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Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-17T19:22:30Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_BibianaCulauLopes.pdf: 2194937 bytes, checksum: 262e67bf2660f0e0bc2210c458d84e70 (MD5) / Made available in DSpace on 2018-08-17T19:22:30Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_BibianaCulauLopes.pdf: 2194937 bytes, checksum: 262e67bf2660f0e0bc2210c458d84e70 (MD5) Previous issue date: 2017-03-31 / One of the most common methods applied to heavy metal removal from contaminated aqueous solutions is adsorption through materials like activated carbon, and silica. In general, those materials are efficient and possible to reuse, although after their lifespan they become an environment liability, especially if inappropriately discharged. So that, it is seeking for materials that show more efficiency, that are easily regenerated, reusable and that generate less environmental impact. It is promising the use of graphene oxide (GO) as an adsorbent for environmental pollutants. GO with metallic nanoparticles attached to it, they confer magnetic features to GO, which makes it separation from the aqueous solution easy. In this study it was synthesized graphene oxide through Hummers & Offeman (1958) adapted method. Synthesized GO as well as commercial graphene oxide (Sigma) were submitted to hydrothermal process for insertion of ferrite (NiFe3O4) in its structure, then forming a nanocomposite NiFe2O4/GO. Nanomaterials were characterized by DRX, FTIR, Raman spectroscopy, MEV, BET and magnetization test, which all prove the formation and magnetization of the material. A solution of 100 mg.L-1 concentration of potassium dichromate (K2Cr2O7), was used as Cr(VI) source, for adsorption tests. The results show great efficiency of adsorption, which was stable in 150 min of stirring for more concentrated solutions of Cr(VI). It was used 500 mg.L-1 concentration of potassium dichromate in the photocatalytic process, which resulted in significant decrease of Cr(VI) and release of Cr(III) in the solution. The results obtained show high efficiency in the adsorption and the removal mechanism defined was through electrostatic attraction, due to the difference between charges of adsorbent and pollutant. A solution with 0.03 g of commercial graphene oxide decorated with ferrite and potassium dichromate in a concentration of 80 mg.L-1, adsorption reaction achieved the equilibrium, approximately, 20 minutes after the reaction started. When tested concentrations of 100, 80 and 40 mg.L-1 of potassium dichromate, the reaction achieved the equilibrium in 30 minutes. Adsorption reactions in concentrations of 300, 250 and 150 mg.L-1 of potassium dichromate stabilized 150 minutes after the reaction started. All tests were done with a fixed mass of 0.30 g of commercial graphene oxide decorated with ferrite. The results indicated that the major efficiency, when higher concentrations of Cr(VI) 9 source, depends on the adjustment of adsorbent added. Photocatalytic reaction promoted the reduction of Cr(VI) to Cr(III), which was proved through the difference in absorbance solution. The removal mechanism was through difference between charges, photocatalytic reaction also promoted the desorption of Cr(III) from the adsorbent surface, as it has negatively charged, they naturally repel. / Um dos métodos mais comuns aplicado para remoção de metais pesados de soluções aquosas contaminadas é por adsorção através de materiais, como carvão ativado e sílica. Em geral esses materiais são eficientes e possibilitam a reutilização, porém ao final de sua vida útil se tornam passivo ambiental, principalmente se não forem descartados de forma correta. Desta forma busca-se por materiais que apresentem maior eficiência, facilidade de regeneração, de reutilização e que gerem menor impacto ambiental. O uso do óxido de grafeno como adsorvente, para remoção de poluentes de amostras ambientais, tem se mostrado promissor, principalmente se tratando de íons de metais. Quando o óxido de grafeno é agregado a nanopartículas metálicas, isso promove um caráter magnético, o que facilita a separação deste da solução aquosa. No presente estudo foi sintetizado o óxido de grafeno através do método adaptado de Hummers, Offeman (1958). O óxido de grafeno sintetizado, assim como óxido de grafeno comercial (Sigma), foram submetidos a um processo para inserção de ferrita (NiFe3O4) em sua estrutura via processo hidrotermal, formando o nanocompósito NiFe2O4/GO. Os nanomateriais obtidos foram caracterizados por difração de raios-x, espectroscopia no infrevermelho, espectroscopia