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Schirra, Laura Kristy. "Charge Transfer at Metal Oxide/Organic Interfaces." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/217090.
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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.
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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.
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Siles, P. F., T. Hahn, G. Salvan, M. Knupfer, F. Zhu, D. R. T. Zahn, and 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.
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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
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Rusu, Paul Constantin. "Charge transfer and dipole formation at metal-organic interfaces." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58034.
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Ding, Bowen. "Localised Charge Transfer in Metal-Organic Frameworks for Catalysis." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19852.
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In natural photosynthetic systems localised charge transfer (CT) interactions are employed to prolong photoexcited charge separated states, facilitating conversion to chemical energy. This thesis explores localised CT in redox-active Metal-Organic Frameworks (MOFs) for applications in electrocatalysis and photoelectrocatalysis. Two design strategies are adopted, the first of which incorporates cofacial dimeric units of the photo- and redox-active N,Nʹ-di(4-pyridyl)-1,4,5,8-naphthalenediimide (DPNDI) ligand into a Cd(II) MOF. Crystallographic characterisation of the structural flexibility in this MOF was achieved and linked to an enhanced capability for the MOF to stabilise photoexcited and radical states through localised Intervalence CT interactions. The ability of the material to stabilise the NDI photoexcited radical monoanion state (redox potential -2.1 V vs. SCE) was capitalised on to reduce a discrete organometallic Re(I) based CO2 electrocatalyst to its catalytically active form. Photoelectrocatalytic conversion of CO2 to CO was confirmed at modest reduction potentials of -1.2 V vs. Ag/Ag+. The second approach adopted in this project was the incorporation of the Ni bisdithiolene redox-active unit into a Zn(II) MOF, in the form of the [Ni(pedt)2]- metalloligand (where pedt represents 1-(pyridine-4-yl)ethylene-1,2-dithiolate). The combination of Zn(II) nodes and carboxylate co-ligand coordination resulted in effective electronic isolation of each [Ni(pedt)2]- ligand. The Ni bisdithiolene MOF was successfully applied as a heterogeneous proton reduction electrocatalyst under acidic conditions of 90 mM CH3COOH in 0.1 M [n-Bu4N]PF6/MeCN electrolyte. Tafel analysis of the electrocatalytic behaviour of both the ligand in solution and the MOF demonstrated similarities in catalytic mechanism, evidencing the conservation of molecular electrocatalytic behaviour.
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Newton, Angus William. "Charge transfer and disorder broadening in disordered transition metal alloys." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343931.
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Cai, Meng. "Investigation of Charge Transfer in Metal-Organic Frameworks for Electrochemical Applications." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97400.
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High-performance functional electrode materials are critical for the development of electrochemical energy conversion and storage technologies. Among various advanced materials, three-dimensional (3D) porous structures have attracted extensive interest due to their high surface area and capability for efficient mass transport. Metal-organic frameworks (MOFs) are a novel class of porous coordination polymers constructed with organic linkers connected by inorganic nodes. Their extraordinarily high surface area, permanent pores/channels, good thermal and chemical stabilities have made MOFs one of the most promising materials for various electrochemical applications, including electrocatalysis, supercapacitors, Lithium-ion batteries, chemical sensors, etc. The present dissertation focuses on the investigation of charge transfer mechanism in MOF films so as to establish design rules for future MOF design, and the exploration of MOF-based materials for electrochemical and photoelectrochemical applications.
To promote the use of MOF-based materials in electrochemical applications, efficient charge transfer is a necessity. In redox-active MOFs, charge transfer can happen through redox hopping, i.e. site-to-site electron hopping coupled to diffusion of counter ions to balance electroneutrality. While the apparent diffusion coefficient (Dapp) has been employed to describe the overall charge transfer efficiency, independent elucidation of electron and ion diffusion is crucial for providing insights into the mechanism of charge transfer in MOFs. In Chapter 2, we investigated the MOF pore size effect on electron and ion diffusion. Three redox-active ferrocene-doped MOF (Fc-MOF) films with different pore sizes immobilized on conductive substrates were prepared, and electron and ion diffusion coefficients and rate constants were quantified by applying a theoretical model to chronoamperometric responses. Increasing MOF pore size led to an increase in ion diffusion rate constant and a decrease in electron diffusion rate constant. The overall charge transfer rate constant increased when MOF pore size increased, implying the ability of promoting efficient charge transfer through control of MOF pore size.
As charge transfer via redox hopping proved to be feasible, Chapter 3 focused on the application of a ruthenium(II)-polypyridyl doped MOF film immobilized on a conductive substrate, UiO-67-Ru@FTO, for solid-state electrochemiluminescence (ECL). In the presence of tripropylamine as a coreactant, UiO-67-Ru@FTO exhibited higher ECL intensity and better reproducibility compared to corresponding solution-based ECL system. Subsequently, UiO-67-Ru@FTO was successfully used for dopamine detection, highlighting the great potential of using MOF-based materials as solid-state ECL detector for practical applications.
Covalent-organic frameworks (COFs) are a recently emerging family of crystalline organic polymers constructed with organic building blocks linked by covalent bonds. In addition to advantages including high surface area and high porosity that are similar to MOFs, COFs possess low density due to the constitution of light-weighted elements and excellent stability owing to the robust covalent bonds. Therefore, it is of our interest to investigate the properties and potential applications of COFs. Two-dimensional (2D) COFs are composed of conjugated organic layers stacked via - interactions. Chapter 4 focused on understanding the effects of intraplanar -conjugation and interplanar -stacking on the photophysical properties of a 2D COF, TpBpy. Compared to the two building blocks, TpBpy exhibited a red-shifted emission, due to the - stacking. Density functional theory (DFT) calculations were performed on energies of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). It was found that the extended structure of the framework resulted in a decrease in the HOMO-LUMO gap. The experimental and computational studies reveal the important influence of intraplanar and interplanar interactions on photophysical properties in 2D COFs.
In Chapter 5, we modified the COF TpBpy with nickel(II) and investigated its application as an electrocatalyst for 5-hydroxymethylfufural (HMF) oxidation. Unlike TpBpy characterized in Chapter 4, TpBpy thin films were prepared by an interfacial crystallization strategy. The films were transferred to conductive substrates and then post-synthetically modified by nickel acetate. Similar to redox-active MOFs, the resulting TpBpy-Ni COF film exhibited redox conductivity. TpBpy-Ni showed good catalytic activity for HMF oxidation under basic conditions. This study suggests the great potential of functionalized COFs for electrochemical applications.Doctor of Philosophy
The increasing demand for clean and efficient energy has triggered a great deal of research interest in developing novel energy conversion and storage technologies. In particular, electrochemical (EC) systems including supercapacitors, Lithium-ion batteries, artificial photosynthetic system, fuel cells, etc. have drawn significant attention. The key component in high-performance EC energy conversion and storage devices is the functional electrode materials. Three-dimensional (3D) porous nanostructures have been widely applied as advanced electrode materials due to their high surface area that enables more liquid/solid interfacial interactions, and pores/channels that allows efficient mass diffusion and transport. Metal-organic frameworks (MOFs), made of organic ligands bridged by inorganic nodes, are a novel kind of porous materials with extraordinarily high surface area and permanent porosity. As a result, there is great potential in developing MOF-based electrode materials for EC applications. As the name itself suggests, EC systems rely on electrochemical reactions that involve transfer of charges (i.e. electrons and ions). Therefore, efficient charge transfer is vital for achieving high performance. While MOFs used for gas separation and storage have been reported, their electrochemical applications are still in early stages. The fundamental understanding of charge transfer in MOFs is in its infancy. As a result, there is an urgent demand for understanding the nature of charge transfer in MOFs. In this dissertation, we investigated the mechanism of charge transfer by independent quantification of electron and ion transfer rate constants. With a better understanding in hand, we also explored two electrochemical applications in MOFs, electrocatalysis and electrogenerated chemiluminescence.
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唐素明 and So-ming Glenna Tong. "Theoretical studies of transition metal containing diatomics and DNA electron transfer." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31244828.
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Forker, Roman. "Electronic Coupling Effects and Charge Transfer between Organic Molecules and Metal Surfaces." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26163.
