Chitosan-based copolymers (CH-GL1:6, CH-GL1:1, CH-GL1:0.5, and CH-GL1:0.25) were prepared at variable weight ratios of chitosan (CH) to glutaraldehyde (GL). Physiochemical properties of cross-linked copolymers were characterized using FTIR (Fourier Transform Infrared) spectroscopy, PXRD (Powder X-ray Diffraction), CHN analysis, and thermogravimetric analysis (TGA). The swelling behaviour of the polymers along with chitosan was investigated. The sorption properties of copolymers with arsenate oxoanions were investigated at various pH using 10 mM phosphate buffer systems and also in aqueous solution without buffer. The Sips sorption model describes the best fit parameters for adsorption. The relative monolayer sorption capacities Qm (mg/g) of the adsorbents are given in parentheses in the following order: CH-GL1:1(14.4) > CH-GL1:0.5(12.0) > CH-GL1:0.25(10.3) > CH-GL1:6(2.24). In general, the sorption capacities are listed in descending order as follow: un-buffered > buffered (pH 5.0) > buffered (pH 8.5). The removal efficiencies for 20 mg of polymers over a variable concentration range ( 1-200 mg/L) of arsenate in aqueous solution without buffer are as follow: CH-GL-1:1(20-95%), CH-GL1:0.5(14-97%), CH-GL1:0.25(10-98%), CH-GL1:6(2.0-56%), and CH (0.007-3.9%). The sorption properties of the adsorbents were also determined in bicarbonate buffer to evaluate the competitive effect of phosphate buffer on adsorption of arsenate oxoanions. X-ray absorption spectroscopy (XAS) of chitosan and CH-GL1:1 was performed after adsorption at different pH conditions using two buffer systems to evaluate the chemical environment around the arsenate species. In addition, sorptive properties of phenolic adsorbate (i.e. PNP) were estimated with CH-GL copolymers at various pH conditions. The estimated sorptive capacities (Qm; mmol/g) for PNP are in the range 0.07-0.21(mmol/g) while removal efficiencies for PNP are greater at lower pH conditions.

This thesis is based on experiments applying synchrotron based X-ray Absorption Spectroscopy(XAS) and Resonant Inelastic X-ray Scattering (RIXS) in the soft X-ray region to energy related systems. The main work of this thesis has been to develop a reaction cell that allowed for in situ XAS and RIXS investigations of the partial epoxidation of ethylene over a Ag catalyst at 1 atm and up to 250C. The developed in situ cell can be used in two sample modes: 1) the Ag catalyst is deposited directly onto the vacuum separating membrane with the reaction gases flowing beneath it or 2) a slightly compressed Ag powder sample is at a distance to the vacuum membrane with the reaction gases flowing between the Ag powder sample and the membrane.Both sample modes offers the total florescence yield, TFY, and the total electron yield, TEY, to be recorded simultaneously. By means of the developed in situ cell a number of oxygen species, residing in/on the Ag surface or in the Ag bulk, have been detected. We claim to detect adsorbed O2 under epoxidation conditions, as well as Ag–O–H groups. We are also able to monitor changes of the absorbed oxygen as we change the composition of the reaction gas feed. The first charging cycle of Li-ion batteries have been investigate by ex situ measurements on the cathode Li2-xMnSiO4 and the anode composite LixNi0:5TiOPO4/C . The initial crystalline material becomes amorphous due to lithiation during the first first charging. We find that the redox behaviors of these two states are significantly different. Sulfidation of natural copper oxides are is found to be strongly promoted when it is grown on the host metal by a disproportionation.

