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Dissertations / Theses on the topic 'Monolayer structure'

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Published: 4 June 2021
Last updated: 4 February 2022

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1

Wei, Ling 1961. "Structure and reactivity of monolayer and micelle interfaces." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56973.

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The research in this thesis is focused on the structure and reactivity of monolayer and micelle interfaces.
The kinetic results of ring formations of a series of $ sigma$-($ omega$-bromoalkoxy)phenoxides in a cationic micellar environment (CTAB) revealed that the ring closure rate constants from the 7-membered ring to the 14-membered ring decrease by $ sim$6-fold. This is much smaller than that observed for a homogeneous reaction environment ($ sim$1500-fold). In addition, micellar effective molarities (EM)$ sb{ rm m}$ for these reactions are found to be 7 to 1900 fold greater than in homogeneous solution. This catatysis can be reasoned to originate from an increase in the ground-state free energy of the substrate induced by localization of the phenolate oxygen and alkyl bromide moieties at the polar micelle interface.
Monolayer isotherm studies establish a dependence of isotherm features on the structure of the phospholipid. It is found that the liftoff area increases as the position of the second hydrophilic group is located further from the dominate polar group. The transition pressure reaches its highest value when the substituent is in the 7-position. The condensed area for almost all these substrates gives nearly the same value ($ sim$45 A$ sp2$/molecule). These may be explained by that the molecules lie flatly on the air/water interface at high surface concentration after which the hydrophobic parts in a molecule are forced out of the water surface. The hydrophilic groups remain on the water surphase so as to produce a loop conformation. At high pressure all the molecules are approximately perpendicular to the water surface so as to form a highly dense packing state. The unusually broad first order phase transition in isotherms of some boloform and macrocyclic phospholipids is consistent with these substrates being reorientated at large areas to yield stable bilayers, trilayers, etc.
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2

York, Ian. "Structure and reactivity of titania-supported bismuth molybdates." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311658.

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3

Arnold, Thomas. "The adsorption of alkanes from their liquids and binary mixtures." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249654.

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4

Rödner, Sandra. "Interfacial colloidal particle films and their structure formation." Licentiate thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1505.

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Abstract to“Interfacial colloidal particle films andtheir structure formation”; a licentiate thesis, whichwill be presented by Sandra Rödner in Q2, 29 November 2002at 13.00.

Colloidal particles can be made to organise themselves intoordered arrays. These colloidal structures acquire interestingand useful properties, not only from their constituentmaterials but also from the spontaneous emergence of mesoscopicorder that characterises their internal structure. Orderedarrays of colloidal particles, with lattice constants rangingfrom a few nanometers to a few microns, have potentialapplications as optical computing elements and chemicalsensors, and also has an important influence on the mechanicalproperties and optical appearance of paint films and papercoatings.

The control of colloidal structure formation starts with theparticle interactions (attractive or repulsive) and colloidaldynamics, which is the topic of this thesis. To enable adetailed understanding of the different factors that controlthe formation of dense 2D colloidal films, a method forstructural characterisation was developed. The degree of orderin the hexagonal close-packed structure, displayed by thecolloidal films, was characterised by the size of ordereddomains and by the distribution of pore sizes. The size ofordered domains was obtained from the pair distributionfunction, and the distribution of pores from a Delaunaytriangulation procedure. These methods are based on theparticle positions in the film, which were determined by lightmicroscopy and processed digital images.

The two methods were used to study the effect of particleinteractions on the structure of colloidal monoparticulatefilms, formed at the air-liquid interface. The size of theordered domains decreased exponentially with increasing bondstrength, while the pore density increased. The transfer andsubsequent drying of the formed film on a solid substrateinduced structural changes; the capillary forces transformedsmall pores into triangular order while some of the largervoids and cracks increased in size.

The structural features of colloidal monolayers, formed bydrying a dilute silica suspension on a substrate, wereinvestigated. Addition of small amounts of salt resulted indrastic changes of the particle film structure. The size of theordered domains decreased exponentially with increasing amountsof added salt (0-2.9% NaCl/Silica ratio), with a simultaneousincrease of the concentration of large defects. This suggeststhat loss of colloidal stability and onset of particle adhesionto the substrate inhibit rearrangement and ordering. Theevaporation rate was controlled by varying the relativehumidity during drying. Colloidal monolayers with the largestordered domains and the lowest concentration of stacking faultswere formed at an intermediate humidity (55% RH).

The rearrangement process during drying of dilute silicasuspensions was followed in detail by studying the changes inthe structural features during growth of colloidal monolayers.Low crystal growth rate promoted the transition of squarelattice domains to a hexagonal close-packed structure. Additionof salt to the electrostatically stabilised dispersionincreased the formation of square structured regions at thecrystal-suspension interface, due to increasing adhesion to thesubstrate. The loss of colloidal stability inhibited therearrangement process, resulting in higher concentrations ofsquare lattice domains at large distances from the crystal edgecompared to systems without added salt.

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5

Kaur, Sandeep. "Modify the electronic structure of monolayer MoS2 through electron-beam-activated fluorination." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-426011.

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6

Mohammed, Avaise [Verfasser], and Hidenori [Akademischer Betreuer] Takagi. "Structure and electronic properties of epitaxial monolayer WSe2 / Avaise Mohammed ; Betreuer: Hidenori Takagi." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1215573952/34.

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7

Castorano, Nicholas Joseph. "The Structure and Dynamics of Diacetylene-Lipid Langmuir Monolayers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1279558411.

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8

Zhang, Minhui. "Investigation of structure and permeability of surfaces modified with self-assembled monolayers." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08222008-063703/.

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9

Becfraft, Kevin Allan. "In-situ spectroscopic investigations of molecular structure at aqueous/solid and aqueous/monolayer/solid interfaces /." view abstract or download file of text, 2004. http://wwwlib.umi.com/cr/uoregon/fullcit?p3147813.

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Thesis (Ph. D.)--University of Oregon, 2004.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 163-173). Also available for download via the World Wide Web; free to University of Oregon users.
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10

Li, Huimin. "Relationship between molecular structure and surface properties of self-assembled monolayers." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29056.

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Polyimides are frequently used as insulating layers in the microelectronics industry. These polymers are tough, have high thermal stability, and have favorable dielectric properties; consequently, polyimides are excellent materials for insulating layers in microelectronic devices. In this research, self-assembled monolayers are investigated for use as an adhesion promoter for metal substrates, and for corrosion protectors of the metal surface. Gold substrates modified by adsorption of 3- and 4-aminothiophenol monolayers, 3- and (4-mercaptophenyl) phthalimide (MPP) monolayers, and by reaction of the 3- and 4-aminothiophenol monolayers with the phthalic anhydride were studied using reflection absorption infrared spectroscopy, contact angle measurement, ellipsometry, and electrochemical measurements. Reactions on the monolayers are used to model the attachment of an insulating polyimide to the substrate. The covalent attachment of the anhydride is confirmed, and the efficiency of the reaction of the aminothiolphenol monolayers is investigated. The reactivity of the aminothiolphenol monolayers is found to depend on the position of the amino-group around the phenyl ring. Impedance spectroscopy is used to investigate the ionic insulating properties of these systems. The 4-mercaptophthalimide monolayer is found to have the highest monolayer resistance to ion transport. This result suggests that it forms the most densely packed monolayer. The monolayer resistance of the surfaces prepared by adsorption of the aminothiolphenol isomers followed by reaction with phthalic anhydride is much lower than the corresponding deposited mercaptophthalimide monolayers. These results suggest that the reaction efficiency is low. Impedance spectroscopy and polarization measurements suggests a higher protection efficiency for 3-mercaptophenylphthalimide. These results will be discussed in the context of the ability of the isomeric mercaptophthalimide monolayers to serve as protectors against substrate corrosion.
Ph. D.
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11

Taylor, Charles Doulgas. "Influence of Molecular Orientation and Surface Coverage of w-Functionalized Mercaptans on Surface Acidity." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28566.

