Tesi sul tema "Charge transfer in biology"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Charge transfer in biology.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Charge transfer in biology".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Zhang, Houyu. "Theories of long-range charge transfer in DNA and quantum dissipation /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202002%20ZHANG.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 169-170). Also available in electronic version. Access restricted to campus users.
2
Bjorklund, Chad Christopher. "The effects of nucleosome core particle packaging on DNA charge transport". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/c_bjorklund_120606.pdf.
Testo completo
3
Amstutz, Michael D. "Development of a charge-shifting polyion-mediated intramammary gene transfer system for production of recombinant proteins in milk /". The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487943610785448.
Testo completo
4
Güler, Gözde. "Part 1 controlling barriers to charge transfer in DNA : Part 2 : DNA-directed assembly of conducting oligomers /". Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26621.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Schuster, Gary; Committee Member: Barry, Bridgette; Committee Member: Collard, David; Committee Member: Tolbert, Laren; Committee Member: Wartell, Roger. Part of the SMARTech Electronic Thesis and Dissertation Collection.
5
Roberts, Lezah Wilette. "Effect of Netropsin on One-electron Oxidation of DNA". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7228.
Testo completoAbstract (sommario):
One electron oxidation of DNA has been studied extensively over the years. When a charge is injected into a DNA duplex, it migrates through the DNA until it reaches a trap. Upon further reactions, damage occurs in this area and strand cleavage can occur. Many works have been performed to see what can affect this damage to DNA. Netropsin is a minor groove binder that can bind to tracts of four to five A:T base pairs. It has been used in the studies within to determine if it can protect DNA against oxidative damage, caused by one-electron oxidation, when it is bound within the minor groove of the DNA. By using a naphthacenedione derivative as a photosensitizer, several DNA duplexes containing netropsin binding sites as well as those without binding sites, were irradiated at 420 nm, analyzed, and visualized to determine its effect on oxidative damage. It has been determined netropsin creates a quenching sphere of an average of 5.8 * 108 Šwhether bound to the DNA or not. Herein we will show netropsin protects DNA against oxidative damage whether it is free in solutions or bound within the minor groove of a DNA duplex.
6
Güler, Gözde. "Part 1: Controlling barriers to charge transfer in DNA Part 2: DNA-directed assembly of conducting oligomers". Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26621.
Testo completoAbstract (sommario):
A series of anthraquinone-linked DNA oligonucleotides was prepared and the efficiency of long-distance radical cation migration was measured. In one set of oligonucleotides, two GG steps are separated by either a TATA or an ATAT bridge. In these two compounds, the efficiency of radical cation migration from GG to GG differs by more than an order of magnitude. Replacement of the thymines in the TATA or ATAT bridges with 3-methyl-2-pyridone (t, a thymine analog) results in the much more efficient radical cation migration across the bridge in both cases. This is attributed to a decrease in the oxidation potential of t to a value below that of A. In contrast, replacement of the thymines in the TATA or ATAT bridges with difluorotoluene (f, a thymine analog with high oxidation potential) does not measurably affect radical cation migration. These findings are readily accommodated by the phonon-assisted polaron-hopping mechanism for long-distance charge transfer in duplex DNA and indicate that DNA in solution behaves as a polaronic semiconductor.
Oligomers containing thiophene-pyrrole-thiphene (SNS) monomers were covalently linked to the nucleobases of DNA. Treatment of these oligomers with horseradish peroxidase and hydrogen peroxide lead to the formation of conducting oligomers conjoined to the DNA. The DNA template aligns the oligomers along one strand of the duplex and limits the intermolecular reaction of monomers. This method enables utilization of the unique self-recognizing properties and programmability of DNA to create tailored oligomers.
7
Ghosh, Avik Kumar. "Charge migration and one-electron oxidation at adenine and thymidine containing DNA strands and role of guanine N1 imino proton in long range charge migration through DNA". Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05132007-000502/.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.Wartell, Roger, Committee Member ; Bunz, Uwe, Committee Member ; Doyle, Donald, Committee Member ; Fahrni, Christoph, Committee Member ; Schuster, Gary, Committee Chair.
8
Das, Prolay. "Long-Range Charge Transfer in Plasmid DNA Condensates and DNA-Directed Assembly of Conducting Polymers". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19856.
Testo completoAbstract (sommario):
Long-distance radical cation transport was studied in DNA condensates where linearized pUC19 plasmid was ligated to an oligomer and transformed into DNA condensates with spermidine. DNA condensates were detected by Dynamic Light Scattering and observed by Transmission Electron Microscopy. Introduction of charge into the condensates causes long-distance charge migration, which is detected by reaction at the remote guanines. The efficiency of charge migration in the condensate is significantly less than it is for the corresponding oligomer in solution. This result is attributed to a lower mobility for the migrating radical cation in the condensate, caused by inhibited formation of charge-transfer-effective states. Radical cation transport was also studied in DNA condensates made from an oligomer sandwiched between two linearized plasmids by double ligation. Unlike the single ligated plasmid condensates, the efficiency of charge migration in the double ligated plasmid-condensates is high, indicative of local structural and conformational transformation of the DNA duplexes.
Organic monomer units having extended ð-conjugation as part of a long conducting polymer was synthesized and characterized. The monomer units were covalently attached to particular positions in DNA oligonucleotides by either the convertible nucleotide approach or by phosphoramidite chemistry. Successful attachment of the monomer units to DNA were confirmed by mass spectral analysis. The DNA-conjoined monomer units can self assemble in the presence of complementary sequences which act as templates that can control polymer formation and structure. By this method the para-direction of the polymer formation can be enforced and may be used to generate materials having nonrecurring, irregular structures.
9
Mecker, Christoph J. Chemistry Faculty of Science UNSW. "The synthesis of advanced " special pair " models for the photosynthetic reaction centre". Awarded by:University of New South Wales. School of Chemistry, 2000. http://handle.unsw.edu.au/1959.4/17835.
