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Дисертації з теми "Charge transfer dynamic"

Автор: Grafiati
Опубліковано: 11 березня 2023

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1

Edirisinghe, Pathirannehelage Neranjan S. "Charge Transfer in Deoxyribonucleic Acid (DNA): Static Disorder, Dynamic Fluctuations and Complex Kinetic." Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/phy_astr_diss/45.

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The fact that loosely bonded DNA bases could tolerate large structural fluctuations, form a dissipative environment for a charge traveling through the DNA. Nonlinear stochastic nature of structural fluctuations facilitates rich charge dynamics in DNA. We study the complex charge dynamics by solving a nonlinear, stochastic, coupled system of differential equations. Charge transfer between donor and acceptor in DNA occurs via different mechanisms depending on the distance between donor and acceptor. It changes from tunneling regime to a polaron assisted hopping regime depending on the donor-acceptor separation. Also we found that charge transport strongly depends on the feasibility of polaron formation. Hence it has complex dependence on temperature and charge-vibrations coupling strength. Mismatched base pairs, such as different conformations of the G・A mispair, cause only minor structural changes in the host DNA molecule, thereby making mispair recognition an arduous task. Electron transport in DNA that depends strongly on the hopping transfer integrals between the nearest base pairs, which in turn are affected by the presence of a mispair, might be an attractive approach in this regard. I report here on our investigations, via the I –V characteristics, of the effect of a mispair on the electrical properties of homogeneous and generic DNA molecules. The I –V characteristics of DNA were studied numerically within the double-stranded tight-binding model. The parameters of the tight-binding model, such as the transfer integrals and on-site energies, are determined from first-principles calculations. The changes in electrical current through the DNA chain due to the presence of a mispair depend on the conformation of the G・A mispair and are appreciable for DNA consisting of up to 90 base pairs. For homogeneous DNA sequences the current through DNA is suppressed and the strongest suppression is realized for the G(anti)・A(syn) conformation of the G・A mispair. For inhomogeneous (generic) DNA molecules, the mispair result can be either suppression or an enhancement of the current, depending on the type of mispairs and actual DNA sequence.
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2

Vilmercati, Paolo. "Ultra-fast charge transfer dynamic in thin and ultra-thin films of organics studied with synchrotron radiation." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2564.

