Dissertations / Theses: 'XAS spectrosopy'

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Seder, Colomina Marina. "Sphaerotilus natans, a neutrophilic iron-related filamentous bacterium : mechanisms of uranium scavenging." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1070/document.

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Les métaux lourds et les radionucléides sont présents dans différents écosystèmes du monde à cause de contaminations naturelles ou des activités anthropiques. L’utilisation de micro-organismes pour restaurer ces écosystèmes pollués, processus connu sous le nom de bioremédiation, suscite beaucoup d’intérêt, spécialement aux pH proches de la neutralité. Les minéraux de fer qui encroûtent les bactéries neutrophiles du fer, notamment les Oxydes de Fer Biogéniques (BIOS en anglais), ont une structure très faiblement cristalline, qui en plus de leur grande surface et réactivité font d’eux d’excellents supports pour le piégeage de polluants inorganiques. Dans cette thèse nous avons étudié les différents mécanismes de piégeage de l’uranium uranium par la bactérie neutrophile Sphaerotilus natans, choisie comme modèle bactérien de micro-organismes du fer capables de filamenter en formant des gaines. S. natans peut croître sous forme de cellules individuelles ou formant des filaments. Ces derniers ont été utilisés pour étudier la biosorption d’U(VI) et sa sorption sur les BIOS. De plus, la sorption d’U(VI) sur les analogues abiotiques de ces minéraux de fer a été testée. Afin d’utiliser les filaments de S. natans pour piéger l’U(VI), il était nécessaire d’identifier les facteurs induisant la filamentation de S. natans. L’influence de l’oxygène a été établie en utilisant des techniques de biologie moléculaire et nos résultats ont démontré que tandis qu’en condition d’oxygène saturé elle croît sous forme de cellules individuelles, une diminution modérée d’oxygène à ~ 3 mg O2.L-1 la fait croître sous la forme désirée, des filaments de S. natans.Les BIOS attachés aux filaments de S. natans ainsi que ses analogues abiotiques ont été analysés pas XAS au seuil K du Fe. Les deux matériaux identifiés sont des phosphates de fer(III) amorphes avec une faible proportion de fer(II), qui présentent une réactivité élevée pour le piégeage de polluants inorganiques. L’EXAFS au seuil LIII de l’U a montré la même structure pour les couches O, tandis que celles P, Fe et C étaient différentes en fonction des sorbants. Une étude intégrée qui combine des techniques expérimentales avec des calculs de spéciation a permis de décrire les isothermes d’adsorption de l’U(VI) en utilisant un modèle de complexation de surface. Ces résultats suggèrent que les groupes phosphoryles et carboxyles sont les groupes fonctionnels principaux pour la biosorption d’U(VI) par des filaments de S. natans. Les résultats de cette thèse vont aider à comprendre les processus contrôlant l’immobilisation de l’U(VI), soit par la biosorption sur S. natans, la sorption sur les BIOS ou la sorption sur les phosphates de fer, et en conséquence le devenir de l’U en conditions neutres
Heavy metals and radionuclides are present in some ecosystems worldwide due to natural contaminations or anthropogenic activities. The use of microorganisms to restore those polluted ecosystems, a process known as bioremediation, is of increasing interest, especially under near-neutral pH conditions. Iron minerals encrusting neutrophilic iron-related bacteria, especially Bacteriogenic Iron Oxides (BIOS), have a poorly crystalline structure, which in addition to their large surface area and reactivity make them excellent scavengers for inorganic pollutants. In this PhD work we studied the different mechanisms of uranium scavenging by the neutrophilic bacterium Sphaerotilus natans, chosen as a model bacterium for iron-related sheath-forming filamentous microorganisms. S. natans can grow as single cells and filaments. The latter were used to investigate U(VI) biosorption and U(VI) sorption onto BIOS. In addition, uranium sorption onto the abiotic analogues of such iron minerals was assessed. In order to use S. natans filaments for U(VI) scavenging, it was necessary to identify factors inducing S. natans filamentation. The influence of oxygen was ascertained by using molecular biology techniques and our results revealed that while saturated oxygen conditions resulted in single cell growth, a moderate oxygen depletion to ~ 3 mg O2.L-1 led to the desired filamentous growth of S. natans. BIOS attached to S. natans filaments as well as the abiotic analogues were analysed by XAS at Fe K-edge. Both materials were identified as amorphous iron(III) phosphates with a small component of Fe(II), with a high reactivity towards scavenging of inorganic pollutants. In addition, EXAFS at the U LIII-edge revealed a common structure for the O shells, while those for P, Fe and C were different for each sorbent. An integrated approach combining experimental techniques and speciation calculations made it possible to describe U(VI) adsorption isotherms by using a surface complexation model. These results suggested the role of phosphoryl and carboxyl groups as the main functional groups involved in the U(VI) biosorption by S. natans. The results of this PhD work will help to better understand the processes governing U(VI) immobilization, either by S. natans biosorption, sorption onto BIOS or sorption onto iron phosphates, an thus the fate of uranium in near-neutral pH environments

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Chalker, Paul R. "The oxidation of nickel and titanium studied by XPS and XAES." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371219.

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Adams, Stephen J. A. "Optical spectroscopy of InxGa1-xAs/GaAs quantum wells." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/816.

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Vegelius, Johan. "X-ray Spectroscopic Studies of Materials for Nuclear Technology." Doctoral thesis, Uppsala universitet, Mjukröntgenfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160362.

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X-ray spectroscopic experiments, including X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS), were performed in a large energy range (60-9000 eV) on a variety of systems, probing different elements and orbitals. The systems can preferably be divided into three groups: Actinides, copper systems and amorphous materials. We studied oxidation states of Pu in PuO2 using a closed-source experimental setup, developed by us, to lower the safety restrictions associated with such experiments. The presence of Pu with higher oxidation state than Pu(IV) was found in polycrystalline PuO2. This is an important finding since Pu with higher oxidation states has higher solubility affecting the safety of a proposed undeground repository of spent nuclear fuel which can eventually be infiltrated by groundwater. In the proposed underground repository the molecular oxygen will vanish at some point due to microbial activity and mineral oxidation. At this stage sulfur is the most important candidate for causing copper corrosion. We studied Cu films and foils exposed to sulfide solutions at both Cu L2,3, Cu K and S L2,3 edges and found for example that S L2,3 XES is useful for distinguishing between different copper sulfides and Cu Kβ XES can be used to identify monovalent Cu compounds. Amorphous, zirconium containing alloys are potentially useful materials for future nuclear reactors. The electronic structure of such materials was also investigated.

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Jahel, Ali. "Étude de l'ajout d'un promoteur au système Pt-Sn supporté sur alumine chlorée utilisé en reformage catalytique." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20233.

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L'objectif de ce travail était d'étudier de manière approfondie l'effet de l'indium dans des catalyseurs trimétalliques de reformage catalytique à base de platine, étain et indium. Des catalyseurs ont ainsi été synthétisés selon différents protocoles de préparation et de multiples caractérisations (spectroscopies Mössbauer d'étain, XANES, EXAFS, IR-CO, MEBT, chimisportion du CO, TPR et TPD) ont été mises en oeuvre afin d'élucider l'impact de l'indium sur la nature des phases métalliques présentes au sein du catalyseur. Il a ainsi été montré que la nature des sites métalliques dépend de la méthode d'introduction de l'indium. Quand l'indium est précipité avec la source d'alumine des alliages de type PtxSn sont obtenus alors que lorsque les métaux sont imprégnés sur la surface de l'alumine des espèces subsitutionnelles Pt-Sn sont formées. Il a aussi été montré que l'augmentation de la teneur en indium entraine une augmentation de la concentration atomique d'étain dans les alliage PtxSn et un remplacement de l'étain par l'indium dans les espèces substitutionnelles. Nous avons également réussi à préparer des catalyseurs avec des quantités élevées d'alliage Pt3Sn sur la base des connaissances acquises sur l'impact de l'indium et en déposant l'étain par une réaction organométallique contrôlée de surface. D'un point de vue catalytique, les tests de reformage du n-heptane mettent en évidence l'impact positif de l'indium puisque les catalyseurs à base de Pt-Sn-In sont moins sélectifs pour les réactions parasites d'hydrogénolyse et d'hydrocraquage et plus sélectifs pour l'isomérisation que les catalyseurs à base de Pt-Sn
This work consists of a detailed study on the effect of indium in alumina supported trimetallic PtSnIn-based naphtha reforming catalysts. These catalysts were reproduced using different preparation protocols and the indium effect was investigated using 119Sn Mössbauer spectroscopy, XANES, EXAFS spectroscopies, IR-CO, STEM, CO chemisorption, TPR and TPD. It appears that the nature of the metallic active centres depends on the method with which indium was introduced. When co-precipitating the indium precursor with the Al source, PtxSn alloys were formed, whereas when metals were impregnated on the surface, substitutional Pt-Sn alloys were observed. Increasing the In content in the frst type of catalysts leads to an increase in the Sn concentration in PtxSn alloys, whereas a gradual replacement of Sn by indium in susbstitutinal alloys is observed in the second type of catalysts. These results allowed preparing catalysts with high Pt3Sn alloy contents using the effect of indium in catalysts prepared by Sn organometallic controlled surface reactions (CSR). From a catalytic point of view, n-heptane reforming tests show that trimetallic PtSnIn-based catalysts are less selective to hydrogenolysis and hydrocracking reactions, and highly selective to isomerisation, compared to the bimetallic PtSn-based catalyst

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Wittee, Lopes Christian. "Characterization of metallic species on porous materials by in situ XAS." Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/107953.