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We employ a variant of optical absorption spectroscopy, namely in situ differential reflectance spectroscopy (DRS), for an analysis of the structure-properties relations of thin epitaxial organic films. Clear correlations between the spectra and the differently intense coupling to the respective substrates are found. While rather broad and almost structureless spectra are obtained for a quaterrylene (QT) monolayer on Au(111), the spectral shape resembles that of isolated molecules when QT is grown on graphite. We even achieve an efficient electronic decoupling from the subjacent Au(111) by inserting an atomically thin organic spacer layer consisting of hexa-peri-hexabenzocoronene (HBC) with a noticeably dissimilar electronic behavior. These observations are further consolidated by a systematic variation of the metal substrate (Au, Ag, and Al), ranging from inert to rather reactive. For this purpose, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is chosen to ensure comparability of the molecular film structures on the different metals, and also because its electronic alignment on various metal surfaces has previously been studied with great intensity. We present evidence for ionized PTCDA at several interfaces and propose the charge transfer to be related to the electronic level alignment governed by interface dipole formation on the respective metalsZur Analyse der Struktur-Eigenschafts-Beziehungen dünner, epitaktischer Molekülfilme wird in situ differentielle Reflexionsspektroskopie (DRS) als Variante der optischen Absorptionsspektroskopie verwendet. Klare Zusammenhänge zwischen den Spektren und der unterschiedlich starken Kopplung zum jeweiligen Substrat werden gefunden. Während man breite und beinahe unstrukturierte Spektren für eine Quaterrylen (QT) Monolage auf Au(111) erhält, ist die spektrale Form von auf Graphit abgeschiedenem QT ähnlich der isolierter Moleküle. Durch Einfügen einer atomar dünnen organischen Zwischenschicht bestehend aus Hexa-peri-hexabenzocoronen (HBC) mit einem deutlich unterschiedlichen elektronischen Verhalten gelingt sogar eine effiziente elektronische Entkopplung vom darunter liegenden Au(111). Diese Ergebnisse werden durch systematische Variation der Metallsubstrate (Au, Ag und Al), welche von inert bis sehr reaktiv reichen, untermauert. Zu diesem Zweck wird 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA) gewählt, um Vergleichbarkeit der molekularen Filmstrukturen zu gewährleisten, und weil dessen elektronische Anordnung auf verschiedenen Metalloberflächen bereits eingehend untersucht worden ist. Wir weisen ionisiertes PTCDA an einigen dieser Grenzflächen nach und schlagen vor, dass der Ladungsübergang mit der elektronischen Niveauanpassung zusammenhängt, welche mit der Ausbildung von Grenzflächendipolen auf den entsprechenden Metallen einhergeht
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Chun, Young Tea. "Charge transfer characteristic of zinc oxide nanowire devices and their applications." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708978.
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Dey, Swagata. "Exploring “Metal to Metal” Charge Transfer Process in AWO4 and AMoO4 type compounds (A= Mn, Fe, Co, Ni, Cu, Zn)." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1377006312.
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Cody, John W. Jr. "Design, Synthesis, and Evaluation of Metal Cation Sensors with Donor-Acceptor Architecture." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13962.
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Copper is an essential trace element present in all living systems and is important for the function of many cellular enzymes. It ranks third in intracellular abundance behind only zinc and iron and plays a very important role as a catalytic cofactor in various cellular processes such as mitochondrial respiration, iron uptake, and the redox processes of a number of enzymes, including superoxide dismutase, lysyl oxidase, or tyrosinase. Any abnormality in copper trafficking pathways can lead to serious diseases such as Wilsons disease, Menkes syndrome and has been implicated in the neurodegenerative diseases amyotropic lateral sclerosis (ALS) and Alzheimers disease. While free copper in the cytoplasm would prove toxic, there is compelling evidence for the existence of a labile pool of copper that remains kinetically accessible. In order to investigate the existence of such a pool the development of Cu(I) selective probes is necessary.
Chapter I provides the background for the role of copper in biology and elucidates the main trafficking pathways discovered to date. This chapter also provides recent developments of fluorescent sensors for selective visualization of biologically relevant metals.
Chapter II discusses the exploration of a phenanthroline-based ligand for the selective detection of Cu(I). A series of derivatives incorporating chelating substituents in the 2- and 9-positions to enforce a 1:1 binding stoichiometry were synthesized and the properties of their respective Cu(I) complexes were characterized by x-ray structural analysis, and their photophysical properties were investigated by absorption and emission spectroscopy. Visible light excitation yielded metal-to-ligand charge-transfer (MLCT) excited states with luminescence lifetimes up to 155 ns. Electrochemical measurements further indicate that coordinative rearrangements are involved in nonradiative deactivation of the excited states. According to time-dependent density functional theory calculations (B3LYP/6-31G**), the major MLCT transitions are polarized along the C2 axis of the complex and originate predominantly from the dxz orbital.
In chapter III, the development of a ratiometric Cu(I) sensor based on a donor-acceptor functionalized biphenyl fluorophore platform is discussed. The fluorescence emission energy for such fluorophores is highly dependent upon the interannular twist angle and this property was harnessed to provide a ratiometric sensor selective for Cu(I). Coordination of Cu(I) leads to a flattening of the biphenyl backbone and was confirmed by absorbance and emission spectroscopy as well as 2D NOESY experiments. The peak emission energy was shifted by 39 nm towards higher energy upon metal cation binding with a concomitant 7 bathochromic shift in absorption energy. The photophysical data accompanied by 1H NMR analysis confirms a well-defined 1:1 binding stoichiometry between metal and ligand. The findings from this study showed ratiometric behavior for this probe, albeit with a lowered quantum yield.
While the quantum yield for the fluorophore discussed in chapter III was low (8.0%), the focus of chapter IV was the elucidation of the fluorescence quenching mechanism. To investigate the possibility of a twisted intramolecular charge transfer (TICT) state a donor-acceptor biphenyl fluorophore was synthesized incorporating a conformationally restricted amine donor group incapable of rotating out of plane in the excited state. Analysis of this derivative, as well as the sensor discussed in chapter III, reveals that fluorescence quenching is most likely due to hydrogen bonding to the acceptor subunit in they excited state.
Finally, in chapter V, a pyrazoline fluorophore library with varying numbers of fluorine substituents was synthesized. The photophysical and electrochemical properties of these fluorophores were measured in order to determine if careful tuning of the excited state electron transfer thermodynamics is possible. The compounds cover a broad range of excited state energies and reduction potentials, and the data suggest that selective and differential tuning of both the reduction potential of the acceptor as well as the excited state equilibrium energy. These findings show that the individual parameters involved in excited state electron transfer can be tuned by the modular architecture of the pyrazoline fluorophore.
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Smithback, Michael T. "Rhenium(I) metal-to-ligand charge-transfer excited states containing sigma-bonded closo-dicarbadodecaboranes." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1212790661&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Wächter, Tobias [Verfasser], and Michael [Akademischer Betreuer] Zharnikov. "Charge Transfer in Monomolecular Films and Metal-Organic Frameworks / Tobias Wächter ; Betreuer: Michael Zharnikov." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180739345/34.
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Gerbert, David [Verfasser], and Annemarie [Akademischer Betreuer] Pucci. "Charge Transfer and Band Formation at Metal/Organic Interfaces / David Gerbert ; Betreuer: Annemarie Pucci." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180985656/34.
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陳容芳 and Yung-fong Yvonne Cheng. "Resonance raman investigation of metal to ligand charge transfer transitions in selected inorganic complexes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224143.
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Cheng, Yung-fong Yvonne. "Resonance raman investigation of metal to ligand charge transfer transitions in selected inorganic complexes." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22713359.
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So, Eric. "Interaction of Rydberg hydrogen atoms with metal surfaces." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:53984973-1766-45cc-8bcf-055be714ed73.
