To see the other types of publications on this topic, follow the link: Chautauqua Assembly (N.Y.).
Dissertations / Theses on the topic 'Chautauqua Assembly (N.Y.)'
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 'Chautauqua Assembly (N.Y.).'
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
Wang, Wei. "Self-Assembly of Dendrimers and Cucurbit[n]uril Complexes." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/176.
Full textAbstract:
This dissertation investigates the preparation and electrochemical studies on a series of novel redox active hybrid dendrimers. The author also describes cucurbit[8]uril (CB8) mediated dendrimer self-assembly and their size selection by applying external electrochemical stimulus. In addition to this, a series of redox active, carboxylic acid terminated dendrimers were deposited onto indium tin oxide (ITO) surfaces. The surface interactions between the dendrimers and the metal oxides were characterized by electrochemical, spectroscopic, and atomic force microscopic methods. Additionally, the author describes molecular recognition behavior studies between several redox active guests and cucurbit[7]uril (CB7) in non-aqueous media. Furthermore, the author also describes the preparation and electronic communication studies on a series of bisferrocenylamino triazine derivatives. Three chapters of this dissertation deal with dendrimer applications in several different topics. A general introduction to dendrimers is given in Chapter I, including a short history, dendrimer structural features, synthetic methodologies, and also including their general applications on several different topics. Chapter II describes the preparation and characterization of a series of novel redox active hybrid dendrimers. These dendrimers consist of a ferrocenylamino nucleus and two series of popular dendrons (Fréchet and Newkome type). Interestingly, the microenvironment surrounding the redox residues is finely adjustable by varying the size of these two types of dendrons. Chapter III describes the molecular recognition studies with selected redox active guests and the macrocyclic host CB7 in non-aqueous media. The extremely strong host-guest interaction between CB7 and ferrocenylmethyl-trimethylammonium (FA) in aqueous media experiences a substantial thermodynamic stability loss when transferred to non-aqueous media. In stark contrast to this, the binding behavior between CB7 and the dicationic guest methyl viologen (MV) exhibits less sensitivity to environmental variation. Furthermore, the electrochemical studies were performed under non-aqueous media. In general, host CB7 encapsulation of these redox active guests in non-aqueous media induces different electrochemical behavior compared to that of aqueous media. For instance, the cyclic voltammetric response of CB7 encapsulated FA in DMSO exhibit substantial cathodic potential shift, which is opposite to the behavior in aqueous media. Chapter IV describes CB8 mediated dendrimer self-assembly. A new series of pi-donor containing Newkome type dendrimers were synthesized. These pi-donor containing dendrimers are found to form stable ternary charge transfer complexes with another series of pi-acceptor (viologen) containing dendrimers. Furthermore, one electron reduction of the viologen residue disrupts the charge transfer complexes and leads to the assembly of viologen radical cation dimmers. And, thus, may result in substantial size selection between these two types of dendrimer assemblies. Chapter V describes the exploration of a series of redox active dendrimers bearing multiple carboxylic acids as surface anchoring groups to attach onto the optical transparent semiconductor material ITO coated glass surfaces. The dendrimer derivatized ITO slides were further prepared as working electrodes, and the subsequent electrochemical studies revealed that these dendrimers strongly adsorb onto ITO surfaces. Especially, the ITO electrodes treated with the second generation dendrimer exhibit rather stable electrochemical behavior. The surface coverages of ITO electrodes treated with dendrimers were estimated by current integration. Atomic force microscopic studies provided insights on surface topographical variation before and after the dendrimer deposition. Infrared spectroscopic studies further revealed the chemical interactions between dendrimer carboxylic acid groups and the metal oxide surfaces. Chapter VI describes the preparation of a series of triazine based bisferrocenylamino derivatives. Variable 1H-NMR and 13C-NMR spectroscopic studies clearly indicate that these bisferrocenylamino triazine derivatives exhibit rotamerization phenomena. And, the rotamer coalescence temperatures are mediated by the third substituent group. The X-ray crystallographic analyses disclose the partial double bond character between the amino nitrogen and the triazine carbon, which reveal the structural proof behind the rotamerization phenomena. Furthermore, electrochemical experiments are performed under two sets of experimental conditions. No electronic communication is observed when using the traditional tetrabultylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. In stark contrast to this, electronic communication between the bisferrocenyl residues is observed when using tetrabultylammonium tetrakis(pentafluorophenyl)borate (TBAB(C6F5)4) as supporting electrolyte. Surprisingly, the electronic communication strength can be mediated by a third substituent group. Computational studies provide insights into the molecular geometry and electronic structure of the mixed valence species. By combining the supporting electrolyte dependant electronic communication behavior, near-IR spectroscopic studies and the computational results, we conclude that, the electronic communication between the bisferrocenyl residues in these investigated triazine derivatives occurs through space metal-metal interactions.
2
Serpe, Michael Joseph. "Self-Assembly of Poly(N-isopropylacrylamide) Microgel Thin Films." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4806.
Full textAbstract:
The assembly of poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) microgel thin films into disordered and ordered arrays was investigated. Disordered pNIPAm-co-AAc microgel arrays were assembled based on electrostatic attractions between polyanionic pNIPAm-co-AAc microgels and polycationic poly(allylamine hydrochloride) (PAH). These interactions were studied in solution and subsequently used to assemble thin films following a Layer-by-Layer assembly protocol. Thin films were assembled as a function of pNIPAm-co-AAc microgel solution temperature and the resultant film thermoresponsivity characterized as a function of microgel layer number and pH. The response of assembled thin films to pH 3.0 and 6.5 exposure was then characterized by quartz crystal impedance and surface plasmon resonance spectroscopy, which showed that the thin film solvation was highly dependent on the pH of the solution it was in. Assembled thin films were also shown to be useful as controlled drug delivery platforms, where it was found that small molecules could be released from the films in a temperature regulated fashion. Microgel thin films also exhibited unique optical properties and were used as microlens arrays, which were able to focus pattern in air as well as in solution and had focal lengths that could be tuned in response to pH and temperature changes. Ordered microgel arrays were assembled following a thermal annealing process, in order to make light diffracting materials. These ordered arrays were photopolymerized and exhibited temperature dependent Bragg diffraction properties.
3
Koh, Ming Liang. "Self assembly of (N-methylated cyclic peptide)-polymer conjugates." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10129.
Full textAbstract:
Posed with the challenge of engineering and characterising nanoscaled objects, this thesis reports on the development of self assembling (cyclic peptide)-polymer conjugates as a versatile supramolecular route to complex nanostructures. A variety of conjugates was synthesised by microwave assisted copper(i)-catalysed azide-alkyne cycloaddition, covalently coupling alt(d,l) α cyclic peptides with synthetic polymers. The product of self assembly was then characterised in solution by small angle neutron scattering. Manipulating the grafted polymer and the chemical functionality of the peptide influenced the stability of the assembly, but was observed to be dependent on the solvating media. H-bonding and solvation strengths of a variety of solvents and mixtures produced nanotubes with lengths >110 nm or as short as 10 nm. Partially N methylated cyclic peptides (NMeCPs) and NMeCP-polymer conjugates were explored as compounds to limit self assembly. While the dimerisation of NMeCPs could be observed by size exclusion chromatography, lateral aggregation was also observed. NMeCP-polymer conjugates formed large (~400 nm) extended structures with small (~1 nm) domains as characterised by differential scanning calorimetry, light and neutron scattering. Monotopic NMeCP species were then investigated as chain stoppers for nanotubes, with the intent of controlling the nanotube length and adding functionality to the tube ends. No change to the geometry of the assembly could be observed, even up to a molar ratio of 1:4 ([CP]/[NMeCP], 80 % NMeCP). To gain insight into this discrepancy, a thermodynamic model was developed to describe the bicomponent system. It is put forward that the decreased availability of NMeCP in monomeric form, due to the lateral aggregation of NMeCP species, could explain the observed inefficiencies in chain stopping.
4
Riddle, Justin. "Assembly of tris(N-salicylideneamine) molecular architectures steric and electronic control of assembly, transport, and luminescence /." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3380124.
Full textAbstract:
Thesis (Ph.D.)--Indiana University, Dept. of Chemistry, 2009.Title from PDF t.p. (viewed on Jul 20, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7579. Adviser: Dongwhan Lee.
5
Khanduja, Nimisha. "Processive Acceleration of Actin Barbed End Assembly by N-WASP." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54933.
Full textAbstract:
Actin-based cell motility plays crucial roles throughout the lifetime of an organism. The dynamic rearrangement of the actin cytoskeleton triggers a plethora of cellular processes including cellular migration. Neural Wiskott Aldrich syndrome protein (N-WASP) is involved in transduction of signals from receptors on the cell surface to the actin cytoskeleton. N-WASP activated actin polymerization drives extension of invadopodia and podosomes into the basement layer. In addition to activating Arp2/3 complex, N-WASP binds actin filament barbed ends, and both N-WASP and barbed ends are tightly clustered in these invasive structures.
We used nanofibers coated with N-WASP WWCA domains as model cell surfaces and single actin filament imaging to determine how clustered N-WASP affects Arp2/3-independent barbed end assembly. Individual barbed ends captured by WWCA domains of N-WASP grew at or below their diffusion limited assembly rate. At high filament densities, overlapping filaments formed buckles between their nanofiber tethers and myosin attachment points. These buckles grew 3.4-fold faster than the diffusion-limited rate of unattached barbed ends. N-WASP constructs with and without the native poly-proline (PP) region showed similar rate enhancements. Increasing polycationic Mg2+ or Spermine to enhance filament bundling increased the frequency of filament buckle formation, consistent with a requirement of accelerated assembly on barbed end bundling.
Our preliminary data shows that tethered N-WASP construct containing one WH2 domain does not generate processive bundles or filament loops leading us to believe that tandem WH2 is required for processivity. We propose that this novel N-WASP assembly activity provides an Arp2/3-independent force that drives nascent filament bundles into the basement layer during cell invasion. Discovery of this bundle mediated unique pathway involved in invasion and metastasis will provide new targets for therapeutic development.Ph. D.
6
Wu, Yuchao. "Cucurbit[n]uril-based colloidal self-assembly in hybrid polymeric systems." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270021.
Full textAbstract:
Supramolecular interactions are of great importance in the fabrication of new functional materials. In particular, colloidal assembly via supramolecular pathway has contributed to numerous innovations in material chemistry, on account of its specific, directional and dynamic non-covalent interactions. By taking advantage of the non-covalent supramolecular interactions, tailored complementary colloidal building blocks which are normally incompatible with each other could be integrated interdependently, forming novel hybrid materials with emerging properties. This thesis mainly focuses on the design, preparation and characterization of novel colloidal assemblies based on cucurbit[n]urils host-guest interactions, including hybrid ‘raspberry-like’ colloids, catalytic polymeric nanocomposites, advanced structured colloids, and supramolecular polymer colloidal hydrogel.
7
Groombridge, Alexander S. "Aqueous self-assembly with cucurbit[n]urils : from solution to emulsion." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271800.
