Thesis (M.S.)--University of Alabama at Birmingham, 2006. / Description based on contents viewed Jan. 29, 2007; title from title screen. Includes bibliographical references (p. 42-44).

Thesis (M.S. in Engineering)--University of Texas at Austin, 2006. / Includes bibliographical references.

This thesis is concerned with analytical studies on the trace analytes barium, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, vanadium and zinc, present in high purity and highly complex matrices. The technique utilises activated alumina microcolumns in a flow injection (FI) system, to perform analyte enrichment and matrix removal. The analytes, after retention on the microcolumn are subsequently eluted and quantified by inductively coupled plasma-emission spectrometry (ICP-ES).Initial studies focus on trace analytes in caesium iodide, however a selection of the alkali metal salts, lithium nitrate, potassium bromide, sodium fluoride and sodium chloride, are investigated. New methodology for the ultratrace determination of high purity alkali metal salts is thus provided. The microcolumn enrichment technique with ICP-ES detection is robust, utilises limited sample handling and simultaneously preconcentrates and separates the analytes from matrix components. Hence possible matrix interferences are eliminated and limits of detection are significantly improved, in comparison to conventional ICP-ES analysis. A technique for the determination of the total content of eleven trace analytes present in natural waters (mineral, reservoir), using microcolumns of activated alumina in a FI-ICP-ES is investigated. The use of the complexing agent tartaric acid is shown to be effective in improving analyte retention. The procedure is successfully applied to determination of these analytes in a certified river water reference material (SLRS-1). Due to low retention and elution efficiencies, the total content of the analytes Fe and V present in Buxton, Redmires and Langsett samples could not be accurately determined by this technique. Activated alumina microcolumns are utilised as a new field sampling tools. Samples are collected in the field and processed through the alumina microcolumns for the effective retention of desired analytes. Hence, an alumina microcolumn sampling stage to effect concentration and isolation prior to analytical measurement is at the core of the investigation. The overall aim is to extend the application of alumina microcolumns, and in particular to provide a new multi-element field sampling device, which gives high sample integrity and preconcentration.

This thesis comprises three chapters united by a single theme: development of alkali metal cation sensors based on ion complexing macrocycles. In part 1, benzo-18-crown-6 and cryptand 2.2.2B were immobilised on polyacrylic acid backbone through an amide linkage. The benzo-18-crown-6 and 2.2.2B were functionalised using the Friedal-Crafts acylation reaction with ω-amino acids. The spacer between the polymer backbone and the crown ether was varied by using co-amino acids with varying numbers of methylene groups [special characters omitted]. Attempts to use co-amino acids with an intermediate spacer length [special characters omitted] failed due to formation of a cyclic imine. The amino crown ethers were immobilised on a poly(acryloyl chloride). Polymers 2a, 5ad and 6a failed to give self supporting membranes but a polymer blend with PVC/Plasticizer was employed for membrane fabrication. Ion Selective Electrodes (ISEs) and Coated Wire Electrodes (CWEs) were made from polymer blend membranes and their response to alkali metal cations was tested. The ISEs made with mobile carriers were active, while those prepared from immobilised carriers were inactive. The reverse was the case with CWEs. This dichotomy existed in all cases. The selectivity of the ionophores among the alkali metals was unaffected by linkage to the polymer backbone. However, the alkali metal/alkaline earth metal selectivity was enhanced. The effect of plasticizer and hydrophilic additives on electrode response was insignificant. The spacer length had considerable influence: the longer the spacer, the better the electrode response of the CWEs. In part 2, the mass transport of ions across the polymer blend membrane under a temperature gradient was investigated. The immobilised polymers prepared in part 1 were used here to fabricate membranes from polymer blends with NOMEX. In thermodialysis experiments, a low level of ion transport was detected. These preliminary experiments led to a rediscovery of membrane distillation. The scope of this latter process with hydrophobic membranes was explored in detail. Part 3 was devoted to the design and synthesis of water soluble photoionophores. Three series of molecules were synthesised: captands, bis crown ether compounds and phenol derivatives of tartaro crown ether carboxylic adds. Captand molecules were synthesised by a capping reaction of crown ether tetraacid chloride 14 with 1,3-bis(aminomwthyl) benzene, 1,4- bis(aminomethyl) benzene and 2,2’-bis(aminomethyl) biphenyl. Crystals of meta- and para xylene capped molecules were grown and their structures solved to establish the conformation of the molecules. Fluorescence quenching studies of these molecules were done in 0.3% methanol:water (v/v). Quenching due to alkali metal ions was insignificant ( < 20%) while copper and mercury cations quenched the emission significantly ( > 90%). Stern-Volmer analysis showed an upward curvature indicating association between the ligand and the cations [special characters omitted] cations, but dynamic and static components of the quenching could not be separated. Potentiometric titration with a potassium selective electrodes was carried out to obtain the stability constants for these ligands with potassium ion. The bis crown ethers 28 and 29, designed to increase water solubility, were prepared by the reaction of anhydride 27 with 9,10-bis(ammomethyl) anthracene and 1,2-bis(aminomethyl) benzene. The pKa values of the ligands and their stability constants with alkali and alkaline earth metal ions were determined by potentiometric titration. Fluorescence quenching studies were done in aqueous buffer at pH 10. These compounds also failed to give an emission quenching in the presence of alkali or alkaline earth metal cations, but both copper and mercury cations showed a significant amount of quenching. Stability constants were derived from emission quenching studies for [special characters omitted]. Chromoionophores, phenol derivatives of tartaro crown ethers, were synthesised from the reaction of crown ether anhydrides and 2-aminophenol. The structure of the compound 31 was assigned as the syn isomer based on nmr data in comparison to literature reports. Absorption studies were carried out in water. The absorption spectra of compound 30 were perturbed by alkali metal as well as alkaline earth metal ions, while the absorption spectrum of compound 31 showed no response to varying cation concentration. The lack of response from compound 31 was attributed to the competitive binding of cations among syn carboxylic groups away from the syn phenolic groups. / Graduate