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This thesis presents a theoretical and experimental investigation of the interaction of electronically excited Rydberg hydrogen atoms with metal surfaces and the associated charge-transfer process. As a Rydberg atom approaches a metal surface, the energies of the Rydberg states are perturbed by the surface potential generated by the image charges of the Rydberg electron and core. At small atom-surface separations, the Rydberg atom may be ionised by resonant charge transfer of the Rydberg electron to the continuum of delocalised unoccupied metal states, with which the Rydberg electron is degenerate in energy. Typically, this ‘surface ionisation’ can be measured by extracting the remaining positively charged ion-cores with externally applied electric fields. By applying various levels of theory, from classical to fully time-dependent quantum calculations, this thesis explores various experimentally relevant effects on the charge-transfer process, such as the magnitude and direction of the externally applied electric field, the atom collisional velocity, the presence of local surface stray fields and electronically structured surfaces. The theoretical results give insight into the previous experimental work carried out for the xenon atom and hydrogen molecule, and point out some of the fundamental differences from the hydrogen atom system. Experiments involving Rydberg hydrogen atoms incident on an atomically flat gold surface, a rough machined aluminium surface and a single crystal copper (100) surface are presented, providing for the first time the opportunity to make a quantitative comparison of theory and experiments. The ability to control the critical distance at which charge-transfer occurs is demonstrated by using Rydberg states of varying dimensions and collisional velocities. By changing the collisional angle of the incident Rydberg beam, the effect of Rydberg trajectory is also investigated. By manipulating the polarisation of the Rydberg electron with electric fields, genuine control over the orientation of the electron density distribution in the charge-transfer process is demonstrated. This property was predicted by the theory and should be unique to the hydrogen atom due to its intrinsic symmetry. By reversing the direction of the electric field with respect to the metal surface, electrons rather than positive ions are detected, with ionisation dynamics that appear to be very different, as predicted by quantum calculations. Experiments involving the single crystal Cu(100) surface also suggests possible resonance effects from image states embedded in the projected bandgap which are shown from quantum calculations to play an important role in the surface charge transfer of electronically structured metal substrates. The experimental technique developed in this work provides some exciting future applications to study quantum confinement effects with thin films, nanoparticles and other bandgap surfaces. The ability to control the Rydberg orbital size, electronic energy, collisional velocity and orientation in the charge-transfer process will provide novel ways of probing the surface’s electronic and physical structure, as well as being a valuable feature in offering new opportunities for controlling reactive processes at metallic surfaces.
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Kearns, Eleanor Rose. "Multi-stimuli Metal-organic frameworks and their composites." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29561.
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Metal-Organic Frameworks (MOFs) are a versatile class of materials. Their high surface area combined with the functionality of their constituent organic ligands make them suitable for a wide range of applications. In their scale-up to industry level uses, MOFs face several roadblocks. The largest of these obstacles are large-scale green syntheses of MOFs and processing the polycrystalline powders into useable forms. This thesis examines structure-activity relationships in a family of TTF-based MOFs, and presents a green synthesis for UiO-66-NH2. Finally, 3D-printing will be examined as a method for preparing MOF-based electrocatalytic electrodes.
Chapter 3 and Chapter 4 will examine the structure-activity relationships (SARs) of charge transfer and photocyclization respectively. Herein, a family of photoactive TTF-based MOFs, generated by systematically varying the framework constituents, are used to probe the effect of structure on the intervalence charge-transfer (IVCT) and [2+2] photocyclisation processes.
Chapter 5 presents a novel one-step mechanochemical synthesis of UiO-66-NH2. This synthesis proceeds from ZrOCl2.8H2O in a 66% yield. The mechanochemical synthesis presented is more scalable than other benign syntheses of UiO-66-NH2, and importantly yields highly crystalline material with comparable surface area to UiO-66-NH2 synthesized via alternative mechanochemical routes.
Chapter 6 presents the first example of 3D-printed MOF electrodes for electrocatalysis, which expands upon previous work on 3-D printed MOF and zeolite-based composite sorbent materials. This represents a new technique for electrochemical analysis of solid analytes, as well as the development of self-supporting solid MOF-based electrodes. This research shows that the properties of the MOF are maintained once printed, and a clear electrochemical response to the analyte of interest is observed.
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Blowey, Phil J. "Probing the geometrical and electronic structure of two-dimensional charge transfer networks on metal surfaces." Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/111281/.
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Due to its ability to form conductive organic salts, the prototypical electron acceptor molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) has attracted considerable interest in the field of organic electronics. This has motivated numerous surface science studies of TCNQ and related molecules, with an aim to understand the molecule-substrate interface and, in particular, the nature of any charge transfer. Although charge transfer is strongly dependent on subtle aspects of the molecular adsorption geometry, there is a dearth of detailed structural investigations for these systems. In this thesis, a variety of surface science techniques were used to characterise model systems of TCNQ adsorbed on coinage metal substrates with the aim to identify key relationships between the adsorption structure and the electronic properties of the surface. Particular focus was given to studying two-dimensional charge-transfer networks formed by TCNQ and alkali metals on the surface of Ag. Scanning tunnelling microscopy and low energy electron diffraction were used to characterise the packing and ordering of molecules and to ascertain whether the adsorbed layer is commensurate with respect to the underlying substrate. X-ray and ultraviolet photoelectron spectroscopy were used to provide complementary information on the chemical composition and electronic properties of the surface. Most significantly, the normal incident X-ray standing wave (NIXSW) technique was used to obtain precise quantitative structural measurements of the surface. On the surfaces of coinage metals, TCNQ is generally believed to adsorb in a significantly bent conformation, with all four cyano groups pointing down towards the substrate. The NIXSW measurements in this thesis show that the conformation adopted by TCNQ on Ag(100) is consistent with this, but on Ag(111), TCNQ adopts a considerably different conformation that was found, through comparison with density functional theory calculations, to result from the participation of Ag adatoms within the surface structure. These results also highlight the need for using both experimental and theoretical quantitative structural methods to obtain a reliable understanding of metal-organic interfaces and that some previously studied systems may need to be re-investigated. On both the (111) and (100) surfaces of Ag, a wide variety of TCNQ/alkali metal network structures were formed with Cs, K and Na. NIXSW measurements obtained from a subset of these structures show that the alkali metals adsorb at elevated heights above the TCNQ molecules. In comparable structures, K adsorbs closer to the surface than Cs and causes a smaller shift to the surface work function. The alkali metal adsorption height was also found to decrease as its coverage relative to TCNQ increased.
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Choi, Taeyoung. "STM studies of charge transfer and transport through metal-molecule complexes on ultrathin insulating films." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299525515.
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Ehamparam, Ramanan. "Band Edge Energetics and Charge Transfer Processes in Semiconductor-Metal Heterostructured Nanorods as Photocatalysts and Metal Oxide Electrode-Organic Semiconductor Interfaces in Organic Photovoltaics." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/566213.
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Energetics, charge selectivity and interfacial charge transfer kinetics affect the efficiency of solar electric energy conversion and solar photochemical formation of fuels. The research described herein focuses on understanding and controlling the energetics, charge selectivity, and interfacial charge transfer processes in organic photovoltaics, as well as new generation semiconductor-semiconductor and metal-semiconductor heterostructured nanorods (NRs) as photocatalysts. Waveguide and transmission based spectroelectrochemistries, photoemission spectroscopies, and impedance spectroscopy were used to characterize the frontier orbital energies, charge selectivity and interfacial charge transfer kinetics in heterostructured NRs and organic photovoltaics. CdSe NRs tipped with Au nanoparticles and CdSe seeded CdS NRs tipped with Pt nanoparticles were used to study the effect of compositional asymmetry and catalytic sites on band edge energies of NRs. We used UV photoemission spectroscopy (UPS) and waveguide and transmission-based spectroelectrochemistry of NR monolayers/multilayers on conductive substrates to estimate valence/conduction band energies. Potential-modulated attenuated total reflectance (PM-ATR) spectroscopy was utilized to measure the apparent heterogeneous rate constants of reversible electron injection into NR films on indium tin oxide (ITO). We conclude from these measurements that metal tipping, which is designed to enhance the photocatalytic activity of semiconductor NRs, altered band edge energies and enhanced electronic coupling to conductive substrates, in ways that are predicted to influence their efficiency as photoelectrocatalysts. Monolayers of functionalized phosphonic acid ruthenium phthalocyanines (RuPcPA) tethered to ITO as a model organic photovoltaic donor/electrode interface were studied to understand the aggregation and orientation dependent charge transfer kinetics and energetics of these systems. The effect of surface roughness on the orientation of RuPcPA was theoretically modeled and compared to the experimental results. Electrochemical and spectroelectrochemical studies revealed the presence of only monomeric species on ITO. Impedance spectroscopy (IS) and PM-ATR were used to measure charge transfer rate constants. Further, frontier orbital energies of RuPcPA modified ITO were measured using UPS, and the results indicated favorable energetics for hole collection at the RuPcPA/ITO interface for OPV applications. The effect of "UV-light soaking" on the performance of organic photovoltaic devices employing metal oxide (MO) electron selective interlayers (ESL) was addressed using sputtered zinc oxide (ZnO) ESL films. This study provides a coherent methodology for differentiating between the proposed origins of the s-shaped current-voltage (J-V) responses in the literature for organic photovoltaics using MO ESLs. We use IS and UPS to demonstrate that the energetic barrier for charge extraction at the ZnO/active layer interface leads to the observed s-shape response in OPVs using ZnO ESLs. Furthermore, this study provides clear guidelines for minimizing the s-shaped J-V response and the effect of UV light on the performances of OPV devices using ZnO ESLs. We have developed solution electrochemical protocols to characterize nanometer-scale porosity and electronic properties of both solution-deposited and sputtered ZnO thin films used as interlayers for electron-harvesting contacts in inverted organic solar cells on ITO substrates. These electrochemical experiments were performed in order to evaluate the hole-blocking abilities of these ZnO ESLs as well as their effective "pinhole density," thus demonstrating a strong correlation to their OPV performances. These electrochemical experiments can be used to characterize and optimize ESLs rapidly, before OPV device fabrication.
