To see the other types of publications on this topic, follow the link: Self-assembly of Organic Nanostructures.
Dissertations / Theses on the topic 'Self-assembly of Organic Nanostructures'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Self-assembly of Organic Nanostructures.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Chang, Ming-Hua. "Organic semiconductor nanostructures based on supramolecular self-assembly." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489419.
Full textAbstract:
This thesis is concerned with two important photophysical questions in the area of organic semiconductors. One is the influence of intermolecular interactions on the excitation transfer and excitonic relaxation dynamics. The other is how dynamic changes of the excited-state excitonic wavefunction may be caused by intramolecular geometric relaxations.
2
Sun, Yuan. "Self-assembly of Organic Nanostructures for Biomedical Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480526082654358.
Full text
3
Balakrishnan, Kaushik. "Self-assembly of organic semiconducting molecules into one-dimensional nanostructures /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1594481341&sid=10&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Full text
4
Alam, Md Shah. "Development of Multicomponent Nanostructures by Self-assembly of Graphene Oxide and Organic Nanotubes." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu159500274123902.
Full text
5
Nardi, Elena. "Growth of organic nanostructures through on-surface reactions : from phthalocyanines self-assembly to polymeric phthalocyanines." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4351/document.
Full textAbstract:
Le couplage covalent de précurseurs moléculaires spécialement conçus, assisté par une surface métallique, a récemment émergé comme nouvelle voie pour la création de nouvelles architectures moléculaires prometteuses pour l’électronique moléculaire. Les phtalocyanines et leurs dérivés ont attiré beaucoup d’intérêt à cause de leurs propriétés chimiques et optoélectroniques. Dans cette thèse la synthèse de composés de phtalocyanine est présentée. Les composés sont obtenus par une réaction en surface entre précurseurs fonctionnalisés avec quatre groupements carbonitriles et des atomes métalliques. L’étude expérimentale est faite par microscopie à effet tunnel et spectroscopie de photoémission X. Les précurseurs moléculaires de TCN-DBTTF et de PPCN ont été étudiés. Les TCN-DBTTF ont été déposés avec les atomes de Mn, Fe ou Cu sur Ag(111) et Au(111). La réaction de cyclotetramerization a été activée par recuits. Dans le cas le plus favorable (TCN-DBTTF avec Fe sur Ag(111)), la réaction peut être activée à 200°C et permet la synthèse de phtalocyanines individuelles. Un recuit à plus haute température permet de continuer la réaction en 1D (250°C) et en 2D (275°C). Des résultats similaires ont été obtenus pour le dépôt de PPCN avec Mn ou Cu sur Au(111). L’évolution des spectres des niveaux de coeur permet d’obtenir une preuve de la réaction. Les différents facteurs qui influencent la cyclotetramerisation ont été étudiés.L'étude démontre la versatilité de la méthode: la synthèse en surface permet la création de polymères 2D originaux connectés par des macrocycles de phtalocyanine susceptibles d’être étendus à un grand nombre de précurseurs et d’atomes métalliques<br>Surface-assisted covalent coupling of suitably designed molecular precursors on metal surfaces has recently emerged as a new route towards the design of novel molecular architectures promising for future applications. Phthalocyanines and their derivatives have been widely studied for their chemical and optoelectronic properties. In this thesis the synthesis of phthalocyanine compounds is presented. The compounds are obtained through an on-surface reaction between tetracarbonitrile-functionalized precursors and metals. The experimental investigation is carried out by means of scanning tunnelling microscopy and X-Ray photoemission spectroscopy. Two molecular precursors, TCN-DBTTF and PPCN, are studied. TCN-DBTTF molecules are deposited with metal atoms (Mn, Fe, or Cu) on Ag(111) and Au(111). Annealing is used to activate the reaction of cyclotetramerization between precursors and metals. In the most favourable case (TCN-DBTTF with Fe on Ag(111)) the reaction can be activated at 200°C and leads to the synthesis of individual phthalocyanines. Increasing the temperature allows the synthesis of polymeric lines, at 250°C, and small 2D domains, at 275°C. Similar results are obtained for PPCN deposition with Mn or Cu on Au(111). In this latter case, the evolution of core level spectra allows a chemical proof of the on-surface reaction. The factors affecting on-surface cyclotetramerization have also been studied. This study demonstrates the versatility of the method: on-surface cyclotetramerization allows creating original 2D polymers connected by phthalocyanine macrocycles, and may work with a wide range of tetracarbonitrile-functionalized precursors and metallic atoms
6
Kazantsev, Roman V. "Self-Assembled, Crystalline Organic Nanostructures for Photocatalysis." Thesis, Northwestern University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=3741384.
Full textAbstract:
<p> The goal of this thesis was to integrate light-absorbing supramolecular materials into a photocatalytic system for solar-to-fuel conversion. Toward this end, a series of perylene-based chromophore amphiphiles was synthesized and their self-assembly properties explored. Characterization of these materials by electron microscopy and x-ray scattering techniques revealed molecular assembly into 1D ribbon nanostructures. Surprisingly, these ribbons were observed to spontaneously crystallize in solution, as observed by wide-angle and grazing incidence X-ray scattering. These crystalline nanostructures could be gelled with oppositely charged electrolytes, forming a 3D light-absorbing scaffold. By designing and synthesizing oppositely charged proton reduction catalysts to electrostatically bind to the light-absorbing scaffold, hydrogen gas was detected by gas chromatography after white light illumination of the scaffold / catalyst system. As a direct result of their crystalline nature, the exciton properties of these materials and the photocatalytic properties of the system could be tuned by slight modification in their molecular packing arrangement. These changes were achieved by creating a library of chromophores with small functional groups directly attached to the PMI core. Some amphiphiles in this library were observed to undergo a crystalline phase transition between two unique packing arrangements as evidenced by variable temperature absorbance and x-ray scattering experiments. This transition involved a substantial change in the exciton properties of the material. Surprisingly, some crystalline phases carried the distinct spectral signature of charge-transfer (CT) excitons, an excitation that is shared among multiple chromophores. Characterization of this CT state was accomplished by ground state and transient absorption spectroscopy, transient electron paramagnetic resonance spectroscopy, and second-order harmonic generation microscopy. The crystalline nanostructures of the library that yielded evidence for CT-excitons were the most photocatalytically active. This observation is consistent with established theories developed elsewhere that connect CT-exciton formation with an enhancement in exciton mobility.</p>
7
Jha, Kshitij Chandra. "Polarization and Self-Assembly at Metal-Organic Interfaces: Models and Molecular-Level Processes." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333644685.
Full text
8
Zhang, Hongyang. "Synthesis, characterization and properties of self-assembled metal complex nanosheets heterostructured organic microrods." HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/607.
Full textAbstract:
Molecular self-assembly or ligand-metal assembly is a process in which several individual molecules and metal ions organize themselves into an ordered arrangement without external stimuli, the defined structures can lead to distinctive electronic and photonic performances. In the meantime, as the scale of materials decreases, various unique properties arise from their minute scaled dimensions, such as surface effect, volume effect, quantum effect and dielectric confinement effect, etc. Therefore, the design and fabrication of the micro- and nanomaterial via the technique of molecular self-assembly or ligand-metal assembly is becoming an emerging research field, for the purpose of meeting the increased demands of multi-functional materials. Chapter 1 gives an overview of the advanced materials prepared by either molecular self-assembly or ligand-metal assembly. We described the interaction nature in detail, and enumerated the applications as well as developments of this scientific field. Furthermore, the detailed classifications as well as previous work of these advanced materials we researched on, such as two dimensional nanosheets, hetero-structured materials and cyclometalated iridium(Ⅲ) complexes were also amply summarized. Two-dimensional nanosheets have always been a research hotspot since graphene was discovered and isolated. In contrast, molecule-based organometallic nanosheets through bottom-up method exhibit more inner structures. In Chapter 2, we constructed two classes of organometallic nanosheets with different intermolecular forces, one is metal-ligand coordination, while the other one is the aromatic (π-π) interaction. Two-dimensional nanosheets with Hg-acetylide linkages, bis(dipyrrinato)metal linkages as well as bis(terpyridine)metal linkages were synthesized and characterized by UV-Vis absorption spectroscopy, FT-IR spectroscopy, optical and electron microscopy, photoluminescence spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy and so on. In addition, the potential applications were explored as well, including the tests of charge mobility and current capacitance. Meanwhile we also investigated the two-dimensional nanosheets self-assembled by aromatic (π-π) interaction. The morphology characterizations, crystal form measurements, besides elemental analyses were conducted. By means of surface control, the hybrid nanosheets could achieve many superior performances, like super hydrophobicity, high conductivity and soft magnetism. In Chapter 3, we firstly mentioned that organic hetero-structured micro- or nanomaterials are widely attractive on account of its extensive applications in lasers, bipolar transistors, field effect transistors and solar cells. In our work, we focus on the diverse microrods assembled from π-conjugated small molecules, especially in the construction of heterogeneous organic heterojunction materials with specific components distribution. Two novel kinds of heterostructure, multilayer core-shell structured heterojunction and heterogeneous rod-tail helix were fabricated and developed both via a stepwise seeded-growth route, in which the different constituents possess different colors of luminescence. Through the media of fluorescence microscopy and confocal microscopy, the core-shell hetero- structures can be observed, testified and recorded quite distinctly. Furthermore, the prepared method by employing seeded-precursor could give us a revelation about constructing more sophisticated and functional organic luminescent heterogeneous materials. Chapter 4 focuses on the syntheses and characterization of eight cyclometalated iridium(Ⅲ) complexes, Ir(TPY)2(Dipyrrinato), Ir(PIQ)2(Dipyrrinato), Ir(Ligand 1)2(Dipyrrinato), Ir(Ligand 2)2(Dipyrrinato), Ir(Ligand 3)2(Dipyrrinato), Ir(PPY)2 (Dipyrrinato), Ir(m-PPY)2(Dipyrrinato) and Ir(PPY-m)2(Dipyrrinato). As is known, iridium(Ⅲ) complexes can exploit the energy of both 25% singlet and 75% triplet excited states. Due to their highly efficient applications in phosphorescent OLEDs, these materials are considered as one of the potential candidates for flexible display screen as well as clearing luminary. Among those full-color light-emitting iridium(Ⅲ) phosphors, near-infrared (NIR) phosphors are broadly utilized in phototherapy as well as biosensors. Herein, our eight synthetic cyclometalated iridium(Ⅲ) complexes all gave photoluminescence at 680 - 700 nm in solution, which could be attributed to the NIR region. We continuously tune the extensive conjugation on the C^N ligands in order to make longer wavelength emitting phosphors. The HOMO and LUMO of eight synthetic iridium(Ⅲ) phosphors were also calculated according to their cyclic voltamograms (CV). The design and preparation strategy in this thesis can inspire us to develop near-infrared as well as higher-performance organometallic phosphors.