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The compounds 12-phenoxy-dodecane-1-thiol, 4-dodecyloxymercaptophenol and 3-dodecyloxymercaptophenol have been synthesized using a novel synthesis to investigate the effect that the orientation of the functional group has on surface acidity. 3-dodeycloxymercaptophenol and 4-dodecyloxymercaptophenol differ in that the hydroxyl group is substituted on different carbons of the benzene ring. The difference in substitution patterns should present the hydroxyl group in different orientations in the interface between a self-assembled monolayer of the compound and aqueous solutions buffered over a pH range of 3-13. By preparing self-assembled monolayers of these molecules on gold substrates, the ability of the hydroxyl group to donate its proton was shown to depend on the hydroxyl group substitution pattern on the benzene ring through contact angle titration experiments. 3-dodecyloxymercaptophenol clearly showed plateaus at low and high pH with a broad transition between the two plateaus. 4-dodecyloxymercaptophenol showed a clear plateau at low pH but not at high pH, although a transition was observed. Using infrared spectroscopy, it was further shown that the long molecular axis of the benzene ring in 3-dodecyloxymercaptophenol was tilted from the surface normal by 55°. The short molecular axis of the ring was twisted out of the plane of the surface by 28° for self-assembled monolayers of this molecule on gold substrates. In contrast, the tilt angle of 4-dodecyloxymercatophenol was measured to be 46° and was twisted out of the surface plane by 36°. It was also found from cyclic voltammetry experiments in 0.5 M KOH, that the ionized monolayers of 4-dodecyloxymercaptophenol were 2.3 kJ/mol less stable than monolayers of 3-dodecyloxymercaptophenols. This finding suggests that hydrogen bonding and other intermolecular interactions in 4-dodecyloxymercaptophenol are greater than in 3-dodecyloxymercaptophenol.
Ph. D.
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12

Shariati, Masumeh-Nina. "Electronic and Geometric Structure of Phthalocyanines on Metals." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173505.

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Adsorption of monolayers and multilayers of metal-free and metal phthalocyanines molecules on metal surfaces has been investigated using complementary microscopic and synchrotron-based spectroscopic techniques. It was observed by STM measurements that at monolayer coverage the adsorption direction of the metal-free phthalocyanine molecules with respect to the gold surface vary as a function of temperature, i.e. at room temperature (RT) and low temperature (LT). It was explained by the difference in strength of intermolecular and adsorbate-substrate interactions at room and low temperatures. Nature of the interaction between adsorbed species and the surfaces as a function of coverage has been further characterized by XPS measurements. Binding energy shifts as a function of coverage have been attributed to initial- and final-state effects, the latter being due to different core-hole screening for the different molecular coverage. The alignment of molecular films at both monolayer and multilayer coverages, which has been determined by XAS measurements in several cases, is also dependent upon the relative strength of molecule-molecule versus molecule-substrate interaction. Parallel alignment of the molecular film with respect to the surface is the result of significant interaction between the adsorbate and the substrate, whilst standing geometry of the molecular film is due to more significant intermolecular interactions. DFT simulations have provided further information on the nature of the adsorbate-substrate interaction as well as contribution of different molecular orbitals in XPS and XAS spectra. Moreover, investigation of alkali interaction with the phthalocyanine films revealed a significant modification in their geometric and electronic structures due to charge transfer from the alkali metal to the molecular film. However, no sign of metallization of the molecules has been observed by spectroscopic and microscopic studies.
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13

Vindigni, Jean-David. "Solubilisation des oléosines de graines d'Arabidopsis thaliana, études structurales pour la valorisation." Thesis, Paris, AgroParisTech, 2011. http://www.theses.fr/2011AGPT0079.

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Les corps lipidiques (CLs) sont des organites de stockage de lipides neutres rencontrés dans des organismes très variés, depuis les procaryotes jusqu’aux organismes complexes (animaux, végétaux). La surface des CLs est constituée d’une monocouche de phospholipides (PLs) entourant un coeur hydrophobe dans lequel sont stockés les lipides neutres. La monocouche de PLs est associée plus ou moins étroitement avec des protéines structurales, capables de stabiliser les CLs et d’accompagner certaines de leurs modifications morphologiques. Dans les graines de plantes oléagineuses, les CLs sont stabilisés par les oléosines. Ces protéines contiennent le plus long domaine hydrophobe connu (70 résidus) situé entre deux extrémités N et C-terminales hydrophiles. Leur mode d’association avec les CLs n’est pas connu et la littérature fait état de résultats contradictoires concernant leur structure secondaire. Nous avons montré que les oléosines de graines d’Arabidopsis thaliana sont maintenues en solution par différentes catégories de surfactants, comme les détergents anioniques ou des polymères amphiphiles appelés amphipols (Apols). La détermination de la structure secondaire des oléosines maintenues en solution dans ces différents surfactants, par dichroïsme circulaire utilisant le rayonnement synchrotron, a mis en évidence des profils contrastés. Les détergents chargés augmentent le contenu en hélices α des oléosines alors que des proportions plus importantes de feuillets β sont observées avec le détergent zwitterionique (Foscholine-12) ou les Apols. Afin d’obtenir un profil structural modèle dans un système proche du naturel, nous avons réalisé une expression hétérologue d’une isoforme d’oléosine pour la cibler dans les CLs de Saccharomyces cerevisiae. Les CLs purifiés de levures restent intacts et contiennent une forte majorité de cette isoforme d’oléosine à leur surface. Nous avons été les premiers à montrer que les oléosines étaient repliées dans un tel environnement, avec un profil structural majoritairement β. Celui-ci se rapproche du profil observé en Foscholine-12. Ce détergent est par conséquent un outil de choix pour envisager des études structurales plus résolutives (structures tridimensionnelles)
Lipid Bodies (LBs) are neutral lipid storage organelles found in various organisms from procaryotic cells to complex organisms. These neutral lipids are packed into the core of the particle which is surrounded by a phospholipid monolayer. The surface of LBs is more or less tightly associated with structural proteins involved in their stabilization and able to assist modifications of their shape or size. In oleaginous seeds, LBs are stabilized by oleosins. These proteins contain the longest known hydrophobic domain (70 residues) flanked by hydrophilic N and C-termini. The way of association of these proteins with LBs is poorly known and secondary structure descriptions in the literature are contradictory. We have shown that Arabidopsis thaliana seed oleosins could be solubilized by various surfactants such as detergents or amphiphatic polymers called amphipols (Apols). Secondary structure determination of solubilized oleosins using synchrotron radiation circular dichroism gave contrasted profiles. Negatively charged detergents increase the α-helix content of oleosins whereas the zwitterionic detergent (Foscholine-12) or Apols allow higher proportions of β-sheets. In order to get closer to the natural environment of olesins, we have opted for the heterologous expression of one oleosin isoform in the yeast Saccharomyces cerevisiae. This approach allows the biological targeting and insertion of oleosins into cytosolic LBs. Purified yeast LBs remain intact and contain a large majority of oleosins at their surface. In this natural like environment, oleosins are folded and contain a majority of β-sheets. This secondary structure profile is close to that of oleosins solubilized by Foscholin-12, making it a suitable detergent for more resolutive structural studies (three-dimensional structures)
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14

Hopkins, Adam Justin 1980. "In situ analysis of aqueous structure and adsorption at fluorocarbon, hydrocarbon and mineral surfaces." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11267.

