WorldCat Identities

Laboratoire de physique et chimie de nano objets (Toulouse / 2007-....).

Overview
Works: 18 works in 24 publications in 2 languages and 24 library holdings
Roles: Other, Degree grantor
Publication Timeline
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Most widely held works by Laboratoire de physique et chimie de nano objets (Toulouse / 2007-....).
Interactions polysaccharides-lipides : étude théorique et expérimentale combinant calculs de dynamique moléculaire, calculs quantiques de spectres RMN 13C et RMN 13C à l'état solide by Adrien Schahl( Book )

2 editions published in 2020 in French and held by 2 WorldCat member libraries worldwide

Polysaccharide-lipid interactions now form a vast domain of study, of particular interest to the pharmaceutical and food industries. We already know that amylose, an essentially linear polysaccharide composed of [alpha 1→4]-linked glucose moieties, can form helices around small hydrophobic molecules and lipidic chains. These helical structures are called V polymorphs and their study may allow the development of new ways to deliver bioactive compounds, or of new vaccine adjuvants. This type of interaction might also be found in other biological systems, such as in the capsule of Mycobacterium tuberculosis. Indeed, this external layer covering the bacillus is composed mostly of a large branched polysaccharide analogous to amylose, called alpha-glucan, but it also contains numerous lipids, such as phtiocerol dimycocerosates or trehalose dimycolates, known to be virulence factors of the mycobacterium. Demonstration of the existence of such interactions and their study may lead to a better understanding of the capsule and its biological functions. This manuscript describes a study combining theoretical and experimental methods to characterize the interactions amongst amylose complexes formed in the presence of classical and mycobacterial lipids and in systems composed of branched polysaccharides. The first part of this work describes two purely theoretical studies on amylose complexed with palmitic acid and on amylose double helices called B polymorphs. Using molecular dynamics (MD) simulations and calculations of Nuclear Magnetic Resonance (NMR) parameters at the Density Functional Theory (DFT) level, we were able to define the minimum number of glucose residues needed to former a stable V polymorph around a palmitic acid molecule. We could also show that the number of residues has a direct impact on the calculation of NMR parameters and that it is crucial to consider the dynamic behavior of these polymers to obtain results that fit well to experimental data. Regarding the B polymorph, we showed that it is essential/necessary to consider the periodic conditions of the system to be able to characterize two different residue positions, as has been observed experimentally. To the best of our knowledge, no V polymorph has been characterized in the presence of lipids composed of several lipidic chains. The second part of this manuscript describes several such complexes, formed in the presence of classical and mycobacterial lipids composed of 1, 2 or 4 lipidic chains, and their analysis by solid-state NMR. We elaborated a model describing the different equilibria implicated in the complexation process and could demonstrate that the primary structure of the lipids was one of the key factors. [...]
Electrical control of the electron spin dynamics in [111]-oriented GaAs/AGaAs quantum wells by Quang ha Duong( Book )

2 editions published in 2013 in English and held by 2 WorldCat member libraries worldwide

We have studied the electron spin dynamics in <111>-oriented GaAs/AlGaAs quantum wells grown on <111>-substrate by time-resolved photoluminescence spectroscopy. By applying an external electric field about 50 kV/cm along growth direction, we observed the spectacular increase of electron spin which can attain values greater than 30 ns. This phenomenon comes from the electrical control of spin-orbit interaction in conduction band that make the Rashba term compensate exactly with the Dresselhaus term. The cancellation effect of these two terms results in the suppression of electron spin relaxation induced by D'yakonov-Perelmechanism which is dominant in undoped quantum wells and at the temperatures greater than 50K. The measurement under an external transverse magnetic field (Voigt configuration) demonstrates that the spin relaxation times in three spatial directions are also controlled simultaneously by electric field. The "total" control of electron spin relaxation can only be observed in <111>-oriented quantum wells. Finally, we also develop the model to interpret the experimental measurement of spin relaxation anisotropy depending on electric field in <111>-oriented quantum wells
Chimie de surface de nanoparticules de ruthénium : approches théoriques by Lucy Cusinato( Book )

2 editions published in 2016 in French and held by 2 WorldCat member libraries worldwide

