<p dir="ltr">With climate change creating the need for renewable energy to replace fossil fuels, solar energy technologies are primed to dominate the energy sector. And while photovoltaics have improved significantly in recent decades, continued evolution of this technology requires research into new fabrication techniques and new materials. The solution processing of metal chalcogenide semiconductors offers an opportunity to fabricate photovoltaics in a low-cost and high-throughput way. However, for this methodology to make a commercial impact a variety of challenges around the fundamental chemistry and materials science need to be addressed. Furthermore, while solution processing has been applied heavily to the Cu(In,Ga)(S,Se)₂ family of materials, these techniques can also open doors for emerging materials like Cu₂ZnSnSe₄, Ag₂ZnSnSe₄, and the chalcogenide perovskites.</p><p dir="ltr">In solution processed Cu(In,Ga)(S,Se)₂ devices, researcher have generally started with a Cu(In,Ga)S₂ film that is then selenized to form the final Cu(In,Ga)(S,Se)₂ material. However, this process has been connected to the formation of a problematic “fine-grain” layer. To solve this issue, the molecular precursors from amine-thiol chemistry were modified to produce soluble molecules with metal selenium bonding. This enabled direct solution deposition of CuInSe₂ films that could be processed without forming a fine grain layer.</p><p dir="ltr">Reactive dissolution chemistry (or “alkahest” chemistry) is useful for solution processing because it can enable the direct use of metal or metal chalcogenide precursors, bypassing the potential impurities from metal salt precursors. However, the commonly used amine-thiol reactive solvent system is better suited to making metal sulfides than metal selenides because the thiol acts as a sulfur source. To address this limitation, a new alkahest based on alkylammonium polyselenide solutions was developed which could reactively dissolve a wide range of metals, metal chalcogenides, and metal oxides. This generalizable chemistry enabled the synthesis of a wide range of binary and multinary metal chalcogenides including Cu(In,Ga)Se₂, Cu₂ZnSnSe₄, and Ag₂ZnSnSe₄.</p><p dir="ltr">Emerging metal chalcogenide semiconductors composed of earth-abundant and non-toxic elements that can exhibit strong optoelectronic properties and high stability are a target of significant interest. Chalcogenide perovskites like BaZrS₃ and BaHfS₃ are an intriguing option to satisfy these requirements but have rarely been studied because of synthesis difficulties, historically being made by solid-state reactions or the sulfurization of oxides around 1000 °C. Here a solution-based approach that only requires moderate temperatures of 550-575 °C was developed utilizing a hybrid ink containing soluble metal thiolates and nanoparticulate metal hydrides.</p><p dir="ltr">The hybrid ink was an important proof of concept that chalcogenide perovskites could be synthesized at these moderate temperatures. However, it relies on complex and difficult to handle precursors. A simpler route would be to use air-stable precursors to make an oxide perovskite and subsequently sulfurize the material. However, this route has historically used excessively high temperatures. Therefore, a new sulfurization step was conceived based on thermodynamic arguments that includes both sulfur and hafnium sulfide as an oxygen sink. This redesigned sulfurization enabled the conversion of BaZrO₃ into BaZrS₃ at temperatures around 575 °C.</p><p dir="ltr">Finally, an energy systems and economic analysis was performed to consider how photovoltaics might be incorporated into agricultural lands. This work showed that when compared with traditional photovoltaics or a PV Aglectric concept, using corn for ethanol is an inefficient way to generate both food and energy from a given unit of land.</p>

Computational modeling of organic interface formation on semiconductors poses a challenge to a density functional theory-based description due to structural and chemical complexity. A hierarchical approach is presented, where parts of the interface are successively removed in order to increase computational efficiency while maintaining the necessary accuracy. First, a benchmark is performed to probe the validity of this approach for three model reactions and five dispersion corrected density functionals. Reaction energies are generally well reproduced by generalized gradient approximation-type functionals but accurate reaction barriers require the use of hybrid functionals. Best performance is found for the model system that does not explicitly consider the substrate but includes its templating effects. Finally, this efficient model is used to provide coverage dependent reaction energies and suggest synthetic principles for the prevention of unwanted growth termination reactions for organic layers on semiconductor surfaces.