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El objetivo de esta tesis es estudiar la agrupación y el crecimiento de especies metálicas confinadas o soportadas en materiales porosos mediante espectroscopia de absorción de rayos X in situ. Para lograrlo, las especies de paladio y plata se han introducido en materiales porosos (¿-alúmina, carbón activo y zeolitas) mediante impregnación vía húmeda y métodos de intercambio iónico, respectivamente. Luego, el agrupamiento de estas especies metálicas se ha controlado mediante tratamientos de activación en diferentes atmósferas (inerte, oxidativa y reductiva) y seguido por XAS de manera detallada. El objetivo principal del trabajo actual es demostrar que tanto XANES como EXAFS pueden proporcionar información valiosa y, en cierto punto, innovadora durante el control de especies metálicas (en términos de tipo y tamaño de las especies). Aprovechando los procedimientos de análisis inusuales, como el análisis de los cumulantes, el ajuste de la parte imaginaria de la transformada de Fourier y otros, es posible obtener información refinada sobre los sistemas investigados. En la sección de introducción, se proporciona una compilación de estudios en los que se ha utilizado XAS como técnica importante para caracterizar especies metálicas en materiales porosos. Conscientes de que las personas pueden usar dicha introducción como base para estudios más complejos en el futuro, la discusión se ha dirigido tentativamente hacia este objetivo. El capítulo 4 se centra en el estudio de la influencia de los precursores de paladio y la naturaleza del soporte en las nanopartículas resultantes. El proceso de activación completo, es decir, la transformación precursor --> nanopartícula, ha sido seguido por XAS in situ. El análisis estuvo compuesto por el punto de partida (material impregnado), calcinación en flujo de O2 y reducción posterior con H2. La consecuencia del uso de diferentes precursores metálicos y soportes se ha discutido en términos del número de coordinación promedio obtenido a partir del análisis de datos de EXAFS, que fue respaldado por técnicas de caracterización de laboratorio. El capítulo 5 está dedicado al estudio de la agrupación de plata durante y después de los tratamientos de activación utilizando zeolitas de poro pequeño intercambiadas con plata como precursores y nanocontenedores. Se ha estudiado la influencia de la estructura y la composición química de los materiales basados en plata sobre las especies metálicas formadas en diferentes condiciones de agrupamiento y redispersión del metal (calcinación usando atmósferas distintas, reducción en H2, redispersión en O2) utilizando métodos de caracterización in situ o ex situ. Después, se discuten las consecuencias catalíticas de las zeolitas que contienen Ag en la reacción de SCO-NH3. En esta sección, la combinación de XAS in situ con varias técnicas de laboratorio ha demostrado ser fundamental para un completo entendimiento del trabajo. Finalmente, una lista de proyectos desarrollados en paralelo a esta tesis se proporciona al final de este documento.
The aim of this thesis is to study the clustering and growth of metallic species either confined or supported in porous materials by in situ X-ray absorption spectroscopy. To accomplish this task, palladium and silver species were introduced into porous materials (¿-alumina, activated carbon and zeolites) by wetness impregnation and ion-exchange methods, respectively. Then, the clustering of these metallic species was controlled by activation treatments in different atmospheres (inert, oxidative and reductive) and followed by XAS in a comprehensive way. The principal goal of current work is to demonstrate that both XANES and EXAFS can provide valuable and, at certain point, innovative information during tuning of metallic species (in terms of type and size). Taking advantage of unusual analysis procedures, such as cumulant approach, fitting of imaginary part of Fourier transform and others, it is possible to obtain refined information about the investigated systems. In the introduction section, a compilation of studies in which XAS was used as important technique to characterize metallic species in porous materials is provided. Conscious that people can use such introduction as a basis for more complex studies in the future, the discussion has been tentatively directed toward this goal. The chapter 4 is focused on the study of the influence of palladium precursors and the nature of support on the resultant nanoparticles. The whole activation process, i.e. the transformation precursor --> nanoparticle, was followed in situ by XAS. The analysis pathway was composed by the starting point (as-impregnated), calcination in O2 flow and posterior reduction with H2. The consequence of using distinct metal precursors and supports were discussed in terms of average coordination number obtained from EXAFS data analysis, which was co-supported by laboratory characterization techniques. The chapter 5 is dedicated to the study of silver clustering during and after activation treatments using Ag-containing small-pore zeolites as precursors and nanocontainers. The influence of framework structure and chemical composition of Ag-based materials on formed Ag species at different clustering and metal redispersion conditions (calcination using distinct atmospheres, reduction in H2, redispersion in O2) were studied using either in situ or ex situ characterization methods. After, the catalytic consequences of tuned Ag-containing zeolites in SCO-NH3 are discussed. In this section, the combination of in situ XAS with several laboratory techniques proved to be pivotal to have a full picture of the investigated system. Finally, a list of projects developed in parallel to this thesis is provided at the end of this document.
L'objectiu d'aquesta tesi és estudiar l'agrupació i el creixement d'espècies metàl·liques confinades o suportades en materials porosos mitjançant espectroscòpia d'absorció de raigs X in situ. Per a això, les espècies de pal·ladi i plata s'han introduït en materials porosos (¿-alúmina, carbó activat i zeolites) per mitjà de la impregnació via humida i mètodes d'intercanvi iònic, respectivament. Una vegada preparats els materials, l'agrupament de les espècies metàl·liques s'ha controlat fent ús de tractaments d'activació en diferents atmosferes (inert, oxidant i reductora) s'ha estudiat exhaustivament per XAS. L'objectiu principal del treball és demostrar que tant el XANES com l'EXAFS proporcionen informació rellevant i, en certa manera, innovadora per al control d'espècies metàl·liques (en termes de tipus i grandària d'aquestes espècies). Fent ús de procediments de tractament de dades no molt habituals com l'anàlisi de cumulants, l'ajust de la part imaginària de la transformada de Fourier i altres, és possible obtenir informació detallada sobre els sistemes estudiats. En l'apartat de la introducció, es proporciona una recopilació d'estudis en els quals s'ha utilitzat XAS com a tècnica principal per a caracteritzar les anomenades espècies metàl·liques en materials porosos. Aquesta introducció ha estat redactada per a que puga servir com a punt de partida per a futurs estudis que requereixen la utilització de XAS per a la caracterització de les espècies metàl·liques presents en els catalitzadors. El capítol 4 es centra en l'estudi de la influència dels precursors de pal·ladi i la naturalesa del suport front a les nanopartícules resultants. El procés d'activació, és a dir, la transformació precursor --> nanopartícula, ha sigut estudiat per XAS in situ. L'anàlisi per XAS va comprendre els següents passos: punt de partida (material impregnat), calcinació en flux d'O2 i reducció posterior amb H2. La utilització de diferents precursors i suports metàl·lics ha permès dur a terme una discussió, referent al nombre de coordinació mitjà obtingut a partir de l'anàlisi de dades de la zona EXAFS, que ha estat recolzat per altres tècniques de caracterització. El capítol 5 s'ha dedicat a l'estudi de l'agrupació de plata intercanviada en els catalitzadors durant i després dels tractaments d'activació. S'han utilitzat zeolites de porus xicotet, com la CHA i RHO, intercanviades amb plata. L'estudi de la influència de l'estructura zeolítica i la composició química dels materials enfront dels diferents tractaments d'activació (calcinació utilitzant diferents atmosferes, reducció en presència d'H2, re-dispersió en atmosfera d'O2) es va realitzar fent ús de mètodes de caracterització in situ o ex situ. A continuació, es discuteix la influència d'aquestes espècies metàl·liques formades, utilitzant els diferents mètodes d'activació, per a la reacció d'SCO-NH3. En aquest sentit, s'ha demostrat que la combinació de XAS in situ amb diverses tècniques habituals de laboratori és fonamental per al desenvolupament d'aquest treball. Finalment, es presenta una llista de projectes, en els quals també s'ha treballat paral·lelament, on s'ha utilitzat XAS com a tècnica de caracterització.
Wittee Lopes, C. (2018). Characterization of metallic species on porous materials by in situ XAS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107953
TESIS

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Zamora, Torres David, and Felix Abeln. "Design of an In-situ cell, for hard X-ray spectroscopy of surfaces used in high-pressure and high-temperature experiments : Design av en In-situ cell för intensiv röntgenspektroskopi i högtryck- högtemperaturexperiment." Thesis, Malmö universitet, Institutionen för materialvetenskap och tillämpad matematik (MTM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-45607.

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This project analyzes how an in-situ cell can be developed to withstand high amounts of pressure and temperature of at least 100 bar and 500 °C. A theoretical prototype will be created as a product for Malmö University and other researchers to use or improve. To make this possible, the five step method was used to present a symmetric geometrical concept for the cell. That geometric concept was designed in PTC Creo (Version 6.0.2.0 & 7.0) in 3D and drawings in 2D. The programs GRANTA EduPack (Version 2020 \& Version 2019) along with Hephaestus was used to determine a material selection that will be able to tolerate temperature, pressure and be at least ten percent transparent, to be able for the X-ray to pass through the material and into the sample. The Finite Element Method (FEM) was used to ensure that the cell adheres to the set values of pressure and not cause a catastrophic failure. The result turn out to be a elliptical three part in-situ cell of boron carbide outer shell, a beryllium main dome and a stainless steel plate for the material sample to be on top. The Finite Element Method also showed that the designed in-situ cells meet the requirements and fulfills the goal and purpose. Further development of safety features and the equipment will be needed to minimise the risk of and dangers of beryllium dust.
Detta projekt analyserar hur en in-situ cell kan utvecklas för att motstå höga mängder tryck och temperatur på minst 100 bar och 500 °C . En teoretisk prototyp kommer att skapas som en produkt för Malmö universitet och andra forskare att använda eller förbättra. För att göra detta möjligt användes femstegsmetoden för att presentera ett symmetriskt och geometriskt koncept för cellen. Det geometriska konceptet kommer att utformas 3-dimensionellt i PTC Creo (Version 6.0.2.0 7.0) och 2-dimensionella ritningar . GRANTA EduPack-programmen (Version 2020 \& Version 2019) tillsammans med Hephaestus användes för att bestämma ett materialval som kommer att kunna tolerera temperatur, tryck och vara minst tio procent transparent för att röntgenstrålningen ska kunna passera genom materialet och in i provet. Finite Element Method (FEM) kommer att användas för att säkerställa att cellen följer de inställda tryckvärdena och inte orsakar katastrofala fel. Resultatet visar sig vara en elliptisk tredelad in-situ cell av borkarbid som ett yttre skal, beryllium som huvudkupol och en rostfri stålplatta som underlag för materialprovet. Finite Element Method visade också att den designade in-situ-cellen uppfyller kraven och därför uppfyller målet och syftet. Detta innebär att vidareutveckling av säkerhetsfunktioner och utrustning kommer att behövas för att minimera risken för berusning från berylliumdammet.