Surface chemistry of small metallic nanoparticles ( ~ 1 nm), mainly ruthenium or ruthenium alloys, has been studied at the DFT level via a theoretical approach. This study is supported by the development of analytical tools, that allow to investigate structural, electronic and thermodynamical properties of those nanoparticles. A first part is dedicated to the structural properties of metallic nanoparticles. Morphological diversity is highlighted as well as the necessity of being able to desing reliable models. The refinement of structural models is made possible via the combined use of generic nanoparticles structure design and of the reverse Monte Carlo method in order to fit experiments. Electronic or morphologic descriptors such as d-band center or generalized coordination number are applied to those nanoparticles, in relationship with their adsorption possibilities and, to a larger extent, with the Sabatier principle. An electronic descriptor of the chemical bond (COHP) is applied to the considered nanoparticles in order to show differences between structures, as well as the interactions within the metallic core and between the core and surface species. Finally, adsorption of surface species is studied. A single ligand probe is used to spot favorable adsorption sites, then higher coverages are considered so as to test its influence on the adsorption of extra ligands, and to investigate the effect of surface ligands on the metallic core morphology. To do this, thermodynamical properties of adsorbed systems have been modeled by taking into account the effect of pressure and temperature on the nanoparticles relative stabilities via ab initio thermodynamics. The same approache was eventually applied to H2/CO coadsorbed at ruthenium and rhenium nanoparticles surface, in the context of the Fischer-Tropsch synthesis, allowing to propose a thermodynamically favorable intermediate for this reaction. Preliminary study of this reaction, of high chemical and societal interest, conclude this manuscript. The combined use of structural, electronic and thermodynamical approaches widens the overview on some aspects of ruthenium nanoparticles chemistry
Développement de techniques avancées de microscopie électronique à transmission pour la cartographie à l'échelle nanométrique by Raghda Makarem( Book )

2 editions published in 2019 in English and held by 2 WorldCat member libraries worldwide

L'un des problèmes clés pour la miniaturisation des nanodispositifs à semi - conducteurs est le contrôle précis de leur dopage. Dans les dispositifs de nouvelle génération, la distribution spatiale du dopage doit être contrôlée avec une précision supérieure à 1 nm, tandis que les concentrations atomiques inférieures à 1% doivent être mesurées. Cela nécessite l'utilisation de techniques de haute résolution. La microscopie électronique à balayage en transmission (STEM) associée à la spectroscopie par rayons X à dispersion d'énergie (EDX) est un excellent candidat en raison de sa polyvalence (presque tous les éléments du tableau périodique peuvent être cartographiés) et de sa haute résolution spatiale. D'autre part, l'analyse quantitative du dopage par STEM/EDX est compliquée par la présence d'artefacts de mesure qui peuvent être ignorés sans risque pour les impuretés à haute concentration, mais deviennent critiques pour les impuretés à faible concentration. Dans cette thèse, une nouvelle méthode basée sur la méthode de de Cliff-Lorimer(C-L) a été développée pour la mesure quantitative de la distribution de dopant dans un dispositif à l'échelle nanométrique. La méthode a été appliquée sur des échantillons préparés par faisceau ionique focalisé, afin de réduire l'influence des rayons X secondaires produits par fluorescence ou par électrons rétrodiffusés, et est basée sur la correction itérative des effets d'absorption des rayons X dans l'échantillon. Afin d'obtenir des résultats fiables, les coefficients de C-L ont été étalonnés à l'aide de la mesure de Rutherford Back Scattering (RBS) et l'erreur expérimentale totale a été calculée à l'aide de techniques de propagation d'erreur standard. Les résultats obtenus sur une structure de test FinFET et sur un substrat de SiGe ayant subi des recuits laser montrent l'applicabilité de cette technique aux dispositifs à l'échelle nanométrique et avec des impuretés à faible concentration
Design de précurseurs organométalliques et synthèse contrôlée de nano-objets de germaniure de fer by Alexandre Sodreau( Book )

2 editions published in 2018 in French and held by 2 WorldCat member libraries worldwide

