Дисертації з теми "Conjugated Molecules for Sensors"
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Zucchero, Anthony Joseph. "Cruciform pi-systems: novel two-dimensional cross-conjugated chromophores possessing spatially separated frontier molecular orbitals." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37206.
Повний текст джерелаАнотація:
The design of chromophores targets materials with optoelectronic properties necessary for advanced applications. Organic materials possess properties which emerge from the collective impact of the constituent backbone and substituents as well as their connectivity (i.e. molecular architecture), necessitating the exploration of novel conjugated architectures. This thesis chronicles our examination of 1,4-distyryl-2,5-bis(arylethynyl)benzenes (cruciforms, XFs). Electronic substitution of this 'X-shaped' cross-conjugated scaffold tunes both the energy levels and the spatial distribution of the frontier molecular orbitals (FMOs) in XFs. The resulting fluorophores exhibit FMO separation, imbuing XFs with desirable properties for sensory applications. Using model analytes, we examine how the underlying FMO arrangement and the nature of analyte interaction elicit observable responses. These studies provide a foundation for future access of functional responsive ratiometric cores. This case study demonstrates the importance and unique potential of FMO-separated fluorophores.
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Davey, Evan Andrew. "Development of advanced cross conjugated systems and applications in ratiometric sensing: altering the electronic properties of cruciforms and poly(para-phenyleneethynylene)s to elicit differing reactivity and response." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/49008.
Повний текст джерелаАнотація:
This research serves as a meticulous examination into cross-conjugated materials and how alterations of the frontier molecular orbitals can be utilized for applications in "chemical tongue" organic sensing devices. With conjugated materials being used in the development of new sensory devices for detection of metals, bacteria, and chemical warfare agents, the field of organic sensing is growing faster than ever. The purpose of this dissertation is to provide a precedence for the synthesis of new cross-conjugated compounds and outline potential applications of these materials as chemical sensors and molecular probes.
3
O'Connor, M. P. "Electronic properties of conjugated molecules." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379188.
Повний текст джерела
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Samori, Paolo. "Self-assembly of conjugated (macro)molecules." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2000. http://dx.doi.org/10.18452/14604.
Повний текст джерелаАнотація:
In dieser Dissertation wird die Selbstorganisation von pi-konjugierten (makro)molekularen Architekturen durch Chemisorption oder Physisorption in hochgeordnete supramolekulare nanoskopische und mikroskopische Strukturen auf festen Trägern untersucht. Ihre Struktur und Dynamik wurden auf molekularer Skala hauptsächlich mit Rastersondenmikroskopien, insbesondere mit Rastertunnel- und Rasterkraftmikroskopie, untersucht. Dies erlaubte die Charakterisierung einer Reihe von Phänomenen, die sowohl an Fest-Flüssig-Grenzflächen auftreten, wie beispielsweise die Dynamik der einzelnen molekularen Nanostäbchen (Ostwald Reifung) und die Fraktionierung steifer Polymerstäbchen durch Physisorption an der Grafitoberfläche aus der Lösung heraus, als auch in trockenen Filmen vorkommen wie die Selbstorganisation steifer Polymerstäbchen zu Nanobändern mit molekularen Querschnitten, die sich epitaktisch auf Oberflächen orientieren lassen und auch die Ausbildung gestapelter Architekturen von diskförmigen Molekülen. Außerdem wurden die elektronischen Eigenschaften der untersuchten Systeme mit Hilfe von Photoelektronenspektroskopie charakterisiert. Die entwickelten Nanostrukturen sind nicht nur für Nanokonstruktionen auf festen Oberflächen von Interesse, sondern besitzen auch Eigenschaften, die sie für Anwendungen in einer zukünftigen molekularen Elektronik prädestiniert, etwa für den Aufbau molekularer Drähte.In this thesis the self-assembly of pi-conjugated (macro)molecular architectures, either through chemisorption or via physisorption, into highly ordered supramolecular nanoscopic and microscopic structures has been studied. On solid substrates structure and dynamics has been investigated on the molecular scale making use primarily of Scanning Probe Microscopies, in particular Scanning Tunneling Microscopy and Scanning Force Microscopy. This allowed to characterize a variety of phenomena occurring both at the solid-liquid interface, such as the dynamics of the single molecular nanorods (known as Ostwald ripening), the fractionation of a solution of rigid-rod polymers upon physisorption on graphite; and in dry films, i.e. the self-assembly of rigid-rod polymers into nanoribbons with molecular cross sections which can be epitaxially oriented at surfaces and the formation ordered layered architectures of disc-like molecules. In addition the electronic properties of the investigated moieties have been studied by means of Photoelectron Spectroscopies. The nanostructures that have been developed are not only of interest for nanoconstructions on solid surfaces, but also exhibit properties that render them candidates for applications in the field of molecular electronics, in particular for building molecular nanowire devices.
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Winfield, Jessica Mary. "Spectroscopy of conjugated polymers and small molecules." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611577.
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Wildman, Jack. "Molecular dynamics simulations of conjugated semiconducting molecules." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3261.
Повний текст джерелаАнотація:
In this thesis, we present a study of conformational disorder in conjugated molecules focussed primarily on molecular dynamics (MD) simulation methods. Along with quantum chemical approaches, we develop and utilise MD simulation methods to study the conformational dynamics of polyfluorenes and polythiophenes and the role of conformational disorder on the optical absorption behaviour observed in these molecules. We first report a classical force-field parameterisation scheme for conjugated molecules which defines a density functional theory method of accuracy comparable to high-order ab-initio calculations. In doing so, we illustrate the role of increasing conjugated backbone and alkyl side-chain length on inter-monomer dihedral angle potentials and atomic partial charge distributions. The scheme we develop forms a minimal route to conjugated force-field parameterisation without substantial loss of accuracy. We then present a validation of our force-field parameterisation scheme based on self-consistent measures, such as dihedral angle distributions, and experimental measures, such as persistence lengths, obtained from MD simulations. We have subsequently utilised MD simulations to investigate the interplay of solvent and increasing side-chain lengths, the emergence of conjugation breaks, and the wormlike chain nature of conjugated oligomers. By utilising MD simulation geometries as input for quantum chemical calculations, we have investigated the role of conformational disorder on absorption spectral broadening and the formation of localised excitations. We conclude that conformational broadening is effectively independent of backbone length due to a reduction in the effect of individual dihedral angles with increasing length and also show that excitation localisation occurs as a result of large dihedral angles and molecular asymmetry.
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Jäckel, Frank. "Self-Assembly and Electronic Properties of Conjugated Molecules." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2005. http://dx.doi.org/10.18452/15267.
Повний текст джерелаАнотація:
Die Verwendung einzelner Moleküle als aktive Elemente elektronischer Bauteile wird derzeit als potentielle Alternative zur halbleiterbasierten Nanoelektronik angesehen, da einzelne Moleküle a priori nur einige Nanometer groß sind. Auß erdem kann dabei eventuell eine vereinfachte Verarbeitung und Herstellung der Bauteile erreicht werden. In dieser Arbeit werden das Selbstaggregationsverhalten und die Elektrontransporteigenschaften konjugierter Moleküle mit Rastertunnelmikroskopie (RTM) und -spektroskopie (RTS) an einer Fest-Flüssig-Grenzfläche und unter Ultrahochvakuumbedingungen bei tiefen Temperaturen untersucht. Ihre mögliche Verwendung in hybrid-molekularen Bauteilen als auch Ansätze für eine mono-molekulare Elektronik werden erkundet. Insbesondere wird die Nano-Phasenseparation von Elektron-Donor-Akzeptor-Multiaden an der Fest-Flüssig-Grenzfläche demonstriert, die zur Integration verschiedener elektronischer Funktionen auf der Nanoskala benutzt werden kann. Desweiteren wird die Abhängigkeit der elektronischen Kopplung scheibenförmiger gestapelter Moleküle vom lateralen Versatz innerhalb des Stapels experimentell nachgewiesen. Dies eröffnet neue Möglichkeiten die elektronischen Eigenschaften solcher dreidimensionaler Architekturen gezielt zu beeinflussen. Außerdem werden die ersten RTM/RTS-Untersuchungen von Ladungstransferprozessen in einzelnen organischer Donor-Akzeptor-Komplexe präsentiert. Schließlich werden die Ladungstransferkomplexe mit dem Ansatz der Nano-Phasenseparation kombiniert, um den ersten Einzelmolekültransistor mit intergrierten Nanogates zu realisieren. In diesem prototypischen Bauteil wird die Strom-Spannungs-Kennlinie einer hybrid-molekularen Diode, die aus einem Hexa-peri-hexabenzocoronen (HBC) im Tunnelspalt eines RTMs besteht, durch einen kovalent an das HBC gebundenen Ladungstransferkomplex modifiziert. Dies wird als wichtiger Schritt in Richtung einer mono-molekularen Elektronik angesehen.The use of single molecules as active components in electronic devices is presently considered a potential alternative to semiconductor-based nano-scale electronics since it directly provides precisely-defined nano-scale components for electronic devices which eventually allows for simple processing and devicefabrication. In this thesis the self-assembly and electron transport properties of conjugated molecules are investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS) at solid-liquid interfaces and under ultrahigh vacuum conditions and low temperatures. The use of the molecules in hybrid-molecular electronic devices and potential approaches to a mono-molecular electronics are explored. In particular, electron-donor-acceptor-multiads are shown to exhibit a nano-phase-segregation at the solid-liquid interface which allows for the integration of different electronic functions at the nano-scale. Furthermore, the dependence of the electronic coupling of stacked disk-like molecules on the lateral off-set in the stack is demonstrated experimentally which offers new possibilities for the control of the electronic properties of these three-dimensional architectures. In addition the first STM/STS experiments on charge transfer in single organic donor-acceptor complexes are presented. Finally, charge transfer complexes are combined with the approach of nano-phase-segregation to realize the first single-molecule transistor with integrated nanometer-sized gates. In this prototypical device the current through a hybrid-molecular diode made from a hexa-peri-hexabenzocoronene (HBC) in the junction of the STM is modified by charge transfer complexes covalently attached to the HBC in the gap. Since the donor which complexes the covalently attached acceptor comes from the ambient fluid the set-up represents a single-molecule chemical field-effect transistor with nanometer-sized gates. This is considered a major step towards mono-molecular electronics.