Raman, microscopia eletrônica de varredura, teste de Brunauer-Emmett-Taller e teste de magnetização, os quais comprovam formação do óxido de grafeno e da magnetização do mesmo. Para os testes de adsorção e fotocatálise, utilizou-se solução de dicromato de potássio (K2Cr2O7) como fonte de Cr(VI). Os resultados obtidos demonstram alta eficiência de adsorção e o mecanismo de remoção definido foi por atração eletrostática, devido a diferença de cargas entre o adsorvente e o poluente. Para uma solução contendo 0,30 g de óxido de grafeno comercial decorado com ferrita e com uma concentração de 80 mg.L-1 de dicromato de potássio, a reação de adsorção atingiu o equilíbrio aproximadamente 20 minutos depois do inicio do processo. Quando testadas as concentrações de 100, 80 e 40 mg.L-1 de dicromato de potássio, a reação atingiu o equilíbrio em 30 minutos. As reações de adsorção em concentrações de 300, 250 e 150 mg.L-1 de dicromato de potássio estabilizaram depois de 150 minutos depois do inicio da reação. Todos os testes foram realizados com a quantidade fixa de 0,30 g de óxido de grafeno comercial decorado com ferrita. Os resultados indicam que a maior eficiência, 7 quando em maiores concentrações de fonte de Cr(VI), depende do ajuste na quantidade de adsorvente adicionado. A reação de fotocatálise promoveu a redução do Cr(VI) para Cr(III), o que foi comprovado através da diferença medida nas absorbâncias da solução. O mecanismo de remoção foi por por diferença de cargas, a reação de fotocatálise promove também a dessorção do Cr(III) da superfície do adsorvente, já que esse é carregado negativamente, eles se repelem naturalmente.

The main objective of this work is to gain basis for rational design of catalysts used in fuel cells for conversion of chemical energy stored in hydrogen molecules into electric energy, as well as photo-catalysts used for hydrogen production from water under solar irradiation. This objective is achieved by applying the first principles computational approach to reveal relationship among compositions of materials under consideration, their electronic structure and catalytic activity. A major part of the work is focused on electro-catalysts for hydrogen fuel cells. Platinum (Pt) is widely used in the electrodes of fuel cells due to its good catalytic properties. However, Pt is an expensive and scarce element, its catalytic activity is not optimal and also it suffers from CO poisoning at anode. Therefore the search for new catalytic materials is needed for large scale implementation of fuel cells. The main direction of search of more efficient electro-catalysts is based in the design in which an active element monoatomic layer (AE) is deposited on a metal substrate (MS) made of a cost-effective material. Two goals are achieved by doing this: on the one hand, the cost of the catalytic system is reduced by reducing the amount of the AE in the system and on the other hand the catalytic properties of the AE can be tuned through its interactions with the MS. In the first part of this work the Pd-based alloys and layered structures have been studied as promising electro-catalysts for the ORR on the fuel cell cathodes, more precisely Pd-Co alloys and Pd/M/Pd (M=Co,Fe). There exists a robust model linking the activity of a surface toward ORR to computable thermodynamic properties of the system and further to the binding energies iv of the ORR intermediates on the catalyst surface. A more challenging task is to find how to tune these binding energies through modification of the surface electronic structure that can be achieved by varying the surface composition and/or morphology. To resolve this challenge, the electronic structure, binding energies of intermediates and the ORR free energies have been calculated within the density functional theory (DFT) approximation. The results presented in this work show that in contrast to the widely accepted notion, the strain exerted by a substrate on AE hardly affects the surface activity toward ORR, while the hybridization of the electronic states of the AE-and MS-electronic states is the key factor controlling the catalytic properties of these systems. Next it is shown that the catalytic activity of the promising anode electrocatalysts, such as Pt/M, M=Au, Ru and Pd, is also determined by the AE-MS hybridization with a minor effect of the strain. Furthermore, we have shown that, if AE is weakly bound to the substrate (as it is for Pt/Au), surface reconstruction occurs. This leads to the breaking of the relation between the electronic structure of the clean surface and the reactivity of the sytem. Other