Testo completoAbstract (sommario):
Multi-step photoinduced electron transfer takes place over a large distance in the photosynthetic reaction centres (PRCs). Electron donor in this life-spending event is the photo-excited 'special pair', a unit of two electronically coupled porphyrinoid chromophores. Bacteriopheophytin and two quinone molecules function as electron acceptors and contribute to the charge separation with almost unit quantum efficiency. The natural photosynthetic reaction centre is the most sophisticated molecular electronic device to date and interest is high in increasing our understanding of the basic quantum mechanical principles behind efficient electron transfer and ultimately copying Nature and construct similar efficient devices. Two main approaches towards a better understanding of the mechanisms involved have been taken. The more biological disciplines isolate, cultivate and alternate reaction centres whereas synthetic chemists prefer to construct well-defined models that mimic certain aspects of the reaction centres. Such a synthetic approach is described in the 'Synthesis of Advanced 'Special Pair' Models for the Photosynthetic Reaction Centre'. The aspect to be mimicked is the 'special pair'. One or two porphyrins in a well-defined spatial disposition (kinked or non-kinked in respect to each other) were to act as electron donor in rigid bichromophoric and trichromophoric systems. A tetracyanonaphthoquinodimethane (TCNQ) unit was employed as the electron acceptor in the series of dyads synthesised. The TCNQ acceptor was replaced by a naphthoquinone (NQ) primary acceptor covalently linked to a TCNQ secondary electron acceptor in the series of triads. Rigid norbornylogous bridges held the chromophores in place and Diels-Alder methodology as well as condensation reactions were applied to link donor, bridge and acceptor components. Despite larger interchromophoric separation than in the natural 'special pair', the two porphyrin chromophores of the series of 'special pair' dyads show some interaction and thereby prove the success of our approach towards 'special pair' mimics. Strong fluorescence quenching in the porphyrin-TCNQ dyads indicates the sought after electron transfer process. A number of synthetic problems experienced and overcome in the synthesis of the series of triads led to discovery of a one-step 'bis-ketonisation' from an olefin under Sharpless bis-hydroxylation conditions with N-methylmorpholine-N-oxide. High pressure was applied to circumvent a lack of reactivity in the condensation reaction used to attach the porphyrin moieties (one or two) to the donor backbone. For the linkage of donor, bridge and acceptor component, a procedure was developed and successfully applied to give the giant mono-porphyrin-NQ-TCNQ trichromophore. In a similar manner 'special pair' trichromophoric systems should be available as part of future work.
10
Umeweni, Chiko. "Synthesis of Internally Linked Carbazole DNA Oligomers: A Potential Monitor for Charge Transfer in DNA Studies". Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-07052005-161648/.
Testo completo
11
Wallrapp, Frank. "Mixed quantum and classical simulation techniques for mapping electron transfer in proteins". Doctoral thesis, Universitat Pompeu Fabra, 2011. http://hdl.handle.net/10803/22685.
Testo completoAbstract (sommario):
El
objetivo
de
esta
tesis
se
centra
en
el
estudio
de
la
transferencia
de
electrones
(ET),
una
de
las
reacciones
más
simples
y
cruciales
en
bioquímica.
Para
dichos
procesos,
obtener
información
directa
de
los
factores
que
lo
promueves,
asi
como
del
camino
de
transferencia
electronica,
no
es
una
tarea
trivial.
Dicha
información
a
un
nivel
de
conocimiento
detallado
atómico
y
electrónico,
sin
embargo,
es
muy
valiosa
en
términos
de
una
mejor
comprensión
del
ciclo
enzimático,
que
podría
conducir,
por
ejemplo,
a
un
diseño
más
eficaz
de
inhibidores.
El
objetivo
principal
de
esta
tesis
es
el
desarrollo
de
una
metodología
para
el
estudio
cuantitativo
de
la
ET
en
los
sistemas
biológicos.
En
este
sentido,
hemos
desarrollado
un
nuevo
método
para
obtener
el
camino
de
transferencia
electrónico,
llamado
QM/MM
e-‐
Pathway,
que
se
puede
aplicar
en
sistemas
complejos
con
ET
de
largo
alcance.
El
método
se
basa
en
una
búsqueda
sucesiva
de
residuos
importantes
para
la
ET,
utilizando
la
modificación
de
la
región
quantica
en
métodos
mixtos
QM/MM,
y
siguiendo
la
evolución
de
la
densidad
de
espín
dentro
de
la
zona
de
transferencia.
Hemos
demostrado
la
utilidad
y
la
aplicabilidad
del
algoritmo
en
el
complejo
P450cam/Pdx,
identificando
el
papel
clave
de
la
Arg112
(en
P450cam)
y
del
Asp48
(en
Pdx),
ambos
conocidos
en
la
literatura.
Además
de
obtener
caminos
de
ET,
hemos
cuantificado
su
importancia
en
términos
del
acoplamiento
electrónico
entre
el
dador
y
aceptor
para
los
diferentes
caminos.
En
este
sentido,
se
realizaron
dos
estudios
de
la
influencia
del
solvente
y
de
la
temperatura
en
el
acoplamiento
electrónico
para
sistemas
modelo
oligopéptidos.
Ambos
estudios
revelaron
que
los
valores
del
acoplamiento
electrónico
fluctúan
fuertemente
a
lo
largo
de
las
trayectorias
de
dinámica
molecular
obtenidas,
y
el
mecanismo
de
transferencia
de
electrones
se
ve
ampliamente
afectado
por
el
espacio
conformacional
del
sistema.
La
combinación
del
QM/MM
e-‐pathway
y
de
los
cálculos
de
acoplamiento
electronico
fueron
utilizados
finalmente
para
investigar
la
ET
en
el
complejo
CCP/Cytc.
