Synthesis and structural studies of NiS and PdS nanoparticles/nanocomposites from dithiocarbamates single source precursors
- Authors: Nqombolo, Azile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11359 , http://hdl.handle.net/10353/d1021326
- Description: The main aim of this research is to synthesize Ni(II) and Pd(II) dithiocarbamate complexes and use them as single source precursors for the synthesis of NiS and PdS nanoparticles and metal sulphides potato starch nanocomposites. Four dithiocarbamate ligands were synthesized and characterized using elemental analysis and spectroscopic techniques. The ligands were used to prepared homoleptic Ni(II) and Pd(II) complexes of the dithiocarbamate ligands. The metal complexes were characterized with elemental analysis, UV-Vis, FTIR and 1H-NMR spectroscopic techniques. Conductivity measurements indicate that all the complexes are non-electrolytes in solution and results from the electronic spectra studies confirmed the proposed 4-coordinate square planar geometry around the metal ions. The nickel complexes showed d-d transitions around 477 nm while in the palladium complexes, no d-d transitions were observed but the compounds showed strong metal to ligand charge transfer transitions. From the FTIR spectra studies, it can be confirmed that the complexes were successfully synthesised because all peaks of interest were observed at expected regions from the literature. The νC-N was observed around 1469-1495 cm-1, νC=S around 1101-1188 cm-1 and νC-S around 738-1060 cm-1 for both Ni(II) and Pd(II) complexes. νNi-S was observed around 375-543 cm-1 and νPd-S around 529-545 cm-1. The FTIR also confirmed that the dithiocarbamate ligands act as bidentate chelating ligands through the sulfur atoms. The complexes were used as single source precursors and thermolysed in hexadecylamine (HDA) at 220 °C to prepare four HDA-capped nickel sulfide nanoparticles and four palladium sulfide nanoparticles. The as-prepared nanoparticles were studied with optical absorption spectra, photoluminescence, powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The optical studies results showed that NiS have large band gaps that are greater than that of the bulk, therefore they are found to be blue shifted relative to the bulk, which shows that they have small particle size and thus confirming their quantum confinement effect. PL spectra reveal that the emission peaks are red shifted compared to the absorption band edges of the nanoparticles. The XRD patterns confirmed the formation of cubic and rhombohedral phase for NiS nanoparticles and cubic phase for PdS nanoparticles. SEM images of both NiS and PdS show uniform surface morphology at low and high magnification with different shapes. EDS analyses confirmed the presence of Ni, S, and Pd in each of the spectrum indicating that the nanoparticles were successfully synthesized. TEM images showed that the synthesised nanoparticles have uniform and narrow size distribution with no agglomeration. The sizes of the NiS nanoparticles were found to be in the range of 12-38 nm for NiS1, 8-11 nm for NiS2, 9-16 nm for NiS3 and 4-9 nm for NiS4. The TEM images for the as-prepared PdS nanoparticles showed that the average crystallite sizes are 6.94-9.62 nm for PdS1, 8-11 nm for PdS2, 9-16 nm for PdS3 and 4-9 nm for PdS4 respectively. The nanoparticles were used to prepare potato starch nanocomposites and SEM images indicate that the surface morphology of starch polymer nanocomposites compose of potato starch and few particles in between the pores of the matrix, this is due to the small ratio of nanoparticles used.
- Full Text:
- Date Issued: 2016
- Authors: Nqombolo, Azile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11359 , http://hdl.handle.net/10353/d1021326
- Description: The main aim of this research is to synthesize Ni(II) and Pd(II) dithiocarbamate complexes and use them as single source precursors for the synthesis of NiS and PdS nanoparticles and metal sulphides potato starch nanocomposites. Four dithiocarbamate ligands were synthesized and characterized using elemental analysis and spectroscopic techniques. The ligands were used to prepared homoleptic Ni(II) and Pd(II) complexes of the dithiocarbamate ligands. The metal complexes were characterized with elemental analysis, UV-Vis, FTIR and 1H-NMR spectroscopic techniques. Conductivity measurements indicate that all the complexes are non-electrolytes in solution and results from the electronic spectra studies confirmed the proposed 4-coordinate square planar geometry around the metal ions. The nickel complexes showed d-d transitions around 477 nm while in the palladium complexes, no d-d transitions were observed but the compounds showed strong metal to ligand charge transfer transitions. From the FTIR spectra studies, it can be confirmed that the complexes were successfully synthesised because all peaks of interest were observed at expected regions from the literature. The νC-N was observed around 1469-1495 cm-1, νC=S around 1101-1188 cm-1 and νC-S around 738-1060 cm-1 for both Ni(II) and Pd(II) complexes. νNi-S was observed around 375-543 cm-1 and νPd-S around 529-545 cm-1. The FTIR also confirmed that the dithiocarbamate ligands act as bidentate chelating ligands through the sulfur atoms. The complexes were used as single source precursors and thermolysed in hexadecylamine (HDA) at 220 °C to prepare four HDA-capped nickel sulfide nanoparticles and four palladium sulfide nanoparticles. The as-prepared nanoparticles were studied with optical absorption spectra, photoluminescence, powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The optical studies results showed that NiS have large band gaps that are greater than that of the bulk, therefore they are found to be blue shifted relative to the bulk, which shows that they have small particle size and thus confirming their quantum confinement effect. PL spectra reveal that the emission peaks are red shifted compared to the absorption band edges of the nanoparticles. The XRD patterns confirmed the formation of cubic and rhombohedral phase for NiS nanoparticles and cubic phase for PdS nanoparticles. SEM images of both NiS and PdS show uniform surface morphology at low and high magnification with different shapes. EDS analyses confirmed the presence of Ni, S, and Pd in each of the spectrum indicating that the nanoparticles were successfully synthesized. TEM images showed that the synthesised nanoparticles have uniform and narrow size distribution with no agglomeration. The sizes of the NiS nanoparticles were found to be in the range of 12-38 nm for NiS1, 8-11 nm for NiS2, 9-16 nm for NiS3 and 4-9 nm for NiS4. The TEM images for the as-prepared PdS nanoparticles showed that the average crystallite sizes are 6.94-9.62 nm for PdS1, 8-11 nm for PdS2, 9-16 nm for PdS3 and 4-9 nm for PdS4 respectively. The nanoparticles were used to prepare potato starch nanocomposites and SEM images indicate that the surface morphology of starch polymer nanocomposites compose of potato starch and few particles in between the pores of the matrix, this is due to the small ratio of nanoparticles used.
- Full Text:
- Date Issued: 2016
Synthesis of bioethanol from lignocellulosic materials: A focus on grass and waste paper as raw materials
- Authors: Vala, Mavula Kikwe
- Date: 2009-12
- Subjects: Ethanol as fuel , Biomass energy , Lignocellulose -- Biotechnology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24499 , vital:63049
- Description: Biofuels are currently recognized as not only a necessity, but an inevitable pathway to secure the planet future energy needs. Food crops have been used (so far) as the biomass for bioethanol and biodiesel production. This has increased concerns over food security and led to the search for diversification and alternative feedstocks for biofuel production. The use of lignocellulosic materials, the most abundant, low cost and easy feedstock to harvest for bioethanol purpose, involves challenging production processes. Several approaches have been used to facilitate the breakdown of the biopolymer structure to produce fermentable sugars that can be converted to ethanol. Most of the approaches have used high temperatures and pressures and have often led to the production of inhibitors of fermentation. In this study, lignocellulosic materials from grass and newsprint were investigated as sources of biomass for bioethanol production using a chemical route (sulfuric acid hydrolysis) which made use of temperatures below 100°C at normal atmospheric pressure. Fermentation of toxic lignocellulosic hydrolyzates was possible after the development of a method for inhibitors removal. The method used treated wood chips as a stationary phase in a chromatographic column to remove inhibitors. This method is expected to be extended to applications such as in municipal wastewater treatment. Sugar yields of 22.26 and 8.9 g/L of hydrolyzate; and an ethanol yield of 184.5 and 130.4 mg/mL of must were achieved for 5g grass and newsprint respectively using optimum conditions of 2percent H2SO4 at 97.5°C for grass and 0.5percent H2SO4 at 97.5°C for newsprint during the hydrolysis process. Pure cellulose was used as a control for the biomass where 254.1 g/L of fermentable sugars were recovered from soluble cellulose and the yield of ethanol was 201.8 mg/mL. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
- Full Text:
- Date Issued: 2009-12
- Authors: Vala, Mavula Kikwe
- Date: 2009-12
- Subjects: Ethanol as fuel , Biomass energy , Lignocellulose -- Biotechnology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24499 , vital:63049
- Description: Biofuels are currently recognized as not only a necessity, but an inevitable pathway to secure the planet future energy needs. Food crops have been used (so far) as the biomass for bioethanol and biodiesel production. This has increased concerns over food security and led to the search for diversification and alternative feedstocks for biofuel production. The use of lignocellulosic materials, the most abundant, low cost and easy feedstock to harvest for bioethanol purpose, involves challenging production processes. Several approaches have been used to facilitate the breakdown of the biopolymer structure to produce fermentable sugars that can be converted to ethanol. Most of the approaches have used high temperatures and pressures and have often led to the production of inhibitors of fermentation. In this study, lignocellulosic materials from grass and newsprint were investigated as sources of biomass for bioethanol production using a chemical route (sulfuric acid hydrolysis) which made use of temperatures below 100°C at normal atmospheric pressure. Fermentation of toxic lignocellulosic hydrolyzates was possible after the development of a method for inhibitors removal. The method used treated wood chips as a stationary phase in a chromatographic column to remove inhibitors. This method is expected to be extended to applications such as in municipal wastewater treatment. Sugar yields of 22.26 and 8.9 g/L of hydrolyzate; and an ethanol yield of 184.5 and 130.4 mg/mL of must were achieved for 5g grass and newsprint respectively using optimum conditions of 2percent H2SO4 at 97.5°C for grass and 0.5percent H2SO4 at 97.5°C for newsprint during the hydrolysis process. Pure cellulose was used as a control for the biomass where 254.1 g/L of fermentable sugars were recovered from soluble cellulose and the yield of ethanol was 201.8 mg/mL. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
- Full Text:
- Date Issued: 2009-12
Synthesis of modified zinc oxide nanoparticles using pneumatic spray pyrolysis for solar cell application
- Authors: Ntozakhe, Luyolo
- Date: 2017
- Subjects: Zinc oxide -- Synthesis Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5862 , vital:29408
- Description: In this work, the pneumatic spray pyrolysis was used to synthesize un-doped and carbon doped zinc oxide (ZnO) nanoparticles. The zinc acetate, tetrabutylammonium bromide and ethanol were used as starting materials for the desired ZnO nanoparticles and the prepared samples were annealed at 400 oC in the furnace. The as synthesized un-doped and carbon doped ZnO NPs were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD analysis of the synthesized NPs revealed peaks at 31.90°, 34.50°, 36.34°, 47.73°, 56.88°, 63.04°, 68.20°, and 77.33° belonging to the hexagonal Wurtzite ZnO crystal structure. The incorporation of C species into ZnO lattice was cross examined by monitoring the peak positions of the (100), (002) and (001) planes. These three main peaks of C-ZnO NPs show a peak shift to higher 2θ values which indicates substitutional carbon doping in ZnO NPs. SEM analysis has revealed that the as synthesized NPs have spherical shape and the morphology of the NPs change as the concentration of carbon increases. The EDX spectra of both un-doped and doped ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV and 9.86 keV. Peaks at, X-ray energies of 0.51 keV and 1.01 keV respectively represent the emissions from the K-shell of oxygen and L-shell of zinc. The L-shell emission at 1.01 keV is considered as convolution of Zn 2p3/2 and Zn 2p1/2 photoelectron energies. The occurrence of these peaks in the EDX endorses the existence of Zn and O atoms in the PSP prepared samples. HRTEM analysis has revealed NPs size modal range from 6.65-14.21 nm for the PSP synthesized samples which is in mutual agreement with the XRD data calculated values. More over the selected area diffraction images displaying the fact that only the diffraction planes of (101), (002) and (100) are responsible for the diffraction pattern belonging to Wurtzite ZnO. RS analysis has revealed that the un-doped ZnO and doped ZnO samples have characteristic Raman vibration modes at 325 cm-1, and 434 cm-1 belonging to Wurtzite ZnO structure. Moreover, the prominent peak at 434 cm-1 which is the characteristic peak of E2(2) (high) mode of the Wurtzite ZnO and the E2(2) (high) has been red shifted by 4 cm-1, as compared to that found in the bulk ZnO. Additionally, the effect of carbon doping through Raman spectroscopy peak shifts of the E2(2) (high) mode, A1(LO) mode and multi-phonon has also been considered and discussed in detail. UV-Vis diffuse reflectance spectroscopy has revealed a red shift of the absorption edge with increase in C doping. Finally, the effect of nano-crystallite size and gradual prominence of C into ZnO lattice due to increase in C doping concentration in the PSP prepared nanoparticles was meticulously elaborated through Raman Spectroscopy analysis.
