Made available in DSpace on 2017-07-21T18:53:23Z (GMT). No. of bitstreams: 1 Doris Oliveira Gregianin.pdf: 1718205 bytes, checksum: 59a8cb966255e87e0fa3f347f2a191cb (MD5) Previous issue date: 2014-08-28 / The increased incidence of cardiovascular disease and various cancers have been the cause of searching for changing habits in a large portion of the population, seeking the physical activity in conjunction with the consumption of healthier foods with higher nutritional content. Considering the high biological value of the proteins of sweet whey and the recognized effect in reducing risk of cardiovascular disease of soy protein, the aim of this study was to develop a mixed chocolate-soluble soybean extract dissolved in sweet whey. The different proportions of carrageenan stabilizers, pectin and tapioca starch were defined by the experimental design of mixtures simplex centroid. By optimizing the response surface was definitely the best formulation in relation to the physic-chemical and sensory parameters. The simultaneous optimization of response variables indicated that the optimal formulation should contain 46% carrageenan and 54% pectin and 0% starch, with a desirability index of 0.929. The formulation indicated for the desirability function was made with water soluble soy extract dissolved in sweet whey and; on sweet whey with reduced lactose content. Serum was hydrolyzed by the action of lactase from Kluyveromyces lactis yeast enzyme at a concentration of 2500 NLU / L in reaction 4 hr at 37 ° C. The sensory attributes were evaluated by nine points hedonic scale and attitude scale in purchase intent. For overall impression, the formulations presented average value of 7.11 ±1.09, while purchase intent the average value was 3.99 ± 1.28, and the multiple regression models proved to be predictive. The most widely accepted formulations were those who had lower viscosity and instrumental containing pectin in its constitution. The results obtained indicate that the combination of sweet whey and soy aqueous extract is a viable option for the preparation of a chocolate beverage. It was also observed that the use of cassava starch as a thickener does not interfere negatively on the rheological and sensory characteristics and; that the combined carrageenan and pectin concentrations defined predictive model ensures greater acceptability of the product. / O aumento da incidência de doenças cardiovasculares e diversos tipos de câncer tem sido a causa da procura por mudanças de hábitos em grande parte da população, buscando-se a prática de atividades físicas em conjunto com o consumo de alimentos mais saudáveis, com maior valor nutricional. Considerando o alto valor biológico das proteínas do soro de leite doce e o reconhecido efeito na diminuição de risco de doenças cardiovasculares da proteína de soja, o objetivo deste trabalho foi desenvolver um achocolatado misto de extrato hidrossolúvel de soja dissolvido em soro de leite doce. As diferentes proporções dos estabilizantes carragena, pectina e amido de mandioca foram definidas pelo planejamento experimental de misturas simplex centróide. Através da otimização da Superfície de Resposta foi definida a melhor formulação em relação aos parâmetros físico-químicos e sensoriais. A otimização simultânea das variáveis de resposta indicou que a formulação ideal deveria conter 46% de carragena e 54% de pectina e 0% de amido, com um índice de desejabilidade de 0,929. A formulação indicada pela função de desejabilidade foi elaborada com extrato hidrossolúvel de soja dissolvido em soro de leite doce e; em soro doce com teor de lactose reduzido. O soro foi hidrolisado pela ação da enzima lactase proveniente da levedura Kluyveromyces lactis, na concentração de 2.500 NLU/L numa reação de 4 horas à temperatura de 37°C. Os atributos sensoriais foram avaliados pela escala hedônica de nove pontos e escala de atitude na intenção de compra. Para impressão global as formulações apresentaram valor médio 7,11 ±1,09, enquanto que para intenção de compra o valor médio foi de 3,99 ±1,28, sendo que os modelos de regressão múltipla mostraram-se preditivos. As formulações mais aceitas foram aquelas que apresentaram menor viscosidade instrumental e que continham pectina em sua constituição. Os resultados obtidos indicam que a combinação do soro doce de leite e extrato aquoso de soja é uma opção viável para a elaboração de uma bebida achocolatada. Também foi possível observar que o uso do amido de mandioca como espessante não interfere negativamente nas características reológicas e sensoriais do produto e; que a carragena e pectinas combinadas, nas concentrações definidas pelo modelo preditivo, garantem maior aceitabilidade ao produto.

