Ce travail de thèse propose une investigation des dynamiques régissant la réactiond’hydrogénation du dioxyde de carbone sur une nanoparticule modèle de rhodium àl’échelle moléculaire. Cette recherche s’inscrit dans le contexte de la valorisation du CO2 parla voie catalytique. Une meilleure compréhension de la relation entre la structurecristallographique de la surface et les mécanismes réactionnels permettrait, à terme,d’améliorer l’optimisation des matériaux catalytiques. Dans ce but, la réaction est étudiée àl’échelle moléculaire sur une nanoparticule modèle de rhodium. Sa surface est observée àl’aide de l’ensemble des techniques d’émission de champ :la microscopie d’émission dechamp (FEM), la microscopie ionique à effet de champ (FIM), la sonde atomique unidimensionnelle(1DAP) et la sonde atomique tomographique (APT). Afin d’identifier lesdifférents phénomènes observés, ces derniers sont comparés à d’autres systèmes réactifsimpliquant l’O2, le N2O et le CO, sur du rhodium, du platine et un alliage de platine rhodium(10% en masse de rhodium).Dans ce travail nous avons observé et caractérisé l’adsorption dissociative du CO2 sur lerhodium et sa réaction avec l’hydrogène. À l’aide d’études comparatives avec les autressystèmes, des phénomènes réactifs ont été identifiés. Les traitements des donnéesrecueillies indiquent qu’à 700 K, les gaz CO2 et H2 réagissent via un processus en surface etforment les produits CO(g) et H2O(g). Cette réaction est connue sous le nom de « réaction dugaz à l’eau inverse ». Cette réaction s’accompagne de transformations observables par FEM.La présence d’atomes d’oxygène adsorbés provoque une augmentation du travail de sortiedes électrons de la plupart des facettes cristallographiques de la surface de rhodium, ce quise traduit par un assombrissement global de l’image FEM. Cependant, certaines régionsparticulières correspondant aux facettes {113} présentent une tendance inverse. Grâce audéveloppement d’une nouvelle méthodologie adaptant la sonde atomique tomographique àl’étude de processus dynamiques, il a été possible de relier les observations faites par FEM àla diffusion d’atomes d’oxygène sous la surface. Cette diffusion n’est pas homogène etdépend de la structure cristallographique des facettes. L’oxygène, formé à la suite d’uneadsorption dissociative sur les facettes du type {012}, ne pénètre le coeur de phase qu’autravers de certaines régions telles que les {113}, les {011} et les {111}. La construction desdiagrammes d’adsorption du CO2 et les diagrammes de phase cinétique du systèmeH2+O2/Rh ont permis de mettre en évidence les mouvements des atomes d’oxygène entre lasurface et la sous-surface. Finalement ces observations ont été étendues à d’autresmatériaux :Le platine et l’alliage PtRh. L’accumulation d’atomes d’oxygène sur et sous lasurface peut donc être observée en temps réel et à l’échelle moléculaire. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Dans cette étude, nous avons déterminé les propriétés électroniques de plusieurs types de composés moléculaires possédant un élément métallique. Notre motivation pour l'étude de tels systèmes était de montrer qu'il était possible d'obtenir une description précise d'états électroniques très proches en énergie, pour lesquels il est connu que les effets relativistes jouent un rôle important. Pour traiter ces effets nous avons mis en oeuvre différentes approches et méthodes, en particulier des méthodes multiconfigurationnelles, des pseudopotentiels atomiques et de grandes bases de fonctions. Dans une première étude nous avons déterminé les propriétés des états électroniques de plus basse énergie de composés diatomiques MX dont l'association en phase solide conduit à des composés semi-conducteurs présentant des propriétés piézoélectrique importantes. A l'aide de calculs électroniques incluant une large part de la corrélation électronique nous avons mis en évidence les propriétés communes à une famille de composés diatomiques possédant huit électrons de valence et qui peuvent être considérés comme précurseurs des solides piézoélectriques. Il a ainsi été possible d'identifier les couples diatomiques qui constituaient les meilleurs candidats pour une production d'effet piézoélectrique en phase solide. Dans la deuxième application, nous avons calculé la structure électronique et les constantes spectroscopiques de l'état fondamental de la molécule HZnF ainsi que les états de plus basse énergie des fragments diatomiques associés. Cette étude était motivée par une analogie avec un système voisin HZnCl dont les premiers états électroniques présentent des caractéristiques non complètement résolues. Après avoir validé notre approche sur l'étude de ZnH et comparé nos résultats à ceux d'études antérieures, nous avons entrepris la détermination