- Full Text:
- Date Issued: 2017
- Authors: Ntozakhe, Luyolo
- Date: 2017
- Subjects: Zinc oxide -- Synthesis Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5862 , vital:29408
- Description: In this work, the pneumatic spray pyrolysis was used to synthesize un-doped and carbon doped zinc oxide (ZnO) nanoparticles. The zinc acetate, tetrabutylammonium bromide and ethanol were used as starting materials for the desired ZnO nanoparticles and the prepared samples were annealed at 400 oC in the furnace. The as synthesized un-doped and carbon doped ZnO NPs were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD analysis of the synthesized NPs revealed peaks at 31.90°, 34.50°, 36.34°, 47.73°, 56.88°, 63.04°, 68.20°, and 77.33° belonging to the hexagonal Wurtzite ZnO crystal structure. The incorporation of C species into ZnO lattice was cross examined by monitoring the peak positions of the (100), (002) and (001) planes. These three main peaks of C-ZnO NPs show a peak shift to higher 2θ values which indicates substitutional carbon doping in ZnO NPs. SEM analysis has revealed that the as synthesized NPs have spherical shape and the morphology of the NPs change as the concentration of carbon increases. The EDX spectra of both un-doped and doped ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV and 9.86 keV. Peaks at, X-ray energies of 0.51 keV and 1.01 keV respectively represent the emissions from the K-shell of oxygen and L-shell of zinc. The L-shell emission at 1.01 keV is considered as convolution of Zn 2p3/2 and Zn 2p1/2 photoelectron energies. The occurrence of these peaks in the EDX endorses the existence of Zn and O atoms in the PSP prepared samples. HRTEM analysis has revealed NPs size modal range from 6.65-14.21 nm for the PSP synthesized samples which is in mutual agreement with the XRD data calculated values. More over the selected area diffraction images displaying the fact that only the diffraction planes of (101), (002) and (100) are responsible for the diffraction pattern belonging to Wurtzite ZnO. RS analysis has revealed that the un-doped ZnO and doped ZnO samples have characteristic Raman vibration modes at 325 cm-1, and 434 cm-1 belonging to Wurtzite ZnO structure. Moreover, the prominent peak at 434 cm-1 which is the characteristic peak of E2(2) (high) mode of the Wurtzite ZnO and the E2(2) (high) has been red shifted by 4 cm-1, as compared to that found in the bulk ZnO. Additionally, the effect of carbon doping through Raman spectroscopy peak shifts of the E2(2) (high) mode, A1(LO) mode and multi-phonon has also been considered and discussed in detail. UV-Vis diffuse reflectance spectroscopy has revealed a red shift of the absorption edge with increase in C doping. Finally, the effect of nano-crystallite size and gradual prominence of C into ZnO lattice due to increase in C doping concentration in the PSP prepared nanoparticles was meticulously elaborated through Raman Spectroscopy analysis.
- Full Text:
- Date Issued: 2017
Synthesis, characterisation and evaluation of functionalized Lignocelluloses-clay nanocomposites for organic pollutant removal from water
- Authors: Mafukidze, Donovan M
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11356 , http://hdl.handle.net/10353/d1021296
- Description: PMPSgLig-NaMMT nanocomposites were prepared from methacryloxypropyltrimethoxysilane (MPS), lignocellulose and montmorillonite clay. The potential enhancement of organic pollutant adsorption capabilities of PMPSgLig-NaMMT nanocomposite from water through functionalization was investigated. PMPSgLig-NaMMT was functionalized by esterification and etherification using different methods so as to increase the surface hydrophobicity of the material and hence improve its compatibility with the target pollutants. Specific chemical routes specially tailored for PMPSgLig-NaMMT were established for functionalization mostly based on the common esterification (Fischer esterification) and etherification (Williamson‟s etherification) reactions. In the functionalization methods, factors such as pH environment, nanocomposite composition, nature of functionalization moiety, and use of or absence of solvents and their variations were studied. FT-IR, XRD, SEM and TGA were used to characterize the synthesized and functionalized nanoadsorbents. The techniques showed successful functionalization via esterification and etherification methods albeit to different extents, with clear retention of the material‟s original structure though there were signs of degradation with some methods. Characterization was supported by adsorption studies to validate implications and draw conclusions. The use of 1,10-phenathroline as a model organic pollutant in water in the adsorption studies showed that adsorbents conformed to monolayer adsorption following pseudo-second order kinetics for adsorption of organic pollutants accurately represented. Most importantly the studies revealed the significant impact of the nanocomposite composition on the overall absorbent performance. Adsorption studies also showed that functionalization via esterification methods gave rise to better adsorbents.
- Full Text:
- Date Issued: 2015
- Authors: Mafukidze, Donovan M
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11356 , http://hdl.handle.net/10353/d1021296
- Description: PMPSgLig-NaMMT nanocomposites were prepared from methacryloxypropyltrimethoxysilane (MPS), lignocellulose and montmorillonite clay. The potential enhancement of organic pollutant adsorption capabilities of PMPSgLig-NaMMT nanocomposite from water through functionalization was investigated. PMPSgLig-NaMMT was functionalized by esterification and etherification using different methods so as to increase the surface hydrophobicity of the material and hence improve its compatibility with the target pollutants. Specific chemical routes specially tailored for PMPSgLig-NaMMT were established for functionalization mostly based on the common esterification (Fischer esterification) and etherification (Williamson‟s etherification) reactions. In the functionalization methods, factors such as pH environment, nanocomposite composition, nature of functionalization moiety, and use of or absence of solvents and their variations were studied. FT-IR, XRD, SEM and TGA were used to characterize the synthesized and functionalized nanoadsorbents. The techniques showed successful functionalization via esterification and etherification methods albeit to different extents, with clear retention of the material‟s original structure though there were signs of degradation with some methods. Characterization was supported by adsorption studies to validate implications and draw conclusions. The use of 1,10-phenathroline as a model organic pollutant in water in the adsorption studies showed that adsorbents conformed to monolayer adsorption following pseudo-second order kinetics for adsorption of organic pollutants accurately represented. Most importantly the studies revealed the significant impact of the nanocomposite composition on the overall absorbent performance. Adsorption studies also showed that functionalization via esterification methods gave rise to better adsorbents.
- Full Text:
- Date Issued: 2015
Synthesis, characterization & application of visible light responsive nitrogen doped Tio2 and copolymer-grafted asymmetric membranes with ozonolysis for water treatment
- Authors: Mungondori, Henry H
- Date: 2015
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11350 , http://hdl.handle.net/10353/d1020257
- Description: The use of titanium dioxide for the photo-catalytic removal of organic, inorganic, and microbial pollutants from natural water and wastewater has been considered a very promising technique. The aim of this study was to prepare nitrogen doped titanium dioxide, immobilize it on asymmetric polymeric membranes of poly (methacrylic acid) grafted onto poly (vinylidene difluoride) (PVDF) blended with poly (acrylonitrile) (PAN), and evaluate the photo-catalytic, antimicrobial, and antifouling properties of the membranes. Nitrogen doped titanium dioxide (N-TiO2) nano-particles were prepared by a low temperature sol gel synthesis technique. The modification of TiO2 with nitrogen allows photo-sensitization of the photo-catalyst towards visible light utilization. The N-TiO2 nano-particles were characterized by fourier transform infrared spectroscopy (FT-IR), scanning x-ray photoelectron spectroscopy (SXPS), X-ray diffraction analysis (XRD), diffuse reflectance spectroscopy (DRS), Brunauer Emmett Teller (BET) surface area analysis, and transmission electron microscopy (TEM). The characterizations revealed the presence of the expected functional groups and confirmed successful doping and that the product was visible light responsive. Novel poly (methacrylic acid) grafted onto poly (vinylidene difluoride)/ poly (acrylonitrile) (PMAA-g-PVDF/ PAN) asymmetric membranes were prepared by the dry-wet phase inversion technique. The poly (methacrylic acid) (PMAA) side chains where grafted onto an activated PVDF backbone by reversible addition fragmentation chain transfer (RAFT) polymerization. The photo-catalytic membranes were generated by blending N-TiO2 with the polymer solution before casting the membranes. The membranes were characterized by FT-IR, nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). FT-IR and NMR analyses confirmed successful grafting of MAA chains onto PVDF while SEM confirmed the successful preparation of membranes with asymmetric structure. The efficacy of the photo-catalytic asymmetric membranes was evaluated on the removal of herbicides from synthetic water. Bentazon was easily degraded while atrazine and paraquat were recalcitrant and proved difficult to degrade. The best results were observed with 3 % N-TiO2-PMAA-g-PVDF/ PAN asymmetric membranes on the photo-degradation of bentazon, atrazine and paraquat in water. Significant enhancement in the photo-degradation of the three herbicides was observed when photo-catalytic degradation was coupled with ozonation. Liquid chromatography-mass spectrometry (LC-MS) analysis confirmed the presence of a degradation by-product during the photo-catalytic degradation of bentazon. The photo-catalytic membranes were also evaluated on the photo-catalytic reduction of heavy metals Pb2+ and Fe3+ in water, and the best results were obtained using 1 % N-TiO2-PMAA-g-PVDF/ PAN and 1 % N-TiO2-PAN asymmetric membranes. All prepared photo-catalytic membranes where capable of completely inactivating E. coli ATCC 8739 within 120 minutes of exposure and inactivation rate increased with increasing N-TiO2 photo-catalyst loading. However, there was an indication from the results obtained that N-TiO2 supported on PMAA-g-PVDF/ PAN showed a higher inactivation rate of E. coli ATCC 8739 compared to N-TiO2-PAN and N-TiO2-PVDF membranes. The 1 % N-TiO2-PMAA-g-PVDF/ PAN membranes gave the highest pure water flux (421.83 L/m2h). This increase (PVDF = 30.50 L/m2h, PAN = 73.85 L/m2h) in pure water flux is owedb to PMAA grafting as well as addition of N-TiO2. These modifications resulted in an increased membrane surface hydrophilicity, which promoted permeation of pure water through the membrane structure. A high bovine serum albumin (BSA) rejection (76.5 %) was noted and can be attributed to steric hindrance brought about by PMAA side chains which prevented the bulky BSA molecules from attaching to the membrane surface for PMAA-g-PVDF/ PAN membranes. However, the supporting porous sub-layer of an asymmetric membrane seemed to play a very important role in the overall permeability of a membrane. PVDF membranes are highly hydrophobic hence they gave a very low pure water flux.