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Vogel, Jörn-Oliver. "Co-deposited films of rod-like conjugated molecules." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/15978.
Повний текст джерелаАнотація:
In dieser Arbeit wird die Phasenseparation und Mischung zwischen konjugierten Stäb-chenmolekülen in dünnen Filmen untersucht. Hauptaugenmerk liegt darauf zu ergrün-den welche molekularen Eigenschaften zu Mischung und/ oder Phasenseparation füh-ren. Mit den 5 Molekülen Pentacen (PEN), Quaterthiophen (4T), Sexithiophen (6T), p-Sexiphenylen (6P), alpha,omega-Dihexylsexithiophen (DH6T) werden Materialpaare zusammen gestellt, die sich in den Parametern „optische und elektrische Eigenschaf-ten“, „Länge des konjugierten Kerns“ und Alkylkettensubstitution unterscheiden. Alle Schichten werden mittels organischer Molekularstrahlabscheidung auf die Substrate Siliziumoxid und Mylar, einer PET Folie, simultan von zwei Quellen aufgedampft. Das Mischungsverhältnis wird mittels der individuellen Aufdampfraten eingestellt und eine Gesamtrate von 0.5 nm/min eingehalten. Es wird Phasenseparation für Materialpaare mit ungleicher konjugierter Kernlänge, z.B. [4T/6T], beobachtet. Erstaunlicherweise führt die Co-Verdampfung von Molekülpaaren mit ähnlicher konjugierter Kernlänge [4T/PEN] und [6T/6P] zu wohlgeordneten Fil-men, in denen die Moleküle in gemischten Lagen parallel zur Substratoberfläche auf-wachsen und die Längsachse der Moleküle fast senkrecht zur Substratoberfläche orien-tiert ist. Molekülpaare mit ähnlicher konjugierter Kernlänge und Alkylsubstitution [6T/DH6T] und [6P/DH6T] zeigten ebenfalls geordneten Schichten, wobei als Besonderheit eine lineare Abhängigkeit des Lagenabstandes vom DH6T-Gehalt zu beobachten ist. Dies wird mit einer Phasenseparation in eine aromatische und eine alkyl Domäne erklärt. Mit abnehmendem DH6T-Gehalt im Film ist die Alkyldomäne weniger dicht gepackt, was auf Grund der Flexibilität der Alkylketten zu einer Abnahme des gesamten Lagenab-standes führt. Die besonders geringe Oberflächenrauhigkeit und die miteinander verbundenen Inseln der [DH6T/6T] Filme prädestinieren sie zur Verwendung in Feldeffekttransistoren. Es wird gezeigt, dass es möglich ist, die Ladungsträgerdichte im Kanal durch Änderung des Verhältnisses zwischen DH6T und 6T so zu verändern, dass der Transistor im Verar-mungs- oder Anreicherungsregime betrieben werden kann. Dabei bleibt die Ladungsträ-germobilität auf gleich bleibend hohem Niveau. Dies entspricht dem Dotieren eines anorganischen Halbleiters.This thesis is centered on studies of phase separation and mixing in co-deposited thin films of rod-like conjugated molecules. The main focus is to determine which molecular properties lead to phase separation and/or mixing of two materials. To address this question I used five materials, of importance in the context of “organic electronics”: pentacene (PEN), quaterthiophene (4T), sexithiophene (6T), p-sexiphenylene (6P), alpha,omega-dihexylsexithiophene (DH6T). With these it was possible to form material pairs which differ in the parameters: energy levels, length of the conjugated core, and alkyl-end-chain-substitution. All films were deposited by organic molecular beam deposition onto the chemically inert substrates silicon oxide and Mylar, a polyethylene terephthalate (PET) foil. The material pairs were deposited simultaneously from two thermal sublima-tion sources. The mixing ratio was controlled by the individual deposition rates, which were measured online by a microbalance. The total deposition rate was 0.5 nm/min, and the film thicknesses ranged from 4 nm to 40 nm. Phase separation is observed for material pairs with dissimilar conjugated core sizes, i.e. [4T/6T]. Noteworthy, the co-deposition of material pairs with similarly sized conju-gated cores [4T/PEN] and [6T/6P] lead to well ordered layered structures. The mole-cules show mixing within layers on a molecular scale and the long molecular axis is ori-ented almost perpendicular to the substrate surface. Material pairs with similarly sized conjugated core and alkyl-end-chain-substitution [6T/DH6T] and [6P/DH6T] show also growth in mixed layered structures. An especially appealing fact is that the interlayer distance increases proportional to the DH6T content in the film. This can be explained with a phase separation into an aromatic and an alkyl domain vertically to the substrate surface. A decrease of the DH6T content in the film leads to a less dense packing in the alkyl domain. This leads, due to the flexibility of the alkyl chains, to a decrease of the overall interlayer distance. The low surface corrugation and the interconnected islands render the material pair [6T/DH6T] well suitable for the use as active layer in organic field effect transistors. It is shown that it is possible to tune the charge carrier density in the channel by changing the ratio between 6T and DH6T. This effect enables switching the transistor from en-hancement to depletion mode, while maintaining a high charge carrier mobility. This is comparable to p-type doping of inorganic semiconductors.
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Samorí, Paolo. "Self-assembly of conjugated (macro)molecules nanostructures for molecular electronics /." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962281530.
Повний текст джерела
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Wright, Helen. "Fused ring conjugated polymers and small molecules for organic-semiconductors." Thesis, University of Manchester, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542784.
Повний текст джерелаАнотація:
Fused ring structures such as cyclopentadithiophenes (CPDT), fluorenes and dithienopyrroles have been shown to have low band gaps and extended conjugation lengths. Both of these properties make them interesting materials for organic semiconductor applications. It has been shown that increasing the planarity of building blocks, and in turn the polymer or molecule they are contained within, can improve charge transport by increasing π-π stacking. While the homo-polymers of dithienopyrrole, and alkene bridged CPDT and fluorene have low band gaps, it is possible to further reduce them by forming co-polymers, either by combination with an acceptor unit or by increasing the planarity of the polymer. Three families of small molecules and corresponding co-polymers were therefore synthesised using three main building blocks - alkene bridged CPDT, alkylidene fluorene and dithienopyrrole - combined with a series of co-monomers. In the cases of CPDT and dithienopyrrole two different alkyl chains were used with the aim of influencing solubility and solid-state packing. The optical and electrochemical properties were studied and trends determined. In addition physical and thermal properties were studied and for several of the small molecules, crystal structures and theoretical structures were also evaluated to probe intermolecular interactions in the solid state.During the synthesis of one alkylidene fluorene small molecule an unexpected impurity was isolated in which the bridging alkene of the fluorene had rearranged. Possible reasons for the formation were investigated and the properties of the compound studied.Several small molecules and one co-polymer were incorporated into preliminary OFET devices, although performance was limited by poor film formation. Film forming studies were also undertaken on the co-polymer.
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Strawbridge, Sharon Mary. "Redox-active sensors for molecules of biological interest." Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414263.
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Wiebeler, Christian [Verfasser]. "Photophysics and photochemistry of conjugated systems and photochromic molecules / Christian Wiebeler." Paderborn : Universitätsbibliothek, 2015. http://d-nb.info/1073201570/34.
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Atherton, Kathryn Jane. "Coherent Raman studies of optical nonlinearities in conjugated molecules and polymers." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298790.
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Clark, Jenny. "Intermolecular interactions in π-conjugated molecules : optical probes of chain conformation". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597713.
