The structure, magnetic behaviour and chemistry of layered oxychalcogenides of composition A₂MO₂X₂Ch₂ (where A = Sr, Ba; M = Mn, Co, Ni, Cu, Zn; X = Cu, Ag and Ch = S, Se, Te) has been investigated by the synthesis of new compounds of this type and control of the properties of these compounds by oxidative deintercalation of Cu/Ag. I₂ can be used to oxidatively deintercalate Cu from Sr₂MnO₂Cu_1.5S₂, forming Sr₂MnO₂Cu_1.33S₂, an incommensurately modulated compound, with a completely different Cu/vacancy ordering and antiferromagnetic ordering structure to the parent. This reaction is also probed in real-time, using in situ powder X-ray diffraction. Sr₂MnO₂Ag_1.5Se₂ was found to have an A-type magnetic ordering structure, similar to Sr₂MnO₂Cu_1.5Se₂. Sr₂MnO₂Cu_1.8Te₂ on the other hand with a lower Mn oxidation state shows only two-dimensional magnetic correlations, rather than long-range order. Extending the reaction with I₂ to several Co-containing analogues revealed that ~ 25% Ag could be removed from Sr₂CoO₂Ag₂Se₂, sufficient to observe a change in magnetic behaviour, from antiferromagnetic to ferromagnetic. By contrast only ~11% Cu can be deintercalated from Sr₂CoO₂Cu₂S₂ and even less (~5%) from Sr₂CoO₂Cu₂Se₂. Neutron diffraction was used to examine the resultant changes in magnetic ordering. The novel compounds Sr₂CuO₂Cu₂Se₂ and Ba₂CuO_2-xCu₂Se₂ are related by substitution of the alkali-earth metal, but while Sr₂CuO₂Cu₂Se₂ is a stoichiometric compound with metal-like character, Ba₂CuO_2-xCu₂Se₂ is an oxygen-deficient semiconductor, with tuneable oxygen content. Unusual features are observed in the magnetic susceptibility measurements of Sr₂NiO₂Cu₂Se₂ that appear unrelated to this compound's long-range magnetic ordering, as probed by neutron diffraction. Furthermore, unusual peak splitting is observed in low-temperature powder X-ray diffraction patterns of this compound; this may plausibly be due to a photon-induced effect arising from the use of a high-energy beamline; although further measurements are required to examine this. Overall the work shows the flexibility and range of behaviour exhibited by a series of the transition metal oxide chalcogenides.

Chan, Mui. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstract also in Chinese. / Abstract --- p.i / Abstract (Chinese) --- p.iii / Declaration --- p.v / Acknowledgement --- p.vi / Table of Contents --- p.viii / List of Tables --- p.xiv / List of Figures --- p.xv / Chapter Chapter 1: --- Introduction / Chapter 1.1 --- Overview --- p.1 / Chapter 1.2 --- Soft-Chemistry --- p.7 / Chapter 1.2.1 --- Sol-Gel Method --- p.7 / Chapter 1.2.2 --- Co-precipitation --- p.9 / Chapter 1.2.3 --- Microemulsion --- p.10 / Chapter 1.3 --- Application of Hydrothermal/Solvothermal Methods in Materials Synthesis --- p.12 / Chapter 1.3.1 --- Fundamentals of Hydrothermal and Solvothermal Methods --- p.12 / Chapter 1.3.2 --- Advantages of Hydrothermal/Solvothermal Methods in contrast to Conventional Synthetic Approaches --- p.13 / Chapter 1.3.3 --- Hydrothermal and Solvothermal Preparation of Materials --- p.14 / Chapter 1.4 --- Application of Transition Metal Oxides As Functional Materials --- p.15 / Chapter 1.5 --- Aim and Scope of Work --- p.16 / Chapter 1.6 --- References --- p.17 / Chapter Chapter 2: --- Solvothermal and Hydrothermal Template Free Synthesis of ZnO Microspheres / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.2 --- Experimental Section --- p.25 / Chapter 2.2.1 --- Synthesis of ZnO Microspheres by Solvothermal Method --- p.25 / Chapter 2.2.2 --- Synthesis of ZnO Microspheres by Hydrothermal Method --- p.26 / Chapter 2.2.3 --- Doping ZnO Microspheres with Silver or Gallium by Solvothermal Method --- p.26 / Chapter 2.2.4 --- Characterization --- p.27 / Chapter 2.2.5 --- Measurement of Photocatalytic Activity --- p.29 / Chapter 2.3 --- Results and Discussion --- p.30 / Chapter 2.3.1 --- X-Ray Diffraction Analysis --- p.30 / Chapter 2.3.1.1 --- ZnO-HT and ZnO-ST --- p.30 / Chapter 2.3.1.2 --- ZnO-ST: Effect of Different Concentrations of Zinc Acetate --- p.33 / Chapter 2.3.1.3 --- Doping ZnO-ST with Silver or Gallium --- p.34 / Chapter 2.3.2 --- SEM study --- p.36 / Chapter 2.3.2.1 --- ZnO-HT and ZnO-ST --- p.36 / Chapter 2.3.2.2 --- ZnO-HT-Different Volume Ratios of Ethylene Glycol to Water --- p.37 / Chapter 2.3.2.3 --- ZnO-ST --- p.39 / Chapter 2.3.2.3.1 --- Different Volume Ratios of Benzyl Alcohol to Ethylene Glycol --- p.40 / Chapter 2.3.2.3.2 --- Different Concentrations of Zinc Acetate --- p.41 / Chapter 2.3.2.3.3 --- Different Concentrations of Urea --- p.42 / Chapter 2.3.3 --- TEM Study --- p.44 / Chapter 2.3.3.1 --- TEM and HRTEM of ZnO-HT --- p.44 / Chapter 2.3.3.2 --- TEM and HRTEM of ZnO-ST --- p.45 / Chapter 2.3.3.3 --- TEM Images of Ga-Doped ZnO-ST --- p.47 / Chapter 2.3.3.4 --- TEM Images of Ag-Doped ZnO-ST --- p.49 / Chapter 2.3.4 --- Nitrogen Adsorption and Desorption --- p.50 / Chapter 2.3.5 --- X-Ray Photoelectron Spectroscopy --- p.52 / Chapter 2.3.5.1 --- XPS Study of ZnO-ST --- p.52 / Chapter 2.3.5.2 --- XPS Study of ZnO-HT --- p.54 / Chapter 2.3.5.3 --- XPS Study of Silver Doped ZnO-ST --- p.56 / Chapter 2.3.5.4 --- XPS Study of Gallium Doped ZnO-ST --- p.58 / Chapter 2.3.6 --- FR-IR Spectra --- p.60 / Chapter 2.3.7 --- Photocatalytic Activity on Degradation of Methylene Blue --- p.61 / Chapter 2.3.8 --- Proposed Formation Mechanism for ZnO-ST --- p.64 / Chapter 2.3.9 --- Proposed Formation Mechanism for ZnO-HT --- p.68 / Chapter 2.3.10 --- Optical Property of ZnO Microspheres --- p.69 / Chapter 2.4 --- Conclusion --- p.73 / Chapter 2.5 --- References --- p.74 / Chapter Chapter 3: --- Synthesis of Hierarchical Porous Lithium Niobate Submicrometer Rods / Chapter 3.1 --- Introduction --- p.79 / Chapter 3.2 --- Experimental Section --- p.81 / Chapter 3.2.1 --- Characterization --- p.82 / Chapter 3.3 --- Results and Discussion --- p.83 / Chapter 3.3.1 --- X-Ray Diffraction Analysis --- p.83 / Chapter 3.3.2 --- SEM Study --- p.86 / Chapter 3.3.2.1 --- Surfactants Dependent Morphologies Change --- p.86 / Chapter 3.3.2.2 --- Concentrations of CTAB --- p.87 / Chapter 3.3.2.3 --- Time Dependent Morphologies Change --- p.88 / Chapter 3.3.3 --- TEM Study --- p.91 / Chapter 3.3.5 --- XPS Analysis --- p.93 / Chapter 3.3.6 --- BET Analysis --- p.96 / Chapter 3.3.7 --- Proposed Formation Mechanism --- p.97 / Chapter 3.3.7.1 --- Effect of Microemulsion --- p.97 / Chapter 3.3.7.2 --- Effect of CTAB --- p.98 / Chapter 3.3.7.3 --- Ostwald Ripening --- p.99 / Chapter 3.3.7.4 --- Formation of LiNi3O8 --- p.101 / Chapter 3.4 --- Conclusion --- p.102 / Chapter 3.5 --- References --- p.103 / Chapter Chapter 4: --- Flower-Like α-Nickel Hydroxide synthesized by hydrothermal method / Chapter 4.1 --- Introduction --- p.106 / Chapter 4.2 --- Experimental Section --- p.108 / Chapter 4.2.1 --- Synthesis of Nickel Hydroxide by Hydrothermal Method --- p.108 / Chapter 4.2.2 --- Characterization --- p.109 / Chapter 4.3 --- Results and Discussion --- p.111 / Chapter 4.3.1 --- X-Ray Diffraction Analysis --- p.111 / Chapter 4.3.2 --- SEM Study --- p.115 / Chapter 4.3.3 --- TEM and HRTEM Study --- p.116 / Chapter 4.3.4 --- XPS Analysis --- p.117 / Chapter 4.3.5 --- FT-IR Analysis --- p.119 / Chapter 4.3.6 --- BET analysis --- p.120 / Chapter 4.3.7 --- Proposed Formation Mechanism of the Flower like α-Ni(OH)2 --- p.122 / Chapter 4.4 --- Conclusion --- p.123 / Chapter 4.5 --- References --- p.124 / Chapter Chapter 5: --- Conclusions and Future Work / Chapter 5.1 --- Conclusions --- p.127 / Chapter 5.2 --- Future work --- p.129

