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Cooper, Sharon. "Nucleation beneath monolayer films." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238881.
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Tenasini, Giulia. "Quantum transport in monolayer WTe2." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14897/.
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Il ditellurio di tungsteno (WTe2) appartiene alla classe dei dicalcogenuri di metalli di transizione (TMDs), che rappresentano attualmente i materiali più promettenti, insieme al grafene, nel campo di ricerca dei cristalli bidimensionali (2D). Grazie ad una caratteristica struttura stratificata, con differenti piani atomici legati da forze di van der Waals, mediante esfoliazione è possibile isolare strati di spessore quasi-atomico di TMDs, detti “monostrati”, con proprietà spesso molto diverse dal materiale bulk originario. Il WTe2 nella sua forma a monostrato, è stato recentemente oggetto di interesse scientifico, in quanto teoricamente predetto essere un isolante topologico (TI) bidimensionale. Un TI è un materiale che internamente si comporta come un isolante elettrico ma che sulla superficie manifesta stati conduttivi. Lo scopo di questa tesi è studiare le proprietà si trasporto di monostrati di WTe2 in micro-dispositivi realizzati con opportune tecniche di nanofabbricazione. L'ossidazione della superficie esterna del WTe2, dovuta ad una non-perfetta stabilità in aria, influenza significativamente il trasporto elettronico in cristalli costituiti da pochi strati atomici ed è causa di una transizione metallo-isolante. Una possibile soluzione per evitare la degradazione del materiale consiste nell' “incapsulamento” di un monostrato di WTe2 fra materiali 2D chimicamente inerti, come il nitruro di boro esagonale. A tale proposito, si è sviluppata una tecnica di “trasferimento” che permette di sollevare e allineare con precisione micrometrica strati di spessore atomico di differenti materiali, assemblando eterostrutture di van der Waals. Campioni selezionati sono studiati mediante misure di magneto-transporto a bassa temperatura (fino a 0.250 K). I dati analizzati evidenziano l'esistenza di un gap di energia in monostrati di WTe2 e la presenza di una corrente localizzata ai bordi del sistema, coerentemente con l'ipotesi di un isolante topologico 2D.
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Palmgren, Pål. "Phthalocyanine interfaces : the monolayer region." Doctoral thesis, KTH, Materialfysik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4571.
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Organic molecules adsorbed on inorganic substrates are the topics of interest in this thesis. Interfaces of this kind are found in dye sensitized solar cells that convert solar energy to electricity, a promising environmentally friendly energy source which might provide a route to replace fossil fuels. Another field where these interfaces play a role is in molecular electronics, an approach to solve the down scaling in the ever increasing hunt for miniaturized electronic devices. The motivation for this work lies among other in these applications and surface science is a suitable approach to investigate the electronic and morphologic properties of the interfaces as it provides detailed knowledge on an atomic level. Phthalocyanines are the organic molecules investigated and the inorganic substrates range from wide band gap via narrow band gap semiconductors to metals. Photoelectron and X-ray spectroscopy experiments are performed to shed light on the electronic properties of the adsorbed molecules and the substrate, as well as the chemical interaction between adsorbate and substrate at the interface. The ordering of the adsorbate at the interface is important as ordered molecular thin films may have other properties than amorphous films due to the anisotropic electronic properties of the organic molecules; this is investigated using scanning tunneling microscopy. We find that the phthalocyanines are affected by adsorption when the substrate is TiO2 or Ag, where charge transfer from the molecule occurs or an interface state is formed respectively. The molecules are adsorbed flat on these surfaces giving a large contact area and a relatively strong bond. On Ag, ordered structures appear with different symmetry depending on initial coverage. The reactivity of the TiO2 surface is not ideal in the solar cell application and by modifying the surface with a thin organic layer, the negative influence on the adsorbed phthalocyanine is reduced. ZnO is not as reactive as TiO2, thanks maybe to the upright adsorption mode of the phthalocyanines. The semiconductor InSb is less reactive leading to self-assembled molecular structures on the (001) surface, either homogenously distributed in a one monolayer thick film or in strands along the reconstruction rows. InAs on the other hand has a larger influence on the adsorbed molecules resulting in a metallic film upon thermal treatment.QC 20100812
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Palmgren, Pål. "Phthalocyanine interfaces : the monolayer region /." Kista : Material Physics, School of Information and Communication Technology, Royal Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4571.
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Lahiri, Jayeeta. "Interface Modifications with Atomic Monolayer." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3641.
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Rivas, Abud Nicolás Alejandro. "Segregation in a Vibrated Granular Monolayer." Tesis, Universidad de Chile, 2011. http://www.repositorio.uchile.cl/handle/2250/102679.
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Siepmann, Jorn Iija. "Monto Carlo calculations for monolayer systems." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385839.
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Ohlwein, Nina. "Endocytosis controlled by monolayer area asymmetry." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16403.