This thesis concerns the thermodynamics of macrocycles and their metal cation complexes in non-aqueous media and these are discussed under two main headings, i) Thermodynamics of Alkali-Metal Cations and Macrocycles in Solution and in the Solid State. Thermodynamic parameters of complexation for alkali-metal cations and macrocycles (18-crown-6 and ethyl p-tert-butylcalix(6)arene hexanoate) in benzo-nitrile at 298.15 K are first reported. These data are compared with those previously reported for cryptand 222 and these cations in this solvent. A 'peak' selectivity for potassium is observed for the complexation of the calix(6)arene ester with alkali metal cations. The process is enthalpy controlled with an exothermic maximum for the potassium cation. Thermodynamic data of complexation are characterised by a lower enthalpic stability and a more favourable entropy (except for K+) than corresponding data involving cryptand 222 or indeed 18-crown-6. Standard enthalpies of solution, DeltasH0, of macrocycles and their sodium and potassium salts in benzonitrile measured calorimetrically are discussed in relation to (i) data for the uncomplexed salts and (ii) previously reported data for sodium and potassium cryptate salts in various solvents. Enthalpies of coordination, DeltacoordH0, for eighteen systems involving sodium and potassium coronates, cryptates and calix(6)arenates are derived and whenever possible these are discussed on the basis of (i) available X-ray crystallographic data and (ii) the anion effect on the coordination process. ii) Thermodynamics of Lower Rim Calix(4)arene Derivatives with the Silver Cation in Different Media at 298.15 K. The DeltasH0 values of p-tert-butyl(bis-diethylamine-bis-methysulphanyl) calix(4)arene (EATCalix4) in various solvents at 298.15 K are reported. Transfer parameters from acetonitrile to other solvents are calculated. The interaction of EATCalix4 and the silver cation was investigated by 1H NMR in deuterated acetonitrile at 298 K showing that the ligand hosts the metal cation through interaction with the different donor atoms (O, N, S). Conductimetric titrations indicate that the stoichiometry of the complex is 1:1. The thermodynamics of complexation of EATCalix4 and silver in six solvents at 298.15 K is reported. The DeltasH0 values of the free and the complex silver perchlorate salts have been also measured in various solvents and these have been combined with DeltacH0 data to derive the DeltacoordH0 of this system. A few representative examples about the use of coordination data are given. The medium effect on the complexation process is assessed in terms of DeltatG0, DeltatH0 and DeltatS0 of the reactants and the product from acetonitrile to the appropriate solvent. The relevance of analysing the solvation changes that these species undergo upon complexation is emphasised.

