Dissertations / Theses on the topic 'Chemisorbed'
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1
Saidy, Madiba. "LEED crystallographic studies for chemisorbed surfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/NQ46413.pdf.
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Unsworth, Larry David Brash J. L. "Protein adsorption to chemisorbed polyethylene oxide thin films." *McMaster only, 2005.
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3
Srepusharawoot, Pornjuk. "Computational Studies of Hydrogen Storage Materials : Physisorbed and Chemisorbed Systems." Doctoral thesis, Uppsala universitet, Materialteori, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132875.
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This thesis deals with first-principles calculations based on density functional theory to investigate hydrogen storage related properties in various high-surface area materials and the ground state crystal structures in alkaline earth dicarbide systems. High-surface area materials have been shown to be very promising for hydrogen storage applications owing to them containing numerous hydrogen adsorption sites and good kinetics for adsorption/desorption. However, one disadvantage of these materials is their very weak interaction with adsorbed hydrogen molecules. Hence, for any feasible applications, the hydrogen interaction energy of these materials must be enhanced. In metal organic frameworks, approaches for improving the hydrogen interaction energy are opening the metal oxide cluster and decorating hydrogen attracting metals, e.g. Li, at the adsorption sites of the host. In covalent organic framework-1, the effects of the H2-H2 interaction are also found to play a significant role for enhancing the hydrogen adsorption energy. Moreover, ab initio molecular dynamics simulations reveal that hydrogen molecules can be trapped in the host material due to the blockage from adjacent adsorbed hydrogen molecules. In light metal hydride systems, hydrogen ions play two different roles, namely they can behave as "promoter" and "inhibitor" of Li diffusion in lithium imide and lithium amide, respectively. By studying thermodynamics of Li+ and proton diffusions in the mixture between lithium amide and lithium hydride, it was found that Li+ and proton diffusions inside lithium amide are more favorable than those between lithium amide and lithium hydride. Finally, our results show that the ground state configuration of BeC2 and MgC2 consists of five-membered carbon rings connected through a carbon atom forming an infinitely repeated chain surrounded by Be/Mg ions, whereas the stable crystal structure of the CaC2, SrC2 and BaC2 is the chain type structure, commonly found in the alkaline earth dicarbide systems.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 712
4
Lei, Jipu. "Cu Electrodeposition on Ru with a Chemisorbed Iodine Surface Layer." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc5577/.
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An iodine surface layer has been prepared on Ru(poly) and Ru(0001) electrodes by exposure to iodine vapor in UHV and polarizing in a 0.1 M HClO4/0.005 M KI solution, respectively. A saturation coverage of I on a Ru(poly) electrode passivates the Ru surface against significant hydroxide, chemisorbed oxygen or oxide formation during exposure to water vapor over an electrochemical cell in a UHV-electrochemistry transfer system. Immersion of I-Ru(poly) results in greater hydroxide and chemisorbed oxygen formation than water vapor exposure, but an inhibition of surface oxide formation relative that of the unmodified Ru(poly) surface is still observed. Studies with combined electrochemical and XPS techniques show that the iodine surface adlayer remained on top of the surface after cycles of overpotential electrodeposition/dissolution of copper on both Ru(poly) and Ru(0001) electrodes. These results indicate the potential bifunctionality of iodine layer to both passivate the Ru surface in the microelectronic processing and to act as a surfactant for copper electrodeposition. The electrodeposition of Cu on Ru(0001) or polycrystalline Ru was studied using XPS with combined ultrahigh vacuum/electrochemistry methodology (UHV-EC) in 0.1 M HClO4 with Cu(ClO4)2 concentrations ranging from 0.005 M to 0.0005 M, and on polycrystalline Ru in a 0.05M H2SO4/0.005 M CuSO4/0.001 M NaCl solution. The electrochemical data show well-defined cyclic voltammograms (CV) with a Cu underpotential deposition (UPD) peak and overpotential deposition (OPD) peak. XPS spectra of Ru electrodes emersed from perchloric acid solution at cathodic potentials indicate that ClO4- anions dissociate to yield specifically adsorbed Cl and ClOx species. Subsequent Cu deposition results in the formation of a thin, insoluble Cu(II) film with Cu(I) underneath. In contrast, similar deposition on polycrystalline Ru in the sulfuric acid/Cu sulfate solution with NaCl added yields only Cu(0), indicating that the formation of Cu(II) and Cu(I) involves both Cl and perchlorate interactions with the deposited Cu. A pre-adsorbed layer of iodine on the Ru(0001) surface inhibits perchlorate dissociation in iodide-free electrolyte and leads to the deposition of Cu(0) in the perchlorate bath. XPS depth profile analysis demonstrates that the iodine monolayer "floats" on top of the deposited film, in agreement with previous results, effectively protecting the Cu film from air oxidation.
