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Mavadat, Maryam. "Characterization of biomedical used plasmas by IR and UV-VIS emission spectroscopy." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30780/30780.pdf.
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La modification de surface par plasma est une technique largement utilisée pour améliorer les propriétés de surface de polymères par le greffage de différents groupes fonctionnels. Dans ce projet de recherche, différentes méthodes pour améliorer les techniques de caractérisation de décharge micro-ondes de N2 et N2-H2 ont été étudiées dans le but d’optimiser le procédé de traitement de surface par plasma. Tout d'abord, un certain nombre de paramètres du plasma ont été mesurés à différentes conditions de traitement. Pour déterminer les paramètres du plasma, la spectroscopie d'émission optique a été utilisée dans la région l’ultraviolet, du visible et l’infrarouge (rarement utilisée dans la littérature scientifique). L’utilisation de la spectroscopie d'émission dans cette dernière région spectrale est avantageuse car elle permet d'éliminer les forts chevauchements entre les transitions atomiques et moléculaires et de pallier la faible intensité du signal observée dans la région de l’ultraviolet et du visible. Par la suite, la composition chimique de surface du PTFE a été analysée par XPS pour déterminer les concentrations en carbone, fluor, azote et des groupements amine suite à un traitement par plasma. Les résultats mentionnés ci-dessus ont été utilisés pour corréler les conditions de traitement et les paramètres de décharge micro-ondes à la composition chimique du PTFE modifié, dans l’objectif de mettre en évidence les paramètres expérimentaux du plasma et les espèces présentes dans le plasma qui jouent un rôle clé pour maximiser la fonctionnalisation de surface du polymère avec des groupements amine. En outre, un modèle mathématique a été développé en utilisant la technique de régression PLS. Pour construire ce modèle, un ensemble de données de variables d'entrée contenant les conditions de traitement et les paramètres spectroscopiques du plasma et une matrice de réponse contenant les propriétés de surface du polymère ont été générées. La base de données obtenue a été utilisée pour établir la relation entre les paramètres du plasma, les conditions de traitement et la chimie de surface du film. Cela a finalement permis de prédire la composition chimique de la surface à partir d’informations relatives au plasma, sans avoir à effectuer des analyses de surface après le traitement.Plasma surface modification is a widely used technique for improving the surface properties of polymers through the introduction of different functional groups. In the current research project, different methods to improve the characterization techniques of N2 and N2-H2 microwave discharge were investigated with the aim of optimizing the plasma surface process. First of all, a number of plasma parameters were measured at different process conditions. To determine the plasma parameters, optical emission spectroscopy was used not only within the well-documented UV-Visible region but also within the rarely studied infrared zone. Using infrared optical emission spectroscopy is advantageous as it eliminates the strong overlap between atomic and molecular transitions as well as the low intensity UV-Visible emission spectroscopy limitations. In the next step, the PTFE surface chemical composition was analyzed via XPS to quantify the concentrations of carbon, fluorine, and nitrogen after a plasma treatment in a N2-H2 gaseous environment. The XPS analyses were also performed after chemical derivatization to quantify the surface concentration of amino groups (%NH2) at different process conditions. The above-mentioned results were used to correlate process conditions and microwave N2-H2 discharge parameters to the chemical composition of the modified PTFE. The purpose was to determine the external plasma parameters and species present within the plasma which play a key role in the introduction of amino groups to the polymer surface. Furthermore, a mathematical model was developed using the Partial Least Squares Regression, (PLSR) using custom scripts written in MATLAB. A data set of input variables including the process conditions and plasma parameters for each experiment were generated along with the corresponding response matrix which in turn contained the surface properties of the film. The resulting database was used to build the relationship between the plasma parameters, process condition and the resulting film surface chemistry. This ultimately enabled to predict the PTFE surface chemistry from data originating from the plasma, without having to proceed to post-plasma surface characterization.
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FIRON, MURIEL. "Caracterisation par ellipsometrie uv. Vis. Et spectroscopie infrarouge de films amorphes : les oxynitrures de silicium." Paris 6, 1994. http://www.theses.fr/1994PA066122.
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Les isolants (sio#2, si#3n#4) sont utilises soit pour passiver la surface des semi-conducteurs, soit pour isoler electriquement les conducteurs. L'association de sio#2 et si#3n#4 permet d'obtenir un bon isolant dont les contraintes mecaniques sont faibles: l'oxynitrure de silicium (sio#xn#y). Les proprietes physico-chimiques de ces films, deposes par plasma (pecvd), dependent essentiellement de leur composition chimique. Afin de la determiner, nous avons utilise plusieurs techniques spectroscopiques. La determination de la composition chimique par xps necessite d'eliminer la contamination superficielle des films par erosion ionique a l'argon. Cette methode est destructive et perturbe la mesure de la composition chimique. L'ellipsometrie spectroscopique uv-vis. Permet une analyse non destructive de la totalite du film. La composition chimique des oxynitrures de silicium est calculee a l'aide du modele de bruggeman. Le resultat de cette mesure n'est qu'une estimation. Dans ce modele, l'oxynitrure de silicium est considere comme un melange de deux phases distinctes (sio#2 et si#3n#4), cependant les resultats ellipsometriques sont reproductibles. Les resultats de ces deux types de mesures sont sous estimes par rapport a ceux de l'analyse par reaction nucleaire. Nous avons montre que l'analyse quantitative et l'arrangement atomique peuvent etre deduits des spectres infrarouges en transmission (films minces) et en reflexion polarisee (films ultraminces), pourvu que l'on dispose d'un modele approprie. Dans le cas du film de sio#xn#y pur, il existe des modeles qui permettent de decrire de maniere satisfaisante la repartition des atomes dans les materiaux et peuvent etre utilises pour deduire la composition chimique, a partir de la position des bandes de vibration. En pratique, de l'hydrogeene est le plus souvent present dans les films d'oxynitrure de silicium. Il est en effet difficile de s'affranchir de sa presence. Il n'existe actuellement aucun modele qui prenne en compte la presence d'hydrogene ; nous avons suggere les modifications qu'il faut apporter au modele existant pour en tenir compte
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Gueneau, Basile. "Etude et utilisation de complexes polypyridiniques du cuivre (II) dans le cadre de la catalyse de la délignification des pâtes papetières." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENV023.
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L’utilisation de dioxygène lors de la délignification des pâtes à papier permet une réduction considérable des coûts de production et de l’impact environnemental du procédé de blanchiment. Seulement, le taux de délignification est limité par le fait qu’une partie de la lignine résiduelle n’est pas réactive vis-à-vis du dioxygène et que la cellulose est partiellement dépolymérisée au cours du procédé. L’utilisation de catalyseur pourrait permettre d’améliorer l’efficacité et la sélectivité de la délignification au dioxygène comme le suggèrent certaines études. Le complexe cuivre(II)-phénanthroline présente des résultats prometteurs en termes d’efficacité, mais entraîne une dégradation importante de la cellulose. Différents ligands polypyridiniques ont été étudiés dans ces travaux, afin de trouver un complexe du cuivre(II) présentant une affinité forte vis-à-vis de la lignine et faible vis-à-vis de la cellulose. Les complexes formés ont été caractérisés par spectroscopie UV/Vis et voltammétrie cyclique et étudiés comme catalyseurs de l’oxydation de différents substrats : un composé modèle de lignine non phénolique et des substrats lignocellulosiques (un modèle de cellulose, un modèle de lignine native et une pâte kraft industrielle). Les résultats ont montré que la nature même du ligand a un effet important sur l’activité catalytique du complexe de Cuivre (II) lors de l’oxydation du composé modèle de lignine. En revanche, les complexes actifs présentent une activité faible lors de la délignification d’une pâte kraft et oxydent fortement les hydrates de carbone. Ce manque de sélectivité ne permet pas une application pour la production de pâte à papier mais oriente l’utilisation de ce type de catalyseur dans de nouvelles applications n’ayant pas les mêmes contraintes sur le degré de polymérisation de la celluloseDioxygen delignification considerably reduces the operating cost of the bleaching process and decreases the environmental impact of the bleaching effluent. Unfortunately the performance of dioxygen delignification is limited since part of the residual lignin is not reactive toward dioxygen while cellulose depolymerisation occurs. Studies suggested that dioxygen delignification could be improved thanks to the use of catalysts such as copper(II)–phenanthroline type complexes which have shown promising results on delignification efficiency. However cellulose was also more degraded. Different polypyridinyl ligands have been studied in this work, in an attempt to find copper(II) complexes that have more affinity toward lignin and less toward cellulose. Complexes have been characterised by UV/Vis spectroscopy, cyclic volammetry, and they were studied for the catalysed oxidation of various substrates: a non phenolic lignin model compound and lignocellulosic substrates (a model of cellulose, a model of native lignin and an industrial kraft pulp). It has been shown that the nature of the ligand had a significant effect on the catalytic activity of Cu(II) complexes in the oxygen oxidation of the lignin model compound. However, the active complexes only show a limited activity during the delignification of a kraft pulp and oxidize carbohydrates. This lack of selectivity prevents from an industrial application for paper pulp production but may be useful for the design of products with fewer constraints on cellulose polymerization degree
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Valverde, Juan. "Study of the modifications induced by various culinary and industrial treatments of pigment systems from immature pods of green beans (Phaseolus vulgaris L. ) : introduction of new analytical methods for the study of these systems." Paris 6, 2008. http://www.theses.fr/2008PA066677.
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La couleur des végétaux verts est un des critères importants d’appréciation de la qualité des aliments. Elle est due notamment aux chlorophylles, aux caroténoïdes et à leurs dérivés, molécules au rôle nutritionnel important. Les procédés culinaires ou de l’industrie alimentaire conduisent à des modifications des molécules qui composent les systèmes pigmentaires. Des études scientifiques récentes n’ayant pas retrouvé, dans certains conditions, de corrélation entre la couleur (déterminée par colorimétrie) et le contenue en pigments, on a étudié les modifications de la couleur et du contenu en pigments de « haricots verts », c’est-à-dire de gousses immatures de Phaseolus vulgaris L. Lors de divers traitements, thermiques ou non (culinaires et industriels). Des échantillons été étudiés à la fois au laboratoire et sur site industriel. Dans les deux cas, la couleur des gousses entières a été déterminée par colorimétrie tristimulus (système L*a*b*). Le contenu en pigments a été déterminé par deux méthodes mise au point au cours du travail et qui ont fait l’objet de publications. Sur site industriel, la composition en pigments a été déterminée par chromatographie quantitative sur couches minces, grâce à un traitement numérique d’images numérisées des couches minces produites. Par cette méthode rapide, peu coûteuse, répétable et qui révèle jusqu’à certains isomères structuraux des chlorophylles, on a étudié les étapes préliminaires des traitements industriels. Pour les analyses au laboratoire, on a mis au point deux méthodes spectroscopiques qui évitent toute séparation chromatographique préalable : la spectroscopie UV-Vis avec régression linéaire multiple, d’une part, et la résonance magnétique nucléaire quantitative, d’autre part. La première méthode est rapide, et facile à utiliser, mais la RMN quantitative donne plus d’information sur les isomères structuraux des pigments (épimères des chlorophylles et isomères cis/trans des caroténoïdes).
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Brazard, Johanna. "Photoactivation femtoseconde de deux nouvelles protéines de la famille des cryptochrome/photolyase, issues de l'algue verte Ostreococcus tauri : photocycle ultrarapide et état signalant de la photophobie du protozoaire Blepharisma japonicum." Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-03184590.
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L’étude de la photoactivité de deux nouvelles flavoprotéines (OtPCF1 et OtCPF2) de l’algue verte Ostreococcus tauri, appartenant à la famille des cryptochromes et photolyases (CPF), a mis en évidence un transfert d’électron ultrarapide (OtCPF1 : 390 fs ; OtCPF2 : 590 fs) après excitation du chromophore flavine adénine dinucléotide (FAD) oxydée. Nous avons caractérisé un tryptophane comme donneur d’électron. Nous expliquons les étapes ultérieures par des transferts d’électron le long d’une chaîne de trois tryptophanes. Nous avons aussi analysé le transfert d’énergie au sein de OtCPF2. Des analyses par modélisation par homologie nous ont permis de rationaliser les résultats de spectroscopie transitoire ultrarapide. Le photocycle ultrarapide de OBIP - photorécepteur supposé du protozoaire cilié Blepharisma japonicum - a été expliqué par un modèle original impliquant un équilibre entre un état localement excité du chromophore (Oxyblépharismine) en interaction par liaison hydrogène avec un résidu proche et un état à transfert de charge intermoléculaire. Nous avons proposé que l’état signalant de la photophobie serait la forme déprotonée du chromophore.