A intercalação de espécies de interesse biológico e terapêutico em Hidróxidos Duplos Lamelares (HDLs) vem se mostrando uma estratégia interessante para a obtenção de sistemas de armazenamento ou carregadores de drogas. No presente trabalho foram investigadas rotas sintéticas e parâmetros experimentais para a intercalação dos ânions derivados dos fármacos ácido mefenâmico e piroxicam em HDL de Mg2+ e Al3+. Os sólidos foram caracterizados por difratometria de raios X, análises elementar e térmica, microscopia eletrônica de varredura e espectroscopia no infravermelho e Raman. Os difratogramas de raios X dos materiais híbridos HDL-mefenamato isolados por co-precipitação (pH=9-9,5) mostram, além de fase do tipo HDL, alguns picos finos e de baixa intensidade que podem estar relacionados com a presença de um sal de mefenamato. Os melhores resultados foram obtidos empregando uma relação molar ânion/Al3+ =1. Nos processos de reconstituição e troca iônica, os picos finos não são observados. Os espectros vibracionais mostram que o ácido mefenâmico está na forma desprotonada e intacto. Os ânions mefenamato se arranjam em uma bicamada no espaço interlamelar (d003 ~21-22 Å). Os híbridos HDL-piroxicamato obtidos por co-precipitação são constituídos de pelo menos duas fases. À medida que a razão ânion/Al3+ diminui, observa-se o aumento na formação de fase HDL. / Intercalation of biological and therapeutical species into Layered Double Hydroxides (LDHs) has been shown an interesting strategy to get drug storage or drug carrier systems. In this work it were investigated synthetic routes and experimental parameters for intercalation of anions derived from mefenamic acid and piroxicam drugs into LDH of Mg2+ and Al3+ composition. The isolated solids were characterized by X-ray diffractometry, elemental and thermal analysis, scanning electron microscopy and infrared and Raman spectroscopies. Besides LDH phase, XRD patterns of LDH-mefenamate hybrid materials isolated by coprecipitation (pH=9-9.5) show some narrow and low intensity peaks that can be related to a mefenamate salt phase. Improved data were obtained using an anion/Al3+ molar ratio equal 1. When employing reconstruction and ion exchange methods, narrow peaks are no observed. Vibrational spectra indicate that mefenamic acid is deprotonated and integral between the layers. Guest anions are arranged in a bylayer in the interlayer space (d003 ~21-22 Å). LDH-piroxicamate hybrid materials obtained by coprecipitation are constituted by at least two phases. An increase in LDH phase formation it is observed when the molar ratio anion/Al3+ decreases.

A intercalação de espécies de interesse biológico e terapêutico em Hidróxidos Duplos Lamelares (HDLs) vem se mostrando uma estratégia interessante para a obtenção de sistemas de armazenamento ou carregadores de drogas. No presente trabalho foram investigadas rotas sintéticas e parâmetros experimentais para a intercalação dos ânions derivados dos fármacos ácido mefenâmico e piroxicam em HDL de Mg2+ e Al3+. Os sólidos foram caracterizados por difratometria de raios X, análises elementar e térmica, microscopia eletrônica de varredura e espectroscopia no infravermelho e Raman. Os difratogramas de raios X dos materiais híbridos HDL-mefenamato isolados por co-precipitação (pH=9-9,5) mostram, além de fase do tipo HDL, alguns picos finos e de baixa intensidade que podem estar relacionados com a presença de um sal de mefenamato. Os melhores resultados foram obtidos empregando uma relação molar ânion/Al3+ =1. Nos processos de reconstituição e troca iônica, os picos finos não são observados. Os espectros vibracionais mostram que o ácido mefenâmico está na forma desprotonada e intacto. Os ânions mefenamato se arranjam em uma bicamada no espaço interlamelar (d003 ~21-22 Å). Os híbridos HDL-piroxicamato obtidos por co-precipitação são constituídos de pelo menos duas fases. À medida que a razão ânion/Al3+ diminui, observa-se o aumento na formação de fase HDL. / Intercalation of biological and therapeutical species into Layered Double Hydroxides (LDHs) has been shown an interesting strategy to get drug storage or drug carrier systems. In this work it were investigated synthetic routes and experimental parameters for intercalation of anions derived from mefenamic acid and piroxicam drugs into LDH of Mg2+ and Al3+ composition. The isolated solids were characterized by X-ray diffractometry, elemental and thermal analysis, scanning electron microscopy and infrared and Raman spectroscopies. Besides LDH phase, XRD patterns of LDH-mefenamate hybrid materials isolated by coprecipitation (pH=9-9.5) show some narrow and low intensity peaks that can be related to a mefenamate salt phase. Improved data were obtained using an anion/Al3+ molar ratio equal 1. When employing reconstruction and ion exchange methods, narrow peaks are no observed. Vibrational spectra indicate that mefenamic acid is deprotonated and integral between the layers. Guest anions are arranged in a bylayer in the interlayer space (d003 ~21-22 Å). LDH-piroxicamate hybrid materials obtained by coprecipitation are constituted by at least two phases. An increase in LDH phase formation it is observed when the molar ratio anion/Al3+ decreases.

