Magister Philosophiae - MPhil (Physics)

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Synthesis of bimetallic immiscible alloy nanoparticles through green and gamma radiolysis approaches for environmental remediation applications
(University of the Western Cape, 2022) Noukelag, Sandrine Kamdoum; Maaza, Malik
The synthesis of bimetallic immiscible alloy nanoparticles (NPs) using versatile routes, is a major concern since physio-chemical methods are not environmentally benign. Breaking down the immiscibility would generate NPs with remarkable properties and consequently more applications. As a result, it urges the development of one-step, eco-friendly, efficient, and reliable methods for getting more metastable bimetallic alloys from immiscible metals. To that aim, unconventional approaches such as green and gamma radiolysis were considered as the paths forward in this thesis. The wide immiscibility gaps of iron-silver (Fe-Ag), and iron-zinc (Fe-Zn) led to their selection
Synthesis of bimetallic immiscible alloy nanoparticles through green and gamma radiolysis approaches for environmental remediation applications
(University of the Western Cape, 2022) Noukelag, Sandrine Kamdoum; Maaza, Malik
The synthesis of bimetallic immiscible alloy nanoparticles (NPs) using versatile routes, is a major concern since physio-chemical methods are not environmentally benign. Breaking down the immiscibility would generate NPs with remarkable properties and consequently more applications. As a result, it urges the development of one-step, eco-friendly, efficient, and reliable methods for getting more metastable bimetallic alloys from immiscible metals. To that aim, unconventional approaches such as green and gamma radiolysis were considered as the paths forward in this thesis. The wide immiscibility gaps of iron-silver (Fe-Ag), and iron-zinc (Fe-Zn) led to their selection
Towards stimuli-responsive functional nanocomposites: Smart tunable plasmonic nanostructures au-v02
(University of the Western Cape, 2010) Kama Kama, Jean Bosco; Maaza, M; Knoesen, D
The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in V02 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-V02 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of V02 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of V02 thin films. A reversible thermal tunability of the optical/dielectric constants of V02 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in V02 host matrix.
Towards stimuli-responsive functional nanocomposites: Smart tunable plasmonic nanostructures au-v02
(University of the Western Cape, 2010) Kama Kama, Jean Bosco; Maaza, M; Knoesen, D
The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in V02 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-V02 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of V02 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of V02 thin films. A reversible thermal tunability of the optical/dielectric constants of V02 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in V02 host matrix.
Selection and optimization of the seeding procedure prior to the synthesis of Pd-based membranes
(University of the Western Cape, 2014) Mc Donald, Earl; Halindintwali, S.; Bladergroen, B.J.; Julies, B.
Pd based membranes are known for their incredible selectivity towards H2. In order for Pd membranes to display high H2 selectivity, a defect free layer of Pd needs to be deposited onto a support. Although various fabrication techniques do exist, many researchers have attempted to produce defect free Pd-based films, using electroless plating. The first step in the preparation technique involves “seeding” of the support structure. Even though these seeds, if well distributed and anchored to the support, are crucial in order to obtain the defect free Pd layer, they hardly ever received attention from the science community. This thesis reports findings on various seeding methods as well as the resulting microstructures of the Pd films formed as a result of the type of seeding method employed. Finally the quality of the membranes using the most promising seeding technique was determined by subjecting the membranes to permeance tests with N2 at both high and low temperatures as well as with H2 at high temperatures.
Selection and optimization of the seeding procedure prior to the synthesis of Pd-based membranes
(University of the Western Cape, 2014) Mc Donald, Earl; Halindintwali, S.; Bladergroen, B.J.; Julies, B.
Pd based membranes are known for their incredible selectivity towards H2. In order for Pd membranes to display high H2 selectivity, a defect free layer of Pd needs to be deposited onto a support. Although various fabrication techniques do exist, many researchers have attempted to produce defect free Pd-based films, using electroless plating. The first step in the preparation technique involves “seeding” of the support structure. Even though these seeds, if well distributed and anchored to the support, are crucial in order to obtain the defect free Pd layer, they hardly ever received attention from the science community. This thesis reports findings on various seeding methods as well as the resulting microstructures of the Pd films formed as a result of the type of seeding method employed. Finally the quality of the membranes using the most promising seeding technique was determined by subjecting the membranes to permeance tests with N2 at both high and low temperatures as well as with H2 at high temperatures.
