No / Elevated plasma concentrations of the sulphur-containing amino acid homocysteine (Hcy) is associated with increased risk of atherosclerosis and arterial thrombosis. The mechanism by which Hcy exerts these effects has yet to be fully elucidated, although a variety of possible mechanisms have been proposed, including endothelial dysfunction or haemostatic abnormalities. However, the influence of Hcy on platelets, cells central to the atherothrombotic process, has never been addressed directly in patient studies. Here, the influence of mild hyperhomocysteinaemia (hHcy) on platelet function was explored in patients with peripheral occlusive arterial disease as evidence by intermittent claudication. Claudicants (n=39) were assigned to one of two subgroups depending on their plasma Hcy concentrations. hHcy claudicants had plasma Hcy concentrations of 18.9±1.0 ¿M (n=24), compared to 11.3±0.5 ¿M for normohomocysteinemic (nHcy) claudicants (n=15) and 12.6±0.7 ¿M for age-matched controls (n=15). Platelet function was evaluated ex vivo in both groups and compared to age-matched controls. Platelet activation and sensitivity to nitric oxide-mediated inhibition was assessed by platelet fibrinogen binding and P-selectin expression. At low concentrations of adenosine diphosphate (ADP; 0.1 ¿M) and thrombin (0.02 U/ml), platelets from hHcy claudicants were more reactive than those from age-matched controls, but not nHcy claudicants. Agonist-induced P-selectin expression was significantly raised in hHcy claudicants compared to all other groups. Interestingly no differences were observed between nHcy claudicants and age-matched controls, indicating that claudication per se did not affect platelet function. Since platelet activity in vivo is determined by the exposure to both agonists and antagonists, we subsequently tested the sensitivity of platelets to inhibition by nitric oxide (NO), using the same platelet markers. Platelets from hHcy claudicants were significantly less sensitive to GSNO (1¿100 ¿M)-mediated inhibition than all other groups. GSNO (1 ¿M) induced 42.6±10 and 39±11.5% inhibition of ADP-induced fibrinogen binding for the nHcy claudicants and age-matched controls, respectively. However, in hHcy claudicants only 16.4±9.7% inhibition was observed, significantly less than the other groups (P<0.01). Again no differences between nHCy claudicants and controls were observed. These results suggest the presence of claudication alone does not influence platelet function but if complicated with mild hyperhomocysteinemia, the sensitivity to agonists is increased, and more importantly, their sensitivity to inhibition is greatly reduced. The overall effect would be an increased propensity for platelet activation. The presence of even mildly elevated plasma Hcy could dramatically increase thrombotic risk.

Graphene sheets, one atom thick, two dimensional layers of carbon atoms, have gained enormous importance over the past few years due to their unique attributes - high electronic, thermal conductivities and exceptional mechanical strength. Chemical reduction of graphene oxide (GO) has been considered as a viable route for large scale production of graphene sheets. The reduced graphene oxide (r -GO) sheets although their conductivities are comparatively lower than that of graphene are nevertheless versatile material for applications in thin films and composites. An important consideration in the design of solution processing techniques for the preparation of processable graphene sheets is the dispersibility of GO and r -GO in different solvents, especially aqueous dispersibility. While GO is dispersible in water over a wide range of pH values, r -GO shows poor dispersibility and over a limited range of pH values. Graphene oxide, the oxidized form of graphene, are single atomic layers with lateral dimension that can extend to hundreds of nanometers. The sheets contain a sizable fraction of carbons that are sp3 hybridized and covalently bonded to oxygen in the form of epoxy, carbonyls as well as ionizable hydroxyl and carboxylic functional groups located on the rim of the sheets. The remaining carbons form isolated sp2 graphene like networks. On reduction the oxygen functionalities are removed and the sp2 network partially restored. This thesis focuses on the aqueous dispersibility of GO and r -GO, and describes a strategy to enhance the dispersibility of r -GO by cyclodextrin functionalization. Chapter 1 of the thesis provides a brief review of the synthetic procedures and structure of GO and r -GO while Chapter 2 describes the experimental methods and characterization techniques used in the thesis. The chemistry underlying the aqueous dispersibility of GO and r -GO at different values of pH have been investigated by zeta potential measurements, pH titrations and infrared spectroscopy (Chapter 3). These measurements show that r -GO sheets have ionizable groups with a single pKa value (8.0) while GO sheets have groups that are more acidic (pKa = 4.3), in addition to groups with pKa values of 6.6 and 9.0. Infrared spectroscopy has been used to follow the sequence of ionization events. In both GO and r -GO sheets, it is ionization of the carboxylic groups that is primarily responsible for the build up of charge, but on GO sheets, the presence of phenolic and hydroxyl groups in close proximity to the carboxylic groups lowers the pKa value by stabilizing the carboxylate anion, resulting in superior water dispersibility. Till recently GO was primarily considered only as an easily available precursor for chemical routes to r -GO but it has now been recognized as an interesting material in its own right. Two such attributes that have attracted wide spread attention are the in- trinsic and tunable fluorescence of GO as well as formation of liquid crystalline phases. Aqueous dispersions of GO exhibit strong pH dependent fluorescence in the visible region that originates, in part, from the oxygenated functionalities present. In Chapter 4, the spectral migration on nanosecond timescales of the pH dependent features in the fluores- cence spectra of GO is described. The changes in the steady state fluorescence spectra with pH have been correlated with the sequence of dissociation events that occur in GO dispersions at different values of pH described in Chapter 3, from time resolved emission spectra (TRES) constructed from the wavelength dependent fluorescence decay curves, it is shown that the migration is associated with excited state proton transfer. Both ‘intramolecular’ and ‘intermolecular’ transfers involving the quasimolecular oxygenated aromatic fragments are observed. Aqueous dispersions of GO constitute a distinctive class of 2D-anisotropic colloids with competing interactions - long range electrostatic repulsion, originating from ionized carboxylic groups located on the rim of the sheets and weak dispersive attractive interactions originating from the un-oxidized sp2 graphitic domains. In Chapter 5, it is shown that, colloidal dispersions of GO are intrinsically frustrated, exhibiting a range of arrested or metastable states, encompassing fluid, glass and gels that coexist with liquid crystalline order. These states can be accessed by varying the relative magnitudes of the repulsive and attractive forces by changing the ionic strength of the medium, by addition of salt and/or the concentration of the dispersion. At low salt concentrations, where long range electrostatic repulsions dominates, the formation of a repulsive Wigner glass is observed while at high salt concentrations, when attractive forces dominate, the formation of gels that exhibits a nematic to columnar liquid crystalline transition. These studies highlights how the chemical structure of GO - hydrophilic ionizable groups and hydrophobic graphitic domains coexisting on a single sheet - gives rise to a rich and complex phase diagram. The poor dispersibility of r -GO in aqueous media limits its use in practical applica- tions. To enhance the dispersibility, r -GO sheets have been functionalized by covalently linking -cyclodextrin ( -CD) cavities to the sheets via an amide linkage (Chapter 6). The functionalized -CD: rGO sheets, in contrast to r -GO, are dispersible over a wide range of pH values (2 - 13). Zeta potential measurements indicate that there is more than one factor responsible for the dispersibility. It is shown that planar aromatic molecules adsorbed on the r -GO sheet as well as nonplanar molecules included in the tethered -CD cavities have their fluorescence effectively quenched by the -CD: rGO sheets. The -CD: rGO sheets combine the hydrophobicity associated with r -GO along with the hydrophobicity of the cyclodextrin cavities in a single water dispersible material. Resonance Raman spectroscopy is a powerful analytical tool for detecting and identi- fying analytes, but the associated strong fluorescence background severely limits the use of the technique. In Chapter 7, it is shown that the cyclodextrin functionalized -CD: rGO sheets, described in Chapter 6, provides a versatile platform for resonance Raman detection. Planar aromatic and dye molecules that adsorb on the r -GO graphitic domains and non-planar molecules included within the tethered -CD cavities have their fluorescence effectively quenched. Using the water dispersible -CD: rGO sheets, it is possible to record the resonance Raman spectra of adsorbed and included organic chromophores directly in aqueous media without having to extract or deposit on a substrate. The Raman signal intensities show a linear dependence with the concentration of analyte present in water. This is significant, as it allows for the identification and estimation of organic analytes present in water by resonance Raman spectroscopy.