Повний текст джерелаАнотація:
A study of interactions between molecules of the same material was performed on a model polymer system. Regio-regular poly(3-hexylthiophene) (P3HT) self-organises into two-dimensional π-stacked lamellar structures. Although the chains pack at a distance of only 3.8Å, the resonant coulomb interaction between nearest-neighbour molecules is small, owing to large average conjugation lengths within the lamellae. When the resonant coulomb (or excitonic) interaction is smaller than the vibrational relaxation energy, the excitation is localised on a single molecule and the coupling is termed weak. Here we demonstrate that the polymer absorption and emission spectra can be comprehensively explained using a weakly interacting H-aggregate model. Using an analytic form of the model we can estimate the excitonic interaction energy from the ratio of the 0-0 and 0-1 absorbance peaks. It was found to vary between 5-30meV. We use this powerfully simple tool to determine how film micromorphology depends on processing. We find that films spun from low boiling point solvents show a decrease in crystalline quality, an increase in excitonic coupling and more amorphous regions, than films spun from high boiling point solvents. We correlate these findings with field-effect transistor characteristics to produce a model of film micro-morphology. We also demonstrate preliminary results that show that due to the aggregate nature of the primary neutral excitation, photo-induced charge generation in P3HT is due to exciton-exciton annihilation. Finally, we study the intermolecular interactions at an interface between two different molecules (a hole transporting polymer, TFB (Poly(9,9-dioctylfluorene –co-N-(4-butylphenyl)diphenylamine)) and an electron-transporting disoctic, HATNA-SC12 (Hexa-azatrinaphthylene)). Depending on the energetics of the interface between two materials, the inter-molecular state can be stabilised by either coulomb interactions (as in the case of single material interfaces) or charge-transfer interactions. In this case, we find that the charge-transfer interactions dominate and an excited-state complex, or exciplex, is formed. The exciplex is generated efficiently in light-emitting diodes, producing a pure red emission. In polymer/polymer blends efficient bulk exciton emission can occur due to endothermic transfer from the exciplex to the bulk exciton. In this system, however the exciplex is stable at the interface, acting as an energy bottleneck with inefficient transfer to bulk exciton states. Furthermore, the yield of charge separation is low.
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O'Keefe, Guy Edward. "Ultrafast optical spectroscopy of the excited-states of conjugated organic molecules." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627580.
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Takeda, Yohei. "Studies on Synthesis and Properties of CF3-Substituted π-Conjugated Molecules". 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120820.
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Lange, Philipp. "Optical and structural properties of systems of conjugated molecules and graphenes." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16938.
Повний текст джерелаАнотація:
Systeme aus konjugierten Molekülen und Graphenen bergen hohes Potential für Anwendungen. Die Untersuchung ihrer Wechselwirkungsmechanismen ist wichtig für die Entwicklung neuer Anwendungen und Fokus dieser Arbeit: Optische Mikroskopie, Spektroskopie und Rasterkraftmikroskopie werden komplementär verwendet, um die optischen und strukturellen Eigenschaften solcher Systeme zu erforschen. Insbesondere werden (i) die Permeationsbarriere-Eigenschaften von Graphen in-situ auf einem halbleitenden Polymerfilm quantifiziert. Weiterhin werden (ii) die Fluoreszenz- und (iii) Raman-Emission von konjugierten Molekülen in der Nähe von Graphen untersucht und die entsprechenden Kopplungsmechanismen diskutiert. (i) Graphene zeigen sich als effizienter Schutz des empfindlichen Polymers [Poly(3-hexylthiophen)] vor Degeneration durch Sauerstoff und Wasser aus der Umgebungsluft. Dies legt nahe, dass Graphene nicht nur als transparente Elektrode, sondern gleichzeitig als Barriereschicht in künftigen optoelektronischen Bauelementen dienen können. (ii) Es wird gezeigt, dass die bekannten optischen Eigenschaften von Graphen die Existenz stark lokalisierter Graphen-Plasmonen im Sichtbaren implizieren. Durch Verwendung von nanoskaligen Emittern [Rhodamin 6G (R6G)], welche die für effiziente Anregung von Graphen-Plasmonen im optischen Frequenzbereich notwendigen großen Wellenvektor bereitstellen, wird Graphen-Plasmonen-induzierte (GPI) Fluoreszenz-Anregungsverstärkung von nahezu 3 Größenordnungen nachgewiesen. Demnach ist Graphen für plasmonische Bauelemente im Sichtbaren interessant. (iii) Außerdem wird GPI Verstärkung des Raman-Querschnittes von R6G um 1 Größenordnung nachgewiesen. Zukünftige Entwicklung von Antennen für zusätzliche direkte Anregung von Graphen-Plasmonen aus dem Fernfeld macht Graphen vielversprechend für leistungsfähige oberflächenverstärkte Raman-Spektroskopie. Zusammenfassend wurden neue und anwendungsrelevante Einblicke in die analysierten Systeme gewonnen.Systems of conjugated molecules and graphenes bear high application potential. The investigation of their interaction mechanisms is important for design of new applications and the focus of this thesis: Optical microscopy, spectroscopy and scanning force microscopy are complementarily used to explore the optical and structural properties of such systems. In particular (i) the permeation barrier properties of graphene are quantified in-situ on a semiconducting polymer film. Furthermore (ii) the fluorescence and (iii) Raman emission of conjugated molecules in proximity to graphene are investigated and the respective coupling mechanisms are discussed. (i) Graphenes are found to efficiently protect the sensitive polymer [poly(3-hexylthiophene)] from degradation by oxygen and water from the ambient atmosphere. This suggests that graphenes can not only serve as transparent electrode, but simultaneously as a barrier layer in future optoelectronic devices. (ii) It is shown that the known optical properties of graphene imply the existence of strongly localized graphene plasmons in the visible. Using nanoscale emitters [rhodamine 6G (R6G)] that provide the high wave vectors necessary to efficiently excite graphene plasmons at optical frequencies, graphene plasmon induced (GPI) fluorescence excitation enhancement by nearly 3 orders of magnitude is demonstrated. Graphene is thus interesting for plasmonic devices in the visible. (iii) In addition GPI enhancement of the Raman cross section of R6G by 1 order of magnitude is demonstrated. The future design of antennas for additional direct farfield excitation of graphene plasmons makes graphene promising for powerful surface enhanced Raman spectroscopy. In summary new and application relevant insights were gained into the studied systems.
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Liao, Jessica Huien 1979. "Particle sensors based on amplified quenching of conjugated polymers for biosensing applications." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39482.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references.
Conjugated polymers (CP)s display unique material properties that allow for implementation as sensors. For sensors to operate in complex biological environments, it is important to address the issues of sensitivity and specificity. To develop these attributes in a biosensor design, CPbased core-shell particles have been investigated as potential material platforms to detect protease activity. CP-based particles have greater sensitivity versus CPs in solution due to interchain and intrachain interactions afforded in the solid state. The CP core of the particle can be made using layer-by-layer assembly, a versatile technique that forms uniform polymeric films through non-covalent interactions. To measure the response of CP core particles in aqueous environments, a quantitative ratiometric approach was developed to account for system fluctuations encountered with particle dispersions. This method can help assess the molecular design of polymers and quenchers in a systematic approach. CP core particles, because of their electrostatic charge, suffer from nonspecific interactions with other charged species, and thus encapsulating CP particles with a hydrogel shell should create sensor materials with higher specificity.
(cont.) To illustrate this concept, CP-particle containing hydrogel films were created to permit selective interactions with designed quenchers. The encapsulation of the individual CPcore particles was accomplished through atom transfer radical polymerization (ATRP) of functional monomers from the surface, and the choice of reactive group on the monomer allows for bioconjugation on the particle shell. Future core-shell materials can also be developed with ATRP, and give prospects to new schemes for CP-based biosensing.
by Jessica Huien Liao.
Ph.D.
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Ji, Eunkyung. "Conjugated polyelectrolytes synthesis, photophysical studies and applications to sensors and biocidal activity /." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024832.
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Jäckel, Frank. "Self assembly and electronic properties of conjugated molecules: towards mono molecular electronics." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975579010.
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Paiboonvorachat, Nattapong. "Density matrix renormalisation group calculations of the electronic structure of conjugated molecules." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606304.
Повний текст джерелаАнотація:
With many interesting electronic and optical properties, conjugated molecules have long been a subject for both theoretical and experimental studies, especially in recent applications in optoelectronics. Most of the properties are controlled by their electronic structures, with the low-lying states predominantly characterised by the 7!'-electrons. We have thus employed the semi-empirical Pariser-Parr-Pople model, whose Hamiltonian parameters are optimised against the excited states, in this study. Despite only considering the π-delocalised system, the model has been widely and successfully applied to study such molecules, giving fairly accurate results. The calculation of these strongly correlated systems requires an accurate computational method, which is usually limited to small molecules due to an enormous amount of resources demanded, as in ab initio calculations. Density Matrix Renormalisation Group (DMRG) provides a systematic way to truncate the size of the Hilbert space while being able to reasonably capture the correlation effect. We have compared three different approaches using both localised and delocalised basis states in the DMRG calculations. First, in the real-space method, atomic sites are aligned on the one-dimensional DMRG lattice as originally developed to study the fermionic systems in condensed matter physics. Alternatively, a collection of atoms, e.g. a monomer unit in conjugated polymers, can be used where an in situ optimisation technique is employed to pre-select the important states. Last, the correlation effect between the Hartree-Fock (HF) molecular orbitals on the lattice sites is calculated in the HF -DMRG scheme. In this post-HF method, the energy converges more slowly than the first but the implementation of t he codes is generic to any geometric structures. In addition to the spin-flip and particle-hole symmetries, which are available in the real-space method, the spatial symmetries can also be applied to target specific states when working in HF space. Calculations have been made on conjugated polymers, i.e. polyacetylene and poly(parophenylene), and aromatic compounds, i.e. pentacene and porphin. The results are compared to other methods, e.g. exact diagonalisation and Configurational Interaction Singles, as well as other theoretical and experimental results in the literature
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Repiscak, Peter. "Computational chemistry for complex systems : open-shell molecules to conjugated organic materials." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3348.