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Endozytose erfordert hohe Membrankrümmung und führt zu Flächenänderungen der Membranhälften. Dies kann durch eine Oberflächendifferenz zwischen den Schichten initiiert werden, die durch geänderte Lipidzusammensetzungen hervorgerufen werden kann. Daher wurde die Hypothese aufgestellt, dass Lipid-Transporter zu Beginn der Endozytose für veränderte Flächenverhältnisse verantwortlich sind. Um den Einfluss veränderter Flächen auf Endozytose zu untersuchen, wurden die Oberflächenverhältnisse der Membran durch Zugabe von Phospholipiden verändert und anschließend Endozytose gemessen. Abhängig von der Sorte wurden die Lipide nur in die äußere Schicht eingebaut oder auch auf die innere Seite transportiert, wodurch die entsprechende Seite vergrößert wurde. Die Zugabe verschiedener Aminophospholipide, die auf die innere Membranseite transportiert werden, führte zu gesteigerter „bulk flow“ Endocytose in K562-Zellen. Darüber hinaus deuten die Ergebnisse darauf hin, dass Clathrin-vermittelte Endozytose von Hep2-Zellen ebenfalls stimuliert wurde. Umgekehrt hatte die Zugabe von Lipiden, die auf der äußeren Hälfte bleiben, reduzierte „bulk flow“- oder Clathrin-vermittelte Endozytose in verschiedenen Zelllinien zur Folge. Bemerkenswert ist, dass auch Clathrin-vermittelte Endozytose durch die Lipidzugabe beeinflusst wurde, obwohl gerade in diesem Weg viele Proteine involviert sind, die Krümmung induzieren können. Dies passt zu einem neuen Modell wie Lipidtransporter in Endozytose involviert sind. Durch den Transport von Lipiden und die zusätzliche Interaktion mit Endozytoseproteinen, könnten diese Transporter zwei Mechanismen zur Erzeugung von Krümmung miteinander verbinden: Membrankrümmung induziert durch eine Flächenasymmetrie zwischen den Membranhälften und durch Wechselwirkung mit Proteinen. Die Ergebnisse dieser Arbeit deuten darauf hin, dass die für Endozytose notwendige Krümmung durch die durch Lipidtransport induzierte Flächenasymmetrie der Membranschichten unterstützt wird.Endocytic engulfment requires high local membrane curvature and causes significant area changes of the membrane leaflets. This can be initiated by differences between the surface areas of the two monolayers related to leaflet specific modulation of lipid composition. Thus, it was proposed that lipid translocators, pumping phospholipids from the outer to the inner leaflet, account for monolayer area asymmetry as an early step in endocytosis. To elucidate the influence of this asymmetry on endocytosis, surface area relation was altered by adding exogenous phospholipids to living cells and changes in endocytic activity were quantified. Depending on the lipid species, exogenous lipids were only incorporated into the outer layer or subsequently translocated across the plasma membrane thereby increasing either the outer or inner surface area. Addition of different analogues of aminophospholipids, which are translocated to the inner leaflet, led to an enhancement of bulk flow endocytosis in K562 cells. Moreover, our data indicate that clathrin-mediated endocytosis of Hep2 cells was stimulated as well. Inversely, addition of phospholipids, which remain on the outer layer, reduced bulk flow or clathrin-mediated endocytosis in various cell lines. Notably, also clathrin-mediated endocytosis was influenced by the addition of lipids, although many proteins noted for their ability to induce membrane curvature are known to be implicated in this pathway. This corroborates a recent model how aminophospholipid translocases are implicated in endocytosis. Upon translocating lipids and additionally interacting with endocytic accessory proteins, lipid translocators could integrate two processes to generate curvature: membrane bending based on monolayer area asymmetry and protein-related mechanisms. Collectively, findings in the present study suggest that curvature generation in endocytosis is supported by the induction of monolayer area asymmetry mediated by the translocation of lipids.
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Lu, Kexin. "Organic semiconductors for self-assembled monolayer field effect transistors." Thesis, University of Manchester, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559330.
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Molecular self-assembly has recently attracted significant attention for possible application in organic electronic and optoelectronic devices, such as self-assembled monolayer field-effect transistors (SAMFETs) and functional self-assembled integrated circuits. Self-assembly combines the advantages of low temperature solution processability, regio-selective monolayer adsorption and nano-scale control of film thickness. Much progress has been made in improving device performance using self-assembled monolayers (SAMs). However, most SAMFET devices reported to date showed current modulation only with submicrometre channels, with low device yields and poor reproducibility as a result of limited lateral interconnection of the semiconducting layer.In an attempt to address these issues, this thesis presents an investigation of the synthesis and properties of conjugated SAM molecules for use as the charge transporting layer in SAMFETs. Chapter 1 gives a comprehensive introduction to SAM-based surface systems, organic semiconductors and their use in OFETs and SAMFETs. Chapter 2 discusses attempts to design and synthesise p-type conjugated molecules capable of self-assembly on oxide surfaces based on a phenylene-bithiophene semiconducting core. The optical and electrochemical properties, as well as the thermal behaviour of these molecules are studied in detail. This theme is carried over to Chapter 3, which describes the synthesis, chemical and physical characterisation of two families of n-type SAM molecules. These molecules consist of NTCDI cores with hexyl or cyclohexyl chains as end-capping groups. Incorporation of a selection of materials as the active layer in OFETs or SAMFETs to evaluate the charge transport is demonstrated in Chapter 4. Monolayer films based on p-type monochlorosilane-terminated SAM molecules are made using the solution assembly technique and characterised by contact angle and AFM. OFETs made from DH-PTTP by both thermal evaporation and spin coating show high mobilities comparable to the best values reported in the literature. Top-contact SAMFETs show a hole mobility of 1.1 × 10-3 cm2V-1s-1 in air, consistent with those of solution processed DH-PTTP based OFETs. Finally, an overview of the project and some suggestions for future work are presented in Chapter 5.
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Hazell, Gavin D. A. "Surface scattering from soft matter at interfaces." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642031.
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The aim of this work has been to make use of surface scattering techniques to study soft matter at interfaces. The work presented herein is composed of two distinct bodies of work. The first comprises a fundamental study of the physical and structural properties of Langmuir monolayers composed of sulfobetaine surfactants. Physiochemical properties of the films have been investigated through the use of Langmuir trough techniques. This has been used to support x-ray and neutron reflectometry data, from which structural parameters were derived. The second body of work involves attempts to find and/or characterize novel ways of aligning proteins at interfaces. Soluble proteins at lipid interfaces have been characterized in terms of their interactions with functionalized lipid monolayers. Specific interactions have been utilized to adsorb protein layers at the interface through interactions with His-tag chelating lipids within the monolayer. These have been characterized using neutron reflectometry and quartz crystal microbalance studies. Work has also been completed to design a suitable system for the adsorption of membrane proteins. This has involved aligning phospholipid bilayer nanodiscs at the lipid interface and subsequent characterization through neutron reflectometry.
