Made available in DSpace on 2014-12-17T15:42:25Z (GMT). No. of bitstreams: 1 VivianeOC_DISSERT.pdf: 3402531 bytes, checksum: e2e7a469bf001a9ef16d573773ea7bda (MD5) Previous issue date: 2014-01-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Metal Organic Frameworks (MOFs) are supramolecular structures consisted of ions or metal clusters coordinated to organic ligands which are repeated in two or three dimensions. These structures have atracted much attention due to their properties such as low density, high specific surface area and large volume of pores. In this work, MOFs consisted of zinc clusters connected by ditopic ligands, terephthalic acid (1,4- H2BDC) or isophthalic acid (1,3-H2BDC) were synthesized. To obtain the proposed materials, different routes and synthetic parameters were tested, such as the molar ratio of the precursors, the addition of template molecules, the type of solvente, the addition of organic base or the type of a counter-ion of Zn salt. It was found that the variation of these parameters led to the formation of different metalorganic structures. The solids obtained were characterized by XRD, SEM and IR. For the samples identified as MOF- 5, it was verified that the structure was composed of both interpenetrated and non interpenetrated structures. These samples showed a low stability, becoming totally transformed into another structure within less than 72 hours. The addition of the nickel and/or cobalt was found to be a promissing method for increasing the stability of MOF- 5, which in this case, still remained unconverted to another structure even after 15 days of exposure to air. The samples prepared from 1,3-H2BDC were probably new, still unknown Metal Organic Frameworks / Redes Metalorg?nicas (MOFs) s?o estruturas supramoleculares constitu?das de ?ons ou clusters met?licos coordenados com ligantes org?nicos que se repetem em duas (2D) ou tr?s (3D) dimens?es. Essas estruturas t?m atra?do muita aten??o devido ?s suas propriedades, como por exemplo, baixa densidade, elevada ?rea superficial espec?fica e elevado volume de poro livre. Neste trabalho foram sintetizadas MOFs formadas por clusters met?licos de zinco conectados por ligantes dit?picos, ?cido tereft?lico (1,4- H2BDC) ou isoft?lico (1,3-H2BDC). Para a obten??o dos materiais propostos foram testadas diferentes rotas e par?metros de s?ntese, tais como, raz?o molar dos precursores, adi??o de mol?culas de molde, tipo de solvente, adi??o de base org?nica ou do contra-?on do sal de Zn. Constatou-se que a varia??o destes par?metros pode conduzir a forma??o de diferentes estruturas metalorg?nicas. Os s?lidos obtidos foram caracterizados por DRX, MEV e IV e TG. Para as amostras onde foi identificada a rede metalorg?nica MOF-5 verificou-se a exist?ncia de por??es de estrutura interpenetrada, assim como de estrutura n?o interpenetrada. Estas amostras apresentaram baixa estabilidade, convertendo-se totalmente em outra estrutura num per?odo de tempo inferior a 72 h. A adi??o de n?quel e/ou cobalto mostrou-se promissora para o aumento de estabilidade da MOF-5, a qual foi identificada mesmo ap?s 15 dias de exposi??o ao ar. Dentre as amostras preparadas com 1,3-H2BDC apenas uma estrutura foi identificada, com base nos bancos de dados de estruturas conhecidas, levando a crer que tr?s redes metalorg?nicas obtidas apresentam estruturas in?ditas

Pour améliorer les performances des batteries au lithium, des ruptures technologiques sont nécessaires. Ceci impose que les aspects fondamentaux liés au fonctionnement de ces dispositifs électroniques soient reconsidérés. Dans cette optique, les méthodes de la chimie quantique peuvent apporter une aide précieuse, notamment pour comprendre les phénomènes électroniques microscopiques, à l'origine du stockage de l'énergie. Établir une relation directe entre la nature de la liaison chimique (microscopique) et les propriétés physico-chimiques (macroscopiques) des matériaux d'électrode pour batteries Li-Ion est donc l'objectif dans lequel s'inscrivent les travaux exposés dans cette thèse. Ce travail explore à la fois des aspects méthodologiques et des applications. Il vise à proposer des méthodologies d'analyse simples permettant de traiter les réactions électrochimiques d'un point de vue théorique et de déterminer les mécanismes microscopiques mis en jeu au cours des cycles de charge et de décharge des batteries. Les systèmes étudiés sont les composés d'insertion du graphite (Li-GICs) et un matériau hybride de type MOFs (« Metal Organic Framework ») basé sur l'ion ferrique (MIL-53(Fe)). Pour les Li-GICs, une nouvelle méthode couplant des calculs premiers principes DFT à un modèle statistique dérivé du modèle de Bethe-Peierls a été développée pour rendre compte des effets d'entropie (de configuration) dans leur diagramme de phase. Les résultats obtenus apportent un nouveau regard sur les processus électrochimiques induits par le lithium, ouvrant des perspectives technologiques intéressantes pour remédier aux problèmes de sécurité posés par ce type d'électrode. Pour le MIL-53(Fe), la méthode DFT+U a été utilisée pour rendre compte des effets de corrélation électronique et pour reproduire l'état fondamental complexe de ce système. Les résultats obtenus ont permis de comprendre l'origine de la faible capacité de ce matériau vis-`a-vis du lithium.