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Duplouy, Lucie. "Etude spectroscopique UV-vis et infrarouge de la photoséparation de charges de molécules adsorbées dans des matériaux zéolithiques de type MFI : cas de dérivés cyano-aromatiques et du trans-stilbène." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R066.
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L’environnement particulier au sein de la structure poreuse des zéolithes permet à ces matériaux de jouer le rôle de microréacteurs pour optimiser la photo-réactivité de molécules adsorbées. Dans ce contexte, nous reportons l’étude des mécanismes réactionnels intervenant après photo-ionisation du t-stilbène confiné dans des cristaux de zéolithes ZSM-5 de tailles et de morphologies différentes. Dans les micro- et nanocristaux de ZSM-5, le radical cation photoinduit évolue vers un complexe de transfert de charge (CTC) très stable, formé par l’éjection d’un électron et stabilisé par un processus de compartimentalisation. Dans les nanofeuillets, le radical cation est l’espèce stabilisée car l’électron éjecté ne peut être piégé suffisamment loin du radical cation pour permettre la formation du CTC. Enfin, dans des nanoéponges, le CTC n’est pas formé et la durée de vie du radial cation est réduite à quelques centaines de µs. Le cas de la formation d’espèce anionique a été étudié. Ainsi, dans des MZSM-5 aluminées (M = H+, Na+ et Cs+), la photo-excitation du 1,4-dicyanobenzène incorporé conduit à la formation d’un radical anion (RA) grâce au caractère donneur de la zéolithe alors que dans la silicalite-1, ne comportant pas d’aluminium, cette réaction n’a pas lieu. La spectroscopie UV-vis résolue à la nanoseconde a notamment permis de mettre en évidence le rôle clé de l’aluminium et l’influence du cation compensateur de charge sur la durée de vie du RA. Les énergies d’activation nécessaires à la recombinaison de l’électron du radical anion avec le trou électronique positif créé dans la zéolithe ont été déterminées et discutées. Enfin, les travaux réalisés sur l’étude des étapes primaires des processus de séparation de charges dans le cas de la molécule de 9,10-dicyanoanthracène (DCA) cristallisée en surface de zéolithes de type ZSM-5 par les techniques de comptage de photons (TCSPC) et de spectroscopie d’absorption IR femtoseconde ont montré la formation ultrarapide et quasi-simultanée de l’état excité singulet S1, d’un état de transfert de charge et de formes excimères dont la distribution dépend du polymorphisme du cristal de DCA sur la surface externe de la zéolithe. (Co-financement Région Hauts-de-France/Université de Lille)The particular environment within the porous structure of zeolites allows these materials to act as micro-reactors to optimize the photoreactivity of adsorbed molecules. In this context, we report the reaction mechanisms occurring after photoionization of t-stilbene confined into crystals of ZSM-5 zeolites of different sizes and morphologies. In the micro and nanocrystals of ZSM-5, the photoinduced cation radical evolves into a very stable charge transfer complex (CTC), formed by the ejection of an electron and stabilized by a compartmentalization process. In nanosheets, the cation radical is the stabilized species because the ejected electron cannot be trapped far enough from the cation radical to allow the formation of the CTC. Finally, in nanosponges, CTC is not formed and the lifetime of the radial cation is reduced to a few hundred µs. The case of anionic species formation was also studied. Thus, in aluminized MZSM-5s (M = H+, Na+ and Cs+), the photoexcitation of the incorporated 1,4-dicyanobenzene leads to the formation of an anion radical (RA) thanks to the zeolite donor character, whereas in silicalite-1, the Al-free MFI analogue, this reaction does not occur. In particular, nanosecond UV-vis spectroscopy highlighted the key role of aluminum and the influence of the charge-compensating cation on the lifetime of the RA. The activation energies required for the recombination of the electron of the anion radical with the positive electron hole created in the zeolite were determined and discussed. Finally, the work carried out on the study of the primary steps of charge separation processes in the case of the 9,10-dicyanoanthracene (DCA) molecule crystallized on the surface of ZSM-5 zeolites by photon counting (TCSPC) and femtosecond IR absorption spectroscopy techniques showed the ultrafast and quasi-simultaneous formation of the excited S1 singlet state, a state of charge transfer and excimer forms whose distribution depends on the polymorphism of the DCA crystal on the external surface of the zeolite. (Co-funding Region Hauts-de-France/Université de Lille)
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Meyer, Thomas. "Caractérisation électrochimique et spectroscopique de protéines membranaires immobilisées sur des nanomatériaux." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF004/document.
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Le domaine de la bioénergétique concerne l’étude des échanges et des transformations de l’énergie au sein des organismes vivants. Cette thèse propose une étude électrochimique et spectroscopique de protéines issues de la chaine respiratoire, les oxydases terminales, afin de comprendre l’influence de différentes propriétés de ces enzymes (potentiels des cofacteurs, dépendance pH…) sur leur mécanisme réactionnel. La première partie de ce travail décrit le développement d’une méthode d’immobilisation permettant de conserver l’intégrité et l’activité de ces enzymes. Cette technique a d’abord été utilisée pour étudier l’inhibition de la cytochrome aa3 oxydase de P. denitrificans et a permis de mettre en avant l’importance du transfert de protons sur la réaction de réduction de l’oxygène. Une deuxième étude propose de comparer deux isoformes de la cytochrome cbb3 oxydase dont aucune différence n’a été observée à ce jour. La spectroscopie IRTF couplée à l’électrochimie montre l’implication de résidus acides différents au cours de la réaction d’oxydoréduction suggérant des différences mécanistiques. La dernière partie propose une étude comparative d’oxydases terminales de différents types et met en perspective l’influence des potentiels relatifs des hèmes sur la réaction de réduction de l’oxygèneThe field of bioenergetics concerns the study of exchange and transformation of energy in living organisms. This manuscript proposes an electrochemical and spectroscopic study of the fourth complex of the respiratory chain, the terminal oxidases. The aim of this study was to understand the influence of some properties of these enzymes (potential of the cofactors, pH dependency…) on the catalytic mechanism. The first part describes an immobilization procedure which retains the protein activity and structure. This procedure has been applied for the study the inhibition of the proton pathways of cytochrome aa3 oxidase from P. denitrificans and shows the importance of proton transfer on the oxygen reduction. In a second study, two isoforms of cytochrome cbb3 oxidase were compared. No differences were observed between them until now. Our electrochemically induced FTIR spectroscopy study suggests the implication of different acidic residues during the redox reaction implying differences in the mechanism of these enzymes. The last part deals with the comparison of terminal oxidases of different types and shows the influence of the relative order of the midpoint potentials of the hemes on the oxygen reduction
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Larina, Nina. "3-(2-Benzylbenzoyl)-4(1H)-quinolinones : une nouvelle classe de composés photochromiques photoréversibles." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22110/document.
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Actuellement, les photochromes photoréversibles présentent un intérêt important en vue de leurs applications éventuelles comme interrupteurs optiques ou pour le traitement et le stockage de données. L’objectif principal de ce travail de thèse a été d’évaluer les 3--(2--benzylbenzoyl)--4--quinolones en tant que système photochromique photoréversible. Afin d’étudier la relation entre la structure chimique et le comportement photochromique de ce système, une série de nouvelles 3--(2--benzylbenzoyl)--4--quinolones à substitution variée a été préparée à l’aide de procédures connues ainsi qu’élaborées lors de ce travail. La photoréaction de ces nouveaux molecules étant très complexe, une méthode d’étude a été établie avec des 2--benzyl--3--benzoyl--4--quinolones photoénolisables au comportement plus simple. Leurs spectres d’absorption modélisés à l’aide de fonctions pekariennes ont été comparés avec les résultats des calculs quantiques. Le mécanisme selon lequel la réaction de décoloration se fait par l’ionisation des photoénols fortement acides via protonation des molécules du solvant a été établi. Enfin, la troisième partie est consacrée à l’étude des nouveaux dérivés de quinolones. D’après l’analyse de leurs spectres d’absorption, ainsi que les résultats des calculs quantiques, nous proposons un mécanisme où le transfert d’hydrogène photo--induit conduirait à la formation d’un intermédiaire biradicalaire, capable de se cycliser en dibenzo[b]acrydinones hydroxysubstituées. Un tel mécanisme expliquerait la forte influence qu’ont la nature des substituants en positions 1 et 2, ainsi que la température et la présence d’oxygène sur la régio-- et stéréo--sélectivité de cette photoréactionPhotoreversible photochromic compounds are currently of considerable interest from the point of view of their potential applications as molecular switches and for data storage and processing. The main target of the present investigation is to evaluate the scope and limitations of 3--(2--benzylbenzoyl)--4--quinolones as a photoreversible photochromic system. In order to investigate the relationship between quinolone chemical structures and photochemical behavior, a large series of new 3--(2--benzylbenzoyl)--4--quinolones with different substituents has been prepared using known as well as newly elaborated synthetic procedures. In the second part of the work a series of simpler photoenolizable 2--benzyl--3--benzoyl quinolones is studied by the means of fitting their UV--Vis absorption spectra and comparison with the results of quantum mechanical calculations at the TD DFT level. It was concluded that the mechanism of the reverse reaction involves ionization of the strongly acidic photoenols via protonation of the solvent molecules. The third part of the work includes investigation of the new quinolone derivatives. From the analyses of their absorption spectra and the results of quantum mechanical calculations, we propose a tentative mechanism, according to which the photoinduced hydrogen transfer yields a biradical, capable of cyclization into the hydroxy substituted dibenzo[b]acrydinones. This mechanism accounts for the observation that the nature of substituents in positions 1 and 2, the temperature and the presence of oxygen strongly affect regio-- and stereoselectivity of the cyclization
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CLAUSE, OLIVIER. "Controle de l'interaction ion support a l'interface fluide-solide lors de la preparation et de l'activation de catalyseurs au nickel et au cuivre supportes sur silice; caracterisation par spectroscopie exafs, xanes, uv-vis, et rtp." Paris 6, 1989. http://www.theses.fr/1989PA066706.
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La these comprend 3 parties: la premiere consiste en une mise au point bibliographique et theorique concernant la preparation de catalyseurs, la seconde partie concerne la preparation de catalyseurs ni/sio#2 et cu/sio#2 par impregnation a sec, echange ionique et deposition-precipitation. La spectroscopie exafs et la reduction en temperature programmee sont mises en uvre pour determiner les differents types d'interaction intervenant entre le support et les ions ni, cu a l'interface solide-liquide puis au cours du sechage. Une classification de ces interactions en fonction des conditions de preparation (ph de la solution d'impregnation, complexation des ions, teneur en metal, etc. . . ) est proposee en fin de chapitre. Il apparait que l'obtention de ni ou de cu tres bien dispersee a la surface de la silice est difficile et necessite l'echange ionique de complexes tres stables tel le bis ethylenediamine cuivre, ou le triethylenediamine nickel. En operant sans precautions particulieres on obtiendra generalement des especes pontees cu-o-cu ou ni-o-ni, allant jusqu'a la formation d'hydroxysilicates dans le cas de ni. La troisieme partie, consacree a l'effet de calcinations a differentes temperatures sur des catalyseurs supportes ni/sio#2, confirme l'importance du mode de preparation sur la stabilite thermique des catalyseurs: la formation d'oxyde de nickel nio intervient a des temperatures s'echelonnant entre 450 et 900c selon les conditions de preparation. Une etude succincte de l'activite et de la selectivite de catalyseurs a base de nickel en dimerisation du propylene est presentee en fin de chapitre
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Li, Jianping. "High-resolution UV-Vis-NIR fourier transform imaging spectroscopy and its applications in biology and chemistry." HKBU Institutional Repository, 2010. http://repository.hkbu.edu.hk/etd_ra/1151.
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Mocking, Tijs. "Studies of Nanostructured Layers with UV-VIS Spectroscopic Ellipsometry." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12053.