Les phases MAX forment une famille de carbures et de nitrures nano-lamellaires de formule chimique Mn+1AXn, où M est un métal de transition des premières colonnes, A appartient aux colonnes 13-16 et X est soit C, soit N, ou une combinaison des deux éléments. Ces phases combinent les mérites des céramiques et des métaux, comme une bonne stabilité chimique, l’usinabilité, la résistance aux chocs mécaniques, de bonnes conductivités thermique et électrique, etc. Malgré tout, l’étude de leurs propriétés intrinsèques et de leurs anisotropies a été jusqu’à présent limitée par l’indisponibilité de monocristaux. Cette thèse traite de la réactivité de tels monocristaux de phases MAX. Grâce à la large taille des cristaux produits au LMGP, il a été possible d’évaluer directement l’anisotropie de la réactivité chimique et d’obtenir des données originales. Nous avons montré le rôle prépondérant joué par l’élément A pour initier des transformations chimiques menant parfois à la synthèse de matériaux originaux, et nous nous sommes concentrés sur quatre aspects différents : Tout d’abord, nous avons tenté de synthétiser des MXènes de grande taille, en profitant de la grande taille des cristaux disponibles. Un effort particulier a été porté sur la description de la réactivité chimique de phases MAX plongées dans diverses solutions d’attaque, avec un accent particulier mis sur l’utilisation de HF. En second lieu, nous avons étudié la chloruration de phases MAX : l’objectif initial était de former des MXènes, mais nous avons finalement développé une méthode pour synthétiser des carbures de chrome poreux avec des propriétés intéressantes. Troisièmement, nous avons utilisé des cristaux de grande taille pour évaluer l’anisotropie des propriétés électrochimiques. Une anisotropie significative a été trouvée, soit en mesurant le courant durant la polarisation électrochimique, soit par mesure de spectroscopie d’impédance. Divers mécanismes ont été proposés afin d’expliquer cette anisotropie des propriétés de corrosion. Enfin, nous avons montré que les résultats électrochimiques pouvaient être utilisés pour révéler indirectement la présence de défauts structurels récemment identifiés dans la littérature. De tels défauts, appelés « ripplocations », sont spécifiques aux matériaux nano-lamellaires. / MAX phases are a family of layered ternary carbides and nitrides with chemical formula Mn+1AXn, where M is an early transition element, A is an element of groups 13 to16 and X is either C, N or both. These phases combine the merits of ceramics and metals, such as chemical stability, machinability, shock resistance, good electrical and thermal conductivity, etc. However, the investigation of their intrinsic properties and anisotropies has heretofore been limited by a lack of availability of single crystals. This thesis mainly deals with the chemical reactivity of MAX phase single crystals. Owing to the large size single crystals grown at LMGP, it was possible to directly assess the anisotropy of the chemical reactivity and to obtain original data. We showed that the prominent role played by the A element for initiating chemical transformations could lead to the synthesis of original materials, and we focused on four different aspects. First, we tried to synthesize MXenes from MAX phase single crystals: The purpose was to obtain large-scale MXenes by taking advantage of the large size of the single crystals. Effort was put on describing the chemical reactivity of MAX phases dipped in different etchants, focusing on HF. Secondly, we studied the MAX phase reactivity with chlorination: the initial purpose was to obtain MXenes, but we finally developed a method for synthesizing porous chromium carbides which exhibit several interesting properties. Thirdly, we used large size single crystals in order to assess the anisotropy of the electrochemical properties. A significant anisotropy was found, either by measuring the current during electrochemical polarization or by frequency-dependent impedance measurements. Several mechanisms were proposed in order to explain this anisotropy of the corrosion properties. Eventually, we showed that the electrochemical results could be used to indirectly evidence the presence of structural defects recently identified in the literature. Such defects, called ripplocations, are specific to nano-lamellar materials.