La synthèse contrôlée de nano-alliages de germaniure de fer a connu un regain d'intérêt grâce à la récente découverte de nouvelles applications dans le domaine du stockage d'informations. Toutefois, la chimie du couple fer-germanium est une chimie complexe qui reste peu étudiée. Ces travaux de thèse associent chimie moléculaire et chimie des nano-objets pour explorer les potentialités de précurseurs mono-sources pour la synthèse en solution et en conditions douces de NPs de germaniure de fer. Dans un premier temps, nous nous sommes intéressés à la formation de nouveaux complexes présentant une architecture de type amidinatogermylène offrant un équilibre entre la stabilisation des complexes et leurs températures de décomposition, par exemple les complexes mono-germylène fer {[iPrNC(tBu)NiPr]GeCl}Fe(CO)4 et {[iPrNC(tBu)NiPr]GeHMDS}Fe(CO)4 ou le complexe bis-germylène fer {[iPrNC(tBu)NiPr]GeCl}2Fe(CO)3. Dans un second temps, nous montrons que cette méthode constitue une voie de choix permettant la formation de nano-alliages de germaniure de fer et que l'architecture des précurseurs mono-sources permet d'obtenir un contrôle sur les nanoparticules finales. En particulier, la décomposition à 200°C du complexe {[iPrNC(tBu)NiPr]GeHMDS}Fe(CO)4 conduit à la formation de nanoparticules sphériques de phase Fe3,2Ge2, de 6,5 ± 0,8 nm, présentant un comportement ferromagnétique
Destruction du microenvironnement tumoral par application de forces mécaniques exercées par des nanoparticules magnétiques by Sara Lopez( Book )

2 editions published in 2019 in French and held by 2 WorldCat member libraries worldwide

Efficiency of anti-cancer treatments is limited by development of resistance to treatments, which has long been considered to depend solely on the genotype of cancer cells. However, these past few years, researchers proved that cancer progression and resistance are not only determined by the inherent characteristics of cancer cells, but also by their interactions with tumor microenvironment. Among other components of the tumor microenvironment, cancer-associated fibroblasts (CAFs) promote tumor growth and cancer cell resistance to treatments. CAFs modify the components and properties of tumor microenvironment (blood vessels, extracellular matrix or tumor immunity) and interact with cancer cells; those actions take a great part in the loss of treatment efficacy. Thus, as CAFs seem to be key players in cancer cell resistance to treatment, their eradication is an interesting strategy to inhibit cancer progression. While magnetic nanoparticles (MNPs) under a high frequency magnetic field produce heat, they generate a mechanical torque in response to low frequency rotating magnetic fields (RMF) Here, we chose this last property to elaborate a nano-therapeutic strategy directed against CAFs. The principle of this strategy is to target CAFs using vectorised MNPs and then apply a RMF that generates enough mechanical stress to induce cell death. The first objective was to target pancreatic CAFs that express the type 2 cholecystokinin receptor (CCK2R). For this, we synthesized gastrin-decorated MNPs (MNP@Gastrin). We showed that MNP@Gastrin bind to the CCK2R on the cell membrane of CAF-CCK2R, then internalize and accumulate in the lysosomes. Then, we tested different amplitudes and frequencies of RMF and demonstrated that RMF exposure induces the death of CAFs having accumulated MNP@Gastrin into their lysosomes. The optimal effect on cell death, namely the death of about 40% of CAFs, was obtained with 40mT and 1Hz RMF. Moreover, we investigated the cell death mechanism involved and we showed that cell death occurs through lysosomal damage. Lysosomes undergo membrane permeabilization, releasing their content, including cathepsin B which are involved in the observed cell death process. On top of that, the engaged cell death pathway seems to be caspase-1 dependent. Finally we used a magnetic setup under a confocal microscope in order to observe real-time cell reaction to RMF. We noticed cellular retraction, lysosomal movements towards the nucleus, and changes in cellular adhesion. This study establishes the proof-of-concept that targeted MNPs can disrupt tumor microenvironment through mechanical forces upon RMF exposure, and thus open new opportunities for cancer therapy
Non-covalent functionalization of carbon nanostructures : a DFT study by Tao Hu( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