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xvii, 209 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Altering and controlling the properties of solid surfaces in aqueous or other liquid phase environments has been a sought after objective for decades. With the discovery of chemisorbed self-assembled monolayers, this dream has become a reality. Oxide and metal surfaces can now be readily coated with an array of commercially available products to produce a desired fnctionality. The presence of these coatings on solid surfaces affects properties of the interfacial region by altering interfacial electrostatic fields, changing the structure of interfacial water molecules and altering the interactions of adsorbed species. This dissertation reports on in situ studies of adsorption at several solid/aqueous interfaces using vibrational sum-frequency spectroscopy, a surface specific technique. These studies are augmented by the use of atomic force microscopy and contact angle goniometry to characterize the prepared surfaces and their interactions with adsorbates. The studies investigate how changes in the surface structure and chemistry, as well as the bulk aqueous phase, affect interfacial structure. The studies within are primarily focused on the interactions of water with bare and functionalized fused silica and the relationship between the aqueous phase composition and the structure of fluorocarbon and hydrocarbon self-assembled monolayers. The variations in aqueous structure are then examined in detail using ionic strength controlled experiments to understand the direct interactions of water hydrophobically coated silica. This analysis is followed by an investigation of the competitive adsorption of methanol and water at fluorocarbon and hydrocarbon monolayers which show spectroscopic signatures of the interaction strength between fluorocarbons and hydrocarbons. Further studies are performed using butylammonium chloride to verify these spectroscopic signatures and reveal different molecular structures of adsorbed species at chemically different hydrophobic surfaces. Lastly, specific ion effects on the CaF 2 /water interface are shown using equilibrium and time-resolved sum-frequency spectroscopy. The results of all these studies have implications for an array of surface chemical applications from mineral flotation to biocompatibility. This dissertation includes previously published co-authored material.
Committee in charge: Thomas Dyke, Chairperson, Chemistry; Geraldine Richmond, Advisor, Chemistry; James Hutchison, Member, Chemistry; Mark Lonergan, Member, Chemistry; Qusheng Jin, Outside Member, Geological Sciences
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15

Liljeblad, Jonathan F. D. "Biomimetic Membranes: : Molecular Structure and Stability Studies by Vibrational Sum Frequency Spectroscopy." Licentiate thesis, KTH, Surface and Corrosion Science, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24465.

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In the research presented in this licentiate thesis the surface specific technique Vibrational Sum Frequency Spectroscopy, VSFS, combined with the Langmuir trough has been utilized to investigate Langmuir monolayers and Langmuir-Blodgett (LB) deposited mono- and bilayers of phospholipids. Their molecular structure, stability, and hydration were probed to gain additional understanding of important properties aiming at facilitating the use of such layers as model systems for biological membranes.

VSFS was applied to in situ studies of the degradation of Langmuir monolayers of 1,2-diacyl-phosphocholines with identical C-18 chains having various degrees of unsaturation. The time-dependent change of the monolayer area at constant surface pressure as well as the sum frequency intensity of the vinyl-CH stretch at the C=C double bonds were measured to monitor the degradation. It was shown that a rapid degradation of the monolayers of unsaturated phospholipids occurred when exposed to the laboratory air compared to the fully saturated lipid, and that the degradation could be inhibited by purging the ambient air with nitrogen. The degradation was attributed to oxidation mediated by reactive species in the air.

The molecular structure and order of Langmuir monolayers of 1,2-distearoyl-phosphocholine (18:0 PC) and their hydrating water were investigated at different surface pressures using VSFS. The spectroscopic data indicated a well ordered monolayer at all surface pressures with a more intense signal at higher pressures attributed to the subsequent increase of the number density and more ordered lipid molecules due to the tighter packing. Water molecules hydrating the headgroups or being in contact with the hydrophobic parts were observed and distinguished by their vibrational frequencies, and found to have different average orientations.

Additionally, monolayers of 18:0 PC, its fully deuterated analogue, and 1,2-distearoyl-phosphoserine (18:0 PS) were Langmuir-Blodgett (LB) deposited on CaF2 substrates and VSFS was used to investigate the structure and order of the films as well as the hydrating water. The CH-region, water region, and lower wavenumber region containing phosphate, ester, carboxylic acid, and amine signals were probed to obtain a complete picture of the molecule. The data indicates that all deposited monolayers formed a well ordered and stable film and the average orientation of the aliphatic chains was determined using the antisymmetric methyl stretch.


I forskningen som presenteras i denna licentiatavhandling har den ytspecifika vibrationssumfrekvensspektroskopin, VSFS, använts tillsammans med Langmuirtråget för att studera Langmuir-monolager och Langmuir-Blod-gett (LB) deponerade monolager och bilager av fosfolipider. För att utvidga förståelsen av egenskaper som är viktiga för att underlätta användandet av dem som modellsystem för biologiska membran undersöktes såväl deras molekylära struktur som stabilitet och hydratisering.

VSFS användes för att genomföra in situ-studier av nedbrytningen av Langmuir-monolager av 1,2-diacyl-fosfokoliner med identiska 18 kolatomer långa sidokedjor med varierande antal omättade kol-kol-bindningar. För att övervaka nedbrytningen mättes såväl den tidsberoende förändringen av monolagernas area vid konstant yttryck som sumfrekevensintensiteten från dubbelbindningarnas CH-vibration. När monolagerna bestående av omättade fosfolipider utsattes för laboratorieluften bröts de ner hastigt jämfört med det helt mättade monolagret. Denna nedbrytning som sannolikt orsakades av reaktiva ämnen i luften kunde inhiberas fullständigt genom att ersätta den omgivande luften med kvävgas.

Den molekylära strukturen och ordningen hos Langmuir-monolager av 1,2-distearoyl-fosfokolin (18:0 PC) och deras hydratiseringsvatten undersöktes vid olika yttryck med VSFS. Den spektroskopiska datan visar att monolagerna är välordnade vid alla yttryck samt att sumfrekvenssignalens styrka ökar med ökande yttryck på grund av såväl det större antalet molekyler per ytenhet som den högre ordningen då molekylerna packas tätare. Vattenmolekyler som hydratiserar huvudgrupperna eller är i kontakt med hydrofoba delar och har olika medelorientering observerades och kunde identifieras genom sina vibrationsfrekvenser.

