materials with quasi-similar chemical compositions. Therefore, new copolymer systems, called "high chi" (with higher repulsion between block) were also studied. Such polymers lead to the reduction of the obtained patterns. Finally the contact hole shrink approach developed at CEA was also studied by GISAXS and compared with results obtained by CD-SAXS.
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Structure électronique et transport quantique dans les nanostructures de Graphène / Electronic Structure and Quantum Transport in Graphene NanostructuresFaizy Namarvar, Omid 20 July 2012 (has links)
Le graphène est un matériau constitué d'une seule couche atomique de carbone et représente un sujet majeur de la physique de la matière condensée. Le graphène possède de nombreuses propriétés remarquables : structure électronique décrite par une equation de Dirac sans masse, forte mobilité électronique, effet Hall quantique anormal, résistance ,rigidité et conductivité thermique élevée. Cette these concerne la structure électronique et le transport dans le graphène. Nous considérons en particulier le cas des bicouches tournées de graphène. Ces systèmes ont été découverts en particulier dans le graphène produit sur le carbure de silicium et présentent des propriétés originales par rapport aux bicouches dans l' empilement AB qui existe par exemple dans le graphite. Nous analysons au moyen d'une théorie perturbative et aussi par des approches numériques la densité d'états dans ces systèmes.Nous montrons que la densité d'états présente des oscillations avec la même période que celle du Moiré produit par ces bicouches. Nous analysons aussi le rôle des défauts sur les propriétés de transport en particulier dans le cas ou les défauts sont répartis uniquement sur une des deux couches. Ici aussi notre approche combine théorie perturbative du couplage interplans et approches purement numérique en liaisons fortes. Nous considérons aussi le role joué par les adatomes comme l'hydrogène par exemple. Nous analysons la modification de la densité d'états induite autour de l'adatome et les variations correspondantes de densité de charge et de potentiel électrostatique. Ces systèmes tendent à produire des états resonants près de l'énergie de Dirac qui dependent beaucoup aussi de la position top ou hollow de l' adsorbat. Pour des orbitales de type “s” la resonance est plus marquée si l'adatome est en position hollow. Nous montrons que l'image par experience STM (microscopie à effet tunnel) depend beaucoup de la distance entre l'adsorbat et la pointe du STM. Dans un régime de champ proche la résonance de l'adsorbat peut même apparaître comme un creux dans le signal dI/dV du STM. / Graphene, a material made of a one-atom-thick carbon layer, is a major topic of modern condensed-matter research. Graphene exhibits exciting properties such as massless Dirac electronic structure, high mobility anomalous quantum Hall effects, strength, stiffness and extraordinary high thermal conductivity. This thesis deals with electronic structure and transport properties of graphene. We consider in particular the case of twisted bilayers of graphene. These systems have been discovered especially in graphene produced on Silicon Carbide and present original properties when compared with standard AB bilayers that occur for example in graphite. We analyze by perturbative theory and by numerical methods the density of states. We show that the electronic density of states presents periodic oscillations with the period of the geometric Moiré produced by these systems. We analyze also the role of defects on transport properties and in particular we consider the case where the defects are on one layer only : the layer exposed to the air. We show how defects on this layer affects the conductivity of the bilayer. Here also we use simple analytical models and numerical approaches. We consider also the role played by atomic impurities like Hydrogen adatom on the graphene plane. We analyze the modification of density of states induced around the adatom and the corresponding modifications of charge density and electrostatic potential. These systems tend to produce a resonant state close to the Dirac energy which depends much on whether the adatom is in a top or hollow position. For hydrogen like orbital (s orbital) the resonance is stronger in the hollow position. We show that the image obtained through STM experiments for these resonant state depends very much on the distance of the STM tip to the adatom. In a near field regime the resonance can even appear as a dip in the STM signal dI/dV.
