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1
LEE, CHERYLYN. "PHOTO-INDUCED RADICAL COPOLYMERIZATIONS OF ELECTRON-RICH OLEFINS WITH ELECTRON-POOR OLEFINS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184135.
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This study is a systematic investigation of the parameters and conditions necessary for photo-induced radical copolymerizations of donor olefins with acceptor olefins in the absence of an initiator. Very few cases have been previously reported and no mechanistic details of the initiation have been proposed in the literature. Our results show that the photoinitiation depends on the relative donor and acceptor strengths of the monomers, as well as the solvent. The highest occupied molecular orbital (HOMO) of the donor and the lowest unoccupied molecular orbital (LUMO) of the acceptor must be at the appropriate energy levels in order to produce a radical initiating species upon photoexcitation of the electron donor-acceptor (EDA) complex. If the donor-acceptor interaction is too weak, no copolymerization occurs. The excited complex (contact ion pair) presumably decays back to the ground state faster than producing an initiating species. If the donor-acceptor interaction is too strong, the excited complex dissociates to the free ions which could initiate ionic homopolymerization rather than radical copolymerization. The solvent may also determine the course of the reaction. In two cases, copolymerizations, which could be photo-induced in 1,2-dichloroethane, could not be photo-induced in acetonitrile. Dissociation of the excited complex (contact ion pair) is favored in polar solvents, such as acetonitrile, which are able to stabilize the ion radicals. This initiation method produces high molecular weight copolymers that may be cast into transparent films.
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Cameron, Joseph. "Small molecules based on novel electron-deficient acceptor units for organic electronic applications." Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26932.
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Demand for photovoltaic cells is ever-increasing due to the diminishing supply of oil-based fuels and the associated harmful environmental effects. Organic photovoltaic devices offer a light and flexible alternative to Si-based PVs. In addition to this, they can be processed using fabrication methods such as spin-coating and inkjet printing hence, such devices have potential to be produced cheaply on a large scale. Although they have been applied as donor materials with success, polymers often show end-group variation and are polydisperse so there can be batch-to-batch variation with respect to OPV performance. A solution to these problems is the use of small donor molecules which are monodisperse and have well-defined structures. However, the shorter conjugation of small molecules with respect to polymers requires measures to shorten the HOMO-LUMO gap. A common approach is the incorporation of electron-deficient acceptor units into the donor molecule, lowering the LUMO level and therefore the HOMO-LUMO gap. Chapter 1 reviews band theory, the development of organic semiconductors, including a summary of oligothiophene based materials and common electron-deficient acceptor units used, the principles behind OPV and OFET devices and how organic semiconductors can be optimised in order to produce the best working devices. The synthesis, physical properties and OPV performance of materials based on naphthyridine-2,6-dione acceptor unit are presented in chapter 2, focussing on the difference between compounds with Donor-Acceptor-Donor and Acceptor-Donor-Acceptor structures. Chapter 3 shows the novel naphthyridin-2-one moiety and the synthesis of materials containing the unit and how they have been used for different applications including ambipolar OFETs and both donor and acceptor materials for bulk heterojunction OPV devices. A study in improving the mobility of OFET devices is presented in chapter 4. Different inorganic nanoparticles were added to organic semiconductor solutions for and the effect of this simple process on the performance of the OFET devices is discussed. Chapter 5 introduces the thieno[3,2-b]thiophene-2,5-dione and novel furo[3,2-b]furan-2,5-dione acceptor units. The synthesis, optical and electrochemical properties, and OFET and OPV device optimisation of materials based on these moieties are presented and discussed. A summary of the work discussed is presented in chapter 6 whilst chapter 7 presents the experimental methods for electrochemistry, device work, and synthetic procedures for each compound presented in Chapters 2, 3, 4 and 5.
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Xu, Yunhua. "Synthesis and Photoinduced Electron Transfer of Donor-Sensitizer-Acceptor Systems." Doctoral thesis, Stockholm : Department of Organic Chemistry, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-411.
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Sujka, Marta. "Alignment and rectifying properties of donor-electron bridge-acceptor molecules." Thesis, Cranfield University, 2007. http://hdl.handle.net/1826/2295.
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Molecular electronics based on the bottom-up approach appears to be a promising
alternative to overcome the limitations of the top-down lithographic fabrication of
electronic devices. The ability to manipulate single or small groups of molecules
provides a great opportunity to build electronic devices at the molecular level. However,
before any device can be constructed, it is vital to understand the parameters that control
the device properties such as: molecular structure, conformation and arrangement at the
surface, the molecule-substrate and molecule-electrode interactions.
This thesis presents an investigation of the alignment of acceptor-electron bridge-donor
structures and describes how the molecular structure and arrangement affect rectifying
properties of the monolayers. Studies included typical Langmuir-Blodgett (LB),
chevron-shaped, and ionically coupled structures that were characterised using various
techniques, such as Quartz Crystal Microbalance (QCM), Surface Plasmon Resonance
(SPR), Second Harmonic Generation (SHG) and Scanning Tunnelling Spectroscopy
(STS).
The results obtained showed that to achieve high rectification the molecules must form
ordered and stable monolayers that are able to withstand the electric field applied to the
junction. It was also shown that due to the disordered monolayer formation and
presence of certain ions, it was extremely difficult to state without doubt whether the
rectification was a result of the donor-electron bridge-acceptor structure proposed by
Aviram and Ratner1.
Studies of chevron-shaped molecules confirmed the possibility of depositing them
using the LB technique. However, the reduction of long aliphatic chains was very likely
balanced by the formation of less ordered or unstable monolayers. The highest
rectification ratio of 30 ± 3 at ± 1 V was obtained for 1-butyl-2,6-bis-[2-(4-
dibutylamino-phenyl)-vinyl]-pyridinium iodide (dye 7) and the origin of the I-V
asymmetry was attributed to back electron transfer from iodide to pyridinium ring.
Although dye 1-butyl-2,6-bis-(2-{4-[2-(4-dibutylamino-phenyl)-ethyl]-phenyl}-vinyl)- pyridinium iodide (dye 9) showed electrical asymmetry (RR=16 at plus/minus 1 V) shortly after
deposition onto the gold-coated highly oriented pyrolytic graphite (HOPG), it seemed
to form an unstable alignment and as a consequence the rectification decayed over a
period of a few hours.
Improved ordering, stability, and rectification were achieved from ionically coupled
structures, where the monolayers were formed using chemisorption and ionic assembly
instead of physisorption.
5
Keiderling, Chaz. "Photo-physical studies of electron acceptor function in organic photovoltaics." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/54645.
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Substantial progress has been made in achieving increasingly high organic photovoltaics (OPV) power conversion efficiencies. Progress has largely been derived from the development of new donor materials, as until recently a notable scarcity of successful electron acceptor materials remained. [6,6]-phenyl C60 butyric acid methyl ester (PC60BM) or other fullerene derivatives have been the centrepiece of the accepting materials used throughout OPV research, and they have only recently been accompanied by rare examples of novel non-fullerene alternatives. However, the current understanding of the properties of effective electron acceptors for OPV is still relatively limited. In this thesis, attention is paid to the photophysical properties of accepting materials with respect to charge photogeneration and recombination. The work is comprised of three closely linked studies. The first is a detailed exploration of the photophysical properties expressed by PCxBM. This is followed by a consideration of a newly synthesised PDI derivative, tasked with specific design rules to address prior limitations identified by previous perylene diimide (PDI) acceptors. The third study entails a broad comparison of a selection of accepting materials utilising bilayer fabrication to remove morphological variation. Chapter 3 outlines detailed understandings of the photophysical properties of PCxBM excitons. In particular, exciton characteristics are reported as a function of film morphology. Transient absorption measurements show a significant reduction in intersystem crossing and strong shifts in excited state absorption spectra in neat PCxBM films when compared to dispersed molecules within an amorphous polystyrene system. Additionally, neat PCxBM films show an increased formation of free charges when compared to the dispersed systems. An alternative model of excitonic formation from PCxBM systems between aggregated and dispersed systems is proposed. Chapter 4 introduces a newly synthesised amorphous perylene, PDISO, that is designed to remove the typical problem of aggregation in blends. Using a range of spectroscopic and microscopy techniques, the progression of absorption to charge formation is characterised for PCDTBT:PDISO blend films, drawing a direct comparison to the same processes in PCDTBT:PC70BM blend films. In this way, PDISO is demonstrated to overcome key loss mechanisms previously reported to limit efficiencies in PDI blends and determines the optimum blend ratio for charge generation with PCDTBT. Chapters 5 and 6 jointly establish an understanding of solution-processed bilayers, which is followed by a comparison across several acceptors with the two polymers PCDTBT & PBDTTT-CT (chosen for their ability to generate charges). The comparison demonstrates that recombination dynamics fundamentally illustrate dramatic differences between acceptors. This provides evidence that morphologically independent charge dynamics can significantly affect overall device performance post separation. Correlations among the bilayer device performance, acceptor dielectric-mobility product and recombination dynamics are demonstrated. The outcomes in this thesis together draw a complex picture of multiple factors that affect the performance of electron-accepting materials in OPV. This provides a suitable platform for identifying important parameters when designing and testing new accepting materials. It also highlights potentially critical gaps in the current experimental understanding of fundamental charge interaction and recombination dynamics.