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In this report a model analysis is presented for three different nanostructured layers: silicon nanotips (SiNTs), gold nanosandwiches and Split Ring Resonators (SRR). The last two materials are metamaterials and both may show a negative refraction index. Experimental data are obtained for every sample using a variable angle spectroscopic ellipsometer. For the gold nanosandwiches, also an infrared ellipsometric measurement is done. For complex layers like these, advanced modeling is necessary. A recently developed analysis program including options for both anisotropic permittivity and permeability is used. A realistic model is presented in this report for the gold nanosandwiches, which also includes the magnetic activity in the layer itself. The results for the nanosandwiches are reasonable, and a magnetic oscillation is found in the horizontal plane at around 260 nm although it was not expected to have a resonance that far in the UV-range. For the SiNTs and the SRR it was not possible to create an acceptable model.
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Khadeeva, Liya. "Photo-isomerization and photo-induced NO release in ruthenium nitrosyl compounds." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S067/document.
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Ce travail de thèse est centré sur l'étude expérimentale de deux types de transformations photo-induites observées dans différents complexes métalliques (Fe, Ru, ...) à ligand nitrosyle: (i) la photo-isomérisation au cours de laquelle le ligand NO passe d'un état lié par l'azote (M-NO, état stable GS) à un état lié par l'oxygène (M-ON, état métastable MSI). C'est un processus réversible et un second état métastable, 'side-on' MSII est observable au cours du processus inverse, MSI --> 'side-on' MSII --> GS; (ii) la libération photo-induite du radical NO°. La photo-isomérisation a été étudiée dans le système [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O (sur monocristal) par la diffraction des RX, l'absorption visible statique et l'absorption UV-Vis résolue en temps. Nous avons pu mettre en évidence un processus d'absorption de photons (473 nm) en deux étapes, suivre la dynamique des transformations directes et inverses par l'évolution des paramètres de maille et des l'absorption optique visible, caractériser structuralement l'état 'side-on' MSII. La nature de l'état intermédiaire, MSII, lors du processus direct semble être différente de l'état 'side-on' mais la très faible population de cet intermédiaire n'a pas permis de trancher définitivement. Le rôle de la molécule d'eau dans la maille du complexe [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O a été testé par diffraction des RX sur les échantillons hydratées, déshydratées et réhydratées. L'effet de déshydratation sur l'évolution des paramètres de maille et sur la génération d'espèces MSII au cours de la photo-commutation inverse, MSI --> MSII --> GS, est présenté. La libération photo-induite du radical NO° a été étudiée dans une solution d'acétonitrile du complexe trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 par spectroscopies d'absorption UV-Vis et Mi-IR, statiques et résolues en temps. En observant la dynamique ultra-rapide de la photo-transformation, nous avons mis en évidence un processus d'absorption de photons (406 nm) en deux étapes. La nature de l'état intermédiaire est discuté par rapport à de récents calculs théoriques et au processus de photo-isomérisationThis Ph. D. thesis is focused on the experimental study of two photo-induced processes observed in various [ML_5NO] complexes, where M=Fe, Ru, ..., L=CN, Cl, ... : (i) photo-isomerization, where the system goes from N-bound state (M-NO, stable GS state) to O-bound state (M-ON, metastable MSI state) and a second metastable state, 'side-on' MSII is observed during the inverse photo-transformation, MSI --> 'side-on' MSII --> GS; (ii) photo-induced release of NO° radical. The photo-isomerization is investigated in single crystals of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O compound by means of X-Ray diffraction, steady state visible and time-resolved UV-visible absorption spectroscopies. During these experiments we observed the evidence of a two-step photon absorption process (473 nm), we followed the dynamics of direct and inverse photo-switching by the evolution of lattice parameters and absorption in the visible range and we caracterised the structure of 'side-on' MSII state. The nature of MSII in the direct photo-switching, GS --> MSI, seems to be different from the 'side-on' configuration, however, we do not have a direct access to this state due to its low population. The role of water molecule in the unit cell of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O complex was tested by X-Ray diffraction studies on hydrated, dehydrated and rehydrated samples. The effect of sample dehydration on the unit cell parameters evolution and MSII species generation during the MSI --> MSII --> GS inverse photo-switching is presented. The photo-induced NO° release in trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 system in acetonitrile solution is studied by the UV-visible and mid-IR absorption spectroscopies, both steady state and time-resolved. By observing the ultra-fast dynamics of photo-transformation we evidenced a two-step photon absorption process (406 nm). The nature of intermediate state is discussed within the recent theoretical calculations and the photo-isomerization process
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Herranz-Lancho, Coral. "Synthesis and characterization of molecules for electronic devices." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAE037.
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La miniaturisation toujours plus poussée des composants électroniques a atteint une limite en arrivant à l’échelle atomique. Afin de fabriquer des circuits à cette échelle, il est nécessaire de intéresser aux plus petits composants pouvant être intégrés : les molécules individuelles et les groupes d’atomes. Dans cette optique, les molécules de 1,4-bis(pyridin-4-ylethynyl) benzène (BPEB), Dibenzo[a,h]thianthrene (DBTH), de Bis{82,92,152,162,222,232- hexa-(2,4,6-trifluorophenoxy)[g,l,q]-5,10,15,20-tetraazaporphyrino)}[b,e]-benzene (H4Pc2) ont été conçues, synthétisées et caractérisées afin d’en étudier le transport de charges et les changements induits proche de la surface. Des techniques de SPM, tels que le STM, le nc-AFM et l’usage conjoint de l’AFM avec le STM ont été mises en pratique pour analyser les molécules reposant intégralement ou partiellement sur un substrat. L’interprétation des résultats expérimentaux a été faite au moyen de calculs de DFT. De plus, l’autoassemblage en solution de nouvelles mono-phthalocyanines métalliques fluorées, MPc (M= Mg2+, 2H+, Co2+) a été étudié.Tout d’abord, les mesures de conductance mirent en évidence, lors d’expériences de manipulation de fils moléculaires (BEPB), les changements de conformation associés aux transport des électrons à travers les molécules. De plus, le mouvement dit de “retournement papillon” (anglais: butterfly flapping) ayant lieu dans la classe des thianthrènes fut bloqué à basse température grâce à l’interaction avec le substrat. Ce blocage a permit de conduire la première étude stéréochimique de dérivés de thianthrènes chiraux (DBTH). Les analyses STM du DBTH ont montrées que le passage entre deux configurations de DBTH est reproductible et non-destructif. Par ailleurs, le nc-AFM utilisé à résolution sub-moléculaire a constitué un outils important pour réaliser une caractérisation complète et distinguer entre les différents isomères de configuration et de constitution déposés sur une surface. D’autre part, la structure moléculaire de la phthalocyanine binucléaire (H4Pc2) a été confirmée en utilisant un STM en mode “courant constant” et un AFM en mode “fréquence constante”. Ces résultats jettent les bases d’une prochaine étude de transport (travail en cours). En outre, l’étude de l’agrégation dans les molécules de MPc mit en évidence le rôle important de la capacité de coordination de l’atome central de la cavité Pc sur la formation d’agrégat. Finalement, des mesures électrochimiques ont démontrées que l’agrégation moléculaire peut bloquer le nature active de l’atome Co2+. Dans ce travail, il a été clairement montré que le SPM est une technique adéquate pour étudier les changements de conformations et de configurations associés aux courant tunnel d’électrons à travers des molécules, qu’elles soient planaire ou pas. Les études d’agrégation des interrupteurs magnétiques ont permis de mieux comprendre l’organisation supramoléculaire. Cette organisation est un point crucial pour le développement de futurs circuits basés sur une fabrication “bottom-up”The demand of downscaling of technology will reach its limit at the atomic length scale. This claim creates the necessity of investigating the smallest components suitable to become devices, single molecules or group of atoms. Therefore, 1,4-bis(pyridin-4-ylethynyl) benzene (BPEB), Dibenzo[a,h]thianthrene (DBTH) and Bis{82,92,152,162,222,232-hexa-(2,4,6-trifluorophenoxy)[g,l,q]-5,10,15,20-tetraazaporphyrino)}[b,e]-benzene (H4Pc2) have been designed, synthesized and characterized to investigate transport of charge through molecules and surface confined molecular switching. Scanning Probe Microscopy (SPM), such as STM, nc-AFM and combined STM/AFM were used to study the molecules on near-surface conditions. Density Functional Theory (DFT) calculations were used to interpret the experimental results. Moreover, the self-assembly of new fluorinated metalo mono-phthalocyanines, MPc (M= Mg2+, 2H+, Co2+) was investigated in solution.Firstly, conductance experiments performed while a molecular wire (BPEB) was being lifted up from a surface revealed the conformational changes associated to the transport of electrons through molecules. Secondly, the “butterfly” flapping motion in the class of the thianthrenes was blocked due to the interaction with a surface at low temperature. This block leads to the first stereochemical study of a quiral thianthere derivative (DBTH). The STM experiments on DBTH revealed a reproducible and non-destructive switching between two surface confined configurations of DBTH. In addition, nc-AFM with submolecular resolution has been proved to be a powerful tool for the full characterization and distinction of configurational and constitutional isomers on surfaces. Thirdly, the molecular structure of a binuclear phthalocyanine (H4Pc2) was confirmed through constant current STM and constant high _f AFM experiments. These results set the state of future spintronic transport experiments (ongoing work). On the other hand, the aggregation studies on MPc revealed that the coordination character of the central atom of the Pc cavity has an important effect on the formation of aggregates. Additionally, electrochemical experiments demonstrated that molecular aggregations can lead to the quenching of the electrochemical-active nature of a Co2+ atom.Herein it has been demonstrated that SPM are suitable techniques to study the conformational and configurational changes associated with the tunneling of electrons through planar and non-planar molecules in real space. Aggregation studies of magnetic switches were carried out to better understand the supramolecular organization under near surface conditions, a key point for the design of future devices based on the bottom up approach
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Juenemann, Jessica C. "UV-VIS and NMR spectroscopic studies of a palladium macroscopic square complex." Virtual Press, 2003. http://liblink.bsu.edu/uhtbin/catkey/1273267.
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Mäkelä-Vaarne, Nora. "Characterisation of group 4 metallocenes and metallocene catalysts : UV/VIS spectroscopic study." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/makela-vaarne/.
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Chen, Xi. "Infrared and Uv-Vis Spectroscopic Studies of Catalytic Reaction of Enzymes and Immobilization Enzyme on Porous Polymers." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1428327122.
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Holland, Torrey. "VIBRATIONAL SPECTROSCOPY ANALYSES OF THE DEGRADATION AND CONTAMINATION OF ENGINE OIL LUBRICANTS COUPLED WITH MULTIPLE SPECTROSCOPIC TECHNIQUES." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2399.
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The spectral analysis techniques afforded us from the field of physics has enabled us to explore the spectral signatures of trace contaminants and degradation products in used or in service engine oil through atomic and molecular spectroscopy. Here we have examined the need to address proper preparation of calibrating samples for infrared spectroscopy analysis by inducing emulsification and have evaluated multiple procedures for proper emulsification of samples with the intent to help establish the protocols that are not explicitly set forth in the ASTM International standard. We have also explored the use of Fourier-transform infrared spectroscopy techniques to examine the suppression of the O–H stretching mode of water due to the influence of ethylene glycol, which may help in the quantification of water when both are present in oil. This was done in conjunction with exploring alternative methods for direct and indirect measurement of the glycol contamination by use of UV/Vis spectroscopy, Raman, and laser-induced breakdown spectroscopy. An exploration of FT-IR and UV/Vis data on the oxidation of oil by means of ANOVA calculations has led to the reporting of highly significant differences in the data of differing oxidation times and in regions of the spectrum not known to have been previously reported.
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Vidoto, Ednalva Aparecida. "Caracterização de Ferroporfirinas através das técnicas de ressonância paramagnética eletrônica (EPR) e absorção eletrônica na região do ultravioleta-visível (UV-Vis)." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-21022014-172954/.