Les médicaments traditionnels à base de plantes (tradimédicaments) sont très utilisés par les populations africaines. Mais leur qualité est difficile à maîtriser, car ce sont des mélanges complexes de plusieurs drogues végétales ou des préparations à base de drogues végétales d’origine souvent inconnue et/ou très variable. Le profil chromatographique des métabolites phytochimiques constitue un outil important pour l’évaluation de la qualité de ces produits.L'objectif de ce travail est de proposer un protocole de préparation des échantillons et d’établissement de profil par chromatographie liquide et chromatographie en phase gazeuse des métabolites apolaires, pour l’évaluation de la qualité des médicaments traditionnels à base de plantes.La méthodologie est basée sur le traitement chimiométrique des profils chromatographiques des métabolites apolaires issus de différents lots de feuilles de Combretum micranthum et Mitracarpus scaber.Le profilage métabolique s’est effectué par chromatographie liquide sur Carbone Graphite Poreux en milieu non-aqueux et par chromatographie en phase gazeuse à haute température, couplées à la spectrométrie de masse, après extraction au dichlorométhane et élimination de la chlorophylle adsorbée sur charbon actif.L'analyse chimiométrique des données utilisant l’analyse PLS-discriminante avec ou sans correction orthogonale du signal, appliquée aux profils chromatographiques des feuilles de Combretum micranthum et Mitracarpus scaber, a montré de faibles différences entre les lots de chaque drogue végétale, et une différenciation claire des deux drogues végétales.Les deux méthodes d'analyse par chromatographie liquide et chromatographie en phase gazeuse permettent de détecter la plupart des métabolites secondaires apolaires bioactifs ou non déjà identifiés dans les feuilles des deux espèces. / The traditional herbal medicines are widely used by African people. But their quality control is difficult, because they are complex mixtures of several herbal drugs or herbal drugs preparations. Their origin is often unknown and/or highly variable. The chromatographic profile of phytochemical metabolites is an important tool for quality assessment of these products.The objective of this work is to propose a protocol for sample preparation and liquid chromatographic and gas chromatographic profiling of non-polar metabolites for quality assessment of africain traditional herbal medicinal products.The methodology is based on the chemometric treatment of chromatographic profiles of non-polar metabolites from different batches of leaves of Combretum micranthum and Mitracarpus scaber.Metabolic profiling is carried out by non-aqueous liquid chromatography on Porous Graphitic Carbon and by high temperature gas chromatography, coupled with mass spectrometry, after extraction with dichloromethane and removal of chlorophyll adsorbed on activated charcoal.The chemometric data analysis using PLS-discriminant analysis with or without orthogonal signal correction applied to the chromatographic profiles of leaves of Combretum micranthum and Mitracarpus scaber showed small differences between batches of each herbal drug, and a clear differentiation two herbal drugs.Both analyses by liquid chromatography and gas chromatography methods detect most non-polar metabolites bioactive or/not already identified in the leaves of both species.

Solubility prediction usually refers to prediction of the intrinsic aqueous solubility, which is the concentration of an unionised molecule in a saturated aqueous solution at thermodynamic equilibrium at a given temperature. Solubility is determined by structural and energetic components emanating from solid-phase structure and packing interactions, solute–solvent interactions, and structural reorganisation in solution. An overview of the most commonly used methods for solubility prediction is given in Chapter 1. In this thesis, we investigate various approaches to solubility prediction and solvation model development, based on informatics and incorporation of empirical and experimental data. These are of a knowledge-based nature, and specifically incorporate information from the Cambridge Structural Database (CSD). A common problem for solubility prediction is the computational cost associated with accurate models. This issue is usually addressed by use of machine learning and regression models, such as the General Solubility Equation (GSE). These types of models are investigated and discussed in Chapter 3, where we evaluate the reliability of the GSE for a set of structures covering a large area of chemical space. We find that molecular descriptors relating to specific atom or functional group counts in the solute molecule almost always appear in improved regression models. In accordance with the findings of Chapter 3, in Chapter 4 we investigate whether radial distribution functions (RDFs) calculated for atoms (defined according to their immediate chemical environment) with water from organic hydrate crystal structures may give a good indication of interactions applicable to the solution phase, and justify this by comparison of our own RDFs to neutron diffraction data for water and ice. We then apply our RDFs to the theory of the Reference Interaction Site Model (RISM) in Chapter 5, and produce novel models for the calculation of Hydration Free Energies (HFEs).