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Cubberley, Mark Stull. "Investigation of solvent effects in aromatic electron donor-acceptor interactions /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Hoefler, Christoph. "Preparation of electron donor and acceptor molecules for porphyrin derivatization." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4317.
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Porphyrins derivatized with electron donating and electron withdrawing groups can be used for artificial photosynthesis. Four new compounds, two electron donors and two electron acceptors, have been synthesized for prospective porphyrin linkages.
8
Bröker, Benjamin. "Electronic and structural properties of interfaces between electron donor & acceptor molecules and conductive electrodes." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16257.
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Die vorliegende Arbeit behandelt Fragestellungen aus der Organischen Elektronik, in der die Ladungsträgerinjektion in alle Arten von Bauteilen kritisch von der elektronischen und morphologischen Struktur der Grenzflächen zwischen Elektrode und den konjugierten organischen Molekülen (KOM) abhängt. Näher betrachtet wurden: die Energieniveauanpassung mit starken (i) Elektronendonatoren und (ii) -akzeptoren und (iii) die dichteabhängige Umorientierung einer molekularen Monolage. Zur Analyse wurden Photoelektronen- und Reflektionsabsorptionsinfrarotspektroskopie angewandt. Weitere Informationen konnten durch Modellierung mit Dichtefunktionaltheory gewonnen werden, die über Kollaborationen zur Verfügung standen. (i) Das Konzept der optimierten Energieniveauanpassung mit starken Elektronenakzeptoren konnte auf Donatoren erweitert und damit erfolgreich von der Anode zur Kathode transferiert werden. Auch hier führte der Ladungstransfer zu einem Dipol über die Grenzfläche, womit die Austrittsarbeit um bis zu 2.2 eV reduziert wurde. Als Resultat konnte die Elektroneninjektionsbarriere in nachfolgende Materialien entscheidend verringert werden (bis zu 0.8 eV). (ii) Ein bis dato unerforschter starker Elektronenaktzeptor [hexaaza-triphenylene-hexacarbonitrile (HATCN)] wurde vollständig verschiedenen Elektroden charakterisiert. HATCN zeigte dabei eine bessere Performance verglichen mit derzeit üblichen Materialien (starke Austrittsarbeitsanhebung und Verringerung der Lochinjektionsbarriere um bis zu 1.0 eV). (iii) Zusätzlich konnte mit HATCN gezeigt werden, dass eine liegende molekulare Monolage durch Erhöhung der Moleküldichte in eine stehende Monolage umgewandelt werden kann. Dies führte zu einer Änderung der chemischen Bindung zum Metall und damit zu einer starken Modifikation der elektronischen Struktur der Grenzfläche. Die vorliegende Arbeit liefert damit wertvolle Informationen für das Verständnis der Grenzfläche zwischen Elektrode und KOM in der Organischen Elektronik.The present work is embedded in the field of organic electronics, where charge injection into devices is critically determined by the electronic and structural properties of the interfaces between the electrodes and the conjugated organic materials (COMs). Three main topics are addressed: energy level tuning with new and strong electron (i) donor and (ii) acceptor materials and (iii) the density dependent re-orientation of a molecular monolayer and its impact on the energy level alignment. To study these topics photoelectron and reflection absorption infrared spectroscopy were used. Moreover, additional information was obtained from density functional theory modelling, which was available through collaboration. (i) A concept of optimizing the energy level alignment at interfaces with strong molecular acceptors was extended to donor materials and thus successfully transferred from the anode to the cathode side of the device. Also in this case, charge transfer leads to a chemisorbed molecular monolayer. Due to the dipole across the interface, the work function of the electrode is reduced by up to 2.2 eV. Consequently, a reduced electron injection barrier into subsequently deposited materials is achieved (up to 0.8 eV). (ii) A yet unexplored strong electron acceptor material [i.e. hexaazatriphenylene- hexacarbonitrile (HATCN)] is thoroughly investigated on various surfaces. HATCN shows superior performance as electron acceptor material compared to presently used materials (e.g. work function modification and hole injection barrier reduction by up to 1 eV). (iii) Also with HATCN, the orientation of a molecular monolayer is observed to change from a face-on to an edge-on depending on layer density. This is accompanied by a re-hybridization of molecular and metal electronic states, which significantly modifies the interface electronic properties. All findings presented are valuable for the understanding of electrode-COM interfaces in organic electronics.
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Andersson, Mikael. "Tuning electron transfer reactions by selective excitation in porphyrin-acceptor assemblies." Doctoral thesis, Uppsala University, Department of Physical Chemistry, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1080.
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This thesis concerns electron transfer reactions from different excited states in porphyrins, and the effect of changing the energy of the link connecting the donor and acceptor. Photoinduced electron transfer, and subsequent processes were studied using ultrashort laser pulses and nanosecond laser flash photolysis.
Excitation of Zn(II)-porphyrins in the Soret band lead to population of the higher lying S2 state. The lifetime and transient absorption spectrum was measured for the S2 state. When an electron acceptor was attached to the Zn(II)-porphyrin, either as an ion pair, or covalently bound through an amide link, electron transfer was found to compete with S2 to S1 relaxation. In the ion pair, electron transfer was faster than 200 fs, with a lifetime of the charge separated state of 1.3 ps. Further, in the covalently linked dyad, the Zn(II) porphyrin triplet state was repopulated from a charge transfer state.
In [2]-rotaxanes, the Zn(II) porphyrin donor (ZnP) and Au(III) porphyrin acceptor (AuP+) are not connected by a direct covalent link. Selective excitation of either the ZnP or the AuP+ resulted in rapid electron transfer from the ZnP to the AuP+. The bis-phenanthroline link connecting the. different porphyrins was changed by coordination of Cu(I) or Ag(I). Electron transfer from the 1ZnP singlet was unaffected by coordination of either Ag(I) or Cu(I), while electron transfer to the 3AuP+ triplet was in the Ag(I) link found to occur by an enhanced superexchange, and by a sequential mechanism in the Cu(I) coordinated link.
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Göransson, Erik. "Bridge Mediated Electron Transfer in Conjugated and Cross-Conjugated Donor-Acceptor Compounds." Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180442.
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Detailed understanding of electron transfer reactions is important in many aspects of chemistry, biology and solar energy conversion. The main aim of this thesis is to provide further insight into electron transfer through highly conjugated bridge structures. Towards this end, three series of donor-acceptor dyads have been studied, all using an oligo(1,4-phenylene-ethynylene) moiety as the bridge. A common theme in these series is that they explore the effects of having either an ethynylene or phenylene as the attachment group between the bridge and the donor or acceptor. Photophysical characterization of these dyads was carried out by means of time resolved laser spectroscopy. The results show that having an ethynylene as attachment group results in higher rates for bridge mediated electron and energy transfer compared to similar systems, where a phenylene was used. It was also found that most of the investigated systems show a fast back electron transfer. A notable exception is a zinc(II) phthalocyanine- gold(III) porphyrin dyad, where very fast photoinduced electron transfer (kPET = 1.0×1012 s-1) was followed by relatively slow back electron transfer (kBET = 1.0×109 s-1). A complementary DFT investigation indicated that the charge shifted state involves a reduction of the gold ion, rather than the porphyrin ring. This results in lower electronic coupling between the reduced gold porphyrin and the bridge and thus slower back electron transfer. A series of zinc porphyrin platinum acetylide dyads was used to explore the effects on electronic coupling of different attachments points on the porphyrin ring. For the investigated system it was found that linking at the meso-position results in an eight-fold increase in electron transfer rate compared to the β-position. In addition, a series of mixed valence compounds was used to investigate electronic coupling mediated by cross-hyperconjugated or cross-π-conjugated bridges. The results indicate coupling elements of 100-400 cm-1, with the cross-π-conjugated bridge having the largest coupling. A complementary TD-DFT study indicates that both through bond and through space coupling can be active in these systems. The relative contribution of these two mechanisms to the electronic coupling is highly conformer dependent.