Full textAbstract:
Making use of the non-covalent bond to make materials is of great interest in many fields of research. This PhD thesis describes a variety of highly interdisciplinary research undertaken at the interface between chemistry, materials science, physics and engineering. Chapter 1 is an introductory chapter into the core concepts underlying this thesis. Supramolecular chemistry as a broad research field is briefly reviewed, followed by a focus on host-guest chemistry. The macrocyclic cucurbit[n]urils (CB[n]s) in particular are highlighted with a discussion on their recent applications since their discovery. Emulsions and their controlled generation with microfluidic techniques are then reviewed, as they have been used as templates for self-assembly processes throughout this thesis. A study into the synthesis of extended polymer networks composed entirely from small molecules held together by non-covalent interactions is described in Chapter 2. These highly dynamic and responsive supramolecular polymer networks have not yet been constructed with CB[n] host-guest chemistry. The ability of the larger CB[8] macrocycle to encapsulate multiple guest molecules in a stepwise fashion was taken advantage on in designing the synthesis of branching monomers. The monomers had two (A$_2$) or three (B$_3$) terminal guest moieties for CB[8], which upon combination formed branching supramolecular polymers that were multi-stimuli responsive. However, the polymers precipitated from solution at high concentrations rather than form a cross-linked network, due to competing intra-chain cyclisation and the limited water solubility of CB[8]. By confining these polymers to microfluidic droplets, directed assembly to the liquid-liquid interface could drive polymerisation to form an interfacial cross-linked gel that was both elastic and self-healing. Chapter 3 follows on from these results, describing attempts into constructing hyperbranched supramolecular polymers from an AB$_2$ guest molecule and CB[8] that would form globular polymers. Intramolecular complexation dominated with the guest molecules synthesised (A and B complexing within the molecule), evidenced by a variety of characterisation. Compared to previous works that relied on linear molecules to form a folded conformation for intramolecular complexes, these molecules were pre-organised with a unique cooperative complexation pathway. The stimuli-responsiveness of the complexes was probed, and the formation of self-sorting mixtures was demonstrated with multiple CB[n] and additional guest molecules. Controlling the self-assembly of semi-conducting nanocrystals with CB[7] is detailed in Chapter 4, a process that typically requires harsh conditions or extensive time-scales. Semi-conducting nanocrystals could be assembled instantaneously from water into extended networks that were highly porous with excess CB[7], retaining their nanoscale properties. Limiting quantities of CB[7] could then form nanoscale aggregates that remained in solution. Confinement of these assemblies within microfluidic droplets allowed the synthesis of dense microparticles, that retained their shape after re-dispersal in water. By simply including metallic nanocrystals as a minor component, mixed aggregates could be synthesised analogously. Finally, Chapter 5 draws overall conclusions from the results of this thesis, looking broadly at the potential for future prospects in these areas of research.
8
Yang, Wenwen. "Synthesis of N-alkyl urea peptoid oligomers." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378197097.
Full text
9
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
10
Datar, Aniket. "AFM investigation of one-dimensional self-assembly of n-type organic semiconducting molecules /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1203563051&sid=13&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Full text
11
August-Schmidt, Elizabeth Melissa. "Mechanisms of Community Assembly Beneath N-Fixing Trees in a Hawaiian Dry Woodland." Thesis, University of California, Santa Barbara, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13423031.
Full textAbstract:
Nitrogen (N) fixing trees are commonly used to promote forest restoration in disturbed areas because they can quickly recreate forest canopy structure. That structure in turn is hypothesized to attract animal seed dispersers and create enough shade to reduce undesirable species (particularly grasses). Yet N-fixers tend to increase soil N availability, which could facilitate the spread of nitrophilous invasive species. This dissertation evaluates the long-term consequences for understory community composition of establishing three N-fixing tree species (Acacia koa, Sophora chrysophylla, and Morella faya) after exotic grass-fueled fire in the seasonally dry subtropical woodland in Hawaii. To understand the restoration potential of these species, I compared discrete single-species stands of N-fixing trees in burned areas to both an intact native woodland and burned, open sites with no tree cover. Although N-fixing species are often assumed to be ecologically similar, trait variation among N-fixing trees in this system was strong enough to differentiate understory communities among stands of the three N-fixer species. To understand the mechanisms driving differences in understory composition among site types, particularly among N-fixing trees, I characterized the abiotic environment created by these species in terms of light and N availability, both of which were important drivers of understory community composition. High light and N availability were associated with greater exotic species cover and unique exotic species. Surprisingly, N availability was highest and N cycled fastest beneath the relatively slow-growing S. chrysophylla despite having much lower litter-N inputs than the faster-growing A. koa and M. faya. In this study, fast N-cycling was associated with high specific leaf area, high foliar N content and low foliar lignin:N. These traits are consistent with fast leaf economic spectrum traits in the general ecological literature, but this approach has not previously been applied to distinguish among N-fixing trees. Native Hawaiian dry forest understory recovery, particularly that of woody species, was limited throughout the burned area regardless of canopy cover. To determine what limits native shrub recovery, I sampled the seed bank and recorded natural seedling germination. I also planted native seedlings into the understory of all site types and either removed or left intact the invasive grass grasses present in the understory. I found that native shrubs were limited by both seed availability and competition with exotic grasses. Although outplant survival did not vary by N-fixer species identity, differences in the mechanisms by which each N-fixing species limited native seedling survival likely play a role in understory community assembly long-term. When restoration occurs in the context of secondary succession, prioritizing the creation of forest structure using N-fixing trees, particularly open-canopied fast-cycling species, such as S. chrysophylla, could make full community recovery more difficult by promoting rather than suppressing exotic grasses.
12
Biedermann, Frank. "Cucurbit[n]uril mediated self-assembly in water : from binding forces to applications." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607771.
Full text
13
Ni, Lingli. "Photoinduced n-alkylsilsesquioxane based hybrid films : peering into corrosion protection and self-assembly." Thesis, Mulhouse, 2012. http://www.theses.fr/2012MULH7172.
Full textAbstract:
Les composés hybrides organiques-inorganiques représentent une classe intéressante de matériaux dotés d'un très large éventail d'applications potentielles dans les revêtements protecteurs, les micro-optiques, conducteurs ioniques, membrane échangeuse de protons etc. Depuis le début des années 1990, le développement de la chimie sol-gel, dite «Chimie Douce», a donné naissance à une nouvelle ère de matériaux hybrides, où des conditions douces de synthèse ont permis un accès simplifié aux matériaux nanocomposites. Parmi les divers précurseurs sol-gel, des organoalkoxysilanes sont très attractifs en raison de leur stabilité, leur faible toxicité et de leur accessibilité. Mais l'insolubilité de ces précurseurs a jusqu'à présent limité leur utilisation dans un procédé sol-gel conventionnel.L'essentiel de la chimie détaillée dans cette thèse porte sur la formation de films hybrides à partir de n-alkylsilanes. Tout d'abord, la partie linéaire et alkyle hydrophobe peut fournir des propriétés barrières à la pénétration de l'eau et des ions, ce qui est un élément clé dans la protection contre la corrosion de substrats métalliques. Deuxièmement, les alkylsilanes possèdent la géométrie et la composition appropriée à un auto-assemblage pour générer des nanostructures périodiquement ordonnées. Récemment, la recherche menée dans le LPIM à Mulhouse démontré le potentiel d’une photopolymérisation inorganique sans solvant. Basée sur la photogénération de superacides par photolyse de sels d'onium qui sont photoamorceurs cationiques classiques, cette voie offre une chance pour étudier l’aptitude de film à base d’alkylsilanes pour la protection des métaux (Partie I) et l'assemblage supramoléculaire (Partie II)Hybrid organic-inorganic materials have attracted tremendous attention due to their wide range of potential applications in protective coatings, micro-optics, ionic conductors, proton-exchange membrane and so on. Since the early 1990s, the development of sol-gel chemistry (“Chimie Douce”) has given birth to a new age of hybrid materials, where mild synthetic conditions allowed a simplified access to well dispersed and chemically designed nanocomposite materials. Among various sol-gel precursors, organo alkoxysilanes are very attractive because of their superior stability compared to other hybrid precursors, low toxicity and accessibility. However, their insolubility in polar solvents and water has so far limited their use in conventional classic hydrolytic sol-gel procedure.In this thesis, the combination of a UV-driven solvent-free sol-gel process simultaneously to organic photopolymerization has been introduced to form hybrid films based on simple n-alkylsilane building blocks. Based on the photogeneration of superacids under photolysis of onium salts that are conventional photoinitiators, this pathway offers a new chance to investigate alkylsilanes in metal corrosion protection (Part I) and supramolecular assembly (Part II). As the linear and hydrophobic alkyl moiety can provide barrier-properties to the penetration of water and ions, which is a key feature in the corrosion protection of metallic substrates, in part I, the effect of alkyl chain structure of the alkylsilanes as well as their proportions on the corrosion resistance properties has been studied by Salt spray tests and Electron impendence spectroscopy. Furthermore, an effort to correlate the corrosion resistance and coating structure was made as a range of characterization techniques have been implemented (Real time FTIR, 29Si solid state NMR and contact angle measurement). Secondly, alkylsilanes have the proper geometry and composition to self-assemble and generate periodically ordered nanostructures. In part II, the influence on the mesostructure, alkyl chain packing arrangement and its conformational order, which come from alkyl chain length of the silane precursors and the experimental conditions (light intensity, temperature and humidity), has been investigated depending on various characterization techniques (X ray diffraction, microscope, solid state NMR, RT-FTIR). As an application example, a patterned 3D multilayer crystalline organosilica film has been amplified via a facile photopattrerning pathway
14
Mejuto, Nieblas Carmen. "Poly-N-Heterocyclic Carbene Ligands with Polyaromatic Linkers. Self-Assembly and Host-Guest Chemistry." Doctoral thesis, Universitat Jaume I, 2017. http://hdl.handle.net/10803/404306.
Full textAbstract:
In summary, a series of polytopic ligands based on NHC and MIC ligands have been synthesized in this Doctoral Thesis by means of different synthetic routes that gave rise to systems with very sophisticated architectures. A large variety of metal complexes have been formed based on these salt precursors that allowed the preparation of homo and heteroleptic mono-, di- and tri-metal complexes with different geometries. The luminescence properties of various imidazolium salts, the catalytic activity of some of the metal complexes obtained, and host-guest molecular recognition studies have been analyzed.En esta Tesis Doctoral se ha sintetizado una serie de ligandos politópicos basados en ligandos NHC y MIC mediante diferentes rutas sintéticas que dieron lugar a sistemas con arquitecturas muy sofisticadas. Se ha procedido a la formación de una gran variedad de complejos metálicos basados en dichas sales precursoras que permitieron la obtención de complejos mono-, di- y tri-metálicos homo y heterolépticos con diferentes geometrías. Se han analizado las propiedades luminiscentes de varias sales de imidazolio, la actividad catalítica de algunos de los complejos metálicos obtenidos y se han llevado a cabo estudios de reconocimiento molecular host-guest.
15
Raeisi, Mersad. "Harnessing the Recognition Properties of Cucurbit[n]urils in Dynamic Supramolecular Polymers." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1565963566821693.
Full text
16
Meddows, Elisabeth. "Identification of the molecular determinants important in the assembly of N-methyl-D-aspartate (NMDA) receptors." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365682.
Full text
17
Pudney, Alexander F. "Role of the Usher N-terminal Domain in Assembly of Fl Polymeric Antigen of Yersinia pestis." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487475.
Full textAbstract:
The fraction 1 antigenic capsule of Yersinia pestis is a homopolymer assembled by the two-component chaperone-usher system; a terminal branch of the general secretory pathway. A periplasmic chaperone (CaflM) is responsible for folding and capping of monomeric Cafl, whilst preserving it in an energy competent conformation for fiber formation. Translocation of Cafl polymer to the cell surface occurs via the outer membrane usher CaflA, and circumstantial evidence suggests that polymerisation is catalysed by the usher. Recovery of OlT-sensitive CaflT10CT139C polymer at the surface of recombinant E. coli demonstrated that donor strand alignment corresponding to the register T10/T139 (donor strand/F strand) was used throughout the fiber. Sucrose density gradient centrifugation was used to show that periplasmic CaflM :Cafl fiber preassembly complexes specifically target CaflA within the outer membrane. CaflM bound to polymerisation-deficient subunit was shown to be degraded in the presence of usher, consistent with a secondary binding event upon interaction with CaflA, resulting sensitivity to periplasmic OegP. Deletion mutagenesis within the N-terminus of CaflA (CaflAN) showed that this domain is essential for capsular Fl biogenesis and that loss of even the 27 N-terminal residues of CaflA led to drastic reduction in assembly. Fl biogenesis was completely abolished in this mutant when periplasmic CaflAN was coexpressed, suggesting that the domain was able to compete for periplasmic Fl preassembly complexes. The usher N-terminus was overproduced as a soluble periplasmic domain and purified. This has recently been used for collaborative crystallographic studies of both the Nterminus alone and in complex with chaperone and subunit. Histagged CaflAN was purified and used for in vitro Biacore binding studies with purified CaflM:Cafl~3 binary complex and Cafl:CaflA9R2 ternary complex. Qualitative analysis was obtained for an interaction between CaflAN and the preassembly complexes, consistent with similar observations made in related chaperone/usher systems for the usher N-terminus.
18
Doan, Thu Hong. "Synthesis, self-assembly and photophysical evaluation of fluorophores derived from acenes, heteroacenes and quinazolines." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC205.
Full textAbstract:
Les semiconducteurs organiques (OSC) tels que les composés organiques photovoltaïques (OPVs), les diodes électroluminescentes organiques (OLEDs) ou encore les transistors organiques à effet de champ (OFETs) constituent un domaine de recherche très attractif en raison de leur potentiel en tant que couches actives dans les dispositifs optoélectroniques. Les composés aromatiques polycycliques ainsi que les hétéroaromatiques sont considérés comme des matériaux prometteurs pour les OSC en raison de leurs conductivités électriques potentielles, de leurs propriétés optiques ainsi que de leurs assemblages géométriques. Ces deux systèmes et leurs propriétés photophysiques ont été étudiés dans les trois chapitres de cette thèse. Dans le premier chapitre, une étude sur un ensemble d'acènes linéaires, angulaires et condensés consistant en des liens hétéroatomes avec des agrégations uniques a été décrite et analysée. Les hétéroacènes N-fusionnés angulaires et π-étendus sont la classe principale étudiée dans le deuxième chapitre. Leurs synthèses sont basées sur la réaction de couplage de Suzuki-Miyaura et la réaction de Cadogan. Outre les acènes et les hétéroacènes N-fusionnés, les N-hétéroaromatiques ont fait l'objet d'une attention particulière dans le domaine de matériaux. L'un d'entre eux est la classe des quinazolines utilisées comme partie acceptrice d'électrons dans les structures push-pull pour le transfert de charge intramoléculaire (TCI). L'étude des relations entre les structures dérivées du motif quinazoline de type donneur d'électron-accepteur-donneur (D-A-D) et leurs propriétés de photoluminescence est le principal travail mentionné dans le troisième chapitreOrganic semiconductors (OSCs) are a highly attractive research field due to their potentials as active layers in optoelectronic devices such as organic field-effect transistors (OFETs), organic photovoltaic (OPVs) and organic light emitting diodes (OLEDs). Polycyclic aromatic compounds as well as heteroaromatics are considered as promising materials for OSCs due to their semi conductivity properties, optical properties and geometric structures. The mentioned systems and their photophysical properties were investigated in three chapters of my thesis. In the first chapter, a study on a set of linear, angular and condensed acenes consisting of heteroatom linkages with unique aggregations was described and analyzed. The angular and π-extended N-fused heteroacenes are the main class studied in the second chapter. Their synthesis is based on the Suzuki-Miyaura coupling and the Cadogan reactions. Besides acenes and N-fused heteroacenes, N-heteroaromatics have gained attention in material area. One of them is the quinazoline class that is known as an electron withdrawing unit in push-pull structures for intramolecular charge transfer (ICT). The investigation of the relationships between the electron donor-acceptor-donor (D-A-D) quinazoline-based structures and their photoluminescence properties is the main work mentioned in the third chapter
19
Yadin, David. "Molecular and structural characterisation of the human fibrillin-1 N-C terminal interaction." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:2a840db6-3b37-4b48-93e3-562626b57faf.
Full textAbstract:
Fibrillins are modular, disulphide-rich glycoproteins that assemble into microfibrils in the extracellular matrix (ECM). These microfibrils are critical structural elements of many non-elastic and elastic connective tissues. They also regulate the availability of transforming growth factor-β signalling molecules in the ECM. Defects in microfibrils are associated with acquired and inherited connective tissue disorders. In particular, mutations in the human FBN1 gene, which encodes fibrillin-1, are associated with a spectrum of diseases, including Marfan syndrome (MFS). One of the proposed initial steps in microfibril assembly is the interaction between the N- and C-terminal regions of fibrillin monomers. The minimal regions of human fibrillin-1 required for an interaction in vitro were previously identified: the four N-terminal domains, from the fibrillin unique N-terminal (FUN) domain to the third epidermal growth factor-like (EGF) domain (FUN-EGF3), and the three C-terminal calcium-binding EGF-like (cbEGF) domains (cbEGF41-43). Here, fragments corresponding to these regions were produced and shown to interact in pull-down and surface plasmon resonance assays. In addition, the structure of the FUN-EGF3 fragment was determined using nuclear magnetic resonance spectroscopy. This showed the novel structure of the FUN domain and the interdomain interfaces in this region of fibrillin. Combining structural and sequence conservation data may help to identify regions of FUN-EGF3 important for binding to cbEGF41-43. Here, the interaction was probed by site-directed mutagenesis. However, substituting individual residues in FUN-EGF3 with alanine did not abrogate binding to cbEGF41-43. Three MFS-associated residue substitutions were also introduced into the FUN-EGF3 fragment. While they did not abolish the interaction with cbEGF41-43, they did cause misfolding. Two of these substitutions, N57D and W71R, also resulted in the defective secretion of a larger N-terminal fragment by fibroblast cells, suggesting a potential mechanism of disease pathogenesis. Although specific residues involved in the N-C interaction were not identified here, the FUN-EGF3 structure will be vital for understanding the molecular surfaces involved in microfibril assembly and growth factor binding.
20
Thangavelu, Sonia G. "Structural Variations and Luminescence of UO22+ Hybrid Materials Containing N-donor Chelating Ligands and/or O-donor Assembly Linkers." Thesis, The George Washington University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3717926.
Full textAbstract:
This dissertation is based on the hydro(solvo)thermal syntheses and characterization of uranyl (UO22+) coordination polymers (CPs) via single-crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), and luminescence spectroscopy. The rich structural portfolio of uranyl CPs arises from the UO22+ cation’s tendency to undergo hydrolysis, and form uranyl oligomeric species (or secondary building units, SBUs). Because of hydrolysis, synthetic control of SBUs is difficult and more often then not, their solid-state crystallization is random and unpredictable. Thus, it is challenging to know what building unit will be observed in a uranyl CP.
Our strategy to address such challenges and potentially thwart hydrolysis is to use N-donor chelating ligands. These ligands offer potential chelating sites that may allow for direct coordination to UO22+ and thus essentially promote specific uranyl building units. The N-donor ligands chosen in our study are 2,2’:6,2”-terpyridine (TPY), analogs of 2,2’-bipyridine (BPY), 2,4,6-tripyridyl-s-triazine (TPTZ), and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (TPPZ). By restricting UO22+ speciation, assembly of aromatic or aliphatic O-donor linkers to available coordination sites on UO22+ allowed us to synthesize a series of uranyl CPs containing N-donor (TPY, TPTZ, BPY analogs) and O-donor co-ligands. These coordination polymers resulted in extended structures with unique structural topologies and luminescent features.
Depending on the choice of N- and O-donors, structural variations in the local UO22+ coordination sphere and global structure within a uranyl CP were observed. N-donor chelating ligands were also explored as guest molecules, in which a series of CPs containing TPTZ, BPY analogs, or TPPZ and different O-donor aliphatic or aromatic linkers were synthesized. These guests were found to stabilize the structure through non-covalent interactions or participate as charge balancing species. Beyond structural manipulation of our materials, we also studied UO22+ luminescence and lifetimes within our uranyl CPs. We observe that modifications on either the N- or O-donor (i.e. sterics, functional groups, and/or non-covalent interactions) or a change in the local and global structure of a CP influences UO2 2+ luminescence thus resulting in unique spectral signatures.
Given the influence of N-donors and O-donors on the structure and luminescence of an uranyl CP, we also explored the synthesis of uranyl complexes using N-donor BPY, 5,5’-dimethyl-2,2’-bipyridine (MeBPY), and TPY ligands exclusively via self assembly conditions in the presence of sunlight and ambient light. Unexpectedly, we observe the presence of peroxo ligands in our crystal structures. To explore the origin of the peroxo ligand, rigorous synthetic experiments were performed in which the presence of peroxo most likely arises from a mechanism consistent to photo-excitation of UO22+ .
21
Zhukhovitskiy, Aleksandr V. (Aleksandr Vadymovich). "Surface chemistry of N-Heterocyclic carbenes and the self-assembly, structure, and properties of polymer metal-organic cage gels." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105052.
Full textAbstract:
Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2016.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references.
Chapter 1. Introduction to Carbene Ligands in Surface Chemistry: From Stabilization of Discrete Elemental Allotropes to Modification of Nanoscale and Bulk Substrates In this chapter, we review the development of carbene surface chemistry from its inception through 2015, covering elemental allotrope substrates, nanomaterials, and bulk surfaces, as well as persistent and non-persistent carbenes. We synthesize from the reviewed reports a mechanistic understanding of this chemistry and outline the road ahead in this field. Chapter 2. Addressable Carbene Anchors for Gold Surfaces New strategies to access functional monolayers could augment current surface modification methods. Here we present addressable N-heterocyclic carbene (ANHC) anchors for gold surfaces and provide experimental and theoretical characterization of ANHC monolayers. Additionally, we demonstrate grafting of highly fluorinated polymers from surface-bound ANHCs. Chapter 3. Reactions of Persistent Carbenes with Hydrogen-Terminated Silicon Surfaces We report here the use of persistent aminocarbenes to functionalize via Si-H insertion reactions a range of hydrogen-terminated silicon surfaces: from model compounds, to nanoparticles, and planar Si(l 11) wafers. In particular, a cyclic(alkyl)(amino)carbene and an acyclic diaminocarbene underwent Si-H insertion, forming persistent C-Si linkages and thereby installing amine or aminal functionality in proximity to the surface. Our results pave the way for the further development of persistent carbenes as universal ligands for silicon and potentially other non-metallic substrates. Chapter 4. Cycloelimination of Imidazolidin-2-Ylidene N-Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable "NHC-CDI" Amidinates We report the discovery that 1,3-bis(aryl)imidazolidin-2-ylidenes, one of the most widely studied classes of N-heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic "NHC-CDI" amidinates upon heating to 100 °C in solution. The mechanism of this novel NHC decomposition process was studied in detail and enabled the rational synthesis of a new class of bench stable amidinates. Chapter 5. Toward Dynamic and Hierarchically Structured Polymer Gels: An Introduction to Polymer Metal-Organic Cage Gels Key challenges in polymer network/gel chemistry are overviewed. Polymer metal-organic cage gels capable of addressing some of these key challenges are introduced. Chapter 6. Highly Branched and Loop-Rich Gels Via Formation of Metal-Organic Cages Linked by Polymers We report here a new class of gels (called 'polyMOC' gels) assembled from polymeric ligands and metal-organic cages (MOCs) as junctions with M₂L₄ or M₁₂L₂₄ stoichiometries. The latter features increased branch functionality and large shear moduli, but also an abundance of elastically inactive loop defects that allow via ligand exchange the introduction of function at no cost to the gel's mechanical properties.
by Aleksandr V. Zhukhovitskiy.
Ph. D. in Organic Chemistry
22
Chaton, Catherine T. "Metal Binding Specificity and N-terminal Function of the Staphylococcal Biofilm Protein Aap." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin151092604272917.
Full text
23
Winges, Christoph [Verfasser], and Arthur [Akademischer Betreuer] Bartels. "Filtering the assembly map in algebraic K-theory and transfer reducibility of Z n Z / Christoph Winges ; Betreuer: Arthur Bartels." Münster : Universitäts- und Landesbibliothek Münster, 2014. http://d-nb.info/1141681617/34.
Full text
24
Tam, Yiu-yan, and 譚耀欣. "Design, synthesis and functionalization of luminescentalkynylplatinum(II) complexes of tridentate N-donor ligands asbuilding blocks for metallogelation and supramolecular assembly." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43223849.
Full text
25
Tu, Siyu. "Part I Asymmetric Allylic Alkylation Catalyzed by Pd-Dendron Complexes Part II Self-assembly of n-/p- type Heterojunction Nanomaterials." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306946050.
Full text
26
Natarajan, Kshama. "Part I- cluster assembly in protein bound iron-sulfur clusters ; Part II- solution structural studies on the N-terminus perforin /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487951907957761.
Full text
27
Sukumaran, Madhav. "Biophysical investigations of AMPA receptor N-terminal domain structure and function reveal mechanisms underlying receptor assembly, dynamics, and allosteric potential." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708278.
Full text
28
Mitsche, Matthew Alvin. "Interfacial properties of the n-terminal lipid-binding domains of apolipoprotein B and their role in triacylglyceride-rich lipoprotein assembly." Thesis, Boston University, 2012. https://hdl.handle.net/2144/12527.
Full textAbstract:
Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.ApolipoproteinB (ApoB) is the principal protein component of triacylglyceride (TAG)-rich lipoproteins that are responsible for distribution of hydrophobic lipids to peripheral tissues and are the precursors to low density lipoprotein (LDL). TAG-rich lipoprotein assembly is initiated by the N-terminus of ApoB co-translationally binding and remodeling the luminal leaflet of the rough-ER. In this thesis, the adsorption and interfacial remodeling of the two N-terminal lipid-binding domains of ApoB (ApoB6-13 and 813-17) were characterized at a triolein/water (TO/W) and TO/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/W interface using drop tensiometry. A method was developed to form a monolayer of POPC at a TO/W interface and protocols were developed to characterize the exchangeability, surface pressure (Π)-area isotherm, and exclusion Π (ΠEX) at a TO/W or TO/POPC/W interface. A model for the behavior of amphipathic α-helices at a lipid/water interface was investigated by comparing the N- and C- termini of ApoA-1 ([1-44]ApoA-1 (N44) and [198-243]ApoA-I (C46)) using these protocols. Both helical peptides had a Π dependent surface conformation and had a higher affinity for a TO/POPC/W interface than a TO/W interface. The N-terminal lipid-binding domain of ApoB (ApoB6-13), the α-helical domain (aHD), has 17 α-helices with a heterogeneous amphipathic cross-section. The second lipid-binding domain, the C-Sheet (ApoB13-17), is 6 amphipathic β-strands. The adsorption, stress response, and viscoelasticity of the αHD and C-Sheet domains were generally consistent with the behavior of model amphipathic α-helices and β-strands, respectively. The αHD domain had a higher affinity for a TO/POPC/W interface than a TOIW interface, while the C-Sheet had a higher affinity for a TO/W interface. POPC shielded the C-Sheet from binding TO. The αHD adsorbed to a TO/W interface in a compact conformation where only the N-terminal eight helices interacted with the surface. When the protein monolayer was decompressed, the C-terminal helices bound the lipid. When adsorbed ApoB6-13 was compressed, theN-terminal four helices were progressively expelled from the surface. The remodeling occurred at five distinct transition points where the helices rearranged. There was no evidence of major remodeling of the C-Sheet during expansion and compression. This evidence was used to develop a more detailed model for the initiation of TAG-rich lipoprotein assembly.
29
El, Samrout Ola. "Molecules at surfaces : formation, reactivity, assembly of (bio)molecules on external and internal surfaces of nanosized/nanostructured materials." Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS085.
Full textAbstract:
Cette thèse vise à étudier en profondeur la polymérisation des monomères Gly sur de la silice amorphe afin de mieux comprendre son mécanisme réactionnel, sa cinétique et les paramètres liés à la nature du produit de condensation obtenu dans différentes conditions environnementales. Dans la première partie, le comportement des différents groupes silanol de la silice a été étudié en profondeur par spectroscopie IR pour avoir un aperçu de la réactivité des groupes fonctionnels de la silice. Par la suite, la réaction de formation de liaison peptidique a été largement étudiée sous atmosphère contrôlée avec des mesures de spectroscopie IR in situ pour étudier le comportement des monomères Gly et ceux des groupes fonctionnels de la silice lors de l'adsorption sur la surface ainsi que pendant les étapes intermédiaires de polymérisation. . Un mécanisme d'adsorption/activation des monomères sur la silice suivi de la polymérisation en chaînes linéaires plus longues de poly-Gly a été suggéré. En utilisant la technique MS avec TGA, il a été possible d'évaluer le nombre de mers qui constituent les longs peptides linéaires obtenus sur la surface. De plus, le comportement du poly-Gly au contact de l'eau a également été étudié où les peptides se déplacent pour former des structures auto-assemblées. Dans la seconde partie, la réaction de polymérisation du Gly sur silice amorphe a été étudiée dans des environnements fluctuants : un système soumis uniquement à des fluctuations de température par rapport à un autre soumis à la fois à des fluctuations de température et d'humidité. Les données recueillies par IR in situ ont montré qu'un système soumis à des fluctuations de température et d'humidité représentait le système le plus favorable pour une polymérisation, Par la suite, un mécanisme d'allongement des chaînes linéaires dans des structures ordonnées et auto-assemblées avec des indications de une polymérisation matricielle a été suggérée. La dynamique structurelle des peptides linéaires ainsi que les différentes structures secondaires ont été évaluées au cours de la réaction. De plus, la résistance et la croissance des structures auto-assemblées sur la surface ont été étudiées pendant une durée prolongée de la réaction de polymérisation. Dans la troisième partie, une étude des paramètres qui déterminent la formation de peptides linéaires et de dimères cycliques (DKP) sur la surface de la silice lors du dépôt de Gly à partir des phases gazeuse et liquide a été réalisée. Concernant le dépôt de Gly en phase gazeuse, les monomères ont été déposés par dépôt chimique en phase vapeur sous flux d'argon sur des surfaces de silice de différentes surfaces spécifiques, sous forme vierge ou traitées thermiquement à différentes températures. Les résultats de la spectroscopie IR combinés à ceux de la TGA, de la spectroscopie Raman, de l'ATR, de la XRD et de l'analyse BET ont montré que la présence de types spécifiques de groupes silanol ainsi qu'un cadre renforcé avec de grands anneaux de siloxane favorisent la formation de peptides linéaires sur la silice. surface sur les cycliques. Concernant le dépôt à partir de la phase liquide, différentes charges de Gly ont été déposées sur de la silice de différentes surfaces spécifiques (SSA) en utilisant la méthode d'imprégnation par humidité naissante suivie d'une simple activation thermique. Le SSA de la surface de la silice montre un impact direct sur le type de produit de condensation obtenu et sur la croissance des cristallins en surface. Le rôle bénéfique des molécules d'eau dans la formation de peptides linéaires sur une silice à SSA relativement élevé a également été mis en évidence. Le DKP considéré jusqu'alors comme un produit cyclique sans intérêt a également été étudié sur des surfaces de silice amorphe. Les résultats ont montré que le DKP au lieu d'être un produit sans issue, il représente un dimère utile pour la prolongation rapide des peptides linéairesThis PhD thesis aims to deeply study the polymerization of Gly monomers on amorphous silica to better understand its reaction mechanism, kinetics, and parameters related to the nature of the condensation product obtained under different environmental conditions. In the first part, the behavior of the different silanol groups of silica were deeply studied by IR spectroscopy to have some insights on the reactivity of the silica functional groups. Subsequently, the peptide bond formation reaction was heavily studied under controlled atmosphere with in-situ IR spectroscopy measurements to investigate the behavior of the Gly monomers and the ones of the functional groups of silica upon adsorption on the surface as well during the intermediate steps of polymerization. A mechanism of adsorption/activation of monomers on silica followed by the polymerization into longer linear chains of poly-Gly was suggested. Using MS technique along with TGA, it was possible to evaluate the number of mers that constitute the long linear peptides obtained on the surface. Furthermore, the behavior of the poly-Gly upon contact with water was also studied where peptides move to form self-assembled structures. In the second part, the polymerization reaction of Gly on amorphous silica was studied under fluctuating environments: a system subjected only to temperature fluctuations in comparison with another one subjected to both temperature and humidity fluctuations. The data collected by in-situ IR showed that a system subjected to fluctuations of both temperature and humidity represented the most favor system for a polymerization, Subsequently, a mechanism about the elongation of the linear chains in ordered and self-assembled structures with indications of a templated polymerization was suggested. The structural dynamics of the linear peptides along with the different secondary structures were evaluated during the reaction. Moreover, the resistance and growth of the self-assembled structures on the surface were investigated for an extended duration of the polymerization reaction. In the third part, a study of the parameters that determine the formation of linear peptides and cyclic dimers (DKP) on silica surface upon Gly deposition from gas and liquid phases was carried out. Regarding the Gly deposition from gas phase, the monomers were deposited using chemical vapor deposition under argon flow on silica surfaces of different specific surface areas, in pristine form or thermal treated at different temperatures. The results of IR spectroscopy combined with the ones of TGA, Raman spectroscopy, ATR, XRD, and BET analysis, showed that the presence of specific types of silanol groups along with a framework enhanced with large siloxane rings favor the formation of linear peptides on silica surface over cyclic ones. Concerning the deposition from liquid phase, various Gly loading were deposited on silica of different specific surface areas (SSA) using incipient wetness impregnation method followed by a simple thermal activation. The SSA of silica surface shows a direct impact on the type of the condensation product obtained and on the growth of crystalline on the surface. The beneficial role of water molecules in the formation of linear peptides on a silica with a relatively high SSA was also highlighted. The DKP considered so far as an uninteresting cyclic product was also studied on amorphous silica surfaces. The results showed that DKP instead of being a dead-end product, it represents a useful dimer for the fast prolongation of linear peptides
30
Jones, Clinton D. "Poly(N-Isopropylacrylamide) based microgels : I Fundamental properties of core/shell microgels II Assembly and photothermal patterning of microgel colloidal crystals." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30355.
Full text
31
Au, Ka-man, and 區嘉雯. "Luminescent cyclometalated gold (III) complexes with ancillary N-heterocyclic carbene and alkynyl ligands : from design, synthesis, photophysics to supramolecular assembly and functions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hdl.handle.net/10722/207995.
Full textAbstract:
A library of luminescent cyclometalated gold(III) complexes containing
various bis-cyclometalating R-C^N^C ligands derived from 2,6-diphenylpyridine
and ancillary alkynyl ligands, [Au(R-C^N^C)(C≡CR’)], has been synthesized.
Some of the complexes have been structurally determined by X-ray
crystallography. These complexes were found to exhibit intense emission in
dichloromethane solution at 298 K, originating from metal-perturbed triplet
intraligand (IL) excited states of the R-C^N^C ligand, with substantial charge
transfer character from the aryl moiety to the pyridyl ring. In the presence of
electron-rich alkynyl ligands, the emission origin could be switched to an
alkynyl-to-cyclometalating ligand ligand-to-ligand charge transfer (LLCT) excited
state. This class of complexes was also demonstrated to show rich
electroluminescence properties as emitters in organic light-emitting devices. In
addition, the supramolecular assembly of this class of complexes has also been
revealed in gelation studies.
N-Heterocyclic carbenes have been incorporated into the gold(III) metal
center to prepare a series of luminescent mononuclear and dinuclear gold(III)
complexes, [{Au(C^N^C)}n(NHC)](PF6)n and [{Au(tBuC^N^CtBu)}n(NHC)]-
(PF6)n
(n = 1, 2). The X-ray crystal structures of most of the complexes have been
determined. The emissions of these complexes were assigned to originate from the
metal-perturbed intraligand excited state of the bis-cyclometalating ligand. One of
the C2-bridged dinuclear complexes was found to exhibit two distinct reduction
couples, tentatively correlated to the presence of significant intramolecular π-π
interaction in the complex.
Two novel series of luminescent mononuclear alkynylgold(III) complexes,
[Au(C^N)(C≡CR)2] (HC^N = 2-phenylpyridine (Hppy) and derivatives) and
[Au(C^N^N)(C≡CR)]PF6 (HC^N^N = 6-phenyl-2,2’-bipyridine and derivatives),
have been synthesized. Some of the X-ray crystal structures have been determined.
The former class of complexes with bidentate C^N ligands has been observed to
show tunable emission spanning across the visible spectrum from 462 to 697 nm.
With the exception of [Au(ppy)(C≡C-C6H4-NH2-p)2] which showed a low-energy
band originated from a 3LLCT [π(C≡C-C6H4-NH2)→π*(C^N)] excited state, all
complexes exhibited vibronic-structured emission bands originated from the
intraligand transition of the cyclometalating C^N ligand in dichloromethane
solution at 298 K. On the other hand, most of the complexes with the tridentate
C^N^N-type ligand have been observed to exhibit vibronic-structured emission
bands attributed to the intraligand transition of the C^N^N ligand in
low-temperature butyronitrile glass.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
32
Tam, Yiu-yan. "Design, synthesis and functionalization of luminescent alkynylplatinum(II) complexes of tridentate N-donor ligands as building blocks for metallogelation and supramolecular assembly." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43223849.
Full text
33
Cao, Guoqing. "Studies on the membrane protein assembly in Escherichia Coli : N-terminal tail translocation and the role of the electrochemical potential in membrane insertion /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487861796818543.
Full text
34
Tanh, Jeazet Harold Brice. "Metallo-supramolecular Architectures based on Multifunctional N-Donor Ligands." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-39665.
Full textAbstract:
Self-assembly processes were used to construct supramolecular architectures based on metal-ligand interactions. The structures formed strongly depend on the used metal ion, the ligand type, the chosen counter ion and solvent as well as on the experimental conditions. The focus of the studies was the design of multifunctional N-donor ligands and the characterization of their complexing and structural properties. This work was divided into three distinct main parts: The bis(2-pyridylimine), the bis(2-hydroxyaryl) imine and the tripodal imine / amine ligand approach.
In the first part a series of bis(2-pyridylimine) derivatives having different linking elements were employed as building blocks for novel supramolecular architectures. Reaction of individual d-block metal salts with these ligands has led to the isolation of coordination polymers, a metallamacrocycle, double-stranded helicates, triple-stranded helicates as well as of circular meso-helicates. The nature of the spacer in the Schiff base ligands, the noncovalent weak interactions, such as hydrogen bond, face-to-face π-π and edge-to-face CH-π interactions, are all important factors influencing the architecture of the final products.
Topological control of the assembly process of the hexanuclear meso-helicates is clearly associated with the bidentate coordination of the sulfate anion which directs the formation of a double- rather than a triple-stranded helicate around the octahedrally coordinated Cu(II). Surprisingly, the variation of the linker function in the ligands, which significantly changes the linking angle of the pyridylimine strands, has only a little influence of the resulting structure. Also the use of a mixture of ligands does not influence the meso-helicate topology; the result is the symmetrically mixed meso-helicate.
The new iron(II) triple helicate [Fe2(L5)3](PF6)4 14 {L5 = bis[4-(2-pyridylmethyleneimino)phenyl]-1,1-cyclohexane} in its chloride form binds strongly to DNA as confirmed by induced circular dichroism signals in both the metal-to-ligand charge transfer (MLCT) and in-ligand bands of the helicate. The induced CD spectrum gives some evidence that [Fe2(L5)3]4+ interacts with the DNA in a single binding mode, which is consistent with major groove binding.
The cytotoxicity of the new iron(II) triple helicate 14 was evaluated on human lung cancer A549 cells and compared with that of cisplatin and that of the previously reported iron(II) triple helicate [Fe2(L1)3]4+{L1 = bis[4-(2-pyridylmethyleneimino)phenyl]methane}. The first results show some distinguishing features for 14 obviously caused by the existing structural differences of the complexes.
In the second part of the thesis, novel uranyl complexes of the bis(2-hydroxyaryl) imine ligands have been synthesized and characterized. 1D coordination polymers and mononuclear structures were formed. In all complexes a distorted hexagonal bipyramidal coordination geometry around the uranyl centre is observed. The imine nitrogen atoms of the ligands do not bind to the metal centre but interact strongly with the hydroxy group via H-bonding. DFT calculations made with L8 ( α,α’-Bis(salicylimino)-m-xylene) are in good agreement with the X-ray crystal structure data. Liquid-liquid extraction studies involving selected ligands and Eu(III) or U(VI) indicate remarkably high selectivity for U(VI) over Eu(III) at weak acidic pH conditions. We believe that the study made opens up new possibilities for uranyl ion extraction which could be interesting in view of the treatment of nuclear waste.
In the third part of the thesis, a series of multifunctional tripodal ligands with different N-donor centres were used for U(VI) and lanthanide, Nd(III), Eu(III) and Yb(III), binding and extraction. Reaction of these metal ions with selected tripodal ligands afforded complexes which were characterized by ESI mass spectroscopy. The complex composition was found to be 1:1 in all cases. The extraction behaviour of the tripodal ligands towards Eu(III) and U(VI) was studied both in the absence and presence of octanoic acid as co-ligand using the extraction system Eu(NO3)3 or UO2(NO3)2–buffer–H2O/ ligand–CHCl3. These separation systems show a remarkably high selectivity for U(VI) over Eu(III). It is interesting to note that the addition of the octanoic acid to the extraction system leads to high synergistic effects. A series of Eu(III) extraction experiments were done to clarify the composition of the extracted complexes. The results clearly point to the formation of various species with changing composition.
35
Cámara, Hernández Verónica. "Nuevos alquinil complejos y carbenos N-Heterocíclicos de oro(I). Autoensamblaje de complejos heteronucleares usando metaligandos de oro(I)= New alkynyl and N-Heterocyclic gold(I) complexes. Self-assembly of heteronuclear complexes usin gold(I) metallaligands." Doctoral thesis, Universidad de Murcia, 2013. http://hdl.handle.net/10803/128934.
Full textAbstract:
Objetivos: Los objetivos planteados para esta tesis han sido la síntesis y caracterización de nuevos alquinil complejos y carbenos N-Heterocíclicos (NHC) de oro(I), así como la utilización de algunos de estos complejos como metalaligandos en reacciones de ensamblaje de nuevos complejos heteronucleares. También nos planteamos llevara a cabo estudios estructurales de los nuevos complejos preparados, así como estudios de su comportamiento en disolución, y sus propiedades fotofísicas. Metodología: En primer lugar, se ha llevado a cabo la síntesis de nuevos alquinil complejos y carbenos N-Heterocíclicos de oro(I) utilizando métodos sintéticos estándar, aunque también hemos desarrollado nuevos métodos de síntesis de alquinil NHC complejos de oro(I). Para llevar a cabo el estudio del autoensamblaje de complejos heteronucleares, hemos utilizado alquinil complejos de oro(I) funcionalizados con grupos 2,2'-bipiridilo o 2,2':6',2"-terpiridilo previamente descritos por nuestro grupo de investigación, así como otros nuevos diseñados especialmente para dichos estudios. Los nuevos complejos preparados han sido caracterizados mediante análisis elemental, espectroscopia infrarroja (IR), espectroscopia de resonancia magnética nuclear (NMR) y espectrometría de masas (MS), así como por difracción de rayos X en monocristal, en aquellos casos en que ha sido posible. También se ha realizado un estudio de sus propiedades quirópticas por espectroscopia de dicroísmo circular, y de sus propiedades fotofísicas mediante espectroscopia electrónica de absorción o emisión. Resultados o Conclusiones: Se han sintetizado y caracterizados nuevos alquinil complejos de oro(I) derivados de la 4- y la 5-etinil-2,2'-bipiridina. Estos complejos incluyen complejos mononucleares con ligandos fosfina o isonitrilo, complejos dinucleares con ligandos difosfina o dicarbeno puente, y un complejo aniónico con dos unidades bipiridilo. Los primeros dialquinilos de oro(I) con ligandos carbenos N-Heterocíclicos (NHC) han sido preparados mediante tres métodos distintos, dos de los cuales han sido utilizados por primera vez para la síntesis de NHC complejos de oro(I). Del estudio de las propiedades fotofísicas se ha concluido que los complejos dinucleares (cloro)NCH de oro(I) preparados son luminiscentes a temperatura ambiente en estado sólido y sus emisiones son similares a las observadas en sus análogos mononucleares. Mientras que la mayoría de los dialquinil complejos de oro(I) son luminiscentes a temperatura ambiente tanto en estado sólido como en disolución, en particular aquellos derivados de aril- o heteroaril alquinos. De las reacciones de ensamblaje con ligandos monoalquinílicos derivados de la etinilbipiridina se han obtenido mezclas en equilibrio de los isómeros fac y mer de los complejos pseudooctaédricos donde tres ligandos se coordinan a un mismo metal. En algunos casos se ha observado una dependencia anómala del equilibrio con el disolvente que se ha explicado como consecuencia de la formación de dímeros fac,fac y de efectos de solvatación. Por otro lado, cuando los metalaligandos con dos unidades oro-etinil-bipiridina conectadas por una difosfina reaccionan con Fe(II), Zn(II) o Co(II), se obtienen complejos de tipo helicato triple selectivamente. La diasteroselectividad del proceso de autoensamblaje se ha estudiado en las reacciones de Fe(II) con metalaligandos quirales, y la configuración absoluta de los principales diastereoisómeros ha sido determinada por espectroscopia de dicroísmo circular. Además los nuevos helicatos de zinc(II) emiten en estado sólido y en disolución a temperatura ambiente. También se han preparado complejos trinucleares de Zn(II) y Co(II) con ligandos terpiridina funcionalizados, así como polímeros de coordinación heterometálicos con estructuras de tipo "varilla rígida". Por último, se ha llevado a cabo la síntesis y caracterización de macrociclos mono- y dinucleares de Ag(I) y Au(I), usando ligandos dicarbeno conectados por cadenas alquílicas de distintas longitudes, lo que nos ha permitido relacionar la longitud de la cadena con la estabilidad de cada tipo de macrociclo y observar a su vez el equilibrio entre ambos tipos de macrociclos. Además, se ha llevado a cabo la síntesis y caracterización del primer complejo de Au(III) con un ligando dicarbeno quelato en disposición trans.Objectives: The main aims of this thesis have focused on the synthesis of new types of alkynyl and N-Heterocyclic carbene (NHC) gold(I) complexes, as well as on the study of coordination-driven self-assembly of complexes presenting helical or rod-like structures using gold(I) metallaligands and metal cations as building blocks. In addition, we were interested in the study of new structural motifs, in particular those derived from aurophilic interactions, as well as in the study of the solution behavior and the photophysical properties of the new compounds. Methodology: Some of the new alkynyl and NHC gold(I) complexes have been prepared by using reported synthetic methods. In addition, we have developed new synthetic methods for the preparation of a new type of dinuclear alkynyl gold(I) complexes containing bis(NHC) ligands. We have used gold(I) alkynyls derived from 2,2'-bipyridine or 2,2':6,6'-terpyridine as metallaligands for the self-assembly studies, some of which were previously described by our group, but other have been specifically designed for these studies. The new complexes have been characterized by elemental analysis, infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS). Crystal structure determinations by X-ray diffraction were carried out for representative members of most of the new families of compounds prepared. The absolute configuration of the helical complexes was determined by circular dichroism spectroscopy, and the photophysical properties of several families of compounds were studied by using absorption or emission electronic spectroscopy. Results and Conclusions: Firstly, new alkynyl gold(I) metallaligands derived from 4- or 5-ethynyl-2,2'-bipyridine have been synthesized and characterized. These include mononuclear complexes with isonitrile or phosphine ligands, dinuclear complexes with bridging diphosphine or dicarbene ligands, and an anionic complex containing two bipyridine units. The first dinuclear gold(I) alkynyls containing bridging bis(NHC) ligands have been prepared by three different methods, two of which have been used for the first time in gold carbene chemistry. Most of these dinuclear alkynyl gold(I) complexes are luminescent at room temperature, in particular those derived from aryl- or heteroaryl alkynes, and their emissions have been assigned to singlet and triplet ligand-based pi-states, with little participation of the gold orbitals. The reactions of monoalkynyl gold(I) complexes derived from ethynyl-bipyridine and Fe(II), Co(II) or Zn(II) cations give mixtures of fac- and mer-pseudooctahedral complexes, where three ligands are coordinated to the same metal center. In some cases, we observed an anomalous solvent-dependence of the equilibrium, which has been explained by solvation effects and formation of fac,fac-dimers. On the other hand, metallaligands containing two gold-ethynyl-bipyridine units linked by a bridging diphosphine, react with Fe(II), Zn(II) or Co(II) salts to give selectively triple helicates containing two gold atoms in each strand. Diastereoselective self-assembly was observed in the reactions of chiral metallaligands with Fe(II), and the absolute configurations of the main diastereomers were determined by circular dichroism spectroscopy. In addition, the zinc(II) helicates are emissive in both solid state and solution at room temperature. New trinuclear Zn(II) or Co(II) complexes and two rod-shaped coordination polymers containing alternated Au and Zn(II) or Co(II) metal centers in its main chain have been synthesized by reaction of the corresponding M(II) cations with terpyridine-functionalized metallaligands. Finally, we have prepared the first family of Ag(I) and Au(I) dicarbene complexes, which exist as mononuclear and dinuclear metallamacrocycles in equilibrium. Some of these complexes have been isolated and the mononuclear/dinuclear interconversion equilibrium has been studied. In addition, an unprecedented Au(III) complex containing a trans-spanning dicarbene ligand has been prepared.
36
Joder, Karin N. [Verfasser], Thomas Akademischer Betreuer] Kiefhaber, Michael [Akademischer Betreuer] [Groll, and Christian F. W. [Akademischer Betreuer] Becker. "Intramolecular and intermolecular diffusion processes in protein folding and assembly / Karin N. Joder. Gutachter: Thomas Kiefhaber ; Michael Groll ; Christian F. W. Becker. Betreuer: Thomas Kiefhaber." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1014330556/34.
Full text
37
Costa, Eunice Margarida Santos. "Bioactive beads for local sensing of proteases in 3D engineered tissues." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/7866.
Full textAbstract:
Dissertação para obtenção do Grau de Doutor em
Bioengenharia (MIT)Metalloproteinases are endopeptidases involved in mediating interactions between cells and the extracellular microenvironment, being ascribed to several cellular processes and signaling events. The dysregulation of protease activity has been correlated with several diseased states, such as cancer and arthritis; hence metalloproteinases constitute potential therapeutic targets. However, these therapies have thus far shown little success due to an ill-defined knowledge of the complex regulatory network dictating protease activity. The availability of 3D in vitro tissues in which cells are able to closely recapitulate native physiological behavior, has been essential for studying tissue physiology and for drug development. Therefore, the design of real-time specific protease activity sensors amenable to 3D tissue constructs would be a valuable tool for understanding fundamental aspects of protease biology as well as monitor drug activity towards proteases. Herein, bio-friendly technologies were combined for the preparation of cell-interactive hydrogel particles functionalized with metalloproteinase fluorogenic sensors to monitor local protease activity in 3D cell cultures. Well-defined and cell-sized smart microgels were prepared by synthesis in supercritical carbon dioxide, a green chemistry approach that enables pure and biocompatible materials, without extensive purification steps. Further aqueous complexation of macromolecules or layer-by-layer assembly of polyelectrolytes was used for the preparation of cell-interactive coatings and for fine-tuning the microbeads physical properties of swelling, stimuli-responsive behavior and overall net charge; being a potential strategy to adjust microbead differential permeability to proteases and thus the sensing construct specificity. The impact of the macromolecules deposition on the smart microbeads behavior was assessed by FT-IR spectroscopy analysis. Finally, protease sensing function was conferred to the microbeads by complexation of a modified polymer or by directly tethering probes on the native microbead. The successful activation of the microbeads by a model protease constitutes a significant step towards the validation of this technological basis for preparing local protease probes for 3D engineered tissues.
38
Meijer, Gerard Johannes. "Appèl met die oog op regsherstel : 'n Gereformerd kerkregtelike studie / G.J. Meijer." Thesis, North-West University, 2006. http://hdl.handle.net/10394/78.
Full textAbstract:
Conflict and injustice are endemic to the imperfectness of human existence, and the Church of
Christ is not immune to them. Various means can be adopted to solve conflict in the church.
This study is concerned with legal restitution through calling at a major assembly, as provided
in Article 31 Church Order.
Statement of the problem
Biblical grounds for the right of appeal are largely lacking in the Reformed church polity. In
addition, there is no clear definition of the concept 'injustice' in Article 31 Church Order. In the
case of appeals brought to a synod of the RCSA, the verdict usually contains no guidelines on
how the matter should be dealt with in practice in order to effect reconciliation. Consequently,
the outcome of an appeal does not necessarily contribute to the solution and restoration of
broken relationships.
Aim and method of work
This study endeavours to
determine the biblical grounds of appeal and legal restitution in Reformed church polity
through scriptural study;
establish the essence and content of appeal in Reformed church polity; and
examine the functioning, treatment and application of appeal with a view to legal restitution
in the RCSA, and address shortcomings in this respect.
Findings
Legal restitution occurs when
an appeal is judged according to clearly defined norms;
the verdict rests on the same norms; and
the necessary steps had been taken to reconcile the parties involved in the appeal
Organisation
The study is divided into four main sections:
biblical foundation of appeal with a view to legal restitution;
historical development of appeal with a view to legal restitution;
fundamental definition of appeal with a view to legal restitution; and practical treatment of appeal with a view to legal restitution. Finally, the research questions born from the problem statement are answered by means of concluding statements.Thesis (Ph.D. (Church Polity))--North-West University, Potchefstroom Campus, 2006.
39
Polander, Lauren E. "Organic charge-transport materials based on oligothiophene and naphthalene diimide: towards ambipolar and air-stable n-channel organic field-effect transistors." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45849.
Full textAbstract:
To better understand the physical and electronic properties of donor and acceptor-based structures used in organic electronic applications, a variety of oligothiophene and naphthalene diimide-based small conjugated molecules were designed, synthesized, and characterized. The materials were initially synthesized using oxidative copper-chloride coupling reactions, palladium-catalyzed amination reactions, Friedal-Crafts acylations, Negishi coupling reactions, and Stille coupling reactions. Once isolated, the physical properties of the compounds were characterized through a combination of X-ray crystal structure, thermogravimetric analysis, differential scanning calorimetry, UV-vis. absorption spectroscopy, cyclic voltammetry, and differential pulse voltammetry, along with comparison to quantum-chemical calculations. In some cases, the radical cations or radical anions were generated by chemical oxidation and analyzed by vis-NIR spectroscopy. Furthermore, the electronic properties of the materials were investigated through incorporation as solution-processed active layers in organic field-effect transistors. Multiple examples exhibited hole- and / or electron-transport properties with electron mobility values of up to 1.5 cm²V⁻¹s⁻¹, which is among the highest yet reported for an n-channel OFET based on a solution-processed small molecule.
40
Jiang, Xuan. "Self-assembly and spin-delocalization of copper clusters built on amidinate ligands and symmetry-reinforced cooperativity in tris(N-salicylideneamine)s for conformational switching and chemical sensing." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3344578.
Full textAbstract:
Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008.Title from home page (viewed Oct 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1017. Adviser: Dongwhan Lee. Includes supplementary digital materials.
41
Maslovskis, Antons. "Responsive hydrogels using self-assembling polymer-peptide conjugates." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/responsive-hydrogels-using-selfassembling-polymerpeptide-conjugates(ca090402-aaa1-4729-8d0d-76dd07401521).html.
Full textAbstract:
Stimuli-responsive polymers and self-assembling peptides represent two classes of materials with interesting properties and great potential to be used as biomaterials. The conjugation of polymer with peptide offers a way to combine the controlled chemical, mechanical, and thermal properties of polymer with the functionality of designed bioactive group. Pure hybrid materials with the characteristics of individual components or systems containing hybrid materials became attractive for applications in drug delivery and tissue engineering. This work focused on systems where the thermo-responsive properties of a polymer were combined with the gelling properties of two different ionic-complementary peptides via conjugation. The prototypical thermo-responsive polymer poly(N-isopropylacrylamide) (PNIPAAm) was chosen due to its lower critical solution temperature (LCST) ~32°C being close to body temperature. Ionic-complementary oligo-peptides, containing the alternating hydrophobic/hydrophilic and charged/uncharged amino acids, phenylalanine (F), glutamic acid (E) and lysine (K), were selected as they are known to form β-sheet rich fibrillar networks at low concentrations. Two peptide sequences with different charge distribution were chosen: FEFEFKFK and FEFKFEFK which form self-supporting gels at ~17 and 10 mg ml-1 respectively. Polymer-peptide conjugates were used to confer self-assembling and thermo-responsive behaviour to the system.Thermo-responsive PNIPAAm-rich hydrogels were obtained by targeting different degrees of functionalisation of PNIPAAm with the self-assembling peptides. Two series of such systems were prepared by using either a thiol-modified FEFEFKFK or a thiol-modified FEFKFEFK peptide as the chain-transfer agent in the free radical polymerisation of NIPAAm. The resulting polymer/conjugate mixtures were studied by proton nuclear magnetic resonance (1H NMR). The polymer/conjugate ratios were calculated and showed that the conjugate fraction in the mixtures increased with increasing concentration of peptide used for the polymerisation. Static light scattering (SLS) and viscometry showed the aggregation of the polymer/conjugate mixtures presumably due to the presence of peptide. The values from gel permeation chromatography (GPC), which were mostly attributed to the unconjugated polymers, were higher than those obtained from 1H NMR and centrifugation for the conjugates. The polymer/conjugate mixtures formed self-supporting gels where the critical gelation concentration decreased with increasing conjugate content. Oscillatory rheology experiments confirmed gels had formed and revealed that their elastic modulus, G' varied from ~ 10 to 400 Pa depending on the sample. TEM and AFM studies proved the formation of β-sheet fibres of ~ 4.5 ± 1.5 nm in diameter. The PNIPAAm-rich hydrogels were also characterised by micro DSC to reveal their thermo-responsiveness and phase separation and showed the LCST at ~ 30°C. The results of the study showed that varying the peptide sequence did not have an effect on thermal, mechanical or morphological properties of the hydrogels. By exploiting the self-assembly of the ionic-complementary peptides, it was possible to create PNIPAAm-rich, thermo-responsive hydrogels with controllable properties.Further in the study pure PNIPAAm-FEFEFKFK conjugate was incorporated into the FEFEFKFK peptide matrix to create peptide-rich thermo-responsive composite gels. Two series of the composite gels were prepared by varying separately the peptide matrix and polymer-peptide conjugate concentration. Micro DSC measurements revealed an endothermic peak at ~ 30ºC characteristic of the LCST of PNIPAAm. Oscillatory rheology studies showed that the composite gels became stronger with increasing conjugate concentration (G' ~ 20 - 200 Pa). Network morphology was studied by SANS. Using contrast variation and contrast matching techniques it was possible to distinguish between the peptide fibres and the PNIPAAm chains. Below and above the LCST the scattering curves showed a q-1 behaviour which is typical of rod-like objects. TEM and AFM also proved the formation of fibres of ~4.0 ± 0.8 nm and ~4.5 ± 1 nm respectively. AFM studies showed that the fibres of the composite gels were decorated with polymer chains. The thermo-responsiveness and the gelation properties of these conjugate-based scaffolds have potential for use as drug delivery vehicles or tissue engineering scaffolds.
42
Asencio, Hernandez Julia. "Novel approaches in NMR and biophysics for the study of complex systems : application to the N-terminal domain of the androgen receptor." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ013/document.
Full textAbstract:
Cette thèse vise à réaliser une étude approfondie sur le développement de méthodologies pour l’analyse de systèmes complexes. Cela comprend l’étude des systèmes hors d’équilibre, des systèmes d’auto-assemblage, et les systèmes biologiques désordonnés. Les méthodes développées recouvrent principalement la RMN, tel que la mesure de diffusion (DOSY) mais également d’autres techniques telles que la spectrométrie de masse, le dichroïsme circulaire (CD), la microscopie électronique (EM) et diffusion des rayons X aux petits angles (SAXS). La partie N-terminale du récepteur des androgènes (AR) est utilisée comme un système complexe. D’après la littérature, il est connu que cette région joue un rôle important pour l’activité du récepteur, et elle est également décrite comme étant intrinsèquement désordonnée. Les résultats que j’ai acquis durant la thèse m’ont permis d’identifier une courte région de ce domaine, impliquée dans la formation réversible de fibres amyloïdes, par modulation des conditions d’oxydo-réduction du milieu. Les résultats révèlent un aspect inconnu du mécanisme de ARMy PhD project was focused on the development of methods for the analysis of complex systems and their biophysical characterization. This includes the study of large chemical libraries, self assembly systems, protein-ligand interaction studies and disordered biological systems. A wide range of biophysical methods were used for this purpose. Specially, Nuclear Magnetic Resonance(NMR) but also other techniques such as mass spectrometry, circular dichroism (CD), electron microscopy (EM) and small angle X-ray scattering (SAXS). The N-terminal Domain of the Androgen Receptor is studied as an example of a complex system. This region plays an important role in receptor activity, and is also described as being intrinsically disordered. The results obtained during my thesis shown a short conserved region involved in the amyloid fibers formation under oxidative conditions. These results open new possibilities to understand the mechanism of the AR activity
43
Acharya, Rajendra. "Synthesis, Characterization and Photophysical Studies of Porphyrin and N-Confused Porphyrin Derivatives and Self-assembled Nano-Morphologies." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1376061548.
Full text
44
Khutia, Anupam [Verfasser], Bernhard [Akademischer Betreuer] Lippert, and Jens [Gutachter] Müller. "Supramolecular Chemistry of Metal Ions and Nitrogen Based Ligands including Pyrimidine Nucleobases : Self-assembly, Metallacalix[n]arenes, Host-Guest Chemistry, Hydrogen Bonding, pKa Values / Anupam Khutia. Betreuer: Bernhard Lippert. Gutachter: Jens Müller." Dortmund : Universitätsbibliothek Dortmund, 2011. http://d-nb.info/1103231626/34.
Full text
45
Pino, Guillaume. "Synthèse et auto-assemblage de copolymères à blocs à paramètre d’interaction de Flory-Huggins élevé." Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0098.
Full textAbstract:
Cette thèse porte sur la synthèse de copolymères à blocs (BCPs) à haut pouvoir de ségrégation pour des applications en nanolithographie. La voie de synthèse qui a été retenue est la polymérisation radicalaire contrôlée par les nitroxydes ou NMP. Parmi tous les copolymères à blocs synthétisés, nous avons choisi de nous intéresser plus particulièrement à l'association de blocs 'hydrophile' et 'hydrophobe' à squelettes polystyrène. Le bloc hydrophile poly(3,4-dihydroxystyrène) (PDHS) s'est montré très intéressant en association avec les blocs poly(4-tertbutylstyrène) (PtBS) et poly(4-triméthylsilylstyrène) (PTMSS) formant respectivement les copolymères à blocs PDHS-b-PtBS et PDHS-b-PTMSS. Ainsi des valeurs de χ très élevées ont pu être quantifiées de l'ordre de 0,7 par exemple pour le PDHS-b-PtBS. L'avantage du bloc PTMSS tient au fait qu'il a permis d'amplifier le phénomène de contraste en gravure. Le bloc PDHS a ensuite été remplacé par le poly(4-méthylétherglycérolstyrène) (PMGS) afin de faire varier notamment les caractéristiques thermiques et d'étudier leur effet sur l'auto-assemblage de copolymères PtBS-b-PMGS. Enfin, les capacités d'infiltration spécifique du bloc PDHS par un précurseur métallique ont mis en évidence la formation d'un masque dur et d'un réseau double oxyde pour respectivement le PDHS-b-PtBS et le PDHS-b-PTMSSThis thesis concerns the synthesis of block copolymers (BCPs) with high segregation power for nanolithography applications. The main synthesis patway that has been followed is the controlled radical polymerization by nitroxides or NMPs. Among all the synthesized block copolymers, we have chosen to focus on the association of 'hydrophilic' and 'hydrophobic' blocks with polystyrene backbones. The hydrophilic poly(3,4-dihydroxystyrene) (PDHS) block has proved to be very interesting in association with the poly(4-tertbutylstyrene) (PtBS) and poly(4-trimethylsilylstyrene) (PTMSS) blocks forming respectively the PDHS-b-PtBS and PDHS-b-PTMSS block copolymers. High χ values could thus be quantified in the range of 0.7 for PDHS-b-PtBS, for example. The main advantage of the PTMSS block is about the contrast amplification during etching. The PDHS block was then replaced by poly(4-methyletherglycerolstyrene) (PMGS) in order to vary, in particular, the thermo-mechanical features and to study in particular their effect on the self-assembly of PtBS-b-PMGS copolymers. Finally, the specific infiltration capacities of the PDHS block by a metallic precursor highlighted the formation of a hard mask and a double oxide network for PDHS-b-PtBS and PDHS-b-PTMSS respectively
46
Pithan, Linus. "On the role of external stimuli to tailor growth of organic thin films." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17749.
