Dissertations / Theses on the topic 'Oxygen Atom'
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Sieker, Anke. "Oxygen atom transfer reactions." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12933.
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Oxygen atom transfer reactions in a series of early transition metal complexes in both solution and solid state were investigated, with a particular interest in O-atom transfer processes from bonded NOx (x= 1,2,3) ligands to adjacent carbonyl groups. The main objective was the synthesis and characterisation of new mixed CO/NO2- species. In Chapter 1 a general review of oxygen atom transfer reactions involving CO and NOx is given. Chapter 2 presents the results gained from reactions of M2(CO)10, ClM(CO)5 and several other carbonyl halides {M=Mn, Re} with [PPN][NO2]/[PPh4][NO2]. Chemical activation by (CH3)3NO prior to interaction with [PPN][NO2]/PPh4][NO2] has also been investigated. Complexes isolated and characterised by IR spectroscopy and X-ray diffraction include [(OC)3Mn(μ2-NO(O))2(μ2-O(NO))Mn(μ2-NO(O))2(μ2-O(NO))Mn(CO)3](PPN)2, {[CIRe(CO)3(NO2)2]C1[(CH3)3NCH2C1]3} and [Re(CO)3(ONO)3](PPN)2. Compounds such as Mn2(CO)8(PPh3)2, [Mn(CO)4C1(PPh3)] and [trans-Mn(CO)3C1(PPh3)2] substituted in part by tertiary phosphines have been tested towards their reactivity with [PPN][NO2]/[PPh4][NO2]. Reaction pathways are discussed on the basis of detailed IR spectroscopy studies. In Chapter 2.3. reactions of M(CO)6, [M(CO)5C1](Et4) {M= Cr, Mo and W} and [(OC)3Mo(μ2-C1)3Mo(CO)3](NEt4)2 with [PPN][NO2]/[PPh4](NO2] are presented. Mixed CO/NO2 species were prepared for all three metals and structurally characterised in the solid state in form of [M(CO)5(NO2)](PPh4) {M=Cr and W}. Mixed CO/NO complexes of Manganese (2.1.3.) and Chromium (2.3.2.) have been synthesised and their reactions with O2 investigated. Oxidation of the nitrosyl ligands was observed in both cases and possible reaction mechanisms are presented.
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Bray, Mark Richard. "The computational modelling of oxygen atom transfer reactions." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245932.
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Green, David Kluttz. "Oxygen atom transfer reactions of oxo-chromium(IV) porphyrins." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/27297.
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McLeod, G. G. "Atomisation and recombination reactions of oxygen, hydrogen and deuterium." Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381363.
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Kafentzi, Maria Chrysanthi. "Reactive copper-oxygen species for C-H activation : influence of nuclearity and oxygen atom donor." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4355/document.
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Les monooxygénases à cuivre sont des systèmes enzymatiques capables de transférer un atome d'oxygène à leur substrat de manière hautement régio et stéréo-spécifique. Les complexes modèles de monooxygénases à cuivre ont fourni de précieuses informations sur la structure et la réactivité des espèces «cuivre-dioxygène» impliquées dans une telle réactivité. Cependant, la découverte récente de deux nouveaux systèmes enzymatiques (LPMO et pMMO) capables d'effectuer l'activation des liaisons C-H très énergétiques a réouvert le débat sur les espèces cuivre--oxygène capables d'une telle réactivité. Dans ce travail, nous avons choisi de préparer des complexes bio-inspirés de Cu(I) et Cu(II) avec un ligand contenant un substrat interne. Ces complexes ont été exposés à différents oxydants ou donneurs d'atome d'oxygène et nous avons étudié la régio- et stéréo-sélectivité de la réaction d'oxydation du substrat interne. De plus, nous avons évalue la capacité de ces systèmes à utiliser l'eau comme donneur d'atome d'oxygène. Pour cela, nous avons l'oxydation ou l'activation de l'eau par voie électrochimique afin de générer des intermédiaires cuivre-oxygène conduisant éventuellement à la production de dioxygène ou à l'oxydation sélective du ligand. Enfin, nous nous sommes intéressés aux propriétés d'espèces hétérobimétalliques à haute valence. Par conséquent, deux nouveaux complexes hétérobimétalliques à haute valence contenant du nickel et du cuivre ont été synthétisés. Nous avons étudié leurs propriétés électroniques et leur réactivité envers des substrats externes et internes (ligands) a été évaluée et comparée à la réactivité de leurs homologues homobimétalliquesCopper-containing monooxygenases are enzymatic systems capable of transferring an oxygen atom to their subtrates in highly regio or stereo-specific modes. Model complexes for copper-containing monooxygenases have provided valuable information on the structure and reactivity of several copper-dioxygen adducts. However, the recent discovery of two new enzymatic systems (LPMO and pMMO) able to perform activation of very strong C-H bonds has re-opened the debate on the catalytically relevant copper-dioxygen species. The use of model systems that mimic an enzyme is a simple approach to obtain a better knowledge of how nature works. For this study, Cu(I) and Cu(II) complexes containing ligand-substrate were prepared. After reaction with different oxidants or O-atom donors, we investigated the regio- and stereo-selectivity of the oxidation of the internal substrate. Based on the relatively well-known chemistry of Cu(I) with dioxygen, we, were also interested in investigating the water as an O-atom donor in C-H bond activation reactions. We have therefore investigated electrochemical water oxidation or activation to generate dioxygen and selective oxygen-insertion into the substrate-bound moiety. Finally, we explored the properties of mixed-metal dioxygen species as compared to their homometalic counter-parts. Indeed heterobimetallic active sites are found in various metalloenzymes such as cytochrome c oxidase. Therefore, two new high-valent Cu-Ni heterobimetallic complexes were synthesized. We investigated their electronic properties using various spectroscopic methods and their reactivity was evaluated towards external and internal substrates (indane)
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Miner, Gilda Ann Newton. "Continuous Electron Stimulated Oxygen Atom Emission from Ag Permeation Membranes." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539625976.
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McGuckin, Margaret Rose Mary. "Synthesis and reactions of three-membered heterocyles containing an oxygen atom." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335934.
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Chang, Liu. "Ghost in the shell : Studies on subsurface oxygen in oxide-derived copper nanocube catalysts." Licentiate thesis, Stockholms universitet, Fysikum, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147215.
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With the passage of time and the advancement of our industrial civilization, environmental concerns have become more and more recognized since the 1990s. Carbon dioxide reduction reactions are capable of converting carbon dioxide into valuable hydrocarbons and reducing the carbon emission from the combustion of fossil fuels. This is a promising direction for sustainable energy resources given that the scarcity of fossil fuels is becoming more threatening to the survival of mankind. In recent years, oxide-derived metal nanostructures have been synthesized and show unique catalytic features. Recently, Sloan et al. synthesized a novel oxide-derived copper nanocube structure, which showed a high selectivity toward ethylene over methane and low overpotentials. In this work, the presence of subsurface oxygen in the catalyst surface is tested with density functional theory (DFT) calculations, as a complement to experimental x-ray photoelectron spectroscopy. Due to limitations on the scale of modeling with DFT, the results indicate a very low stability of subsurface oxygen, which give rise to a question if subsurface oxygen would be stable with a reasonably large cluster model. Self-consistent charge density functional tight binding (SCC-DFTB) is adopted to investigate a nanocube model. In this model, a manually reduced cuprious oxide nanocube is constructed and investigated. Subsurface oxygen atoms close to facets are found to be more stable inside. A higher degree of disorder is proposed to be the cause of this difference in stabilizing subsurface oxygen atoms between the slab and nanocube models. The presence of subsurface oxygen enhances the adsorption of CO on the Cu(100) surface, increasing the likelihood for adsorbed CO molecules to dimerize, which is the rate determining step for ethylene production on Cu(100) under low-overpotential conditions. With subsurface electronegative atoms such as oxygen or fluorine, it is also found that the d-band scaling relation could be broken.