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Hunger, Christoph [Verfasser], and Mukundan [Akademischer Betreuer] Thelakkat. "Alternative Concepts for Electron Acceptor and Transparent Conducting Electrode in Organic Photovoltaics / Christoph Hunger ; Betreuer: Mukundan Thelakkat." Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/112406396X/34.
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Tsutsumi, Jun'ya. "Solid-state structures and electronic properties of organic molecules fabricated by connecting electron donor and acceptor components." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124380.
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Caulfield, Jason M. "Magnetic quantum oscillations in organic metals based on the molecule bis(ethylenedithio)tetrathiafulvalene." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:5fbf2599-96d8-4eac-b882-ac74213ac3a5.
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ET charge transfer salts (where ET is
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Brinkert, Katharina. "Protein film voltammetry and spectroelectrochemistry of the electron acceptor site in Photosystem II." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/42225.
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The key reaction of oxygenic photosynthesis, the light-driven oxidation of water, is carried out by Photosystem II (PSII), a light-driven water-plastoquinone oxidoreductase. Photosystem II is a multi-cofactor protein and its energetic characterization is quite a difficult undertaking. Electrochemical approaches play an important role as a tool for completing the energetic picture and for carrying out fundamental studies of the enzyme. In this work, two electrochemical methods have been applied to study the electron acceptor site of the Photosystem II: spectroelectrochemistry and protein film voltammetry. The first part focuses on the re-measurement of the midpoint potential of the primary quinone electron acceptor, QA, in PSII core complexes isolated from Thermosynechococcus elongatus and in PSII enriched membranes from spinach using an optical transparent thin layer (OTTLE) cell. The obtained results show that the bicarbonate anion, ligated to the non-heme iron at the electron acceptor site in close proximity to QA, plays a significant role in controlling the redox properties of the QA/QA--couple. This finding explains various controversies about existing literature values of the QA/QA-midpoint potential. The second part describes investigations of photocurrents generated by Photosystem II in metal oxide hybrid systems. PSII isolated from T. elongatus was immobilized onto nanostructured titanium dioxide/indium tin oxide electrodes (TiO2/ITO) and the origin of photocurrent upon illumination was studied. Using conditions in which PSII was immobilized as a monolayer, it was demonstrated that direct electron transfer occurs from the redox cofactor QA to the electrode surface, but that the electron transfer through the metal oxide is the rate-limiting step. Redox mediators enhance the photocurrent by taking electrons from the TiO2 surface to the ITO and not from PSII. Furthermore, the origin of cathodic photocurrents (i.e. electron flow from the electrode) was investigated. The results indicate that a one-electron reduction of oxygen to the superoxide anion radical (O₂·⁻) occurs at the ITO surface in darkness when an external bias lower than +300 mV vs NHE was applied. The findings can explain the light-driven and catalytic nature of this current by the fact that the reduction of O₂·⁻ occurs at the non-heme iron, which is driven by the photo-reduction of QA.
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Robertson, Kevin A. "Anaerobic biodegradation of polycyclic aromatic hydrocarbons using ferric iron as terminal electron acceptor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0003/MQ36074.pdf.
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Pokethitiyook, Prayad. "Nitrate utilization as the final electron acceptor in a biological phosphorus removal system." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040836/.
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Maligaspe, Eranda. "Carbon nanostructured based donor-acceptor conjugates for light-induced energy and electron transfer." Diss., Wichita State University, 2010. http://hdl.handle.net/10057/3636.
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The research presented in this dissertation deals with the syntheses, characterization, electrochemical, computational and photophysical studies of carbon nanostructures such fullerenes, single-wall carbon nanotubes (SWCNT) and highly colored pigment containing donor-acceptor supramolecular assembles. Using these fascinating chromophores, we have designed and synthesized donor-acceptor systems to mimic natural photosynthesis. Photosynthesis involves two major steps, absorption and transportation of light energy to the reaction center, and photoinduced electron transfer (PET) to generate charge separated entities by using the electronic excitation energy.
We have designed elegant photosynthetic architectures using fullerene as carbon nanostructure based material for mimicry of antenna, mimicry of reaction center and mimicry of 'combined antenna-reaction center' functionalities in the natural photosynthetic system. Semiconducting single-wall carbon nanotube (SWNT)-based supramolecular nanoarchitectures are constructed using photosensitizing donor and acceptor molecules which reveal efficient photoinduced charge separation. The kinetic and thermodynamic data suggests feasibility of these nanohybrids for the construction of photovoltaic cell and other devices. Interestingly, the photoelectrochemical behavior of the nanohybrids indicates that by choosing nanotubes of appropriate diameter, it is possible to improve the light-harvesting conversion efficiency.Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
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FERNANDO, AMANDA FABIANA BAIAO. "FE(III) AS ELECTRON ACCEPTOR FOR GASOLINE-ETHANOL BIODEGRADATION IN TROPICAL RESIDUAL SOIL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15948@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOROs hidrocarbonetos monoaromáticos constituintes da gasolina (BTEX) têm sido encontrados em aquiferos devido aos vazamentos de tanques de armazenamento e sua consequente dissolução na água subterrânea. No Brasil existe ainda um agravante: o etanol é utilizado como aditivo à gasolina, o que promove um aumento na profundidade de percolação dos poluentes, já que atua como cossolvente e possui degradação preferencial. Alterações nas condições químicas do meio ambiente proporcionam, por conseqüência, adaptações na dinâmica de sobrevivência da microbiota residente. Em um ambiente redutor com baixo nível de manganês, ausência de nitratos e presença significativa de óxidos de ferro, o Fe(III) passa a ser o receptor de elétrons preferencial para a biodegradação anaeróbia da matéria orgânica. Com o objetivo de avaliar a biodegradação anaeróbia da mistura BTEX-Etanol em aquífero tropical, mediada pela redução de Fe(III), foram desenvolvidos microcosmos anaeróbios, envolvendo solo homogêneo saturado com água não contaminada e água contaminada com mistura de BTEX-Etanol. A partir da quantificação e análise da atividade microbiana degradadora, dos resíduos da contaminação e do teor de Fe(+2), foi possível verificar o aumento da disponibilização de ferro oriundo dos respectivos óxidos e também da produção de Fe(+2) durante o tempo de incubação, bem como o período de adaptação dos microorganismos, variação de sua atividade e a queda dos níveis dos BTEX-Etanol. Estes resultados podem ser um indicativo da ocorrência de uma atenuação natural, porém, estudos mais extensos são necessários, incluindo uma metodologia mais adequada para medir as especiações do ferro.
Gasoline monoaromatic hydrocarbons (BTEX) have been detected in aquifers due to storage tank spills from gas stations that lead to their consequent dissolution on groundwater. An aggravating factor in Brazil is ethanol being used as additive to gasoline, promoting an increase on pollutants percolation in soil since it works as co-solvent and is preferentially degraded. Therefore, changes on environmental chemical conditions promote adaptations of the survival dynamic of native microorganisms. In a reducing environment with low levels of manganese, absence of nitrate and significant presence of iron oxides, Fe(III) becomes the preferential electron acceptor for anaerobic biodegradation of organic matter. In order to evaluate this anaerobic biodegradation of BTEXEthanol mixture in a tropical aquifer, mediated by Fe(III) reduction, anaerobic microcosms were developed involving homogeneous soil saturated with noncontaminated and BTEX-Ethanol contaminated water. Quantifying and analyzing microbial activity, contamination residues and Fe(+2) contents allowed to verify increases of iron availability from the respective oxides and Fe(+2) production throughout the assay, as well as the period of microbial adaptation, the variation of microbial activity and the decrease of BTEX-Ethanol levels. These results may be indicative of the occurrence of natural attenuation. However, more studies are needed, including a better methodology to measure iron speciation in these experimental conditions.
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Holman, K. Travis. "The host-guest chemistry of new members in the cyclotriveratrylene family of cavitands /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924887.
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Lauck, Maximilian Thomas Johannes [Verfasser]. "Cobaltocenium Amides - Photoinduced Electron Transfer Processes in Donor-Acceptor Amides / Maximilian Thomas Johannes Lauck." Mainz : Universitätsbibliothek Mainz, 2020. http://d-nb.info/1205943900/34.