kind of promising ORR catalysts is designed in the form of Ru nanoparticles modified by chalcogens. In this work, I present the results obtained for small Ru clusters and flat Ru facets modified with chalcogens (S, Se and Te). The O and OH binding energies are chosen as descriptors of the ORR. The results on the two systems are compared, concluding that large clusters with relative large flat facets have higher catalytic activity due to the absence of low coordinated and thus high reactive Ru atoms. Regarding the problem of the hydrogen production via photo-catalytic splitting of water, one of the challenges is tuning the band gap of the photo-anodes to optimal levels. Graphitic carbon nitride (g-C3N4) is a promising material to be used as a photo-anode, however, a v reduction of the band gap width by rational doping of the material would improve the efficiency significantly. This issue is addressed in the last chapter of this work. Two problems are considered: a) the stability of the doped system and b) the band gap width. To address the first problem the ab-initio thermodynamics approach has been used, finding that the substitution of C and N with the doping agent (B, C, N, O, Si and P) is thermodynamically preferred over the interstitial addition of dopant to the g-C3N4 structure. However, due to high kinetic energy barriers for the detachment of C and N atoms, involved in the substitution doping, the interstitial addition found to be kinetically more favorable. Since the density functional theory fails to reproduce the band gap of semiconductors correctly, the GW approximation was used to study the band gap of the system. The results indicate that the g-C3N4 system maintain its semiconductor character if doped with B, O and P under certain conditions, while reducing the band gap.

À ce jour, l’humanité est confrontée simultanément à une crise énergétique et environnementale due principalement à deux facteurs: la croissance démographique et la dépendance aux combustibles fossiles. C'est pourquoi l'urgence d'utiliser des sources d'énergie renouvelables, comme l'énergie solaire est une, solution potentielle. A ce titre, la production d'H2 décarboné par dissociation solaire de l'eau est une voie prometteuse. Néanmoins, pour atteindre l'objectif mentionné, il faut trouver un système photocatalytique (semi-conducteurs, SCs) idéal, qui nécessite quatre caractéristiques majeures: (1) une bonne capacité d'absorption de la lumière visible (2) des positions adéquates de BV et BC des SCs par rapport aux potentiels d’oxydation de l’eau et de réduction du proton (3) une utilisation efficace des photons absorbés et charges générées et (4) une bonne stabilité dans le temps. À cette fin, cette thèse contribue à la conception et à l’optimisation de trois matériaux innovants: les composites Au/g-C3N4, Au/TiO2 (P25)-gC3N4, et Au/TiO2 (NTs)-gC3N4 dont l’activité photocatalytique a été corrélé avec les propriétés physico-chimiques pour comprendre leurs performances photocatalytiques de production d'H2 sous irradiation solaire et visible. De manière annexe, certains de ces matériaux se sont également montrés performants pour les conversions du CO. Pour mettre en évidence l'efficacité des composites préparés, des études comparatives ont été testées en utilisant des références commerciales, pertinentes et les mélanges physiques correspondant. / To date, mankind is facing an energy and environmental crisis simultaneously due to mainly two factors: growth population and the dependency on fossil fuels. For this reason, the urgency of using renewables sources, e.g., solar energy, is a potential solution. For example, non-carbon based H2 production from solar light driven water photodissociation is a promising approach. Nevertheless, to target the mentioned objective, an ideal photocatalytic system (semiconductors, SCs) has to meet four main features: (1) capacity of absorption of visible-light (2) suitable VB and CB positions of SCs to undergo the two half reactions of water splitting (3) efficient use of absorbed photons and generated charges and (4) good stability over time. For this purpose, this thesis contributes to the design and optimization of three innovative materials: Au/g-C3N4, Au/TiO2 (P25)-gC3N4, and Au/TiO2 (NTs)-gC3N4 composites. Their photocatalytic activities were correlated with their physico-chemical properties. In addition some of these composites also exhibited interesting CO conversion yields. To highlight the efficiency on the as-prepared composites, comparative studies were tested using commercial, pertinent references, and physical mixtures homologs.

