Este trabalho apresenta a síntese, caracterização e estudo fotoluminescente de nanopartículas à base de óxido misto de estanho e titânio dopadas com európio, térbio e neodímio visando à utilização como marcadores luminescentes em sistemas biológicos. As sínteses foram feitas pelos métodos de coprecipitação, sol-gel proteico e Pechini e as partículas foram caracterizadas por espectroscopia de infravermelho, análise termogravimétrica, microscopia eletrônica de varredura, difração de raios X e espectroscopia de absorção de raios X. Os estudos das propriedades fotoluminescentes foram realizados para os luminóforos dopados com európio, térbio e neodímio, sintetizados pelo método de coprecipitação. Para o luminóforo dopado com európio foi possível calcular os parâmetros de intensidade e o rendimento quântico e este apresentou resultados satisfatórios. Tratando-se de uma marcação em sistemas biológicos fez-se necessário a funcionalização destas partículas para que as mesmas se liguem à parte biológica a ser estudada. Sendo assim, funcionalizou-se as nanopartículas pelos métodos de microondas e Stöber e caracterizou-se por espectroscopia de infravermelho, microscopia eletrônica de varredura, espectroscopia por dispersão de energia e difração de raios X, obtendo-se resposta qualitativa da eficácia da funcionalização. O método espectroscópico da ninidrina foi utilizado para a quantificação da funcionalização dos luminóforos. Os estudos fotoluminescentes das partículas funcionalizadas demonstram a viabilidade do uso destes luminóforos como marcadores luminescentes. / This work presents the synthesis, characterization and photoluminescent study of tin and titanium mixed oxide nanoparticles doped with europium, terbium and neodymium to be used with luminescent markers on biological systems. The syntheses were done by co-precipitation, protein sol-gel and Pechini methods and the nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy. The photoluminescent properties studies were conducted for luminophores doped with europium, terbium and neodymium synthesized by coprecipitation method. For luminophore doped with europium it was possible to calculate the intensity parameters and quantum yield and it showed satisfactory results. In the case of biological system marking it was necessary the functionalization of these particles to allow them to bind to the biological part to be studied. So the nanoparticles were functionalized by microwave and Stöber methods and characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction obtaining qualitative response of functionalization efficacy. The ninhydrin spectroscopic method was used for quantification of luminophores functionalization. The photoluminescent studies of functionalized particles demonstrate the potential applying of these luminophores as luminescent markers.

This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.

This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.

Este trabalho apresenta a síntese, caracterização e estudo fotoluminescente de nanopartículas à base de óxido misto de estanho e titânio dopadas com európio, térbio e neodímio visando à utilização como marcadores luminescentes em sistemas biológicos. As sínteses foram feitas pelos métodos de coprecipitação, sol-gel proteico e Pechini e as partículas foram caracterizadas por espectroscopia de infravermelho, análise termogravimétrica, microscopia eletrônica de varredura, difração de raios X e espectroscopia de absorção de raios X. Os estudos das propriedades fotoluminescentes foram realizados para os luminóforos dopados com európio, térbio e neodímio, sintetizados pelo método de coprecipitação. Para o luminóforo dopado com európio foi possível calcular os parâmetros de intensidade e o rendimento quântico e este apresentou resultados satisfatórios. Tratando-se de uma marcação em sistemas biológicos fez-se necessário a funcionalização destas partículas para que as mesmas se liguem à parte biológica a ser estudada. Sendo assim, funcionalizou-se as nanopartículas pelos métodos de microondas e Stöber e caracterizou-se por espectroscopia de infravermelho, microscopia eletrônica de varredura, espectroscopia por dispersão de energia e difração de raios X, obtendo-se resposta qualitativa da eficácia da funcionalização. O método espectroscópico da ninidrina foi utilizado para a quantificação da funcionalização dos luminóforos. Os estudos fotoluminescentes das partículas funcionalizadas demonstram a viabilidade do uso destes luminóforos como marcadores luminescentes. / This work presents the synthesis, characterization and photoluminescent study of tin and titanium mixed oxide nanoparticles doped with europium, terbium and neodymium to be used with luminescent markers on biological systems. The syntheses were done by co-precipitation, protein sol-gel and Pechini methods and the nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy. The photoluminescent properties studies were conducted for luminophores doped with europium, terbium and neodymium synthesized by coprecipitation method. For luminophore doped with europium it was possible to calculate the intensity parameters and quantum yield and it showed satisfactory results. In the case of biological system marking it was necessary the functionalization of these particles to allow them to bind to the biological part to be studied. So the nanoparticles were functionalized by microwave and Stöber methods and characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction obtaining qualitative response of functionalization efficacy. The ninhydrin spectroscopic method was used for quantification of luminophores functionalization. The photoluminescent studies of functionalized particles demonstrate the potential applying of these luminophores as luminescent markers.

