A two-dimensional simulation of atomic layer deposition process on substrate trenches
- Authors: Olotu, Olufunsho Oladipo
- Date: 2019
- Subjects: Atomic layer deposition , Thin films , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413228 , uj:34805
- Description: Abstract: In the cause of the increasing need for miniaturisation of devices, a more sophisticated nano-manufacturing technique of component was rummage around for, which has led to the adoption of atomic layer deposition (ALD) technique due to its competency of accomplishing superb uniformity, conformality, pinhole-free and ultra-thinness. In this dissertation, the ALD process within the cavity and surface of substrate trench was studied numerically with the intent to optimise the deposition process while formulating suitable ALD recipe. In the cause of optimising the process of an atomic layer deposition (ALD) for trenched substrate, a numerical model was presented, and two-dimensional simulations of the ALD process of substrate trenches in an arbitrary reactor were performed. Here, the deposition of aluminium oxide (Al2O3) was illustrated with trimethylaluminum (TMA) and ozone (O3) precursors as Aluminum (Al) and oxygen (O2) sources respectively while inert argon was used as purging gas in an arbitrary reactor. The flow is similar to a typical top-to-bottom type ALD reactor. The gases are assumed to enter at an inlet temperature of 150°C while the substrate, reactor walls and outlet temperature of 250°C is used. The TMA and O3 precursors are both pulsed separately, according to the sequence, into the reactor at 0.085 m/s for 0.2 and 1 second, respectively. While inert-purge gas (Ar) is used to purge the reactor domain at 0.17 m/s for 5 seconds between the pulse and exposure times. For this work the ALD sequence follows in a pulse-exposure-purge-exposure-pulse-exposure-purge manner to form a complete ALD cycle. After the reactive and inert-gases have flown and penetrated into the trenched substrate the excess and by-products are then exhausted past the edges of the trenched substrate towards the outlet of the reactor. The reactor flow domain is meshed into 67023 nodes. The ALD process within the arbitrary reactor is investigated by numerical simulating the reactor using computational fluid dynamics (CFD) within commercial software packages ANSYS FLUENT and CHEMKINPRO. This transient process is implemented by the coupled algorithm approach... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Olotu, Olufunsho Oladipo
- Date: 2019
- Subjects: Atomic layer deposition , Thin films , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413228 , uj:34805
- Description: Abstract: In the cause of the increasing need for miniaturisation of devices, a more sophisticated nano-manufacturing technique of component was rummage around for, which has led to the adoption of atomic layer deposition (ALD) technique due to its competency of accomplishing superb uniformity, conformality, pinhole-free and ultra-thinness. In this dissertation, the ALD process within the cavity and surface of substrate trench was studied numerically with the intent to optimise the deposition process while formulating suitable ALD recipe. In the cause of optimising the process of an atomic layer deposition (ALD) for trenched substrate, a numerical model was presented, and two-dimensional simulations of the ALD process of substrate trenches in an arbitrary reactor were performed. Here, the deposition of aluminium oxide (Al2O3) was illustrated with trimethylaluminum (TMA) and ozone (O3) precursors as Aluminum (Al) and oxygen (O2) sources respectively while inert argon was used as purging gas in an arbitrary reactor. The flow is similar to a typical top-to-bottom type ALD reactor. The gases are assumed to enter at an inlet temperature of 150°C while the substrate, reactor walls and outlet temperature of 250°C is used. The TMA and O3 precursors are both pulsed separately, according to the sequence, into the reactor at 0.085 m/s for 0.2 and 1 second, respectively. While inert-purge gas (Ar) is used to purge the reactor domain at 0.17 m/s for 5 seconds between the pulse and exposure times. For this work the ALD sequence follows in a pulse-exposure-purge-exposure-pulse-exposure-purge manner to form a complete ALD cycle. After the reactive and inert-gases have flown and penetrated into the trenched substrate the excess and by-products are then exhausted past the edges of the trenched substrate towards the outlet of the reactor. The reactor flow domain is meshed into 67023 nodes. The ALD process within the arbitrary reactor is investigated by numerical simulating the reactor using computational fluid dynamics (CFD) within commercial software packages ANSYS FLUENT and CHEMKINPRO. This transient process is implemented by the coupled algorithm approach... , M.Ing. (Mechanical Engineering)
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Application of monometallic and bimetallic dendrimer encapsulated nanoparticles (DENs) and their catalytic evaluation on reduction of 4-nitrophenol
- Authors: Patala, Rapelang
- Date: 2016
- Subjects: Dendrimers , Dendrimers - Synthesis , Catalysis , Inorganic compounds - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/226086 , uj:22850
- Description: M.Sc. (Chemistry) , Abstract: The compound 4-nitrophenol found in wastewater streams is mainly the result of industrial and agricultural production. Having adverse health effects associated with it, 4-nitrophenol should be removed from the environment or converted to less hazardous forms as efficiently as possible. Feasible techniques to get rid of this chemical compound are of great research interest. The synthesized nanoparticles encapsulated inside dendrimers (DENs) will be evaluated for catalytic activity against the reaction of 4-nitrophenol reduction. Transition metal nanoparticles find their application in catalysis; this makes them to be of great technological importance. They can be synthesized by evaporation, condensation and chemical or electrochemical reduction of metal salts in the presence of stabilizers. Dendrimers were used as templates for the synthesis of both monometallic and bimetallic nanoparticles which were evaluated as catalysts for the reduction of 4-nitrophenol. We also focused on comprehensive kinetic analysis of 4-nitrophenol reduction using dendrimer encapsulated metal nanoparticles (DENs). The adsorption rates and reaction rates were found and evaluated, and it could be concluded that bimetallic catalysts were more catalytically active than monometallic ones. Different ratios of bimetallic (AuPd) nanoparticles were also supported on different mesoporous metal oxides (MMOs) and their catalytic activity evaluated on reduction of 4-nitrophenol. The results were interpreted in the light of Langmuir Hinshelwood model. The AuPd bimetallic nanoparticles supported on MMOs showed synergistic effect. With the use of power rate law it was shown that 4-nitrophenol reduction follows first order kinetics.