One of the critical challenges in the Canadian oil sand industry is improving processes used to separate bitumen from oil sands and to remove clay particulates from produced oil. The fine clay particles are believed to play a significant role in the oil sands industry, from stabilizing process emulsions to fouling problems in water treatment. Addressing the problems caused by these fine clay particulates is limited by the ability to characterize the hydrocarbon-clay interactions. Scanning Transmission X-ray Microscopy (STXM) is used to study hydrocarbon-clay interactions in controlled model systems, where all components are known, and in process samples extracted from oil sands. To use STXM to study our desired systems, many experimental developments were required. Well developed sample preparation was needed to provide samples free from contaminants and experiments free of artifacts. Clean clays, free of extraneous carbon were required for model studies. A device to reduce photodeposition in the STXM chamber was also required to examine interactions of hydrocarbons on clay surfaces. <p>Using these developments, Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of model clays and model hydrocarbon mixtures were recorded using the STXM microscope on beamline 5.3.2 at the Advanced Light Source, in Berkeley CA. Using NEXAFS spectroscopy in conjunction with the STXM microscope, allowed us to explore preferential interactions between specific hydrocarbon and fine clay particles (smaller than 1 µm) in our model studies. We were also able to assess the chemistry of the hydrocarbons before association with the clay particles. <p>Process samples, consisting of a set of four bitumen froths extracted from the oil sands were investigated. The carbon chemistry of the froths was assessed and quantitatively analyzed. The findings were correlated with previous confocal microscopy results from our collaborators at CANMET Energy Technology Centre in Devon, Alberta.

The study presented in this thesis was aimed to gain the fundamental knowledge regarding the mechanism of H2S measurement in sera by using carbon nanotubes (CNT) and fluorescence response. Characterization techniques such as Raman spectroscopy, X-ray absorption spectroscopy (XAS) and confocal laser scanning microscopy (CLSM) were employed to achieve this goal. The model system used for this study was composed of H2S, distilled water, two major serum proteins (albumin and globulin), serum, hemoglobin, and CNT. The results of this study showed that: (1) Two major serum proteins (albumin and globulin) are physically adsorbed on the sidewall of the CNTs; while H2S is adsorbed on the defect site of the CNTs. (2) Presence of the proteins on the CNTs did not affect the CNTs adsorption of H2S. (3) Using CLSM with the incident wavelength of 514 nm and the emission wavelength of 530 to 580 nm to acquire the fluorescence response of the H2S adsorbed on the CNTs is a reliable approach to measure H2S in sera. (4) Single-wall carbon nanotubes (SWNTs) outperform multi-wall carbon nanotubes (MWNTs) in measurement sensitivity. (5) Presence of hemoglobin in a H2S solution did not affect the measurement of H2S with CNTs and CLMS. The study described in this thesis has provided new knowledge of the interaction behaviors of CNTs with H2S and major proteins in sera along with the mechanism which governs these behaviors. Such knowledge is very useful to further advance the CNT approach to sensing H2S in sera and water solution and to further extend the approach to sensing H2S in other mammalian tissues such as blood.

One of the critical challenges in the Canadian oil sand industry is improving processes used to separate bitumen from oil sands and to remove clay particulates from produced oil. The fine clay particles are believed to play a significant role in the oil sands industry, from stabilizing process emulsions to fouling problems in water treatment. Addressing the problems caused by these fine clay particulates is limited by the ability to characterize the hydrocarbon-clay interactions. Scanning Transmission X-ray Microscopy (STXM) is used to study hydrocarbon-clay interactions in controlled model systems, where all components are known, and in process samples extracted from oil sands. To use STXM to study our desired systems, many experimental developments were required. Well developed sample preparation was needed to provide samples free from contaminants and experiments free of artifacts. Clean clays, free of extraneous carbon were required for model studies. A device to reduce photodeposition in the STXM chamber was also required to examine interactions of hydrocarbons on clay surfaces. <p>Using these developments, Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of model clays and model hydrocarbon mixtures were recorded using the STXM microscope on beamline 5.3.2 at the Advanced Light Source, in Berkeley CA. Using NEXAFS spectroscopy in conjunction with the STXM microscope, allowed us to explore preferential interactions between specific hydrocarbon and fine clay particles (smaller than 1 µm) in our model studies. We were also able to assess the chemistry of the hydrocarbons before association with the clay particles. <p>Process samples, consisting of a set of four bitumen froths extracted from the oil sands were investigated. The carbon chemistry of the froths was assessed and quantitatively analyzed. The findings were correlated with previous confocal microscopy results from our collaborators at CANMET Energy Technology Centre in Devon, Alberta.