Повний текст джерелаАнотація:
This thesis focuses on two different, but equally challenging, areas of computational chemistry: transition metal organic molecule interactions and parameterisation of organic conjugated polymers for molecular dynamics simulations. The metal-binding properties are important for understanding of biomolecular action of type 2 diabetes drug and development of novel protocols for redox calculations of copper systems. In this area the challenge is mainly related to the complex electronic structure of the open-shell transition metals. The main challenges for the parameterisation of conjugated polymers are due to the size of the studied systems, their conjugated nature and inclusion of environment. Metal-binding properties as well as electronic structures of copper complexes of type 2 diabetes drug metformin (Metf) and other similar, but often inactive, compounds were examined using DFT method. It was found that for neutral compounds it is not possible to explain the differences in their biological effects solely by examining the copper-binding properties. Further, the proposed mechanism potentially explaining the difference in the biomolecular mode of action involves a possible deprotonation of biguanide and Metf compounds under higher mitochondrial pH which would lead to formation of more stable copper complexes and potentially affecting the mitochondrial copper homeostasis. In addition, redox properties of copper-biguanide complexes could interfere with the sensitive redox chemistry or interact with important metalloproteins in the mitochondria. Understanding the copper-binding properties is also important for a systematic development and testing of computational protocols for calculations of reduction potentials of copper complexes. Copper macrocyclic complexes previously used as model systems for redox-active metalloenzymes and for which experimentally determined redox potentials are available were used as model systems. First adequacy of using single reference methods such as DFT was examined for these systems and then various DFT functionals and basis sets were tested in order to develop accurate redox potential protocol. It was shown that good relative cor-relations were obtained for several functionals while the best absolute agreement was obtained with either the M06/cc-pVTZ functional with the SMD or either M06L or TPSSTPSS functional with cc-pVTZ basis set and the PCM solvation model. Organic conjugated polymers have a great potential due to their application in organic optoelectronics. Various wavefunction and DFT methods are utilized in order to systematically develop parameterisation scheme that can be used to derive selected force-field parameters such as torsional potentials between monomer units that are critical for these systems and partial charges. Moreover, critical points of such a parameterisation are addressed in order to obtain accurate MD simulations that could provide valuable insight into material morphology and conformation that affect their optical properties and conductivity. It was shown that a two step approach of geometry optimisation with CAM-B3LYP/631G* and single point (SP) energy scan with CAM-B3LYP/cc-pVTZ is able to yield accurate dihedral potentials in agreement with the potentials calculated using higher level methods such as MP2 and CBS limit CCSD(T). Further, investigating partial charge distribution for increasing backbone length of fluorene and thiophene it has been found that it is possible to obtain a three residue model of converged charge distributions using the RESP scheme. The three partial charge residues can be then used to build and simulate much longer polymers without the need to re-parametrize charge distributions. In the case of side-chains, it was found that it is not possible to obtain converged charge sets for sidechain lengths of up to 10 carbons due to the strong asymmetry between the side-chain ends. Initial validation of derived force-field parameters performed by simulations of 32mers of fluorene with octyl side-chains (PF8) and thiophene with hexyl side-chains (P3HT) in chloroform and calculation of persistence lengths and end-to-end lengths showed close correspondence to experimentally obtained values.
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Esipenko, Nina A. "Design, Synthesis, and Application of Sensors for Biologically Relevant Molecules." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1395589938.
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Wang, Xinyang. "Conjugated polymers for the elaboration of optical and ohmic sensors for water monitoring." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX078/document.
Повний текст джерелаАнотація:
Le but de mon projet est de développer des capteurs moins chers qui sont capables de détecter rapidement les présences des ions métalliques dans l'eau. Deux types de capteurs sont élaborés dans la cadre de ce projet: des capteurs optiques sont développés à partir de polymères conjugués (PCs) avec des ligands spécifiques car ils peuvent amplifier le signal de fluorescence et faciliter la migration des électrons, améliorant ainsi la sensibilité des capteurs1 ; et des capteurs ohmiques qui permettent des mesures in-situ.Concernant les capteurs optiques, deux séries de polymères conjugués avec trois ligands différents sont synthétisés pour étudier l’influence des groupes ligands ainsi les structures des squelettes des polymères sur leur capacité à reconnaître des ions métalliques (Figure 1). Les titrations photoluminescences de ces polymères avec dix ions métalliques (Al3+, Ca2+, Cd2+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, et Zn2+) ont montré que le polymère nommé P1 est sensible à Cu2+ et Ni2+, et le polymère P6 émet une couleur orange en présence des ions Cd2+ et Zn2+ sous lumière UV (Figure 2). Ces faits permettent d’utiliser les polymères comme capteurs optiques pour ces ions à partir des quantités en ppb (µg/L). Nous avons aussi montré la possibilité d’utiliser ces polymères sous forme solide ce qui permet de recycler ces capteurs en films (Figure 3).Les capteurs ohmiques sont développés en combinant des PCs avec des nanotubes de carbone (NTC) comme éléments de détection2. Une telle combinaison devrait apporter à la fois une sélectivité par une fonctionnalisation chimique adéquate des PC3, et une sensibilité grâce aux propriétés électriques des NTC. En effet, dans les nanohybrides PC/NTC, les squelettes conjugués des polymères sont physisorbés sur les parois du NTC par des interactions d'empilement (Figure 4 - a). La modification électronique induite par l'interaction entre les PC et les analytes devrait être transférée aux NTC, qui agissent comme des transducteurs dans les capteurs, en modifiant leur conductivité. Les polymères synthétisés précédemment sont fonctionnalisés sur les parois de NTC afin de formuler des nanohybrides PCs/NTC pour l’élaboration des capteurs ohmiques. Les nanohybrides PCs/NTC sont caractérisés par des méthodes expérimentales (microscopie électronique en transmission, Raman, etc.) et numérique (simulation, Figure 4 - b) pour confirmer l’interaction entre PCs et NTC. Les nanohybrides sont ensuite déposés sous forme de films sur des puces avec les électrodes (Figure 4 - c) qui servent d’éléments résistif dans les dispositifs. La réponse des dispositifs aux concentrations métalliques est mesurée et étudiéeDifferent pollutants can be found in water, inorganic material (chloride, chlorine, heavy metal ions…) and organic material (trace of medicament…). Among them, heavy metal ions are of among the most toxic for human and the environment. Analysis of water contaminants that are toxic for human being and aquatic life is of primary importance. Especially, the measurements of the quality of drinking water delivered in private dwelling is a significant public health concern. A family of undesired contaminants is heavy metals. An elevated concentration of metal ions in water is mostly due to an intensive human activity (industry, farming, and housing). In small quantities, certain heavy metals (e.g., iron, copper, manganese, and zinc) are nutritionally essential for a healthy life. However, heavy metals show a great trend to form complexes, especially with ligands of biological matter containing nitrogen, sulfur, and oxygen. As a result, changes in the molecular structure of proteins, breaking of hydrogen bonds, or inhibition of enzymes can occur[1]. These interactions, among others, may explain the toxicological and carcinogenic effects of heavy metals. These ions can cause damages to many organs and are responsible of diseases, including Parkinson’s and Alzheimer’s diseases[2-6]{Liu, 2015 #101;Liu, 2015 #101;Kim, 2012 #102;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101;Kim, 2012 #102;Liu, 2015 #101}. Respiratory and cardiac problems can be caused by nickel ingestion[7], and accumulation of the Ni2+ ion in the body leads to oxidative stress[8]; Ni2+ and Cu2+ are also noxious to teeth and bones. These negative effects result from the formation of coordination complexes between the metal ions and biological matter.Heavy metals are not biodegradable and therefore they remain in ecological systems and in the food chain indefinitely, exposing top-level predators to very high levels of pollution.Different methods are used to determine their quantity concentration in aqueous phase such as anodic stripping voltammetry (ASV) [4, 6], solid phase extraction combined with inductively coupled plasma optical emission spectrometry ICP-OES[4, 6] and cold-vapor atomic absorption spectroscopy (AAS) method[9]. These methods are well established, but are costly, time consuming, lack portability, and rely on trained personnel because of their complexity[10].Therefore, cheap, portable and real-time response real-time sensors for the determination of heavy metals in aqueous solutions are needed, particularly in sensitive environments, such as drinking water and industrial wastewater effluents. Here we design and elaborate The aim of the project is to develop these kinds of sensors to satisfy the current need. Two kinds of sensors have been elaborated in the project: the first one is optical sensors based on functionalized conjugated polymers (CPs). The second one is a communicating resistive sensors based on conjugated polymers (CPs)/carbon nanotubes (CNTs) nanohybride for the quick detection of pollutants in aqueous water. To our knowledge, no this kind of resistive of sensors has been developed yet. The start of the project focuses onWe start the project for the detection of metal ions, however, it can later be extended to other kinds of pollutants (such as nitrate, chloride, even drugs) using different polymers with the same working mechanism
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Bangcuyo, Carlito Ganayo. "Synthesis of Heterocyclic Poly(aryleneetheynylene)s." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14011.