- Full Text:
- Authors: Patala, Rapelang
- Date: 2016
- Subjects: Dendrimers , Dendrimers - Synthesis , Catalysis , Inorganic compounds - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/226086 , uj:22850
- Description: M.Sc. (Chemistry) , Abstract: The compound 4-nitrophenol found in wastewater streams is mainly the result of industrial and agricultural production. Having adverse health effects associated with it, 4-nitrophenol should be removed from the environment or converted to less hazardous forms as efficiently as possible. Feasible techniques to get rid of this chemical compound are of great research interest. The synthesized nanoparticles encapsulated inside dendrimers (DENs) will be evaluated for catalytic activity against the reaction of 4-nitrophenol reduction. Transition metal nanoparticles find their application in catalysis; this makes them to be of great technological importance. They can be synthesized by evaporation, condensation and chemical or electrochemical reduction of metal salts in the presence of stabilizers. Dendrimers were used as templates for the synthesis of both monometallic and bimetallic nanoparticles which were evaluated as catalysts for the reduction of 4-nitrophenol. We also focused on comprehensive kinetic analysis of 4-nitrophenol reduction using dendrimer encapsulated metal nanoparticles (DENs). The adsorption rates and reaction rates were found and evaluated, and it could be concluded that bimetallic catalysts were more catalytically active than monometallic ones. Different ratios of bimetallic (AuPd) nanoparticles were also supported on different mesoporous metal oxides (MMOs) and their catalytic activity evaluated on reduction of 4-nitrophenol. The results were interpreted in the light of Langmuir Hinshelwood model. The AuPd bimetallic nanoparticles supported on MMOs showed synergistic effect. With the use of power rate law it was shown that 4-nitrophenol reduction follows first order kinetics.
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Biosynthesis, characterization and antibacterial activity of silver and gold nanoparticles from the leaf and bark extracts of Zanthoxylum Capense
- Authors: Nephawe, Mbavhalelo Jade
- Date: 2015
- Subjects: Nanotechnology , Nanoparticles , Nanostructured materials , Gold , Silver
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/372050 , http://hdl.handle.net/10210/84769 , uj:19260
- Description: Abstract: The biosynthesis of nanoparticles has many advantages over tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form nanoparticles. In this study, aqueous leaf and bark extracts of Zanthoxylum capense were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au nanoparticles capabilities. The goal was to develop a reliable, eco-friendly and easy process for the synthesis of silver and gold nanoparticles using extracts of medicinal plant Zanthoxylum capense. Characterization of the nanoparticles formed by the aqueous extracts was performed using Ultraviolet visible (UV-vis) spectroscopy, Dynamic light scattering, Fourier transforms infrared spectroscopy (FTIR), Transmission electron microscope (TEM). Nanoparticles were characterised by measuring their relevant physicochemical properties. Among the determined properties are size, shape, zeta potential and surface charge. UV-vis spectrophotometry was used as a confirmatory as well as a characterizing tool. Phytochemical tests revealed that the leaf and bark extracts of the plant contained “alkaloids, sterols, terpenoids, flavonoids, steroids, phlabotannins and reducing sugars” which were linked as potential reducing agents... , M.Sc.
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- Authors: Nephawe, Mbavhalelo Jade
- Date: 2015
- Subjects: Nanotechnology , Nanoparticles , Nanostructured materials , Gold , Silver
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/372050 , http://hdl.handle.net/10210/84769 , uj:19260
- Description: Abstract: The biosynthesis of nanoparticles has many advantages over tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form nanoparticles. In this study, aqueous leaf and bark extracts of Zanthoxylum capense were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au nanoparticles capabilities. The goal was to develop a reliable, eco-friendly and easy process for the synthesis of silver and gold nanoparticles using extracts of medicinal plant Zanthoxylum capense. Characterization of the nanoparticles formed by the aqueous extracts was performed using Ultraviolet visible (UV-vis) spectroscopy, Dynamic light scattering, Fourier transforms infrared spectroscopy (FTIR), Transmission electron microscope (TEM). Nanoparticles were characterised by measuring their relevant physicochemical properties. Among the determined properties are size, shape, zeta potential and surface charge. UV-vis spectrophotometry was used as a confirmatory as well as a characterizing tool. Phytochemical tests revealed that the leaf and bark extracts of the plant contained “alkaloids, sterols, terpenoids, flavonoids, steroids, phlabotannins and reducing sugars” which were linked as potential reducing agents... , M.Sc.
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Cadmium removal from water using nanoparticles embedded on a membrane and detection using anodic stripping voltammetry
- Authors: Sam, Simanye
- Date: 2019
- Subjects: Cadmium , Carbon , Nanostructured materials , Water - Purification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401568 , uj:33567
- Description: Abstract : Water pollution by heavy metals is a serious problem in South Africa due to mining activities, electroplating industries, weathering of minerals and soils and coal combustion. Most river systems have been exposed to heavy metals contamination due to effluent disposal and this directly affects communities that use these sources for domestic purposes. For example, Umtata River which is exposed to Cd(II) is used for various purposes by a large population of the Transkei, most of which is rural - domestic (cooking, drinking and washing), agricultural (that is, livestock watering and irrigation), and recreational purposes (swimming). Water pollution by heavy metals such as, Cd(II) in particular is unavoidable and it causes undesirable health effects, such as hypertension and kidney failure. Thus, it is very important to find new ways to efficiently remove these metals from water. Nanostructured membranes are amongst other water treatment methods that have shown the ability to efficiently remove heavy metals from water. Therefore, this study seeks to provide a facile and effective method to remove heavy metals such as cadmium(II) from synthetic solutions and industrial water effluents. This was achieved by embedding carbon