En esta tesis se realiza un estudio teórico de la adsorción de especies de arsénico sobre clusters y nanopartículas metálicas de hierro cero-valente (Fe°) e hidroxiladas, como material adsorbente. También se estudia el efecto sobre las propiedades adsortivas que tienen las impurezas de otros metales. Se consideran fenómenos vinculados a procesos superficiales tales como: adsorción, reacción, y el reordenamiento estructural de los átomos luego de las interacciones. Con el objetivo de evaluar los fenómenos a nanoescala, se estudian inicialmente las superficies extendidas de Fe° más estables, (111) y (110), y se identifican las más reactivas, así como diferente tamaño de partículas y la combinación de éstas con tres metales (Cu, Ni y Pd). El estudio se centra en las propiedades electrónicas, geométricas y moleculares, caracterizando el tipo de interacción presente entre los sustratos y los adsorbatos, utilizando herramientas de simulación molecular. Haciendo uso de la Teoría del Funcional de la Densidad (DFT), se puede observar cómo el ácido arsénico (H³AsO4) se reduce espontáneamente en ambas superficies extendidas de hierro, produciendo ácido arsenioso (H³AsO³) y oxidando la superficie del metal. También se evalúa el efecto que tiene la inclusión explícita de grupos hidroxilo y moléculas de agua en la formación de los complejos superficiales, tanto con los ácidos como con sus especies disociadas, con el objeto de simular las propiedades de estas partículas en agua. Para concluir, se analizan clusters bimetálicos de 32 átomos con dopantes superficiales de Cu, Ni y Pd y nanopartículas bimetálicas core-shell de 80 átomos. Hemos encontrado características muy peculiares en estos sistemas debido a que la adición de una segunda especie de metal afecta la densidad electrónica y, por lo tanto, los fenómenos de adsorción/desorción. Palabras claves: Hierro cero-valente, Fe (110) y Fe (111), transferencia de carga, DFT, H³AsO³, nanopartículas bimetálicas. / The study of the As species adsorption on zerovalent iron (Fe°) and hydroxylate particles of different sizes is carried out from theoretical simulations. The effect on the adsorptive properties of metal impurities (Cu, Ni and Pd) is also studied. Phenomena linked to surface processes such as adsorption, reaction, and structural rearrangement of atoms after interactions, are considered. In order to evaluate the nanoscale phenomena, the most stable extended Fe° surfaces, (111) and (110), are initially studied, and the most reactive one is identified. Afterwords, different particle sizes and the combination of these with three metals (Cu, Ni and Pd) are analized. This work has been focalized on electronic, geometrical and molecular properties, characterizing the type of interactions between substrates and adsorbates, using molecular simulation tools. Using the Density Functional Theory (DFT), it is observed how arsenic acid (H³AsO4) is spontaneously reduced on both extended iron surfaces, producing arsenious acid (H³AsO³) and oxidizing the metal surface. The effect of the explicit inclusion of hydroxyl groups and water molecules in the surface complexes formation, both with acids and their dissociated species, is also evaluated in order to simulate the properties of these particles in water. Finally, bimetallic clusters of 32 atoms with surface dopants of Cu, Ni and Pd atoms and bimetallic core-shell nanoparticles of 80 atoms are analyzed. Peculiar characteristics are found in these systems due to the addition of a second kind of metal significantly affects the electronic density of the surface and, therefore, the phenomena of adsorption / desorption. Keywords: zerovalent iron (ZVI), Fe (110) y Fe (111), charge transfer, DFT, H³AsO³, bimetallic nanoparticles.