The study presented in this thesis was aimed to gain the fundamental knowledge regarding the mechanism of H2S measurement in sera by using carbon nanotubes (CNT) and fluorescence response. Characterization techniques such as Raman spectroscopy, X-ray absorption spectroscopy (XAS) and confocal laser scanning microscopy (CLSM) were employed to achieve this goal. The model system used for this study was composed of H2S, distilled water, two major serum proteins (albumin and globulin), serum, hemoglobin, and CNT. The results of this study showed that: (1) Two major serum proteins (albumin and globulin) are physically adsorbed on the sidewall of the CNTs; while H2S is adsorbed on the defect site of the CNTs. (2) Presence of the proteins on the CNTs did not affect the CNTs adsorption of H2S. (3) Using CLSM with the incident wavelength of 514 nm and the emission wavelength of 530 to 580 nm to acquire the fluorescence response of the H2S adsorbed on the CNTs is a reliable approach to measure H2S in sera. (4) Single-wall carbon nanotubes (SWNTs) outperform multi-wall carbon nanotubes (MWNTs) in measurement sensitivity. (5) Presence of hemoglobin in a H2S solution did not affect the measurement of H2S with CNTs and CLMS. The study described in this thesis has provided new knowledge of the interaction behaviors of CNTs with H2S and major proteins in sera along with the mechanism which governs these behaviors. Such knowledge is very useful to further advance the CNT approach to sensing H2S in sera and water solution and to further extend the approach to sensing H2S in other mammalian tissues such as blood.

The strain effect on La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 thin films on SrTiO3 (001) substrate with different thicknesses has been studied by X-ray absorption near edge spectroscopy (XANES), which can reveal the details of the coupling between cations and anions. The strain may suppress the TC of LCMO films while enhancing that of LBMO films. The theoretical calculation results suggest the unoccupied states of the third structure of XANES are formed by much more complex hybridization of O 2p to Mn 4sp, La 6s and (Ca 4sp or Ba 6sp) orbitals. The change of the absorption intensity of the second and third structures is compatible to the TC change of both films due to the strain effect. This strongly suggests that the strain effect on LCMO and LBMO thin films is mainly associated with the bonding situation between O and La(Ca or Ba) ions.

As computational methods for the prediction of metallic nanoparticle structure and reactivity continue to advance, a need has developed for simple experimental models that can mimic and confirm theoretical predictions. Dendrimer-encapsulated nanoparticles, or DENs, are ideal to fill this role. DENs are synthesized within poly(amido amine) dendrimer templates which allows for the controlled synthesis of monodisperse nanoparticles in the 50-250 atom (1-2 nm) size range. These are small enough to be accessible to high-level theoretical calculations while being large enough to study experimentally. The research reported here consists of several independent but closely related studies. First, the synthesis, structural, and electrochemical properties of Au@Pt (core@shell) DENs are described. These materials are prepared by underpotentially depositing Cu onto Au DENs followed by galvanic exchange of Cu for Pt. Second, Pb UPD onto Au DENs and a detailed experimental and theoretical study of the resulting core@shell particle structures and catalytic activity is discussed. It is found that no matter how much Pt is deposited onto the surface of Au₁₄₇ DENs, a surface reorganization occurs resulting in similar electrocatalytic activity for the oxygen reduction reaction. Third, an in-depth X-ray absorption spectroscopy study of the structural properties of thiol-capped Au₁₄₇ DENs is described. Here, the surfaces of uncapped Au₁₄₇ nanoparticles are titrated with strongly binding thiol ligands to tune the extent of surface disorder. The effect of the increased surface disorder on the standard EXAFS fitting results is discussed from experimental and theoretical perspectives. Lastly, an in-situ electrochemical study of Au₁₄₇ DENs structure is reported. The key result is that the Au lattice expands during electrochemical surface oxidation. This is an important result for understanding electrocatalytic processes on Au nanoparticle / text