Perovskita de LaFeO3 sintetizadas pelo método de Pechini foram avaliadas como catalisadores para a reação de oxidação parcial do metano. Foi impregnado níquel por via úmida como fase ativa em concentrações de 15 e 30 %, sobre as perovskitas, 15NLF e 30NLF, respectivamente, e o seu efeito foi avaliado para a mesma reação. Foi realizado análises termogravimétricas (TGA/DTGA) nos precursores da perovskitas, constatando a sua formação a 650 °C. A análise de microscopia de varredura (MEV) foi realizada nas amostras da perovskita pura, sendo que em uma delas foi realizada um banho de ultrassom para diminuir o tamanho de suas partículas e avaliar este efeito na reação de POM. Análises de difração de raio X (DRX) mostraram que todas as amostras apresentam as mesmas propriedades cristalográficas, sendo que, nas amostras contendo níquel, o metal apresentou-se na forma de NiO. O tamanho dos cristais, cálculado através da equação de Scherer, foi na ordem de 20 nm. Este resultado apontou que o níquel impregnado não participa da estrutura perovskita, mas sim está sobreposto a esta. Através da microscopia eletrônica de transmissão (TEM) foi possível visualizar a dispersão da fase ativa na superfície óxida e tamanhos de partículas na ordem de 20 nm. A redução a temperatura programada (TPR) apresentou as temperaturas de redução de espécies níquel e de ferro, presente na perovskita, e permitiu compreender a atuação das espécies Ni+2 e Fe0 na formação de H2 e CO. Os testes catalíticos foram realizados a 700ºC e 750°C, a pressão atmosférica, para uma vazão de alimentação de 200 cm3.min-1. Os testes cataliticos mostraram que a conversão de H2 dobrou para perovskita Ni/LaFeO3 em relação a LaFeO3. O catalisador 15NLF apresentou melhor estabilidade que o catalisador 30NLF para a reação. / LaFeO3 perovskite synthesized by the Pechini method were evaluated for the partial oxidation reaction of methane. Nickel was impregnated as the active phase in concentrations of 15 and 30%, on perovskites, 15NLF and 30NLF, respectively, and its effect was evaluated for the same reaction. Thermogravimetric analyzes (TGA / DTGA) were carried out on the perovskite precursors, confirming their formation at 650 °C. Scanning microscopy (SEM) was performed on pure perovskite samples, in one of them an ultrasonic bath was performed to reduce the size of its particles and to evaluate this effect in the POM reaction. X-ray diffraction (XRD) analyzes showed that all samples had the same crystallographic properties, and in the samples containing nickel, the metal was present as NiO. The size of the crystals, calculated through the Scherer equation, was in the order of 20 nm. This result pointed out that the impregnated nickel does not participate in the perovskite structure. Through transmission electron microscopy (TEM) it was possible to visualize the dispersion of the active phase on the oxide surface and particle sizes in the order of 20 nm. The programmed temperature reduction (TPR) showed the iron and nickel species reduction temperatures present in the perovskite, and allowed to understand the Ni+ 2 and Fe0 species in the H2 and CO formation. The catalytic tests were performed at 700 °C and 750 °C at atmospheric pressure for a flow rate of 200 cm3.min-1. The catalytic tests showed that the conversion of H2 doubled to perovskite Ni/LaFeO3 in relation to LaFeO3. 15NLF catalyst presented better stability than the 30NLF catalyst for the reaction.

