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<p> This Thesis extends the fundamental chemistry of the noble-gas elements, namely, xenon and krypton. More specifically, the chemistry of Xe(IV) has been extended by the synthesis and characterization of Xe(IV) oxide and oxide fluoride derivatives. The syntheses ofXeOF2, F20XeN=CCH3, and XeOF2·nHF and their structural characterizations are described. All three compounds are endothermic and explosive at temperatures approaching 0 °C. Although Xe0F2had been previously reported, it had not been isolated as a pure compound. Xenon oxide difluoride has now been characterized in CH3CN solution by 19F, 170, and 129Xe NMR spectroscopy and XeOF2, F20XeN=CCH3, and XeOF2·nHF have been characterized in the solid-state by Raman spectroscopy. The low temperature X-ray crystal structure ofF20XeN=CCH3 reveals a long Xe-N bond trans to the Xe-0 bond and a geometrical arrangement about xenon in which the atoms directly bonded to xenon are coplanar and CH3C=N acts as a fourth ligand in the equatorial plane. The geometry about xenon is consistent with an AX2YZE2 VSEPR arrangement of bond pairs and electron lone pairs and represents a rare example of a Xe(IV)-N bond. </p> <p> The missing Xe(IV) oxide, Xe02, has been synthesized at 0 °C by hydrolysis of XeF4 in water and 2.00 M H2S04(aq) and characterized by low-temperature Raman Spectroscopy. The Raman spectra ofXe02 amend prior vibrational assignments of xenon doped Si02 and are in accordance with prior speculation that xenon depletion from the Earth's atmosphere could occur by xenon insertion at high temperatures and high pressures into Si02 in the Earth's crust. </p> <p> The XeOF3-anion has been synthesized as its Cs + and N(CH3)/ salts, and structurally characterized in the solid state bylow-temperature Raman spectroscopy. The calculated anion geometry is based on a square planar AX3YE2VSEPR arrangement with the longest Xe-F bond trans to the oxygen atom. The F-Xe-F angle is bent away from the oxygen atom to accommodate the greater spatial requirement of the oxygen double bond domain. The XeOF3-anion of the Cs + salt is fluorine-bridged in the solid-state, whereas the anion ofthe N(CH3)/ salt approximates the gas-phase anion. </p> <p> The [H(OXeF2)n][AsF6] and [FXerr(OXe1vF2)n][AsF6] (n = 1, 2) salts have been synthesized and structurally characterized in the solid state by low-temperature Raman spectroscopy. The chain length of each cation is limited to one or two OXeF2 subunits, which are oxygen-bridged and are strongly ion-paired with the AsF 6-anion. The reaction of XeOF2·xHF in superacidic HF/SbFs solvent mixtures resulted in a mixture of ([XeF3·HF][Sb2Fu])2-[HsF4][SbF6], [XeF3·HF][Sb2Fu], and [XeF3][SbF6]. The XeF/ cations in each structure are very similar, displaying T -shaped coordination of three fluorine atoms, and a short contact to the fluorine atom of HF, m ([XeF3·HF][Sb2F u])2-[H5F4][SbF6] and [XeF3·HF][Sb2Fu], or to a fluorine atom of SbF6in [XeF3][SbF6]. </p> <p> Vibrational frequency assignments for the aforementioned compounds were aided by comparison with frequencies derived from quantum-chemical calculations, by ^(18)O enrichment, and, where appropriate, by 2H enrichment. </p> <p> The syntheses and structural characterizations of [XOF2][AsF6] (X = Cl, Br), the XeF2 adduct-salts, [BrOF2][AsF6}nXeF2 (n = 1, 2), and the KrF2 adduct-salt, [BrOF2][AsF6]'2KrFz, are also described. The crystal structure of [BrOF2][AsF6] shows a positional disorder among the oxygen atom and the fluorine atoms. The low-temperature Raman spectra of [XOFz][AsF6], the complex cation salts, [BrOF2][AsF6]'nXeFz (n = 1, 2), and [BrOF2][AsF6]·2KrF2 have been assigned on the basis ofthe crystal structures and with the aid of quantum-chemical calculations. The low-temperature ( -173 °C) X -ray crystal structure of [Br0Fz][AsF6]'2KrF2 consists of isolated molecular units and represents an example of KrF2 coordinated to a main-group atom. The contact distances between bromine and fluorine atom of NgFz (Ng = Kr, Xe) is shorter in [BrOFz][AsF6]·2XeFz than in the KrFz analogue, which is attributed to the more polar nature of the Xe-F bonds. The ELF and QTAIM analyses of [BrOFz][AsF6h2-and [BrOFz][AsF6]'2XeFz were carried out and are compared with those of free BrOF/ and [BrOFz][AsF6]'2KrFz to better understand the effect of Br(V) coordination number on the localization domain of the Br(V) valence electron lone pair. </p> <p> The syntheses of FXeON160 2 and FXeoNe800) has shed light on the mechanism leading to the formation of FXeON02• Raman spectroscopy indicated the absence of 161180 isotopic scrambling among the oxygen sites of FXeON02 which was confirmed by factor-group analyses ofthe 16 isotopomeric crystallographic unit cells that result from syn-/anti-isomerization, FXe160Ne6oA180s)/FXe160Ne6os180A), among the four FXeON02 molecules of the unit cell. The intermediate oxide fluoride, O(XeF)2, was observed in the synthesis of FXeON02, providing valuable insight into the reaction pathway. A reinterpretation of the solid-state 160-and 180-enriched Raman spectra of O(XeF)z was also carried out. </p> / Thesis / Doctor of Philosophy (PhD)