Nuestros
hallazgos
indican
el
papel
fundamental
del
Trp191
en
localizar
un
estadio
intermedio
para
la
transferencia
electronica,
así
como
el
camino
ET
principal
que
incluye
Ala194,
Ala193,
Gly192
y
Trp191.
Ambos
hallazgos
fueron
confirmados
a
través
de
la
literatura.
Los
resultados
obtenidos
para
el
muestro
de
manios
de
ET,
junto
con
su
evaluación
a
través
de
cálculos
de
acoplamiento
electrónico,
sugieren
un
enfoque
sencillo
y
prometedor
para
investigar
ET
de
largo
alcance
en
proteínas.The focus of this PhD thesis lies on electron transfer (ET) processes, belonging to the simplest but most crucial reactions in biochemistry. Getting direct information of the forces driving the process and the actual electron pathway is not a trivial task. Such atomic and electronic detailed information, however, is very valuable in terms of a better understanding of the enzymatic cycle, which might lead, for example, to more efficient protein inhibitor design. The main objective of this thesis was the development of a methodology for the quantitative study of ET in biological systems. In this regard, we developed a novel approach to map long-‐range electron transfer pathways, called QM/MM e-‐Pathway. The method is based on a successive search for important ET residues in terms of modifying the QM region following the evolution of the spin density of the electron (hole) within a given transfer region. We proved the usefulness and applicability of the algorithm on the P450cam/Pdx complex, indicating the key role of Arg112 of P450cam and Asp48 of Pdx for its ET pathway, both being known to be important from the literature. Besides only identifying the ET pathways, we further quantified their importance in terms of electronic coupling of donor and acceptor incorporating the particular pathway residues. Within this regard, we performed two systematic evaluations of the underlying reasons for the influence of solvent and temperature onto electronic coupling in oligopeptide model systems. Both studies revealed that electronic coupling values strongly fluctuate throughout the molecular dynamics trajectories obtained, and the mechanism of electron transfer is affected by the conformational space the system is able to occupy. Combining both ET mapping and electronic coupling calculations, we finally investigated the electron transfer in the CcP/Cytc complex. Our findings indicate the key role of Trp191 being the bridge-‐localized state of the ET as well as the main pathway consisting of Ala194, Ala193, Gly192 and Trp191 between CcP and Cytc. Both findings were confirmed through the literature. Moreover, our calculations on several snapshots state a nongated ET mechanism in this protein complex. The methodology developed along this thesis, mapping ET pathways together with their evaluation through electronic coupling calculations, suggests a straightforward and promising approach to investigate long-‐range ET in proteins.
12
Ding, Yanli. "Studies of charge translocation by Bufo marinus Na⁺/K⁺ ATPase in its Na⁺/Na⁺ exchange mode". Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1258082803.
Testo completo
13
Lüdemann, Gesa [Verfasser], e M. [Akademischer Betreuer] Elstner. "Light-induced Charge Transfer in Proteins of the Cryptochrome/Photolyase Family / Gesa Lüdemann. Betreuer: M. Elstner". Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1075253667/34.
Testo completo
14
Holub, Daniel [Verfasser], e M. [Akademischer Betreuer] Elstner. "Application and Development of Charge Transfer Simulations in Biological and Organic Systems / Daniel Holub ; Betreuer: M. Elstner". Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/1192373723/34.
Testo completo
15
Odlander, Paulina. "Optimisation and Validation of PCR Method for HLA Gene Expression to Enable PCR System Transfer and Master Mix Change". Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-171826.
Testo completoAbstract (sommario):
Health Tech company Dynamic Code AB provides a PCR test for determination of HLA DQ-genes connected to development of celiac disease. The PCR method is probe based and in real time and is at this time carried through on the, somewhat outdated, PCR instrument from Thermo Fisher/Applied Biosystems called 7300 Real-Time PCR System. The run time for this analysis on the instrument is 1 hour and 50 minutes. The Master Mix in use is TaqMan™ Gene Expression Master Mix, from the same manufacturer. Moving on to a more modern PCR instrument is a natural step for the company and is favourable in several regards, one of them being the run time that will be cut by 50 minutes, allowing for more samples to be analysed in the same amount of time. The objective is to move the HLA analysis to Thermo Fisher’s QuantStudio™ 6 and 7 Flex Systems and at the same time change the Master Mix to SolisFast® Probe qPCR Mix (Purple) from Solis BioDyne, in order to achieve better accuracy as this Master Mix is more compatible with the latter instrument, along with reducing reagent cost as it is less expensive. In order to find the optimal primer and probe concentration for each target included in the HLA analysis, their concentrations were varied and tested with the new Master Mix on the new instrument. PCR instrument transfer and Master Mix change was successful and validation experiments showed a 98,9% accuracy for the new method compared to the original method.
16
Mohideen, Mohamed Farhaan. "Charge transfer process". Thesis, Staffordshire University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246022.
Testo completo
17
Liu, Chuan. "Charge transport and charge transfer at organic semiconductor heterojunctions". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611516.
Testo completo
18
Stanger, Jonathan Jeffrey. "Charge Transfer Mechanisms in Electrospinning". Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/1667.
Testo completoAbstract (sommario):
Electrospinning is a method of producing nano structured material from a polymer solution or melt using high strength electric fields. It is a process that has yet to find extensive industrial application yet shows promise if obstacles such as low rate of production overcome perhaps by more complete theoretical modelling. This work examines the effects of adding an ionic salt to a solution of poly(vinyl alcohol) in water. The direct effect was an increase the charge density and electric current. It was found that an increase in charge density decreases the mass deposition rate and forms a thinner initial jet. When the sign of the charge on the polymer solution was changed from positive to negative the charge density increased and the initial jet diameter and mass deposition rate also decreased. It was proposed that a smaller radius of curvature is formed by the Taylor cone at higher charge densities resulting in a smaller “virtual orifice”. The extent of the bending instability was explored and it was found that adding ionic salt results in a decrease in the bending instability resulting in thicker fibres. Changing the sign of the charge on the polymer solution from positive to negative resulted in an increase in the bending instability and resulted in thinner fibres. The charge transfer mechanisms used in different electrospinning models are explored and some assumptions not explicitly stated are discussed. From this discussion a generalized equation describing the charge transport mechanisms is proposed.