Perovskita de LaFeO3 sintetizadas pelo método de Pechini foram avaliadas como catalisadores para a reação de oxidação parcial do metano. Foi impregnado níquel por via úmida como fase ativa em concentrações de 15 e 30 %, sobre as perovskitas, 15NLF e 30NLF, respectivamente, e o seu efeito foi avaliado para a mesma reação. Foi realizado análises termogravimétricas (TGA/DTGA) nos precursores da perovskitas, constatando a sua formação a 650 °C. A análise de microscopia de varredura (MEV) foi realizada nas amostras da perovskita pura, sendo que em uma delas foi realizada um banho de ultrassom para diminuir o tamanho de suas partículas e avaliar este efeito na reação de POM. Análises de difração de raio X (DRX) mostraram que todas as amostras apresentam as mesmas propriedades cristalográficas, sendo que, nas amostras contendo níquel, o metal apresentou-se na forma de NiO. O tamanho dos cristais, cálculado através da equação de Scherer, foi na ordem de 20 nm. Este resultado apontou que o níquel impregnado não participa da estrutura perovskita, mas sim está sobreposto a esta. Através da microscopia eletrônica de transmissão (TEM) foi possível visualizar a dispersão da fase ativa na superfície óxida e tamanhos de partículas na ordem de 20 nm. A redução a temperatura programada (TPR) apresentou as temperaturas de redução de espécies níquel e de ferro, presente na perovskita, e permitiu compreender a atuação das espécies Ni+2 e Fe0 na formação de H2 e CO. Os testes catalíticos foram realizados a 700ºC e 750°C, a pressão atmosférica, para uma vazão de alimentação de 200 cm3.min-1. Os testes cataliticos mostraram que a conversão de H2 dobrou para perovskita Ni/LaFeO3 em relação a LaFeO3. O catalisador 15NLF apresentou melhor estabilidade que o catalisador 30NLF para a reação. / LaFeO3 perovskite synthesized by the Pechini method were evaluated for the partial oxidation reaction of methane. Nickel was impregnated as the active phase in concentrations of 15 and 30%, on perovskites, 15NLF and 30NLF, respectively, and its effect was evaluated for the same reaction. Thermogravimetric analyzes (TGA / DTGA) were carried out on the perovskite precursors, confirming their formation at 650 °C. Scanning microscopy (SEM) was performed on pure perovskite samples, in one of them an ultrasonic bath was performed to reduce the size of its particles and to evaluate this effect in the POM reaction. X-ray diffraction (XRD) analyzes showed that all samples had the same crystallographic properties, and in the samples containing nickel, the metal was present as NiO. The size of the crystals, calculated through the Scherer equation, was in the order of 20 nm. This result pointed out that the impregnated nickel does not participate in the perovskite structure. Through transmission electron microscopy (TEM) it was possible to visualize the dispersion of the active phase on the oxide surface and particle sizes in the order of 20 nm. The programmed temperature reduction (TPR) showed the iron and nickel species reduction temperatures present in the perovskite, and allowed to understand the Ni+ 2 and Fe0 species in the H2 and CO formation. The catalytic tests were performed at 700 °C and 750 °C at atmospheric pressure for a flow rate of 200 cm3.min-1. The catalytic tests showed that the conversion of H2 doubled to perovskite Ni/LaFeO3 in relation to LaFeO3. 15NLF catalyst presented better stability than the 30NLF catalyst for the reaction.