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Browne, V. M. "Experimental and theoretical infra-red studies of chemisorbed molecules and their interactions." Thesis, Bucks New University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384768.
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Sanabria-Chinchilla, Jean. "Electrochemical hydrogenation of aromatic compounds chemisorbed at polycrystalline and single-crystal Pd surfaces." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1750.
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Alcantara, Ortigoza Marisol. "Theoretical studies of electronic, vibrational, and magnetic properties of chemisorbed surfaces and nanoalloys." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/496.
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Wu, Yuk Kuen. "LEED crystallographic studies of sulfur chemisorbed on the (111) surfaces of nickel and rhodium." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27751.
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The work in this thesis includes investigations of adsorbate-induced metal relaxations with low-energy electron diffraction (LEED) for the surface structures designated Ni(111)-(2x2)-S and Rh(111)-(√3x√3)30'-S; a set of LEED intensity-versus-energy (I(E)) curves have also been measured for normal incidence on the Ni(111)-(2x2)-O surface. In the investigations of adsorbate-induced metal relaxations, 1(E) curves measured for a set of diffracted beams were compared with the corresponding curves calculated by multiple scattering methods for various structural models. The objective is to find the structure that gives the best correspondence between experiment and calculation. Levels of correspondence between experimental and calculated I(E) curves were assessed with the reliability indices proposed by Zanazzi-Jona and Pendry as well as with visual comparison.
In the LEED intensity analysis for the Ni(111)-(2x2)-S surface structure, the S-Ni interlayer spacing (d₀₁), the lateral displacement (Δ) of the first nickel layer and vertical
relaxations of the first two Ni-Ni interlayer spacings (d₁₂, d₂₃) were investigated. The best geometrical parameters were determined to be d₀₁=1.50 Å, Δ =+0.02 Å (1.4% expansion), d₁₂=2.09 Å (2.8% expansion) and d₂₃=2.08 Å (2.3% expansion) with the S atoms adsorbed on the "expected" 3f sites of the Ni(111) surface. The present study leads to a nearest-neighbour S-Ni bond distance of 2.10 Å, which is a little shorter than those obtained by low energy ion scattering (2.16 Å) and the surface extended X-ray adsorption fine structure technique (2.20 Å) but agrees rather well with the value 2.12 Å predicted by a bond length-bond order analysis.
In the investigation of adsorbate-induced metal relaxations for the Rh(111)-(√3x√3)30°-S surface, theoretical I(E) curves were calculated for a range of models involving either unreconstructed or reconstructed rhodium structure at the surface. These calculations were done over appropriate ranges of the S-Rh interlayer spacing (d₀₁), the lateral displacement (Δ) for the first Rh layer, and the first Rh-Rh interlayer spacing (d₁₂). The best level of correspondence between calculation and experiment appears for the 3F1 model with d₀₁=1.57 Å, Δ =M).025 A (1.6 % contraction) and d₁₂=2.18 Å (0.5 % contraction). In this model the nearest-neighbor S-Rh bond distance is found to be 2.19 Å.Science, Faculty of
Chemistry, Department of
Graduate
9
Zolfaghari-Hesari, Alireza. "Thermodynamic states of adsorbed hydrogen at noble-metal electrocatalysts in absence/presence of chemisorbed sulfur." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ35782.pdf.