19
Lindner, Susi. "Charge transfer at phthalocyanine interfaces". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-146526.
Testo completoAbstract (sommario):
Using X-ray photoelectron (XPS) and X-ray absorbtion spectroscopy (XAS) we demonstrate charge transfer at an interface between two transition metal phthalocyanines, MnPc and F16CoPc, resulting in charged MnPc + and F16CoPc -, species. Density functional theory calculations reveal that a hybrid state is formed between the two types of phthalocyanines, which causes this charge transfer. For the hybrid state the Mn3dxz interacts with the Co 3dz2 orbital leading to a two-level system.
Moreover, we have prepared mixed films out of this pair, which were characterized also by means of electron energy-loss spectroscopy. Our data reveal the formation of MnPc/F16CoPc charge transfer dimers in analogy to the heterojunction. The electronic excitation spectrum of these blends is characterized by a new low energy excitation at 0.6 eV.
20
Rickman, Edward E. "Study of resonant charge transfer". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/101461.
Testo completoAbstract (sommario):
Experimental measurements ol N₂ resonant charge transfer cross sections were performed. It was found that the energy of electrons used to produce the N₂⁺ ions is an important variable with respect to cross section. An examination of the experimental precision was performed and it was found that the precision of measurement was insufficient to determine the exact form of this relationship. The effect of ion energy (collisional energy) was too small to be seen.
Modulated detection was used to improve precision and permit measurement at high noise levels. A description of the apparatus is provided. Consideration of other systems and the suitability of their resonant charge transfer reactions for experimental investigation is discussed. Various theoretical models for estimation of cross section were examined.M.S.
21
Zhu, Yongbao. "Charge transfer in conjugated organometallic materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ56656.pdf.
Testo completo
22
Bradley, J. P. "Charge transfer during ion-atom collisions". Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426960.
Testo completo
23
Kambhampati, Patanjali. "Adsorbate-substrate charge transfer excited states /". Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Testo completo
24
Adamczyk, Katrin. "Ultrafast charge transfer processes in solution". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16202.
Testo completoAbstract (sommario):
Die Reaktionspfade und Reaktionsdynamik photoinduzierter bimolekularer Ladungstransferreaktionen werden mit Hilfe der ultraschnellen polarisationsabhängigen UV-Pump/IR-Probe-Spektroskopie charakterisiert. Allgemein akzeptierte Modelle zur Beschreibung von bimolekularen Elektrontranserreaktionen nehmen an, dass Ladungstrennung in polaren Lösungsmitteln zu zwei Arten von Ionenpaaren führt, den lockeren (LIPs) und den engen Ionenpaaren (TIPs). TIPs und LIPs können durch die Beobachtung von Schwingungsmoden spektroskopisch unterschieden werden. Allerdings deuten die multiplen Zeitskalen sowohl für die Bildung von TIPs als auch LIPs darauf hin, dass eine Unterscheidung in zwei Arten von Ionenpaaren mit definierter Geometrie eine erhebliche Vereinfachung ist. TIPs und LIPs sind vielmehr als Grenzfälle zu betrachten, zwischen derer eine kontinuierliche Verteilung verschiedener Ionenpaare existiert. Die Natur der Ionenpaare wird durch die Verteilung der neutralen Reaktionspaare vor Initiation der Reaktion bestimmt. Außerdem wird gezeigt, dass TIPs höchst anisotrop sind. Die Wichtigkeit der beidseitigen Orientierung der Reaktanten wird dabei offengelegt. Weiterhin wird erstmalig ein femtosekundenspektroskopischer Beweis für die Existenz von Kohlensäure in wäßriger Lösung präsentiert. Eine Photosäure wurde verwendet, um die ultraschnelle Protonierung von Bikarbonat optisch auszulösen. Kohlensäure wurde bisher als Feststoff in Eismatrizen und in der Gasphase detektiert. Da Kohlensäure als Intermediat zwischen Kohlenstoffdioxid und Bikarbonat postuliert wird, ist ihre Charakterisierung von immenser Bedeutung für das Verständnis grundlegender Säure-Base Chemie von Karbonaten in wäßriger Lösung. Die Analyse der zeitabhängigen Signale unter Verwendung eines theoretischen Modells erlaubt die Bestimmung der bimolekularen Reaktionsdynamik. Dies ermöglicht einen Einblick in die Säure-Base Chemie von Kohlensäure.The reaction pathways and dynamics of photoinduced bimolecular charge transfer reactions are characterised with ultrafast polarisation-sensitive UV-pump/IR-probe-spectroscopy. Generally accepted models for bimolecular electron transfer reactions suppose that charge separation in polar solvents leads to two geminate ion pairs, namely loose (LIPs) and tight ion pairs (TIPs). By monitoring vibrational marker modes TIPs and LIPs can be distinguished spectroscopically. However, multiple time scales for the formation of TIPs and LIPs indicate that a distinction between two kinds of ion pairs with well-defined geometries is a considerable simplification. TIPs and LIPs should rather be regarded as limiting cases, as there is a continuous distribution of different ion pairs between these two limits. The crucial parameter governing the nature of the ion pairs is the distribution of neutral reaction pairs subsequent to initiation of the reaction. Furthermore, TIPs are found to be highly anisotropic, revealing the importance of mutual orientation of the reactants. This thesis also presents for the first time femtosecond infrared spectroscopic results proving the existence of carbonic acid in aqueous solution. A photoacid is used to optically trigger the ultrafast protonation of bicarbonate. Carbonic acid has only been detected as solid existing in ice matrices and in the gas phase, so far. Because carbonic acid is often postulated as intermediate between carbon dioxide and bicarbonate its characterisation is of substantial support in understanding fundamental acid-base chemistry of carbonates in aqueous solution as well as in biophysical situations. Analysing the time-dependent signals using a theoretical model to describe bimolecular reaction dynamics an on-contact proton transfer reaction rate is derived. This gives an insight into the acid-base chemistry of carbonic acid.