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Alessi, Dario <1990>. "Reviewing interactions between uranyl’s oxygen atom, hydrogen, p block elements, and their effects in uranium-oxygen bond length." Master's Degree Thesis, Università Ca' Foscari Venezia, 2020. http://hdl.handle.net/10579/18359.
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Thanks to the Cambridge Structural Database, in this thesis work has been selected several uranyl’s ion crystal structures, which share interactions between uranyl’s oxygen and block p elements, or hydrogen. These interactions belong to hydrogen bond, chalcogen and halogen bond or, in a more generic way, short contact interactions. In order to select the structures, the research fields were limited for certain elements to a value within their Van der Waals peak. It was evaluated the influence that these interactions provide to the uranyl’s ion bond length (U=Oyl) from two points of view: a) by considering the type of interacting element and b) by considering the type of donor atom in equatorial position. The data collected were also used to verify the existence of a trend that correlates the interaction length, or nature of equatorial ligands, to the uranyl’s bond length. A comparation between the IR and Raman data, provided by the original works, completes the overview. In conclusion, the main synthetic routes to achieve the structures analysed in this research were highlighted.
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Haley, Craig Stuart. "A feasibility study of the Microsatellite Experiment for Sounding Oxygen atom densities (MESO)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0024/MQ39198.pdf.
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Hansen, Craig Allen. "Carbonyl cyclopentadienylnitro complexes of iron and ruthenium and their oxygen atom transfer reactions." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184482.
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New and reactive nitro organometallics, Fe(C₅H₅)(CO)₂(NO₂), Ru(C₅H₅)(CO)₂(NO₂), their nitrogen-15 derivatives, Fe(C₅H₅)(CO)(PPh₃)(NO₂), and [Fe(C₅H₅)(CO)(PPh₃)L]NOₓ (where L = MeOH or MeCN and x = 2 or 3), were isolated and characterized by elemental analysis, IR, and NMR. The compounds were made by reactions of [Fe(C₅H₅)(CO)₂]₂, Fe(C₅H₅)(CO)₂I, [Ru(C₅H₅)(CO)₂]₂, and Fe(C₅H₅)(CO)(PPh₃)I with silver nitrite. The molecular and packing structures of Fe(C₅H₅)(CO)₂(NO₂) and Ru(C₅H₅)(CO)₂(NO₂) were determined by single-crystal X-ray diffractometry at -100°C and 26°C, respectively. Although stable at low temperature, Fe(C₅H₅)(CO)₂(NO₂) and Fe(C₅H₅)(CO)(PPh₃)(NO₂) decomposed at room temperature with evolution of CO₂ and concomitant formation of unstable metal nitrosyl complexes. In the case of Fe(C₅H₅)(CO)₂(NO₂), the mixture of products included Fe(C₅H₅)(CO)(NO), [Fe(C₅H₅)(NO)]₂, Fe(C₅H₅)₂, N₂O, CO, intractable material, and [Fe(C₅H₅)(CO)₂]₂. The kinetics of the oxygen transfer reactions of Fe(C₅H₅)(CO)₂(NO₂) and Fe(C₅H₅)(CO)(PPh₃)(NO₂) have been studied by NMR and IR of the solution, by IR and manometry of the gas phase, and by IR and elemental analysis of the intractable residues. The enthalpies and entropies of activation were obtained from Eyring plots of the reaction rate constants of Fe(C₅H₅)(CO)₂(NO₂) at 20, 30, and 40°C. Ru(C₅H₅)(CO)₂(NO₂) decomposes slowly with evolution of CO₂ at 40°C. In addition to the experiments outlined above, the dissertation includes discussions of the coordination chemistry of the new compounds in light of the few reports of other nitro organometallics and the calculations of molecular orbitals and energies. Also, the angular orientation of the basicity of the nitrite ion was probed by extended Huckel calculations of the orbital energies of hydrogen nitrite as the proton was moved around the nitrite ion. Lastly, ⁵⁷Fe-¹³P spin-spin coupling was measured in Fe(CO)₄(PPh₃) by ³¹P NMR.
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Vo, Nhat Tam. "Bioinspired semi-hemic iron(III) complex for chemical and photochemical oxygen atom transfer reactions." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS319.
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L’oxydation des hydrocarbures est une transformation chimique difficile aussi bien en biologie qu’en chimie. Les espèces active métal-oxo en de haut degré d’oxydation sont des intermédiaires capables d’effectuer ces transformations. Dans ce manuscrit, nous rapportons la synthèse et la caractérisation d'un complexe de fer (III) supporté par un ligand hémi-porphyrinique non innocent, construit avec un fragment dipyrrine et deux fonctions pyridines. Les complexes de fer (III) ont été préparés et caractérisés, en mettant l'accent sur leur comportement électrochimique et leur utilisation potentielle en tant que catalyseurs pouvant achiver des sources d'oxygène vertes telles que le dioxygène et l'eau en vue d’oxyder des hydrocarbures. Nous avons constaté que ces complexes peuvent catalyser l'oxydation d'une grande variété de substrats en utilisant un agent oxydant tel que l'iodosylbenzène. Curieusement, nos résultats rassemblés suggèrent un schéma de réactivité qui découle d’une espèce de fer de bas degré d’oxydation. Les analyses de résonance paramagnétique électronique et de Mössbauer confirment l'existence d'une espèce réactive de fer (III) haut spin. De plus, les données de spectrométrie de masse et de spectroscopie infrarouge appuyées par des calculs de DFT nous ont aidés à proposer la formulation chimique de cet intermédiaire généré chimiquement où le ligand a été oxydé de manière réversible. En outre, ces complexes ont été utilisés comme catalyseurs dans un système photocatalytique utilisant un accepteur d'électron réversible permettant d'éviter le recours néfaste à un donneur d'électrons sacrificiel. Notre étude fournit un nouveau paradigme pour effectuer des réactions photoinduites de transfert d'atome d'oxygène utilisant la lumière comme la source d'énergie et de l'O₂ comme la source d'atome d'oxygène en solution aqueuseHydrocarbon oxidation is a real challenging chemical transformation both in biology and chemistry. Highly oxidized metal-oxo species are the active intermediates to perform these transformations. In this manuscript we report the synthesis and characterization of an iron(III) complex supported by a non-innocent hemi-porphyrinic ligand, constructed with a dipyrrin fragment and two pyridine functions. The iron(III) complexes have been prepared and characterized, with a focus on their electrochemical behavior and their potential use as catalysts in the activation of green oxygen source such as dioxygen and water for hydrocarbon oxidation. We found that these complexes can catalyze the oxidation of a fair variety of substrates using oxidant agent such as iodosylbenzene. Intriguingly, our gathered results point to a reactivity pattern that stems from a low-oxidation state iron species. Electron Paramagnetic Resonance and Mössbauer analyses support a high spin iron(III) reactive species. Furthermore, data from mass spectrometry and Infra-red spectroscopy supported by DFT calculations helped us to propose the chemical formulation of this chemically generated intermediate where the ligand has been reversibly oxidized. Additionally, these complexes were used as catalysts in a photocatalytic system using a reversible electron acceptor to preclude the “evil necessity” of a sacrificial electron donor. Our study provides a new paradigm to perform photoinduced oxygen atom transfer reactions with solely light as energy input and O₂ as oxygen atom source in aqueous solution
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Sakurai, Hideo. "Theoretical study on the interaction between first row transition metal atom and oxygen molecule." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/150008.