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Davies, Graeme John. "Optically detected X-ray absorption spectroscopy (OD-XAS) study of InGaN/GaN quantum well and quantum dot nanostructures." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516410.

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InGaN/GaN single quantum well (SQW) and quantum dot (QD) samples were studied using optically detected X-ray absorption spectroscopy (OD-XAS). This is a powerful technique, capable of linking local structural environment information with the luminescence emission processes present. Ga K-edge OD-EXAFS analysis shows this technique to be site-selective for these samples and, from the emission related to the QW or QD structure, a percentage indium value was determined for each sample. Possible reasons why this siteselectivity is observed are considered, along with the implication of the results with respect to the nature of the mechanism responsible for exciton localisation within these structures. Further investigations were performed on the QD sample, including a depth profiling study based on spectra obtained at several different excitation energies and an analysis of the OD-XANES at the N K-edge. The application of pumpprobe micro-imaging OD-XAS to these types of samples is also examined.

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Kristiansen, Paw. "In situ X-Ray Spectroscopy of Ethylene Epoxidation over Ag and studies of Li-ion batteries and Cu sulfidation." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-209204.

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This thesis is based on experiments applying synchrotron based X-ray Absorption Spectroscopy(XAS) and Resonant Inelastic X-ray Scattering (RIXS) in the soft X-ray region to energy related systems. The main work of this thesis has been to develop a reaction cell that allowed for in situ XAS and RIXS investigations of the partial epoxidation of ethylene over a Ag catalyst at 1 atm and up to 250C. The developed in situ cell can be used in two sample modes: 1) the Ag catalyst is deposited directly onto the vacuum separating membrane with the reaction gases flowing beneath it or 2) a slightly compressed Ag powder sample is at a distance to the vacuum membrane with the reaction gases flowing between the Ag powder sample and the membrane.Both sample modes offers the total florescence yield, TFY, and the total electron yield, TEY, to be recorded simultaneously. By means of the developed in situ cell a number of oxygen species, residing in/on the Ag surface or in the Ag bulk, have been detected. We claim to detect adsorbed O2 under epoxidation conditions, as well as Ag–O–H groups. We are also able to monitor changes of the absorbed oxygen as we change the composition of the reaction gas feed. The first charging cycle of Li-ion batteries have been investigate by ex situ measurements on the cathode Li2-xMnSiO4 and the anode composite LixNi0:5TiOPO4/C . The initial crystalline material becomes amorphous due to lithiation during the first first charging. We find that the redox behaviors of these two states are significantly different. Sulfidation of natural copper oxides are is found to be strongly promoted when it is grown on the host metal by a disproportionation.

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Hung, Wing Wa. "FTIR and XPS of congruent and stoichiometric LiNbO3." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/442.

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Helmstedt, Andreas [Verfasser]. "Probing the magnetic properties of [MnIII6CrIII]3+ single-molecule magnets by XAS, XMCD and spin-resolved electron spectroscopy / Andreas Helmstedt." Bielefeld : Universitätsbibliothek Bielefeld, 2014. http://d-nb.info/1068621702/34.

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Dehlinger, Mael. "XAS-XEOL and XRF spectroscopies using near field microscope probes for high-resolution photon collection." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4048/document.

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Les microscopes en champ proche permettent d'obtenir la topographie d'un échantillon avec une résolution pouvant atteindre la résolution atomique. Les spectroscopies de rayons-X sont des méthodes de caractérisation qui permettent de déterminer la composition et la structure élémentaire de l'échantillon avec une précision inférieure à l'Ångström. Nous avons choisi de coupler ces deux techniques en collectant localement la luminescence visible issue de l'échantillon par la pointe-sonde d'un microscope à force de cisaillement, constituée d'une fibre optique effilée de faible ouverture. Cette technique a été utilisée pour caractériser des échantillons semiconducteurs micro- et nano-structurés afin d'en obtenir simultanément la topographie et la cartographie de luminescence locale. Afin de pouvoir étendre ce concept à d'autres types de matériaux, la faisabilité de la collecte de la fluorescence X locale a été évaluée avec la microsource. Pour cela la fluorescence X émise par un échantillon a été collectée par un capillaire cylindrique équipant un détecteur EDX. L'influence du diamètre du capillaire sur le niveau de signal a été mesurée. Une simulation numérique a été développée afin d'estimer le niveau de signal obtenu en utilisant un capillaire de 1 µm de diamètre et d'optimiser la géométrie du système. En couplant la microscopie en champ proche et l'analyse XRF, à la lumière de ces résultats, il sera possible d'atteindre 100 nm de résolution latérale en environnement synchrotron et moins de 1 µm à l'aide d'une source de laboratoire. Il serait alors possible de sélectionner un objet particulier sur une surface et d'en faire l'analyse élémentaire
Scanning Probe Microscopes allow to obtain sample topography up to atomic resolution. X-ray spectroscopies allow elemental and structural analysis of a sample with accuracy better than 1 Å. The lateral resolution is limited by the primary beam diameter, currently a few µm². We have chosen to couple this two technics. Local sample visible luminescence is collected through a low aperture sharp optical fibre, probe of a shear force microscope. This technique was used to characterize microstructured semiconducting samples to achieve simultaneously the surface topography and luminescence mapping. The results were obtained using either synchrotron radiation or a laboratory microsource equipped with a polycapillary lens. To extend this concept to a wider variety of materials, local XRF collection by an EDX detector equipped with a cylindrical X-ray capillary was tested. A cobalt sample irradiated with the microsource was used for technique evaluation. The signal magnitude dependence with the capillary diameter was measured. Modelling and numerical calculations were developed to estimate the signal magnitude that could be detected using a 1 µm diameter capillary. The optimal system geometry was determined. Scanning Probe Microscopy combined to XRF analysis could thereby lead to simultaneous acquisition of sample topography and chemical mapping. The expected lateral resolution using synchrotron radiation is 100 nm while sub 1 µm resolution is realistic with a laboratory source. This technique would allow to point a peculiar micro- or nano-object on the surface and to perform its chemical analysis

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13

Haskel, Daniel. "Local structural studies of oriented high temperature superconducting cuprates by polarized XAFS spectroscopy /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9712.

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14

Olthof, Selina. "Photoelectron Spectroscopy on Doped Organic Semiconductors and Related Interfaces." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-38320.

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Using photoelectron spectroscopy, we show measurements of energy level alignment of organic semiconducting layers. The main focus is on the properties and the influence of doped layers. The investigations on the p-doping process in organic semiconductors show typical charge carrier concentrations up to 2*10E20 cm-3. By a variation of the doping concentration, an over proportional influence on the position of the Fermi energy is observed. Comparing the number of charge carriers with the amount of dopants present in the layer, it is found that only 5% of the dopants undergo a full charge transfer. Furthermore, a detailed investigation of the density of states beyond the HOMO onset reveals that an exponentially decaying density of states reaches further into the band gap than commonly assumed. For an increasing amount of doping, the Fermi energy gets pinned on these states which suggests that a significant amount of charge carriers is present there. The investigation of metal top and bottom contacts aims at understanding the asymmetric current-voltage characteristics found for some symmetrically built device stacks. It can be shown that a reaction between the atoms from the top contact with the molecules of the layer leads to a change in energy level alignment that produces a 1.16eV lower electron injection barrier from the top. Further detailed investigations on such contacts show that the formation of a silver top contact is dominated by diffusion processes, leading to a broadened interface. However, upon insertion of a thin aluminum interlayer this diffusion can be stopped and an abrupt interface is achieved. Furthermore, in the case of a thick silver top contact, a monolayer of molecules is found to float on top of the metal layer, almost independent on the metal layer thickness. Finally, several device stacks are investigated, regarding interface dipoles, formation of depletion regions, energy alignment in mixed layers, and the influence of the built-in voltage. We show schematic energy level alignments of pn junctions, pin homojunctions, more complex pin heterojunctions with Zener-diode characteristics, as well as a complete OLED stack. The results allow a deeper insight in the working principle of such devices
Mit Hilfe der Photoelektronenspektroskopie werden in der vorliegenden Arbeit Energieniveaus an Grenzflächen von organischen Halbleitern untersucht, wobei ein Hauptaugenmerk auf dem Einfluss und den Eigenschaften dotierter Schichten liegt. Bei der Untersuchung grundlegender Eigenschaften eines p-dotierten organischen Halbleiters können Ladungsträgerkonzentrationen bis zu 2*10E20 cm-3 nachgewiesen werden. Eine Variation der Dotierkonzentration zeigt einen überproportionalen Einfluss der Ladungsträger auf die Position des Ferminiveaus verglichen mit Experimenten an anorganischen Schichten. Durch den Vergleich mit der Anzahl Dotanden in der Schicht kann gezeigt werden, dass dabei nur etwa 5% der Dotanden einen vollständigen Ladungstransfer eingehen. Eine detaillierte Untersuchungen der Zustandsdichte jenseits des HOMOs (Highest Occupied Molecular Orbital) zeigt, dass die exponentiell abfallende Flanke der Zustandsdichte weiter in die Bandlücke hineinreicht als üblicherweise angenommen. Das Ferminiveau erfährt bei steigender Dotierung ein Pinning an diesen Zuständen, was für eine signifikante Ladungsträgerkonzentration spricht. Weiterhin wurden Untersuchungen zu Metal Top- und Grundkontakten durchgeführt. Es kann gezeigt werden, dass die Ursache für die Entstehung unsymmetrischer Strom-Spannungskurven, trotz eines symmetrischen Probenaufbaus, an einer Reaktion zwischen dem Molekül und den Metallatomen liegt. Dadurch entsteht eine um 1.16eV reduzierte Injektionsbarriere für Elektronen am Topkontakt. Weitere detaillierte Untersuchungen an diesen Topkontakten zeigen, dass im Falle von Silber als Metall diese Grenzfläche von Diffusionsprozessen dominiert ist. Im Gegensatz dazu zeigt das unedle Metall Aluminium keine Diffusion und führt zu abrupten Grenzflächen. Im ersten Fall kann zudem eine Monolage vom Molekül auf dem Metallkontakt nachgewiesen werden, die unabhängig von der Metalldicke aufschwimmt. Zuletzt werden Bauelemente oder Teile solcher mit Photoelektronenspektroskopie vermessen. Hierbei werden die Grenzflächendipole, die Ausbildung von Verarmungszonen, die Energieangleichung in Mischschichten und der Einfluss der Eingebauten Spannung untersucht. Es können die Banddiagramme von pn-Übergängen, einfachen pin Homoübergängen, komplexeren pin Heteroübergänge mit Zener-Dioden Verhalten sowie eine gesamte OLED gezeigt werden. Die Ergebnisse erlauben einen tieferen Einblick in die Arbeitsweise solcher Bauelemente

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15

Lebrun, Delphine. "Thiolsulfinates/Thiolsulfonates formation: X-ray photoelectron spectroscopy (XPS) of oxidized thiols on flat surfaces." Thesis, Uppsala universitet, Materialfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160332.

