The objectives of this thesis were to optimize the synthesis and surface coating of metallic and semiconductor nanoparticles, to understand how these materials interact with cells and physiological systems and to investigate how they can be used to deliver thermal therapy for medical applications. Reproducible high-yield synthesis of gold nanorods and surface coating with a variety of polymers and silica was optimized. Using gold nanorods as a model system, the relationship between particle surface chemistry, surface charge and cellular uptake was studied, as well as the toxicity of nanoparticles of different surface chemistry. Low toxicity in vitro was encouraging and was confirmed in vivo by intravenously injecting Sprague-Dawley rats with semiconductor quantum dots of various surface coatings. Low toxicity was found during biochemical, haematological and pathological assessment, and these results indicate that applications of nanoparticles should be further investigated. One such application is the use of near infrared absorbing gold nanorods in remotely activated hyperthermia. It was shown that gold nanorods act synergistically with the chemotherapeutic cisplatin to improve cytotoxicity, and reduce the required cytotoxic drug dose to 33% of the unheated amount. Due to the success of hyperthermia treatment in vitro, continuing and future work involves the use of gold nanorods ex vivo on excised human corneas in a novel application to weld corneal tissue for improved wound closure following cataract surgery.

The experimental work described in this thesis is aimed primarily towards elucidation of the speciation of zinc-cyanide systems at elevated pH. In this study the formation and stability of H+-eN-, binary Zn2+-eN- and ternary Zn2+-CN--QH- complexes were studied by glass electrode potentiometry in aqueous solutions at 25.0°0 and in a medium of ionic strength of 0.1 mol dm-3. The solution pH was varied to cover the range 4 to 11. The study was undertaken with a view to establishing whether and under what conditions soluble binary zinc-cyanide complexes and ternary zinc-cyanide-hydroxide complexes form, and to determine formation constants for any such species that are found. This information would be useful in defining more precisely the speciation of solutions containing zinc and cyanide ions at elevated pH values. A titration method was used, in which hydrogen ion concentration was monitored by means of a glass indicating electrode. The cell was calibrated to allow measurements of hydrogen ion concentration rather than hydrogen ion activity. Owing to precipitation difficulties, the reagents were used at sub-millimolar concentration levels. The potentiometric data was interpreted with the aid of various formation function plots together with the use of various computer programs, such as HALTAFALL and ESTA. The results show that the ternary complex Zn(ON)3(OH)2- is formed in significant amounts in solutions of pH > 8.5. Some evidence was also obtained for the existence of the five coordinated species Zn(CN)3(OH)~- and Zn(CN)~- in these solutions, but existence of the latter two species cannot yet be regarded as firmly established. No polynuclear complexes were detected at the sub-millimolar concentrations used. Formation constants are reported for H+-eN- and both binary Zn2+-eN- and ternary Zn2+-eN--QH- species. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

Silica nanoparticles are effective fluorophore carriers with high potential in imaging, diagnostics, and therapy. The particles are resistant to drastic change of environmental conditions (pH, temperature etc.) and insulate the dyes so as to protect them from photobleaching. Silica chemistry is also versatile and affords an easy modification of the particle composition and surface to integrate targeting ligands or to integrate other nanoparticles. Regardless of their advantages, there exists a lack of dye diversity in the literature that is connected to a low affinity for potential tools for biology and medicineThis thesis describes the development of an alternative method for the synthesis of fluorescent silica nanoparticles and their modification to incorporate iron oxide and gold. cont/d.