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Niklas, Jens. "Investigation of the electron donor P700 and the electron acceptor A1 in photosystem I of oxygenic photosynthesis using EPR spectroscopy." [S.l.] : [s.n.], 2007. http://opus.kobv.de/tuberlin/volltexte/2007/1552.
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Bhattacharyya, Anjan Kumar. "Intramolecular and intracomplex electron transfer in water soluble redox proteins." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184339.
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Electron transfer to and between the redox centers of milk xanthine oxidase was investigated by laser flash-photolysis. Evidence is presented for slow equilibration of electrons (k < 38 s⁻¹) between the various redox centers of the enzyme. The enzyme-bound flavin and the heme moieties of the flavoprotein and cytochrome subunits of p-cresol methyl hydroxylase from Pseudomonas putida are both reduced rapidly in a second order manner by 5-dRF generated by the laser flash, followed by slower first order intramolecular electron transfer (k = 220 s⁻¹) from the protein-bound neutral flavin radical to the oxidized cytochrome. Complex formation between spinach ferredoxin:NADP⁺-reductase (FNRₒᵪ), spinach ferredoxin (Fdₒᵪ), rubredoxin (Rdₒᵪ) from Clostridium pasteurianum, two homologous HIPIP's from Ectothiorhodospira halophila (iso-1 and iso-2) and two homologous cytochromes (cytochromes-c₂ from Paracoccus denitrificans and Rhodospirrilum rubrum) have been investigated. Evidence is presented supporting the formation of 1:1 complexes that are stabilized by attractive electrostatic interactions at low ionic strength. Kinetic studies of the above-mentioned complexes provide evidence for extremely rapid to relatively slower intracomplex electron transfer rates (k 7000 s⁻¹ to 4 s⁻¹). In addition the effect of complexation on the degree of accessibility of the various redox centers of the respective complexes to reduction by small reductants such as 5-dRF· and LfH· generated by the laser flash has been evaluated. The effect of both pH and ionic strength on the second order rate of reduction and the intracomplex rates in the respective complexes have also been investigated. The results have been interpreted in terms of redox potential differences, electrostatic and structural features that influence the electron transfer rates in these systems.
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Malvisi, Lucio. "Functional characterization of cytochrome b5 reductase and its electron acceptor cytochrome b5 in Plasmodium falciparum." Scholar Commons, 2009. http://scholarcommons.usf.edu/etd/2082.
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Malaria is a disease of major public health importance, killing approximately one million people and causing about 250 million cases of fever annually. It mostly affects children under the age of five and pregnant women in many developing countries, making it a prominent issue in international health and maternal and child health. The most aggressive form of malaria is caused by the parasite Plasmodium falciparum which is responsible for 80% of infections and 90% of deaths from malaria, and is most prevalent in sub-Saharan Africa. Public Health interventions include the implementation of prevention programs, health education, and chemotherapy. The latter has experienced multiple problems in the past years whereby resistance of the parasite to the available drugs has emerged, rendering the majority of them ineffective.
Furthermore, the high cost of those drugs represents a major obstacle to their dispensation in areas of the world where the affected people are often the less fortunate. The enzyme Cytochrome b5 Reductase (cb5r) and its electron acceptor Cytochrome b5 (cb5) play a role in fatty acid elongation, cholesterol biosynthesis, and cytochrome P450-mediated detoxification of xenobiotics. Therefore, these proteins are suitable as potential novel drug targets for malaria. These two proteins have been thoroughly studied in mammals but have to be characterized in microorganisms such as fungi and parasites, including Plasmodium falciparum. It is important to note that plant cb5r has been identified as a novel herbicidal target. Considering the close phylogenetic relationship between plant cb5r and Plasmodium falciparum cb5r, we conclude that these plant inhibitors may also serve as promising candidates for a new class of antimalarial drugs against the parasite.
In this project, we want to obtain the biochemical and enzymatic characterization of cb5r and cb5 in order to establish whether these two proteins represent potential novel drug targets in Plasmodium falciparum malaria. This initial work may lead to the development of novel drugs which will consequently affect the field of public health with respect to drug delivery, drug resistance, and drug chemotherapy.
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Matos, Mariana Campos de. "Efficient succinic acid production from glycerol by actinobacillus succinogenes using dimethyl sulfoxid as electron acceptor." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/7818.
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Malvisi, Lucio. "Functional characterization of cytochrome b₅ reductase and its electron acceptor cytochrome b₅ in Plasmodium falciparum." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003265.
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Webre, Whitney Ann. "Spectral, Electrochemical, Electron Transfer, and Photoelectrochemical Studies of Tetrapyrrole Derived Supramolecular Systems." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609091/.
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Energy- and electron-transfer processes in molecular and supramolecular donor-acceptor systems are of current interest in order to develop light-energy harvesting systems through designing covalently linked donor-acceptor systems or utilizing self-assembled donor-acceptor systems. The research presented in this dissertation deals with the electrochemical, anion binding, and photochemical studies of various oxoporphyrinogen (OxPs), porphyrin, corrole, and phenothiazine systems. The first chapter provides a brief introduction to the material discussed in the subsequent chapters. The second chapter discusses the bromination of meso-tetraarylporphyrings and how that affects their electrochemical, catalytic, and other properties. Bromination of these porphyrins and oxoporphyrinogens allow the HOMO-LUMO gap to increase revealing blue-shifted absorption. Brominated OxPs and bis-crown ether OxP self-assembled with anions depending on strength of the anion and size of the binding site. The addition of crown ethers allows a cation binding site which makes a self-assembled donor-acceptor supramolecular system.Chapters 5 and 6 discuss a series of donor-acceptor conjugates based on zinc porphyrin as the electron donor and copper(III) corrole as the electron acceptor. These studies illustrate the importance of copper(III) corrole as a potent electron acceptor for the construction of energy harvesting model compounds, and constitute the first definitive proof of charge separation in ZnP-CuIIIC systems.Chapter 7 summarizes several interesting observations made in the present study on DSSCs built on two types of phenothiazine dyes having one or two cyanocinnamic acid groups.
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Svarovsky, Serge A. "Structure, stability and reactivity of small organic sulfinic and sulfonic acids toxicological implications ; Role of charge transfer complexes in oxidation cleavage of benzpinacols by iron (III) trispenanthroline /." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1231.
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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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Wallin, Staffan. "The Fate of Electronically Excited States : Ultrafast Electron and Energy Transfer in Solvated Donor-Acceptor Systems." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis (AUU) : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6135.
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Gobeze, Habtom Berhane. "Ultrafast Photoinduced Energy and Electron Transfer Studies in Closely Bound Molecular and Nanocarbon Donor-Acceptor Systems." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248516/.
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As part of the study, photosynthetic system constructs based on BF2-chelated dipyrromethene (BODIPY), BF2-chelated azadipyrromethene (AzaBODIPY), porphyrin, phthalocyanine, oxasmaragdyrin, polythiophene, fullerene (C60), single-walled carbon nanotube and graphene are investigated. Antenna systems of BODIPY dyads and oligomers having BODIPY as an excitation energy donor connected to different acceptors including BODIPY, azaBODIPY, oxasmaragdyrin and aluminum porphyrin are studied. Different synthetic methodologies are used to afford donor-acceptor systems either directly linked with no spacer or with short spacers of varying length and orientation. The effect of donor orientation, donor optical gap as well as nature of donor-acceptor coupling on the donor-acceptor spectral overlap and hence the rate of excitation energy transfer is investigated. In all these systems, an ultrafast energy transfer followed by electron transfer is observed. In particular, in a directly connected BODIPY-azaBODIPY dyad an unusually ultrafast energy transfer (~ 150−200 f) via Förster mechanism is observed. The observation of energy transfer via Förster instead of Dexter mechanism in such closely coupled donor-acceptor systems shows the balance between spatial and electronic coupling achieved in the donor-acceptor system.