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2006/2007
The increasing energy crisis has induced science and technology world to drive a lot of efforts in the study of new materials suitable to develop renewable and with a low environmental impact energy sources as an alternative to petroleum. In this context photo-voltaic cells are a good solution, nevertheless the high costs and the low light-to-current efficiency still inhibits a large production and a common usage. The employment of organic based materials, i.e. the materials inspired by biological processes, finds a place in this research field. The wide availability of these materials in nature, the ease in material processing and the intriguing chemical and physical properties places the organics as good candidates in the production of photovoltaic devices. Moreover, their electronic properties allow a usage as charge injector to enhance the light-to-current efficiency in inorganic-based photovoltaic devices (Gratzel-cells). The aim of this thesis is to study the growth, the electronic properties, and the chargetransfer dynamic in thin and ultra-thin film(single molecular layer) composed by zinc-tetraphenylporphyrin and C70 and thicker melanin films. We choose these molecules both because of their high visible light sensitivity and because porphyrins are electron donor and fullerenes are electron acceptors. In fact, it is well know in biology that the chlorophyll (Mg-poprhyrin) when illuminated with visible light, act as an electron injector in the biochemical environment supplying the amount of energy needed to activate the production of glucose starting from water and carbon dioxide (chlorophyll synthesis). The fullerene C70 consist in an arrangement of 70 carbon atoms in a closed cage structure and is a good electron acceptor. Then, the our purpose is to use the different electronic properties of these molecules to generate donor/acceptor junctions at the molecular scale. Melanin is a natural pigment present in living beings responsible, in human body, of the colour of skin and of its variation due to the exposition to the sun light; it is a semiconductor with electron donor properties. The combined usage of the properties of these molecules opens the way to the production of complexes to realize high-efficiency and low cost photovoltaic devices. In this context, and at the present state of the art in the production of organic-based photovoltaic devices, investigations about the basic mechanism of molecular interaction and electronic properties are needed to clarify the problems that are still open. In fact the light-tocurrent conversion is just one of the possible processes successive to the absorption of a visible photon in a material. In fact the large number of dissipative processes dissipates the charges excited by the light and inhibits the light-to-current conversion efficiency. In this context, two aspect are fundamental: the presence of empty states in the conduction band that are not allowed for dipole transitions from the valence band but energetically favourable with respect to the first allowed ones, in order to brake the excitonic bond and a good charge mobility in order to transport the excited charges up to the collecting electrodes of the device. because the mobility is higher in ordered systems instead of non ordered ones, the molecular interaction and the growth condition have a fundamental role because they determine the molecular packing in the film. In this sense we used soft X-rays and UV-rays photoemission to study the interaction between ZnTPP and C70 and between these molecules and the Si(111)7x7 surface, one of the most common substrate used to produce electronic devices. We studied the order in the various films in the sense of “orientational order” using Near Edge Absorption Fine structure Spectroscopy at SuperESCA and ALOISA beamlines at ELETTRA synchrotron radiation facility in Trieste. Because the NEXAFS spectra, obtained with linearly polarized radiation, are sensitive to the direction of the chemical bonds, the dependence of the absorption structures intensity on the angle between the electrical field of the incoming radiation and the direction of the empty states yields informations about the geometrical (orientational) arrangements of the molecules in the film. The films were produced by sublimation in ultra-high-vacuum in order to obtain a film as pure as possible. We produced a melanin film via “drop casting”, by in air deposition of a suspension of synthetic melanin powder in mineral free water on a polycristal copper surface and drying the water. We obtained the first photoemission data available in literature about this system. A particular attention was dedicated to the ultra-fast delocalization processes of the excited charges. We used Resonant Photoemission technique (SuperESCA beamline at ELETTRA) to study the excitation de-excitation processes: a core electron is pumped to an empty state in the conduction band, the following decay of the core hole (scale of fs) reveals time scale of the excited charge delocalization with a chemical sensitivity typical of core spectroscopies
La crescente crisi energetica ha indotto la scienza e la tecnologia ad indirizzarsi verso lo studio di nuovi materiali da utilizzarsi per sviluppare fonti di energia alternative al petrolio che siano rinnovabili e a basso impatto ambientale. In questo ambito le celle foto-voltaiche sono una buona risposta, tuttavia i costi elevati e la bassa efficienza nella conversione luce-corrente fanno sì che esse non siano ancora di uso comune. Lo studio dei materiali organici, ovvero di quelli ispirati da processi biologici, trova spazio in questo ambito di ricerca. La larga diffusione in natura dei costituenti, la facilità nel processare il materiale, e le interessanti proprietà chimico-fisiche fanno dei materiali organici una delle possibili scelte nella realizzazione di dispositivi fotovoltaici. Inoltre, la versatilità di questi materiali li rende utilizzabili anche come iniettori di cariche per aumentare l’efficienza di conversione luce-corrente se accoppiati con semiconduttori inorganici (Gratzel-cells). Oggetto di questa tesi è lo studio della crescita e delle proprietà elettroniche di trasferimento di carica di film sottili e monostrati molecolari composti di zinco-tetrafenil-porfirina e C70, e film di melanina. La scelta di queste molecole origina sia dalle loro proprietà di sensibilità alla luce visibile che dalle loro proprietà elettroniche di essere donori ed accettori di elettroni. Infatti, è ben noto in natura che la clorofilla (magnesio-porfirina) svolge la funzione di iniettore di carica nell’ambiente biochimico per fornire l’energia necessaria all’attivazione della produzione di glucosio a partire da acqua e anidride carbonica, quando esposta a luce solare. Il fullerene C70 è una molecola costituita da settanta atomi di carbonio disposti in una struttura chiusa a gabbia ed ha la proprietà di essere un accettare di elettroni. Uno degli obiettivi è, quindi sfruttare le diverse proprietà elettroniche di queste molecole per realizzare delle giunzioni donore/accettore su scala molecolare. La melanina è il pigmento naturale presente negli esseri viventi responsabile, nel corpo umano, del colore della pelle e del suo cambiamento in seguito all’esposizione alla luce ed è anch’essa un semiconduttore con proprietà di donore di elettroni. L’uso combinato di queste caratteristiche apre la strada alla realizzazione di materiali complessi che possano essere utilizzati nella realizzazione di dispositivi fotovoltaici. In questo contesto, e all’attuale stato dell’arte della realizzazione di dispositivi fotovoltaici basati su molecole organiche è necessario lo studio di base delle proprietà elettroniche dei film composti di queste molecole per affrontare problematiche aperte. Infatti il processo di conversione della luce in corrente è solo uno di quelli possibili in seguito all’assorbimento di un fotone visibile da parte di un materiale. Infatti un gran numero di processi dissipativi rende le cariche eccitate in gran parte inutilizzabili ai fini della conversione della luce in corrente. Due aspetti sono fondamentali affinché il materiale possa essere efficiente nella conversione luce-corrente: la presenza di stati di conduzione vuoti non accessibili tramite eccitazione con radiazione elettromagnetica ma energeticamente favorevoli rispetto a quelli accessibili, e una buona mobilità delle cariche eccitate in modo da essere trasportate senza dissipazione verso gli elettrodi di raccolta. Dal momento che la mobilità delle cariche è maggiore in sistemi ordinati, diventano cruciali sia le tecniche di crescita che le interazioni molecolari che determinano l’impacchettamento delle molecole a formare il film. In questo senso ci siamo avvalsi della spettroscopia di fotoemissione nel regime dei raggi X soffici e di raggi UV per studiare sia l’interazione tra le due specie molecolari e substrato (superficie (111) del silicio) che tra porfirina e porfirina e porfirina e fullerene, crescendo films a spessori via via crescenti. Per quanto riguarda la crescita, e quindi l’ordine con cui sono stati cresciuti i films abbiamo utilizzato la spettroscopia di assorbimento vicino soglia (NEXAFS, esperimenti eseguiti sulla beamline ALOISA ad ELETTRA). Poiché gli spettri di assorbimento sono sensibili alla direzione di legami chimici qualora eccitati con radiazione polarizzata linearmente, la dipendenza dell’intensità dei singoli picchi di assorbimento dall’angolo tra il vettore campo elettrico della radiazione e la direzione del legame fornisce informazioni circa la geometria del sistema. I films sono stati ottenuti per sublimazione di polveri in ultra alto vuoto al fine di ottenere un sistema chimicamente puro. Per quanto riguarda la melanina, abbiamo realizzato un film utilizzando la tecnica del “drop casting” depositando una sospensione di acqua e melanina su una superficie di rame policristallino e lasciando evaporare l’acqua. Sono stati raccolti, quindi, i primi dati di fotoemissione presenti in letteratura riguardo questo sistema. Particolare attenzione è stata rivolta ai processi ultraveloci di delocalizzazione delle cariche in stati eccitati. A tale scopo abbiamo utilizzato la tecnica di fotoemissione risonante (ResPES, esperimenti eseguiti sulla beamline SuperESCA ad ELETTRA), in cui un elettrone di core viene eccitato da radiazione di sincrotrone a riempire uno stato di conduzione, il successivo decadimento della buca di core (scala temporale dei fs) permette di individuare l’avvenuta delocalizzazione dell’elettrone eccitato ed ottenere una stima dell’efficienza di trasferimento di carica con specificità chimica
XX Ciclo
1973
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3

Zerdane, Serhane. "Exploring photoswitching pathways in photomagnetic materials with ultrafast optical and X-ray spectroscopies." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S150/document.

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Ce travail de thèse porte sur l’étude de la dynamique femtoseconde de photo-commutation de matériaux moléculaires bistables, à l’aide d’expériences pompe-sonde basées sur les spectroscopies optiques et rayons X. Une partie des expériences a été réalisée sur synchrotron et X-FEL (X-ray Free Electron Laser). La première partie de la thèse, qui est consacrée à l’étude de systèmes à transition de spin non-octaédriques, a révélé différents chemins de transformations sur la surface de potentiel, associés à différents mécanismes de changement d’état électronique et modulant la cohérence de la dynamique structurale pilotant le processus. La seconde partie porte sur l’étude d’analogues du bleu de Prusse (CoFe) où les expériences ultra-rapides ont permis de d’étudier les dynamiques de transformation autour des sites de fer et de cobalt
This thesis focuses on the study of the femtosecond photoswitching dynamic in the bistable molecular materials, using the pump-probe experiments which are based on the optical and x-ray spectroscopies. Part of these experiments was performed at synchrotron and X-FEL (X-ray Free Electron Laser). The first part of the thesis, which is devoted to the study of non-octahedral spin transition systems, revealed different pathways of transformation on the potential surface. The second part focuses on the study of the Prussian Blue Analogues (CoFe), where the ultra-fast experiments allowed to follow the dynamics around the two metal ions
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4

Schill, Alexander Wilhem. "Interesting Electronic and Dynamic Properties of Quantum Dot Quantum Wells and other Semiconductor Nanocrystal Heterostructures." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11514.