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Nagai, Hisao, Mineo Hiramatsu, Masaru Hori, and Toshio Goto. "Measurement of oxygen atom density employing vacuum ultraviolet absorption spectroscopy with microdischarge hollow cathode lamp." American Institute of Physics, 2003. http://hdl.handle.net/2237/7098.
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McEwan, John Allison. "Synthesis, characterisation and oxygen atom transfer reactions of a series of cis-dioxomolybdenum(VI) complexes." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1374.
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Kelso, Hailey. "Dynamics of oxygen atom reactions with hydrocarbons in the gas phase and at the gas - liquid interface." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/327.
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Hodgkiss, Justin M. (Justin Mark) 1978. "Mechanistic studies of photo-induced proton-coupled electron transfer and oxygen atom transfer reactions in model systems." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38539.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, February 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references.
Time-resolved optical spectroscopy has been employed for mechanistic studies in model systems designed to undergo photo-induced proton-coupled electron transfer (PCET) and oxygen atom transfer (OAT) reactions, both of which are important to energy conversion chemistry (Chapter I). The effect of coupling proton transfer (PT) to electron transfer (ET) depends on their spatial configuration, thus model PCET systems must control both. Noncovalent amidinium-carboxylate PT interfaces are used assemble an electron D/A pairs (D = donor, A = acceptor), establishing uni-directional ET and PT coordinates. A highly conjugated porphyrin-amidinium derivative bears optical signatures that report on the structure of PT interfaces formed upon association with carboxylate acceptors (Chapter II). PT is supported within the interface and the mediating proton's position is sensitive to the peripheral electronic structure. Transient absorption (TA) spectroscopy is applied to a related porphyrin D---[H+]---A assembly, where ---[H+]--- = amidinecarboxylic acid (Chapter III). Specific probe wavelengths are targeted in order to amplify the optical signatures of PCET over those of competing quenching mechanisms.
(cont.) The observed PCET rates are strongly attenuated compared with comparable covalentlybridged analogues, indicating that the PT interface reduces electronic coupling. Temperature-isotope dependence of the PCET rates reveals an unusual inverse isotope effect at low temperature, which is interpreted in a model of vibrationally-assisted PCET (chapter IV). Hangman porphyrin dyads have been developed to study bi-directional PCET in relation to oxygen activation. ET and PT coordinates are orthogonalized at fixed distances about a FeIII-OH center (Chapters V and VI). TA spectroscopy and electronic structure calculations reveal that the structural reorganization attendant to metal-centered PCET imposes a severe kinetic cost and alternative quenching pathways prevail. Finally, TA spectroscopy has been used to elucidate the mechanism of photocatalytic OAT for bridged diiron [mu]-oxo bisporphyrins (Chapter VII). The [mu]-oxo bond is photo-cleaved to generate a terminal iron(IV) oxo, which undergoes OAT to nucleophilic substrates. OAT rates are maximized when the bridge actively splays the porphyrin subunits apart to present the oxo before reclamping can occur.
by Justin M. Hodgkiss.
Ph.D.
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Hjelm, Vivien. "Optimizing a Single Atom Catalyst for theOxygen Evolution Reaction using DensityFunctional Theory." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259703.
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The growing interest of renewable fuel and energy sources has steadily increased over time due to climate changes. Research is being made around the world to find solutions for the different problems; one possible solution is to produce hydrogen gas to help phase out the usage of fossil fuels. So far, the technology for the hydrogen gas production is expensive for various reasons, one of the challenges is to minimize the energy usage for the production. Hydrogen could be used in fuel cells which can be used to fuel an electric car. In a fuel cell, hydrogen and oxygen gas are mixed to produce electrical energy as the main product, but it also forms thermal energy and water. Hydrogen gas can be produced from the reversed reaction; by electrolysis of water. This reaction requires energy and one way to minimize the energy usage for this is by using acatalyst. The goal with this master thesis was to see how the reaction rate of the oxygen evolution reaction can be affected by different single atom catalyst systems. The main structure for this catalyst in this thesis is aporphyrin molecule where different transition metals were tried as the active site. Different modifications on the structure were also made by exchanging some of the structures atoms and by adding different ligands.The purpose of this is to see how these modifications change the activity of the catalyst. The catalysts were optimized and calculated in a computational chemistry program called Gaussian 16. The calculations was made by using the DFT functional PBE0 and the basis sets Def2svp and Def2tzvpp. The results show that different modifications do affect the activity of the catalyst. The biggest variations in activity are from placing ligands under the active site while exchanging hydrogens to other substituents on the outer radial position can fine tune the results. The best active sites for this system came by using iridium, rhodium and cobalt which are all elements in group 9 of the periodic table. The lowest overpotential of 0.513 V was given by an iridium based system with four hydrogens exchanged by fluorides.Runt om i världen finns ett ökat intresse för förnyelsebara energi och bränslekällor för att tackla klimat förändringarna. Stor del av forskningen som görs idag har i syfte att hitta nya lösningar för att minska klimatpåverkan i olika områden. Ett av forskningsområderna är hitta vägar till en miljövänligare vätgasproduktion där vätgasen skulle kunna användas i bränsleceller. Dessa celler kan sättas i elbilar och på så sätt fasa ut användingen av fossila bränslen. En av utmaningarna för vätgasproduktionen är att den idag är kostsam och kräver mycket energi. Forskare försöker hitta olika katalysatorer som kan minska energiåtgången som krävs vid elektrolys av vatten där syrgas och vätgas produceras. Målet med det här examensarbetet är att se hur en single atom catalyst kan påverka reaktionskinitiken för den syrgasbildande reaktionen vid elektrolys av vatten. Huvudstrukturen för katalysatorn som beräkningarna är gjorda på är en porphyrinmolekyl där olika övergångsmetaller kommer testas som det aktiva sätet i katalysatorn. Olika ligander kommer även tillsättas systemet samt utbyte av några väteatomer till olika substituenter i porfyrinstrukturen. Katalysatorn optimerades i det kvantkemiska beräkningsprogrammet Gaussian 16 med funktionalen PBE0 med basset Def2svp och Def2tzvpp. Resultaten visade att olika modifikationer på systemet hade en påverkan på katalysatorns aktivitet. Den största påverkan hade de olika liganderna som placerades under det aktiva sätet jämfört med de olika substituenterna. De bästa metallerna för katalysatorn var iridium, rhodium och kobolt vilket alla ligger i grupp nio i det periodiska systemet. Den lägsta överpotentialen på 0.513 V gavs av iridium systemet med fyra utbyta väten till fluor.
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Hanning-Lee, Mark Adrian. "A study of atom and radical kinetics." Thesis, University of Oxford, 1990. http://ora.ox.ac.uk/objects/uuid:89cabe5d-7cc8-43b3-8c2a-686563ff1b3f.