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Brushes of self-assembled nanotubes for temperature-responsive biocatalysis / Brosses de nanotubes autoassemblés pour la biocatalyse contrôlée par la températureRamirez Wong, Diana Guadalupe 09 September 2014 (has links)
Nous nous sommes inspirés des solutions élégantes que la Nature propose, concernant le contrôle et l’optimisation de réactions spécifiques, pour présenter une tentative d’imitation des interfaces biocatalytiques au niveau de nanotubes. Des brosses de nanotubes auto-assemblés à l’aide d’un composé enzymatique, la bêta-lactamase, ont été préparées via des techniques de nanofabrication comme le «layer-by-layer» et le «hard templating».En premier lieu, les effets de confinement géométriques et ses conséquences ont été étudiés et comparés pour des assemblages de films de chitosan/bêta-lactamase sur des surfaces planes et au sein de membranes nanoporeuses.Ensuite, des nanotubes de polyélectrolytes de dimensions contrôlées ont été préparés dans des membranes nanoporeuses puis ancrés sur une surface par couplage chimique pour obtenir des brosses de nanotubes. Des études cinétiques révèlent la présence d’enzymes actives dans ces brosses et une amélioration de la préservation de l’activité quand la bêta-lactamase a été déposée dans les couches intérieures des nanotubes.Enfin, une variété de couches thermo-sensibles avec différentes architectures a été testée pour contrôler la diffusion du substrat sur les films multicouches de bêta-lactamase. L’intégration d’éléments thermo-sensibles stables a été prouvée. Mais des expériences complémentaires avec des mécanismes plus complexes tels que le couplage des réponses thermiques et mécaniques sont nécessaires pour contrôler la biocatalyse impliquant des couches supplémentaires.En résumé, cette étude présente des éléments ouvrant la voie à l’intégration de techniques pour la fabrication de nanostructures complexes pour la biocatalyse. / Inspired by the elegant solutions that Nature has provided to control and promote specific site-reactions, my work presents an attempt to mimic filamentous biocatalytic interfaces. Brushes of self-assembled nanotubes with an enzymatic component (beta-lactamase) were prepared taking advantage of preexisting nanofabrication techniques, such as layer-by-layer and hard-templating.First, the effects of geometrical confinement and its consequences were investigated by comparison of (chitosan/beta-lactamase) multilayer film assembly on flat surfaces and in nanoporous membranes. In a second stage, polyelectrolyte nanotubes with controlled dimensions were prepared in nanoporous membranes and further anchored on a surface by chemical crosslinking to obtain brushes of nanotubes. The kinetic studies revealed the presence of active enzyme in the brushes and enhanced activity preservation when beta-lactamase was deposited as the inner layers of the nanotubes.As a final step, a variety of thermo-responsive coatings with different architectures were tested to control substrate diffusion on top of beta-lactamase-based multilayer films. The integration of stable thermo-responsive elements was proven, although further experiments are required to control biocatalysis with additional layers and using more complex mechanisms, such as coupled thermal and mechanical responses. Knowing that there are more challenges to face before reaching optimum nanotube brushes and apply them for controlled biocatalysis, this study contributes with some elements that may pave the way towards the integration of different techniques for the fabrication of complex biocatalytic nanostructures.
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Nanostructures pour l'exaltation d'effets non linéaires / Nanostructures for nonlinear effects enhancementHéron, Sébastien 18 November 2016 (has links)
Les sources infrarouges basées sur des effets d'optique du second ordre constituent de très bons outils de spectrométrie des polluants présents dans l'atmosphère, grâce notamment à leur grande accordabilité spectrale. Ils demandent toutefois une forte puissance lumineuse incidente et une grande quantité de matériau non linéaire pour être efficaces. On peut les rendre très compactes en réalisant la conversion de fréquence à l'aide de nanostructures plasmoniques contenant des inclusions diélectriques présentant une susceptibilité du deuxième ordre non nulle. La lumière y est très fortement concentrée à la résonance augmentant fortement la quantité de polarisation non linéaire produite, afin d'y exalter les effets d'optique non linéaire.Ce travail s'attaque d'abord à la conception de nano-résonateurs grâce au développement d'un outil de simulation d’empilements nanostructurés selon une dimension. Trois architectures sont étudiées : les nanorésonateurs de type sillon, les nanorésonateurs de Helmholtz et les guides d'ondes à résonances de modes guidés. Dans chaque cas, le dimensionnement passe par la détermination de géométries bi- voire tri-résonantes pour la réalisation d'accord de modes en génération de second harmonique ou de différence de fréquences.La fabrication en salle blanche des résonateurs sillons et guides d'ondes est ensuite exposée, suite à un important travail de développement technologique, qui a permis l’obtention d’échantillons de très bonne qualité. / Infrared sources based on second order effects are interesting tools for atmospheric pollutants spectrometry thanks to their wide tunability. Such effects nevertheless demand strong incident powers or massive non linear crystals to be efficient. A new way to reduce their size consists in realizing frequency conversion with the help of plasmonic nanostructures containing dielectric inclusions showing a non zero second order susceptibility. Light is greatly harvested and concentrated at resonance leading to the creation of a great quantity of non linear polarization, so as to further enhance non linear optics effects.This work begins with a study of nanoresonators through developing a simulation tool for one dimensional nanostructured multilayered structures. Three architectures are retained : slit nanoresonators, optical Helmholtz nanoresonators and waveguides based on guided mode resonances. In every case, the conception focuses on the finding of bi- and even of tri-resonant geometries to achieve mode matching for second harmonic of difference frequency generation.Clean room fabrication is then detailed step by step following the important works that have permitted the fabrication of samples showing a very good quality.
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