Vidare deponerades monolager av 18:0 PC, dess fullt deuterade analog och 1,2-distearoyl-fofsfoserin (18:0 PS) på substrat av CaF2 och VSFS användes för att undersöka filmernas struktur och ordning såväl som hydratiseringsvattnet. CH- och vattenregionerna samt lågvågtalsområdet som innehåller fosfat-, ester-, karboxylsyra- och aminsignaler undersöktes för att få en fullständig bild av den molekylära strukturen. Data visar att alla deponerade monolager bildade en välordnad och stabil film och kolvätekedjornas medelorientering bestämdes med hjälp av signalen från den antisymmetriska metylvibrationen.


QC 20100924
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16

Knock, Mona Marie. "Monolayers of cationic surfactants at the air-water and oil-water interfaces." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:c0cdaf66-716a-4b48-b22c-659d1fe2a342.

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Monolayers of the cationic surfactant hexadecyltrimethylammonium halide (CTAX, where X = F¯, Cl¯, Br¯, and I¯) have been studied at the air-water and oilwater interfaces. At the air-water interface, the effects of the halide counterion and the addition of counterion were investigated. Sum-frequency spectroscopy (SFS), ellipsometry, and surface tensiometry indicated that the counterion changed the efficiency and effectiveness of the surfactant, both decreasing in the order of Br¯> Cl¯>F¯. The addition of salt in the form of 0.1 M KX was found to reduce the cmc but had little effect on the limiting area per molecule attained at the cmc, which increased from 44 Å2 for CTAB to 65 Å2 for CTAC and ca. 94 Å2 for CTAF. Neither SFS nor ellipsometry provided any firm evidence for specific effects of the halide ions on the structure of the surfactant monolayers. For CTAB monolayers in the absence of excess electrolyte, the effect of area per molecule on the sum-frequency (SF) spectra was studied. Mixed monolayers of CTAB and tetradecane at the air-water interface exhibit a first-order phase transition from a conformationally disordered to a conformationally ordered state as the temperature is lowered. The phase transition occurs ca. 11 °C above the bulk melting point of tetradecane. A new experimental arrangement is described for acquiring SF spectra from surfactants at the oil-water interface. The key features of this approach are the stabilisation of a thin oil film between a sapphire prism and an aqueous phase, and the use of total internal reflection to enhance the total signal and discriminate against signals from other interfaces in the system. With this new methodology, the first SF vibrational spectra of surfactant monolayers at an alkane-water interface were obtained. Surface tensiometry was used to characterise the monolayers further. The structure of CTAB monolayers at the hexadecane-water interface was determined by SFS and compared with monolayers of CTAB at the air-water interface. At low concentrations, CTAB/hexadecane showed the expected features in the C-H stretching region, characteristic of a conformationally disordered monolayer. As the bulk concentration approached the critical micelle concentration, the spectra changed to one characteristic of a more ordered, upright conformation. Ellipsometric measurements supported this conclusion. This qualitative structural change is not observed in analogous monolayers at the air-water interface or CCl4-water interface, or in surfactant solutions in contact with a hydrophobic solid surface.
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17

Watcharinyanon, Somsakul. "Structure of Self-Assembled Monolayers on Gold Studied by NEXAFS and Photoelectron Spectroscopy." Doctoral thesis, Karlstad : Faculty of Technology and Science, Physics, Karlstads universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2723.

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18

Zhenghua, Tang. "Synthesis and Energetics of Gold Nanoclusters Tailored by Interfacial Bonding Structure." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/chemistry_diss/67.

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In addition to the well known quantum confinement effects resulted from size and shape, interfacial bond structure is another factor, affecting the properties of the nanomaterial that is rarely studied. Inspired by the “Au-S-Au” staple motif discovered from the crystal structure of monothiol protected Au102 nanocluster (Science, 2007, 318, 430), dithiol molecules (e. g. 1, 2-dithiol, 1, 4-dithiol, etc.) with molecular structural constraint have been employed to create dithiolate protected clusters or mixed monothiolate and dithiolate protected clusters. The structure and properties of the Au clusters are expected to change due to two effects: The entropy gain of dithiol over monothiol protection and the constraint to the formation of the thiol bridging motif. DMPS (1, 2-dithiol molecule) stabilized clusters with characteristic absorption bands have been obtained, and characterized by multiple techniques. Monolayer reaction on gold core surface between the monothiol tiopronin and dithiol DMPS has been performed, and the mechanism has been probed. Mixed phenylethanethiolate and durene-dithiolate (1, 4-dithiol molecule) protected Au130 clusters with rich electrochemical features have been created, and the optical and electrochemical energetics have been successfully correlated based on core and core-ligand energy states. Furthermore, the impact of 1, 4-dithiolate-Au bonding on the near infrared luminescence has been studied.
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19

Conn, Brian E. "Revealing the Magic in Silver Magic Number Clusters: The Development of Size-Evolutionary Patterns for Monolayer Coated Silver-Thiolate Nanoclusters." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1481294367098454.

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20

Nilson, Katharina. "Phthalocyanines on Surfaces : Monolayers, Films and Alkali Modified Structures." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8209.

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21

Carter-Fenk, Kimberly Anne. "Structure, Adsorption Mechanisms, and Vibrational Exciton Formation at Proxy Marine Interfaces." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1617809603306859.

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22

Saint-Pierre-Chazalet, Michèle. "Structure et interactions en mono et multicouches de cyanine a longues chaines et d'amphotericine b." Paris 6, 1987. http://www.theses.fr/1987PA066208.

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23

Sautot, Pascale. "Propriétés d'auto-assemblage de phospholipides riches en acides gras polyinsaturés : caractérisation physico-chimique et simulation de bicouches par dynamique moléculaire." Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL032N/document.

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La littérature des dernières décennies regorge de références concernant les bienfaits des acides gras oméga 3, tels que l’EPA (C20:5 n-3) et le DHA (C22:6 n-3) qui jouent un rôle essentiel dans la prévention de nombreuses pathologies comme les maladies neurodégénératives (type Alzheimer). Les sources majeures d’EPA et DHA sont celles d’origine marine. C’est dans ce contexte que cette étude a choisi de s’intéresser aux phospholipides provenant de têtes de saumon. L’objectif était de les extraire, de purifier la phosphatidylcholine (PC) issue du mélange de lipides et d’en déterminer ses propriétés d’auto-assemblage en bicouches. Une approche expérimentale par la caractérisation physico-chimique de ce PC a été complétée par une étude théorique du même composé en utilisant les techniques de simulation par dynamique moléculaire qui a permis une caractérisation à l’échelle moléculaire des bicouches lipidiques. La caractérisation a permis d’aboutir au profil détaillé de la composition du mélange PC saumon, d’élaborer le diagramme de phase PC –eau, de déterminer les propriétés d’empaquetage d’hydratation de ce lipide. Les paramètres choisis pour l’étude en dynamique moléculaire ont permis de reproduire de manière fidèle les résultats expérimentaux, validant ainsi le modèle et les conditions de simulations déterminés au préalable. La caractérisation des propriétés structurales de la PC de saumon sous forme de multicouches a permis d’approfondir la compréhension des mécanismes d’interactions à l’échelle moléculaire existant entre les lipides insaturés eux-mêmes
The literature of recent decades is replete with references regarding the benefits of omega 3 fatty acids such as EPA (C20:5 n-3) and DHA (C22:6 n-3) which play an essential role in preventing many diseases such as neurodegenerative diseases (Alzheimer's type). The major sources of EPA and DHA are those of marine origin. It is within this context that this study chose to deal with phospholipids from salmon heads. The objective was to extract, purify phosphatidylcholine (PC) derived from the mixture of lipids and determine its properties of self-assembly into bilayers. An experimental approach by the physicochemical characterization of this PC was supplemented by a theoretical study of the same compound using the techniques of molecular dynamics simulation that allowed a molecular-scale characterization of lipid bilayers. The characterization resulted in detailed profile of the mixture composition of salmon PC, to draw up the phase diagram of PC-water, to determine the packing and hydration properties of this lipid. The parameters chosen for the study of molecular dynamics have faithfully reproduced the experimental results, thus validating the model and simulation conditions determined in advance. The characterization of structural properties of the PC as a multilayer salmon has deepened the understanding of interaction mechanisms at the molecular level between unsaturated lipids themselves
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24