- Full Text:
- Date Issued: 2015
- Authors: Mungondori, Henry H
- Date: 2015
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11350 , http://hdl.handle.net/10353/d1020257
- Description: The use of titanium dioxide for the photo-catalytic removal of organic, inorganic, and microbial pollutants from natural water and wastewater has been considered a very promising technique. The aim of this study was to prepare nitrogen doped titanium dioxide, immobilize it on asymmetric polymeric membranes of poly (methacrylic acid) grafted onto poly (vinylidene difluoride) (PVDF) blended with poly (acrylonitrile) (PAN), and evaluate the photo-catalytic, antimicrobial, and antifouling properties of the membranes. Nitrogen doped titanium dioxide (N-TiO2) nano-particles were prepared by a low temperature sol gel synthesis technique. The modification of TiO2 with nitrogen allows photo-sensitization of the photo-catalyst towards visible light utilization. The N-TiO2 nano-particles were characterized by fourier transform infrared spectroscopy (FT-IR), scanning x-ray photoelectron spectroscopy (SXPS), X-ray diffraction analysis (XRD), diffuse reflectance spectroscopy (DRS), Brunauer Emmett Teller (BET) surface area analysis, and transmission electron microscopy (TEM). The characterizations revealed the presence of the expected functional groups and confirmed successful doping and that the product was visible light responsive. Novel poly (methacrylic acid) grafted onto poly (vinylidene difluoride)/ poly (acrylonitrile) (PMAA-g-PVDF/ PAN) asymmetric membranes were prepared by the dry-wet phase inversion technique. The poly (methacrylic acid) (PMAA) side chains where grafted onto an activated PVDF backbone by reversible addition fragmentation chain transfer (RAFT) polymerization. The photo-catalytic membranes were generated by blending N-TiO2 with the polymer solution before casting the membranes. The membranes were characterized by FT-IR, nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). FT-IR and NMR analyses confirmed successful grafting of MAA chains onto PVDF while SEM confirmed the successful preparation of membranes with asymmetric structure. The efficacy of the photo-catalytic asymmetric membranes was evaluated on the removal of herbicides from synthetic water. Bentazon was easily degraded while atrazine and paraquat were recalcitrant and proved difficult to degrade. The best results were observed with 3 % N-TiO2-PMAA-g-PVDF/ PAN asymmetric membranes on the photo-degradation of bentazon, atrazine and paraquat in water. Significant enhancement in the photo-degradation of the three herbicides was observed when photo-catalytic degradation was coupled with ozonation. Liquid chromatography-mass spectrometry (LC-MS) analysis confirmed the presence of a degradation by-product during the photo-catalytic degradation of bentazon. The photo-catalytic membranes were also evaluated on the photo-catalytic reduction of heavy metals Pb2+ and Fe3+ in water, and the best results were obtained using 1 % N-TiO2-PMAA-g-PVDF/ PAN and 1 % N-TiO2-PAN asymmetric membranes. All prepared photo-catalytic membranes where capable of completely inactivating E. coli ATCC 8739 within 120 minutes of exposure and inactivation rate increased with increasing N-TiO2 photo-catalyst loading. However, there was an indication from the results obtained that N-TiO2 supported on PMAA-g-PVDF/ PAN showed a higher inactivation rate of E. coli ATCC 8739 compared to N-TiO2-PAN and N-TiO2-PVDF membranes. The 1 % N-TiO2-PMAA-g-PVDF/ PAN membranes gave the highest pure water flux (421.83 L/m2h). This increase (PVDF = 30.50 L/m2h, PAN = 73.85 L/m2h) in pure water flux is owedb to PMAA grafting as well as addition of N-TiO2. These modifications resulted in an increased membrane surface hydrophilicity, which promoted permeation of pure water through the membrane structure. A high bovine serum albumin (BSA) rejection (76.5 %) was noted and can be attributed to steric hindrance brought about by PMAA side chains which prevented the bulky BSA molecules from attaching to the membrane surface for PMAA-g-PVDF/ PAN membranes. However, the supporting porous sub-layer of an asymmetric membrane seemed to play a very important role in the overall permeability of a membrane. PVDF membranes are highly hydrophobic hence they gave a very low pure water flux.
- Full Text:
- Date Issued: 2015
Synthesis, characterization & comparative evaluation of photo-catalytic & antimicrobial activity of Ag2O and TiO2 immobilized on nanofibres for treatment
- Authors: Gxumisa, Xoliswa
- Date: 2014
- Subjects: Pollution http://id.loc.gov/authorities/subjects/sh85104530 , Titanium dioxide http://id.loc.gov/authorities/subjects/sh85135627 , Photocatalysis http://id.loc.gov/authorities/subjects/sh93001301
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19545 , vital:43138
- Description: Water is a very essential substance for the existence of organisms and the environment where it functions as a transport medium for valuable chemicals, minerals, nutrients and also as a reaction medium. However, the remarkable water properties are not just limited to the dissolution of biological valuable substances, but also to harmful entities during pollution. This has led to research in the improvement and development of new techniques for water treatment. In this study, titanium dioxide (TiO2) and silver oxide (Ag2O) were prepared using the sol gel process and precipitation method respectively. The TiO2 was doped using a sol gel process with carbon and nitrogen so as to reduce the band gap. TiO2/Ag2O, N-TiO2/Ag2O and C-TiO2/Ag2O composites were also prepared using a precipitation method. The average particle size of prepared TiO2, C-TiO2, N-TiO2, Ag2O, TiO2/Ag2O, N-TiO2/Ag2O and CTiO2/Ag2O was found to be 13nm, 7nm, 10nm, 23nm, 28nm, 24nm and 21nm respectively as measured by TEM analysis. The photo-catalysts, Ag2O and TiO2 and their composites were immobilized on stabilized nanofibres using the electrospinning process to allow subsequent separation and reconciliation of the photo-catalyst after use in water treatment. The photocatalytic and antimicrobial activities of photo-catalysts were also evaluated using water contaminated with phenol red dye and Escherichia coli. The prepared materials were characterized by XRD, TEM, HRSEM, DRS, EDX, FT-IR, and TGA. Carbon was found to be more effective as a dopant than nitrogen. It reduced the band gap by 0.4 while nitrogen doping showed a reduction in band gap of 0.2 compared to undoped titanium dioxide. The doped TiO2 exhibited higher photo-catalytic and antimicrobial activity than the undoped TiO2. Introduction of Ag2O allowed utilization of visible light by the TiO2- Ag2O nano-composite leading to an improved rate of photo-degradation of phenol red and inactivation of E coli. Photo-catalytic properties showed that carbon doped materials have a higher photo-catalytic activity than nitrogen doped materials, while for antimicrobial v properties it is vice-versa. The immobilization of photo-catalysts on support material made it less effective towards the degradation of phenol red. The rate of photo-oxidation of phenol red was three times faster using powder TiO2 compared to immobilized TiO2. Therefore, this study suggests that photo-catalysis can be used as an effective method for water disinfection and production of potable and pathogen free drinking water even though better methods of immobilization should be sought. , Thesis (MSc) (Chemistry) -- University of Fort Hare, 2014
- Full Text:
- Date Issued: 2014
- Authors: Gxumisa, Xoliswa
- Date: 2014
- Subjects: Pollution http://id.loc.gov/authorities/subjects/sh85104530 , Titanium dioxide http://id.loc.gov/authorities/subjects/sh85135627 , Photocatalysis http://id.loc.gov/authorities/subjects/sh93001301
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19545 , vital:43138
- Description: Water is a very essential substance for the existence of organisms and the environment where it functions as a transport medium for valuable chemicals, minerals, nutrients and also as a reaction medium. However, the remarkable water properties are not just limited to the dissolution of biological valuable substances, but also to harmful entities during pollution. This has led to research in the improvement and development of new techniques for water treatment. In this study, titanium dioxide (TiO2) and silver oxide (Ag2O) were prepared using the sol gel process and precipitation method respectively. The TiO2 was doped using a sol gel process with carbon and nitrogen so as to reduce the band gap. TiO2/Ag2O, N-TiO2/Ag2O and C-TiO2/Ag2O composites were also prepared using a precipitation method. The average particle size of prepared TiO2, C-TiO2, N-TiO2, Ag2O, TiO2/Ag2O, N-TiO2/Ag2O and CTiO2/Ag2O was found to be 13nm, 7nm, 10nm, 23nm, 28nm, 24nm and 21nm respectively as measured by TEM analysis. The photo-catalysts, Ag2O and TiO2 and their composites were immobilized on stabilized nanofibres using the electrospinning process to allow subsequent separation and reconciliation of the photo-catalyst after use in water treatment. The photocatalytic and antimicrobial activities of photo-catalysts were also evaluated using water contaminated with phenol red dye and Escherichia coli. The prepared materials were characterized by XRD, TEM, HRSEM, DRS, EDX, FT-IR, and TGA. Carbon was found to be more effective as a dopant than nitrogen. It reduced the band gap by 0.4 while nitrogen doping showed a reduction in band gap of 0.2 compared to undoped titanium dioxide. The doped TiO2 exhibited higher photo-catalytic and antimicrobial activity than the undoped TiO2. Introduction of Ag2O allowed utilization of visible light by the TiO2- Ag2O nano-composite leading to an improved rate of photo-degradation of phenol red and inactivation of E coli. Photo-catalytic properties showed that carbon doped materials have a higher photo-catalytic activity than nitrogen doped materials, while for antimicrobial v properties it is vice-versa. The immobilization of photo-catalysts on support material made it less effective towards the degradation of phenol red. The rate of photo-oxidation of phenol red was three times faster using powder TiO2 compared to immobilized TiO2. Therefore, this study suggests that photo-catalysis can be used as an effective method for water disinfection and production of potable and pathogen free drinking water even though better methods of immobilization should be sought. , Thesis (MSc) (Chemistry) -- University of Fort Hare, 2014
- Full Text:
- Date Issued: 2014
Synthesis, characterization and antibacterial studies of metal complexes of substituted thiourea
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
Synthesis, characterization and anticancer studies of Oxovanadium(iv) Dithiocarbamate complexes
- Authors: Hlobo, Priscilla Vuyiswa
- Date: 2019
- Subjects: Inorganic compounds -- Synthesis Chemistry, Inorganic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19131 , vital:39880
- Description: Eight new oxovanadium(IV) dithiocarbamate complexes, formed by the interaction of vanadyl sulfate pentahydrate and as-synthesized dithiocarbamate ligands, potassium N-morpholine-4- dithiocarbamate ligand (L1), potassium N-piperidinedithiocarbamate (L2), potassium N-(4- methoxyphenyl)dithiocarbamate ligand (L3), potassium N-diallyldithiocarbamate ligand (L4), potassium N-phenyldithiocarbamate ligand (L5), potassium N-dibenzylminedithiocarbamate ligand (L6), potassium N-(4-methylphenyl)dithiocarbamate ligand (L7), N-(1Himidazoledithiocarbamate) fluoride ligand (L8) in aqueous ethanol are described. The resulting complexes were elemental analyses, molar conductance, infrared, electronic, and nuclear magnetic resonance spectral studies. The spectral studies confirmed the formation of the ligands and complexes. Four complexes [VO(L1)2], [VO(L3)2], [VO(L6)2], and [VO(L8)2] derived from potassium N-morpholine-4-dithiocarbamate ligand (L1), potassium N-(4- methoxyphenyl)dithiocarbamate ligand (L3), potassium N-dibenzylminedithiocarbamate ligand (L6), and N-(1H-imidazoledithiocarbamate) fluoride ligand (L8) were characterized using cyclic voltammetry, to study their electrochemical behavior. Square pyramid oxovanadium(IV) complexes were proposed with the metal ion coordinated to two bidentate dithiocarbamate ligands through sulphur to complete its square pyramidal geometry. The anticancer screening of four oxovanadium(IV) dithiocarbamate complexes [VO(L1)2], [VO(L3)2], [VO(L6)2], and [VO(L8)2] are described.