25
Taylor, Gordon. "Simulation of charge transfer at ultramicrointerfaces". Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/13078.
Testo completoAbstract (sommario):
This work details the simulation of charge transfer at ultramicrointerfaces. A novel algorithm is presented for the simulation of electrochemical techniques applied to both ultramicrodisc and ultramicropipette electrodes. Numerical Method. The simulations employ the Crank-Nicolson finite differences or the Alternating Direction Implicit (ADI) method extended to include expansion of the space grid in two dimensions, a n-point current calculation and implicit determination of boundary conditions. The effects are determined of; point separation, choice of grid expansion equation, boundary conditions and relative number of points on electrode and in solution. Also, diffusion geometry, time increment, and the stability of the algorithm are considered in detail. The various methods currently available to model electrochemical response at ultramicrointerfaces are discussed, together with their limitations and a suggested protocol for their use. Computing. All programs are written in FORTRAN and all calculations performed in double precision. Source codes were compiled and run on the Edinburgh Multi-Access System (EMAS). Electrochemical techniques. Techniques simulated include cyclic voltammetry and chronoamperometry at macro, ultramicrodisc and ultramicropipette electrodes, including asymmetric sweep voltammetry at ultramicropipette electrodes. Results are presented for both reversible and quasi-reversible charge transfer. Effects of sweep rate, electrode radius, charge transfer coefficient and rate of charge transfer are studied. Disc and pipette electrochemical responses are compared over a range of experimental parameters. The simulation method presented is fast, accurate and stable over a wide range of experimental parameters and is easily adapted to different electrode geometries and experimental techniques.
26
Clay, R. T., A. B. Ward, N. Gomes e S. Mazumdar. "Bond patterns and charge-order amplitude in quarter-filled charge-transfer solids". AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/623194.
Testo completoAbstract (sommario):
Most quasi-one-dimensional (quasi-1D) quarter-filled organic charge-transfer solids (CTS) with insulating ground states have two thermodynamic transitions: a high-temperature metal-insulator transition followed by a low-temperature magnetic transition. This sequence of transitions can be understood within the 1D Peierlsextended Hubbard (PEH) model. However, in some quasi-1D CTS both transitions occur simultaneously in a direct metal to spin-gapped insulator transition. In this second class of materials the organic stack bond distortion pattern does not follow the pattern of a second dimerization of a dimer lattice. These materials also display charge ordering of a large amplitude below the transition. Using quantum Monte Carlo methods we show that the same PEH model can be used to understand both classes of materials, however, within different parameter regions. We discuss the relevance of our work to experiments on several quarter-filled conductors, focusing in particular on the materials (EDO-TTF) 2X and (DMEDO-TTF) 2X.
27
Preuss, Kathryn Elvia. "Sulfur nitrogen heterocycles as charge transfer materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ53510.pdf.
Testo completo
28
Schirra, Laura Kristy. "Charge Transfer at Metal Oxide/Organic Interfaces". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/217090.
Testo completoAbstract (sommario):
Interfacial charge transfer between metal oxides and organic semiconductors has been found to limit the efficiency of organic optoelectronic devices. Although a number of investigations of inorganic/organic systems exist, very few generally applicable rules for oxide/organic interfaces have been developed and many questions about these systems remain unanswered. Thus the studies presented in this dissertation were designed to improve the understanding of the fundamental interface physics of metal oxide/organic systems. Single molecule fluorescence microscopy was employed to determine the charge transfer mechanism while photoelectron spectroscopy was used to determine the energy level alignment of model systems. Additional computational studies allowed the examination of the properties of the charged organic molecules involved in charge transfer and modeling of the molecule-surface interaction. Calculations of the ground state properties and excited state transitions of the neutral and singly charged states of a modified perylene molecule were performed to provide insight into the orbitals of the initial and final states involved in the interfacial charge transfer process. The design and implementation of a novel UHV single molecule microscope is described. This microscope was used to observe the excited state charge transfer between a modified perylene molecule and Al₂O₃ (0001). The charge transfer mechanism was identified as involving activated trapping and detrapping of the defect derived states within the Al₂O₃ band gap, which resulted in the observation of strongly distributed kinetics for this system. The influence of defects and adsorbates on the electronic structure of ZnO and its interface with organic semiconductors was determined from photoelectron spectroscopy. Modified perylene molecules were found to have strong chemisorptive interactions with the ZnO surface involving charge transfer from defect derived ZnO states to the LUMO, while magnesium phthalocyanine molecules appear to have only weak physisorptive interactions with the ZnO surface. The interfacial investigations of the organic/oxide systems demonstrate the rich defect structure present in metal oxides. In both cases, defects were found to control the interfacial interactions between the metal oxide surface and the modified perylene molecules. Thus the manipulation of these defects states is of fundamental importance for optoelectronic device design.
29
Williams, Alvin Scott. "Charge transfer induced osmylation of aromatic compounds". Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309472.
Testo completo
30
Pradhan, Sulolit. "Solid state charge transfer in nanoparticle solids /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
Testo completo
31
Treadway, Christopher Ryan Gray Harry B. Barton Jacqueline K. "Spectroscopic characterization of DNA-mediated charge transfer /". Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05252003-231704.
Testo completo
32
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.
Testo completo
33
Batty, Simon V. "The investigation of novel charge transfer systems". Thesis, Sheffield Hallam University, 1991. http://shura.shu.ac.uk/19330/.