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Grisenti, David L. "The effect of bimolecular quenching reactions on energy transfer processes in oligometallic metal to ligand charge transfer excited states." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1495960661&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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D'Acchioli, Jason S. "On the nature of the electronics structure of metal-metal quadruply bonded complexes." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1126621699.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xii, 286 p.; also includes graphics (some col.). Includes bibliographical references (p. 273-286). Available online via OhioLINK's ETD Center
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Sathiosatham, Muhunthan. "The synthesis and noncovalent electron-transfer studies of anthracene and dimethylaniline substituted nucleic acid bases and G-quartet formation in the absence of templating metal ions." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992906.
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Koumousi, Evangelia S. "Synthesis and characterization of dinuclear {Fe(μ-CN)Co} complexes exhibiting metal-to-metal electron transfer properties." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0306/document.
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Cette thèse porte sur la synthèse de nouveaux complexes binucléaires à ponts cyanures de type {Fe(μ-CN)Co}, qui reproduisent au sein d'une seule molécule les propriétés originales du réseau de coordination d'analogue de bleu de Prusse AxCo[Fe(CN)6]y•nH2O (A=ions alcalins), i.e. un transfert d'électron intramoléculaire thermo- et photo-induit à l'état solide. Au sein de ce travail, nous nous sommes intéressés à l'étude des propriétés physiques des paires moléculaires Fe/Co, avec l’objectif de comprendre les mécanismes du phénomène de transfert d'électrons. Le chapitre I contient les exemples les plus représentatifs des réseaux de coordination d'analogues de bleu de Prusse et de leurs analogues moléculaires Fe/Co, en se concentrant sur les techniques utilisées pour comprendre leurs propriétés photomagnétiques et les stratégies synthétiques employées pour contrôller leur dimensionnalité et obtenir ces analogues moléculaires. Les bases théoriques du transfert d'électron ainsi que la motivation de ce travail sont décrites à la fin du chapitre. Après une introduction sur l’utilisation des briques moléculaires employées au cours de ce travail à travers l’étude de leurs potentiels redox, le chapitre II est consacré à la synthèse et la caractérisation de nouveaux composés dinucléaires à ponts cyanures Fe/Co. Des études structurales, spectroscopiques, magnétiques, photomagnétiques, diélectriques et d’absorption des rayons-X révèlent qu'un transfert d’électron métal-métal peut être déclenché à l'état solide en faisant varier la température et par application de la lumière. Dans le chapitre III est présenté l'influence de l'environnement des complexes binucléaires Fe/Co, à savoir les contre-ions, sur le transfert d’électron thermo- et / ou photo-induit à l'état solide. Enfin le chapitre IV porte sur la possibilité de transférer le phénomène de transfert d'électron des paires Fe/Co étudiées de l'état solide à la solutionThis thesis is dedicated to the synthesis of new dinuclear cyanido-bridged Co/Fe complexes, which mimics on a single molecule the original properties of the coordination network of Prussian Blue Analogues AxCo[Fe(CN)6]y•nH2O (A= alkaline ions), i.e. intramolecular thermal and photo-induced electron transfer in the solid state. We focus on the study of the physical properties of the simplest Fe/Co PBA, a dinuclear complex, with the hope to understand the fundamental concepts of this fascinating phenomenon. Chapter I contains the most representative examples of Fe/Co PBAs, focusing on the synthetic strategies employed in order to obtain Fe/Co PBAs of different dimensionalities and the techniques used to understand their photomagnetic properties. The theoretical background of the electron transfer phenomenon and the motivation of our work are described in the end of the chapter. After introducing the choice of the building blocks used in this work through the study of their redox potential properties, chapter II is devoted to the synthesis and the characterization of a novel dinuclear Fe/Co cyanido-bridged complex, which exhibits metal-to-metal electron transfer properties in solid state triggered by temperature and light. The ET phenomenon has been also studied by X-ray absorption spectroscopy and dielectric measurements. In Chapter III is illustrated the influence of the environment content of the dinuclear Fe/Co complexes, such as the counter ions, on the occurrence of the thermally and/or photo-induced electron transfer in solid state, thus highlighting the versatility of these molecular materials. Finally in chapter IV, the possibility of transferring the electron transfer phenomenon of the studied Fe/Co pairs from solid state to solution is investigated
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Ahmadi, Sareh. "Structure-dependent charge transfer at the interafce between organic thin films, and metals and metal oxides." Doctoral thesis, KTH, Materialfysik, MF, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134841.
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The purpose of the research work, presented in this thesis is to offer a detailed atomic level study of interfaces created by adsorption of organic molecules on metals and metal oxides to point out significant impact of substrate, dye structure as well as different mediators on the charge transfer at these interfaces, which is proven to influence the device performance to a great extent. Adsorption of organic photosensitive molecules on metals and metal-oxides is the main focus of this thesis. Phthalocyanines which are organic semiconductors offer a broad range of properties, such as thermal and chemical stability, high charge mobility and strong absorption coefficient in the visible and near-IR regions, which make them very attractive to be applied in various systems and devices. Fuel cells, organic field-effect transistors (OFETs), organic light emitting diodes (OLEDs) and solar cells are examples of phthalocyanine’s applications. The main focus of this work is to characterize the interfaces of Dye Sensitized Solar Cells (DSSCs). DSSC was invented by Michael Grätzel and Brian O’Regan in 1988. At the heart of this cell there is an oxide which is coated by a photosensitive dye. Under illumination, an electron is excited from HOMO to LUMO of the molecule, which can be further transferred to the conduction band of the oxide by a proper energy level alignment. The original state of the dye is regenerated by electron donation via the electrolyte, which usually is an organic solvent containing a redox couple e.g., iodide/triiodide. The iodide is regenerated by reduction of triiodide at the counter electrode. To improve the functionality of the cell, different additives can be added to the electrolyte. To mimic the interfaces of this cell, molecular layers of MPc (M: Fe, Zn, Mg) are adsorbed on both metallic surfaces, Au(111) and Pt(111), and rutile TiO2(110). Layers of iodine were inserted between metallic substrates and dyes to investigate the electronic properties and charge transfer at these multi-interface systems. 4-tert-butyl pyridine is a significant additive to the electrolyte and has proven to enhance the cell’s performance. This molecule was also adsorbed on Pt(111) and TiO2(110). Phthalocyanines were deposited by organic molecular beam deposition and 4TBP was evaporated at room temperature. Surface structures and reconstructions were confirmed by LEED measurements. Surface sensitive synchrotron radiation based spectroscopy methods, XPS and NEXAFS were applied to characterize these surfaces and interfaces. STM images directly give a topographical and electronic map over the surface. All measurements were carried out in UHV condition. When MPc was adsorbed on Au(111) and TiO2(110), charge transfer from molecule to substrate is suggested, while the opposite holds for MPc adsorbed on Pt(111). Moreover, stronger interaction between MPc and Pt(111) and TiO2(110) compared to Au(111) also demonstrates the effect of substrate on the charge transfer at the interface. The stronger interaction observed for these two substrates disturbed the smooth growth of a monolayer; it also resulted in bending of the molecular plane. Interaction of MPc with metallic surfaces was modified by inserting iodine at the interface. Another substrate-related effect was observed when MgPc was adsorbed on TiO2(110); and -cross linked surfaces, where the surface reconstruction directly affect the molecular configuration as well as electronic structure at the interface. Besides, it is shown that the d-orbital filling of the central metal atom in MPc plays an important role for the properties of the molecular layer as well as charge transfer at the interface. Upon adsorption of 4TBP on Pt(111), C-H bond is dissociatively broken and molecules is adsorbed with N atoms down. Modification of surface by iodine, prevent this dissociation. In the low coverage of iodine, there is a competition between 4TBP and iodine to directly bind to Pt(111). Investigation on the adsorption of 4TBP on TiO2(110) illustrated that these molecules in low coverage regime, prefer the oxygen vacancy sites and their adsorption on these sites, results in a downward band bending at the substrate’s surface.QC 20131203
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Dell'angela, Martina. "Organic molecules at metal surfaces: the role of functional groups in self-assembly and charge transfer." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3071.