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As ferroporfirinas sintéticas são sistemas complexos que vêm sendo amplamente estudadas. A dificuldade em obter informações estruturais, reações químicas e ligantes do íon central vêm estimulando o estudo pormenorizado desses sistemas. Nestes trabalho é apresentada a caracterização da série de FeP fluorosubstituídas, que compreende as mono-, di-, tri e tetra- fluorofenilporfirina, denominadas FeTF5PP, FeTF10PP, FeTF15PP e FeTF20PP, respectivamente. Essas FeP são estudadas em função dos solventes diclorometano (DCM), metanol (MeOH) e das várias misturas em volume desses dois. As técnicas espectroscópicas de Absorção Eletrônica na região do Ultravioleta ao Visível (UV-Vis) e Ressonância Paramagnética Eletrônica (EPR) são as duas ferramentas de estudos escolhidas para caracterizar esses sistemas. Partindo-se de uma solução de FeP dissolvida em DCM, foram adicionadas alíquotas de Me0H até completar-se 50% em volume desses dois solventes. Através dessa titulação, observamos a formação de diferentes espécies como conseqüência da coordenação do Me0H à FeP. Notamos também, as modificações estruturais reveladas principalmente pelo EPR, ocasionadas pelos diferentes números de substituintes fluorofenis. Essa técnica espectroscópica revelou ainda a existência de interações que não foram anteriormente observadas. Para a FeTFloPP foi verificada a interação super hiperfina entre o Fe e o ligante CF além da interação super hiperfina entre o Fe e os nitrogênios do anel porfirínico. Para a FeTF20PP foi verificada apenas a interação super hipeOna entre o Fe e o ligante Cl-. As demais FeP não apresentaram essas interaçõesSynthetic iron porphyrins are complex systems that have been largely studied. Difficulties to obtain structural information, chemical reactions and ligands of the central ions have been a subject to investigate details of these systems. In this work, a systematic characterization of one series of fluorophenyl iron porphyrins is presented. Mono-, di-, tri- and tetrafluorophenyl substituents called FeTF5PP, FeTF10PP, FeTF15PP, and FeTF20PP, respectively, are included in this series. Iron porphyrins were studied as a function of dichloromethane, methanol solvents and several of their mixture in volume. These systems were characterized by Ultraviolet- Visible and Electron Paramagnetic Resonance Spectroscopes. From iron porphyrin solutions, dissolved in dichloromethane, aliquots of methanol were added up to 50% in volume of these two solvents. With this titration, we found different species because of the methanol coordination to the iron porphyrins. We also observed the structures modification revealed by the EPR spectroscopy, as a function of different numbers of fluorophenyl substituents. The EPR spectroscopy also revealed the existence of the super hyperfine interactions not observed before. It was found for FeTFloPP between the central ion and the axial ligand chlorine Cl - ion, besides the hyperfine interaction between iron and the nitrogen of the pyrrole ring. For FeTF20PP only the super hyperfine interaction, Fe-C1 was found. These interactions were not observed for the other iron porphyrins
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Takara, Marcelo. "Propriedades ópticas de absorção e emissão fluorescente do ácido orto-aminobenzóico e seus derivados em meio solvente." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-20042010-171410/.
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Nesta tese, apresentamos estudos experimentais e teóricos realizados com o Ácido orto-Aminobenzóico (o-Abz) e seus derivados 2-amino-benzamida (o-Abz-NH2), 2-amino-metil-benzamida (o-Abz-NH(CH3)) e 2-amino -dimetilbenzamida (o-Abz-N(CH3)2). Foram feitas medidas de absorção óptica, fluorescência estática e resolvida no tempo e anisotropia de fluorescência em solventes com diferentes graus de polaridade e diferentes capacidades de doar e aceitar prótons. Os resultados experimentais foram comparados aos resultados de simulações computacionais que simularam o sistema solventesoluto. Restrições impostas pelas limitações computacionais impedem cálculos totalmente quânticos via métodos ab-initio, porém uma metodologia que tem apresentado resultados satisfatórios é o método híbrido que envolve a mecânica quântica associada à mecânica molecular (QM/MM). No presente trabalho, foram combinados cálculos quânticos ab-initio e semi-empíricos na otimização de geometrias de moléculas isoladas e no cálculo de energias de transições respectivamente. Foram simulados os sistemas soluto+solvente via Método de Monte Carlo. Os espectros de absorção ótica obtidos via simulação demonstraram boa concordância com os resultados experimentais, identificando-se as bandas como oriundas das transições p-p*. Verificamos que a forma ácida aniônica do o-Abz é responsável pelo deslocamento para o azul, observado em solvente aquoso. A forma aniônica incrementa a eletronegatividade dos átomos de Oxigênio, aumentando a energia das ligações de hidrogênio. Essas ligações mais intensas estabilizam o estado excitado do o- Abz, e isso se reflete no deslocamento para azul. Da simulação, verificou-se também que na forma aniônica há uma inibição das ligações de hidrogênio do tipo doadoras por parte do grupo amina. Os derivados do o-Abz apresentam aumento na capacidade do grupo amina atuar como doador em ligações de hidrogênio e diminuição na soma de todas as ligações de hidrogênio entre soluto-solvente. Os derivados amida e monometilamida mantiveram elevado rendimento quântico e sensibilidade à polaridade ambiente. Por outro lado, o derivado o-Abz-N(CH3)2 mostra sensibilidade à presença de metilas que incrementam as vias de desexcitação não radiativa.In the present, we report experimental and theoretical studies on orthoaminobenzoic acid (o-Abz) and its derivatives 2 amino-benzamide (o-Abz-NH2), 2 amino-monomethyl-benzamide (o-Abz-NH(CH3)) and 2 amino-dimethyl-benzamide (o-Abz-N(CH3)2. We measured optical absorption, steady state and time-resolved fluorescence and fluorescence anisotropy of the compounds in solvents with different donor/acceptor character. The experimental results were compared with results of computational calculations which simulated solvent-solute systems. Due to the restrictions imposed by the computer limitations, it was not possible to do entire quantum calculations by ab-initio methods. We used then QM/MM methods, which involves quantum calculation with molecular mechanics simulations. In this work, ab-initio and semi-empiric quantum calculations were combined in the single molecule geometry optimization and energy transitions calculus, respectively. The solute-solvent system was simulated by Monte Carlo method. The optical absorption spectra obtained from simulations showed good agreement with experimental results, identifying the bands relative to p-p* transitions. It was observed that the anionic acid form of the o-Abz is responsible for the blue shift when it is in aqueous solution. Anionic form increases the electronegativity of Oxygen atoms, rising the energy of the hidrogen bonds. These strong bonds stabilize the fundamental state of o-Abz, resulting in a blue shift in absorption spetrum. From simulation, it was verified that in the anionic form of o-Abz there is also an inhibition of hidrogen bonds of the donor type by the amine group. Compared to o-Abz alone, the derivatives present an increase in the amine group capacity to act as a hidrogen bond donor. The o-Abz-NH2 and o-Abz- NH(CH3) derivatives preserved the high quantum yield and the sensitivity for the environment polarity, while in the dimethyl amide derivative, the presence of methyl groups increases the deexcitation by non-radiactive pathways.
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NZULU, GABRIEL. "Optical analysis of doped PbTe samples using UV- VIS and IR ellipsometry." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10435.
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Lead-tin telluride alloy, Pb1-xSnxTe, is a narrow band gap group IV–VI semiconductor with NaCl-like crystalline structure. This material has interesting electronic properties, which makes it suitable for designing infrared photo detectors, diode lasers, and thermo-photovoltaic energy converters. In this project, we used spectroscopic ellipsometry in the spectral range of 0.74–6.5 eV to probe the linear optical response of Pb1-xSnxTe alloys in terms of the complex dielectric function. A strong optical response in the range of 0.7-2.0 eV arising from optical absorption was found. We studied eleven different samples of Pb1-xSnxTe of p-type origin with x values in the range (0 ≤ x ≤ 1). They were prepared by means of molecular beam epitaxy (MBE) on BaF2 substrates with 15mm2 area.
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Lai, Sin Pin. "Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach." Curtin University of Technology, Department of Electrical and Computer Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=128452.
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An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
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Rüger, Robert, Thomas Niehaus, Lenthe Erik van, Thomas Heine, and Lucas Visscher. "Vibrationally resolved UV/Vis spectroscopy with time-dependent density functional based tight binding." AIP Publishing, 2016. https://ul.qucosa.de/id/qucosa%3A21502.
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We report a time-dependent density functional based tight-binding (TD-DFTB) scheme for the calculation of UV/Vis spectra, explicitly taking into account the excitation of nuclear vibrations via the adiabatic Hessian Franck-Condon method with a harmonic approximation for the nuclear wavefunction. The theory of vibrationally resolved UV/Vis spectroscopy is first summarized from the viewpoint of TD-DFTB. The method is benchmarked against time-dependent density functional theory (TD-DFT) calculations for strongly dipole allowed excitations in various aromatic and polar molecules. Using the recent 3ob:freq parameter set of Elstner’s group, very good agreement with TD-DFT calculations using local functionals was achieved.
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Sátorová, Kateřina. "Optimalizace stanovení rozdělení tenzidu při fázové separaci v systému polymer-tenzid." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2015. http://www.nusl.cz/ntk/nusl-217116.
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This diploma thesis is focused on the determination of distribution a surfactant at phase separation in polymer-surfactant system. Sodium hyaluronate of three molecular weights was chosen as a polymer, CTAB was used as a surfactant. The experiments were performed in an environment of 0,15 M NaCl. The measurement of the CTAB concentration in samples was based on the formation of coloured complexes of CTAB and picric acid in chloroform. UV-VIS spectroscopy was used for the detection of these complexes. The content of CTAB was determined in four gels of different composition (2% Hya + 200 mM CTAB, 2 % Hya + 50 mM CTAB, 0,5 % Hya + 200 mM CTAB, 0,5 % Hya + 50 mM CTAB). All gels were gradually washed five times with 0,15 M NaCl. The content of CTAB was determined for newly prepared gels and for gels after 2 and 4 months since the preparation. Initial concentrations of CTAB and hyaluronan have greater influence on the distribution of CTAB after phase separation, than the molecular weight of hyaluronan. The content of CTAB in newly prepared gels and after 4 months since preparation is very similar and demonstrates the stability of the system.
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Chan-Thaw, Carine. "Sulfated zirconia deactivation during n-butane isomerization : An in situ UV-vis-NIR spectroscopic study." Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/CHAN-THAW_Carine_2008.pdf.