nanodots (CNDs) on a polyethersulfone (PES) membrane as support via phase inversion. The synthesized CNDs and fabricated membranes were characterized using Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscope (SEM), Atomic Force Microscope (AFM), contact angle and pure water flux assessment. TEM analysis confirmed that the synthesized CNDs were well dispersed with uniform shape and size (6.7±2.8 nm). Raman analysis illustrated that the CNDs were embedded on the PES and that after blending the PES with CNDs the ID/IG ratio slightly increased after modification of the membranes with CNDs showing that the membranes maintained good structural integrity. The CNDs/PES membranes showed improved hydrophilicity compared to the pristine PES. vi At constant pressure of 300 kPa the flux of pristine PES, 0.01% CNDs/PES, 0.05% CNDs/PES and CNDs/PES was 60.00 L.m-2.h-1, 96.93 L.m-2.h-1, 142.16 L.m-2.h-1 and 196.62 L.m-2.h-1 respectively. The performance of the membrane was optimised using batch adsorption experiments. The analysis revealed that 95.71, 96.32, 97.69 and 99.78% Cd2+ was removed by PES, 0.01% CNDs/PES, 0.05% CNDs/PES and 0.5% CNDs/PES, respectively at optimum conditions: 30 minutes contact time, at pH 5 and 0.5 ppm Cd(II) solution. The membrane, which contained 0.5% CNDs/PES, showed the highest percentage removal. This was due to the –OH and enhanced -COO- on the membrane composite, which could be attributed to the increase in the presence of CNDs within the membrane. , M.Sc. (Chemistry)
- Full Text:
- Authors: Sam, Simanye
- Date: 2019
- Subjects: Cadmium , Carbon , Nanostructured materials , Water - Purification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401568 , uj:33567
- Description: Abstract : Water pollution by heavy metals is a serious problem in South Africa due to mining activities, electroplating industries, weathering of minerals and soils and coal combustion. Most river systems have been exposed to heavy metals contamination due to effluent disposal and this directly affects communities that use these sources for domestic purposes. For example, Umtata River which is exposed to Cd(II) is used for various purposes by a large population of the Transkei, most of which is rural - domestic (cooking, drinking and washing), agricultural (that is, livestock watering and irrigation), and recreational purposes (swimming). Water pollution by heavy metals such as, Cd(II) in particular is unavoidable and it causes undesirable health effects, such as hypertension and kidney failure. Thus, it is very important to find new ways to efficiently remove these metals from water. Nanostructured membranes are amongst other water treatment methods that have shown the ability to efficiently remove heavy metals from water. Therefore, this study seeks to provide a facile and effective method to remove heavy metals such as cadmium(II) from synthetic solutions and industrial water effluents. This was achieved by embedding carbon nanodots (CNDs) on a polyethersulfone (PES) membrane as support via phase inversion. The synthesized CNDs and fabricated membranes were characterized using Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscope (SEM), Atomic Force Microscope (AFM), contact angle and pure water flux assessment. TEM analysis confirmed that the synthesized CNDs were well dispersed with uniform shape and size (6.7±2.8 nm). Raman analysis illustrated that the CNDs were embedded on the PES and that after blending the PES with CNDs the ID/IG ratio slightly increased after modification of the membranes with CNDs showing that the membranes maintained good structural integrity. The CNDs/PES membranes showed improved hydrophilicity compared to the pristine PES. vi At constant pressure of 300 kPa the flux of pristine PES, 0.01% CNDs/PES, 0.05% CNDs/PES and CNDs/PES was 60.00 L.m-2.h-1, 96.93 L.m-2.h-1, 142.16 L.m-2.h-1 and 196.62 L.m-2.h-1 respectively. The performance of the membrane was optimised using batch adsorption experiments. The analysis revealed that 95.71, 96.32, 97.69 and 99.78% Cd2+ was removed by PES, 0.01% CNDs/PES, 0.05% CNDs/PES and 0.5% CNDs/PES, respectively at optimum conditions: 30 minutes contact time, at pH 5 and 0.5 ppm Cd(II) solution. The membrane, which contained 0.5% CNDs/PES, showed the highest percentage removal. This was due to the –OH and enhanced -COO- on the membrane composite, which could be attributed to the increase in the presence of CNDs within the membrane. , M.Sc. (Chemistry)
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Characterization, in vitro cytotoxicity studies and photoactive effect of gold nanorods on colorectal cancer cells
- Authors: Kadanyo, Sania
- Date: 2016
- Subjects: Nanostructured materials , Rectum - Cancer - Treatment , Cancer - Treatment , Nanomedicine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124772 , uj:20958
- Description: Abstract: Cancer is a disease formed from abnormal growth of cells affecting any part of the body. It is reported that cancer is the third leading cause of death after stroke and heart disease in developed countries. Colorectal cancer (CRC) incidence and mortality rates vary markedly around the world; according to the World Health Organization (WHO) colorectal cancer is the third most commonly diagnosed cancer as well as being the third leading cause of cancer death after lung and gastric cancer worldwide in both sexes. Thus each year over 1 million new patients develop colorectal cancer and over 600,000 patients die from it. The main problem in using most conventional cancer therapies such as anticancer drugs (chemotherapy); as well as radiation is their low selectivity for cancer cells coupled with their often high toxicity to non-targeted cells in the body and they often cause side effects that may be more unbearable than the disease at that particular point in time. In contrast with conventional cancer therapy’s photodynamic therapy (PDT) was developed to try and address the disadvantages caused by conventional therapy’s. Photodynamic therapy is a non-invasive method which yields satisfactory clinical results with fewer adverse side effects accompanied by higher selectivity. Although photodynamic therapy has significantly improved the quality of life and life expectancy of patients with cancer, further advances in therapeutic efficacy are required to overcome numerous side effects for example hydrophobicity and poor selectivity between deceased cells and healthy cells related to conventional PDT. Much attention has been directed to improving photosensitizers. Due to the highly desirable and tunable optical properties of light sensitive nanoparticles they are deemed resourceful in developing phototherapeutic agents for cancer therapy. Gold nanorods (GNRs) showing a surface plasmon resonance (SPR) band at the near infra-red (NIR) region are of great interest for the development of nanomedicine in particular phototherapy of cancer and drug delivery. The main concerns usually encountered when using metal nanoparticles for general bio-applications are their potential toxicity and biological interactions of the nanoparticles with the cells... , M.Sc. (Nanoscience)