The focus of this work is to investigate the dissolution of MW25, a non-radioactive simulant of UK high-level nuclear waste borosilicate glass, and to predict its performance in the near field of a geological repository. A single-pass flow-through (SPFT) experimental system was used to measure the forward dissolution rates of MW25. Experiments were conducted in two parts. Experiment Part 1 considers the dissolution of the waste glass in deionised water at 40 and 90 oC and circum-neutral pH. Experiment Part 2 considers the dissolution of the waste glass in simulant groundwaters, with similar compositions to groundwaters of Callovo-Oxfordian clay (lower-strength sedimentary rock (LSSR)) and Borrowdale Volcanic Group rocks (higher-strength rock (HSR)), at 40 oC and pH 7. The forward dissolution rate measured in deionised water was found to be approximately one order of magnitude higher at 90 oC than at 40 oC. A similar release was observed for Si, Mg and Al at 40 oC and 90 oC, whereas the B, Cs, Na, Li and Mo showed an order of magnitude increase when the temperature was increased from 40 to 90 oC for low q/S values. The activation energy (Ea) of the reactions shows that the dissolution process is a surface phenomenon. At 90 oC the net effect of the processes governing MW25 dissolution led to the preferential release of boron and alkali metals relative to the release of Si during the transient dissolution stage, accompanied by an increase in the concentration of silicic acid. This suggests that the solution activity of silicic acid at a higher temperature has a weak influence on the release of the mobile elements. The forward dissolution rate measured in LSSR simulant groundwater was found to be slightly higher than that measured in HSR simulant groundwater. The dissolution behaviour of MW25 in both groundwaters is consistent with its behaviour in deionised water at 40 oC, with the dissolution rates of elements increasing as flow rates were increased. However, forward dissolution rates measured in the simulant groundwaters were lower than the forward dissolution rates measured in deionised water under these experimental conditions. This is attributable to the interaction of the components of the simulant groundwaters with the glass, as revealed by post-reaction surface analyses, and a consequential lower alkalinity of the leachates collected in the experiments with simulant groundwater than in deionised water. Reactive chemical transport simulations of waste glass dissolution and radionuclide release in a hypothetical near field were conducted over a time span of a million years with GoldSim. The results showed that enclosing the waste glass in a steel canister covered by a copper canister and emplacing the waste package in a granite host rock is optimal for the long-term isolation of the radionuclides. The waste glass was found to play a significant role in the overall performance of the near field. This study features a new method for estimating the surface area of reacted glass powder more accurately than the geometric surface area estimate, which is the preferred standard method among researchers.

Ce travail de thèse est une étude par des méthodes de simulation de structure électronique du phénomène de dégradation en milieu aqueux de la zircone yttriée. La zircone yttriée est notamment utilisée pour la fabrication de prothèses dont la durée de vie dépend du matériau et de son environnement. Pour ces applications, la zircone yttriée est de structure tétragone, mais en fonction du dopage en yttrium et de l'environnement, cette phase est en compétition avec des structures monoclinique et cubique. Cette compétition est cruciale dans ce travail car elle peut à la fois, augmenter la résistance, ou favoriser la détérioration de ce matériau. L'étude réalisée se concentre sur des taux de dopage inférieurs à 20% mol. en oxyde d'yttrium Y2O3.Dans un premier temps, les structures atomiques d'équilibre à basse température ont été déterminées dans les trois phases en utilisant une méthode de calcul basée sur la Théorie de la Fonctionnelle de la Densité, dans l'approximation de la densité locale. Les résultats incluent de nouvelles structures qui n'ont jusqu'alors pas été discutées dans la littérature et qui sont cohérentes avec le diagramme de phase de la zircone yttriée à basse température. Une analyse plus détaillée suggère que le mécanisme de stabilisation de la zircone yttriée tetragonale est un effet du dépistage ionocovalent particulièrement efficace dans cette phase et dont la signature dans la structure s'exprime par la présence d'ions zirconium en coordination 7. Ceci représente un point important permettant de lier stabilité et structure dans ces systèmes. Une deuxième partie de ce travail est consacrée à l’effet de l'eau dans la zircone yttriée en volume. Pour conclure, ce manuscrit représente une contribution originale à la compréhension de mécanismes à l'échelle atomique qui sont à l'origine des propriétés de la zircone yttriée et de ses applications.yttriée et de ses applications. / This PhD thesis is an electronic structure simulation work to study the stabilization mechanism of yttria stabilized zirconia (YSZ) and the phenomena of the degradation of YSZ due to the presence of an aqueous media. YSZ is used especially in dental and orthopedics application sbut its service depends on the environment. For these biomedical applications a crystallographic tetragonal YSZ (t-YSZ) structure is used, but depending on the concentration of yttria (Y2O3) and the environment, this tetragonal structure is thermodynamically in competition with a monoclinic and cubic phases. This competition is crucial in this work, because it has both effects : increase the resistance or promote the degradation of this material. The study is conducted for Y2O3 concentrations less than 20% mol. First, atomic structures of the three phases at low temperature were determined using density functional theory (DFT)with the local density approximations (LDA). The results include new structures that were not discussed in the literature and which are consistent with the phase diagram of YSZ at low temperature. A more detailed analysis suggests that the stabilization mechanism in YSZ is due to an effective ionocovalent screening : particularly in t-YSZ phase, its signature is expressed in Zr-ions with a coordination number of 7. This represents an important point for linking stability and structure in these systems. A second part of this work is devoted to the effect of water on YSZ bulk systems which leads to low temperature degradation (LTD) of YSZ based bioceramics materials. In conclusion, this PhD thesis represents an original contribution to the understanding of the mechanism and properties of YSZ and its applications at the atomic scale.

