Dissertations / Theses on the topic 'Charge vs energy transfer'
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Gillespie, Peter N. O. "Theory of charge transfer in solar energy materials." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22771/.
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Canola, Sofia <1989>. "Modeling charge and energy transfer in organic molecular materials." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/8131/1/Canola_Sofia_tesi.pdf.
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The understanding of nanoscale physics, chemistry and biology still poses unanswered questions such as how the optical and electrical properties of materials evolve from those of individual molecules, and organic semiconductors fall in this class of materials. The main processes occurring in such systems are both charge and energy transfer, responsible for the practical operation of electronic devices. Therefore, an understanding at a fundamental level of the electronic properties of the involved molecules can help the optimization of each process, for a better global performance of the material.
My three years PhD activity was developed along two major lines of research: charge and energy transport, both based on the computational investigation of intramolecular properties and intermolecular interactions. Strictly related to energy transport are the optical properties of condensed phase materials and how they evolve from those of isolated molecular components. The charge transport properties were investigated for several organic molecular crystals showing semiconducting behavior, whose experimental crystal structure and charge mobilities are available. As the same interactions that drive the transport of charge play also a role in determining the optical properties and the energy transport in molecular aggregates, in my research activity I investigated such processes as well. In this regard, I took into account a dimer of perylene-bisimide, with the aim of elucidating the role of charge transfer states and their effect on optoelectronic properties. Additionally, to assess the propagation of excited states in a molecular material a kinetic constant is required, similarly to charge transport, but the expression in this case includes the overlap between the absorption spectrum of the acceptor and the emission spectrum of the donor. To this end I also developed a code devoted to the simulation of linear absorption and emission spectra of an isolated molecule, starting from computed quantum mechanical properties.
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Huang, Zhongjie. "Investigation of Interfacial Charge Transfer Processes in Energy Conversion Devices." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448663899.
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Byrne, Ciaran Martin. "Energy loss and charge transfer effects of low energy protons in thin organic films." Thesis, Queen Mary, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393732.
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Bdžoch, Juraj [Verfasser]. "Ultrafast energy and charge transfer in D2O/Ru(0001) / Juraj Bdžoch." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1025169107/34.
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Mutz, Niklas. "Energy and Charge Transfer at Hybrid Interfaces Probed by Optical Spectroscopy." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22797.
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Hybride anorganisch/organischen Systeme können die individuellen Vorteile, etwa eine hohe elektronische Mobilität in anorganischen und starke Licht-Materie-Wechselwirkung in organischen Halbleitern, kombinieren. Ein sinnvoller Nutzen dieser Heterostrukturen benötigt ein umfassendes Verständnis der Grenzfläche. Zwei Grenzflächenprozesse werden in dieser Arbeit behandelt.
Förster-Resonanzenergietransfer (FRET) wird zwischen einem InGaN/GaN Quantengraben und dem Polymer Cn-ether PPV untersucht. Trotz des hohen internen elektrischen Feldes im Quantengraben, ist effizienter Energietransfer möglich, solange andere nicht-strahlende Zerfallsprozesse unterdrückt werden. Dies wird mittels temperaturabhängiger PL und PLE Spektroskopie gezeigt. PLE demonstriert eine eindeutige Erhöhung der Emission des Akzeptors. Bei höheren Temperaturen dominieren nicht-strahlende Zerfallskanäle.
Ladungstransfer wird zwischen MoS2 und dem Molekül H2Pc untersucht. Die Kombination mit organischen Molekülen kann die Funktionalität von MoS2 erweitern. Photoelektronenspektroskopie (PES) zeigt einen Typ-II Heteroübergang an der MoS2/H2Pc Grenzfläche. Angeregte Elektronen gehen von den H2Pc Molekülen in die MoS2 Monolage über, wie mittels einer Verkürzung der PL Lebenszeit von H2Pc gezeigt wird. Photostrommessungen demonstrieren zudem, dass die transferierten Elektronen zu einer erhöhten Photoleitfähigkeit beitragen.
Zusätzlich werden auch einzelne 2D Übergangsmetall Dichalkogenide (TMDCs) untersucht. Um TMDCs von hoher Qualität herzustellen, wurde intern eine Wachstumsmethode entwickelt. Mittels PL Spektroskopie werden die so hergestellten Schichten charakterisiert. Die Vielseitigkeit der Methode wird anhand des Wachstums von Mischkristallen und Heterostrukturen gezeigt. Der Einfluss der dielektrischen Funktion des Substrates wird erforscht. Durch die Kombination von PES und Reflexionsmessungen kann eine gleichzeitige Abnahme sowohl der Bandlücke als auch der Exzitonen Bindungsenergie gezeigt werden.Hybrid inorganic/organic systems can combine the advantages of both materials such as high carrier mobilities in inorganic semiconductors and large light-matter interaction in organic ones. In order to benefit from these heterostructures, a thorough understanding of the interface is needed. Two processes occurring at the interface are looked at in this thesis. Förster resonance energy transfer (FRET) is studied between a single InGaN/GaN quantum well and the polymer Cn-ether PPV. Despite the large internal electric fields in the quantum well, efficient FRET is possible as long as other non-radiative decay channels are suppressed. This is shown by temperature dependent PL and PLE spectroscopy. PLE spectra clearly demonstrate an enhanced light emission from the acceptor. At elevated temperatures, non-radiative decay pathways become dominant. Excited-state charge transfer is studied on MoS2 in combination with the molecule H2Pc. The combination with molecules can extend the functionality of MoS2. Photoelectron spectroscopy (PES) reveals a type II energy level alignment at the MoS2/H2Pc interface. Excited electrons are transferred from H2Pc to MoS2, deduced from a shortening of the H2Pc PL decay time. Photocurrent spectra further show that the transferred electrons contribute to an enhanced photoconductivity. Additionally, bare 2D transition-metal dichalcogenides (TMDCs) are studied. In order to fabricate high-quality TMDC monolayers, a growth method was developed in-house. The grown monolayers are characterised by optical spectroscopy. The versatility of the method is demonstrated by the growth of alloys and heterostructures. The influence of the substrate dielectric function is investigated by comparing band-gaps measured by PES with the exciton transition energies obtained by reflectance measurements. An almost equal reduction in both energies with the substrate dielectric constant is seen.
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Weber, Fabian [Verfasser]. "Structure-Property Relationships for Energy- and Charge-Transfer Processes / Fabian Weber." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1204429324/34.
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Guo, Fangyeong. "High energy excited states in conjugated polymers and charge-transfer solids." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186708.
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Within the framework of the extended-Hubbard model, theoretical studies on the intensities of two-photon absorption (TPA) of the even-parity states in conjugated polymers show relatively large contributions from the exciton mA(g) state. The TPA intensities due to the 2A(g) as well as other sub-gap even-parity states are demonstrated to be extremely weak in the long chain limit, independent of their locations relative to the optically allowed exciton. We show our results have important implications for the interpretation of third harmonic generation (THG) and TPA spectra of several conjugated polymers. We have also probed the higher energy states that are reached by two-electron excitations from the ground state. Evidence for the biexciton, a bound state of two excitons that occurs below the two-electron continuum, is found. The lowest biexciton state is of even parity, call be reached by optical excitation from the 1Bᵤ exciton, and also by two-photon excitation from the ground state. Interpretation of a recent picosecond photoinduced absorption experiment on polyparavinylene (PPV) and TPA on polysilanes (PS) in terms of the biexciton will be given. Multiexciton states have experimentally found in a linear chain mixed-stack charge-transfer solid. Our theoretical studies based on the extended-Hubbard Hamiltonian demonstrate that such stable multiexciton states in this class of organic systems are due to the Coulomb interactions.
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Menting, Raoul. "Light-induced energy and charge transfer processes in artificial photosynthetic systems." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16656.
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Der Gegenstand der vorliegenden Arbeit ist die Untersuchung von photoinduzierten Energietransferprozessen (EET) und Elektronentransferprozessen (ET) in Modellsystemen, die als potentiell geeignet für eine Nutzung in der artifiziellen Photosynthese angesehen werden. Den beiden wesentlichen Zugängen zur Architektur artifizieller Photosynthese-Systeme entsprechend wurden vergleichend kovalente und sich selbst organisierende Systeme untersucht. In beiden Zugängen wurden ähnliche chemische Komponenten als optisch aktive Moleküle eingesetzt, insbesondere Phthalocyanine mit einem Silizium-Zentralatom (SiPc). Durch eine Kombination von stationären und zeitaufgelösten optisch-spektroskopischen Methoden konnten die lichtinduzierten ET- und EET-Prozesse identifiziert und quantifiziert werden. Im ersten Teil der Arbeit wurden mehrere kovalent gebundene Triaden und eine Pentade untersucht. In allen Systemen finden sehr effiziente ET und EET Prozesse statt. Es wurde gezeigt, dass das Lösungsmittel großen Einfluss auf die photophysikalischen Eigenschaften der Systeme ausübt. Die Lebensdauer des ladungsseparierten Zustandes variiert von 1,7 ns in Toluol bis 30 ps in DMF. Im zweiten Teil der Arbeit wurde erstmals gezeigt, dass sich in wässriger Lösung ein supramolekularer Komplex, bestehend aus einem Beta-Cyklodextrin (CD), einem konjugierten Subphthylocyanin (SubPc), einem Porphyrin (Por) und einem SiPc bilden kann. Letzteres wurde über unterschiedliche Ketten an zwei CDs kovalent gebunden. Die Selbstorganisation wird über hydrophobe Wechselwirkungen vermittelt und die Bildung der Komplexe ist sehr effizient. Nach selektiver Anregung von SubPc finden sequenzielle ET- und EET-Prozesse von SubPc zu SiPc statt. Das Por spielt die Rolle einer energetischen und elektronischen Brücke und ermöglicht die ET und EET-Prozesse von SubPc zu SiPc. Die Ladungsrekombination in den Grundzustand geschieht innerhalb von 1,7 ns.The main objective of the present thesis was to conduct investigations of photo-induced electron transfer (ET) and excitation energy transfer (EET) processes in model compounds that are considered potentially appropriate for use in artificial photosynthesis. Two approaches have been used to construct the artificial photosynthetic systems, namely covalent and supramolecular approach. In both systems similar optically active molecules have been employed, particularly silicon-based phthalocyanines (SiPc). A comparative study between the covalently-linked and self-assembled systems had been conducted. For these purposes, thorough spectroscopic measurements in the UV/Vis range had been performed on these conjugates. A combination of steady-state and time-resolved experiments allowed an identification and quantification of the photo-induced ET and EET processes. In the first part of the work several covalently bound triads and a pentad bearing a central SiPc unit were studied. In all systems highly efficient ET and EET processes take place. It was found that the solvent exerts great influence on the photophysical properties of the systems. The lifetime of the charge-separated state varied from 1.7 ns (toluene) down to 30 ps (DMF). In the second part of the thesis, for the first time the formation of ternary supramolecular complexes consisting of a beta-cyclodextrin (CD), a conjugated subphthalocyanine (SubPc), a porphyrin (Por) and a series of SiPcs substituted axially with two CDs via different spacers was shown. These components are held in water by host-guest interactions and the formation of these host-guest complexes was found to be very efficient. Upon excitation of the SubPc-part of the complex sequential ET and EET processes from SubPc to SiPc take place. The Por dye acts as a transfer bridge enabling these processes. The probability of ET is controlled by the linker between CD and SiPc. Charge recombination to the ground state occurs within 1.7 ns.
