M.Sc. / This dissertation describes the synthesis and characterization of CdSe/ZnO and Ag/ZnO core/shell nanoparticles using water as a solvent. The effects of the concentration of the shell precursor, pH, and stabilizing agents on the properties of the nanoparticles were investigated. In general, the type of capping agents had an influence on the crystallite size of the core nanocrystals. The particle size distributions which were calculated from TEM images show that thioglycolic acid as a capping agent produced larger particle sizes compared to thioglycerol. For example, thioglycolic acid produced on average 5.0 nm CdSe nanoparticles while 4.0 nm average CdSe particle size was obtained when using thioglycerol as stabilizer. This observation was confirmed by UV/Vis absorption results which showed that thioglycerol capped CdSe NCs exhibited excitonic peaks positioned at lower wavelength than thioglycolic capped CdSe NCs. XRD results showed that the capping agents used in the current work had no influence upon crystal structure of the CdSe nanocrystals as the cubic structure was obtained with both stabilizers. The effect of shell precursor concentration at pH 12 showed heterogeneous formation of ZnO nanoparticles at high shell precursor concentrations. Various ZnO morphologies including nanoflowers and nanotriangles were observed on TEM images when 50 mL and 25 mL of zinc nitrate solution were used as shell precursors. UV/Vis absorption results also confirmed the presence of ZnO absorption peaks for samples prepared with 50 mL and 25 mL of zinc nitrate solution as shell precursors. PL results showed an increase in peak intensity as a function of precursor volumes. XRD results showed diffraction patterns due to the wurtzite structure of ZnO. CdSe diffraction patterns in these samples were not detected by the XRD instrument. At low volume of the shell precursor, which was 5 mL of 0.05 M zinc nitrate, TEM results showed that spherical CdSe/ZnO core/shell nanoparticles were obtained at pH 12 with 5 mL of 0.05 M zinc nitrate solution and 0.1 M sodium hydroxide used as shell precursor solutions, and thioglycerol as a stabilizer. XRD analysis of the v sample exhibited ZnO diffraction patterns and the CdSe patterns were not detected owing to their low peak intensities compared to those of the ZnO. Similar results were obtained when thioglycolic acid was used a stabilizing agent. However, TEM images showed the hexagonal shape of the CdSe/ZnO core/shell nanoparticles. The pH level was found to influence the photoluminescence properties of the CdSe/ZnO core/shell nanoparticles. The enhanced PL intensity was obtained with CdSe/ZnO core/shell nanoparticles with pH 9 in comparison with CdSe/ZnO core/shell nanoparticles prepared at pH 12. TEM images showed the presence of a thin ZnO shell on the surface of CdSe cores for CdSe/ZnO prepared at pH 9 which could be attributed to the PL enhancement. Although EDS results confirmed the presence of elements such as Cd, Se, Zn and O for both the CdSe core and ZnO shell, the XRD results confirmed the presence of only CdSe diffraction patterns, which suggested the ZnO shell had low peak intensity or was amorphous. A similar effect of these capping agents was observed for Ag nanoparticles as thioglycerol produced average particle size of 16.0 nm whereas 31.0 nm as the average particle size was obtained with thioglycolic acid as stabilizing agent. The crystal phase of Ag NPs was independent of the type of stabilizer. The Ag NPs precipitated in face centred cubic phase. Core/shell Ag/ZnO nanoparticles were produced with 5 ml of zinc nitrate as shell precursor. Higher volumes (50 ml and 25 ml) of zinc nitrate shell precursor induced heterogeneous precipitation of ZnO nanoparticles. XRD patterns confirmed peaks due to ZnO and Ag for Ag/ZnO core/shell nanoparticles.