9
Masuda, Koji. "Design and Fabrication of Nanostructures by Layer-by-Layer Assembly for Organic Photovoltaic Devices." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/123342.
Full text
10
Peyrot, David. "Engineering 2D organic nanoarchitectures on Au(111) by self-assembly and on-surface reactions." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX007/document.
Full textAbstract:
Ces dernières années ont été marquées par de grandes évolutions technologiques à travers notamment une course à la miniaturisation. De gros efforts de recherche se concentrent en particulier sur le domaine de l’électronique organique mais aussi sur de nouveaux matériaux bidimensionnels comme le graphène. Ces matériaux 2D présentent des propriétés physiques exceptionnelles et sont des candidats prometteurs pour le développement de futurs dispositifs électroniques. Au cours de cette thèse, l’approche ascendante, qui consiste à assembler ensemble des petites briques élémentaires, a été utilisée pour élaborer des nanostructures bidimensionnelles originales sur des surfaces. Des états électroniques localisés dus à un couplage électronique latéral particulier entre les molécules ont été observés. Quatre nanoarchitectures hybrides ioniques-organiques différentes ont été réalisées en faisant varier la température de la surface. Des nanostructures organiques covalentes ont aussi été élaborées par une réaction de couplage d’Ullmann sur la surface. Deux précurseurs différents en forme d’étoile avec des substituants iodés et bromés respectivement, ont été étudiés. De grandes nanostructures carbonées hexagonales poreuses ont notamment été synthétisées en faisant varier la température du substrat. Ces travaux ouvrent de nouvelles perspectives pour la réalisation de matériaux organiques bidimensionnels aux propriétés contrôlées<br>Over the last few years, important technological developments were made following a trend towards miniaturization. In particular, lots of research efforts are put into the research on organic electronics and on 2D materials like graphene. Such 2D materials show great physical properties and are promising candidates for the development of future electronic devices.In this project, bottom-up approach consisting in assembling elementary building blocks together, was used to engineer novel twodimensional nanostructures on metal surfaces. The properties of these two-dimensional nanostructures were investigated using Scanning Tunneling Microscopy (STM) and X-ray Photoemission Spectroscopy (XPS). Two-dimensional nanostructures based on the self-assembly of organic building blocks stabilized by intermolecular interactions were engineered. In particular, nanostructures stabilized by hydrogen bonds, halogen bonds and ionic-organic interactions were investigated. Localized electronic states due to specific molecular lateral electronic coupling were observed. Four different ionic-organic nanoarchitectures were engineered varying the substrate temperature. Covalent organic nanostructures were also engineered by onsurface Ullmann coupling reaction. Two different star-shaped precursors with iodine and bromine substituents respectively, were investigated. Large periodic porous 2D covalent hexagonal carbon nanostructures weresuccessfully engineered by temperature driven hierarchal Ullmann coupling. These results open new perspectives for the development of 2D organic materials with controlled structures and properties
11
Carter, Austin Roberts. "Magnetic field effects and self-assembled n-type nanostructures to increase charge collection in organic photovoltaics." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1324960593.
Full text
12
Uddin, MD Hanif. "Polymeric Hairy Nanoparticles with Helical Hairs: Synthesis and Self-Assembly." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/137.
Full textAbstract:
Nanoscale particles based on the nature of building blocks often self-assemble into superstructures with distinctive spatial arrangements which can be used as functional materials for different application. Micro-phase separated hairy nanoparticle with helical hair can self-assemble to form supramolecular material which may mimic the properties and functions of the natural polymers such as protein and cellulose. Beside this hairy/core-shell nanoparticles also may find many applications such as in asymmetric catalysis, nano-fillers in tire and rubbers, model systems for biology, lithography and as sensors. In this work, we have successfully synthesized two hairy nanoparticles both of which has cross-linked polystyrene core with helical poly (3- methyl 4- vinyl pyridine) and poly (2- methoxystyrene) brushes respectively by living anionic polymerization via one-pot synthesis. NMR spectroscopy was used to determine that polymerization was successful and compositions of HNPs have the agreement with the targeted HNPs structure. By tailoring the architecture (functionalization of polymer chains, the degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. Differential Scanning Calorimetry was used to demonstrate the thermal properties of the synthesized HNPs which corresponds to polymer composition. Dynamic light scattering, SEM and AFM images were recorded to measure the particle size and morphology of the particles. Circular dichroism spectroscopy was used to determine the induced chirality of helical polymer brushes by complexing it with the small chiral molecule. SEM and AFM imaging were recorded to find out the morphology and hierarchically self-assembly of the hairy nanoparticle system. The synthesized particles may have great potential to successfully generate self-assembled suprastructures which can further solve the chiral resolution problem and can also find different applications.
13
Summerfield, Alex. "Studies of self-assembled metal-organic nanostructures and the MBE growth of graphene." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33067/.
Full textAbstract:
This thesis discusses the formation of metal-organic and organic structures grown on surfaces using bottom-up self-assembly techniques. Three systems are investigated primarily using scanning probe microscopy techniques. The growth of metal-organic frameworks (MOFs) on functionalised surfaces is investigated using high resolution atomic force microscopy (AFM). The earliest stages of MOF crystal nucleation are imaged using a layer-by-layer (LBL) growth technique and the ability to track the growth of individual nanocrystallites throughout the LBL process is demonstrated. This LBL method has been suggested as a route to fabricating epitaxially grown, oriented thin-films of MOFs. However, results from these studies indicate that, rather than a uniform crystalline layer, the morphology is that of a preferentially oriented but laterally polycrystalline film and the growth rates of the individual nanocrystallites exceed those expected for a LBL growth mode. This has significant implications for the fabrication of novel devices that incorporate MOFs due to the presence of domain boundaries and defects. Self-assembled monolayers of light-harvesting porphyrin nanorings are investigated with scanning tunnelling microscopy (STM) and AFM. The nanorings are found to form large supramolecular networks in ambient conditions on graphite and boron nitride surfaces. The size and order of these networks is found to be dependent on the number of porphyrin macrocycles that make up each ring. In addition, simulations of isolated nanorings are also performed using Monte Carlo methods to model the distortion previously been observed for isolated nanorings on gold surfaces. These are discussed in the context of spectroscopic measurements which suggest that both size dependent and thermally induced distortion affects the lifetime and delocalisation of excited states in these molecules. Graphene is grown on hexagonal boron nitride surfaces using high-temperature molecular beam epitaxy. Large domains of monolayer graphene are successfully grown and are investigated using AFM and Raman spectroscopy. These domains are found to exhibit hexagonal moiré patterns on the graphene surface which is suggestive of orientational alignment with the underlying boron nitride substrate. Regions with high period and distorted moiré patterns are also observed which suggest that the graphene is under tensile strain which is attributed to the high growth temperatures used. The strain is found to significantly affect the Raman spectrum of graphene and a relationship between the strain and the shifting of Raman spectral peaks is determined. Successful attempts are also made to modify the strain in the graphene monolayer using an AFM tip which is observed to relax when defects are introduced in a controlled manner to the graphene monolayer. These results represent new approaches to the introduction and control of strain in graphene which may be useful for the fabrication of high-performance graphene devices.
14
Qi, Ling. "Design of hybrid organic-inorganic nanostructures via electroastic assembly in solutions and at interfaces : structure, organization and functionalities." Paris 6, 2009. http://www.theses.fr/2009PA066213.
Full textAbstract:
Des nano-objets hybrides organiques-inorganiques formés par assemblages électrostatiques de nanoparticules minérales, de nanotubes de carbone et de polymères/oligomères en volume et à une interface sont étudiés dans ce travail de thèse. En fonction de la nature des briques/composants élémentaires, différents types de complexes sont générés : nano-colloïdes singulets stables, coacervats cœurs-écorces, agrégats fractals et tubes décorés. Ces objets possèdent des propriétés de volume et de surface intéressantes ce qui leur permet d’être utilisés pour générer des interfaces fonctionnelles. L’influence du procédé de mise œuvre sur leur nanostructure et leur morphologie finale est étudié dans un deuxième temps ; la possibilité de développer des morphologies diverses à partir d’un nombre limité de composés chimiques différents est également souligné. Finalement, une nouvelle méthode de croissance de couches hétéro-structurées à partir d’une interface solide/liquide est décrite ; certains mécanismes de croissance sont proposés ; le potentiel de cette approche dans le domaine de la fonctionnalisation de surface est discuté au travers d’exemples
15
Hassan, Mohammad Rokib, and University of Lethbridge Faculty of Arts and Science. "Self-assembled molecular rods and squares with chalcogenadiazole framework ligands." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Chemistry and Biochemistry, c2010, 2010. http://hdl.handle.net/10133/2639.