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Nam, Yoon Sung. "Nanostructures templated on biological scaffolds for light harvesting, energy transfer, charge transfer, and redox reactions." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60784.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 149-160).
Solar energy provides an unparalleled promise to generate enormous amounts of clean energy. As the solar industry grows rapidly with a focus on power generation, new, but equally important challenges are emerging, including how to store and transfer the generated solar energy. Light-driven water splitting to generate hydrogen has received increasing attention as a means of storing solar energy. However, in order to evolve hydrogen with no energy input beyond sunlight, it is important to develop a stable and efficient catalytic system for water oxidation, which is the more challenging half-reaction of photocatalytic water splitting. Over several billion years, cyanobacteria and plants have evolved highly organized photosynthetic systems for the efficient oxidation of water. Water oxidation by mimicking photosynthesis has been pursued since the early 1970s; however, the approaches have been primarily limited to the extraction and reconstitution of the existing natural pigments, photosystems, and photosynthetic organisms, which suffer from instability. Metal oxide catalysts, often coupled with pigments, are similar to the reaction centers in natural photosystems and have been shown to photochemically oxidize water. Unfortunately, various approaches involving molecular design of ligands, surface modification, and immobilization still show low catalytic efficiencies unless they are used under relatively harsh conditions (i.e., in highly alkaline or acidic solutions under ultraviolet radiation). The current work aims to demonstrate the impact of nano-scale assembly of organic and inorganic molecules on energy and charge transfers, and related redox reactions. Genetically modified M13 viruses are explored as biological scaffolds to guide the formation of metal oxide catalysts-pigments hybrid nanostructures that enable efficient transports of both energy and electrons for photochemical water oxidation. This dissertation deals with three aspects of the virus-templated nanostructures - photonic, photochemical, and electrochemical properties. First, organic pigments are arranged into a one-dimensional light-harvesting antenna on the M13 virus. Chemical grafting of zinc porphyrins to the M13 virus induces spectroscopic changes, including fluorescence quenching, the extensive band broadening and small red-shift of their absorption spectrum, and the shortened lifetime of the excited states. Based on these optical signatures a hypothetical model is suggested to explain the energy transfer occurring in the supramolecular porphyrin structures templated on the virus. Second, through further genetic engineering of M13 viruses, iridium oxide hydrosol clusters (catalysts) are co-assembled with zinc porphyrins. When illuminated with visible light, this system evolves about 100 oxygen molecules per surface iridium molecule per minute in a prolonged manner. In addition, porous polymer microgels are used as an immobilization matrix to improve the structural durability of the assembled nanostructures and enable the recycling of the materials. The system also maintains a substantial level of its catalytic performance after repeated uses, producing about 1,200 oxygen molecules per molecule of catalyst during 4 cycles. These results suggest that the multiscale assembly of functional components, which can improve energy transfer and structural stability, should be a promising route for significant improvement of photocatalytic water oxidation. Lastly, electrochemical properties of the virus-templated iridium oxide nanowires are examined as an electrochromic film on a transparent conductive electrode. The prepared nanowire film has a highly open porous morphology that facilitates ion transport, and the redox responses of the nanowires are limited by the electron mobility of the nanowire film. These results demonstrate that a bio-templating approach provides a versatile platform for designing complex nanostructures that can facilitate the transport of electrochemical molecules in a broad range of photoelectrochemical devices.
by Yoon Sung Nam.
Ph.D.
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Hu, He. "INFRARED STUDY OF CHARGE TRANSFER BETWEEN ORGANIC MOLECULES AND SEMICONDUCTORS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522444435463025.
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Ray, Matthew Preston. "The dynamics of energy and charge transfer in low and hyperthermal energy ion-solid interactions." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1252424536/.
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Grisenti, David L. "The effect of bimolecular quenching reactions on energy transfer processes in oligometallic metal to ligand charge transfer excited states." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1495960661&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Herman, Leslie. "Ru(II) under illumination: a study of charge and energy transfer elementary processes." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210399.
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Une compréhension sans cesse plus pointue des processus élémentaires de transferts de charges et d’énergie, qui sont à la base même de nombreux processus biologiques, permet non seulement l’élaboration mais aussi l’amélioration de la mise au point de molécules photoactives utiles dans différentes applications. C'est le cas (i) de systèmes moléculaires et supramoléculaires destinés à mimer efficacement la photosynthèse, ou encore (ii) de molécules photoactives capables d’interagir avec des macromolécules biologiques et d’induire une transformation de ces biomolécules. C’est dans ce cadre général que s’inscrit l’élaboration de nouveaux complexes polyazaaromatiques de Ru(II) capables d’interagir avec la double hélice d’ADN et de photoréagir avec sa base la plus réductrice, la guanine, par transfert d’électron photoinduit. C’est sur la base de ces processus que des nouveaux agents antitumoraux photoactivables ont pu être développés. L’utilisation de complexes de Ru(II) dans le design d’entités supramoléculaires polymétalliques destinées à jouer le rôle de collecteurs de lumière et permettant ainsi de mimer les systèmes d’antennes naturels s’intègre également dans cette démarche. L’ensemble de notre travail s’est concentré sur ces deux domaines d’applications. Par l’étude de différents processus de transfert de charges/d’énergie au sein des complexes seuls (processus intramoléculaires) ou en interaction avec un environnement spécifique (processus intermoléculaires), nous avons souhaité mettre en évidence l’intérêt de l’utilisation d’un nouveau ligand plan étendu, le tpac, au sein de complexes du Ru(II). Un tel ligand permet en effet de conférer d’une part une affinité élevée des complexes résultants pour l’ADN, et d’autre part, de par sa nature pontante, de connecter des unités métalliques entre elles au sein d’entités supramoléculaires de taille importante.
Les propriétés photophysiques de quatre complexes basés sur le ligand plan étendu tpac, le [Ru(phen)2tpac]2+ (P) et son homologue dinucléaire le [(phen)2Ru tpac Ru(phen)2]4+ (PP) (à base de ligands ancillaires phen), ainsi que le [Ru(tap)2tpac]2+ (T) et son homologue dinucléaire le [(tap)2Ru tpac Ru(tap)2]4+ (TT) (à base de ligands ancillaires tap), ont été étudiées et comparées entre elles.
L’examen de ces propriétés, d’abord pour les complexes seuls en solution, en parallèle avec celles de complexes dinucléaires contenant un ligand pontant PHEHAT, a permis de mettre en évidence l’importance de la nature du ligand pontant utilisé. Ces résultats ont ainsi révélé qu’un choix judicieux du ligand pontant permet de construire des entités de grande taille capables de transférer l’énergie lumineuse vers un centre (cas du ligand PHEHAT), ou, au contraire, de relier entre elles des entités ne s’influençant pas l’une l’autre d’un point de vue photophysique (cas du ligand tpac).
Les propriétés des complexes du tpac, étudiés cette fois en présence de matériel génétique (mononucléotide GMP, ADN ou polynucléotides synthétiques), se sont révélées très différentes selon que le complexe portait des ligands ancillaires phen (P, PP) ou tap (T, TT). Seuls les complexes à base de tap sont en effet photoréactifs envers les résidus guanine. Nous avons dès lors focalisé cette partie de notre travail sur les deux complexes T et TT. Cette photoréaction, ainsi que le transfert d’électron photoinduit entre ces complexes excités et la guanine, ont pu être mis en évidence par différentes techniques de spectroscopie d’émission tant stationnaire que résolue dans le temps, ainsi que par des mesures d’absorption transitoire dans des échelles de temps de la nano à la femto/picoseconde. L’étude du comportement photophysique des complexes en fonction du pH a en outre révélé de manière très intéressante que, pour des études en présence d’ADN, la protonation des états excités des complexes devait être considérée. Les résultats de cette étude nous ont fourni des pistes quant à l’attribution des processus observés en absorption transitoire.
Le transfert d’électron a également fait l’objet d’une étude par des méthodes théoriques. Ces calculs ab initio ont permis de mettre en évidence une faible influence de l’énergie de réorganisation sur la vitesse de transfert d’électron, qui semble dépendre plus sensiblement de la non-adiabaticité du processus, mais surtout de l’énergie libre de la réaction et d’un éventuel couplage à un transfert de proton.
L’ensemble des résultats obtenus avec les complexes T et TT en présence de matériel génétique, qui, de manière assez inattendue, sont très semblables, indiquent que ces complexes présentent tous deux un grand intérêt pour le développement de nouvelles drogues antitumorales photoactivables.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Cheng, Yuan-Chung Ph D. Massachusetts Institute of Technology. "Quantum dynamics in condensed phases : charge carrier mobility, decoherence, and excitation energy transfer." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34496.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.
Includes bibliographical references.