Moreover, in donor-acceptor systems involving semiconducting 1D and 2D materials, covalently functionalized single-walled carbon nanotubes via charge stabilizing (TPA)3ZnP and noncovalently hybridized exfoliated graphene via polythiophene chromophores are studied for their charge transportation functions. In both cases, not only an ultrafast charge transfer in the range of (~ 2−5 p) is observed but also the charge-separated states were long lived implying the potential of these functionalized materials as efficient charge transporting substrates with organic chromophores for photovoltaic and optoelectronic applications where ultrafast intercomponent charge transfer is vital. In addition, as a final part of this dissertation, the mechanisms of electron injection and back electron transfer in heterogeneous systems involving supramolecularly anchored high potential chromophores on TiO2 film are studied by femtosecond transient absorption spectroscopy. In this study, not only are important insights gained on the utilization of supramolecular anchoring of chromophores such as porphyrins, phthalocyanines, and their perflorinated high potential analogues, chromophores currently showing promise as highly efficient sensitizers in dye sensitized solar cells, on TiO2 film but also on the effect of anchor length and sensitizer orientation on the rates of electron injection and back electron transfer at the sensitizer-TiO2 interface.
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Ramashia, Thinavhuyo Albert. "Effect of the additional electron acceptor in hybrid ZnO: P3HT:PCBM spin-coated films for photovoltaic application." University of the Western Cape, 2015. http://hdl.handle.net/11394/4779.
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>Magister Scientiae - MScIn a quest for low operational and maintenance cost solar cell devices, organic photovoltaics remain a potential source of energy worthy to be explored. In order to generate cost- effective electricity from solar energy, either the efficiency of the solar cells must be improved or alternatively the manufacturing cost must be lowered. The power conversion efficiency (PCE) of organic photovoltaics is influenced by the choice of electron acceptor material, the structure of the polymer, the morphology of the film, the interfaces between the layers and the ratio between the electron acceptor material and the polymer. Nevertheless, efficiency is still limited compared to conventional silicon based PV cells due to low mobility of charge carriers with a short exciton diffusion length in the active layer. Currently, hybrid solar cells have been considered as one of the most promising concepts to address the limited efficiency of organic solar cells. Therefore in this thesis ZnO nanoparticles were synthesized using hydrothermal assisted method. These nanoparticles were incorporated in the poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), and used as additional acceptors of electrons released from the polymer donor material, with the anticipation to increase the electron mobility, and ultimately the PCE. The thermo-gravimetric analyses revealed improved thermal stability of P3HT upon incorporating ZnO in the polymer matrix. X-ray diffraction analyses revealed that the diffraction peaks shift to higher angles when incorporating the ZnO in the P3HT:PCBM surface and this is consistent with the Raman observation. The photovoltaic properties demonstrated that the addition of ZnO nanoparticles in P3HT:PCBM bulk-heterojunction increases PCE from a baseline of ∼1.0 % in the P3HT:PCBM system to 1.7% in the P3HT:PCBM:ZnO ternary system. The enhanced PCE was due to improved absorption as compared to its counterparts. Upon increasing the addition of ZnO nanoparticles in the P3HT:PCBM matrix, the PCE decreases, due to a large phase separation between the polymer, PCBM and ZnO induced by ZnO agglomerations which resulted in increased surface roughness of the active layer. These findings signify that incorporation of ZnO nanostructures in the P3HT:PCBM polymer matrix facilitates the electron transport in the photoactive layer which results to improved efficiency.
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Catterall, Kylie. "Development of a Rapid Microbial-Based Toxicity Assay Employing Ferricyanide as an Artificial Respiratory Electron Acceptor." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/367811.
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The use of ferricyanide-mediated microbial reactions was investigated with a view to developing a rapid microbial-based toxicity assay to overcome the short falls of existing techniques currently employed in the water and wastewater industry. This assay, known as the ferricyanide-mediated toxicity (FMTOX) assay, employs ferricyanide in place of oxygen as an artificial electron acceptor during microbial respiration. The principle behind this assay is similar to conventional microbial-based toxicity assays that quantify the inhibition of the electron transport system of microorganisms. In this case, however, rather than monitoring changes in bioluminescence (Microtox), oxygen (OEeD 209 Activated Sludge Respiration Inhibition Assay) or the production of oxidised nitrogen (ISO 9509 Activated Sludge Nitrification Inhibition Assay), the FMTOX assay quantifies microbially produced ferrocyanide derived from ferricyanide cellular respiration using an electrochemical detection system.
In order to ascertain the relevance and practicality of the newly developed FMTOX assay, a tool box was developed that included a list features that an ideal microbialbased toxicity assay would have when applied to the water and wastewater industry. An assessment of other available microbial-based toxicity assays against the ideal toxicity assay was also made. Throughout this study, the use of this tool box approach served as a means to direct systematic research on FMTOX development and optimisation and also to evaluate if this new assay improves on the currently available microbial toxicity assays.
FMTOX method validation, proof of concept investigations and optimisation of key experimental parameters was facilitated employing, Escherichia coli and 3,5-Dichlorophenol (3,5-DCP) as a model microorganism and test substance respectively. Following a concentration-response experimental design using a range of organic and inorganic test substances, the versatility of the generic FMTOX assay developed using E. coli was successfully applied without further modification (excluding exposure temperature) to three other microbial test species (Pseudomonas jluorescens, Bacillus subtilis and Acetobacter calcoaceticus). Furthermore, when a test substance exerted a measurable inhibitory effect, the trends obtained were found to display classic sigmoid shaped concentration-response curves reported for conventional toxicity assays.
The degree of similarity between the ranked IC50 values calculated for the FMTOX microorganisms and literature values reported for standard microbial-based toxicity assays were compared using the Bray Curtis similarity matrix and visually displayed using hierarchal cluster analysis. While the trends obtained revealed that each of the microorganisms within the assays have their own sensitivity profiles, some similarities were evident. For example, of the microorganisms investigated in the FMTOX assay, B. subtilis was generally found to be the most sensitive test microorganism and the toxicity profiles obtained were found to be 88% similar to the ranked IC50 values reported for the Microtox assay. Consequently, it was proposed that the FMTOX B. subtilis assay would be relevant for applications where the Microtox assay has been typically employed, such as those requiring high sensitivity. On the other hand, owing to generally higher IC50 values, the FMTOX assay using A. calcoaceticus was found to be more comparable the activated sludge based assays as evidenced by relatively high percent similarities (93%) for both the OECD 209 assay and the ISO 9509 assay. It was therefore suggested that FMTOX A. calcoaceticus would be more suitable for applications where the activated sludge based toxicity assays are employed, such as WWTP influent monitoring, WWTP process control, and compliance monitoring of industries discharging into sewers.
The successful application of the single microorganisms in the FMTOX assay prompted the investigation and development of a FMTOX assay employing activated sludge obtained from a WWTP. The results of this investigation are significant for a number of reasons. Firstly, this is the first report that has demonstrated that a mixed microbial consortium of activated sludge is able to reduce the artificial electron acceptor, ferricyanide, to ferrocyanide during cellular respiration. Secondly, using the test substances employed for the FMTOX single microorganisms, 97% (45 and 75 minutes total exposure times) and 100% similarity (135 minute total exposure time) in the ranked IC50 values were found between the OECD 209 assay and the FMTOX activated sludge. Comparison with the ISO 9509 assay also yielded excellent agreement as percent similarities ranging from 87% to 90% were found for each of the three FMTOX activated sludge assay exposure times. Importantly, the FMTOX activated sludge assay was able to achieve these comparable results in a much faster time frame (45 min.-135 min.) compared to the OECD 209 assay (3 hours) and the ISO 9509 assay (4 hours). Finally, the FMTOX activated sludge assay was also found to be much simpler to perform and required significantly reduced preparation and analysis time. Based on these very promising results it was concluded that the FMTOX assay employing activated sludge assay would be more appropriate for assessing the impact of wastewaters to the specific activated sludge community inhabiting any WWTP.
The flexibility of being able to modify the biocatalyst(s) in the FMTOX assay demonstrates the versatility of the assay as it means that biocatalysts can be selected based on the indigenous species present in the environment being monitored and/or on the sensitivity and selectivity profiles required for specific applications. Importantly, this flexibility together with other significant advantages means that the FMTOX assay shows the necessary attributes of an ideal microbial-based toxicity assay that would be relevant to a wide variety of applications in the water and wastewater industry. Nevertheless, it is acknowledged that additional developmental work is still required, such as, analysis of the day to day variability of the FMTOX assay, further investigations of more test microorganisms, including tailor made mixed microbial consortiums and test batteries; further investigations of more test substances including mixtures and real samples; and further investigations of possible interferences to the FMTOX detection system.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental and Applied Science
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Schubert, Marcel. "Elementary processes in layers of electron transporting Donor-acceptor copolymers : investigation of charge transport and application to organic solar cells." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7079/.