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In order to find another way to fix peptides on surfaces we study the chemical and electro oxidation of a Silicon flat surface after silanization. Traditional experimental setup is used to make the oxidations and Xray photoelectron spectroscope (XPS) is used to analyze the surfaces. We find that chemical oxidation works well but we cannot fix the Alanine molecule on the surface, unlike the electro oxidation which works for peptides fixation. We need to focus on the electro oxidation process, use a more accurate method to analyze the samples and probably used a higher Alanine concentration.

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16

Bao, Zhuo. "Synchrotron Radiation Studies of Free and Adsorbed Molecules." Doctoral thesis, Uppsala University, Surface and Interface Science Division, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8610.

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This thesis contains two parts. The first part concerns the research work on free molecules using synchrotron-radiation-related techniques. Auger electron spectra of two free open-shell molecules, O₂ and NO, were studied experimentally and theoretically. Photoionization experimental technique with tunable synchrotron radiation source was used to induce core-level electron ionization and obtain the KVV normal Auger electron spectra. A quantitative assignment of O₂ normal Auger spectrum was obtained by applying ab initio CI calculations and LVI Auger line shape simulations including the bond length dependence of Auger transition rates. The photon energy dependence of normal Auger electron spectra was focused on with photon energies in the vicinities of core-ionization threshold energies. Consequently, the MAPCI (Molecular Auger Post Collision Interaction) theory was developed. Taking the near-threshold O₂ normal Auger spectrum as an example, the two extreme cases of MAPCI effect, “atomic-like PCI” and “molecular PCI”, were discovered and discussed. The effect of shape resonance on near-threshold molecular normal Auger spectrum was discussed taking NO near threshold normal Auger spectra as example.

The second part deals with research work on the chemisorption of small epoxy organic molecules, ethylene oxide, methyl oxirane, on Si (100) surfaces. Synchrotron radiation related techniques, UPS, XPS and NEXAFS, were applied. Based on the valence photoemission spectra, C 1s and Si 2p XPS spectra, the epoxy ring opening reactions of these molecules in chemisorption process were proved. Further tentative search for the surface-adsorbate CDAD effect was performed, and no evident circular dichroism was confirmed.

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17

Lunt, Patrick Joseph Brian. "XPS studies of surface ageing and discharge processes in polymeric insulators." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/xps-studies-of-surface-ageing-and-discharge-processes-in-polymeric-insulators(2329d184-6677-4981-988e-e17b95bae229).html.

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The ageing of polymer insulation occurs under long-term exposure to high electric fields and has attracted research due its relevance to high voltage insulation. In this work, polymers that have been electrically aged via a number of methods have been investigated using X-ray photoelectron spectroscopy (XPS). Despite some use in the investigation of outdoor insulation surfaces, XPS has not been used for investigations of polymer bulk electrical ageing before now. The first XPS measurements, using both small spot analysis and XPS imaging, are presented from the exposed inner surfaces of electrically aged artificial voids and electrical breakdown channels, as well as corona discharge aged surfaces and spark discharge by-products. XPS is shown to be a valuable technique for the investigation of polymer electrical ageing. Investigations into breakdown channels are supported by data acquired using X-ray photoemission electron microscopy (XPEEM) and scanning electron microscopy (SEM).Results show that the chemistry present at these surfaces takes the form of significant oxidation over a wide area with localised production of graphitic carbon. C-O-, C=O, and O-C=O species are detected in all cases. It is found that similar ageing products are present regardless of the ageing process or material investigated. However, the level of oxidation and relative ratio of the species seen with XPS is shown to be highly dependant on oxygen availability. Greater intensity of carbon oxides, and a shift towards highly oxidised species, is observed when there is more oxygen in the system. XPS imaging of breakdown channels reveals that high concentrations of oxidised components form on the outer edges of the channel, with graphitic carbon forming in the central regions. In addition, evidence for degradation is seen to extend at least 300 μm from channels in XPS imaging and at least ~650 μm in XPS line scans. Variation with the applied discharge energy was investigated for breakdown channels and spark discharge ageing. Evidence is seen for an energy dependence on the breakdown products, with higher energies producing relatively higher graphitic carbon and reduced oxidation products. Further, the relationship between the applied voltage and graphitic carbon concentration suggests an activated process with an energy barrier before graphitic carbon formation starts. XPS observations are supported by confocal Raman microprobe spectroscopy (CRMS) results from artificial voids and electrical breakdown channels, which identify graphitic carbon on a fluorescent background as the main features. XPS data indicate oxidised species are the origin of the fluorescence seen and provides quantitative information on the levels, chemical states and spatial distribution of these species and of graphitic carbon.

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18

Clarke, Coby James. "Ionic liquids as designer molecules for XPS peak fitting." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33303/.

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X-ray photoelectron spectroscopy (XPS) of ionic liquids (ILs) has become a valuable tool for the investigations of IL interfacial and physicochemical properties. The complex signals that result from elements which occupy a variety of chemical states, for example the C 1s photoemission, are often interpreted through chemical intuition and peak fitting parameters. This Thesis will present a new method to determine exact photoemission binding energies (B.E.s), through the comparison of multiple spectra. The designer aspect of ILs has been exploited in order to produce salts with small structural modifications. By comparing the C 1s and N 1s photoemissions of the structurally related samples, difference spectra have been produced. These spectra show the relative shifting of electron density between the two signals, revealing the initial and final locations of the changing photoemission. Using this technique, the current C 1s peak fitting models of imidazolium and pyridinium ILs have been examined. A variety of 4,4’-bipyridinium salts have also been used as a structural variation of pyridinium ILs to show how molecular symmetry and normalisation may be utilised in order to produce photoemissions equivalent to fragments of molecules. The subsequent C 1s difference spectra have provided carbon peak fitting models for mono- and di-alkylated 4,4’-bipyridinium salts. Without the use of XP difference spectra, these known fitting models would be almost impossible to determine. Finally, multiple complex difference spectra have been used to identify the exact B.E.s of C 1s photoemissions from a series of nitrile functionalised ILs. The complex difference spectra have also been analysed by inverse Gaussian fittings to show how additional information may be extracted from the characteristic shapes. The ‘construction’ of photoemissions is also demonstrated, whereby known B.E. peaks are assembled to accurately reproduce experimentally determined XP spectra.

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19

Adnan, Rohul. "Gold-based Nanomaterials: Spectroscopy, Microscopy and Applications in Catalysis and Sensing." Thesis, University of Canterbury. Chemistry, 2015. http://hdl.handle.net/10092/10507.

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The birth of nanotechnology era has revolutionized materials science, catalysis and field of optoelectronics. Novel and unique phenomena emerge when material dimensions are reduced to ultra-small size regime and enter nanometre (2-100 nm) realm. Such novel materials are expected to replace bulk materials, offering lower cost of manufacturing and enabling progress in many areas such as solar cell, drug delivery, quantum communication and computing, catalysis and sensing applications. With the progress in nanomaterial synthesis and fabrication, the need for the state-of-art characterization techniques became obvious; such techniques help to establish a complete understanding of the nature and interactions of nanosized materials. In this thesis, the first part focuses on the synthesis of gold and ruthenium clusters, namely Au8, Au9, Au101, Ru3, Ru4 and AuRu3, using the well-established synthetic protocols in the literature. Apart from the standard lab-based characterization techniques such as nuclear magnetic resonance (NMR), UV-visible spectroscopy (UV-vis) and Fourier Transform Infra-red (FTIR), a less explored but useful technique far infra-red (far IR) spectroscopy, available at the Australian Synchrotron (AS), was employed to investigate the vibrational modes in these clusters. Peaks in the experimental far IR spectra were assigned unambiguously to specific vibrations by comparing with the ones generated via DFT calculations with the help of collaborators, group of Professor Gregory Metha, University of Adelaide. For the Au9 cluster, three significant gold core vibrations are observed at 157, 177 and 197 cm-1 in the experimental spectrum. In the case of the Ru3 cluster, only a single ruthenium core vibration is identified within the spectrum, at 150 cm-1 with the calculated force constant, k = 0.33 mdyne/Å. The Ru4 cluster exhibits two metal core vibrations at 153 and 170 cm-1 with force constants of 0.35 and 0.53 mdyne/Å, respectively. Substitution with a gold atom yielding a mixed metal AuRu3 cluster shifts the core transitions toward higher wavenumbers at 177 and 299 cm-1 with an increase in force constants to 0.37 and 1.65 mdyne/Å, respectively. This is attributed to the change in chemical composition and geometry of the metal cluster core. A combination of the DFT calculations and high quality synchrotron-based experimental measurements allowed the full assignment of the key transitions in these clusters. Next, these clusters were fabricated into heterogeneous catalysts by depositing on different metal oxide nanopowders. Synchrotron X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies were performed at the Australian Synchrotron and the Photon Factory synchrotron in Japan to investigate the electronic structure of Au8, Au9 and Au101 on TiO2 catalysts. The XPS analysis reveals that “as-deposited” Au8 and Au9 retain some un-aggregated clusters while Au101 show bulk-like gold. These findings are in line with TEM observations, where the aggregates (large particles, > 2 nm) of Au8, Au9 and Au101 are hardly seen under HRTEM. UV-visible diffuse reflectance spectroscopy (UV-vis DRS) studies show the absence of localised surface plasmon resonance (LSPR) peaks in these “as-deposited” clusters, suggesting they are below 2 nm in size. Importantly, the XAS spectrum of “as-deposited” Au9 clusters estimates that 60% of pure, un-aggregated Au9 clusters and 40% of bulk gold in the sample. Upon calcination under O2 and combined O2 and H2 (O2-H2), Au8, Au9 and Au101 clusters form larger nanoparticles (> 2 nm) with the appearance of LSPE peak in UV-vis DR spectra. In addition, majority of the phosphine ligands (that stabilise the gold core) dislodge and form phosphine oxide-like species by interacting with oxygen on the TiO2 surface. The third part focused on testing the catalytic performance of the supported Au8, Au9, Au101, Ru3, Ru4 and AuRu3 clusters on different TiO2, SiO2, ZnO and ZrO2 in benzyl alcohol oxidation. Au101-based catalysts display the highest catalytic activity with a turn-over frequency (TOF) up to 0.69 s-1. The high catalytic activity is attributed to the formation of large Au nanoparticles (> 2 nm) that coincides with the partial removal of capping ligands. Au8 and Au9 clusters which contain NO3- counter anions are found to be inactive in benzyl alcohol oxidation. Further work shows that the presence of NO3- species diminishes the catalytic activity. Monometallic ruthenium clusters, Ru3 and Ru4, are found to be inactive yet the bimetallic AuRu3 clusters are active in benzyl alcohol oxidation, suggesting the synergistic effect between ruthenium and gold metal. Investigation of catalytic testing parameters reveals that tuning selectivity of the product is possible through manipulating the reaction temperature. Finally, a joint experiment with Prof. Wojtek Wlodarski’s group at RMIT, Melbourne was undertaken to test the sensing ability of Au9 clusters for hydrogen detection. Au9 clusters were deposited onto radio-frequency (RF) sputtered WO3 films at two different concentrations; 0.01(S1) and 0.1(S2) mg/mL. It was found that the optimal temperatures for sensor S1 and S2 were 300 °C and 350 °C, respectively. The sensor with lower Au9 concentration (S1) displays a faster response and recovery time, and a higher sensitivity toward H2. HRTEM studies reveal that the sensor S1 contain a significant population of sub-5 nm Au nanoparticles which might be responsible for a faster rate of H2 adsorption and dissociation. The key finding in this study suggest that the addition of catalytic layer such as ultra-small Au9 clusters results in improved sensitivity and dynamic performance (response and recovery time) of H2 sensors. In summary, this thesis demonstrated that cluster-based nanomaterials have wide range of applications spanning from catalysis to sensing. Further improvements in material synthesis and use of multiple complimentary characterization techniques allowed better understanding of the nature of the key active species (metal nanoparticles) assisting design of catalysts and sensors with enhanced performance.