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Hong, Sampyo. "First-principles study of chemisorbed light gases on transition metal and transition metal oxide surfaces : structure, dynamics and reaction /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Qian, Shiyuan. "Kinetic interpretation of promoting/inhibiting effects of chemisorbed species on H sorption at/in Fe, mild-steel and Pd." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0035/NQ67589.pdf.
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Qian, Shiyuan. "Kinetic interpretation of promoting/inhibiting effects of chemisorbed species on hydrogen sorption at/in iron, mild-steel and palladium." Thèse, Université de Sherbrooke, 1999. http://savoirs.usherbrooke.ca/handle/11143/4995.
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The aim of the studies described in this thesis was to examine the effects of chemisorbed catalyst poisons on the behaviour of the hydrogen evolution reaction (HER) and especially the enhancement by poisons of the coupled absorption and permeation of H that occurs at various transition metals. Such effects were studied comparatively at Fe, mild-steel and Pd electrodes in aqueous NaOH solutions using a Devanathan-Stachurski bi-electrode cell to follow H permeation currents in relation to simultaneously measured polarization behaviour on the H [subscript 2] evolution side of the electrodes. The poisoning effects associated with competitive chemisorption of As-containing compounds on the behaviour of the HER, and hydrogen permeation at Fe and mild-steel, have been investigated. By means of an equation-fitting procedure, applied to the kinetics of all the constituent partial reactions involved, including cathodic reduction of added AsO[subscript 2] to As(0) and AsH[subscript 3] , and also considering the factors which represent modification of the rate constants due to induced heterogeneity caused by communal interactions between the adsorbed H and poison species on the surfaces of Fe and mild steel, a good account of the mechanism of the effects of As-species was able to be achieved. It was found that the presence of As species, initially as AsO [subscript 2] , significantly enhances H permeation into Fe and mild-steel but only at appreciable cathodic potentials; however, it reduces H permeation currents at less cathodic potentials. The effect involves reductive desorption of As-containing species, eventually to AsH [subscript 3] (gas), coupled with increased H coverage at high cathodic overpotentials, leading to enhancement of H absorption and permeation. The effect of chemisorption of S-containing species on H transfer into and through Fe and mild-steel was studied comparatively and complementarily in relation to poisoning by species derived from AsO[subscript 2] . The S-containing compound, HS- , has a different effect on the H surface coverage, [straight theta]H, ([straight theta]H becomes decreased, compared to the poison-free case) at high cathodic overpotentials, but its poisoning effects are similar to those of arsenic species on H absorption and permeation. The H absorption and permeation are enhanced at high and inhibited at less cathodic overpotentials in both situations of decreased or increased limiting H coverage values, [straight theta]H. The effect of chemisorption of S species (as HS- ) on H transfer into and through Pd has also been studied. The relations of surface coverage by H on the Pd surface in UPD region (also extended to the OPD region) to the subsurface concentration of H, and the effect of chemisorption of sulphide species on H transfer into and through a Pd membrane bielectrode, has also been examined. The [straight theta]H over the UPD region is diminished by the chemisorption of the S species. The H adsorption and the H permeation rates are related in a 1:1 ratio in the UPD region in both the absence and presence of poison solutions, thus a 100% permeation efficiency, [varepsilon], in this potential region"-- Résumé abrégé par UMI
13
Qian, Shiyuan. "Kinetic interpretation of promoting/inhibiting effects of chemisorbed species on hydrogen sorption at/in iron, mild-steel and palladium." Sherbrooke : Université de Sherbrooke, 2000.
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14
Bruzzi, Mara, Riccardo Mori, Andrea Baldi, Ennio Carnevale, Alessandro Cavallaro, and Monica Scaringella. "Thermally Stimulated Currents in Nanocrystalline Titania." MDPI AG, 2018. http://hdl.handle.net/10150/627084.
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A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO2. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5-630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 10(14)-10(18) cm(-3), associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies.
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Byloos, Martin. "Spectroelectrochemical study of the reductive desorption and the oxidative redeposition of a monolayer of 1-hexadecanethiols chemisorbed on gold(111)." Thesis, University of Ottawa (Canada), 2000. http://hdl.handle.net/10393/8865.