Non-covalent doping of carbon nanostructures by charge transfer from/to donor/acceptor molecules (EDA) or by H2SO4 molecules, be it with holes or electrons, is usually thought as potentially interesting for many applications of carbon based nano-devices. However, from a theoretical point of view, little is known about such "charge transfer" processes.Employing first-principles method based on Density Functional Theory (DFT), we have studied in details, and proposed a model to rationalize, the interaction between a prototypical donor molecule the tetrathiafulvalene (TTF), a standard acceptor organic molecule, tetracyanoethylene (TCNE) and carbon nanostructures: graphene layer and SWNTs with various chiral indices. Main results concern structural and thermodynamic aspects including dispersion forces effects, and evidently electronic structure modifications of the nanostructures. Various adsorption modes and concentration effects have been investigated. At very low coverage values, we have reported a charge transfer between graphene and TCNE or TTF. Moreover, we have shown that the charge transfer can be enhanced by increasing the concentration of those two EDA molecules, as it has been demonstrated experimentally. Those results are beneficial for comprehending the nonchemical doping mechanism in graphene structure by means of charge transfers. Considering the interaction between these prototypical molecules and carbon nanotubes, we have found that charge transfers tend to decrease while the curvature of nanotube is increasing. Besides, a strong influence of the metallic/semi-conductor character of the SWNTs can be observed and be explained by the change of polarisability of the curved carboneous substrates. Additionally, we have studied the adsorption properties of sulfuric acid molecules, in its non-hydrated form, on carboneous nanostructures. Against the common believe, no charge transfer is observed in the H2SO4@graphene or H2SO4@CNTs cases, even at very high concentrations. Instead, in order to elucidate the origin of p-doping observed experimentally, we have proposed that molecule is responsible of the reversible doping. Besides we have shown that a proton transfer could cause the experimental phenomenon of crystallization of H2SO4 molecules on SWNT's surface. Finally in such process, defects like vacancy are of first importance, since they could provide anchorage points for hydrogen atoms. The results of the present work will certainly help to understand the charge transfer and doping mechanism of carbon nanostructures by means of non-covalent functionalization, which is a promising method for their future applications
Croissance par voie chimique et propriétés de transport électronique de nanofils d'or by Anais Loubat( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

Les nanofils d'or ultrafins sont des objets fascinants présentant une morphologie quasi 1D, leur diamètre n'excédant par 2 nm pour une longueur micrométrique. Les quelques 30 atomes qui composent la section de ses fils sont principalement des atomes de surface, permettant d'envisager des applications de type capteurs. De plus, l'anisotropie de forme unique pourrait permettre un confinement électronique unidimensionnel, menant à de nouvelles propriétés physiques. Nous avons réalisé une étude fondamentale de la synthèse et réaliser une première étude de transport sur une assemblée de nanofils.La première partie du manuscrit, divisée en quatre chapitres, consiste en l'étude du mécanisme de croissance de ces nanofils ultrafins. Suite à une analyse détaillée des modèles proposés, nous introduisons la technique de diffusion des rayons X aux petits angles (SAXS) utilisée pour nos études mécanistiques. Le chapitre 3 est consacré à l'étude de la synthèse de nanofils en milieu confiné. Contrairement aux postulats précédents, un suivi cinétique in-situ par SAXS nous a permis de montrer que la phase lamellaire n'intervenait pas dans la croissance des objets, voir même qu'elle était détrimentaire à leur formation. Le dernier chapitre présente la synthèse en milieu isotrope. Un mécanisme de croissance efficace où les sphères jouent le rôle de germe est avancé. L'auto-organisation des fils en solution suivant une phase hexagonale appuie l'hypothèse d'une stabilisation des fils par une double couche d'oleylamine et de chlorure d'ammonium. Un mécanisme de croissance analogue aux mécanismes proposés pour les bâtonnets d'or dans l'eau est donc proposé.La deuxième partie du manuscrit, divisée en trois chapitres, consiste en une caractérisation des propriétés de transport électronique dans ces nanofils d'or ultrafins. Nous dressons, dans un premier temps, un bilan des différents régimes de transport observés au sein de nano-objets de basse dimensionnalité. Suite aux étapes indispensables de dépôt et de connexion, le troisième chapitre présente les premières mesures de transport effectuées sur des assemblées de nanofils d'or faiblement couplées. Nous mettons ainsi en évidence, grâce à une étude sur une large gamme de températures et de tensions de polarisation, un transport de charge coopératif dans le cadre d'un régime de blocage de Coulomb
Spin dynamics in GaN- and InGaAs-based semiconductor structures by Cong Tu Nguyen( )

1 edition published in 2014 in English and held by 1 WorldCat member library worldwide