The optical properties of gold in the visible are dominated by the response of the free conduction electrons to light. In gold nanostructures, the surface charge density adopts a configuration that is constrained by the shape of the nanoparticles. As a result, the scattering of light by gold nanoparticles exhibits a resonant response characterised by a strong scattering and absorption in a narrow range of frequencies. The spectral range of this \emph{localised surface plasmon resonance} (LSPR) can be tuned by varying the size and shape of the gold nanoparticle --- the nanoparticles act as nanoscale antennas for the visible light. Confirmation of this scaling rule is obtained by conducting experiments with nanoparticles of varying size and aspect ratio. Such particles are fabricated by electron-beam lithography, and characterised by dark-field spectroscopy. Not only does the LSPR shift in frequency with a change of particle size, but its spectral lineshape is also modified. The intensity and width of the LSPR are dictated by a variety of factors that are related to the intrinsic material properties (the complex dielectric function of gold), and to the particle geometry and environment. The optical response of small gold nanorods is well described by a simple oscillating dipole model --- the incident electromagnetic field induces a current in the particle that re-radiates light (scattering). A series of refinements can be made to model more accurately the optical response of realistic particles. If the dipole moment characterising the particle is allowed to vary in phase across the particle, retardation effects provide a correction for the effective dipole moment of the particle. As the particle size approaches the wave length in the surrounding medium, the dipolar approximation breaks down and higher order multipoles need to be considered. The Mie theory provides a very accurate description of the response of spheres of arbitrary size. Further, the T-matrix and other numerical techniques can be employed to accurately reproduce the scattering properties of particles of arbitrary shapes. When the scattering sample consists of a collection of gold nanoparticles, the collective optical response is affected by two key factors. First, the measured LSPR is a convolution of the distribution of particle sizes with the individual response of a single particle. This leads to an inhomogeneous broadening of the LSPR lineshape. Second, the light that is scattered by one such particle near resonance can strongly affect its neighbours which scatter light in proportion to the net field they experience, that is the sum of the incident field plus the perturbation arising from the neighbouring particles. The onset of such multiple scattering events is observed even for particle separations that are several times larger than the particle size. Several regimes of interaction can be distinguished according to the ratio separation / wavelength. First, when the particles are in close proximity (separation $\ll$ wavelength), near-field interactions dominate and result in a spectral shift of the LSPR accompanied with a spectral broadening. Second, when the separation is commensurate with the wavelength, a coherent interaction can develop that couples a large number of particles. In ordered arrays, such coupling gives rise to a geometrical resonance that can strongly affect the LSPR of the particles. In particular a sharp spectral feature is observed that depends on both the single particle response and the geometrical arrangement of the particles in the array. The coherence of such multiple scattering in diffractive arrays of gold nanoparticles can be broken by introducing disorder in the distribution of particle sizes, or in the particle positions. The optical properties of an irregular array reflect the departure from a periodic system and the spectral lineshape evolves as the level of disorder is increased. In the limit of uncorrelated positions, the diffractive coupling is suppressed and the response of the collection of the particles rejoins the response of isolated particles.

The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous-organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet-visible spectroscopy and scanning transmission electron micrographs.

This paper examines the role that gold and other precious metals play in portfolio construction as hedges and safe havens in comparison with the Volatility Index (VIX), a derivative of market volatility. Gold has long been considered to be among the best assets for reducing portfolio volatility due to its lack of correlation with the overall market. However, the major finding of this paper is that while gold and the other precious metals do serve in this role to varying extents, the VIX performs this function far better. Both econometric and portfolio analyses reveal that the VIX improves overall portfolio performance to a greater extent, and most importantly serves as an effective safe haven relative to the market.

M.Sc. (Nanoscience) / Please refer to full text to view abstract

M.Com. (Business Management) / Please refer to full text to view abstract

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<p>The prevalence of cancer has increasingly become a significant threat to human health and as such, there exists a strong need for developing novel methods for early detection and effective therapy. Nanotheranostics, a combination of diagnostic and therapeutic functions into a single nanoplatform, has great potential to be used for cancer management by allowing detection, real-time tracking, image-guided therapy and therapeutic response monitoring. Gold nanostars (GNS) with tip-enhanced plasmonics have become one of the most promising platforms for cancer nanotheranostics. This work is aimed at addressing the challenges of sensitive cancer detection, metastasis treatment and recurrence prevention by combining state-of-the-art nanotechnology, molecular imaging and immunotherapy. A multifunctional GNS nanoprobe is developed with capabilities ranging from non-invasive, multi-modality cancer detection using positron emission tomography (PET), magnetic resonance imaging (MRI) and X-ray computed tomography (CT), to intraoperative tumor margin delineation with surface enhanced Raman spectroscopy (SERS) and high-resolution nanoprobe tracking with two-photon photoluminescence (TPL), as well as cancer treatment with photoimmunotherapy. The GNS nanoprobe with PET scans is particularly exceptional in detecting brain malignancies as small as 0.5 mm. To the best of our knowledge, the developed GNS nanoprobe for PET imaging provides the most sensitive means of brain tumor detection reported so far. In addition, the GNS nanoprobe exhibits superior performance as photon-to-heat transducer and can be used for specific photothermal therapy (PTT). More importantly, GNS-mediated PTT combined with checkpoint inhibitor immunotherapy has been found to trigger a memorized immunoresponse to treat cancer metastasis and prevent recurrence in mouse model studies. Furthermore, a 6-month in vivo toxicity study including body weight monitoring, blood chemistry test and histopathology examination demonstrate GNS nanoparticles’ biocompatibility. Therefore, the multifunctional GNS nanoprobe exhibits superior cancer detection and treatment capabilities and has great promise for future clinical translation in cancer management.</p> / Dissertation