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We present a spectroelectrochemical study of the reductive desorption and the oxidative redeposition of a monolayer of 1-hexadecanethiols on Au(111) in an aqueous alkaline electrolyte solution. The solvent/thiol interactions were found to play an important role in the electrodeposition of self-assembled monolayers of low-solubility thiols. The orientation of the alkane chains in a monolayer remains unchanged after its reductive desorption and oxidative redeposition. The reductive desorption/oxidative redeposition of low-solubility thiols on Au(111) proceed through a two step mechanism. The first step of the reductive desorption is ascribed to the reduction of chemisorbed thiols. The second step of the reductive desorption occurs at a more negative potential and is assigned to the reorientation of the monolayer of physisorbed thiolates into micelles. The unblocking of the Au(111) surface caused by this reorientation of the thiolates allows the formation of an electrical double layer. (Abstract shortened by UMI.)
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Byloos, Martin. "Spectroelectrochemical study of the reductive desorption and the oxidative redeposition of a monolayer of 1-hexadecanethiols chemisorbed on Au(111)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ48139.pdf.
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Iqbal, Danish [Verfasser], Martin [Gutachter] Muhler, and Andreas [Gutachter] Erbe. "Ultrathin chemisorbed polymer coatings : corrosion protection and nanostructuring of ZnO / Danish Iqbal ; Gutachter: Martin Muhler, Andreas Erbe ; Fakultät für Chemie und Biochemie." Bochum : Ruhr-Universität Bochum, 2015. http://d-nb.info/1223172155/34.
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Zeng, Yang. "Using surface spectroscopy to help Interpret STM images of chemisorbed molecules : application to the study of the hydrogenation of ketones and a-ketoesters on Pt." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26793.
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Depuis que la haute énantiopureté est nécessaire dans l'industrie pharmaceutique, les études visant à découvrir les mécanismes pour l'hydrogénation énantiosélective de cétones ou céto-esters sur les surfaces, et à rechercher de nouveaux et plus performants catalyseurs asymétriques, sont d'une grande importance. La microscopie à effet tunnel (STM), la spectroscopie infrarouge de réflexion-absorption, la spectroscopie de désorption à température programmée et la spectrométrie de photoélectrons induits par rayons X sont des méthodes performantes facilitant la compréhension des mécanismes de réaction. En plus de nous permettre de comprendre les mécanismes réactionnels, les études peuvent fournir des informations sur la dynamique des réactions en catalyse hétérogène ainsi que sur le développement de la théorie de la fonctionnelle de la densité (DFT) afin de calculer des interactions faibles dans les processus de surface. D’autres parts, les calculs DFT fournissent une aide essentielle à l'interprétation des données de STM et spectroscopie de surface. Dans cette thèse, certains cétones et céto-esters sur la surface de platine sont étudiées par les techniques sophistiquées mentionnées ci-dessus. Mes études démontrent que la combinaison de l'utilisation de la spectroscopie de routine, des nanotechnologies et de nombreux calculs élaborés, est une méthode efficace pour étudier les réactions à la surface car ces techniques explorent les différents aspects de la surface ainsi que s’entraident mutuellement lors de certaines interprétations.Since high enantiopurity is required in the pharmaceutical industry, studies aimed at discovering the mechanisms for the enantioselective hydrogenation of ketones or keto-esters on surfaces and at successfully seeking out new or better performing asymmetric catalysts are of great significance. Scanning tunneling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), temperature-programmed desorption spectroscopy (TPD) and X-ray photoelectron spectroscopy (XPS) are powerful methods to facilitate an understanding of the reaction mechanisms. In addition to insight on reaction mechanisms, the studies can contribute information on reaction dynamics in heterogeneous catalysis and on the development of density functional theory (DFT) methods to compute weak interactions in surface processes. In turn, DFT calculations provide critical help in the interpretation of STM and surface spectroscopy data. In this thesis, some ketones and keto-esters on platinum surface are studied by the above mentioned sophisticated techniques. My studies demonstrate that the combination of using routine spectroscopy, nanotechnology, and state of the art calculations is an effective method to study reactions on surface as they explore different aspect of surface, and mutually help each other for some interpretations.
