Lithium-ion batteries have revolutionized the portable electronics market, and they are currently pursued intensively for vehicle applications and storage of renewable energies (solar and wind energy). Cost, safety, cycle life, and energy and power densities are the critical parameters for these applications. With this perspective, there has been immense interest to develop new cathode and anode materials as well as to develop novel synthesis and processing approaches. This dissertation explores the use of novel synthesis approaches to obtain high-performance, nanostructured phosphate and silicate cathodes and iron oxide nanowire anodes and investigates their structure-property relationships. First, a novel microwave-solvothermal (MW-ST) approach has been developed to synthesize phase-pure, highly crystalline LiFePO₄ nanorods within 5-15 minutes at low temperatures of < 300 °C, without requiring reducing gas atmospheres. The LiFePO₄ nanorods, after forming a nanocomposite with conducting polymer or multi-walled carbon nanotubes or coating with conductive carbon, offer excellent cycle life and rate performance when implemented as cathodes in lithium-ion cells. In addition, other LiMPO₄ (M = Mn, Co, and Ni) olivine nanorods have also been synthesized by the MW-ST approach and characterized. The MW-ST process has then been extended to prepare a new class of carbon-coated, nanostructured silicates of the formula Li₂MSiO₄ (M = Fe and Mn). These materials have two times higher theoretical capacities (~ 330 mAh/g) than olivine phosphates (~ 170 mAh/g). Li₂FeSiO₄ exhibits practical discharge capacities of 148 mAh/g at room temperature and 203 mAh/g at 55 °C, with good rate capability and stable cycle life. Li₂MnSiO₄, on the other hand, shows higher discharge capacities of 210 mAh/g at room temperature and 250 mAh/g at 55 °C, but it exhibits poor rate performance and rapid capacity fade during cycling. In addition, carbon-coated olivine solid solution nano-particles of the formula LiM[subscript 1-y]M[subscript y]PO₄ (M = Fe, Mn, Co, and Mg), synthesized by a facile, high-energy mechanical milling process (HMME), have also been investigated. The electrochemical data reveal a systematic shift in the redox potential (open-circuit voltage) of the M²⁺/³⁺ couples in the LiM[subscript 1-y]M[subscript y]PO₄ solid solutions compared to those of the pristine LiMPO₄. The shifts in the redox potentials have been explained by the changes in the M-O covalence (inductive effect), which are caused by changes in the electronegativity of M or the M-O bond length or M-O-M interactions. Finally, a two-step microwave-hydrothermal process has been developed to synthesize carbon-decorated, single-crystalline Fe₃O₄ nanowires. The resulting iron oxide nanowires exhibit capacity values > 800 mAh/g with stable cycle life and high rate performance as an anode in lithium-ion cells. / text

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A series of alkyldithiolatodiironhexacarbonyl complexes of the form &mu:-(RS2)Fe2(CO)6, where RS2 is: 1,2-ethanedithiolate (eth-cat), cis-1,2-cyclopentanedithiolate (pent-cat), cis-1,2-cyclohexanedithiolate (hex-cat), and 2-exo,3-exo-bicyclo[2.2.1]heptanedithiolate (norbor-cat), are reported. These complexes display structures and catalytic behavior toward production of molecular hydrogen with similarities to the active site of the diiron hydrogenase enzymes. Hydrogen production is desirable as an alternative fuel source and these catalysts are capable of producing H2 in the presence of weak acid under electrochemical conditions. Through understanding of the factors which control the catalytic activity of these catalysts it may be possible to contribute to the development of a hydrogen fuel economy.Significant scan-rate dependence under electrochemical conditions is observed, resulting in an initial 1-to-2 electron reduction depending on how quickly the singly reduced species can reorganize. The rate of this reorganization directly corresponds to the internal strain within the system and can be ranked in the following order of increasing rate of reorganization: pent-cat < norbor-cat < eth-cat < hex-cat. Additionally, these catalysts all successfully catalyze protons to molecular hydrogen under electrochemical conditions in the presence of acetic acid via an ECEC catalytic mechanism, where, E is an electrochemical step (reduction) and C is a chemical step (protonation).Density functional theory computations support the reported catalytic processes by calculating physically observable quantities, such as: pKa values, reduction potentials, adiabatic ionization energies and carbonyl stretching frequencies in the infrared (IR) region. These quantities were used to suggest reasonable reactive intermediates within the catalytic cycle. The electronic structure of each catalyst was examined using photoelectron spectroscopy and the global minimum cationic structure, in all cases, involves a structure with a bridging carbonyl ligand, akin to that of the enzyme active site.The most significant outcome of this work is the unprecedented diiron center rotation upon reduction. As conformational strain involving the dithiolate ligand increases, the rate of reorganization of the anion increases leading to cleavage of an iron-sulfur bond to provide an alternative protonation site, a key step toward molecular hydrogen formation. This site is less basic than the unrotated form and helps evolve H2 with thermodynamic favorability.

