Os ionômeros de vidro vêm sendo utilizados largamente na odontologia com diversas funções. Suas formulações sofreram alterações durante os anos, como a incorporação de componentes resinosos, para a melhoria de suas propriedades físicas e aumento do tempo de trabalho. Com isso, o estudo teve como objetivo avaliar o grau de conversão e a microdureza Knoop dos cimentos de ionômero de vidro modificados por resina (Rely X Luting e Vitremer, ambos da 3M ESPE) de acordo a forma de polimerização (química ou fotopolimerável por lâmpada halógena Ultralux EL ? Gnatus e LED LEC 1000 ? MMOptics) e o tempo de armazenagem. Três espécimes de cada material, autopolimerizável e fotopolimerizável, e tipo de fotopolimerização (por luz halógena e LED) foram confeccionados para cada tempo experimental de 6 horas, 1, 2, 3, 5, 7 ,11 e 14 dias (n=72). Os espécimes foram armazenados em ambiente escuro a 37°C durante esses períodos. Os 72 espécimes foram analisados pela espectroscopia FT-IR para a medição do grau de conversão (GC). Três espécimes de cada material e tipo de polimerização (n=9) foram confeccionados para a medição da microdureza, com um penetrador diamantado piramidal, tipo Knoop, carga estática de 50 gramas por 30 segundos. Os resultados encontrados demonstraram que o material fotopolimerizado com LED apresentou os maiores valores do grau de conversão e da microdureza. O grau de conversão aumentou com o tempo de armazenagem enquanto a microdureza obteve os maiores resultados entre 24-48 horas. Os resultados permitiram concluir que para os cimentos de ionômero de vidro modificados por resina, Vitremer e Rely X Luting, o material fotopolimerizável onde se utilizou o LED apresentou os melhores resultados e que a microdureza Knoop foi ineficaz para predizer o grau de conversão. / Glass ionomer cement have been widely used for many functions. Over the years, some alterations have been made to improve some physico-mechanical properties and to prolong working time. The purpose of this study was to evaluate the relation of the degree of conversion (DC) and Knoop microhardness of resin modified glass ionomer cements (Rely X Luting and Vitremer - 3M ESPE) with polymerization type (chemical curing and light curing reactions, using halogen light or LED) and time of storage. Three specimens of each material, self-cured and light-cured, and light-curing type (halogen light or LED) were prepared for each period of time (n=72). Specimens were stored in dark and dry conditions, at 37oC, during 6 hours, 1, 2, 3, 5, 7, 11 and 14 days. All the specimens were analyzed by FT-IR spectroscopy to measure the DC. Three specimens of each material and polimeryzation type (n=9) were prepared for the microhardness determination, equipped with a Knoop indenter, 50g load for 30 seconds. Results showed that higher values of DC and Knoop microhardness were found on the LED light-cured material. DC values increased with storage time while the Knoop microhardness achieved its higher values between 24-48 hours. Results showed that the LED light-curing unit used to polymerize the resin modified glass ionomer cement Vitremer achieved better values of DC, between light and self-cured materials, and that the Knoop microhardness could not predict the DC.

Biochemische Prozesse treten in wässriger Umgebung auf und Wechselwirkungen der Wasserhülle mit Biomolekülen spielt eine Schlüsselrolle für deren Struktur und Funktion. In dieser Arbeit wird die Strukturdynamik der Wassermoleküle und Gegenionen in der umgebenden Wasserhülle der DNA mit der Methode der zweidimensionalen Infrarotspektroskopie (2D IR) sowie Anrege-Abfrage-Spektroskopie untersucht. Die Ergebnisse der vorliegenden Arbeit zeigt das starke Potenzial von Schwingungsmoden an Grenzflächen für die Abbildung und das Verständnis von Wechselwirkungen zwischen Biomolekülen und ihrer Wasserhülle. In Zukunft soll dieses Konzept auch auf andere Biomoleküle angewendet werden. / Biochemical processes occur in an aqueous environment and interactions of the water shell with biomolecules play a key role for their structure and function. In this thesis, the structural dynamics of water molecules and counterions in the hydration shell of DNA is investigated by two-dimensional infrared (2D IR) spectroscopy and pump-probe transient spectroscopy. 2D IR spectroscopy is a powerful technique that can track molecular couplings between different vibrational modes and structural fluctuations of the chemical environment on a femto- to picosecond time scale. In the present study, vibrational modes of the DNA backbone serve as probes located at the DNA-water interface. The results of this thesis demonstrate the strong potential of interfacial vibrational modes for mapping and understanding interactions between biomolecules and their water shell. In future, this concept will be applied to other biomolecular systems.