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2007/2008The understanding of the interaction of organic molecules with metal surfaces is crucial for tailoring the desired properties of future devices that can be employed for molecular electronics or biomedical applications. Self-assembly of complex supramolecular structures and charge transfer through molecular films or even through single molecules are some of the properties that have recently attracted much interest both for possible applications and for more fundamental studies. The molecule-surface interaction takes place thanks to the functional groups that constitute the molecule. The choice of appropriate functional groups of the molecules allows their use as building blocks in the fabrication of complicate architectures [1]. In fact, the functional entities can influence molecule-molecule and molecule-surface interactions, governing the self-assembly of the molecules on the surface. In particular, in the thesis I will report on the characterization by means of Helium Atom Scattering (HAS), X-ray Photoemission Spectroscopy (XPS), Near Edge X-ray Absorption Fine Structure (NEXAFS) and Scanning Tunneling Microscopy (STM) of the self-assembly in ultra high vacuum (UHV) conditions of L-methionine molecules on different metal substrates (Ag(111), Cu(111), Au(111), Au(110)). L-methionine is an amino acid with three functional groups which can interact with the substrate or with other molecules: the amino (-NH2), the carboxyl (-COOH) and the thioether (-S-). Moreover, the first two can change their charge state in a protonated amino group (-NH+ 3 ) and a deprotonated carboxyl group (-COO−): the molecules are called zwitterionic and it is allowed the formation of hydrogen bonds between them. Hydrogen bonding between zwitterionic molecules is responsible for the crystallization in the solid state. In the thesis I have studied how, depending on the choice of the substrate and the growth conditions, L-methionine molecules form assemblies with different morphologies and different chemical states of the building blocks. L-methionine molecules deposited on Ag(111) and Au(111) are in the zwitterionic state and interact strongly via hydrogen bonding forming dimers of molecules. The weak interaction with the substrate allows the organization of these dimers in extended bidimensional nanogratings composed of chains of length extending in the micrometer range and with tunable periodicity across the chains. At temperatures below 270K, L-methionine on Cu(111) forms short aggregates of zwitterionic dimers. By increasing the substrate temperature above 300K the charge state of the amino group changes and also the interaction with the surface. Molecules are anionic (-NH2 and -COO−) and form again charged nanogratings. The anionic state of the molecules can also be obtained on the Au(110) surface, where the interaction of the amino and thioether groups with the gold inhibits the formation of zwitterionic dimers via hydrogen bonding. The functional groups in the molecules can also influence their transport properties. The final goal of miniaturization in molecular electronics research is the formation and characterization of a nanoelectronic device in which a molecule between two electrodes plays the role of an active conducting element. In such a device the interaction between the functional groups anchoring the molecule to the electrodes and the electrodes is a crucial element in order to understand and control the conduction. Recent STM-break junction experiments [2] have shown that Au-molecule-Au contacts with amino (- NH2) terminated molecules are better defined than Au-molecule-Au contacts formed with thiol (-SH) terminated molecules [3]. The strong interaction of thiols with gold surfaces is well known in literature and the self-assembly of thiolated molecules is widely employed in many applications. In contrast, the weak interaction of amino terminated molecules with gold is poorly studied. Theoretical calculations suggest that the amine lone pair is responsible for bonding and that it prefers to bind to undercoordinated gold atoms. Within this framework, in the thesis I report on the study of growth of thin films of 1,4-benzenediamine and p-toluidine on two different Au surfaces, where the atoms present different coordination: Au(111) and Au(110). Both molecules interact more strongly with the low coordination (110) surface. By means of Resonant Photoemission Spectroscopy (RPES) it has been possible to disentangle molecular orbitals and determine the ones involved in the charge transfer at the surface. In both cases the charge transfer involves states localized also on the nitrogen atoms indicating a possible interaction of the molecule with the surface through nitrogen atoms. I also studied the assembly of three benzene substituted diamines on Au(111). These results complement very well the results obtained from conduction experiments of different amine-terminated molecules and combined with theoretical investigations can help understanding the basics of the molecular charge transport mechanism. [1] Barth J.V., Costantini G., Kern K., Nature, 437 (2005) 671 [2] Venkataraman L., Klare J. E., Nuckolls C., Hybertsen M. S., Steigerwald M. L., Nature, 442 (7105), 904 (2006) [3] Schreiber F., Progress in Surface Science, 65 (5-8) (2000) 151
Lo studio dell’interazione di molecole organiche con superfici metalliche è di fondamentale importanza per la progettazione di futuri dispositivi che possiedano proprietà ben controllabili in modo tale che possano essere usati per l’elettronica molecolare o per applicazioni biomediche. L’autoassemblaggio di complesse strutture ”supramolecolari” e il trasferimento di carica attraverso film molecolari o anche attraverso singole molecole sono alcune delle proprietà che hanno attratto di recente grande interesse sia per le possibili applicazioni future che per studi di tipo più fondamentale. L’interazione molecola-superficie avviene attraverso i gruppi funzionali che costituiscono le molecole. Molecole con appropriate funzionalizzazioni possono essere usate come mattoni elementari nella fabbricazione di architetture complesse [1]. Infatti, tali gruppi funzionali possono influenzare le interazioni del tipo molecola-molecola e molecola-superficie che governano l’autoassemblaggio delle molecole sulla superficie. In particolare, in questa tesi riporter`o circa la caratterizzazione mediante diffrazione di atomi di elio (HAS), spettroscopia di fotoemissione di raggi X (XPS), misure di assorbimento di raggi X (NEXAFS) e microscopia ad effetto tunnel (STM) dell’autoassemblaggio in condizioni di ultra alto vuoto (UHV) di molecole di L-metionina su diversi substrati metallici (Ag(111), Cu(111), Au(111), Au(110)). La molecola di L-metionina `e un amminoacido che presenta tre gruppi funzionali i quali possono interagire con il substrato o con altre molecole: il gruppo amminico (-NH2), il gruppo carbossilico (- COOH) e il gruppo tioetere (-S-). I primi due possono inoltre cambiare il loro stato di carica originando un gruppo amminico protonato (-NH+ 3 ) e un gruppo carbossilico deprotonato (COO−): in tal caso le molecole sono dette zwitterioniche ed è permessa la formazione di legami a idrogeno tra esse. I legami a idrogeno tra molecole zwitterioniche sono responsabili della loro cristallizzazione nello stato solido. In questa tesi ho studiato come, a seconda della scelta del substrato e delle condizioni di cescita, le molecole di L-metionina formino strutture assemblate che presentano diverse morfologie e diversi stati chimici delle molecole costituenti. Le molecole di L-metionina depositate su Ag(111) e Au(111) sono zwitterioniche e interagiscono fortemente tra di loro tramite legami a idrogeno a formare dimeri di molecole sulla superficie. La debole interazione con il substrato permette l’organizzazione di questi dimeri in estesi reticoli bidimensionali di dimensione nanometrica composti da catene di lunghezza nel range micrometrico e con spaziatura tra le catene controllabile. A temperature sotto 270K, le molecole di L-metionina su Cu(111) formano corti aggregati di dimeri zwitterionici. Aumentando la temperatura del substrato oltre 300K lo stato di carica del gruppo amminico cambia e quindi l’interazione con la superficie. Le molecole sono anioniche (-NH2 e COO−) e formano di nuovo reticoli carichi. Lo stato anionico delle molecole si può ottenere anche sulla superficie di Au(110) dove l’interazione dei gruppi amminico e tioetere con l’oro inibisce la formazione di dimeri zwitterionici via legami a idrogeno. I gruppi funzionali nelle molecole possono anche influenzare le loro proprietà di trasporto. Lo scopo finale della miniaturizzazione nella ricerca nel campo dell’elettronica molecolare è la formazione e caratterizzazione di un dispositivo nanoelettronico in cui una molecola immobilizzata tra due elettrodi gioca il ruolo di elemento conduttivo attivo. In tale dispositivo il controllo dell’interazione tra i gruppi funzionali che tengono la molecola attaccata gli elettrodi e gli elettrodi è un elemento cruciale per la comprensione e il controllo della conduzione. Recenti esperimenti del tipo STM break junction [2] hanno motrato che contatti del tipo Au-molecola-Au con molecole con terminazioni amminiche (NH2) sono meglio definiti che contatti del medesimo tipo con molecole con terminazione tiolica (-SH) [3]. La forte interazione dei tioli con superfici d’oro è ben nota in letteratura e l’autoassemblaggio di molecole con terminazione tiolica è largamente utilizzato in molte applicazioni. In contrasto, la debole interazione di molecole con terminazione amminica con superfici d’oro è stata poco studiata. Recenti calcoli teorici hanno previsto che le molecole si legano alla superficie d’oro attraverso il ”lone pair” localizzato sull’azoto e che sono preferiti i legami con atomi di oro di bassa coordinazione. In particolare, nella tesi riporterò i risultati dello studio della crescita di film sottili di 1,4-benzenediamina e p-toluidina su due diverse superfici d’oro, i cui atomi di superficie presentano diversa coordinazione: Au(111) e Au(110). Ambedue le molecole interagiscono più fortemente con la superficie di bassa coordinazione (110). Tramite la tecnica di fotoemissione risonante (RPES) è stato possibile individuare gli orbitali molecolari e determinare quelli coinvolti nel trasferimento di carica all’interfaccia. In ambedue i casi il trasferimento di carica coinvolge stati che sono localizzati anche sull’atomo di azoto, il che indica una possibile interazione della molecola con la superficie attraverso i gruppi amminici. Ho anche studiato l’assemblaggio su Au(111) di tre diverse benzene-diamine con vii diversi sostituenti legati all’anello. Questi risultati sono un complemento ai risultati ottenuti da esperimenti di conduzione di molecole con diverse terminazioni amminiche e combinati con le investigazioni teoriche possono aiutare nella comprensione dei fondamenti dei meccanismi di trasporto di carica nelle molecole. [1] Barth J.V., Costantini G., Kern K., Nature, 437 (2005) 671 [2] Venkataraman L., Klare J. E., Nuckolls C., Hybertsen M. S., Steigerwald M. L., Nature, 442 (7105), 904 (2006) [3] Schreiber F., Progress in Surface Science, 65 (5-8) (2000) 151
XXI Ciclo
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Ko, Chi-chiu. "Design, synthesis and studies of novel classes of photochromic spirooxazine and diarylethene ligands and their metal-to-ligand charge transfer complexes." Click to view the E-thesis via HKUTO, 2003. http://sunzi.lib.hku.hk/hkuto/record/B43895311.