In this thesis, we develop analytical models for quantum systems and perform theoretical investigations on several dynamical processes in condensed phases. First, we study charge-carrier mobilities in organic molecular crystals, and develop a microscopic theory that describes both the coherent band-like and incoherent hopping transport observed in organic crystals. We investigate the structures of polaron states using a variational scheme, and calculate both band-like and hopping mobilities at a broad range of parameters. Our mobility calculations in 1-D nearest-neighbor systems predict universal band-like to hopping transitions, in agreement with experiments. Second, motivated by recent developments in quantum computing with solid-state systems, we propose an effective Hamiltonian approach to describe quantum dissipation and decoherence. We then applied this method to study the effect of noise in a number of quantum algorithms and calculate noise threshold for fault-tolerant quantum error corrections (QEC). In addition, we perform a systematic investigation on several variables that can affect the efficiency of the fault-tolerant QEC scheme, aiming to generate a generic picture on how to search for optimal circuit design for real physical implementations.
(cont.) Third, we investigate the quantum coherence in the B800 ring of' of the purple bacterium Rps. acidophila and how it affects the dynamics of excitation energy transfer in a single LH2 complex. Our calculations suggest that the coherence in the B800 ring plays a significant role in both spectral and dynamical properties. Finally, we discussed the validity of Markovian master equations, and propose a concatenation scheme for applying Markovian master equations that absorbs the non-Markovian effects at short times in a natural manner. Applications of the concatenation scheme on the spin-boson problem show excellent agreements with the results obtained from the non-Markovian master equation at all parameter range studied.
by Yuan-Chung Cheng.
Ph.D.
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Mutz, Niklas [Verfasser]. "Energy and Charge Transfer at Hybrid Interfaces Probed by Optical Spectroscopy / Niklas Mutz." Berlin : Humboldt-Universität zu Berlin, 2021. http://d-nb.info/1232726060/34.
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Acharya, Khem. "Excitation energy transfer and charge separation dynamics in photosystem II: hole-burning study." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13600.
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Doctor of PhilosophyDepartment of Chemistry
Ryszard J. Jankowiak
The constituents of oxygen-evolving photosystem II core complexes—antenna proteins (CP43 and CP47) and reaction center (RC)—have been the subject of many studies over the years. However, the various issues related to electronic structure, including the origin/composition of the lowest-energy traps, origin of various emission bands, excitation energy transfer (EET), primary charge separation (CS) processes and pigment site energies remain yet to be fully resolved. Exploiting our state-of-the-art techniques such as low-T absorption, fluorescence, and hole burning (HB) spectroscopies, we resolved some of the issues particularly related to CP47 and isolated RC protein complexes. For example, we demonstrated that the fluorescence origin band maximum (~695 nm) originates from the lowest-energy state ~693 nm of intact CP47. In intact CP47 in contrast to destablished protein complexes, the band (~695 nm) does not shift in the temperature range of 5–77 K unless hole-burning takes place. We also studied a large number of isolated RC preparations from spinach, and wild-type Chlamydomonas reinhardtii (at different levels of intactness), as well as its mutant (D2-L209H), in which the active branch pheophytin (PheoD1) has been genetically replaced with chlorophyll a (Chl a). We showed that the Qx-/Qy-region site-energies of PheoD1 and PheoD2 are ~545/680 nm and ~541.5/670 nm, respectively, in good agreement with our previous assignment [Jankowiak et al. J. Phys. Chem. B 2002, 106, 8803]. Finally, we demonstrated that the primary electron donor in isolated algal RCs from C. reinhardtii (referred to as RC684) is PD1 and/or PD2 of the special Chl pair (analogous to PL and PM, the special BChl pair of the bacterial RC) and not ChlD1. However, the latter can also be the primary electron donor (minor pathway) in RC684 depending on the realization of the energetic disorder. We further demonstrate that transient HB spectra in RC684 are very similar to P+QA - PQA spectra measured in PSII core, providing the first evidence that RC684 represent intact isolated RC that also possesses the secondary electron acceptor, QA. In summary, a new insight into possible charge separation pathways in isolated PSII RCs has been provided.
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Latimer, Darin Rae. "Determination of charge, atom, momentum and energy transfer rate coefficients near 5 K." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186873.
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This dissertation presents the results of several investigations into nonadiabatic reaction dynamics in the 0.5 to 10 K temperature regime. The free jet flow reactor technique for production of very low local temperatures and the method for extraction of reaction rate coefficients in this unique environment is reviewed. Ion-neutral reactions which exhibit nonadiabatic behavior are initiated by state selective resonantly enhanced multiphoton ionization and the reactions are subsequently studied using time of flight mass spectrometric detection. The importance of long lived collision complexes in nonadiabatic ion-neutral reactions is reemphasized. Collisional electronic spin orbit relaxation of Xe⁺(²P(½) is shown to be very inefficient for a wide variety of collision partners. A sequential two electron charge transfer mechanism is proposed to account for the high efficiency of the fine structure relaxation by methane and nitrous oxide both of which have open charge transfer channels. The results of fine structure state specific reactions of Ar⁺(²P(J)) with H₂, D₂, HD, CH₄ and CD₄ are presented as examples of nonadiabatic atom and electron transfer reactions. Preliminary results on vibrational-rotational relaxation of neutrals in the free jet at very low temperatures using a pump-probe technique are presented.
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Bengtsson, Kristoffer. "C/O+ charge transfer & the Olson-Demkov model." Thesis, Uppsala universitet, Teoretisk astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-453883.
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Charge transfer reactions and their rates play a key role in correctly estimating element abundances in astrophysical objects such as supernovae. The reaction $C + O^+ \rightarrow C^+ + O(^1D) + \Delta E$ has been shown to be of significance when estimating oxygen abundances through model spectrum evaluations, and the relative rate of this reaction can under certain circumstances completely dictate the neutralization rate of oxygen ions. In this project, the rate of this reaction for four different temperatures is estimated using the Olson-Demkov model to calculate the cross section of the reaction as well as calculating rates for a few more reactions to compare to established literature values. We find that the Olson-Demkov model produces good estimates for reactions that have small energy defects (within an order of magnitude of more rigorous quantum mechanical calculations), but the model underestimates the rate coefficient by several orders of magnitude as the energy defect increases. As the investigated reactions are all exothermic, the energy defect is the released energy from the reaction (i.e., the energy defect is positive). It is also found in most cases that the Olson-Demkov model rate is poorly estimated by the rate coefficient based only on the cross section at the mean velocity, caused by the cross section rising rapidly for velocities higher than the mean. The rate estimates produced for C+O$^+$ are also likely to be underestimated, especially for the temperatures 100 and 1000 Kelvin. No literature comparison is available for this specific reaction, but this conclusion is consistent with the other investigated reactions.Supernovor är bland de mest extrema fenomen vi kan observera i hela Universum. Dessa våldsamma explosioner lämnar spår efter sig i många år och har varit ovärdeliga objekt att observera för att lära oss mer hur vår galax och Universum har utvecklats över tid. Ljuset från supernovor och deras kvarlevor kan analyseras för att ta reda på vad för ämnen som finns kvar eller som har bildats av både explosionen och de processer som ägt rum efteråt. En typ av reaktion som är viktig för att fullt ut förstå dessa miljöer är så kallade "laddningsöverföringar", en reaktion där en laddad och en oladdad partikel interagerar med varandra varvid laddningen förflyttas mellan de två. Detta projekt har fokuserat på en modell som avser att räkna ut uppskattningar på hur sannolikt det är för dessa reaktioner att äga rum. Modellen, som kallas för Olson-Demkov-modellen, har även jämförts med andra modeller för att se under vilka förhållanden som den fungerar.
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Borgström, Magnus. "Controlling Charge and Energy Transfer Processes in Artificial Photosynthesis : From Picosecond to Millisecond Dynamics." Doctoral thesis, Uppsala University, Department of Physical Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6017.
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This thesis describes an interdisciplinary project, where the aim is to mimic the initial reactions in photosynthesis. In photosynthesis, the absorption of light is followed by the formation of charge-separated states. The energy stored in these charge-separated states is further used for the oxidation of water and reduction of carbon dioxide. In this thesis the photo-induced processes in a range of supramolecular complexes have been investigated with time resolved spectroscopic techniques. The complexes studied consist of three types of units; photosensitizers (P) capable of absorbing light, electron acceptors (A) that are easily reduced and electron donors (D) that are easily oxidised. Our results are important for the future design of artificial photosystems, where the goal is to produce hydrogen from light and water.
Two molecular triads with a D-P-A architecture are presented. In the first one, a photo-induced charge-separated state was formed in an unusually high yield (φ>90%). In the second triad, photo-irradiation led to the formation of an extremely long-lived charge-separated state (τ = 500 ms at 140K). This is also the first synthetically made triad containing a dinuclear manganese unit as electron donor.
Further, two sets of P-A dyads are presented. In both, the expected photo-induced reduction of the electron acceptor is diminished due to competing energy transfer to the triplet state of the acceptor.
Finally, a P-P-A complex containing two separate photosensitizers is described. The idea is to produce high-energy charge-separated states by using the energy from two photons.
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Borgström, Magnus. "Controlling charge and energy transfer processes in artificial photosynthesis : from picosecond to millisecond dynamics /." Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6017.
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Shao, Shuai. "Synthesis and Studies of Wide-Band Capturing BODIPY-Fullerene Based Donor-Acceptor Systems." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703394/.
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Artificial photosynthesis is the process, which mimics the natural photosynthesis process in order to convert solar energy to chemical energy. This process can be separated into four parts, which are antenna system, reaction center, water oxidation center, and proton reduction center. If we only focus on the ‘antenna system and reaction center' modules, expanding the absorption band in antenna system and generating long-lived charge separated state in reaction center are two fantastic strategies to design the molecules in order to improve the efficiency of the artificial photosynthesis process.
In the first work of this dissertation, mono-18-crown-6 and mono-ammonium binding strategy was used to connect BODIPY- C60 supramolecular based donor–acceptor conjugates. The meso- position of BODIPY was modified by benzo-18-crown-6, and the 3, 5 methyl positions were replaced by two styryl groups, which covered additional donor (triphenylamine or 10-methylphenothiazine). The acceptor is a fulleropyrrolidine derivative, which included an ethyl ammonium cation. The absorbance wavelengths of the donor covered 300-850 nm, which is the visible/near IR region (wide band capturing). The ultrafast charge separation and relatively slow charge recombination was found from femtosecond transient absorption study.