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Some interesting electronic and dynamic properties of semiconductor nanocrystal heterostructures have been investigated using various spectroscopic methods. Semiconductor nanocrystal heterostructures were prepared using colloidal synthesis techniques. Ultrafast transient absorption spectroscopy was used to monitor the relaxation of hot electrons in CdS/HgS/CdS quantum dot quantum wells. Careful analysis of the hot electron relaxation in CdS/HgS/CdS quantum dot quantum wells reveals an energy dependent relaxation mechanism involving electronic states of varying CdS and HgS composition. The composition of the electronic states, combined with the layered structure of the nanocrystal permits the assignment of CdS localized and HgS localized excited states. The dynamic effect of surface passivation is then shown to have the strongest influence on excited states that are localized in the HgS layer. New quantum dot quantum well heterostructures of different sizes and compositions were also prepared and studied. The dynamic properties of CdS/CdSe/CdS colloidal quantum wells suggest simultaneous relaxation of excited electrons within the CdS core and CdSe shell on the sub-picosecond time scale. Despite the very different electronic structure of CdS/CdSe/CdS compared to CdS/HgS/CdS, the time scales of the relaxation and electron localization were very similar. Enhancement of trap luminescence was observed when CdS quantum dots were coated with silver. The mechanism of the enhancement was investigated using time-resolved spectroscopic techniques.
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5

Morgenstern, Frederik Stephan Franz. "Charge transfer dynamics in hybrid nanocrystal systems." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708746.

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6

Alavi, Ali. "Molecular-dynamics studies of thin films and charge-transfer." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358367.

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7

Tan, Jenna. "Investigating the Charge-Transfer Dynamics of Single-Molecule Sensitizers." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639563.

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Dye-sensitized solar cells (DSSCs) can reduce the cost of photovoltaic electricity generation to meet global energy needs. Optimizing DSSC efficiency requires a detailed understanding of the underlying charge transfer processes at the dye-semiconductor interface. By modifying the sensitizer structure, we gain insight into these charge transfer mechanisms. In this thesis, two hydroxyanthraquinone dyes are compared to investigate the impact of structure on charge-transfer and photobleaching dynamics. A combination of ensemble-averaged and single-molecule spectroscopy approaches are used to interpret the underlying ET kinetics.
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8

Webb, Mark Adam. "Excited-state charge-transfer dynamics of azurin from resonance Raman spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0012/NQ59696.pdf.

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9

Weston, Matthew. "Adsorption and charge transfer dynamics of photovoltaic and photocatalytic dye-sensitizers." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14258/.

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In this thesis photovoltaic and photocatalytic water-splitting dye complexes have been studied adsorbed onto the rutile TiO2(110) surface. The photovoltaic dye-sensitizer N3 (cis-bis(isothiocyanato)bis(2,2’-bipyridyl-4,4’-dicarboxylato)-ruthenium(II)) was studied along with Ru 455 (cis-bis(2,2’-bipyridyl)-(2,2’-bipyridyl-4,4’-dicarboxylic acid) ruthenium(II)) and Ru 470 (tris(2,2’-bipyridyl-4,4’-dicarboxylic acid) ruthenium(II)) which have very similar chemical structures. Dipyrrin-based dye complexes PY1 bis(5-(4-carboxyphenyl)-4,6-dipyrrin)bis(dimethylsulfoxide)Ruthenium(II)) and PY2 (bis(5-(4-carboxyphenyl)-4,6-dipyrrin)(2,2’-bipyridine) Ruthenium(II)) were also studied which should have different bonding geometries on the TiO2 surface. A single centre water-splitting dye complex (aqua(2,2’-bipyridyl-4,4’-dicarboxylic acid)-(2,2’:6’,6”-terpyridine) Ruthenium(II)) was studied along with a chloride containing analog ((2,2’-bipyridyl-4,4’-dicarboxylic acid)-(2,2’:6’,6”-terpyridine)chloride Ruthenium(II)). The molecules studied here would have been damaged using traditional UHV deposition techniques so electrospray deposition was used to deposit intact molecules in situ for experiments in UHV. Adsorption geometries of the molecules on the TiO2 surface were investigated using experimental photoemission data supported by density functional theory (DFT) calculations. Dipyrrin-based dye complexes were found to bond with both available carboxylic acid groups to the TiO2 surface. Also the results suggest that Ru 470 is most likely to bond to the TiO2 surface with a different bonding geometry to other bipyridine-based complexes with very similar chemical structures. The molecular orbitals of the dye complexes were investigated using near-edge x-ray absorption fine structure spectroscopy (NEXAFS). DFT calculations provided possible spatial distributions of the molecular orbitals involved in charge transfer. Energetic alignments were performed using data from visible light spectroscopy to compare energetics for core and valence-hole excitation. The core-hole clock implementation of resonant photoemission spectroscopy was used to measure upper limits on the timescale of charge transfer from the excited adsorbate molecules to the TiO2 surface. The results show charge transfer timescales mostly within the low-femtosecond timescale. The Ru 470 complex was found to be relatively slow at charge transfer possibly due to the different bonding geometry it appears to adopt on the TiO2 surface.
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10

Weisspfennig, Christian Thomas. "Investigation of charge-transfer dynamics in organic materials for solar cells." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:add81bd2-f953-44ed-b977-d3e15ea4c411.

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This thesis improves our understanding of the charge-transfer dynamics in organic materials employed in dye-sensitized and nanotube-thiophene solar cells. For the purpose of this work, a femtosecond transient absorption spectroscopy setup was built. Additionally, microsecond transient absorption spectroscopy was utilised to explore dynamics on a longer time-scale. In the first study, the dependence of dye regeneration and charge collection on the pore- filling fraction (PFF) in solid-state dye-sensitized solar cells (DSSCs) is investigated. It is shown that while complete hole transfer with PFFs as low as ~30% can be achieved, improvements beyond this PFF are assigned to a stepwise increase in the charge-collection efficiency in agreement with percolation theory. It is further predicted that the chargecollection efficiency saturates at a PFF of ~82%. The study is followed by an investigation of three novel hole-transporting materials for DSSCs with slightly varying HOMO levels to systematically explore the possibility of reducing the loss-in-potential and thus improving the device efficiency. It is shown that despite one new HTM showing a 100% hole-transfer yield, all devices based on the new HTMs performed worse than those incorporating spiro-OMeTAD. Furthermore, it is demonstrated that the design of the HTM has an additional impact on the electronic density of states present at the TiO2 electrode surface, and hence influences not only hole- but also electron-transfer from the sensitizer. Finally, a study on a polymer-single-walled carbon nanotube (SWNT) molecular junction is presented. Results from femtosecond spectroscopic techniques show that the polymer poly(3-hexylthiophene) (P3HT) is able to transfer charges to the SWNT within 430 fs. Addition of excess P3HT polymer leads to long-lived free charges making these materials a viable option for solar cells.
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11

Trejo, Peimbert Esli. "Dynamics and Transfers in two phase flows with phase change in normal and microgravity conditions." Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/23986/1/Trejo_Esli.pdf.