published_or_final_version / abstract / Anatomy / Doctoral / Doctor of Philosophy

A successful transition from fossil fuels to renewable energies such as wind and solar will require the implementation of high-energy-density storage technologies. Promising energy storage technologies include lithium-ion batteries, metal-air batteries, and hydrogen production via photoelectrochemical water splitting. While these technologies differ substantially in their mode of operation, they often involve transition-metal oxides as a component. Thus, fundamental materials research on metal oxides will continue to provide much needed advances in these technologies. In this thesis, the electrochemical and electrocatalytic properties of Fe- and Mn-substituted layered LiNiO₂ materials were investigated. These materials were prepared by heating mixed nitrate precursors in O₂ atmosphere at 700-850 °C for 12 h with intermediate grindings. The products were chemically delithiated with NO₂BF₄, and the delithiated samples were annealed at moderate temperatures in order to transform them to a spinel-like phase. Samples were characterized by inductively coupled plasma analysis and Rietveld refinement of the X-ray diffraction patterns, which were found to be in reasonably close agreement regarding lithium stoichiometry. Spinel-like materials were found to possess an imperfect spinel structure when heated at lower temperatures and a significant amount of NiO impurity was formed when heated to higher temperatures. This structural disorder was manifested during electrochemical cycling -- only Mn-rich compositions showed reversible capacities at a voltage of around 4.5 V. The layered materials exhibited significant capacity loss upon cycling, and this effect was magnified with increasing Fe content. These materials were further investigated as catalysts for the oxygen evolution reaction (OER). All samples containing Mn exhibited low OER activity. In addition, delithiation degraded catalyst performance and moderate temperature annealing resulted in further degradation. Because delithiation significantly increased surface area, activities were compared to the relative to BET surface area. Li₀.₉₂Ni₀.₉Fe₀.₁O₂ exhibited significantly higher catalytic activity than Li₀.₈₉Ni₀.₇Fe₀.₃O₂. This prompted testing of Li[subscript x]Ni₁₋[subscript y]Fe[subscript y]O₂ (y = 0, 0.05, 0.1, 0.2, and 0.3) samples. It was found that a Fe content of approximately 10% resulted in the highest OER activity, with decreased activities for both larger and smaller Fe contents. These results were found to be consistent with studies of Fe substituted nickel oxides and oxyhydroxides, suggesting a similar activation mechanism. / text

Interest in nanomaterials is motivated partly by their potential for sensor arrays to detect different gases. Nanowires in particular are of interest because their high surface-to-volume ratio promises the possibility of high sensitivity. However, because of their discrete quasi-one-dimensional geometry, electrical integration of nanowires into photolithographically defined devices and circuits is challenging and remains one of the obstacles to their widespread use. In this thesis, a novel method for fabricating electrically integrated zinc oxide nanobridge devices using carbonized photoresist is investigated. The conductivity of carbonized photoresist is known and nanowire growth on carbonized photoresist has recently been reported, suggesting the possibility of simultaneous use as a nucleation layer and electrode. However, these reports did not characterize the contact between the ZnO nanowires and carbonized photoresist. In this work, ZnO nanobridges are fabricated between opposing carbonized photoresist electrodes and characterized both electrically and with electron microscopy. Operation of nanobridge devices as bottom gate transistors, UV sensors, and gas sensors is demonstrated. / Graduation date: 2010

Nitroglycerin and isoamyl nitrate have been used as nitrovasodilators since the nineteeth century. However, not until recently has it been known that these compounds were useful since they promoted the release of NO in the body. More recently, a new class of drugs, NO donors, has been developed. These include S-nitrosothiols (RSNO), sydnonimines, and nucleophilic NO adducts.