Повний текст джерелаАнотація:
Poly(arylenenethynylene)s or PAEs are an interesting class of conjugated polymers that have potential uses in the field of thin film transistors, organic LEDs, sensors, and molecular wires. The field of PAEs have grown in recent years, however very few of its conjugated polymers have a heterocyclic motif contained within them. We have designed some conjugated heterocyclic polymers that contain quinoline, benzothidiazole, and quinoxaline. These polymers show interesting ionochromic and solvochromic effects as well as unusual solid state properties. Some of these polymers will demonstrate their ability to form fascinating nanostructures by use of either mesoporous discs or gold mediated nanotubes. Finally, we also have produced peralkynylated heterocyclic molecules for use in potential n-semiconductive devices. These molecules are not only aesthtically pleasing, but versatile molecules that could be used in conjugated PAEs.
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Aydemir, Murat. "Investigation of delayed fluorescence phenomena in conjugated molecules using time-resolved laser spectroscopy." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11712/.
Повний текст джерелаАнотація:
This thesis reports structure-property relationships in a range of conjugated molecules where the nature of the delayed fluorescence (DF) is used as a powerful diagnostic tool in order to gain insight into the nature of the molecules. All the investigations revolve around using three spectroscopic methods; steady state, single-photon counting and particularly time-resolved nanosecond spectroscopy. The rarely observed optically generated geminate electron-hole (e-h) pair recombination is designated as the origin of DF in Rhodamine 6G and its derivative ATTO-532 molecules. The DF shows a strong dependence on excitation energy, which is due to emission arising from higher energy excited dimeric states. In addition, the complex excited-state nature of the polyspirobifluorene (PSBF) polymer is investigated in both dilute solutions and spin-coated films. According to investigations carried out in dilute solutions, solvent polarity and temperature dependent charge transfer (CT) state formation is observed as arising from the “inter/intrachain” interaction phenomena. The stabilisation of the intra- CT state at low temperatures exhibits the presence of both triplet-triplet annihilation (TTA) and monomolecular processes. These findings are used to interpret the up-conversion data of PSBF in thin films, clearly revealing that both TTA and thermally activated delayed fluorescence (TADF) are involved in indirect singlet generation. The same mixed contribution is also confirmed in anthracene based, small molecule, thin films. Consequentially, these findings highlight the investigated system as one of the desirable alternative molecular systems through which high efficiencies in organic light emitting device (OLED) applications can be attained. Finally, an understanding of novel anthracene based novel acceptor molecule is developed through the use of a sensitizer based up-conversion experimental method, in which the question of how the side groups (having different electron affinities) affect the TTA efficiency and triplet energy transfer efficiency is clarified. Lastly, the investigations show that novel pyridine derivatives have solvent polarity and viscosity dependent excited state configurations, which are designated as twisted/wagged intramolecular charge transfer states. The DF, in this case, predominantly originates from monomolecular recombination of the geminately bound e-h pairs. It is believed that this can be a major loss mechanism for quantum yield in ICT systems.
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Sobczyk, Sandra [Verfasser]. "STM transport theory for pi-conjugated molecules on thin insulating films / Sandra Sobczyk." München : Verlag Dr. Hut, 2012. http://d-nb.info/1028784856/34.
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Chen, Xufang. "Synthesis and Characterization of Molecules and π-Conjugated Materials Containing Low-Coordinate Phosphorus". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1102137178.
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Yang, Kun. "CONJUGATED POLYMERS AND SMALL MOLECULES WITH LATENT HYDROGEN-BONDING FOR ORGANIC ELECTRONIC APPLICATIONS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron149083508357808.
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Mao, Yifan. "SYNTHESIS AND CHARACTERIZATION OF NOVEL p-CONJUGATED MOLECULES FOR ORGANIC REDOX-FLOW BATTERIES." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522333087480595.
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Chen, Xufang. "Synthesis and characterization of molecules and [pi]-conjugated materials containing low-coordinate phosphorus." online version, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1102137178.
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Davoudzadeh, Gholami Mahnaz. "Highly sensitive materials and sensors for the detection of bioactive molecules." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/227476/1/Mahnaz_Davoudzadeh%20Gholami_Thesis.pdf.
Повний текст джерелаАнотація:
This thesis demonstrates comprehensive research on novel sensors of multifunctional applications. It presents novel materials (dye-coated paper strips, functionalized gold nanoparticles/gold nanostructured substrates, antibody-coated conductive polymers, SERS tags) for the determination of bioactive molecules. A novel thiol chemistry approach, bioconjugation of recognition molecules, and surface functionalizations were developed for the ultrasensitive detection of target analytes. The newly developed materials, multimodal sensors (optical, fluorescence, SERS, electrochemical) of high sensitivity and selectivity were utilised and validated for the rapid screening/quantification of bioactive molecules (diseases biomarkers, amino acids, and toxic substances) in biological and environmental matrices.
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Wild, Kirstie Yvette. "Redox-active host molecules for the electrochemical recognition of charged and neutral species." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358700.
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Dahlstrand, Christian. "Ground and Excited State Aromaticity : Design Tools for π-Conjugated Functional Molecules and Materials". Doctoral thesis, Uppsala universitet, Fysikalisk-organisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173115.
Повний текст джерелаАнотація:
The main focus of this thesis is on the aromaticity of the ground state and electronically excited states of π-conjugated molecules and polymers, as well as how aromaticity is connected to their properties. The electronic structures of polybenzenoid hydrocarbons (PBHs) were explored through density functional theory (DFT) calculations and the π-component of the electron localization function (ELFπ). The study revealed how the π-electronic structure is influenced by the fusion of double bonds or benzene rings to the PBHs. We also demonstrated that the π-electrons of benzene extend to accommodate as much aromaticity as possible when bond length distorted. The aromatic chameleon property displayed by fulvenes, isobenzofulvenes, fulvalenes, bis(fulvene)s, and polyfulvenes were investigated using DFT calculations. The tria-, penta-, and heptafulvenes were shown to possess ionization energies and electron affinities which can be tuned extensively by substitution, some of which even outperform TTF and TCNQ, the prototypical electron donor and acceptor, respectively. The singlet-triplet energy gap of pentafulvenes can be tuned extensively by substitution to the point that the triplet state is lower than the singlet state and thus becomes the ground state. The ELFπ of isobenzofulvene shows that the benzene ring in an electronically excited state can be more aromatic than the corresponding ring in the ground state. We have shown that the 6-ring of [5.6.7]quinarene is influenced by a Hückel aromatic resonance structure with 4n+2 π-electrons in the excited quintet state. The bis(fulvene)s which are composed of a donor type heptafulvene and an acceptor type pentafulvene, retain the basic donor-acceptor properties of the two fragments and could function as compact donor-acceptor dyads. A few of the designed polyfulvenes were found to have band gaps below 1 eV at the PBC-B3LYP/6-31G(d) level. Various 2,7-disubstituted fluorenones and dibenzofulvenes were synthesized and their excited state properties were investigated by absorption spectroscopy and time-dependent DFT calculations. It was found that the 1A → 1B transition of ππ* character can be tuned by substitution in the 2,7-positions. The 2,7-bis(N,N-dimethyl) derivatives of fluorenone and dibenzofulvene displayed low energy transitions at 2.18 and 1.61 eV, respectively, in toluene.
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Magnan, François. "Sulphur- & Nitrogen-Containing π-Conjugated Organic Molecules as Potential Semiconductors for Optoelectronic Devices". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36754.
Повний текст джерелаАнотація:
Organic semiconductors (OSCs), compared to the more traditional silicon, are enticing materials for the fabrication of optoelectronic devices (e.g., transistors, photovoltaic cells, light-emitting diodes) due notably to the lower cost associated with their preparation and purification, as well as their increased solubility in solvents which can accommodate large-scale fabrication. However, a higher degree of molecular disorder typically results in lower performance than silicon and remains an issue to be adressed. As the structure of an OSC is crucial to its performance, understanding the nature of this structure-property relationship is key to further the field of OSCs. In this regard, this thesis explores the optoelectronic properties of different π-conjugated organic frameworks which incorporate sulphur and nitrogen atoms along the rigid conjugated backbone for their desirable impacts on charge mobilities and stability.
After a brief review of both small-molecule OSCs as well as key experimental techniques employed in the course of this work, chapter three covers the synthesis and characterization of dithiatetrazocines (DTTA), electron-deficient sulphur-nitrogen heterocycles, which were functionalized with various (oligo)thienyls pendants. The impact of both the substitution patterns and the degree of conjugation on the optoelectronic and solid-state properties of the ring system was investigated.
The fourth chapter expands on previous work from the Brusso group that focused on extending the 2D conjugation of tetrathienoanthracene. While oligothienyls were previously shown to effectively increase the degree of conjugation, little to no change in device performance were observed, which was ascribed to disorder of the rotatable pendants. Here, rigid thieno[3,2-b]thiophene was used instead to increase both the degree of conjugation while maintaining structural rigidity, as assessed by optical, electrochemical and theoretical studies.
The fifth chapter introduces preliminary work toward expanding the electron-deficient hexaazatrinaphtylene core with thiophene rings. The resulting concentric donor-acceptor structure promotes luminescent behavior with pronounced emission solvatochromism. Optical measurements were performed before and after intramolecular cyclization of the thiophene rings, to study the impact of aromatization on the optoelectronic properties of the system.
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BARRETO, ARTHUR RODRIGUES JARDIM. "DEVELOPMENT AND CHARACTERIZATION OF ORGANIC LIGHT-EMITTING TRANSISTORS (OLETS) BASED ON CONJUGATED SMALL MOLECULES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35241@1.