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This thesis is an account of a detailed investigation of the properties of a recently-discovered gas discharge - a discharge that operates at a few volts or tens of volts, and which carries a current of the order of amps through a mixture consisting of a hot, atmospheric-pressure rare gas (the "diluent") to which a small amount of alkali metal vapour has been added as an easily-ionised "seed". It is shown that the establishment of the discharge under study is brought about by the breakdown of the gas, which occurs at a breakdown voltage that depends mainly on the electrode spacing, seed pressure, and choice of diluent gas. The discharge itself is shown to consist of two main regions, namely, a constricted, cylindrical positive column that extends from the anode to within a short distance of the cathode, and a thin, glowing sheath that covers the entire cathode surface; the two regions are separated by a dark space. The positive column is shown to expand as current increases, while the value of its electric field is shown to depend mainly on the discharge current, seed pressure, and choice of diluent gas, and hardly at all on the gas temperature or choice of seed metal. The cathode fall is shown to depend mainly on the discharge current, seed pressure, and choice of seed metal. The breakdown of the gas, the positive column of the discharge, and the cathode regions of the discharge are discussed in successive chapters.

This thesis outlines a study carried out to understand the effects of coal dissolution variables. Several parameters that are thought to have a direct influence on the degree of coal dissolution in organic solvents were investigated by means of a series of experiments. The work done constitutes part of the research being carried out for the PBMR Company, whose aim is to synthesise nuclear-grade graphite from coal based materials. To enhance the efficiency of the process, it was necessary to gain a clear-cut understanding of the parameters that affect the process. The work carried in this project was divided into two sections. The first section involved the solubilisation of coal in polar aprotic organic solvents with the addition of a small amount of alkali. In this section as well, many parameters that influence the process were investigated. The second section involved the use of various analytical techniques to obtain information on the composition of coal extracts. The conclusions reached were as follows: <ul> <li>An alkali is required for the solubilisation of coal to occur in polar organic solvents. This also gives an overall high extraction percentage of ~ 92%. In pure dimethylformamide (DMF), the sodium hyroxide (NaOH) does not go into solution but on the addition of coal, the NaOH goes into solution.</li> The characteristic smell of the Refcoal solution confirms the presence of dimethylamine, although the titration results show otherwise. <ul> <li>The texture of the alkali used in the extraction affects the rate and degree of extraction. Finely ground alkali gives a faster dissolution rate, as well as a high extraction percentage.</li> <li>There is no hydrolysis of solvent during the extraction of coal.</li> <li>The concentration of the alkali used in the extraction process affects the degree to which coal can be extracted.</li> <li>The use of a strong alkali increases the rate at which coal can be dissolved in the solvent.</li> <li>Temperature does not affect the degree of extraction, as shown by the closeness of the extractions done at different temperatures. Also, external factors, such as oxidation and weathering of coal, have little effect on the extent of extraction.</li> <li>Coal characterization techniques provide information about the composition of coal extracts. The coals used in this process consisted of aliphatic and aromatic compounds. </li> / Dissertation (MSc (Chemistry))--University of Pretoria, 2007. / Chemistry / unrestricted