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Biednov, Mykola [Verfasser], and Michael [Akademischer Betreuer] Rübhausen. "Investigation of the charge transfer processes in bio-inorganic transition metal complexes / Mykola Biednov ; Betreuer: Michael Rübhausen." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1173323058/34.
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Vargas, Hernandez Jesus. "Structural and Morphological modification of TiO2 doped metal ions and investigation of photo-induced charge transfer processes." Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1018/document.
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Le travail de thèse porte sur les méthodes de synthèse de nanostructures de dioxyde de titane et de leurs études physicochimiques afin de préciser les corrélations entre la morphologie, le dopage métallique, les caractéristiques structurales avec l'efficacité photocatalytique. Le grand intérêt pour les nanomatériaux TiO2 réside dans la mise au point de nouvelles sources d'énergie ou la conservation de l’environnement par des processus photocatalytiques. Cependant, la limitation principale de TiO2 est du au large gap électronique (eV ~3,2) du polymorphe Anatase. Ainsi, un des objectifs importants pour l'amélioration de l’efficacité des nanomatériaux TiO2 est d'augmenter leur photoactivité en décalantla création de paires d'électron-trou de l’UV à la gamme du visible. D'ailleurs, on a montré que l'utilisation de nanostructures 1D de TiO2 (nanotubes) a amélioré la collection de charges, en favorisant leur transport dans les structures 1D, qui par conséquent réduit au minimum la recombinaison et prolonge les durées de vie des électrons.La première partie de ce travail est dédiée à la synthèse des nanopoudres TiO2 dopées par des ions métalliques (Ag, Cu, Eu) préparés par sol-gel. Même avec différents éléments de dopage qui apparemment peuvent adopter le même état de valence (2+) (Cu2+, Ag2+, Eu2+), différents comportements ont été démontrés pour l'incorporation efficace de ces ions dans la structure de TiO2. L'anomalie entre les rayons ioniques des différents éléments utilisés module le rapport du dopage substitutionnel. Ceci est en effet réalisé pour Cu2+ mais dans moins d'ampleur pour Ag2+ tandis que les ions d'europium forment une ségrégation de phase Eu2Ti2O7. La dégradation de colorants de bleu de méthylène (MB) a étéaméliorée légèrement avec les échantillons dopés Ag. La raison a été attribuée aux clusters métalliques Ag qui ont été en effet mis en évidence à travers leur bande d’absorption plasmonique. La deuxième partie porte sur des couches minces de TiO2 dopés (Cu, Ag, et Eu) qui ont été élaborés par sol-gel et spin-coating et dipcoating. Les paramètres optimaux ont été obtenus pour réaliser les films cristallins mais présentant une organisation mésoporeuse qui dépend également du processus de dopage. Des études de Photocatalyse ont été également réalisées et l'efficacité des films ont été comparées en fonction des éléments dopants. La troisième partie de la thèse est liée à la modification morphologique des nanoparticules pour former des nanotubes à l'aide de la méthode hydrothermale sous pression contrôlée. Un plan d'expérience basé sur la méthode Taguchi a été utilisé pour la détermination des paramètres optimaux.Les nanotubes TiO2 augmentent la surface spécifique en comparaison avec les nanoparticules. La dégradation de bleu deméthylène par les nanotubes a montré une efficacité photocatalytique plus élevée qu’avec les nanopoudres TiO2 pures etdopés AgThe thesis work is focused on the synthesis methods of titanium dioxide nanostructures and their physico-chemical studies in order to point out the correlations between the morphology, metal doping, structural features with the photocatalytic efficiency. The great interest on TiO2 nanomaterials deals with new sources of energy or in the environment preservation through the photocatalytic properties. However, the main limitations is due to the wide band gap (~3.2 eV) of the anatase polymorph. Thus, a major objective for improvement of the performance of TiO2 nanomaterials is to increase theirphotoactivity by shifting the onset of the electron-hole pairs creation from UV to the visible range. Moreover, it was found that using onedimensional (1-D) TiO2 (nanotubes) improved the charge collection by 1D nanostructures which consequently minimizes the recombination and prolongate the electron lifetimes. The first part of this work is focused on the synthesis of TiO2 nanopowders doped with metallic ions (Ag, Cu, Eu) prepared by Solgel. Even with different doping elements which apparently can adopt the same valence state (2+) such as (Cu2+, Ag2+,Eu2+), different behaviors were demonstrated for the effective incorporation of these ions in the host structure of TiO2. The discrepancy between ionic radii of the different used elements modulates the ratio of the substitutional doping. This is indeed achieved for Cu2+ but in less extent for Ag2+ while Europium ions form segregated phase as Eu2Ti2O7. The experiments on the degradation of methylene blue (MB)dyes have shown slight improvement with Ag-doped samples. The reason was tentatively attributed to the Ag clusters which were indeed demonstrated through their plasmon optical band. The second part of the work concerns thin films of TiO2 doped (Cu, Ag, and Eu) which were elaborated by spin coating and dip coating. The optimal parameters were obtained to achieve crystalline films but presenting mesoporous organisation which also depends on the doping process. Photocatalysis investigations were also realized and the efficiency of the films compared as function of the doping elements.The third part of the thesis is related to the morphological modification from nanoparticles to nanotubes by using the hydrothermal method with controlled pressure. An experimental design based on Taguchi Method was employed for the determination of the optimal parameters. TiO2 nanotubes increase the surface area in comparison with TiO2nanoparticles. TiO2 nanotubes were tested for the methylene blue degradation and show a higher photocatalytic efficiency than TiO2 nanopowders and TIO2 doped with Ag
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Mader, Elizabeth Anne. "Hydrogen atom transfer reactions of iron and cobalt tris alpha-diimines : a study of intrinsic and thermodynamic effects /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8617.
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Stevens, Hendrik. "Mechanistic Investigations of Metal-Metal Cooperativity in Dinickel Complexes and Iron/Cobalt Prussian Blue Analogues." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-13DA-0.
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Marble, William J. "Design and analysis of charge-transfer amplifiers for low-power analog-to-digital converter applications /." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd418.pdf.
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Soper, Jake D. "Reactions at nitrogenous ligands on oxidizing group 8 metal centers /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8589.
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Law, Yuen-chi, and 羅婉芝. "Platinum-ligand PI bonding interactions: the ligand-to-ligand charge transfer transitions and supramolecularchemistry of platinum(II) acetylide and thiolate complexes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38746827.