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Two-phase flows with or without phase change are present in terrestrial and space applications like thermal control of satellites, propellant supply for launchers, and waste water treatment for space exploration missions. Flow boiling experiment with HFE7000 were conducted in a heated tube in vertical upward flow on ground and in microgravity conditions to collect data on flow patterns, pressure drops, heat transfers, void fraction. Void fraction measurements allowed to measure mean gas velocity and the liquid film thickness in annular flow. In microgravity condition, the liquid film thickness and the interfacial shear stress are significantly lower than in normal gravity. A detail analysis of the film structure was performed by image processing. The impact of gravity and liquid and vapour superficial velocities on the disturbance waves velocities and frequencies was investigated. Two different measurement techniques were used and compared to determine the heat transfer coefficient. For quality values greater than 0.2, HTC is not sensitive to gravity and is in good agreement with classical correlations of the literature. For qualities smaller than 0.1, in the subcooled nucleate boiling regime HTC is significantly smaller in microgravityconditions.
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12

Lammers, Christian [Verfasser], and Martin [Akademischer Betreuer] Koch. "Über die Dynamik des Charge-Transfer-Exzitons / Christian Lammers ; Betreuer: Martin Koch." Marburg : Philipps-Universität Marburg, 2018. http://d-nb.info/1164156144/34.

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13

Taylor, John Benjamin. "The adsorption , charge transfer dynamics and kinetics of organic molecules at surfaces." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479335.

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14

Hess, Stephan. "Dynamics of photoinduced charge transfer processes in modified DNA and an engineered protein." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964811359.

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15

Siriwong, Khatcharin. "A combined quantum mechanics and molecular dynamics study of charge transfer in DNA." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972057528.

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16

Mayor, Louise Charlotte. "The adsorption and charge-transfer dynamics of model dye-sensitised solar cell surfaces." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/13521/.

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In this thesis, the dye molecule cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II) (N3) is studied on the rutile TiO2(110) and Au(111) surfaces. The molecules were deposited onto the surfaces using an ultra-high vacuum (UHV) electrospray deposition system. Thermally labile molecules such as N3 cannot be deposited using the typical method of thermal sublimation, so development of this deposition technique was a necessary step for entirely in situ experiments. The geometric and electronic structure of the samples are characterised using core-level and valence band photoemission spectroscopy, x-ray absorption fine structure spectroscopy, density functional theory, resonant x-ray emission spectroscopy and scanning tunnelling microscopy. These reveal that N3 bonds to TiO2(110) by deprotonation of the carboxyl groups of one bi-isonicotinic acid ligand so that its oxygen atoms bond to titanium atoms of the substrate, and one of the thiocyanate groups bonds via a sulphur atom to an oxygen atom of the substrate. N3 bonds to Au(111) via sulphur atoms with no deprotonation of the carboxylic groups, and at low coverages decorates the Au(111) herringbone reconstruction. For N3 on TiO2, a consideration of the energetics in relation to optical absorption is used to identify the main photoexcitation channel between occupied and unoccupied molecular orbitals in this system, and also to quantify the relative binding energies of core and valence excitons. For N3 on Au(111), the energetics show that the highest occupied molecular orbital overlaps with the Au conduction band. The transfer of charge between the N3 molecule and the TiO2(110) and Au(111) surfaces was studied using resonant photoemission spectroscopy and resonant x-ray emission spectroscopy. These techniques, combined with knowledge gained about the geometric and electronic structure, are used to determine the locations and electronic levels of N3 from which charge is readily transferred to the substrate. The core-hole clock implementation of resonant photoemission spectroscopy is used to reveal that electron delocalisation from N3 to TiO2(110) occurs within 16 femtoseconds.
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17

Döring, Robin Carl [Verfasser]. "Charge-transfer dynamics in molecular donor-acceptor systems and heterostructures / Robin Carl Döring." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/116655855X/34.

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18

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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Анотація:
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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19

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 Philosophy
Department 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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20

Döring, Robin [Verfasser]. "Charge-transfer dynamics in molecular donor-acceptor systems and heterostructures / Robin Carl Döring." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/116655855X/34.

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21

Stier, William. "Non-adiabatic molecular dynamics of electron transfer in dye sensitized semiconductor systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8656.

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22

Prince, Beth Marie. "Vibrational dynamics of excited states probed by fs/ps CARS simulations and applications to ultrafast charge transfer dynamics /." [Ames, Iowa : Iowa State University], 2008.

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23

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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24

Loreau, Jérôme. "Non-adiabatic wave packet dynamics of the charge transfer and photodissociation processes involving HeH+." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210050.

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In this thesis, we present a theoretical investigation of reactive processes involving the HeH$^+$ molecular ion, with applications in laboratory and astrophysical plasma physics. We consider in particular two processes, which are the charge transfer in H + He$^+$ collisions at low energy from a molecular approach and the photodissociation of HeH$^+$.

At the molecular level, the cross section is the basic quantity that has to be determined in order to achieve an understanding of reactive processes. Its calculation will be based on the description of the reactions using an emph{ab initio}, quantum mechanical approach. In this work, we will rely on the Born-Oppenheimer approximation, which allows the molecular motion to be separated into an electronic and a nuclear motion. The evaluation of cross sections then follows two steps.

The first is the determination of the electronic structure of the molecule. We will calculate the adiabatic potential energy curves of the excited electronic states as well as the dipole matrix elements between these states. The non-adiabatic radial and rotational couplings, which result from the breakdown of the Born-Oppenheimer approximation, are also estimated. The second step is to solve the nuclear motion, which we achieve using a time-dependent method based on the propagation of wave packets on the coupled electronic states.

A particular emphasis will be put on the importance of the excited states and of the non-adiabatic couplings in the description of reactive processes.

In the treatment of the charge transfer reaction between H and He$^+$ in excited states, it is well known that the non-adiabatic radial couplings cannot be neglected. However, we will show that the inclusion of the non-adiabatic rotational couplings is also necessary in order to obtain accurate state-to-state cross sections.

In the description of the photodissociation of HeH$^+$ from its ground state, we will show the influence of the excited states on the rate constant and the role of the non-adiabatic radial couplings in the determination of partial cross sections.

We will also consider the possible astrophysical applications of the first triplet state of HeH$^+$. We will show that this state is metastable by evaluating its lifetime, and calculate the cross sections and rate constants for the photodissociation and radiative association of HeH$^+$ in this state.


Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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25

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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26

Yudiarsah, Efta. "Change transport through molecules structural and dynamical effects /." Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1219343872.

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27

Kothe, Alexander [Verfasser]. "Charge Transfer to Solvent Dynamics in Iodide Aqueous Solution Studied at Ionization Threshold / Alexander Kothe." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1070820032/34.

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28

Soniat, Marielle. "Incorporation of Charge Transfer into Classical Molecular Dynamics Force Fields with Applications in Physical Chemistry." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1945.