Submitted in fulfillment of the requirements of the Degree of M.Tech.: Chemistry, Durban University of Technology, 2017. / The presence of dyes in effluent poses various environmental as well as health hazards for many organisms. Although various remediation strategies have been implemented to reduce their effect, dyes still manage to infiltrate into the environment and hence new strategies are required to address some of the problems. This study investigated the innovation of two cationic water-soluble polymers viz., Proline-Epichlorohydrin-Ethylenediamine Polymer (PEP) and Thiazolidine-Epichlorohydrin-Ethylenediamine Polymer (TEP) that were used to remediate selected synthetic dyes from synthetic effluent by adsorption and dye reduction. Both polymers were synthesized using monomers of a secondary amine, epichlorohydrin and ethylenediamine and were subsequently characterized and modified and their remediation potential studied. In the first study, PEP was synthesized and characterized by 1H-NMR Spectroscopy, FT-IR Spectroscopy, dynamic light scattering, and thermogravimetric analysis (TGA). Thereafter PEP was modified with bentonite clay, by simple mixing of the reactants, to form a Proline-Epichlorohydrin-Ethylenediamine Polymer-bentonite composite (PRO-BEN); it was characterized by FT-IR Spectroscopy, scanning electron microscopy (SEM)/ energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Adsorption studies were then undertaken with a synthetic effluent containing three textile dyes, viz., Reactive Blue 222 (RB 222), Reactive Red 195 (RR 195) and Reactive Yellow (RY 145). Various conditions were investigated including pH of the solution, temperature, sodium chloride concentration, initial dye concentration and the dosage of adsorbent used. The experimental data for all dyes followed a Langmuir isotherm. The adsorption process was found to be pseudo-second order. According to the thermodynamic parameters, the adsorption of the dyes was classified as physisorption and the reaction was spontaneous and exothermic. The data were also compared using studies with alumina as an adsorbent. Results showed that PRO-BEN exhibited better absorptivity and desorption than alumina making its use a better recyclable remediation strategy for the removal of organic dyes in wastewater treatment plants. In the second study, TEP was synthesized and then characterized by FT-IR Spectroscopy, 1H-NMR Spectroscopy, TGA and DLS. Thereafter, TEP was used to prepare TEP capped gold nanoparticles (TEP-AuNPs). Herein, two methods were investigated: the Turkevich method and an adaptation of the Turkevich method using bagasse extract. The TEP-AuNPs was characterized by FT-IR Spectroscopy, SEM, EDX, DLS and TEM. Thereafter the reduction of each of Allura Red, Congo Red and Methylene Blue was investigated with the TEP-AuNPs for its catalytic activity toward dye reduction. This study showed that the batch of AuNPs prepared by the Turkevich method had higher rates of dye reduction compared with AuNPs prepared using bagasse extract. Also the quantity of TEP used as capping agent greatly influenced the size, shape and surface charge of the nanoparticles as well as their catalytic performance: the Vroman effect explained this behavior of the TEP-AuNPs. It was finally concluded that whilst PRO-BEN, in the first study, showed excellent dye remediation properties, the second study on TEP-AuNPs showed good catalytic activity for the reduction of selected dyes, however, it was more effective at lower polymer concentration. Finally, both materials displayed good potential for the clean-up of selected synthetic dyes from synthetic effluents. / M

No description available.

The complex [IrH(COD)(PMe3)3][Cl]2o2HCl was prepared by the reaction between [Ir(COD)(PMe3)3]Cl and HCl gas in methylene chloride. The product precipitated from the solution and is soluble in polar solvents such as water, acetonitrile, and acetone. [IrH(COD)(PMe3)3][Cl]2o2HCl undergoes reaction in water to form fac-IrCl3(PMe3)3. Also, other [IrH(COD)(PMe3)3][X]2 salts were prepared with X being PF6, OTF, or BF4. It was determined that each salt retained a certain amount of excess acids and [IrH(COD)(PMe3)3][OTF]HOTf was the most stable in the solvent acetonitrile while [IrH(COD)(PMe3)3][PF6]2 showed signs of reaction in acetonitrile after 4 hours. The dicationic salts were also reductively deprotonated by DMSO to form the Ir(I) starting material. Finally a slow equilibrium was noted for [IrH(COD)(PMe3)3][BF4]2 in water by the observation of the reductive deprotonation product. The grignard reaction was employed to synthesize Ir(CH3)3(PMe3)3. IrCl3(PMe3)3 reacts with methyl grignard in THF/Benzene to form fac-Ir(CH3)3(PMe3)3. Only the facial isomer of this reaction was observed and the product was soluble in nonpolar solvents. Acidolysis was utilized to synthesize fac-IrCH3Cl2(PMe3).3 from the reaction between Ir(CH3)3(PMe3)3 and 2 equivalents of HCl. Ir(III) methyl dications have also been synthesized by the reaction of 2 equivalents triflic acids with fac-Ir(CH3)3(PMe3)3. The product of the reaction, mer-IrCH3(OTf)2(PMe3)3 was used to study the insertion of alkynes into the Iridium methyl bond. IrHCl2(PMe3)3 was synthesized by the careful acidolysis of IrH2Cl(PMe3)3 using 1 equivalent of HCl. IrH(OTf)2(PMe3)3 was also synthesized by the metathesis of IrHCl2(PMe3)3 with 2.04 equivalents of silver triflate. The product of that reaction, IrH(OTf)2(PMe3)3, has been used to form dimers and trimers of styrene via catalysis and to isomerize alkene alcohols to aldehydes. IrH(OTf)2(PMe3)3 was also used as a polymerization initiator for vinyl and allyl ethers. / Ph. D.