In this thesis, graphene (i.e. monolayer carbon film) and carbon clusters supported on a transition metal surface are systematically studied by local probe techniques, with respect to their structures, electronic properties and formation mechanisms. The main tools used are low-temperature scanning tunnelling microscopy and spectroscopy (STM and STS), which are introduced in Chapter 2. The mechanism of the resonance tunnelling at electron energies higher than the work function of the surface is discussed in detail, and a qualitative explanation of the Gundlach oscillations in the corresponding spectroscopy is presented. Epitaxial graphene synthesised on the Rh(111) surface by ethylene dehydrogenation is investigated by STM in Chapter 4. Such carbon film exhibits a hexagonal Moiré pattern due to a lattice mismatch between graphene and the rhodium substrate. The periodicity and local registries of the graphene/Rh(111) superstructure are carefully analysed. Based on a thorough discussion about the “commensurate vs. incommensurate” nature of the Moiré pattern in surface science field, the graphene/Rh(111) system is identified to have a non-simple-commensurate superstructure. The surface electronic properties and geometric buckling of graphene/Rh(111) are investigated by resonance tunnelling spectroscopy (RTS) and density functional theory (DFT) calculations in Chapter 5. Spectroscopy measurements reveal a modulation of the electronic surface potential (or work function Φ) across the supercell of epitaxial graphene. Based on the microscopy/spectroscopy data and the extended DFT calculations, we examined the electronic coupling of the various local C-Rh registries, and identified both experimentally and theoretically the local atomic configurations of maximum and minimum chemical bonding between graphene and the rhodium substrate. We studied in Chapter 6 the growth mechanism of graphene on Rh(111) at elevated temperatures. This part starts by investigating the dehydrogenation of ethylene into ethylidyne. When the dehydrogenation process is complete, monodispersed carbon species, identified as 7C6, are found to dominate the cluster population on the rhodium terraces. A significant coalescence of the 7C6 clusters into graphene islands occurs at temperatures higher than 873 K. The structural and electronic properties of the 7C6 carbon clusters are examined by high-resolution STM and STS, and compared with coronene molecules, i.e. the hydrogenated analogues of 7C6. DFT calculations are further used to explain the stability of 7C6 supported on the Rh(111) surface, and also the structural characteristics of such magic-sized carbon clusters.

AL'objectif de cette recherche est une réinterprétation de la pensée esthétique de Maurice Merleau-Ponty visant à la découverte de sa matrice morphologique, c’est-à-dire de sa pertinence et de ses dettes à l’égard la tradition goethéenne et de ses développements dans le domaine de la théorie de l'art et la philosophie de la nature. La thèse est divisée en trois chapitres, dont chacun cherche à mettre l'accent sur les différents aspects de cette filiation morphologique, suivant son développement dans la chronologie de la production merleau-pontienne. Le premier chapitre tente de relier la méthode morphologique et la méthode phénoménologique en évaluant la similarité de leurs contenus esthétologiques. Ce premier chapitre est organisé autour de trois concepts clés de la morphologie, à travers les quels il opère un premier examen de la philosophie merleau-pontienne, depuis ses débuts dans les années Quarante jusqu’à ses résultats ontologiques dans les années Cinquante et les années Soixante: l'ambiguïté de la notion goethéenne de forme nous permet de remonter à la genèse de la philosophie merleau-pontienne de la forme dans La structure du comportement et dans Phénoménologie de la perception; la notion corrélative de symbole permet d'aborder les notions merleau-pontiennes d’idée sensible et matrice symbolique, en les rapprochant à l’Urphänomen de Goethe; la catégorie transversale de style est configuré comme un outil d'enquête des questions morphologiques dans la pensée esthétique de la «nouvelle ontologie» (L’œil et l’esprit [1958] e le Notes de Cours au Collège de France 1958-1959 et 1960-1961). Dans ce chapitre, nous démontrons la confrontation essentielle et constante avec des expériences artistiques (Cézanne, Klee, Rodin, Bazaine et l’Ecole de Paris), convoquées par Merleau-Ponty à l'appui de ses théories esthétologiques. Le chapitre est clôt par un bref appendice sur la question de la fondation “scientifique” de l'esthétique, mis au point par une comparaison entre Merleau-Ponty et Konrad Fiedler. Cette annexe ouvre en même temps le champ de recherche du deuxième chapitre: en fait, compte tenu de la contribution à l'esthétique fournie par la psychologie et la physiologie de la perception, la thèse se plonge dans l'analyse de la voie gestaltiste de la dette merleau-pontienne de la morphologie. Le deuxième chapitre suit le passage qui porte – au sein de la production merleau-pontienne des années Cinquante – d’une philosophie de la forme à une philosophie de l’expression et il fournit la reconstruction de celle qui apparaît comme une véritable esthétique de l’expression et du mouvement. Cette recherche se fonde sur l’analyse attentive de