Повний текст джерелаАнотація:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
PROGRAMA DE EXCELENCIA ACADEMICA
Este trabalho teve como objetivo fabricar e caracterizar Transistores Orgânicos Emissores de Luz (OLETs, Organic light-Emitting Transistors). Os OLETs combinam em um único dispositivo a funcionalidade elétrica de um transistor de efeito de campo orgânico e a capacidade de geração de luz, representando uma nova classe de dispositivos orgânicos com alto potencial de inovação em aplicações, como sistemas ópticos de comunicação, tecnologia de displays avançada, lasers orgânicos, fontes de luz em nanoescala e optoeletrônica orgânica integrada. Portanto, esta tese possui um caráter pioneiro, tanto para grupo de pesquisa quanto para o país, uma vez que ocorre a junção dos conhecimentos e domínio adquiridos sobre OFETs e OLEDs. Efetivamente, este trabalho de doutorado consistiu na fabricação e caracterização sistemática de diversos dispositivos OLET utilizando variadas arquiteturas e diversos materiais, comerciais e não comerciais, como o NT4N, o P13 e uma bicamada de C8-BTBT com TcTa:Ir(ppy)3. Os dispositivos foram caracterizados através de medidas elétricas e óticas, obtendo-se as curvas características. Também foram determinados seus parâmetros e propriedades de funcionamento, com destaque para as mobilidades de carga e para as eficiências obtidas. Houve também o entendimento e a implementação de um tratamento térmico na camada dielétrica, sendo parte fundamental da fabricação dos dispositivos. Os dispositivos fabricados apresentaram diferentes graus de desempenho, com destaque para a arquitetura bicamada, por apresentar a maior potência luminosa (4 microwatt) e a maior eficiência (0,5 por cento), sendo suficientes para inserir os dispositivos fabricados na categoria de dispositivos orgânicos altamente eficientes. Tal fato demonstra que o domínio da fabricação e da caracterização desta nova classe de dispositivos foi alcançado.
The aim of this work was to achieve the knowledge of the fabrication and the characterization of Organic Light Emitting Transistors, OLETs, considered as one of the innovative technologies nowadays. The OLETs combine in a single device the electrical functionality of an organic field-effect transistor (OFET) and the light-generating capability. They represent a promising new class of organic devices with high potential for innovation in applications such as communication systems, advanced display technology, organic lasers, nanoscale light sources and integrated organic optoelectronics. In some way, this thesis has a pioneer character, both for our research group and for the country, since it combines different knowledge and skills about OFETs and OLEDs to achieve a new device. Actually, this work involved the systematic manufacture and characterization of several OLETs using different architectures employing commercial and noncommercial materials, such NT4N, P13 and a bilayer of C8-BTBT with TcTa:Ir(ppy)3. The devices were then characterized by electrical and optical measurements. The working parameters and properties were determined as well, highlighting the charge carrier mobilities and efficiencies obtained. The understanding and the implementation of a specific heat treatment in the dielectric layer was a fundamental part of this work for the manufacture of the devices which have different degrees of performance. With emphasis on the bilayer architecture, that presented the highest luminous power (4 microwatt) and efficiency (0,5 percent), inserting the devices manufactured in the category of highly efficient organic devices. Such fact shows that the fabrication and characterization of this new class of devices has been achieved.
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Shibano, Yuki. "Energy and Electron Transfer in Novel Conjugated Molecules and Their Application to Photoelectrochemical Devices." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/49146.
Повний текст джерелаАнотація:
学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2867号 ; 請求記号: 新制/工/1421 ; 整理番号: 25552Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13396号
工博第2867号
新制||工||1421(附属図書館)
25552
UT51-2007-Q797
京都大学大学院工学研究科分子工学専攻
(主査)教授 今堀 博, 教授 川﨑 昌博, 教授 榊 茂好
学位規則第4条第1項該当
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Bhatta, Ram S. "Dynamics of Coupled Large Amplitude Motions from Small Non-Rigid Molecules to Conjugated Polymers." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353339449.
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Pietilä, Lars-Olof. "Molecular mechanics and force field studies of weakly coupled conjugated molecules and molecular crystals." Hki : Finnish Society of Sciences and Letters : Academic Bookstore [distr.], 1988. http://catalog.hathitrust.org/api/volumes/oclc/57854229.html.
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Jiang, Yue. "Structure-properties relationships in small pi-conjugated molecules : electrochromism, photovoltaic conversion and mechano-fluorochromism." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0026/document.
Повний текст джерелаАнотація:
Ce travail porte sur la synthèse et l’évaluation de systèmes pi-conjugués en tant matériaux actifs pour des dispositifs opto(électroniques). Un premier chapitre décrit une série d’oligothiophènes cruciformes et leur évaluation dans des dispositifs électrochromes. Le second chapitre décrit la synthèse d’accepteurs moléculaires à base de benzodithiophène et l’analyse de leur potentialités comme matériaux accepteurs dans des cellules solaires organiques. La plus large part du travail porte sur l’analyse des relations structure-propriétés d’une série de petites molécules push-pull comportant un groupe donneur triphénylamine (TPA) relié à un groupe accepteur par un espaceur thiényl. Une première étape a consisté à remplacer l’un des cycles phényles de la TPA par des groupes aromatiques tels que p-fluorophényle, anthryle et naphtyle. Ces modifications ont peu d’influence sur les propriétés électroniques de la molécule mais induisent de large variations des propriétés de transport de charge et de conversion photovoltaïque des matériaux correspondants. Au cours d’une seconde étape l’un des groupes phényles de la TPA a été remplacé par des chaînes alkyle, perfluoroalkyle et oligo(oxyethylene). Les résultats de diffraction X, spectroscopie d’absorption et de fluorescence, génération de second harmonique et électrochimie démontrent que certaines de ces molécules présentent des propriétés d’émission contrôlées par agrégation tandis que les matériaux correspondants se réorganisent spontanément à l’état solide sous forme d’agrégats H ou J dotés de propriétés de transport de charges et de conversion photovoltaïque fortement améliorées et de propriétés d’absorption, d’émission et de génération de second harmonique mécaniquement modulablesThis work deals with the design, synthesis and evaluation of molecular pi-conjugated systems as active materials for (opto)electronics devices. A short first chapter describes three X-shaped oligothiophenes, thecharacterization of their structure and properties and a first evaluation of their performances in electrochromic devices. The second chapter describes the synthesis of molecular acceptors based on a benzodithiophene and the analysis of their potentialities when combined with molecular donors in organic solar cells.The major part of the work is focused on the analysis of structure-properties relationships of a series of smallpush-pull molecules involving di- or tri-arylamine donorblocks linked to an acceptor group by a thienyl bridge. In a first step, a phenyl ring of triphenylamine (TPA) is replaced by p-fluorophenyl, anthryl and naphtyl groups.Optical and electrochemical results show that substitution has little effect at the molecular level but can markedly affect solid-state properties with in particular an improvement of charge-transport and short-circuit current density of solar cells based on these donor materials.In a second step, a phenyl ring of TPA is replaced by alkyl, perfluoroalkyl and oligo(oxyethylene) chains. Results of X-ray diffraction, absorption and photoluminescence spectroscopies, second harmonic generation, and electrochemistry demonstrate that some of these molecules under go aggregation controlled photoluminescence emission wave length while the corresponding materials spontaneous lyre organize in the solid-state to form either H or Jaggregates with enhanced charge mobility, photovoltaic conversion efficiency and mechanically-induced chromism, fluorochromism and NLO-chromism
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Liang, Pingping. "Gold Nanoparticle-Based Colorimetric Sensors for Detection of DNA and Small Molecules." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2595.
Повний текст джерелаАнотація:
Biosensors have proven to be a powerful tool for detecting diverse targets, such as proteins, DNA, and small molecules representing disease biomarkers, toxins, drugs and their metabolites, environmental pollutants, agrichemicals, and antibiotics with high sensitivity and specificity.
The major objective of the research described in this dissertation was to develop low cost, low sample volume, highly sensitive and specific AuNP-based colorimetric sensor platforms for the detection of DNA and small molecules. With this in mind, we propose an instrument-free approach in chapter three for the detection of NADH with a sensor constructed on a paper substrate, based on the target-induced inhibition of AuNP dissolution. The successful detection of this important molecule opens the door to numerous possibilities for dehydrogenase characterization, because NAD+/NADH are essential cofactors for more than 300 dehydrogenase enzymes. To further increase the sensitivity of our hybridization-based assay for DNA detection, we developed an enzyme-assisted target recycling (EATR) strategy in chapter four and have applied such an EATR-based colorimetric assay to detect single-nucleotide mismatches in a target DNA with DNA-functionalized AuNPs. This assay is based on the principle that nuclease enzymes recognize probe–target complexes, cleaving only the probe strand. This results in target release, enabling subsequent binding to and cleavage of another probe molecule. When the probe is conjugated onto AuNPs, complete cleavage from the AuNP surface produces a detectable signal in high ionic strength environments as the nanoparticles undergo aggregation. With such enzyme-assisted amplification, target detection can occur with a very low nM detection limit within 15 minutes. The extent of DNA loading on the AuNP surface plays an important role in the efficiency of DNA hybridization and aptamer-target assembly. Many studies have shown that high surface-coverage is associated with steric hindrance, electrostatic repulsive interactions and elevated surface salt concentration, whereas low surface-coverage can result in nonspecific binding of oligonucleotides to the particle surface. In chapter five, we investigated DNA surface coverage effects, and apply this optimization in conjunction with a highly-specific aptamer to develop a sensitive colorimetric sensor for rapid cocaine detection based on the inhibition of nuclease enzyme activity.