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Donor-acceptor (D-A) copolymers have revolutionized the field of organic electronics over the last decade. Comprised of a electron rich and an electron deficient molecular unit, these copolymers facilitate the systematic modification of the material's optoelectronic properties. The ability to tune the optical band gap and to optimize the molecular frontier orbitals as well as the manifold of structural sites that enable chemical modifications has created a tremendous variety of copolymer structures. Today, these materials reach or even exceed the performance of amorphous inorganic semiconductors. Most impressively, the charge carrier mobility of D-A copolymers has been pushed to the technologically important value of 10 cm^{2}V^{-1}s^{-1}. Furthermore, owed to their enormous variability they are the material of choice for the donor component in organic solar cells, which have recently surpassed the efficiency threshold of 10%.
Because of the great number of available D-A copolymers and due to their fast chemical evolution, there is a significant lack of understanding of the fundamental physical properties of these materials. Furthermore, the complex chemical and electronic structure of D-A copolymers in combination with their semi-crystalline morphology impede a straightforward identification of the microscopic origin of their superior performance. In this thesis, two aspects of prototype D-A copolymers were analysed. These are the investigation of electron transport in several copolymers and the application of low band gap copolymers as acceptor component in organic solar cells.
In the first part, the investigation of a series of chemically modified fluorene-based copolymers is presented. The charge carrier mobility varies strongly between the different derivatives, although only moderate structural changes on the copolymers structure were made. Furthermore, rather unusual photocurrent transients were observed for one of the copolymers. Numerical simulations of the experimental results reveal that this behavior arises from a severe trapping of electrons in an exponential distribution of trap states. Based on the comparison of simulation and experiment, the general impact of charge carrier trapping on the shape of photo-CELIV and time-of-flight transients is discussed.
In addition, the high performance naphthalenediimide (NDI)-based copolymer P(NDI2OD-T2) was characterized. It is shown that the copolymer posses one of the highest electron mobilities reported so far, which makes it attractive to be used as the electron accepting component in organic photovoltaic cells.par
Solar cells were prepared from two NDI-containing copolymers, blended with the hole transporting polymer P3HT. I demonstrate that the use of appropriate, high boiling point solvents can significantly increase the power conversion efficiency of these devices. Spectroscopic studies reveal that the pre-aggregation of the copolymers is suppressed in these solvents, which has a strong impact on the blend morphology.
Finally, a systematic study of P3HT:P(NDI2OD-T2) blends is presented, which quantifies the processes that limit the efficiency of devices. The major loss channel for excited states was determined by transient and steady state spectroscopic investigations: the majority of initially generated electron-hole pairs is annihilated by an ultrafast geminate recombination process. Furthermore, exciton self-trapping in P(NDI2OD-T2) domains account for an additional reduction of the efficiency. The correlation of the photocurrent to microscopic morphology parameters was used to disclose the factors that limit the charge generation efficiency. Our results suggest that the orientation of the donor and acceptor crystallites relative to each other represents the main factor that determines the free charge carrier yield in this material system. This provides an explanation for the overall low efficiencies that are generally observed in all-polymer solar cells.Donator-Akzeptor (D-A) Copolymere haben das Feld der organischen Elektronik revolutioniert. Bestehend aus einer elektronen-reichen und einer elektronen-armen molekularen Einheit,ermöglichen diese Polymere die systematische Anpassung ihrer optischen und elektronischen Eigenschaften. Zu diesen zählen insbesondere die optische Bandlücke und die Lage der Energiezustände. Dabei lassen sie sich sehr vielseitig chemisch modifizieren, was zu einer imensen Anzahl an unterschiedlichen Polymerstrukturen geführt hat. Dies hat entscheidend dazu beigetragen, dass D-A-Copolymere heute in Bezug auf ihren Ladungstransport die Effizienz von anorganischen Halbleitern erreichen oder bereits übetreffen. Des Weiteren lassen sich diese Materialien auch hervorragend in Organischen Solarzellen verwenden, welche jüngst eine Effizienz von über 10% überschritten haben. Als Folge der beträchtlichen Anzahl an unterschiedlichen D-A-Copolymeren konnte das physikalische Verständnis ihrer Eigenschaften bisher nicht mit dieser rasanten Entwicklung Schritt halten. Dies liegt nicht zuletzt an der komplexen chemischen und mikroskopischen Struktur im Film, in welchem die Polymere in einem teil-kristallinen Zustand vorliegen. Um ein besseres Verständnis der grundlegenden Funktionsweise zu erlangen, habe ich in meiner Arbeit sowohl den Ladungstransport als auch die photovoltaischen Eigenschaften einer Reihe von prototypischen, elektronen-transportierenden D-A Copolymeren beleuchtet. Im ersten Teil wurden Copolymere mit geringfügigen chemischen Variationen untersucht. Diese Variationen führen zu einer starken Änderung des Ladungstransportverhaltens. Besonders auffällig waren hier die Ergebnisse eines Polymers, welches sehr ungewöhnliche transiente Strom-Charakteristiken zeigte. Die nähere Untersuchung ergab, dass in diesem Material elektrisch aktive Fallenzustände existieren. Dieser Effekt wurde dann benutzt um den Einfluss solcher Fallen auf transiente Messung im Allgemeinen zu beschreiben. Zusätzlich wurde der Elektronentransport in einem neuartigen Copolymer untersucht, welche die bis dato größte gemesse Elektronenmobilität für konjugierte Polymere zeigte. Darauf basierend wurde versucht, die neuartigen Copolymere als Akzeptoren in Organischen Solarzellen zu implementieren. Die Optimierung dieser Zellen erwies sich jedoch als schwierig, konnte aber erreicht werden, indem die Lösungseigenschaften der Copolymere untersucht und systematisch gesteuert wurden. Im Weiteren werden umfangreiche Untersuchungen zu den relevanten Verlustprozessen gezeigt. Besonders hervorzuheben ist hier die Beobachtung, dass hohe Effizienzen nur bei einer coplanaren Packung der Donator/Akzeptor-Kristalle erreicht werden können. Diese Struktureigenschaft wird hier zum ersten Mal beschrieben und stellt einen wichtigen Erkenntnisgewinn zum Verständnis von Polymersolarzellen dar.
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Peckus, D., A. Devizis, D. Hertel, and V. Gulbinas. "Excited State Relaxation in Vacuum Deposited and Solution Processed Films of Merocyanine/Fulerene Blends." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35299.
Full textAbstract:
Exciton dynamics in merocyanine/fulerene blend films made by vacuum deposition and solution processing
techniques were investigated by means of steady-state and time resolved fluorescence and
absorption spectroscopy. Intermolecular charge transfer states are formed during several ps in neat
merocianine films, which determine their fluorescence properties. Fullerene additives cause formation of
new heterogeneous charge transfer states. Even a small fullerene concentration significantly influences
the exciton dynamics by quenching inherent merocianine fluorescent states and causing appearance of new
fluorescence bands caused by the charge transfer states between merocyanine and fullerene molecules. All
fluorescence bands are quenched in films with high fulerence concentration due to the charge carrier generation,
and the quenching effect is stronger in vacuum deposited films.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35299
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Furman, Gary S. "The contribution of charge-transfer complexes to the color of kraft lignin." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5644.
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Dornan, Thomas Joseph. "Calcium Transport Inhibition, Stimulation, and Light Dependent Modulation of the Skeletal Calcium Release Channel (RyR1) by the Prototropic Forms of Pelargonidin." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1931.
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The principle calcium regulator in the muscle cell is the calcium ion release channel (RyR). Improper calcium homeostasis in the muscle cell is the foundation of many pathological states and has been targeted as a contributing factor to ventricular tachycardia, which is known to precede sudden cardiac arrest.
Numerous endogenous and exogenous compounds can affect the way RyR regulates calcium. In this study the anthocyanidin Pelargonidin (Pg), an important natural colorant and dietary antioxidant, is evaluated for its effect on regulating the transport of calcium through the RyR1 of skeletal muscle sarcoplasmic reticulum. Pelargonidin undergoes time dependent structural changes in aqueous solutions at physiological pH and a mixture of up to seven forms of Pelargonidin are present in solution simultaneously. Pelargonidin is a unique RyR1 modulator. It can both stimulate and inhibit the RyR1 depending on the experimental conditions. In addition, when Pelargonidin is irradiated with white light, its inhibition properties on the RyR1 are essentially nullified. Proposed mechanisms include excited state charge shift within RyR1-Pg complexes.
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Thomas, Christopher A. "Donor-acceptor methods for band gap reduction in conjugated polymers the role of electron rich donor heterocycles /." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1000167.