de la structure électronique des molécules ZnF et ZnCl pour lesquelles nous avons pu identifier des états électroniques encore mal connus. Utilisant les résultats obtenus sur ZnH et ZnF, nous avons déterminé la surface d'énergie potentielle de l'état fondamental de HZnF et nous en avons déduit plusieurs grandeurs spectroscopiques caractérisant cet état / In this work we have investigated the electronic properties of several types of molecular systems involving a metallic element. Our motivation for such applications on metallic compounds was to obtain an accurate description of close lying electronic states, in which the relativistic effects of heavy atoms are known to be important. Thus various approaches and methods have been employed to treat these effects, including the multi-configurational method, with atomic pseudopotentials and large basis sets. In the first study, we have determined the properties of the low lying electronic states of the diatomic compounds MX, whose combinations in the solid phase produce ionic semi-conductor materials with piezoelectric properties. Based on highly correlated ab initio calculations, we have elucidated the common properties of the low lying electronic states of these diatomic compounds with eight valence electrons, which can be considered as precursors for piezoelectric effects in their solid phase. Based on our electronic structure calculations, we could identify among these diatomic compounds those who could lead to good candidates for piezoelectric effects. As the second application, we have determined the electronic structure and the spectroscopic constants for the ground state of the HZnF molecule and for the low lying electronic states of its diatomic fragments. This application was initiated and motivated by interesting and puzzling results on the close system HZnCl. Comforted by our experience with the previous studies, we used the pseudopotentials approach to obtain an accurate description of the low lying states of ZnH which could be satisfactorily compared with existing data. Next, the ZnF and ZnCl diatomic molecules have been studied with the same ansatz to reveal the properties of so far unknown electronic states. Finally, the potential energy surface of the ground state of HZnF has been determined, and several spectroscopic properties have been deduced

Ce mémoire présente le développement d'un dispositif expérimental permettant de mesurer deux composantes du gradient de pesanteur, Γzz et Γzx, ainsi que l'accélération de pesanteur. Ces grandeurs sont déterminées en mesurant l'accélération d'atomes froids de rubidium, en chute libre dans le vide, par interférométrie atomique. Pour la gradiométrie, la mesure différentielle est réalisée entre deux nuages atomiques spatialement distants. Pour la mesure de Γzz, l'utilisation de réseaux optiques mobiles permet d'obtenir deux nuages atomiques à partir d'une unique source atomique. Ce travail présente la mise en place du dispositif complet, avec notamment la réalisation de l'enceinte à vide, et des systèmes laser et micro-onde. Les lasers sont basés sur la technologie télécom doublée, permettant d'obtenir des modules compacts et robustes, afin d'envisager des applications embarquées. L'architecture laser originale permet de réaliser des expériences d'atomes froids combinant interférométrie atomique et réseaux optiques, en réduisant au minimum le nombre de composants. Le bruit du laser a été caractérisé, et il limite la sensibilité gravimétrique à 10-9 g en monocoup, la sensibilité différentielle à 10-10 g en monocoup, et la sensibilité gradiométrique à 38 E, en monocoup. / This thesis presents the development of the experimental setup allowing the measurement of two gravity gradient components, Γzz and Γzx, and the gravity acceleration. These quantities are resulted from the measuring of rubidium cold atoms acceleration, in free fall in vacuum, by atom interferometry. For gradiometry, the differential measurement is realized between two atomic clouds spatially separated. For the measurement of Γzz, the use of mobile optical lattices allows to get two atom clouds from a single atomic source. This work presents the setting up of the complete device, in particular with the built of the vaccum chamber, laser and micro-wave systems. Lasers are based on frequency-doubled telecom technology, which allows to obtain compact and robust systems, dedicated for onboard applications. The innovative laser architecture allows to combine atom interferometry and optical lattices, while minimizing the amount of components. The laser noise has been characterized, and limits the single shot gravimetric sensitivity to 10-9 g, the single shot differential sensitivity to 10-10 g, and the single shot gradiometric sensitivity to 38 E.