Lenne, Pierre-François. "Deux exemples de cristallisation à la surface de l'eau : cristaux 2-D de protéines ; monocouches d'alcools en présence d'amphiphiles solubles." Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10039.

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La premiere partie de cette these est consacree a la cristallisation de proteines a la surface de l'eau. Les etapes de formation des cristaux 2-d de proteines sont mises en evidence par ellipsometrie et mesure de la constante elastique de cisaillement. Des correlations sont etablies entre mesures physiques et observation en microscopie electronique apres transfert des cristaux. Quatre proteines differentes ont ete etudiees par diffraction des rayons x en incidence rasante sur un montage haute resolution. Trois d'entre elles, l'annexine v, la hupr marquee par une sequence d'histidines et la streptavidine presentent un spectre de diffraction montrant des pics de bragg fins. La longueur de coherence des cristaux est au moins de 4 m. La meilleure resolution dans le plan de l'interface est 9 a, atteinte avec la streptavidine pour laquelle 19 pics ont ete detectes. Les experiences de diffraction ont montre que les cristaux 2-d de proteines sont rapidement endommages par les rayons x. Nous mettons egalement en evidence des effets de l'addition de glutaraldehyde (cross-linker des proteines) : celui-ci augmente la rigidite laterale des monocouches, la resolution atteinte en diffraction x et diminue le dommage par irradiation. Dans la seconde partie, nous presentons des observations de microscopie de fluorescence de domaines solides en croissance dans des monocouches d'alcool, etalees sur une sous-phase contenant des molecules solubles et amphiphiles d'acide octanoique (pka=4,9). Les morphologies sont fortement branchees quand ph>pka et assez compactes dans le cas oppose. Pour ph
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25

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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26

Cafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." University of Sydney, 2008. http://hdl.handle.net/2123/3870.

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PhD
SYNOPSIS OF THIS THESIS The aim of this thesis is to more fully understand and explain the binding mechanism of organic molecules to the Au(111) surface and to explore the conduction of such molecules. It consists of five discreet chapters connected to each other by the central theme of “The Single Molecule Device: Conductance and Binding”. There is a deliberate concentration on azine linkers, in particular those with a 1,10-phenanthroline-type bidentate configuration at each end. This linker unit is called a “molecular alligator clip” and is investigated as an alternative to the thiol linker unit more commonly used. Chapter 1 places the work in the broad context of Molecular Electronics and establishes the need for this research. In Chapter 2 the multiple break-junction technique (using a Scanning Tunnelling Microscope or similar device) was used to investigate the conductance of various molecules with azine linkers. A major finding of those experiments is that solvent interactions are a key factor in the conductance signal of particular molecules. Some solvents interfere with the molecule’s interaction with and attachment to the gold electrodes. One indicator of the degree of this interference is the extent of the enhancement or otherwise of the gold quantized conduction peak at 1.0 G0. Below 1.0 G0 a broad range for which the molecule enhances conduction indicates that solvent interactions contribute to a variety of structures which could bridge the electrodes, each with their own specific conductance value. The use of histograms with a Log10 scale for conductance proved useful for observing broad range features. vi Another factor which affects the conductance signal is the geometric alignment of the molecule (or the molecule-solvent structure) to the gold electrode, and the molecular alignment is explored in Chapters 3 for 1,10-phenanthroline (PHEN) and Chapter 4 for thiols. In Chapter 3 STM images, electrochemistry, and Density Functional Theory (DFT) are used to determine 1,10-phenanthroline (PHEN) structures on the Au(111) surface. It is established that PHEN binds in two modes, a physisorbed state and a chemisorbed state. The chemisorbed state is more stable and involves the extraction of gold from the bulk to form adatom-PHEN entities which are highly mobile on the gold surface. Surface pitting is viewed as evidential of the formation of the adatom-molecule entities. DFT calculations in this chapter were performed by Ante Bilic and Jeffery Reimers. The conclusions to Chapter 3 implicate the adatom as a binding mode of thiols to gold and this is explored in Chapter 4 by a timely review of nascent research in the field. The adatom motif is identified as the major binding structure for thiol terminated molecules to gold, using the explanation of surface pitting in Chapter 3 as major evidence and substantiated by emergent literature, both experimental and theoretical. Furthermore, the effect of this binding mode on conductance is explored and structures relevant to the break-junction experiment of Chapter 2 are identified and their conductance values compared. Finally, as a result of researching extensive reports of molecular conductance values, and having attempted the same, a simple method for predicting the conductance of single molecules is presented based upon the tunneling conductance formula.
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27

Ringstad, Lovisa. "Interaction Between Antimicrobial Peptides and Phospholipid Membranes Effects of Peptide Length and Composition /." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-101989.

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28

Borthwick, Matthew A. "X-ray techniques for probing self-assembled monolayer structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ44129.pdf.

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29

Bhinde, Tej. "Adsorption of alkyl amides : monolayer structures and mixing behaviour." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/236781.

