School of Chemistry - Theses
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ItemSynthesis and optical properties of CdSe core and core/shell nanocrystals( 2008)The synthesis of nanocrystals is unique compared to the formation of larger micron-sizesspecies as the final crystal sizes are not much larger than the primary nuclei. As a consequencethe final outcome of a nanocrystal synthesis i.e mean crystal size, concentrationand standard deviation is almost solely determined by the end of the nucleation phase. Directingthe growth of crystals beginning from aggregates of only tens of atoms into maturemonodisperse nanocrystals requires that the governing kinetics are strictly controlled at everymoment of the reaction. To effect this task various different ligands need to be employed,each performing a particular function during both nucleation and growth. (For complete abstract open document)
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ItemSpectroscopic studies of gas phase ion-neutral interactions( 2007-10)Gas phase experimental and computational investigations are described for F--H2 and the halide-methane complexes and clusters, F--(CH4)n and Cl--(CH4)n. Vibrational predissociation spectroscopy in conjunction with tandem mass spectrometry are used to obtain mid-infrared spectra of each complex in the ligand’s hydrogen stretch region. Ab initio calculations are used to predict structures, binding energies and vibrational frequencies and intensities. By examining the changes in both the vibrational frequencies and intensities of the neutral moiety upon complexation with the anion, and comparing these with the theoretical predictions, structures are able to be inferred. (For complete abstract open document)
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ItemThe coordination of nickel in hyperaccumulating plants( 2007-10)The co-ordination of Ni in hyperaccumulator plants was investigated using a number of mass spectrometry (MS)-based analytical techniques. Initial field studies on nickeliferous (lateritic) soils in Western Australia failed to identify plants containing elevated metal concentrations. For this reason, Ni-hyperaccumulators were collected from known ultramafic sites in New Caledonia, as well as grown under controlled conditions. Using electrospray ionization MS a Ni-nicotianamine (Ni-NA) complex [NiII(C12H20N3O6)]+ was identified in the South African Ni-hyperaccumulator Berkheya coddii. The association between Ni and NA was examined further in a range of Thlaspi species which accumulate different concentrations of Ni and Zn in their foliar tissues. In order to quantitate the concentration of NA a new liquid chromatography-MS (LC-MS) based analytical protocol was developed which allowed the quantification of NA and free amino acids. From the analysis of the leaf tissue in Thlaspi a strong correlation emerged between Ni and NA but not Zn. This suggested that NA plays a role in the transport of Ni in Ni-hyperaccumulating Thlaspi plants. An inverse proportionality was found between Fe and Ni. Higher NA production could be related to maintenance of Fe homeostasis. A correlation was also found between Zn and asparagine. These results are consistent with the operation of separate transport mechanisms for Ni and Zn. Further extreme examples of Ni-hyperaccumulation were also examined using LC-MS and metabolite profiling based on gas chromatography-MS (GC-MS). (For complete abstract open document)
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ItemIon trap studies of single microparticles: optical resonances and mass spectrometry( 2006-12)Microparticle experiments conducted using a newly commissioned quadrupole ion trap (QIT) are reported. Single polystyrene microparticles are confined using three dimensional electrodynamic quadrupole fields and characterised by their fluorescence emission and secular frequency measurements. The advantages of this confinement technique are that single particle properties can be measured free from ensemble averaging effects and unperturbed by solvents and (or) substrates. (For complete abstract open document)
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ItemHigh power carbon-based supercapacitors( 2006)Energy storage devices are generally evaluated on two main requirements; power and energy. In supercapacitors these two performance criteria are altered by the capacitance, resistance and voltage. (For complete abstract open document)
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ItemThe chemistry of Salvia divinorum( 2006-04)Salvia divinorum is a hallucinogenic sage used to treat illness by the Mazatec Indians of Mexico. Salvinorin A (1a), a neoclerodane diterpenoid isolated from the plant, is a potent, selective agonist at the kappa opioid receptor (KOR), and is the first non-nitrogenous opioid. The plant is used recreationally as a hallucinogen, but is unpopular due to its dysphoric effects. 1a has been prohibited in Australia under an invalid systematic name. An early report of psychoactive alkaloids in S. divinorum proved to be irreproducible. Similarly, tests in mice suggesting the presence of psychoactive compounds other than 1a were confounded and therefore unreliable. In this work, an improved isolation method for 1a was developed, using filtration through activated carbon to decolourise the crude extract. Six new diterpenoids were isolated: salvinorins D–F (1d–1f) and divinatorins A–C (28a–28c). Five known terpenoids not previously reported from this species were also isolated. The structure–activity relationships of 1a were evaluated via selective modifications of each functional group. Useful synthetic methods are reviewed, including the first thorough review of furanolactone hydrogenations. Testing of the derivatives at the KOR suggests that the methyl ester and furan ring of 1a are required for activity, but that the lactone and ketone functionalities are not. Other compounds from S. divinorum did not bind to the KOR, suggesting that 1a is the plant’s active principle.