Simulation of silicon and diamond detector systems by GEANT4 simulation techniques
(University of the Western Cape, 2014) Erasmus, Nicholas Rattray; Orce, J.N.; Halindintwali, S
There is a constant need for improvement in nuclear particle detection methods. Silicon surface barrier detectors have proved very valuable during the last decades. Diamond is a viable alternative to silicon as a semiconductor detector. It offers significant advantages over silicon due to its high radiation hardness and low drift currents. A Coulomb-excitation study has been carried out at TRIUMF using a 59.7 MeV 12C beam impinging on a 194Pt target. The particles underwent elastic Rutherford scattering in the target, and a double sided silicon S3 CD detector was used to measure the resulting particle energy spectra. These spectra were simulated in GEANT4 and compared to the experimental results. Subsequently, the silicon was replaced with diamond and the simulation was repeated. Such simulations of particle energy spectra, properly incorporating elastic Rutherford scattering, have not been carried out with GEANT4 before. An accurate simulation of the elastic peak obtained from particle spectra will provide a methodology for applying particle-gamma coincidence techniques. The study of the inelastic peak in 12C and similar nuclei will benefit from such developments. Such simulations will also offer high energy calibration points for the experimental data, and the possibility of testing the experimental conditions including the target thickness, beam energy, and linearity of electronic modules (e.g. the preamplifier). The simulation offered results comparable to the experimental case. GEANT4 was found to simulate the Rutherford cross sections at specific scattering angles as well as the position of the simulated energy peaks accurately when compared with the experimental case. As expected, the experimentally obtained particle energy spectra displayed more broadening than the simulated spectra, though the shape of the peaks was very similar. The simulation of the double sided diamond detector was a tentative first step in its testing as a particle detector. The sophisticated methods required to properly simulate and test diamond for nuclear physics experiments were not implemented. This simulation may serve as a starting point for further testing of diamond detectors, using advanced simulation techniques
Simulation of silicon and diamond detector systems by GEANT4 simulation techniques
(University of the Western Cape, 2014) Erasmus, Nicholas Rattray; Orce, J.N.; Halindintwali, S
There is a constant need for improvement in nuclear particle detection methods. Silicon surface barrier detectors have proved very valuable during the last decades. Diamond is a viable alternative to silicon as a semiconductor detector. It offers significant advantages over silicon due to its high radiation hardness and low drift currents. A Coulomb-excitation study has been carried out at TRIUMF using a 59.7 MeV 12C beam impinging on a 194Pt target. The particles underwent elastic Rutherford scattering in the target, and a double sided silicon S3 CD detector was used to measure the resulting particle energy spectra. These spectra were simulated in GEANT4 and compared to the experimental results. Subsequently, the silicon was replaced with diamond and the simulation was repeated. Such simulations of particle energy spectra, properly incorporating elastic Rutherford scattering, have not been carried out with GEANT4 before. An accurate simulation of the elastic peak obtained from particle spectra will provide a methodology for applying particle-gamma coincidence techniques. The study of the inelastic peak in 12C and similar nuclei will benefit from such developments. Such simulations will also offer high energy calibration points for the experimental data, and the possibility of testing the experimental conditions including the target thickness, beam energy, and linearity of electronic modules (e.g. the preamplifier). The simulation offered results comparable to the experimental case. GEANT4 was found to simulate the Rutherford cross sections at specific scattering angles as well as the position of the simulated energy peaks accurately when compared with the experimental case. As expected, the experimentally obtained particle energy spectra displayed more broadening than the simulated spectra, though the shape of the peaks was very similar. The simulation of the double sided diamond detector was a tentative first step in its testing as a particle detector. The sophisticated methods required to properly simulate and test diamond for nuclear physics experiments were not implemented. This simulation may serve as a starting point for further testing of diamond detectors, using advanced simulation techniques
Synthesis and characterization of Ceria with an optimal oxygen storage capacity as potential medium to remove SO2 from flue gas emissions
(University of Western Cape, 2013) Andrews, Gary Lyndl; Bladergroen, B.J.; Hallindintwali, S.; Julies, B.
Due to an increasing demand for energy, alternative renewable energy sources are investigated globally. However fossil fuels are still one of the main energy sources. The combustion of these fuels produces by-products such as SOx, NOx and CO2, which have detrimental effects on the environment and human health. Therefore, effective methods are needed to minimize the pollution and affects that these by-products cause. Catalysts are commonly employed to convert these by-products to less harmful and/or resalable products. Ceria and ceria based materials are good candidates for the removal and conversion of SOx and NOx. Ceria and ceria related materials are most effective as catalysts when they are in the nano-form with good crystallinity and nanoparticles that are uniform. The growth of nanoparticles is preceded by a nucleation process which can occur by solid-state restructuring of a gel or precipitation from a saturated solution. The precipitation method was selected to synthesize Ceria nanoparticles. Synthesis conditions such as temperature, solution type and ageing time and their effect on the physical and chemical forms of the Ceria particles were investigated. The morphology and structural properties were investigated using Scanning Electron Microscopy, X-ray diffraction and Transmission Electron Microscopy. X-ray Photoelectron Spectroscopy was used to investigate the chemical properties. It was found that low temperatures, low base volume and a solvent with a small dielectric constant favor the formation of small crystallites with a relatively large concentration of defects. These defects are desirable since they enhance the catalytic activity of ceria.
Synthesis and characterization of Ceria with an optimal oxygen storage capacity as potential medium to remove SO2 from flue gas emissions
(University of Western Cape, 2013) Andrews, Gary Lyndl; Bladergroen, B.J.; Hallindintwali, S.; Julies, B.
Due to an increasing demand for energy, alternative renewable energy sources are investigated globally. However fossil fuels are still one of the main energy sources. The combustion of these fuels produces by-products such as SOx, NOx and CO2, which have detrimental effects on the environment and human health. Therefore, effective methods are needed to minimize the pollution and affects that these by-products cause. Catalysts are commonly employed to convert these by-products to less harmful and/or resalable products. Ceria and ceria based materials are good candidates for the removal and conversion of SOx and NOx. Ceria and ceria related materials are most effective as catalysts when they are in the nano-form with good crystallinity and nanoparticles that are uniform. The growth of nanoparticles is preceded by a nucleation process which can occur by solid-state restructuring of a gel or precipitation from a saturated solution. The precipitation method was selected to synthesize Ceria nanoparticles. Synthesis conditions such as temperature, solution type and ageing time and their effect on the physical and chemical forms of the Ceria particles were investigated. The morphology and structural properties were investigated using Scanning Electron Microscopy, X-ray diffraction and Transmission Electron Microscopy. X-ray Photoelectron Spectroscopy was used to investigate the chemical properties. It was found that low temperatures, low base volume and a solvent with a small dielectric constant favor the formation of small crystallites with a relatively large concentration of defects. These defects are desirable since they enhance the catalytic activity of ceria.

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