Testo completoAbstract (sommario):
In this project a number of synthetic procedures were investigated with a view to preparing a new type of charge transfer polymer system having a structure based on that of side chain liquid crystal polymers, in that the hoped for polymer was composed of charge transfer acceptors connected to a polymer backbone via a flexible alkyl spacer linkage. As part of this work new charge transfer complexes were prepared some of which have shown possible novel properties, such as, co-operative magnetic effects and film forming capabilities. Finally, in order to characterise materials prepared, a Faraday magnetic susceptibility balance and instrumentation for measuring electrical conductivity has been built.
34
Campbell, J. A. "Charge transfer processes at liquid/liquid interfaces". Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/13298.
Testo completoAbstract (sommario):
An approximate analytical expression for the current potential characteristic for charge transfer at a microdisc interface under steady state conditions is given for reversible, quasireversible and irreversible kinetics. The quasireversible expression is proposed as a simple means for analysis of experimental voltammograms thus gaining access to the potential dependent forward rate constant and the charge transfer coefficient, α. It is used to analyse simulated data and the results compared to the simulation parameters. The mathematics of the linear diffusion of cyclic voltammetry for electron transfer at the Interface between Two Immiscible Electrolyte Solutions (ITIES) is addressed, and the numerical solution of the resulting integral equation is evaluated. The results show how the cyclic voltammograms for reversible electron transfer at the ITIES vary when different ratios of reactants and products are used, and how these differ from the classical reversible cyclic voltammograms. A microhole formed by eximer laser ablation in a polyester membrane is proposed as a useful support for a micro-ITIES providing symmetrical diffusion characteristics analogous to an inlaid disc electrode. This support (and also regular arrays of microholes) has been used to obtain symmetrical steady state voltammograms for the transfer of the acetylcholine cation from water to 1,2-dichloroethane. A micro-ITIES suported at the tip of a micropipette has been used to study the transfer of alkali metal ions assisted by crown ethers which gave a lower limit for the pseudo first order interfacial transfer rate constants of 10^-2 cm s^-1, and provided data on the complexation constants of Li^+ , Na^+ , K^+ Rb^+ and Cs^+ with dibenzo-18-crown-6. The oxidations of di-n-butylferrocene and ferrocene by hexacyanoferrate III at the ITIES were investigated using both microinterfaces supported at the tip of a micropipette, and large interfaces.
35
Rice, Elisabeth. "Computational modelling of electronic states, charge transfer and charge transport in organic semiconductors". Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59946.
Testo completoAbstract (sommario):
In this thesis, we model electronic states, charge transfer and charge transport in organic semiconductors (OSCs). We are interested in the effect of chemical structure, molecular packing and different types of disorder on the charge transport in these materials, which is an important factor determining the efficiencies of devices made with OSCs. This is an intrinsically multiscale problem, and we use computational methods than span length and time-scales. We investigate the effect of molecular packing and crystal structure on charge carrier mobility in molecular crystals. We also model the electron mobility in disordered small molecules containing different defects to find the effect of these defects on the performance of devices. We perform electronic structure calculations to investigate the HOMO and LUMO levels in the presence of different defects, as well as to generate absorption, photoluminescence and infrared spectra to compare to experimental spectra. We develop a computationally efficient method for modelling polarons in organic semiconductors within a tight-binding framework. We apply the method to large assemblies of fullerene molecules generated with coarse-grained molecular dynamics. The method allows us to explore the effect of energetic and configurational disorder, as well as polaron formation, on the density of states and size of charge states in these systems. We further develop a method for calculating transfer integrals between molecules or molecular fragments, based on performing calculations of molecular orbitals in a counterpoise basis set. We apply it to calculating intramolecular transfer integrals and transfer integrals between donor and acceptor molecules at interfaces in organic photovoltaics, and between dopant and host molecules.
36
Cao, Huachuan. "Probe Oxidative Damage in DNA Charge Transfer Process". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6983.
Testo completoAbstract (sommario):
As a hydrophilic biopolymer, a DNA molecule is surrounded by water molecules in aqueous solution. The charge hopping mechanism indicates the competition between radical cation quenching by water molecules and migration along DNA partially determines the distance and efficiency of charge transport in DNA. Lipid can effectively bind DNA to induce hydrophobic environment around the DNA helix and reduce the water contact with bases in the DNA duplex. Therefore, the effect of water molecules on charge transport can be studied by comparison between nature DNA and DNA-lipid complexes. We synthesized several cationic lipids with various lengths of dialkyl chain (2, 8, 18) and spermine (Sp4+) binding core in this research, which posses strong DNA binding affinity due to their multi-charged spermine head-groups. Among those, C8GlySp4+ and C2GlySp4+ can form stable complex with DNA oligomer in aqueous solution, characterized by time dependent UV and CD spectrometry. C2GlySp4+ showed the similar inhibition on oxidative damage in GG steps as spermine while C8GlySp4+ demonstrated much more significant prohibitive effect at the same concentration. Since all the lipids bear the same binding core, they should afford the similar binding affinity towards DNA duplexes. we attributed the observation to the longer length of dialkyl group in C8GlySp4+, which can more effectively shield the DNA duplex from the water molecules than either spermine or C2GlySp4+. A kinetic model based on phonon-assist polaron hopping mechanism was proposed to rationalize the experimental results. The finding may give insight on the protection of DNA oxidative damage by reducing the access of the water molecule to DNA duplex and may have potential impact on the application of DNA as conducting biopolymer and protection of DNA in biological system.
37
Appling, Jeffrey Robert. "Gaseous charge transfer reactions of multiply charged ions". Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/27382.
Testo completo
38
Ieta, Adrian C. "Charge transfer & dielectric properties in hydrocarbon mixtures". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39835.pdf.
Testo completo
39
Pearson, C. "Langmuir-Blodgett films of organic charge-transfer complexes". Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5390/.