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Robuck, Holly Elizabeth. "Molecule-Based Negative Differential Resistance Across a Self-Assembled Monolayer: Its Dependence on Monolayer Coverage and Tunneling Gap." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-05192004-143129/.
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A scanning tunneling microscope (STM) was used to perform current-voltage (I-V) measurements over electroactive self-assembled monolayers (SAMs). It was hypothesized that the redox potential of an electroactive molecule influences the peak position of negative differential resistance (NDR). For this research, a ferrocene terminated alkanethiol, a ferrocenyl-ketone terminated alkanethiol, and a methyl viologen terminated alkanethiol were used, giving a range of redox potentials. Variability from the tip and the sample made the detection of any discernable differences impossible in the NDR peak position when the different SAMs were used. To address the variability, experiments were conducted where the order of the SAM was increased. The STM tip was also coated with 2,2,2-trifluoroethanethiol to make the tip surface more homogeneous. The results of the experiments discussed in this thesis suggest that the mechanism that leads to NDR is much more complicated than the resonant tunneling model suggests.
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Vasilic, Rastko. "Epitaxial growth by monolayer restricted galvanic displacement." Diss., Online access via UMI:, 2006.
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Davies, R. J. "Monolayer studies on intrinsic erythrocyte membrane proteins." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356110.
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Wu, Diana J. "Evaluation of monolayer protected metal nanoparticle technology." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33617.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (p. 73-77).
Self assembling nanostructured nanoparticles represent a new class of synthesized materials with unique functionality. Such monolayer protected metal nanoparticles are capable of resisting protein adsorption, and if utilized as a coating could have broad application in a wide range of industries from consumer products to maritime shipping to medical instruments. The formation of proteic films can adversely affect the performance of materials and is often a limiting factor in device effectiveness. In many instances such as sensors or medical implants, regular cleaning or disposal of the instrument is not a viable option, thus there exists a demand for additional means to prevent nonspecific protein adsorption. Existing protein resistant coating options are still not completely effective, and monolayer protected metal nanoparticle coatings could be a superior means by which to prevent protein adsorption onto material surfaces.
(cont.) This paper explores the commercialization potential of monolayer protected metal nanoparticle coatings for protein resistance; identifying application potential, evaluating potential markets, exploring intellectual property, analyzing the economics of monolayer protected metal nanoparticle synthesis, examining existing technologies, and assessing in depth the medical device industry and entry into the US cardiovascular device market.
by Diana J. Wu.
M.Eng.
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Ikenberry, Myles. "Acid monolayer functionalized iron oxide nanoparticle catalysts." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17060.
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Doctor of PhilosophyDepartment of Chemical Engineering
Keith L. Hohn
Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80˚C and starch at 130˚C, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.
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Wang, Shanshan. "Synthesis and characterization of monolayer molybdenum disulphide." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:182cdf51-c6e2-40bc-abf8-8057130bc2f5.
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Monolayer molybdenum disulphide (MoS2) is a semiconductor with a direct bandgap of ∼1.9 eV. Much research attention has been attracted to its potential applications in nanoelectronics and optoelectronics recently, all of which are based upon a scalable production of high-quality monolayer MoS2 and the in-depth comprehension of its fundamental properties. The PhD project focused on developing chemical vapour deposition (CVD) methods to grow monolayer MoS2 and its related two-dimensional (2D) vertical heterostructures with an understanding of the growth mechanism. Subsequently, a range of characterizations were conducted to investigate the structural, vibrational, optical and mechanical properties of as-grown samples. An atmospheric-pressure CVD (APCVD) approach was first developed to grow monolayer MoS2 crystals on silicon substrates with a 300 nm oxide layer (SiO2/Si) by using molybdenum trioxide (MoO3) and sulphur (S) as precursors. A sharp gradient of MoO3 was intentionally created, which induced a location-dependent shape evolution of MoS2 domains. A qualitative explanation was proposed, attributing this phenomenon to local changes in the Mo:S ratio of precursors and its influence on the kinetic growth dynamics of edges. Subsequently, the CVD setup was improved in both the precursor loading manner and the substrate orientation to achieve centimetre-scale monolayer MoS2 films with large domain sizes of 10-20μm. Finally, 2D MoS2/hexagonal boron nitride (h-BN) vertical heterostructures were fabricated via an all-CVD method. Raman and photoluminescence (PL) spectroscopy were applied to show its merits of smaller lattice strain, lower doping level and better interlayer contact compared with CVD-grown MoS2 on SiO2/Si substrates and mechanically stacked samples. Aberration-corrected transmission electron microscopy (AC-TEM) was carried out to study the defect structure and fracture mechanics of monolayer MoS2 at a single atom level. Subtle lattice reconstructions of line defects in various lengths and widths were resolved. Density functional theory (DFT) predicted a reduction of the bandgap as the line defects broaden, which eventually makes them behave as metallic channels embedded in the semiconducting MoS2. Another joint experimental and theoretical study was conducted to track the real-time crack propagation in monolayer MoS2. The atomically sharp crack tip went through the preferential lattice direction with least energy release. Increasing defect density was found to induce an enhanced fracture toughness and a fracture mechanism transition from brittle to ductile.
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Sporakowski, Laura. "Controlled patterning of self-assembled monolayer films." Master's thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03172010-020130/.
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Leon, Prieto Carlos Manuel. "Carbohydrate recogonition by monolayer protected gold nanoparticles." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3425741.