L'interaction de l'eau avec les surfaces d'oxyde d'actinides demeure relativement peu étudiée. L'adsorption d'eau à la surface de PuO2 et (U,Pu)O2 conduit à la génération de H2 par radiolyse mais également à l'évolution de l'état de surface. L'étude de l'interaction de l'eau avec les surfaces d'oxydes mixtes (U,Pu)O2 requiert de mettre en œuvre des techniques d'analyses peu intrusives. L'étude de l'hydratation de la surface de CeO2 permet d'étudier la pertinence de différentes techniques d'analyses. Les résultats montrent que l'adsorption d'eau à la surface de CeO2 conduit à une évolution de l'état de surface et la formation d'une couche superficielle de type hydroxyde. La réactivité de l'eau à la surface de CeO2 dépend de la température de calcination du précurseur de l'oxyde. Le traitement thermique des surfaces hydratées permet de régénérer l'état de surface. Cette étude sur CeO2 souligne l'intérêt des techniques d'analyse mises en œuvre quant à l'étude de l'hydratation des surfaces. La génération de dihydrogène par radiolyse de l'eau adsorbée est étudiée par une méthode expérimentale fondée sur le renouvellement d'eau à la surface du matériau. L'accumulation de H2 est linéaire durant les premières heures puis tend vers un état stationnaire. Un mécanisme de consommation de H2 est proposé pour expliquer cet équilibre et également l'évolution des surfaces d'oxyde mixtes (U,Pu)O2 témoignée par l'évolution des cinétiques d'accumulation de H2. La cinétique d'accumulation dépend du débit de dose, de la surface spécifique de l'oxyde, de l'humidité relative de l'atmosphère en équilibre ainsi que du taux de plutonium et de l'état de surface. / The interaction of water with actinides oxide surfaces remains poorly understood. The adsorption of water on PuO2 surface and (U,Pu)O2 surface leads to hydrogen generation through radiolysis but also surface evolution.The study of water interaction with mixed oxide (U,Pu)O2 and PuO2 surfaces requires the implementation of non intrusive techniques. The study of the hydration of CeO2 surface is used to study the effectiveness of different techniques. The results show that the water adsorption leads to the surface evolution through the formation of a hydroxide superficial layer. The reactivity of water on the surface depends on the calcination temperature of the oxide precursor. The thermal treatment of hydrated surfaces can regenerate the surface. The study on CeO2 hydration emphasizes the relevancies of these techniques in studying the hydration of surfaces.The hydrogen generation through water radiolysis is studied with an experimental methodology based on constant relative humidity in the radiolysis cell. The hydrogen accumulation is linear for the first hours and then tends to a steady state content. A mechanism of hydrogen consumption is proposed to explain the existence of the steady state of hydrogen content. This mechanism enables to explain also the evolution of the oxide surface during hydrogen generation experiments as shown by the evolution of hydrogen accumulation kinetics. The accumulation kinetics depends on the dose rate, specific surface area and the relative humidity but also on the oxide aging. The plutonium percentage appears to be a crucial parameter in hydrogen accumulation kinetics.

The main objective of this Thesis is the synthesis, characterization and application in the PROX reaction of several series of catalysts synthesized using different methods, in order to find efficient materials with high catalytic activity. This work has been divided in six chapters. Chapter I presents an introduction about current energy problems and hydrogen (energy carrier) as a solution, with its limitations and advances on its use: storage, transport and security. Finally, its use as a fuel in PEMFC (Proton Exchange Membrane Fuel Cells) and the advantages comparing other existent fuel cells has been discussed. A brief summary was done about the catalytic systems studied in literature for PROX reaction and their characteristics. Following, Chapter 2 describes all the characterization techniques which were used to study the properties of the synthesized supports and catalysts, together with the experimental system employed for the catalytic tests. Most of these equipments belong to SSTTI of University of Alicante or are hand-made systems in the LMA group. DRIFTs and DTP were done at TUDelft, Catalysis Engineering Section. Next chapters contain the most important results obtained during the complete research work; they have been divided in two parts. On one hand, Chapter 3 describes the synthesis of pure TiO2 using five different methods, and its use as platinum support for PROX catalysts. On the other hand, taking into account the obtained results, three synthesis methods were chosen, and the study was centered in the addition of CeO2 to TiO2. Chapter 4 discusses the TixCe(1-x)O2 series synthesized using the sol-gel method. In Chapter 5 a solvothermal procedure was employed for the synthesis of supports with similar composition and, finally, impregnation of cerium over commercial P25 titania was compared in Chapter 6. Each chapter contains a complete study of characterization of both supports and catalysts. Synthesis parameters, pretreatment and reaction conditions were also modified for the best catalyst of the three series. Analyzing the catalysts’ behavior, a reaction mechanism was proposed. Finally, general conclusions summarize the most relevant results obtained in each chapter.