High quality ammonium oxofluorotitanate discoid crystal is successfully grown on glass with an aqueous solution of ammonium hexafluorotitanate and boric acid at the molar ratio of 0.6. The concentration of hydrofluoric acid is less on the glass substrate surface and enhances the ammonium oxofluorotitanate nucleation growth. The growth rate is much higher than that grown on dioctadecyldimethylammonium. From the examinations of X-ray diffraction and high-resolution transmission electron microscopy, the crystal shows high crystalline quality and uniformity. Each titanium oxide octahedral is linked with fluorine and nitrogen atoms. Therefore, ammonium oxofluorotitanate has high potential to be thermally decomposed into high crystalline fluorine and nitrogen co-doped titanium oxide. A simple process for the preparation of nanocrystalline anatase phase titanium oxide converted from ammonium oxofluorotitanate by thermal treatment was developed. The nanocrystalline anatase phase titanium oxide shows a large bandgap reduction due to the co-doping of high concentrations of fluorine and nitrogen. Due to the excellent nanocrystalline quality and the co-doping of higher concentrations of fluorine and nitrogen at the thermal treatment temperature of 800 OC, it is 1.3 times the photocatalytic activities of P-25 due to the visble region usage of Hg lamp light source. The 11.2 times the visible photocatalytic activities of P-25 using blue light-emitting diode as the light source is obtained from thermal treatment temperature of 600 OC. There is one to one correspondence between carrier lifetime and photocatalytic activity. As a result, a highly reactive and visible-light-driven photocatalysis is achieved. The heterostructure of zinc selenide/titanium oxide and zinc sulfide/titanium oxide were prepared by metal-organic chemical vapor deposition on the above-prepared titanium oxide. The energy bandgap of zinc sulfide is much larger than that of titanium oxide and can act as a window for titanium oxide. It would not hinder titanium oxide absorption and preserve the role of fluorine and nitrogen co-doping. The energy bandgap of zinc selenide is near the maximum intensity of solar spectrum and acts as a sensitizer of titanium oxide. The lifetime of electron and hole pairs of heterostructure are about 240 and 207 nsec, which are longer than 65 nsec of titanium oxide prepared at 800 oC thermal treatment. Their photocatalytic activities are further improved to 2.0 and 1.5 times higher than that of commercial P-25. The photocatalysis of titanium oxide is very sensitive to the surface states. Titanium oxide surface defects can act as trapping sites for photo-induced holes and facilitate the separation of photo-induced carriers. Zinc selenide and zinc sulfide can passivate the surface well. It may say that titanium oxide surface defects removal has a negative impact. The density, height, diameter, PL wavelength and intensity of zinc selenide self-assembled quantum dots grown on zinc sulfide/gallium arsenide with the zinc sulfide thickness from 15 to 160 nm are studied. For a fixed 30 sec zinc selenide self-assembled quantum dots growth, it cannot be formed with the zinc sulfide thickness below 15 nm due to the close lattice match between zinc sulfide and gallium arsenide. The zinc sulfide/gallium arsenide is fully lattice relaxed with the zinc sulfide thickness higher than 130 nm examined by X-ray diffraction. The higher quality and density of zinc selenide self-assembled quantum dots can be obtained on zinc sulfide/gallium arsenide with the zinc sulfide thickness far beyond its critical thickness. The maximum zinc selenide self-assembled quantum dots density of 4.9 x 109 cm-2 with the strongest photoluminescence intensity is obtained at the zinc sulfide/gallium arsenide thickness of 130 nm. Clusters are formed on the surface of zinc selenide/gallium arsenide. The selenium segregation is the main mechanism for the formation of clusters. The dislocations will enhance the selenium segregation. Higher zinc selenide cluster corresponds to higher density of dislocations. The non-spherical cluster is formed from the mergence of the two clusters. High quality zinc oxide rods and zinc hydroxide slices are successfully grown on gallium arsenide with the aqueous solution of zinc nitrate and hexamethylenetetramine. The growth can be controlled by the appropriate nitric acid concentration incorporation in the solution. After thermal annealing, the zinc oxide slices transformed from zinc hydroxide slices can contribute much higher photocatalytic activity to 1.2 times to P-25.

No description available.