Durant ces deux dernières décennies, de nouvelles techniques pour refroidir et manipuler les atomes ont permis le développement de capteurs inertiels basés sur l'interférométrie atomique. Dans ce contexte, le projet ICE est basé sur l'utilisation d'un interféromètre atomique double espèce compacte et transportable dans le but de tester le principe d'équivalence faible. Nous comparons ainsi l'accélération de deux espèces chimiques et nous vérifions leur égalité en mesurant le paramètre d'Eötvös à un niveau de 10-6. Cette expérience a été réalisée en laboratoire et en micropesanteur lors de vols paraboliques à bord de l'Airbus A310 ZERO-G de Novespace. L'interféromètre est composé de deux échantillons de 87Rb et 39K refroidis par laser, possédant des longueurs d'onde de transitions atomiques similaires (780 nm et 767 nm) qui sont générées par un doublage de fréquence laser Télécom. Récemment, nous avons réalisé le premier interféromètre double espèce en micropesanteur. Cette expérience a ainsi permis le premier test du principe d'équivalence faible dans cet environnement en utilisant des objets quantiques, ce qui représente une première étape majeure vers une future mission spatiale. Dans le cadre de ces travaux, nous avons installé une source laser à 770 nm, accordée sur la transition D1 du 39K, afin de réaliser un refroidissement par mélasse grise. Nous avons également mis en place une nouvelle séquence pour préparer les atomes dans l'état mF = 0 avec une efficacité de transfert supérieure à 90%. Ces techniques ont amélioré le contraste de notre interféromètre de 39K d'un facteur 4, ce qui a mené à l'obtention d'une sensibilité sur le paramètre d'Eötvös dans le laboratoire de 5 x 10-8 après 5000 s d'intégration. / During the last two decades, new techniques to cool and manipulate atoms have enabled the development of inertial sensors based on atom interferometry. In this context, the ICE project is based on a compact and transportable dual-species atom interferometer in order to verify the weak equivalence principle (WEP). Thus, we compare the acceleration of two chemical species and verify their equality by measuring the Eötvös parameter at the 10-6 level.This experiment was performed both in the laboratory and in the microgravity environment during parabolic flights onboard the Novespace ZERO-G aircraft. The interferometer is composed of laser-cooled samples of 87Rb and 39K, which exhibit similar transition wavelengths (780 nm and 767 nm) derived from frequency-doubled telecom lasers. Recently, we have performed the first dual species interferometer in microgravity. This enables the first test of the WEP in weightlessness using quantum objects, which represents a major first step toward future mission in space.As part of these experiments, we have implemented a 770 nm laser source, resonant with the D1 transition of 39K, in order to perform a gray molasses cooling. We have also devised a new sequence to prepare atoms in the mF = 0 state with a transfer efficiency above 90%. These techniques improved the contrast of our 39K interferometer by a factor 4, which led to the obtention of a sensitivity on the Eötvös parameter in the laboratory of 5 x 10-8 after 5000 s of integration.