Mit Hilfe von linearer und nichtlinearer Infrarotspektroskopie im Femtosekundenbereich wurden Schwingungsdynamiken von H2PO4- und BH4- Ionen untersucht sowie ein Volumenplasmon in einem Schichtsystem aus Ga-dotiertem ZnO. Phosphatgruppen stellen Hydratisierungsstellen in Biomolekülen wie DNS oder Phospholipiden dar und wechselwirken intensiv mit wässrigen Solvatationsschalen. Die Untersuchung einer isolierten Phosphatgruppe in Wasser, dem Phosphation H2PO4-, hat ergeben, dass Phosphatschwingungen sehr sensitive Sonden für die ausgeprägte Fluktuationsdynamik von Volumenwasser darstellen, was experimentell mit homogen verbreiterten Linienformen nachgewiesen werden konnte. Komplexe Hydride wie NaBH4 werden wegen ihres großen Wasserstoffgehalts als potenzielle Wasserstoff- bzw. Energieträger für mobile Anwendungen diskutiert. Jedoch ist die Wasserstoffabsorption- bzw. emission energieaufwendig. Für ein detailliertes Verständnis der Wasserstoffdynamiken im BH4- Tetraeder wurden die Energieverlustkanäle nach optischer Anregung von B-H Schwingungen untersucht. Es konnte experimentell gezeigt werden, dass eine Energieumverteilung von hoch- zu niederfrequenten B-H Schwingungen stattfindet mit abschließender Dissipation in das umgebende Medium, z.B. ein Lösungsmittel oder ein NaBH4 Festkörper. Volumenplasmonen repräsentieren kollektive, longitudinale Anregungen eines freien Elektronengases in ionischen oder polaren Kristallstrukturen. In einer hoch Ga-dotierten ZnO-Schicht eines speziellen Schichtsystems konnte eine Volumenplasmon in Reflektionsgeometrie optisch angeregt werden. Dabei führte Intrabandanregung von Leitungsbandelektronen zur Erhitzung des Elektronengases und, durch das nichtparabolische ZnO-Leitungsband, zu einer Erhöhung der effektiven Elektronenmasse und damit zu einer Rotverschiebung der Plasmafrequenz auf einer sub-ps Zeitskala. Damit konnte ein Mechanismus aufgezeigt werden, um Plasmafrequenzen von Volumenplasmonen gezielt transient zu kontrollieren. / The vibrational dynamics of H2PO4- and BH4- ions and a bulk plasmon in Ga-doped ZnO were studied with methods of linear and nonlinear infrared spectroscopy in the femtosecond range. Phosphates constitute the major hydration sites of biomolecules such as DNA or phospholipds and, thus, strongly interact with aqueous hydrations shells. The investigation of isolated phosphate ions (H2PO4-) revealed a distinct sensitivity of phosphate vibrations on the fluctuation dynamics of bulk water that could be experimentally shown by homogeneously broadened line shapes of phosphate vibrations. Complex hydrides such as NaBH4 constitute a large hydrogen content and, accordingly, are discussed as energy- and hydrogen carriers for mobile applications. However, hydrogen uptake and release are energetically unfavourable. In order to gain detailed insights into hydrogen dynamics within the BH4- tetrahedrons energy relaxation mechanisms were studied after optical excitation of B-H vibrations. It could be experimentally shown that energy dissipation proceeds from high-frequency to low-frequency B-H vibrations into the heat bath of the environment, such as e.g. a liquid solvent or the solid state NaBH4. Bulk plasmons represent collective, longitudinal excitations of a free electron gas in an ionic or polar crystal. Within a specifically designed system of Ga-doped ZnO layers, a bulk plasmon could be optically excited in a reflection geometry. Intraband excitation of conduction band electrons resulted in a heating of the electron gas. Due to a non-parabolic ZnO conduction band hot electrons exhibit an increased effective electron mass and, thereby, reduce the plasma frequency. A redshift of the bulk plasma frequency that possesses sub-ps dynamics could be experimentally shown which represents a mechanism for the time-dependent control of plasma frequencies.