Full textAbstract:
During the attempts to carry out Suzuki coupling reactions, the σ-bonded Pd−Caryl
benzochalcogenadiazolyl complexes trans-[ClPd(PPh3)2(C6H2BrN2E)] (E = S, Se) were
isolated. The corresponding bromo derivatives were also synthesized on purpose to
investigate their activity in Stille coupling reactions. A head-to-tail dimer trans-
[{ClPd(PPh3)(μ-C6H2BrN2Se)}2] was synthesized from the thermolysis of trans-
[ClPd(PPh3)2(C6H2BrN2Se)] in the presence of SeO2. The reduction potentials of the
mononuclear and dinuclear complexes were measured by cyclic voltammetry (CV) and
square wave voltammetry (SWV).
4,7-bis(2/4-pyridyl)benzochalcogenadiazole ligands were synthesized by Stille coupling
reactions and the 1,5-bis(4-pyridyl)naphthalene ligand was prepared by a Suzuki
coupling reaction. Reactions of the labile complex [BrRe(CO)4(NCMe)] with 4,7-bis(4-
pyridyl)benzochalcogenadiazole ligands in a 2:1 ratio afforded self-assembled molecular
rods [{ReBr(CO)4}2(μ-4,7-bis(4-pyridyl)benzochalcogenadiazoles)]. Palladium directed
molecular squares [(enPd)(μ-4,7-bis(4-pyridyl)benzochalcogenadiazole)]4[PF6]8 were
prepared by reactions of enPd(PF6)2 and 4,7-bis(4-pyridyl)benzochalco-genadiazoles in a
1:1 ratio. The optoelectronic properties of the ligands and the molecular rods were
investigated by CV and SWV, and by luminescence spectroscopy. The optical properties
of the square complexes were also studied by luminescence spectroscopy.<br>xvii, 152 leaves : ill. (some col.) ; 29 cm
16
Yahya, Wan Zaireen Nisa. "Synthèse et caractérisation des oligomères et polymères Ä-conjugués nanostructurés pour applications en photovoltaïque." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENV074/document.
Full textAbstract:
Les cellules photovoltaïques organiques ont fait l'objet d'un intérêt croissant au cours de ces dernières décennies car elles offrent un grand potentiel pour une production d'énergie renouvelable à faible coût. Afin d'obtenir des cellules solaires organiques à haut rendement de conversion d'énergie, beaucoup de recherches se focalisent sur les matériaux ayant des capacités à absorber la lumière efficacement. Dans ce contexte, le présent travail se concentre sur la conception et le développement de nouveaux matériaux donneurs d'électrons (oligomères et polymères) comme matériaux absorbant de la lumière basée sur l'approche « Donneur-Accepteur » alternant des segments riches en électron (donneur d'électron) et des unités pauvres en électron (accepteur d'électron). Trois séries d'unités riches en électron ont été étudiées: oligothiophènes, fluorène et indacenodithiophene. L'unité fluorénone est la principale unité « accepteur d'électron » étudiée. Une comparaison directe avec le système basé sur l'unité benzothiadiazole comme accepteur d'électron est également rapportée. Trois méthodes principales de synthèse ont été utilisées: polymérisation oxydante par le chlorure de fer (III), et les couplages croisés au palladium de type Suzuki ou de Stille. Les études spectroscopique UV-Visible en absorption et en photoluminescence sur ces oligomères et polymères ont démontré la présence de complexes à transfert de charges permettant d'élargir le spectre d'absorption. Les oligomères et les polymères possèdent des faibles largeurs de bande interdite de 1,6 eV à 2 eV. Les systèmes ayant des unités fluorénones présentent des spectres d'absorption étendus allant jusqu'à 600-700 nm, tandis que les systèmes ayant des unités benzothiadiazoles présentent des spectres d'absorption allant jusqu'à 700- 800 nm. La nature des bandes de complexes à transfert de charge se révèle d'être dépendant de la force de respective des unités « donneur d'électrons » et des unités « accepteur d'électrons ». Les niveaux d'énergies HOMO et LUMO des oligomères et les polymères sont déterminés par des mesures électrochimiques. Les polymères à base de fluorène possèdent des niveaux d'énergie HOMO les plus bas. Ces polymères testés en mélange avec les fullerenes PCBM en cellules photovoltaïques ont démontré des valeurs élevées de tension en circuit ouvert (Voc) proche de 0,9 V. Tous les oligomères et les polymères ont été testés dans des dispositifs photovoltaïques et ont montré des résultats encourageants avec des rendements de conversion allant jusqu'à 2,1 %. Ce sont des premièrs résultats obtenus après seulement quelques optimisations (ratios oligomères ou polymères : fullerènes et recuit thermique). Ce travail prometteur permet ainsi d'envisager des résultats plus élevés dans le futur<br>Organic photovoltaic (OPV) cells have been a subject of increasing interest during the last decade as they are promising candidates for low cost renewable energy production. In order to obtain reasonably high performance organic solar cells, development of efficient light absorbing materials are of primary focus in the OPV field. In this context, the present work is focused on the design and development of new electron donor materials (oligomers and polymers) as light absorbing materials based on “Donor-Acceptor” approach alternating electron donating group and electron withdrawing group. Three main families of electron donating group are studied: oligothiophenes, fluorene and indacenodithiophene. Fluorenone unit is the principal electron withdrawing group studied and a direct comparison with the system based on benzothiadiazole unit as electron withdrawing unit is also provided. Three main synthetic methods were employed: oxidative polymerization mediated by Iron (III) chloride and Palladium cross-coupling reactions according to Suzuki coupling or Stille coupling conditions. Spectroscopic studies on absorption and photoluminescence have demonstrated the presence of characteristic charge transfer complex in all the studied D-A oligomers and polymers allowing the extension of the absorption spectrum. The D-A oligomers and polymers have shown an overall low optical band gap of 1.6-2 eV with absorption spectra up to 600 to 800 nm. The nature of the charge transfer complex transitions bands were found to be depending on the strength of the electron donating unit and the electron withdrawing unit. Furthermore molecular packing in solution and in solid state has also demonstrated to contribute to extension of absorption spectrum. The HOMO and LUMO energy levels of the oligomers and polymers were determined by electrochemical measurements. Fluorene-based polymers have shown low lying HOMO energy levels, and these polymers demonstrate high open circuit voltage (Voc) in photovoltaic cell when combined with fullerenes derivatives PCBM with Voc values close to 0.9 V. The oligomers and polymers tested in photovoltaic devices have shown promising results with the highest power conversion efficiency obtained of 2.1 % when combined with fullerenes PCBMC70. These results were obtained after only limited numbers of device optimizations such as the active materials ratios and thermal annealing. Therefore further optimization of devices may exhibit higher power conversion efficiencies
17
Masillamani, Appan Merari. "Propriétés électriques des nanostructures π-conjugués". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00836614.
Full textAbstract:
Cette thèse traite de l'étude du transport de charge à travers les semi-conducteurs organiques au sein de transistors à effet de champ organiques (OFET). Une grande attention a été accordée aux interfaces dans les OFET dont les propriétés ont été accordées pour moduler la réponse transistor. La stabilité de l'appareil en état de commutation et le mécanisme régissant l'injection de charges ont été étudiés systématiquement. Le transport de charge au niveau fondamental à travers les monocouches auto-assemblées comprenant une grande variété des molécules π-conjuguées a été étudié. Dans cette thèse, le processus de transport de charge et différents paramètres affectant ce phénomène sont examinées en détail par la fabrication et la caractérisation de trois terminaux basés sur des architectures OFET et deux dispositifs de jonctions terminales constituées d'une couche mono-moléculaire sur la surface de l'électrode métallique. Parmi les différents aspects relatifs à l'injection de charge dans des transistors organiques macroscopiques à couches minces, un accent particulier a été mis sur l'interface de l'engineering en réglant (i) le diélectrique / l'interface semi-conducteur, et (ii) l'électrode en métal / le semi-conducteur. Pour explorer les aspects régissant le transport de charge dans le canal de l'appareil, nous avons étudié la propriété de (iii) la mobilité intrinsèque dans la semi-conductivité des matériaux et (iv) l'utilisation de mélanges dans la couche active du dispositif. A l'échelle nanométrique, le transport de charge, grâce à une mono-couche moléculaire chimisorbé sur des électrodes métalliques, a été étudié. Pour effectuer la caractérisation électrique sur la mono couche auto-assemblée (SAM), nous avons construit un système de configuration comprenant des alliages eutectiques de gallium et d'indium liquide métallique (GainE) comme électrode.
18
Yin, Jinsong. "Self-assembly of ordered nanostructures." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19116.
Full text
19
Nagpure, Suraj R. "SYNTHESIS OF TITANIA THIN FILMS WITH CONTROLLED MESOPORE ORIENTATION: NANOSTRUCTURE FOR ENERGY CONVERSION AND STORAGE." UKnowledge, 2016. http://uknowledge.uky.edu/cme_etds/67.
Full textAbstract:
This dissertation addresses the synthesis mechanism of mesoporous titania thin films with 2D Hexagonal Close Packed (HCP) cylindrical nanopores by an evaporation-induced self-assembly (EISA) method with Pluronic surfactants P123 and F127 as structure directing agents, and their applications in photovoltaics and lithium ion batteries. To provide orthogonal alignment of the pores, surface modification of substrates with crosslinked surfactant has been used to provide a chemically neutral surface. GISAXS studies show not only that aging at 4°C facilitates ordered mesostructure development, but also that aging at this temperature helps to provide orthogonal orientation of the cylindrical micelles which assemble into an ordered mesophase directly by a disorder-order transition. These films provide pores with 8-9 nm diameter, which is precisely the structure expected to provide short carrier diffusion length and high hole conductivity required for efficient bulk heterojunction solar cells. In addition, anatase titania is a n-type semiconductor with a band gap of +3.2 eV. Therefore, titania readily absorbs UV light with a wavelength below 387 nm. Because of this, these titania films can be used as window layers with a p-type semiconductor incorporated into the pores and at the top surface of the device to synthesize a photovoltaic cell. The pores provide opportunities to increase the surface area for contact between the two semiconductors, to align a p-type semiconductor at the junction, and to induce quantum confinement effects.