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In this work monolayers of alkyl amides adsorbed on a graphite surface have been successfully identified and investigated using a combination of synchrotron X-ray and neutron diffraction and Differential Scanning Calorimetry (DSC). Exceptionally stable solid layers have been observed at temperatures well above the bulk melting point, at both high multilayer coverages and, very unusually, at sub-monolayer coverages. The molecular structure of the two-dimensional crystals of these alkyl amides has been obtained from diffraction and interpreted in terms of the subtle intermolecular interactions, particularly the contribution of hydrogen bonding in monolayer assembly. Thermodynamic information provides insight on the mixing behaviour in adsorbed amide layers. A systematic study on the variation in monolayer crystal structures with alkyl chain length (between five and sixteen carbon atoms) of saturated alkyl amides using diffraction identifies that all the amide molecules investigated lie flat on the graphite surface. An odd-even variation isobserved in the monolayer crystal structures and this is supported by the melting enthalpies of the amides determined by DSC. The structure of the even members is found to support the qualitative monolayer arrangement proposed by an STM report of one member of the series, but with more quantitative insight here. Significantly, a new monolayer symmetry group for odd members of the homologous series has been identified. Characteristics of the hydrogen bond geometrybetween the molecules in the solid monolayers are reported exploiting the high level of detail available from the diffraction techniques. Secondly, the formation of solid monolayers of unsaturated alkyl amides has been reported and their crystal structures determined. This is believed to be the first report of these monolayer structures. The position and nature of the double bond have an important effect in the stability of the monolayer. Unusually, certain unsaturated amides that have a double bond conjugated with the amide group are found to form considerably more stable layers than their saturated homologues. The abnormally high melting points and enhanced stability of amide monolayers have been attributed to the existence of a network of hydrogen bonds in the layer. Phase diagrams obtained by DSC for binary mixtures of alkyl amides on graphite have been quantitatively analysed using a combination of thermodynamic models (ideal, eutectic and the regular solution models). The determined mixing behaviour is supported by conclusions based on the monolayer crystal structures of the individual components calculated using diffraction. Saturated amide mixtures that have the same plane group symmetry are found to mix non-ideally in the solid layer and phase separate if the symmetry is different, whereas the mixing behaviour of saturated/unsaturated amides considered here was found to depend on the nature of the double bond (cis/trans). Results from an initial investigation into the adsorption of alkyl amides at the polymer/air interface are also presented. This complements the study above and provides an alternative situation where amide monolayers have a central role. A reduction in the coefficient of friction is seen with increasing bulk concentration of the amide and with increasing time indicating migration of the amide to the surface. A powerful combination of surface reflection techniquesincluding neutron and X-ray reflection and ellipsometry have been used to gain uniquelyquantitative insight into this system. Initial estimates of the concentration of amides at the polystyrene surface are presented for the first time.
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30

Wolak, Matthaeus Anton. "The Electronic Structure of Biomolecular Self-Assembled Monolayers." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4258.

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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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31

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.

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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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32

Zonglong, Yang. "Auto-organisation des Acyl Steroid Glycosides (ASG) : Etude des relations structure-propriétés pour les cas de l’α-CAG et du BbGL 1, constituants de membranes bactériennes." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI041.

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Les acyl stéryl glycosides (ASGs) appartiennent à une famille de glycolipides qui possèdent un caractère amphiphile particulier dû à la présence de deux parties hydrophobes, un stéroïde et une chaine grasse. Dans le cadre de nos études des propriétés d’auto-organisation des glycoamphiphiles, ce travail est dédié à l’étude de deux ASGs, α-CAG et BbGL 1, composés naturels présents respectivement dans les membranes des bactéries Helicobacter pylori et Borrelia burgdorferi., présentant des structures similaires mais des activités biologiques différentes. Notre travail a consisté à déterminer les paramètres structuraux qui gouvernent leurs propriétés d’auto-assemblage. Deux séries de 6-O-acyl cholestéryl glycosides (glucosides et galactosides) variant dans leur configuration anomérique et la longueur et le niveau d’insaturation de leur chaine grasse ont été synthétisées et leur capacité à former des cristaux liquides et à promouvoir une ségrégation lipidique dans des monocouches de Langmuir modèles de membrane ont été étudiées. Les relations structure-propriétés établies montrent que la longueur de la chaine grasse est le paramètre le plus discriminant dans le comportement d’auto-assemblage dans les deux types d’expériences. Pour les cristaux liquides thermotropes, l’autre facteur discriminant est la configuration anomérique, deux phases colonnaires successives rectangulaires puis hexagonales étant observées pour les séries α alors qu’une seule a été observée en séries β Changer de sucre n’induit pas de différence significative dans le comportement LC. Concernant la formation de domaines lipidiques, les modifications de la configuration (α/β) et du sucre influencent significativement leur temps d’apparition, apportant pour la première fois une définition claire des paramètres structuraux et physicochimiques qui gouvernent le comportement de l’α-CAG et ses analogues, en lien avec les données commues sur l’augmentation de pathogénicité d’Helicobacter pylori. Ce travail de thèse donne une illustration de l’importance de la structure des carbohydrates dans les processus biologiques et du concept de glycoamphiphilie
Acyl steryl glycosides (ASGs) are a family of glycolipids which exhibit a peculiar amphiphilic character based on the presence of two hydrophobic appendages, one steroid moiety and one fatty alkyl chain, attached on a polar carbohydrate backbone. In the frame of our studies on the self-organisation properties of carbohydrate-based amphiphiles, this thesis is an investigation of the behavior of ASGs, in particular α-CAG and BbGL 1, two natural compounds found in bacterial membranes, Helicobacter pylori, Borrelia burgdorferi repectively, who exhibit close structures but different bioactivity. Our work has aimed at determining the key structural parameters governing their self-organization behavior. Two series of acyl cholesteryl glycosides (glucosides or galactosides) have been synthesized, with variations in the anomeric configuration, the 6-O-acyl chain length and level of unsaturation, and investigated with respect to their ability to form liquid crystalline mesophases, and to drive lipid domain segregation in Langmuir monolayers as model membranes. Structure-properties relationships have been established, indicating that the fatty chain length showed the most remarkable influence on the self-organization behavior, in LC and model membrane experiments. For the LC mesophases, the other important parameter is the anomeric configuration, two successive columnar phases, rectangular then hexagonal, being observed for the α-anomers, whereas only one was found for the β-anomers. No significant changes were observed when comparing glucosides and galactosides. With respect the formation of domains, configuration modifications at both C-1 (α or β) and C-4 (gluco or galacto) influenced significantly the domains appearance time, giving the first, clear physicochemical proof of the structural influential factors in the behavior of α-CAG and analogues, in the context of the known increased pathogenicity of Helicobacter pylori. Overall, this thesis provides a nice illustration of the subtlety and the importance of carbohydrate structure in biological processes, and of the concept of glycoamphiphilicity
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33

Badin, Mihaela Georgeta. "Self-assembled monolayers on gold substrates structure and characterization." Saarbrücken VDM Verlag Dr. Müller, 2007. http://d-nb.info/988947358/04.

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34

Godin, Michel. "Surface stress, kinetics, and structure of alkanethiol self-assembled monolayers." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85551.

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The surface stress induced during the formation of alkanethiol [HS(CH 2)nCH3] self-assembled monolayers (SAMs) on gold from the vapor phase was measured using a differential cantilever-based sensor. This custom-built system is capable of surface stress measurements with a sensitivity of 5 x 10-5 N/m using commercially-available atomic force microscopy cantilevers. A second system combining cantilever-based sensing and ellipsometry was also designed and built, capable of yielding simultaneous in situ surface stress and film thickness measurements. Scanning tunneling microscopy (STM) with molecular resolution was also performed ex situ in order to characterize the structure of the resulting SAMs. The complementary use of these tools has provided an all-around view of the self-assembly process.
These measurements were performed in order to gain insight into the mechanisms involved in the self-assembly process and into the origins of the associated surface stress. Moreover, these studies were used to characterize and optimize the response of cantilever-based sensors based on functionalized SAM technology in terms of reliability, sensitivity, and reproducibility.
The evolution of the surface stress induced during alkanethiol SAM formation reveals features associated with coverage-dependent structural phase transitions. These results show that both the kinetics of SAM formation and the resulting SAM structure are strongly influenced by the surface structure of the underlying gold substrate, by the impingement rate of the alkanethiol molecules onto the gold surface, and by the cleanliness of the gold surface. In particular, it was found that a minimum gold grain size is necessary in order for the SAM to achieve the standing-up phase, for which large compressive surface stresses (~10 N/m) are measured. In addition, these results show that alkanethiol SAMs can become kinetically trapped in metastable intermediate states (lying-down phase) for formation on small-grained gold surfaces and/or at low alkanethiol vapor concentrations. Theoretical modeling of the origins of the induced surface stress reveals that inter-molecular Lennard-Jones interactions and electrostatic repulsion between adsorbed species play minimal roles in the development of the surface stress. Changes in the electronic structure of the underlying gold substrate are more likely to account for the large compressive surface stresses observed during alkanethiol SAM formation.
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35

Bulut, Ahmet. "An in-situ glancing incidence EXAFS study of the structure of some electrochemically formed submonolayer adsorbates." Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319704.