This thesis describes the synthesis, characterisation and application of artificial metalloenzymes as catalysts. The focus was on two mutants of SCP-2L (SCP-2L A100C and SCP-2L V83C) both of which possess a hydrophobic tunnel in which apolar substrates can accumulate. The crystal structure of SCP-2L A100C was determined and discussed with a special emphasis on its hydrophobic tunnel. The SCP-2L mutants were covalently modified at their unique cysteine with two different N-ligands (phenanthroline or dipicolylamine based) or three different phosphine ligands (all based on triphenylphosphine) in order to increase their binding capabilities towards metals. The metal binding capabilities of these artificial proteins towards different transition metals was determined. Phenanthroline modified SCP-2L was found to be a promising scaffold for Pd(II)-, Cu(II)-, Ni(II)- and Co(II)-enzymes while dipicolylamine-modified SCP-2L was found to be a promising scaffold for Pd(II)-enzymes. The rhodium binding capacity of two additional phosphine modified protein scaffolds was also investigated. Promising scaffolds for Rh(I)- and Ir(I)-enzymes were identified. Rh-enzymes of the phosphine modified proteins were tested in the aqueous-organic biphasic hydroformylation of linear long chain 1-alkenes and compared to the Rh/TPPTS reference system. Some Rh-enzymes were found to be several orders of magnitude more active than the model system while yielding comparable selectivities. The reason for this remarkable reactivity increase could not be fully elucidated but several potential modes of action could be excluded. Cu-, Co-, and Ni-enzymes of N-ligand modified SCP-2L A100C were tested in the asymmetric Diels-Alder reaction between cyclopentadiene and trans-azachalcone. A promising 29% ee for the exo-product was found for the phenanthroline modified protein in the presence of nickel. Further improvement of these catalyst systems by chemical means (e.g. optimisation of ligand structure) and bio-molecular tools (e.g. optimisation of protein environment) can lead to even more active and (enantio)selective catalysts in the future.