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Maniš, Jaroslav. "Modifikace grafenových struktur ionty o nízké energii (E." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254316.

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Diploma thesis deals with the influence of low energy ions on graphene structures. Graphene structures were modified by nitrogen and argon ions of energies lower than 100 eV. Modified structures were analysed by Raman spectroscopy and x-ray photoelectron spectroscopy. The influence of the dose of ions on quality of graphene were investigated as well. In addition, this diploma thesis includes the literature search which focuses on modification of graphene by charged particles.

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21

Svensson, Pamela. "DFT investigations of the donor-acceptor couple CuPc/C60." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-297935.

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The donor-acceptor couple CuPc/C60 has been the subject of recent studies in organic solar cells due to its combined abilities in light absorption (CuPc) and charge transport (C60). By better understanding the electronic and geometric nature of the system it is possible to shed light on how the molecules act under different conditions. In this study the geometric properties for three different configurations have been studied by means of Density Functional Theory (DFT). By comparing the molecular structure of pristine CuPc with the structure of CuPc in the presence of C60, a slight elongation of the bonds is observed when the fullerene is present. This is especially true for the Cu-N bonds. By further including van der Waals interactions, no change in bond lengths is observed. This, in turn, suggests that, most likely, the interaction between the two molecules is relatively weak and the C60 will not have a major influence on the electronic structure of CuPc. The N1s X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) calculations confirm these conclusions, as only very small changes in peak positions are observed when comparing pristine CuPc with CuPc/C60.
Tack vare sina egenskaper inom absorption och laddningsöverföring har CuPc och fullerenen C60 varit föremål för omfattande studier bland forskare inom organiska solceller. Genom att få större förståelse för den geometriska såväl som den elektroniska konfigurationen inom och mellan paret kan man förutse hur dessa kommer att bete sig i olika sammansättningar. I denna studie har de geometriska förutsättningarna studerats där olika konfigurationer beräknats genom täthetsfunktionalteori (DFT). Genom att mäta bindningslängderna mellan koppar, kol och de olika typer av kväve i CuPc i de olika systemen, kan det inses att bindningarna förlängs då C60 läggs till. Då van der Waals-interaktioner inkluderades observerades ingen större förändring i bindingslängderna i jämförelse med fallet utan van der Waals-interaktioner. Detta tyder på att växelverkan mellan de två molekylerna är relativt svag och att C60-fullerenen ej har någon större påverkan på elektronkonfigurationen i CuPc. Beräkningarna av N1s X-ray Photoelectron Spectroscopy (XPS) och Near Edge X-ray Absorption Fine Structure (NEXAFS) stödjer denna slutsats då endast små skiftningar i topparna observerades vid jämförelse mellan rent CuPc och CuPc/C60.

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Jagst, Eda [Verfasser]. "Surface functional group characterization using Chemical Derivatization X-ray Photoelectron Spectroscopy (CD-XPS) / Eda Jagst." Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024743934/34.

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23

Pereira, Luis Gustavo da Silva. "Avaliação do mecanismo de oxidação de hidrogênio contaminado por monóxido de carbono em células PEMFC contendo catalisadores anódicos baseados em Pt-M/C (M=Ru, Mo, Fe e W)." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-11032010-110241/.

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A busca por fontes alternativas de energia é uma tendência mundial e, neste contexto, as células a combustível alimentadas com hidrogênio obtido pela reforma de biocombustíveis constitui uma das alternativas mais promissoras. Entretanto, o desempenho das células a combustível de membrana de troca protônica (PEMFC) com ânodos baseados em Pt é drasticamente reduzido quando se utiliza hidrogênio contaminado por CO, o qual é produzido no processo de reforma. Neste trabalho, a eletrocatálise da tolerância ao CO e a estabilidade de Pt/C, PtRu/C, PtFe/C, PtMo/C e PtW/C como eletrocatlisadores anódicos de célula a combustível PEM foram investigadas através de curvas de polarização e medidas on line de espectrometria de massas (EMS), análises de voltametria cíclica, difração de raios X (DRX) e absorção de raios X (XAS). Para todos os eletrocatalisadores bimetálicos, os quais apresentaram alta tolerância ao CO, os resultado de EMS mostraram que a produção de CO2 inicia-se a menores sobrepotenciais em relação ao eletrodo de hidrogênio quando comparado a Pt/C, confirmando a ocorrência do conhecido mecanismo bifuncional. Por outro lado, os resultados de XANES indicam um aumento de vacância da banda 5d da Pt para todos os catalisadores bimetálicos, particularmente para PtFe/C, o que leva a um enfraquecimento da ligação Pt-CO e conseqüente aumento da tolerância ao CO (efeito eletrônico). Para PtMo/C e PtRu/C alimentado com H2/CO, a formação de CO2 é observada mesmo quando a célula opera em circuito aberto, confirmando alguma eliminação de CO por um processo químico, muito provavelmente uma reação de deslocamento gás-água. Uma deterioração do desempenho de célula a combustível foi observada em uma função do tempo de operação. As causas desta degradação durante a operação a longo prazo fazem parte de um processo complexo que envolve diversos mecanismos paralelos, tais como: perda ou redistribuição do eletrocatalisador, corrosão do suporte de carbono e degradação do eletrólito (Nafion®).
The search for alternative sources of energy is a global trend, and in this context, the fuel cell supplied with hydrogen obtained by biofuels reforming is one of the most promising alternative. However, the performance of proton exchange membrane fuel cells (PEMFC) with Pt-based anode is drastically lowered when using CO-contain hydrogen, as that produced by reform. In this work, the electrocatalysis of CO tolerance and the stability of Pt/C, PtRu/C, PtFe/C, PtMo/C, and PtW/C electrocatalysts at a PEM fuel cell anode has been investigated using single cell polarization and on line electrochemical mass spectrometry (EMS) measurements, and cyclic voltammetry, X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES) analyses of the electrocatalysts. For all bimetallic electrocatalysts, which presented higher CO tolerance, EMS results have shown that the production of CO2 starts at lower hydrogen electrode overpotentials as compared to Pt/C, confirming the occurrence of the so-called bifunctional mechanism. On the other hand, XANES results indicate an increase in the Pt 5d-band vacancies for the bimetallic catalysts, particularly for PtFe/C, this leading to a weakening of the Pt-CO bond, helping to increase the CO tolerance (the so-called electronic effect). For PtMo/C and PtRu/C supplied with H2/CO, the formation of CO2 is observed even when the cell is at open circuit, confirming some elimination of CO by a chemical process, most probably the water gas shift reaction. A decay of the fuel cell performance was observed as a function of the operation time. The causes of degradation during long-term operation were found to be a complex process that involves several parallel mechanisms, including: electrocatalyst loss or redistribution, carbon corrosion, and electrolyte (Nafion®) degradation.

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Lemon, Christine Elizabeth. "Atmospheric Corrosion of Silver Investigated by X-ray Photoelectron Spectroscopy." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1350660429.

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Pinto, Rui Montenegro Val-do-Rio. "Photoelectron spectroscopy of nitrogen containing molecules of biological and industrial interest." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/7077.

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26

Zhang, Hanyu. "ANALYZING THE SHORT-RANGE ORDER OF METALLIC GLASS THROUGH X-RAY ABSORPTION FINE STRUCTURE (XAFS) SPECTROSCOPY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1554911796709215.

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27

Asakura, Hiroyuki. "Study of X-ray Absorption Spectroscopy of Heavy Elements and Transient Chemical Species." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/198946.

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Gargagliano, Roy. "Characterization of L-cysteine thin films via photoemission spectroscopy." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001355.

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29

Brumboiu, Iulia Emilia. "Molecules and Light : A Journey into the World of Theoretical Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300123.