Novel highly functionalized hybrid organic-inorganic materials were synthesized by polycondensation of bis[3-(trimethoxysilyl)propyl]amine in presence of cationic and anionic surfactants. Reaction media strongly affected gelation time. Thus, in basic media gelation occurred immediately while acid increased gelation time. Material structures were studied by IR spectroscopy, porosimetry, XRD, and SAXS methods. In spite of the absence of an inorganic linker, obtained bridged silsesquioxanes had mesoporous structure. A material prepared in the presence of dodecylamine as a template had higher surface area and narrow pore size distribution while the use of sodium dodecylbenzene sulfate resulted in formation of mesopores with wide size ranges. Accessibility of surface amine groups in silsesquioxanes was studied for molecules of acidic nature and different sizes: HCl, CO2 and picric acid. High contents of accessible amine groups in these materials make them prospective adsorbents for post-combustion CO2 capture.

<p dir="ltr">Thin film materials are used in many areas of our daily lives. From memory storage chips to optical coatings, these thin films are essential to the technologies on which we rely. Multiferroic thin films, a group of materials that simultaneously exhibit ferromagnetism and ferroelectricity, are of particular interest because of the new opportunities that they enable in memory storage and sensors. Bismuth-based oxide materials have proven to be excellent candidates for these applications, with multiferroic properties and anisotropic structures. This novel self-assembled structure found in layered supercell systems has applications in optical devices, such as isolators and beamsplitters. Throughout this study, thin film strain and epitaxy must be tended to as the fundamentals of film growth, adding to the complexity of these challenges.</p><p dir="ltr">In this dissertation, bismuth-based oxides, and more specifically the Bi₃Fe₂Mn₂O_x (BFMO) layered supercell phase, are studied from three perspectives. First, BFMO is integrated onto silicon substrates for commercialization using a complex buffer layer stack to mediate the differences in the crystal lattice. This allows for a demonstration of device fabrication with this film. Second, the growth and impact of strain are examined through geometric phase analysis, discovering that strain is essential for the growth of the supercell phase in BFMO. This strain can be tuned through buffer layer addition to optimize the growth of this phase. Third, two methods are demonstrated to free the BFMO material from the typical film-substrate lattice matching requirements. The process of transferring the film from the original substrate onto a different substrate removes these restrictions, allowing virtually unlimited access to applications that were previously not possible. The two methods demonstrate different solutions to the specific challenges of transferring the highly strained BFMO thin film. These findings pave a practical way to integrate multiferroic layered oxide thin films onto chips for the next generation of devices.</p>

Transition-metal chemistry in ionic liquids (IL) has achieved intrinsic fascination in the last few years. The use of an IL as environmental friendly solvent, offers many advantages over traditional materials synthesis methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room-temperature IL have been found to be excellent media for stabilising transition-metal clusters in solution and to crystallise homo- and heteronuclear transition-metal complexes and clusters. Furthermore, the use of IL as solvent provides the option to replace high-temperature routes, such as crystallisation from the melt or gas-phase deposition, by convenient room- or low-temperature syntheses. Inorganic IL composed of alkali metal cations and polynuclear transition-metal cluster anions are also known. Each of these areas will be discussed briefly in this contribution. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