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This thesis describes the measurement of rate constants for gas phase reactions as a function of temperature (285 ≤ T/K ≤ 850) and pressure (48 ≤ P/Torr ≤ 700). One or both reactants was monitored directly in real time, using time–resolved resonance fluorescence (for atoms) and u.v. absorption (for radicals). Reactants were produced by exciplex laser flash photolysis. The technique was used to measure rate constants to high precision for the following reactions under the stated conditions: • H+O2+He->HO2+He and H+O2−→OH+O, for 800 ≤ T/K ≤ 850 and 100 ≤ P/Torr ≤ 259. A time–resolved study was performed at conditions close to criticality in the H2–O2 system. The competition between the two reactions affected the behaviour of the system after photolysis, and the rate constants were inferred from this behaviour. • H+C2H4+He<-->C2H5+He (T = 800 K, 97 ≤ P/Torr ≤ 600). The reactions were well into the fall–off region at all conditions studied. At 800 K, the system was studied under equilibrating conditions. The study provided values of the forward and reverse rate constants at high temperatures and enabled a test of a new theory of reversible unimolecular reactions. The controversial standard enthalpy of formation of ethyl, DH0f,298 (C2H5), was determined to be 120.2±0.8 kJ mol−1. Master Equation calculations showed that reversible and irreversible treatments of an equilibrating system should yield the same value for both thermal rate constants. • H+C3H5+He->C3H6+He (T = 291 K, 98 ≤ P/Torr ≤ 600) and O+C3H5 −→ products (286 ≤ T/K ≤ 500, 48 ≤ P/Torr ≤ 348). Both reactions were pressure–independent, and the latter was also independent of temperature with a value of (2.0±0.2) ×10−10 cm3 molecule−1 s−1. • H+C2H2+He<-->C2H3+He (298 ≤ T/K ≤ 845, 50 ≤ P/Torr ≤ 600). At 845 K, both reactions were in the fall–off region; rate constants were used to determine the standard enthalpy of formation of vinyl, ¢H0f,298 (C2H3), as 293±7 kJ mol−1. The value of this quantity has until recently been very controversial. • H+CH4 <--> CH3+H2. The standard enthalpy of formation of methyl, DH0 f,298 (CH3), was determined by re–analysing existing kinetic data at T = 825 K and 875 K. A value of 144.7±1.1 kJ mol−1 was determined. Preliminary models were examined to describe the loss of reactants from the observation region by diffusion and pump–out. Such models, including diffusion and drift, should prove useful in describing the loss of reactive species in many slow–flow systems, enabling more accurate rate constants to be determined.
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Ma, Xiaoli. "Syntheses, structures, electrochemical and oxygen atom transfer properties of molybdenum and tungsten complexes with sulfur and selenium containing ligands." Doctoral thesis, [S.l.] : [s.n.], 2007. http://webdoc.sub.gwdg.de/diss/2007/ma.
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Chen, Junbo. "Effect of Defects and Photoexcited Electrons on CO2 Reduction using Supported Single Atom Catalysts." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1266.
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Excessive CO2 emissions can negatively impact society and our planet. Reduction of CO2 is one potential avenue for its abatement. One of the most significant challenges to reducing CO2 is its extremely stable linear form. Experimentally, Cu/TiO2 has shown promise for CO2 photocatalytic reduction. Dispersed atomic catalysts can achieve high catalytic efficiency on a per atom basis. Active sites also typically having lower coordination number, and therefore may be more reactive. Using density functional theory and experimental techniques, we have investigated the role of surface oxygen vacancies (Ov) and photoexcited electrons on supported single atom catalysts and CO2 reduction. Cu atoms with Ov have shown to aid in the process of bent, anionic CO2 formation. In the first step involving CO2 dissociation (CO2* --> CO* + O*), a single Cu atom in Ov lowered the activation barrier to 0.10 - 0.19 eV, which could enable fast reduction of CO2 even at room temperature, in agreement with experimental findings. A photoexcited electron model was shown to readily promote Cu binding to the surface vacancy, and CO2 adsorption and direct dissociation. Finally, we briefly compare our results to calculations of supported single Pt atoms to determine how metals besides Cu may behave as photocatalysts for CO2 reduction, and we found a single Pt with Ov can promote CO2 dissociation. Our results show that tailoring TiO2 surfaces with defects in conjunction with atomic catalysts may lead to useful catalysts in the photoreduction of CO2.
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Yip, Ka-lai, and 葉嘉麗. "Ruthenium and osmium-nitrogen mulitple bonded complexes with chelatingnitrogen and/or oxygen atom donor ligands: synthesis, structures and reactivity studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B4501517X.
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Quichaud, Viviane. "Etude des processus elementaires : de synthese de la molecule no, en post-decharge en ecoulement, de collisions titane-gaz rares, titane-molecules, par perturbation laser resolue en temps." Paris 6, 1987. http://www.theses.fr/1987PA066135.
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I. Etude de la preparation des etats excites de no dans un dispositif de post-decharge en ecoulement a partir de n::(2) excite (prepare par transfert d'excitation a partir d'atomes ar metastables dans une decharge basse pression) et de o (obtenu par dissociation de o::(2) dans une decharge de he). Observation d'une emission intense des bandes gamma de no, qui implique un etat a courte duree de vie (b) de n::(2) et le premier etat metastable de o. Ii. Analyse des processus d'extinction et de transfert d'excitation a partir d'etats a courte duree de vie de ti (crees dans un dispositif a cathode creuse) lors de collisions avec des gaz rares (ar, ne, he) et des molecules (n::(2),h::(2)). Ces experiences permettent l'etude de cinetiques de reactions elementaires au sein d'un plasma basse pression ensemence de vapeurs metalliques, a l'aide du dispositif de post-decharge en ecoulement
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Penfold, Hazel. "Towards Oxygen and Temperature Sensitive Paints : The Use of Non-Aqueous Dispersion Polymerisation and Atom Transfer Radical Polymerisation to Control Photoluminescent Environments." Thesis, University of Kent, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499758.
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Azordegan, Amir R. (Amir Reza). "Charge State Dependence of L-Shell X-Ray Production Cross Sections of ₂₈Ni, ₂₉Cu, ₃₀Zn, ₃₁Ga, and ₃₂Ge by Energetic Oxygen Ions." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc277981/.
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Charge state dependence of L-shell x-ray production cross sections have been measured for 4-14 MeV ¹⁶O^q (q=3⁺-8⁺) ions incident on ultra-clean, ultra-thin copper, and for 12 MeV ¹⁶O^q (q=3⁺-8⁺) on nickel, zinc, gallium and germanium solid foils. L-shell x-ray production cross section were measured using target foils of thickness ≤0.6 μg/cm² evaporated onto 5 μg/cm² carbon backings. Oxygen ions at MeV energies and charge state q were produced using a 3MV 9SDH-2 National Electrostatics Corporation tandem Pelletron accelerator. Different charge states, with and without K-vacancies, were produced using a post acceleration nitrogen striping gas cell or ¹²C stripping foils. L-shell x-rays from ultra-thin ₂₈Ni, ₂₉Cu,₃₀Zn,₃₁Ga, and ₃₂Ge targets were measured using a Si(Li) x-ray detector with a FWHM resolution of 135 eV at 5.9 keV. The scattered projectiles were detected simultaneously by means of silicon surface barrier detectors at angle of 45° and 169° with respect to the beam direction. The electron capture (EC) as well as direct ionization (DI) contributions were determined from the projectile charge state dependence of the target x-ray production cross sections under single collision conditions. The present work was undertaken to expand the measurements of L-shell x-ray production cross sections upon selected elements with low L-shell binding energies by energetic ¹⁶O^q (q=3⁺,4⁺,5⁺,6⁺,7⁺,8⁺) incident ions. Collision systems chosen for this work have sufficiently large Z₁/Z₂ ratios (0.25-0.28) so that EC may noticeably contribute to the x-ray production enhancement. In this region, reliable experimental data are particularly scarce, thus, fundamental work in this area is still necessary. DI and EC cross section measurements were compared with the ECPSSR and the first Born theories over the range of 0.25
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Cecchini, Chiara. "Late Transition Metal-Oxo complexes: Synthesis, and Biorelevant Reactivity." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11249/.