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Cui, Peng. "First Principle Study on Interfacial Energetic Alignment and Charge Transfer in Quantum Dots Functionalized via Metal-Organic Dye." Diss., North Dakota State University, 2016. http://hdl.handle.net/10365/25925.
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Quantum dots (QDs) are promising materials for applications in solar energy conversion because of tunable band gap, multi-exciton generation, photon-upconversion, etc. One of the main challenges of increasing solar energy conversion is to extend the lifetime of photoexcited charge-carriers in conduction band, and one of the strategies is to functionalize QD with mediator molecules. Functionalizing QD with metal-organic dye serves as the additional channel of manipulating charge transfer ? the key process increasing solar energy conversion. When metal-organic dye is attached to QD, the interfacial charge transfer direction as well as the rates are determined by a balance between the energetic alignment, QD-dye interaction as well as charge-carrier relaxation dynamics. In this dissertation, we explore the effect of dye functionalization on these elements. We change the metal ion, organic ligands as well as binding geometry of dye, size of QD, polarity of solvent, and use density functional theory to study their effects on energetic alignment. Embedding density functional calculation is used to study the dipole interaction between QD and dye providing additional controllability on charge transfer excitation. At last, we apply Tully surface hopping scheme in combining with density functional theory in time domain to study the charge-carrier relaxation dynamics and charge transfer across the heterogeneous interface in QD/dye nanocrystal composite.
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Law, Yuen-chi. "Platinum-ligand PI bonding interactions the ligand-to-ligand charge transfer transitions and supramolecular chemistry of platinum(II) acetylide and thiolate complexes /." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38746827.
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Brown-Xu, Samantha E. "Photophysical and Photosensitizing Properties of Dimetal Quadruply Bonded Paddlewheel Complexes Probed Through Ultrafast Spectroscopy." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405491729.
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Reed, Carly R. "The Photophysical Properties of Multiply Bonded Metal Complexes of Molybdenum, Tungsten, and Rhenium." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1309880937.
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Siegel, Nisan Naftali. "Two-photon absorption in cruciform and dipolar chromophores: excitonic interactions and response to metal ions." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41127.
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Structure-property relationships for two-photon absorption (2PA) in branched organic chromophores is a topic of current interest, as is the design of chromophores with advantageous properties for two-photon laser scanning microscopy (2PLSM). The main goals of this dissertation were to study and explain the one-photon absorption (1PA) and 2PA properties of cruciform chromophores based on 1,4-distyryl-2,5-bis(phenylethynyl)benzene with varying electron donor (D) and acceptor (A) groups, and to characterize the 2PLSM-relevant response of some of these chromophores and a set of dipolar chromophores to binding with zinc ions. The compounds were studied by 1PA, fluorescence and 2PA spectroscopy. A ππ* exciton model was developed to explain the spectral properties of the 1,4-distyryl-2,5-bis(phenylethynyl)benzene cruciform with no D or A groups or with four identical D groups at the termini of the linear arms of the chromophore. This model indicated that there is some coupling and mixing of the lowest excited states e of the linear arms, leading to splitting of the 1PA spectrum of the cruciform. There was little coupling or mixing of the higher excited states e′ accessed in 2PA, leading to a two-band 2PA spectrum for the chromophore, in contrast to cruciform compounds in the literature with identical conjugated arms, which have one visible 2PA band. For cruciforms with D groups on the styryl arm and A character on the terminal phenyls of the phenylethynyl arms (D/A cruciforms), the ππ* exciton model was complemented with a charge-transfer (CT) exciton model describing interactions of charge-transfer pathways between the D and A groups. This model explained the broadness of the 1PA band of D/A cruciforms as well as the two 2PA bands observed for these chromophores.
The fluorescence and 2PA spectral responses to binding of Zn²⁺ ions to the D or A groups of some cruciform compounds were also assessed, to provide insight into the design of new analyte-sensing cruciforms for 2PLSM that take advantage of enhancement or reduction of D/A character upon analyte binding. It was found that canceling charge donation from the D groups in differing D/A cruciforms resulted in fluorescence and 2PA spectra nearly indistinguishable from each other, suggesting that turn-off of D groups is not an optimal modality of 2PLSM analyte sensing in cruciforms. Binding Zn²⁺ to A groups was shown to result in an increase in the D/A character of the cruciform, with fluorescence peak energies that changed depending on the location of the A group. It is suggested that the use of non-binding donors and analyte-binding A groups in differing patterns on the arms could be a valuable design motif to achieve 2PLSM sensor compounds based on this cruciform structure.
The 2PA spectra of a set of dipolar Zn²⁺ sensing dyes designed for ratiometric imaging in 2PLSM were also studied. These dyes had moderate 2PA strength, with redshifts of fluorescence 2PA spectra on Zn²⁺ binding. The isosbestic point of 2PA of most chromophores was within the range of 2PLSM excitation sources commonly used, rendering these dyes good candidates for use in ratiometric sensing in 2PLSM.
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Lin, Chun-Yu. "Design Principles for Metal-Coordinated Frameworks as Electrocatalysts for Energy Storage and Conversion." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404610/.
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In this dissertation, density functional theory calculations are performed to calculate the thermodynamic and electrochemical properties of metal coordinated frameworks for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Gibb's free energy, overpotential, charge transfer and ligands effect are evaluated. The charge transfer analysis shows the positive charges on the metal coordinated frameworks play an essential role in improving the electrochemical properties of the metal coordinated frameworks. Based on the calculations, design principles are introduced to rationally design and predict the electrochemical properties of metal coordinated frameworks as efficient catalysts for ORR and OER. An intrinsic descriptor is discovered for the first time, which can be used as a materials parameter for rational design of the metal coordinated frameworks for energy storage and conversion. The success of the design principles provides a better understanding of the mechanism behind ORR and OER and a screening approach for the best catalyst for energy storage and conversion.
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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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Wei, Haoming, Jose Luis Barzola-Quiquia, Chang Yang, Christian Patzig, Thomas Höche, Pablo Esquinazi, Marius Grundmann, and Michael Lorenz. "Charge transfer-induced magnetic exchange bias and electron localization in (111)- and (001)-oriented LaNiO3/LaMnO3 superlattices." American Institute of Physics, 2017. https://ul.qucosa.de/id/qucosa%3A23554.
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High-quality lattice-matched LaNiO3/LaMnO3 superlattices with monolayer terrace structure have
been grown on both (111)- and (001)-oriented SrTiO3 substrates by pulsed laser deposition. In contrast
to the previously reported experiments, a magnetic exchange bias is observed that reproducibly
occurs in both (111)- and (001)-oriented superlattices with the thin single layers of 5 and 7 unit cells,
respectively. The exchange bias is theoretically explained by charge transfer-induced magnetic
moments at Ni atoms. Furthermore, magnetization data at low temperature suggest two magnetic
phases in the superlattices, with Néel temperature around 10 K. Electrical transport measurements
reveal a metal-insulator transition with strong localization of electrons in the superlattices with the
thin LaNiO3 layers of 4 unit cells, in which the electrical transport is dominated by two-dimensional
variable range hopping.
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Mutz, Niklas. "Energy and Charge Transfer at Hybrid Interfaces Probed by Optical Spectroscopy." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22797.
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Hybride anorganisch/organischen Systeme können die individuellen Vorteile, etwa eine hohe elektronische Mobilität in anorganischen und starke Licht-Materie-Wechselwirkung in organischen Halbleitern, kombinieren. Ein sinnvoller Nutzen dieser Heterostrukturen benötigt ein umfassendes Verständnis der Grenzfläche. Zwei Grenzflächenprozesse werden in dieser Arbeit behandelt.
Förster-Resonanzenergietransfer (FRET) wird zwischen einem InGaN/GaN Quantengraben und dem Polymer Cn-ether PPV untersucht. Trotz des hohen internen elektrischen Feldes im Quantengraben, ist effizienter Energietransfer möglich, solange andere nicht-strahlende Zerfallsprozesse unterdrückt werden. Dies wird mittels temperaturabhängiger PL und PLE Spektroskopie gezeigt. PLE demonstriert eine eindeutige Erhöhung der Emission des Akzeptors. Bei höheren Temperaturen dominieren nicht-strahlende Zerfallskanäle.
Ladungstransfer wird zwischen MoS2 und dem Molekül H2Pc untersucht. Die Kombination mit organischen Molekülen kann die Funktionalität von MoS2 erweitern. Photoelektronenspektroskopie (PES) zeigt einen Typ-II Heteroübergang an der MoS2/H2Pc Grenzfläche. Angeregte Elektronen gehen von den H2Pc Molekülen in die MoS2 Monolage über, wie mittels einer Verkürzung der PL Lebenszeit von H2Pc gezeigt wird. Photostrommessungen demonstrieren zudem, dass die transferierten Elektronen zu einer erhöhten Photoleitfähigkeit beitragen.
