Cette thèse porte sur l'effet de l'incorporation du polymère adsorbant polyéthylène glycol (PEG) sur les propriétés structurelles et élastiques des mésophases lamellaires lyotropes. En particulier, ces phases lamellaires dopées au polymère sont d'un grand intérêt pour la compréhension des interactions inter-membranaires médiées par la macromolécule. Dans un premier temps, le module élastique de courbure des membranes a été étudié le long de plusieurs lignes de dilution de polymère. Il a été obtenu à partir des mesures des couplages quadrupolaires par spectroscopie de résonance magnétique nucléaire (RMN) à l'état solide de deutérium des molécules de cotensioactif perdeuteré incorporée dans la membrane. En présence du polymère adsorbé, nous avons constaté que la valeur du module élastique de courbure augmentait d'environ 20% dès que la solution de polymère était semi-diluée. Deuxièmement, nous discutons le coefficient de diffusion du polymère dans l'eau et confiné dans la phase lamellaire. La structure des mésophases a été étudiée par diffusion aux petits angles par rayons X et par microscopie électronique après cryofracture. Finalement, les mesures directes du module de compressibilité des mésophases lamellaires ont également été réalisées. / This thesis deals with the effect of the incorporation of the adsorbing polymer polyethylene glycole (PEG) on the structural and elastic properties of lyotropic lamellar mesophases. In particular, these polymer doped-lamellar phases are of great interest for understanding the intermembrane interactions mediated by the macromolecule. Firstly, the bending elastic modulus of the membranes has been investigated along several dilution lines of polymer. It was obtained from the measurements of quadrupolar splittings by deuterium solid state Nuclear Magnetic Resonance (NMR) spectroscopy of the perdeuterated cosurfactant molecule embedded in the membrane. In the presence of the adsorbed polymer the value of the bending elastic modulus was found to increase of about 20% as soon as the polymer solution becomes semi-diluted. Secondly, the diffusion coefficient of the polymer in water and confined in the lamellar phase is discussed. The structure of the mesophases was investigated by small angle X-ray scattering and freeze-fracture electon microscopy. Finally, the direct measurements of the compressibility modulus of the lamellar mesophases were also carried out.

No description available.

La greffe lamellaire postérieure, ou greffe endothéliale, consiste à remplacer l’endothélium défectueux d’une cornée par un endothélium sain prélevé sur un donneur décédé, en laissant en place l’épithélium et le stroma du patient. La découpe du greffon lamellaire endothéliale est l’une des étapes critiques de la greffe de cornée postérieure. Supérieur au microkeratome pour la réalisation de capots cornéens peu profonds, le laser femtoseconde montre cependant des résultats plutôt décevant concernant les découpes cornéennes profondes. L’objectif de cette thèse est d’étudier et d’optimiser les découpes lamellaires endothéliales cornéennes, réalisées au microkeratome et au laser femtoseconde. Ces optimisations passent par le développement d’un bioréacteur cornéen, ainsi que par l’amélioration des techniques d’estimation de la viabilité endothéliale cornéenne / Posterior lamellar graft, also named endothelial graft, consist in a replacement of a defective corneal endothelium by a healthy one take on a deceased donor. The epithelial and stromal layers of the patient stay untouched. A critical step of this technic is the preparation of the lamellar graft. Femtosecond lasers are better in comparison with microkeratome for low depth lamellar cut. However, femtosecond high depth corneal lamellar cuts show disappointing results. The aim of this thesis is to study and optimize corneal endothelial lamellar cuts, realized by microkeratome and femtosecond laser. Development of a corneal bioreactor and improve of corneal endothelial viability assessment are necessary for the realization of these objectives

Dans cette thèse, on a étudié les propriétés rhéologiques et moussantes de phases de bicouches, de type lamellaire et éponge, en utilisant le système expérimental SDS/hexanol/saumure. On a également préparé des mousses avec ces deux phases de bicouches, dont on a étudié la stabilité et les mécanismes d’évolution dans le temps. En premier lieu, les propriétés rhéologiques de la phase éponge ont été examinées. Les échantillons ayant une fraction volumique de membrane phi ≥ 0.08 se comportent comme des fluides Newtoniens. Avec les moins concentrés, phi = 0.05 et 0.024, un changement de viscosité est observé à environ 1000 et 100 s⁻¹, respectivement. Ce changement pourrait être lié à une transition de la phase éponge vers une phase lamellaire induite par cisaillement. Les changements de viscosité qui suggèrent une transition éponge-lamellaire induite par