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Cafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/3870.
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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.
20
Cafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." University of Sydney, 2008. http://hdl.handle.net/2123/3870.
Full textAbstract:
PhDSYNOPSIS 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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Fang, Sheng-Shiun, and 方聖熏. "Theoretical Study of Oxygen Atoms Chemisorbed on SWCNTs." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/77121166425524961462.
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碩士國立成功大學
化學系碩博士班
93
In the present work, theoretical study utlizing DFT and AM1 method to calculate single point energies and structure optimizations of capped finite length single-walled carbon nanotubes (SWCNTs), respectively, including (5,5), (6,4), (7,3), (8,1), (9,0), (10, 0), (9, 2), (8, 4), (8, 3), (7, 5), (7, 4), (6, 5), and (6, 6), chemisorbed by an oxygen atom were carried out by means of GAUSSIAN suite of programs. It reveals that the C-C bond adsorbed by an oxygen atom elongates universally. Based on the extent of elongation of the C-C bond on the SWCNT adsorbed chemically by an oxygen atom, it can be devided as two areas: DA, drastic-alteration area (sin2θ > 0.5) and SA, slight-alteration area (sin2θ < 0.5). In DA area, adsorption energies are much higher than those in other angle range; in other words, that is, DA is more stable than SA. According to DOS data, the conductivity of SWCNTs in DA is almost equivalent to that before adsorption and that of SWCNTs in SA changes significantly. Consequently, due to the oxygen atom adsorption is more stable in DA than in SA, it is reasonable to conjecture that oxygenation is not the main cause to ameliorate the conductance of SWCNTs.
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Chapman, Christopher Rodney Leon. "Multiple Scale Theoretical Insights on the Switching Behavior of Chemisorbed Azobenzene." Thesis, 2011. http://hdl.handle.net/1828/4953.
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Azobenzene derivatives have been shown to act as a molecular switch when ex-
posed to an applied electric field. Many applications require the switching molecule
to be adsorbed on a surface. The behavior of chemisorbed N-(2-mercaptoethyl)-4-
phenylazobenzamide on a Au(111) surface has been investigated using a mean-field
theoretical approach for azobenzene in alkylthiol monolayers and density functional
theory calculations at the zero-density limit. Azobenzene switching in monolayers
was found to be dependent on surface coverage, as well as the strength and polarity
of an electric field. In the zero-density regime, azobenzene derivatives adopted paral-
lel and upright geometries for both trans and cis isomers. Charged states for upright,
adsorbed structures were also analyzed and were found to lower the isomerization
energy barrier.Graduate
0485
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Lee, Shang Yu, and 李尚諭. "Preparation of Nanogold Chemisorbed onto the Side Chain of Polystyrene via living Polymerization." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/25435378710039642785.
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碩士國立中正大學
化學工程研究所
99
The work is mainly to use anionic polymerization and living-free radical polymerization for our research. The way is to prepare polystyrene containing sulfide group onto the polymer side chain. And then, blok homo-polystyrene to become a diblock copolymer. On the other hand, we can control the proportion of anchor group. So, we can control the solubility of our polymer by control the proportion of polystyrene and poly(2-methylthio-1-para-styrene-ethylane). The synthesize steps are as followed. First, we prepare homo-poly(p-cms) by RITP, and then block polystyrene to become diblock copolymer. The second step, we use anionic polymerization replace Cl group of poly(p-cms) to become dimethysulfide. Finally, we can combine the polymerization technique and gold nanoparticle for synthesizing gold nanoparticle/polystyrene-b-poly(2-methylthio-1-para- styrene-ethylane) nanocomposite. Also, we observe the gold nanoparticle size via adding different amount of polymer to chemisorbed gold nanoparticles . The composite is analyzed useing GPC , NMR, XPS, TGA, DSC, UV/VIS, SEM and TEM.