Next, a ‘two point' bis-18-crown-6 and bis-ammonium binding strategy was utilized to link BODIPY- C60 supramolecular based donor–acceptor conjugates. In this case, the meso- position of the BODIPY was modified by a secondary donor (triphenylamine, phenothiazine, or ferrocene). And the 3, 5 methyl positions were replaced by two styryl groups, which included benzo-18-crown-6. The acceptor (fulleropyrrolidine) was functionalized by bis-alky ammonium cations. The absorbance/ fluorescence emission titration and computational studies supported that the ‘two-point' strategy has stronger binding than ‘one-point' strategy. The relatively slow charge separation was found in these donor-acceptor conjugates.
To extend the second work, a pristine BODIPY was linked to the meso- position of the BODIPY-bis-benzo-18-crown-6. When the acceptor (C60-bis- ammonium) was added to the system, a sequential energy transfer (EnT) followed by electron transfer (ET) process was performed. The energy transfer was found from absorbance/ fluorescence emission studies, and the photoinduced electron transfer was observed from femtosecond and nanosecond transient absorption study. This is a great mode to mimic the ‘antenna-reaction center' events of natural photosynthesis.
In the last work of this dissertation, triplet sensitizers (I2BODIPY and I2azaBODIPY) covalently linked with a C60 to form the donor-acceptor system. In this work, triplet charge separated state (long-lived charge separated state) was expected. According to the femtosecond transient absorption studies, we observed the singlet charge separation was faster than the intersystem crossing process, that was the reason that only singlet charge separated state was found for I2BODIPY-C60, and no electron transfer was found for I2 azaBODIPY-C60.
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Lim, Gary Lloyd Nogra. "Elucidation of Photoinduced Energy and Electron Transfer Mechanisms in Multimodular Artificial Photosynthetic Systems." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984185/.
Full textAbstract:
Multimodular designs of electron donor-acceptor systems are the ultimate strategy in fabricating antenna-reaction center mimics for artificial photosynthetic applications. The studied photosystems clearly demonstrated efficient energy transfer from the antenna system to the primary electron donor, and charge stabilization of the radical ion pair achieved with the utilization of secondary electron donors that permits either electron migration or hole transfer. Moreover, the molecular arrangement of the photoactive components also influences the route of energy and electron transfer as observed from the aluminum(III) porphyrin-based photosystems. Furthermore, modulation of the photophysical and electronic properties of these photoactive units were illustrated from the thio-aryl substitution of subphthalocyanines yielding red-shifted Q bands of the said chromophore; hence, regulating the rate of charge separation and recombination in the subphthalocyanine-fullerene conjugates.
These multicomponent photosystems has the potential to absorb the entire UV-visible-NIR spectrum of the light energy allowing maximum light-harvesting capability. Furthermore, it permits charge stabilization of the radical ion pair enabling the utilization of the transferred electron/s to be used by water oxidizing and proton reducing catalysts in full-scale artificial photosynthetic apparatuses.
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Banjoko, Victor O. "Design, synthesis and spectroscopy of terpyridine materials: from energy and charge transfer to chemosensor applications." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2010. http://digitalcommons.auctr.edu/dissertations/168.
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The research presented in this dissertation focuses on the design, synthesis, photophysical characterization, and metal ion sensing properties of a conjugated polymer and enhancing the photophysical and acid-base properties of Ru(mtpy)(tpycooh)- a transition metal complex. All the synthesized compounds were based on terpyridine ligans. The objective of the first project is to investigate the effect of positioning the terpyridine unit in the meta position, which does not allow extended conjugation through the polymer backbone, on the metal ion sensing ability of this conjugated Poly(phenylenevinylene) (PPV) material. A novel PPV containing meta-linked pendant terpyridine ligand was synthesized. Absorption and fluorescence studies indicated that Fe2+ was coordinate in 1:2 ratio to the terpyridyl groups and Cu2+ bound in 1:1 ratio to the terpyridyl groups. A more selective response was observed for this meta-derivative compared to para derivative. Cu2+ selectively quenches the fluorescence of the polymer, with slight interference from Zn2+, Cd2+ and Hg2+. These ions induce partial fluorescence quenching accompanied by a broad new emission band due to the complex formation between the terpyridine (tpy) ligand and the metal ion. The objective of the second project is to synthesize a new mixed-ligand comllex [Ru(mtpy)(tpycooh)](la), where mtpy = 4'- methy1-2,2' : 6'2" - terpyridine and tpycooh = 2,2':6',2"- terpyridine-4' - carboxylic acid. This new complex incorporated mixed ligands to enhance the photophysical propertics of Ru(II) terpyrine complex like its bypyridine analog. The methyl group on tpy acts as an electron-donating group (EDG) while COOH group on tpy acts as an electron-withdrawing group (EWG). The new enhanced complex showed redshifted Metal Ligand Charge Transfer (MLCT) band in the absorption and emission spectra, larger quantum yield and improved redox properties over the non-enhanced model terpyridine-Ru compex. These results implied that the combination of mixed ligands of electron donating and electron withdrawing substituents on tpy ligand improved the luminescence and the photophysical properties of the complex.
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Linderl, Theresa [Verfasser], and Wolfgang [Akademischer Betreuer] Brütting. "Charge Transfer States and Energy Losses in Organic Solar Cells / Theresa Linderl ; Betreuer: Wolfgang Brütting." Augsburg : Universität Augsburg, 2018. http://d-nb.info/1159880476/34.
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Pruttivarasin, Thaned. "Study of low energy Ytterbium atom-ion charge transfer collisions using a surface-electrode trap." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45339.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 113-114).
We demonstrate a new isotope-selective system to measure low energy charge transfer collisions between ytterbium ions and atoms in the range of collisional energy from 2.2x 10-5 eV to 4.3x 10-3 eV, corresponding to effective temperature from 250 mK to 50 K. The charge transfer collisions are observed by spatially overlapping the 172yb+ ions in the surface-electrode trap and 174Yb atoms in the magneto-optical trap, and measuring ion loss. We confirm that, in the Langevin regime, the charge transfer collisional rate is independent of the collisional energy. The measured Langevin cross section is consistent with a theoretical value for the ytterbium atomic polarizability of 143 a.u., as calculated by Zhang and Dalgarno [1].
by Thaned Pruttivarasin.
S.B.
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Rozsályi, Emese Tünde. "Theoretical study of charge transfer in ion-molecule collisions." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10152/document.
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Les processus de transfert de charge sont très importants dans de nombreux domaines de la physique et de la chimie. Ils interviennent en particulier dans la conception ds plasmas astrophysiques ainsi que des plasmas de fusion. Les particules secondaires, électrons lents ou ions, générés le long du trajet des radiations jouent également un rôle crucial dans l’action des radaitions sur le milieu biologique, en relation en particulier avec les traitements du cancer. Il est donc fondamental d’avoir une connaissance approfondie des mécanismes mis en jeu dans ce type de processus, à l’échelle moléculaire. Pour cela, nous avons étudié dans cette thèse deux systèmes voisins, la collision des ions C2+ avec les molécules HF et HCI afin d’ananllyser en détail le mécanisme de transfert de charge dans ces deux réactions en d’en déduire des éléments permettant d’avoir une vue plus générals de ce type de processus. Nous nous sommes en particulier intéressés à l’anisotropie de la réaction de transfert de charge ainsi qu’aux effets dus à la vibration de la molécule diatomique cible lors de la collision. Une étude comparée des ces deux système a montré un mécanisme différent dans chaque cas liés aux interactions non-adiabatiques mises en jeuCollisiosns of slow multiply charged ions with molecular species have been widely investigated in the past few years. Imortant experimental and theoretical effort has been focused on reactions with simple targets. Consideration of more complex molecular targets are now of increasing interest, in particular with regardto possible direect or indirect processes occuring in the irradiation of the biological medium.. In these reactions generally at relativity low energies, different processes have to be considered: exitation and fragmentation on the molecule, ionization of the gaseous target, and also possible charge transfer from the multicharged ion toward the biomolecule..Charge transfer can be investigated theoretically in the framework of the molecular representation of the collision. Such studies provides important information on the mecanism as well as on the electronic structure of the projectile and target during the reaction. The charge-transfer process in collisions on C2+ ions with hydrogen halide molecule (HF, HCI) has been studied by means of ab initio quantum chemistry molecular methods followed by semiclassical dynamical treatment in the keV collision energy range. The mechanism has been investigated in detail in each reaction, in connection with nonadiabatic interactions around avoided crodssings between states involved in the process
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Steeger, Markus [Verfasser], Christoph [Gutachter] Lambert, and Tobias [Gutachter] Brixner. "Energy and Charge Transfer in Donor-Acceptor Substituted Hexaarylbenzenes / Markus Steeger. Gutachter: Christoph Lambert ; Tobias Brixner." Würzburg : Universität Würzburg, 2015. http://d-nb.info/1108781551/34.