The functional and mechanical properties of a material are often determined by the defects in them. A thorough understanding of the relationship between the defects and the properties allows for tailoring a material’s properties into the desired combinations. Amongst the different classes of defects, experimental identification of point defects is typically difficult and indirect, usually requiring an ingenious combination of different techniques. In this context, first-principles calculations, complemented with experiments, offer insights into the formation of defects and their role in properties. This was demonstrated in this thesis through investigations on the effect of calcium vacancies on structure, vibrational and elastic properties hydroxyapatite (HAp), and oxygen vacancies on elastic properties of zinc oxide (ZnO) using first-principles calculations based on density functional theory (DFT). Our results confirm a considerable reduction in the elastic constants of HAp—the inorganic constituent of bone—due to Ca-deficiency, which was experimentally reported earlier. Elastic anisotropic behavior of stoichiometric and Ca-deficient HAp is analyzed, which will be useful in understanding the effects of crystal orientation in designing synthetic bone. Local structural stability of HAp and Ca-deficient HAp structures is assessed with full phonon dispersion studies and the specific signatures in the computed vibrational spectra for Ca deficiency in HAp can be utilized in experimental characterization of different types of defected HAp. In ZnO, formation energies of oxygen vacancies in different types of oxygen deficient structures are analyzed to ascertain their stability. Our results show considerable degradation of some of the elastic moduli due to the presence of such vacancies. Further, the charge state of the defect structure is found to influence the shear elastic constants. Evaluation of elastic anisotropy of stoichiometric and oxygen deficient ZnO indicates the significant anisotropy in elastic properties and stiff c-axis orientation. The second part of the thesis deals with developing some understanding of the pressure-induced phase transformations (PIPT) in an inorganic material, titanium nitride (TiN), and in a metal-organic framework (MOF), erbium formate crystal. PIPT, which is a common phenomenon in many materials, is of great interest in materials science as the properties of the transformation product can diverge significantly from those of the parent phase. Hence, it is important to understand the pressure induced changes so to improve the component reliability and to enhance service life of materials used in high pressure applications. TiN undergoes PIPT from NaCl to CsCl structure. On the basis of our DFT calculations, we propose a new transformation path, which shows that the stress required for this transformation is substantially lower when it is deviatoric in nature than that under hydrostatic pressure. Local stability of the structure is assessed with phonon dispersion determined at different pressures, and we find that CsCl structure of TiN is expected to distort after the transformation. Further, we provide a quantitative comparison of electronic structure of TiN in NaCl structure with that of high pressure phase with implication to electrical conduction properties. Next, we investigate the PIPT associated with bond rearrangement in erbium formate framework. Phase transition pressure is estimated and the corresponding changes in bonding characteristics are analyzed. Estimated lattice constants for both the phases agree well with the earlier experimental results. While the transformation pressure of the framework is overestimated with respect to experiment, our calculations confirm PIPT, and thus provide a theoretical evidence for the experimental finding.