- Full Text:
- Date Issued: 2019
- Authors: Hlobo, Priscilla Vuyiswa
- Date: 2019
- Subjects: Inorganic compounds -- Synthesis Chemistry, Inorganic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19131 , vital:39880
- Description: Eight new oxovanadium(IV) dithiocarbamate complexes, formed by the interaction of vanadyl sulfate pentahydrate and as-synthesized dithiocarbamate ligands, potassium N-morpholine-4- dithiocarbamate ligand (L1), potassium N-piperidinedithiocarbamate (L2), potassium N-(4- methoxyphenyl)dithiocarbamate ligand (L3), potassium N-diallyldithiocarbamate ligand (L4), potassium N-phenyldithiocarbamate ligand (L5), potassium N-dibenzylminedithiocarbamate ligand (L6), potassium N-(4-methylphenyl)dithiocarbamate ligand (L7), N-(1Himidazoledithiocarbamate) fluoride ligand (L8) in aqueous ethanol are described. The resulting complexes were elemental analyses, molar conductance, infrared, electronic, and nuclear magnetic resonance spectral studies. The spectral studies confirmed the formation of the ligands and complexes. Four complexes [VO(L1)2], [VO(L3)2], [VO(L6)2], and [VO(L8)2] derived from potassium N-morpholine-4-dithiocarbamate ligand (L1), potassium N-(4- methoxyphenyl)dithiocarbamate ligand (L3), potassium N-dibenzylminedithiocarbamate ligand (L6), and N-(1H-imidazoledithiocarbamate) fluoride ligand (L8) were characterized using cyclic voltammetry, to study their electrochemical behavior. Square pyramid oxovanadium(IV) complexes were proposed with the metal ion coordinated to two bidentate dithiocarbamate ligands through sulphur to complete its square pyramidal geometry. The anticancer screening of four oxovanadium(IV) dithiocarbamate complexes [VO(L1)2], [VO(L3)2], [VO(L6)2], and [VO(L8)2] are described.
- Full Text:
- Date Issued: 2019
Synthesis, characterization and biological evaluation of xanthate metal complexes
- Authors: Casa, Sandisiwe
- Date: 2014-01
- Subjects: Metal complexes , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24250 , vital:62594
- Description: Ni(II), Ag(I), Cu(II), Pd(II) and Pt(II) complexes of xanthate were synthesized and characterized by elemental analysis, UV‒Vis, FTIR, conductivity measurements, decomposition temperatures, and Pd(II), Pt(II) complexes and the xanthate ligands were further characterized by 1H-NMR spectroscopy. Conductivity measurements displayed that the complexes are non‒electrolytes in solution with conductivity values in the range 0.05 ‒ 18.30 μS. Generally all the xanthate ligands are soluble in water and the complexes are insoluble both in non-polar solvents except polar coordinating solvents such as DMSO and DMF. The xanthate complexes are formulated as four coordinate (tetrahedral or square planar), and six coordinate (octahedral) compounds. However, in each of the complexes xanthate acted as bidentate ligand through the two sulfur atoms. The geometries around the metal ions are completed by triphenylphosphine. The ligands and complexes were screened against two bacterial isolates to determine their antibacterial activities. Antibacterial activity of the synthesized metal complexes shows a generally increased activity in comparison with that of their respective free ligands. At a lower concentration some of the complexes did not show any activity, a good number of complexes however showed activity at a higher concentration of 40 mg/ml. The degree of activity varies with metals. Silver complex have been observed to show the highest activity of MIC value of 1.25 mg/mL with regards to antibacterial strength, although it varies with different ligands. , Thesis (MSc) -- Faculty of Science and Agriculture, 2014
- Full Text:
- Date Issued: 2014-01
- Authors: Casa, Sandisiwe
- Date: 2014-01
- Subjects: Metal complexes , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24250 , vital:62594
- Description: Ni(II), Ag(I), Cu(II), Pd(II) and Pt(II) complexes of xanthate were synthesized and characterized by elemental analysis, UV‒Vis, FTIR, conductivity measurements, decomposition temperatures, and Pd(II), Pt(II) complexes and the xanthate ligands were further characterized by 1H-NMR spectroscopy. Conductivity measurements displayed that the complexes are non‒electrolytes in solution with conductivity values in the range 0.05 ‒ 18.30 μS. Generally all the xanthate ligands are soluble in water and the complexes are insoluble both in non-polar solvents except polar coordinating solvents such as DMSO and DMF. The xanthate complexes are formulated as four coordinate (tetrahedral or square planar), and six coordinate (octahedral) compounds. However, in each of the complexes xanthate acted as bidentate ligand through the two sulfur atoms. The geometries around the metal ions are completed by triphenylphosphine. The ligands and complexes were screened against two bacterial isolates to determine their antibacterial activities. Antibacterial activity of the synthesized metal complexes shows a generally increased activity in comparison with that of their respective free ligands. At a lower concentration some of the complexes did not show any activity, a good number of complexes however showed activity at a higher concentration of 40 mg/ml. The degree of activity varies with metals. Silver complex have been observed to show the highest activity of MIC value of 1.25 mg/mL with regards to antibacterial strength, although it varies with different ligands. , Thesis (MSc) -- Faculty of Science and Agriculture, 2014
- Full Text:
- Date Issued: 2014-01
Synthesis, characterization and evaluation of photophysical and electrochemical properties of ruthenium(II) complexes for dye-sensitized solar cells
- Authors: Adjogri, Shadrack John
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/17828 , vital:41363
- Description: Eight series of thirty (30) novel heteroleptic ruthenium(II) complexes were designed, synthesized and spectroscopically characterized, with the following general molecular formulae as [Ru(bdmpmar)(H2dcbpy)(NCS)]+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2+,[Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ where bdmpmar is a tridentate ligand of N,N-bis(3, 5-dimethylpyrazol-1-yl-methyl) aromatic organic compound (such aromatic organic compounds(Ar) are anthranilic acid, 4-methoxy-2-nitroaniline, aniline, toluidine, cyclohexylamine and anisidine), vpdiinp represents a monodentate ligand of 11-(4-vinylphenyl)diindeno[1,2-b:2’,1’-e]pyridine, vpbpp represents a monodentate ligand of 4-(4-vinylphenyl)-2.6-bis(phenyl)pyridine and vptpy represents a tridentate ligand of 4’-(4-vinyl)-2,2’:6’,2’’-terpyridine. Meanwhile, N^ represents any of the monodentate ligands of either vpdiinp or vpbpp and (N^^^) represents any of the monodentate ligands either of vpdiinp or vpbpp or NCS as disclosed in series VIII. The complexes were characterized by conductivity measurement, solubility, melting point, UV-Vis, PL, FTIR (ATR), NMR, Cyclic and square wave voltammetry. Nine chelating ligands, comprising of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand, were used for the synthesis of ruthenium(II) complexes ATR-FTIR spectra of all the ruthenium(II) complexes measured as solid samples, exhibited fine resolution IR bands in region between 3473-3438 cm-1 of carboxylic group in H2dcbpy. The bands in the range 3040-2950 cm-1 were ascribed to C-H bond stretching for the CH3 groups. The coordination of NCS group in the sphere of ruthenium(II) complexes related to series I, IV, VI VII and one compound of series VIII was investigated by ATR-FTIR spectroscopy. Bands in the range of 2116-2106 cm-1 and 777-770 cm-1 are ascribed to the respective N=C and the C=S bond stretching vibration which confirms the N-coordination of the SCN group. For all the complexes, the stretching vibration of Ru-N bonding was between 466 and 411 cm-1 due to coordination of the nitrogen atoms of the ligands to ruthenium central metal atom. The introduction of the two vinyl monodentate ligands (vpdiinp and vpbpp) in the coordination sphere of [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2+, [Ru(bdmpmar) (vpbpp)(H2dcbpy)]2+, [Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, all related to series II, III, IV, V, VI, VII and two compounds of series VIII ruthenium(II) complexes, has been studied using the 1H and 13C NMR spectroscopy techniques. The 1H NMR spectra of series II-VII and the two compounds of series VIII of the ruthenium(II) complexes show multiplets in the aromatic region above 6 ppm due to the presence of either vpdiinp or vpbpp ligand, situated in different magnetic environment. However, no splitting pattern was observed in series I and part of VIII complexes possibly due to the absence vinyl monodentate subunits (vpdiinp and vpbpp) in series I and one of compound in series VIII ruthenium(II) complexes show no signals of complex splitting patterns. Carbon-13 NMR spectra data of series I to VIII ruthenium(II) complexes show most resonance signals range in the aromatic region of (δ 116.54-199.63ppm) corresponding to the molecular formulation of ruthenium(II) complexes incorporating 4,4-dicarboxy-2,2’-bipyridine, bdmpmar, vptpy, vpdiinp or vpbpp and NCS ligands respectively, depending on the intrinsic ligand variations. Carbon-13 NMR spectra data of series I, IV, VI VII and one compound in VIII show resonance peaks within the range 130-135 ppm are ascribed to NCS ligand confirming the presence of N-coordinated thiocyanate. Cyclic voltammograms of series I-IV and VI-VIII complexes display ruthenium-based oxidative peaks and the pyridines ligand-based reductive peaks. The redox behavior of complexes 4-12, 14-16, 18-20, 24-26 and 30 is dominated by the Ru(II)/R(III) redox couple in region (E1/2 between 0.53 and 1.18) and the pyridines ligand-based redox couples in the region between (E1/2 between −0.25 and −1.45). The photophysical property studies of the Ru(II) complexes are determined through the acquisitions of the absorption spectra, which tends to have profound effect on the short circuit current of DSSC. The absorption maxima were tuned by the introduction and variation of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand. From the studies, the results show that series IV, V, VI, VII and VIII complexes of molecular formula [Ru(H2dcbpy)2(N^)(NCS)]2+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2]2+, [Ru(H2dcbpy)(N^)(NCS)3]2+ and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, have higher and multiple local absorption maxima near-IR region than the complexes of series I, II and III of molecular [Ru(bdmpmar)(H2dcbpy)(NCS)]2,+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2,+respectively.