These titania films with hexagonal phase are infiltrated with a hole conducting polymer, poly(3-hexylthiophene) (P3HT), in order to create a p-n junctions for organic-inorganic hybrid solar cells, by spin coating followed by thermal annealing. This assembly is hypothesized to give better photovoltaic performance compared to disordered or bicontinuous cubic nanopore arrangements; confinement in cylindrical nanopores is expected to provide isolated, regioregular “wires” of conjugated polymers with tunable optoelectronic properties, such as improved hole conductivity over that in bicontinuous cubic structure. The kinetics of infiltration into the pores show that maximum infiltration occurs within less than one hour in these films, and give materials with improved photovoltaic performance relative to planar TiO2/P3HT assemblies. These oriented mesoporous titania films are also used to develop an inorganic solar cell by depositing CdTe at the top using the Close Spaced Sublimation (CSS) technique. A power conversion efficiency of 5.53% is measured for heterostructures built using mesoporous titania films, which is significantly enhanced relative to planar TiO2/CdTe devices and prior reports in the literature. These mesoporous titania films have a great potential in inorganic solar cell development and can potentially replace CdS window layers which are conventionally used in inorganic CdS-CdTe solar cells. The last part of the dissertation addresses layer-by-layer synthesis to increase the thickness of mesoporous titania films with vertically oriented 2D-HCP nanopores, and their use in lithium ion batteries as negative electrodes because of advantages such as good cycling stability, small volume expansion (~3%) during intercalation/extraction and high discharge voltage plateau. The high surface area and small wall thickness of these titania films provide excellent lithium ion insertion and reduced Li-ion diffusion length, resulting in stable capacities as high as 200-250 mAh/g over 200 cycles.
20
Diebold, Morgane. "Systèmes composites organogélateurs/polymères semi-conducteurs : de la preuve conceptuelle aux matériaux nanostructurés pour l'électronique plastique." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE002.
Full textAbstract:
L’amélioration des performances des dispositifs photovoltaïques organiques passe par le contrôle de la morphologie de leurs couches actives. Nous avons cherché à préparer une hétérojonction volumique donneur-accepteur nanostructurée en utilisant la nucléation hétérogène du poly (3-hexylthiophène) (P3HT, donneur) par des fibres d’organogélateurs à base de naphthalène diimide (NDI, accepteur). La première partie de ce travail présente l’étude des propriétés d’auto-assemblage d’organogélateurs à cœur NDI substitué par des groupements amides et des dendrons trialkoxyphényles. Nous avons évalué l’influence de la longueur de la chaîne flexible entre le cœur naphthalène et les groupements amides (2 liaisons C-C pour NDI2 et 4 pour NDI4) sur les propriétés physico-chimiques des organogélateurs. La seconde partie de ce travail met en évidence le polymorphisme du composé NDI2 en identifiant 4 polymorphes ainsi que leurs signatures optiques, spectroscopiques et structurales. Un diagramme de phase de l’état solide du NDI2 est proposé. La dernière partie de la thèse concerne l’élaboration de nano-composites donneur-accepteur entre les organogélateurs à cœur NDI et le P3HT. Le processus de formation en solution de ces nano-composites est analysé en suivant les cinétiques de cristallisation du P3HT par spectroscopie d’absorption UV-Visible et les morphologies obtenues (structures shish-kebab) par microscopie électronique en transmission. L’effet nucléant des organogélateurs sur le P3HT a été montré. Les études en cellules solaires des composés P3HT:PCBM : organogélateur ont prouvé que le rendement de conversion énergétique peut être augmenté en présence d’organogélateurs<br>Improving the performances of organic photovoltaic devices requires morphology control of the active layers. Highly nanostructured donor-acceptor bulk heterojunctions were prepared by heterogeneous nucleation of poly (3-hexylthiophene) (P3HT, donor) on naphthalene diimide organogelators fibers (NDI, acceptor). The first part of this work was dedicated to the self-assembly of NDI-core organogelators substituted by amide groups and trialkoxyphenyls dendrons. We evaluated the influence of the flexible chain between the naphthalene core and the amide groups (2 C-C bonds for NDI2 and 4 for NDI4) on the physico-chemical properties of the organogelators.The second part of this work focused on the polymorphism of NDI2 with identification of four different polymorphs with their optical, spectroscopic and structural signatures. A phase diagram of NDI2 in the solid state was determined. The last part of this manuscript concerns the fabrication of donor-acceptor nano-composites between NDI organogelators and P3HT. The formation process in solution of these nano-composites was analyzed by following the crystallization kinetics of P3HT by UV-Vis absorption spectroscopy and the thin film morphology (shish-kebab structures) by transmission electron microscopy. The nucleating effect of various organogelators on P3HT was demonstrated. Solar cells were made from the composites P3HT:PCBM : organogelator and their energetic conversion yield was shown to be increased in the presence of organogelators
21
Otsuka, Yoko. "Films minces nanostructurés de domaines sub-10 nm à partir de copolymères biosourcés pour des applications dans le photovoltaïque organique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV024/document.
Full textAbstract:
La structuration nanométrique par l'auto-assemblage des copolymères à blocs est l'une des stratégies « bottom-up » prometteuses pour contrôler la morphologie de la couche active de cellules photovoltaïques organiques. Dans cette thèse, une nouvelle classe de copolymère constitué d’un bloc semi-conducteur π-conjugué poly(3-hexylthiophène) (P3HT) regioregulier et d’un bloc oligosaccharidique a été synthétisée et a montré une auto-organisation en nanostructures périodiques de domaine inférieure à 10 nm. Deux systèmes de copolymères à blocs ont été synthétisés, le P3HT-bloc-maltoheptaose peracétylé (P3HT-b-AcMal7) et le P3HT-bloc-maltoheptaose (P3HT-b-Mal7), via une réaction de chimie "clic" entre les segments oligosaccharidiques et P3HT fonctionnalisés en extrémité. Une étude exhaustive sur leur comportement d'auto-assemblage par des analyses AFM, TEM et de diffusion des rayons X a révélé que le copolymère à bloc P3HT-b-AcMal7 montre une propension à s'auto-assembler par recuit thermique en structures lamellaires avec une résolution inférieure à 10 nm, c’est-à-dire la morphologie et la taille idéale pour la couche active d’une cellule photovoltaïque organique. De plus, ce système présente l’une des plus petites tailles de domaines réalisées par l'auto-assemblage de copolymères à blocs à base de P3HT. Un réseau lamellaire composé uniquement du P3HT a été obtenu par gravure chimique sélective du bloc sacrificiel AcMal7 à partir d'un film nano-organisé de P3HT-b-AcMal7 et ceci sans affecter la structure lamellaire initiale. Les domaines vides du AcMal7 gravé pourront être remplis par un composé accepteur d'électrons tel que le [6,6]-phényl-C61-butanoate de méthyle (PCBM) pour l’application photovoltaïque comme perspective de cette thèse. Les résultats et les connaissances acquises dans cette étude devraient permettre d'augmenter les performances des prochaines générations de cellules photovoltaïques organiques<br>Nanoscale patterning through self-assembly of block copolymers is one of the promising bottom-up strategies for controlling active layer morphology in organic photovoltaics. In this thesis, a new class of carbohydrate-based semiconducting block copolymers consisting of π-conjugated regioregular poly(3-hexylthiophene) (P3HT) and oligosaccharides were synthesized and self-organized into sub-10 nm scale periodic nanostructures. Two different diblock copolymers, i.e. P3HT-block-peracetylated maltoheptaose (P3HT-b-AcMal7) and P3HT-block-maltoheptaose (P3HT-b-Mal7) were synthesized via "click" reaction between end-functionalized oligosaccharide and P3HT moieties. A comprehensive investigation of their self-assembly behavior by AFM, TEM, and X-ray scattering analyses revealed that the P3HT-b-AcMal7 diblock copolymer has the ability to self-assemble into sub-10 nm scale lamellar structure, which is the ideal morphology of the active layer in organic photovoltaics and one of the smallest domain sizes achieved by self-assembly of P3HT-based block copolymers, via thermal annealing. Nano-patterned film made of P3HT was attained by selective chemical etching of AcMal7 block from microphase-separated P3HT-b-AcMal7 template without affecting the original lamellar structure. The resultant void where the etched-out AcMal7 block existed will be filled with electron acceptor compounds such as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) for photovoltaic application as a perspective of this thesis. The results and knowledge obtained in this study are expected to provide further advances and innovation in organic photovoltaics
22
Ong, Luvena Le-Yun. "Self-assembly of three-dimensional nucleic acid nanostructures." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106741.
Full textAbstract:
Thesis: Ph. D. in Medical Engineering and Medical Physics, Harvard-MIT Program in Health Sciences and Technology, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 137-148).<br>Patterning complex 3D features at the nanoscale offers potential applications for a wide range of fields from materials to medicine. While numerous methods have been developed to manipulate nanoscale materials, these methods are typically limited by their difficulty in creating arbitrary 3D patterns. Self-assembly of nucleic acids has emerged as a promising method for addressing this challenge due to the predictability and programmability of the material and its structure. While a diversity of DNA nanostructures have been designed by specifying complementarity rules between strands, creation of 3D nanostructures requires careful design of strand architecture, and patterns are often limited to a volume of 25 x 25 x 25 nm³ Here, we address the challenges in structural DNA nanotechnology by developing a modular DNA "brick" approach. These bricks are short, single-stranded oliogomers that can self-assemble in a single-pot reaction to a prescribed 3D shape. Using this modular approach, we demonstrate high efficiency in 3D design by generating 100 distinct, discrete 3D structures from a library of strands. We also created long-range ordering of channels, tunnels, and pores by growing micron-sized 3D periodic crystals made from DNA bricks. Finally, we applied this approach to control over 30,000 unique component strands to selfassemble into cuboids measuring over 100 nm in each dimension. These structures were further used to pattern highly complex cavities. Together, this work represents a simple, modular, and versatile method for 3D nanofabrication. This unique patterning capability of DNA bricks may enable development of new applications by providing a foundation for intricate and complex control of an unprecedented number of independent components.<br>by Luvena Le-Yun Ong.<br>Ph. D. in Medical Engineering and Medical Physics
23
Lunn, David John. "Towards functional nanostructures by crystallisation-driven self-assembly." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653077.