l’écoulement ont été plus facilement détectés pour l'échantillon de fraction volumique phi = 0.024. Pour cet échantillon, il a été constaté qu’à des températures plus basses ou lors de l’ajout d’un polymère hydrosoluble (PEG), la variation de la viscosité liée à la transition de phase éponge-lamellaire se produit à des valeurs inférieures de la vitesse de cisaillement. L’étude des propriétés rhéologiques de la phase lamellaire a ensuite été menée. Les expériences ont révélé le comportement de gel faible des échantillons. A une fréquence de 10 rad/s et dans un intervalle de température compris entre 5 à 50 °C, il n’y a aucun changement perceptible des modules G’ et G’’, donc pas de transition de phase, sauf pour les échantillons les moins concentrés : dans ce cas, la température a un effet plus marqué, et la structure lamellaire évolue probablement. Lorsque le taux de cisaillement augmente, il a été observé que les échantillons avec phi ≥ 0.10 présentent une forte augmentation de la viscosité à partir d’une valeur seuil du taux de cisaillement. Cette observation, combinée avec des résultats de Rhéo-SAXS, a permis de conclure qu’il y a une transition vers une phase de vésicules (ou oignons) induite par l’écoulement. Les expériences de Rhéo-SAXS ont montré que, après l’arrêt du cisaillement, la phase de vésicules relaxe vers la phase lamellaire initiale au bout d’un temps typique d’une demi-heure. Enfin, des mousses ont été obtenues par incorporation de bulles d’air dans les phases lamellaire et éponge précédemment étudiées. Les mousses faites avec les phases lamellaires présentent une grande stabilité, probablement en raison de la viscosité élevée de ces gels. De plus, ces gels présentent des contraintes seuils d’écoulement faibles. Lorsque les bulles sont petites, la contrainte seuil est supérieure à la contrainte de pesanteur sur les bulles de la mousse (force d’Archimède). Mais ces bulles grossissent avec le temps (mûrissement dû aux différences de pression de Laplace entre bulles) et lorsque la contrainte de pesanteur dépasse la contrainte seuil du gel, le drainage de la mousse commence. On a constaté que la taille des bulles évoluait avec le temps en suivant une loi de puissance. Cependant, l’exposant (≈ 0.25) est plus petit que ceux trouvés pour le mûrissement d’Ostwald (0.333, valable pour des bulles isolées) ou le mûrissement des mousses (0.5). Le fait que l’exposant trouvé soit plus petit pourrait être lié à la réorientation des domaines lamellaires lors du mûrissement. Enfin, les mousses préparées avec des phases éponge présentent une faible stabilité probablement due aux passages internes entre bicouches qui forment la structure éponge, passages qui pourraient faciliter la coalescence des bulles. Deux scénarii ont été détectés lors de l’évolution de ces mousses: à basse fraction volumique de membrane, l’effondrement de la mousse commence pendant son drainage, alors que les mousses faites avec les échantillons les plus concentrés ont le temps de mûrir avant de s’effondrer. / In this thesis a study of the rheological and foaming properties of the lamellar and sponge phases of the SDS/hexanol/brine system was performed. Shear rate and temperature sweeps were done to analyze the rheology of the lamellar and sponge phases, adding frequency sweeps for the lamellar phase samples. Also, foamability and foam stability tests of foams made with these two phases were done. Sponge phase samples with membrane volume fractions phi ≥ 0.08 showed a Newtonian behavior, whereas in the less concentrated ones, phi 0.05 and 0.024, a change in viscosity was seen at shear rate values near to 1000 and 100 s ⁻¹, respectively. This change can be linked to a shear induced transition sponge to lamellar phase. Results indicate that temperature and the addition of the hydrosoluble polymer PEG affect the shear rate value at which this transition occurs. Lamellar phase samples with phi ≥ 0.10 presented a sharp increase in viscosity at intermediate shear rate values. The standard rheology technique together with Rheo-SAXS experiments allowed us to infer that there is a shear induced phase transition to vesicle phase. Rheo-SAXS data confirmed that the average interlamellar vesicle phase decreases by the effect of shear rate, and, when shear is stopped, the vesicle structure is relaxed and goes back to the lamellar phase after certain time. Foams made with lamellar phase samples showed a high stability and it was found that the time evolution of the bubble diameter follows a power law equation with exponents smaller than those reported for coarsening and Ostwald ripening. The small values of these exponents seem to be related with orientation defects of the liquid crystalline phase. On the opposite, the foams made with the sponge phase samples presented poor stability, as a possible consequence of the passages that form their structure that could facilitate coalescence of bubbles.