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Les phénomènes de désactivation des zircones sulfatées (ZS) dopées ou non au manganèse (MnZS; 0,5 et 2,0 % en masse) au cours de la réaction d’isomérisation du n-butane sont étudiés, à 323 ou 373 K, tout au long d´une réaction (mesures in situ) par spectroscopie à réflexion diffuse dans l´ultraviolet visible et proche infra rouge (UV-vis-NIR) et par l’analyse en ligne des gaz de réaction par chromatographie en phase gazeuse. Les catalyseurs « zircone sulfatée » se désactivent en deux étapes distinctes à 373 K : une phase initiale très rapide, et une seconde plus lente. L´étape initiale de la réaction est toujours en discussion, mais plusieurs travaux scientifiques sont en faveur de la déshydrogénation oxydante (ODH). ZS contient très peu de sites actifs, et leur accès peut être bloqué quand certaines espèces y sont adsorbées. Ce travail confirme le double caractère des produits de l´ODH : l´eau et le butène – leur effets positif et négatif sur l´isomérisation du n-butane. L´activité du catalyseur dépend du degré d´hydratation de ce dernier. Les conditions dans lesquelles (milieu gazeux et température) est activée la ZS sont d´une grande importance. De l´eau en excès, à la surface du catalyseur, peut bloquer l´accès des réactifs aux sites actifs ; diminuant ainsi l´activité de la ZS. Il est montré, dans ce travail, que l´eau formée lors des premières heures est responsable de la première étape de désactivation. Comme reporté dans la littérature, le butène est un des produits de l´ODH. La protonation de ce butène par les sites actifs de Brønsted conduit à la formation des ions carbénium sec-butyle /groupes alkoxy adsorbés à la surface. Un mécanisme bimoléculaire faisant intervenir l´alkylation de l´ion carbénium sec-butyle avec une autre oléfine conduit à un réarrangement C-C. Les oléfines, en grande quantité, peuvent aussi être une des raisons de la désactivation du catalyseur. Nous avons montré que l´addition de propène au milieu réactionnel favorise la formation d´oligomères. Le même phénomène est aussi observé lorsque de l´oxygène est ajouté au système. Lors de la combustion, en présence d´oxygène, des espèces carbonées adsorbées à la surface du catalyseur, de l´eau, du dioxyde de carbone et de la chaleur sont produits. Cette chaleur peut favoriser la formation de polymères. Des oligomères absorbant à 370 et 450 nm ont été détectées à la surface de la ZS. Il est prouvé dans ce travail que qu´il existe une corrélation entre leur formation et la seconde étape de désactivation de la ZS. Ces espèces sont donc d’excellentes candidates pour expliquer la seconde phase de désactivation du catalyseur. Il est mis en évidence que les espèces monoénic allylique (absorbant à 295 nm) détectées à la surface de la ZS, au cours de la réaction d´isomérisation du n-butane, ne sont pas responsables de la désactivation du catalyseur, comme reporté dans la littérature, mais seulement des espèces spectatrices. Ces espèces ne sont pas détectées dans les spectres UV-vis de la MnZS bien que ce catalyseur se désactive très vite. Les spectres UV-vis de la MnZS montrent deux bandes. Une attribution erronée de ces bandes dans la littérature a pu être corrigée grâce à des calculs. La bande d’absorption à 580 nm émane du Mn4+ et celle à 680 nm correspond à Mn3+The deactivation phenomena during n-butane isomerization on sulfated zirconia (SZ) and manganese-promoted sulfated zirconia (MnSZ, 0. 5 or 2 wt% Mn) are investigated at 323 or 373 K by in situ UV-vis-NIR diffuse reflectance spectroscopy and on-line gas chromatography. Sulfated zirconia (SZ) catalysts are found to deactivate in two steps at 373 K: a fast initial and a slow second phase. The well accepted mechanism for the initiation step of the isomerization is the oxidative dehydrogenation (ODH). SZ is an acid catalyst with very few active sites. The access to these sites can be blocked when some species are adsorbed on them. This work confirms the duality effect of the products of ODH: water and butene - their positive and negative effects on n-butane isomerization. An appropriate hydration level of SZ is important for the activity of the catalyst. Thus, the activation conditions (atmosphere and temperature) play a major role. However, excess water on the catalyst surface (band at 1910 nm in the NIR range) can block the access of the reactant to the active sites and thus diminishes the catalyst activity. In this work, it is shown that the water formed during the first few hours on stream is responsible for the first deactivation step. As it has been reported in the literature, butene is another product of ODH and after its protonation by the Brønsted acid sites; sec-butyl carbenium ions stabilized by alkoxy groups are formed. The skeletal rearrangement can proceed through a bimolecular mechanism via an alkylation of the secondary butyl carbenium ion with another olefin. However, the presence of olefin in high quantities can be another reason for the deactivation of the catalyst. The addition of propene to the feed leads to the formation of oligomers. A similar effect on the deactivation of the catalyst is observed when oxygen is present in the system. The addition of oxygen to the feed leads to the combustion of carbonaceous deposits with the formation of water, carbon dioxide and heat. Moreover the heat can favour the formation of polymers. Oligomers were detected on the catalyst surface, with their absorption bands at 370 nm and 450 nm. The experiments showed that their formation corresponds to the second phase in SZ activity decline. These species are good candidates to explain the second step of SZ deactivation. Our study demonstrates that the monoenic allylic species (absorbing at 295 nm) detected on the catalyst during reaction, are only spectators, and not responsible for the deactivation phenomena, as reported in the literature. These species were not detected in the UV-vis spectra of MnSZ in spite of its severe deactivation. However, two bands were observed in the visible range of MnSZ spectra. An erroneous assignment of these bands in the literature could be corrected with the help of calculations. The absorption band at 580 nm arises from Mn4+ and the one at 680 nm from Mn3+
Katalysatoren auf der Basis von sulfatiertem Zirkondioxid (SZ) desaktivieren, während der Isomeriesierung von kurzkettigen Alkanen, sehr schnell. Dieser schnellen Desaktivierung zu Reaktionsbeginn folgt eine zweite Phase mit verlangsamter Desaktivierung. Das Desaktivierungverhalten während der n-Butan-Isomerisierung über sulfatiertem Zirkonoxid (SZ) und mangandotiertem sulfatierten Zirkonoxid (MnSZ; 0,5 or 2,0 wt% Mn) wurden mit Hilfe der in situ UV-vis-NIR-Spektroskopie in diffuser Reflexion, d. H. Simultane Analyse des Reaktiongases durch gaschromatographische Verfahren, untersucht. Der derzeit akzeptierte Mechanismus für den Reaktionsstart ist eine oxidative Dehydrogenierung (ODH). SZ ist ein saurer Katalysator mit wenigen aktiven Oberflächenzentren, welche leicht durch Adsorption von Edukten/Reaktionsprodukten blockiert werden können. Diese Arbeit zeigt die Dualität des Einflusses von Wasser und Buten, der Reaktionsprodukte der ODH, ihren positiven und negativen Effekt auf die n- Butan-Isomerisierung. Ein optimaler Hydratisierungsgrad des SZ ist entscheidend für die Aktivität des Katalysators. Der Hydratisierungsgrad wird maßgeblich durch die Aktivierungsbedingungen (Gaszusammensetzung und Temperatur) bestimmt. Bei nicht Einhaltung des optimalen Hydratisierungsgrades kann Wasser (Absorptionband bei 1910 nm) die aktiven Zentren blockieren und somit die Aktivität des Katalysators herabsetzen. In der vorliegenden Arbeit kann gezeigt werden, dass die Bildung von Wasser in den ersten Stunden der Reaktion für die schnelle Desaktivierung zu Reaktionsbeginn verantwortlich ist. Wie in der Literatur bereits beschrieben ist, wird Buten durch Protonierung an sauren Brønsted-Zentren, über Carbenium-Intermediate, in das entsprechende Alkoxid überführt. Die Skelettisomerisierung von n-Butan folgt einem bimolekularen Mechanismus und verläuft über die Alkylierung von Gasphasenolefinen mit sec-Butyl-Carbeniumionen. Die Gegenwart von größeren Mengen an Olefinen ist jedoch ein weiterer Grund für die Katalysatordeaktivierung. Die Zugabe von Propen zum Reaktionsgemisch führte zur Bildung von Polymeren. Die Zugabe von Sauerstoff zum Reaktionsgemisch führt zur Verbrennung von kohlenstoffhaltigen Ablagerungen auf der Katalysatoroberfläche und zur Bildung von Wasser, Kohlendioxid sowie Wärme, was vergleichbare Desaktivierungserscheinungen hervorruft. Die Freisetzung von Wärme fördert zusätzlich die Bildung von Polymeren. Oligomere konnten durch ihre Absorptionsbanden bei 370 und 450 nm auf der Katalysatoroberfläche nachgewiesen werden. Die vorliegende Arbeit zeigt, dass die Bildung oligomerer Spezies eine mögliche Ursache für den zweiten, langsameren Desaktivierungsvorgang ist. Die während der Reaktion gebildete monomere Allyl-Spezies (Absorption bei 295 nm) ist entgegen der Literatur nicht für die Desaktivierungsphänomene verantwortlich. Keine der auf SZ gefundenen allylischen Spezies konnte auf MnSZ nachgewiesen werden. Jedoch desaktiviert MnSZ sehr schnell. Zwei Banden im UV-vis Bereich von Spektren der MnSZ-Katalysatoren werden beobachtet. Die fehlerhafte Zuordnung dieser Banden in der Literatur konnte durch Simulation der Spektren korrigiert werden. Die Absorption bei 580 nm ist auf Mn4+, die bei 680 nm auf Mn3+ zurückzuführen
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Gulses, Alkan Ali. "Ellipsometric And Uv-vis Transmittance Analysis Of Amorphous Silicon Carbide Thin Films." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605589/index.pdf.
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The fundamentals of the ellipsometry are reviewed in order to point out the strengths and weaknesses of the ellipsometric measurements. The effects of the surface conditions (such as degree of cleanliness, contaminated thin layer, roughness etc&hellip) on the ellipsometric variables are experimentally studied
the optimum procedures have been determined. Hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films are produced by plasma enhanced chemical vapor deposition (PECVD) technique with a circular reactor, in a way that RF power and carbon contents are taken as variables. These samples are analyzed using multiple angle of incidence ellipsometer and uv-vis spectrometer. These measurements have inhomogeneities in optical constants, such as thicknesses, refractive indices and optical energy gaps along the radial direction of the reactor electrode for different power and carbon contents.
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Templeton, John Andrew. "Magnetite Oxidation in Aqueous Systems." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/43468.
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Magnetite, an iron oxide, is a possible candidate for in situ remediation of contaminated groundwater systems due to its oxidation/reduction potential for reduction of contaminants such as carbon tetrachloride. Little characterization and analysis has been done to describe the kinetics of magnetite transformation during oxidation. This work focuses on monitoring the concentrations of magnetite and one of its oxidation transformation products, maghemite, by the use of UV-Vis-NIR spectroscopy. As oxidation proceeded at a constant specific temperature, the concentration of magnetite decreases, which was indicated by a decrease in absorption in the NIR-region of the spectrum. As magnetite concentrations decreased, the concentration of maghemite increased, which was indicated by an increase in absorption in the UV-region. The temperature at which the suspensions of magnetite and maghemite were measured was of great importance for complete understanding of the magnetite transformation as seen by UV-Vis-NIR spectroscopy analysis. Higher measurement temperatures produced higher absorptivities of FeII-FeIII electron hopping transitions, while decreasing the absorptivity of FeIII-FeIII in the NIR and UV-regions respectively. Lower temperatures produced the opposite effects on the iron oxidesâ transitions. Higher temperature increased the rate of oxidation.Master of Science
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Šejnohová, Michaela. "Studium interakcí hyaluronan-tenzidy dialyzační technikou." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217017.
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This diploma thesis is concentrated on the interactions between polyelectrolyte (hyaluronan) and cationic surfactant (CTAB). The experiments were performed in an aqueous solution and in an environment of physiological ionic strength (0,15mmoldm-3 NaCl). The determination of the surfactant concentration in solutions was based on the formation of colored complexes of CTAB and picric acid in chloroform. The concentrations of surfactant were measured by UV-VIS spectroscopy. The stability of CTAB+HyA was examined by a dialysis method. The results showed that, regardless of the environment, the presence of HyA in solution reduces the number of free molecules of CTAB which can be determined in the sample. It has been proved that there is an interaction between HyA and surfactant and that CTAB has greater affinity for HyA then for the picric acid. The stability of CTAB+HyA was determined by dialysis of 120 hours. After that time, the concentrations of the retentate and permeate were settled. The results showed that in the membrane remains a certain amount of CTAB bounded to hyaluronan. The system can be suitable for the preparation of targeted carriers of biologically active substances.
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Tumová, Šárka. "Vliv fotochromního aditiva na optické a elektrické vlastnosti polymerních matric." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316197.
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This thesis is focused on the photochromic molecule of spiropyran, which changes its structure as well as physical and chemical properties after UV irradiation. These changes are reversible, the molecule thermally restore its initial structure. For the study, the molecule SP1 with the systematic name 1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] was used. This molecule was incorporated within polymers PVK, Tg PPV, PCBTDPP and PCDTBT and the method of UV-VIS spectroscopy was used to observe the photochromic activity within these matrices. The influence of matrices to the ability to undergo UV induced photochromic conversion as well as to the reverse conversion to the initial structure induced by heat was monitored. Furthermore, the influence of spiropyran to the electrical properties of individual matrices was studied. The effect of photochromic conversion to both, the mobility of charge carriers and to the photogeneration was observed. For this purpose, the method of current-voltage measurement was used.
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Williams, Elizabeth Mary. "Oxidation of human nitrosylhemoglobin monitored by UV-Vis and EPR Spectroscopies: detection of products and intermediates." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/williams/WilliamsE0805.pdf.
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Noumet, Anne-Gaëlle. "Effets du niobium sur les mécanismes réactionnels d'oxydation des aluminiures de titane." Paris 6, 2006. http://www.theses.fr/2006PA066478.
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Les TiAl présentent des avantages pour des applications aéronautiques. Grâce à leurs bonnes propriétés, les TiAl sont candidats pour remplacer les superalliages. Ces alliages présentent une mauvaise résistance à l’oxydation, ce qui limite leur mise en service. L’effet du niobium sur les mécanismes de l’oxydation a été déterminé des premiers instants d’oxydation à pression réduite jusqu’à des stades avancés à pression atmosphérique à 650°C. L’étude des premiers instants d’oxydation des alliages dopés entre 2 et 30 %at de niobium a montré que le niobium accélère l’absorption de l’oxygène, favorise la formation d’une couche d’alumine et retarde l’apparition de TiO2. L’étude de l’oxydation longue durée a montré que le niobium freine l’absorption de l’azote retardant l’apparition de TiN stabilisé aux temps longs d’oxydation, il diffuse vers la couche de rutile ralentissant les cinétiques de diffusion de l’oxygène, il favorise la formation d’une couche d’alumine continue à la surface.