- Full Text:
- Authors: Kadanyo, Sania
- Date: 2016
- Subjects: Nanostructured materials , Rectum - Cancer - Treatment , Cancer - Treatment , Nanomedicine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124772 , uj:20958
- Description: Abstract: Cancer is a disease formed from abnormal growth of cells affecting any part of the body. It is reported that cancer is the third leading cause of death after stroke and heart disease in developed countries. Colorectal cancer (CRC) incidence and mortality rates vary markedly around the world; according to the World Health Organization (WHO) colorectal cancer is the third most commonly diagnosed cancer as well as being the third leading cause of cancer death after lung and gastric cancer worldwide in both sexes. Thus each year over 1 million new patients develop colorectal cancer and over 600,000 patients die from it. The main problem in using most conventional cancer therapies such as anticancer drugs (chemotherapy); as well as radiation is their low selectivity for cancer cells coupled with their often high toxicity to non-targeted cells in the body and they often cause side effects that may be more unbearable than the disease at that particular point in time. In contrast with conventional cancer therapy’s photodynamic therapy (PDT) was developed to try and address the disadvantages caused by conventional therapy’s. Photodynamic therapy is a non-invasive method which yields satisfactory clinical results with fewer adverse side effects accompanied by higher selectivity. Although photodynamic therapy has significantly improved the quality of life and life expectancy of patients with cancer, further advances in therapeutic efficacy are required to overcome numerous side effects for example hydrophobicity and poor selectivity between deceased cells and healthy cells related to conventional PDT. Much attention has been directed to improving photosensitizers. Due to the highly desirable and tunable optical properties of light sensitive nanoparticles they are deemed resourceful in developing phototherapeutic agents for cancer therapy. Gold nanorods (GNRs) showing a surface plasmon resonance (SPR) band at the near infra-red (NIR) region are of great interest for the development of nanomedicine in particular phototherapy of cancer and drug delivery. The main concerns usually encountered when using metal nanoparticles for general bio-applications are their potential toxicity and biological interactions of the nanoparticles with the cells... , M.Sc. (Nanoscience)
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Corrosion inhibition of mild steel in 1 M Hcl using synthesized eco-friendly polymer composites
- Authors: ‘Mofu, Ts’oeunyane George
- Date: 2017
- Subjects: Corrosion resistant materials , Nanostructured materials , Stainless steel - Corrosion , Corrosion and anti-corrosives
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269731 , uj:28658
- Description: M.Tech. (Metallurgy) , Abstract: In this work, two polymer composites namely PBSLP and PBSLH were synthesized and characterized by FTIR, NMR, XRD, SEM, CHNS and TGA. The results revealed that the formed polymer composite were graft polymer composites. The two synthesized polymer composites were investigated as corrosion inhibitors for MS in 1 M HCl. The corrosion inhibition characteristics including, corrosion rate, corrosion inhibition efficiency, and inhibitor adsorption to the metal surface were studied with gravimetric and electrochemical studies. The gravimetric studies revealed that adsorption of the polymer composites to the MS surface were both physisorption and chemisorption although physisorption appeared to be the more dominant process. Moreover, both polymer composites obeyed Langmuir isotherm. Electrochemical studies were also used to characterize that inhibitory mechanism of the said polymer composites. PDP, specifically Tafel plot and VASP with used to determine the corrosion parameters while EIS was employed to determine the charge transfer characteristics during corrosion. The results indicated that PBSLP and PBSLH are both mixed type corrosion inhibitors with cathodic reaction being the most affected reaction. In addition, the charge transfer resistance during corrosion increased with the increase in concentration of inhibitors. SEM was also used to examine the morphology of MS coupons before and after exposure to corrosive, the results revealed that PBSLP and PBSLH reduce corrosion of MS by forming a film on MS surface.
- Full Text:
- Authors: ‘Mofu, Ts’oeunyane George
- Date: 2017
- Subjects: Corrosion resistant materials , Nanostructured materials , Stainless steel - Corrosion , Corrosion and anti-corrosives
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269731 , uj:28658
- Description: M.Tech. (Metallurgy) , Abstract: In this work, two polymer composites namely PBSLP and PBSLH were synthesized and characterized by FTIR, NMR, XRD, SEM, CHNS and TGA. The results revealed that the formed polymer composite were graft polymer composites. The two synthesized polymer composites were investigated as corrosion inhibitors for MS in 1 M HCl. The corrosion inhibition characteristics including, corrosion rate, corrosion inhibition efficiency, and inhibitor adsorption to the metal surface were studied with gravimetric and electrochemical studies. The gravimetric studies revealed that adsorption of the polymer composites to the MS surface were both physisorption and chemisorption although physisorption appeared to be the more dominant process. Moreover, both polymer composites obeyed Langmuir isotherm. Electrochemical studies were also used to characterize that inhibitory mechanism of the said polymer composites. PDP, specifically Tafel plot and VASP with used to determine the corrosion parameters while EIS was employed to determine the charge transfer characteristics during corrosion. The results indicated that PBSLP and PBSLH are both mixed type corrosion inhibitors with cathodic reaction being the most affected reaction. In addition, the charge transfer resistance during corrosion increased with the increase in concentration of inhibitors. SEM was also used to examine the morphology of MS coupons before and after exposure to corrosive, the results revealed that PBSLP and PBSLH reduce corrosion of MS by forming a film on MS surface.