Thesis advisor: Dunwei Wang / Solar water splitting refers to the reaction that converts solar energy into chemical fuel. It is an attractive means to store solar energy. This process, analogous to nature photosynthesis, uses semiconductor to capture and convert solar irradiation and, as such, is called artificial photosynthesis. Despite its promising prospect, the lack of materials that can satisfy all requirements to achieve efficient solar water splitting becomes an important challenge. In this thesis, we aim to develop a strategy of forming heteronanostructure to tackle the challenge faced by metal oxide-based photoanode for water oxidation. The challenge associated with metal oxide-based photoanodes and current approach to alleviate the challenge is first discussed. We propose a strategy of combining multiple components to form heteronanostructure to meet the challenges, in particular the charge transport issue. By introducing a dedicated charge transporter, we fabricate various heteronanostructure including TiO₂/TiSi₂, Fe₂O₃/TiSi₂ and Fe₂O₃/AZO nanotubes to improve the charge collection and therefore overall efficiency. Additionally, the growth of several important metal oxides by atomic layer deposition is developed and its utilization as photoanode for water splitting is studied for the first time. Because this strategy is based on the rational design and synthesis of materials, it has the potential to produce electrodes with a combination of properties that have not been exhibited simultaneously by single-component materials. In addition, the strategy is highly versatile and can incorporate the latest developments produced by parallel efforts. We are confident that the rational design and synthesis of materials such as the strategy proposed here will play an increasingly more important role in energy research. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Shu King-hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 80-81). / ABSTRACT --- p.1 / Chapter CHAPTER I. --- INTRODUCTION --- p.3 / REFERENCES --- p.6 / Chapter CHAPTER II. --- BRIEF REVIEW OF THE ANALYTICAL METHODS USED / Chapter 1. --- Spectrophotometry --- p.8 / Chapter 2. --- Derivative spectrophotometry --- p.9 / Chapter 3. --- Atomic absorption spectrometry --- p.12 / Chapter 4. --- X - Ray fluorescence --- p.12 / REFERENCES --- p.14 / Chapter CHAPTER III. --- SIMULTANEOUS DETERMINATION OF ALUMINIUM OXIDE AND IRON (III) OXIDE / Chapter 1. --- Introduction / Review of the reported methods --- p.15 / Determination of aluminium and iron with / 8-hydroxyquinoline --- p.18 / Chapter 2. --- Experimental --- p.21 / Chapter 3. --- Results and discussion / Determination of iron --- p.28 / Determination of aluminium --- p.38 / Chapter 4. --- Conclusion --- p.52 / REFERENCES --- p.53 / Chapter CHAPTER IV. --- RAPID DETERMINATION OF CALCIUM OXIDE / Chapter 1. --- Introduction --- p.56 / Chapter 2. --- Experimental --- p.62 / Chapter 3. --- Results and discussion --- p.66 / Chapter 4. --- Conclusion --- p.79 / REFERENCES --- p.80 / FIGURES / Chapter II-1 --- Attenuation of a beam of radiation by an absorbing solution --- p.8 / Chapter II-2 --- Gaussian curve and its first to fourth derivatives --- p.11 / Chapter III-l --- Effect of pH on the extraction of metals with8- hydroxyquinoline --- p.19 / Chapter III-2 --- "Normal absorbance spectra of the metal - oxinates: A1 (5ppm), Fe (5ppm)" --- p.20 / Chapter III-3 --- Effect of pH on the determination of iron (5ppm) --- p.29 / Chapter III-4 --- Calibration curve for the determination of iron (III) by spectrophotometry at 580 nm --- p.33 / Chapter III-5 --- "The first derivative spectra of metal-oxinates A1: 5ppm, Fe : 5ppm" --- p.39 / Chapter III-6 --- "The second derivative spectra of metal-oxinates, A1: 5ppm, Fe : 5ppm" --- p.39 / Chapter III-7 --- "Normal absorption spectra of the metal-oxinates : A1(5 ppm), Ti (5 ppm)" --- p.41 / Chapter III-8 --- Effect of pH on the determination of aluminium --- p.43 / Chapter III-9 --- Calibration curve for the determination of aluminium by second derivative spectrophotometry at 390 nm --- p.47 / Chapter IV-1 --- "Effect of pH on the development of colour of Ca- GBHA complex. Ca : 1.2 ppm, wavelength : 530 nm" --- p.68

Wang Xiaofeng = Hf基高K介电薄膜的微观结构和电子结构研究 / 王晓峰. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 62-67). / Text in English; abstracts in English and Chinese. / Wang Xiaofeng = Hf ji gao K jie dian bo mo de wei guan jie gou he dian zi jie gou yan jiu / Wang Xiaofeng. / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.3 / Chapter 2.1 --- Ideal high-k materials --- p.3 / Chapter 2.1.1 --- Current problems with Si02 and possible solutions --- p.3 / Chapter 2.1.2 --- Requirements on the high-k gate dielectric materials --- p.6 / Chapter 2.2 --- Recent results on high-k gate dielectrics --- p.8 / Chapter 2.2.1 --- A1203 --- p.8 / Chapter 2.2.2 --- Y203 and La203 --- p.9 / Chapter 2.2.3 --- Hf02 and Zr02 --- p.10 / Chapter 2.2.4 --- Pseudo-binary Alloys --- p.10 / Chapter 3 --- Experimental and Instrumentation --- p.13 / Chapter 3.1 --- Transmission electron microscopy (TEM) --- p.13 / Chapter 3.2 --- Transmission electron diffraction (TED) --- p.15 / Chapter 3.3 --- Electron energy loss spectroscopy (EELS) --- p.16 / Chapter 4 --- Data Analysis Methodology --- p.22 / Chapter 4.1 --- Diffraction analysis --- p.22 / Chapter 4.1.1 --- Ring ratio analysis for polycrystal diffraction pattern --- p.23 / Chapter 4.1.2 --- RDF analysis for amorphous materials --- p.24 / Chapter 4.2 --- Eliminating the plural scattering in EELS --- p.29 / Chapter 4.2.1 --- Removal of plural scattering from inner-shell edges --- p.30 / Chapter 4.2.2 --- Fourier-Ratio deconvolution --- p.30 / Chapter 4.2.3 --- "Demonstration using Co L2,3 core-loss spectrum" --- p.31 / Chapter 5 --- The Temperature Effect on the Microstructure of HfO2 Films --- p.37 / Chapter 5.1 --- Experimental --- p.38 / Chapter 5.2 --- Phase identification and crystallinity analysis of the Hf02 thin films --- p.38 / Chapter 5.2.1 --- Phase and crystallinity analysis from TEDs --- p.38 / Chapter 5.2.2 --- The phase and crystallinity evolution with the growth temperature --- p.39 / Chapter 5.3 --- The local symmetry of Hf atom in the films --- p.40 / Chapter 6 --- Effect of A1 Addition on the Microstructure and Electronic Structure of HfO2 Films --- p.43 / Chapter 6.1 --- Experimental --- p.44 / Chapter 6.2 --- RDF analysis of HfAlO films --- p.45 / Chapter 6.3 --- The local symmetry of Hf atom in the HfAlO films --- p.46 / Chapter 6.4 --- Loss functions of HfAlO films --- p.48 / Chapter 7 --- Comparison of A1 and Y Addition on the Microstructure of Hf02 Films --- p.56 / Chapter 7.1 --- Experimental --- p.57 / Chapter 7.2 --- Phase identification and crystallinity analysis of the alloy thin films --- p.57 / Chapter 7.2.1 --- Phase and crystallinity analysis from TEDs --- p.57 / Chapter 7.2.2 --- The phase and crystallinity evolution with the Y and A1 incorporation --- p.58 / Chapter 7.3 --- The local symmetry of Hf atom in the alloy thin films --- p.59 / Chapter 8 --- Conclusion --- p.61 / Bibliography --- p.62