The aim of this thesis was to assess the degree of conformity between the mechanical properties evaluated by numerical simulation in software MAGMA5 and the measured values of hardness and ultimate tensile strength of lamellar graphite iron castings. The theoretical part of this thesis deals with the classification of cast iron, structural components of lamellar graphite iron, and the factors defining the resulting mechanical properties of the material. The practical part presents an attempt to find empirical dependencies between input parameters and results evaluated by simulation software. At the end, an analysis of the correlation between reality and simulation software is performed.

Ce travail de thèse concerne l’étude de nouveaux matériaux hybrides organiques-inorganiques lamellaires magnétiques et luminescents synthétisés par voie hydrothermale. Ces matériaux ont été obtenus à partir de sels de métaux de transition de configuration électronique 3d (Cu2+, Co2+, Mn2+, Zn2+) et de molécules organiques de basse symétrie constituées d’au moins un acide phosphonique greffé sur une plateforme rigide aromatique (phényle ou naphtalène). Le choix du cation métallique ainsi que l’ajout d’autres fonctions (halogène : F, Cl, Br, I, acide carboxylique ou méthyle) sur ces systèmes cycliques ont conduit à des matériaux hybrides bidimensionnels aux architectures et propriétés physiques (luminescence, magnétisme et/ou couplage magnétoélectrique) diverses. La compréhension du lien entre les propriétés structurales et physiques de ces métallophosphonates ouvre la voie vers la conception de nouveaux matériaux multifonctionnels originaux. / This PhD work deals with the study of new lamellar magnetic and luminescent organic-inorganic hybrid materials synthesized by hydrothermal process. These materials were obtained from 3d transition metal salts (Cu2+, Co2+, Mn2+, Zn2+) and low symmetric organic molecules bearing at least one phosphonic acid function grafted onto a rigid aromatic platform (phenyl or naphthalene). The choice of the metal cation as well as additional functions (halogen: F, Cl, Br, I, carboxylic acid or methyl) on these cyclic systems led to two-dimensional hybrid materials with various architectures and physical properties (luminescence, magnetism and/or magnetoelectric coupling). Understanding the interconnections between the structural and physical properties of these metal phosphonates paves the way for the design of novel multifunctional materials.