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Determination of Cd(II) in water using aptamer-based electrochemical biosensors
- Authors: Fakude, Colani Thembinkosi
- Date: 2020
- Subjects: Water - Analysis , Cadmium , Electrochemical analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458431 , uj:40718
- Description: Abstract: The World Health Organisation has recommended strict permissible limits for cadmium(II) in drinking water owing to the harmful threats it poses to humans and the environment. As a result, strict monitoring of cadmium(II) is a necessity. This dissertation reports on the design of monitoring tools referred to as electrochemical aptamer biosensors (aptasensors) based on nano-platforms for selective detection of Cd(II) in water. Nanomaterials such as carbon black, gold nanoparticles and carbon nanofibres were the smart materials of choice used in the fabrication of electrode supports for enhancement of detection signals. A screen-printed electrode was modified using carbon black following the dropcoating technique and then gold nanoparticles were electrodeposited by cyclic voltammetry (CV) at 50 mVs-1 in a potential window of -400 mV to 1100 mV. A thiolated single stranded DNA aptamer was immobilised on the nano-platform via a Au-S covalent linkage. The aptasensor was characterised using CV and electrochemical impedance spectroscopy ((EIS). The designed electrochemical aptasensor selectively detected Cd(II) using the square wave voltammetry (SWV) technique with a detection limit (LOD) of 0.14 ppb in the presence of interferents like chromium, copper and other ions. The second electrochemical aptasensor was based on the fabrication of a screen-printed electrode using acid treated carbon nanofibres. The characterisation procedure was similar with the first aptasensor and upon application, the aptasensor was found to be selective towards Cd(II) detection. A detection limit of 0.11 ppb was obtained using SWV and the aptasensor. Both the aptasensor findings were validated with inductively coupled plasma optical emission spectroscopy (ICP-OES) which showed an LOD of 1.4 ppb. Both electrochemical aptasensor provide a cost effective approach for the mitigation of interferences during electrochemical detection of Cd(II) and they can be applied in the monitoring of Cd(II) in environmental samples. , M.Sc. (Chemistry)
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- Authors: Fakude, Colani Thembinkosi
- Date: 2020
- Subjects: Water - Analysis , Cadmium , Electrochemical analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458431 , uj:40718
- Description: Abstract: The World Health Organisation has recommended strict permissible limits for cadmium(II) in drinking water owing to the harmful threats it poses to humans and the environment. As a result, strict monitoring of cadmium(II) is a necessity. This dissertation reports on the design of monitoring tools referred to as electrochemical aptamer biosensors (aptasensors) based on nano-platforms for selective detection of Cd(II) in water. Nanomaterials such as carbon black, gold nanoparticles and carbon nanofibres were the smart materials of choice used in the fabrication of electrode supports for enhancement of detection signals. A screen-printed electrode was modified using carbon black following the dropcoating technique and then gold nanoparticles were electrodeposited by cyclic voltammetry (CV) at 50 mVs-1 in a potential window of -400 mV to 1100 mV. A thiolated single stranded DNA aptamer was immobilised on the nano-platform via a Au-S covalent linkage. The aptasensor was characterised using CV and electrochemical impedance spectroscopy ((EIS). The designed electrochemical aptasensor selectively detected Cd(II) using the square wave voltammetry (SWV) technique with a detection limit (LOD) of 0.14 ppb in the presence of interferents like chromium, copper and other ions. The second electrochemical aptasensor was based on the fabrication of a screen-printed electrode using acid treated carbon nanofibres. The characterisation procedure was similar with the first aptasensor and upon application, the aptasensor was found to be selective towards Cd(II) detection. A detection limit of 0.11 ppb was obtained using SWV and the aptasensor. Both the aptasensor findings were validated with inductively coupled plasma optical emission spectroscopy (ICP-OES) which showed an LOD of 1.4 ppb. Both electrochemical aptasensor provide a cost effective approach for the mitigation of interferences during electrochemical detection of Cd(II) and they can be applied in the monitoring of Cd(II) in environmental samples. , M.Sc. (Chemistry)
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Development of an electrochemical cholesterol biosensor based on poly (propylene imine) dendrimer- quantum dots nanocomposite
- Authors: Mokwebo, Kefilwe Vanessa
- Date: 2018
- Subjects: Electrochemical sensors , Biosensors , Quantum dots , Nanostructured materials , Dendrimers in medicine , Cholesterol - Physiological effect
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279597 , uj:30029
- Description: M.Sc. (Nanoscience) , Abstract: One of the parameters that cause cardiovascular diseases (CVDs) is high level of cholesterol in the blood. Therefore, monitoring of cholesterol level is of great importance, especially to elderly people and people with high risk of such diseases. This work explores the applicability of poly (propylene imine) dendrimer (PPI) and CdTe/CdSe/ZnSe quantum dots (QDs) in developing a suitable platform for the development of an enzyme-based electrochemical cholesterol biosensor with enhanced analytical performance. The as-synthesized mercaptopropionic acid (MPA) capped CdTe/CdSe/ZnSe QDs was synthesized in an aqueous phase and characterized using photoluminescence (PL) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), powdered X-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The absorption and emission maxima red-shifted as the reaction time and shell growth increased. The increase in PL intensities shows proper passivation of the QDs surface with PL quantum yield (PLQY) of 33.8 %, 69.2 % and 57 %, for CdTe, CdTe/CdSe and CdTe/CdSe/ZnSe QDs respectively. The XRD patterns of all the as-synthesized QDs consist of three diffraction peaks corresponding to (111), (220) and (311) cubic zinc blended structures. The estimated particle size of CdTe/CdSe/ZnSe QDs from XRD and TEM are 4.32 and 4.08 nm, respectively while the EDX confirmed the presence of corresponding elements. For biosensor design, PPI dendrimer was electrochemically deposited on glassy carbon electrode (GCE) and characterized using cyclic voltammetry (CV) and impedance spectroscopy (EIS) in both phosphate buffer solution (PBS) and ferricyanide solution ([Fe(CN)6]-3/-4) This was followed by drop-drying the QDs on the electrode to form GCE/PPI/QDs. Finally, cholesterol oxidase (ChOx) was drop-dried on the GCE/PPI/QDs electrode to produce GCE/PPI/QDs/ChOx-based electrochemical cholesterol biosensor. Scanning electron microscopy (SEM) was used to characterize screen printed carbon electrode (SPCE) as it was modified with different materials and was able to capture the nano-globular morphology of PPI dendrimer. The GCE/PPI/QDs/ChOx based cholesterol biosensor was able to detect cholesterol in the range 0.1-10 mM with a...