Pure g-C3N4 and MoS2 modified g-C3N4 materials were synthesized using a facile heating method and a low-temperature hydrothermal method, respectively. The obtained samples were characterized by XRD pattern and N2 adsorption-desorption technique at 77K. The adsorption and photocatalytic performance of all obtained samples were investigated by discoloration of direct black 38 dye in the dark and under visible light irradiation. The results showed that all obtained samples exhibited good discoloration efficiency of direct black 38 dye. The two factors including pH values and Mo loading effected mainly on elimination efficiency of direct black 38 dye. MoS2 modified g-C3N4 materials possessed the more enhanced adsorption and photocatalytic performance in comparison to pure g-C3N4 at pH value of 3.5, with adsorbent dosage of 0.1 g/L. Furthermore, it was found that the adsorption process and photo-catalysis simultaneously occurred under visible light irradiation and followed up a pseudo-second-order kinetic reaction of Langmuir - Hinshelwood model. / g-C3N4 và g-C3N4 biến tính bởi MoS2 đã được tổng hợp theo phương pháp nung đơn giản và phương pháp thủy nhiệt ở nhiệt độ thấp tương ứng. Các mẫu tổng hợp đã được đánh giá đặc trưng bởi các phương pháp hiện đại như giản đồ nhiễu xạ tia X, phương pháp hấp phụ-khử hấp phụ N2 ở 77K. Khả năng hấp phụ và quang hóa xúc tác của các vật liệu tổng hợp đã được nghiên cứu bởi quá trình phân hủy màu thuốc nhuộm direct black 38 trong điều kiện bóng tối và chiếu sáng bởi ảnh sáng nhìn thấy của đèn chiếu sáng sợi đốt wolfram (220V-100W). Các kết quả nghiên cứu chỉ ra rằng các mẫu tổng hợp đều có hiệu suất xử lý màu cao đối với thuốc nhuộm direct black 38. Hai yếu tố gồm pH dung dịch và hàm lượng MoS2 ảnh hưởng chính đến hiệu suất xử lý màu direct black 38. g-C3N4 biến tính bởi MoS2 luôn thể hiện hiệu suất hấp phụ và quang hóa cao hơn so với g-C3N4 tinh khiết. Hơn nữa, khi được chiếu sáng bởi ánh sáng nhìn thấy thì quá trình hấp phụ và quá trình quang hóa thuốc nhuộm direct black 38 trên các vật liệu tổng hợp đã xảy ra đồng thời và mô hình Langmuir - Hinshelwood động học bậc 2 đã được đề xuất cho quá trình này.

Les objectifs de cette thèse sont articulés autour de deux axes principaux : la synthèse et l’étude de cages moléculaires photo-modulables, et la génération de nano-cristaux d’or par photo-catalyse supramoléculaire. Ces deux thématiques sont reliées entre elles par l’exploitation des propriétés photophysiques et photochimiques d’un motif commun, le 9,10-diphénylanthracène (DPA). Dans un premier temps, de nouvelles architectures tridimensionnelles photo-modulables de type cage moléculaire ont été conçues et étudiées. En présence d’oxygène, l’irradiation directe ou sensibilisée du DPA permet de former réversiblement le dérivé endoperoxyde et ainsi moduler les propriétés de complexation de la cage. Les différentes stratégies de synthèse mises en place reposent sur l’exploitation conjuguée de la réactivité de la 2,4,6-trichloro-1,3,5-triazine, et de réactions de chimie « click » (métathèse des oléfines, cycloaddition de Huisgen). L’étude et la modulation des propriétés des reconnaissances ont été effectuées sur des sels de cations alcalins (sodium et césium) et suivies par émission de fluorescence et spectroscopie d’absorption UV-visible. Les résultats obtenus avec deux cages possédant des constantes d'associations élevées (logK = 8,7 pour le cation sodium) montrent une augmentation de la constante d’association d’un facteur 10 et 20 pour respectivement le sodium et le césium entre la forme DPA et la forme endoperoxyde. Dans un second temps, des photocatalyseurs supramoléculaires basés sur le chromophore DPA ont été étudiés en vue de la synthèse de nano-cristaux d’or nus. L’association du chromophore avec des thioéthers permet de former un complexe en phase organique par extraction de sels d’or(III) depuis une phase aqueuse. L’irradiation à 400nm permet la réduction de l’or(III) par transfert d’énergie depuis le 9,10-diphénylanthracène. Les atomes d’or sont ensuite relargués en phase aqueuse pour former des nano-cristaux nus qui ont pu être caractérisés par MET, XPS, AFM et DLS. Par