No description available.

No description available.

The application of gold and silver nanoparticles to areas such as medical research is based on unique optical properties exhibited by some metals. These properties are a direct consequence of localised excitations occurring at visible frequencies known as Surface Plasmon Resonances (SPRs). The exact frequency of an SPR induced in a nanoparticle can be 'tuned' in the optical range by, for example, changing the size of gold and silver nanoparticles, or by varying the relative concentrations of gold and silver within an alloy nanoparticle. Whatever the desired frequency, it is critical that the majority of nanoparticles exhibit the frequency within the resolution limit of the imaging system. The research presented here utilises the high resolution imaging and spectroscopy techniques of (Scanning) Transmission Electron Microscopy ((S)TEM) and Electron Energy Loss Spectroscopy (EELS). It is common practice to analyse the optical properties of alloy nanoparticles using techniques that acquire a single spectrum averaged over multiple particles such as Ultraviolet-Visible (UV-Vis) spectroscopy. However, this technique cannot detect any optical variation between the nanoparticles resulting from compositional change. In this research the author demonstrates through the use of EELS that the SPR can be determined for individual gold/silver alloy nanoparticles, for the purpose of determining the extent of their homogeneity. Importantly, the data presented here suggest dramatic variation in SPR frequency between particles and even within the same particle, indicative of large variations in alloy composition. This puts the assumption that alloying can be scaled down to the nanometre-scale to the test. In order to resolve and extract the SPR in both the pure gold and gold and silver alloy nanoparticles, the author has successfully applied multiple post acquisition techniques such as Richardson-Lucy deconvolution and Principle Component Analysis (PCA) to the EELS Spectrum Imaging (SI) acquisition method. Additionally, the valence band EELS data are supported by complementary electron microscopy techniques; Core loss EELS, Energy Dispersive X-Ray Spectroscopy (EDX) and High Angle Annular Dark Field (HAADF) imaging.

The specific interaction between saccharide molecules and saccharide-binding proteins, lectins, can be exploited in order to actively target nanostructures to specific cell types for diagnostic or therapeutic purposes. However, the conjugation of saccharides to nanostructures can be complex, leading to a lack of versatility in the functionalities that can be achieved, or poorly characterized and therefore potentially inconsistent. Herein is reported a new procedure by which novel saccharide-containing molecules, for the functionalization of nanostructures, could be synthesized rapidly and with good yields. The synthesis was found to be versatile, providing coating molecules for magnetite nanoparticles and phospholipid vesicles from a number of different hydrazides and reducing sugars. The stability of the synthesized coating molecules was assessed, both in aqueous solution and when bound to the surface of a magnetite nanoparticle, and found to be satisfactory for cell culture purposes. The availability of the saccharide units for lectin binding was confirmed using a Quartz crystal microbalance (QCM-D) in addition to a number of assays. Finally, microscopy techniques were used to study the interactions between saccharide-functionalized magnetite nanoparticles and two cell types, fibroblasts (3T3) and hepatocytes (HepG2).This work demonstrated the ability of saccharide coatings to improve the uptake of nanostructures in a cell culture environment and highlighted the potential cell manipulation application of saccharide-coated magnetite nanoparticles.

The major topics discussed are all relevant to interfacing brightly phosphorescent and non-luminescent coinage metal complexes of [Ag(I) and Au(I)] with biopolymers and thermoresponsive gels for making hybrid nanomaterials with an explanation on syntheses, characterization and their significance in biomedical fields. Experimental results and ongoing work on determining outreaching consequences of these hybrid nanomaterials for various biomedical applications like cancer therapy, bio-imaging and antibacterial abilities are described. In vitro and in vivo studies have been performed on majority of the discussed hybrid nanomaterials and determined that the cytotoxicity or antibacterial activity are comparatively superior when compared to analogues in literature. Consequential differences are noticed in photoluminescence enhancement from hybrid phosphorescent hydrogels, phosphorescent complex ability to physically crosslink, Au(I) sulfides tendency to form NIR (near-infrared) absorbing AuNPs compared to any similar work in literature. Syntheses of these hybrid nanomaterials has been thoroughly investigated and it is determined that either metallic nanoparticles syntheses or syntheses of phosphorescent hydrogels can be carried in single step without involving any hazardous reducing agents or crosslinkers or stabilizers that are commonly employed during multiple step syntheses protocols for syntheses of similar materials in literature. These astounding results that have been discovered within studies of hybrid nanomaterials are an asset to applications ranging from materials development to health science and will have striking effect on environmental and green chemistry approaches.