Full textAbstract:
This Thesis describes the synthesis, functionalisation and self-assembly of a series of PFS-b-polyvinylsiloxane copolymers (PFS = polyferrocenylsilane). This simple crystalline-coil block copolymer (BCP), containing a PFS block suitable for crystallisation-driven self-assembly (CDSA) and a siloxane block suitable for the introduction of molecular complexity, is an ideal starting point for the bottom-up preparation of functional nanostructures. Chapter 2 outlines enabling chemistry that provides a platform for the majority of the work in this Thesis. It describes the preparation of PFS-b-polyvinylsiloxane copolymers and their subsequent functionalisation to tune the properties of the resulting materials or incorporate more complex functionality for subsequent applications. Chapter 3 describes the CDSA of brush BCPs prepared by the thiol-ene functionalisation of poly( ferrocenyldimethylsilane )-b-poly(methylviny lsiloxane) (PFDMS-b-PMVS) with n-alkane thiols. The rate of CDSA is influenced by the cocrystallisation of brush and linear BCPs and can be manipulated to afford micelles with nanosegregated coronas by gradient CDSA, an analogous process to a covalent gradient copolymerisation. Chapter 4 describes the immobilisation of red, green and blue emitting fluorophores on PFDMS-b-polysiloxane copolymers. By the sequential CDSA of fluorescent BCPs, or mixtures thereof, multicompartment micelles are prepared in which the emission of each segment is precisely controlled to produce colours throughout the visible spectrum and prepare structures analogous to nanoscale pixels and barcodes. Chapter 5 describes the radical hydrophosphination and CDSA of PFDMS-b-PMVS to afford monodisperse cylindrical micelles. On addition of a Pd precursor, · intermicelle crosslinking occurs affording tunable Pd-coated fibres that remain active to further CDSA. FUl1hermore, chains and networks can be prepared by the coordination-driven self-assembly of multicompartment micelle building blocks. Chapter 6 describes future directions and preliminary results for the use of crystalline-coil BCPs, where creativity and control at the small molecule scale is desirable for the transfer of complexity through hierarchical self-assembly processes for the optimisation of end nanostructure function.
24
He, Zhixing. "Self-assembly of anisotropic nanostructures and interferometric spectroscopy." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97402.
Full textAbstract:
With the development of controlled and predictable nanoparticle fabrication, assembling multiple nano-objects into larger functional nanostructure has attracted increasing attention. As the most basic structure, assembly of one-dimensional (1D) structures is a good model for investigating the assembly mechanism of a nanostructure's formation from individual particles. In this dissertation, the dynamics and the growth mechanism of anisotropic 1D nanostructures is investigated.
In our first study, we demonstrate a simple method for assembling superparamagnetic nanoparticles (SPIONs) into structure-controlled 1D chains in a rotating magnetic field. The length of the SPION chains can be well described by an exponential distribution, as is also seen in SPION chains in a static field. In addition, the maximum chain length is limited by the field's rotational speed, as is seen in micro-sized beads forming chains in a rotating field. However, due to a combination of thermal fluctuations and hydrodynamic forces, the chain length in our case is shorter than either limit. In addition to chain length, the disorder of chains was also studied. Because of the friction between particles, kinetic potential traps prevent relaxation to the global free energy minimum. The traps are too deep to be overcome through thermal fluctuations, and assemblies captured by the kinetic traps therefore form disordered chains. We demonstrate that this disorder gradually heals over a timescale of tens of minutes and that the healing process can be promoted by increasing particle concentration or solution ionic strength, suggesting that the chain growth process provides the energy required to overcome the kinetic trapping.
Next, we introduce a novel optical technique we term Quantitative Optical Anisotropy Imaging (QOAI). A fast and precise single-particle characterizing technique for anisotropic nanostructures, QOAI allows real-time tracking of particle orientation as well as the spectroscopic characterization of polarizabilities of nanoparticles on a microsecond timescale. The abilities of QOAI are demonstrated by the detection and the characterization of single gold nanorods. We also show that single particle diffusions and the process of particle binding to a wall can be tracked through QOAI. The rotational diffusivities of gold nanorods near the wall were determined by autocorrelation analysis, which shows that the diffusivity in the polar direction is slightly smaller than in the azimuthal direction. This result demonstrates that a detailed correlation analysis with QOAI may provide the opportunity to analyze both the translational and rotational motion of particles simultaneously, enabling true 3-dimensional orientation tracking.
Finally, optical methods including QOAI are applied to the investigation of magnetic assembly, demonstrating that optical anisotropy is generated during particle binding, which can be used as a probe of the magnetic assembly process. QOAI is employed to track the dynamics of magnetic clusters in real time, attempting to capture insights on the self-assembly of the magnetic nanoparticles. By turning the external magnetic field on and off, the processes of combining superparamagnetic colloidal nanoparticle clusters into chain assemblies are monitored along with the chain growth. This fast and orientation-sensitive single-particle measurement opens the door to detailed studies of self-assembly away from equilibrium.<br>Doctor of Philosophy<br>Nanotechnology is the study and application of phenomena at the nanoscale, which is between 1 and 100 nm. Due to quantum effects, nanomaterials exhibit many interesting properties that cannot be found in bulk materials and are highly influenced by the shape of the nanostructures. One of the most promising strategies for forming complex nanostructures is to use smaller nanoparticles as building blocks. Therefore, significant efforts have been spent on the studies of the fabrication and modeling of the assembly of nanostructures.
As a good starting point for analyzing the mechanism of self-assembly, we focus on the most basic structure, one-dimensional (1D) nanowires and chains. First, we demonstrate a simple method to fabricate one-dimensional magnetic chains from spherical magnetic nanoparticles in a rotating magnetic field. The growth mechanism of the nanochains is investigated, indicating the theory developed for chains formed with larger beads is not applicable at the nanoscale, and additional factors, such as the effect of temperature, need to be considered. Second, we introduce a fast, sensitive optical technique for characterizing anisotropic nanostructures. Because of their unique optical properties, gold nanorods are used to demonstrate the capabilities of the optical system. Not only static properties (orientation, aspect ratio), but also dynamics properties (rotational motion), of single gold nanorods are characterized quantitatively. Finally, this optical technique is extended to preliminary work on characterizing magnetic chain assembly. The processes of magnetic cluster binding and dissociation in a magnetic field are monitored and analyzed.
25
Guldin, Stefan. "Inorganic nanoarchitectures by organic self assembly." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245290.
Full text
26
Dufil, Yannick. "Monocouches auto‐assemblées et nanostructures de métaux nobles : préparation et application au photovoltaïque." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0380/document.
Full textAbstract:
Au cours de ce travail, dans une première approche descendante, nous avons étudié la réalisation de cellules solaires multicouches évaporées à base de matériaux organiques : le pentacène et le PTCDI-C5. Nous nous sommes servis de cela pour bâtir des cellules simple jonction bicouches et les caractériser. Ces cellules ont servi de modèle de référence à notre étude et démontrent des capacités en accord avec la littérature. Nous avons ensuite produit et caractérisé des cellules multijonctions en bicouches. Une rapide étude sur le comportement d’une couche d’argent d’épaisseur nanométrique a servi à déposer la couche de recombinaison de ces cellules. Nous nous sommes ensuite attelés à la réalisation de monocouches auto-assemblées sur silicium dans le but de développer des couches actives donneur-accepteur et de pouvoir les empiler par l’approche ascendante. Après avoir étudié les groupements d’accroche silanes et acides phosphoniques, nous avons investigué la réalisation de SAM de (3-Triméthoxysilylpropyl) diéthylènetriamine (DETAS) sur silicium en tant que couche d’accroche pour les molécules actives. Nous avons mis en évidence la présence de liaisons hydrogènes aidant à l’organisation de la SAM grâce à des analyses ATR-FTIR. Nous nous sommes servis de cette SAM comme couche d’accroche pour la greffe d’une molécule photo-active le pérylène tétracarboxylique dianhydride (PTCDA). Les techniques de caractérisation par AFM, ellipsométrie et spectroscopie Raman nous ont servi à caractériser notre surface après la greffe de PTCDA<br>During this study, in a first top-down approach, we investigated evaporated multilayer organic solar cells built from pentacene and PTCDI-C5. We studied spectral response from these materials as well as their vacuum deposition characteristics. We used that knowledge to build simple junction and bi-layer solar cells. Those cells were the reference that allowed us to build and characterised multijonctions bi-layer solar cells with a nanostructured silver layer as recombination layer. A simple study of that silver layer was also conducted. We then switched to self-assembled monolayers on silicon in order to build donor-acceptor active layers that could be stacked, in a bottom-up approach. First, we compared silane and phosphonic acid grafting groups with an 18 carbon long alkane chain. Then we studied (3- trimethoxysilylpropyl) diethylentrimaine (DETAS) on silicon with extra care on relative humidity as a grafting parameter. We also investigated DETAS SAM to highlight hydrogen bonding within the monolayer using ATR-FTIR. DETAS SAM were then used as an anchor molecule for a photoactive molecule perylene tetracarboxylicdianhydrid (PTCDA). Characterisation technics used were AFM, ellipsometry, and Raman spectroscopy
27
Högberg, Björn. "DNA-mediated self-assembly of nanostructures : theory and experiments." Doctoral thesis, Mittuniversitetet, Institutionen för teknik, fysik och matematik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-8882.
Full text
28
Scott, Shelley Ann. "Self-assembly of Sb and Bi nanostructures on graphite." Thesis, University of Canterbury. Physics and Astronomy, 2005. http://hdl.handle.net/10092/5562.