I started writing this thesis not only to obtain a doctoral degree, but also to compile in a particular way all the work that I have done during this time. The articles published during these years can only give a short overview of my research task. I decided to give my own perspective of the things I have learned and the results I have obtained. Some sections are directly the published articles, but some other are not and contain a significant amount of unpublished data. Even in some cases the published plots have been modified / altered to provide more insight or to maintain consistency. Historical perspectives often provide a deep understanding of the problems and have been briefly discussed in some chapters. This thesis contains theoretical and computer simulation studies to under-stand effects of spatial correlation on dynamics in several complex systems. Based on the different phenomena studied, the thesis has been divided into three major parts: I. Pair hydrophobicity, composition-dependent anomalies and structural trans-formations in aqueous binary mixtures II. Microscopic analysis of hydrophobic force law in a two dimensional (2D) water-like model system III. Diffusion of a tagged particle on a rugged energy landscape with spatial correlations The three parts have been further divided into ten chapters. In the following we provide part-wise and chapter-wise outline of the thesis. Part I consists of six chapters, where we focus on several important aqueous binary mixtures of amphiphilic molecules. To start with, Chapter 1 provides an introduction to non-ideality often encountered in aqueous binary mixtures. Here we briefly discuss the existing ideas of structural transformations associated with solvation of a foreign molecule in water, with particular emphasis on the classic “iceberg” model. Over the last decade, several investigations, especially neutron scattering and diffraction experiments, have questioned the validity of existing theories and have given rise to an alternate molecular picture involving micro aggregation of amphiphilic co-solvents in their aqueous binary mixtures. Such microheterogeneity was also supported by other experiments and simulations. In Chapter 2, we present our calculation of the separation dependence of potential of mean force (PMF) between two methane molecules in water-dimethyl sulfoxide (DMSO) mixture, using constrained molecular dynamics simulation. It helps us to understand the composition-dependence of pair hydrophobicity in this binary solvent. We find that pair hydrophobicity in the medium is surprisingly enhanced at DMSO mole fraction xDMSO ≈ 0.15, which explains several anomalous properties of this binary mixture – including the age-old mystery of DMSO being a protein stabilizer at lower concentration and protein destabilizer at higher concentration. Chapter 3 starts with discussion of non-monotonic composition dependence of several other properties in water-DMSO binary mixture, like diffusion coefficient, local composition fluctuation and fluctuations in total dipole moment of the system. All these properties exhibit weak to strong anomalies at low solute concentration. We attempt to provide a physical interpretation of such anomalies. Previous analyses often suggested occurrence of a “structural transformation” (or, microheterogeneity) in aqueous binary mixtures of amphiphilic molecules. We show that this structural transformation can be characterized and better understood under the purview of percolation theory. We define the self-aggregates of DMSO as clusters. Analysis of fractal dimension and cluster size distribution with reference to corresponding “universal” scaling exponents, combined with calculation of weight-averaged fraction of largest cluster and cluster size weight average, reveal a percolation transition of the clusters of DMSO in the anomalous concentration range. The percolation threshold appears at xDMSO ≈ 0.15. The molecular picture suggests that DMSO molecules form segregated islands or micro-aggregates at concentrations below the percolation threshold. Close to the critical concentration, DMSO molecules start forming a spanning cluster which gives rise to a bi-continuous phase (of water-rich region and DMSO-rich region) beyond the threshold of xDMSO ≈ 0.15. This percolation transition might be responsible for composition-dependent anomalies of the binary mixture in this low concentration regime. Similar phenomenon is observed for another amphiphilic molecule – ethanol, as discussed in Chapter 4. We again find composition dependent anomalies in several thermophysical properties, such as local composition fluctuation, radial distribution function of ethyl groups and self-diffusion co-efficient of ethanol. Earlier experiments often suggested distinct structural regimes in water-ethanol mixture at different concentrations. Using the statistical mechanical techniques introduced in the previous chapter, we show that ethanol clusters undergo a percolation transition in the anomalous concentration range. Despite the lack of a precise determination of the percolation threshold, estimate lies in the ethanol mole fraction range xEtOH ≈ 0.075 - 0.10. This difficulty is probably due to transient nature of the clusters (as will be discussed in Chapter 6) and finite size of the system. The scaling of ethanol cluster size distribution and the fractal behavior of ethanol clusters, however, conclusively demonstrate their “spanning” nature. To develop a unified understanding, we further study the composition-dependent anomalies and structural transformations in another amphiphilic molecule, tertiary butyl alcohol (TBA) in Chapter 5. Similar to the above-mentioned aqueous binary mixtures of DMSO and ethanol, we demonstrate here that the anomalies occur due to local structural changes involving self-aggregation of TBA molecules and percolation transition of TBA clusters at xTBA ≈ 0.05. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration ≈ 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of the largest water cluster. This second transition gives rise to another set of anomalies around. We conclude this part of the thesis with Chapter 6, where we introduce a novel method for understanding the stability of fluctuating clusters of DMSO, ethanol and TBA in their respective aqueous binary mixtures. We find that TBA clusters are the most stable, whereas ethanol clusters are the most transient among the three representative amphiphilic co-solvents. This correlates well with the amplitude of anomalies observed in these three binary mixtures. Part II deals with the topic of hydrophobic force law in water. In the introductory Chapter 7 of this part, we briefly discuss the concept of hydrophobicity which is believed to be of importance in understanding / explaining the initial processes involved in protein folding. We also discuss the experimental observations of Israelachvili (on the force between hydrophobic plates) and the empirical hydrophobic force law. We briefly touch upon the theoretical back-ground, including Lum-Chandler-Weeks theory. We conclude this chapter with a brief account of relevant and important in silico studies so far. In Chapter 8, we present our studies on Mercedes-Benz (MB) model – a two dimensional model system where circular disks interact with an anisotropic potential. This model was introduced by Ben-Naim and was later parametrized by Dill and co-workers to reproduce many of the anomalous properties of water. Using molecular dynamics simulation, we show that hydrophobic force law is indeed observed in MB model, with a correlation length of ξ=3.79. The simplicity of the model enables us to unravel the underlying physics that leads to this long range force between hydrophobic plates. In accordance with Lum-Chandler-Weeks theory, density fluctuation of MB particles (leading to cavitation) between the hydrophobic rods is clearly distinguishable – but it is not sufficiently long ranged, with density correlation extending only up to ζ=2.45. We find that relative orientation of MB molecules plays an important role in the origin of the hydrophobic force in long range. We define appropriate order parameters to capture the role of orientation, and briefly discuss a plausible approach of an orientation-dependent theory to explain this phenomenon. Part III consists of two chapters and focuses on the diffusion of a Brownian particle on a Gaussian random energy landscape. We articulate the rich history of the problem in the introductory Chapter 9. Despite broad applicability and historical importance of the problem, we have little knowledge about the effect of ruggedness on diffusion at a quantitative level. Every study seems to use the expression of Zwanzig [Proc. Natl. Acad. U.S.A, 85, 2029 (1988)] who derived the effective diffusion coefficient, Deff =D0 exp (-β2ε2 )for a Gaussian random surface with variance ε, but validity of the same has never been tested rigorously. In Chapter 10, we introduce two models of Gaussian random energy surface – a discrete lattice and a continuous field. Using computer simulation and theoretical analyses, we explore many different aspects of the diffusion process. We show that the elegant expression of Zwanzig can be reproduced ex-actly by Rosenfeld diffusion-entropy scaling relationship. Our simulations show that Zwanzig’s expression overestimates diffusion in the uncorrelated Gaussian random lattice – differing even by more than an order of magnitude at moderately high ruggedness (ε>3.0). The disparity originates from the presence of “three-site traps” (TST) on the landscape – which are formed by deep minima flanked by high barriers on either side. Using mean first passage time (MFPT) formalism, we derive an expression for the effective diffusion coefficient, Deff =D0 exp ( -β2ε2)[1 +erf (βε/2)]−1 in the presence of TSTs. This modified expression reproduces the simulation results accurately. Further, in presence of spatial correlation we derive a general expression, which reduces to Zwanzig’s form in the limit of infinite spatial correlation and to the above-mentioned equation in absence of correlation. The Gaussian random field has an inherent spatial correlation. Diffusion coefficient obtained from the Gaussian field – both by simulations and analytical methods – establish the effect of spatial correlation on random walk. We make special note of the fact that presence of TSTs at large ruggedness gives rise to an apparent breakdown of ergodicity of the type often encountered in glassy liquids. We characterize the same using non-Gaussian order parameter, and show that this “breakdown” scales with ruggedness following an asymptotic power law. We have discussed the scope of future work at the end of each chapter when-ever appropriate.