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Mukherjee, Jhindan. "Electrocatalytic Enzyme Sensors for Selective and Sensitive Detection of Biologically Important Molecules." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1225164344.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Toledo, 2008.Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy degree in Chemistry." Includes bibliographical references (leaves 32-37, 74-75, 112-114, 155-157, 187-188, 193).
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Mirra, Silvia. "Fluorescence-based sensors for the detection of biologically and environmentally relevant molecules." Doctoral thesis, Universita degli studi di Salerno, 2016. http://hdl.handle.net/10556/2204.
Повний текст джерелаАнотація:
2014 - 2015Hydrogen sulfide (H2S) has been known for long time as a toxic molecule in biological systems. More recent studies have shown that mammals can produce H2S in a controlled fashion, suggesting that it’s important in maintaining normal physiology. In particular, recent efforts are mostly devoted to implement sensitive and selective detection techniques to monitor the distribution and function of this molecule in complicated biological systems. Depending on the mechanism by which the recognition event occurs there are three main approaches in the literature. 1) Azide-to-amine reduction, 2) Nucleophilic addition and 3) Copper displacement. The idea behind this doctoral thesis project is based on a different approach: a coordinative mechanism. In this way one may, in principle, be able to remove H2S from the metal center of the sensor and ensure a reversible H2S binding process. This would be advantageous for practical sensing applications allowing reusability of the sensing device... [edited by author]
XIV n.s.
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Starovoytov, A. A., E. N. Kaliteevskaya, V. P. Krutyakova, and T. K. Razumova. "Influence of Substituent in Conjugated Chain of Molecules on Nanocomponents Composition of Polymethine Dye Films." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34890.
Повний текст джерелаАнотація:
Molecular layers of polymethine dye long conjugation chain on glass contain several types of molecular
nanocomponents. The number and type of the components depend on the thickness of a layer. In thin layers,
only monomolecular components (all-trans-stereoisomers and cis-isomers) are present. We studied a
series of four dicarbocyanines and determined the steric structure of the nanocomponents of the layers.
The layers of less than 1 monolayer thick contain up to 4 monomeric components. For monocis- and dicisisomers
of the dyes studied, which are obtained from the all-trans form upon rotation of fragments of a
molecule around different bonds in the conjugated chain, the steric models were constructed. It was shown
that in the series of polymethine molecules differing in the substituents and their positions in the chain
there is a correlation between the intensity of the absorption bands of the certain components and the steric
hindrance of molecular isomers. The above correlation may be used for the determination of the steric
structure of monomeric components of the layer.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34890
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Ren, He. "Crystal Engineering of Giant Molecules Based on Perylene Diimide Conjugated Polyhedral Oligomeric Silsesquioxane Nano-Atom." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461014185.
Повний текст джерела
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Niederhausen, Jens. "Electronic and structural properties of conjugated molecules at molecular hetero-interfaces and on metal surfaces." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17218.
Повний текст джерелаАнотація:
Diese Arbeit behandelt elektronische und strukturelle Eigenschaften dünner Schichten aus konjugierten organischen Molekülen (COMs), aufgebracht auf Metalloberflächen per Vakuum-Sublimation. Diese Eigenschaften sind essenziell für Funktionsrealisierung und -optimierung organischer Elektronikbauteile. Teil 1 diskutiert zwei Ansätze zur Energieniveauanpassung (ELA) an Organik-Metall-Grenzflächen zur Einstellung der dortigen Löcherinjektionsbarrieren (HIBs) durch (Über-)Kompensation des abträglichen "Push-back"-Effekts: - Ausnutzung der besonderen ELA bei Chalkogen-Metall-Bindungen, hier gezeigt mit Hilfe von Röntgen- und Ultraviolettphotoelektronenspektroskopie (UPS/XPS) für ein Seleno-funktionalisiertes COM - Einfügen von COMs mit ausgeprägtem Elektronen-Akzeptorcharakter vor dem Aufbringen der aktiven Schicht. UPS-Messungen zeigen, dass beide Ansätze HIBs von ca. 0.3 eV ermöglichen. Teil 2 untersucht ausgewählte organische Heterostrukturen auf Metallen. Die Untersuchungen identifizieren einen Ladungstransfer vom Metall zur Überschicht (MOCT) als verantwortlich dafür, das System bei Ferminiveau-Pinning in den Gleichgewichtszustand zu überführen. Detaillierte Untersuchungen gestatten die Identifikaton von ganzzahligem Ladungstransfer zu einem Teil der Moleküle in der ersten Überschichtlage und den Einfluss der Dipol-Abstoßung in der Überschicht. In Teil 3 dienen Metalloberflächen als Auflage für supramolekulare Architekturen mit dipolaren Bausteinen. Rastertunnelmikroskopie (STM) an einer Serie von teils partiell fluorierten, stäbchenförmigen COMs mit unterschiedlich großen Dipolmomenten ermöglicht die Entflechtung von Dipol-Dipol- und konkurierenden Wechselwirkungen physisorbierter Submonolagen auf Ag(111). Ein anderes, stark dipolares COM bildet bei Monolagenbedeckung auf Au(111) sechs Phasen, alle mit antiferroelektrischer Einheitszellen. UPS-Messungen ergeben eine bevorzugte Ausrichtung der Moleküle in Multilagen.In this thesis, the electronic and structural properties of thin films of conjugated organic molecules (COMs) vacuum-deposited on metal surfaces are studied. These properties are essential for realization and optimization of device functionalities in the field of organic electronics. Part 1 discusses two approaches for engineering the energy-level alignment (ELA), and, thereby, optimizing hole injection barriers (HIBs), at organic/metal interfaces via (over)compensation of the detrimental "push-back": - Exploiting the peculiar ELA at chalcogen-metal bonds, shown here (with X-ray and ultraviolet photoelectron spectroscopy, UPS/XPS) for a seleno-functionalized COM - inserting electron-accepting COMs prior to deposition of active layers. UPS shows that both approaches realize HIBs into the active COM as low as 0.3 eV. Part 2 studies selected organic/organic heterostructures on metal surfaces. These studies allow to propose that metal to overlayer charge transfer (MOCT), is responsible for achieving electronic equilibrium when such systems are Fermi-level pinned. Detailed investigations allowed identifying integer charge transfer to a fraction of the molecules in the first overlayer and the influence of the dipole-repulsion on the overlayer. In Part 3, metal surfaces are used as support for supramolecular architecture with polar building blocks. Scanning tunneling microscopy (STM) of a series of rod-like COMs with and without partial fluorination and with different dipole moments help disentangling the delicate balance dipole-dipole and competing interactions for sub-monolayer films physisorbed on Ag(111). For another, highly-polar COM at ca. monolayer coverage on Au(111), STM identifies six phases. All phases are found to exhibit anti-ferroelectric unit cells. UPS evidences a preferential alignment of multilayer molecules.
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Ben, Aziza Zeineb. "Graphene based gas sensors : Fabrication, characterization, and study of gas molecules detection mechanism." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0102.
Повний текст джерелаАнотація:
Ce travail nous a permis de réaliser une étude de capteurs de gaz et d’humidité à base de graphène. Cette étude pourrait être utile non seulement pour améliorer les performances des capteurs à base de graphène mais aussi pour mieux comprendre l’interaction entre le graphène et les molécules de gaz. Ceci semble indispensable pour faire avancer les applications du graphène comme un matériau prometteur pour la détection des gaz. Des avancées significatives ont été présentées au niveau de la fabrication de ces capteurs, leurs différentes caractérisations électriques ainsi que d’autres techniques employées pour analyser le mécanisme contrôlant la détection des molécules de gaz/vapeur. Ces outils ont été mis en place pour concevoir et fabriquer plusieurs structures de capteur en utilisant différents substrats support du graphène d’une part et en modifiant les propriétés du graphène par utilisation des produits chimiques d’autres part. La caractérisation de ces capteurs sous différents environnements a permis de comparer les différentes réponses des capteurs et d’en tirer plusieurs conclusions sur le fonctionnement de ces dispositifs. En effet, le Mica, un substrat lisse et transparent, a été utilisé comme substrat pour le graphène. Le dopage induit par le mica a été étudié ainsi que son impact sur la sensibilité du graphène au gaz d’ammoniac. Ceci a permis de mettre en évidence le fait que le substrat joue un rôle important pour la détection de l’ammoniac. De plus, ces capteurs fabriques sur mica et SiO2 ont été testés sous différentes conditions de températures et d’oxygène. Dans une autre approche, un polymère a été utilisé pour doper le graphène. Une étude détaillée a été menée pour analyser le comportement de ce graphène fonctionnalisé par rapport aux molécules d’eau. Ces nouveaux résultats expérimentaux obtenus pendant cette thèse constituent un bon support à plusieurs résultats théoriques établis et permettent d’optimiser la conception des capteurs de gaz à base de graphène pour des meilleures performancesIn this research, we report on a study of graphene based gas and humidity sensors. This study could be useful not only to improve the performance of graphene based sensors but also to better understand the interaction between graphene and gas molecules. This seems necessary to promote the applications of graphene as a promising material for gas sensing. Significant advances have been made to design and fabricate these sensors: the different electrical characterizations as well as other techniques used to analyze the mechanism controlling the detection of gas/vapor molecules. These tools have been set up to design and manufacture various sensor structures using different underlying substrates for graphene on one hand and chemical modification of graphene properties on the other hand. The characterization of these sensors under different environments was used to compare the different responses of the sensors and draw several conclusions about gas sensing mechanism. Indeed, Mica, a smooth and transparent substrate, was used as a supporting substrate for graphene. Doping induced to graphene by mica and its impact on graphene sensitivity to ammonia gas were studied. This has made it possible to highlight the fact that the substrate plays an important role for the detection of ammonia. In addition, these sensors made on mica and SiO2 were tested under a variety of temperatures and oxygen. In another approach, a polymer was used to dope graphene. A detailed study was realized about the behavior of water molecules on functionalized graphene. The obtained experimental results, reported for the first time, represent a good support for several theoretical studies already made and could be used to optimize the design of graphene based gas sensors
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Ramos-Ortiz, Gabriel. "Frequency conversion in conjugated organic molecules and its applications to ultra-fast pulse diagnostic and imaging." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289952.