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36

Gurau, Marc Cory. "The structure of langmuir monolayers probed with vibrational sum frequency spectroscopy." Diss., Texas A&M University, 2002. http://hdl.handle.net/1969.1/2199.

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Langmuir monolayers can be employed as simple model systems to study interactions at surfaces. Such investigations are important to fields ranging from biology to materials science. Herein, several aspects of these films and their associated water structure have been examined with vibrational sum frequency spectroscopy (VSFS). This second order nonlinear optical spectroscopy is particularly well suited for simultaneous investigations of the monolayer and the associated water structure with unprecedented surface specificity. The structures of these systems were altered through the control of experimental parameters including monolayer pressure, subphase temperature, pH and ionic content. Thermodynamic information about structural changes in a fatty amine monolayer's hydrophobic region was obtained by observation of the pressure and temperature dependence of the monolayer's solid to liquid phase transition. Further studies used the coordination of divalent cations to acid monolayers to perturb the water layers nearest to the film which enabled a better understanding of the water related VSFS features from these hydrophilic interfaces. Information from both the monolayer and water structure was then combined in order to examine the role of water in mediating ion-biomaterial interactions, often expressed in terms of the Hofmeister series.
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37

Roper, Mark Geoffrey. "Structure and bonding of self-assembled monolayers : thiolates on Au (111)." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415868.

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38

Can, Süleyman Zühtü. "Molecular structure and organization in organic monolayers at aqueous/vapor interfaces." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8030.

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Thesis (Ph. D.)--University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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39

Colangelo, E. L. "Elucidating the structure of peptide self-assembled monolayers on gold nanoparticles." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3006293/.

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Controlling gold nanoparticles (GNPs) surface chemistry is a fundamental prerequisite to tailor their properties and envision their assembly into complex nanomaterials from a “bottom-up” approach. Short peptides have been specifically designed to form self-assembled monolayers on GNPs surface and used to increase their stability. However, their structural characterization is often poorly investigated and challenging to assess. This body of work examines different approaches to elucidate the structure and organization of peptide self-assembled monolayers on GNPs. First, the current knowledge and the methods available to characterize the GNPs surface are reviewed. Second, the attempt at using benzophenone-derivative peptides, to provide insights into the molecular organization and compactness of mixed monolayers self-assembled on GNPs, is reported. Under irradiation at 350 nm, the carbonyl group of the benzophenone moiety crosslinks to an adjacent molecule. However, the photo-cross-linking reaction, monitored by FTIR spectroscopy in solution, was not detected on the GNPs surface. Third, to probe the accessibility of a functional group at the GNPs surface, fluorescently labelled peptides, quenched when bound to the gold surface, and bearing a cleavage site for thrombin enzyme at different positions along the chain, were inserted into different peptide self-assembled monolayers on GNPs. The timings of the increase in fluorescence, upon cleavage by thrombin, probed the accessibility, and hence the molecular environment, of the site within the different monolayers investigated. Fourth, a computational model for peptide-capped GNPs was developed using experimentally characterized CALNN- and CFGAILSS-capped GNPs as a benchmark. The molecular dynamics simulations not only reproduced the experimentally observed dependence of the monolayer secondary structure on peptide capping density and on nanoparticle size, but provided also further insights into the monolayers and inter-peptide interactions at the molecular level.
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40

Vogt, Leslie. "Electronic Structure Predictions for Properties of Organic Materials." Thesis, Harvard University, 2011. http://dissertations.umi.com/gsas.harvard:10041.

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Electronic structure calculations of organic molecules are an important set of tools to gain understanding of molecular structures. This thesis presents two separate contributions to applying quantum chemistry to organic molecules. In the first section, the computational cost of a post-Hartree-Fock method is improved for large molecules by using graphical processing units. In this work, the resolution-of-the-identity second-order Møller-Plesset perturbation theory (RI-MP2) algorithm was adapted to send the large matrix multiplication steps to be run on a graphics co-processor. As a result, the calculations were performed up to 15x faster than a standard implementation for large molecules such as taxol. In the second section of the thesis, density functional theory is used to predict the molecular dipole moments of molecules that form self-assembled monolayers (SAMs) on metal surfaces. The dipole moment of the molecule that is aligned perpendicular to the surface in a SAM changes the work function of the surface. The calculated dipole moments correlate with the current density measured for the junctions by experimental collaborators. This result holds for a series of alkane chains with even and odd numbers of carbons and for molecules that have an amide group substituted for an ethylene unit.
Chemistry and Chemical Biology
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41

Ma, Gary. "Structural studies of non-ionic surfactant monolayers and vesicles." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299877.

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42

Duesing, Peter Michael. "Effects of pressure on lyotropic liquid-crystalline phase behaviour and structure." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294919.

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43

Adamczyk, Leslie Ann. "Understanding the Structure and Properties of Self-Assembled Monolayers for Interfacial Patterning." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28018.

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This dissertation describes the impact of defects on monolayer properties for self-assembled monolayers (SAMs) created by interfacial patterning methods. When forming a two-dimensional interfacial pattern with n-alkanethiols on gold, the desired electrochemical properties are those of a homogeneous, solution adsorbed monolayer. However, even well-ordered SAMs contain a small degree of defects, especially at domain boundaries where two nucleating domains converge. Patterning a surface creates user-defined domain boundaries within the monolayer, potentially having a significant impact on the properties of the interface. This dissertation investigates the effect that user-created domain boundaries have on the properties of a monolayer, as studied by electrochemical impedance spectroscopy. Two patterning methods are investigated for creating user-defined domain boundaries: the soft lithography method of contact printing and site-selective reductive desorption. The electrochemical properties of homogeneous contact printed monolayers are measured and compared to those of monolayers prepared by solution adsorption. The contact printed monolayers are found to have dramatically different impedance behavior from the solution prepared monolayers, consistent with the contact printed monolayers having greater defect density. In addition, these studies show that the overall defect density depends on the concentration of the solutions used for contact printing. In this work, simple patterns are created by contact printing a pattern onto the substrate and then backfilling the remaining gold substrate by solution adsorption. Backfilling with the same alkanethiol used to create the pattern generates a homogeneous monolayer; however, it is found that the contact printed/backfilled monolayer has an impedance intermediate between the homogeneous contact printed and the homogeneous solution adsorbed monolayer. This result suggests that the backfilling process also saturates the pinhole defects associated with the contact printed areas. In addition to exploring defects that arise from contact printing, simple patterns with user-defined defects, created by site-selective reductive desorption (SSRD), were also investigated. Following the backfill step, the impedance behavior of the SSRD produced patterns was similar to that of the impedance of the initial pattern before backfilling. This important result implies that the domain boundaries play the most important role in defining the overall impedance of the patterned interface.
Ph. D.
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44

Villar, Gabriel. "Aqueous droplet networks for functional tissue-like materials." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:602f9161-368c-48c0-9619-7974f743f2f2.