Testo completoAbstract (sommario):
This thesis is concerned with the preparation of floating films of electrically conductive organic charge-transfer complexes and their subsequent transfer to solid substrates by the Langmuir-Blodgett (LB) technique. Characterisation of the morphology (using ellipsometry, surface profiling, optical and scanning electron microscopy, energy dispersive spectroscopy and optical absorption spectroscopy) and electrical properties (at room temperature and low temperature) of the resulting multilayer structures is discussed. Three different systems were investigated: (i) mixed films containing the long chain tetrathiafulvalene (TTF) derivative octadecanoyl-TTF (ODTTF) and either octadecanoic acid (OA) or pentacosa-10,12-diynoic acid (PA); (ii) pure films of the charge-transfer complex Ν-octadecylpyridiniura-bis-(4,5-dimercapto-1,3-dithiole-2- thione) palladium (Ci8Py-Pd(dmit)2); and (iii) pure films of the charge-transfer complex N-octadecylpyridinium-bis-(4,5-dimercapto-1,3-dithiole-2-thione) nickel (CigPy- Ni(dmit)2). Some interesting electrical properties were observed in these films. Also, Ci8Py-Ni(dmit)2 has been incorporated as the active layer in a thin film field effect transistor structure. Carrier mobility values of 1.9 ± 0.5 x l0(^-5) cm(^2) V(^-1) S(^-1) and 0.3 ± 0.1 cm(^2) V(^-1) s-(^-1) were calculated from the device characteristics, before and after doping with iodine, respectively In the case of films containing ODTTF, a maximum room temperature in-plane dc conductivity after iodine doping of 2±lxl0(^-2) S cm(^-1) was recorded. This conductivity was found to be strongly dependent on the molar ratio of the two components present in the film. The behaviour has been explained using two-site percolation models. For C(_18)Py-Pd(dmit)(_2) and C(_18)Py-Ni(dmit)(_2), the properties of the floating layers and transferred films were found to be influenced by the exact experimental conditions. Ci8Py-Pd(dmit)(_2) films were conductive as deposited, with a stable maximum room temperature in-plane dc conductivity value of 1.5±1.0xl0(^-l) S cm(^-1). C(_18)Py-Ni(dmit)(_2) samples became conductive after exposure to iodine vapour, with a stable peak conductivity value of 1.3±0.8 x10(^-1)S cm(^-1).
40
Couves, John W. "Photocurrent processes in macrocylic and charge transfer complexes". Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328637.
Testo completo
41
Wilkins, P. M. "Double detachment and charge transfer from H'- ions". Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373903.
Testo completo
42
Gregory, David. "Charge transfer studies of alkali-metal/semiconductor interfaces". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240051.
Testo completo
43
Zilic, Elvis. "Radiation curing and grafting of charge transfer complexes". View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/19385.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--University of Western Sydney, 2008.Thesis submitted to the University of Western Sydney, College of Health and Science, School of Natural Sciences, in fulfilment of the requirements for admission to the Doctor of Philosophy. Includes bibliography.
44
Gillespie, Peter N. O. "Theory of charge transfer in solar energy materials". Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22771/.
Testo completo
45
Speck, J. Matthäus. "Ferrocenyl-substituted Thiophenes – Electrochemical Behavior and Charge Transfer". Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-208811.
Testo completoAbstract (sommario):
Die vorliegende Dissertation beschäftigt sich mit dem elektrochemischen Verhalten verschiedener Ferrocenyl-substituierter Thiophene. Dabei wird sich zunächst mit dem elektrochemischen Verhalten der Serie der Ferrocenylthiophene beschäftigt, die Anzahl der Ferrocenyleinheiten variiert von n = 1 – 4. Die Abhängigkeit der elektronischen Eigenschaften von numerischen und konstitutionellen Veränderungen der redox-aktiven Gruppen wird evaluiert. Daraus resultierend wird sich einer eingehenderen Untersuchung und Modifikation des 2,5-Diferrocenylthiophen-Motivs zugewandt. Diese Modifikationen werden im Kontext möglicher Ladungstransferprozesse zwischen den Ferrocenyleinheiten in den verschiedenen Redoxzuständen und unter Beeinflussung durch den Thiophen-Brückenliganden diskutiert. Es folgen des Weiteren Ausführungen zu Substitutionen an den Ferrocenylen (Einführung elektronen-ziehender Funktionalitäten) sowie der Vergleich zwischen einer Thiophen- und der Ethylendioxythiophen-Brückeneinheit. Anschließend wird sich mit der elektronischen Variation des Brückenliganden durch die Einführung von N-haltigen Substituenten befasst. In den abschließenden Kapiteln wird der Einfluss zusätzlicher σ- (Fischercarben-Komplexe) oder π-gebundener ([Ru(η5-C5H5)]+/[Ru(η5-C5Me5)]+) Übergangsmetallkomplexfragmente auf Ladungstransferwechselwirkungen im 2,5-Diferrocenylthiophen in verschiedenen Redoxzuständen beleuchtet.
46
Siles, P. F., T. Hahn, G. Salvan, M. Knupfer, F. Zhu, D. R. T. Zahn e O. G. Schmidt. "Tunable charge transfer properties in metal-phthalocyanine heterojunctions". Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-219903.