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Paulus, Geraldine L. C. (Geraldine Laura Caroline). "Understanding and engineering interfacial charge transfer of carbon nanotubes and graphene for energy and sensing applications." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81686.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Graphene is a one-atom thick planar monolayer of sp2 -bonded carbon atoms organized in a hexagonal crystal lattice. A single walled carbon nanotube (SWCNT) can be thought of as a graphene sheet rolled up into a seamless hollow cylinder with extremely high length-to-diameter ratio. Their large surface area, and exceptional optical, mechanical and electronic properties make these low-dimensional carbon materials ideal candidates for (opto-)electronic and sensing applications. In this thesis I studied the charge transfer processes that occur at their interface, and developed applications based on the discovered properties. When light is incident on a semiconducting SWCNT, it can excite an electron from the valence band to the conduction band, thereby creating a Coulombically bound electron-hole pair, also known as an exciton. Excitons can decay via radiative or non-radiative recombination or by colliding with other excitons. They can diffuse along the length of a SWCNT or hop from larger band gap SWCNTs to smaller band gap SWCNTs, a process known as exciton energy transfer (EET). We studied their behavior as a function of temperature in SWCNT fibers and showed that at room temperature the rate constant for EET is more than two orders of magnitude larger than that of each of the different recombination processes. This led us to construct a core-shell SWCNT fiber, which consists of a core of smaller band gap SWCNTs, surrounded by a shell of larger band gap SWCNTs, essentially forming what is known as a type I heterojunction. In agreement with a model that describes exciton behavior in the SWCNT fibers, we found that upon illumination all the energy (in the form of excitons) was quickly transferred from the shell to the core, faster than the excitons would otherwise recombine. The SWCNT fiber proved to be an efficient optical and energetic concentrator. We showed that SWCNTs and poly(3-hexylthiophene) (P3HT) form a type II heterojunction, which implies that excitons generated in the P3HT can easily dissociate into free charge carriers at the interface with the SWCNTs. Despite this, the efficiency of a P3HT/SWCNT bulk heterojunction (BHJ) photovoltaic is subpar. We developed a P3HT/SWCNT planar heterojunction (PHJ) and achieved efficiencies that were 30 times higher, which showed that the formation of bundled aggregates in BHJs was the cause: metallic SWCNTs can quench the excitons in an entire bundle. Another interesting feature of our SWCNT/P3HT PHJ is that a maximum efficiency was reached when -60 nm of P3HT was used, which is surprising since in a planar photovoltaic a maximum is expected for ~8.5 nm of P3HT, the value of the exciton diffusion length. A Kinetic Monte Carlo simulation revealed that bulk exciton dissociation was responsible for the lower efficiencies observed in devices with low P3HT thickness. Next we created and studied a junction between SWCNTs and a monolayer of graphene, an ideal one-dimensional/two-dimensional carbon interface. We used Raman spectroscopy to probe the degree of charge transfer at the interface and based on a shift in the G peak position of the graphene Raman signal at the junction deduced that a typical metallic (semiconducting) SWCNT dopes the graphene with 1.12 x 1013 cm-2 (0.325 x 101 cm-2) electrons upon contact, in agreement with the fact that the Fermi level of the SWCNTs is more shallow than that of the graphene. A molecular dynamics simulation ruled out that the observed Raman peak shifts are due to strain, although it did show that SWCNTs are being compressed radially by the graphene sheet, resulting in a widening of their Raman peaks. We studied charge transfer between diazonium molecules and graphene, to better inform transistor and sensor design. The reaction rate depends on the degree of overlap between the filled energy levels in graphene and the unoccupied ones in the diazonium molecule. We showed that with increasing degree of functionalization the charge transfer characteristics of a graphene field effect transistor (FET) alter in the following ways: the minimum conductivity decreases, the Dirac point upshifts, the conductivity plateau at high carrier density decreases and the electronhole conduction asymmetry increases. We developed a theoretical model of charge transport in graphene FETs that takes into account the effect of both short-range and long-range scatterers. Fitting it to the charge-transport data reveals quantitative information about the number of impurities in the substrate supporting the graphene, about the number of defects created as a result of the reaction, and about the degree of electron-hole conduction asymmetry. Graphene functionalization also affects the graphene Raman signal. After reaction, the D to G intensity ratio to increases, which is a sign of covalent modification of the graphene lattice. Additionally, the G peak and 2D peak positions increase while the 2D/G intensity ratio decreases, which are signs of hole-doping. Based on a Raman analysis, we were also able to show that the end group of the diazonium salt can affect both the degree of chemisorption (covalent modification) as well as the degree of physisorption (doping). Finally, we studied the effects of charge transfer between graphene and biological cells on the graphene Raman signal and designed a fundamentally new type of biosensor. Graphene can be thought of as a continuous array of information units (sensor units). The Raman signal collected in each unit can report on its local environment. In contrast to graphene FET biosensors, the graphene Raman biosensor offers subcellular spatial resolution. The graphene Raman signal was shown to display a strong dependence on pH. Metabolically active cells acidify their local environment; therefore, pH is a proxy for cellular metabolism. We placed both human embryonic kidney (HEK) cells that were genetically engineered to produce mouse antibodies and control HEK cells that were not genetically modified onto the graphene. Based on the change in the graphene Raman signal we deduced the former have a metabolic rate that is four times higher than that of the control cells. Increased cellular adhesion allows the cells to interact more closely with the graphene monolayer and intensifies the observed Raman effects.
by Geraldine L.C. Paulus.
Ph.D.
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Harper, Theresa F. "I, Energy and charge transfer at nanocystalline Si interfaces ; II, reactions of porous Si with ketones /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9906493.
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Jenkins, Judith Lynn. "Spectroscopic and Spectroelectrochemical Characterization of Fundamental Interfacial Charge Transfer Processes Relevant to Efficient Solar Energy Conversion." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255173.
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Solar energy conversion is accomplished by multilayered devices consisting of various conducting and semiconducting materials. Because the layers are only 10s - 100s of nm thick, device behavior is governed primarily by interfacial molecular dynamics that often differ from the bulk behavior of these materials. The thermodynamics and kinetics of the interfacial interactions are particularly interesting, as interfacial electron transfer strongly influence the efficiency of photovoltaics and devices used in solar hydrogen production. This work focuses specifically on interfacial charge transfer processes occurring at three interfaces relevant to thin film organic/inorganic solar energy conversion devices. i) A potential-step polymer electrochemical deposition and doping procedure was developed and used to create poly(3-hexylthiophene) (e-P3HT) interlayer films for organic photovoltaics. Photoelectron spectroscopies suggest that an interface dipole forms spontaneously at the polymer donor/fullerene acceptor interface through partial interfacial charge transfer prior to photoexcitation; this doping-dependent interfacial dipole was correlated to the electrical properties of these critical heterojunctions. ii) Potential-modulated fluorescence spectroscopy (PMF) was developed and used examine the kinetics of the reversible oxidation of the (e-P3HT) films in attempt to elucidate the ITO/e-P3HT charge transfer rates. However, the optical switching increased linearly as the polymer film decreased, indicating that the molecular-level process probed by PMF was rate-limited by counter-ion movement into and out of the polymer film. iii) Potential-modulated attenuated total reflectance spectroscopy (PM-ATR) was used to examine the reversible reduction of CdSe semiconductor nanocrystals tethered to indium tin oxide electrodes as well as the surface-coverage dependent bleaching of these nanocrystals. A new equivalent circuit model describing the CdSe/ITO electrode is proposed, and a PM-ATR simulation program was used to quantify Faradiac resistances to interfacial charge transfer that trend with the magnitude of overpotential. The insights gained through these experiments add to a growing understanding of the fundamental, molecular-level competition between photoinduced charge generation and parasitic charge recombination at these critical interfaces.
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Garrison, Shana A. "SYNTHESIS AND PHOTOPHYSICAL CHARACTERIZATION OF PORPHYRIN-CONTAINING SUPRAMOLECULAR SYSTEMS: STRUCTURAL ISSUES FOR PORPHYRIN PHOTOPHYSICS AND ELECTRON TRANSFER." Akron, OH : University of Akron, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1123616344.
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Thesis (Ph. D.)--University of Akron, Dept. of Chemistry, 2005."August, 2005." Title from electronic dissertation title page (viewed 09/24/2005). Advisor, David A. Modarelli; Committee members, Matthew Espe, Michael Taschner, Chrys Wesdemiotis, Stephanie Lopina; Department Chair, David Perry; Dean of the College, Charles B. Monroe; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Ziemann, Dirk. "Theory of Excitation Energy Transfer in Nanohybrid Systems." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/22142.
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Im Folgenden werden Transferprozesse in Nanohybridsystemen theoretisch untersucht.
Diese Hybridsysteme sind vielversprechende Kandidaten für neue optoelektronische Anwendungen und erfahren daher ein erhebliches Forschungsinteresse.
Jedoch beschränken sich Arbeiten darüber hauptsächlich auf experimentelle Untersuchungen und kaum auf die dazugehörige theoretische Beschreibung.
Bei den theoretischen Betrachtungen treten entscheidende Limitierungen auf.
Es werden entweder Details auf der atomaren Ebene vernachlässigt oder Systemgrößen betrachtet, die wesentlich kleiner als im Experiment sind.
Diese Thesis zeigt, wie die bestehenden Theorien verbessert werden können und erweitert die bisherigen Untersuchungen durch die Betrachtung von vier neuen hoch relevanten Nanohybridsystemen.
Das erste System ist eine Nanostruktur, die aus einem Au-Kern und einer CdS-Schale besteht.
Beim zweiten System wurde eine ZnO/Para-Sexiphenyl Nanogrenzfläche untersucht.
Die zwei anderen Systeme beinhalten jeweils einen CdSe-Nanokristall, der entweder mit einem Pheophorbide-a-Molekül oder mit einem röhrenförmigen Farbstoffaggregat wechselwirkt.
In allen Systemen ist der Anregungsenergie-Transfer ein entscheidender Transfermechanismus und steht im Fokus dieser Arbeit.
Die betrachteten Hybridsysteme bestehen aus zehntausenden Atomen und machen daher eine individuelle Berechnung der einzelnen Subsysteme sowie deren gegenseitiger Wechselwirkung notwendig.
Die Halbleiter-Nanostrukturen werden mit der Tight-Binding-Methode und der Methode der Konfigurationswechselwirkung beschrieben.
Für das molekulare System wird die Dichtefunktionaltheorie verwendet.
Die dazugehörigen Rechnungen wurden von T. Plehn ausgeführt.
Das metallische Nanoteilchen wird durch quantisierte Plasmon-Moden beschrieben.
Die verwendeten Theorien ermöglichen eine Berechnung von Anregungsenergietransfer in Nanohybridsystemen von bisher nicht gekannter Systemgröße und Detailgrad.In the following, transfer phenomena in nanohybrid systems are investigated theoretically. Such hybrid systems are promising candidates for novel optoelectronic devices and have attracted considerable interest. Despite a vast amount of experimental studies, only a small number of theoretical investigations exist so far. Furthermore, most of the theoretical work shows substantial limitations by either neglecting the atomistic details of the structure or drastically reducing the system size far below the typical device extension. The present thesis shows how existing theories can be improved. This thesis also expands previous theoretical investigations by developing models for four new and highly relevant nanohybrid systems. The first system is a spherical nanostructure consisting of an Au core and a CdS shell. By contrast, the second system resembles a finite nanointerface built up by a ZnO nanocrystal and a para-sexiphenyl aggregate. For the last two systems, a CdSe nanocrystal couples either to a pheophorbide-a molecule or to a tubular dye aggregate. In all of these systems, excitation energy transfer is an essential transfer mechanism and is, therefore, in the focus of this work. The considered hybrid systems consist of tens of thousands of atoms and, consequently, require an individual modeling of the constituents and their mutual coupling. For each material class, suitable methods are applied. The modeling of semiconductor nanocrystals is done by the tight-binding method, combined with a configuration interaction scheme. For the simulation of the molecular systems, the density functional theory is applied. T. Plehn performed the corresponding calculations. For the metal nanoparticle, a model based on quantized plasmon modes is utilized. As a consequence of these theories, excitation energy transfer calculations in hybrid systems are possible with unprecedented system size and complexity.