With a unique blend of power and energy densities, as well as long cycling lives, electrochemical supercapacitors are finding greater application in energy storage solutions. Among candidate materials for supercapacitors, MnO2 has garnered a great deal of attention. However, its low intrinsic electrical conductivity has proven to be a serious hindrance on performance when used in supercapacitor electrodes. Efficient use of conductive additives is a demonstrated, effective method to combat this problem, however there is still a great need for improvement. Two new colloidal processing techniques have been developed to mix chemically synthesized MnO2 and conductive multi-walled carbon nanotubes (MWCNT). The first strategy involved the linking of MnO2 and MWCNT through the formation of a Schiff base. 3,4-dihydroxybenzaldehyde (DB) was used to modify MnO2, while MWCNT were dispersed with the dye New Fuchsin (NF). These compounds were selected due to the presence of molecular features previously identified as conducive to strong adsorption and good colloidal dispersion, as well as the necessary functional groups required to form a Schiff base. The second involved the use of liquid-liquid extraction, primarily in an attempt to prevent post synthesis MnO2 particle agglomeration. Lauryl gallate (LG) was used as an extracting and dispersing agent for MnO2 synthesized via the reaction between aqueous potassium permanganate (KMnO4) and 1-butanol. LG facilitated the co-dispersion and mixing of both MnO2 and MWCNT in the 1-butanol phase. V2O3 was also investigated as a replacement for MnO2, as its high intrinsic electrical conductivity gives it a potential advantage over MnO2. In each of these three projects, electrodes were produced with exceptionally high areal normalized capacitances at high active mass loadings. The MnO2-MWCNT composites were used to fabricate full asymmetric supercapacitor devices that were able to deliver a useable amount of energy. / Thesis / Master of Applied Science (MASc) / The modern world has an insatiable appetite for energy and must have access to it for stationary and mobile applications. To meet this demand, it is of paramount importance to develop new, high performance energy storage technologies. The energy requirements for different applications, however, necessitate storage devices that have suitable properties. The energy stored in a large pool of hot water is not in a suitable form to power a cellphone. The key goal of this work was to further develop one particular energy storage technology, called electrochemical supercapacitors. Novel processing techniques were developed and new materials investigated with the aim of producing supercapacitor electrodes that would exceed the performance of what is already available today. The materials that were produced exhibited very high performance and offered new insight and direction for further research in this exciting field.

Nonlinear luminescence quenching has been documented in numerous systems such as organic crystals, rare earth insulators, laser materials, semiconductors, and phosphors. In each of these systems nonlinear luminescence quenching occurs under conditions of high excitation density from interactions between excited centers, the result is an additional nonradiative decay pathway that lowers luminescence quantum efficiency. During investigations into the spectra and dynamics of Eu2O3, an apparent saturation dip in the excitation spectra of nano-sized Eu2O3 particles was observed. This thesis describes the investigation into the nature of the saturation effect. The samples studied using luminescent spectroscopy included micron sized Eu2O3 crystals of both cubic and monoclinic phases, nanocrystal monoclinic Eu2O3, and a large fused crystal of monoclinic Eu2O3. It was determined that the saturation effect was due to nonlinear luminescence quenching occurring at the wavelengths of absorption maxima. The mechanism of nonlinear luminescence quenching was concluded to be upconversion by energy transfer. / Master of Science