Lextraction par fluide supercritique fait partie des nouvelles techniques de préparation déchantillons solides qui ont émergé au cours de ces dernières années. Elle constitue une alternative intéressante aux techniques classiques dextraction liquide-solide car le pouvoir solvant du fluide supercritique est ajustable, non seulement par la température, mais aussi par la pression. Lextraction par le CO2 supercritique de la tagitinine C, lactone sesquiterpénique photo sensible à lactivité anti-inflammatoire, anti-malarique et anticancéreuse à partir des parties aériennes de Tithonia diversifolia constituait une application intéressante de ce procédé et a été sélectionnée comme molécule cible dans le cadre de ce travail. Son optimisation a impliqué des dosages répétés de lanalyte dont la vibration délongation de la fonction diénone absorbe intensément à des fréquences particulières dans le domaine de linfrarouge. Aussi, avons-nous tout dabord développé et validé, dans la première partie de ce travail, une technique IRTF danalyse en différé sélective, rapide, non destructrice et sensible fondée sur ses propriétés. Les différents paramètres (température, pression, quantité de CO2, granulométrie de léchantillon) influençant le rendement dextraction de lanalyte ont pu être étudiés à cette occasion. Dans les conditions optimales, nous avons montré que lextraction par le CO2 supercritique extrayait rapidement et avec une meilleure sélectivité la tagitinine C tout en conservant un taux de récupération comparable aux techniques classiques dextraction. Parallèlement à ces travaux et compte tenu de la photo-dégradation de la tagitinine C en tagitinine F, la formation de complexes dinclusion avec la β, 2,6-di-O-méthyle-β et la -cyclodextrine a été investiguée. Différentes techniques ont été employées pour caractériser les complexes formés au niveau de la stchiométrie, de la constante de formation et de la structure. Aucun effet photo-protecteur significatif na été démontré avec la β et la -cyclodextrine. En revanche, nous avons mis en évidence une diminution de la vitesse de la photo-dégradation en présence de la 2,6-di-O-méthyle-β-cyclodextrine. Malheureusement, celle-ci reste trop limitée pour envisager lutilisation de cette cyclodextrine pour éviter la dégradation de la tagitinine C lors de son exposition à la lumière directe. Dans la dernière partie de notre travail, nous nous sommes plus particulièrement focalisés sur linterfaçage EFSC/IRTF qui constituait un indéniable défi. Le développement de linterfaçage a été réalisé à laide de fibres optiques en chalcogène darsenic entre un extracteur à fluide supercritique et un spectrophotomètre IR et a ainsi permis deffectuer le dosage en ligne de la tagitinine C dans le CO2 supercritique après passage de celui-ci au travers dune cartouche dextraction contenant la matrice végétale. Par ailleurs, le développement de cet outil répond parfaitement aux nouvelles approches (Process and Analytical Technology) préconisées par la FDA. Le processus dextraction de lanalyte a pu dès lors être étudié de manière approfondie et en temps réel en fonction des caractéristiques physico-chimiques du fluide supercritique et de la durée de lextraction. Lutilisation de la vibration délongation CH comme marqueur a permis de mettre en évidence lobtention dextraits de composition variable qui pourront être utilisés directement dans des études defficacité thérapeutique. Enfin, la méthode dextraction et de dosage en ligne de la tagitinine C a fait lobjet dune validation poussée selon la nouvelle approche faisant appel aux profils dexactitude dans un intervalle de dosage allant 500 à 2500 µg. Sur la base des différents profils dexactitude obtenus, le modèle de régression linéaire a été choisi pour décrire la relation concentration-réponse. En effet, ce modèle présentait des valeurs de biais relatif inférieures à 2%, des valeurs de coefficient de variation ne dépassant pas 4% et des limites de tolérance comprises dans les limites dacceptation de ±15% sur toute la gamme de concentration. De plus, le modèle de régression linéaire était en parfaite adéquation avec la méthode des ajouts dosés. In the last two decades, supercritical fluid extraction processing with carbon dioxide has emerged as an alternative to the conventional solvent extractions of solid matrices and especially for the extraction of natural products for foods and medicines. Indeed, carbon dioxide is an inert, inexpensive, widely available, odourless, environment-friendly solvent and its solvent strength can be tuned by changing the pressure and temperature conditions. In the first part of our work, supercritical fluid extraction of tagitinin C, a known sesquiterpene lactone which shows significant antiplasmodial and antiproliferative activity, was investigated using an off-line FTIR method for the determination of this compound in the aerial parts of Tithonia diversifolia. Different parameters as temperature, pressure, solvent mass and sample granulometry governing the supercritical fluid extraction process were optimised. Finally, we demonstrated that the optimised supercritical fluid extraction gave extraction yields comparable to those of the classical methods of extraction but with an improvement of the selectivity and a reduction of the extraction time. At the same time, the formation of inclusion complexes of tagitinin C with β-, 2,6-di-O-methyl-β and -cyclodextrin was investigated according to its photochemical conversion into tagitinin F. Several techniques were used to characterize the tagitininC/CyD complexes in