Wang Lei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / List of Figures --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Scaling issues of Metal-Oxide-Semiconductor field effect transistor --- p.1 / Chapter 1.2 --- Alternative high-k gate dielectrics --- p.4 / Chapter 1.3 --- Overview of this thesis --- p.9 / References --- p.10 / Chapter Chapter 2 --- Deposition and characterization techniques for ultrathin HfO2 films --- p.11 / Chapter 2.1 --- Introduction --- p.11 / Chapter 2.2 --- Ultrathin Hf02 Films Growth and Post Deposition Modification --- p.11 / Chapter 2.2.1 --- Ultrahigh Vacuum Electron-beam Evaporation --- p.11 / Chapter 2.2.2 --- High Concentration Ozone Annealing --- p.12 / Chapter 2.2.3 --- Plasma Immersion Ion Implantation --- p.14 / Chapter 2.2.4 --- Rapid Thermal Annealing --- p.16 / Chapter 2.3 --- Compositional Characterization Techniques --- p.17 / Chapter 2.3.1 --- X-ray Photoelectron Spectroscopy --- p.17 / Chapter 2.3.2 --- Rutherford Backscattering Spectrometry --- p.18 / Chapter 2.4 --- Structural and Surface Morphological Characterization Techniques --- p.19 / Chapter 2.4.1 --- High-Resolution Transmission Electron Microscopy --- p.19 / Chapter 2.4.2 --- Ultrahigh Vacuum Scanning Tunneling Microscopy --- p.20 / Chapter 2.4.3 --- Ultrahigh Vacuum Atomic Force Microscopy --- p.22 / Chapter 2.5 --- Electrical Characterization --- p.24 / Chapter 2.5.1 --- Capacitance-voltage (C-V) Measurement --- p.24 / Chapter 2.5.2 --- Current-voltage (I-V) Measurement --- p.25 / References --- p.26 / Chapter Chapter 3 --- Control of interfacial silicate between Hf and SiO2 by high concentration ozone --- p.27 / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Experimental procedure --- p.28 / Chapter 3.3 --- Results and discussion --- p.29 / Chapter 3.4 --- Conclusion --- p.35 / References --- p.36 / Chapter Chapter 4 --- Electrical characteristics of postdepositon annealed ultrathin Hf02 films --- p.37 / Chapter 4.1 --- Introduction --- p.37 / Chapter 4.2 --- Capacitance of gate stack in metal-insulator-semiconductor structure --- p.38 / Chapter 4.3 --- Electrical characteristics of ultrathin HfO2 films by high temperature Ozone oxidation --- p.39 / Chapter 4.4 --- Electrical and structural properties of ultrathin HfO2 films by high temperature rapid thermal annealing --- p.46 / Chapter 4.5 --- Conclusion --- p.48 / References --- p.50 / Chapter Chapter 5 --- Effect of nitrogen incorporation on thermal stability of ultrathin Hf02 films --- p.51 / Chapter 5.1 --- Introduction --- p.51 / Chapter 5.2 --- Experimental procedure --- p.52 / Chapter 5.3 --- Results and discussion --- p.52 / Chapter 5.4 --- Conclusion --- p.58 / References --- p.59 / Chapter Chapter 6 --- Local characterization of ultrathin HfO2 films by in-situ Ultrahigh Vacuum Scanning Probe Microscopy --- p.61 / Chapter 6.1 --- Introduction --- p.61 / Chapter 6.2 --- Experimental procedure --- p.62 / Chapter 6.3 --- Morphology and structure of initial growth of HfO2 --- p.63 / Chapter 6.4 --- Local characterization of ultrathin HfO2 films by in-situ UHV-STM --- p.66 / Chapter 6.5 --- UHV c-AFM study of leakage path evolution in ultrathin Hf02 films --- p.71 / Chapter 6.6 --- Conclusion --- p.72 / References --- p.73 / Chapter Chapter 7 --- Conclusion --- p.74 / Publications --- p.76