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Two of the main technological challenges of the century are the production of clean energy, on the one hand, and the development of new materials for electronic and spintronic applications that could increase the speed and the storage capacity of regular electronic devices, on the other hand. Organic materials, including fullerenes, organic polymers and organic molecules with metal centres are promising candidates for low-cost, flexible and clean technologies that can address these challenges. A thorough description of the electronic properties of such materials is, therefore, crucial. The interaction of electromagnetic radiation with the molecule can provide the needed insight into the electronic and vibrational levels and on possible chemical interactions. In order to explain and interpret experimentally measured spectra, a good theoretical description of the particular spectroscopy is necessary. Within density functional theory (DFT), the current thesis discusses the theoretical tools used to describe the spectroscopic properties of molecules with emphasis on two classes of organic materials for photovoltaics, molecular electronics and spintronics. Specifically, the stability of the fullerene derivative PC60BM is investigated in connection with its use as an electron acceptor in organic solar cells and the valence band electronic structure of several transition metal phthalocyanines is studied for their possible application in electronics and spintronics. The spectroscopies discussed in the current work are: the photoelectron spectroscopy of the valence band, X-ray photoelectron spectroscopy of the core levels, near-edge X-ray absorption fine structure, Infrared and Raman vibrational spectroscopies

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Jain, Varun. "Preparation, Functionalization, and/or Characterization by X-ray Photoelectron Spectroscopy of Carbon Surfaces for Biosensors and Other Materials." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8113.

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My dissertation is primarily divided into two parts. The first deals with the preparation, functionalization, and characterization of carbon surfaces prepared by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) as substrates for bioarrays. Part two discusses applications of XPS peak fitting in surface chemical analysis. Chapter 1, the introduction, includes (i) a discussion of the construction of bioarrays and the preparation of sputtered surfaces, e.g., by DCMS and HiPIMS, and also functionalization (bioconjugate) chemistry with special emphasis on the importance of covalent functionalization of surfaces, and (ii) a discussion of the surface characterization techniques and accompanying analysis methods I have primarily used, which include X-ray photoelectron spectroscopy (XPS), near-ambient pressure XPS (NAP-XPS), XPS peak fitting, and contact angle goniometry (wetting). Chapter 2 discusses the preparation, characterization, and functionalization of DCMS and HiPIMS carbon surfaces for bioarrays. Here, two functionalization chemistries are explored, where the activity of DCMS and HiPIMS carbon towards amidation and amination is compared. Chapter 3 focuses on the use of Gaussian-Lorentzian sum (GLS) and Gaussian-Lorentzian product (GLP) line shapes in the context of peak fitting XPS narrow scans. This discussion includes a comparison of the GLS and GLP line shapes with the Voigt function. Chapters 4 and 5 discuss the applications of XPS peak fitting in materials characterization. Chapter 4 talks about XPS data analysis in the context of the chemical vapor deposition of various aminosilanes and their effect on peptide stability and purity. Chapters 5 describes the surface chemical analysis of various materials by NAP-XPS, including accompanying data analysis and/or peak fitting. The materials probed here cannot be analyzed at ultra-high vacuum by conventional XPS, hence, they are analyzed by NAP-XPS. Chapter 5 is divided into 5 sections. Section 5.1.1 discusses the characterization and analysis of a solution of bovine serum albumin (BSA) by peak fitting the C 1s and O 1s peak envelopes. Section 5.1.2 discusses the analysis of polytetrafluoroethylene (PTFE) at different pressures. Here, the effect of increasing background pressure and X-ray illumination time on the equivalent widths of the F 1s narrows scans is shown. Environmental charge compensation is also discussed here. Section 5.1.3 includes the analysis of poly(γ-benzyl L-glutamate) (PBLG), where the C 1s and O 1s peak envelopes were peak fitted to determine/confirm the structure and composition of this polymer. Section 5.1.4 contains an analysis and comparison of three different human hair samples: (i) untreated, (ii) colored, and (iii) bleached. Here, a comparison of the Si 2p, S 2p, and C 1s peaks illustrates the effects of the different treatments. Section 5.1.5 shows the characterization and analysis of liquid and solid phosphate buffered saline (PBS). Chapter 6 presents conclusion of my work and discusses future work.

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Lei, Yu-Guo. "Surface morphology and chemical composition of polymers studied by AFM, XPS and ToF-SIMS /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CENG%202002%20LEI.

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32

Philippe, Bertrand. "Insights in Li-ion Battery Interfaces through Photoelectron Spectroscopy Depth Profiling." Doctoral thesis, Uppsala universitet, Strukturkemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197250.

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Compounds forming alloys with lithium, such as silicon or tin, are promising negative electrode materials for the next generation of Li-ion batteries due to their higher theoretical capacity compared to the current commercial electrode materials. An important issue is to better understand the phenomena occurring at the electrode/electrolyte interfaces of these new materials. The stability of the passivation layer (SEI) is crucial for good battery performance and its nature, formation and evolution have to be investigated. It is important to follow upon cycling alloying/dealloying processes, the evolution of surface oxides with battery cycling and the change in surface chemistry when storing electrodes in the electrolyte. The aim of this thesis is to improve the knowledge of these surface reactions through a non-destructive depth-resolved PES (Photoelectron spectroscopy) analysis of the surface of new negative electrodes. A unique combination utilizing hard and soft-ray photoelectron spectroscopy allows by variation of the photon energy an analysis from the extreme surface (soft X-ray) to the bulk (hard X-ray) of the particles. This experimental approach was used to access the interfacial phase transitions at the surface of silicon or tin particles as well as the composition and thickness/covering of the SEI. Interfacial mechanisms occurring upon the first electrochemical cycle of Si-based electrodes cycled with the classical salt LiPF6 were investigated. The mechanisms of Li insertion (LixSi formation) have been illustrated as well as the formation of a new irreversible compound, Li4SiO4, at the outermost surface of the particles. Upon long cycling, the formation of SiOxFy was shown at the extreme surface of the particles by reaction of SiO2 with HF contributing to battery capacity fading. The LiFSI salt, more stable than LiPF6, improved the electrochemical performances. This behaviour is correlated to the absence of SiOxFy upon long-term cycling. Some degradation of LiFSI was shown by PES and supported by calculations. Finally, interfacial reactions occurring upon the first cycle of an intermetallic compound MnSn2 were studied. Compared to Si based electrodes, the SEI chemical composition is similar but the alloying process and the role played by the surface metal oxide are different.

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Poirier, Mathilde. "Fonctionnalisation et cristallochimie de talcs synthétiques submicroniques." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30237.

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Le talc synthétique est un matériau à fort intérêt industriel du fait de sa taille submicronique, de sa large surface spécifique (> 300 m²/g), et de ses propriétés hydrophiles, qui lui offrent un large éventail d'applications dans des secteurs industriels variés (polymères, cosmétiques, papiers, peintures, médecine, ...). Dans cette thèse, les potentialités d'adsorption du matériau ont été testées vis-à-vis de différents composés organiques et/ou inorganiques à propriétés physico-chimiques souhaitées (composés colorés et/ou fluorescents, nanoparticules métalliques), afin d'élaborer de nouvelles charges minérales fonctionnelles et innovantes (e.g. talcs synthétiques fluorescents). Les résultats montrent que le matériau présente une forte capacité à adsorber les composés testés, qui est bien supérieure à celle de son homologue naturel de taille pluri-micronique. La recherche des mécanismes d'adsorption se produisant à l'interface "minéral - adsorbat" a par la suite conduit à étudier de plus près la cristallochimie du talc synthétique non fonctionnalisé, en utilisant plusieurs méthodes de caractérisation comme la Diffraction des Rayons (DRX), la spectroscopie de Résonance Magnétique Nucléaire (RMN), ou bien encore la spectroscopie d'Absorption des Rayons X (XAS). Outre le fait que de grandes avancées ont été faites sur la caractérisation cristallochimique des particules, les résultats majeurs montrent que les minéraux synthétiques ne doivent pas être regardés de la même manière que les minéraux naturels, du fait de leur taille nanométrique qui engendre obligatoirement une perturbation des signaux observés. Les résultats montrent notamment que les méthodes de caractérisation qui sont classiquement utilisées en DRX pour calculer les distances inter-réticulaires ne doivent pas être appliquées sur les nanomatériaux du fait du faible empilement des particules suivant l'axe cristallographique c*. Il faut pour cela faire appel à des méthodes de simulation numériques pour déterminer les valeurs des distances inter-réticulaires réelles. De la même manière, les résultats montrent que les signaux RMN sont également impactés par la taille nanométrique des particules du fait d'une différenciation des signaux provenant du cœur des particules, de ceux provenant des surfaces externes des particules. Ces résultats ont été mis en évidence en combinant une approche expérimentale par RMN à une approche théorique par DFT (Density Functional Theory).[;;;]
Synthetic talc is a material of great industrial interest because of its submicronic size, its large specific surface area (> 300 m²/g), and its hydrophilic properties, offering a wide range of applications in the fields of polymers, cosmetics, papers, paints, or medecine. In this thesis, the adsorption capacity of the material was tested towards different organic and/or inorganic compounds of desired physicochemical properties (coloured and/or fluorescent compounds, metallic nanoparticles), to elaborate new mineral fillers with functional and innovative characteristics (e.g. fluorescent synthetic talc particles). The results show that synthetic talc particles possess a much higher adsorption capacity towards organic and inorganic compounds, compared to natural plurimicron-sized talc particles. Research on the adsorption mechanisms occuring at the " mineral - adsorbate " interface was followed by the study of the crystal-chemistry of the material, using a combination of several characterization techniques such as X-Ray Diffraction (XRD), Nuclear Magnetic Resonance spectroscopy (NMR), or X-Ray Absorption spectroscopy (XAS). Beyond the fact that a great progress was made on the overall crystal-chemistry of the particles, the main results show that " synthetic minerals " should not be considered in the same way as " natural minerals " due to their nanometric size which necessarily disturbed the observed signals. As an example, the methods conventionally used in XRD to determine the interplanar spacings should not be applied on nanomaterials because of their very low particle stacking and numerical simulations shall be used instead. Similarly, our study shows that NMR signals are also impacted by the nanometric size of the particles because of a spectral differentiation of the signals coming from the bulk of the particles versus the ones coming from the external surfaces of the particles. These results were highlighted by combining an experimental NMR approach and a theoretical DFT (Density Functional Theory). Those external surfaces, which contain crystalline defects, are probably responsible for the high adsorption capacity of the material, and may explain some of the crystallogenesis processes that have been observed by XAS spectroscopy. To conclude, nano-sized lamellar synthetic materials represent a great tool to investigate the surface crystal-chemistry of natural minerals, as they revealed new contributions which were previously undetectable in larger-sized minerals

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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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Mueanngern, Yutichai. "Mechanistic Studies of Crotonadehyde Partial Hydrogenation and Ethanol Steam Reforming Reactions on Planar Catalysts—A Gas-Phase and Ambient Pressure XPS Study." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576076945070127.