Full textAbstract:
Spontaneous pattern formation in the natural world provides a constant source of wonder. Remarkable similarities exist between the patterns observed in the likes of snowflake growth, electrodeposition, and bacterial colonies. The driving force which creates similar patterns from these seemingly different processes is a non-equilibrium growth environment, which results from a diffusion field at the structures' boundary.
Thin film growth from the vapour phase is an interesting and technologically important non-equilibrium system. Particles deposited on atomically flat and weakly interacting substrates diffuse over substantial distances, nucleating islands via collisions with other adatoms and with defects. The final island morphologies are governed by an interplay between kinetics and thermodynamics. Compact structures are thermodynamically favoured, but the kinetics of particle diffusion to the growth front often results in dendritic and irregular shapes. Manipulating this balance between kinetics and thermodynamics can allow the self-assembly of nanoscale structures with tailored morphologies.
This study uses scanning electron microscopy, atomic force microscopy, and electron backscatter diffraction to investigate the morphology and structure of antimony and bismuth aggregates on highly oriented pyrolitic graphite (HOPG) substrates. In particular the islands are characterized with varying experimental growth conditions.
For the case of the Sb/HOPG system, altering the deposition flux and the deposited dose results in a transition from compact to branched structures, consistent with other studies. However, the correlation of island heights with varying growth environments has not been performed previously, and in the present case, reveals a transition to flatter structures when the deposition rate is increased.
Also, the heights of the branches are found to be strongly dependent on their length.
Island aggregation in the Bi/HOPG system was the primary focus of this work, and on the graphite terraces, revealed the formation of elongated 6-point star shaped islands, with a well defined stripe morphology. Increasing the flux resulted in a transition to more branched and disordered morphologies. Decoration of graphite step edges in a low flux environment, produced ordered arrays of nano-rods at the step edges.
Both the step edge and terrace nucleated Bi aggregates were aligned with the high symmetry directions of the graphite substrate with Bi {0112} planes parallel to the plane of the substrate. With increasing deposited dose, a continuous film forms, which undergoes a crystallographic orientation transition to the Bi {0001} orientation.
29
Ansari, Haris M. "Self-assembled nanostructures in oxide ceramics." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1348592818.
Full text
30
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.
Full text
31
Ramaswamy, Sivaraman. "Simulation and control of dynamic directed self-assembly of nanostructures." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98713.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 111-117).<br>Self-assembled nanoscale structures are the basis for various technological advancements in functional materials, sensors, and molecular circuits and factories. With significant progress in self-assembly of periodic nanostructures (such as monolayers), the focus is now shifting towards non-periodic structures. Control of various interaction force fields (electrostatic, Van der Waals, etc.) between the nanoparticles and external controls can result in the formation of nanostructures with desired geometry. The aim is to design the nanoparticles and the external actuators such that the desired structure can be self-assembled rapidly with high reliability and avoiding any kinetic trapping that an ill-designed energy landscape might cause. Deterministic dynamic modeling of such self-assembled nanostructures, directed by external fields, through a Master Equation approach, leads to a set of differential equations of such large size that even the most efficient solution algorithms are overwhelmed. Thus, model reduction is a key necessity. This thesis presents a methodological approach and specific algorithms, which generate time-varying, reduced-order models for the description of directed self-assembly of nanoparticles by external fields. The approach is based on Finite State Projection and is adaptive, i.e., it generates reduced-order models that vary over time. The algorithm uses event-detection concepts to determine automatically, during simulation, suitable time points at which the projection space and thus the structure of the reduced-order model change, in such a way that the computational load remains low while the upper bound on the simulation error, resulting from model reduction, is lower than a prescribed maximum limit. The thesis also presents an optimal control strategy that can guide any initial random configuration of nanoparticles to a final structure of desired geometry, in minimum time. It employs a multi-resolution view of the dynamically evolving configurations of nanoparticles, which are described through the simulation methodology described before. External charges, attracting or repelling the nanoparticles, are the controls, whose location and intensity are determined by the optimality conditions of the optimal control strategy. To ensure analytic consistency of the parametric sensitivities, during the computation of the optimal controls, and thus guarantee the optimality of the resulting control policy, a priori determination of enlarged constant projection spaces is shown to be essential. The thesis also presents a series of case studies, which illustrate how the proposed methods can be used to simulate effectively directed self-assembly of an appreciable number of nanoparticles, and reach the desired geometry. These case studies also illuminate several of its features, such as: superiority over a static optimal solution; evasion of kinetic traps; and effective handling of combinatorial complications arising for systems with large-size domains and many particles.<br>by Sivaraman Ramaswamy.<br>Ph. D.
32
Grant, A. "Self-assembly in side-chain polymers." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/271980.
Full text
33
Brady, Ryan. "Crystalline frameworks self-assembled from amphiphilic DNA nanostructures." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289706.
Full textAbstract:
Many emerging technologies would greatly benefit from reliable methods for the production of functional materials with well-defined 3D nanoscale structure. Conceptually, approaches to produce such architectures are divided into two broad classes; top down and bottom up manufacture. In the top down approach, nanoscale structure is created through the controlled removal of material from a bulk starting object. Top down methods have a proven record of reliability in the fabrication of extended two dimensional arrays with fine control over nanoscale features. However, such approaches become increasingly cumbersome when attempting to define structure in three dimensions rather than two. Bottom up methods promise a more reliable route to the formation of such materials. Here, molecular scale building units self-assemble to form a desired structure, driven by pre-defined interactions between individual motifs. Due to the highly specific molecular recognition properties of nucleic acids, along with their relatively simple synthesis and wide range of potential chemical modifications, DNA nanotechnology is now regarded as a prime route for the bottom up fabrication of nanostructured materials. However, current approaches to the formation of designed 3D DNA crystals are complicated by the difficulties in designing sub-units able to assemble in a predictable fashion over length-scales orders of magnitude larger than themselves. Amphiphiles are able to self-assemble into a variety of 3D crystalline phases driven by the frustrated micro-phase separation of hydrophobic and hydrophilic domains, with the structural properties reliant primarily on overall topology of the molecules rather than their exact chemical and geometrical features. Although the mechanism underlying amphiphile self-assembly is robust, it inherently limits control over the fine-scale structural details. This thesis reports on a new class of self-assembling DNA motifs; amphiphilic cholesterol-functionalised DNA nanostars, \emph {C-stars}. C-stars combine key advantages of all-DNA motifs and conventional amphiphilic molecules -- allowing for the preparation of expanded crystalline frameworks with tunable properties and embedded functionality.
34
Lim, I.-Im Stephanie. "Molecularly mediated assembly of nanoparticles towards functional nanostructures." Diss., Online access via UMI:, 2008.
Find full text
35
Young, Michael Christopher. "Self-Assembly of Functionalized Supramolecular Structures." Thesis, University of California, Riverside, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3644049.
Full textAbstract:
<p>Enzymes are capable of exquisite selectivity in catalysis chemical reactions because of a well-evolved mechanism that binds substrates in internal active sites based on size and shape complementarity. The cavities of these enzymes are decorated with organic or inorganic groups which can promote reactivity once the substrate is non-covalently bound. Synthetic molecular hosts to date have been able to bind to substrates in a similar, biomimetic fashion, but functionalized molecular hosts are still virtually unknown. </p><p> One convenient way to prepare molecular hosts is by the self-assembly of organic coordinating ligands with suitable metal salts. The reversible dative bonds holding these cage structures together allow incorrect products to break apart and reform, favoring creation of the most thermodynamically stable product. This leads to discrete, solution phase cages that can function as cavity-containing hosts. Some of these hosts have shown efficacy as catalysts for pericyclic reactions due to favorable transition states of the bound substrates. These cages, however, fail to orient reactive functional groups into their interiors. Truly biomimetic cages will require modifying traditional self-assembled targets to incorporate these reactive functionalities. </p><p> This work explores the self-assembly of metal-organic cages displaying covalent modifications on their interior. Incorporation of unreactive and poorly reactive groups was found to have a significant impact on the outcome of the self-assembly process. Cages with endohedral alcoholic functionality were found to have different binding properties than unfunctionalized analogs. Cages with introverted alcohol groups were also exploited for their ability to self-catalyze reactions <i>on the interior</i> of the hosts. The metal vertices themselves could also be used as functional groups, and showed the ability to sense neutral analytes in hybrid dative/hydrogen bonded self-assemblies. </p>
36
Eghtesadi, Seyed Ali. "SUPRAMOLECULAR ASSEMBLY OF DENDRITIC POLYIONS INTORESPONSIVE NANOSTRUCTURES." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522527868518926.
Full text
37
Tung, Shih-Huang. "Self-assembly of amphiphilic molecules in organic liquids." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7349.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
38
Lee, Kwang Soo. "Stimuli Responsive Self-Assembly of Functional Organic Nanomaterials." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452106891.
Full text
39
Yoshii, Tatsuyuki. "Development of functional biomaterials by self-assembled nanostructures." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192195.
Full text
40
Rauscher, Michael D. "Strain mediated self-assembly of ceramic nano islands." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196195105.
Full text
41
Ringk, Andreas [Verfasser], and Strohriegl [Akademischer Betreuer]. "Organic Electronics by Self-Assembly / Andreas Ringk. Betreuer: Strohriegl." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059353261/34.
Full text
42
Tong, Yongfeng. "Self-Assembly of Organic Molecules on Reactive Metal Substrates." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS522/document.