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ItemStudies of the interaction of metal complexes with ligands and biomolecules in the gas phase using mass spectrometry( 2005)Introduction of soft ionization techniques, such as electrospray ionization (ESI), has resulted in extensive use of mass spectrometry based techniques to study biomolecules in the gas phase. Despite thorough studies of the gas-phase chemistry of even-electron biomolecules, the examination of their odd-electron counterparts has to this point been much less extensive due to the inefficiency of ESI in generating such species. Among various methods that could be employed to generate and study odd-electron biomolecules in the gas phase, redox processes involving metal ions and homolytic cleavage of metallated amino acid or peptide derivatives would be attractive from a chemical perspective since, in principle, a wide range of metals and biomolecules or biomolecule derivatives could be explored. An important aspect of these approaches is that they can be carried out on a wide range of tandem mass spectrometers equipped with electrospray ionization and collision induced dissociation capabilities. (For complete abstract open document)
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ItemInfrared spectroscopy of size selected anion complexes and clusters( 2003-03)Gas phase anion clusters, consisting of solvent molecules hydrogen bonded to halide anions, are characterised by vibrational predissociation spectroscopy using a combination of mass spectrometry and laser spectroscopy. Monitoring changes in the vibrational properties of neutral solvent molecules when they are attached to a halide anion allows one to infer cluster structures. In some cases, the spectra contain rotationally resolved features, so that quantitative structural parameters can be obtained. (For complete abstract open document)
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ItemInterfacial tension study and rheological characterisation of water-in-oil emulsion explosives( 2007)Highly concentrated emulsion explosives are complex colloidal systems that remain robust for very many years after production. In this work a poly-isobutyl succinic anhydride (PIBSA) derived emulsions have been studied to understand the extraordinary nature of the stability and flow of these emulsions. In this study a model sodium oleate emulsion system is developed to further confirmation of the nature emulsion explosives. Two PIBSA based emulsifiers were used to prepare the emulsions. The main emulsifier of interest was comprised of an amide, ester and imide head group attached to a PIBSA chain, the second was entirely comprised of an imide head group attached to a PIBSA chain. The pendant drop method was used to obtain dynamic interfacial tension measurements for an interface between of paraffin oil/PIBSA-imide and ammonium nitrate, and dodecane/sodium oleate and sodium nitrate. The IsoFit-WardTordai computer package that incorporated Langmuir, Frumkin, Reorientation and Aggregation adsorption isotherms was used to calculate diffusion coefficients for total time adsorption. Diffusion coefficients for short time adsorption with Langmuir and Frumkin isotherms were determined and long time adsorption with the Langmuir isotherm were calculated. All of the diffusion coefficients results suggested that direct diffusion controlled adsorption was not the mechanism these surface active agents employed, rather, the results suggested that an activation barrier controlled adsorption process dominated the kinetics of the interfacial adsorption. There is much evidence to suggest that rheological properties of highly concentrated emulsions have not been characterised correctly for some time. This is mainly due to wall depletion or wall slip effect phenomenon inherent to rheological investigations performed on smooth stainless steel surfaces. The effect of wall slip was eliminated through physical means by performing rheological investigations with a sand blasted cone and plate, and the use of the vane geometry as a rheomter. Another method to eliminate wall slip effects in steady shear for highly concentrated emulsions was formulated and established in this investigation. A two-stage Tikhonov regularisation procedure that converts steady shear data into rheological property functions has been developed. The two-stage method is able to obtain not only the shear-stress shear-rate function but also the slip velocity as a function of wall shear- stress. The method is such that it obtains the rheological functions over the maximum range of shear-rate covered by the data. The results obtained using the new method were compared to those obtained using the sand blasted cone and plate and vane geometry with good agreement being observed. Over a 17 month period, a PIBSA based emulsion was observed in order to determine if any dramatic rheological changes were taking place with time, the results obtained in both shear and dynamic analysis effectively concluded that the PIBSA emulsion explosive was extremely stable and the minor changes observed were within experimental uncertainty of the measurements. Various microscopy techniques were used to determine the droplet structure and size distribution within various emulsions. Optical microscopy, Qualitative Phase Imaging, Differential Interference Contrast imaging were employed, and it was found that the PIBSA and PIBSA-imide emulsions had a spherical shape rather than a hexagonal close packed structure that was previously assumed for these emulsion explosives. Images of the sodium oleate emulsion indicated that there were obvious destabilising mechanisms at work, affecting the longevity of the emulsion.
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ItemReactions of kaolinite in the predesilication processing of bauxite ores( 2005)Bauxite ores, primarily a mixture of hydrated aluminium oxides, are refined to gibbsite (γ-AI(OH)3) by dissolution in superheated concentrated sodium hydroxide and reprecipitation from the cooled liquor in the Bayer process. The raw bauxite ore also contains iron oxides, organic materials, quartz and aluminium silicates such as kaolinite. ...