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Gonçalves, Tássia de Souza. "Rare earth doped fluorophosphate glass and glass-ceramics: structure-property relations." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-30102018-100600/.
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Rare earth RE3+ doped fluorophosphates glasses and glass ceramics are among the most promising candidates for high efficiency laser generation in the near-infrared spectral region. Glass ceramics are polycrystalline materials of fine microstructure that are produced by the controlled crystallization (devitrification) of a glass. By developing fluorophosphate base glasses with appropriate compositions and by controlling crystal nucleation and growth in them, glass ceramics with special properties can be fabricated combining the advantages of fluorides (low phonon energy, low refractive indexes, extensive optical window, lower hygroscopicity) and oxides (high chemical and mechanical stability and high dopant solubility), resulting in enhancement of the RE3+ emissive properties. In this study, we present the synthesis by melting/quenting and structural/spectroscopic investigation of new glasses and glass ceramics with composition 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3: zREF3, where x = 15, 20 or 25, RE = Er3+ an/or Yb3+ and Nd3+. A detailed structural investigation of a series of this glasses has been conducted, using Raman, solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies.Vidros e vitrocerâmicas fluorofosfatos dopados com íons terras raras (TR3+) estão entre os candidatos mais promissores para a geração de laser de alta eficiência na região espectral do infravermelho próximo. As vitrocerâmicas são materiais policristalinos com microestrutura bem definida obtida a partir da cristalização controlada do vidro base. Desenvolvendo vidros base de fluorofosfato com composições apropriadas e controlando a nucleação e crescimento de cristais, vitrocerâmicas com propriedades especiais podem ser fabricadas combinando as vantagens dos fluoretos (baixa energia de fônons, baixos índices de refração, janela ótica extensa, baixa higroscopicidade) e óxidos (alta estabilidade química e mecânica e alta solubilidade dopante), resultando no aumento das propriedades emissoras dos íons TR3+. Neste estudo, apresentamos a síntese por fusão/resfriamento e investigação estrutural/espectroscópica de novos vidros e vitrocerâmicas com composição 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3: zREF3, onde x = 15, 20 ou 25, RE = Er3+ an / ou Yb3+ e Nd3+. Uma investigação estrutural detalhada de uma série destes vidros foi conduzida utilizando espectroscopias Raman, de ressonância magnética nuclear de estado sólido (RMN) e de ressonância paramagnética eletrônica (EPR).
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Gonçalves, Tássia de Souza. "Caracterização estrutural e espectroscópica de vidros fluorofosfatos dopados e co-dopados com Er3+ e Yb3+." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-18082014-150349/.
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Atualmente, vidros e vitrocerâmicas dopados com íons terras raras trivalentes TR3+ constituem a mais importante classe de materiais para aplicações laser e em outros dispositivos ópticos, na região do infravermelho próximo e visível. Neste contexto, um dos desafios está em encontrar uma matriz hospedeira adequada que assegure qualidade óptica e um ótimo desempenho dos íons dopantes (altas seções de choque de absorção e emissão, baixa probabilidade de decaimentos não radiativos, tempos de vida de estado excitado suficientemente longos), mantendo estabilidade térmica e mecânica. Entre os possíveis candidatos, estão os vidros fosfatos com alta capacidade de dispersão dos dopantes, baixo índice de refração e propriedades termo-ópticas superiores aos silicatos, calcogenetos e fluoretos. Contudo, estes vidros apresentam alta energia de fônons, menor estabilidade química e mecânica e são higroscópicos, o que pode constituir um significativo mecanismo de supressão da luminescência devido ao acoplamento de transições dos TR3+ com vibrações de grupos hidroxila. Se por um lado vidros fluoretos podem ser obtidos com baixas energias de fônon e alta estabilidade química, os mesmos são mecanicamente frágeis e apresentam más características termo-ópticas. Para superar estas limitações, vidros oxifluoretos como fluorofosfatos têm sido explorados com a promessa de combinar os méritos dos fluoretos (baixas energias de fônon, baixos índices de refração, extensa janela de transmissão óptica) e dos óxidos (alta estabilidade química e resistência mecânica, maior solubilidade dos TR3+). Do ponto de vista das aplicações, considerando a transmissão e amplificação de sinais em telecomunicação em torno de 1,5 µm, e geração de ação laser de alta potência em torno de 1,0 µm, materiais dopados com Er3+ e Yb3+ estão entre os mais importantes. Neste trabalho apresenta-se a síntese e caracterização estrutural e espectroscópica de novos vidros fluorofosfatos dopados com Er3+ ou Yb3+ e co-dopados com ambos, no sistema composicional 25BaF225SrF2(30-x)Al(PO3)3xAlF3 (20-z)YF3:zTRF3 com x = 20 ou 15, TR = Er3+ e/ou Yb3+ e z = 0,25, 0,5, 1,0, 2,0, 3,0, 4,0 e 5,0 mol%. As amostras foram obtidas pelo método convencional de fusão e resfriamento e caracterizadas por Raman, Ressonância Magnética Nuclear de estado sólido e espectroscopia UV-VIS. Dos estudos por RMN de 19F verificou-se que há uma perda máxima de fluoreto de ~20% nas amostras. Ainda assim, a quantidade remanescente foi suficiente para garantir um ambiente químico favorável às emissões e poucas diferenças foram notadas entre as amostras com 20 e 15 mol% AlF3 contendo a mesma concentração de dopantes. Para o Er3+, tempos de vida do estado emissor 4I13/2 da ordem de 10 ms implicam em altos valores de eficiência quântica (η= 85%) e para o Yb3+ tempos de vida do estado emissor 2F5/2 similarmente longos (τ = 1,7 ms) foram medidos. Em amostras co-dopadas com 4,0 mol% YbF3 e 0,25, 1,0 e 2,0 mol% ErF3 o decréscimo do tempo de vida do Yb3+ e acréscimo do tempo de vida do Er3+ indicam que a transferência Yb→Er foi eficiente neste sistema. De maneira geral, os resultados indicam que os vidros estudados são potenciais candidatos a aplicações ópticas como as mencionadas acima.Currently, glasses and glass ceramics doped with trivalent rare earth ions RE3+ represent the most important class of materials for laser and other optical applications in the visible and near-infrared spectral regions. In this context, one of the challenges is to find host matrices that assure good optical quality and optimum performance of the dopant ions (high absorption and emission cross sections, low probability of non-radiative decays, sufficiently long excited state lifetimes), while still maintaining thermal and mechanical stabilities. Among the candidates, phosphate glasses with high capacity for RE3+ dispersion, low refractive index and superior thermo-optical properties than silicate, chalcogenide and fluoride glasses are largely studied. However, phosphates present high phonon energies, lower chemical and mechanical stabilities and they are hygroscopic, which can imply in significant luminescence quenching effects. If on one hand fluoride glasses may be designed with low phonon energies and higher chemical stability, they are frail and present less than ideal thermo-optical properties. In order to overcome these drawbacks, oxyfluoride glasses such as fluorophosphates have been explored with the promise to combine the merits of fluorides (low phonon energies and refractive index, extensive optical window) and of oxides (high chemical stability and chemical resistance, higher solubility of RE3+). From the viewpoint of applications, when it comes to the transmission and amplification of signal in telecommunications around 1.5 µm, and the generation of high power lasers around 1.0 µm, materials doped with Er3+ and Yb3+ are among the favorite. Furthermore, because Yb3+ presents higher absorption cross-section than Er3+ at the preferred excitation wavelength for both these ions (980 nm), the former can act as an efficient sensitizer of excitation energy with subsequent transfer to the latter. We present the synthesis, and structural and spectroscopic characterization of new flurophosphate glasses doped with Er3+ or Yb3+ and co-doped with both, in the compositional system 25BaF225SrF2(30x)Al(PO3)3 xAlF3 (20- z)YF3:zREF3 with x = 20 or 15, RE = Er3+ and/or Yb3+ and z = 0.25, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mol%. The samples were obtained by conventional melt quenching technique and characterized by Raman, solid state NMR and UV-VIS spectroscopy. From the NMR studies of 19F, it was shown that there is a maximum fluoride loss of 20% in the samples. Even so, the remaining quantity was enough to assure a favorable chemical environment to the RE3+ emissions. Little differences were detected between the samples with 20 and 15 mol% AlF3 for the same dopant concentration. For Er3+, lifetimes of the emitting level 4I13/2 of the order of 10 ms result in fluorescence quantum efficiency values (η = 85%), and similarly, for Yb3+, long lifetimes of the excited state 2F5/2 (τ = 1,7 ms) were measured. In co-doped samples with 4.0 mol% YbF3 and 0.25, 1.0 and 2.0 mol% ErF3 the decrease in lifetime of Yb3+ and increase in lifetime of Er3+ indicate that the Yb→Er energy transfer is efficient in this system. In general, the results indicate that the studied glasses are potential candidates for optical applications.
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Lambert, Alexander S. "Application of UV-Vis Spectroscopy to the Monitoring, Characterization and Analysis of Chemical Equilibria of Copper Etching Baths." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011880/.
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The continuously increasing demand for innovation in the miniaturization of microelectronics has driven the need for ever more precise fabrication strategies for device packaging, especially for printed circuit boards (PCBs). Subtractive copper etching is a fundamental step in the fabrication process, requiring very precise control of etch rate and etch factor. Changes in the etching chemical equilibrium have significant effects on etching behavior, and CuCl2 / HCl etching baths are typically monitored with several parameters including oxidation-reduction potential, conductivity, and specific gravity. However, the etch rate and etch factor can be difficult to control even under strict engineering controls of those monitoring parameters. The mechanism of acidic cupric chloride etching, regeneration and recovery is complex, and the current monitoring strategies can have difficulty controlling the interlocking chemical equilibria. A complimentary tool, thin-film UV-Vis spectroscopy, can be utilized to improve the current monitoring strategies, as UV-Vis is capable of identifying and predicting etching behavior that the current standard methodologies have difficulty predicting. Furthermore, as a chemically-sensitive probe, UV-Vis can investigate the complex changes to the chemical equilibrium and speciation of the etch bath, and can contribute overall to significant improvements in the control of the copper etching system in order to meet the demands of next-level design strategies.
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Schutte, Carol Lynn. "Sol-gel coatings containing inorganic and organic compounds--studies using Rutherford backscattering spectrometry and UV-VIS spectroscopy." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13639.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.Vita.
Includes bibliographical references (leaves 135-139).
by Carol Lynn Schutte.
Ph.D.
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Shao, Lei. "Surface chemistry and structural studies of photosystem II using UV-VIS and fluorescence spectroscopies and atomic force microscopy." Thèse, Trois-Rivières : Université du Québec à Trois-Rivières, 1998. http://www.uqtr.ca/biblio/notice/resume/03-2190303R.html.
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Thèse (Ph.D.) - Université du Québec à Trois-Rivières, 1998.Résumé en fraçais. Le résumé et la table des matières sont disponibles en format électronique sur le site Web de la bibliothèque. CaQTU Bibliogr. : f. [135]-167.