ailleurs, ce procédé est catalytique dans le toluène et un système de réduction en flux continu a été mis au point permettant un turnover moyen de 150. / The goals of this thesis are organized around two major axes: the synthesis and study of photo-gated molecular cages, and the generation of gold nanocrystals by supramolecular photocatalysis. These two themes are connected by the use of the photochemical and photophysical properties of a common chromophore, 9,10-diphenylanthracene (DPA). Three-dimensional photo-gated cage-like architectures were designed and synthesized. Various synthetic strategies based on the combined use of the 2,4,6-trichloro-1,3,5-triazine unit and "click" chemistry reactions (olefin metathesis, Huisgen cycloaddition) were employed for the synthesis. In the presence of oxygen, sensitized or direct irradiation of the DPA chromophore forms the corresponding endoperoxide derivative, thereby modulating the binding properties of the cage. The study and the modulation of the recognition properties were performed on various alkali metal cations and a strong binding of sodium and cesium was evidenced by fluorescence emission and UV-visible absorption spectroscopy. The cages investigated possessed high association constants towards sodium and cesium cations (logK = 8.7 for the sodium cation) which could be reversibly increased by a factor 10 and 20 for sodium and cesium, respectively, upon formation of the endoperoxide. Supramolecular photocatalysis of gold(III) reduction based on the DPA chromophore was also studied for the preparation of uncapped gold nanocrystals. The combination of the DPA chromophore with thioether chains allows the formation of a complex in the organic phase by extraction of gold(III) chloride from an aqueous phase. Irradiation at 400 nm enables the reduction gold(III) by energy transfer from the 9,10-diphenylanthracene followed by oxidation of the solvent. The gold atoms are subsequently released in the aqueous phase to form uncapped nanocrystals characterized using TEM, XPS, AFM, and DLS techniques. Furthermore, the process is catalytic in toluene, where a continuous flow reactor was developed. The latter allowed an average catalytic turnover of 150 to be determined.

Les MOFs sont des solides à la structure cristalline poreuse à base de clusters métalliques et de ligands organiques qui font l'objet de très nombreuses études, dans des champs d'applications très variés, qui vont de la catalyse au « drug delivery », en passant par le stockage de gaz et, plus récemment, en tant que senseurs biologiques. Les ligands organiques, qui les constituent, peuvent lorsqu'ils possèdent un point d'ancrage, comme des groupements amino, être fonctionnalisés grâce à des réactions chimiques. Les travaux présentés dans cette thèse reportent la fonctionnalisation de MOFs, via différentes stratégies, comme des greffages covalent et issues de la chimie de coordination, tel que le couplage peptidique ou encore la synthèse d'urée. Dans cette thèse, est notamment présentée une nouvelle méthode permettant de greffer très rapidement des peptides chiraux dans les nanopores des MOFs. Une large bibliothèque MOF-peptides a ainsi été obtenue et caractérisée. Ces nouveaux composés ont également été utilisés pour l'ancrage de complexes organométalliques dans les cavités des MOFs. Suivant un échange de ligands post-synthétique, il a aussi été possible d'intégrer un complexe organométallique photo-catalytique dans la structure d'un MOF, améliorant ainsi ses activités et sélectivités pour la photo-réduction de CO2. Enfin, les performances catalytiques de ces derniers matériaux MOFs se sont révélées supérieures aux versions homogènes des complexes, ce qui offre de nouvelles opportunités pour la catalyse fine / Metal Organic Frameworks, MOFs, are porous crystalline solid based on metal clusters and organic ligands, investigated for numerous applications such as catalysis, drug delivery, gas storage and, more recently, biosensors. The work presented in this thesis focuses on functionalizing MOFs through different strategies, such as covalent grafting or surface coordination chemistry, through chemical reactions, such as