l’inédit Le monde sensible et le monde de l’expression, actuellement conservé dans le Département de Manuscrits Occidentaux de la Bibliothèque Nationale de France et correspondant à la préparation du Cours du Jeudi tenu par Merleau-Ponty au Collège de France dans l’année académique 19952-1953. Le travail d’analyse de l’inédit nous a permis d’évaluer, en plus des inhérences déjà confirmées de l’esthétique merleau-pontienne à la Gestalttheorie (Köhler, Koffka, Wertheimer, Guillaume), une autre comparaison théorique capitale – et assez méconnue -, c’est-à-dire celle avec Viktor Von Weizsäcker par rapport les relations entre la perception et le mouvement. Le troisième chapitre se concentre sur la phase ontologique de la pensée merleau-pontienne, celle qui correspond à la production tardive de Merleau-Ponty et brusquement interrompue par sa mort prématurée en 1961. Central, dans ce troisième chapitre, est la reconstruction du destin de la notion de Gestalt dans Le visible et invisible, qui présente la novelle ontologie de la chair et un contexte philosophique complètement reformé par rapport aux écrits merleau-pontiens des années Quarante. Les paragraphes centraux de ce dernier chapitre se concentre - à travers une comparaison avec des auteurs étroitement liée à Merleau-Ponty - etc / The aim of this project is to provide an alternative reading of Merleau-Ponty’s aesthetics by discovering its morphological matrix and its debts towards the Goethean tradition and towards its developments in the field of art theory and the philosophy of nature. The dissertation is divided into three chapters, each of which seeks to focus on different aspects of the morphological roots of phenomenological aesthetics, in order to follow its developments in the Merleau-Ponty’s production. The first chapter is an attempt to relate morphological method and phenomenological method by evaluating the similarity of their aesthetological contents. This initial chapter is organized around three key concepts of morphology, through which it operates a first screening of merleaupontian philosophy, from its beginnings in the Forties up to its ontological outcomes during the Fifties and the Sixties: the ambiguity of Goethe's notion of form allows us to reconstruct the genesis of the philosophy of form in Merleau-Ponty’s Structure of Behavior and Phenomenology of Perception; the related concept of symbol helps us to realte Merleau-Ponty’s notions of idée sensible and symbolic matrix to Goethe’s Urphänomen; the transversal category of style is configured as a tool for investigation of the morphological issues in the aesthetic thought of the merleaupontian "new ontology". In this chapter we also demonstrate the crucial importance of constant confrontation of Merleau-Ponty with artistic experiences (such as Cézanne, Klee, Rodin, Bazaine and the Ecole de Paris), convened by the philosopher in support of his aesthetological theories. The chapter ends with a brief appendix on the question of the scientific foundation of aesthetics, developed through a comparison between Merleau-Ponty and Konrad Fiedler. This appendix opens simultaneously the search field of the second chapter: in fact, considering the contributions to the aesthetics provided by psychology and physiology of perception, the dissertation goes into the analysis of the role of the Gestalttheorie in Merleau-Ponty’s morphological debt. The second chapter follows the evolution of a theoretical passage in Merleau-Ponty’s production of the Fifties - from a philosophy of form to a philosophy of expression – ending up in the reconstruction of what seems to be a complete aesthetic of expression and of movement. This part of the research project is based on the deep analysis of an unpublished document (Le monde sensible et le monde de l'expression) - currently preserved at the Bibliothèque National de France - corresponding to the lectures given by Merleau-Ponty in the biennium 1952-1953 at the Collège de France. The work of analysis of the document was to assess, in addition to already confirmed inherences of Merleau-Ponty’s aesthetics to Gestalt psychology (Köhler, Koffka, Wertheimer, Guillaume), another crucial theoretical comparison of those years, the one with Viktor von Weizsäcker on the relations between perception and movement. The chapter closes with an appendix which tries to pick up the threads of the contributions to aesthetics theories that Merleau-Ponty develops within his philosophy of nature; this appendix embodies the attempt to read Merleau-Ponty’s aesthetics in terms of philosophy of morphogenesis and productivity The third chapter concentrates on the late ontological phase of Merleau-Ponty’s production - corresponding to the years between 1958 and 1961 - abruptly interrupted by his early death. Central, in this third chapter, is the reconstruction of the fate of the concept of Gestalt in the framework of the text The visible and the invisible, that is structured within the newly formed ontology of the flesh and on the background of a completely reformed philosophical landscape. The central paragraph of this chapter concentrate, through a comparison with two authors closely related to Merleau-Ponty - etc