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High-valent terminal metal-oxygen adducts are supposed to be potent oxidising intermediates in enzymatic catalyses. In contrast to those from groups 6-8, oxidants that contain late transition metals (Co, Ni, Cu) are poorly understood. Because of their high reactivity, only a few examples of these compounds have been observed. The aim of this project was to investigate the reactivity of high-valent Ni(III) complexes, containing a monodentate oxygen-donor ligands, in hydrogen atom abstraction (HAA) and oxygen atom transfer (OAT) reactions which are typical of biological high-valent metal-oxygen species. Particularly, the Ni(III) complexes were generated in situ, at low temperature, from the oxidation of the Ni(II) species.The nickel complexes studied during this work were supported by tridentate ligands, with a strong σ-donating ability and exceedingly resistant to several common degradation pathways. These complexes vary based on the monodentate group in the fourth coordination position site, which can be neutral or anionic. In particular, we prepared four different Ni(III) complexes [NiIII(pyN2Me2)(OCO2H)] (12), [NiIII(pyN2Me2)(ONO2)] (14), [NiIII(pyN2Me2)(OC(O)CH3)] (18) and [NiIII(pyN2Me2)(OC(O)H)] (25). They feature a bicarbonate (-OCO2H), nitrate (-ONO2), acetate (-OC(O)CH3) and formate (-OC(O)H) group, respectively.HAA and OAT reactions were performed by adding 2,6-di-tert-butylphenol (2,6-DTBP) at -40°C, and triphenylphosphine (PPh3) at -80°C, to the in situ generated Ni(III) complexes, respectively. These reactions were carried out by adding 7 to 500 equivalents of substrate, in order to ensure pseudo-first order conditions. Since, the reactivity of the Ni(III) complex featured by the bicarbonate group has been studied in a previous work, we only investigated that of the species bearing the nitrate, acetate and formate ligand. Finally we compared the value of the reaction rate of all the four species in the HAA and OAT reactions.
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Mach, Jindřich. "Vývoj a aplikace UHV zařízení pro depozice tenkých vrstev (Atomární a iontové svazkové systémy)." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233933.
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In the thesis the development of two equipment for preparation of ultrathin films under ultrahign vacuum conditions (UHV) is discussed. Here, additionally to a brief description of theoretical principles, more details on the design of these units are given. In the first part the design of a thermal source of oxygen or hydrogen atomic beams is discussed. Further, a design and construction of an ion–atomic beam source for ion-beam assisted deposition of thin films is detailed. The source combines the principles of an efusion cell and electron-impact ion beam source generating ions of (30 – 100) eV energy. The source has been successfully applied for the growth of GaN on the Si(111) 7x7 substrate under room temperature.
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Samimi, Peyman. "Combinatorial Assessment of the Influence of Composition and Exposure Time on the Oxidation Behavior and Concurrent Oxygen-induced Phase Transformations of Binary Ti-x Systems." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801898/.
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The relatively low oxidation resistance and subsequent surface embrittlement have often limited the use of titanium alloys in elevated temperature structural applications. Although extensive effort is spent to investigate the high temperature oxidation performance of titanium alloys, the studies are often constrained to complex technical titanium alloys and neither the mechanisms associated with evolution of the oxide scale nor the effect of oxygen ingress on the microstructure of the base metal are well-understood. In addition lack of systematic oxidation studies across a wider domain of the alloy composition has complicated the determination of composition-mechanism-property relationships. Clearly, it would be ideal to assess the influence of composition and exposure time on the oxidation resistance, independent of experimental variabilities regarding time, temperature and atmosphere as the potential source of error. Such studies might also provide a series of metrics (e.g., hardness, scale, etc) that could be interpreted together and related to the alloy composition. In this thesis a novel combinatorial approach was adopted whereby a series of compositionally graded specimens, (Ti-xMo, Ti-xCr, Ti-xAl and Ti-xW) were prepared using Laser Engineered Net Shaping (LENS™) technology and exposed to still-air at 650 °C. A suite of the state-of-the-art characterization techniques were employed to assess several aspects of the oxidation reaction as a function of local average composition including: the operating oxidation mechanisms; the structure and composition of the oxides; the oxide adherence and porosity; the thickness of the oxide layers; the depth of oxygen ingress; and microstructural evolution of the base material just below the surface but within the oxygen-enriched region. The results showed that for the Ti-Mo, Ti-Al and Ti-W systems a parabolic oxidation rate law is obeyed in the studied composition-time domain while Ti-Cr system experiences a rapid breakaway oxidation regime at low solute concentrations. The only titanium oxide phase present in the scale for all the binary systems was identified as rutile (TiO2) and formation of multiphase oxide scales TiO2+Al2O3 in Ti-Al system and TiO2+TiCr2 in Ti-Cr system was observed. A thermodynamic framework has been used to rationalize the oxygen-induced subsurface microstructural transformations including: homogeneous precipitation of nano-scaled β particles and discontinuous precipitation of +β phases in Ti-Mo and Ti-W system, evolution of TiCr2 intermetallic phase in Ti-Cr system and ordering phase transformation in Ti-Al system.
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Yu, Bin. "Development of silver nanocatalyst for propylene selective oxidation reaction." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:0f3f0556-bff1-4af1-bfe0-0e62b0425bff.
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Propylene is the second most important starting chemical in the petrochemical industry after ethylene. Unlike ethylene, propylene readily undergoes substitution reactions including polymerisation, oxidation, halogenation, hydrohalogenation, alkylation, hydration, oligomerization and hydroformylation, which lead to a wide variety of important downstream products. One of the principal uses of propylene is to produce key chemicals from selective oxidation. In 2016, the world annual production of propylene is about 94 million tonnes, and the global proportion used to produce selective oxidation product is over 18%. They constitute a key part of the chemical industry and contribute towards substantial economic benefits. The application of Ag based heterogeneous catalysts to selective propylene oxidation is a key factor in the synthesis of nearly all downstream chemicals, however billions of pounds are lost every year due to unplanned reactor shutdown, safety control and environment unfriendly emission control as a results of inefficiency catalytic selectivity and activity. Despite, both theoretical and experimental research works have been intensively involved, the fundamental reason leading to these effects are not yet well understood. The work presented in this thesis explores a range of novel modification techniques that alter the activity of Ag nanocatalysts for selective propylene oxidation, especially in propylene epoxidation. Particular focus is placed on developing surface modified Ag catalysts through morphology control, surface architecture engineering with another sublayer metal. Using a combination of modelling, novel and traditional materials characterisation methods, it is found that these modification result in some significant electronic and/or geometric alterations to the Ag nanoparticles surface. The Ag-Ag bond distance can be dramatically enlarged by exposing a high-index Ag surface or a core-shell structure with monolayer Ag shell. When interacting with molecular oxygen, the molecular oxygen adsorption and dissociation behaviour is sensitive to the geometric changes in Ag surface. This leads to an enhanced selectivity toward propylene epoxidation than combustion resulting from preventing a C-H bond cleavage. Finally, be creating atomically dispersed Ag on zeolite, a completely different interaction between molecular oxygen and single atom Ag were discovered comparing to on a extensive silver surface. This leads to the observation of an excitingly new propylene oxidation reaction producing ethanol and CO2 resulting from C=C bond cleavage. Overall, the research presented within this thesis demonstrated a number of methods for the intelligent design of novel heterogeneous Ag catalysts with remarkable activity and selectivity toward specific selective propylene oxidation. These modification methods are believed to be potentially applicable to a wide range of other catalytic reactions.