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FILHO, LUIZ DA SILVA GOES. "SOLVENT EFFECTS ON SPECTROSCOPIC PROPERTIES OF THE ANTIBIOTIC NORFLOXACIN: UV-VIS ABSORPTION, STEADY STATE AND TIME-RESOLVED FLUORESCENCE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=17692@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRONorfloxacina (NOR) é um antibiótico e antitumoral sintético da classe das fluorquinolonas. A carga elétrica de seu íon molecular é determinada principalmente pelo estado de protonação de dois grupos funcionais: o grupo carboxílico no anel quinolônico e a amina do grupo piperazinil. O equilíbrio de espécies com diferentes estados de protonação influencia tanto as propriedades espectroscópicas quanto a atividade farmacológica da droga. NOR apresenta-se positivamente carregada em meio ácido, neutra ou zwiteriônica em meio neutro e negativamente carregada em meio básico. No presente trabalho, investigamos as propriedades espectroscópicas da norfloxacina, através de absorção ótica e de fluorescência estacionária e resolvida no tempo, em soluções aquosas de diferentes pH e em diferentes solventes orgânicos. Parâmetros fotofísicos como coeficiente de absorção molar, deslocamento de Stokes, rendimento quântico, e tempo de vida de fluorescência foram obtidos. O deslocamento de Stokes e a frequência de emissão foram analisados em 16 solventes, agrupados principalmente em solventes próticos e apróticos, levando em consideração efeitos gerais, como a polarizabilidade de orientação dos solventes, e efeitos específicos. Foi observado que, apesar de os espectros de absorção UV-visível não apresentarem diferenças substanciais na maioria dos solventes, o deslocamento de Stokes e, especialmente, o rendimento quântico de fluorescência são fortemente afetados pelo solvente. Foram construídos gráficos de Lippert, do desvio de Stokes ou da frequência de emissão como função da polarizabilidade de orientação do solvente. Mesmo introduzindo correção para transferências de carga fotoinduzidas, segundo a teoria de Weller, não foram obtidas boas correlações. Por outro lado, para a maioria dos solventes, encontrou-se correlação entre os desvios de Stokes e os valores do parâmetro ET(30) da escala empírica de polaridades elaborada por Reichardt e baseada no forte solvatocromismo da absorção do corante betaína 30. Decaimentos de fluorescência de NOR nos diferentes solventes foram obtidos por contagem de fótons e foram ajustados com expressão para distribuição de tempos de vida em torno de um único tempo, ou de múltiplas exponenciais no caso de mais de um tempo de vida. Foram também estudadas absorção e fluorescência de NOR em misturas binárias de solventes: etanol-tampão e DMSO-tampão, com tampões de pH 4.2 e 7.5. As curvas obtidas para as modificações no rendimento quântico em função da proporção de tampão na mistura são características de efeitos específicos de solventes e apontam o equilíbrio de protonação-desprotonação dos grupos amina e carboxílico como tendo papel fundamental no rendimento quântico e no deslocamento de Stokes. Os resultados mostraram que, sendo a fluorescência de NOR particularmente sensível a pequenas quantidades de solventes orgânicos, especialmente em pH fisiológico, constitui um importante sensor espectroscópico para sondar interações do antibiótico com moléculas biologicamente relevantes.
Norfloxacin (NOR) is a synthetic antibiotic and antitumoral drug of the class of fluoroquinolones. The electric charge of this molecular ion is mainly determined by the protonation equilibrium of two functional groups: the carboxyl of the quinolone heterocycle, and the distal amine of the piperazinyl group. The equilibrium of species with different charge distributions influences both the spectroscopic properties and pharmacological activity of the drug: NOR is positively charged in acidic medium, neutral or zwitterionic in neutral medium, and negatively charged in basic medium. In the present work, we investigated the spectroscopic properties of norfloxacin using UV-vis optical absorption, and steady state and time-resolved fluorescence in different aqueous solutions and organic solvents. Photophysical parameters such as molar absorption coefficients, Stokes shifts, quantum yields, and fluorescence lifetimes were obtained. The Stokes shift and the emission frequency were analyzed in 16 solvents, mainly grouped as protic and aprotic solvents, taking into account general effects of the solvents, such as orientation polarizability, and specific effects. It was observed that, although the UV-vis absorption spectra do not present substantial difference in most solvents, the Stokes shift and specially the fluorescence quantum yield are strongly affected by the solvent. Lippert plots of the Stokes shift and the emission frequency versus solvent orientation polarizability were constructed. Even introducing a correction for photoinduced charge transfer, according to the Weller’s theory, a good correlation was not found. On the other hand, a good correlation was found between the Stokes shift and the parameter ET(30), of the empirical scale developed by Reichardt and based on the strong solvatochromism of the betain 30 dye. Fluorescence decays in different solvents were obtained using time correlated single photon counting (TCSPC) and were fitted with the expression for lifetime distribution around a single lifetime, or using a multiexponential expression in the case of more than one lifetime. Optical absorption and fluorescence of NOR were also studied in binary mixtures of solvents: ethanol-buffer and DMSO-buffer, with pH 4.2 and 7.5 buffers. The curves of the fluorescence intensity as a function of the proportion of buffer in the mixture are characteristic of specific solvent effects, and point out that the protonation-deprotonation equilibrium of the amine and carboxylic groups plays a fundamental role in determining the quantum yield and the Stokes shift. The results showed that the fluorescence of NOR is an important spectroscopic sensor to explore interactions with biologically relevant molecules, since it is particularly sensitive to small amounts of organic solvents, especially at physiological pH.
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Rouxinol, Maria Inês Silva Caçador Pereira. "Determinação das principais antocianinas em castas tintas no Alentejo." Master's thesis, Universidade de Évora, 2016. http://hdl.handle.net/10174/20869.
Full textAbstract:
Os compostos fenólicos (incluindo as antocianinas) estão presentes no vinho e possuem
atividade antioxidante relevante, protegendo as células contra processos oxidativos, podendo
ser importantes na prevenção de doenças cardiovasculares, neurodegenerativas e
cancerígenas, entre outras.
O objetivo deste trabalho é a avaliação da composição em antocianinas em castas de uvas
tintas desde ao pintor até ao final da maturação. As antocianinas foram quantificadas por
HPLC. Adicionalmente o conteúdo total em compostos fenólicos foi determinado por
espectrometria UV-Vis. Observou-se nos resultados de todas as análises efetuadas um
padrão repetido e consistente de evolução dos compostos em estudo.
Foi ainda testado neste trabalho a quantificação das antocianinas totais, de malvidina-3-
glucósido e dos compostos fenólicos totais através de um método espectroscópico baseado
no espectro de absorção da zona UV. Embora a calibração deste método não tenha
apresentado valores muito robustos, poderá no futuro ser utilizada como método alternativo
rápido para a quantificação de antocianinas e compostos fenólicos; Abstract:
«Quantification of Anthocyanins in Red Wine Grapes in Alentejo»
Phenolic Compounds (including anthocyanins) are present in wine and possess significant
antioxidant activity, protecting cells against oxidative processes, and preventing prevent
cardiovascular, neurodegenerative and cancer diseases, among others.
The aim of this study is the evaluation of the anthocyanins composition in red wine grapes
from the verásion until the end of ripening. Anthocyanins were quantified by HPLC.
Additionally the total content of phenolic compounds was determined by UV-Vis
spectrometry. It was possible to verify in all tests that the results have a consistent evolution
pattern considering different tested compounds.
Anthocyanins, malvidin-3-glucoside and phenolic compounds were also quantified by a
spectroscopic method based on the UV absorption spectrum. Although the calibration of this
method has not presented very sturdy values, it should be improved in the future and used as
an alternative method for rapid quantification of anthocyanins and phenolic content.
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Bradshaw, John Thomas. "BROADBAND COUPLING INTO SINGLE MODE, PLANAR INTEGRATED OPTICAL WAVEGUIDE STRUCTURES FOR SPECTRAL ANALYSIS OF THIN FILM ANALYTES AND INTERFACIAL CHEMICAL ENVIRONMENTS." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1144%5F1%5Fm.pdf&type=application/pdf.
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Lenartová, Radka. "Solubilizační schopnosti polysacharidů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216402.
Full textAbstract:
In this diploma thesis were studied solubilization properties of polysaccharides by using hydrophobic solutes (Sudan Orange G, Sudan Red G, (±)-alpha-Tocopherol, Pyrene, Perylene, Nile red), which were represented by alkyl derivates of hyaluronan. At first, a behaviour of individual hydrophobic solutes was investigated in variously polar solvents (Methanol, 1 Propanol, Chloroforme, Cyklohexane, n Heptane) and in the environment of varying ionic strength (water, 0.1 M and 0.4 M NaCl). Afterwards, solubilization properties of Sodium Dodecyl Sulfate model solubilizated the hydrophobic solutes into a core of micelles was examinate. We were interested in the solubilization capacity as the mol of solubilized molecules per mol micelles of surfactant corresponding with a state of micelles saturation. In the case of the solubilization of (±)-alpha-Tocopherol into the core of micelles, it was not possible to determine the solubilization capacity. So we changed the determination of universally solubilization power. The solubilization power is defined as mol of molecules solubilized per mol surfactant relative to the quantity solubilizate at the micelles saturation. Model system of Sodium Dodecyl Sulfate as a simple surfactant carrying a negative charge as the alkyl derivates of hyaluronan was selected bacause of its characteristics.The surfactant forms unimolar micelles and its critical micelle concentrations and aggregation numbers are tabelated for the investigated microenvironment. The main aim of the study was investigating of hydrophobic domains of alkyl derivates of hyaluronan as free places for incorporation hydropbobic solutes in the microenvironment of varying ionic strength. The critical aggregation concentrations were determined by the Pyrene 1:3 ratio method. For the research of micropolarity of alkyl derivates hyaluronan’s domains were selected two concentrations of derivates for the next research of solubilization experiments - the first concentration near the critical aggregation concentration and the second concentration above it. The effect of concentration of Pyrene on a core polarity of derivates was investigated. We discovered the influence of the concentration and the other we found a stationary area of the concentration. In the end we investigated the influence of preparation of solutions of derivates of hyaluronan on the core polarity by the concentration of pyrene which corresponds to the stationary area. The study of solubilization properties of alkyl derivates of hyaluronan is not a simple case as we assumed. When we measured spectra of the absorbance, higher concentration of derivates of hyaluronan belittle absorbance of solubilizates. At the experiment of solubilization with Sudan Red G we found out that Sudan Red G is not able to solubilizate into the hydrophobic core of micelles of hyaluronan’s derivates because of lipophilic or steric effects. We had to change Perylene as a new solubilizate. From the measured emission spectra we found saturation micelles. We can express the solubilization power of hyaluronan’s derivates for the concentration of Perylene. The main aim of the diploma thesis was to determine optimal way of the preparation of hyaluronan’s derivates solutions with required degree of solubilization.
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May, John. "Investigating the binding mode of azide labelled derivatives of Hoechst 33258 by NMR, UV-Vis and IR spectroscopy." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27859.
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This thesis describes attempts to develop a method for studying the dynamics of dsDNA: small molecule ligand association and dissociation through 2D-IR spectroscopy. The strategy employed was to synthesise azide-bearing derivatives of the archetypal minor groove binding ligand, Hoechst 33258, with the azide acting as a reporter functional group. Chapter 1 describes both the state of the art, and also what is unknown regarding the processes of association and dissociation of small molecules from dsDNA, and how this project aims to gain a fuller understanding of the dynamics of association between dsDNA and a smallmolecule MGB. The clinical significance of minor groove binders is also discussed. Chapter 2 describes the synthesis of two azide-bearing derivatives of H33258 through an amide coupling strategy, and the significant problems encountered with the purification of these compounds. Future alternative pathways to these compounds are proposed. An investigation into the spectroscopic properties of the azide functional groups in the free compounds is also presented. Chapter 3 describes the investigation of the utility of the azide functional group through a comparative study of the thermal dissociation of these compounds from dsDNA. It was found that the utility of the azide was dependent on the position of the azide within the molecule, and is sensitive to the changes in solvation of the minor groove of dsDNA. One compound in particular exhibited a marked change in both the shape and the intensity of the azide absorptionband and was commensurate with the melting temperature, Tm of the complex. Chapter 4 describes the investigation into the structural origins of the marked difference in the azide absorption band of one MGB when in complex with a dsDNA oligomer through structural characterization of this complex by NMR spectroscopy. It was found that the azidefunctional group is in close proximity to the exocyclic amine of guanosine, and this specificinteraction is proposed to give rise to the observed changes in the azide absorption band. The orientation of the molecule was found to be opposite to that reported for H33258, a reason why this is the case is also proposed.
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Aritani, Hirofumi. "Characterization of Active Species in Molybdenum-and Copper-Based Catalysts by Means of XAFS and UV-VIS Spectroscopy." Kyoto University, 1996. http://hdl.handle.net/2433/77836.
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Rodrigues, Matthew. "An investigation into the catalytic mechanism of vitamin B6 biosynthesis using X-ray crystallography and UV-Vis spectroscopy." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/405821/.