order to understand and to interpret the data obtained from the photochemical study. This letter mainly showed that the photodegradation rate of tagitinin C was slowed in presence of 2,6-di-O-methyl-β-cyclodextrin while no significant effect was observed in presence of β- and -cyclodextrin. The second part of our work was devoted to the SFE/FTIR interfacing which was a great challenge. This interface was constructed from a stainless steel cross cell equipped with chalcogenide-glass infrared fibers. This hyphenated system allowed to determine on-line tagitinin C in supercritical CO2 after this one flowed through the extraction vessel containing the plant material. Consequently, the extraction process of the analyte was studied thoroughly and in real time according to the physicochemical characteristics of the supercritical fluid and to the extraction time. The use of the CH stretching vibration as tracer allowed to highlight the composition change of extracts which could be used directly in studies of therapeutic efficiency. In addition, the development of this tool answers perfectly the new approaches (Process and Analytical Technology) recommended by the FDA. Finally, the extraction and on-line determination method of tagitinin C was successfully validated using a new approach based on accuracy profiles as decision tool. On this basis, a linear regression model was chosen for the calibration curve. Regarding trueness, precision and accuracy, mean measured values were close to the theoretical concentrations (lower than 1.6%) and the RSD values were relatively low (less than 4% for the middle of the range). Moreover, the method was found to be accurate as the two-sided 95 % beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115 % on the concentration range from 500 to 2500 µg.

Ziel dieser Arbeit ist es, ein sequentielles Extraktionsverfahren zur Erfassung unterschiedlich stabiler Anteile der orgnischen Bodensubstanz (OBS) zu entwickeln und zu klären, ob ein Zusammenhang zwischen Löslichkeit und Stabilität besteht. Darüber hinaus sollen der Einfluss von Bewirtschaftungsmaßnahmen auf Menge und Zusammensetzung dieser OBS-Anteile und Zusammenhänge zwischen Fourier Transform Infrarot (FT-IR)-Spektroskopiedaten und der Kationenaustauschkapazität (KAK) der OBS analysiert werden. <br><br> Für die Untersuchungen wurden Böden der Langzeitfeldexperimente (LFE) in Halle, Bad Lauchstädt und Rotthalmünster beprobt. Zur Erfassung unterschiedlicher OBS-Fraktionen wurden im ersten Schritt die wasserlöslichen OBS-Anteile (OBS(W)-Fraktion) aus den Böden isoliert. Im zweiten Schritt wurden aus den Extraktionsrückständen der Wasserextraktion OBS-Anteile mit einer Natrium (Na)-Pyrophosphatlösung extrahiert (OBS(PY)-Fraktion). Die Stabilität der OBS-Fraktionen wurde anhand von &#948;13C-Bestimmungen und 14C-Messungen untersucht. Die Charakterisierung der Zusammensetzung der OBS-Fraktionen erfolgte mittels FT-IR Spektroskopie. <br><br> Generell wird mit der OBS(PY)-Fraktion ein größerer Anteil am organischen Kohlenstoffgehalt der Böden erfasst als mit der OBS(W)-Fraktion. Die &#948;13C- und 14C-Daten zeigen, dass die OBS(W)-Fraktion höhere Anteile jungen organischen Materials als die OBS(PY)-Fraktion enthält. Das entwickelte sequentielle Extraktionsverfahren ist also prinzipiell geeignet unterschiedlich stabile OBS-Anteile anhand ihrer Löslichkeit zu isolieren. <br><br> Mittels FT-IR spektroskopischer Untersuchungen wird festgestellt, dass Bewirtschaftungsmaßnahmen, wie die Düngung, sowie Standorteigenschaften die Zusammensetzung der OBS-Fraktionen beeinflussen. Für die OBS(PY)-Fraktion ist dies stärker ausgeprägt als für die OBS(W)-Fraktion. Die KAK der OBS(PY)-Fraktion aus den Böden der LFE in Halle und Bad Lauchstädt ist positiv mit der Absorptionsintensität der C=O-Bande in den FT-IR Spektren dieser OBS-Fraktion korreliert. / The aim of this work is the development of a sequential extraction procedure for the isolation of different stable parts of soil organic matter (SOM) according to their solubility and to prove the relationship between solubility and stability. Additionally, the effects of management on amount and composition of different SOM fractions as well as relationships between data sets from Fourier Transform Infrared (FT-IR) spectroscopy and cation exchange capacitity (CEC) of SOM should be analysed. <br><br> Soils from long term field experiments at Halle, Bad Lauchstädt and Rotthalmünster were sampled from the soil surface up to 30 cm depth. To obtain different SOM fractions water soluble SOM (SOM(W) fraction) were extracted at first before Na-pyrophosphat soluble SOM (SOM (PY) fraction) were isolated from the residue of water extraction. Stability of different SOM fractions were analyzed using 14C- and &#948;13C-measurements. Functional composition was studied with FT-IR spectroscopy. <br><br> Generally, SOM(PY) represents a larger part of soil organic carbon (SOC) than SOM(W) in relation to the total SOC-content of the investigated soils. &#948;13C- and 14C-measurements show that SOM(W) contains more younger material than SOM(PY). The findings suggest that different stable SOM fractions can be obtained according to their solubility by the sequential extraction procedure. <br><br> FTIR spectra show that SOM composition is influenced by management options like fertilization and field conditions. Such effects are more pronounced for SOM(PY) than for SOM(W). Furthermore data from FT-IR spectra and CEC measurements of SOMPY) show that the CEC is closely related to the C=O absorption intensities.