Ce mémoire présente la réalisation d'un dispositif expérimental de deuxième génération pour le projet FORCA-G (FORce de CAsimir et Gravitation à courte distance). L'objectif de ce projet est la mesure des interactions à faible distance entre un atome et une surface massive. La mesure de force est réalisée à l'aide d'interféromètres atomiques utilisant des atomes confinés dans un réseau optique 1D vertical basé sur le déplacement des atomes de puits en puits. La dégénérescence des niveaux d'énergies des atomes dans les puits du réseau est levée par la force que l'on cherche à mesurer. Des transitions Raman permettent de séparer les atomes dans des puits adjacents, puis de les recombiner, créant ainsi un interféromètre atomique qui permet de mesurer la différence d'énergie entre puits, liée à la fréquence de Bloch nu B du réseau. Ce travail présente la mise en place d'un dispositif proprement dédié au projet, qui permettra à terme de mesurer les forces à faible distance. Il rend compte des améliorations obtenues en configuration de gravimètre sur la sensibilité court terme de la mesure qui atteint 5. 10^-6 à 1 s. Il regroupe l'étude des limitations de la sensibilité, de l'exactitude et l'étude de la perte de contraste des interféromètres. Il présente aussi la mise en place d'une étape supplémentaire : l'implémentation d'un piège dipolaire visant obtenir un échantillon d'atomes plus dense et plus froid. / The thesis presents the set up of the second version of the experiment FORCA-G (CAsimir FORce and Gravitation at short range). The purpose of this experiment is the measurement of short-range interactions between an atom and a massive surface. The measurement is realised thanks to atom interferometers using atoms trapped in a 1D vertical optical lattice. The energy levels of atoms in such a trap are shifted from lattice site to another by the force we aim at measuring. We move the atoms from site to site using counter-propagating Raman transitions. The atoms are moved from Δm lattice sites only if the Raman frequency matches υHFS +∆m.υB where υHFS is the frequency of the hyperfine ground state transition and υB is the Bloch frequency and represents the difference of potential energy between two wells in the case where the atoms are far from the surface. This thesis presents the implementation of a setup properly dedicated to FORCA-G in which the measurement of short-range forces will be possible. It reaches an improved short-term relative sensitivity on the measurement of the Bloch frequency of at 3.9 10-6 at 1s. It contains the studies of the limits in the sensitivity, the accuracy and the contrast losses. It also presents the implementation of a dipolar trap to further cool the atoms and increase their density (crossed dipolar trap with a 1064 broadband laser).

(3aR)-14a-Acetoxy-3aß,4,14,14aa-tetrahydro-6,7,8-trimethoxybenzo[3,4]furo[3',4':6,7]cycloocta[1,2-f][1,3]benzodioxol-3(1H)-one (steganacin), 56, has been a popular synthetic target due to its perceived cytotoxic activity. Our proposed strategy for the construction of the key 8-membered ring embedded within steganacin was via an oxidative phenolic coupling of an appropriate (3R,4R)-4-(benzo[d][1,3]dioxol-5-ylmethyl)-3-benzyldihydrofuran-2(3H)-one analogue which were shown to be readily available from commercially available piperonal in six linear steps involving chain extension, reduction, trichloroacetylation and cyclisation via a copper-catalysed Atom Transfer Radical Cyclisation (ATRC) reaction. In this way, copper-catalysed ATRC reaction of (E)-6-(benzo[d][7’,9’]dioxol-1’-yl)allyl-1,1,1-trichloroacetate afforded (R)-4-{(R)-benzo[d][1,3]dioxol-5-ylchloromethyl}-3,3-dichlorodihydrofuran-2(3H)-one in good isolated yield as a mixture of diastereosiomers. Regiospecific functionalisation of these trihalides at the benzylic position (via an SN1, solvolysis, pathway), followed by dehalogenatioin and subsequent enolate alkylation afforded the key butyrolactone intermediates whose oxidative cyclisation was the key bond construct in our approach to steganacin. Contrary to our expectations it was observed that these substrates suffer intramolecular Friedel-Crafts alkylation reactions, favouring a 3a,4,9,9a-tetrahydronaphtho[2,3-c]furan-1(3H)-one (6 member ring) formation, rather than phenolic oxidative coupling reactions that would favour the steganacin-like (3aR,11aR,Z)-3a,4,11,11a-tetrahydrobenzo[4,5]cycloocta[1,2-c]furan-1(3H)-one (8 member ring) formation, when the oxidant has any Lewis acid capacity. Taking these observations into account we believe that by judicious choice of synthetic route the ATRC chemistry developed during the current research could be applied to a highly convergent (9 step) route to the synthesis of deoxypodophylotoxin.This work also describes, in detail, the efforts of this worker to establish and optimise a robust route that potentially can lead to the formation of steganacin via the alternative route of an initial microwave-assisted Pd-mediated biaryl coupling of either bromopiperonal or an halogenated derivative of the described γ-butyrolactones with an appropriate boronic acid derived from commercially available 3,4,5-trimethoxybenzalcohol to afford the biaryl scaffold present in steganacin. The completion of this synthesis was unfortunately left unaccomplished due to time constraints.