[pt] A estearamidopropil dimetilamina (SAPDMA) é um surfactante presente em diversos cosméticos do mercado, principalmente em condicionadores e máscaras capilares. Devido ao seu caráter pseudo-catiônico, essa amidoamina alquílica neutraliza as cargas negativas presentes no cabelo, diminuindo o frizz e deixando-os macios e fáceis de pentear. Além disso, essa molécula é uma ótima substituta aos catiônicos tradicionais, por apresentar menor toxicidade aquática e maior biodegradabilidade. Porém, a SAPDMA é uma molécula não-iônica e insolúvel em água pura, tornando-se positivamente carregada apenas quando em menores valores de pH. Atualmente, sabe-se que diferentes ácidos podem originar formulações com diferentes propriedades físico-químicas, porém este fenômeno ainda não é totalmente compreendido. Este trabalho visa avaliar sistemas com 8 ácidos diferentes, e compreender como essa escolha tem impacto nas estruturas coloidais formadas pelo surfactante. Além disso, também tem como objetivo entender como a presença de álcool graxo influencia na formação da fase líquido-cristalina lamelar, alterando as propriedades finais desses diferentes sistemas. As técnicas de caracterização adotadas neste estudo foram a microscopia óptica convencional e de polarização, o espalhamento de luz dinâmico (DLS), o espalhamento de raios X a baixos ângulos (SAXS) e a reologia. Os resultados mostram o impacto da escolha dos ácidos nas estruturas coloidais, implicando diferenças que não dependem exclusivamente da variação de pH, mas também das diferentes interações entre a SAPDMA e os ânions envolvidos. A tendência do sistema é formar a fase líquido-cristalina lamelar, mas dependendo do ácido utilizado, as lamelas podem apresentar diferentes morfologias, com alterações em sua curvatura. Dessa forma, a escolha do ácido pode impactar na formação, ou não, de vesículas, além de ter enorme papel na estabilidade dos sistemas e nas propriedades sensoriais dos produtos, as quais são fundamentais para atender as necessidades dos consumidores. Sabe-se que, por um lado, as bicamadas fornecem maior viscosidade para o sistema do que as vesículas, sendo essa uma propriedade de enorme importância para aplicação em cosméticos. Porém, por outro lado, as bicamadas mais maleáveis, as quais podem se fechar mais facilmente formando as vesículas, são uma melhor opção em sistemas de emulsões, já que conseguem estabilizar melhor as gotas de óleo dispersas. Este estudo mostra a importância de se compreender melhor esses sistemas e o impacto do ácido utilizado, para que melhores formulações possam ser elaboradas pelas indústrias de cosméticos, que já fazem uso desse surfactante em diversos produtos consumidos pela sociedade. Segundo o nosso colaborador direto, Dr. Heitor de Oliveira (Coty Inc., Darmstadt/Alemanha), este estudo foi fundamental para que o grupo de P(e)D o qual ele gerencia pudesse otimizar e gerar redução de custos em um grupo de fórmulas de condicionadores capilares, considerados como best seller entre as marcas Clairol NNE e Wella Koleston, ambas pertencentes ao grupo Coty Inc.. As respectivas fórmulas já se encontram em fase de teste final para produção. / [en] Stearamidopropyl dimethylamine (SAPDMA) is a surfactant and it has been widely used in the cosmetics industries, particularly in hair conditioners and masks. Because of its pseudo-cationic nature, this alkyl amidoamine neutralizes the negative charges of hair strands, decreasing frizz, providing greater softness and combing force reduction. Besides that, alkyl amidoamines are excellent substitutes for traditional cationic surfactants, because they present less toxicity and improved biodegradability. However, SAPDMA is insoluble in water, as it behaves as a non-ionic molecule. At low pH values, SAPDMA becomes positively charged and, consequently, soluble in water. Currently, it is known that different acids can induce different colloid structures in formulations containing SAPDMA, which have particular physico-chemical properties. From the best of our knowledge, this phenomenon it not completely understood yet. This study intends to understand how 8 different acids can impact on colloidal structures formed by SAPDMA. In addition, we also aim to understand how fatty alcohols change the final properties of these different systems. The techniques employed to characterize all systems were conventional and polarized optical microscopy, dynamic light scattering (DLS), small angle X ray scattering (SAXS) and rheology. The results revealed that the chosen acids impact differently on the colloidal structures and that the observed differences are not limited only to pH variations, but also to different interactions between SAPDMA and the anions involved, the respective conjugated bases. The systems tendency is to form lamellar liquid-crystalline phase, but depending on the chosen acid, bilayers may have different morphologies, with changes in its curvature. So, the acid choice can impact on the formation, or not, of vesicles, besides it has a huge role in systems stability as well as the sensorial properties of the products, which are key to address the consumer needs that we aim to comply with. On one hand, bilayers can provide increased viscosity that is a property of enormous importance for application in cosmetics. On the other hand, malleable bilayers can easily close and form vesicles, which are better choice for emulsion systems, since they can easier stabilize dispersed oil droplets. This study shows the importance of better understanding systems containing SAPDMA and the impact that different acids have on them. Hence, better formulations could be developed by cosmetic industries, which already use this pseudo-cationic surfactant in several products consumed by society. Accordingly to our direct collaborator Dr. Heitor de Oliveira (Coty Inc., Darmstadt/Germany), this study was essential for the R(and)D group which he manages in order to optimize and generate cost reduction in a group of conditioner formulas considered as best seller within the brands Clairol NNE as well as Wella Koleston, both from Coty Inc.. The respective formulas are already in the final teste phase for production.