The successful application of Tppts, and its derivatives, in biphasic transition metal-catalysed reactions opened up a new field of chemistry requiring a rational design of water-soluble ligands. The main objective of the research described in this dissertation was the preparation and the application of new water-soluble phosphine ligands. The ligands were prepared by the use of carbon nucleophiles and chlorophenylphosphine derivatives. The carbon nucleophiles included malonate derivates, which were subsequently reduced to the di-alcohols and were transformed into water-soluble phosphines by the reaction with 1,4-butanesultone. Secondary and tertiary malonate nucleophiles were used and the steric demands of compounds containing more than one malonate group were investigated. Various attempts to obtain water-soluble compounds from dimalonate phosphine oxides failed. TBDMS-protected aryl halides were also used as nucleophiles. One (or two) of these silyl ethers was reacted with chlorophenylphosphine derivatives and after deprotection with TBAF the compounds were made water-soluble by a reaction with 1,4-butanesultone. The hydrogenation of arylphosphine oxides to form cyclohexylphosphine oxide derivatives was also investigated. However, these cyclohexylphosphines were more easily obtained by the reaction between the previously mentioned carbon nucleophiles and chlorocyclohexylphosphine derivatives, which were freshly prepared. A series of cyclohexyl-containing water-soluble phosphines was prepared in this way. The oxygen sensitive nature of phosphines lead to two different approaches in the reaction route: the phosphines were either borane protected followed by a subsequent deprotection step, or the phosphines were allowed to oxidise and were reduced back to the free phosphine at a later stage. The efficiency of both approaches in the reaction routes was examined. The deprotection of phosphine-boranes was performed using various “new” deprotecting reagents and the borane-species and free phosphines were separated using water/organic extractions. The various extraction coefficients of the amine-borane complexes were determined. The newly prepared ligands were used in a variety of palladium-catalysed reactions as well as in the hydroformylation of 1-octene employing rhodium. The reactions were performed in both neat organic solvents as well as mixtures between water and DMF or toluene and the results were compared to the use of Tpp and Tppts. It was found that many of the new ligands afforded superior yields compared to those of Tpp and Tppts. In the last part of the study, various diphenylphosphinic amides were used as DoM-groups. Sec- and tert-BuLi were used together with a variety of electrophiles to facilitate ortho-substitution on either one or two rings on the amides. This was seen as a start of a new approach towards functionalised phosphine ligands. / Prof. D.B.G. Williams

Through chemical analysis and ion exchange chromatography of watersoluble antigens, this investigation supports the view that the majority of differences between the biotypes are quantitative. It was also found that strains demonstrate distinct, qualitative differences when compared to the attenuated strain 19 by immunodiffusion and thin-layer polyacrylamide gel, isoelectric focusing. These differences include the presence of antigens on virulent strains that are absent on strain 19. In addition, one antigen absent on strain 19, was found common to each virulent biotype. Finally, the results from immunodiffusion experiments, employing adsorbed and non-adsorbed immune globulins, indicate that at least some water-soluble antigens are exposed on the cell surface and that their distribution among the biotypes varies.

Thesis (Ph.D.)--McMaster University, 2004. / Supervisor: Harald D. H. Stöver.

Development of opto-electronic polymers has been focused on conjugated rigid-rod polymers which assume a para-catenated backbone yielding a rod-like configuration. As a consequence of their rigidity, the rod-like molecules display superior mechanical properties, thermo-oxidative stability and solvent resistance. The later two characters cause difficulties in processing these high-performance rigid-rod polymers. This in terms limits their applications in critical technologies, such as conducting polymers, nonlinear optics, and solid polyelectrolytes. In this study, chemical derivatives of the rigid-rod polymers were synthesized using pendants of propane-sulfonated ionomers to (1) enhance the solubility of the rigid-rod polymers, and (2) generate a solid polyelectrolyte suitable for energy storage. Extensive synthesis efforts were focused on generating monomers and polymers of propane-sulfonated poly(p-phenylene-benzobisimidazole), PBI, making it a water soluble electrolyte. Various analysis techniques were applied to ascertain the chemical structure and the purity of the monomers and of the polymers. The polymer molecular weight was also determined using viscometry. An intrinsic viscosity of 4.9 dL/g was achieved for the 2-sulfo-PBI and of 0.58 dL/g for the propane-sulfonated PBI with Na+ ionomer pendants

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 286-299). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 150-159). Also available on the Internet.