Physical properties of materials and their constituents are interrelated. Though the basic structural unit involved also plays a role in deciding the properties, this can be manipulated to a certain extent, by carefully selecting the basic ingredients or by varying the composition. In order to tailor the properties of the materials according to the need, the relationship between the properties and the structure has to be established. Glasses, due to their inherent disorder, don’t have the privilege of using symmetry as enjoyed by their crystalline counterparts. Given their components and composition there is no immediate and easy way of predicting all the observed properties of glasses. This is not considering computer simulations and DFT calculations. Hence we go back to play with nature, i.e., do experiments. Technological applications like LASERs, optic fibers, photosensitive semiconducting thin films, solid state batteries for energy storage etc. have greatly increased the interest in the fundamental properties of disordered materials. Large coefficient of linear expansion of germanate glasses is made use in glass-to-metal seals for ultra high vacuum. More over, many germanate based glasses with specially tailored dispersion properties have been developed. GeO2 based glasses are in fibre optics in the IR region of 1.5 to 1.8 microns. Borate glasses are resistant to thermal and chemical attack. They lower the melting temperature of glasses thus facilitating large scale production.Both borates and germanates have been worked upon extensively. Alkali boro germanate systems are interesting inherently. Borates and Germanates both are glass formers by themselves. The continuous random network formed by this base glass is modified by the presence of alkali ions. It is interesting to see to what extent the alkali ions can maintain the local charge neutrality in their neighborhood by creating non bridging oxygen atoms and how the presence of two formers is stabilizing the glass matrix. Present Work This thesis work is an attempt to understand the structure of alkali borogermanate glasses 25R2O-25GeO2-(50-x)B2O3-xNd2O3:(R=Li, Na, K and Rb; x=0,0.5). A variety of experimental techniques are available to give a good insight of the structure of glass systems. In this thesis, we have carried out  Optical studies at room temperature to probe the environment of RE ion  AC conductivity at high temperature to probe the alkali ion dynamics  11B MASS NMR of doped systems at room temperature to probe the Boron sites  Raman and Mid-IR experiments at room temperature to probe the various structural groups to get a comprehensive understanding of the structure of these glasses. To facilitate the analysis of the data and discussion of the results from these experiments, the thesis is divided in to four chapters excluding the introduction as categorized above and is presented accordingly. The second chapter begins with the preparation of the glass samples and their characterization. We have used Differential Scanning Calorimetry (DSC), powder XRD and elemental analysis using ICP-OES for characterizing the sample. We have also measured the density and refractive index of the glasses under study. After this section, we describe the results from Optical Absorption and Photoluminescence studies. A brief description of Judd-Ofelt (JO) theory used for the analysis of the results is given. We have calculated the optical parameters and JO parameters and the energy levels of Nd ions in the glass matrix based on absorption studies using program written in Matlab. The procedure to calculate these parameters and their relevance in estimating the important quantities like radiative transfers, branching ratios are discussed. The effect of variation of the alkali ions on these properties is also discussed. In the third chapter, we have investigated AC conductivity in these glasses. These experiments are carried out both as a function of frequency (40 Hz - 15 MHz) and temperature (220 C – 500 C) using a home made portable furnace with a temperature controller. The cable compensation using open and short standards were done at the high temperature end. The data has been analyzed in Electric modulus (M*) formalism using Kohlrausch William Watts (KWW) function. The other basic models used in the literature like Debye, Cole-Cole, Cole Davidson and Havriliak Negami are briefly discussed. The frequency dependence of conductivity in these systems has been ascribed to the hopping motion of the alkali ions. Non-symmetric nature of the imaginary part of M* shows an evidence of non-exponential relaxation. Activation energies were estimated from the temperature variation of the KWW and DC. The fit parameters KWW and KWW shows interesting behavior. KWW in LGBNd and NGBNd show an initial increase with increasing temperature reaching a value of 1, while a contrasting behavior is observed in KGBNd and RGBNd. Barton-Nakajima-Namikawa (BNN) plot of the present study gives a value of 0.67 and 0.7 for the slope parameter p for doped and un-doped samples respectively. BNN plot is used to correlate the ac and dc conductivities in the sample. The deviation of the slope parameter from unity may be an indication of different charge carriers for ac and dc transport. Fourth Chapter describes the room temperature 11B MASS NMR studies in Nd doped glass system. The relevant theory of Zeeman, Dipolar, Quadrupolar and Chemical shift interactions are discussed briefly before the results. The principle used in obtaining high resolution NMR in solids by means Sample spinning is also described. NMR line shape for the central transition (1/2  -1/2) of I=3/2 nuclei (11B) was simulated in Mathematica and fitting was tried in Matlab. Using this background we have analyzed the line shape. In the next part, the results of 11B MASS NMR experiments of doped glasses carried out using Bruker DSX300 at 96.3MHz are presented. The fraction of contribution from four and three co-ordinated 11B to NMR line-shape were identified and calculated. The results show unambiguously the presence of two 3 coordinated 11B sites which were differentiated on the basis of the quadrupolar parameters. In the last chapter we discuss the results of Raman and Mid-IR investigations carried out in these glasses at room temperature. These two important techniques are well established in identifying the structural groups in glass systems. Raman bands observed in the range 200 cm-1 to 1600 cm-1 in these glasses are deconvoluted using gaussian peaks and they have been assigned to various modes of possible structural groups. Two broad MIR absorption bands were observed between 600cm-1 - 1600cm-1 in both doped and undoped glasses. Each band was resolved into gaussian peaks. The band shifts and the changes in the intensities are ascribed to the effects of variation of alkali, as the presence of GeO2 (up to 25mol%) is known not to affect the borate bands as it is a former by itself.