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Carbohydrate recognition plays an important role in many biological processes such as cell-cell recognition or bacterial infection. It is important to develop methodologies for carbohydrate recognition to expand the knowledge about the recognition process, but also for applications in diagnostic and medical fields. However, carbohydrate recognition in aqueous media is a difficult task. Carbohydrates are highly hydrophilic species with an impressive line-up of hydroxyl groups blending easily into a background of water molecules. In addition, the structural differences between many carbohydrates are often very subtle. This makes the development of synthetic receptors for carbohydrate recognition in water highly challenging. AuNPs present very interesting features which can be exploited for the design of novel chemical and biological sensors. In the Prins’ group AuNP 1, which are gold nanoparticles (d= 1.8 ± 0.4 nm) covered with hydrophobic C9-thiols terminating with a 1,4,7-triazacyclonone (TACN)·Zn2+, have been extensively used for application in sensing, catalysis and system chemistry. In this thesis AuNP 1 have been used for the study of carbohydrate recognition. The studies aim at providing the initial bases for the development of innovative synthetic carbohydrate receptors that bind carbohydrates in water using non-covalent interactions.Il riconoscimento dei carboidrati svolge un ruolo importante in molti processi biologici come il riconoscimento delle cellule o l'infezione batterica. È importante sviluppare metodologie per il riconoscimento dei carboidrati per ampliare le conoscenze sul processo di riconoscimento, ma anche per applicazioni in campo diagnostico e medico. Tuttavia, il riconoscimento di carboidrati in mezzi acquosi è un compito difficile. I carboidrati sono specie altamente idrofile con un impressionante allineamento di gruppi ossidrile che si fondono facilmente in uno sfondo di molecole d'acqua. Inoltre, le differenze strutturali tra molti carboidrati sono spesso molto sottili. Questo rende lo sviluppo di recettori sintetici per il riconoscimento di carboidrati in acqua molto impegnativo. Gli AuNP presentano caratteristiche molto interessanti che possono essere sfruttate per la progettazione di nuovi sensori chimici e biologici. Nel gruppo Prins, l'AuNP 1, che sono nanoparticelle d'oro (d = 1,8 ± 0,4 nm) ricoperte di C9-tioli idrofobi terminanti con un 1,4,7-triazaciclonone (TACN) · Zn2 +, sono state ampiamente utilizzate per l'applicazione nel sensing , catalisi e chimica del sistema. In questa tesi l'AuNP 1 è stato utilizzato per lo studio del riconoscimento dei carboidrati. Gli studi mirano a fornire le basi iniziali per lo sviluppo di innovativi recettori sintetici dei carboidrati che legano i carboidrati in acqua usando interazioni non covalenti.
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Römer, Daniel Urs. "Monolayer und Langmuir-Blodgett Filme von röhrenförmigen Oligopeptiden /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10835.
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Chow, Colin M., Hongyi Yu, Aaron M. Jones, John R. Schaibley, Michael Koehler, David G. Mandrus, R. Merlin, Wang Yao, and Xiaodong Xu. "Phonon-assisted oscillatory exciton dynamics in monolayer MoSe2." NATURE PUBLISHING GROUP, 2017. http://hdl.handle.net/10150/627085.
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In monolayer semiconductor transition metal dichalcogenides, the exciton-phonon interaction strongly affects the photocarrier dynamics. Here, we report on an unusual oscillatory enhancement of the neutral exciton photoluminescence with the excitation laser frequency in monolayer MoSe2. The frequency of oscillation matches that of the M-point longitudinal acoustic phonon, LA(M), suggesting the significance of zone-edge acoustic phonons and hence the deformation potential in exciton-phonon coupling in MoSe2. Moreover, oscillatory behavior is observed in the steady-state emission linewidth and in time-resolved PLE data, which reveals variation with excitation energy in the exciton lifetime. These results clearly expose the key role played by phonons in the exciton formation and relaxation dynamics of two-dimensional van der Waals semiconductors.
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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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Matthaiakakis, Nikolaos. "Dynamic modulation of plasmon excitations in monolayer graphene." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/419657/.
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Plasmonic devices based on noble metals have offered solutions in numerous scientific and commercial fields over the past decades. Nevertheless the optical properties of noble metals are hardly tuneable thus not allowing for dynamic control of device properties. Offering a solution for achieving efficient dynamically tuneable plasmonic devices is a crucial since it would significantly widen the range of plasmonic applications and open the way for on-chip photonic logic systems. Graphene has demonstrated high quantum efficiency for light matter interactions, strong optical nonlinearity, high optical damage threshold, and plasmons with high confinement and long propagation distances. Having a linear dispersion, zero bandgap, as well as very few free electrons available under zero doping conditions, has made this material a strong candidate for realising dynamic and highly tuneable photonic and plasmonic devices. The interest of graphene as a platform for photonic applications is enormous with numerous publications focusing on the realisation of electrostatically controlled optical devices utilizing novel properties offered by this material. Graphene plasmonics in particular have great promise in realising highly efficient on-chip modulators, optical interconnects, waveguides, sensors, and even photonic logic gates. Naturally, several issues need to be overcome in order for such devices to reach commercialization. Obtaining strong coupling of light with plasmons in graphene while also providing efficient long range frequency and intensity modulation of the plasmon absorption is a crucial and highly anticipated goal for graphene based plasmonic devices. This work overcomes these issues by utilizing a novel diffraction grating/gold-insulator-graphene combined structure to dynamically couple, enhance, and manipulate plasmons in a graphene monolayer. The proposed structure consists of a two-dimensional inverted pyramid grating on a Si wafer, which acts as a phase matching component, and utilizes a gold back reflector and a transparent spacer in order to enhance coupling of plasmons on the graphene layer that lies above. An extra ionic gel layer above the monolayer of graphene is used to achieve efficient electrostatic control of the plasmon frequency and absorption efficiency. The pyramid grating structure properties were studied experimentally. Theoretical calculations as well as Rigorous Coupling Wave Analysis simulations of the final device setup provide evidence of extremely efficient plasmon modulation both in terms of frequency and absorption efficiency, reaching even total optical absorption under certain conditions. Furthermore the device configuration allows for dynamic switching of plasmon excitations thus providing a possible solution for photonic switching applications. Finally, alternative materials for achieving tuneable plasmonic devices are also discussed.
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King, Katrice. "Phosphoinositide Phase Behavior in Complex Lipid Monolayer Systems." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/129.
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Although phosphatidylinositol (PI) and phosphoinositides (PIPs) only comprise a small percentage of the inner leaflet of the plasma membrane, they mediate a large variety of signaling events. In previous studies, we have observed the absence of macroscopically discernible domains in mixtures of PI/PC and PI(4,5)P2/PC. The addition of cholesterol to these mixtures results in condensation of the monolayer and hence domain formation. To better mimic the ionic conditions and hydrogen bonding properties of the inner leaflet plasma membrane, we investigated in this study the effect of common inner leaflet plasma membrane lipids like phosphatidylethanolamine (PE), phosphatidylserine (PS) and PI, on phosphoinositide domain behavior in the presence of cholesterol and/or bivalent cations.
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Kusner, Robert Edward. "Melting of electric dipoles in a colloidal monolayer." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057004514.
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Ma, Yingqiao. "A Two-dimensional Semiconducting GaN-based Ferromagnetic Monolayer." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1541513207541646.
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De, La Garza Richard. "Determination of neuronal morphology in spinal monolayer cultures." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc798395/.
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The objective of the completed research was to characterize the morphology of individual neurons within monolayer networks of fetal mouse spinal tissue via intraperikaryal injections of horseradish peroxidase (HRP). Thirty labelled neurons were reconstructed via camera lucida drawings and morphometrically analyzed.
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Nakajima, Kaoru. "MONOLAYER ANALYSIS USING HIGH-RESOLUTION RUTHERFORD BACKSCATTERING SPECTROSCOPY." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/85403.
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Kyoto University (京都大学)0048
新制・論文博士
博士(工学)
乙第12399号
論工博第4030号
新制||工||1477(附属図書館)
27429
UT51-2009-M905
京都大学大学院工学研究科機械物理工学専攻
(主査)教授 木村 健二, 教授 井手 亜里, 教授 河合 潤
学位規則第4条第2項該当
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Sun, Xiaohuan/XH. "Monolayer Protected Gold Nanoparticles: Application in Molecular Recognition." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3427180.
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In the last years, a relevant attention has been paid to monolayer protected gold nanoparticles (AuNPs), which are nanometer-sized gold colloids coated with a monolayer of organic molecules. Indeed, they have several interesting features.The first one is the easiness to synthesize gold cores with various sizes. Second, the versatile chemistry of AuNPs allows the grafting of functional groups and co-factors onto their surface. Taking advantage of different kinds of non-covalent interactions (namely hydrophobic, ion pairing, and metal-ligand coordination), such functional groupscan in turn provide tailored binding sites for virtually any class of substrates. The variety of monolayers that can be potentially assembled endows a fine-tuning of these interactions not only in terms of selectivity, but also in terms of their strength. Therefore, AuNPs were emerging as great scaffolds for molecular recognition.
In this thesis, chapter 1, the introductive chapter, will present the methods for the preparation of AuNPs, the recent progress of AuNPs as chemosensors and the approaches that have been developed to investigate the monolayer morphology of mixed AuNPs. In chapter 2, the aims and objectives of this thesis will be addressed. In chapter 3 and 4, a series of water soluble AuNPs were prepared and investigated as nanoreceptors and chemosensors using nuclear magnetic resonance (NMR) protocols. The results of chapter 3 indicated that by appropriate design of the coating ligands, the spontaneous formation of the sensing pockets in the monolayer of the gold nanoparticles can be achieved. The results in chapter 4 confirmed the possibility that the rational design of AuNPs with intrinsic binding cavities and controlled sensing ability can be aided by molecular dynamic (MD) simulations. In chapter 5, three kinds of positive charged AuNPs were prepared and they were able to detect and discriminate nonsteroidal anti-inflammatory drugs in a quantitative manner. In the field of molecular recognition, unique properties can also be obtained by the preparation of mixed AuNPs. Previous studies have already demonstrated that the morphology of the mixed monolayer is closely related to their properties. For this reason, in chapter 6, we will describe a method which combines NMR and electron paramagnetic resonance (EPR) techniques to investigate the morphology of mixed AuNPs. Furthermore, in chapter 7we demonstrated that the morphology of the mixed monolayer can be transformed when in the presence of proper interacting analytes.
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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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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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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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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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Lee, Joohee Forest M. Gregory. "Mathematical descriptions of nematic polymers in the monolayer limit." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1126.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Mathematics." Discipline: Mathematics; Department/School: Mathematics.
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Douglas, Alicia D. Murray Royce W. "Characterization of bimetal and mono-metal monolayer protected clusters." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1466.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry Analytical Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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Hatcher, Jancie Stinecipher. "Synthesis, characterization, and monolayer formation of sulfur-substituted tetraphenylporphyrins." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/29977.
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Lee, Lita. "Preparation of monolayer tethers via reduction of aryldiazonium salts." Thesis, University of Canterbury. Chemistry, 2015. http://hdl.handle.net/10092/10500.
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This thesis describes the preparation of surface-attached monolayer tethers from electroreduction of aryldiazonium ions using a protection-deprotection strategy. Monolayers of ethynylphenyl, carboxyphenyl, aminophenyl and aminomethylphenyl were prepared. Glassy carbon (GC) and pyrolysed photoresist film (PPF) surfaces were modified electrochemically and characterised by redox probe voltammetry. The monolayer tethers were coupled with electro-active ferrocenyl (Fc) and nitrophenyl (NP) groups for the indirect electrochemical estimation of the surface concentration. Film thickness measurement was carried out using an atomic force microscopy (AFM) depth profiling technique. The surface concentration and film thickness measurement results were consistent with the formation of monolayer films after removal of the protecting groups.
Preparation of mixed monolayers was studied using three different modification strategies: i) grafting from a solution containing two different protected aryldiazonium ions, ii) sequential grafting of two different protected aryldiazonium ions, and iii) grafting of protected aryldiazonium ions followed by removal of the protecting group and reaction of an amine or carboxylic acid derivative directly with the GC surface. The composition of the mixed layer prepared using the first method is difficult to control, whereas the possibility of multilayer formation cannot be discounted using the second method. Multilayer formation is unlikely using the third method. The electrocatalysis of oxygen reduction at mixed monolayer films was investigated briefly.
The origin of the two reduction peaks frequently observed for electroreduction of aryldiazonium ions at carbon surfaces was studied. Electroreduction was carried out at GC and HOPG surfaces. The reduction peak at the more positive potential is surface sensitive, while the peak at the more negative potential is not. However, both reduction peaks lead to deposition of films and it is tentatively proposed that the more positive peak corresponds to reduction at a ‘clean’ GC electrode, and the more negative peak corresponds to reduction at the already grafted layer.
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Sie, Edbert Jarvis. "Coherent light-matter interactions in monolayer transition-metal dichalcogenides." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112070.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 155-164).
Semiconductors that are thinned down to a few atomic layers can exhibit novel properties beyond those encountered in bulk forms. Transition-metal dichalcogenides (TMDs) such as MoS 2, WS2 and WSe2 are prime examples of such semiconductors. They appear in layered structure that can be reduced to a stable single layer where remarkable electronic properties can emerge. Monolayer TMDs have a pair of electronic valleys which have been proposed as a new way to carry information in next generation devices, called valleytronics. However, these valleys are normally locked in the same energy level, which limits their potential use for applications. This dissertation presents the optical methods to split their energy levels by means of coherent light-matter interactions. Experiments were performed in a pump-probe technique using a transient absorption spectroscopy on MoS2 and WS2, and a newly developed XUV light source for time and angle-resolved photoemission spectroscopy (TR-ARPES) on WSe2 and WTe 2 Hybridizing the electronic valleys with light allows us to optically tune their energy levels in a controllable valley-selective manner. In particular, by using off-resonance circularly polarized light at small detuning, we can tune the energy level of one valley through the optical Stark effect. At larger detuning, we observe a separate contribution from the so-called Bloch-Siegert effect, a delicate phenomenon that has eluded direct observation in solids. The two effects obey opposite selection rules, which enables us to separate the two effects at two different valleys. Monolayer TMDs also possess strong Coulomb interaction that enhances many-body interactions between excitons, both bonding and non-bonding interactions. In the former, bound excitonic quasiparticles such as biexcitons play a unique role in coherent light-matter interactions where they couple the two valleys to induce opposite energy shifts. In the latter, non-bonding interactions between excitons are found to exhibit energy shifts that effectively mimics the Lennard-Jones interactions between atoms. Through these works, we demonstrate new methods to optically tune the energy levels of electronic valleys in monolayer TMDs.
by Edbert Jarvis Sie.
Ph. D.
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Myerson, Jacob W. "Anomalous solubility behavior of mixed monolayer protected metal nanoparticles." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32849.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (leaves 30-32).
The solubility of mixed monolayer protected gold nanoparticles was studied. Monolayer protected metal nanoparticles are attractive materials because of the optical and electronic properties of their metal cores and because of the surface properties of their ligand coating. Recently, it was discovered that a mixture of ligands phase separate into ordered domains of single nanometer or subnanometer width on the surface of metal nanoparticles. The morphology and length of the ligand domains (which take the form of ripples on the particle surface) has given these nanoparticles novel properties. Because monolayer protected nanoparticles can be dissolved and dried many times, they can be handled and processed in ways not available to other nanomaterials. Understanding the solubility of mixed monolayer protected metal nanoparticles could help in implementing their unique new properties. This study demonstrates that the solubility of these particles in organic solvents cannot be explained only in terms of the composition of the ligand shell. Instead, solubility is also closely linked to morphology of the ligand shell via relationships between the size of the solvent molecule and the size of the features in the morphology.
by Jacob W. Myerson.
S.B.
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Addai, Frederick Kwaku. "Human villous placenta in monolayer culture : vital mitochondrial studies." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/34200.
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A protocol adapted for the propagation of monolayer cultures from human villous placenta is described. Keratin immunofluorescent localization was utilized to characterize trophoblast cells in sub-cultivated cultures derived from first trimester placentae. The appearance of autofluorescent particles in long-term first trimester placental cultures is reported. The monolayer culture system was employed to study living mitochondria. Using the vital fluorescent dye rhodamine 123, fluorescence microscopy of living first trimester human placental cells and choriocarcinoma cells was carried out. The length and intracellular distribution of mitochondria are described for normal placental cells, somatic hybrids of normal cells, and choriocarcinoma cells. In normal first trimester placental cells, quantitative relationships between the projected cell surface areas and numbers/lengths of their mitochondria are described by regression equations. From the equations, it is deduced that the total (aggregate) length of mitochondria per cell is directly proportional to the 0.86 +/- 0.07 power of the cell's projected surface area. The number of mitochondria per cell is also a direct function of the cellular surface area, with an exponent of 0.82 +/- 0.07; whilst the total length of mitochondria per unit projected cell surface area is an inverse function (exponent = -0.14 + 0.07) of the cell surface area. The reaction of living mitochondria in cultured first trimester placental cells to a number of chemical agents including colchicine was investigated. In the presence of colchicine, it appears that the distribution of mitochondria becomes more restricted to the perinuclear cytoplasm and that the mean length of the organelles is reduced. However, the total length of all mitochondria in colchicine-treated cells was not significantly different from that in similar cells which were not exposed to the drug. Experiments investigating the recovery of cells from colchicine-mediated changes in their mitochondrial orientation and length is presented.