peptide coupling or synthesis of urea. In particular, a new method to very quickly graft chiral peptides into the nanopores of MOFs is reported. A large library of MOF-peptides has thus been obtained and characterized. These novel compounds have also been used for grafting organometallics in the cavities of MOFs. Following a post-synthetic ligand exchange, it was also possible to integrate a photocatalytic complex in the structure of a MOF, improving its activities and selectivities for the photocatalytic CO2 reduction. In general, the catalytic performances of these materials were superior to those of their homogeneous counterparts, thus further expanding the potential of MOFs as well-defined heterogeneous catalysts for fine chemistry

Ce travail de thèse a porté sur l'élaboration de nanoparticules et de couches minces d'oxydes spinelles mixtes de MxCo2-xMnO4 (M = Ni, Cu, Zn ; x = 0, 0,15, 0,30, 0,60) semi-conducteurs, absorbants de lumière avec d'intéressantes applications potentielles pour la photo-catalyse et le photovoltaïque. Le premier chapitre présente tout d'abord une vue globale du contexte énergétique à l'échelle mondiale et des ressources d'énergie renouvelables, alternatives aux énergies fossiles les plus répandues. Une revue détaillée est ensuite faite des différents matériaux et systèmes employés dans la fabrication de cellules solaires, en portant une attention plus particulière à un nouveau type de cellules photovoltaïques en couches minces, dites " Tout-oxyde ", basées notamment sur l'utilisation d'oxydes de type spinelle utilisés comme absorbeurs solaires. Le deuxième chapitre présente les techniques expérimentales de synthèse et de caractérisation utilisées lors de ce travail de thèse. Le procédé de polycondensation inorganique, optimisé au laboratoire, utilisé pour synthétiser les poudres d'oxydes à basse température (T < 120 °C) sans agent organique complexe est décrit. Ensuite, les méthodes de préparation de dispersions colloïdales à l'ambiante dans l'éthanol et de films minces homogènes d'oxydes par trempage-retrait sont explicitées. Le troisième chapitre présente les résultats détaillés des structures atomiques et électroniques des matériaux de base à l'étude, issus de calculs par la méthode Density Functional Theory (DFT), réalisés en collaboration avec le laboratoire CEMES de Toulouse. Les résultats des calculs de densités électroniques et détermination de structures de bandes, réalisés pour la première fois à notre connaissance, sur l'ensemble de la solution solide MnxCo3-xO4 (0 = x = 3), sont comparés à nos données expérimentales, obtenues notamment sur les largeurs de bande interdite (gap) à partir de mesures optiques faites sur couches minces. Un gap de 0,8 eV est calculé, qui serait dû à des transitions inter-métalliques en sites B. Deux gaps à 1,5 et 2,2 eV, obtenus expérimentalement dans l'UV-VIS, qui augmentent avec la quantité de manganèse, correspondraient à des transitions respectives B-A et O-B, respectivement. Les propriétés magnétiques de ces matériaux sont également discutées. Le quatrième chapitre présente l'élaboration et la caractérisation (micro-)structurale des poudres et des couches minces d'oxydes de type spinelle. Toutes les compositions (Co2MnO4 dopé au Ni, Cu ou Zn) cristallisent dans une phase cubique. Les nanoparticules sont sphériques avec la taille variant entre 20 et 50 nm. Les couches minces homogènes ont été déposées sur quartz, alumine, nitrure de titane et platine afin de mesurer leurs propriétés électriques et optiques. Une température de frittage environ de 1000 °C sous air a été déterminée par dilatométrie et les couches sont stables jusqu'à 900 °C quel que soit le substrat. En revanche, seules les couches déposées sur platine permettent d'atteindre la température de frittage sous air (et d'accroitre la compacité donc la conductivité des couches) sans réaction avec le substrat. Le chapitre cinq présente les variations des propriétés optiques et électriques des couches minces avec le frittage. Les propriétés d'absorbance de lumière des couches minces ainsi préparées, mesurées sur une gamme de longueurs d'ondes du domaine spectral UV-visible, montrent