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The presence of charge transfer (CT) interactions is clear in a variety of systems. In CT, some electron density is shifted from one molecule to another (non-bonded) molecule. The importance of this CT interaction is unclear. Previous attempts to look at the conse- quences of CT required the use of ab initio molecular dynamics (AIMD), a computationally intensive method. Herein, a method for including CT in force field (FF) simulations is described. It is efficient, produces charges in agreement with AIMD, and prevents long- ranged CT. This CT MD method has been applied to monatomic ions in water. When solvated, ions do not have an integer charge. Anions give up some electron density to their ligands, and cations receive some electron density from their ligands. In bulk, the first solvation shell does not compensate for all CT, i.e. the charge is not smeared out over the first solvation shell. Rather, some charge is also found in the second solvation shell and further into the bulk. The charge of the first solvation shell depends on the balance between ion-water and water-water CT. When an interface is present, the charge outside of the second solvation shell will reside at the interface. This occurs even when the ion is over 15 Å away from the surface. The effect of long-ranged CT is mediated by changes in the hydrogen bonding patterns in water induced by the ions (not direct CT from the ions to distant waters). The model has also been applied to water’s ‘‘self-ions’’ hydronium and hydroxide. Trajectories from the multi-state empirical valence bond model (MS-EVB3) are analyzed. The differences between monatomic and molecular ions are explored. The direction of CT and the effect of hydrogen bonding with the ion are considered. The damping of CT as ligands are added is discussed and a method to improve the MD model, in order to account for damping, is proposed.
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29

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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30

Salzillo, Tommaso <1986&gt. "Structure, Dynamics and Reactivity in the Organic Solid State: Anthracene Derivatives and Charge Transfer Crystals." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6882/1/Salzillo_Tommaso_tesi.pdf.

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The work presented in this thesis tackles some important points concerning the collective properties of two typical categories of molecular crystals, i.e., anthracene derivatives and charge transfer crystals. Anthracene derivatives have constituted the class of materials from which systematical investigations of crystal-to-crystal photodimerization reactions started, developed and have been the subject of a new awakening in the recent years. In this work some of these compounds, namely, 9-cyanoanthacene, 9-anthacenecarboxylic acid and 9-methylanthracene, have been selected as model systems for a phenomenological approach to some key properties of the solid state, investigated by spectroscopic methods. The present results show that, on the basis of the solid state organization and the chemical nature of each compound, photo-reaction dynamics and kinetics display distinctive behaviors, which allows for a classification of the various processes in topochemical, non topochemical, reversible or topophysical. The second part of the thesis was focused on charge transfer crystals, binary systems formed by stoichiometric combinations of the charge donating perylene (D) and the charge accepting tetracyano-quinodimethane (A), this latter also in its fluorinated derivatives. The work was focused on the growth of single crystals, some of which not yet reported in the literature, by PVT technique. Structural and spectroscopic characterizations have been performed, with the aim of determining the degree of charge transfer between donor and acceptor in the co-crystals. An interesting outcome of the systematic search performed in this work is the definition of the experimental conditions which drive the crystal growth of the binary systems either towards the low (1:1) or the high ratio (3:1 or 3:2) stoichiometries.
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31

Salzillo, Tommaso <1986&gt. "Structure, Dynamics and Reactivity in the Organic Solid State: Anthracene Derivatives and Charge Transfer Crystals." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6882/.

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Анотація:
The work presented in this thesis tackles some important points concerning the collective properties of two typical categories of molecular crystals, i.e., anthracene derivatives and charge transfer crystals. Anthracene derivatives have constituted the class of materials from which systematical investigations of crystal-to-crystal photodimerization reactions started, developed and have been the subject of a new awakening in the recent years. In this work some of these compounds, namely, 9-cyanoanthacene, 9-anthacenecarboxylic acid and 9-methylanthracene, have been selected as model systems for a phenomenological approach to some key properties of the solid state, investigated by spectroscopic methods. The present results show that, on the basis of the solid state organization and the chemical nature of each compound, photo-reaction dynamics and kinetics display distinctive behaviors, which allows for a classification of the various processes in topochemical, non topochemical, reversible or topophysical. The second part of the thesis was focused on charge transfer crystals, binary systems formed by stoichiometric combinations of the charge donating perylene (D) and the charge accepting tetracyano-quinodimethane (A), this latter also in its fluorinated derivatives. The work was focused on the growth of single crystals, some of which not yet reported in the literature, by PVT technique. Structural and spectroscopic characterizations have been performed, with the aim of determining the degree of charge transfer between donor and acceptor in the co-crystals. An interesting outcome of the systematic search performed in this work is the definition of the experimental conditions which drive the crystal growth of the binary systems either towards the low (1:1) or the high ratio (3:1 or 3:2) stoichiometries.
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32

Ding, Xuesong. "Towards sequence stratigraphy 2.0: Dynamic topography, sea level change and sediment transfer from source to sink." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20665.

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Earth’s sedimentary successions are an archive of past climatic and tectonic events and sea level changes by recording the complex interactions between those processes across a wide range of time and space scales. Numerous efforts have been made to decipher this archive to obtain signatures of deep Earth dynamics (e.g. dynamic topography induced by mantle flow). However, it remains a challenge as the signals generated by dynamic topography are usually concealed by signals generated by plate tectonic processes. Sequence stratigraphy is an effective tool to analyse sedimentary units. Recently, quantitative stratigraphic analysis has been used to achieve more precise interpretations, which will likely advance the quantification of the role of controlling factors in shaping stratigraphic record. This thesis consists of two parts. The first part presents stratigraphic modelling using the surface process code pyBadlands and quantitative stratigraphic interpretations based on two well-established techniques: the trajectory analysis and the accommodation succession methods. This numerical framework contributes to the development of quantitative sequence stratigraphy which is an important component of “sequence stratigraphy 2.0”. The second part further investigates the large-scale and long-term drainage and sedimentary responses to dynamic topography. Our models predict distinct erosional and depositional landscapes, comparing with that induced by eustatic sea level changes, which provides insights into differentiating the geological signals induced by dynamic topography in tectonically-stable regions. The propagating wave of positive dynamic topography under a plateau produces a landscape that is comparable to southern Africa during Cretaceous times. The propagating wave of negative dynamic topography tilts the surface and generates depositional patterns similar to the continental interior of North America during Cretaceous times and South America during Miocene times.
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33

Saleh, Nail Asad. "Dynamical solvent effect in 1-(9-anthryl)-3-(4-dimethylaniline) propane charge transfer reactions /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060138.

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34

Smart, Martin James. "Deglaciation dynamics of the Feegletscher Nord, Switzerland : implications for glacio-fluvial sediment transfer." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/17094.