Full textAbstract:
The catalytic mechanism of the Pdx1 subunit of the pyridoxal 5’-phosphate (PLP) syn-thase enzyme complex has been the subject of intense study since its discovery in 1999. Pdx1 uses two active sites (P1 and P2) to perform a complex reaction combining ribose 5-phosphate, ammonia and glyceraldehyde 3-phosphate to form PLP. While some aspects of the Pdx1 mechanism are now understood, several questions re-main, in particular how the enzyme transfers the reaction from one active site to the next and how the reactions in the two sites are coordinated. In this investigation, X-ray crystallography and UV-Vis spectrophotometry have been used to determine the struc-ture of the protein in various intermediate states and elucidate the catalytic mechanism. The role of specific active site residues in catalysis of PLP biosynthesis by the Arabidop-sis thaliana Pdx1 protein is investigated using site-directed mutagenesis. The crystal structures presented in this thesis demonstrate that the Pdx1 enzyme uses a novel relay mechanism to covalently transfer intermediates between active sites and to coordinate substrate binding, intermediate shuttling and catalysis. Chapter 1 provides an introduction to the biological role of pyridoxal 5’-phosphate and its biosynthesis by the PLP synthase enzyme complex. Chapter 1 also describes the use of X-ray crystallography to understand how proteins function and how complementary methods such as UV-Vis spectrophotometry can be used to track the effects of site-specific radiation damage during collection of X-ray diffraction data. The methods used to produce, purify and investigate the Pdx1 enzyme are described in Chapter 2. Chapter 3 provides an analysis of the activity of wild type AtPdx1.3 using UV-Vis spectropho-tometry and X-ray crystallography to monitor the accumulation of chromophoric inter-mediates and the product, PLP. Chapter 4 describes the use of site-directed mutagenesis to trap the Pdx1 protein in additional intermediate states and the characterisation of these intermediate states using UV-Vis spectroscopy and crystallography. UV-Vis spectra of Pdx1 crystals were collected to ensure that the Pdx1 enzyme was in the desired intermediate state before collection of X-ray diffraction data. It became clear that the UV-Vis spectra of the Pdx1 crystals in some intermediate states were changing during X-ray data collection. Chapter 5 describes the experiments that were performed to check that the Pdx1 structures obtained were not affected by site-specific radiation damage. The use of multi-crystal data collection strategies and UV-Vis spectroscopy showed that changes in the spectra were instead caused by radiolysis of the solvent surrounding the crystals.
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Čuboň, Tomáš. "Studium optických vlastností tenkých vrstev organických fotovoltaických článků." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316198.
Full textAbstract:
This master´s thesis is focused on measurement of optical properties of thin layer of materials used in organic solar cells (OSC). The usage of graphene oxides and its reduced forms as parts of hole transport layer (HLT) in OSC were studied. At the beginning of the thesis, there is described basic theory necessary to understand the optical properties of thin layers. The thin layer deposition and reduction of GO are discussed too. The experimental part is aimed to the optical characterization of prepared thin films. The results from optical microscopy, UV-VIS spectroscopy, FT-IR spectroscopy and spectroscopic ellipsometry were obtained. At the end of the thesis, the results are concluded and compared with already published literature.
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Bauer, Matthias. "Investigations of alkoxide precursor solutions and homogeneous catalyzed reactions by X-ray absorption and multi dimensional spectroscopy." Berlin mbv, Mensch-und-Buch-Verl, 2008. http://d-nb.info/995894655/04.
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Gerlach, Daniela. "Neuartige höherkoordinierte Siliciumkomplexe mit Pyrrol-2-carbaldimin-Liganden." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-104526.
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Im Rahmen dieser Arbeit wurden Siliciumkomplexe mit dianionischen Pyrrol-2-carbaldimin-funktionalisierten N,N,O- und N,N,N,N-Chelatliganden synthetisiert und kristallografisch, NMR- und UV/Vis-spektroskopisch und mittels quantenchemischer Berechnungen charakterisiert. Die pentakoordinierten Si-Komplexe mit N,N,O-Ligandrückgraten wiesen in Abhängigkeit von den weiteren Si-gebundenen Substituenten unterschiedlich konfigurierte verzerrt trigonal-bipyramidale Si-Koordinationssphären auf. Die Ursache der Farbigkeit dieser Verbindungen konnte mittels quantenchemischer Berechnungen detailliert erklärt werden. – Die Si-Komplexe mit N,N,N,N-Ligandrückgraten liegen in Abhängigkeit von den weiteren Si-gebundenen Substituenten als 5-fach koordinierte kationische oder neutrale 6-fach koordinierte Si-Komplexe vor. Deren Farbigkeit wurde mittels UV/VIS-Spektroskopie untersucht. Von ausgewählten Komplexen wurden die Tensoren der 29Si-NMR-Verschiebung rechnerisch und CP/MAS-NMR-spektroskopisch bestimmt.
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Anisur, Rahman. "PREDICTION OF FISH FRESHNESS USING UV-VISIBLE SPECTROSCOPY OF EYE FLUID." Kyoto University, 2015. http://hdl.handle.net/2433/202812.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第19378号
農博第2148号
新制||農||1037(附属図書館)
学位論文||H28||N4958(農学部図書室)
32392
新制||農||1037
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 近藤 直, 教授 飯田 訓久, 准教授 小川 雄一
学位規則第4条第1項該当
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Franco, González Olga. "Structural and spectroscopical study of crystals of 1,3,4-oxadiazole derivatives at high pressure." Phd thesis, Universität Potsdam, 2002. http://opus.kobv.de/ubp/volltexte/2005/53/.
Full textAbstract:
Die Suche nach neuen Materialien von technischem Interesse hat in den letzten Jahren neue Antriebe zu der Untersuchung organischer Verbindungen gegeben. Organische Substanzen haben viele Vorteile wie z.B. die Möglichkeit, ihre Eigenschaften durch verschiedene chemische und physikalische Techniken im Herstellung-Prozess für ein bestimmtes Ziel zu modifizieren. Oxadiazolverbindungen sind interessant aufgrund ihrer Nutzung als Material für Licht emittierende Dioden und Scintillatoren. Die physikalischen Eigenschaften eines Festkörpers hängen von seiner Struktur ab. Unterschiedliche Strukturen entwickeln unterschiedliche intra- und intermolekülare Wechselwirkungen. Eine ausgezeichnete Weise, um sowohl die intra- als auch die intermolekularen Wechselwirkungen eines bestimmtes Stoffes zu beeinflussen, ohne seine chemischen Charakteristiken zu ändern, ist die Verwendung von hohem Druck.
Wir haben den Einfluss von hohem Druck und hoher Temperatur auf die super-molekulare Struktur einiger Oxadiazolverbindungen im kristallinem Zustand untersucht. Aus diesen Untersuchungsergebnissen wurde eine Zustandsgleichung für diese Kristalle bestimmt. Überdies wurden die spektroskopischen Eigenschaften dieser Materialien unter hohem Druck charakterisiert.
In recent years the search for new materials of technological interest has given new impulses to the study of organic compounds. Organic substances possess a great number of advantages such as the possibility to adjust their properties for a given purpose by different chemical and physical techniques in the preparation process. Oxadiazole derivatives are interesting due to their use as material for light emitting diodes (LED) as well as scintillators.
The physical properties of a solid depend on its structure. Different structures induce different intra- and intermolecular interactions. An advantageous method to modify the intra- as well as the intermolecular interactions of a given substance is the application of high pressure. Furthermore, using this method the chemical features of the compound are not influenced.
We have investigated the influence of high pressure and high temperature on the super-molecular structure of several oxadiazole derivatives in crystalline state. From the results of this investigation an equation of state for these crystals was determined. Furthermore, the spectroscopical features of these materials under high pressure were characterized.
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Schmiedová, Veronika. "Studium optických a interferenčních jevů na tenkých vrstvách organických materiálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-256591.
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Ph.D. thesis is focused on the study and determination of layer thickness and optical properties, such as the dispersion dependence of the refractive index of various materials prepared in the form of thin layer. In the first part of this work the theoretical findings in the field of spectroscopic ellipsometry are summarised. These findings are followed by the description and characterization of the light polarization, evaluation of experimental data and determination of the physical properties of studied materials. Experimental and result section of this work is devoted to the preparation and characterization of thin films of the studied materials: titanum dioxide (TiO2), new organic materials (MDMO-PPV, PCDTBT, PCBTDPP, PC60BM, PC70BM) and reduced graphene oxide (rGO). These were all selected with respect to their potential use in the organic photovoltaics.
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Postal, Victor. "Estudo da degradação térmica de emulsões via espectroscopia UV-Vis aplicado a fluidos de corte." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-23012017-113619/.
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O monitoramento de emulsões utilizadas na indústria metalmecânica compõe uma importante atividade para o controle da qualidade das peças trabalhadas, proporcionando também o aumento da vida útil de ferramentas e maquinários utilizados neste setor através da lubrificação e refrigeração da região de corte. Em grande parte dos casos, estas emulsões são preparadas pela diluição de um fluido de corte em meio aquoso, constituindo assim um conjunto de gotículas estabilizadas em um meio contínuo devido à presença de compostos emulsificantes, estando constantemente sujeitas a ciclos de aquecimento e resfriamento durante os processos de usinagem. Apesar do acompanhamento deste material ser realizado através de análises periódicas usuais, não há um método eficiente estabelecido para verificar sua qualidade em tempo real e em linha de processo. Neste contexto, torna-se possível aplicar técnicas relacionadas à espectroscopia UV-Vis para se obterem informações sobre a estabilidade destes sistemas, correlacionando intensidades de espalhamento de luz com as dimensões das gotas presentes no meio. Dessa forma, tornou-se possível o estudo da desestabilização térmica de emulsões de um fluido de corte comercial, a qual mostrou-se, através do acompanhamento do cálculo do expoente do comprimento de onda, dependente do tempo de exposição ao aquecimento e de sua temperatura média temporal, não sendo influenciada pela perda de meio contínuo por processos evaporativos ou sua posterior reposição. Também se verificou que parâmetros típicos do processo de preparo de emulsões, como a temperatura do meio dispersante e o tempo de repouso do fluido de corte sobre a superfície do mesmo, apresentam fundamental importância para a definição do tamanho médio de gota inicial destes sistemas, o que forneceu evidência da possibilidade de se relacionar a área sob espectros de extinção de luz com tamanhos médios de gota.The monitoring of emulsions used in the metal-mechanical industry comprise an important activity to the quality control of the products manufectured, also providing an increase in the working life of the tools and machinery employed in this sector through the lubrication and refrigeration of the cutting zone. In the majority of cases, these emulsions are prepared diluting a metalworking fluid in an aqueous media, constituting a collection of particles stabilized by emulsifiers and undergoing heating and cooling cycles during metalworking processes. Currently, monitoring routines are based on regular analyses of samples taken from the process fluid, and an effective in-line method is not available to monitor emulsion quality in real time. In this context, it is possible to apply techniques related to UV-Vis spectrocopy in order to obtain information concerning the stability of those systems, correlating light scattering intensities to the droplet dimensions. In this study, it was possible to investigate the thermal destabilisation of a commercial metalworking fluid emulsion, which showed, through the evaluation of the wavelength exponent, to be dependant on the exposure time to heating and its time-averaged temperature. It was also noted that the loss of continuous phase by evaporation and its reposition do not affect the emulsion stability. Moreover, it was observed that important emulsion preparation parameters, such as continuous phase temperature and the time span between the addition of the metalworking fluid on the water surface and the stirring, have fundamental roles in defining the initial average droplet size, which made possible to correlate the area under the light extinction spectra with average droplet sizes.
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Friebe, Nadine, Katja Schreiter, Joachim Kübel, Benjamin Dietzek, Norbert Moszner, Peter Burtscher, Alexander Oehlke, and Stefan Spange. "Fluorosolvatochromism of furanyl- and thiophenyl-substituted acetophenones." Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-197572.
Full textAbstract:
A series of para-substituted acetophenones bearing a furanyl or a thiophenyl moiety show a large Stokes-shift, which is a function of various solvent properties. Photophysical properties such as emission lifetime of the compounds have been determined using time-correlated-single photon counting to secure the intrinsic fluorescence behaviour. The solvent dependent position of the UV/Vis emission band [small nu, Greek, tilde]max,em of the compounds has been measured in 26 various solvents. The influence of the solvent on [small nu, Greek, tilde]max,em is of very complex nature and mathematically analysed by multiple square linear solvation energy (LSE)-correlation analysis using Catalán's four-solvent parameter set. Solvent acidity has a strong influence on the bathochromic shift of 2,5-disubstituted furan derivatives compared to the non-5-substituted furan and thiophene derivatives, which show a contrary behaviour. Therefore, the 5-cyanofuranyl-substituted acetophenone derivative is useful as a probe for measuring environmental properties by fluorescence spectroscopyDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich