Tesi sul tema "Monolayers"
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1
Murdaugh, Anne E. "Epitaxy of Crystal Monolayers". Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194150.
Testo completoAbstract (sommario):
Epitaxial growth, or the oriented growth of a crystalline monolayer on an ordered substrate, appears in a wide range of systems and applications, from novel device fabrication to freshwater remediation. Despite this, methodical studies of the phenomenon are rare, and the mechanisms governing epitaxial growth are poorly understood. This investigation employs AFM techniques to monitor the epitaxial growth of ion crystal systems at the initial stages of growth. By using systems with well-known physical properties, we are able to relate growth modes to two key parameters, crystal lattice mismatch, Δr/r₀, and affinity between the overgrowth and the substrate ions, ξ. We found wetting growth occurs for systems in which Δr/r₀ is expansive (overgrowth lattice must expand to accommodate substrate) or mildly compressive (overgrowth compresses to accommodate substrate). Additionally, a strong affinity between the substrate and overgrowth ions, in combination with an expansive system, allows for epitaxial growth from undersaturated solutions. We also have observed several instances where the lateral force contrast on the growing film exhibits a strong dependence on the time of exposure to the growth solution and on the driving force for growth (solute concentration). We present results for three epitaxial growth systems in aqueous solutions: CaSO₃ on CaCO₃, PbSO₄ on BaSO₄, and BaSO₃ on BaSO₄. Chemically and topographically identical regions grown at higher concentrations exhibit higher friction than regions grown at lower concentrations. These observations suggest that epitaxial growth occurs by a fast condensation step incorporating a high defect density.
2
Ren, Qiang. "Dislocations in monolayers and semiconductors". Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10014.
Testo completoAbstract (sommario):
Four different aspects of the properties of dislocations in monolayer and semiconductors have been investigated: (i) Using atomic relaxation techniques, dislocation dipoles of various sizes and orientations have been studied for monolayers with the Lennard-Jones potential (LJP) and the nearest-neighbour piecewise linear force (PLF) interactions. In the WP system the lower energy vacancy dipoles have over a wide range of angles an energy which is mainly a function of the vacancy content of the dipole. There is a competition between the elastic forces and the topological constraints which favour a five-fold coordinate vacancy (FCV) at the centre of each core. For the short range PLF system the lattice usually compresses upon the introduction of a dislocation, a consequence of the soft core of the interaction potential, and interstitial dipoles are lower in energy. For the long range LJP system the dislocations are mobile whereas for the PLF system they are pinned. The relevance of these results to existing theories of melting are discussed. (ii) Using generalized stacking-fault (GSF) energies obtained from first-principles density-functional calculations, a zero-temperature model for dislocations in silicon is constructed within the framework of a Peierls-Nabarro (PN) model. Core widths, core energies, PN pinning energies, and stresses are calculated for various possible perfect and imperfect dislocations. Both shuffle and glide sets are considered. 90$\sp\circ$ partials are shown to have a lower Peierls stress (PS) than 30$\sp\circ$ partials in accord with experiment. (iii) We have also studied by atomic relaxation techniques the properties of dislocations in silicon, modelled by the empirical potential of Stillinger and Weber. In order to compare with the preceding calculation no reconstruction is allowed. We find no evidence of dissociation in the shuffle dislocations. Within this model shuffle dislocations glide along their slipping planes. On the other hand, glide sets are shown to glide only in dissociated form. The dislocation displacement fields are essentially planar. The PS is found to be isotropic within the (111) plane. In other words the minimum stress at 0K required to move the dislocation in any direction with in that plane has the same projection unto the Burgers vector, the PS of the dislocation. Our PS are in good agreement with those from (ii). (iv) Using a simple two dimensional UP model, relaxation mechanisms of the epitaxial strain layers (ESL) have been simulated for various misfits and layer thickness. In this model, the relationship of two competing relaxation mechanisms is found. At small misfit, strain is released by nucleating misfit dislocations from the edges of system. This process is more favourable for the thicker layer. At large misfit, stress is relaxed through surface instability, allowing easy generation of misfit dislocations from the surface. Those results are qualitatively in agreement with experiments.
3
Poirier, Jason S. "Polymer Templating in Surfactant Monolayers". Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/PoirierJS2004.pdf.
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4
Casson, Brian Derek. "Phase transitions in surfactant monolayers". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300797.
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5
Cheadle, Edward Martin. "Characterisation of self-assembled monolayers". Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250878.
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6
Muslim, Abdul-Mueed. "Computer simulations of surfactant monolayers". Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248123.
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7
Nicholls, Joel. "Polyomino models of molecular monolayers". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/98236/.
Testo completoAbstract (sommario):
In this thesis, we describe periodic 2D supramolecular networks using a simple polyomino model with nearest-neighbour interactions. In particular, we focus on design rules for ordered molecular tilings, describing how the realised molecular tiling depends on the parameters of the system, such as the interactions, molecular shape, temperature, and defects. A major component of our analysis is in keeping the interaction parameters free and exploring the polyomino system from the perspective of the space of interaction counts. The design principles and methods outlined in this thesis include several different themes, which give a complementary view on the properties of 2D supramolecular networks. Within the thesis we describe our algorithm for enumerating polyomino patterns and identifying their symmetries, making use of group theory methods that are specific for polyomino tilings. This information is used to analyse properties such as chirality, lowest energy states, degeneracy, and heat capacity curves, as depending on system parameters. The domino tilings are considered in terms of enumeration by periodicity, and in terms of the kinetically accessible subsets of configurations. The generalisation to polyominoes gives a wider sense in which many of the techniques can be used, showing similarities and some differences with the domino system. A probabilistic version of algorithm DLX is described and tested that allows us to gather sample statistics of domino configurations for larger unit cells. Finally, fixed defects are considered and their effect on the kinetically accessible domino subsets is elucidated.
8
Cicuta, Pietro. "Viscoelasticity of insoluble macromolecular monolayers". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619766.
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9
Opps, Sheldon B. "Phase behaviour of model Langmuir monolayers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ47405.pdf.
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10
Sun, Jizhong. "Molecular dynamics simulation of colloidal monolayers". Thesis, University of Hull, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397087.
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11
Khalifa, Youssef. "Organic reactions on self-assembled monolayers". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531241.
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12
Cotier, Bradley Neville. "Fullerene nanostructures, monolayers and thin films". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342471.
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13
Garcia-Gonzalez, Monica. "Electron transfer across self-assembled monolayers". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385394.
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Rankin, Alexander John. "Dynamic interfacial properties of surfactant monolayers". Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393948.
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15
Tong, Angela 1983. "Nano-contact printing of DNA monolayers". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32856.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (leaf 23).
Technology today is directed towards building smaller devices. To accommodate this development, printing methods are needed. Some printing methods that are used include lithography, micro-contact printing, and inkjet printing. These methods all require specialized instrumentation, hazardous chemicals, and complicated and tedious steps that increase cost of manufacturing. Nano-contact printing is an alternative solution which relies on the specificity of DNA to direct molecules into precise patterns. This study attempts to find the limitations of nano-contact printing through the printing of oligonucleotide monolayers. Eight pattern transfers were made with one master copy and the oligonucleotide surface coverage was analyzed using tapping mode atomic force microscopy (AFM). The percent coverage of oligonucleotide was then calculated from the tapping mode AFM phase images. Two general trends were found. The oligonucleotide surface coverage on the master increased slightly, while the surface coverage on the pattern transfers decreased. One possible explanation for the trends is that the decrease in contact between master and secondary substrate is due to both the accumulation of dirt and the wear and tear of' the master. By improving the contact between master and secondary substrate, the printing method can be expanded from printing monolayers to high resolution patterns.
by Angela Tong.
S.B.
16
Ransley, Chau Diem Nguyen. "Secondary electron emission from organic monolayers". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612907.
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17
Moia, Davide. "Intermolecular charge transport in dye monolayers". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/29104.
Testo completoAbstract (sommario):
This thesis reports the experimental investigation of intermolecular charge transport in dye monolayers anchored to the surface of nanocrystalline oxides. I use electrochemistry and transient spectroscopy to measure diffusion of holes within dye monolayers and interpret my observations on the basis of the non-adiabatic Marcus theory of charge transfer. I observe thermally activated hole diffusion for dyes used in dye sensitized solar cells (DSSCs) anchored to TiO2 and immersed in an inert acetonitrile based electrolyte. The corresponding values of reorganization energy of charge transfer between the dyes range between 700 and 1500 meV. Assuming negligible contribution from energetic disorder, this shows agreement with previously reported calculations of reorganization energy. Low outer sphere and low inner sphere reorganization energies correlate with delocalization of the HOMO and with rigid molecular structures showing extended conjugation. I show that hole diffusion in the monolayer can be controlled both at the μm and at the nm scale by varying the fraction of TiO2 surface covered with dyes. I present the effect of decreasing the dye surface coverage and consequently stopping hole diffusion on photo-electrochemical device structures. First, I observe a slowdown of the photo-induced recombination reaction of holes in the dye monolayer to electrons in the TiO2 when decreasing the dye loading. This result is consistent with the hypothesis that hole diffusion in the dye monolayer contributes to faster recombination. Second, I show that hole transport in the dye monolayer is responsible for increased dye regeneration efficiency in solid state DSSCs. I quantify improved regeneration yield by between 50% and 5% depending on the degree of the pore filling by the hole transporting material spiro OMeTAD. Finally I demonstrate that effective photo-conversion can occur in solar cell structures where dye monolayers function as the only hole transport phase.
18
Balachander, Natarajan. "Chemical transformations of siloxane-anchored monolayers". Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1059068908.
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Khalilgharibi, N. "The rheology of living cell monolayers". Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1537354/.
Testo completoAbstract (sommario):
Cell monolayers are a group of tissues in the body that, compared to other tissue types, have a simple structure, yet they play critical roles by acting as mechanical and physical barriers and partitioning the body into distinct organs. Cell monolayers are continuously exposed to external stresses applied to different extents and at various rates. Previous studies have shown that the mechanical response of monolayers to a sudden deformation is biphasic, however, what mechanisms are involved in these two phases is poorly understood. The aim of this work is to identify these mechanisms, their respective importance and their respective timescales. For this purpose, a new mechanical testing setup, based on a previous device developed in the Charras lab[1] was designed, calibrated and used to perform stress relaxation experiments on monolayers. ATP depletion experiments revealed that the first phase of the relaxation (t < 5 s) is dominated by physical ATP-independent processes, while the second phase (5 < t < 100 s) is dominated by biological ATP-dependent processes. Monitoring the changes in cell shape after stretch showed that cellular-level processes do not contribute to relaxation, suggesting that only molecular scale processes are at play. Chemical and genetic perturbations were used to identify the molecular origins of the ATP-dependent phase. It was shown that presence of the actin cytoskeleton is essential for the second phase of the relaxation. Furthermore, myosin contractility is a key player in the second phase, such that its perturbations lead to a decrease in the relaxation rate. The role of different crosslinkers in the active relaxation was also investigated. Finally, a computational model developed by the group of Dr José J Muñoz was adapted to simulate monolayer stress relaxation and to determine contributions of the cytoplasm and intercellular junctions.
20
Lin, Wan-Ing. "Enhanced Raman scattering of molecular monolayers". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17758.
Testo completoAbstract (sommario):
Um hochsensitive räumliche Auflösung zu erreichen, wurden oberflächenverstärkte Raman-Spektroskopie (SERS) und spitzenverstärkte Raman-Spektroskopie (TERS) weiterentwickelt. Das grundlegende Funktionsprinzip ist jedoch noch nicht vollständig verstanden und auch Experimente dazu fehlen teilweise. In dieser Arbeit habe ich zuerst Gap-mode TERS eingesetzt, bei welcher ein starkes elektromagnetisches Feld es ermöglicht, dünne Schichten von sehr schwach streuenden Molekülen zu untersuchen. Mit der Nanometerauflösung von TERS konnte ein auf der Goldoberfläche spontan phasen-getrennten, gemischtes Thiolsystem räumlich aufgelöst werden, während STM die Nanodomänen nicht über ihre Höhenunterschiede erkennen konnte. Neue Studien deuten auf eine Raman-Verstärkung durch Graphen und Flachgold aufgrund eines chemischen Mechanismus hin. Kupfer Phthalocyanin (CuPc)-Moleküle zwischen Graphen und einer flachen Goldoberfläche erlauben Elektronenübertragungen in beide Richtungen und damit stellt sich die Frage, ob chemische Verstärkungen von SERS zueinander addiert werden können. Die Ergebnisse deuten auf eine Kopplung von den zwei einzelnen Oberflächen hin. Es wurde eine 68-fache Verstärkung von geschichtetem CuPc zwischen Graphen und Gold beobachtet, jeweils bezogen auf CuPc auf Glimmer. Zuletzt wurde mittels TERS diese Schichtstruktur untersucht. Moleküle, die sich auf der Goldoberfläche selbstanordnen und mit Graphen bedeckt worden sind, fungieren als optische Sensoren, bei welchen die Graphenverkapselung die Moleküle beschützt. Außerdem kann eine sehr hohe Raman-Verstärkung mit großer lokaler Auflösung aufgrund der kombinierten Effekte von SERS und TERS herbeigeführt werden. Die Ergebnisse zeigen, dass eine Spitze, die Graphen-verstärkte Raman-Streuung (GERS) zusätzlich um vier Größenordnungen verbessern kann, aber Gap-mode TERS abschirmt.The quest to achieve ultrahigh sensitivity, surface specificity and high spatial resolution has led to the development of plasmon- and chemically- enhanced Raman spectroscopy, including techniques such as surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). However, a lack of fundamentally experimental demonstrations still remains. In this thesis, I firstly used gap-mode TERS, which allows studying even molecularly thin layers of very weakly scattering molecules. With the nanoscale spatial resolution provided by TERS, the spontaneous segregation in a mixed thiol system on a gold surface could be resolved, while scanning tunneling microscopy (STM) could not discern the nanodomains via their apparent height difference. Furthermore, since graphene and a flat gold surface both were known to provide some Raman enhancement through mainly a chemical mechanism, sandwiching copper phthalocyanine (CuPc) molecules between graphene and a flat gold surface allowed electrons to be transferred in both directions, and thereby to address the question whether chemical enhancements with different origins in SERS can add to each other. The results suggest that the chemical enhancements were influenced by the two individual surfaces, and a 68-fold enhancement of sandwiched CuPc between graphene and gold was observed, as compared to CuPc on mica. Last, TERS was applied to study this sandwiched structure. Molecules self-assembled on a gold surface and covered by transferred graphene acted as optical probes. Such an arrangement has interesting properties in the sense that molecules are protected and encapsulated by graphene. Also, a possible ultrahigh Raman enhancement together with localized spatial resolution may be achieved due to the combined effects from SERS and TERS. The results showed that a tip can improve graphene-enhanced Raman scattering (GERS) further by 4 orders of magnitude, but graphene exerts some shielding effect to gap-mode TERS.
21
Brito, Kazh. "Hole Closure in Langmuir Fluid Monolayers". Scholarship @ Claremont, 2007. https://scholarship.claremont.edu/hmc_theses/192.
Testo completoAbstract (sommario):
Amphipathic molecules are basically long chains, one end of which likes water (is hydrophilic) and the other end abhors it (is hydrophobic). These molecules tend to sit vertically in a fluid and adhere to each other. This attraction of adjacent molecules causes the molecules to condense into regions, referred to as polymer Langmuir layer domains, which are a single molecule thick and behave like a two dimensional fluid. This attraction also manifests itself as a line tension, analogous to surface tension in a fluid droplet, which causes the regions to become circular as they attempt to minimize the length of their perimeter. Often the layer will form holes, gaps in the liquid monolayer which contain a much smaller density of molecules. In the presence of humidity, the holes are observed to close up, pulled together by the line tension as well as condensation of the hole molecules at the boundary. Previous researchers have computed the fluid velocity for the process when the hole is assumed to be a vacuum. I, however, propose to replace this model with a gas, adding condensation of gas from the hole into the liquid domain of the monolayer to the line tension force. The hope is to obtain a mathematical model that better corresponds to the physical problem than current models do.
22
Zheng, Li-Yang. "Granular monolayers : wave dynamics and topological properties". Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1035/document.
Testo completoAbstract (sommario):
Les cristaux granulaires sont des structures périodiques de particules disposées en réseau cristallin. Les interactions entre ces billes peuvent être modélisées par leurs contacts, qui ont des dimensions et des masses effectives beaucoup plus petites que celles des billes. Ceci induit une propagation d'ondes élastiques dans les structures granulaires avec des vitesses significativement plus lentes que dans le matériau des grains individuels. En outre, en raison de forces de cisaillement non centrales, les rotations de particules peuvent être initiées, conduisant à des modes de phononiques supplémentaires dans ces cristaux. Dans ce manuscrit, on étudie la propagation d’ondes dans les cristaux granulaires monocouche bidimensionnels avec un mouvement des particules hors-plan ou dans le plan. Les propriétés phononiques sont étudiées, y compris les points de Dirac, les modes de fréquence nulle, les modes à vitesse de groupe nulle et leur transformation en modes de propagation lente. En outre, en présence de bords, on peut prévoir également des ondes de bord élastiques à fréquence nulle et extrêmement lentes dans des cristaux granulaires en « nid d'abeille » (graphène granulaire). En outre, les propriétés topologiques des ondes de bord rotationelles-transverses dans un graphène granulaire sont théoriquement démontrées. En induisant une transition topologique, qui transforme l'ordre topologique du graphène granulaire de trivial en non trivial, on peut observer le transport de bord topologique dans le graphène granulaire. Les théories développées pourraient mener potentiellement à des applications sur le contrôle des ondes élastiques par des structures granulairesGranular crystals are spatially periodic structures of elastic particles arranged in crystal lattices. The interactions between particles take place via their elastic interconnections, which are of much smaller dimensions and weights than the beads. This induces propagation of elastic waves in granular structures at significantly slower velocities than in the individual grains. In addition, due to the existence of non-central shear forces, rotations of particles can be initiated, leading to extra phononic modes in the crystals. In the manuscript, wave dynamics in two-dimensional monolayer granular crystals with either out-of-plane or in-plane particle motion is studied. The phononic properties are investigated, including Dirac points, zero-frequency modes, zero-group-velocity modes and their transformation into slow propagating phononic modes. Furthermore, in the presence of edges/boundaries, zero-frequency and extremely slow elastic edge waves can be also predicted in mechanical granular honeycomb crystals (granular graphene). In addition, topological properties of rotational edge waves in a granular graphene are theoretically demonstrated. By inducing topological transition, which turns the topological order of granular graphene from trivial to nontrivial, topological edge transport in the granular graphene can be observed. The developed theories could promote the potential applications of designed granular structures with novel elastic wave propagation properties
23
Wang, Qin Shannon Curtis. "Self-assembled monolayers as platform for biosensors". Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/WANG_QIN_39.pdf.
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Vogel, Nicolas [Verfasser]. "Surface patterning with colloidal monolayers / Nicolas Vogel". Mainz : Universitätsbibliothek Mainz, 2011. http://d-nb.info/1026803209/34.
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Brett, Daniel John Leslie. "An electrochemical study of Self-Assembled Monolayers". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394167.
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Wilkinson, Katherine Mary. "Phase transitions in monolayers of soluble surfactants". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408682.
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Gilbert, Freestone Bayes. "Modelling the surface potential of Langmuir monolayers". Thesis, Bangor University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282220.
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28
Stuart-Cole, Simone. "Patterned self-assembled monolayers as reactivity templates". Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540580.
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Brown, Andrew Simon. "Copolyelectrolyte monolayers : organisation and surface wave dynamics". Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4970/.
Testo completoAbstract (sommario):
The organisation and dynamic behaviour of a copolyelectrolyte monolayer is discussed A linear diblock copolymer of poly(methyl methacrylate) (PMMA) and poly(4-viny ethylpyridinium bromide) (QP4VP) has been the main focus of the study, although films of both the unquaternised copolymer, PMMA-P4VP and a PMMA homopolymei have also been examined for comparative purposes. The polymers were spread or subphases of water and potassium chloride solutions of varying concentrations to determine changes in structure and dynamics with polymer surface concentration and subphase salt concentration. Monolayer behaviour has been characterised from surface pressure isotherms and the use of Brewster angle microscopy. It has been demonstrated that the shape of the isotherm is dependent on the potassium chloride concentration of the subphase. Information on the organisation of the system has been determined by neutron reflectometry. A systematic variation in organisation occurs as both polymer surface concentration and subphase potassium chloride concentration change. The polyelectrolytic QP4VP block stretches more into the subphase with increasing surface concentration or decreasing salt concentration. The results have been compared to scaling laws for polymer brushes. Dynamic behaviour has been studied by the use of surface quasi-elastic light scattering (SQELS) and resonance between the capillary and dilational waves of the system is observed. The phenomenon of mode mixing and the application of viscoelastic models to the system have also been examined. It has been discovered that an accurate description of the surface viscoelastic properties of the system could not be obtained by the use of standard viscoelastic models. Mode mixing was not observed, even in those systems where negative dilational viscosities were found.
30
Coomber, Stuart David. "Vibrational spectroscopy of thin films and monolayers". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285641.
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Marenco, Claudia. "Calixarene monolayers as surface-enhanced raman sensors". Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287632.
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Cavadas, Francisco T. "Self-Assembled Monolayers As Models For Silica". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31671.
Testo completoAbstract (sommario):
The reaction of hydroquinone and 1,12-dibromododecane affords 4-(12-bromo-dodecyloxy)phenol (4, 7% yield). The alkyl bromide (4) was converted to the corresponding thiol with thiourea to afford 4-(12-mercaptododecyloxy)phenol (1) in 52% yield. The reaction of t-butyllithium with 4-bromoanisole followed by reaction with 1-12-dibromododecane affords a mixture of 4-bromoanisole, 1,12-dibromododecane ,and 4-(12-bromododecyl)-anisole (6). Silica gel chromatography resulted in an inseperable mixture of 4-bromoanisole and (6). Reaction of the mixture with BBr3 afforded 4-(12-bromododecyl)phenol (7) in 34% yield. The alkyl bromide (7) was converted to the corresponding thiol with thiourea to afford 4-(12-mercaptododecyl)phenol (2) in 9% yield. Reduction of 16-mercaptohexadecanoic acid with BH3â hTHF afforded 16-mercaptohexadecanol (3) in 53% yield. All new compounds were characterized by 1H NMR, 13C NMR, transmission IR, HRMS, and, where possible, elemental microanalysis.
Self-assembled monolayers (SAMs) on gold were prepared using thiols 1, 2, and 3. SAMs were characterized using reflectance-absorbance infrared spectroscopy (RAIRS). Diagnostic vibrational modes were assigned by comparing RAIRS spectra to normal mode frequencies and intensities calculated using DFT methods at the 6-31G* level using commercial software. Water droplet goiniometry found contact angles of 52o, 53o, and 64o for SAMs prepared from 1, 2, and 3, respectively. SAMs of 1 and 2 were found to be hydrophilic. When SAMs prepared from 1, 2, and 3 were silylated with phenyldimethylchlorosilane, the resulting contact angles were 78o, 74o, and 75o respectively. A significant increase in contact angles for silylated SAMs of 1 and 2 indicated facile silanization of the surface hydroxides. RAIRS spectra were also obtained for the functionalized SAMs. Silylated SAMs prepared from 1, 2, and 3 are currently under investigation as models for silica-immobilized metallocene olefin polymerization catalysts.Master of Science
33
Jang, Chang-Hyun. "AFM-Assisted Nanofabrication using Self-Assembled Monolayers". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11103.
Testo completoAbstract (sommario):
This study describes the covalent and the electrostatic attachment of molecules, nano-particles, and proteins to patterned self-assembled monolayers. A scanning probe nanografting technique was employed to produce patterns of various sizes, down to 10 nm. Thus, we are able to demonstrate a degree of surface patterning which is an order of magnitude smaller than that used in the semiconductor industry.
One efficient strategy for creating chemically specific nanostructures is to use the extraordinary catalytic properties of enzymes. However, as the dimension of a catalyst patch is reduced down to nanometer scale, it is difficult to detect the very low concentration of product. This study resolves the problem by developing a new strategy: the surface trapping of a product generated by a nanometer-scale patch of surface-bound enzyme.
An array of proteins finds use when the array contains a number of different proteins. Toward this end, a new and convenient method for immobilizing enzymes is developed, which will allow the preparation of thin films containing several different catalytically-active enzymes on the nanoscale.
The disadvantage of scanning probe nanografting technique is that the AFM tip loses resolution through wear during the patterning procedure. This study examines the possibility of developing a new AFM lithographic method to avoid wear: the use of enzymes covalently attached to a tip as a site-specific catalyst.Ph. D.
34
Skabardonis, John Gregory. "Structure and reactions in novel organic monolayers". Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054930052.
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Jalkh, Joanna. "Engineering of functionalized monolayers for molecular electronics". Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S153.
Testo completoAbstract (sommario):
La modification des surfaces revêt un intérêt primordial dans de nombreux champs d'applications de la chimie, comme la chimie analytique et l'électronique moléculaire. Ce travail a porté sur l'étude de différentes monocouches liées de façon covalente à des surfaces conductrices (principalement le carbone) et préparées à partir de l'électroréduction de sels d'aryldiazonium. Ces monocouches organiques ont été fonctionnalisées avec des groupements terminaux électroactifs différents, et l'on s'est intéressé aux propriétés de transfert de charge (au sens large) des couches résultantes. Tout d'abord des couches portant un système redox simple à base de ferrocène ont été étudiées dans différents milieux organiques conventionnels et en milieu liquides ioniques. L'effet de l'éloignement du système redox vis-à-vis de la surface a été également analysé en variant la longueur du pont ancrant. Dans un second temps, les monocouches organiques ont été fonctionnalisées par des unités tétrathiafulvalène (TTF). Les TTF sont des molécules (donneur d'électrons) connues pour former des complexes à transfert de charge avec le tétracyanoquinodiméthane (TCNQ), accepteur d'électrons. La formation de complexes à transfert de charge entre des TTF immobilisées dans la monocouche et des dérivés TCNQ a été étudiée et modulée selon l'éloignement du TTF vis-à-vis de la surface (variation de la longueur du lien ancrant) et en fonction de la force de l'accepteur. Enfin, des monocouches avec des groupements terminaux de type fluorène ou spirobifluorène (SBF) ont été préparées. Le comportement bloquant vis-à-vis-du transfert d'électron a été étudié par microscopie électrochimique (SECM) en présence de deux médiateurs redox différents et la conductivité des couches a été évaluée par CP-AFM (microscopie à force atomique – mesure de courants locaux). Il est montré que les propriétés de transfert/transport de charges sont influencées par l'encombrement stérique associé au fluorène ou au SBF (variation de la substitution). Ces monocouches organiques stables, bien organisées apparaissent très prometteuses comme composants dans des dispositifs d'électronique moléculaireSurface modification is of paramount importance in many fields of chemistry like analytical chemistry and molecular electronics. This work deals with the study of different monolayers covalently bound on conducting (mainly carbon) surfaces, and produced from the electroreduction of aryldiazonium salts. By introducing electroactive components in the resulting monolayers, the different studies in this work mainly focused on charge-transfer properties (in a large sense). First, monolayers bearing simple redox-active ferrocenyl terminal groups were investigated. The electrochemical behavior of these monolayers was analyzed in different conventional organic media and in ionic liquids (RTILs) and by varying the length of the bridging unit between the surface and the ferrocene groups. Second, redox-active tetrathiafulvalene (TTF) molecules were used to functionalize the monolayers. TTF molecules are well-known donor molecules able to form charge-transfer complexes with tetracyanoquinodimethane (TCNQ) as an electron-acceptor. The formation of charge-transfer complexes between immobilized TTF and TCNQ derivatives was studied and modulated by varying the chain length of the bridging unit between the TTF donor and the surface and by varying the electron-withdrawing ability of the TCNQ acceptors. Third, monolayers with fluorene and spirobifluorene (SBF) terminal groups were prepared. The blocking behavior towards electron transfer was studied by electrochemical microscopy (SECM) with two redox mediators and the conductivity of the layers was investigated by CP-AFM (Conducting Probe-Atomic Force Microscopy). Effects due to the steric hindrance of the fluorene or SBF derivatives were evidenced. Such stable, organized and organic monolayers seem to be promising candidates for molecular electronic devices
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Chen, Danti. "Local electron transport of organic semiconducting monolayers /". Connect to online version, 2009. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2009/363.pdf.
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Durmaz, Firat. "A modular approach to functional self-assembled monolayers /". Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16942.
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Desawy, Mohamed el. "Characterization and application of aromatic self assembled monolayers". [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984793658.
Testo completo
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Morell, Bennasser Nicolás. "Optomechanical resonators based on transition metal dichalcogenide monolayers". Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/664927.
Testo completoAbstract (sommario):
Suspended monolayer transition metal dichalcogenides (TMD) aremembranes that combine ultralow mass and exceptional optical prop-erties, making them intriguing materials for opto-mechanical applica-tions. However, the low measured quality factor of TMD resonatorshas been a roadblock so far. In this thesis, we first show an ultra-sensitive optical readout of monolayer TMD resonators that allows usto reveal their mechanical properties at cryogenic temperatures. Wefind that the quality factor of monolayer WSe2resonators greatly in-creases below room temperature, reaching values as high as 16000 at liquid nitrogen temperature and 47000 at liquid helium temper-ature. This surpasses the quality factor of monolayer graphene res-onators with similar surface areas. Upon cooling the resonator, the res-onant frequency increases significantly due to the thermal contractionof the WSe2lattice. These measurements allow us to experimentallystudy the thermal expansion coefficient of WSe2 monolayers for thefirst time. High Q-factors are also found in resonators based on MoS2 and MoSe2 monolayers. The high quality-factor found in this workopens new possibilities for coupling mechanical vibrational states totwo-dimensional excitons, valley pseudospins, and single quantumemitters and for quantum opto-mechanical experiments based on theCasimir interaction.The sensing capabilities offered by these high Q-factor nanome-chanical oscillators are also of interest for studying thermodynamicproperties in condensed matter regimes that are difficult to access. Inthe second part of the thesis, we use optomechanical systems basedon a MoSe2 monolayer to probe the thermal properties of phononsin two-dimensional lattices. We measure the thermal conductivityand the specific heat capacity down to cryogenic temperature. Thephonon transport crossovers from the diffusive to the ballistic regimewhen lowering the temperature below~100 K. The temperature de-pendence of the specific heat capacity approaches a quadratic depen-dence, the signature of two-dimensional lattices. Both the thermalconductivity and the specific heat capacity measurements are consis-tent with predictions based on first-principles. Our result establishes anew strategy to investigate thermal transport in two-dimensional ma-terials, and allows for exploring the phonon hydrodynamic regime,the anomalous heat conduction, and the phase transitions of electronicmany-body collective phenomena in monolayersLos dicalcogenuros de metal de transición (TMD) monocapa suspendidos combinan una masa ultrabaja y propiedades ópticas excepcionales, lo que los convierte en materiales intrigantes para aplicaciones opto-mecánicas. Sin embargo, el bajo factor de calidad Q medido en los resonadores de TMD ha sido un obstáculo hasta ahora. En esta tesis, primero mostramos una lectura óptica ultra sensible de resonadores TMD de monocapa que nos permite revelar sus propiedades mecánicas a temperaturas criogénicas. Encontramos que el factor de calidad de los resonadores WSe2 monocapa aumenta considerablemente por debajo de la temperatura ambiente, alcanzando valores tan altos como 1.6 x 104 en temperatura de nitrógeno líquido y 4.7 x 104 en temperatura de helio líquido. Esto supera el factor de calidad de los resonadores de grafeno monocapa con áreas de superficie similares. Al enfriar el resonador, la frecuencia de resonancia aumenta significativamente debido a la contracción térmica la red del cristal de WSe2. Estas mediciones nos permiten estudiar experimentalmente el coeficiente de expansión térmica de las monocapas de WSe2 por primera vez. Los altos factores Q también se encuentran en los resonadores basados en las monocapas de MoS2 y MoSe2. El alto factor de calidad que se encuentra en este trabajo abre nuevas posibilidades para acoplar estados vibracionales mecánicos a excitones bidimensionales, valley pseudo-spins y emisores cuánticos únicos y para experimentos opto-mecánicos cuánticos basados en la interacción de Casimir. Las capacidades de detección ofrecidas por este nano-resonador mecánico de alto factor Q también son interesantes para estudiar propiedades termodinámicas en regímenes de la materia condensada a los que es difícil acceder. En la segunda parte de la tesis, utilizamos sistemas optomecánicos basados en una monocapa de MoSe2 para probar las propiedades térmicas de los fonones en redes de cristales bidimensionales. Medimos la conductividad térmica y la capacidad calorífica específica hasta temperaturas criogénicas. Los régimenes de transporte de fonones pasan de el difuso al balístico al bajar la temperatura por debajo de 100 K. La dependencia de la temperatura de la capacidad calorífica específica se aproxima a una dependencia cuadrática, lo cual es la firma de las redes bidimensionales. Tanto la conductividad térmica como las mediciones de la capacidad calorífica específica son coherentes con las predicciones basadas en primeros principios. Nuestro resultado establece una nueva estrategia para investigar el transporte térmico en materiales bidimensionales y permite explorar el régimen hidrodinámico de fonones, la conducción de calor anómala y las transiciones de fase de los fenómenos colectivos de cuerpos electrónicos en monocapas.
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Bergström, Anna. "SPR Sensor Surfaces based on Self-Assembled Monolayers". Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16664.
Testo completoAbstract (sommario):
The study and understanding of molecular interactions is fundamentally important in today's field of life sciences and there is a demand for well designed surfaces for biosensor applications. The biosensor has to be able to detect specific molecular interactions, while non-specific binding of other substances to the sensor surface should be kept to a minimum. The objective of this master´s thesis was to design sensor surfaces based on self-assembled monolayers (SAMs) and evaluate their structural characteristics as well as their performance in Biacore systems. By mixing different oligo (ethylene glycol) terminated thiol compounds in the SAMs, the density of functional groups for bimolecular attachment could be controlled. Structural characteristics of the SAMs were studied using Ellipsometry, Contact Angle Goniometry, IRAS and XPS. Surfaces showing promising results were examined further with Surface Plasmon Resonance in Biacore instruments.
Mixed SAM surfaces with a tailored degree of functional COOH groups could be prepared. The surfaces showed promising characteristics in terms of stability, immobilization capacity of biomolecules, non-specific binding and kinetic assay performance, while further work needs to be dedicated to the improvement of their storage stability. In conclusion, the SAM based sensor surfaces studied in this thesis are interesting candidates for Biacore applications.
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Shrimpton, Neil Douglas. "Low temperature behavior of krypton monolayers on graphite". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27531.
Testo completoAbstract (sommario):
The low temperature behaviour of a system of incommensurate krypton monolayers on graphite was analysed. The free energy was calculated for a variety of monolayer configurations and the misfit and orientation of the minimum energy configuration determined as a function of the temperature and chemical potential of the system. The free energy did not vary significantly over the temperature range from 0 K to 4 K. The zero point energy contributes significantly to the free energy and could not be neglected.
The lowest energy vibrational modes were determined; these modes correspond to motion of the domain walls. For configurations with clearly separated domain walls the vibrational modes separated into groups of three (triads). In the lowest energy triad, the lowest energy mode was a compressional mode. The second and third lowest modes were shearing modes. These three modes describe the fundamental forms of domain wall motion. The modes of the higher energy triads are more energetic forms of the lowest energy triad.Science, Faculty of
Physics and Astronomy, Department of
Graduate
42
Henderson, Livia. "Cellular stress responses in equine tendon fibroblast monolayers". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/6725/.
Testo completoAbstract (sommario):
The superficial digital flexor tendon (SDFT) is one of the most frequently injured tendons in Thoroughbred racehorses. Exercise associated factors including hyperthermia are thought to lead to cellular dysfunction and cell death of the resident tendon fibroblasts, the cells responsible for the repair of the tendon lesions. The main aim of this thesis was to investigate the sensitivity of SDFT fibroblasts to hyperthermia and to compare this with the deep digital flexor tendon (DDFT), a non-injury prone tendon. Understanding the physiological mechanisms of the heat shock response in these cells e.g. the use of protein markers will allow preventative strategies to be devised to protect these cells from damage. I determined whether thermotolerance associated with the induction of heat shock proteins (a survival mechanism that allows cells to withstand a subsequent lethal shock) could be induced with both heat and cold shock in these cells. Firstly, the basal DNA damage levels were quantified in both SDFT and DDFT fibroblasts as the cell culture environment is known to damage cells. My research showed both SDFT and DDFT fibroblasts were susceptible to replication induced DNA damage in vitro. The SDFT in particular had high levels of DNA damage when cultured on a fibronectin matrix in ambient oxygen. SDFT and DDFT fibroblasts were shown to be susceptible to a lethal heat shock (52oC). When a preconditioned sub-lethal heat shock was given to both tendons, induction of thermotolerance occurred and these cells survived a lethal heat shock. Thermotolerance was induced in preconditioned cold shocked SDFT fibroblasts but not in DDFT fibroblasts. Finally, a useful protein marker, DAXX (that is involved in cellular stress pathways as a transcriptional repressor and in apoptosis) was shown to disperse into the nucleoplasm during a mild heat shock in SDFT fibroblasts. One of the limitations of this thesis is that sample size was small and as a result, larger numbers of animals will be required for future experiments to determine whether my results are of biological significance.
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MacDairmid, Allan. "Self-assembly of dithiol monolayers on Au(111)". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ64725.pdf.
Testo completo
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Basabe, Desmonts Lourdes. "Fluorescent self-assembled monolayers as new sensing materials". Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/51101.
Testo completo
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Fang, Guanjiu. "Orientation dynamics of azobenzene-based self-assembled monolayers". Connect to online resource, 2007. 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:3284493.
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Wolak, Matthaeus Anton. "The Electronic Structure of Biomolecular Self-Assembled Monolayers". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4258.
Testo completoAbstract (sommario):
The studies presented here address the characterization of the electronic structure of various self-assembled monolayers (SAMs) of peptide nucleic acid (PNA) and tetraphenylporphyrin (TPP) SAMs and arrays, formed on gold substrates.
PNA is a promising alternative to DNA for bio-sensing applications, as well as for strategies for self-assembly based on nucleic acid hybridization. In recent years charge transfer through PNA molecules was a focus of research due to possible applications in self-assembled molecular circuits and molecular tools. In light of this research it is interesting to investigate the electronic structure of PNA interfaces to gold, a potential electrode material.
TPP is, due to its electronic structure, an organic p-type molecular semiconductor. Such a material can provide an alternative to standard micro- and optoelectronic devices and in recent years more attention was paid to semiconducting polymers and organic compounds offering these low-cost and flexible alternatives. Therefore, it is of high importance to investigate the prospect of using modified TPP molecules for the formation of interconnected molecular networks on metallic surfaces.
All investigated monolayers were formed from solution in a nitrogen atmosphere inside a homemade glove box. This process allowed for PNA SAM and TPP SAM and array formation on clean Au substrates without the exposure to the ambient atmosphere. Ultraviolet and X-ray photoemission spectroscopy (UPS and XPS) measurements on the resulting PNA SAMs and TPP SAMs and arrays, which were performed in a to the glove box attached vacuum chamber containing a photoemission spectrometer, revealed the hole injection barriers at the interfaces and the interface dipoles.
In addition to the UPS and XPS measurements on PNA, electronic structure calculations based on molecular dynamics sampling of the PNA structure were obtained, yielding the HOMO-LUMO gap and the electronic density of states for PNA. Combined with the UPS data, the theoretical calculations enabled estimation of the charge injection barriers for the PNA SAMs at the interface, as well as the assignment of individual UP-spectral features to specific molecular orbitals.
The orbital line-up at the interface between the Au substrate and the PNA indicated a significant interface dipole resulting in the alignment of the Au Fermi level near the center of the PNA HOMO-LUMO gap. This alignment causes large charge injection barriers for both holes and electrons, and thus impedes charge transfer from Au into the PNA SAM. The study of PNA molecules with ferrocene termini showed that this hole injection barrier is shifted to lower energies at the PNA/ferrocene interface. This shift was explained with a molecular orbital reconfiguration through the presence of the ferrocene terminus. The further investigation of the dependence of the electronic structure of PNA SAMs, based on their orientation, showed that incomplete films containing flat lying molecules can have a significant impact on the charge injection barriers. The close proximity of the nucleobases to the Au surface offers new ways for charge transfer between the substrate and the PNA molecule through its nitrogen sites, leading to a lowering of the hole injection barrier at the interface.
The TPP arrays were formed by depositing AgNO3 on the Au substrate prior to TPP incubation using the electrospray technique. The interaction of AgNO3 with the TPP promoted the formation of an interconnected thin film forming a network on the Au substrate. The line-up at the Au/TPP interface without AgNO3 exposure showed an interface dipole formation with injection barriers that would potentially obstruct charge injection into the molecule. However, the addition of AgNO3 to the process resulted in the formation of fine structures, and lead to a lower hole injection barrier due to an induced dipole, which would ultimately improve charge transfer between the substrate and the thin film. A separate thiolated TPP derivative was used to form SAMs on a gold substrate. The SAM exhibited an even lower injection barrier than the mentioned TPP thin film with AgNO3 exposure, leading to the conclusion that a mix of both TPP derivatives could potentially lead to a SAM with long range interconnectivity and a low hole injection barrier towards the substrate.
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Badia, Antonella. "Structure and dynamics in self-assembled alkylthiolgold monolayers". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40313.
Testo completoAbstract (sommario):
Les monocouches auto-assemblees de n-alcanethiols sur des surfaces d'or, d'argent et de cuivre ont ete tres utilisees pour modeler les surfaces organiques et modifier les proprietes des surfaces metalliques. Cependant, a cause du caractere monomoleculaire du recouvrement et de la petite surface des substrats m'etalliques, la caracterisation des monocouches auto-assemblees n'est possible que si des techniques amplifiant le signal sont utilisees. Par consequent, les facteurs-cles tels que la nature de l'interaction metal-soufre, l'arrangement des chai nes hydrocarbonees et le diagramme de phase des especes adsorbees sur les surfaces metalliques restent a etre definis. La caracterisation des proprietes thermotropiques des monocouches auto-assemblees est tres importante non seulement du point de vue de l'elaboration de monocouches organiques stables et bien ordonnees, mais aussi pour la comprehension fondamentale des facteurs qui controlent les interactions moleculaires en deux dimensions. Les differentes phases des monocouches auto-assemblees ont ete etudiees en utilisant la technique du transfert electronique entre un couple redox soluble dans l'eau et une electrode recouverte de molecules d'alcanethiols. Le couple redox constitue le moyen par lequel la structure de la monocouche organique peut etre caracterisee. Le courant du couple redox a l'interface metal/thiol (RS/Au, ou R = n-$ rm C sb{16}H sb{33}$ a n-C$ rm sb{20}H sb{41}$ et HO(CH$ sb2) sb{16})$ montre un maximum a des temperatures precises. Ces temperatures sont definies par la longeur de la chai ne hydrocarbonee ainsi que par la presence de liaisons hydrogenes a l'interface monocouche organique/eau. Il existe un parallele entre ces resultats et l'augmentation de la permeabilite des ions dans les vesicules de phospholipides aux temperatures de transition de phase, ainsi qu'aux temperatures auxquelles les chai nes engendrent des changements d'inclinaison. En ce qui concerne la temperature de pre-transition
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Lee, Lawrence Yoon Suk 1972. "Probing and controlling defects in self-assembled monolayers". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102674.
Testo completoAbstract (sommario):
This thesis is focused on the development of a tool for probing defects in self-assembled monolayers (SAMs). Such a tool is necessary for the detailed understanding of fundamental issues in SAM composition and structure. The electrochemical properties of single component and binary ferrocenylalkylthiol SAMs on polycrystalline gold (FcC12S-Au and FcC12S-/CH 3RS-Au) have been investigated in detail. The complex voltammetry obtained for various mixtures of FcC12S-Au SAMs is shown to be linked to local electrostatics caused by the formation of the ferrocenium ion. A procedure involving a Gaussian-Lorentzian fit is used to deconvolute the two peaks consistently observed in the SAMs when the surface mole fraction of the FcC12S-Au ( csurfFc ) ≥ 0.2. The lower potential (Eº' = 250 mV) and higher potential (Eº' = 350 mV) voltammetric peaks are thus assigned to Fc moieties in "isolated" and "clustered" states, respectively. Use of this method to better understand SAM structure is demonstrated by distinguishing the degree of homogeneity in two binary SAMs of similar composition.This characteristic electrochemical property of FcC12S-Au system allows for the quantification of defects in SAMs. This is important because coverage defects, or voids in alkylthiol SAMs, are a critical component of electron transfer mechanisms of soluble redox probes. Short time exposure of a defective SAM to FcC12SH leads to a quantifiable defect-related Fc coverage (GammaFc), with GammaFc < 1% being readily measurable. Using FcC12SH as a label, a number of alkylthiol SAM preparation conditions have been assessed.
FcC12SH is further used to probe the progress of the important alkylthiol-for-alkylthiol exchange reaction in SAMs. It is shown that variation of chain length, reaction temperature, terminal group, applied potential, and the initial defect density determines the extent and the rate of the exchange reaction. Kinetics studies of binary (FcC12S-/CH3RS-Au) SAM formation via co-incubation reveal that although csurfFc is initially close to the solution mole fraction of the FcC12 SH ( csolnFc ), the subsequent exchange reaction leads to a csurfFc which is often quite different from csolnFc .
Finally, the FcC12SH probe is used to further study the reductive voltammetric desorption of alkylthiol SAMs. Defects in a C14S-Au SAM created by excursions to desorptive reduction potentials were quantified by use of the FcC12SH label. A reductive desorption potential followed by re-adsorption, applied to a binary (FcC12S-/C14S-Au) SAM, results in mixing of the phase separated components of the binary SAM.
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Bowen, James. "Nanoadhesion : investigating nanoscale adhesion using self-assembled monolayers". Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491265.
Testo completo
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Bramble, Jonathan Peter. "Liquid crystal anchoring on patterned self-assembled monolayers". Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487706.
Testo completoAbstract (sommario):
The anchoring of Liquid Crystals (LCs) on surfaces patterned with functionalised Self Assembled Monolayers (SAMs) has been investigated. A range of pattern geometries and length scales have been used to explore the effects of surface patterning on the alignment of n-cyanobiphenyl (nCBs) LCs in their Smectic and Nematic phases and at the Nematic to Isotropic phase transition.