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Banert, Klaus, Sandra Bochmann, Andreas Ihle, Oliver Plefka, Florian Taubert, Tina Walther, Marcus Korb, Tobias Rüffer, and Heinrich Lang. "Synthesis with Perfect Atom Economy: Generation of Furan Derivatives by 1,3-Dipolar Cycloaddition of Acetylenedicarboxylates at Cyclooctynes." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152891.
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Cyclooctyne and cycloocten-5-yne undergo, at room temperature, a 1,3-dipolar cycloaddition with dialkyl acetylenedicarboxylates 1a,b to generate furan-derived short-lived intermediates 2, which can be trapped by two additional equivalents of 1a,b or alternatively by methanol, phenol, water or aldehydes to yield polycyclic products 3b–d, orthoesters 4a–c, ketones 5 or epoxides 6a,b, respectively. Treatment of bis(trimethylsilyl) acetylenedicarboxylate (1c) with cyclooctyne leads to the ketone 7 via retro-Brook rearrangement of the dipolar intermediate 2c. In all cases, the products are formed with perfect atom economy.
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He, Tianwei. "Computational discovery and design of nanocatalysts for high efficiency electrochemical reactions." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/203969/1/Tianwei_He_Thesis.pdf.
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This thesis reports a computational discovery and design of highly efficient electrocatalysts for various of electrochemical reactions. The method is based on the Density Functional Theory (DFT) by using Vienna ab initio simulation package (VASP). This project is a step forward in developing the low-cost, high activity, selectivity, stability and scalability for the electrochemical reactions, which could make a contribution to the global-scale green energy system for a clean and sustainable energy future.
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Astruc, Jean-Pierre. "Transfert d'électron entre atomes excités et molécules dans une expérience en jets croisés avec fluorescence résolue dans le temps." Paris 13, 1987. http://www.theses.fr/1987PA132020.
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Etude experimentale avec résolution temporelle à l'échelle de la nanoseconde des valeurs absolues des séctions efficaces pour les transferts partiels d'énergie électronique entre Na(4d) et He, Ar, N(2), O(2), N(2)o et SF(6). Développement quantitatif de deux modèles à intermediaire ionique : réseau de multicroisement et diffusion résonnants atome excité-molecule. Emploi de l'approximation d'impact avec correction d'effet de coeur pour la transfert de moment orbital na(4d -> 4f)
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Zawadzki, Andressa de. "Reações envolvendo NOx mediadas por Fe-heme em alimentos e sistemas biológicos." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/75/75133/tde-04042013-145133/.
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Os ânions inorgânicos nitrato (NO3-) e nitrito (NO2-) por muito tempo foram considerados produtos finais inertes do metabolismo do óxido nítrico (NO) e constituintes indesejáveis da dieta. Entretanto, é crescente o interesse das potenciais reações que podem se processar em meio fisiológico e, que envolvem especialmente o íon nitrito mediadas por complexos de metais de transição. Ferro-heme presente em proteínas como a mioglobina podem formar complexos porfirínicos com NO, gerando espécies que podem atuar principalmente como catalisadores em diversas vias biológicos importantes. Complexos com NOx coordenado a ferro-heme estão envolvidos tanto no processo da cura da carne (pigmentação da carne), como em processos redox, nos quais são capazes de oxidar substratos indiretamente pela produção de espécies reativas ou diretamente por reações de transferência de átomo de oxigênio (TAO). Os lipídeos, constituintes celulares fundamentais na composição de membranas e lipoproteínas, podem servir como substratos para essas reações e, sua oxidação pode ocasionar danos ao organismo. Tióis, importantes antioxidantes e constituintes de proteínas, também podem participar desse tipo de reações e, conseqüentemente gerar danos ao organismo. Considerando que o mecanismo e os parâmetros cinéticos e termodinâmicos destas reações ainda não foram completamente estabelecidos para explicar a vasta funcionalidade destes complexos, o presente projeto de pesquisa visa proporcionar um melhor conhecimento das reações redox envolvendo NOx e mediadas por porfirinas de ferro em alimentos e sistemas biológicos.For long time, the anions nitrate (NO3-) and nitrite (NO2-) were considered inert end products of nitric oxide (NO) metabolism and undesirable constituents of the diet. Currently, there is an increasing interest for potential reactions which may occur in physiological conditions involving specially the nitrite ion and mediated by transition metal complexes. Heme NOx iron complexes are involved in meat curing process (meat pigmentation) and are able to oxidize substrates indirectly generating reactive species or directly by oxygen atom transfer reactions (OAT). Lipids, fundamental cellular constituents of membranes and lipoproteins, and thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism Considering that the mechanism and kinetic and thermodinamic parameters of these reaction have not yet been fully elucidated to explain the varied functionality of these complexes, the present research project aim to bring a better understanding of redox reactions involving NOx mediated by iron porphyrins in foods and biological systems. Thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism. The present work aims to bring a better understanding of the mechanism, kinetic and thermodynamic parameters of the reaction involving nitrite mediated by iron-porphyrins in food and biological systems.
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Tipping, A. K. "Bonded interstitial carbon, boron and oxygen atoms in silicon." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378165.
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Ralph, D. G. "Studies of reactions of excited oxygen atoms of atmospheric importance." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355794.
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Ward, M. D. "Reactions of hydrogen and oxygen atoms on interstellar grain analogues." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1355953/.
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The region of space between stars, the interstellar medium, has been found to contain over 160 chemical species to date. These molecules are contained within regions of gas and dust, measuring several light years across, known as interstellar dust clouds. Many of these molecular species are formed in the gas phase, for example, via the reactions of molecules with ions. However, some critical gas phase processes are often slow due to the low temperatures and pressures found in the interstellar medium and cannot readily account for the abundances of some species. Consequently reactions on the surfaces of interstellar dust grains are often invoked to explain the abundances some molecules. These dust grains represent approximately 1 % of the mass of a typical interstellar dust cloud and typically consist of carbon, silicates or metal oxides. The temperature of these interstellar dust grains is low enough (~ 10 K) that over time icy mantles consisting of simple atomic and molecular species can build up on their surfaces. Whether and how these simple species can be processed to form more complex molecules such as alcohols, simple sugars and potentially amino acids is a key astrochemical problem. One way in which astrophysical ices can be processed to form more complex species is via the reactions of species within the ice with simple free radicals such as H, C, N and O. This thesis therefore presents experimental studies of the reactions of atomic species with some astrophysically relevant molecular ices under interstellar conditions. Since hydrogen and oxygen are the first and third most abundant elements in the interstellar medium respectively, these experiments have specifically focussed upon the reactions of hydrogen and oxygen atoms. In addition to the characterization of surface reactions between key astrochemical species, kinetic parameters for use in astrochemical models are derived from these experiments.