Cylinder liners in heavy-duty truck engines are subjected to intense vibrations and may sustain damage from the cavitation of bubbles in the coolant liquid, with some risks of leakage and engine breakdown. An ultrasonic oscillating probe was used to simulate the pitting rates and behavior of samples extracted from cylinder liners, which are made of grey cast iron, with differences in surface roughness, glycol and inhibitor content in coolant, coolant temperature and graphite flake class; bainitic microstructures were also tested. Measurements consisted of mass losses under set intervals during experiments lasting 2.5 or 4 hours. Affected surfaces were later evaluated with scanning electron microscopy and confocal microscopy. Results indicate higher cavitation damage with: lower concentrations of glycol and absence of corrosion/cavitation inhibitors in the coolant liquid, lower liquid temperatures between 76⁰C and 90⁰C, and presence of B-type graphite class in the microstructure. Results regarding surface roughness were inconclusive. A sequence of surface damage mechanisms has been proposed, with corresponding microscope observations, to explain the mass loss trends and the associated microstructural changes over time.

[ES] La presente tesis doctoral se centró en el desarrollo y modificación de materiales microestructurados basados en sulfuros metálicos para la producción de combustibles solares. Se obtuvieron y caracterizaron dos nuevos materiales laminares basados en sulfuro de estaño y zinc, IZM-5 e ITQ-75. Dado que se pretende utilizar dichos materiales en procesos basados en el uso de energía solar, fue necesario ajustar su estructura electrónica mediante una estrategia de dopaje y su accesibilidad mediante la modificación de la composición del gel de síntesis o mediante métodos posteriores a la síntesis. Se probaron diferentes agentes dopantes como cobre, cobalto, níquel y hierro, así como la inserción de un complejo de rutenio. Los más exitosos fueron el cobre y el cobalto, ya que con su presencia es posible reducir el valor de la band gap a 2,0 eV, un valor dentro del rango óptimo para procesos de producción de combustibles solares. Cuando estos agentes dopantes estuvieron presentes en el gel de síntesis de IZM-5, se descubrió que no se obtenía el patrón de difracción esperado, sino uno de un nuevo material, denominado ITQ-76. Al igual que con las zeolitas, los primeros intentos para permitir el acceso a los centros fotoactivos consistieron en liberar la microporosidad, la superficie interna, mediante la eliminación del agente orgánico director de estructura utilizado durante el proceso de síntesis. Se intentó alternativamente mejorar la superficie externa (tamaño de partícula o mesoporosidad). De las diferentes estrategias probadas, se descubrió que variar la composición del gel de síntesis fue la más exitosa. Se probaron la inserción de sacáridos, previamente estudiados en la literatura como agentes inductores de mesoporosidad, y el aumento de la viscosidad del gel de síntesis para disminuir el tamaño de cristal final. Sin embargo, la presencia de sacáridos no condujo a la formación de un sistema mesoporoso; la mejora en la accesibilidad se debió a la disminución del tamaño de partícula. Al aumentar la viscosidad del gel, también fue posible disminuir el tamaño promedio de los cristales y, en consecuencia, aumentar la superficie externa. Después de la modificación de las estructuras estudiadas con el fin de obtener una amplia gama de propiedades, se evaluó su rendimiento fotocatalítico mediante la reacción de ruptura de la molécula de agua. Parecía existir una relación tipo "volcano" entre el rendimiento fotocatalítico y la superficie externa. Según la literatura revisada, este comportamiento podría explicarse por el equilibrio entre el aumento de los centros activos disponibles y el aumento de los defectos en la superficie, los cuales son centros potenciales de recombinación. En cuanto a la relación entre el rendimiento fotocatalítico y el valor de la band gap, nuevamente parece existir una relación tipo "volcano". Según la bibliografía revisada, se encontró que con la reducción del valor de la band gap aumenta el número de fotones absorbidos y, como tal, se espera que aumente el rendimiento. Sin embargo, es necesario que las cargas fotogeneradas tengan un potencial suficiente para participar en la reacción deseada. Como resultado, por debajo de cierto valor de band gap, las cargas fotogeneradas ya no tienen un potencial suficiente y, por ello, el rendimiento disminuye. De las diferentes muestras probadas, las modificadas con sacarosa destacaron por tener el mejor rendimiento. Hasta ahora no ha sido posible desentrañar el fenómeno detrás de esta mayor reactividad. Por lo tanto, se requiere una caracterización más detallada de estas muestras para