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Thesis (Ph. D.)--University of Florida, 2002.Title from title page of source document. Document formatted into pages; contains viii, 226 p.; also contains graphics. Includes vita. Includes bibliographical references.
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Rempe, Margaret Eileen. "Electron donor and acceptor properties of trimethylphosphine, triphenylphosphine, and related ligands with transition metals by photoelectron spectroscopy." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186698.
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Gas-phase photoelectron spectroscopy is used to evaluate the a-donation and 1t-acceptance abilities of a series of Group 15 ligands. The free ligands PMe(3-n)Ph(n) (n=0-3), EMe₃ (E=As) and EPh₃ (E=As, Sb, Bi) are examined (Me=CH₃, Ph=C₆H₅) and the trends in lone pair ionizations are discussed. Organometallic compounds investigated include CpMn(CO)2L (L=PPh₃, AsPh₃), Cp'Mn(CO)₂L (L=PPh₃, PMe₃, AsPh₃, SbPh₃), and Mo(CO)₅L (L=PMe₃, PPh₃). Contrary to initial predictions based on electronegativities and solution pKₐ's, the trend in ionization energies for the series PMe(3-n)Ph(n) is PPh₃ < PMePh₂ < PMe₂Ph < PMe₃. The trend in first ionizations is governed by a filled-filled interaction between the lone pair and phenyl rings. The metal ionization energies of organometallic compounds containing PMe₃ and PPh₃ reflect this trend indicating that the above order is also the order of a-donation. These metal ionizations also indicate that all members of the series, PMe(3-n)Ph(n), have the same amount of π-acceptance. Just as in the phenyl containing phosphine ligands, the ligands EPh₃ exhibit filled-filled interactions between the lone pair and phenyl orbitals, but not uniformly. This filled-filled interaction decreases with the heavier elements. The order of lone pair ionizations for EPh₃ is PPh₃ < AsPh₃, SbPh₃, BiPh₃. The destabilization expected upon descent of the periodic table is offset by the effects of decreasing relaxation energy and decreasing filled-filled interactions. Metal ionizations do not strictly follow the trends of the free ligands EPh₃. These metal ionization energies coincide for organometallic compounds where E is phosphorus or arsenic. Metal ionization energies for E=Sb are very slightly stabilized compared to E=P, As. The ligands EPh₃ display the same amount of σ and π interactions in the organometallic compounds examined. It is observed that the identity of R is more important in determining σ/π interactions than the element directly bound to the metal. This work serves to bring together previous literature and current experimental results to understand the structure and bonding in the ligands ER₃ (E=P, As, Sb, Bi and R=Me, Ph).
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Pujol, Vila Ferran. "Fast and low-cost microbial toxicity bioassays based on electrochromic electron acceptors." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456178.
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This thesis proposes the use of compounds that change their colour when reduced by living cells, i.e. electrochromic electron acceptors, in the development of fast and low-cost microbial toxicity bioassays suitable for in situ analysis. Electrochromism enables the monitoring of cell respiration by simple colorimetric measurement or even with the bare eye. Thus, allowing for toxicity determination without the need for complex instrumentation. Hexacyanoferrate compounds have been selected from the wide spectrum of reported electrochromic electron acceptors due to their suitable solubility and stability.
To this end, a microbial acute toxicity bioassay was developed based on metabolic reduction of ferricyanide and optical determination with standard laboratory equipment, using Escherichia coli (E. coli) as model bacterium. Interferences in the optical measurement due to biomass light scattering were minimized by dual wavelength detection at 405 nm (ferricyanide absorption and biomass scattering) and 550 nm (biomass scattering). On the other hand, modification of the refractive index (RI) of the medium until matching with refractive index of bacterial cells with (i.e. RI matching) was achieved by addition of 27% (w/v) sucrose, which reduced bacterial light scattering around 50%. The toxic impact of various compounds on E. coli was determined by analysis of ferricyanide reduction kinetics (variation of ferricyanide absorption with time) and single absorbance measurements. Kinetic analysis of bacterial ferricyanide reduction allowed for fast assays (assay time of 10 min) with half maximal effective concentrations (EC50) similar to standard methods (i.e. biolumiscence inhibition test) for organic and inorganic toxic compounds.
Technological implementation of the microbial toxicity bioassay was carried out by developing a low-cost miniaturized optofluidic analysis system. The optofluidic system was composed of a poly(methyl methacrylate) (PMMA) optofluidic structure incorporating discrete auxiliary optical elements (i.e. light emitting diodes, LEDs, and detectors) and an electronic circuit enabling for subtraction of ambient light interference. The optical performance of the analytical system for ferricyanide determination was tested. It was insensitive to environmental light changes and compared favourably to commercially available instrumentation. The simplicity, portability and robustness of the analysis system make it suitable for fast and low-cost determination of toxic pollutants in situ.
To reduce bioassay instrumentation requirements, we designed a low-cost solid system by trapping bacteria in hygroscopic paper matrices. E. coli cells were stably trapped on low-cost paper matrices (cellulose-based paper discs) and remained viable for long times (1 month when stored at -20 ºC). Apart of acting as bacterial carriers, paper matrices also acted as a fluidic element, allowing fluid management without the need of external pumps. Optical properties of individual paper matrices were analysed showing good comparability between them. Chromatic changes associated with bacterial ferricyanide reduction were determined by three different transduction methods, i.e. optical reflectometry, image analysis and visual inspection. Validation of the bioassay was performed by analysis of real samples from natural sources (i.e. wastewater influents/effluents and leachates from contaminated soils) using the mentioned transduction methods and the bioluminiscence inhibition test (Microtox, as standard method). Toxicity values obtained showed good agreement between them and with our reference method (70% of coincidence in toxic samples and 80% in non-toxic samples). The use of a light and inexpensive material and minimum instrumentation requirements of the bioassay make it a true low-cost method for in-situ assessment of toxic water pollution.
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Pui, Yung-lin. "Syntheses, luminescence studies and host-guest chemistry of d10 and d6 metal complexes containing diimine and/or chalcogenolate ligand." Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B43894367.
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裴雍蓮 and Yung-lin Pui. "Syntheses, luminescence studies and host-guest chemistry of d10 and d6metal complexes containing diimine and/or chalcogenolate ligand." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B43894367.
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Refojo, Patrícia N. "The alternative complex III from Rhodothermus marinus - a prototype of a new family of quinol: electron acceptor oxidoreductase." Doctoral thesis, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2010. http://hdl.handle.net/10362/5159.
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Dissertation presented to obtain a PhD degree in Biochemistry at the Instituto de Tecnologia Química e Biológica, Universidade Nova de LisboaThe aim of the work presented in this thesis was the characterization of a complex with quinol: electron carrier oxidodoreductase activity present in the membranes of the thermohalophilic bacterium Rhodothermus (R.) marinus. The complexes involved in the R. marinus respiratory chain have been extensively studied in the past few years. Specifically, the purification and characterization of a complex I (NADH: quinone oxidoreductase), a complex II (succinate:quinone oxidoreductase) and of three different oxygen reductases from the heme-copper oxygen reductases superfamily have been performed. Since those oxygen reductases are unable to receive electrons from quinol molecules, the presence of a complex linking complexes I and II to the oxygen reductases was needed. In fact, a complex with quinol: HiPIP oxidoreductase activity was purified and partially characterized. The absence of the Rieske protein indicated that the complex isolated from R. marinus has a different composition when compared with the typical cytochrome bc1 complex.(...)
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Tucker, Kenneth D. "Use of nitrous oxide as the terminal electron acceptor during growth and respiration of Bradyrhizobium Japonicum USDA 143." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80111.
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Bradyrhizobium japonicum USDA 143 grew chemoorganotrophically when supplied with exogenous nitrous oxide as the terminal electron acceptor, or as the alternate terminal electron acceptor to nitrate under anoxic conditions. Cell growth and dissimilatory N₂O reduction were significantly inhibited by acetylene when either N₂O or N₂O plus nitrate served as terminal electron acceptor(s). Reduction of nitrous oxide accounted for 20% of the energy for cell growth in cultures supplied with nitrate as the terminal electron acceptor. Nitrous oxide was produced stoichiometrically in cultures supplied with nitrate and acetylene and growth was proportionately reduced compared to cultures supplied with an equal amount of nitrate. Exogenous nitrous oxide delayed the reduction of nitrate in cultures supplied with both electron acceptors. The final cell yield and/or growth rate of the cells were reduced when N₂O was ≥ 15% of the culture flask headspace. Direct amperometric monitoring of nitrous oxide respiration indicated a specific activity of 0.082 ± 0.004 µmoles N₂O/min/mg cell-protein. The respiration was inhibited by azide.