The research described in this thesis contributes to the development of new strategies facilitating advanced understanding of the fundamental principles governing selective recognition of molecularly imprinted polymers (MIPs) at a molecular level for the rational optimization of biomimetic materials. The nature of non-covalent interactions involved in the templating process of molecularly imprinted polymers based on the self-assembly approach were investigated with a variety of analytical techniques addressing molecular level interactions. For this purpose, the concerted application of IR and 1H-NMR spectroscopy enabled studying the complexation of the template molecules 2,4-dichlorophenoxyacetic acid, quercetin, and o-, m-, and p-nitrophenol with a variety of functional monomers in the pre-polymerization solution by systematically varying the ratio of the involved components. In aqueous and non protic porogenic solvents, information on the interaction types, thermodynamics, and complex stoichiometry was applied toward predicting the optimum imprinting building blocks and ratios. Molecular dynamics simulations of 2,4-dichlorophenoxyacetic acid and its interactions with the functional monomer 4-vinylpyridine in aqueous and aprotic explicit solvent allowed demonstrating the fundamental potential of computer MD simulations for predicting optimized pre-polymerization ratios and the involved interaction types. The obtained results clearly demonstrate that the application of rapid IR/NMR pre-screening methods in combination with molecular modeling strategies is a promising strategy towards optimized imprinting protocols in lieu of the conventionally applied labor intensive and time-consuming trial-and-error approach. Furthermore, HPLC characterization of the produced MIPs compared to control polymers enabled a systematic approach to imprinting based on advanced understanding of the factors governing the formation of high-affinity binding sites during the polymerization. In addition, the importance of the combination of size, shape, and molecular functionalities for the selective recognition properties of MIPs was investigated. MIPs for the mycotoxins deoxynivalenol and zearalenone and for the antioxidant quercetin were applied as separation materials for advanced sample preparation in beverage analysis. The obtained results demonstrated the potential of MIPs for rapid one-step sample clean-up and pre-concentration from beverages such as wine and beer.

Tyrosyl radicals can facilitate proton-coupled electron transfer (PCET) reactions that are linked to catalysis in many biological systems. One such protein system is ribonucleotide reductase (RNR). This enzyme is responsible for the conversion of ribonucleotides to deoxyribonucleotides. The beta2 subunit of class Ia RNRs contains a diiron cluster and a stable tyrosyl radical (Y122*). Reduction of ribonucleotides is dependent on reversible, long-distance PCET reactions involving Y122* located 35 Å from the active site. Protein conformational dynamics are postulated to precede diiron cluster assembly and PCET reactions in RNR. Using UV resonance Raman spectroscopy, we identified structural changes to histidine, tyrosine, and tryptophan residues with metal cluster assembly in beta2. With a reaction-induced infrared spectroscopic technique, local amide bond structural changes, which are associated with the reduction of Y122*, were observed. Moreover, infrared spectroscopy of tyrosine-containing pentapeptide model compounds supported the hypothesis that local amide bonds are perturbed with tyrosyl radical formation. These findings demonstrate the importance of the amino acid primary sequence and amide bonds on tyrosyl radical redox changes. We also investigated the function of a unique tyrosine-histidine cross-link, which is found in the active site of cytochrome c oxidase (CcO). Spectrophotometric titrations of model compounds that mimic the cross-link were consistent with a proton transfer role in CcO. Infrared spectroscopic data support the formation of tyrosyl radicals in these model compounds. Collectively, the effect of the local structure and the corresponding protein dynamics involved in tyrosyl radical-mediated PCET reactions are illustrated in this work.