In the present thesis, we propose a modification of silicone surfaces using the controlled deposition of amphiphilic block copolymers from aqueous colloidal dispersions. The surface modifiers are based on poly(dimethylsiloxane) (PDMS) as the hydrophobic part, in order to allow a good compatibility with PDMS artefacts, and poly(glycerol monomethacrylate) (PGMMA) as the hydrophilic block, since this polymer has demonstrated good biocompatibility and low cell attachment. The hydroxyl groups present on PGMMA offer the possibility of further surface functionalization. We have demonstrated the convenience of preparing well-defined amphiphilic block copolymers of PDMS and PGMMA (which we refer to as Sil-GMMA polymers) via atom transfer radical polymerization using a protection/deprotection route (i.e. the silylation of GMMA alcohols groups). Depending on the ratio between hydrophobic and hydrophilic blocks, Sil-GMMA copolymers can self-assemble into micellar and other colloidal structures. Diffusion ordered nuclear magnetic resonance experiments have shown that those micelles did not interact with albumin, suggesting a “stealth” behaviour. Once a library of Sil-GMMA polymers with various block ratio was prepared, the adsorption of Sil-GMMA colloidal dispersions in water/ethanol on PDMS surfaces by simple physisorption was studied. As expected, high PDMS content favoured Sil-GMMA adsorption on silicone surfaces. The presence of our surface modifiers on silicone surfaces was confirmed by a decrease in water contact angle and spectroscopy techniques. We have shown that the surface coatings were stable upon storage in water. Additionally, fibrinogen adsorption was decreased by Sil-GMMA adsorption while albumin adsorption appeared to increase. The preparation of surfaces repellent to fibrinogen and interacting with a “passivating” protein such as albumin is promising. At the same time, this thesis also reports preliminary investigations on the use of enzymes in order to incorporate new functionality to GMMA containing polymers. Although enzymatic activity was observed when using PGMMA instead of glycerol with two different enzymes (glycerol kinase and glycerol dehydrogenase), PGMMA conversions were always low (< 2%).

Cette thèse porte sur deux sujets principaux: l'évaluation de la stabilité d'une horloge sur microcircuit utilisant des atomes piégés (Trapped Atom Clock on a Chip - TACC) et l'extension de cette technologie vers la réalisation d'un interféromètre atomique sur la même puce. Cette combinaison constitue la base pour la réalisation de capteurs inertiels intégrés pour la navigation. Des travaux antérieurs ont installé l'horloge et ont découvert, entre autres, des temps de cohérence très longs, qui permettent une interrogation Ramsey jusqu'à 5 s, une condition préalable pour le fonctionnement à grande stabilité. Je présente ici la première évaluation approfondie de la stabilité de l'horloge. Avec mon prédécesseur, nous avons démontré les fluctuations de fréquences relatives de 5.8 10-13 à 1 s intégrant jusqu'à 6 10-15 à 30000 s.La deuxième partie de cette thèse vise à étendre la polyvalence de notre puce atomique pour créer un interféromètre. J'ai étudié divers régimes d'interféromètres en utilisant des potentiels habillés par microondes. Le premier régime consiste à déplacer l'un des états d'horloge verticalement pendant une séquence d'horloge Ramsey. Ceci permet la mesure de gradients de potentiel en exploitant la différence de fréquences entre les deux états. Le second régime utilise des champs microondes pour générer un potentiel de double puits dans l'un des états d'horloge et un seul puits dans l'autre.À partir du seul puits, un pulse-π sur la transition d'horloge constitue la séparatrice de l'interféromètre et conduit une séparation spatiale tout en préservant le même état interne pour les deux bras de l'interféromètre. / This thesis covers two main subjects: the evaluation of the stability of a Trapped Atom Clock on a Chip (TACC) and the expansion of this technology towards creating an atom interferometer on the same chip. The combination of a clock and an interferometer on the same chip constitutes the basis for the realization of atom-based integrated inertial navigation units. Previous work installed the clock operation and discovered, among others, very long coherence times, which allow Ramsey interrogations of up to 5 s, a prerequisite for high stability operation. I present the first thorough evaluation of the clock stability. Together with my predecessor we have demonstrated relative frequency fluctuations of 5.8 10-13 at 1 s integrating down to 6 10-15 at 30,000 s. The second part of this thesis aims to expand the versatility of our atom chip to create an atom interferometer. I have studied various interferometer schemes using microwave dressed potentials and implemented these to the set-up. The first scheme, following work by P. Treutlein et al., involves displacing one of the clock states vertically during a Ramsey clock sequence thereby allowing the measurement of potential gradients by exploiting the differential frequency shift accumulated between the two states. Ramsey fringes where recorded for different durations of the splitting, resulting in a clear signal of the wavepacket separation. The second scheme uses microwave dressing to generate a double well potential in one of the clock states and a single well in the other. Starting in the single well, a π-pulse on the clock transition constitutes the beam splitter and leads to a spatial separation for the same internal state.