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Droschke, Sonja. "X-Ray Photoemission Spectroscopy Characterization of Fe(II)- and Fe(III)-Phthalocyanine Molecular Films." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257183.

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This thesis investigates the electronic structure of iron phthalocyanine (Fe(II)Pc) andiron phthalocyanine chloride (Fe(III)PcCl) immobilized on surfaces. For this purposetwo different deposition methods are used and compared: smearing the molecularpowder under atmosphere condition and evaporation of a molecular layer inultra-high vacuum. The electronic states of FePc and FePcCl are probed withphotoelectron spectroscopy (PES) and compared in relation to the ionic state of thecentral metal (Fe). The PE spectra show that evaporation of FePcCl at around 350°Cresults in dissociation of the chlorine from the FePc molecule, which is stable at thistemperature. Mass spectroscopic measurements during heating of FePcCl in ultra-highvacuum (UHV) show a clear Cl signal for temperature still below 250°C. Theoreticalcalculations of the binding energy for Cl in FePcCl seem to indicate dissociation of theCl from the molecules.

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Fredriksson, Wendy. "Depth Profiling of the Passive Layer on Stainless Steel using Photoelectron Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179399.

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The physical properties of the protective passive films formed on the surface of stainless steels under electrochemical polarization in different electrolytes were studied. The structure of these films was analyzed as a function of depth using photoelectron spectroscopy (PES). Depth profiling (using PES) of the surface layer was achieved by either changing the angle of incidence to achieve different analysis depths (ARXPS), by argon ion etching, or by varying the energy of the incoming x-rays by the use of synchrotron radiation. The use of hard x-rays with high resolution (HAXPES) provided novel quantified information about the nickel content underneath the passive films. A complex environment was found in these surface layers composed of an outermost monolayer of iron on top of a layer of chromium hydroxides covering an underlayer of chromium oxides. Molybdenum was enriched in the interface between the metal and oxide. Nickel is enriched underneath the passive film and therefore nickeloxides are only present in the surface layer in low concentrations. A comparison was performed on austenitic and duplex stainless prepared by hot isostatically pressed (HIP) or cast and forged processes. HIP stainless steel was produced using the burgeoning technique of pressing gas atomized powders together. The structure of these steels is far more homogenous with a lower porosity than that of the conventionally prepared equivalents. It was shown that hot HIP austenitic steel had better pitting corrosion resistance than its conventional counterpart. Finally, the duplex steel was cycled in a Li-ion battery to explore its potential application as a current collector. It was shown that the passive film formed in the organic solvents is similar in composition and thickness to the films formed in aqueous solutions. However, it is doubtful if steel could be used as current collector in batteries due to its high reactivity with lithium.

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Younesi, Reza. "Characterization of Reaction Products in the Li-O2 Battery Using Photoelectron Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183887.

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The rechargeable Li-O2 battery has attracted interest due to its high theoretical energy density (about 10 times better than today’s Li-ion batteries). In this PhD thesis the cycling instability of the Li-O2 battery has been studied. Degradation of the battery has been followed by studying the interface between the electrodes and electrolyte and determining the chemical composition and quantity of degradation products formed after varied cycling conditions. For this in-house and synchrotron based Photoelectron Spectroscopy (PES) were used as a powerful surface sensitive technique. Using these methods quantitative and qualitative information was obtained of both amorphous and crystalline compounds. To make the most realistic studies the carbon cathode pore structure was optimised by varying the binder to carbon ratio. This was shown to have an effect on improving the discharge capacity. For Li-O2 batteries electrolyte decomposition is a major challenge. The stability of different electrolyte solvents and salts were investigated. Aprotic carbonate and ether based solvents such as PC, EC/DEC, TEGDME, and PEGDME were found to decompose during electrochemical cycling of the cells. The carbonate based electrolytes decompose to form a 5-10 nm thick surface layer on the carbon cathode during discharge which was then removed during battery charging. The degradation products of the ether based electrolytes consisted mainly of ether and carbonate based surface species. It is also shown that Li2O2 as the final discharge product of the cell is chemically reactive and decomposes carbonate and ether based solvents. The stability of lithium electrolyte salts (such as LiPF6, LiBF4, LiB(CN)4, LiBOB, and LiClO4) was also studied. The PES results revealed that all salts are unstable during the cell cycling and in contact with Li2O2. Decomposition layers thinner than 5 nm were observed on Li2O2. Furthermore, it is shown that the stability of the interface on the lithium anode is a chief issue. When compared to Li batteries (where oxygen levels are below 10 ppm) working in the presence of excess oxygen leads to the decomposition of carbonate based electrolytes to a larger degree.

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McGovern, William Robert. "Characterization of carbon-molecule-metal junctions by cyclic voltammetry, raman spectroscopy and X-Ray photoelectron spectroscopy." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1114560996.

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Gråsjö, Johan. "Molecular Arrangement, Electronic Structure and Transport Properties in Surfactant Gel- and Related Systems Studied by Soft X-ray and Dielectric Spectroscopy." Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205072.

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This thesis concerns studies of aqueous soft matter systems, especially surfactant micelle systems. The aim has been to study the molecular arrangement and electronic structure of the constituents of, as well as transport properties in such a system. The molecular arrangement and electronic structure has been studied by means of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray spectroscopy (RIXS). The transport properties have been investigated by low-frequency dielectric spectroscopy (LFDS) and small angle X-ray scattering (SAXS) as well as a theoretical modelling. The latter was based on Fick’s laws of the release from binary surfactant system and was validated by experiments. The RIXS and XAS measurements show the electronic structure in bulk water and the influence of the chemical surrounding of the water molecule in bulk water and of the water molecules confined in a micelle lattice. The spectra are highly dependent on the molecular arrangement in such systems. For glycine and sodium polyacrylate RIXS and XAS spectra show features which are unique for carboxyl and carboxylate groups and such measurements can thus be used for fingerprinting. The LFDS and SAXS measurements show a strong correlation between structure in a surfactant/poly-ion system and apparent mobility of surfactants. This conclusion is in line with earlier observations. By the theoretical modelling a predictive model for the surfactant release from a binary surfactant micelle system has been obtained and the importance of different factors for surfactant release has been further clarified.

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Jagst, Eda [Verfasser], Manfred [Gutachter] Hennecke, and Rainer [Gutachter] Haag. "Surface Functional Group Characterization Using Chemical Derivatization X-ray Photoelectron Spectroscopy (CD-XPS) / Eda Jagst ; Gutachter: Manfred Hennecke, Rainer Haag." Berlin : Bundesanstalt für Materialforschung und -prüfung (BAM), 2011. http://d-nb.info/1122741030/34.

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Lyon, John. "Fabrication and Analysis of Poly(3-hexylthiophene) Interfaces Using Electrospray Deposition and Photoemission Spectroscopy." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3937.

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P3HT (Poly(3-hexylthiophene)) is an organic polymer that shows promise as an active material in semiconducting electronics. It is important to study the electronic properties of this material in order to determine its efficacy in such devices. However, many current studies of thiophene only examine the oligomer, since it is a simpler material to investigate. In this study, several P3HT interfaces were analyzed to determine their electronic properties. The P3HT was deposited on Au, highly-ordered pyrolitic graphite (HOPG), and indium tin oxide (ITO) substrates via electrospray deposition. The depositions were performed in several steps, with x-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) measurements taken between each step without breaking the vacuum. The resulting series of spectra allowed orbital line-up diagrams to be generated for each interface, giving detailed analysis of the interfacial properties, including the charge injection barriers and interface dipoles. The results, when compared to similar oligomer-based investigations, show a difference in the orbital line-up between oligomeric and polymeric P3HT junctions.

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Zhang, Teng. "Synchrotron radiation study of free and adsorbed organic molecules." Licentiate thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-307787.

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In this licentiate thesis, organic molecules, namely Cobalt Phthalocyanine (CoPc) and Biphenylene, have been studied by means of synchrotron radiation-based spectroscopic methods (Photoemission Spectroscopy (PES) and X-ray Absorption Spectroscopy (XAS) in combination with Density Functional Theory (DFT) calculations. Paper I is a combined experimental and theoretical investigation of electronic structure of CoPc. addressing the atomic character of the Highest Occupied Molecular Orbital (HOMO) and the electronic configuration of the molecular ground state. Both these aspects are still under discussion since different experimental and theoretical studies have given controversial results. Previous works have indicated the CoPc ground state to either be described by the 2A1g or 2Eg, or by a mix of the two electronic configurations. Regrading the debated the atomic character of the HOMO of CoPc, it has been suggested to be either metal 3d-like and localized on the central Co atom or originating in the organic ligand of the molecule. In this thesis the valence photoemission results for CoPc in gas phase and as adsorbed films on Au(111) together with the DFT simulations, consistently indicate that the HOMO is derived only by the organic ligand, with mainly contribution from the carbon atoms with no metal character. Moreover, the good agreement between the experimental and theoretical results, confirms that the ground state of CoPc is correctly described by the 2A1g configuration. In Paper II, PES and XAS have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, XAS measurements allowed the characterizion of the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction.