O estudo de processos inflamatórios e infecciosos em Medicina Nuclear apresenta grande relevância para a clínica médica diagnostica. Enquanto em alguns casos o diagnóstico é óbvio, baseado na história clínica e exame físico do paciente, em outros é mais difícil, por serem assintomáticos ou por apresentarem sintomas não específicos. O diagnóstico precoce do processo inflamatório ou infeccioso permite tratamento rápido e também o impedimento de outras complicações. Além disto, a distinção entre inflamação e infecção é de extrema importância, bem como a provável localização. O uso de leucócitos radiomarcados, já estudados e aplicados em várias patologias, é o método de escolha para visualização de focos de infecção e inflamação. A cintilografia de leucócitos radiomarcados foi introduzida em 1976 por McAffe e Thakur e desde então é usada para diagnosticar diferentes patologias que envolvem infiltração leucocitária como distúrbios inflamatórios do intestino, infecção óssea ou prótese-vasculares entre outras. A marcação dos leucócitos in vitro pode ser realizada com 111In utilizando-se oxima ou tropolona como ligante ou com 99mTc, tendo a hexametilpropileno amino oxima (HMPAO) como ligante, resultando em um complexo lipofílico. A melhor disponibilidade, menor tempo de realização do exame, melhor propriedade física e menor dose de radiação para o paciente, resultou na preferência pelo agente HMPAO marcado com 99mTc, ao invés do 111In, para a maioria das indicações na maioria dos países. Entretanto, a marcação empregando o agente HMPAO apresenta como desvantagens a curta estabilidade do reagente marcado, as exigências relacionadas ao processo de marcação (tempo pós-eluição do 99mTc), além do custo elevado, pois se trata de produto importado. Este trabalho visou o desenvolvimento do reagente liofilizado de glucoheptonatoestanho para marcação de leucócitos com 99mTc in vitro pelo método de préestanização. A otimização da técnica de marcação foi realizada através da incubação dos leucócitos, isolados de sangue total, com diferentes volumes do reagente de glucoheptonato-estanho por diferentes tempos à 37°C (préestanização), com posterior marcação com 99mTc (185 MBq), incubados à temperatura ambiente por 20 minutos. O rendimento da marcação foi superior a 90% na condição ótima de marcação. O reagente liofilizado mostrou-se estável por mais de 90 dias. As imagens cintilográficas obtidas 1, 2 e 3 horas após a administração dos leucócitos radiomarcados em coelho New Zeland demonstraram a alta eficiência de marcação de processo inflamatório provocado a partir da administração local de terebentina. O método de marcação de leucócitos desenvolvido apresenta aplicação promissora na clínica médica, com proposta de redução de custo do procedimento, apesar de ser um procedimento mais demorado quando comparado ao procedimento que utiliza o quelante lipofílico de HMPAO. / The study and localization of inflammatory and infection process in Nuclear Medicine represents a relevant tool in diagnostic procedures. In same cases, the diagnostic is easy and based on anamnesis and clinical observation; in other cases, the patients are asymptomatic or present non specific symptoms that difficult the diagnostic. The early diagnostic of inflammatory or infectious process allow the early introduction of therapy and prevents complications. Farther, the differentiation between inflammation and infection is of extreme importance as well as the localization of the focus. The use of labeled leucocytes, studied and applied in much pathologies, is the method of choice for the visualization of inflammation and infection. The scintigraphy using labeled leucocytes was introduced at 1976 by McAffe and Thakur and since of this is used in the diagnostic of different pathologies related to leucocyte infiltration like intestinal inflammatory disease, bone or prosthetic-vascular infections. The in vitro labeling of leucocytes with 111In was performed using oxime or tropolone as ligand and with 99mTc using hexamethylpropylene amine oxime (HMPAO) as ligand, resulting in a lipophilic complex. The 99mTc-HMPAG complex was preferably employed in many indications and countries do to the ideal physical properties of 99mTc that results in low dose to the patient. However, the labeling employing the HMPAO complex results in some disadvantages like the low stability of the complex, and some requirements related to the 99mTc elution (like the time pos elution), beyond the high cost of the compound that is imported. The aim of this work was the development of a tin-glucoheptonate lyophilized kit for in vitro leucocytes labeling with 99mTc using the pre-stannization method. The optimization of the labeling technique was developed using leucocytes isolated from total blood and employing different volumes of the tinglucoheptonate reagent and different incubation times at 37 deg C (pre-stannization), and posterior labeling with 99mTc (185 MBq), after 20 minutes reaction at room temperature. The labeling yield was superior to 90% using the optimized labeling conditions. Lyophilized reagent was stable after 90 days. Scintilographic images obtained 1, 2 e 3 hours after the administration of labeled leucocytes in New Zealand rabbit, showed good uptake on inflammatory focus promoted by tupertine injection. The leucocytes labeling method developed can be probably applied in clinical procedures and represents cost effective method in substitution of the lipophilic complex of HMPAO.

O estudo de processos inflamatórios e infecciosos em Medicina Nuclear apresenta grande relevância para a clínica médica diagnostica. Enquanto em alguns casos o diagnóstico é óbvio, baseado na história clínica e exame físico do paciente, em outros é mais difícil, por serem assintomáticos ou por apresentarem sintomas não específicos. O diagnóstico precoce do processo inflamatório ou infeccioso permite tratamento rápido e também o impedimento de outras complicações. Além disto, a distinção entre inflamação e infecção é de extrema importância, bem como a provável localização. O uso de leucócitos radiomarcados, já estudados e aplicados em várias patologias, é o método de escolha para visualização de focos de infecção e inflamação. A cintilografia de leucócitos radiomarcados foi introduzida em 1976 por McAffe e Thakur e desde então é usada para diagnosticar diferentes patologias que envolvem infiltração leucocitária como distúrbios inflamatórios do intestino, infecção óssea ou prótese-vasculares entre outras. A marcação dos leucócitos in vitro pode ser realizada com 111In utilizando-se oxima ou tropolona como ligante ou com 99mTc, tendo a hexametilpropileno amino oxima (HMPAO) como ligante, resultando em um complexo lipofílico. A melhor disponibilidade, menor tempo de realização do exame, melhor propriedade física e menor dose de radiação para o paciente, resultou na preferência pelo agente HMPAO marcado com 99mTc, ao invés do 111In, para a maioria das indicações na maioria dos países. Entretanto, a marcação empregando o agente HMPAO apresenta como desvantagens a curta estabilidade do reagente marcado, as exigências relacionadas ao processo de marcação (tempo pós-eluição do 99mTc), além do custo elevado, pois se trata de produto importado. Este trabalho visou o desenvolvimento do reagente liofilizado de glucoheptonatoestanho para marcação de leucócitos com 99mTc in vitro pelo método de préestanização. A otimização da técnica de marcação foi realizada através da incubação dos leucócitos, isolados de sangue total, com diferentes volumes do reagente de glucoheptonato-estanho por diferentes tempos à 37°C (préestanização), com posterior marcação com 99mTc (185 MBq), incubados à temperatura ambiente por 20 minutos. O rendimento da marcação foi superior a 90% na condição ótima de marcação. O reagente liofilizado mostrou-se estável por mais de 90 dias. As imagens cintilográficas obtidas 1, 2 e 3 horas após a administração dos leucócitos radiomarcados em coelho New Zeland demonstraram a alta eficiência de marcação de processo inflamatório provocado a partir da administração local de terebentina. O método de marcação de leucócitos desenvolvido apresenta aplicação promissora na clínica médica, com proposta de redução de custo do procedimento, apesar de ser um procedimento mais demorado quando comparado ao procedimento que utiliza o quelante lipofílico de HMPAO. / The study and localization of inflammatory and infection process in Nuclear Medicine represents a relevant tool in diagnostic procedures. In same cases, the diagnostic is easy and based on anamnesis and clinical observation; in other cases, the patients are asymptomatic or present non specific symptoms that difficult the diagnostic. The early diagnostic of inflammatory or infectious process allow the early introduction of therapy and prevents complications. Farther, the differentiation between inflammation and infection is of extreme importance as well as the localization of the focus. The use of labeled leucocytes, studied and applied in much pathologies, is the method of choice for the visualization of inflammation and infection. The scintigraphy using labeled leucocytes was introduced at 1976 by McAffe and Thakur and since of this is used in the diagnostic of different pathologies related to leucocyte infiltration like intestinal inflammatory disease, bone or prosthetic-vascular infections. The in vitro labeling of leucocytes with 111In was performed using oxime or tropolone as ligand and with 99mTc using hexamethylpropylene amine oxime (HMPAO) as ligand, resulting in a lipophilic complex. The 99mTc-HMPAG complex was preferably employed in many indications and countries do to the ideal physical properties of 99mTc that results in low dose to the patient. However, the labeling employing the HMPAO complex results in some disadvantages like the low stability of the complex, and some requirements related to the 99mTc elution (like the time pos elution), beyond the high cost of the compound that is imported. The aim of this work was the development of a tin-glucoheptonate lyophilized kit for in vitro leucocytes labeling with 99mTc using the pre-stannization method. The optimization of the labeling technique was developed using leucocytes isolated from total blood and employing different volumes of the tinglucoheptonate reagent and different incubation times at 37 deg C (pre-stannization), and posterior labeling with 99mTc (185 MBq), after 20 minutes reaction at room temperature. The labeling yield was superior to 90% using the optimized labeling conditions. Lyophilized reagent was stable after 90 days. Scintilographic images obtained 1, 2 e 3 hours after the administration of labeled leucocytes in New Zealand rabbit, showed good uptake on inflammatory focus promoted by tupertine injection. The leucocytes labeling method developed can be probably applied in clinical procedures and represents cost effective method in substitution of the lipophilic complex of HMPAO.

Nous avons étudiée le magnétisme et la morphologie de dépôt de Co, CoAu et Rh sur la surface d'Au(111), à différentes températures, par effet Kerr, microscopie à effet tunnel, diffraction d'électrons lents et spectroscopie Auger. En exploitant la reconstruction de l'Au(111) à 300 K, il est possible de former des agrégats auto-organisés, des chaînes et films d'atomes de Rh ou Co à partir d'un dépôt unique ou d'un codépôt CoAu. Contrairement aux dépôts à 300 K qui ont une anisotropie perpendiculaire entre 1.7 et 4 monocouches (MC), les dépôts de Co à 30 K ont une aimantation planaire dans cette gamme d'épaisseur. Lorsque ces films sont recuits à 300 K, une réorientation de l'aimantion se produit. L'évolution du magnétisme et de la morphologie du film après recuit, à 450 K, suggère une interdiffusion Co-Au qui nous a conduit à étudier l'influence de la température sur le magnétisme de films d'alliage CoAu sur l'Au(111). Pour les codépôts (0.4 à 14 MC) réalisés à 300 K, une démixtion ordonnée est observée sur les images STM. Les codépôts riches en Co (>50%) sont ferromagnétiques avec une anisotropie perpendiculaire, alors que ceux de Co50Au50 sont constitués d'amas de Co superparamagnétiques. Un codépôt de Co et Au à 30 K permet une croissance d'alliage métastable d'éléments immiscibles dans le volume, par limitation de la diffusion atomique. Nous avons étudié l'évolution de films entre 2 et 20 MC, riches en Co, en fonction de la température. A 30 K, les codépôts sont amorphes et non magnétiques. Après recuit à une température critique, un signal magnétique d'anisotropie perpendiculaire, apparaît. Cette évolution qui s'étale sur plusieurs minutes, voire heures selon l'épaisseur du film, est due à une séparation de phase dans le film d'alliage conduisant à une percolation ferromagnétique. Concernant le Rh, il s'agissait de vérifier l'existence du magnétisme prédit par des calculs, pour 1 MC sur métal noble. Dans nos conditions de croissance et de mesure, aucun signal magnétique n'a été détecté. Cette absence de signal magnétique peut s'expliquer, à 300 K par la formation d'un film rugueux et à 30 K par la formation d'un alliage de surface Rh-Au dans les premiers stades de la croissance.

Nous avons développé un système de transfert des surfaces monocristallines préparées sous ultra-haut vide (UHV) vers un milieu électrolytique pour effectuer des mesures voltampérométriques. Ce système original très compact comprend une valise sous vide et une cellule électrochimique dédiée. Le système a été testé avec succès sur des surfaces monocristallines de platine, en particulier la surface Pt(111) très sensible à la qualité de la préparation sous UHV. Puis nous avons utilisé ce système pour caractériser les propriétés électrochimiques du système Pt/W(111) avec d'une part l'effet des contraintes élastiques pour les couches ultra-minces planaires de Pt épitaxié ainsi que la stabilité en milieu électrolytique de nano-pyramides obtenues par déstabilisation en température des surfaces Pt/W(111). Ce travail ouvre des perspectives intéressantes pour l'étude électrochimiques des surfaces modèles préparées sous UHV.