Full textAbstract:
Dans cette thèse, la formation de monocouches auto-assemblées de différentes molécules de chalcogénure et de molécules p-conjuguées planaire et leurs caractéristiques structurelles et électroniques ont été systématiquement étudiées principalement par spectroscopie photoélectronique à rayons X effectuée utilisant la lumière synchrotron, microscopie à effet tunnel à balayage et diffraction d'électrons à faible énergie. Une étude de la formation de structures hybrides organiques-inorganiques auto-assemblées a été réalisée par assemblage couche par couche d'un dithiol sur ZnO (0001) avec dépôt de métal intermédiaire. De plus en complément de l'étude des molécules comportant un atome de chalcogènure, les caractéristiques d'adsorption du sélénium et du soufre ont été étudiées. La spectroscopie XPS à haute résolution et la spectroscopie de structure fine d’absorption au seuil d’excitation (NEXAFS) ont permis d'étudier les caractéristiques des monocouches auto-assemblées du sélénure de benzène et du sélénophène sur Cu (100) et dihexyldiselénure sur Ni (111) et Pd (111) et ont montré en particulier l’existence de processus de rupture de liaison Se-C ainsi que l’existence de différents sites d'adsorption de molécules. Ces conclusions ont été soutenues par l'étude de l'adsorption atomique du sélénium, qui montre également l'existence de différents sites d'adsorption pour le Se atomique avec différents environnements chimiques. Ces conclusions sont principalement basées sur une étude XPS haute résolution des spectres caractéristiques Se3d, Se3p, du spectre de bande de valence et de l'imagerie LEED. La formation de monocouche de 5,5-bis (mercaptéthyl) -2,20-bipyridine (BPD) avec terminaison SH libre sur ZnO(0001) a été démontrée, permettant le greffage ultérieur d'Ag et Ni et de l’ assemblage d’une autre couche de BPD sur cette couche de métal-dithiol. Les changements dans les propriétés électroniques ont été déterminés à partir des spectres de la bande de valence. La molécule π-conjuguée, NTCDA, a été déposée sur différentes surfaces métalliques et sa morphologie structurelle et ses propriétés chimiques par rapport à la surface métallique ont été étudiées. Les molécules NTCDA affichent une structure « couchée » avec deux domaines différents sur Ag (110) et Cu (100) mais trois domaines sur la surface de Cu (111). Par rapport à celui sur la surface inerte de Au, une forte interaction entre les molécules et les substrats de Cu, Ag existe et joue un rôle important dans la détermination de l'orientation et de l'état de liaison des films organiques<br>In this thesis, the formation of self-assembled monolayers of different chalcogenide molecules and planer π-conjugated molecules and their electronic and structural characteristics were systematically studied mainly by synchrotron based X-ray photoelectron spectroscopy, scanning tunneling microscopy and low energy electron diffraction. A study of formation of hybrid organic-inorganic self assembled structure was performed by layer by layer assembly of a dithiol on ZnO(0001) with intermediate metal deposition. Additionally as a complement to the study of chalcogen head group molecules the adsorption characteristics of selenium and sulfur were investigated. The high resolution XPS and near edge absorption fine structure spectroscopy allowed to investigate the characteristics of self-assembled monolayers of benzene selenide and selenophene on Cu (100), and dihexyldiselenide on Ni(111) and Pd(111) and showed in particular the existence of Se-C bond breaking processes and existence of different adsorption sites of molecules. These conclusions were supported by the study of atomic selenium adsorption, which also shows existence different adsorption sites for the atomic Se with different chemical environments. These conclusions are mainly based on high resolution XPS study of characteristic Se3d, Se3p spectra, valance band spectrum and LEED imaging. The formation of a 5,5- bis (mercaptomethyl)-2,20- bipyridine (BPD) with SH termination on ZnO(0001) was demonstrated allowing subsequent grafting of Ag and Ni and further assembly of BPD on this metal-dithiol layer. The changes in electronic properties were determined from valence band spectra. The large π-conjugated molecule, NTCDA, was deposited on different metal surfaces and its structure morphology and chemical properties with respect to the metal surface was investigated. The NTCDA molecules displays a lying down structure with two different domains on Ag (110) and Cu(100) but three domain on Cu(111) surface. Compared with the one on the inert Au surface, a strong interface interaction between the molecules and Cu, Ag substrates plays an important role in determining the orientation and bonding state of the organic films
43
Sanchez, Daniel Antonio. "Amphiphilic Self-Assembly & Post-Polymerization of N-type Conjugated Optoelectronic Nanostructures." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429039468.
Full text
44
Ma, Zhipeng. "Characterization of Self-Assembly Dynamics and Mechanical Properties of DNA Origami Nanostructures." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217167.
Full text
45
Shajkumar, Aruni. "Yolk-Shell Nanostructures Prepared via Block Copolymer Self-Assembly for Catalytic Applications." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-232735.
Full textAbstract:
Yolk-shell nanostructures/yolk-shell nanoparticles are defined as a hybrid structure, a mixture of core/shell and hollow particles, where a core particle is encapsulated inside the hollow shell and may move freely inside the shell. Of the various classifications of yolk-shell nanostructures, a structure with an inorganic core and inorganic shell (inorganic/inorganic) has been studied widely due to their unique optical, magnetic, electrical, mechanical, and catalytic properties. In the work presented here, among the different inorganic/inorganic yolk-shell nanostructures noble metal@silica yolk-shell nanostructures has been chosen as the topic of interest. Silica shell possesses many advantages such as chemical inertness, tunable pore sizes, diverse surface morphologies, increasing suspension stability, no reduction in LSPR properties of noble metal nanoparticles when used as a coating for such particles. Noble metal nanoparticles such as AgNPs and AuNPs, on the other hand, possess unique structural, optical, catalytic, and quantum properties. Hence yolk-shell nanostructures with a combination of Ag or Au core and a silica shell (Ag@SiO2 and Au@SiO2) would open to endless possibilities.
In this study, four areas were mainly explored: mechanism of silica shell formation over a given template, the synthetic modifications of Ag@SiO2 and Au@SiO2 yolk-shell nanostructures, their application as a potential catalyst, and devising of a flow type catalytic reactor. Despite the growing number of contributions on the topic of yolk-shell nanostructures, particularly Au@SiO2 and Ag@SiO2 yolk-shell nanostructures, a potential for improvement lies in all four aforementioned areas.
As an initial study, the effect of different processing conditions as well as the mechanism of silica shell formation over reactive block copolymer templates was investigated. An asymmetric PS-b-P4VP block copolymer was chosen as a structure directing component to deposit silica shell. In order to deposit silica shell, PS-b-P4VP micelles with a collapsed PS core and a swollen P4VP corona was prepared via a solvent exchange method. The growth of silica shell over the PS-b-P4VP micelles (reactive template) was done using in-situ DLS and TEM. The experimental data obtained revealed the 4 distinct stages involved in the silica shell formation over the reactive BCP micellar template starting from the accumulation of silica precursor around the P4VP corona followed by a reactive template mediated hydrolysis-condensation reaction of the silica precursor which eventually lead to the shell densification and shell growth around the micelles. An understanding of the mechanism of silica shell formation over reactive templates provides a direct way to encapsulate various active species such as metal nanoparticles and quantum dots and paves the way for the template mediated synthesis of hybrid nanostructures such as yolk-shell nanoparticles. These studies also serve as a platform to fine-tune the properties of such hybrid nanostructures by varying the reaction parameters during silica shell deposition and reaction time.
The next part of the work focused mainly on the synthesis, process optimisation and characterization of Ag@SiO2 and Au@SiO2 yolk-shell nanostructures, and their potential use as a nanocatalyst. A well-known soft template mediated synthesis of the yolk-shell nanostructure was adopted for the present work. For this PS-b-P4VP micelle was used as a dual template for both encapsulation of nanoparticle and the deposition of silica shell. The nanoparticles were entrapped selectively to the BCP micellar core and silica deposition was done by reacting the nanoparticle-loaded micelles with an acidic silica sol which lead to the formation of Ag@PS-b-P4VP@SiO2 or Au@PS-b-P4VP@SiO2 particles with respect to the nanoparticle used. In the case of Ag@PS-b-P4VP particles, upon silica deposition, a partial dissolution of AgNPs was observed whereas AuNPs were stable against dissolution. Hence yolk-shell nanostructures with AuNPs were studied further. As-prepared Au@PS-b-P4VP@SiO2 particles were then subjected to pyrolysis to remove the BCP template. The resulting yolk-shell nanostructures comprised of an AuNP core and a hollow mesoporous silica shell. Upon removal of the BCP template, the Au@SiO2 particles fused together and formed large aggregates. The catalytic properties of Au@SiO2 yolk-shell nanoparticles were explored using a model reaction of reduction of 4-nitrophenol and proved to have good catalytic activity and efficient recyclability. It was observed that catalytic efficiency was hindered by the particle aggregates formed after pyrolysis by creating an inhomogeneity in the system and inaccessibility of the catalytic surface for the reactants. Hence synthetic modifications were needed to overcome such drawbacks.
Next part of the work deals with the synthetic modification of Au@SiO2 yolk-shell nanoparticles done by embedding them in a porous silica structure (PSS). Such structural morphology was attained by gelating the excess silica precursor while synthesising the Au@PS-b-P4VP@SiO2 particles. The pyrolytic removal of block copolymer results in the formation of Au@SiO2@PSS catalyst and the porous nature of both the shell and the silica structure provides an easy access for the reactants to the nanocatalyst surface located inside. The catalytic properties of Au@SiO2@PSS were studied using a model reaction of catalytic reduction of 4-nitrophenol (4-NP) and reductive degradation of different dyes. Kinetic studies show that Au@SiO2@PSS catalyst possesses enhanced catalytic activity as compared to other analogous systems reported in the literature so far. Furthermore, catalytic experiments on the reductive degradation of different dyes show that Au@SiO2@PSS catalyst can be considered as a very promising candidate for wastewater treatment.
Another proposed direction of applying the Au@SiO2 yolk-shells is by devising a continuous flow catalytic system composed of Au@SiO2 yolk-shell nanoparticles for the effective degradation of azo dyes as a promising candidate for wastewater treatment. This was done by infiltrating the Au@PS-b-P4VP@SiO2 particles inside a porous glass substrate (frits) and the subsequent pyrolytic removal of the BCP template resulting in the formation of Au@SiO2 yolk-shell nanostructures sintered inside the frit pores. The flow catalytic reactor was exploited in terms of studying its catalytic activity in the degradation of azo dyes and 4-nitrophenol and proved to have a catalytic efficiency of ca. 99% in terms of reagent conversion and has a long-term stability under flow. Thus, with a few modifications, these flow type systems can open the doors to a very promising continuous flow catalytic reactor in the future.