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Curcio, Ana Laura [UNESP]. "Síntese e caracterização de materiais semicondutores nanoestruturados luminescentes à base de ZnS." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138154.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Nanocristais tem sido extensivamente investigados nos últimos anos devido à sua ampla gama de aplicações em vários dispositivos tais como sensores, células solares, lasers, fotocatalisadores, fotodetectores, detectores de infravermelhos, diodos emissores de luz, materiais eletroluminescentes e outros materiais emissores de luz. Semicondutores nanocristalinos apresentam propriedades eletrônicas intermediárias entre aqueles de estrutura molecular e sólidos macrocristalinos, proporcionando uma ampla gama de aplicações. Entre estes materiais, o sulfeto de zinco (ZnS) puro ou dopado tem recebido notável atenção por causa de suas propriedades estruturais ópticas, versatilidade e potencial para várias aplicações tecnológicas. O ZnS é um típico semicondutor II-VI, com um gap direto de 3,6 eV à temperatura ambiente e aproximadamente 40 meV de energia de gap, sendo um bom material luminescente utilizado em telas, sensores e lasers. Como material de gap largo, o ZnS pode facilmente hospedar diferentes metais de transição como centros luminescentes. Entre estes íons de metais de transição para estruturas dopadas, os íons Cu2+e Mn2+ são atraentes pelas emissões de luz características e por apresentarem propriedades eficientes para aplicações como luminóforos. A inserção desses íons na estrutura do ZnS proporcionam defeitos que resultam em emissão no verde para os íons Cu2+e emissão no laranja para os íons Mn2+. Neste estudo, as amostras de ZnS pura e dopadas com Cu2+ e Mn2+ foram preparados pelo método solvotermal, que demonstra ser um processo eficaz para preparar nanopartículas. Uma vez preparadas, as estruturas das amostras nanoestruturadas foram caracterizadas e correlacionada s com propriedades fotoluminescentes. Os resultados de difração de raios X mostram que as amostras de ZnS foram cristalizadas completamente sem a presença de fases secundárias e os difratogramas correspondem à estrutura blenda cúbica de zinco com grupo espacial F-43m. Os espectros de XANES (X-ray Absorption Near Edge Structure) teóricos e experimentais na borda K do Zn indicam que a incorporação de átomos de Mn na matriz ZnS causam a formação de vacâncias de Zn e S, a qual é confirmada por ajustes de espectros EXAFS (Extended X-ray Absorption Fine Structure). Estas vacâncias estão relacionadas com um desvio para o vermelho observado no pico do espectro de fotoluminescência devido a adição de Mn na estrutura do ZnS. Para o ZnS puro, o pico é centrado em ~ 504 nm, relativo as vacâncias de S na amostra nanoestruturada. À medida que se aumenta a porcentagem de Mn na matriz ZnS, uma emissão no amarelo-laranja centrada em ~ 590 nm pode ser observada, associada com a transição 4T1-6A1 no interior de níveis 3d de Mn2+. A adição de íons Cu2+ ao ZnS resulta em um alargamento no pico do espectro de fotoluminescência decorrente de emissão no azul-verde, que está relacionada a recombinação de elétrons de níveis de defeitos mais profundos dos estados t2 do Cu próximos da banda de valência.
Nanocrystals has been extensively investigated in recent years due to its wide range of applications in various devices light emitting materials such as sensors, solar cells, lasers, photocatalysts, photodetectors, IR detectors, light emitting diodes and others. Nanocrystalline Semiconductors have electronic properties between those intermediate molecular macrocristalinos and solid structure, providing a wide range of applications. Among these materials, zinc sulfide (ZnS) pure or doped has received considerable attention because of its optical structural properties, versatility and potential for several technological applications. The ZnS is a typical II-VI semiconductor with a direct band gap of 3.6 eV at room temperature and about 40 meV in energy gap, and a good luminescent material for constrution of displays, lasers and sensors. As wide band gap material, ZnS can easily host different transition metals as luminescent centers. Among these ions of transition metal doped structures, Cu2+ and Mn2+ ions are attractive for light emission characteristics and for having effective properties for applications such as phosphors. The addition of these ions in ZnS structure provide defects that result in emission in the green for the Cu2+ ions and emission in orange for the Mn2+ ions. In this study, samples of pure ZnS and doped with Cu2+ and Mn2+ ions were prepared by solvotermal method, which demonstrate to be an effective process for preparing nanoparticles. Once prepared, the structures of the nanostructured samples were characterized and correlated with photoluminescent properties. The results of X-ray diffraction showed that the ZnS samples were completely crystallized without the presence of secondary phases and XRD patterns correspond to the structure of zinc blende to cubic space group F-43m. spectra XANES (X-ray Absorption Near Edge Structure) theoretical and experimental in the Zn K edge indicates that the inclusion of Mn atoms in the ZnS matrix cause the formation of Zn and S vacancies, which is confirmed by spectral adjustments EXAFS (Extended X-ray Absorption Fine Structure). These vacancies are associated with a red shift observed in the photoluminescence spectrum peak due to the addition of Mn in ZnS structure. For pure ZnS, the peak is centered at ~ 504 nm concerning the vacancies in the S nanostructured sample. As it increases the percentage of Mn in the ZnS matrix, in yellow-orange emission centered at ~ 590 nm can be observed, associated with the transition 4 T1- 6A1 inside 3d levels of Mn2+. Adding Cu2+ to the ZnS results in a broadening of the peak of the photoluminescence spectrum due to emission in blue-green, which is related to recombination deeper defect levels of electrons of t2 Cu states near the valence band.

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Doran, Brian. "Preparation and characterization of Ribonucleic acid (RNA)/inorganic materials interfaces using photoemission spectroscopy." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000385.

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46

Ehrman, James D. "X-Ray Photoelectron Spectroscopy Studies of Orthopedic Materials." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1248115447.

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47

Pašiškevičius, Audrius. "Synthesis of the Vanadium Oxide Compounds and Investigation by X-Ray Photoelectron Spectroscopy Method." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110219_122819-95620.

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The thin films of oxide xerogels and bronzes and molecular oxide xerogels and bronzes of vanadium compounds were synthesized by sol-gel technology method. The chemical composition of mentioned compounds was investigated using XPS method in order to determine the valence of metal ions. It is shown that it is possible to produce the thin films of vanadium oxide bronzes using simple methods. The possibility to use vanadium-ammonium oxide hydrated compounds as materials for producing the ammonium sensors is shown in the dissertation.
Šiame darbe panaudojant zolis-gelis technologiją, susintetinti vanadžio junginių oksidinių kserogelių ir bronzos bei molekulinių oksidinių kserogelių ir bronzų plonieji sluoksniai. Visų minėtų medžiagų cheminė sudėtis ištirta Rentgeno fotoelektronų spektroskopijos metodu, siekiant nustatyti metalų jonų valentines būsenas. Panaudojant zolis-gelis technologiją, galima gana paprastais metodais, nenaudojant sudėtingos technologinės įrangos, gaminti vanadžio oksidinių bronzų plonuosius sluoksnius. Vanadžio amonio hidratuoti oksidiniai junginiai gali būti naudojami kaip medžiagos amoniako dujų jutikliams gaminti.

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48

Galicka, Karolina Laffez Patrick Ratuszna Alicja. "Contribution to the study of the electronic states of rare earth oxide thin films by the XPS and the Raman spectroscopy." [S.l.] : [s.n.], 2005. http://cyberdoc.univ-lemans.fr/theses/2005/2005LEMA1006.pdf.

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Reproduction de : Thèse de doctorat : Physique : Le Mans : 2005. Reproduction de : Thèse de doctorat : Physique : Katowice (Pologne) : 2005.
Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre.

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49

Galicka, Karolina. "Contribution to the study of the electronic states of rare earth oxide thin films by the XPS and the Raman spectroscopy." Le Mans, 2005. http://cyberdoc.univ-lemans.fr/theses/2005/2005LEMA1006.pdf.

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L'étude en spectrométrie Raman et XPS de films minces de nickelates de terre rare NdNiO3 déposés sur NdGaO3 par pulvérisation cathodique a été entreprise. L'objectif était double. Tout d'abord, tenter d'identifier la cause responsable de propriétés de commutations en température différentes en fonction de l'épaisseur déposée (transition métal – isolant abrupte pour des films de 150 nm, absence de transition pour des films de 17 nm). L'objectif a été atteint grâce à la spectroscopie XPS, qui a permis d'analyser la bande de valence et le niveau de coeur du Ni2p, O1s, et Nd3d. Le second objectif était de montrer la disproportion de charge du Ni3+ en Ni3+d et 3-d, en tentant d'interpréter le spectre de phonon au passage de la transition métal – isolant. Cette étude a été réalisée grâce à la spectroscopie Raman et par des calculs théoriques de dynamique de réseau (programme LADY). Cette thèse a contribué à la compréhension générale de la transition métal – isolant dans les pérovskites NdNiO3. Les spectrométries Raman et XPS apparaissent comme des outils pertinents pour l'analyse des oxydes de métaux de transition et terre rares qui sont très prometteurs pour de nombreuses applications
The thesis concerned the NdNiO3/NdGaO3 thin films with various thicknesses 150 nm, 73 nm and 17 nm. Samples have been obtained by RF – sputtering and post annealing deposition treatment at the 800°C and O2 250 bar, during 48h. The thesis had two mainly goals. First one, identify source responsible for different switching properties of the thin films NdNiO3/NdGaO3 (observed in DC measurements 150 nm abrupt while for 17 nm film vanishing metal – insulator transition). This goal has been achieved thanks XPS studies, i. E. , analysis of the valence bands and core level of Ni2p, O1s and Nd3d spectra. The attempt to establish an effect of charge disproportion of nickel ion 2Ni3+ ® Ni3+d + Ni3-d and observed it in experimental phonon spectra across metal – insulator transition have been a second goal of the thesis. These studies have been performed thanks the Raman scattering studies and theoretical lattice dynamics calculation (LADY). This thesis contributed to the general understanding of the metal – insulator transition in RNiO3 perovskite. The XPS and Raman spectroscopy studies appeared as pertinent tools to investigate the properties of rare earth oxides thin films that are also promising for various applications

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50

Jakubowicz, Agnieszka. "Investigation of growth kinetics of self-assembling monolayers by means of contact angle, optical ellipsometry, angle-resolved XPS and IR spectroscopy." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4602/.

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Absorption of octadecanethiol and p-nitrobenzenethiol onto gold surfaces from ethanol solutions has been studied by means of contact angle, optical ellipsometry, angle-resolved XPS (ARXPS), and with grazing angle total reflection FTIR. Growth of the monolayers from dilute solutions has been monitored and Langmuir isotherm adsorption curves were fitted to experimental data. A saturated film is formed within approximately 5h after immersion in solutions of concentrations ranging from 0.0005mM to 0.01mM. We found, that the final density of monolayer depends on the concentration of the solution.

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Dissertations / Theses on the topic 'XAS spectrosopy'

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