Ce travail présente la formation et la caractérisation sous ultravide de monocouches moléculaires issu de l'auto-assemblage et de la polymérisation de molécules organiques (hexahydroxy triphenyléne-HHTP et acide diborique benzoique-BDBA) sur des surfaces monocristallines métalliques et isolantes. L'adsorption de molécules HHTP sur Ag(111) donne lieu à plusieurs réseaux moléculaires dépendants de la température. Cette étude, menée par microscopie à effet tunnel (STM), montre qu'un réseau robuste est obtenu suite à la déshydrogénation, activée thermiquement, des groupes alcool périphériques. Cela induit la formation de liaisons hydrogène entre les fonctions alcools et cétones ainsi obtenues. L'étude STM de molécules de BDBA vapo-déposées sur Ag(111) a démontrée la formation d'architectures bidimensionnelles étendues, liées de manière covalente, suite à la polymérisation des précurseurs en surface. Un résultat similaire a pu être obtenu par la copolymérisation des molécules de BDBA et d'HHTP. Ces polymères nanoporeux s'étendent en monocouche et présentent une stabilité en température exceptionnelle. Enfin, l'étude de BDBA sur le substrat isolant de KCl, menée par microscopie à force atomique en mode non contact (nc-AFM), montre un auto-assemblage étendu par des liaisons hydrogène, et met en évidence le rôle décisif de la nature chimique du substrat sur la faisabilité de la polymérisation de ces molécules en surface. L'approche développée dans ce travail, mettant en jeu des réactions chimiques en surface, constitue une voie nouvelle pour la conception de nano-architectures moléculaires originales et robustes sur surfaces.

A pair of studies investigating the deposition and surface chemical properties of ultrathin metal films were pursued: (i) Pt-Co alloys on Mo(110); and (ii) Pd on Pt(111). Experimental measurement was based on a combination of electron spectroscopy (low energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and low energy electron diffraction) and electrochemistry (voltage efficiency, voltammetry, and coulometry). Mixed-metal preparation of Pt-Co films by thermal vapor deposition (TVD) resulted in a thin-film binary alloy. Careful analysis revealed a substantial divergence between the composition at the interface and that in the interior. This outcome was observed for all compositions and allowed for the construction of a ?surface phase diagram?. The proclivities of the alloys of pre-selected compositions towards enhanced catalysis of the oxygen-reduction reaction were assessed in terms of their voltage efficiencies, as manifested by the open-circuit potential (OCP) in O2-saturated dilute sulfuric acid electrolyte. The particular alloy surface, Pt3Co (XPt=3,XCo=1), whether from the thin film or a bulk single crystal, exhibited the highest OCP, a significant improvement over pure Pt but still appreciably lower than the thermodynamic limit. Under test conditions, the degradation of thusly-prepared films was primarily due to Co corrosion. Ultrathin Pd films on well-defined Pt(111) surfaces, with coverages from 0.5 to 8 monolayers (ML), were prepared by surface-limited redox replacement reaction (galvanic exchange) of underpotentially deposited Cu. Spectroscopic data revealed that films prepared in this manner are elementally pure, pseudomorphic to the substrate, and stable, independent of the surface coverage (?) of palladium. Analysis of the voltammetric profiles in the hydrogen evolution region revealed unique properties of hydrogen adsorption unseen in bulk electrodes. Notably, at 1 ML coverage, a step-free film was produced that did not exhibit hydrogen absorption. At higher coverages, digital (layer-by-layer) deposition gave way to 3D islands in a Stranski- Krastanov growth mode; under these conditions, onset of bulk-like behavior was observed. This method makes possible the synthesis of well-ordered noble-metal films in the absence of high-temperature treatment

This thesis presents a new theoretical formalism which incorporates dynamical effects in atomistic electronic structure and related calculations. This research, fundamental by nature, brings about a deeper understanding of the dynamical processes in a range of materials. This establishes technologically important correlation with experimentally measured macroscopic properties and materials characterization. This method—the first of its kind—is a natural and long overdue extension of customary adiabatically separated time-independent electronic structure methods. It accounts explicitly for atomic motion due to thermal and zero-point vibration. The approach developed requires no direct treatment of time dependence in the quantum mechanical calculations, making the method widely applicable utilizing currently available electronic structure and ab-initio molecular dynamics software. The formalism is extensively applied and demonstrated for the linear optical response of bulk gallium arsenide and electronic structure of the C(111) 2 x 1 surface. Both cases are complimented by comparison of key observables to experimental data which may be used to judge the quality of the results. The results are found to be in good agreement with experimental data, with most exceptions being readily explainable and well understood.