This thesis work is a contribution to the investigation by photoluminescence spectroscopy of the spin properties of III-V semiconductors with possible applications to the emerging semiconductor spintronics field. Two approaches have been explored in this work to achieve a long and robust spin polarization: i) Spatial confinement of the carriers in 0D nanostructured systems (quantum dots). ii) Defect engineering of paramagnetic centres in a bulk systems. Concerning the first approach, we have investigated the polarization properties of excitons in nanowire-embedded GaN/AlN quantum dots. We first evidence a low temperature sizeable linear polarization degree of the photoluminescence (~15 %) under quasi-resonant excitation with no temporal decay during the exciton lifetime. Moreover, we demonstrate that this stable exciton spin polarization is unaffected by the temperature up to 300 K. A detailed theoretical model based on the density matrix approach has also been developed to account for the observed polarization degree and its angular dependence.Regarding the second approach, we have demonstrated a proof-of-concept of conduction band spin-filtering device based on the implantation of paramagnetic centres in InGaAs epilayers. The principle relies on the creation of Ga interstitial defects as previously demonstrated in our group in dilute nitride GaAsN compounds. The driving force behind this work has been to overcome the limitations inherent to the introduction of N in the compounds: a) The dependence of the photoluminescence energy on the spin-filtering efficiency. b) The lack of spatial patterning of the active regions.In this work we show how the spin-filtering defects can be created by ion implantation creating a chosen density and spatial distribution of gallium paramagnetic centers in N-free epilayers. We demonstrate by photoluminescence spectroscopy that spin-dependent recombination (SDR) ratios as high as 240 % can be achieved in the implanted areas. The optimum implantation conditions for the most efficient SDR are also determined by the systematic analysis of different ion doses spanning four orders of magnitude. We finally show how the application of a weak external magnetic field leads to a sizable enhancement of the SDR ratio from the spin polarization of the implanted nuclei
Assemblage électrostatique dirigé de nanoparticules colloïdales sur des surfaces par nanoxérographie par microscopie à force atomique by Etienne Palleau( )

1 edition published in 2011 in French and held by 1 WorldCat member library worldwide

L'étude des propriétés singulières de nanoparticules colloïdales synthétisées par voie chimique et leur intégration dans des nano-composants requiert leur assemblage dirigé sur des zones parfaitement définies et localisées de surfaces solides. L'objet de cette thèse est le développement d'une méthode d'assemblage dirigé originale: la nanoxérographie par microscope à force atomique (AFM). Cette technique consiste à injecter localement, sur des zones spécifiques, des charges électrostatiques dans un matériau électret par l'intermédiaire d'une pointe d'AFM. Ces charges servent ensuite de pièges électrostatiques sur la surface pour les nanoparticules en solution. Dans le cadre de ce travail, l'injection, la rétention de charges dans de fines couches électrets de PolyMéthylMéthAcrylate (PMMA) et la quantification des densités de charges surfaciques des motifs chargés, ont été étudiées grâce au mode électrique dérivé de l'AFM, le microscope à force Kelvin (KFM). L'étude de l'assemblage de nanoparticules de différentes natures (métal, polymère (organique ou inorganique)), de taille moyenne variable dans un large domaine (2 nm - 1µm) et de potentiel zêta contrôlé a permis d'analyser les mécanismes de dépôt et de montrer les performances de la méthode et son aspect générique. Enfin deux techniques d'injection de charges parallèles ont été mises en place afin d'offrir des perspectives industrielles: le microcontact printing électrique et la nanoimpression électrique
Selective arene and polyarene hydrogenation catalysed by ruthenium nanoparticles by Emma Breso( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Transition metal nanoparticles have generated considerable attention in recent years as a result of their potential catalytic activity and selectivity. They are at the frontier between homogeneous and heterogeneous catalysis and combine the advantages of both. For this reason, nanoparticles emerged as promising catalyst for different reactions such as for the hydrogenation of arenes. The final goal of this thesis is the synthesis and characterization of ruthenium nanoparticles to explore their performance in arene and polyarene hydrogenation reactions. Chapter 1 contains a general introduction to the synthesis, characterization and application of nanoparticles in catalysis. Chapter 2 sets out the general objectives of this thesis. The research in Chapter 3 describes the synthesis and characterization of ruthenium and rhodium nanoparticles stabilized by phosphine donor ligands and their application in a comparative study in the reduction of a wide range of substituted phenyl, benzyl and phenethyl ketones. In the case of arylketones, ruthenium nanoparticles were found to be more selective than the rhodium ones towards the hydrogenation of the aryl group. Interestingly, only rhodium nanoparticles provided hydrogenolysis products. Concerning the non-conjugated aryl ketones, both metals were found to be really selective towards arene hydrogenation.The research in Chapter 4 describes the use of ruthenium nanoparticles stabilised by triphenylphosphine in the hydrogenation of polyaromatic substrates under mild reaction conditions. Systems containing 2, 3 or more fused benzene rings are reduced obtaining high selectivities towards the partial hydrogenation. The recovering of the total hydrogenated product is only achieved for the less hindered substrates like naphthalene and anthracene. Moreover, the influence on the hydrogenation of naphthalenes containing a substituent (reducible or not) is also studied. The research in Chapter 5 explores the synthesis of a new chiral phosphine ligand, which is obtained in good yield and with 97% optical purity. Then, this phosphine and commercial cinchonidine (Figure 1) are used as stabilizing agents for the synthesis of chiral nanoparticles. These nanoparticles are tested in the asymmetric hydrogenation of different substituted arenes but unsuccessful results in terms of enantioselectivity are obtained. Moreover, deuteration studies to elucidate the coordination of the different substrates to the nanoparticles surface are performed.Chapter 6 presents the final remarks and conclusions extracted from the results obtained in this thesis
Développement de jauges de contrainte à base de nanoparticules colloïdales : Application à la réalisation de surfaces tactiles souples by Nicolas Decorde( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