46
Maerten, Clément. "Bio-inspired self-construction and self-assembly of organic films triggered by electrochemistry." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE045.
Full textAbstract:
Les architectures moléculaires qui se forment exclusivement sur une surface sont encore rares. L’électrodéposition est un procédé exploitant des « signaux » électriques afin de déclencher et contrôler l’assemblage de films. Récemment, une nouvelle méthode : l’autoconstruction de films en « une étape » par l’utilisation d’un morphogène (un gradient de catalyseur généré depuis une électrode), a attiré l’attention de la communauté scientifique. En effet, elle permet l’auto-assemblage rapide de films polymériques robustes. Cependant, cette technique était limitée à des systèmes basés sur la chimie click du Cu (I). Le but de ce travail était d’étendre cette stratégie à d’autres systèmes en utilisant une approche bio-inspirée. Le concept du morphogène a été appliqué pour développer deux nouveaux systèmes d’autoconstruction déclenchées par électrochimie. Le premier système est basé sur l’autoconstruction covalente de films polymériques induite par l’oxydation d’une molécule organique, inspirée de la moule. Le deuxième est basé sur l’auto-assemblage de films de polyphénols par électro-assemblage par liaisons de coordinations. Enfin, nous avons appliqué ces deux concepts pour immobiliser électrochimiquement une enzyme sur une électrode afin de créer un biosenseur<br>Molecular architectures that spontaneously grow exclusively near a surface are rare. Electrodeposition is a process in which imposed electrical « signals » are employed to direct the assembly of thin films. Recently, a new method based on the one-pot self-construction of films by means of a morphogen (a catalyst gradient generated from a surface) has attracted attention since it allows the quick self-assembly of robust films. Nevertheless, this technique was quite limited to systems based on click chemistry.The purpose of this work was to extend this strategy to other systems using a bio-inspired approach. The one-pot morphogen concept was applied to design two new electro-triggered self-construction concepts. The first one is based on the self-construction of covalent polymer films triggered by mussel-inspired molecule oxidation. The second one is based on the electro-self-assembly of polyphenols films based on ionic bonds coordination. Finally, we tried to apply these concepts in order to electrochemically immobilize an enzyme on an electrode to create a biosensor
47
Morse, Ada. "Networks, (K)nots, Nucleotides, and Nanostructures." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/863.
Full textAbstract:
Designing self-assembling DNA nanostructures often requires the identification of a route for a scaffolding strand of DNA through the target structure. When the target structure is modeled as a graph, these scaffolding routes correspond to Eulerian circuits subject to turning restrictions imposed by physical constraints on the strands of DNA. Existence of such Eulerian circuits is an NP-hard problem, which can be approached by adapting solutions to a version of the Traveling Salesperson Problem. However, the author and collaborators have demonstrated that even Eulerian circuits obeying these turning restrictions are not necessarily feasible as scaffolding routes by giving examples of nontrivially knotted circuits which cannot be traced by the unknotted scaffolding strand.
Often, targets of DNA nanostructure self-assembly are modeled as graphs embedded on surfaces in space. In this case, Eulerian circuits obeying the turning restrictions correspond to A-trails, circuits which turn immediately left or right at each vertex. In any graph embedded on the sphere, all A-trails are unknotted regardless of the embedding of the sphere in space. We show that this does not hold in general for graphs on the torus. However, we show this property does hold for checkerboard-colorable graphs on the torus, that is, those graphs whose faces can be properly 2-colored, and provide a partial converse to this result. As a consequence, we characterize (with one exceptional family) regular triangulations of the torus containing unknotted A-trails. By developing a theory of sums of A-trails, we lift constructions from the torus to arbitrary n-tori, and by generalizing our work on A-trails to smooth circuit decompositions, we construct all torus links and certain sums of torus links from circuit decompositions of rectangular torus grids.
Graphs embedded on surfaces are equivalent to ribbon graphs, which are particularly well-suited to modeling DNA nanostructures, as their boundary components correspond to strands of DNA and their twisted ribbons correspond to double-helices. Every ribbon graph has a corresponding delta-matroid, a combinatorial object encoding the structure of the ribbon-graph's spanning quasi-trees (substructures having exactly one boundary component). We show that interlacement with respect to quasi-trees can be generalized to delta-matroids, and use the resulting structure on delta-matroids to provide feasible-set expansions for a family of delta-matroid polynomials, both recovering well-known expansions of this type (such as the spanning-tree expansion of the Tutte polynnomial) as well as providing several previously unknown expansions. Among these are expansions for the transition polynomial, a version of which has been used to study DNA nanostructure self-assembly, and the interlace polynomial, which solves a problem in DNA recombination.
48
Dienstmaier, Jürgen. "From supramolecular self-assembly to two-dimensional covalent organic frameworks." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-156623.
Full textAbstract:
The two main subjects of this thesis are the realization of supramolecular self-assembled monolayers at surfaces and the formation of surface-supported two-dimensional covalent organic frameworks. Both topics, albeit different, yield long-range ordered open-pore networks with quite different stabilities, depending on the strength and type of bonds holding them together. The surface of choice is mainly graphite, which is considered an inert substrate. Graphite yields pristine clean, very large and flat surfaces when cleaved, facilitating the observation in real space of the molecular networks adsorbed on these surfaces by means of the Scanning Tunneling Microscope (STM). STM is the main experimental technique used here. It was used to image mostly at the liquid-solid interface under ambient conditions.
Using a large tricarboxylic acid adsorbate, long-range order supramolecular self-assembled monolayers were obtained. These monolayers are formed via a delicate interaction balance between adsorbates, substrate, and solvent molecules. Weak van der Waal forces mediate the adsorbate-substrate interaction; hydrogen bonds, the adsorbate-adsorbate interaction. Also, depending on the solvent used and the concentration of adsorbates dissolved in it, different polymorphs are found on the substrate. To understand the nucleation and growth mechanism that give rise to the different self-assembled monolayers, thermodynamical considerations are used. Enthalpic and entropic contributions are evaluated for several of the polymorphs found, explaining their occurance on the basis of the Gibbs free energy per unit area. However, even if this work sheds some light on supramolecular self-assembly, adding also that much research has been done in this field, it is still very difficult to know a priori how adsorbates will behave on a substrate. Thus predictions of which patterns will ultimately arise are hampered.
To realize structures that are more stable than those formed via supramolecular self-assembly, several strategies have been proposed. Covalent bond formation is one of them, yielding strong and lightweight structures by using organic molecules composed primarily of light elements. The strength of covalent bonds ranges from strong to very strong, when compared to van der Waals and hydrogen bonds. This characteristic makes correction of possible structural errors difficult to almost impossible. However, when molecules with suitable functional groups are allowed to react under reversible conditions, error correction of covalent bonds becomes feasible, yielding regular structures with the energetically most favorable configurations. In this thesis, this is exemplified with the small 1,4-benzenediboronic acid molecules, yielding monolayers composed of very regular, long-range ordered covalent organic frameworks on graphite. Thermal stability is probed by exposing the structures to relatively high temperatures for prolonged times under atmospheric conditions. Further experiments with larger para-diboronic acids, under similar reversible conditions, yield the expected isotopological regular frameworks with larger unit cell parameters. This demonstrates the proof of principle for the formation of two-dimensional covalent organic frameworks.
These two main topics, supramolecular self-assembly and covalent bond formation on surfaces, constitute the basis of this thesis. It is organized as follows: A first part deals with the theoretical background of the main analytical instruments used in this work. Then, the thermodynamics of supramolecular self-assembly is presented, along with the studies of the different polymorphs found using a large tricarboxylic acid as building block. The final part deals with the formation of two-dimensional, long-range ordered covalent organic frameworks, made from organic molecules composed only of light elements. This work show that these last mentioned networks exhibit higher thermal stabilities when compared to self-assembled monolayers held together mainly by strong hydrogen bonds. The viability of larger heteromeric isotopological networks is also explored.
49
Keltie, Sam M. "Towards novel metal-organic frameworks : synthesis, characterisation and self-assembly." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/366974/.
Full textAbstract:
The synthesis, characterisation and self-assembly of novel metal-organic frameworks was investigated and reported in this thesis with a view for these materials to be used in heterogeneous catalysis after further modification. Three new materials have been synthesised and their properties discussed with all three structures being solved by single crystal X-ray diffraction methods. Three known and five new elaborate, chiral MOF ligands were synthesised in this investigation. The new ligands were a dicarboxylic acid, two tetracarboxylic acids and two dipyridinyl compounds. All the ligands are based on a bi-2-naphthol core unit. The carbon-carbon cross-coupling reactions used in the synthesis of the new ligands were optimised. All of the ligands produced that contained unprotected, free diols were found not to form novel MOFs in an extensive investigation. A wide range of synthetic conditions were employed in attempt to produce novel MOFs. The ligand with protected diols in conjugation with an achiral co-ligand forms a highly interpenetrated novel MOF, with Zn2+ secondary building units. Two other MOF-like coordination polymers were also successfully synthesised and characterised. One completes a void in the well-known series of MOFs containing the Zn4O secondary building unit and simple dicarboxylic acids. The self-assembly of a series of prototypical MOFs was investigated by a novel solution 1H NMR technique. The solution behaviour of the MOF ligands during the MOF synthesis in these systems is discussed. MOFs containing the Zn4O secondary building unit appear to show fluctuations in ligand concentration, indicating the formation of crystallite species during the first few hours of the synthesis. Some insights are gained about the crystallisation mechanism of the pillared MOFs that were investigated. A dual decrease in the concentrations of both the dicarboxylate and pillaring ligands during the reaction is observed.
50
Hales, Kelly D. "Design and characterization of self-assembled nanostructures of block copolymers in solution." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 130 p, 2009. http://proquest.umi.com/pqdweb?did=1679669801&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text