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- Authors: Mokwebo, Kefilwe Vanessa
- Date: 2018
- Subjects: Electrochemical sensors , Biosensors , Quantum dots , Nanostructured materials , Dendrimers in medicine , Cholesterol - Physiological effect
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279597 , uj:30029
- Description: M.Sc. (Nanoscience) , Abstract: One of the parameters that cause cardiovascular diseases (CVDs) is high level of cholesterol in the blood. Therefore, monitoring of cholesterol level is of great importance, especially to elderly people and people with high risk of such diseases. This work explores the applicability of poly (propylene imine) dendrimer (PPI) and CdTe/CdSe/ZnSe quantum dots (QDs) in developing a suitable platform for the development of an enzyme-based electrochemical cholesterol biosensor with enhanced analytical performance. The as-synthesized mercaptopropionic acid (MPA) capped CdTe/CdSe/ZnSe QDs was synthesized in an aqueous phase and characterized using photoluminescence (PL) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), powdered X-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The absorption and emission maxima red-shifted as the reaction time and shell growth increased. The increase in PL intensities shows proper passivation of the QDs surface with PL quantum yield (PLQY) of 33.8 %, 69.2 % and 57 %, for CdTe, CdTe/CdSe and CdTe/CdSe/ZnSe QDs respectively. The XRD patterns of all the as-synthesized QDs consist of three diffraction peaks corresponding to (111), (220) and (311) cubic zinc blended structures. The estimated particle size of CdTe/CdSe/ZnSe QDs from XRD and TEM are 4.32 and 4.08 nm, respectively while the EDX confirmed the presence of corresponding elements. For biosensor design, PPI dendrimer was electrochemically deposited on glassy carbon electrode (GCE) and characterized using cyclic voltammetry (CV) and impedance spectroscopy (EIS) in both phosphate buffer solution (PBS) and ferricyanide solution ([Fe(CN)6]-3/-4) This was followed by drop-drying the QDs on the electrode to form GCE/PPI/QDs. Finally, cholesterol oxidase (ChOx) was drop-dried on the GCE/PPI/QDs electrode to produce GCE/PPI/QDs/ChOx-based electrochemical cholesterol biosensor. Scanning electron microscopy (SEM) was used to characterize screen printed carbon electrode (SPCE) as it was modified with different materials and was able to capture the nano-globular morphology of PPI dendrimer. The GCE/PPI/QDs/ChOx based cholesterol biosensor was able to detect cholesterol in the range 0.1-10 mM with a...
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Electrocatalytic properties of platinum and platinum-based carbon nanodots nanocomposites as electrocatalysts for direct alcohol fuel cells
- Authors: Gwebu, Sandile Surprise
- Date: 2018
- Subjects: Electrocatalysis , Fuel cells , Solid oxide fuel cells , Nanostructured materials , Platinum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/271337 , uj:28856
- Description: M.Tech. (Chemistry) , Abstract: Direct alcohol fuel cells are potential future energy sources for mobile and stationary appliances. They are fascinating more than the hydrogen fuel cells because they utilise a liquid fuel that is easy to store and transport. However, several drawbacks such as the high cost of pure platinum and the instability of carbon electrodes in the fuel cell environment are hindering the commercialisation of the DAFC technology. The platinum electrocatalyst is easily poisoned by the intermediates that are produced during alcohol electro-oxidation reactions, this result in low energy output. This study was devoted in synthesising a carbon support material with high surface area and to prepare platinum-based electrocatalysts with anti-poisoning and anti-corrosion properties. Carbon nanodots (CNDs) with sizes below 10 nm were synthesised by pyrolysing oats grains. The BET surface area of the CNDs was found to be 312.5 m2 g-1. XPS and FTIR results jointly revealed that the CNDs contain oxygen-containing functional groups which facilitate the attachment of metal nanoparticles. The Pt/CNDs electrocatalyst was synthesised using water as a solvent without adding any reducing agent. The Pt/CNDs electrocatalyst was tested against the commercial Pt/C standard to evaluate the performance of the CNDs (support material). Cyclic voltammetry results showed that the Pt/CNDs electrocatalyst prepared by this method exhibit superior performance for methanol and ethanol electro-oxidation at room temperature. The Pt-Sn/CNDs electrocatalyst was synthesised by the alcohol reduction method with the aim to reduce platinum loading and improve electroactivity. XPS results showed that the nanoparticles were present in the form of Pt-Sn metallic alloy with a significant amount of SnO- species. The lattice parameter of Pt in Pt-Sn/CNDs electrocatalyst was calculated to be 0.3926 nm; this value is higher than 0.3921 nm, the lattice parameter of Pt in Pt/CNDs electrocatalyst. XRD results proved that...
- Full Text:
- Authors: Gwebu, Sandile Surprise
- Date: 2018
- Subjects: Electrocatalysis , Fuel cells , Solid oxide fuel cells , Nanostructured materials , Platinum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/271337 , uj:28856
- Description: M.Tech. (Chemistry) , Abstract: Direct alcohol fuel cells are potential future energy sources for mobile and stationary appliances. They are fascinating more than the hydrogen fuel cells because they utilise a liquid fuel that is easy to store and transport. However, several drawbacks such as the high cost of pure platinum and the instability of carbon electrodes in the fuel cell environment are hindering the commercialisation of the DAFC technology. The platinum electrocatalyst is easily poisoned by the intermediates that are produced during alcohol electro-oxidation reactions, this result in low energy output. This study was devoted in synthesising a carbon support material with high surface area and to prepare platinum-based electrocatalysts with anti-poisoning and anti-corrosion properties. Carbon nanodots (CNDs) with sizes below 10 nm were synthesised by pyrolysing oats grains. The BET surface area of the CNDs was found to be 312.5 m2 g-1. XPS and FTIR results jointly revealed that the CNDs contain oxygen-containing functional groups which facilitate the attachment of metal nanoparticles. The Pt/CNDs electrocatalyst was synthesised using water as a solvent without adding any reducing agent. The Pt/CNDs electrocatalyst was tested against the commercial Pt/C standard to evaluate the performance of the CNDs (support material). Cyclic voltammetry results showed that the Pt/CNDs electrocatalyst prepared by this method exhibit superior performance for methanol and ethanol electro-oxidation at room temperature. The Pt-Sn/CNDs electrocatalyst was synthesised by the alcohol reduction method with the aim to reduce platinum loading and improve electroactivity. XPS results showed that the nanoparticles were present in the form of Pt-Sn metallic alloy with a significant amount of SnO- species. The lattice parameter of Pt in Pt-Sn/CNDs electrocatalyst was calculated to be 0.3926 nm; this value is higher than 0.3921 nm, the lattice parameter of Pt in Pt/CNDs electrocatalyst. XRD results proved that...