Un grand défi actuel consiste à réaliser des capteurs innovants tirant partie des propriétés singulières de nanoparticules colloïdales synthétisées par voie chimique et assemblées de manière contrôlée sur des surfaces. L'objet de cette thèse est le développement de jauges de contrainte résistives à base de nanoparticules. Ces jauges de contrainte sont constituées de lignes parallèles, de quelques micromètres de large, denses, de nanoparticules colloïdales d'or synthétisées par voie chimique et assemblées sur des substrats souples par assemblage convectif contrôlé. Le principe de ces capteurs résistifs repose sur la conduction tunnel entre les nanoparticules qui varie de manière exponentielle lorsque que l'assemblée est déformée. Des mesures électro-mécaniques couplées à des observations en microscopie électronique à balayage et à force atomique ont permis d'identifier, de quantifier et de comprendre l'impact de la taille et de la nature des ligands des nanoparticules sur la sensibilité et les phénomènes de dérive de la résistance à vide des jauges de contrainte. Ces travaux, associés à des mesures de diffusion de rayons X aux petits angles ont permis de corréler les variations macroscopiques de résistance électrique des jauges de contrainte aux déplacements relatifs des nanoparticules. Finalement, ces jauges de contrainte ultra-sensibles et miniatures, mises en matrices, ont été exploitées pour réaliser des surfaces tactiles souples multi-points et sensibles à l'intensité de l'appui
Nanocristaux luminescents de phosphures d'indium et de zinc : synthèse, enrobage et caractérisation by Heloise Virieux( )

1 edition published in 2013 in French and held by 1 WorldCat member library worldwide

Résumé de la thèse en anglais : This PhD investigation focuses on organometallic synthesis of indium phosphide (InP), zinc phosphide (Zn3P2) colloidal semiconductor nanoparticles (NPs) and core/shell structures which were obtained by the growth of a layer of zinc sulfide (ZnS) on the surface. The objectives are to understand and control the synthesis in order to shift the absorption and emission wavelengths to the near infra-red range, interesting for biomedical imaging.The first chapter presents the state of the art on the InP and InP/ZnS nanocrystals (NCx). A brief recall on the physical and chemical properties of semiconductor NCx is presented and various syntheses are described. Particular attention was paid to the size of NCx, the shift of the fluorescence emission to higher wavelengths and the optimization of quantum yields. The potential of these objects for white light emitting diodes (LED) or biomedical imaging shows the value added of using InP/ZnS NCx rather than other materials based on toxic elements such as cadmium, lead elements...The second chapter focuses on a synthesis from indium carboxylates known in the literature. The goal is to characterize the structure of NPs to understand the procedure of the synthesis and the coating. Measurements by Nuclear Magnetic Resonance (NMR) in solid state and Photoelectronic X-ray spectroscopy (XPS) revealed the oxidation of InP of the NPs. This oxide layer increases during the coating. This originates from a decarboxylating coupling of carboxylic acids at high temperature in the presence of NPs. This oxidation is believed to inhibit the growth of the object, which restricts the attainable range of wavelengths.The third chapter provides a novel synthesis from indium amidinate instead of indium carboxylate. The advantage of this approach is the potential to lower significantly the reaction temperature (150°C instead of 280°C) and to avoid secondary decarboxylation reaction. A coating with ZnS at low temperature (150°C) is also developed. The synthesis of InP NPs also causes an oxidation of the surface. A coupling takes place again between the ligands, palmitic acid and hexadecylamine providing new oxidizing conditions. The study of different ratios of ligands shows that when the reaction medium is modified, the InP NPs do not exhibit a conclusive luminescence response. Synthesis and coating are carried out under an atmosphere of hydrogen (H2) in Fisher-Porter reactor in order to counter these oxidizing conditions. NPs with diameters of the order of 3,4 nm (a necessary condition to approach the infra-red emission) and a quantum yield of 18-20% are thus obtained. These had never been observed before during this thesis.The last chapter is devoted to an exploratory study on Zn3P2 NPs. Zinc phosphide is a promising material because of non-toxic and abundant constituents, and potential access to near infra-red wavelengths. Different synthesis parameters are studied and the structural and optical properties are characterized. Preliminary results on the coating show instabilities of the Zn3P2 NPs. The use of trioctylphoshine oxide (TOPO) appears to allow the passivation of the NPs in the air and a better stability is possible under an atmosphere of H2
Organometallic approach to the growth of metallic magnetic nanoparticles in solution and on substrates by Nikolaos Liakakos( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