comprender cómo la presencia del componente orgánico influye en la estructura electrónica del material y, en consecuencia, en su rendimiento. También sería importante evaluar la estabilidad del componente orgánico durante la reacción, específicamente para verificar que no sufra un proceso de oxidación que pueda producir protones, que luego sean capaces de formar hidrógeno. / [CA] La present tesi doctoral es va centrar en el desenvolupament i modificació de materials microestructurats basats en sulfurs metàl·lics per a la producció de combustibles solars. Es van obtenir i caracteritzar dos nous materials lamel·lars basats en sulfur d'estany i zinc, IZM-5 i ITQ-75. Com que es pretén utilitzar aquests materials en processos basats en l'ús d'energia solar, va ser necessari ajustar la seua estructura electrònica mitjançant una estratègia de dopatge i la seua accessibilitat mitjançant la modificació de la composició del gel de síntesi o mitjançant mètodes posteriors a la síntesi. Es van provar diferents agents dopants com coure, cobalt, níquel i ferro, així com la inserció d'un complex de ruteni. Els més reeixits van ser el coure i el cobalt, ja que amb la seua presència és possible reduir el valor de la band gap a 2,0 eV, un valor dins de l'abast òptim per a processos de producció de combustibles solars. Quan aquests agents dopants van estar presents en el gel de síntesi d'IZM-5, es va descobrir que no s'obtenia el patró de difracció esperat, sinó un de nou material, anomenat ITQ-76. Al igual que amb les zeolites, els primers intents per a permetre l'accés als centres fotoactius van consistir en alliberar la microporositat, la superfície interna, mitjançant l'eliminació de l'agent orgànic director d'estructura utilitzat durant el procés de síntesi. Es va intentar alternativament millorar la superfície externa (mida de partícula o mesoporositat). De les diferents estratègies provades, es va descobrir que variar la composició del gel de síntesi va ser la més reeixida. Es van provar la inserció de sacàrids, prèviament estudiats en la literatura com a agents inductors de mesoporositat, i l'augment de la viscositat del gel de síntesi per a disminuir la dimensió del cristall final. No obstant això, la presència de sacàrids no va conduir a la formació d'un sistema mesoporós; la millora en l'accessibilitat va ser a causa de la disminució de la mida de partícula. Augmentant la viscositat del gel, també es va poder disminuir la mida mitjana dels cristalls i, en conseqüència, augmentar la superfície externa. Després de la modificació de les estructures estudiades amb l'objectiu d'obtenir una àmplia gamma de propietats, es va avaluar el seu rendiment fotocatalític mitjançant la reacció de ruptura de la molècula d'aigua. Hi semblava haver una relació tipus "volcà" entre el rendiment fotocatalític i la superfície externa. Segons la literatura revisada, aquest comportament podria explicar-se per l'equilibri entre l'augment dels centres actius disponibles i l'augment de les defectes en la superfície, els quals són centres potencials de recombinació. Pel que fa a la relació entre el rendiment fotocatalític i el valor de la band gap, de nou sembla existir una relació tipus "volcà". Segons la bibliografia revisada, es va trobar que amb la reducció del valor de band gap augmenta el nombre de fotons absorbits i, com a tal, s'espera que augmenti el rendiment. No obstant això, és necessari que les càrregues fotogenerades tinguin un potencial suficient per a participar en la reacció desitjada. Com a resultat, per sota d'un cert valor de band gap, les càrregues fotogenerades ja no tenen un potencial suficient i, per tant, el rendiment disminueix. De les diferents mostres provades, les modificades amb sacarosa van destacar per tenir el millor rendiment. Fins ara no ha estat possible desxifrar el fenomen darrere d'aquesta major reactivitat. Per tant, es requereix una caracterització més detallada d'aquestes mostres per a comprendre com la presència del component orgànic influeix en l'estructura electrònica del material i, en conseqüència, en el seu rendiment. També seria important avaluar l'estabilitat del component orgànic durant la reacció, específicament per a verificar que no patisca un procés d'oxidació que puga produir protons, que després siguen capaços de formar hidrogen. / [EN] The present doctoral thesis focused on the development and modification of metal sulfide based microstructured materials for the solar fuels production. Two new materials, IZM-5 and ITQ-75 made of tin and zinc sulfide, were obtained and characterized. Since it is intended to use such materials on solar-driven processes, it was necessary to fine tune their electronic structure, through a doping strategy, and their accessibility, through the modification of the synthesis gel composition or by post synthesis