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Huang, Hsuan-Ming, and 黃宣銘. "Preparation of Polystyrene-chemisorbed Nanogold and Polystyrene-grafted Carbon Nanotubes (Nanocapsules) Nanocomposites via Anionic Polymerization." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/69321303752706809554.
Full textAbstract:
博士國立中正大學
化學工程所
94
The first section of paper is mainly to combine the anionic polymerization technique and gold nanoparticle for synthesizing gold nanoparticle/poly p-methylstyrene nanocomposite. The way is to prepare poly p-methylstyrene containing sulfide group and use this sulfide group for chemisorption of gold nanoparticl. The steps are: first, polymerization of p-methylstyrene. Second, chlorination by sodium hypochlorite and phase transfer catalyst of the polymer to produce CH2Cl group. Third, lithiation of dimethyl sulfide by n-butyllithium and capping with the chlorinated polymer. The feature of the study is that functionalization of polymer occurs on side-chains rather than main-chain ends. Therefore more bonding points are available for reaction. Finally, the composite is analyzed using TEM, UV-VIS, TGA, EDS and XPS. The second section of paper describes the method for preparing polystyrene- functionalized multiple-walled carbon nanotubes (MWNTs) by terminating anionically synthesized living polystyryllithium with acyl chlorides on the MWNTs. The acyl chloride functionalities on the MWNTs were in turn obtained by first forming the carboxyls via chemical oxidation and then converting them to acyl chlorides. The polystyrene- functionalized MWNTs had good dispersion in common organic solvents and thus indicated a good compatibility for use in the preparation of styrenic nanocomposite materials. In the last section, the novel polymeric composite material, polystyrene- grafted CNCs, has been prepared. sec-Butyllithium was first used to introduce negative charges on CNCs and the these CNC carbanions acted then as initiators for anionic polymerization of styrene. The polystyrene-grafted CNCs had good dispersion in common organic solvents and thus indicated a good compatibility when further blended with other styrenic polymers. Synthesis results and the characterization data of the grafted CNCs, collected from FTIR, TGA, DSC, UV/Vis, Raman spectrum and electron microscopy are presented and discussed.
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Mattson, Philip J. "Sputtering of chemisorbed nitrogen from the (100)--planes of tungsten and molybdenum: a comparison of computer simulation and experimental results." Thesis, 1986. http://hdl.handle.net/10945/22117.
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Weymouth, Alfred John. "Scanning Tunneling Microscopy Studies of Small Aromatic Molecules on Semiconductor Surfaces." Thesis, 2009. http://hdl.handle.net/1974/7328.
Full textAbstract:
Understanding the behaviour of molecules on a semiconductor surface is necessary if molecular self-assembly is going to be employed, with existing semiconductor technology, to create useful devices. Si(111)-7x7 is an invaluable surface upon which to study molecular adsorption. The surface reconstruction has been well characterized and it possesses seven symmetrically distinct dangling bonds that can serve as reaction sites. Aromatic molecules on Si(111)-7x7 have been investigated with a variety of techniques and have been shown to chemisorb at room temperature. However, it is not trivial to predict how an ensemble of aromatic molecules might distribute themselves amongst the available bonding sites on this surface. The work presented in this thesis begins with a joint STM and ab initio investigation of thiophene on 7x7 that demonstrates kinetics are necessary to describe the chemisorption sites occupied at various coverages. A kinetic Monte Carlo model, taking into account a mobile physisorbed state, is shown to accurately describe this site occupancy at room temperature. This model disregards molecule-molecule interaction because thiophene does not sterically hinder chemisorption to a neighbouring dangling bond. A larger molecule, mesitylene, was then studied on Si(111)-7x7, and shown to form an ordered molecular lattice on the Si(111)-7x7 surface. This is the first demonstration of a porous molecular lattice grown on Si(111)-7x7 at room temperature. Finally, molecular chemisorption on the related 5x5 reconstruction, grown by depositing Ge on 7x7, is studied. It is found that the presence of Ge hinders molecular chemisorption, preventing formation of the mesitylene lattice.Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-09-11 10:14:10.118