Two new fuel assembly designs for light water reactors using advanced mixed-oxide fuels have been proposed to reduce the radiotoxicity of used nuclear fuel discharged from nuclear power plants. The research efforts of this thesis are the first to consider the effects of burnup on advanced mixed-oxide fuel assembly performance and thermal safety margin over an assembly?s expected operational burnup lifetime. In order to accomplish this, a new burnup-dependent thermal-hydraulic analysis methodology has been developed. The new methodology models many of the effects of burnup on an assembly design by including burnup-dependent variations in fuel pin relative power from neutronic calculations, assembly power reductions due to fissile content depletion and core reshuffling, and fuel material thermal-physical properties. Additionally, a text-based coupling method is developed to facilitate the exchange of information between the neutronic code DRAGON and thermal-hydraulic code VIPRE-01. The new methodology effectively covers the entire assembly burnup lifetime and evaluates the thermal-hydraulic performance against ANS Condition I, II, and III events with respect to the minimum departure from nucleate boiling ratio, peak cladding temperatures, and fuel centerline temperatures. A comprehensive literature survey on the thermal conductivity of posed fuel materials with burnup-dependence has been carried out to model the advanced materials in the thermal-hydraulic code VIPRE-01. Where documented conductivity values are not available, a simplified method for estimating the thermal conductivity has been developed. The new thermal conductivity models are based on established FRAPCON-3 fuel property models used in the nuclear industry, with small adjustments having been made to account for actinide additions. Steady-state and transient thermal-hydraulic analyses are performed with VIPRE- 01 for a reference UO2 assembly design, and two advanced mixed-oxide fuel assembly designs using the new burnup-dependent thermal-hydraulic analysis methodology. All three designs maintain a sufficiently large thermal margin with respect to the minimum departure from nucleate boiling ratio, and maximum cladding and fuel temperatures during partial and complete loss-of-flow accident scenarios. The presence of a thin (Am,Zr)O2 outer layer on the fuel pellet in the two advanced mixed-oxide fuel assembly designs increases maximum fuel temperatures during transient conditions, but does not otherwise greatly compromise the thermal margin of the new designs.

NOx storage and reduction activities of Pt/BaO/CexZr1-xO2 (x= 1, 0.75, 0.5, 0.25, 0) catalysts were investigated by transient reaction analysis and Diffuse Reflectance Infrared Fourier Tramsform Spectroscopy (DRIFTS). Pt/BaO/Al2O3 catalyst was used as reference catalyst. Ce-Zr mixed oxides were synthesized by means of Pechini Method. Pechini method is a sol-gel like method based on mixing the related mixed oxide precursors with an &amp / #945 / -hydroxy carboxylic acid. 10% BaO (w/w) and 1% Pt (w/w) were deposited on synthesized mixed oxide and reference alumina support via incipient wetness impregnation. Prepared catalysts were characterized by BET, XRD and in-situ DRIFTS. Pt/BaO/CexZr1-xO2 catalysts (x= 0.75, 0.5, 0.25) exhibited higher surface than pure ceria and zirconia supported catalysts and highest surface was observed for Pt/BaO/Ce0.5Zr0.5O2. The reducibility of catalysts was tested by Temperature Programmed Reduction (TPR). It was observed that the reducibility of Pt/BaO/CexZr1-xO2 catalysts increases with incorporation of Zr into ceria lattice. Pt/BaO/Ce0.25Zr0.75O2 showed the highest reducibility. The Pt dispersions of catalysts were determined by CO chemisorption. The highest Pt disperison was observed in the presence of Pt/BaO/Ce0.5Zr0.5O2 catalyst. NOx storage and reduction efficiency of the catalysts were determined by transient reaction analysis in a home-built setup at 350oC. The reaction results revealed that all catalysts exhibit similar NOX storage and reduction performance. The NOX storage performances of all catalysts were differentiated via in-situ DRIFTS analysis. Pt/BaO/CexZr1-xO2 (x= 0.75, 0.5, 0.25) catalysts revealed higher performance than the ceria and zirconia supported catalysts. Pt/BaO/Ce0.5Zr0.5O2 catalyst absorbed highest amount of NO on the surface in the form of nitrate. The reduction behaviours of catalysts also were investigated by in-situ DRIFTS. It was observed that nitrates and nitrites were completely removed from the surface after reduction by H2 at 300oC.