Magister Pharmaceuticae - MPharm / The author’s objective was to follow the product life-cycle process of a novel antiretroviral, nevirapine formulation in South Africa, to generate and compile data to pursue market registration. Five supramolecular co-crystals, viz. nevirapine-saccharin (NVSC), nevirapine-DL-tartaric acid (NVTTA), nevirapine-maleic acid (NVMLE), nevirapine-glutaric acid (NVGLT) and nevirapine-salicylic acid (NVSLI) were reproduced and confirmed by powder X-ray diffraction (PXRD). A pre-formulation study ensued to identify the most appropriate co-former candidate to formulate a tablet dosage form comparative to the proprietor brand, Viramune®. The co-crystals were synthesized by the co-precipitation and solvent-drop grinding techniques and identified by hot stage microscopy (HSM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), fourier transform infra-red spectrophotometry (FTIR), PXRD and single X-ray diffraction (SXRD). The solubility, dissolution and antiviral activity profiles of these co-crystals were assessed and compared to pure NV and NV:co-former mixtures in a 1:1 ratio. The preliminary dissolution analysis applied the BP 2005 rotating-basket method with water as dissolution medium. Initially, the dissolution samples were assayed with UV/VIS spectrophotometry which led to a more convincing quantitative approach where dissolution samples were assayed by HPLC. Solubility data revealed a fivefold increase in solubility of NV co-crystallized with maleic acid. Dissolution data, however revealed NVGLT as the best performing co-crystal with a 59 % NV drug release in water (dissolution media) with the remaining 4 co-crystals all indicating an enhanced aqueous solubility of NV. The antiviral activity of all 5 co-crystals performed by the National Institute of Communicable Diseases of South Africa determined whether the co-crystals had an improved antiviral activity against HIV-1 compared to pure NV. The results indicated that NVSC and NVSLI had the greatest antiviral activity compared to pure NV and the remaining co-crystals. The pre-formulation results formed the basis for the selection of the best co-former candidate for a NV co-crystal tablet formulation by direct compression. All solid dosage form quality control tests according to the USP 364 was performed on the prototype co-crystal tablet and the Viramune® tablet. Comparative dissolution analysis to evaluate bioequivalence was conducted and assayed by HPLC. The dissolution analysis utilized 3 media, viz. HCl buffer (pH 1.2), acetate buffer (pH 4.5) and a phosphate buffer (pH 6.8) which displayed no similarity in the dissolution profile of the prototype and the proprietor brand. Solution stability of NV in these buffered media was assessed after 4 weeks exposure of the dissolution samples to cold chain (2 - 8 °C, 0 % RH) and accelerated environmental conditions (40 °C, 75 % RH). The results indicated no significant degradation of NV in the prototype co-crystal tablet and the proprietor brand during the accelerated stability tests. Cytotoxicity against a host cell 293T and antiviral activity against the pseudo-HIV-1 virus of the prototype and proprietor brand was further determined. The antiviral activity results were favourable for both the prototype co-crystal and the proprietor brand tablet.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

Solid-state NMR (ssNMR) has matured into a versatile method to provide structural information, probe protein dynamics and detect small molecule binding and -protein interaction of a variety of biomolecular assemblies including amyloid fibrils, viral particles and membrane proteins. Membrane proteins embedded in liposomes are natural targets for ssNMR as their native states are solids. Magic angle spinning (MAS) ssNMR studies using moderate spinning frequencies provide detailed structural information and probe subtle conformational change. Development of fast magic angle spinning ssNMR enables proton-detection which increases sensitivity and facilitates protein dynamics measurements. In this dissertation, we applied moderate and fast MAS ssNMR to study potassium ion channel and protein dynamics Chapter 1 will introduce concepts and theory of solid-state NMR pulse sequences and experiments. Chapter 2 will discuss the application and perspectives of solid-state NMR to membrane protein systems. In Chapter 3, we test an allostery mechanism for inactivation using a KcsA mutant (H25R/E118A) that exhibits an open pH gate across a broad range of pH values. We present solid-state NMR measurements of this open mutant at neutral pH to probe the affinity for potassium at the selectivity filter. This result strongly supports our assertion that the open pH gate allosterically affects the potassium binding affinity of the selectivity filter. In this mutant the protonation state of a glutamate residue (E120) in the pH sensor is sensitive to potassium binding, suggesting that this mutant also has flexibility in the activation gate and is subject to transmembrane allostery. In Chapter 4, I optimize protein expression, purification and reconstitution into native environment protocols of a bacterial potassium transporter, KtrB. In chapter 5, methods and experimental details of setting up 60 and 40 kHz fast MAS ssNMR are discussed. With fast MAS ssNMR setup, multidimensional NMR experiments with higher sensitivity could be collected on a perdeuterated sample with less sample mass required. In Chapter 6, we employ fast MAS ssNMR to measure bulk and residue site-specific 15N and carbonyl 13C relaxation of microcrystalline ubiquitin. Carbonyl R1ρ relaxation profiles provide additional information on protein backbone dynamics.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21782号 / 工博第4599号 / 新制||工||1717(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 安部 武志, 教授 藤田 晃司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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