methods. Different doping agents, such as copper, cobalt, nickel and iron, as well as the insertion of a ruthenium complex were tested. The most successful ones were copper and cobalt, since with their presence it is possible to reduce the optical band gap value to 2,0 eV, a value within the optimal range of optical band gaps for solar fuel production processes. When such doping agents were present into the IZM-5 gel, it was found that the expected diffraction pattern was not obtained, but one of a new material, entitled ITQ-76. As with zeolites, the firsts attempts to allow accessibility to photoactive sites was about releasing the microporosity, the internal surface, by removing the organic structure directing agent used during the synthesis process. Because no strategy was successful, it was alternatively attempted to enhance the external surface (grain surface or mesoporosity). Of the different strategies tested, it was found that varying the gel composition was the most successful one. The insertion of saccharides, previously studied in the literature as mesoporosity agents, and increasing the synthesis gel viscosity in order to decrease the final crystal size were tested. However, the presence of saccharides did not lead to the formation of a mesoporous system. The improvement in accessibility was due to the decrease of particle sizes. By increasing the gel viscosity it was also possible to decrease the average size of the crystals and consequently increase the external surface area. After the modification of the structures under study in order to obtain a wide range of properties, their photocatalytic performance was evaluated by using the water splitting reaction. A volcano-like relationship seemed to exist between photocatalytic performance and the external surface area. According to the literature reviewed, this behavior might be explained by the balance between the increase of available active centers and the increase of surface defects which are potential recombination sites. Regarding the relation between the photocatalytic performance and the optical band gap value, again a volcano-like relationship seems to exist. According to the reviewed bibliography, it was found that with the reduction of the optical band gap value the number of absorbed photons increases and, as such, the performance is expected to increase. However, it is necessary that the photogenerated charges have a sufficient potential to participate in the desired reaction. As a result, below a certain optical band gap value, the photogenerated charges no longer have sufficient potential and, as such, the performance decreases. Of the different samples tested, those modified with sucrose stand out as having the best performance. So far it was not possible to unravel the phenomenon behind those enhanced reactivity. Hence, a more detailed characterization of these samples is necessary in order to understand how the presence of the organic component influences the electronic structure of the material and, consequently, its performance. It would also be important to assess the stability of the organic component during the reaction, more specifically to verify that it does not undergo an oxidation process that might produce protons, which are then able to form dihydrogen. / Silva Gaspar, B. (2024). Porous Sulfur-Based Materials for Photocatalytic Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202895

The first part of the thesis includes examining inorganic/organic hybird layered solids, also termed “clay mimics.” Transmission and scanning electron microscopy techniques were used to characterize particles before and after intercalation of pyridine based groups. The particle sizes, shape, and surface morphology were studied for a control and five intercalated species, and evidence for change in particle size and shape was found. The second part of the thesis involves a study in the area of inorganic-organic perovskite networks. Variations in the nature of the cationic organic portion as well as the divalent metal halides have been used to try to better predict the type of network formed. In the work reported here, metal halide and ortho-substituted anilines are combined to relate metal halide network dimensionalities to the steric demands of the ortho- substituents on aniline species. The study involved divalent d10 metal halides, and the halides used were: chloride, iodide, and bromide. The anilines used had varied substituents ortho- to the ammonium group, in order to encompass a wide range of substituents. The goal of the study was to determine if the nature of the ortho-substituent caused consistent effects on the resulting crystal structure. Crystals were grown using slow evaporation techniques and viable crystals were characterized using single crystal X-ray diffraction.