Die vorliegende Arbeit hat neben der Untersuchung der Synthese über den Controlled SBU-Approach von HKUST-1, ein poröses Kupfertrimesat, die Abscheidung dieses Metal-Organic Frameworks in dünnen Quarzglaskapillaren mit einer Länge von 10 bis 30 m und Innendurchmessern zwischen 0,53 und 0,25 mm zum Thema. Diese Säulen werden zur gaschromatographischen Trennung wie auch zur Bestimmung physikochemischer Kenngrößen, die den Adsorptionsvorgang verschiedener Analyten auf der HKUST-1 Oberfläche beschreiben, verwendet. Zu den untersuchten Stoffen gehören neben unpolaren n-Alkanen, unterschiedlich substituierte Phenylaromaten und starke Lewisbasen, wie Alkoxyalkane. Bei diesen kann der Einfluss der Gestalt und Länge der an den Sauerstoffatomen befindlichen Alkylgruppen auf die Adsorption an HKUST-1 in Form von spezifischen und unspezifischen Wechselwirkungsenthalpien, bestimmt aus gaschromatographischen Messungen, und infrarotspektroskopischen Auswertungen untersucht werden. Abschließend wird eine quantitative Aussage über das Verhältnis von Acidität und Basizität der HKUST-1 Oberfläche getroffen.

I studied organic semiconductor/ferromagnet interfaces by characterizing them by spin-polarized electron scattering and photoemission spectroscopy experiments. In the first part, a completely unexpected behaviour of the spin-dependent electron reflection properties of these interfaces is observed. In fact, sub-monolayer coverage of the organic molecules makes the electron reflection amplitude independent of the spin, i.e. both the reflectivity and the reflection phase become independent of the spin orientation of the incident electrons. Although I am not able at the moment to identify the cause of this phenomenon, I show that it is a very general phenomenon which is independent of the energy of the primary electrons, the choice of the ferromagnetic substrate, the choice of the organic molecule, and of the orientation of the initial spin polarization. It is not due to a change of the surface magnetization, a depolarization of the primary electrons, or a direct interaction of the molecules with the ferromagnetic substrate. Moreover, theory does not predict so far the experimental results and further research is required to unveil the physics behind these observations. In the second part of my thesis, spin-resolved photoemission experiments have been performed at the synchrotron SOLEIL. The main result is the observation of a highly spin-polarized molecule-induced electronic state close to the Fermi level. Measurements as a function of the organic layer thickness allow us to determine the interfacial character of this electronic state. Finally, these results are compared with theoretical calculations performed at the institute.

Mes travaux de thèse ont porté sur les matériaux hybrides organiques-inorganiques (Metal-Organic Frameworks, ou MOFs) qui constituent une nouvelle classe de matériaux cristallins et nanoporeux, formés de centres métalliques interconnectés par des ligands organiques, dont les applications dans le domaine des technologies de séparation et d'adsorption de gaz d'intérêt industriel sont très prometteuses. Je me suis particulièrement intéressée aux Soft Porous Crystals, qui présentent une flexibilité structurale de grande amplitude en réponse à des stimuli externes tels que la température, la pression mécanique ou l'adsorption de molécules. Afin de mieux comprendre la très large gamme des comportements observés pour la flexibilité des matériaux hybrides organiques-inorganiques, j'ai développé au cours de ma thèse une méthodologie complète de ces matériaux en combinant différentes méthodes de simulation moléculaire classique et quantique. Dans un premier temps, j'ai étudié les propriétés mécaniques de ces nouveaux matériaux flexibles dans le régime élastique. J'ai ainsi pu identifier la signature élastique des Soft Porous Crystals et mettre en évidence l'origine microscopique de la flexibilité structurale de ces matériaux hybrides. Je me suis ensuite intéressée à la stabilité mécanique de ces matériaux en fonction de la température, de la pression mécanique et de l'adsorption de molécules. Et notamment au phénomène d'amorphisation sous pression et au polymorphisme induit par l'intrusion de fluide de certaines MOFs. Dans un dernier temps, j'ai étudié l'influence de la géométrie, de la topologie structurale et de la fonctionnalisation des matériaux de la famille des ZIFs sur leurs propriétés d'adsorption d'eau. J'ai alors montré comment les propriétés d'hydrophobicité de ces matériaux peuvent être modulées.

MOF-5 ist der Archetyp einer neuartigen Klasse hochporöser Materialien, den Metal Organic Frameworks, die unter anderem zur Anwendung als effektive Gasspeicher geeignet sind. Im Rahmen dieser Arbeit werden die seiner Bildung zugrunde liegenden Reaktionen untersucht. Aus den Erkenntnissen dieser Untersuchungen wurden zwei neue Syntheseverfahren entwickelt. Eines der Verfahren beruht auf der Phasenumwandlung von Zinkterephthalaten und ermöglichte die Laborsynthese von MOF-5 in 100 g-Mengen. Ein zweites Verfahren bedient sich des Strukturaufbaus mit Hilfe vorgefertigter anorganischer Cluster, wodurch erstmals die Synthese von MOF-5-Homologen anderer Metalle als Zink gelang.