L’objectif de ce travail a été de mettre en place un système original capable de produire et stocker l’énergie à partir de la lumière dans un dispositif unique. Pour ce faire, nous avons choisi d’adapter l’électrode photo-sensible d’une DSSC sur un système d’accumulateur électrochimique. La première partie de ce travail a été de mettre en place la technique de spectroscopie EIS-λ, basée sur la spectroscopie d’impédance électrochimique couplée à un balayage en longueur d’onde de la lumière incidente. L’objectif de cette mesure est d’identifier et de quantifier les différents mécanismes de transfert électroniques, photo-dépendant ou non, ayant lieu à la surface de l’électrode photo-sensible, ainsi que les processus de désactivation des états excités des sensibilisateurs. Nous nous sommes ensuite penchés sur la recherche des conditions optimales d’utilisation de deux coadsorbants — l’acide bismethoxyphenyl phosphinique ou BMPP et l’acide chenodesoxycholique ou CDCA — avec le sensibilisateur de référence N719. Nous avons également quantifié leurs activités shield et anti-π-stacking grâce à la technique EIS-λ. Nous avons ainsi réalisé une DSSC présentant un rendement de photo-conversion de 8,3% en utilisant le co-adsorbant BMPP dans un ratio [co-ads]/[S] = 1, contre 7,2% dans les conditions de référence — avec le coadsorbant CDCA utilisé dans un ratio [co-ads]/[S] = 10. Par la suite, nous avons imaginé et synthétisé trois complexes de ruthénium hydrophiles originaux dont nous avons testé le pouvoir de photo-conversion dans des DSSC à électrolyte 100% aqueux, en présence des co-adsorbants sélectionnés. Ces systèmes ont permis de dépasser le pouvoir de photo-conversion du sensibilisateur N719, dans l’eau, avec un rendement maximal obtenu de 1,31%. Enfin, nous avons sélectionné la meilleure combinaison sensibilisateur / co-adsorbant afin de réaliser une électrode photo-sensible que nous avons implémentée dans un système original d’accumulateur électrochimique à base d’électrolytes aqueux. Le système ainsi mis en place constitue aujourd’hui le premier dispositif fonctionnel d’accumulateur 100% aqueux photo-rechargeable à partir d’une électrode mésoporeuse photo-sensibilisée / The aim of this work was to imagine and to develop a new system able to produce and store energy from sunlight in a single device. For this purpose, the photo-sensitive electrode of a DSSC has been adapted to an electrochemical accumulator. The first part of this work was to develop a new spectroscopic technique, called EIS-λ and based on electrochemical impedance spectroscopy combined to incident light wavelength sweep. This technique has proved its capacity to identify and quantify the different mechanisms of electron transfer over the surface of the semiconducting material and their dependency to incident wavelength, together with the various deactivation processes of the excited state of the sensitizer. Then, we investigated the best conditions to use two different co-adsorbents — namely bis-methoxyphenylphosphinic acid, or BMPP, and chenodesoxycholic acid, or CDCA — with the reference sensitizer N719. The shield and anti-π-stacking activities of the two coadsorbents has been characterized using EIS-λ technique. DSSC with a photo-conversion yield of 8,3% has been prepared in the lab using BMPP in a ratio [co-ads]/[S] = 1 while reference conditions – namely with CDCA in a ratio [co-ads]/[S] = 10 — only gave 7,2%. Besides, we have designed and synthesized three original hydrophilic ruthenium complexes, then tested their photo-conversion properties in DSSC with 100% aqueous electrolytes. Such systems, with the selected co-adsorbents, allowed 1,31% photo-conversion yield to be obtained, which is two times larger than the efficiency exhibited by N719 in the same electrolyte conditions. Finally the best combination sensitizer / co-adsorbent has been selected to achieve a photo-sensitive electrode which has been implemented in an original electrochemical accumulator with aqueous electrolytes. This system represents the first functional device of a 100% aqueous accumulator, which is photo-reloadable with a photosensitized mesoporous electrode

Dans ce travail de thèse, la synthèse de nanoparticules d'argent (Ag) est réalisée par une méthode simple, efficace et rapide basée sur la réduction du nitrate d'argent (AgNO3) dans un milieu organique (éthanol) sous chauffage par irradiation micro-ondes (MW) pendant quelques secondes en présence d'une émulsion aqueuse de copolymère latex. Les expériences ont été effectuées soit de manière séquentielle en faisant varier les paramètres expérimentaux les uns après les autres (approche classique) ou bien en moyennant la méthodologie des plans d'expérience qui sert à varier simultanément ces conditions expérimentales dans le but à la fois d'optimiser et d'évaluer l'impact de ces facteurs sur les propriétés physico-chimiques des particules produites. L'objectif est d'arriver à préparer un maximum de concentration en nanoparticules d'argent avec un minimum de concentration en copolymère latex et en AgNO3. Les nanoparticules préparées sont trouvées extrêmement stables en solution colloïdale avec des distributions de taille très étroites, ce qui confirme la qualité élevée et le diamètre uniforme des nanoparticules obtenues par l'approche de synthèse micro-ondes. Ceci pourrait être probablement dû à l'effet de stabilisation produit par les molécules du latex, qui est un bon environnement pour contrôler efficacement la croissance de nanoparticules métalliques d'argent. En tant que principal objectif d'une telle réalisation de la synthèse de nanoparticules d'argent par la méthode MW ouvre la voie à l'exploitation d'effets plasmoniques de surface dans des réactions photocatalytiques en utilisant des structures semi-conductrices bien définies (Bi2O3, In2O3, TiO2...). / In this thesis work, the synthesis of silver nanoparticles (Ag) is carried out by a simple, efficient and fast method based on the reduction of silver nitrate (AgNO3) in an organic medium (ethanol) under heating by micro irradiation (MW) for a few seconds in the presence of an aqueous emulsion of latex copolymer. The experiments were performed either by varying the experimental parameters one after the other (classical approach) or by means of the experimental design methodology which serves to vary simultaneously these experimental conditions in order to both optimize and evaluate the impact of these factors on the physicochemical properties of the nanoparticles. The main goal is to prepare a maximum concentration of silver nanoparticles with a minimum concentration of latex copolymer and AgNO3. The prepared nanoparticles were found to be extremely stable in colloidal solution with very narrow size distributions, which confirms the high quality and the uniform diameter of the nanoparticles obtained by the microwave synthesis approach. This could possibly be due to the stabilizing effect produced by the latex molecules, which is a good environment for effectively controlling the growth of metallic silver nanoparticles. As the main objective of such realization of the silver nanoparticle synthesis by the MW method opens the way to the exploration of surface plasmonic effects in photocatalytic reactions using well-defined semiconducting structures (Bi2O3 , In2O3, TiO2 ...).