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Understanding of the processes of sediment transfer within, and from, glaciated catchments is of fundamental importance in order to establish rates of sediment transfer and resultant landscape evolution. Rates of glacio-fluvial sediment transfer are strongly controlled by glacier meltwater runoff and the availability of sediments for entrainment. However, it is becoming apparent that recently deglaciated forefields can modify the patterns of suspended sediment transfer. Glacier shrinkage exposes areas of unstable glacigenic sediments that can be subject to reworking and redistribution, and, as these environments become ice-free, heightened levels of geomorphological activity (so-called 'paraglacial' activity) are also likely to have a significant impact on both sediment and water yields from deglaciating catchments. Consequently, questions are raised as to the impacts of deglaciation upon contemporary and future rates of suspended sediment transfer, and the resultant fluvial sediments loads and rates of landscape adjustment. Therefore, the aim of this research was to present an integrated study of how sediment transfer in a glaciated catchment functions during, and is responding to, deglaciation. A variety of techniques were employed to examine the hydrological functioning of an Alpine glacier, the Feegletscher Nord, Switzerland, and the resultant temporal and spatial patterns of sediment transfer in light of catchment hydrology, ablation processes and forefield geomorphology. Data was collected over two field campaigns in 2010 and 2012 to capture the inputs, throughputs and outputs of meltwater and sediment. This research found that patterns of sediment transfer were modified within the proglacial zone, reinforcing previous findings that the location of proglacial monitoring is important in determining the observed patterns of sediment transfer. These patterns of sediment transfer were attributed to variations in forefield sediment availability, which appeared to demonstrate marked spatial variability. This variability was hypothesised to be influenced by the geomorphological characteristics of the forefield, including rock fall debris that appeared to limit sediment availability, and glacigenic sediment deposits that enhanced the availability of in-channel and channel-marginal sediments. These findings suggest that the investigation of rates of sediment transfer and paraglacial sedimentation may be complicated in catchments that have experienced complex geomorphological responses to deglaciation. In addition, the investigation of sediment transfer processes and the development of a glacier runoff model enabled the exploration of future suspended sediment loads with progressive deglaciation and a changing climate. Suspended sediment loads were predicted to experience rapid declines until the end of the 21st Century due to reductions in meltwater runoff as glacier extent is reduced. However, it is suggested that uncertainties in future sediment availability limit the usefulness of such forecasts. Consequently, this research highlights how the understanding of both sedimentary and hydrological processes in glaciated catchments may be enhanced by consideration of the changes that can occur in these environments associated with glacier shrinkage and a changing climate.
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35

Albero, Sancho Josep. "Photo-induced charge transfer reactions in quantum dot based solar cells." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/81717.

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En esta tesis doctoral se han estudiado procesos fundamentales de reacciones de transferencia de carga en películas mesoporosas de dióxido de titanio sensitivizado con puntos cuánticos, en películas finas de mezclas polímero:puntos cuánticos y en dispositivos completos de mezclas del polímero PCPDTBT y puntos cuánticos de CdSe en operaciones de trabajo reales. Los resultados obtenidos permiten abordar la fabricación de dispositivos fotovoltaicos con un conocimiento de los procesos de recombinación que limitan la eficiencia de las celdas más amplio. Y por tanto, se demuestra la posibilidad de fabricar celdas solares basadas en puntos cuánticos con eficiencias iguales o superiores a los dispositivos fotovoltaicos orgánicos.
The fundamental processes of the charge transfer reactions between titania dioxide mesoporous films and quantum dots, in blend films of the semiconductor polymer P3HT and CdSe quantum dots and in complete devices fabricated with the polymer PDPCTBT and CdSe quantum dots in working conditions have been studied in this doctoral thesis. The obtained results allow the fabrication of photovoltaic devices with a deeper and wider knowledge of the recombination processes that limit the device efficiency. Therefore, it is demonstrated the possibility of fabrication of quantum dot based solar cells with efficiencies similar or higher than the organic photovoltaic devices.
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36

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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37

Schnadt, Joachim. "Studies of Model Nanostructured Materials : Geometric and Electronic Structure, and sub-10 fs Charge Transfer Dynamics." Doctoral thesis, Uppsala University, Department of Physics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2636.

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A number of nanostructured systems has been investigated by means of Photoemission and X-ray absorption spectroscopies and by Scanning tunneling microscopy with emphasis on the geometric and electronic structure and the excited-state charge transfer dynamics. These systems comprise aromatic molecules on semiconductor surfaces (titanium dioxide), metal clusters, and an alkali-C60 compound.

Electronic and geometric structure are complementary to each other, and changes in the geometric structure are accompanied by changes in the electronic structure. Therefore, a detailed investigation of the latter makes it possible to draw conclusions on the former. In particular, this close relationship has been used to characterise the adsorbate geometry of the pyridine-carboxylic acid monomers on rutile TiO2(110), which is determined by the strong substrate bond as well as interadsorbate interactions. Similarly, it has been found that bi-isonicotinic acid adsorbs on a nanostructured anatase TiO2 film by forming strong bonds between both carboxylic groups and the substrate titanium atoms. For deposited metal clusters, the core binding energies are found to mirror the cluster size.

Resonant core electron spectroscopies have been employed to elucidate the excited-state charge transfer dynamics with respect to the transfer of an excited electron from the bi-isonicotinic acid and isonicotinic acid adsorbates to a titanium dioxide semiconductor surface. An important aspect has been the development of new variations of the method in order to be able to unravel the spectra of these relatively complex systems. While a strong excitonic effect localises the excited electron on the adsorbate for the lowest excited state, excitation to the higher excited states leads to an ultrarapid charge transfer on a low- to sub-femtosecond timescale.

In LiC60 the character of the alkali-C60 bond has been investigated. The balance between the different energy contributions points to an ionic bond with an important element of covalency.

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38

Kuhnt, Christian [Verfasser], Jürgen [Akademischer Betreuer] Popp, and Benjamin [Akademischer Betreuer] Dietzek. "Light-induced charge-transfer dynamics in Ruthenium-polypyridine complexes / Christian Kuhnt. Gutachter: Jürgen Popp ; Benjamin Dietzek." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2013. http://d-nb.info/1041874235/34.

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39

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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40

Fröbel, Friedrich Georg [Verfasser], Stefanie [Gutachter] Gräfe, and Ulf [Gutachter] Peschel. "Attosecond ionization dynamics in a molecular charge-transfer system / Friedrich Georg Fröbel ; Gutachter: Stefanie Gräfe, Ulf Peschel." Jena : Friedrich-Schiller-Universität Jena, 2019. http://d-nb.info/1207273090/34.

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41

Gori, Paul-Antoine. "Transmission dynamique d'énergie par induction : application au véhicule électrique." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC063/document.