This thesis entails the utilisation of ab initio density functional theory (DFT) in conjunction with neutron and synchrotron spectroscopy to study the mechanical, vibrational, and dielectric response of metal-organic framework (MOF) materials at the molecular level. MOFs are crystalline materials with nanoscale porosity, which have garnered immense scientific and technological interest for a wide variety of innovative engineering applications. One part of the thesis involves using low-frequency lattice vibrations to characterise the various physical motions that are possible for framework materials. These collective modes detected at terahertz (THz) frequencies have been used to reveal a broad range of exciting possibilities. New evidence has been established to demonstrate that THz modes are intrinsically linked to anomalous elasticity underpinning gate-opening and pore-breathing mechanisms, and to shear-induced phase transitions and the onset of structural instability. The phenomenon of molecular rotor mechanisms and trampoline-like motions are also observed, along with the first experimental confirmation of coordinated shear dynamics. Additionally, a new method to characterise the effects of temperature, and hence thermally-induced structural amorphisation is reported. Finally, for the first time, the frequency-dependent (dynamic) dielectric response of MOF materials, across the extended infrared (IR) spectral region was reported. The results were obtained from experimental synchrotron radiation IR reflectivity and DFT to reveal the low-к dielectric response of MOFs and established structure-property trends that highlight them as promising systems for microelectronic device applications.

[pt] Espectroscopia de ressonância plasmônica de superfície (SPR) é uma técnica óptica amplamente utilizada para monitorizar as alterações físicas ou químicas que ocorrem em uma interface metal - dielétrico. A medição simultânea da espessura e do índice de refração de filmes finos orgânicos, adsorvidos ou depositados sobre a superfície plana de um metal, requer duas medições independentes seguindo uma metodologia designada na literatura como método de duas cores ou método de dois meios. Na primeira, as duas medições são realizadas utilizando diferentes comprimentos de onda da radiação eletromagnética interagindo com a amostra. Na segunda, o índice de refração do meio externo (gás, líquido) é alterado entre as duas medições. Enquanto o primeiro método implica no conhecimento da função de dispersão da fase orgânica, o segundo só produz resultados precisos quando as moléculas orgânicas não interagem quimicamente com o fluido externo. Ambos os métodos apresentam dificuldades quando são aplicados à caracterização de materiais luminescentes orgânicos, os quais são na maior parte do tempo altamente reativos à umidade e ao contato com solventes orgânicos. Neste trabalho foi montado um espectrômetro de SPR automatizado. Primeiramente, ele foi testado na caracterização de amostras feitas no laboratório em termos do valor absoluto, e da homogeneidade das constantes ópticas da deposição metálica que suporta a onda de plasma. Nós demonstramos que medições precisas de constantes ópticas permitem a determinação do índice de refração de filmes finos orgânicos luminescentes, evaporados termicamente utilizando o método de substrato com dois metais. Este método, que até onde sabemos é apenas teorizado na literatura, foi aplicado a uma amostra encapsulada com um filme fino de Alq3 comercial. Além disso, a interface metal/Alq3 foi exposta a ar, e a degradação foi monitorada em tempo real, indicando uma diminuição progressiva do ângulo de ressonância da amostra. / [en] Surface Plasmon Resonance Spectroscopy (SPR) is an optical technique widely used to monitor the physical or chemical changes occurring at a metal-dielectric interface. The simultaneous measurement of the thickness and the index of refraction of organic thin films adsorbed or deposited on the metal flat surface require two independent measurements following a methodology commonly named in literature as Two-Colors Method or Two-Medium Method. In the first one, the two measurements are performed using different wavelength of the electromagnetic radiation interacting with the sample. In the second one the index of refraction of the external medium (gas, liquid) is changed between the two measurements.While the first method implies the knowledge of the dispersion function of the organic layer, the second one gives accurate results only when the organic molecules don t interact chemically with the external fluid. Both of these methods present difficulties when applied to the characterization of luminescent organic materials, most of the time highly reactive to humidity and to the contact with organic solvents. In this work an automated SPR spectrometer was assembled and first tested on the characterization of home-made samples in terms of the absolute value and homogeneity of the optical constants of the metal deposition supporting the plasma wave. We demonstrate that accurate measurements of such optical constants allow the determination of the index of refraction of thermally evaporated luminescent organic thin films using a Two-Metal Substrate Method. This method, to our knowledge only theorized up to now in literature, has been applied to an encapsulated sample containing a thin film of commercial Alq3. Further, the degradation of the metal/Alq3 interface exposed to air has been real time monitored indicating a progressive drop in the angle of resonance of the sample.