La modélisation du transport réactif du contaminant en milieu poreux est un problème complexe cumulant les difficultés de la modélisation du transport avec celles de la modélisation de la chimie et surtout du couplage entre les deux. Cette modélisation conduit à un système d'équations aux dérivées partielles et algébriques dont les inconnues sont les quantités d'espèces chimiques. Une approche possible, déjà utilisée par ailleurs, est de choisir la méthode globale DAE : l'utilisation d'une méthode de lignes, correspondant à la discrétisation en espace seulement, conduit à un système différentiel algébrique (DAE) qui doit être résolu par un solveur adapté. Dans notre cas, on utilise le solveur IDA de Sundials qui s'appuie sur une méthode implicite, à ordre et pas variables, et qui requiert à chaque pas de temps la résolution d'un grand système non linéaire associé à une matrice jacobienne. Cette méthode est implémentée dans un logiciel qui s'appelle GRT3D (Transport Réactif Global en 3D). Le présent travail présente une amélioration de la méthode GDAE, du point de vue de la performance, de la stabilité et de la robustesse. Nous avons ainsi enrichi les possibilités de GRT3D, par la prise en compte complète des équations de précipitation-dissolution permettant l'apparition ou la disparition d'une espèce précipitée. En complément de l'étude de la méthode GDAE, nous présentons aussi une méthode séquentielle non itérative (SNIA), qui est une méthode basée sur le schéma d'Euler explicite : à chaque pas de temps, on résout explicitement l'équation de transport et on utilise ces calculs comme données pour le système chimique, résolu dans chaque maille de façon indépendante. Nous présentons aussi une comparaison entre cette méthode et l'approche GDAE. Des résultats numériques pour deux cas tests, celui proposé par l'ANDRA (cas-test 2D) d'une part, celui proposé par le groupe MoMas (Benchmark "easy case") d'autre part, sont enfin présentés, commentés et analysés. / Modeling reactive transport of contaminants in porous media is a complex problem combining the difficulties of modeling the trasport with those of modeling the chemistry and especially the coupling between the two .This model leads to a system of partial differential equations and algebraic equations whose unknowns are the quantities of chemical species. One approach , already used elsewhere , is choosing the global DAE method : using the method of lines, discretization in space only, leads to a differential algebraic system (DAE ) to be solved by a suitable solver . In our case , the solver IDA Sundials relies on an implicit method, order is used but not variables, and requires at each time solving a large nonlinear system associated with a Jacobian matrix . This method is implemented in a software called GRT3D (Global Reactive Transport in 3D). This paper presents an improved GDAE method , from the standpoint of performance, the stability and robustness. We have enriched the possibilities of GRT3D , by taking full account of the equations of dissolution – precipitation for the appearance or disappearance of precipitated species. In addition to the study of the GDAE method, we also present a non-iterative sequential method ( SNIA ) which is a method based on the explicit Euler scheme : at each time step, we explicitly solve the transport equation and we use these calculations as data for the chemical system which is resolved in each cell independently. We also present a comparison between this method and GDAE approach . Numerical results for two test cases , one proposed by ANDRA ( 2D test case ) on one hand and one proposed by the group MOMAS ( Benchmark "easy case" ) on the other hand, are finally presented , discussed and analyzed.