Arsenic taken up by plants and fungi from contaminated soils can subsequently be introduced into food chains. Given the toxic properties of some arsenic compounds, this may be a cause for concern. Much remains to be learned about how these compounds are transformed and distributed in terrestrial organisms. Radishes, white button mushrooms, fur, and feather samples were thus investigated to gain a better understanding of arsenic biotransformations in terrestrial organisms. In this study, we utilized two analytical techniques for the detection and identification of arsenic compounds (“arsenic speciation analysis”). High performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) provided a highly sensitive method for detecting low levels (ng•g-1) of methanol:water extractable arsenic compounds. X-ray absorption spectroscopy (XAS) techniques provided direct arsenic speciation analysis of tissues, resulting in a more representative arsenic profile of the original organisms, without the need to extract arsenic first. Overall, the results for speciation analysis underline the complementary nature of the HPLC-ICP-MS and XAS techniques. Mushrooms contained organic arsenic compounds which were not identified in the radish. In particular arsenobetaine (AB), which is usually found as a minor constituent of terrestrial organisms, was a predominant arsenic compound found in mushroom extracts. How AB is synthesized in the environment remains unclear; however, results presented here suggest it was a product of fungal biotransformation and we speculate it may play a role in osmoregulation. In radish, fur and feather samples, direct analysis identified arsenic(III)-sulphur compounds not observed using HPLC-ICP-MS. In plants, these compounds are likely to be metal/metalloid binding phytochelatin proteins the formation of which has yet to be confirmed in planta. In radish plant vasculature, XAS imaging revealed segregation of pentavalent and trivalent arsenic compounds, suggesting differences in arsenic transport. In hair and feathers the formation of arsenic(III)-sulphur compounds may be evidence of arsenic binding to keratin proteins which has been hypothesized to occur, and may contribute to the observed reduction of exogenous arsenic contamination. / Thesis (Ph.D, Biology) -- Queen's University, 2007-05-30 11:55:40.157

Dans la technologie à l'hydrogène, l'oxydation préférentielle du CO en excès d'hydrogène (réaction PrOx) est un processus important pour l'obtention d'hydrogène sans CO pour les piles à combustible à membrane échangeuse de protons (PEMFC). Les catalyseurs à base de PtCu sont l’un des systèmes les plus étudiés pour les dispositifs mobiles en raison de leur bilan d’activité / sélectivité élevé et de leurs propriétés chimiques et mécaniques appropriées pour les procédures de démarrage / arrêt dans les conditions de fonctionnement des processeurs de combustible.Récemment, l'utilisation de catalyseurs bimétalliques Pt-Cu avec une activité et une sélectivité excellentes vis-à-vis de l'oxydation du CO a été rapportée pour la réaction PrOx. Cependant, la nature des phases actives et le rôle des deux métaux au cours de la réaction ne sont pas clairement démontrés.Pour comprendre ce système, il est nécessaire de créer un catalyseur modèle qui facilite l’étude. Ainsi, des nanoparticules d'alliage bimétallique Pt-Cu bien définies ont été synthétisées et étudiées par des techniques d'Operando permettant de comprendre les modifications électroniques de surface de l'interface solide-gaz du catalyseur modèle mentionné ci-dessus dans des conditions de réaction PrOx.Dans ce travail, la composition et la nature des espèces présentes à la surface du catalyseur dans des conditions de réaction bien contrôlées ont été étudiées, en particulier du point de vue de la dynamique de surface, des transitions structurelles et des effets possibles de l’atmosphère de réaction et des couches superposées adsorbées sur la surface. composition superficielle et structure de l'alliage. / In the Hydrogen technology, the preferential oxidation of CO in excess of hydrogen (PrOx reaction) is an important process for obtaining CO-free hydrogen for proton exchange membrane fuel cells (PEMFCs). PtCu based catalysts are one of the most studied systems for mobile devices because of their high activity/selectivity balance and their appropriate chemical and mechanical properties for the start-up/shut-down procedures during fuel processors operation conditions.Recently, the use of Pt-Cu bimetallic catalysts with excellent activity and selectivity towards CO oxidation was reported for PrOx reaction. However, there are not clear evidences off the nature of the active phases and the role of both metals during the reaction.To understand this system it is necessary to create a model catalyst which facilitates the study. Thus, well-defined Pt-Cu bimetallic alloy nanoparticles were synthetized and studied by Operando techniques allowing the comprehension of the surface electronic modifications in the solid-gas interface of the above mentioned model catalyst under PrOx reaction conditions.In this work, the composition and nature of the species present on the catalyst surface upon well-controlled reaction conditions were studied, in particular from the point of view of surface dynamics, structural transitions and the possible effects of reaction atmosphere and adsorbed overlayers on the surface composition and structure of the alloy.