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Bacia, Maria. "Comportement du carbone aux joints de grains du molybdène." Grenoble INPG, 1994. http://www.theses.fr/1994INPG4210.
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La mise en evidence et l'interpretation du role benefique du carbone et du role nefaste de l'oxygene sur la cohesion intergranulaire du molybdene en l'absence de precipitation visible au meb constituaient le but de cette etude. Une methode efficace de purification du molybdene a ete mise au point. Les mesures de la concentration intergranulaire de carbone en fonction de la temperature de carburation et de la teneur volumique ont ete effectuees a l'aide d'un spectrometre auger. Un modele d'enrichissement des joints de grains au cours du refroidissement a ete propose. Les structures des joints purs et contenant des atomes de solute ont ete determinees par des simulations statiques a l'aide de potentiels a n corps calcules en se fondant sur la methode de l'atome immerge (eam). La comparaison des segregations intergranulaires d'oxygene et de carbone (sites de segregation, sequence d'occupation des sites, enthalpies de melange) a ete effectuee pour le cas du joint symetrique de flexion 37 autour de l'axe 100. Les structures atomiques du joint 37 a l'etat pur et a l'etat carbure ont ete observees au microscope electronique a haute resolution. Apres la carburation ne conduisant pas a la formation de precipites mo#2c visibles au meb, la presence d'une phase bidimensionnelle moc#x (x 0,4) formant un film continu au joint a ete mise en evidence. Elle peut etre rendue responsable du renforcement du joint. Sa faible largeur ( 10 a) et son accommodation parfaite aux reseaux cristallographiques des deux grains rendent son observation impossible par des methodes classiques (meb, met), ce qui explique que son existence etait jusqu'a maintenant ignoree. Il n'est pas exclu qu'il s'agisse de la premiere observation d'un etat intermediaire entre la segregation et un compose tridimensionnel discontinu
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Taylor, Craig A. (Craig Allan). "Kinetic Study of the Reactions of Oxygen Atoms with Nitric Oxide and Silane." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc935556/.
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The rate constant for the reactions of oxygen atoms with nitric oxide and silane were determined using a discharge flow apparatus. A microwave discharge through O2N2 and Ar was used to produce oxygen atoms. The rate constant for the reaction O + NO + Ar was determined to be (7.0+0.4) x 10^32 cm^6 s^-1 and is in good agreement with previous measurements. Modeling of the O +SiH₄ reaction was performed to determine the correction to the rate constant due to secondary reactions. The rate constant for the reaction O + SiH₄ was determined to be (3.3 +/- 0.3) x 10⁻¹³ cm³ s⁻¹ and is in good agreement with previous measurements. Previous literature, thermochemistry, and spin conservation were used to determine a probable mechanism for the O + SiH₄ reaction.
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Billington, Andrew P. "High and low temperature studies of nitrogen atoms and singlet molecular oxygen." Thesis, Keele University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716857.
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Ferger, Neil Michael. "Some gas phase reactions of oxygen and halogen atoms under single collision conditions." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257953.
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Sweeney, Gillian Michelle. "The state-to-state dynamics of the reactions of oxygen atoms with hydrocarbons." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/13060.
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Pulsed laser photolysis-probe techniques have been used to investigate the nascent internal state distributions of OH(X2Π) produced in reactions of the type: O(3P) + RH → OH(X2Π) + R RH is a saturated hydrocarbon, which is chosen to contain representative primary, secondary or tertiary C-H bonds. Reactive superthermal O(3P) atoms are generated by photolysis of NO2 at either 337, 308 or 248 nm. By changing the wavelength of photolysis of NO2, the collision energy of the reaction can be effectively altered. The OH product is detected in a state-specific manner by laser-induced fluorescence (LIF) on the A2Σ+ ←X2Π transition. The delay between the photolysis and probe pulses is kept short enough to allow the partitioning of the available energy amongst the possible vibrational, rotational and fine-structure states to be determined from collisionally unmodified OH LIF spectra. The OH product, from the reaction between O(3P) and RH, is found to be rotationally cold. It is also apparent that the rotational distribution is largely independent of the nature of the R group. These findings have been interpreted as evidence that the reaction exhibits a strong preference for collinear approach of the O(3P) atom to the C-H bond from which the H atom is abstracted. In contrast, the degree of vibrational excitation depends strongly on both the type of C-H bond and the collision energy. These observations are consistent with the shift towards an "earlier" reaction barrier with increasing reaction exothermicity, which occurs as the H atom being abstracted is changed from primary to secondary to tertiary. The OH spin-orbit state distribution is non-statistical. The correlations between the spin-orbit states of the O(3P) reactant and OH product have been clarified. A purely adiabatic correlation does not correctly predict the observed product spin-orbit state distribution but a model, which includes non-adiabatic coupling of surfaces with the same projection of total electronic angular momentum, gives much improved agreement. This model has interesting but yet unstudied corollaries for the differential reactivity of the O(3Pj) states.
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Rander, Torbjörn. "Photoelectron Spectroscopy on Atoms, Molecules and Clusters : The Geometric and Electronic Structure Studied by Synchrotron Radiation and Lasers." Doctoral thesis, Uppsala University, Department of Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8343.
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Atoms, molecules and clusters all constitute building blocks of macroscopic matter. Therefore, understanding the electronic and geometrical properties of such systems is the key to understanding the properties of solid state objects.
In this thesis, some atomic, molecular and cluster systems (clusters of O2, CH3Br, Ar/O2, Ar/Xe and Ar/Kr; dimers of Na; Na and K atoms) have been investigated using synchrotron radiation, and in the two last instances, laser light. We have performed x-ray photoelectron spectroscopy (XPS) on all of these systems. We have also applied ultraviolet photoelectron spectroscopy (UPS), resonant Auger spectroscopy (RAS) and near-edge x-ray absorption spectroscopy (NEXAFS) to study many of the systems. Calculations using ab initio methods, namely density functional theory (DFT) and Møller-Plesset perturbation theory (MP), were employed for electronic structure calculations. The geometrical structure was studied using a combination of ab initio and molecular dynamics (MD) methods.
Results on the dissociation behavior of CH3Br and O2 molecules in clusters are presented. The dissociation of the Na2 molecule has been characterized and the molecular field splitting of the Na 2p level in the dimer has been measured. The molecular field splitting of the CH3Br 3d level has been measured and the structure of CH3Br clusters has been determined to be similar to the structure of the bulk solid. The diffusion behavior of O2, Kr and Xe on large Ar clusters, as a function of doping rate, has been investigated. The shake-down process has been observed from excited states of Na and K. Laser excited Na atoms have been shown to be magnetically aligned. The shake-down process was used to characterize the origin of various final states that can be observed in the spectrum of ground-state K.
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Matengaifa, R. "Adsorption of oxygen molecules on platinum surfaces modified with subsurface atoms of vanadium : a DFT study." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13302.