The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces. Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques. In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral – water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases. From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI). For both actinides, the formation of similar species is suggested at pH ≤ 4, whereas at higher pH, the infrared spectra evidence structurally different species. At pH 5, the formation of a carbonate-containing dimeric complex, that is (NpO2)2CO3(OH)3−, is strongly suggested, whereas carbonate complexation occurs only under more alkaline conditions in the U(VI) system. The results from the experiments of the sorption processes clearly demonstrate the formation of stable U(VI) surface complexes at all investigated mineral phases. This includes several metal oxides, namely TiO2, Al2O3, and SiO2, serving as model systems for the elucidation of more complex mineral systems, and several alumosilicates, such as kaolinite, muscovite and biotite. From a multiplicity of in situ experiments, the impact of sorbent characteristics and variations in the aqueous U(VI) system on the sorption processes was considered. A preferential formation of an inner-sphere complex is derived from the spectra of the TiO2 and SiO2 phases. In addition, since the in situ FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes, the course of the formation of the U(VI) surface complexes can be observed spectroscopically. It is shown that after prolonged sorption time on TiO2, resulting in a highly covered surface, outer-sphere complexation predominates the sorption processes. The prevailing crystallographic modification, namely anatase and rutile, does not significantly contribute to the spectra, whereas surface specific parameters, e.g. surface area or porosity are important. A significant different surface complexation is observed for Al2O3. The formation of inner-spheric species is assumed at low U(VI) surface coverage which is fostered at low pH, high ionic strength and short contact times. At proceeded sorption the surface complexation changes. From the spectra, an outer-spheric coordination followed by surface precipitation or polymerization is deduced. Moreover, in contrast to TiO2, the appearance of ternary U(VI) carbonate complexes on the γ-Al2O3 surface is suggested. The first results of the surface reactions on more complex, naturally occurring minerals (kaolinite, muscovite and biotite) show the formation of U(VI) inner-sphere sorption complexes. These findings are supported by the spectral information of the metal oxide surfaces. In this work, first spectroscopic results from sorption of aqueous Np(V) on solid mineral phases are provided. It is shown that stable inner-sphere surface species of NpO2+ are formed on TiO2. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 – 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2, and ZnO indicate structurally similar bidentate surface complexes. The multiplicity of IR spectroscopic experiments carried out within this study yields a profound collection of spectroscopic data which will be used as references for future investigations of more complex sorption systems in aqueous solution. Furthermore, from a methodological point of view, this study comprehensively extends the application of ATR FT-IR spectroscopic experiments to a wide range in the field of radioecology. The results obtained in this work contribute to a better understanding of the geochemical interactions of actinides, in particular U(VI) and Np(V/VI), in the environment. Consequently, more reliable predictions of actinides migration which are essential for the safety assessment of nuclear waste repositories can be performed. / Das Migrationsverhalten von Aktiniden und anderen radioaktiven Schadstoffen in der Umwelt wird von wichtigen molekularen Prozessen entlang der Grundwasserfließwege reguliert. Dazu gehören sowohl die Hydrolyse und Komplexierung in wässrigen Lösungen als auch Diffusion und Sorption der Schwermetalle an Mineralen. Diese Reaktionen beeinflussen entscheidend die Mobilität und Bioverfügbarkeit der Metallionen in der Umwelt, insbesondere an den fest-flüssig Grenzflächen. Genaue Kenntnisse über die an diesen Grenzflächen stattfindenden Mechanismen sind somit entscheidend, um Migrationsprozesse verlässlich abschätzen zu können. Die benötigten strukturellen Informationen können mit verschiedenen spektroskopischen Techniken ermittelt werden. Das Ziel der vorliegenden Arbeit war die Untersuchung der Speziation von Uran(VI) und Neptunium(V) an umweltrelevanten Grenzflächen von Oxiden des Titans, Aluminiums, Siliziums und Zinks und von Alumosilikaten mittels ATR FT-IR Spektroskopie. Des Weiteren wurde die Verteilung aquatischer Spezies in mikromolaren