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Abdelhameed, Mohammed. "Transfert de charge et d’énergie dans les dyades et oligomères de porphyrine." Mémoire, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/5360.
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Résumé : Le travail de recherche présenté dans ce mémoire fut inspiré par le processus de la photosynthèse qui se produit chez les plantes. Au cours de ce processus l’énergie solaire est convertie en énergie chimique via différentes étapes de transferts d’électrons et d’énergie. En maîtrisant bien ces concepts, de nombreuses applications, telles que les cellules photovoltaïques ou les DEL (Diodes électro-luminescentes) peuvent être améliorées. Pour se faire, il est important d’optimiser les propriétés des matériaux existants (oligomères, polymères, etc…) en préparant des systèmes conjugués plus efficaces, mais aussi de pleinement comprendre les processus qui s’y produisent (processus de transferts d’électrons et d’énergie photo-induist). La série d’oligomères et de polymères présentée dans ce mémoire le sont pour leurs applications dans des systèmes photoniques. Dans cette optique, ce mémoire a été divisé en cinq grands chapitres. Le premier présente les principes théoriques de la photophysique. Le second présente le suivi du transfert d’énergie T[indice inférieur 1] dans les états triplets, T[indice inférieur 1], une dyade constituée de la tétraphénylporphyrine de zinc(II), [ZnTPP], et de la bis(phénylpyridinato)(bipyridine) d’iridium(III), [Ir], chromophores liés avec un pont trans-diéthynylbis(phosphine)-platine(II). Malgré que cette dyade soit entièrement conjuguée et qu’elle soit constituée d’un donneur ([ZnTPP]) et d’un accepteur ([Ir]), aucun transfert d’énergie T[indice inférieur 1] [Ir] → S[indice inférieur 1]/T[indice inférieur 1] [ZnTTP] n’a été observé. Ce résultat fut attribué à l’absence de recouvrement des orbitales moléculaires entre la HSOMO(donneur*) et la HSOMO(accepteur), LSOMO(accepteur) and LSOMO (donneur*) (mécanisme de Dexter). Ainsi, l’échange d’électrons est impossible. Ce chapitre suggère que l’équation de Dexter, k[indice inférieur Dexter] = KJexp(-2r[indice inférieur DA]/L) ne reste qu’une approximation. Ce travail a été publié dans ChemComm (2013, 49, 5544-5546). Le troisième chapitre présente le transfert d’énergie singulet beaucoup lent qu’attendu se produisant dans une dyade constituée d’une porphyrine de zinc(II) avec une porphyrine base libre liées par un pont palladium(II) (trans-PdI[indice inférieur 2]). Sachant que cette dyade est entièrement conjuguée et que la distance entre les deux centres de masse des porphyrines est relativement courte, ce système aurait dû présenter un transfert d’énergie très rapide, d’après la théorie de Förster. Dans ce cas, ce comportement a été expliqué par le faible recouvrement des orbitales frontières (OM) du donneur et de l’accepteur. Ce travail a été accepté le 2014-05-26 dans Chemistry – A European Journal (chem.201403146). Le quatrième chapitre rapporte une étude du transfert d’énergie ultra-rapide (650 fs) entre des états singulets dans une dyade composé d’une porphyrine de zinc(II) (le donneur) et une porphyrine base libre (l’accepteur) liées à l’aide d’un pont de palladium ([beta],[beta]--trans-Pd(NH)[indice inférieur 2](CO)[indice inférieur 2]). Ces résultats ont été attribués à la présence d’un couplage fort entre les OM du donneur et de l’accepteur et de la très faible contribution (atomique) du Pd(II) vers ces OM. Cette dyade montre la plus rapide constante de transfert d’énergie k[indice inférieur ET] que nous connaissons pour des dyades similaires contentant un fragment métallique. Les résultats du troisième et quatrième chapitre montrent que la théorie de Förster tel quel ne suffit pas pour prédire les vitesses de transferts d’énergie dans certains systèmes : d’autres facteurs doivent être pris en compte. Ce travail a été soumis dans JACS ( ja-2014-061774, 19-6-2014). Dans le cinquième chapitre de ce mémoire, la synthèse du bis(-[alpha]-(amino(4-éthynylbenzene (triméthylsilane)(R))))bis(4-éthynylbenzene-(triméthylsilane))quinone diimine (R= H, Boc) comme modèle pour des polymères conjugués et non-conjugués contenant le colorant porphyrine a été proposée. Le corps du composé désiré (tétrakis(4-éthynlyphenyl)quinone-1,4-diimine-2,5-diamine) a montré un transfert de charge partant des groupes terminaux riches en électrons une la benzoquinone centrale plus pauvre. La nature de l’émission fut observée uniquement à 77K pour le cas où R = H et fut attribuée à de la fluorescence. À température ambiante, l’intensité était trop faible pour être observée. Dans le cas où R = Boc, aucune emission n’a été détectée. Malheureusement, le composé espéré ne fut pas obtenu, le procédé de synthèse employé engendra uniquement la forme réduite. Cette forme fut malgré tous analysé, et ne présenta pas de transfert de charge ni de communication entre les différents chromophores. Ceci a été expliqué simplement par le fait que la conjugaison est brisée quand ce composé est sous sa forme réduite. Ce travail sera soumis au Journal of Inorganic and Organometallic Polymers and Materials. // Abstract : The research work presented in this master thesis is inspired by the photosynthetic process occurring in plants where solar energy is converted into chemical energy via several energy and electron transfer processes. In the light of these concepts, several applications such as solar cells and light emitting diodes can be improved. To do so, we need to optimize the properties of polyads, oligomers and polymers to device more efficient conjugated materials as well as developing a full understanding of the photo-induced energy and electron transfer processes that occur. Several organometallic oligomers and polymers are presented in this thesis due to their potential photonic applications. In this respect, this master thesis has five chapters. The first one introduces some theoritical principles of photophysics. The second one presents the monitoring of triplet state (T[subscript 1]) energy transfer in a dyad that consists of zinc(II)tetraphenylporphyrin, [ZnTPP], and bis(phenylpyridinato)-(bipyridine)iridium(III), [Ir], chromophores linked by a platinum(II) containing bridge. Despite the conjugation in this dyad and the presence of the [ZnTPP] energy donor and the [Ir] energy acceptor species, no T[subscript 1] [Ir] → S[subscript 1]/T[subscript 1] [ZnTTP] energy transfer occurs. This result was explained by the absence of MO overlap between HSOMO(donor*) and HSOMO(acceptor), LSOMO(donor*) and LSOMO(acceptor) , and hence no efficient double electron transfer exchange (i.e. Dexter mechanism) is likely to occur. This chapter suggested that Dexter formulation, k[subscript Dexter] = KJexp(-2r[subscript DA]/L), appears as an approximation. This work has been published in ChemComm (2013, 49, 5544-5546). The third chapter shows an unexpected slow singlet energy transfer in a dyad built upon a zinc(II)porphyrin and the corresponding free base chromophores linked by a palladium(II)- containing bridge (trans-PdI[subscript 2]), despite the presence of conjugation and the relative short center-to-center distance. This behavior was explained by two factors, the first is the lack of large molecular orbitals (MOs) overlaps between the frontier MOs of the donor and acceptor, and thus preventing a double electron exchange to occur through the trans-PdI[subscript 2] bridge. The second factor affected the energy transfer is the electronic shielding induced by the presence of this same linker, namely the electron rich iodides, preventing the two VI chromophores to fully interact via their transition dipoles. This work has been accepted on 2014-05-26 in Chemistry-A European Journal (chem.201403146). The fourth chapter reports an ultrafast singlet energy transfer (650 fs) in a dyad composed of a zinc(II)porphyrin (donor) and a free base porphyrin (acceptor) [beta],[beta]-linked via trans- Pd(NH)[subscript2](C=O)[subscript 2]. These results were explained by the presence of strong MO couplings of the donor and acceptor and the very weak atomic contribution of the Pd(II) atom to this MO. This dyad shows the fastest energy transfer rate k[subscript ET] among other similar dyad systems incorporating a bridge either in the form of a metal fragment or carbon-based. The results of these third and fourth chapters showed that the Förster mechanism is not enough to account for the energy transfer in some systems and other factors affect that transfer. This work has been submitted in JACS ( ja-2014-061774, 19-6-2014). In chapter 5, the synthesis of bis-[alpha]-(amino(4-ethynylbenzene (trimethylsilane)(R))bis(4- ethynylbenzene-(trimethylsilane))quinone diimine (R = H, Boc) as a model for conjugated and unconjugated porphyrin dye polymers was proposed. The central core of the desired compound, tetrakis(4-ethynlypenyl)quinone-1,4-diimine-2,5-diamine, provided evidence for a charge transfer interaction from the electron richer terminal groups to be more electron poorer benzoquinone ring. The nature of the emission of the core compound was found to be fluorescence at 77K for the case R = H but was too weak to be observed at 298K. No emission was detected for the case R = Boc. Unfortunately, the synthetic route of the desired compound gave the reduced form. The analyses of the reduced compound showed the complete absence of the charge transfer or any communication between the different chromophores due to the broken conjugation between the porphyrin units in the reduced product. This work will be submitted to Journal of Inorganic and Organometallic Polymers and Materials.
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Hofmann-Mees, Dirk [Verfasser], and Stephan [Akademischer Betreuer] Kümmel. "Charge and excitation-energy transfer in time-dependent density functional theory / Dirk Hofmann-Mees. Betreuer: Stephan Kümmel." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059353652/34.
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Kohlhoff, Mike. "Developing surface ionisation charge-transfer dynamics of hydrogen Rydberg atoms into an energy-resolved probe of surfaces." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:dd2cd7ea-689a-4707-88e3-0d5f0eb01e88.