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Includes bibliographical references.The aim of this work was to investigate changes in the electronic structure of platinum as a result of alloying with vanadium, and the effects of these changes on O2 adsorption. This is important for the further development of hydrogen fuel cells, because the oxygen reduction reaction (ORR) presently requires O2 adsorption to occur on pure platinum, which is a prohibitively expensive material. A computational study has therefore been undertaken on alloying platinum (which reduces cost) with vanadium (for which there is plentiful experimental data) and the consequences for O2 adsorption. The first moment of the d-band of platinum alloy DOS was used to represent the d-band centre. The d-band centre of Pt-PDOS became lower as a result of hybridisation between platinum and vanadium. The d-band centre of a pure platinum surface with respect to the Fermi level is -1.99eV, but it is shifted to -3.23eV when vanadium atoms are added to the subsurface layer. The adsorption energies of O2 are sensitive to a combination of calculation parameters used. In this work, the calculations were executed using the CASTEP code. This is a plane wave pseudo potential code. The most stabilised geometry of an adsorbed molecule on pure Pt (111) was at the fcc site and had an adsorption energy of -1,91eV. The adsorption energy at the bridge site of Pt (111) is -1.81eV. When subsurface vanadium atoms were introduced, the equilibrium surface-molecule bond lengths increased. The adsorption energy at the fcc site shifted to -1.37eV, -1.43 for the bridge site and -1.45eV for the hcp site. It was concluded that the presence of vanadium atoms in the surface region destabilises an adsorbed oxygen molecule but a more detailed study is needed to show the effect of the solute atoms on the thermodynamics and kinetics of the whole oxygen reduction reaction chain.
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Deutsch, Kerry Ann. "Behavior of the atomic oxygen 5577 Ångström emission intensity at mid-latitudes : a climatological view /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6803.
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Herrera-Morales, Paulo Emilio. "Quantum chemistry calculations of the reactions of gaseous oxygen atoms with clean and adsorbate-terminated Si(100)-(2x1)." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0008393.
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Raffanel, Sylvie. "Proprietes thermodynamiques et de transport de melanges gazeux : azote/oxygene/argon dans les domaines 1p200 atm, 1000t30000 k." Toulouse 3, 1987. http://www.theses.fr/1987TOU30165.
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Calcul des compositions, des potentiels thermodynamiques et des coefficients de transport de melanges azote-oxygene supposes en equilibre thermodynamique complet. L'air est traite comme un cas particulier pour lequel la presence de 0,97 % d'argon est prise en compte. Le calcul est effectue dans des gammes etendues de pression (1 a 200 atm) et de temperature (1000 a 30000 k) pour constituer une banque de donnees pour un code numerique de calcul d'ecoulement turbulent du plasma. Etude de l'influence des particules chargees sur les compositions et potentiels thermodynamiques et sur les interactions entre particules
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Bowman, Sherrie S. "Atomic and Molecular Oxygen Kinetics Involved in Low Temperature Repetitively Pulsed Nonequilibrium Plasmas." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1370365358.
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Suraud, Marie-Gabrielle. "Etude par spectrométrie X (10 [angström] [inférieur ou égal à] [lamda] [inférieur ou égal à] 100 [angström]) de l'échange de charge lors de collision à basse énergie, entre un ion multichargé et une cible neutre." Grenoble 1, 1988. http://www.theses.fr/1988GRE10038.
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Mesures des valeurs absolues des sections efficaces d'emission de rayons x, dont on deduit les valeurs absolues des sections efficaces de capture, pour les systemes c**(6+)-he,h::(2), n**(7+)-he,h::(2), o**(8+)-he,h::(c). Pour les projectiles a 2 electrons dans l'etat metastable 1s2s **(3)s, l'echange de charge peut s'accompagner de l'excitation de l'electron "2s" de l'ion incident vers des etats 1s2pnl **(3)p avec une probabilite variant suivant le systeme de collision, l'echange de charge simple restant preponderant dans tous les cas
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Mane, Mane. "Adsorption des hydrocarbures insaturés (éthylène et propylène) sur la surface Pt(111) nue et en présence de coadsorbats (alcalins, oxygène, alcalins oxydés) : étude par AES, TDS, UPS, XPS et NEXAFS." Nancy 1, 1993. http://www.theses.fr/1993NAN10062.
Full textAbstract:
Nous avons étudié l'influence de la température d'adsorption et des coadsorbats (atomes alcalins, oxygène atomique, alcalins oxydés) sur les modes d'adsorption des hydrocarbures éthyléniques (éthylène, propylène) sur Pt(111). Ces différents modes d'adsorption ont été identifiés sous ultravide par des méthodes spectroscopiques complémentaires (UPS, XPS, NEXAFS, TDS). L'étalonnage des quantités d'alcalins déposes a été obtenu par la spectrométrie des électrons Auger et les mesures de potentiel de sortie en UPS. Les oxydes de potassium ont été préparés et identifiés en utilisant la technique UPS et en comparant le nombre et les positions des orbitales moléculaires dans le régime de la sous-monocouche d'alcalin aux résultats en couches épaisses de la littérature et aux prédictions théoriques. Les résultats expérimentaux obtenus sont interprétés sur la base de modèles théoriques existants. Des conséquences probables de l'utilisation des oxydes d'alcalins comme promoteurs des catalyseurs utilises dans la synthèse catalytique des hydrocarbures ont été soulignées
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Morin, Julien. "Etudes expérimentales des réactions des radicaux OH et des atomes d’oxygène d’intérêt pour l’atmosphère et la combustion." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2034/document.
Full textAbstract:
L’objectif de ce travail consiste à étudier, d’une part, les réactions des nitrates d’alkyles avec OH qui ont un intérêt atmosphérique, et d’autre part, les réactions des radicaux OH avec les alcanes et des atomes d’oxygène avec les oléfines qui ont un intérêt pour la combustion. Toutes les réactions ont été étudiées dans des réacteurs à écoulement à basse pression, y compris le réacteur à écoulement à haute température mis en place dans le cadre de la thèse, couplés à un spectromètre de masse quadripolaire à ionisation par impact électronique. Pour les réactions OH + nitrate d’alkyle, la dépendance en température de la constante de vitesse a été mesurée pour dix nitrates d'alkyles, dont pour huit nitrates pour la première fois, sur une large plage de température. Pour six nitrates, les produits de la voie réactionnelle menant au recyclage direct de NO₂, arrachement d’atome H de carbone α, ont été observés et leur rendements mesurés. La grande quantité de données obtenues dans ce travail a été utilisée pour une mise à jour de la relation structure-activité (SAR) pour les réactions d'alkyles nitrates avec OH et a permis d'améliorer les modèles atmosphériques actuels. Les études de réactions de radicaux OH avec les trois alcanes et de l'atome O avec l’éthylène et le propène ont permis de déterminer les constantes de vitesse respectives sur une large gamme de température allant de 220 à 900 K. De plus, la distribution des produits de réactions multivoies O + oléfine en fonction de la température a été déterminée pour la première fois. Ces résultats permettront d’améliorer les modèles de combustion actuellement utilisésThe objective of this work was to study the reactions of alkyl nitrates with OH radicals relevant to atmosphere and reactions of OH radical with alkanes and oxygen atoms with olefins of interest for combustion chemistry. All reactions were studied in low pressure flow reactors (including high temperature flow reactor developed during the thesis) coupled to a quadrupole mass spectrometer with electron impact ionization. For OH reaction with nitrates, the temperature dependence of the rate constant was measured in an extended temperature range for ten alkyl nitrates, for eight of them for the first time. For six nitrates, the products of reaction pathway leading to direct recycling of NO₂ (H atom abstraction from α carbon) were observed and their yields were measured. The large amount of data obtained in this work has been used for an update of the structure-activity relation (SAR) for the reactions of alkyl nitrates with OH and will improve existing atmospheric models. For the reactions of OH radicals with three alkanes and O atoms with ethene and propene the rate constants were measured over a wide temperature range, 220-900 K. Moreover, the distribution of the products of the multichannel reactions O + olefin was determined as a function of temperature for the first time. These results are expected to improve current combustion models