- Full Text:
- Date Issued: 2018
- Authors: Adjogri, Shadrack John
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/17828 , vital:41363
- Description: Eight series of thirty (30) novel heteroleptic ruthenium(II) complexes were designed, synthesized and spectroscopically characterized, with the following general molecular formulae as [Ru(bdmpmar)(H2dcbpy)(NCS)]+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2+,[Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ where bdmpmar is a tridentate ligand of N,N-bis(3, 5-dimethylpyrazol-1-yl-methyl) aromatic organic compound (such aromatic organic compounds(Ar) are anthranilic acid, 4-methoxy-2-nitroaniline, aniline, toluidine, cyclohexylamine and anisidine), vpdiinp represents a monodentate ligand of 11-(4-vinylphenyl)diindeno[1,2-b:2’,1’-e]pyridine, vpbpp represents a monodentate ligand of 4-(4-vinylphenyl)-2.6-bis(phenyl)pyridine and vptpy represents a tridentate ligand of 4’-(4-vinyl)-2,2’:6’,2’’-terpyridine. Meanwhile, N^ represents any of the monodentate ligands of either vpdiinp or vpbpp and (N^^^) represents any of the monodentate ligands either of vpdiinp or vpbpp or NCS as disclosed in series VIII. The complexes were characterized by conductivity measurement, solubility, melting point, UV-Vis, PL, FTIR (ATR), NMR, Cyclic and square wave voltammetry. Nine chelating ligands, comprising of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand, were used for the synthesis of ruthenium(II) complexes ATR-FTIR spectra of all the ruthenium(II) complexes measured as solid samples, exhibited fine resolution IR bands in region between 3473-3438 cm-1 of carboxylic group in H2dcbpy. The bands in the range 3040-2950 cm-1 were ascribed to C-H bond stretching for the CH3 groups. The coordination of NCS group in the sphere of ruthenium(II) complexes related to series I, IV, VI VII and one compound of series VIII was investigated by ATR-FTIR spectroscopy. Bands in the range of 2116-2106 cm-1 and 777-770 cm-1 are ascribed to the respective N=C and the C=S bond stretching vibration which confirms the N-coordination of the SCN group. For all the complexes, the stretching vibration of Ru-N bonding was between 466 and 411 cm-1 due to coordination of the nitrogen atoms of the ligands to ruthenium central metal atom. The introduction of the two vinyl monodentate ligands (vpdiinp and vpbpp) in the coordination sphere of [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2+, [Ru(bdmpmar) (vpbpp)(H2dcbpy)]2+, [Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, all related to series II, III, IV, V, VI, VII and two compounds of series VIII ruthenium(II) complexes, has been studied using the 1H and 13C NMR spectroscopy techniques. The 1H NMR spectra of series II-VII and the two compounds of series VIII of the ruthenium(II) complexes show multiplets in the aromatic region above 6 ppm due to the presence of either vpdiinp or vpbpp ligand, situated in different magnetic environment. However, no splitting pattern was observed in series I and part of VIII complexes possibly due to the absence vinyl monodentate subunits (vpdiinp and vpbpp) in series I and one of compound in series VIII ruthenium(II) complexes show no signals of complex splitting patterns. Carbon-13 NMR spectra data of series I to VIII ruthenium(II) complexes show most resonance signals range in the aromatic region of (δ 116.54-199.63ppm) corresponding to the molecular formulation of ruthenium(II) complexes incorporating 4,4-dicarboxy-2,2’-bipyridine, bdmpmar, vptpy, vpdiinp or vpbpp and NCS ligands respectively, depending on the intrinsic ligand variations. Carbon-13 NMR spectra data of series I, IV, VI VII and one compound in VIII show resonance peaks within the range 130-135 ppm are ascribed to NCS ligand confirming the presence of N-coordinated thiocyanate. Cyclic voltammograms of series I-IV and VI-VIII complexes display ruthenium-based oxidative peaks and the pyridines ligand-based reductive peaks. The redox behavior of complexes 4-12, 14-16, 18-20, 24-26 and 30 is dominated by the Ru(II)/R(III) redox couple in region (E1/2 between 0.53 and 1.18) and the pyridines ligand-based redox couples in the region between (E1/2 between −0.25 and −1.45). The photophysical property studies of the Ru(II) complexes are determined through the acquisitions of the absorption spectra, which tends to have profound effect on the short circuit current of DSSC. The absorption maxima were tuned by the introduction and variation of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand. From the studies, the results show that series IV, V, VI, VII and VIII complexes of molecular formula [Ru(H2dcbpy)2(N^)(NCS)]2+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2]2+, [Ru(H2dcbpy)(N^)(NCS)3]2+ and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, have higher and multiple local absorption maxima near-IR region than the complexes of series I, II and III of molecular [Ru(bdmpmar)(H2dcbpy)(NCS)]2,+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2,+respectively.
- Full Text:
- Date Issued: 2018
Synthesis, characterization and in vitro antibacterial analysis of carvacrol based-hybrid analogues
- Authors: Mbese, Zintle
- Date: 2019
- Subjects: Medicinal plants Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14527 , vital:39998
- Description: he focus of this research was to synthesize and characterize carvacrol hybrid analogues. Twenty-one (21) carvacrol analogues were synthesized by reacting carvacrol with (1. 4- aminosalicylic acid, 2. ferrocene keto-butanoic acid, 3. Ferrocene butanoic acid, 4. succinic anhydride, 5. folic acid, 6. cinnamic acid, 7. leucovorin, 8. oleanolic acid, 9. artesunate, 10. cholesterol, 11. cholesterol succinate, 12. curcumin, 13. curcumin succinate, 14. zidovudine, 15. Zidovudine succinate, 16. 8-hydroxyquinoline, 17. 8-hydroxyquinoline succinate, 18. 2- (7-chloroquinolin-4-ylamino)ethyl 5-isopropyl-2-methylphenyl, 19. 2-(7-chloroquinolin-4- ylamino)ethyl 5-isopropyl-2-methylphenyl succinate, 20. 2-(2-(7-chloroquinolin-4- ylamino)ethoxy)ethyl 5-isopropyl-2-methylphenyl, 21. 2-(2-(7-chloroquinolin-4- ylamino)ethoxy)ethyl 5-isopropyl-2-methylphenyl succinate). The carvacrol analogues were characterized using FTIR, UHPLC-HRMS, 1H- and 13C-NMR spectroscopy. The antibacterial analysis was performed to evaluate the carvacrol analogues against bacterial strains. FTIR spectra of carvacrol analogues were found to exhibit peaks of C-O stretch and Ar-C in a range of 1014-1280 cm-1 and a range of 1414-1697 cm-1 which confirm the successful formation of esters. The proposed structures of carvacrol analogues were confirmed by the 1H- and 13C-NMR. The selected 1H-NMR signal for aromatic protons ranged at 6.00-8.95 ppm/δ. The selected 13C-NMR signal for ester carbon and aromatic carbons ranged at 160.0-175.0 ppm/δ and at 110.00-154.00 ppm/δ. The structures were also confirmed by UHPLC-HRMS. Carvacrol analogues exhibited the highest inhibitory effect against Gram-positive and Gram-negative tested bacterial strains.
- Full Text:
- Date Issued: 2019
- Authors: Mbese, Zintle
- Date: 2019
- Subjects: Medicinal plants Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14527 , vital:39998
- Description: he focus of this research was to synthesize and characterize carvacrol hybrid analogues. Twenty-one (21) carvacrol analogues were synthesized by reacting carvacrol with (1. 4- aminosalicylic acid, 2. ferrocene keto-butanoic acid, 3. Ferrocene butanoic acid, 4. succinic anhydride, 5. folic acid, 6. cinnamic acid, 7. leucovorin, 8. oleanolic acid, 9. artesunate, 10. cholesterol, 11. cholesterol succinate, 12. curcumin, 13. curcumin succinate, 14. zidovudine, 15. Zidovudine succinate, 16. 8-hydroxyquinoline, 17. 8-hydroxyquinoline succinate, 18. 2- (7-chloroquinolin-4-ylamino)ethyl 5-isopropyl-2-methylphenyl, 19. 2-(7-chloroquinolin-4- ylamino)ethyl 5-isopropyl-2-methylphenyl succinate, 20. 2-(2-(7-chloroquinolin-4- ylamino)ethoxy)ethyl 5-isopropyl-2-methylphenyl, 21. 2-(2-(7-chloroquinolin-4- ylamino)ethoxy)ethyl 5-isopropyl-2-methylphenyl succinate). The carvacrol analogues were characterized using FTIR, UHPLC-HRMS, 1H- and 13C-NMR spectroscopy. The antibacterial analysis was performed to evaluate the carvacrol analogues against bacterial strains. FTIR spectra of carvacrol analogues were found to exhibit peaks of C-O stretch and Ar-C in a range of 1014-1280 cm-1 and a range of 1414-1697 cm-1 which confirm the successful formation of esters. The proposed structures of carvacrol analogues were confirmed by the 1H- and 13C-NMR. The selected 1H-NMR signal for aromatic protons ranged at 6.00-8.95 ppm/δ. The selected 13C-NMR signal for ester carbon and aromatic carbons ranged at 160.0-175.0 ppm/δ and at 110.00-154.00 ppm/δ. The structures were also confirmed by UHPLC-HRMS. Carvacrol analogues exhibited the highest inhibitory effect against Gram-positive and Gram-negative tested bacterial strains.