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Rong, Youmin. "Synthesis and characterisation of large area monolayer tungsten disulphide." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:32933029-c6bc-4066-8efd-51a958434c45.
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Two-dimensional (2D) transition metal dichalcogenides (TMDs), equipped with direct bandgaps in the visible range of electromagnetic spectrum have extended the promise of 2D materials (graphene) to optoelectronics. Towards facilitating the future industrialization of 2D TMDs, this project focused on developing chemical vapour deposition (CVD) techniques for the growth of large area monolayer tungsten disulphide (WS2), which was followed by characterisations of their structural and semiconducting properties. It was demonstrated that controlling the introduction time and the amount of sulphur (S) vapour relative to the tungsten trioxide (WO3) precursor during the CVD growth of WS2 was critical to achieving large crystal domains on the surface of silicon wafers with a 300 nm oxide layer. This improvement for CVD techniques enabled the formation of single crystalline WS2 monolayers with edges up to 370 μm which were visible to the naked eye. Synthetic 2D materials grown by CVD are typically polycrystalline, and determining grain size within domains and continuous films is crucial for determining their structure. The thesis showed that grain boundaries (GBs) in monolayer WS2, grown by CVD, could be preferentially oxidized by controlled heating in air. Under apposite conditions, the degradation of GBs led to their clear and rapid identification using a standard optical microscope. Subsequent studies showed that how these monolayer WS2 GBs influenced the electroluminescence (EL) behaviour in lateral source-drain devices under bias. Real time imaging of the WS2 EL detected arcing between the electrodes when probing across a GB, which then localized at the GB region as it eroded under high bias conditions. Analysis of the eroded GB region showed the formation of micro- and nanoribbons across the monolayer WS2 domains. These results provide important insights into future EL devices that utilize CVD grown monolayer TMDs when GBs are present in the active device region.
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Matemadombo, Fungisai. "Substituted phthalocyanines development and self-assembled monolayer sensor studies." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005029.
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Zinc, cobalt and iron phenylthio substituted phthalocyanines have been synthesized and characterized. Cyclic and square wave voltammetry in dimethylformamide containing tetrabutylammonium perchlorate revealed five and six redox processes respectively for the cobalt and iron phenylthio substituted phthalocyanines. These complexes are easier to reduce compared to the corresponding unsubstituted MPc and to butylthio substituted derivatives. Spectroelectrochemistry (in dimethylformamide containing tetrabutylammonium perchlorate) was employed to assign the cyclic voltammetry peaks, and gave spectra characteristic of Fe(I)Pc for reduction of iron phenylthio substituted phthalocyanine and Co(I)Pc for the reduction of cobalt phenylthio substituted phthalocyanine. The spectrum of the former is particularly of importance since such species have not received much attention in literature. Cobalt and iron phenylthio substituted phthalocyanines have been deposited on Au electrode surfaces through the self assembled monolayer (SAM) technique. The so formed layers were studied using voltammetric techniques. These SAMs blocked a number of Faradic processes and electrocatalyzed the oxidation of L-cysteine. Amine substituted cobalt phthalocyanine (CoTAPc) was deposited on gold surfaces by using an interconnecting SAM of mercaptopropionic acid or dithiobis(N-succinimidyl propionate) through the creation of an amide. Reductive and oxidative desorption of the SAMs limit the useful potential window. The SAM-CoTAPc layers show electrocatalytic activities towards oxygen reduction through the Co(I) central metal ion. Both SAMs were highly stable and hence will be interesting tools for further research in surface modification and sensor development.
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Thorat, Ruhi P. "Opto-Electronic Properties of Self-Contacted MoS2 Monolayer Devices." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1512731597427663.
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Curley, Sheridan Sharer. "Identifications of Monolayer Molybdenum Disulfide Flakes for Transistor Devices." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297548.
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This thesis covers useful methods for the identification of atomically thin molybdenum disulfide (MoS₂) flakes, outlines fabrication steps for transistors from identified monolayer MoS₂ samples, and details several potential measurements from such transistors. Identification techniques covered include atomic force microscopy, Raman analysis, and photoluminescence measurements of MoS₂. Detailed manufacturing procedures for different types of transistor devices are presented, beginning from large, bulk MoS₂ crystals, proceeding to wiring and testing of functional devices. Although transport measurements are not provided, all necessary theory and fabrication steps are covered to begin such measurements quickly from a basic initial setup.
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Khair, Khadija Abul. "DIFFUSIVE TRANSPORT IN MONOLAYER MOLYBDENUM DISULFIDE (MoS2) UNDER STRAIN." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1665.