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Electrochemical co-detection of arsenic, lead and mercury on exfoliated graphite nanocomposite electrodes
- Authors: Mafa, Potlako John
- Date: 2016
- Subjects: Electrochemical analysis , Nanostructured materials , Graphite , Electrodes , Trace elements - Analysis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84607 , uj:19241
- Description: Abstract: Please refer to full text to view abstract , M.Sc. (Chemistry)
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- Authors: Mafa, Potlako John
- Date: 2016
- Subjects: Electrochemical analysis , Nanostructured materials , Graphite , Electrodes , Trace elements - Analysis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84607 , uj:19241
- Description: Abstract: Please refer to full text to view abstract , M.Sc. (Chemistry)
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Electrochemical detection of arsenic and selenium on modified carbon based nanocomposite electrodes
- Authors: Idris, Azeez Olayiwola
- Date: 2016
- Subjects: Nanostructured materials , Electrodes, Carbon , Electrochemical analysis , Organic water pollutants , Carbon composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124946 , uj:20978
- Description: Abstract: This study explores the applications of nanomaterial modified on glassy carbon electrode (GCE) in the electroanalysis of arsenic and selenium ions in water. GCE was modified with gold nanoparticles and reduced graphene oxide. Gold nanoparticle (AuNPs) modified GCE (GCE-AuNPs) was prepared by electrochemical deposition of gold from 5 mM of HAuCl4 solutions by cycling the potential from -400 mV to 1100 mV for 10 cycles at a scan rate of 50 mVs-1. GCEAuNPs was electrochemically investigated using redox probes which are [Fe (CN) 6]3-/4- and Ru (NH3)62+/3+. The current and the reversibility of the redox probes were enhanced in the presence of modifiers. The electrochemical determination of selenium by square wave anodic stripping voltammetry (SWASV) using GCE-AuNPs was carried out under the optimised conditions: pH 1, deposition potential of -100 mV, deposition time of 60 s and 0.1 M H2SO4 as supporting electrolyte. A detection limit of 0.64 μg L-1 was obtained. Cu and Cd were the only significant interferences observed for the electrochemical detection of selenium. Attempt was also made to sense selenium in tap water, concentration of 8.86 (± 0.34) ppb Se, was calculated for the tap water. The electrochemical method was validated with ICP-OES. Furthermore, arsenic was detected on GCE-AuNPs by SWASV. The sensing of arsenic was also optimised at different analytical conditions and a detection limit of 0.75 μgL-1 was obtained. Cu, Cd and Hg were the major interferences in arsenic sensing. Ammonia, EDTA and G3 PPI were used as ligands to mask the interference effect of copper on arsenic sensing in the bid to remove interference. Graphene oxide was synthesised by using Hummer`s methods and was further reduced to reduced graphene oxide using ascorbic acid. The reduced graphene oxide was used to modify GCE, the modification of GCE with rGO-GCE resulted in an increase in the electroactive surface area of the electrode which led to enhance the redox peak of [Fe(CN)6]3-/4- in comparison to the bare GCE. SWASV was used to detect Se (IV) in water at the following optimum conditions: 0.1 M HNO3 as supporting electrolyte, deposition potential of -100 mV and pre-concentration time of 240 s. The rGO-GCE sensor was able to detect Se (IV) to the limit of 2.2 ppb and was not susceptible to many interfering cations except Cu (II) and Cd (II). , M.Sc. (Chemistry)
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- Authors: Idris, Azeez Olayiwola
- Date: 2016
- Subjects: Nanostructured materials , Electrodes, Carbon , Electrochemical analysis , Organic water pollutants , Carbon composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124946 , uj:20978
- Description: Abstract: This study explores the applications of nanomaterial modified on glassy carbon electrode (GCE) in the electroanalysis of arsenic and selenium ions in water. GCE was modified with gold nanoparticles and reduced graphene oxide. Gold nanoparticle (AuNPs) modified GCE (GCE-AuNPs) was prepared by electrochemical deposition of gold from 5 mM of HAuCl4 solutions by cycling the potential from -400 mV to 1100 mV for 10 cycles at a scan rate of 50 mVs-1. GCEAuNPs was electrochemically investigated using redox probes which are [Fe (CN) 6]3-/4- and Ru (NH3)62+/3+. The current and the reversibility of the redox probes were enhanced in the presence of modifiers. The electrochemical determination of selenium by square wave anodic stripping voltammetry (SWASV) using GCE-AuNPs was carried out under the optimised conditions: pH 1, deposition potential of -100 mV, deposition time of 60 s and 0.1 M H2SO4 as supporting electrolyte. A detection limit of 0.64 μg L-1 was obtained. Cu and Cd were the only significant interferences observed for the electrochemical detection of selenium. Attempt was also made to sense selenium in tap water, concentration of 8.86 (± 0.34) ppb Se, was calculated for the tap water. The electrochemical method was validated with ICP-OES. Furthermore, arsenic was detected on GCE-AuNPs by SWASV. The sensing of arsenic was also optimised at different analytical conditions and a detection limit of 0.75 μgL-1 was obtained. Cu, Cd and Hg were the major interferences in arsenic sensing. Ammonia, EDTA and G3 PPI were used as ligands to mask the interference effect of copper on arsenic sensing in the bid to remove interference. Graphene oxide was synthesised by using Hummer`s methods and was further reduced to reduced graphene oxide using ascorbic acid. The reduced graphene oxide was used to modify GCE, the modification of GCE with rGO-GCE resulted in an increase in the electroactive surface area of the electrode which led to enhance the redox peak of [Fe(CN)6]3-/4- in comparison to the bare GCE. SWASV was used to detect Se (IV) in water at the following optimum conditions: 0.1 M HNO3 as supporting electrolyte, deposition potential of -100 mV and pre-concentration time of 240 s. The rGO-GCE sensor was able to detect Se (IV) to the limit of 2.2 ppb and was not susceptible to many interfering cations except Cu (II) and Cd (II). , M.Sc. (Chemistry)
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Electrochemical/photoelectrochemical studies of nickel(II) dimethylglyoxime and gold nanoparticles and their applications in the detection of phenolic water pollutants
- Authors: Olorundare, Foluke O. Grace
- Date: 2017
- Subjects: Organic water pollutants , Nanostructured materials , Phenols , Mass spectrometry , Phenols - Identification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235745 , uj:24114
- Description: M.Sc. (Chemistry) , Abstract: The electrochemical behaviour and detection of phenols such as o-nitrophenol (o-NP) and p-nitrophenol (p-NP) and also 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP), has been studied on a gold nanoparticle - nickel dimethylglyoxime complex (N(II)DMG) modified glassy carbon electrode (GCE). The electrode was prepared by drop coating nickel dimethylglyoxime complex on a GCE followed by the electrodeposition of gold nanoparticle. Each step in the electrode modification was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and high resolution scanning electron microscopy (HRSEM). There two redox probes hexacyanoferrate (III) - hexacyanoferrate(II) ion ([Fe(CN)6]3−/4− ) and hexaammineruthenium (III) chloride – hexaammineruthenium (II) chloride [Ru(NH3)6 ]2+/3+ were applied to verify the suitability of the modified electrode (i.e. GCE/NiDMG-AuNP) with satisfactory results. The results showed that nickel dimethylglyoxime complex/gold nanoparticles electrode had improved conductivity, reversibility and electron transfer rate in selected redox probe than the unmodified GCE. The GCE/NiDMG-AuNP electrode was used in the determination of o-NP and p-NP in water. Under the optimal conditions, detection limits of 0.58 μM and 0.103 μM were calculated for o-NP and p-NP respectively. The GCE/NiDMG-AuNP electrode was applied to real water sample and the effects of interferences were studied. Photoelectrochemical analysis was done with p-NP with substantial results. The GCE/NiDMG-AuNP electrode was also used to investigate the electrochemical behaviour of 2-CP and 3-CP by Cyclic Voltammetry (CV) and differential pulse voltammetry (DPV). The results demonstrated that the GCE/NiDMG-AuNP exhibited remarkable enhancement effects towards 2-CP and 3-CP. Under the optimized conditions, the oxidation peak currents displayed a good linear relationship to concentration in the ranges from 0.5 to 30 μM for 2-CP and 0.5 to 35 μM for 3-CP, with detection limits of 0.097 and 0.093 μM, respectively. This sensor was successfully used in the detection 2-CP and 3-CP of real water samples with good results.