- Full Text:
- Date Issued: 2019
Synthesis, characterization and in vitro antiplasmodial evaluation of 4-& 8-aminoquinoline based-hybrid compounds
- Authors: Nqoro, Xhamla
- Date: 2018
- Subjects: Plasmodium falciparum
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14649 , vital:40026
- Description: Malaria is a deadly disease and its drug resistance has been reported to be a challenge globally. The death toll caused by malaria has increased rapidly in different regions of the world. Quinoline scaffold molecules are combined with other classes of antimalarials to tackle drug resistance. The combination of quinoline scaffolds with other antimalarial compounds and metals-based drugs have been reported to be a potential approach to overcome drug resistance common in the currently used antimalarials. 4-Aminoquinoline was hybridized with selected organic molecules and metal-based compounds to form a class of hybrid compounds containing either an amide bond or ester bond as a linker between the parent molecules. 4-Aminoquinoline derivatives are known compounds and they were prepared via known synthetic routes and characterized. The hybrid compounds were characterized and the FTIR results confirmed the successful linkage of 4-aminoquinoline derivatives to selected organic scaffolds to form hybrid compounds. NMR results confirmed the successful formation of hybrid compounds. MS showed signals of the hybrid molecules confirming the successful isolation of the hybrid compounds. In vitro antiplasmodial assay was performed against asexual parasite and chloroquine was used as a reference drug. The percentage inhibition effects of the hybrid compounds were in a range of 96-102% at 5 µM and 36-96% at 1 µM suggesting that the percentage inhibition effect of the hybrid compounds was influenced by the drug concentration. Hybridization of either 4-aminosalicylic scaffold or ferrocene butanoic acid with 4- aminoquinoline derivatives is a potential synthetic route that can result in potent antimalarials. However, more research is needed to fully understand the structure-activity relationship of these hybrid compounds.
- Full Text:
- Date Issued: 2018
- Authors: Nqoro, Xhamla
- Date: 2018
- Subjects: Plasmodium falciparum
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14649 , vital:40026
- Description: Malaria is a deadly disease and its drug resistance has been reported to be a challenge globally. The death toll caused by malaria has increased rapidly in different regions of the world. Quinoline scaffold molecules are combined with other classes of antimalarials to tackle drug resistance. The combination of quinoline scaffolds with other antimalarial compounds and metals-based drugs have been reported to be a potential approach to overcome drug resistance common in the currently used antimalarials. 4-Aminoquinoline was hybridized with selected organic molecules and metal-based compounds to form a class of hybrid compounds containing either an amide bond or ester bond as a linker between the parent molecules. 4-Aminoquinoline derivatives are known compounds and they were prepared via known synthetic routes and characterized. The hybrid compounds were characterized and the FTIR results confirmed the successful linkage of 4-aminoquinoline derivatives to selected organic scaffolds to form hybrid compounds. NMR results confirmed the successful formation of hybrid compounds. MS showed signals of the hybrid molecules confirming the successful isolation of the hybrid compounds. In vitro antiplasmodial assay was performed against asexual parasite and chloroquine was used as a reference drug. The percentage inhibition effects of the hybrid compounds were in a range of 96-102% at 5 µM and 36-96% at 1 µM suggesting that the percentage inhibition effect of the hybrid compounds was influenced by the drug concentration. Hybridization of either 4-aminosalicylic scaffold or ferrocene butanoic acid with 4- aminoquinoline derivatives is a potential synthetic route that can result in potent antimalarials. However, more research is needed to fully understand the structure-activity relationship of these hybrid compounds.
- Full Text:
- Date Issued: 2018
Synthesis, characterization and photophysical studies of RU(II)bipyridyl-dithiocarbamate complexes as sensitizers for dye sensitized solar cells
- Authors: Fudo, Zintle
- Date: 2018
- Subjects: Dye-sensitized solar cells Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6168 , vital:29498
- Description: The depletion of fossil fuels and the increasing energy demand for energy has led to the search for better and improved technologies with special focus renewable energy, especially solar cells. The first generation solar cells based on silicon are expensive, hence dye sensitized solar cells come in as a better alternative as these solar cells are environmental friendly, they have moderately good conversion efficiency and they are relatively cheap to produce. Dithiocarbamate ligands have been widely used in many research fields, as these are versatile ligands. Coordination of dithiocarbamates with metals such as ruthenium has produced high conversion efficiency and have the ability to extend the MLCT absorptions, and this can further extend their wavelength. In this study five dithiocarbamate sodium salt ligands were prepared and were coded as FL1= Aniline, FL2= p- toluidine, FL3= p- anisidine, FL4=dibenzyl, FL5=diphenyl. These ligands were used to synthesize Ru(II) metal complexes which were formulated as [Ru(FLx)(dcbpy)(NCS)] and [Ru(FLx)2(dcbpy)] where FLx is the dithiocarbamate ligand and dcbpy is 2,2-bipyridine-4,4’-dicarboxylic acid and the complexes were coded as FCx. The synthesized compounds were characterized using techniques such as the melting point, molar conductivity, FT-IR and NMR spectroscopy. For spectroelectrochemical studies of the metal complexes, techniques such as UV-Vis and photoluminescence spectroscopy were carried out. Furthermore, redox properties of the complexes were analyzed using cyclic and square wave voltammetry. The FT-IR displayed all the expected peaks of interest both in the dithiocarbamate ligands and in the metal complexes. The electronic spectra confirmed the successful coordination of ligand to the metal centre, the electronic spectra of the complexes also confirmed the six coordinate octahedral geometry of the complexes. The complexes exhibited some photoluminescence properties that are suitable for dye sensitization. The cyclic voltammogram of the complexes displayed more reduction potentials that could be attributed to the π-conjugation in the ligands incorporated during synthesis. The square wave voltammogram of the complexes is in agreement with the results obtained in cyclic voltammetry.
- Full Text:
- Date Issued: 2018
- Authors: Fudo, Zintle
- Date: 2018
- Subjects: Dye-sensitized solar cells Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6168 , vital:29498
- Description: The depletion of fossil fuels and the increasing energy demand for energy has led to the search for better and improved technologies with special focus renewable energy, especially solar cells. The first generation solar cells based on silicon are expensive, hence dye sensitized solar cells come in as a better alternative as these solar cells are environmental friendly, they have moderately good conversion efficiency and they are relatively cheap to produce. Dithiocarbamate ligands have been widely used in many research fields, as these are versatile ligands. Coordination of dithiocarbamates with metals such as ruthenium has produced high conversion efficiency and have the ability to extend the MLCT absorptions, and this can further extend their wavelength. In this study five dithiocarbamate sodium salt ligands were prepared and were coded as FL1= Aniline, FL2= p- toluidine, FL3= p- anisidine, FL4=dibenzyl, FL5=diphenyl. These ligands were used to synthesize Ru(II) metal complexes which were formulated as [Ru(FLx)(dcbpy)(NCS)] and [Ru(FLx)2(dcbpy)] where FLx is the dithiocarbamate ligand and dcbpy is 2,2-bipyridine-4,4’-dicarboxylic acid and the complexes were coded as FCx. The synthesized compounds were characterized using techniques such as the melting point, molar conductivity, FT-IR and NMR spectroscopy. For spectroelectrochemical studies of the metal complexes, techniques such as UV-Vis and photoluminescence spectroscopy were carried out. Furthermore, redox properties of the complexes were analyzed using cyclic and square wave voltammetry. The FT-IR displayed all the expected peaks of interest both in the dithiocarbamate ligands and in the metal complexes. The electronic spectra confirmed the successful coordination of ligand to the metal centre, the electronic spectra of the complexes also confirmed the six coordinate octahedral geometry of the complexes. The complexes exhibited some photoluminescence properties that are suitable for dye sensitization. The cyclic voltammogram of the complexes displayed more reduction potentials that could be attributed to the π-conjugation in the ligands incorporated during synthesis. The square wave voltammogram of the complexes is in agreement with the results obtained in cyclic voltammetry.
- Full Text:
- Date Issued: 2018
Synthesis, characterization, and biological studies of pyrazolone Schiff bases and their transition metal complexes
- Authors: Idemudia, Omoruyi Gold
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11340 , http://hdl.handle.net/10353/d1016068
- Description: Some new acylpyrazolone Schiff bases have been synthesized from the condensation reaction of two acylpyrazolone diketone precursors with phenylhydrazine, 2,4-dinitrophenylhydrazine and sulfanilamide. They have been fully characterized by elemental analysis and spectroscopic techniques (IR,1H and 13C NMR, and mass-spectra). The single crystal structure of the benzoyl derivative acylpyrazolone Schiff bases have been obtained and analyzed by X-ray crystallography technique. Solid state X-ray diffraction revealed a keto tautomer Schiff base in solid state. Mn(II), Co(II), Ni(II) and Cu(II) complexes with the Schiff bases have been synthesized and characterized by elemental analysis, IR and UV-VIS spectroscopy, magnetic susceptibility measurements, and thermal studies (TGA and DTG). An octahedral geometry around the transition metal ion, consisting of two bidentate Schiff base ligands bonding through the azometine nitrogen and ketonic oxygen have been proposed based on careful interpretation of available analytical and spectroscopic characterization results. Two water molecules as ligands complete the octahedral geometry in all cases. Using the invitro disc diffusion method for screening synthesized compounds against selected gram positive and gram negative bacterial at 40 mg/mL, and the DPPH free radical scavenging methods at 0.50, 0.25 and 0.13 mg/mL, the synthesized Schiff base and metal complexes showed varying biological activities. 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one sul29 fanilamide showed more activity generally, exhibiting a broad spectrum activity against all selected bacterial in some cases. Mn(II), Co(II) and Ni(II) complexes of sulfanilamide Schiff base with the acetylpyrazolone derivative 4-acetyl-3-methyl-1-phenyl-2-pyrazolin-5-one sulfanilamide, exhibited a stronger and very good DPPH radical scavenging activity as good as ascorbic acid on comparing, but not with Cu(II). As such they could be important antitumour candidates.
- Full Text:
- Date Issued: 2014
- Authors: Idemudia, Omoruyi Gold
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11340 , http://hdl.handle.net/10353/d1016068
- Description: Some new acylpyrazolone Schiff bases have been synthesized from the condensation reaction of two acylpyrazolone diketone precursors with phenylhydrazine, 2,4-dinitrophenylhydrazine and sulfanilamide. They have been fully characterized by elemental analysis and spectroscopic techniques (IR,1H and 13C NMR, and mass-spectra). The single crystal structure of the benzoyl derivative acylpyrazolone Schiff bases have been obtained and analyzed by X-ray crystallography technique. Solid state X-ray diffraction revealed a keto tautomer Schiff base in solid state. Mn(II), Co(II), Ni(II) and Cu(II) complexes with the Schiff bases have been synthesized and characterized by elemental analysis, IR and UV-VIS spectroscopy, magnetic susceptibility measurements, and thermal studies (TGA and DTG). An octahedral geometry around the transition metal ion, consisting of two bidentate Schiff base ligands bonding through the azometine nitrogen and ketonic oxygen have been proposed based on careful interpretation of available analytical and spectroscopic characterization results. Two water molecules as ligands complete the octahedral geometry in all cases. Using the invitro disc diffusion method for screening synthesized compounds against selected gram positive and gram negative bacterial at 40 mg/mL, and the DPPH free radical scavenging methods at 0.50, 0.25 and 0.13 mg/mL, the synthesized Schiff base and metal complexes showed varying biological activities. 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one sul29 fanilamide showed more activity generally, exhibiting a broad spectrum activity against all selected bacterial in some cases. Mn(II), Co(II) and Ni(II) complexes of sulfanilamide Schiff base with the acetylpyrazolone derivative 4-acetyl-3-methyl-1-phenyl-2-pyrazolin-5-one sulfanilamide, exhibited a stronger and very good DPPH radical scavenging activity as good as ascorbic acid on comparing, but not with Cu(II). As such they could be important antitumour candidates.