Prestes a completar 80 anos e tida como a melhor universidade do país segundo o Índice Geral de Cursos (IGC), a Universidade Federal do Rio Grande do Sul (UFRGS) tem suas origens nas Escolas Superiores e Faculdades, berços do Ensino Superior no Rio Grande do Sul, que passaram a funcionar em Porto Alegre no final do Século XIX. Devido a sua excelência acadêmica, a UFRGS tem produzido e acumulado, ao longo dos anos, um rico patrimônio documental arquivístico. Assim, esta pesquisa tem como objetivo a identificação e a proposição de uma sistemática de arranjo para esse patrimônio documental, através da plataforma digital -ICA-AtoM, com fins à descrição e à difusão dos instrumentos de pesquisa - guia e inventário. A justificativa para esta pesquisa permeia a condição da UFRGS enquanto instituição de ensino superior com uma importância significativa tanto no cenário rio-grandense como nacional, através do ensino, da pesquisa e da extensão desenvolvidos por ela. Como embasamento teórico para esta pesquisa, foram utilizados referenciais que conceituassem o patrimônio cultural, passando pelo identificação do patrimônio documental arquivístico neste contexto. Também, foram discutidos e contextualizados temáticas da Arquivologia, tais como a identificação da Arquivologia como ciência, as funções arquivísticas, destacando-se o Arranjo, a Descrição arquivística e a Difusão de arquivos. O contexto de estudo foi dado através de um breve histórico da UFRGS, como foi estruturada a Divisão de Documentação e como está constituído o acervo arquivístico. Esta pesquisa é de natureza aplicada, descritiva, qualitativa e configurou-se em um estudo de caso. A coleta de dados foi realizada a partir de observação direta, bem como de pesquisa bibliográfica e documental. Com esta pesquisa foi possível: identificar o documento arquivístico como patrimônio documental e cultural; estabelecer uma sistemática de arranjo para o acervo arquivístico da UFRGS; elaborar a descrição arquivística e a difusão através da criação do guia e do inventário; implementar os instrumentos de pesquisa no software ICA-AtoM. Como produto desenvolvido, está o Guia e Inventário do acervo custodiado pela Divisão de Documentação, instrumentos estes imprescindíveis para o acesso, preservação e difusão do patrimônio documental arquivístico. Por fim, cabe destacar a necessidade de continuidade deste trabalho que foi pioneiro em seu contexto de aplicação, devendo ser ampliado e reavaliado a medida em que se fizer necessário. / About to turn 80 and known as the best university of the country according to the General Courses Index (IGC), the Federal University of Rio Grande do Sul (UFRGS) has its origins with Higher Education Schools and Colleges, home of the Higher Education in Rio Grande do Sul, which started working in Porto Alegre in the late 19th century. Due to its academic excellence, UFRGS has produced and accumulated over the years a rich archival heritage. So this research's goal is to identify and to propose an arrangement system for this archival heritage through the digital platform ICA-AtoM to describe and disseminate finding aids – guide and inventory. This research is justified by the condition of UFRGS as a higher education institution with a significant importance in the state scenario as a national institution, through education, research and extension developed by it. As theoretical ground for this research, were used references that contemplated the concept of cultural heritage linked with the identification of archival heritage in this context. Also were debated and put into context archives administration themes, as the identification of archives administration as a science, archival functions, emphasizing Arrangement, Description and Diffusion of archives. The context of this study was given through a brief UFRGS historic, of how the Documentation Division was structured and how the archival holdings are organized. This is an applied, descriptive, qualitative research and a case study. The data collection was made through direct observation, as well as bibliographic and documental research. With this study it was able to identify the archival document as archival heritage, to set an arrangement system for UFRGS's archival holdings, to make an archival description and diffusion through the creation of a guide and an inventory and to implement these finding aids on the ICA-AtoM software. As the developed product, there are the guide and inventory of the holdings in custody by the Documentation Division, indispensable instruments for access, conservation and diffusion of the archival heritage. Lastly, it is important to highlight the need to continue this work that was a pioneer in its context of application, and it should be amplified and reevaluated when necessary.