This thesis concerns a new wet chemical seeded growth method that can produce arrays of metal nanostructures epitaxially grown on crystalline macroscopic surfaces which act as seeds. This approach produces wafer-scale organized 2D hexagonal arrays of perpendicularly oriented, monodisperse and monocrystalline metallic Co nanowires with diameters below 10 nm which exhibit perpendicular magnetic anisotropy and are interesting for applications in ultra high density magnetic recording. Extension of this approach to iron gives rise to nanostructured iron films. The orientation of the nanostructures on the solid substrate depends on the substrate crystallographic orientation, whereas their morphology is dictated by the solution composition. This objective was attained through parallel studies on the growth mechanism of cobalt nano-crystals in solution which revealed an unexpected influence of the stock solution preparation procedure on the nanocrystal morphology. In addition, the use of nanoscopicseeds for the overgrowth of cobalt and iron gave rise to long Co nanowires and Co-Fe dumbbells and contributed to the definition and the improvement of the experimental conditions for the seeded growth of Co and Fe on the solid substrates
Valley dynamics and excitonic properties in monolayer transition metal dichalcogenides by Louis Bouet( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

The possibility of isolating transition metal dichalcogenide monolayers by simple experimental means has been demonstrated in 2005, by the same technique used for graphene. This has sparked extremely diverse and active research by material scientists, physicists and chemists on these perfectly two-dimensional (2D) materials. Their physical properties inmonolayer formare appealing both fromthe point of view of fundamental science and for potential applications. Transition metal dichalcogenidemonolayers such asMoS2 have a direct optical bandgap in the visible and show strong absorption of the order of 10% per monolayer. For transistors based on single atomic layers, the presence of a gap allows to obtain high on/off ratios.In addition to potential applications in electronics and opto-electronics these 2D materials allow manipulating a new degree of freedom of electrons, in addition to the spin and the charge : Inversion symmetry breaking in addition to the strong spin-orbit coupling result in very original optical selection rules. The direct bandgap is situated at two non-equivalent valleys in k-space, K+ and K-. Using a specific laser polarization, carriers can be initialized either in the K+ or K- valley, allowing manipulating the valley index of the electronic states. This opens up an emerging research field termed "valleytronics". The present manuscript contains a set of experiments allowing understanding and characterizing the optoelectronic properties of these new materials. The first chapter is dedicated to the presentation of the scientific context. The original optical and electronic properties of monolayer transition metal dichalcogenides are demonstrated using a simple theoreticalmodel. The second chapter presents details of the samples and the experimental setup. Chapters 3 to 6 present details of the experiments carried out and the results obtained. We verify experimentally the optical selection rules. We identify the different emission peaks in the monolayer materials MoS2, WSe2 and MoSe2. In time resolved photoluminescence measurements we study the dynamics of photo-generated carriersand their polarization. An important part of this study is dedicated to experimental investigations of the properties of excitons, Coulomb bound electron-hole pairs. In the final experimental chapter, magneto-Photoluminescence allows us to probe the electronic band structure and to lift the valley degeneracy
Etudes de nanostructures magnétiques auto-organisées et épitaxiées par synthèse organométallique en solution sur des surfaces cristallines by Charbel Achkar( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