- Full Text:
- Date Issued: 2014
Taking gendered harms seriously : the utility of rape trauma syndrome evidence in dispelling rape myths in criminal trials
- Authors: Nkala, Amanda Nothabo
- Date: 2016
- Subjects: Rape trauma syndrome Women -- Crimes against Rape -- Psychological aspects
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10353/13458 , vital:39668
- Description: Rape is a violent crime marked by underreporting and low conviction rates. Notwithstanding the fact that most rape laws have been made to be gender-neutral, the statistics of rape are still devastatingly high even on a global scale. The majority of the victims are still predominantly females especially in the context of acquaintance rape. It is an uncontestable fact that rape usually occurs in secret making it possible for one to falsely accuse another and effectively rendering it difficult to refute. In light of this, victims who have managed to reach the courts have come face to face with a myriad of stereotypical beliefs and rape myths about rape victims. These have dealt a blow to their cases once their credibility is doubted because they may have exhibited behaviour that does not match with the classic or real rape victim as expected by the society. However rape is an egregiously unique crime that presents with serious psychological issues for the victim. As such it is possible for a rape victim to exhibit counterintuitive behaviour that can only be sensibly explained by an expert who has delved in human behavioural sciences. The alleged victim will be questioned on things like lengthy delay in reporting, returning to the scene of the crime, asking for taxi money the morning after the rape or even failing to scream and fight off the alleged assailant. Unfortunately, the psychological effects of rape have more often than not been overlooked in our criminal justice system giving way for blame shifting in that the female victim is called upon to account for why the rape may have happened to her. These psychological reactions, responses and counterintuitive behaviour have been characterized as Rape Trauma Syndrome by specialists in psychology and psychiatry. In the context of this study, Rape Trauma Syndrome is a form of expert opinion evidence which is relevant, helpful and necessary because it can dispel rape myths and stereotypical beliefs about rape victims by educating the courts about the psychological reactions of rape victims. Against this backdrop, this research project investigates the utility of Rape Trauma Syndrome evidence in dispelling rape myths in rape trials, focusing especially on the admissibility and use of that syndrome as evidence in other jurisdictions at the level of comparative analysis in order to establish whether it can be utilised in the South African context.
- Full Text:
- Date Issued: 2016
- Authors: Nkala, Amanda Nothabo
- Date: 2016
- Subjects: Rape trauma syndrome Women -- Crimes against Rape -- Psychological aspects
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10353/13458 , vital:39668
- Description: Rape is a violent crime marked by underreporting and low conviction rates. Notwithstanding the fact that most rape laws have been made to be gender-neutral, the statistics of rape are still devastatingly high even on a global scale. The majority of the victims are still predominantly females especially in the context of acquaintance rape. It is an uncontestable fact that rape usually occurs in secret making it possible for one to falsely accuse another and effectively rendering it difficult to refute. In light of this, victims who have managed to reach the courts have come face to face with a myriad of stereotypical beliefs and rape myths about rape victims. These have dealt a blow to their cases once their credibility is doubted because they may have exhibited behaviour that does not match with the classic or real rape victim as expected by the society. However rape is an egregiously unique crime that presents with serious psychological issues for the victim. As such it is possible for a rape victim to exhibit counterintuitive behaviour that can only be sensibly explained by an expert who has delved in human behavioural sciences. The alleged victim will be questioned on things like lengthy delay in reporting, returning to the scene of the crime, asking for taxi money the morning after the rape or even failing to scream and fight off the alleged assailant. Unfortunately, the psychological effects of rape have more often than not been overlooked in our criminal justice system giving way for blame shifting in that the female victim is called upon to account for why the rape may have happened to her. These psychological reactions, responses and counterintuitive behaviour have been characterized as Rape Trauma Syndrome by specialists in psychology and psychiatry. In the context of this study, Rape Trauma Syndrome is a form of expert opinion evidence which is relevant, helpful and necessary because it can dispel rape myths and stereotypical beliefs about rape victims by educating the courts about the psychological reactions of rape victims. Against this backdrop, this research project investigates the utility of Rape Trauma Syndrome evidence in dispelling rape myths in rape trials, focusing especially on the admissibility and use of that syndrome as evidence in other jurisdictions at the level of comparative analysis in order to establish whether it can be utilised in the South African context.
- Full Text:
- Date Issued: 2016
Tanzania's development agenda and poverty reduction : a case of Mkukuta I1
- Authors: Mandalu, Martin Petro
- Date: 2016
- Subjects: Poverty--Tanzania Tanzania--Economic conditions
- Language: English
- Type: Thesis , Doctoral , Development Studies
- Identifier: http://hdl.handle.net/10353/15616 , vital:40487
- Description: Poverty reduction has always been part of Tanzania‘s development agenda since independence in 1961. Despite wealth of natural resources, peace and political stability, the country has continued to be poor for decades. A number of strategies have been employed to address the problem; however, they have not been so successful. Studies have explored the problem and came up with explanations that are insufficient. In recent years, more studies on poverty reduction increased, following the country‘s magnificent economic growth which, however, fails to alleviate poverty in the country. Recent literature on poverty reduction calls for improvement in the productive sectors such as agriculture and construction to increase their contribution in poverty reduction. However, most studies did not pay attention to the development model/s that led the economy since independence. Motivated by the unsatisfactory results of the previous poverty reduction strategies, and lacunas of the preceding studies, this research, through MKUKUTA I, examines factors affecting the development agenda in Tanzania and their influence on poverty reduction. It investigates, as well, the development models employed in the country since independence. The study is guided by the change of development theories: from socialism to neo-liberalism. Furthermore, the study proposes an alternative development model beyond dependency and neo-liberalism schools of thoughts that have been struggling to influence development in the country for over five decades. The study employs mainly secondary data and primary data as supplementary methods to analyse and explain the mismatch between economic growth and poverty reduction in the country. The study argues that the productive sectors fail to produce sufficiently and contribute to poverty reduction since they are not guided by any specific development model. Findings suggest that failure in poverty reduction despite remarkable economic growth is caused by failure of growth in the agriculture sector which employs the largest part of the workforce in the country. Economic transformation in the country, which contributed to economic growth, failed to generate more jobs in the productive sectors. Incorrect methodologies used for obtaining economic data are alleged as possible logical explanation for the mismatch between economic growth and failure in poverty reduction. Failure in poverty reduction had a negative impact on human development as the poor, especially in the rural areas, had limited access to quality services of education, health care, water and sanitation. Moreover, findings revealed that neoliberal policies in the country are not effective enough in guiding the development agenda and poverty reduction. Despite the rule of law, peace, political stability and favourable conditions for capitalism in the country, significant features of a neoliberal economy have not been effectively developed. The local private sector is still weak at the embryonic stage, and the market is weakened by corruption and poor infrastructure for doing business. Moreover, findings suggest that for about three decades, Tanzania has not had a clear and distinct development model to guide its development agenda in poverty alleviation. The constitution suggests that the country is guided by a socialist development philosophy whereas the official government website and practices indicate that the country is run by neoliberal policies. To resolve the matter and in view of attaining the TDV 2025 and poverty reduction, this study proposes that Tanzania becomes a democratic developmental state while governed by a dependency-neoliberal theory from the amalgamation of reviewed dependency and neo-liberal schools of thoughts as a guiding principle since all developmental states need guiding philosophies to lead them. Moreover, the study proposes pragmatic interventions to implement the development model.
- Full Text:
- Date Issued: 2016
- Authors: Mandalu, Martin Petro
- Date: 2016
- Subjects: Poverty--Tanzania Tanzania--Economic conditions
- Language: English
- Type: Thesis , Doctoral , Development Studies
- Identifier: http://hdl.handle.net/10353/15616 , vital:40487
- Description: Poverty reduction has always been part of Tanzania‘s development agenda since independence in 1961. Despite wealth of natural resources, peace and political stability, the country has continued to be poor for decades. A number of strategies have been employed to address the problem; however, they have not been so successful. Studies have explored the problem and came up with explanations that are insufficient. In recent years, more studies on poverty reduction increased, following the country‘s magnificent economic growth which, however, fails to alleviate poverty in the country. Recent literature on poverty reduction calls for improvement in the productive sectors such as agriculture and construction to increase their contribution in poverty reduction. However, most studies did not pay attention to the development model/s that led the economy since independence. Motivated by the unsatisfactory results of the previous poverty reduction strategies, and lacunas of the preceding studies, this research, through MKUKUTA I, examines factors affecting the development agenda in Tanzania and their influence on poverty reduction. It investigates, as well, the development models employed in the country since independence. The study is guided by the change of development theories: from socialism to neo-liberalism. Furthermore, the study proposes an alternative development model beyond dependency and neo-liberalism schools of thoughts that have been struggling to influence development in the country for over five decades. The study employs mainly secondary data and primary data as supplementary methods to analyse and explain the mismatch between economic growth and poverty reduction in the country. The study argues that the productive sectors fail to produce sufficiently and contribute to poverty reduction since they are not guided by any specific development model. Findings suggest that failure in poverty reduction despite remarkable economic growth is caused by failure of growth in the agriculture sector which employs the largest part of the workforce in the country. Economic transformation in the country, which contributed to economic growth, failed to generate more jobs in the productive sectors. Incorrect methodologies used for obtaining economic data are alleged as possible logical explanation for the mismatch between economic growth and failure in poverty reduction. Failure in poverty reduction had a negative impact on human development as the poor, especially in the rural areas, had limited access to quality services of education, health care, water and sanitation. Moreover, findings revealed that neoliberal policies in the country are not effective enough in guiding the development agenda and poverty reduction. Despite the rule of law, peace, political stability and favourable conditions for capitalism in the country, significant features of a neoliberal economy have not been effectively developed. The local private sector is still weak at the embryonic stage, and the market is weakened by corruption and poor infrastructure for doing business. Moreover, findings suggest that for about three decades, Tanzania has not had a clear and distinct development model to guide its development agenda in poverty alleviation. The constitution suggests that the country is guided by a socialist development philosophy whereas the official government website and practices indicate that the country is run by neoliberal policies. To resolve the matter and in view of attaining the TDV 2025 and poverty reduction, this study proposes that Tanzania becomes a democratic developmental state while governed by a dependency-neoliberal theory from the amalgamation of reviewed dependency and neo-liberal schools of thoughts as a guiding principle since all developmental states need guiding philosophies to lead them. Moreover, the study proposes pragmatic interventions to implement the development model.