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L’autonomie limitée du véhicule électrique est le premier frein au développement du marché de l’électrique. La charge inductive dynamique répond à ce problème, en offrant de charger son véhicule en roulant. La principale difficulté est de gérer les variations importantes du couplage magnétique lors du déplacement du véhicule, et ce pendant le transfert de puissance. Une précédente thèse dans l’équipe de recherche sur un prototype de 3 kW avait abouti au concept de recopie de tension, qui stabilise la tension en sortie du coupleur malgré la variation de couplage, et facilite notablement la conception du convertisseur DC/DC faisant interface avec la batterie. La thèse présentée ici porte sur l’adaptation du système pour fonctionner de 20 kW à 30 kW. Cette montée en puissance n’est pas évidente, du fait des importantes contraintes électriques sur les bobines du coupleur (1,4 kV sur le système de 3 kW), et du champ rayonné limité par des références normatives. Tout d’abord, nous proposons une nouvelle commande du circuit résonnant, qui permet de modifier le dimensionnement pour aboutir à des contraintes électriques plus faibles tout en conservant la recopie de tension. Ensuite, une forme de bobine en huit est étudiée pour aider à réduire le champ rayonné. Enfin, une démarche de dimensionnement est établie pour la partie électrique du système, ainsi que pour le coupleur magnétique, alliant modèle analytique et simulations à éléments finis et réduisant considérablement les temps de simulations. Les résultats de l’évaluation des performances du système dimensionné pour la haute puissance sont prometteurs
The limited electric-vehicle distance range is the main reason hindering the development of the electric transportation market. Dynamic inductive charging solves this problem, offering the possibility to charge while driving. The main issue consists in handling wide magnetic coupling variations when the vehicle is moving, while charging. A previous thesis in the research team on a 3-kW prototype led to the concept of voltage copying, which stabilises the coupler output voltage despite the varying coupling, making it easier to design the DC/DC converter linking the coupler to the battery. The hereby thesis deals with adapting this system to transfer from 20 kW to 30 kW. Raising the power is no small matter, due to the high electrical constraints on the coupled coils (1.4 kV on the 3-kW system), and the radiated field, limited by standardised thresholds. Firstly, a new control of the resonating circuit is proposed, allowing to change the system design to get lower electrical constraints and maintaining voltage copying properties. Then, an eight-shape coil was investigated in order to reduce the radiated field. Finally, a design method was conceived for the electrical part of the system, as well as the magnetic coupler, using jointly analytical models and finite element simulations to reduce simulation times. Results of the evaluated performance for such a high-power system are quite promising
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42

Liu, William K. "Electron spin dynamics in quantum dots, and the roles of charge transfer excited states in diluted magnetic semiconductors /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8588.

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43

Schneider, Katharina Elisabeth [Verfasser], and Daniel [Akademischer Betreuer] Fischer. "Dynamics in charge transfer and ionization processes in fast ion-helium collisions / Katharina Elisabeth Schneider ; Betreuer: Daniel Fischer." Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/117978491X/34.

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44

Lee, Alexis J. "Theoretical Approaches to the Characterization of Water, Aqueous Interfaces, and Improved Sampling of Protein Conformational Changes." ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1511.

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Methods to advance the understanding of water and other aqueous systems are devel- oped. This work falls into three areas: The creation of better interaction potentials for water, improved methods for sampling configurational space, and the applications of these methods to understand systems of interest. Charge transfer has been shown by ab initio methods to be important in the water–water and water–ion interactions. A model for treating charge transfer in liquid water and aqueous systems is presented in this manuscript. The model is called Discrete Charge Transfer (DCT) and is based on the commonly-used TIP4P/2005 model, which represents the charge distribution of water molecules with three charge sites. Such models have been very successful in reproducing many of the physical properties of water. Charge transfer is introduced by transferring a small amount of charge, -0.02e, from the hydrogen bond acceptor to the hydrogen bond donor, as has been indicated by electronic structure calculations. We have parameterized both polarizable and non-polarizable potentials, optimized to include charge transfer. Methods to surmount the obstacles incurred by the introduction of charge transfer, which involve the amount of charge transfer at large distances and implementation into Molecular Dynamics simulation, is presented, along with our results assessing the importance of charge transfer in liquid water and aqueous systems. Also presented is a method for improving eciency of a sampling technique, Replica Exchange, by reducing the number of replicas. The improved method is called Replica Exchange with Driven Scaling (REDS2).
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45

Zhang, Lei. "Exploring Electron Transfer Dynamics of Novel Dye Sensitized Photocathodes : Towards Solar Cells and Solar Fuels." Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302263.

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The design of dyes for NiO-based dye-sensitized solar cells (DSSCs) has drawn attention owing to their potential applications in photocatalysis and because they are indispensable for the development of tandem dye-sensitized solar cells. The understanding of the electron transfer mechanisms and dynamics is beneficial to guide further dye design and further improve the performance of photocathode in solar cells and solar fuel devices. Time-resolved spectroscopy techniques, especially femtosecond and nanosecond transient absorption spectroscopy, supply sufficient resolution to get insights into the charge transfer processes in p-type dye sensitized solar cell and solar fuel devices. In paper I-V, several kinds of novel organic “push-pull” and inorganic charge transfer dyes for sensitization of p-type NiO, were systematically investigated by time-resolved spectroscopy, and photo-induced charge transfer dynamics of the organic/inorganic dyes were summarized. The excited state and reduced state intermediates were investigated in solution phase as references to confirm the charge injection and recombination on the NiO surface. The charge recombination kinetics is remarkably heterogeneous in some cases occurring on time scales spanning at least six orders of magnitude even for the same dye. In this thesis, we also proposed a novel concept of solid state p-type dye sensitized solar cells (p-ssDSSCs) for the first time (paper VI), using an organic dye P1 as sensitizer on mesoporous NiO and phenyl-C61-butyric acid methyl ester (PCBM) as electron conductor. Femtosecond and nanosecond transient absorption spectroscopy gave evidence for sub-ps hole injection from excited P1 to NiO, followed by electron transfer from P1●- to PCBM. The p-ssDSSCs device showed an impressive 620 mV open circuit photovoltage. Chapter 6 (paper VII) covers the study of electron transfer mechanisms in a covalently linked dye-catalyst (PB-2) sensitized NiO photocathode, towards hydrogen producing solar fuel devices. Hole injection from excited dye (PB-2*) into NiO VB takes place on dual time scales, and the reduced PB-2 (PB-2●-) formed then donates an electron to the catalyst unit.  The subsequent regeneration efficiency of PB-2 by the catalyst unit (the efficiency of catalyst reduction) is determined to ca. 70%.
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46

Richier, Mathieu. "Conception de dispositifs actifs de maintien de stabilité pour les véhicules évoluant en milieux naturels." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-01066614.