The elaboration of this thesis aims to characterize the magnetic and structural properties of magnetic nanostructures obtained by a new mixed physical / chemical synthesis method, called hybrid growth. The first part of the work consists in the development of thin metal films on substrates by cathode sputtering. Furthermore, the chemical synthesis conducted by organometallic chemistry on those thin films, results in an array of ultra-dense Co monocristallins hcp nanowires, or nanostructured Fe films. Additionally, The SEM/TEM observations and the X-ray diffraction measurements conducted on the substrates and induced by the crystlalline structure of the thin film, show the high impact on the magnetic nanostructures morphology and growth direction.Moreover, the magnetic measurements executed on the Co nanowires array show a strong magnetic anisotropy perpendicular to the substrate. This observation is obtained due to the magnetocrystalline anisotropy acting along the nanowire axis (Co hcp structure with the c axis parallel to the nanowire axis) in the same direction of the nanowires shape anisotropy. The magnetization within these structures is thermally stable. It follows a coherent magnetization reversal mode that has not been observed in the polycrystalline structures up to now. Finally, the self-organization of the nanowires as well as their high density and stable magnetization nominate this system for their application in high density magnetic storage devices
Orientation de spin par pompage optique dans les boîtes quantiques InAs/GaAs : effets nucléaires by Pierre-François Braun( Book )

1 edition published in 2007 in French and held by 1 WorldCat member library worldwide

L'étude et le contrôle du spin d'un porteur dans une boîte quantique unique (BQ) est un élément clé en vue du développement de la spintronique et des composants de base nécessaires au stockage et à la manipulation de l'information quantique (e.g. pour la création d'un ordinateur quantique). Dans cette thèse, on s'intéresse donc aux spins électroniques et nucléaires, couplés par interaction hyperfine, dans des BQs individuelles auto-organisées d'InAs/GaAs. Ce travail met plus particulièrement en avant la dynamique de spin des électrons, des noyaux et du système couplé. Une des motivations en est que, si l'on parvient à polariser fortement en spin les noyaux d'une boîte quantique, il devient dès lors imaginable de transférer un état cohérent électronique à un ensemble de noyaux pour en assurer le stockage. Pour ce faire, des expériences de pompage optique orienté par photoluminescence sont réalisées. Un microscope confocal original résolu en temps, en température, en champ magnétique et en polarisation, destiné à l'analyse par micro-photoluminescence de boîtes individuelles, est conçu et développé. Les mesures effectuées mettent d'une part en évidence le déphasage du spin électronique dû aux fluctuations du champ nucléaire. Cependant, nous montrons que s'il est possible de supprimer l'effet de déphasage pour la composante longitudinale du spin électronique, il n'en est rien concernant la composante transverse. D'autre part, les conditions d'obtention d'une forte polarisation nucléaire équivalente à un champ effectif de plusieurs Teslas ont été déterminées et des effets originaux de bistabilité de la polarisation nucléaire sur nano-objets uniques sont décrits et modélisés
Intégration et mesures de magnéto-transport de nano-objets magnétiques obtenus par voie chimique by Julien Dugay( )

1 edition published in 2012 in French and held by 1 WorldCat member library worldwide

The study of charge transport in metallic and magnetic nano-objects chemically synthesized is a challenge in spintronic. Particularly, the lack of experimental results reveals the difficulty in locating such nano-objects in between electrodes while preserving their good properties. This thesis aims to overcome these difficulties in order to study the magnetotransport in such systems. Therefore, we have designed and developed technical processes which induce the self-assembly of the nano-objects inside a glove box-sputtering system. After studying the mechanisms involved in the self-assembly obtained by dip coating, we succeeded to deposit monolayers of nanoparticles (NPs) of different materials (FeCo, Fe, Co) on gold surfaces, SiO2 and thin resin film (40 nm). These results, coupled with a nanoindentation technique allows us to measure a few or a unique NP(s). Another technique, called dielectrophoresis, has been proved to be a simple and versatile way to trap (and align) nano-objects with different (aspect ratio), size, nature, and shape in between the electrodes. Thanks to this technique and the deposit of a protective capping layer of alumina, we studied the magnetotransport properties of a large number of nano-objects sensitive to oxidation or humidity: Fe, Co, FeCo and [Fe(H-trz)2(trz)](BF4)] (spin crossover compounds). Three sets of organic tunnel barriers surrounding different Fe NPs presented tunnel magnetoresistance up to room temperature. Moreover, [Fe(H-trz)2(trz)](BF4)] nano-objects with different aspect ratio, highlighted a change in conductance connected to the spin transition. Finally, we validated our ligands exchange methods by studying the influence of the ligands length on the conduction properties of Co NPs, which have been analyzed quantitatively. Our works demonstrate the possibility to use the chemical NPs in different fields of spintronics
 
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Alternative Names
Laboratoire de physique et chimie de nano-objets

LPCNO

UMR 5215

UMR5215

Languages
French (15)

English (9)