Testo completoAbstract (sommario):
Organic materials such as phthalocyanine-based systems present a great potential for organic device applications due to the possibility of integrating films of different organic materials to create organic heterostructures which combine the electrical capabilities of each material. This opens the possibility to precisely engineer and tune new electrical properties. In particular, similar transition metal phthalocyanines demonstrate hybridization and charge transfer properties which could lead to interesting physical phenomena. Although, when considering device dimensions, a better understanding and control of the tuning of the transport properties still remain in the focus of research. Here, by employing conductive atomic force microscopy techniques, we provide an insight about the nanoscale electrical properties and transport mechanisms of MnPc and fluorinated phthalocyanines such as F16CuPc and F16CoPc. We report a transition from typical diode-like transport mechanisms for pure MnPc thin films to space-charge-limited current transport regime (SCLC) for Pc-based heterostructures. The controlled addition of fluorinated phthalocyanine also provides highly uniform and symmetric-polarized transport characteristics with conductance enhancements up to two orders of magnitude depending on the polarization. We present a method to spatially map the mobility of the MnPc/F16CuPc structures with a nanoscale resolution and provide theoretical calculations to support our experimental findings. This well-controlled nanoscale tuning of the electrical properties for metal transition phthalocyanine junctions stands as key step for future phthalocyanine-based electronic devices, where the low dimension charge transfer, mediated by transition metal atoms could be intrinsically linked to a transfer of magnetic moment or spinDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
47
Schlientz, Nathan William. "Charge Migration through Duplex DNA: A Study of the Mechanism for Charge Migration and Oxidative Damage". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-05182006-164757/.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.Laren M. Tolbert, Committee Member ; Uzi Landman, Committee Member ; Nicholas V. Hud, Committee Member ; David M. Collard, Committee Member ; Gary B. Schuster, Committee Chair.
48
Florentin, Emmanuel. "Régulation de l'activité de la Protéine humaine de Transfert des Esters de Cholestérol (CETP) :Interactions électrostatiques avec les dérivés carboxylés (acides gras non estérifiés et rétinoïdes)". Phd thesis, Université de Bourgogne, 1997. http://tel.archives-ouvertes.fr/tel-00297283.
Testo completoAbstract (sommario):
Dans le plasma, la protéine humaine de transfert des esters de cholestérol joueun rôle central dans le métabolisme des lipoprotéines plasmatiques en catalysant le transfert net massique d'esters de cholestérol des HDL vers les lipoprotéines contenant de l'Apo.B, et de triglycérides des VLDL vers les HDL et LDL. Bien que le rôle de la CETP sur l'athérogénicité du profil lipoprotéique reste à l'heure actuelle encore ambigu, l'étude des mécanismes de régulation de cette protéine suscite un intérêt croissant d'un point de vue pharmacologique en particulier en ce qui concerne le développement d'inhibiteurs. Une approche in vitro nous a permis de montrer que des composés amphipathiques (acides gras non estérifiés et rétinoïdes) constitués d'une chaîne carbonée hydrophobe et d'un groupement carboxylique ionisable induisaient une augmentation de l'activité de transfert des esters de cholestérol en augmentant l'électronégativité des particules lipoprotéiques.
In vivo, nos études ont permis de mettre en évidence une corrélation significative entre la concentration en acides gras non estérifiés liés aux protéines et l'activité de la CETP plasmatique chez des sujets normolipidémiques. L'effet des acides gras non estérifiés est encore plus marqué dans des situations pathologiques associées à une redistribution des AGNE de l'albumine vers les lipoprotéines plasmatiques (analbuminémie ou syndrôme néphrotique). La mise au point d'une méthode électrophorétique spécifique nous a permis de confirmer que, chez des sujets analbuminémiques, les échanges d'esters de cholestérol s'effectuent préférentiellement avec les lipoprotéines les plus électronégatives dont le contenu en AGNE est le plus élevé.
Globalement, les résultats de cette étude montrent que les AGNE constituent des modérateurs potentiels de l'activité de transfert des esters de cholestérol au niveau plasmatique et qu'ils pourraient ainsi influencer l'athérogénicité du profil lipoprotéique.
49
Fonari, Alexandr. "Theoretical description of charge-transport and charge-generation parameters in single-component and bimolecular charge-transfer organic semiconductors". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54323.
Testo completoAbstract (sommario):
In this dissertation, we employ a number of computational methods, including Ab Initio, Density Functional Theory, and Molecular Dynamics simulations to investigate key microscopic parameters that govern charge-transport and charge-generation in single-component and bimolecular charge-transfer organic semiconductors.
First, electronic (transfer integrals, bandwidths, effective masses) and electron-phonon couplings of single-component organic semiconductors are discussed. In particular, we evaluate microscopic charge-transport parameters in a series of nonlinear acenes with extended pi-conjugated cores. Our studies suggest that high charge-carrier mobilities are expected in these materials, since large electronic couplings are obtained and the formation of self-localized polarons due to local and nonlocal electron-phonon couplings is unlikely. Next, we evaluate charge detrapping due to interaction with intra-molecular crystal vibrations in order to explain changes in experimentally measured electric conductivity generated by pulse excitations in the IR region of a photoresistor based on pentacene/C60 thin film. Here, we directly relate the nonlocal electron-phonon coupling constants with variations in photoconductivity.
In terms of charge-generation from an excited manifold, we evaluate the modulation of the state couplings between singlet and triplet excited states due to crystal vibrations, in order to understand the effect of lattice vibrations on singlet fission in tetracene crystal. We find that the state coupling between localized singlet and correlated triplet states is much more strongly affected by the dynamical disorder due to lattice vibrations than the coupling between the charge-transfer singlet and triplet states.
Next, the impact of Hartree-Fock exchange in the description of transport properties in crystalline organic semiconductors is discussed. Depending on the nature of the electronic coupling, transfer integrals and bandwidths can show a significant increase as a function of the amount of the Hartree-Fock exchange included in the functional. Similar trend is observed for lattice relaxation energy. It is also shown that the ratio between electronic coupling and lattice relaxation energy is practically independent of the amount of the Hartree-Fock exchange, making this quantity a good candidate for incorporation into tight-binding transport models. We also demonstrate that it is possible to find an amount of the Hartree-Fock exchange that recovers (quasi-particle) band structure obtained from a highly accurate G0W0 approach. Finally, a microscopic understanding of a phase transition in charge-carrier mobility from temperature independent to thermally activated in stilbene-tetrafluoro-tetracyanoquinodimethane crystal is provided.
50
Mason, Brian L. "An experimental investigation of charge transfer during ice contact interactions /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9769.
Testo completo