No description available.

Nanoscale zero-valent iron (NZVI) particles and iron cross-linked alginate (FCA) beads were successfully used for the first time for phosphate removal and recovery. NZVI was successfully used for phosphate removal and recovery. Batch studies indicated a removal of ~96 to 100% phosphate in 30 min (1, 5, and 10 mg PO43--P/L with 400 mg NZVI/L). Phosphate removal efficiency by NZVI was 13.9 times higher compared to Microscale ZVI (MZVI) particles. The successful rapid removal of phosphate by NZVI from aqueous solution is expected to have great ramification for cleaning up nutrient rich waters. The presence of sulfate, nitrate, and humic substances and the change in ionic strength in the water marginally affected phosphate removal by NZVI. A maximum phosphate recovery of ~78% was achieved in 30 min at pH 12. Novel iron cross-linked alginate (FCA) beads were synthesized, characterized and used for phosphate removal. The beads removed up to 37-100% phosphate from aqueous solution in 24 h. Freundlich isotherm was found to most closely fit with experimental data and the maximum adsorption capacity was found to be 14.77 mg/g of dry beads. The presence of chloride, bicarbonate, sulfate, nitrate, and natural organic matters in aqueous solution did not interfere in phosphate removal by FCA beads. The phosphate removal efficacy FCA beads was not affected due to change in pH (4-9). Nanosacle zero-valent iron (NZVI) and iron cross-linked alginate beads were also tested for phosphate removal using actual wastewater treatment plant effluent and animal feedlot runoff. The FCA beads could remove ~63% and ~77% phosphate from wastewater and feedlot runoff in 15 min, respectively. Bioavailability of phosphate was examined using algae and higher plants. Phosphate and iron bioavailability of the NZVI sorbed phosphate was examined by supplying spent particles (NZVI with sorbed phosphate) to Tyee Spinach (Spinacia oleracea) and algae (Selenastrum capricornutum). Results revealed that the phosphate was bioavailable for both the algae and spinach. Also, presence of the nanoparticles enhanced the algae growth and plant growth and increases in biomass and plant length were observed. Iron (from spent NZVI) was found to be bioavailable for spinach.

Doctor Scientiae / Living organisms are constantly being exposed to nanoparticles (NPs) in the environment via air, water, soil. Routes of exposure are usually in the form of industrial, occupational exposure, as well as therapeutic applications. This exposure could result in toxicity with potential harmful effects. The toxicity of nanoparticles depends on various factors such as surface interaction, shape, size, composition, aggregation and interaction with various cellular components. Nanotoxicity refers to the possible harmful effects of environmentally generated and man-made nanoparticles on biological and environmental system. Assessing potential toxicity is vital for the probable use and safety of nanoparticles as well as understanding the routes of entry into organisms and their mechanism of action. Proteomics is a developing field of science that is being explored to understand protein composition, structure and interaction at the cellular level. This helps in detecting the presence, quantity, alteration and regulation of proteins within the biological system. The proteome analysis brings an additional information as it enables measurement of wholeprotein (enzyme) expression levels, facilitating the construction of metabolic pathways and biomarker discovery for early disease diagnosis. Essentially, proteomic analysis reveals the consequence of stress on metabolic pathways necessary to maintain the energy homeostasis within the cells.