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La problématique de cette thèse réside dans la caractérisation et le maintien de la stabilité des Véhicules Légers Tout Terrain (VLTT). Elle se concentre plus particulièrement sur le développement de systèmes de sécurité actifs capables à la fois de prévenir le conducteur des risques encourus mais aussi de les limiter afin d'assurer l'évolution du véhicule dans une zone de stabilité prédéfinie. Comme le cadre expérimental privilégié est l'application à la stabilité des quadricycles légers à moteurs, plus connus sous le terme anglophone "quad", une des contraintes du projet a été de se limiter à un système sensoriel bas-coût afin d'être en mesure d'industrialiser un tel système. En premier lieu, les métriques de stabilité (Transfert de Charge Latéral et Longitudinal : TCLa et TCLo) ont été choisies grâce à une étude préliminaire sur la stabilité des VLTT. Par la suite, une modélisation 2D en roulis et en tangage avec la prise en compte des déplacements du pilote sur le véhicule sont présentées, ce qui permet d'estimer respectivement le TCLa et le TCLo uniquement à partir de la mesure de l'accélération latérale et longitudinale. Étant donné que pour la suite des travaux, l'anticipation du risque de renversement latéral est nécessaire, un modèle 2D en lacet du véhicule est proposé afin d'obtenir un modèle analytique décrivant la dynamique latérale du véhicule. La suite du mémoire présente les différentes techniques d'observation proposées pour l'estimation des variables et paramètres non-directement mesurables du modèle en lacet du véhicule et qui influencent sa stabilité latérale : les glissements, les conditions d'adhérence et les inclinaisons du véhicule. Plusieurs observateurs ont été proposés, dont le dernier permet de considérer des conditions d'adhérence différentes entre les essieux avant et arrière en utilisant plus largement les accélérations mesurées. Cela permet d'intégrer les passages de sous- à sur-vireur qu'il est essentiel de considérer quand on étudie la stabilité de ce type de véhicule. Ainsi, l'estimation des glissements est toujours pertinente, ce qui permet d'obtenir par la suite une meilleure prédiction de la métrique de stabilité latérale (TCLa) quel que soit le comportement du véhicule. Puis en s'appuyant sur les estimations des observateurs couplées aux modèles dynamiques du véhicule et sur l'extrapolation des commandes du conducteur sur un horizon de prédiction, il est possible de prédire les évolutions du TCLa. Cette valeur prédite ainsi que les estimations en ligne des métriques de stabilité constituent alors le point d'entrée pour la synthétisation d'un système de sécurité actif dédié aux VLTT. Celui-ci est basé sur la génération d'un retour d'effort au niveau de la gâchette des gaz permettant soit d'informer le pilote du risque encouru par la création d'une sensation de dureté, soit d'imposer le retour complet de la gâchette des gaz, ce qui implique une diminution de la vitesse et donc la réduction du risque. Finalement, dans le cas où il est possible de maîtriser la vitesse du véhicule par l'installation d'un système de rétroaction sur les freins (Quad haut de gamme ou robot mobile), les derniers travaux présentés s'intéressent aux techniques de commande prédictive à modèle afin de calculer en temps-réel la vitesse maximale admissible, qui assure l'évolution du critère de stabilité choisi dans un domaine de stabilité. Les modèles, les observateurs, la prédiction du TCLa et les 2 systèmes de prévention présentés dans ce mémoire ont été validés et testés au travers de simulations avancées et d'essais expérimentaux réalisés sur un quad agricole et un robot autonome. Il apparaît alors qu'en plus d'être efficace pour la prévention des risques de renversement à hautes dynamiques, le système de sécurité est industriellement viable. Cela a été rendu possible grâce à une conception reposant uniquement sur des actionneurs et un système sensoriel, dont les coûts sont en adéquation avec le prix d'un VLTT.
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47

Bender, Shana Lynn. "A study of protein dynamics and cofactor interactions in Photosystem I." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26463.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Barry, Bridette; Committee Member: Doyle, Donald; Committee Member: Kelly, Wendy; Committee Member: McCarty, Nael; Committee Member: Schimdt-Krey, Ingaborg. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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48

Olive, Alexandre. "Transferts d’énergie, de charge et d’information optique dans des matériaux nano-structurés, conception et spectroscopie à l’échelle moléculaire." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13691.

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Les 2,3-dialcoxy-acènes possèdent la faculté de s’auto-assembler en solution dans un empilement remarquable, conduisant à la formation de nano-fibres. Les interactions moléculaires au sein de ces nano-fibres et l’orientation des molécules, favorisent le transport d’énergie après exposition à la lumière. Les mécanismes de transfert d’énergie ont été élucidés en incorporant des accepteurs d’énergie permettant de sonder les états excités de la matrice hôte, et d’extraire l’énergie ; La microscopie confocale de fluorescence (spectrale, dynamique, sous lumière polarisée) a été la technique privilégiée pour la caractérisation de ces systèmes. La morphologie des nanostructures a également été déterminée par mesures en AFM. Des données spectroscopiques obtenues sur des cristaux à base de 2,3-dialcoxy-acènes nous ont permis d’affiner les résultats obtenus sur les fibres, et d’étudier l’effet du nano-confinement sur la diffusion des états excités
2,3-dialkoxy-acenes can self-assemble in solution, with a remarkable packing, leading to the formation nanofibers. The molecular interaction inside the nano-fiber and the relative orientation of the molecules, promote energy transport after light exposure. The energy transfer mechanisms have been elucidated incorporating energy acceptor which can allow to probe excited states inside the host matrix, extracting the energy. Fluorescence confocal microscopy (spectral, dynamic, under polarized light) has been used to characterize the photo-physic properties of these nanofibers. The nanostructure morphologies have also been determined by AFM measurements. Spectroscopic data obtained on 2,3-dialkoxy-acenes crystal , have allow us to refine the data obtained on the fibers, and to study nano-confinement effect on the dynamic of the excited state
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49

Ri, Songyon. "Spectroscopic Studies on the Excited States of 4-(9-anthryl) aniline and its Dynamics of the Charge Transfer State Formation." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/202453.

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50

Britton, Andrew James. "Charge transfer dynamics of adsorbate molecules on metal and semiconductor surfaces relating to fundamental processes in dye-sensitized solar cells." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13459/.

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The charge transfer dynamics between adsorbate molecules and surfaces are important for a variety of different technologies but especially for dye-sensitized solar cells. The main aim of this thesis was to study charge transfer between organic molecules and surfaces, especially relating to the situation observed in dye sensitized solar cells. This broad aim can be split into two distinct research objectives. One of these was to study the charge transfer between a Au (111) surface and a variety of different molecules using synchrotron-based photoemission spectroscopy. Resonant photoemission spectra of a C60 monolayer on Au (111) showed distinctive superspectator features which were not observed for the multilayer or clean gold spectra. These features were determined to be resultant from spectator decay involving electrons transferred from the gold substrate to the adsorbed molecule, either in the ground state or during the timescale of the core-hole lifetime. These features were also found for monolayers of bi-isonicotinic, isonicotinic, nicotinic and picolinic acid on gold, but not for the dye molecule, N3, on gold. This suggests that, although charge transfer occurs between the surface and the ligand molecules that constitute N3, no charge transfer occurs between the N3 dye molecule and the gold. The other objective was to determine whether the core-hole clock technique, previously only used in photoemission spectroscopy, could be adapted for resonant inelastic x-ray scattering. For this, bi-isonicotinic acid on TiO2 was studied because this system had already been explored using photoemission spectroscopy. The charge transfer times were measured using the relative decrease in the elastic peaks for the LUMO and LUMO+1 photon energies of the multilayer and monolayer. This gave a similar result to the photoemission studies providing more confidence for using this adaptation in situations where photoemission would be impossible, such as buried interfaces.
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