Повний текст джерелаАнотація:
This dissertation is devoted to the study of third-harmonic generation (THG) in push-pull chromophore-doped polymer films. This kind of films, with amorphous structure, exhibit null second harmonic generation but strong THG when pumped at the fundamental wavelengths within the telecommunication range (1.4-1.6 μm). It is demonstrated that at 1550 nm, micrometer-thick samples generate up to 17 muW of green light with an input power of 250 mW delivered by an optical parametric oscillator. This high conversion efficiency is achieved without the use of phase matching or cascading of quadratic nonlinear effects and it is due to high values of the third-order nonlinear susceptibility combined with weak film absorption at the third harmonic wavelength. The efficient THG process opens the doors to low cost and sensitive third-order optical autocorrelation and cross-correlation applications. So, in addition to the basic research performed about the characterization of the THG in push-pull chromophore-doped polymer films, two applications are demonstrated. The first is the complete diagnostic of femtosecond pulses by THG-Interferometric Autocorrelation and by THG Frequency-Resolved Optical Gating. The second is the THG-Cross-correlation Time-Gated Imaging of objects embedded in highly scattering conditions.
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Sandoval-Salinas, María Eugenia. "Conjugated organic radicals and polyradicals: electronic structure and photophysics." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/670990.
Повний текст джерелаАнотація:
The principal aim of this thesis is the understanding of the electronic structure of organic diradical and polyradical molecules. Unveiling the properties that give them the electronic, magnetic, and optical properties to be applied as main components in optoelectronic devices. Specifically, the objectives that have been achieved are i) the characterization of organic compounds with diradical and polyradical character, and their electronic, magnetic, and spectroscopic properties; ii) the detailed description of the singlet fission mechanism, as well as the proposal of a new system that, theoretically, is able of carrying out efficiently the singlet fission process; and iii) the use of quantum mechanical methods (specifically RAS-SF) and computational tools to get a proper description of the electronic structure of the ground state of systems in which non-dynamic correlation plays an important role.
In the first place, organic compounds whose optical and magnetic properties make them interesting in the field of optoelectronic materials were studied. The relationship between molecular structure and the radical character was found by the study of linear and cyclic acenes and small triangular fragments derivatives of graphene. While the diradical and tetraradical character increase together with the size of the linear and cyclic compounds, the triangular structures (TGNF, the acronym for Triangulene Graphene Nano Fragments) are open-shell systems with high-spin ground state multiplicity. Furthermore, a manner to tune the spin multiplicity in the ground state of TGNFs is proposed through heteroatom doping or hydrogenation, which offers a way to design larger graphene nanofragments with well-defined spin-multiplicity. Towards larger systems, the increment of the size is associated with the increase of the polyradical character. This thesis presents the rationalization of the electronic structure of organic macrocycles with high polyradical character. Concretely, from triradicals to decaradicaloids (up to 10 radical centers). The properties triggered by the open-shell character of the ground state are as diverse as surprising. For instance, AWA systems (annulenes-within-annulenes) have been characterized in collaboration with experimental groups for the first time. The global aromaticity exhibit by these macrocycles responds to the radical interaction in each of the annulenes and is governed by both aromaticity rules, Hückel's, and Baird's simultaneously.
On the other hand, the singlet fission process (SF) was expanded from the classical model, which involves five electronic states, to a model that includes double excitations (D states), a seven-state model. Using a simple model, it is estimated that the D states can play an active role in SF, as well as the necessary conditions to maximize their participation as an initial or intermediate state in the process. The feasibility of spiro systems carrying out SF is exposed.El principal objetivo de esta tesis es poner al descubierto las propiedades químicas que permiten que procesos fotofísicos complejos tomen lugar en moléculas orgánicas, y que les permite tener aplicaciones en materiales optoelectrónicos. Puntualmente, los objetivos que se han cumplido son i) la caracterización de di y poliradicales orgánicos y sus propiedades electrónicas, magnéticas y espectroscópicas; ii) la descripción detallada del mecanismo de fisión de singuletes, así como proponer un sistema que teóricamente es capaz de realizarlo eficientemente; y iii) la utilización de métodos de la mecánica cuántica (específicamente RAS-SF) y herramientas computacionales que permiten la descripción apropiada de la estructura electrónica del estado fundamental de sistemas en los que la correlación no-dinámica representa un papel importante. En primer lugar, se estudiaron compuestos orgánicos cuyas propiedades ópticas y magnéticas los hacen interesantes en el campo de materiales optoelectrónicos. Se encontró la dependencia del carácter radical en la topología de nanoestructuras de grafeno (acenos) lineales y cíclicos, y pequeñas laminas de estructura triangular. Mientras el carácter diradical y tetraradical crece con el tamaño de los compuestos lineales y cíclicos, las estructuras triangulares (TGNF, siglas en inglés de Triangulene Graphene Nano Fragments) son compuestos de capa abierta. Además, se propone una forma de modular la multiplicidad de espín en el estado basal de los TGNF mediante el dopaje con heteroátomos. El incremento del tamaño del sistema permite obtener molecular con alto carácter poliradical. En esta tesis se presenta la racionalización de la estructura electrónica de macrociclos orgánicos con carácter triradical hasta decaradicaloide (10 centros radicalarios). Las propiedades que se derivan de estas características son tan variadas como sorprendentes, por ejemplo, se han caracterizado sistemas AWA (anulenos-dentro de-anulenos) cuya aromaticidad global responde a la suma de la aromaticidad en cada uno de los anulenos y esta regida por las reglas de aromaticidad de Hückel y Baird simultaneamente. El proceso de fisión de singuletes (SF) fue expandido del modelo clásico, que involucra cinco estados electrónicos, a un modelo que incluye excitaciones dobles (estados D), modelo de siete estados. Usando un modelo sencillo se estima que los estados D pueden jugar un papel activo en SF, así como las condiciones necesarias para maximizar su participación como estado inicial o intermediario en el proceso. Se expone la factibilidad de que los sistemas spiro lleven a cabo SF.
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Sumranjit, Jitapa. "Conjugated organic molecules as models for potential sensors." 2007. https://scholarworks.umass.edu/dissertations/AAI3254940.
Повний текст джерелаАнотація:
This dissertation focuses on water-soluble phenylenevinylene (PV) and sensor-capable PV systems. All oligo PVs and poly(phenylenevinylenes) (PPVs) described below were synthesized using standard Heck coupling methodology. New water-soluble PV systems have been made by two different strategies. As ionic side chain substituted water-soluble PVs, two oligo-PV systems with pyridinium groups were made and shown to be more water-soluble than analogous systems with triethylammonium groups, even though two out of three systems of the triethylammonium-based systems were polymeric and so had numerous ionic side chains. The triethylammonium-bearing systems showed blue fluorescence in solution but emission of the pyridinium-based systems was not visible due to photoinduced electron transfer quenching. Another type of water-soluble, segmented copolymer based on PPV was made that incorporated a nonionic but hydrophilic poly(ethylene glycol) (PEG). This PEGylated PPV was readily soluble in water, and exhibited strong blue fluorescence. Cleavable amide bonds were tested as a basis for producing model systems for making sensors. A functionalizable diamino side-chain 2.5-oligo PV was used as a basic core synthetic unit. This system is described as “sticky molecule” since the amino groups can be easily functionalized. Two types of electron transfer quenchers, phthalimide and pyridinium, were attached to the sticky molecule by amide linkages. The luminescence of both systems was drastically quenched, but was shown to increase greatly when the amide bonds were cleaved by bases. These systems can be considered as "turn-on" sensor systems. Two pyrene units were also linked to the sticky molecule. This multichromophoric system displayed energy transfer from the pyrene to the PV core, such that the emission spectrum only shows the PV core peak, even when excited at wavelengths where the pyrene is the absorber. The energy transfer efficiency was calculated to be ∼60%. After the amide bonds were cleaved by acids, the pyrene emission was observed upon excitation at pyrene absorption wavelengths, which showed disruption of the energy transfer by allowing the pyrene the "escape" the core PV group. This can be considered either a "turn-off" process for the core PV, or a "turn-on" process for the pendant pyrene group.