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As a Rydberg atom approaches a surface, it will eventually undergo ionisation by charge transfer into the surface at a distance of about 100nm (for principal quantum numbers n > 20). The dynamics of this process are sensitive to the electronic and geometric structure of the surface and can display signature characteristics. As such, Rydberg atoms can be used to probe image-charge effects or to measure small superficial electric stray or patch fields. The charge-transfer process can be in resonance between the Rydberg energies and the energetically discrete surface states (image states) in a bandgap. Surface ionisation of Rydberg atoms is investigated for graphene, which is a zero-bandgap semiconductor and can behave either as a metal or a semiconductor. The charge-transfer dynamics observed here exhibit the characteristics of a metal with enlarged ion detection efficiency compared to a copper sample -- in accordance with other properties of graphene, such as conductivity, that are enlarged compared with a regular metal. For hydrogen Rydberg atoms, surface ionisation is detected for distances up to 10 µm, with a double series of high-lying image states extending far from the graphene film possibly creating a quasi-continuum at large atom-surface separations with a density of states beyond the resolution of the Rydberg states from n=20 to 40. The resonance behaviour for graphene is explored with a range of Rydberg H-atom collisional velocities whose effect on the charge transfer process introduces an additional handle on the probing of electronically discrete features of a surface. A wave-packet propagation study of a hydrogen atom incident at a free-metal surface up to n=20 displays shifts in ionisation towards greater distances and over a narrower range when acceleration of the ion core is not included. The thereby significantly reduced effect of the collisional velocity of Rydberg surface ionisation is also observed in an experimental study with a limited velocity range available from supersonic expansion directed at a gold sample. This either suggests that the range of Rydberg projectile velocities is to narrow to have observable effects or that a pronounced velocity dependency is merely detected for distinct electronic resonances. With the aim to further elucidate the velocity dependence and to prospectively remove ambiguities that arise from the nature of the experiment, a chip-based decelerator is constructed and integrated into the experimental apparatus for the first time. Within the constraints of the design and the existing apparatus, the chip device is not able to produce sufficient densities of decelerated particles to be employed in surface-ionisation experiments. Extensive modelling of the deceleration process indicates that modifications to the existing design and the experimental apparatus could achieve a tunable-velocity source of hydrogen Rydberg atoms with greatly enhanced densities for future investigations.
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Han, Jie [Verfasser], and Andreas [Akademischer Betreuer] Dreuw. "A Quantum Chemical Look at Energy and Charge Transfer in N-Heteropolycycles / Jie Han ; Betreuer: Andreas Dreuw." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1210647729/34.
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Abrahams, Dhielnawaaz. "Charge Transfer and Capacitive Properties of Polyaniline/ Polyamide Thin Films." University of the Western Cape, 2018. http://hdl.handle.net/11394/6361.
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Magister Scientiae - MSc (Chemistry)Blending polymers together offers researchers the ability to create novel materials that have a combination of desired properties of the individual polymers for a variety of functions as well as improving specific properties. The behaviour of the resulting blended polymer or blend is determined by the interactions between the two polymers. The resultant synergy from blending an intrinsically conducting polymer like polyaniline (PANI), is that it possesses the electrical, electronic, magnetic and optical properties of a metal while retaining the poor mechanical properties, solubility and processibility commonly associated with a conventional polymer. Aromatic polyamic acid has outstanding thermal, mechanical, electrical, and solvent resistance properties that can overcome the poor mechanical properties and instability of the conventional conducting polymers, such as polyaniline.
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Glik, Elena A. "Spectroscopic Investigation of the Excited State Properties of Platinum(Ii) Charge Transfer Chromophores." Bowling Green, Ohio : Bowling Green State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1256141493.
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Wang, Jianren. "Nanostructured Redox-Active Mesoporous Silica Films Based on An Electron-Hopping Mechanism : Charge Transfer Behaviors And Energy Storage Potentials." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0216.
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Un nouveau type de matériaux de stockage d'énergie à base de silice fonctionnant avec un mécanisme de saut d'électrons a été préparé en combinant une méthode d'auto-assemblage électrochimique (EASA) et une réaction de clic d'azide-alcyne catalysée par le cuivre (CuAAC). Les centres actifs redox (molécules de ferrocène ou de cobaltocénium) répartis à la surface du film de silice peuvent directement commuter les électrons par le biais du processus de saut d'électrons. Les résultats démontrent que ce mécanisme de transfert de charge est capable de fournir un taux de transfert d'électrons rapide même sur le substrat de silice isolant, ce qui se traduit par une performance de taux supérieure par rapport aux matériaux faradiques traditionnels. La haute densité des molécules redox et la voie de diffusion des contre-ions lisses ont été identifiées comme jouant un rôle essentiel pour assurer le processus de saut d'électrons rapide. En outre, l'assemblage à grande échelle du système de saut d'électrons a été réalisé en générant le film de silice fonctionnalisé au ferrocène sur une électrode autoportante en mousse de graphène, présentant une densité de capacité 100 fois plus élevée que celle générée sur une électrode ITO, tout en maintenant la performance de taux élevé. Enfin, une tentative a été faite pour assembler la silice fonctionnalisée au ferrocène sur un dispositif planaire flexible, et les résultats préliminaires ont prouvé la faisabilité de l'idée que nous proposons. Globalement, dans cette thèse, l'étude systématique du potentiel du processus de saut d'électrons dans le domaine du stockage de l'énergie, qui pourrait ouvrir une nouvelle voie pour la construction de matériaux de stockage de l'énergieA new type of silica-based energy storage materials operating with electron-hopping mechanism has been prepared by combining electrochemically-induced self-assembly method (EASA) and a copper-catalyzed azide-alkyne click (CuAAC) reaction. The redox active centers (ferrocene or cobaltocenium molecules) distributed on the surface of the silica film can directly commute electrons via the electron-hopping process. The results demonstrate this charge transfer mechanism is able to deliver a fast electron transfer rate even on the insulating silica substrate, resulting in a superior rate performance in comparison to the traditional faradic materials. The high density of redox molecules and the smooth counter ions diffusion pathway have been identified playing a pivotal role to ensure the fast electron-hopping process. Besides, the large-scale assembly of the electron-hopping system has been achieved by further generating the ferrocene functionalized silica film on a free-standing graphene foam electrode, exhibiting a 100-times higher capacity density, in comparison to that generating on ITO electrode, while maintaining the high rate performance. Finally, an attempt has been tried to assemble the graphene-supported ferrocene-functionalized silica into a flexible planar device, and the preliminary results has proved the feasibility of our proposed idea. Overall, in this thesis, the systematical study for the potential of the electron-hopping process in the energy storage field, which may pave a new way for the construction of energy storage materials
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Unal, Ridvan. "Energy and charge state dependences of transfer ionization to single capture ratio for fast multiply charged ions on Helium /." Search for this dissertation online, 2001. http://wwwlib.umi.com/cr/ksu/main.
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Forker, Roman. "Electronic Coupling Effects and Charge Transfer between Organic Molecules and Metal Surfaces." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26163.
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We employ a variant of optical absorption spectroscopy, namely in situ differential reflectance spectroscopy (DRS), for an analysis of the structure-properties relations of thin epitaxial organic films. Clear correlations between the spectra and the differently intense coupling to the respective substrates are found. While rather broad and almost structureless spectra are obtained for a quaterrylene (QT) monolayer on Au(111), the spectral shape resembles that of isolated molecules when QT is grown on graphite. We even achieve an efficient electronic decoupling from the subjacent Au(111) by inserting an atomically thin organic spacer layer consisting of hexa-peri-hexabenzocoronene (HBC) with a noticeably dissimilar electronic behavior. These observations are further consolidated by a systematic variation of the metal substrate (Au, Ag, and Al), ranging from inert to rather reactive. For this purpose, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is chosen to ensure comparability of the molecular film structures on the different metals, and also because its electronic alignment on various metal surfaces has previously been studied with great intensity. We present evidence for ionized PTCDA at several interfaces and propose the charge transfer to be related to the electronic level alignment governed by interface dipole formation on the respective metalsZur Analyse der Struktur-Eigenschafts-Beziehungen dünner, epitaktischer Molekülfilme wird in situ differentielle Reflexionsspektroskopie (DRS) als Variante der optischen Absorptionsspektroskopie verwendet. Klare Zusammenhänge zwischen den Spektren und der unterschiedlich starken Kopplung zum jeweiligen Substrat werden gefunden. Während man breite und beinahe unstrukturierte Spektren für eine Quaterrylen (QT) Monolage auf Au(111) erhält, ist die spektrale Form von auf Graphit abgeschiedenem QT ähnlich der isolierter Moleküle. Durch Einfügen einer atomar dünnen organischen Zwischenschicht bestehend aus Hexa-peri-hexabenzocoronen (HBC) mit einem deutlich unterschiedlichen elektronischen Verhalten gelingt sogar eine effiziente elektronische Entkopplung vom darunter liegenden Au(111). Diese Ergebnisse werden durch systematische Variation der Metallsubstrate (Au, Ag und Al), welche von inert bis sehr reaktiv reichen, untermauert. Zu diesem Zweck wird 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA) gewählt, um Vergleichbarkeit der molekularen Filmstrukturen zu gewährleisten, und weil dessen elektronische Anordnung auf verschiedenen Metalloberflächen bereits eingehend untersucht worden ist. Wir weisen ionisiertes PTCDA an einigen dieser Grenzflächen nach und schlagen vor, dass der Ladungsübergang mit der elektronischen Niveauanpassung zusammenhängt, welche mit der Ausbildung von Grenzflächendipolen auf den entsprechenden Metallen einhergeht
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Yu, Yongze Yu. "Interfacial Electron Transfer in p-Type Dye-Sensitized Nickel Oxide and Machine Learning for Energy Materials." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1564756409299145.
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Menting, Raoul Verfasser], Beate [Akademischer Betreuer] Röder, Oliver [Akademischer Betreuer] [Benson, and Christian [Akademischer Betreuer] Brückner. "Light-induced energy and charge transfer processes in artificial photosynthetic systems / Raoul Menting. Gutachter: Beate Röder ; Oliver Benson ; Christian Brückner." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://d-nb.info/1030313601/34.