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An aqueous droplet in a solution of lipids in oil acquires a lipid monolayer coat, and two such droplets adhere to form a bilayer at their interface. Networks of droplets have been constructed in this way that function as light sensors, batteries and electrical circuits by using membrane proteins incorporated into the bilayers. However, the droplets have been confined to a bulk oil phase, which precludes direct communication with physiological environments. Further, the networks typically have been assembled manually, which limits their scale and complexity. This thesis addresses these limitations, and thereby enables prospective medical and technological applications for droplet networks. In the first part of the work, defined droplet networks are encapsulated within mm-scale drops of oil in water to form structures called multisomes. The encapsulated droplets adhere to one another and to the surface of the oil drop to form interface bilayers that allow them to communicate with each other and with the surrounding aqueous environment through membrane pores. The contents of the droplets can be released by changing the pH or temperature of the surrounding solution. Multisomes have potential applications in synthetic biology and medicine. In the second part of the work, a three-dimensional printing technique is developed that allows the construction of complex networks of tens of thousands of heterologous droplets ~50 µm in diameter. The droplets form a self-supporting material in bulk oil or water analogous to biological tissue. The mechanical properties of the material are calculated to be similar to those of soft tissues. Membrane proteins can be printed in specific droplets, for example to establish a conductive pathway through an otherwise insulating network. Further, the networks can be programmed by osmolarity gradients to fold into designed shapes. Printed droplet networks can serve as platforms for soft devices, and might be interfaced with living tissues for medical applications.
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45

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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46

Hanyu, Yuki. "Chemical scanning probe lithography and molecular construction." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:409308ed-4806-44fc-87c3-5c1fe8971f79.

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The initiation and high resolution control of surface confined chemical reactions would be both beneficial for nanofabrication and fundamentally interesting. In this work, spatially controlled scanning probe directed organometallic coupling, patterned functional protein immobilisation and highly localised reversible redox reactions on SAMs were investigated. Catalytically active palladium nanoparticles were mounted on a scanning probe and an appropriate reagent SAM was scanned in a reagent solution. This instigated a spatially resolved organometallic coupling reaction between the solution and SAM-phase reagents. Within this catalytic nanolithography a spatial resolution of ~10nm is possible, equating to zeptomole-scale reaction. The methodology was applied to reactions such as Sonogashira coupling and local oligo(phenylene vinylene) synthesis. By altering the experimental protocols, relating probe scan velocity to reaction yield and characterising the nanopattern, a PVP matrix model describing a proposed mechanism of catalytic nanolithography, was presented. Though ultimately limited by probe deactivation, calculations indicated that activity per immobilised nanoparticle is very high in this configuration. For biopatterning, surface nanopatterns defined by carboxylic functionality were generated from methyl-terminated SAMs by local anodic oxidation (LAO) initiated by a conductive AFM probe. By employing suitable linker compounds, avidin and Stefin-A quadruple Mutant (SQM) receptive peptide aptamers were patterned at sub-100nm resolution. The multiplexed sensing capability of an SQM array was demonstrated by reacting generated patterns with single or a mixture of multiple antibodies. The reversible redox conversion and switching of reactivity of hydroquinone-terminated SAMs was electrochemically demonstrated prior to an application in redox nanolithography. In this methodology, spatially controlled probe-induced in situ "writing" and "erasing" based on reversible redox conversion were conducted on hydroquinone terminated SAM. In combination with dip-pen nanolithography, a novel method of redox electro-pen nanolithography was designed and the method’s application for lithography was examined.
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47

Domènech, Cabrera Òscar. "Structure and Physicochemical Properties of Phospholipidic Monolayers and Bilayers. LB and AFM Studies." Doctoral thesis, Universitat de Barcelona, 2007. http://hdl.handle.net/10803/2758.

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The main objective of this Ph. D. Thesis work was to study the physicochemical properties of the inner membrane of mitochondria and the interaction of "cyt c" with model membranes. Suitable techniques were used to accomplish this objective: Langmuir and Langmuir Blodgett films, fluorescence spectroscopy, Brewster Angle Microscopy and Atomic Force Microscopy.

The general conclusion of this Thesis is: "Calcium induces HII phases in POPE:CL (0.8:0.2, mol:mol) samples in solution. This composition is the most stable mixed monolayer of both phospholipids and corresponds to the native molar fraction in the inner membrane of the mitochondrion. The extension of these inverted micelles forms planar bilayers on solid supports displaying lateral lipid segregation of CL enriched domains where cyt "c can" bind specifically. In this configuration POPC can remain as a spacer in POPE enriched domains forming the matrix of the membrane". The inverse process would be a possible vindication to the release of "cyt c" from the inner membrane of mitochondrion during apoptosis.
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48

Mudiyanselage, Asanga B. Arampath. "Structural and electronic properties of boron monolayer sheets and nitrogen-seeded epitaxial graphene." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2014. http://digitalcommons.auctr.edu/dissertations/1597.

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We employ a global optimization method to predict two-dimensional (2D) nanostructures through the particle swarm optimization (PSO) algorithm. By performing PSO simulations, we predict new stable structures of boron monolayer sheets for a wide range of boron concentrations. We present a new class of boron sheets, composed of triangular and hexagonal motifs, which are more likely to be the precursors of boron nanotubes. We describe a simple and clear picture of electronic bonding in boron sheets and highlight the importance of three-center bonding and its competition with two-center bonding, which can also explain the stability of recently discovered boron monolayer sheets. The graphene-based electronics is an intriguing prospective for replacing silicon for next-generation of transistors. Practical application of graphene based materials requests a band gap. We present results from first-principles density-function calculation for semiconducting graphene based on nitrogen-seeded epitaxial graphene. A small fraction of covalently-bonded nitrogen leads to a band gap opening in epitaxial graphene and a transition from a semi metallic to a semiconducting state. The induced gap is shown to be attributed to the modification of the 1t conjugation of epitaxial graphene. The resulting nitrogen-seeded graphene opens a band gap about 0.8 eV, in good agreement with experimental observations.
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49

Clegg, Robert Samuel. "Structure, stability and electron transfer characteristics of self-assembled monolayers containing internal peptide groups /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9955917.

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Thesis (Ph. D.)--University of Oregon, 1999.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 303-350). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9955917.
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50

Fujita, Akito. "Investigations of the Local Hydration Structure of Alkanethiol Self-Assembled Monolayers by FM-AFM." Kyoto University, 2019. http://hdl.handle.net/2433/242511.

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