- Full Text:
- Date Issued: 2016
Targeting and characterizing potentially high yield aquifers in the neotectonic zones in the Eastern Cape Province in South Africa
- Authors: Madi, Kakaba
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: vital:11530 , http://hdl.handle.net/10353/d1021270
- Description: The Eastern Cape Province has, besides the three known neotectonic belts (southern, eastern and northern) a fourth zone, which is inactive. This inactive zone is located almost in its central part north of the southern neotectonic zone, and south of the northern neotectonic belt. The three above mentioned neotectonic belts (southern, eastern and northern) were chosen for this study, each one with its own characteristics. This study aims at characterizing and targeting potentially high yield aquifers in the neotectonic zones in the Eastern Cape Province. The methods used in this study include: 1) A comprehensive literature review on neotectonics in South Africa in general and in the Eastern Cape Province in particular; 2) Extraction of lineaments through remote sensing and examination of digital elevation models; 3) Examination of seismic data for the subsurface visualization onshore and offshore; 4) Study on the genesis of the Grahamstown kaolin deposits through the structural component; and 5) Acquisition and interpretation of magnetic, electromagnetic and radiometric data from three of the hot springs in the northern neotectonic belt. The results indicate the following: 1) Old map of seismic epicentres in South Africa need to be reviewed continually. The Eastern Cape was regarded as quiescent in terms of seismicity. However, the investigation from recent seismic epicenters downloadable from the IRIS website has shown that recent seismic events occurred in the Eastern Cape Province especially in the northern and southern neotectonic belts. The central part located north of the southern neotectonic belt and south of the northern neotectonic belt is inactive. This inactive zone can be considered for the storage of nuclear wastes. 2) The eastern neotectonic belt has, like the northern neotectonic belt, a higher density of lineaments oriented northwest-southeast, which makes it the second important neotectonic belt. These lineaments correlate with the normalized difference vegetation index indicative of a good circulation of groundwater. In the south, the Eastern Cape great lineament oriented east-west is now considered a neotectonic domain because many seismic epicentres occur therein. Its geomorphologic shape in graben type form is a favourable structure for groundwater catchment. The surface topography is not uniform and high elevations in the east are related to the uplift that took place in the Quaternary. Most vector gradients are oriented east-west, a fact to be reckon with in the study of surface water flow and aquifers characterization. 3) Offshore along the east coast, the subsurface is affected by neotectonic faults, which are probably splays of the Agulhas Falkland Fractured Zone (AFFZ). The folds that occur are related to the regional compressional stress known as the Wegener Stress Anomaly (WSM). On land, straight lines from seismic profiles indicate that weathering occurs in consolidated materials probably along faults or fractures, unconsolidated sediments always have wavy profiles. On the other hand, field observations in King Williams Town have clearly shown that a tectonic uplift took place on a dolerite sill overlain by mudstones and sandstones. The uplift is possibly related to the Amatole-Swaziland event that occurred in the last five millions years. The escarpment along this dolerite sill overlain by sedimentary rocks is a meso-scale fault with a dip-slip component. Healthy vegetation and a river flowing parallel to the cliff indicate groundwater flow in the zone of weakness. 4) In the southern neotectonic belt there is a clear northwest-southeast horizontal compression and a southwest-northeast vertical to sub-vertical extension. Enrichment of granitic breccias and feldspar in the Grahamstown Dwyka tillite is the source for the formation of kaolin deposits. The weathering starts in the granitic breccias through their extensional fractures and then extends in the matrix, which has micro-fractures that are only visible with the transmitted microscope. Combined extensional strike-slip and dip-slip faulting is responsible for the earthquakes in the region of Grahamstown where the kaolin is formed. There is also an unreported thermal (quartz veins) and neotectonic event identified in this region. 5) The hot springs in the northern neotectonic belt are connected by a regional neotectonic fault. The use of magnetic and electromagnetic methods helped to decipher the occurrence of faults, fractures, dolerite dykes, and variable degree of weathering. Uranium/potassium ratios derived from radiometric surveys show that areas around some hot springs are characterized by enrichment in uranium. High concentrations of thorium are related to its low capacity of being easily dissolved in water. It can be concluded that seismicity, hot springs and accordingly deep groundwater circulation, high density of lineaments, quaternary tectonic uplift, are the predominate characteristics of the three neotectonic zones. Furthermore, on the environmental point of view, thorium concentration is higher than that of either uranium or potassium. Although it is nonetheless below the world average threshold of 7.4 ppm according to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), it may be a source of radiation hazard to humans and animals if they are subjected to prolonged exposure. All the neotectonic zones in the Eastern Cape Province present potentials to host good and important aquifers. It is suggested that the Eastern Cape great lineament in the southern neotectonic belt and the Kokstad-Koffiefontein seismic belt in the northern neotectonic belt, be monitored for future research regarding, neotectonics, seismic risk assessment and hydrogeology.
- Full Text:
- Date Issued: 2014
- Authors: Madi, Kakaba
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: vital:11530 , http://hdl.handle.net/10353/d1021270
- Description: The Eastern Cape Province has, besides the three known neotectonic belts (southern, eastern and northern) a fourth zone, which is inactive. This inactive zone is located almost in its central part north of the southern neotectonic zone, and south of the northern neotectonic belt. The three above mentioned neotectonic belts (southern, eastern and northern) were chosen for this study, each one with its own characteristics. This study aims at characterizing and targeting potentially high yield aquifers in the neotectonic zones in the Eastern Cape Province. The methods used in this study include: 1) A comprehensive literature review on neotectonics in South Africa in general and in the Eastern Cape Province in particular; 2) Extraction of lineaments through remote sensing and examination of digital elevation models; 3) Examination of seismic data for the subsurface visualization onshore and offshore; 4) Study on the genesis of the Grahamstown kaolin deposits through the structural component; and 5) Acquisition and interpretation of magnetic, electromagnetic and radiometric data from three of the hot springs in the northern neotectonic belt. The results indicate the following: 1) Old map of seismic epicentres in South Africa need to be reviewed continually. The Eastern Cape was regarded as quiescent in terms of seismicity. However, the investigation from recent seismic epicenters downloadable from the IRIS website has shown that recent seismic events occurred in the Eastern Cape Province especially in the northern and southern neotectonic belts. The central part located north of the southern neotectonic belt and south of the northern neotectonic belt is inactive. This inactive zone can be considered for the storage of nuclear wastes. 2) The eastern neotectonic belt has, like the northern neotectonic belt, a higher density of lineaments oriented northwest-southeast, which makes it the second important neotectonic belt. These lineaments correlate with the normalized difference vegetation index indicative of a good circulation of groundwater. In the south, the Eastern Cape great lineament oriented east-west is now considered a neotectonic domain because many seismic epicentres occur therein. Its geomorphologic shape in graben type form is a favourable structure for groundwater catchment. The surface topography is not uniform and high elevations in the east are related to the uplift that took place in the Quaternary. Most vector gradients are oriented east-west, a fact to be reckon with in the study of surface water flow and aquifers characterization. 3) Offshore along the east coast, the subsurface is affected by neotectonic faults, which are probably splays of the Agulhas Falkland Fractured Zone (AFFZ). The folds that occur are related to the regional compressional stress known as the Wegener Stress Anomaly (WSM). On land, straight lines from seismic profiles indicate that weathering occurs in consolidated materials probably along faults or fractures, unconsolidated sediments always have wavy profiles. On the other hand, field observations in King Williams Town have clearly shown that a tectonic uplift took place on a dolerite sill overlain by mudstones and sandstones. The uplift is possibly related to the Amatole-Swaziland event that occurred in the last five millions years. The escarpment along this dolerite sill overlain by sedimentary rocks is a meso-scale fault with a dip-slip component. Healthy vegetation and a river flowing parallel to the cliff indicate groundwater flow in the zone of weakness. 4) In the southern neotectonic belt there is a clear northwest-southeast horizontal compression and a southwest-northeast vertical to sub-vertical extension. Enrichment of granitic breccias and feldspar in the Grahamstown Dwyka tillite is the source for the formation of kaolin deposits. The weathering starts in the granitic breccias through their extensional fractures and then extends in the matrix, which has micro-fractures that are only visible with the transmitted microscope. Combined extensional strike-slip and dip-slip faulting is responsible for the earthquakes in the region of Grahamstown where the kaolin is formed. There is also an unreported thermal (quartz veins) and neotectonic event identified in this region. 5) The hot springs in the northern neotectonic belt are connected by a regional neotectonic fault. The use of magnetic and electromagnetic methods helped to decipher the occurrence of faults, fractures, dolerite dykes, and variable degree of weathering. Uranium/potassium ratios derived from radiometric surveys show that areas around some hot springs are characterized by enrichment in uranium. High concentrations of thorium are related to its low capacity of being easily dissolved in water. It can be concluded that seismicity, hot springs and accordingly deep groundwater circulation, high density of lineaments, quaternary tectonic uplift, are the predominate characteristics of the three neotectonic zones. Furthermore, on the environmental point of view, thorium concentration is higher than that of either uranium or potassium. Although it is nonetheless below the world average threshold of 7.4 ppm according to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), it may be a source of radiation hazard to humans and animals if they are subjected to prolonged exposure. All the neotectonic zones in the Eastern Cape Province present potentials to host good and important aquifers. It is suggested that the Eastern Cape great lineament in the southern neotectonic belt and the Kokstad-Koffiefontein seismic belt in the northern neotectonic belt, be monitored for future research regarding, neotectonics, seismic risk assessment and hydrogeology.
- Full Text:
- Date Issued: 2014
Taxation 3: ATA 311E/ ATV 311E
- Hirschbeck, L, Stevens, N, Olivier, J
- Authors: Hirschbeck, L , Stevens, N , Olivier, J
- Date: 2010-06
- Subjects: Accounting
- Language: English
- Type: Examination paper
- Identifier: vital:17404 , http://hdl.handle.net/10353/d1009765
- Description: Taxation 3: ATA 311E / ATV 311E, June 2010 Final Examination.
- Full Text:
- Date Issued: 2010-06
- Authors: Hirschbeck, L , Stevens, N , Olivier, J
- Date: 2010-06
- Subjects: Accounting
- Language: English
- Type: Examination paper
- Identifier: vital:17404 , http://hdl.handle.net/10353/d1009765
- Description: Taxation 3: ATA 311E / ATV 311E, June 2010 Final Examination.
- Full Text:
- Date Issued: 2010-06
Taxation 3: ATA321E / ATV321E
- Authors: Stevens, N , Olivier, J
- Date: 2010-11
- Subjects: Taxation
- Language: English
- Type: Examination paper
- Identifier: vital:17405 , http://hdl.handle.net/10353/d1009766
- Description: Taxation 3: ATA321E / ATV321E, final assessment November 2010.
- Full Text:
- Date Issued: 2010-11
- Authors: Stevens, N , Olivier, J
- Date: 2010-11
- Subjects: Taxation
- Language: English
- Type: Examination paper
- Identifier: vital:17405 , http://hdl.handle.net/10353/d1009766
- Description: Taxation 3: ATA321E / ATV321E, final assessment November 2010.
- Full Text:
- Date Issued: 2010-11
Taxation 3: ATV 311E
- Stevens, N, Hirschbeck, L, Olivier, J
- Authors: Stevens, N , Hirschbeck, L , Olivier, J
- Date: 2012-06
- Language: English
- Type: Examination paper
- Identifier: vital:17406 , http://hdl.handle.net/10353/d1009767
- Description: Taxation 3: ATV 311E, final assessment 15 June 2012.
- Full Text:
- Date Issued: 2012-06
- Authors: Stevens, N , Hirschbeck, L , Olivier, J
- Date: 2012-06
- Language: English
- Type: Examination paper
- Identifier: vital:17406 , http://hdl.handle.net/10353/d1009767
- Description: Taxation 3: ATV 311E, final assessment 15 June 2012.
- Full Text:
- Date Issued: 2012-06