A Clark-type electrode with a platinum cathode, and the instrumentation for monitoring hydrogen uptake amperometrically were used to monitor the reduction of N₂O during anaerobic respiration.Master of Science
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Lade, Nancy. "Sequential Electron Acceptor Model of Intrinsic Bioremediation at a BTEX Contaminated LUST Site in Laurel Bay, South Carolina." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35009.
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Contaminant transport modeling is being used more often at petroleum hydrocarbon contaminated sites in an attempt to aid engineers in evaluating the feasibility of natural attenuation as a remediation alternative in groundwater systems. In this research, a three-dimensional sequential electron acceptor computer model, SEAM3D, developed by Waddill and Widdowson (1997) was used to simulate contaminant transport at a leaking underground storage tank site in Beaufort, South Carolina. Gasoline containing benzene, toluene, ethylbenzene, and xylene (BTEX) as well as methyl tertiary butyl ether (MTBE) leaked into the subsurface at the site late in 1990, and monitoring of the water table elevations and contaminant concentrations began in 1993.
Using the field data, the groundwater flow model MODFLOW was used to develop and calibrate a flow model for the Laurel Bay site using GMS (Groundwater Modeling System) v2.1. MODFLOW was coupled with the SEAM3D contaminant transport model, and the available concentration levels were used to calibrate, verify, and validate the site model. The results indicated that SEAM3D simulated complex, interconnected processes including biodegradation, and the transport of multiple hydrocarbon compounds, electron acceptors, and end products over time and space at a specific petroleum hydrocarbon contaminated site.
Once the model was calibrated and verified, the model output was used to study the changes in contaminant mass distribution, contaminant mass loss, and mass loss rates for each terminal electron accepting process (TEAP) over time. It was found that the natural attenuation capacity of the aquifer was insufficient to stabilize the plume and prevent it from reaching the defined point of contact (POC). Contamination was shown to have reached the POC by 1994, just four years into the simulation. Results indicated that despite oxygen limitation within the BTEX plume, aerobic biodegradation was responsible for the greatest amount of mass loss, close to 70 %, relative to the sum of the anaerobic processes after 20 years.Master of Science
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Farid, Ramy Samir Gray Harry B. Gray Harry B. "Electron transfer in rigid and semi-rigid iridium d [superscript 8]-d [superscript 8] donor-spacer-acceptor complexes /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06212007-154303.
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Samuelsson, Catrin. "Mineralization rates of organic matter in freshwater sediments when different electron acceptors dominate." Thesis, Linköping University, Department of Thematic Studies, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2417.
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Microbial decomposition of organic matter in aquatic environments plays an important role in natural fluxes of methane and carbon dioxide because the gases are end-products in microbial energy metabolism of organic matter. Microbial metabolism depends on the use of electron donors and electron acceptors in redox reactions that generate energy for growth and maintenance. Energy yields can be used to envisage specific patterns of microbial redox reactions and these predictions depend on the hypothesis that, in a specified environment, the metabolic reaction that yields most energy will dominate over any competing reactions. The energy yield hypothesis indicates a sequential order in electron acceptor use by microbes and also make it tempting to conclude that degradation rate of organic matter is different depending on available electron acceptors. The main purpose of this thesis was to study how the presences of different electron acceptors in freshwater sediments influence organic matter decomposition. Mineralization rates of organic matter under six different conditions regarding the electron acceptor availability were investigated in a river sediment sample from Stångån, Sweden, by measuring carbon dioxide and methane production using gas chromatography. This was done during a fixed time period, in vials containing a mixture of water, sediment, buffer solution and a dominating electron acceptor. Six different metabolic processes; aerobic respiration, denitrification, manganese reduction, iron reduction, sulphate reduction and methanogenesis were included. The overall result indicates similar mineralization rates in both oxic and anoxic treatments. The result also indicates that methane formation was present in the iron reduction and methanogenesis treatments and not evident in the oxic treatments. Sulphate reduction, denitrification and manganese reduction seems to inhibit methanogenesis, but the result also indicates that no significant total mineralization was apparent when NO3- and Mn(IV) were the dominating electron acceptors. The similarities between oxic and anoxic mineralization rates indicates that organic matter degradation rates are not dependent on available electron acceptors and that degradation rates of organic matter are independent of the thermodynamically based energy yield.
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Ekhagen, Sebastian. "Stability of electron acceptor materials for organic solar cells : a work function study of C60/C70 derivatives and N2200." Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-72727.
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Thin films of the fullerenes PC60BM and PC70BM and the non-fullerene N2200, three popular electron acceptor materials in organic photovoltaics, have been studied, using both the Kelvin probe method as well as ultraviolet photoelectron spectroscopy. With these methods the work function was measured, as well as the highest occupied molecular orbital (HOMO) onset. Additionally band bending effects were studied by illuminating the samples while measuring the work function with the Kelvin probe so called surface photovoltage. Sample of each material was exposed to either air and simulated sunlight or N2 and simulated sunlight, for different length of time, to observe how the materials work function evolves after exposure to the different conditions. It was observed that, as expected from previous studies, that PC60BM was less photo-stable than PC70BM. Additionally, the work function of PC60BM changed significantly by storage in N2. Each material after exposure for 24h to air and light, was annealed and measured with the Kelvin probe. A restoring effect was observed, for the non-fullerene material N2200. All three materials developed an increasing surface photovoltage, which suggest increased band bending, when exposed to air and light, indicating that due phot-oxidization, charges are redistributed at the surface of the film. The fullerenes showed a larger surface photovoltage effect than the non-fullerene materials. A difference between the work function values obtained from the Kelvin probe method and the ultraviolet photoelectron spectroscopy could be seen, however the exact reason for this couldn't be isolated within this thesis, but was discussed.
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Bröker, Benjamin [Verfasser], Norbert [Akademischer Betreuer] Koch, Jean-Jacques [Akademischer Betreuer] Pireaux, and Antoine [Akademischer Betreuer] Kahn. "Electronic and structural properties of interfaces between electron donor & acceptor molecules and conductive electrodes / Benjamin Bröker. Gutachter: Norbert Koch ; Jean-Jacques Pireaux ; Antoine Kahn." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://d-nb.info/1014975263/34.
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Karlsson, Susanne. "Single and Accumulative Electron Transfer – Prerequisites for Artificial Photosynthesis." Doctoral thesis, Uppsala universitet, Kemisk fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122206.
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Photoinduced electron transfer is involved in a number of photochemical and photobiological processes. One example of this is photosynthesis, where the absorption of sunlight leads to the formation of charge-separated states by electron transfer. The redox equivalents built up by successive photoabsorption and electron transfer is further used for the oxidation of water and reduction of carbon dioxide to sugars. The work presented in this thesis is part of an interdisciplinary effort aiming at a functional mimic of photosynthesis. The goal of this project is to utilize sunlight to produce renewable fuels from sun and water. Specifically, this thesis concerns photoinduced electron transfer in donor(D)-photosensitizer(P)-acceptor(A) systems, in mimic of the primary events of photosynthesis. The absorption of a photon typically leads to transfer of a single electron, i.e., charge separation to produce a single electron-hole pair. This fundamental process was studied in several molecular systems. The purpose of these studies was optimization of single electron transfer as to obtain charge separation in high yields, with minimum losses to competing photoreactions such as energy transfer.Also, the lifetime of the charge separated state and the confinement of the electron and hole in three-dimensional space are important in practical applications. This led us to explore molecular motifs for linear arrays based on Ru(II)bis-tridentate and Ru(II)tris-bidentate complexes. The target multi-electron catalytic reactions of water-splitting and fuel production require a build-up of redox equivalents upon successive photoexcitation and electron transfer events. The possibilities and challenges associated with such processes in molecular systems were investigated. One of the studied systems was shown to accumulate two electrons and two holes upon two successive excitations, without sacrificial redox agents and with minimum yield losses. From these studies, we have gained better understanding of the obstacles associated with step-wise photoaccumulation of charge and how to overcome them.
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Feilitzsch, Till von. "On the mechanism of photoinduced electron transfer in bridged donor-acceptor systems ferrocenophane-nileblue and rhodamine6G endcapping the DNA duplex /." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972589198.
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