Dans le cadre de la conservation et de la réhabilitation des bâtis anciens, les matériaux utilisés pour leur construction doivent être caractérisés vis-à-vis de leurs propriétés de transferts thermiques et hydriques. La première étape du travail de recherche a concerné la mise au point d'un capteur de conductivité thermique et de teneur en eau des matériaux inorganiques poreux (pierres, bétons, enduits) constitutifs des monuments. Les méthodes d’investigation doivent rester non intrusives. Dans cet objectif, la voie suivie a été d'adapter la mesure de conductivité thermique par une méthode simplifiée du fil chaud, précédemment développée pour les fluides corrosifs, aux pierres de taille utilisées dans le bâti ancien. Afin de transférer cette technologie des fluides vers les solides, plusieurs étapes ont été effectuées : (1) des mesures avec le fil intégré, (2) des mesures de surface, (3) estimation de l'influence de la rugosité de la surface et (4) utilisation de la méthode pour l'estimation de la teneur en eau des matériaux tests.La seconde étape de la recherche a consisté en deux suivis microclimatiques effectués sur deux sites historiques : l'Hypogée des Dunes et l'abbatiale de Saint-Savin-sur-Gartempe. Le travail de thèse a consisté à évaluer l'impact des travaux effectués sur les conditions climatiques dans l'hypogée, et à déterminer l’influence des variations climatiques sur la formation d'un voile biologique dans la crypte de Saint-Savin. Pour ce faire, l'analyse corrélatoire est appliquée au traitement des donnés climatiques. / In the framework of preservation and rehabilitation of ancient buildings, materials used for their construction must be characterized with regards to thermal and hydric transfer properties. The first stage of our research work focused on the development of a sensor of thermal conductivity and moisture content of the inorganic porous materials (stone, concrete, render) making up the monuments. The methods of investigation have to remain non-invasive. For this purpose, the path followed was to adapt the measure of thermal conductivity by a simplified transient hot-wire method, previously developed for corrosive fluids, to dressed stones used in built heritage. In order to transfer this technology from fluids to the solids, several stages were carried out : (1) measures with the integrated wire, (2) surface measures, (3) estimation of the influence of surface roughness and (4) use of this method to estimate the moisture content of several test materials.The second stage of the research consisted in the microclimatic monitoring of two historical sites: the Hypogeum of the Dunes in Poitiers and the crypt of the abbey church of Saint-Savin-sur-Gartempe. The thesis work sought to evaluate the impact of construction work performed in the Hypogeum on the internal climatic conditions, and to determine the influence of climatic variations on the formation of a biological veil in the crypt of Saint-Savin. To this aim, correlative analysis is applied to the treatment of climatic data.

L’objectif de cette thèse est la synthèse de composés de manganèse et de matériaux hybrides qui soient intéressants du point de vue bioinorganique et magnétique. Pour accomplir ce but, nous avons découpé la stratégie en trois étapes constituant les différents chapitres de ce manuscrit :(a) Synthèse et caractérisation des composés moléculaires de manganèse et l’étude de leurs propriétés magnétiques.Nous avons réussi à obtenir la structure cristalline des vingt-trois nouveaux composés de Mn de différentes nucléarités, d’état d’oxydation II, III ou IV. Nous avons étudié les propriétés magnétiques de ces composés et nous avons établi des corrélations magnéto-structurales. Les composés de MnII ont été aussi étudiés par spectroscopie RPE.(b) Synthèse et caractérisation des matériaux hybrides basés sur des composés moléculaires de manganèse insérés dans de la silice mésoporeuse. Les composés moléculaires sélectionnés ont été insérés dans de la silice mésoporeuse (du type MCM-41). Les complexes de Mn dans les supports ont été caractérisés par ATG, XPS, ICP-OES, spectroscopie IR et mesures magnétiques. (c) Étude des propriétés catalytiques des composés moléculaires et des matériaux hybrides.Une famille de composés moléculaires obtenus dans cette thèse sont des modèles structuraux et fonctionnels de la catalase à Mn, une enzyme présente dans certaines bactéries, ayant des propriétés antioxydantes (H2O2 « scavenger »). L’activité catalase pour ces composés et les matériaux hybrides dérivés a été étudiée dans l’acétonitrile et dans l’eau. / The main objective of this work is the synthesis of manganese compounds and hybrid materials that may be relevant from a bioinorganic and magnetic point of view. The developed strategy comprises three main steps that form different sections in this thesis:(a) Synthesis and characterization of molecular manganese compounds and study of the magnetic propertiesThe crystal structure of twenty-three new Mn compounds of different nucleartities were obtained in which the Mn oxidation state is II, III, or IV. The magnetic properties of all these compounds were profoundly studied and they have been rationalized with their structural and electronic parameters. The MnII compounds were also studied with EPR spectroscopy. (b) Synthesis and characterization of hybrid materials based on molecular manganese compounds inside mesoporous silica.Selected molecular compounds were inserted inside mesoporous silica (MCM-41 type). The Mn complexes inside the supports were characterized with TGA, XPS, ICP-OES, IR spectroscopy, and magnetic measurements.(c) Study of the catalytic properties of both molecular compounds and hybrid materials.A family of the molecular compounds obtained in this work are structural and functional models of the Mn catalase, an enzyme found in some bacteria with antioxidant properties (H2O2 scavenger). The catalase activity for these compounds and the hybrid materials was studied in acetonitrile and water.