Full textAbstract:
In dieser Arbeit werden neue Strategien zur Wachstumskontrolle funktionaler organischer Dünnschichtmaterialien aufgezeigt, mit denen sich die Eigenschaften molekularer Schichtsysteme gezielt beeinflussen lassen. Ein Fokus liegt dabei auf der Untersuchung des Einflusses von optischen Feldern auf das Wachstumsverhalten. Ein weiterer Schwerpunkt wird auf das Grundlagenverständnis von thermisch aktivierten, kinetischen Prozessen, die die Morphologie während und nach dem Schichtwachstum beeinflussen, gelegt. Zuerst wird am Beispiel des molekularen Halbleiters Sexithiophen (6T) gezeigt, wie sich Kontrolle über das Kristallphasengleichgewicht während des Wachstums auf Kaliumchlorid (KCl) erzielen lässt. Im zweiten Teil der Arbeit wird eine neue Herangehensweise zur direkten Ausrichtung von Molekülkristallen im optischen Feld während ihrer Entstehung studiert. Am Beispiel von Tetracene wird gezeigt wie sich so optische anisotrope Absorptionseigenschaften von Molekülen dazu nutzen lassen den Brechungsindex eines polykristallinen Films lokal durch ein photolitographisches Verfahren zu beeinflussen. Im dritten Teil wird der Einfluss von dynamisch variierenden Wachstumsbedingungen während des Schichtwachstums von PTCDI-C8 studiert. Es wird gezeigt, dass sich die Oberflächenrauigkeit stark reduzieren lässt, indem zu Beginn des Wachstums jeder individuellen molekularen Monolage die Nukleationsdichte stark erhöht und in den darauf folgenden Wachstumsphasen die Diffusivität gezielt gesteigert wird. Im vierten Teil wird das Diffusionsverhalten von n-Alkan Schichten unter thermischen Einflüssen betrachtet. Es wird gezeigt, dass die inhärente molekulare Anisotropie von C44H90 Molekülen (TTC) sowie die sehr geringe, stark anisotrope, Oberflächenenergie dieses Materials ein ungewöhnliches Diffusionsverhalten auslöst.The research performed in the framework of this thesis focuses on new strategies to effectively control the growth of crystalline thin films of functional organic molecules and attributes the quest for additional growth control parameters in organic molecular beam deposition (OMBD). First the influence of light on the growth process of the sexithiophene (6T) is studied. We find that 6T thin films deposited as conventional in dark environments on KCl exhibit a bimodal growth with phase coexistence of two crystal polymorphs. In contrast, films grown under illumination with 532 nm light show increased phase purity. Further, we establish light-directed molecular self-assembly (LDSA) to generate permanently aligned thin films of tetracene (C18H12) and demonstrate direct patterning with light. Polarized light illumination leads to azimuthally photoaligned films on isotropic, amorphous substrates. Thus, LDSA can be regarded as a new degree of freedom in the quest for control-parameters in organic thin film growth. Next the impact of dynamic temperature oscillations on the time scales of molecular monolayer growth during organic molecular beam deposition is discussed. We strongly increase the island density during nucleation and selectively increase interlayer diffusion at later stages of monolayer growth. We analyse the interplay between molecular interlayer transport and island sizes to understand kinetic processes during growth. In a fourth experiment we show how thermal annealing can be used to improve smoothness and to increase the lateral size of crystalline islands of n-alkane (TTC, C44H90) films. We employ real-time optical phase contrast microscopy to track the diffusion across monomolecular step edges which causes the unusual smoothing during annealing. We rationalise the smoothing behaviour with the highly anisotropic attachment energies and low surface energies of TTC.
47
Charbonneau, Céline. "Structures et propriétés rhéologiques d’hydrogels à dynamique contrôlée obtenus par l’auto-assemblage de copolymères à blocs amphiphiles." Thesis, Le Mans, 2012. http://www.theses.fr/2012LEMA1016/document.
Full textAbstract:
Les copolymères à blocs amphiphiles sont des macromolécules composées d’au moins un bloc hydrophile lié chimiquement à un ou plusieurs blocs hydrophobes. En milieu aqueux, ils s’auto-associent pour former des micelles dont les cœurs constitués des blocs hydrophobes sont protégés de l’eau par une couronne constituée des blocs hydrophiles hydratés. La majorité des copolymères à blocs amphiphiles génèrent dans l’eau des micelles « gelées » ne présentant aucun échange de chaînes entre elles. Ceci vient du fait que l’énergie nécessaire pour extraire un bloc hydrophobe du cœur des objets est beaucoup trop importante. Par conséquent, les caractéristiques des micelles sont plus contrôlées cinétiquement que thermodynamiquement. Pour diminuer cette énergie nous avons incorporé des unités hydrophile acide acrylique (AA) dans le bloc hydrophobe de poly(acrylate de n-butyle) (PnBA). L’incorporation de 50% molaire d’unités AA dans le bloc hydrophobe conduit à la formation d’agrégats pH-sensibles dans le cas du dibloc PAA-b-P(AA0.5-stat-nBA0.5) comme montré dans une étude antérieure. Cette thèse a consisté en une analyse quantitative de la dynamique d’auto-association de copolymères dibloc et tribloc amphiphiles à base d’acrylate de n-butyle et d’acide acrylique dont les blocs hydrophobes contiennent 50% d’unités hydrophiles réparties de manière statistique. Les copolymères à blocs ont été synthétisés par polymérisation radicalaire contrôlée par ATRP. L’influence de la concentration, du pH, de la température et de la force ionique sur la structure et les propriétés mécaniques des systèmes auto-assemblés a été systématiquement étudiée. Par diffusion statique de la lumière nous avons montré la présence d’une concentration d’agrégation critique (CAC) au-dessus de laquelle, des micelles de type étoile (dibloc) ou fleur (tribloc) sont formées par auto-association des blocs hydrophobes. A plus fortes concentrations, des interactions répulsives de type volume exclu apparaissent entre les micelles étoiles. Pour les micelles fleurs, à l’inverse des interactions attractives conduisent au pontage des fleurs jusqu’à l’obtention de réseaux tri-dimensionnels au-dessus de la concentration de percolation. Une attraction trop importante entre les fleurs peut même conduire à une séparation de phase à forte force ionique et bas pH. En diffusion dynamique de la lumière, nous avons montré que la formation des réseaux s’accompagnait de l’apparition d’un mode lent dont l’origine a été expliquée par un mouvement balistique d’hétérogénéités relaxées dans les systèmes. La vitesse de relaxation de ces hétérogénéités s’avèrent être dépendantes des propriétés mécaniques des hydrogels. La formation des réseaux et la dynamique d’échange des chaînes ont été étudiées par rhéologie. La viscosité augmente régulièrement avec la concentration jusqu’à la concentration de percolation où une augmentation brusque de la viscosité se produit et un temps de relaxation apparaît. Le temps de vie des ponts a été finement contrôlé et modulé sur plusieurs décades par modification du pH, de la température et de la force ionique. La formation in-situ des hydrogels nous a permis de mettre en évidence un phénomène de vieillissement des réseaux après leur formation avant d’atteindre un état stationnaire. Ce phénomène s’est traduit par une augmentation du temps de relaxation au cours du temps avant d’atteindre une valeur plateau. Ceci nous a également permis de comprendre pourquoi il était possible de générer des réseaux homogènes, par vieillissement, possédant une dynamique extrêmement lente voir nulleAmphiphilic block copolymers are macromolecules composed of at least one hydrophilic block chemically linked to one or several hydrophobic blocks. In water, these macromolecules self-assemble to form micelles composed of a hydrophobic core surrounded by a hydrated hydrophilic corona. The majority of amphiphilic block copolymers form “frozen” micelles in aqueous solution. This means that there is no dynamic exchange of chains between micelles because the energy necessary to extract a hydrophobic block from the core of micelles is too high. Consequently, the characteristics of the micelles are controlled kinetically and not thermodynamically. In order to decrease this energy, we have incorporated acrylic acid units (AA) in the hydrophobic block of poly(n-butyl acrylate) (PnBA). It was previously shown that the incorporation of 50% molar of AA units in the hydrophobic block led to generation of pH-sensitive micelles in the case of PAA-b-P(AA0.5-stat-nBA0.5) diblocks. This thesis presents of a quantitative analysis of the dynamics of self-assembled amphiphilic diblock and triblock copolymer based on acrylic acid units and n-butyl acrylate units. The hydrophobic blocks contained 50% of acrylic acids units incorporated randomly. The block copolymers were synthesized by controlled radical polymerization (ATRP). The influence of the concentration, pH, temperature and the ionic strength on the structure and the mechanical properties of the self-assembled systems was systematically studied. At low concentrations, static light scattering measurements showed the formation of star-like micelles (diblock) or flower-like micelles (triblock) above a critical aggregation concentration (CAC). At higher concentrations, purely repulsive excluded volume interactions between micelles appeared in the case of diblock copolymers. In the case of triblock copolymers bridging of flower-like micelles induced in addition attractive interactions leading to network formation above the percolation concentration. At high ionic strength and low pH, we showed that the attraction between flower-like micelles became sufficiently stong to induce phase separation. Dynamic light scattering measurements showed besides a fast mode due to cooperative diffusion, a second slow relaxation mode that appeared at the percolation concentration. The origin of this mode was explained by a balistic motion induced by the relaxation of heterogeneities inside the system. The velocity of heterogeneities was determined by the mechanical relaxation of the hydrogels. The formation of the network and the exchange dynamic of chains were studied by rheology. The viscosity of solutions increased sharply at the percolation concentration. The terminal visco-elastic relaxation time of the network is related to the lifetime of bridges. It could be controlled and tuned over several decades by varing of pH, temperature and the ionic strength. The in-situ formation of networks revealed an aging of networks after their formation before they reached their stationary state. Aging caused a slow increase of the relaxation time before reaching its steady value. This explains why it is possible to generate homogeneous networks even if the network at steady is kinetically frozen
48
Goh, Roland Ghim Siong. "Carbon nanotubes for organic electronics." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/20849/1/Roland_Goh_Thesis.pdf.
Full textAbstract:
This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.
49
Goh, Roland Ghim Siong. "Carbon nanotubes for organic electronics." Queensland University of Technology, 2008. http://eprints.qut.edu.au/20849/.
Full textAbstract:
This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.
50
Šimek, Ondřej. "Návrh inspekčního sloupu pro kontroly stavu použitého jaderného paliva." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377081.
Full textAbstract:
The diploma thesis aim to the design of equipment for ŠKODA JS a.s., which is part of a new inspection stand (N-SIO). This equipment is an inspection column that provides the possibility to inspect spent fuel assemblies at the operation of the Temelín nuclear power plant. This master thesis is also a summary of the whole design of the new inspection stand and a description of the individual inspection components and devices. One of the parts of the thesis is also a basic strength analysis and a drawing of the main assembly of inspection equipment.