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While silicon-based transistors approach their physical limit and naturally scaled-down 2D graphene layers have low ON/OFF current ratio due to zero bandgap, monolayer 2D molybdenum disulphide (MoS2) holds promise as channel material for future field-effect transistors (FETs) with a finite non-zero energy bandgap and a high ON/OFF current ratio. Besides having a direct energy bandgap, strong covalent bond, high thermal stability, absence of dangling bonds, and an atomic scale thickness of 0.65 nm make MoS2 an excellent candidate for channel material. Recently, a research team at the Lawrence Berkeley National Laboratory has been able to demonstrate a 2-D MoS2-CNT (Carbon Nanotube) based transistor with a gate length of 1 nm. Also, MoS2 transistors operating at gigahertz frequencies (with a cutoff frequency of ~6 GHz) have been reported. Nevertheless, given the realistic construction of an FET with multiple contacts and interfaces, electron mobility in monolayer MoS2 is degraded by various scattering mechanisms.
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Bidoggia, Silvia. "Mixed-monolayer protected gold nanoparticles for applications in medicine." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8573.
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2011/2012In the last years, gold nanoparticles (AuNPs) protected by an organic shell of ligands have received a large interest for applications in the biomedical field in particular for diagnosis, imaging and therapy. This class of nanomaterials is largely used because of the easy of synthesis with different core sizes and shapes and controlled dispersion. Moreover, NPs can be protected by a large variety of organic compounds, with different functionalities and to allow the linkage of drugs and biomolecules. The nature of the ligand is responsible of the solubility of the NPs and could be also tuned in order to have NPs soluble in water and in the biological environment. Additionally, at least gold is no toxic, biocompatible and could be easily released from the body. The present thesis is focused on three projects. The first one deals with the study of the morphology of gold nanoparticles coated by a mixture of hydrogenated and fluorinated ligands which solubility in water is favored by the presence of PEG chains. Few years ago, our research group has shown that mixtures of these hydrogenated and fluorinated ligands, forming the monolayer of gold nanoparticles, phase-segregate in separated domains because of the reciprocal immiscibility of the two chains. During this thesis, we wanted to investigate more deeply the organization of such monolayers and in particular, to understand the shape and the size of these domains. In collaboration with the group of Prof. S. Pricl and Prof. M. Fermeglia of the University of Trieste, in silico experiments have been performed in order to predict the size and the shape of these domains. Moreover, we have studied how the shape and the size of these domains is influenced by the ratio between the two thiols, the size of the core and the difference in length between the two ligands. The obtained results were supported by further ESR experiments performed by Prof. Lucarini of the University of Bologna. ESR experiments have allowed us to estimate the value of the affinity constants of the probe for the fluorinated and hydrogenated domains of the monolayer and to establish that mixed monolayers have chemical and physical properties that cannot be predicted by simply knowing the properties of homoligand monolayers. The results that have been reported in a recent publication on ACS Nano are presented in Chapter 3. The second project of this PhD thesis is based on the synthesis and characterization of water soluble gold nanoparticles coated by different ratios of charged hydrogenated ligands and commercially available fluorinated ligands. Some of these nanoparticles, with an average core diameter between 3 and 4 nm, have been used for preliminary investigations in vitro. In particular, cell membrane permeation and the cellular toxicity have been evaluated. These experiments have been performed in collaboration with the group of Prof. Stellacci in IFOM-IEO, Milan. Preliminary results are described in Chapter 4. The last part of this PhD project is focused on the synthesis and characterization of NPs coated by mixtures of commercially available fluorinated and hydrogenated thiols. These NPs present the advantages over those described in Chapter 3 and Chapter 4 because they are suited for a direct “visualization” by STM experiments and may help us in understanding the rules governing the organization of mixtures of fluorinated and hydrogenated ligands on a curved surface. The choice to synthesize NPs without charged groups is dictated by the limitations of STM technique. In Chapter 5 synthetic aspects and preliminary STM results would be presented.
XXV Ciclo
1983
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Svedhem, Sofia. "Biomolecular interactions at model interfaces : a self-assembled monolayer approach /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek677s.pdf.
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Wolfe, Rebecca L. Murray Royce W. "Novel gold monolayer protected clusters synthesis, characterization, separation, and functionalization /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1168.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry Analytical Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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Itoh, Shintaro, Kenichiro Takahashi, Kenji Fukuzawa, Hiroaki Amakawa, and Zhang Hedong. "Spreading Properties of Monolayer Lubricant Films: Effect of Bonded Molecules." IEEE, 2009. http://hdl.handle.net/2237/13893.
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Feldman, Benjamin Ezekiel. "Measurements of Interaction-Driven States in Monolayer and Bilayer Graphene." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11192.
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In materials systems with flat energy bands and limited disorder, interactions among electrons dominate and can dramatically alter physical behavior. Traditionally, two-dimensional electron gases (2DEGs) have offered excellent platforms to study these effects because the kinetic energy of the electrons is effectively quenched by a perpendicular magnetic field. The recent discovery of graphene, a two-dimensional form of carbon, has opened the door for further exploration into many-body phenomena. Graphene, unlike conventional 2DEGs, has fourfold degenerate electronic states due to its spin and valley degrees of freedom. This thesis describes several experiments that show how these underlying symmetries combine with electron-electron interactions to produce novel and tunable correlated electronic phases of matter.Physics
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Girot, Christine Stoll. "Infrared characterization of a self-assembled catenane monolayer on gold." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1027114.
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The synthesis of the catenane components, a dithiol and a cyclophane, are described using previously reported methods. 1-3 The preparation techniques used to obtain a self-assembled dithiol monolayer and a self-assembled catenane monolayer from dilute solution onto a gold's surface are also reported. Grazing angle reflectance infrared spectroscopy was used to characterize the selfassembled dithiol and catenane monolayers. The infrared spectra revealed evidence for the existence of the dithiol monolayer and possible evidence for the existence of the catenane monolayer. A catenane transmission film spectrum was obtained to provide evidence for the existence of the catenane itself. When the transmission and the monolayer spectra were compared, shifts in a few of the absorption bands revealed some association between the dithiol and the cyclophane.Department of Chemistry