Lösungen des U(VI) und Np(V/VI) unter Normalbedingungen charakterisiert. Diese erstmalige Untersuchung wurde mit einer Kombination aus Speziationsmodellierung unter Anwendung aktueller thermodynamischer Daten und ATR FT-IR und NIR Absorptionsspektroskopie realisiert. Die Infrarotspektren zeigen eine deutliche Änderung der Speziesverteilung im Konzentrationsverlauf vom millimolaren zum mikromolaren Bereich. Dies verweist auf die Bildung monomerer U(VI) Hydrolyseprodukte. Im Gegensatz zu berechneten Speziationen werden diese monomeren Komplexe schon bei pH ≥ 2,5 gebildet und dominieren die Speziation bei pH 3. Bei höheren pH-Werten (> 6) konnte eine komplexe Speziesverteilung mit Anteilen von Karbonatkomplexen nachgewiesen werden. Erstmals konnten im Rahmen dieser Arbeit spektroskopische Befunde der Hydrolysereaktionen des Np(VI) im submillimolaren Konzentrationsbereich bis pH 5,3 erhalten werden. Diese wurden im Vergleich mit der U(VI) Speziation diskutiert. Obwohl im sauren Bereich (pH ≤ 4) die Bildung ähnlicher Komplexe nachgewiesen wurde, zeigen die bei höheren pH-Werten erhaltenen Spektren eine unterschiedliche Speziesverteilung. Im Gegensatz zum U(VI) bildet das Np(VI) schon bei pH 5 karbonathaltige aquatische Spezies wie (NpO2)2CO3(OH)3−. Die Ergebnisse der Sorptionsexperimente von U(VI) zeigen die Bildung stabiler Oberflächenkomplexe an allen untersuchten Mineralphasen. Dies umfasst mehrere als Modellsystem dienende Metalloxide wie TiO2, Al2O3 und SiO2, als auch komplexere Alumosilikate wie Kaolinit, Muskovit und Biotit. Für eine detaillierte Charakterisierung der Oberflächenkomplexe wurde eine Vielzahl von in situ Sorptionsexperimenten durchgeführt, die den Einfluss unterschiedlicher Parameter der mineralischen Phase als auch des wässrigen U(VI) Systems berücksichtigen. Die bevorzugte Bildung von innersphärischen Komplexen an TiO2 und SiO2 wird aus den spektroskopischen Daten abgeleitet. Da die in situ FT-IR Spektroskopie eine kontinuierliche Registrierung der Absorptionsänderungen während der ablaufenden Sorptionsprozesse erlaubt, kann somit der Verlauf dieser Prozesse quasi in Echtzeit spektroskopisch verfolgt werden. Es konnte gezeigt werden, dass mit fortschreitender Sorptionsdauer, d.h. bei hohen Beladungsdichten, die Bildung einer weiteren außersphärischen Spezies die Sorption dominert. Die vorliegende kristallographische Modifikation, Anatas und Rutil, ist nicht maßgeblich für das Auftreten unterschiedlicher Sorptionsprozesse verantwortlich, obwohl Parameter wie die spezifische Oberfläche und die Porosität für den Sorptionsprozess von Bedeutung sind. Deutlich verschiedene Oberflächenreaktionen werden für Al2O3 beobachtet. Aus den Spektren kann die Ausbildung einer innersphärischen Spezies bei sehr niedrigen U(VI) Beladungen, niedrigen pH-Werten, hohen Ionenstärken und kurzen Kontaktzeiten abgeleitet werden. Bei fortschreitender Sorption ändert sich die Art der Oberflächenkomplexe. Zunächst bilden sich außersphärische Spezies, während im weiteren Verlauf die Spektren auf eine beginnende Oberflächenausfällung bzw. Polymerisation hinweisen. Weiterhin wird das Auftreten von ternären U(VI) Karbonatkomplexen an γ-Al2O3 aus den spektroskopischen Daten abgeleitet. Die ersten Ergebnisse der Sorptionsexperimente an komplexeren, natürlich auftretenden Mineralphasen (Kaolinit, Muskovit und Biotit) zeigen eine bevorzugte Ausbildung von innersphärischen U(VI) Komplexen. Diese Resultate werden durch die spektralen Befunde der Experimente der Metalloxide gestützt. Erstmalig werden in dieser Arbeit spektroskopische Ergebnisse der Sorptionsprozesse von wässrigen Np(V) an verschiedenen Mineralphasen präsentiert. Wie U(VI) bildet Np(V) stabile innersphärische Oberflächenkomplexe an TiO2. Die Speziesverteilung an der TiO2 Oberfläche ist im pH Bereich 4 – 7,6 konstant. Daher ist zu erwarten, dass eine außersphärische Komplexierung hier nur eine untergeordnete Rolle spielt. Der Vergleich von Spektren der Np(V) Sorptionskomplexe an TiO2, SiO2 und ZnO weist auf die Bildung strukturell ähnlicher bidentater Komplexe hin. Die Vielzahl der hier vorgestellten infrarotspektroskopischen Experimente bietet eine fundierte Sammlung spektroskopischer Daten, die für zukünftige Untersuchungen komplexer aquatischer und mineralischer Systeme unerlässlich ist. Gleichzeitig wurde der Anwendungsbereich der ATR FT-IR Technik auf dem Gebiet der Radioökologie umfassend erweitert. Die im Rahmen dieser Arbeit gewonnenen Ergebnisse tragen zu einem besseren Verständnis der geochemischen Wechselwirkungen von Aktiniden, im Speziellen von U(VI) und Np(V) in der Umwelt bei. Damit unterstützen sie den Aufklärungsprozess der Migration von radioaktiven Kontaminationen und dienen als Grundlage für zuverlässige Prognosen für die Sicherheitsbewertung von Endlagern für nukleare Abfälle.