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Menting, Raoul Merijn [Verfasser], Beate Akademischer Betreuer] Röder, Oliver [Akademischer Betreuer] [Benson, and Christian [Akademischer Betreuer] Brückner. "Light-induced energy and charge transfer processes in artificial photosynthetic systems / Raoul Menting. Gutachter: Beate Röder ; Oliver Benson ; Christian Brückner." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://nbn-resolving.de/urn:nbn:de:kobv:11-100206833.
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Ratza, Viktor [Verfasser]. "Multi-stage Micropattern Gaseous Detectors for the ALICE TPC Upgrade - Studying and Modelling Charge Transfer and Energy Resolution / Viktor Ratza." Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1218301554/34.
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Planells, Dillundé Miquel Angel. "Design and synthesis of organic sensitizers for dye solar cells: molecular structure vs device performance." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/9054.
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La present tesi esta focalitzada tant en la síntesi de molècules orgàniques òpticament actives així com en la seva aplicació i caracterització en dispositius fotovoltaics, concretament per a les cel·les solars sensibilitzades amb colorant (DSSC en anglès). Les DSSC són cel·les foto-electroquímiques formades per colorant ancorat a un semiconductor (normalment TiO2) i en presencia d'un electròlit. En aquests dispositius, cada component té un efecte clau en la eficiència final de la cel·la, degut als processos de transferència electrònica que tenen lloc la interfície TiO2/colorant/electròlit. Aquests processos varen ser estudiat en gran detall utilitzant porfirines, perilens i D - - A com a colorants, per poder així definir uns paràmetres amb els quals l'eficiència final del dispositiu es pugui correlacionar amb l'estructura molecular del colorant. Entendre aquesta relació entre l'estructura química i l'eficiència del dispositiu permet un millor diseny de futures molecules per a DSSC.The present thesis focuses on the synthesis of organic chromophores as well as their use in optoelectronic devices, particulary in Dye Sensitized Solar Cells (DSSC). This kind of solar cell is based on a photoactive unit, a dye, anchored to a nanostructured metal-oxide semiconductor, usually TiO2, in a redox electrolyte media and sandwiched between two contact electrodes. In DSSC devices, each component (semiconductor, sensitizer and electrolyte) plays an important role in determining the final device efficiency, in a large part due to the charge transfer processes that take place at the TiO2/dye/electrolyte interface. Therefore, these charge transfer kinetics were studied using porphyrins, perylenes and donor - - acceptor organic dyes in order to understand and establish a relationship between the molecular structure and the device performance. Improved understanding of this relationship is crucial for improved molecular design of future dyes for DSSC.
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Moberg, Simon. "Artificial photosynthesis - 4-Aminobenzoic acids effect on charge transfer in a photo catalytic system." Thesis, Uppsala universitet, Materialteori, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-390835.
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Artificial photosynthesis is used to harvest solar energy and store it in the form of chemical bonds. The system of interest in this study does this by splitting water into hydrogen and oxygen gas through a plasmon assisted process, collective oscillations from free electron gas. This is a renewable way to store energy that could be used as an alternative to fossil based fuel. In this study, a small part of this photo catalytic system is studied, namely the interaction between plasmonically active silver nanoparticles (Ag NPs) transferring photo-excited electrons via a linker molecule, 4-aminobenzoic acid (pABA). The pABA linker molecule transfers charge from the Ag surface to a semiconductor and a catalyst performing the water splitting. The pABA can bind in different ways onto the Ag-surface and the aim of this study is to examine which bond is strongest and which best enables charge transfer. To this purpose three systems where simulated quantum mechanically using a supercomputer. The total free energy of the systems was computed and compared. Out of the three studied binding sites, the hollow-site bond (pABA binding to three silver atoms) was found to have the lowest energy, meaningit's the strongest of the possible bonds. Additionally it was found that the band gap (the energy needed to transfer charge) for the pABA decreased when bound to the Ag-surface. The hollow-site bound pABA also had the smallest band gap, meaning it requires the least energy to transfer a charge and should therefore be the best bond fitted for the photo catalytic system.Artificiell fotosyntes används för att absorbera solenergi och förvara den i formen av kemiska bindningar. Systemet som används i denna studie gör detta genom att splittra vatten till vätgas och syrgas genom en plasmon assisterad process. Detta är ett förnyelsebart sätt att förvara energi och kan användas som ett alternativ till fossila bränslen. I denna studie studeras en liten del utav detta fotokatalytiska system nämligen interaktionen där plasmonaktiva silvernanopartiklar (Ag NPs) överför foto-exciterade elektroner genom molekyllänken 4-aminobensoesyra (pABA). Molekyllänken pABA överför laddning från silverytan till en halvledare och en katalys som utför splittringen av vattnet. pABA kan binda på olika sätt tillen silveryta och denna studie syftar till att undersöka vilken utav bindningarna som är starkast och vilken som effektivast överför laddning. För att göra detta simulerades tre system kvantmekaniskt med hjälp av en superdator, ett system för varje sorts bindning. Den totala fria energin av systemen beräknades och jämfördes. Av de tre undersökta bindningarna hadehollow-site bindningen (pABA som binder till tre silveratomer) längst energi, vilket betyder att det är den starkaste av bindningarna. Utöver detta så visade det sig att bandgapet (energin som krävs för att överföra laddning) minskade för pABA när den var bunden till Ag-ytan. Hollow-site bundet pABA hade även minst bandgap, vilket betyder att den kräver minst energi för att överföra laddning och är därmed den mest effektiva bindningen för det fotokatalytiska systemet.
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Valenta, Christopher Ryan. "Microwave-energy harvesting at 5.8 GHz for passive devices." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52295.
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The wireless transfer of power is the enabling technology for realizing a true internet-of-things. Broad sensor networks capable of monitoring environmental pollutants, health-related biological data, and building utility usage are just a small fraction of the myriad of applications which are part of an ever evolving ubiquitous lifestyle. Realizing these systems requires a means of powering their electronics sans batteries. Removing the batteries from the billions or trillions of these envisioned devices not only reduces their size and lowers their cost, but also avoids an ecological catastrophe.
Increasing the efficiency of microwave-to-DC power conversion in energy-harvesting circuits extends the range and reliability of passive sensor networks. Multi-frequency waveforms are one technique that assists in overcoming the energy-harvesting circuit diode voltage threshold which limit the energy-conversion efficiency at low RF input powers typically encountered by sensors at the fringe of their coverage area.
This thesis discusses a systematic optimization approach to the design of energy-conversion circuits along with multi-frequency waveform excitation. Using this methodology, a low-power 5.8 GHz rectenna showed an output power improvement of over 20 dB at -20 dBm input power using a 3-POW (power-optimized waveform) compared to continuous waveforms (CW). The resultant efficiency is the highest reported efficiency for low-power 5.8 GHz energy harvesters. Additionally, new theoretical models help to predict the maximum possible range of the next generation of passive electronics based upon trends in the semiconductor industry. These models predict improvements in diode turn-on power of over 20 dB using modern Schottky diodes. This improvement in turn-on power includes an improvement in output power of hundreds of dB when compared to CW.
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Nano, Adela. "Towards optical memories : switchable optical systems for electron and energy transfer processes." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF011/document.
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Le travail de cette thèse de doctorat est axé sur le design, la synthèse et la caractérisation de systèmes moléculaires organiques et organométalliques luminescents dans le but de déclencher des processus de transfert photoinduit d’électron (PeT) ou d’énergie (EET) pour des applications dans les dispositifs optiques ou électroniques. Nous nous sommes d’abord intéressés aux molécules de type push-pull car elless’avèrent être des modèles intéressants pour l’étude du PeT. Nos systèmes sont construits autour de BτDIPY qui sert d’espaceur entre le donneur d’électron (julolidine ou triazatruxène) et l’accepteur d’électron (une unité dicyanovinyl). Les études en électrochimie et spectroscopie ont montrés un caractère à transfert de charge très prononcé. Entre autre nous avons synthétisé et étudié une série de ligands de type N^O (type base de Schiff) dérivés de la julolidine, une amine cyclique avec des propriétés électroniques très inattendues. Ces ligands, subissent des processus de transfert photoinduit de proton à l’état excité (ESIPT) et leurs spectres d’émission présentent une luminescence panchromatique. La compléxation desligands N^O au BF2 supprime l’ESIPT et augment les rendements quantiques de fluorescence. Les ligands derivés de la julolidine sont combinés avec d’autres unités chromophoriques i.e. Ir(III), Pt(II) afin de construire des systèmes multichromophoriques et stimuler des processus de EET entre les composants.Lors de ces travaux de thèse nous nous somme particulièrement intéressés aux systèmes moléculaires photocommutables dont l’unité centrale est un photochrome, le [1,3]oxazine. L’oxazine est combiné à un module moléculaire qui sert de donneur d’énergie et un module accepteur d’énergie choisie de façon optimale afin d’induire un transfert électronique d’énergie de manière contrôléThe present doctoral thesis work deals with the design, synthesis and characterization of organic and organometallic luminescent molecular frameworks for triggering Photoinduced electron Transfer (PeT) and Electronic Energy Transfer (EET) processes for applications in optical andelectronic devices. First, we turned toward the organic push-pull chromophores because they are useful model systems for studying the mechanism of PeT process. We synthesized new push-pull systems bearing a dicyanovinyl fragment as the electron-acceptor and a strong electron-donorsuch as julolidine and triazatruxene covalently linked through a BODIPY dye bridge. Electrochemical and photophysical studies showed a pronounced charge transfer character within the new push-pull systems. Furthermore, we synthesized and studied a series of chelating N^O-type ligands (Schiff base-type), based on the strong electron-donating julolidine motif, displaying ESIPT process. Their luminescence profiles exhibited panchromatic luminescence band covering the whole visible spectrum. Complexation of N^O-site with boron difluoride fragment suppressed the ESPIT process and highly increased the fluorescence quantum yield. The N^O-chelating ligands were combined with Pt(II) chromophore, B(III) and Ir(III) such as to obtainmultichromophoric frameworks. According to the photophysical studies, EET processes were observed within the multichromophoric systems. We successfully obtained a new florescent switching triad constructed around a photochromic core, [1,3]oxazine, which bears an energy-donor and an energy-acceptor module such as to directly control the EET process