deux bandes d'absorbance, correspondantes à deux valeurs de gap pour chaque composition. La propriété d'absorbance des couches minces augmente dans la gamme du visible après frittage et les gaps diminuent. Les couches minces sont plus compactées. La résistivité des couches minces diminue de 105 à 102 Omega.cm avec l'augmentation de la température de 20 à 300 ºC. Une étude parallèle, basée sur la préparation de films minces absorbants de lumière de Co2MnO4 et Cu2O par la technique de Pulsed Laser Deposition (PLD) est également présentée. / The present thesis deals with the synthesis and structural characterization of transition metals doped cobalt and manganese based spinel oxides MxCo2-xMnO4 (with M = Ni, Cu, Zn and x = 0, 0.15, 0.30, 0.60), in relationships with their conduction and optical properties. These materials are good p-type semiconductors and light absorbers in the UV and visible regions, therefore interesting for photo-catalysis and photovoltaics. The first chapter is a brief overview of the energy context and nature of global warming, renewable energy resources and a literature review of materials used for solar cells including the newly studied system type based on all-oxide photovoltaics. Chapter two presents all the experimental methods and characterization techniques used for this research work. The inorganic polycondensation method optimized in our laboratory and used for synthesizing spinel oxide powders at low temperature (T < 120 °C) without complex organic agents is described. Then, the preparation of colloidal dispersions stabilized at room temperature using an azeotrope solution based on absolute ethanol and water only is described, in order to obtain homogenous oxide thin films by the dip-coating technique. The third chapter presents detailed results on the atomic and electronic structures of the materials under study performed by using a full density functional theory investigation thanks to a collaboration with the CEMES. First principles electronic structure calculations were performed for the first time to our knowledge over the whole spinel oxide solid solution range MnxCo3-xO4 (0 = x = 3), and compared with our experimental data. A small band gap of ~ 0.8 eV is calculated, due to metal-metal transitions in B sites. The experimental band gaps observed at 1.5 and 2.2 eV, which increase with the amount of manganese, would correspond to B-A and O-B transitions, respectively. The magnetic properties of these materials are also discussed. Chapter four shows the experimental details of the preparation and characterization of the spinel oxide powders, colloidal dispersions and thin films. All samples (Ni, Cu or Zn-doped Co2MnO4) are well crystallized with a single cubic spinel oxide phase. Nanoparticles are spherical and their diameters vary from 20 to 50 nm, doping with Zn, Ni to Cu, mainly due to steric effects. Homogenous oxide thin films were deposited on quartz, alumina, titanium nitride and platinum in order to measure their optical and electrical properties, and to increase the film compactness (thus electrical conductivity and light absorbance) after thermal treatment. Thin films are well preserved up to 900 °C in air and can handle higher temperatures (up to 1000 ºC) on platinum without reaction with the substrate. Chapter five deals with the optical and electrical properties of thin films before and after sintering. The optical properties were measured over a wide range of wavelengths (UV-VIS). The optical properties of spinel oxide thin films show two strong absorption band gaps for each composition at the UV front and close to 700 nm in wavelength. These band gaps are direct and mostly lower than 2 eV for the first band. Both band gaps increase with further doping and decrease after annealing. Thin film resistivity is about 105 .cm at room temperature and decreases with increasing temperature (a few tens of 20cm at 300 ºC). In parallel to the soft chemistry method and dip-coating technique used to prepare our spinel oxide thin layers, Pulsed Laser Deposition technique was used to prepare pure Co2MnO4 and Cu2O dense thin films. Their structural and optical main features are discussed.