This dissertation has investigated the adsorption, thermal behavior, and radiation (both photon and electron) processing of prebiotically-relevant ices and surfaces. A custom ultra-high vacuum (UHV) chamber has been built that is coupled with a Fourier Transform-Infrared (FT IR) spectrometer and a Temperature Programmed Desorption (TPD) system that utilizes Quadrupole Mass Spectrometry (QMS) to study selected organic:surface systems. Formamide (HCONH₂) has been studied in two related but distinct studies relevant to primitive Earth and interstellar chemistry. First, in collaboration with a theory group, formamide’s interaction with kaolinite (Al6Si6O36H30), a clay mineral relevant to early Earth chemistry, has been studied experimentally and theoretically. Experimental infrared results are compared with calculated infrared frequencies obtained by our collaborators. TPD analysis is compared with the calculated values of adsorption energy, and the optimal kaolinite termination site for adsorption is reported. Second, the first thermal and radiation damage study of pure formamide and HCONH₂:H₂O mixed ices on an interstellar icy grain analog (SiO₂) is reported. A discussion of the pure formamide ice phases identified with FT-IR upon warm-up, as well as the TPD binding energies of HCONH₂ on SiO₂, is presented. The observed Lyman-alpha photochemical products and proposed formation mechanisms from pure formamide ice is reported and discussed. In addition, results of Lyman alpha processing of mixed HCONH₂:H₂O ices are provided. Low-energy electron irradiation of pure HCONH₂ and HCONH₂:H₂O mixed ices has also been reported for the first time. A third investigation has studied acetylene (C₂D₂) and acetonitrile (CH₃CN) interactions and radiation stability in mixed low-temperature ices to simulate possible prebiotic reactions that may occur on Saturn’s moon, Titan. This investigation contributes to understanding the possible consumption, trapping, and degradation of these species on the surface of Titan.

In the last decade there has been increasing research interest in the value of bio-sourced materials from lignocellulosic biomass. The dissolution of cellulose by ionic liquids (ILs) has led to investigations including the dissolution of cellulose, lignin, and complete biomass samples and the in situ processing of cellulose. Rapid quantitative measurement of cellulose dissolution in ILs is difficult. In this work, Fourier transform infrared spectroscopy (FTIR) spectra of cellulose dissolved in 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) were subjected to partial least squares (PLS) regression to model dissolved cellulose content. PLS regression was used due to the ease in developing predictive models with this technique in addition to linear regression being ineffectual for modeling when applied to potentially thousands of variables. Applying a normalization data treatment, before regression, generated a model that estimated cellulose content within 0.533 wt%. The methods described provided the basis for a rapid methodology to determine dissolved cellulose content. Development of rapid and facile screening techniques to determine the effectiveness of various ILs as solvents for cellulose or lignin will aid in the development of lignocellulosic based bioproducts. In this work, optical microscopy with and without the use of cross-polarized lenses, was used to monitor cellulose and lignin dissolution in two imidazolium-based and two phosphonium-based ILs as well as n,n-dimethylacetamide/lithium chloride (DMAc/LiCl), demonstrating that this technique could be applied more broadly than solely for ILs. The described optical microscopy methodology was more rapid and sensitive than more traditional techniques, such as visual inspection. The viscosity of [emim][OAc] (162 cP) is 100 times that of water at 20°C and could inhibit its use as a solvent for cellulose. There is a need for simple, low-cost and environmentally benign methods to reduce the viscosity of ILs to aid in cellulose dissolution. In this work, 4 wt% cellulose dissolved in [emim][OAc] was subjected to 50 psi CO2 and 20 psi N2, as a control environment, at both 50°C and 75°C. After 24 hours a nearly 2-fold increase in dissolved cellulose over the N2 control was demonstrated through the application of a 50 psi CO2 environment for cellulose dissolution in [emim][OAc] at 50°C. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-05-25 22:58:17.744