Copper-based materials are one of the most promising catalysts for performing transformations of important organic compounds in both academic and industrial operations. However, it is challenging to consistently synthesize highly active and stable copper species as heterogeneous catalysts due to their relatively high surface energy. As a result, agglomeration usually occurs, which limits the catalytic activities of the copper species. The work presented in this dissertation shows different synthetic strategies for obtaining active and stable copper-based materials by modifying chemical/physical properties of copper nanoparticles (NPs). Emphasis is placed on discussing specific catalytic systems, including carbon-supported catalysts (monometallic and bimetallic copper-based heterogeneous catalysts) and titania-supported catalysts, and their advantages in terms of catalytic performance. In recent years, there has been increasing interest in using metal-organic frameworks (MOFs) as a sacrificial template to obtain carbon-supported NPs via a thermolysis process. The advantages of using MOFs to prepare carbon supported nanomaterials are a fine distribution of active particles on carbon matrix without post-synthesis treatments and corresponding increased catalytic activity and stability in many reaction conditions. To better understand the potential of this synthetic approach, MOF pyrolyzed products have been characterized. Then, they were applied as heterogeneous catalysts for several chemical reactions. In particular, the high energy copper-based MOF, CuNbO-1, was decomposed to obtain an amorphous copper species supported on carbon (a-Cu@C). This catalyst was found to be highly active for reduction, oxidation, and N-arylation reactions without further tuning or optimization. Higher catalyst turnover numbers for each of these transformations were obtained when comparing a-Cu@C activity to that of similar Cu-based materials. To improve catalyst performance, a secondary metal can be introduced to create synergistic effects with the parent copper species. In order to gain insights into the role of the second metal, a well-known Cu-MOF, HKUST-1, was doped with nickel, cobalt, and silver solutions, followed by a decomposition process with 2,4,6-trinitrotoluene (TNT) as additive. This additive was used to enhance the rapid thermolysis of the bimetallic MOFs. In these bimetallic systems, the addition of a second metal was found to help in dispersing both metals over the carbon composite support and in influencing the particle size and oxidation state of the metals. Catalytic performance showed that even <1% of a secondary metal increased the rate for nitrophenol reduction. Optimal catalytic performance was achieved using a Ni-CuO@C bimetallic catalyst. Another synthetic strategy for Cu-catalyst preparation involves using the deposition-precipitation method, in which a copper catalyst anchored on a titania support was synthesized at low weight % in order to obtain a single atom catalyst (1-Cu/TiO2). The higher copper loading catalyst, 5-Cu/TiO2, was synthesized as a benchmark catalyst for comparison. The copper structure in the synthesized catalysts was investigated by powder X-ray diffraction (PXRD), Raman, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX), X-ray photoelectron spectroscopy (XPS), N2 physisorption and inductively coupled plasma mass spectrometry (ICP-MS) in order to characterize physical and chemical properties. STEM-EDX observations showed single atom copper species less than 0.75 nm in size, as well as nanoparticles with an average diameter of ~1.31 nm. This catalyst was highly active in the reduction of nitro-aromatic compounds with NaBH4 at room temperature. The small to atomic level sizes of the Cu species and multiple oxidation states of Ti species were found to play a crucial role in the catalytic activity.