Zusätzlich werden auch einzelne 2D Übergangsmetall Dichalkogenide (TMDCs) untersucht. Um TMDCs von hoher Qualität herzustellen, wurde intern eine Wachstumsmethode entwickelt. Mittels PL Spektroskopie werden die so hergestellten Schichten charakterisiert. Die Vielseitigkeit der Methode wird anhand des Wachstums von Mischkristallen und Heterostrukturen gezeigt. Der Einfluss der dielektrischen Funktion des Substrates wird erforscht. Durch die Kombination von PES und Reflexionsmessungen kann eine gleichzeitige Abnahme sowohl der Bandlücke als auch der Exzitonen Bindungsenergie gezeigt werden.Hybrid inorganic/organic systems can combine the advantages of both materials such as high carrier mobilities in inorganic semiconductors and large light-matter interaction in organic ones. In order to benefit from these heterostructures, a thorough understanding of the interface is needed. Two processes occurring at the interface are looked at in this thesis. Förster resonance energy transfer (FRET) is studied between a single InGaN/GaN quantum well and the polymer Cn-ether PPV. Despite the large internal electric fields in the quantum well, efficient FRET is possible as long as other non-radiative decay channels are suppressed. This is shown by temperature dependent PL and PLE spectroscopy. PLE spectra clearly demonstrate an enhanced light emission from the acceptor. At elevated temperatures, non-radiative decay pathways become dominant. Excited-state charge transfer is studied on MoS2 in combination with the molecule H2Pc. The combination with molecules can extend the functionality of MoS2. Photoelectron spectroscopy (PES) reveals a type II energy level alignment at the MoS2/H2Pc interface. Excited electrons are transferred from H2Pc to MoS2, deduced from a shortening of the H2Pc PL decay time. Photocurrent spectra further show that the transferred electrons contribute to an enhanced photoconductivity. Additionally, bare 2D transition-metal dichalcogenides (TMDCs) are studied. In order to fabricate high-quality TMDC monolayers, a growth method was developed in-house. The grown monolayers are characterised by optical spectroscopy. The versatility of the method is demonstrated by the growth of alloys and heterostructures. The influence of the substrate dielectric function is investigated by comparing band-gaps measured by PES with the exciton transition energies obtained by reflectance measurements. An almost equal reduction in both energies with the substrate dielectric constant is seen.
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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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Loukova, G. V., V. V. Vasiliev, V. L. Ivanov, M. Ya Melnikov, V. A. Smirnov, and E. E. Melnichuk. "Two−photon Processes in Organometallic Molecules and Clusters: T−T Absorption of Group IV Metal Complexes." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35395.
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Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35395
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Kim, Yee Seul. "Investigation of charge transport/transfer and charge storage at mesoporous TiO2 electrodes in aqueous electrolytes." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC161/document.
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Améliorer notre compréhension des mécanismes de transport/transfert de charges et de stockage de charges dans les films d'oxyde métallique semi-conducteur mésoporeux transparents (fonctionnalisés ou non par des chromophores redox-actifs) dans des électrolytes aqueux est d'une importance fondamentale pour le développement et l'optimisation d'une large gamme de dispositifs de production ou de stockage d'énergie éco-compatibles et/ou éco-durables (cellules solaires à colorants, batteries, photoélectrolyseurs, ….). Dans ce but, des films de TiO2 semi-conducteur mésoporeux préparés par dépôt sous incidence rasante (GLAD-TiO2) ont été sélectionnés pour leur grande surface spécifique, leur morphologie bien contrôlée, leur transparence élevée dans le visible et leur semiconductivité bien définie qui peut être facilement ajustée par l’application d’un potentiel externe, autorisant ainsi leur caractérisation aisée par spectroélectrochimie en temps réel. Nous avons d'abord étudié le transfert et transport de charges dans des électrodes GLAD-ITO et GLAD-TiO2 fonctionnalisées par une porphyrine de manganèse redox-active jouant à la fois le rôle de chromophore et de catalyseur. Nous avons démontré que la réponse électrochimique des électrodes ainsi modifiées, enregistrée en l'absence ou en présence du substrat O2, dépend fortement de la conductivité du film mésoporeux. En utilisant la voltamétrie cyclique couplée à la spectroscopie d'absorption UV-visible, nous avons pu extraire des informations clés telles que la vitesse du transfert d'électrons hétérogène entre le chromophore redox immobilisé et le matériau semi-conducteur, et aussi pu rationaliser le comportement électrochimique spécifique obtenu sur un film GLAD-TiO2 modifié par la porphyrine en condition catalytique. En parallèle, nous avons développé un procédé de fonctionnalisation de ces films d'oxyde métallique mésoporeux (en l’occurrence des films GLAD-ITO) par électrogreffage de sels d'aryldiazonium générés in situ, permettant d'obtenir des électrodes fonctionnalisées avec un taux de recouvrement surfacique élevé et une stabilité dans le temps particulièrement bonne en conditions hydrolytiques. Nous avons également étudié le stockage de charges au sein d’électrodes GLAD-TiO2 dans divers électrolytes aqueux. Nous avons notamment démontré pour la première fois qu’une insertion rapide, massive et réversible de protons peut être effectuée dans des films de TiO2 nanostructurés amorphes immergés dans un tampon aqueux neutre, le donneur de protons étant alors la forme acide faible du tampon. Nous avons également démontré que ce processus de stockage d’électrons couplé à l’insertion de protons peut se produire sur toute la gamme de pH et pour un vaste panel d'acides faibles organiques ou inorganiques, mais aussi de complexes aqueux d'ions métalliques multivalents, à condition que le potentiel appliqué et le pKa de l'acide faible soient correctement ajustésBetter understanding of the mechanisms of charge transport/transfer and charge storage in transparent mesoporous semiconductive metal oxide films (either functionalized or not by redox-active chromophores) in aqueous electrolytes is of fundamental importance for the development and optimization of a wide range of safe, eco-compatible and sustainable energy producing or energy storage devices (e.g., dye-sensitized solar cells, batteries, photoelectrocatalytic cells, …). To address this question, mesoporous semiconductive TiO2 films prepared by glancing angle deposition (GLAD-TiO2) were selected for their unique high surface area, well-controlled morphology, high transparency in the visible, and well-defined semiconductivity that can be easily adjusted through an external bias, allowing thus their characterization by real-time spectroelectrochemistry. We first investigated charge transfer/transport at GLAD-ITO and GLAD-TiO2 electrodes functionalized by a redox-active manganese porphyrin that can play both the role of chromophore and catalyst. We demonstrate that the electrochemical response of the modified electrodes, recorded either in the absence or presence of O2 as substrate, is strongly dependent on the mesoporous film conductivity. By using cyclic voltammetry coupled to UV-visible absorption spectroscopy, we were able to recover some key information such as the heterogeneous electron transfer rate between the immobilized redox-active dye and the semiconductive material, and also to rationalize the specific electrochemical behavior obtained at a porphyrin-modified GLAD TiO2 film under catalytic turnover. In parallel, we developed a new functionalization procedure of mesoporous metal oxide films (GLAD-ITO in the present case) by electrografting of in-situ generated aryldiazonium salts, allowing for modified electrodes characterized by both a high surface coverage and a particularly good stability over time under hydrolytic conditions. Also, we investigated charge storage at GLAD-TiO2 electrodes under various aqueous electrolytic conditions. We notably evidenced for the first time that fast, massive, and reversible insertion of protons can occur in amorphous nanostructured TiO2 films immersed in near neutral aqueous buffer, with the proton donor being the weak acid form of the buffer but not water. We also demonstrated that this proton-coupled electron charge storage process can occur over the entire range of pH and for a wide range of organic or inorganic weak acids, but also of multivalent metal ion aquo complexes, as long as the applied potential and pKa of weak acid are properly adjusted
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Hua, Fei. "Synthesis and Photophysics of Platinum (II) Diimine Acetylide Complexes." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1187329346.
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Munisamy, Thiruvengadam Gipson Stephen L. "Electrochemistry and electron transfer induced substitution reactions of methylcyclopentadienylmolybdenum tricarbonyl complexes and electrospray ionization mass spectrometry and x-ray crystallographic characterization of related molybdenum complexes." Waco, Tex. : Baylor University, 2007. http://hdl.handle.net/2104/5234.
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