Silica (inorganic)-g-polymer (organic) hybrid materials with a large variety of functionality have been studied intensively because of the improvement in their physical and chemical properties (e.g., thermal, mechanical, electrical, magnetic properties, etc.) with respect to conventional organic and inorganic materials. 1–3 This research work introduces a new strategy based on in situ formation of poly(methyl methacrylate) block copolymer grafted silica nanoparticles. The thesis is divided into two major parts. In the first part, the atom transfer radical polymerization (ATRP) method was used to synthesize poly(methyl methacrylate-b-trimethoxysilyl propyl methacrylate) (PMMA-b-PTMSPMA); and poly(methyl methacrylate-b-trimethoxysilyl propyl acrylate) (PMMA-b-PTMSPA) block copolymers. Gel permeation chromatography (GPC) was performed to determine the number-average molecular weight (Mn) and polydispersity index (Đ) of PMMA-b PTMSPMA and PMMA-b-PTMSPA. In addition, proton nuclear magnetic resonance spectroscopy (1H NMR) was used to confirm the successful synthesis of the above copolymers. In the second part, the copolymers were used to form silica nanoparticles grafted with poly(propyl methacrylate-b-methyl methacrylate) [silica-g-(PPMA-b PMMA)] and silica nanoparticles grafted with poly(propyl acrylate-b-methyl methacrylate) [silica-g-(PPA-b-PMMA)]. Fourier transform infrared spectroscopy (FT-IR) and 29Si solid-state NMR were performed to confirm the formation of silica-g-(PPMA-b PMMA) and silica-g-(PPA-b-PMMA). Additionally, thermogravimetric analysis (TGA) was performed to assess the thermal decomposition of silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA). Multiple microscopic techniques such as TEM, cryo-TEM, SEM, and AFM were used to study micellization of the silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA) in tetrahydrofuran (THF) and chloroform

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 29 May 2018. / The relatively unknown resin-gel synthesis technique has the potential to form multi-mode mixed metal oxide nanoparticles with differing stoichiometries. These oxides can be employed in a plethora of applications. In order to exploit these benefits, the mechanism of nanoparticle formation must be understood. To this end, this study embarked on a parametric investigation to gain insights on the formation of the less stable anatase and more stable rutile (titanium dioxide) using resin-gel synthesis. By adjusting parameters such as the type of polymer, solvent, acid, and metal ion precursor, and by varying other parameters such as the polymer chain length, polymer stoichiometry, and heating rate, a model for nanoparticle formation was developed and refined. This model considered the formation of hydroxylated metal ion species following the addition of a metal ion precursor to a hydroxyl-containing solvent. These species were protected and stabilised by the remaining fragments of solvent components. In addition, the size of the ligands attached to the metal ion precursor governed the amount of protection and stabilisation afforded to the hydroxylated species by the precursor. These complexes were coordinated to polymer chains that underwent degradation during the course of heating and ignition. Polymer degradation produced polymer reaction chambers. The formation, action, and interaction of these chambers with developing titania crystallites are a novel finding of this work. The sizes of these chambers were controlled largely by the quantity of polymer present in the reaction. The number of accessible oxygen sites on the precursor determined the degree of association between the metal ion complexes and the reaction chambers. If the association was intimate, the polymer reaction chambers served to stabilise and protect the newly nucleated anatase particles. If the combination of protection effects afforded by the solvent components, precursor ligands, and association of reaction chambers of appropriate sizes was insufficient to stabilise nucleated anatase, it readily converted into the rutile phase. Anisotropic growth along [0 0 1] then caused rutile to form nanorods. Rutile mesocrystals developed following sufficient polymer degradation. The association of nanoparticles with polymer fragments was viewed using TEM. Additionally, TEM investigations revealed the presence of polymer-derived superstructures containing reaction chambers. Reaction chambers presented with various morphologies and were composed of crystalline carbon. / LG2018