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The interaction of different formulations of the antifungal drug amphotericin B (AmB) with model cell membranes was studied and new techniques of measuring this interaction using electrochemical and/or spectroscopic methods were developed. Two model cell membrane systems were used: sterol-free lipid monolayers adsorbed to a Hg electrode and sterol-free or sterol-containing floating lipid monolayers on a Langmuir trough. Electrochemical control over the adsorbed monolayer allowed the defectiveness of the layer to be varied and the interaction of AmB with both well-ordered and defective monolayers characterized. Measurements of monolayer capacitance and permeability were used to indicate the nature of the interaction. Capacitance provides a measure of the lipid organization, while permeability was measured via electro reduction of thallium (I)cation. The three AmB formulations and two control samples were examined and showed different interaction behaviour. The disruption of lipid order and permeabilization induced by the two commercial formulations correlated generally with in vivo studies of their toxicity. An experimental and possibly less toxic AmB formulation made monolayer significantly more permeable. In situ fluorescence microscopy of the monolayer on Hg was carried out after introducing a low concentration of fluorophore into the layer. Fluorescence intensity as a function of electrode potential was measured and was used to characterize the lipid on Hg model membrane system before we attempted to measure AmB's influence on the fluorescence. The fluorescence excitation and emission spectra of AmB itself were measured ex situ for two of the formulations. Using added surfactant to control AmB aggregation state, the relationship between AmB aggregation and its fluorescence properties was examined. We discovered AmB to have unusual dual fluorescence properties, the extent of which differed between formulations. We measured AmB's fluorescence in situ as the drug interacted with floating lipid monolayers on the Langmuir trough. Both the variation in fluorescence during compression of a mixed AmB/lipid monolayer and penetration of AmB into a phospholipid monolayer were measured. This experimental setup was configured to collect fluorescence only from AmB at the monolayer, and not from AmB in bulk solution. Fluorescence excitation was made using a laser diode extracted from a consumer electronics device.

Three samples of Ti(C,N) were fabricated with 40 vol.% Ni3Al: Ti(C0.3N07), Ti(C0.5N0.5) and Ti(C0.7N0.3), as well as TiC with 10, 20, 30 and 40 vol.% Ni3Al binder addition by means of melt infiltration and sintering. Each sample was evaluated for density and microstructure before being placed in a flat cell for electrochemical testing. Open circuit potential was evaluated, followed by the application of a cathodic potential, whereby the response was tracked using Corrware corrosion software throughout the duration of potentiodynamic testing. Following corrosion testing, each sample was reevaluated for changes in microstructure and chemical composition. Ti(C,N) samples were found to have adequate resistance to corrosion, with increased resistance with increasing carbon content, however these samples demonstrated a greater frequency of breakdown and repassivation, suggesting a greater susceptibility to corrosion, despite the initial improved resistance. SEM imaging demonstrated significant crevice corrosion throughout. TiC-cermets demonstrated similar results in terms of SEM evaluation of microstructure. TiC-cermets with the lowest binder content (10 vol.% Ni3Al) demonstrated greater initial resistance to corrosion but also had the greatest potential for breakdown.

The anodic polarization of Ni electrode in 0.5 M aqueous KOH solution at various polarization potential (Ep), time (tp) and temperature (T) values leads to the formation of β-Ni(OH)2 films. The growth of the hydroxide layers are irreversible and cannot be reduced electrochemically to metallic Ni. The hydroxide layer becomes thicker at higher values of Ep and/or tp and/or T. The thickness of β-Ni(OH)2 hydroxide were determined using ex–situ XPS and depth–profile techniques. Application of the oxide growth theories to our data indicate that the development of the β-Ni(OH)2 layer follows inverse logarithmic growth kinetics. The driving force of the process is the strong electric field that is established across the oxide layer. The strength of electric field is in the range of 0.015 – 0.197 x 109 V m–1. The oxidation mechanism of the Ni(II) surface compound to Ni(III) is electrochemically irreversible and the process is treated according to Randles–Sevcik equation. A linear relation was determined between the peak current density (jp) and the square root of the potential scan rate (v1/2) for the entire range of Ep, tp and T. The diffusion coefficient (D) values calculated for anodic and cathodic processes are 8.1 ± 0.2 x 10–12 and 4.3 ± 0.2 x 10–12 cm2 s–1, respectively. The activation energy (Ea) values for the diffusion process are 23 ± 2 kJ mol–1 (anodic) and 26 ± 2 kJ mol–1 (cathodic). The D and Ea values calculated from chronoamperometry measurements are comparable with those calculated from jp vs. v1/2 plots. The electro–reduction of PtO electrochemically pre–formed on Pt electrode in 0.5 M aqueous H2SO4 solution was also investigated. A well–controlled reduction conditions (Er, tr and T) were applied to determine the amount of the reduced PtO oxide. The reduction of the PtO requires much less time once ca. 1 monolayer (ML) of the oxide has been removed (ca. 1 ML of PtO remains). As expected, the longer tr and/or lower Er values, the greater the amount of the reduced oxide and consequently the smaller the amount of the remaining PtO oxide. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-02-08 10:58:54.114

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The negative epoxy-based photoresist of SU-8 has a variety of applications within microelectromechanical systems (MEMS) and lab-on-a-chip systems. Herein, SU-8 was functionalized with antigenic peptides to HIV-1 gp41 or HIV-2 gp36 and the detection of antibody against HIV-1/2 was carried out by an electrochemical immunoassay combining an alkaline phosphatase conjugated secondary antibody and p-aminophenyl phosphate. The by- product of the reaction (p-aminophenol) was quantitated electrochemically using differential pulse voltammetry, and the current derived from the oxidation of the hydrolysis product increased linearly over a wide primary antibody concentration range (0.001 – 1 μg/mL), with a detection limit of 1 ng mL-1 (6.7 pM) for both HIV-1 and HIV-2. This level of sensitivity is clinically relevant, and feasibility of this approach for clinical sample testing was also evaluated with HIV clinical patient samples.