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- Authors: Olorundare, Foluke O. Grace
- Date: 2017
- Subjects: Organic water pollutants , Nanostructured materials , Phenols , Mass spectrometry , Phenols - Identification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235745 , uj:24114
- Description: M.Sc. (Chemistry) , Abstract: The electrochemical behaviour and detection of phenols such as o-nitrophenol (o-NP) and p-nitrophenol (p-NP) and also 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP), has been studied on a gold nanoparticle - nickel dimethylglyoxime complex (N(II)DMG) modified glassy carbon electrode (GCE). The electrode was prepared by drop coating nickel dimethylglyoxime complex on a GCE followed by the electrodeposition of gold nanoparticle. Each step in the electrode modification was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and high resolution scanning electron microscopy (HRSEM). There two redox probes hexacyanoferrate (III) - hexacyanoferrate(II) ion ([Fe(CN)6]3−/4− ) and hexaammineruthenium (III) chloride – hexaammineruthenium (II) chloride [Ru(NH3)6 ]2+/3+ were applied to verify the suitability of the modified electrode (i.e. GCE/NiDMG-AuNP) with satisfactory results. The results showed that nickel dimethylglyoxime complex/gold nanoparticles electrode had improved conductivity, reversibility and electron transfer rate in selected redox probe than the unmodified GCE. The GCE/NiDMG-AuNP electrode was used in the determination of o-NP and p-NP in water. Under the optimal conditions, detection limits of 0.58 μM and 0.103 μM were calculated for o-NP and p-NP respectively. The GCE/NiDMG-AuNP electrode was applied to real water sample and the effects of interferences were studied. Photoelectrochemical analysis was done with p-NP with substantial results. The GCE/NiDMG-AuNP electrode was also used to investigate the electrochemical behaviour of 2-CP and 3-CP by Cyclic Voltammetry (CV) and differential pulse voltammetry (DPV). The results demonstrated that the GCE/NiDMG-AuNP exhibited remarkable enhancement effects towards 2-CP and 3-CP. Under the optimized conditions, the oxidation peak currents displayed a good linear relationship to concentration in the ranges from 0.5 to 30 μM for 2-CP and 0.5 to 35 μM for 3-CP, with detection limits of 0.097 and 0.093 μM, respectively. This sensor was successfully used in the detection 2-CP and 3-CP of real water samples with good results.
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Electrospun antibacterial cyclodextrin and chitosan based nanocomposite filtration materials for use in drinking water purification
- Authors: Nthunya, Lebea Nathnael
- Date: 2016
- Subjects: Water - Purification - Organic compounds removal , Nanostructured materials , Nanofibers , Electrospinning , Cyclodextrins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/85070 , uj:19298
- Description: Abstract: The quality of drinking water sources in a rural settlement within the Chief Albert Luthuli Local Municipality in Mpumalanga, South Africa was studied over a period of 8 months (from June 2014 – February 2015). Specifically the community that was used as a case study in this project is Lochiel, which has approximately 5000 residents. The community has no supply of purified water. It relies on open wells and boreholes as direct sources of drinking water and water for domestic purposes. At the inception of the study, no existing information could be found on the quality of these drinking water sources. The quality of these water sources was studied by determining the levels of toxic metals, organics, and bacteria using a range of analytical methods. The results obtained showed that the quality of the drinking water was generally acceptable and differed for each source and with change in seasons of the year. However, the study revealed that the concentrations of Co, Pb, Mn, Fe, chlorophenols, nitrophenols, E. coli and total coliforms were higher than the acceptable limits in some of the sources. In an attempt to develop materials to remove the detected pollutants in the water sources, antibacterial nanofibres based on chitosan (CS) and β-cyclodextrins (β- CDs) were synthesized for use in a point-of-use (POU) system. The CS and -CDs polymer powders were chosen due to their remarkable properties such as biodegradability, biocompatibility, low toxicity, gratifying design flexibility and cost effectiveness. The polymer powders were fabricated in the form of nanofibres using an electrospinning technique. Their ability to be electrospun was enhanced by the addition of other polymers prior to the preparation of the electrospinning solutions. Polyacrylamide (PAA), polyethylene glycol (PEG) and polyisoprene (PIP) were blended with CS to prevent its stream break-up, reduce its surface tension, improve its entanglement during electrospinning (polymers with high molecular weight assist in formation and entanglement of the jet, thereby resulting in fibre formation) and to reduce the swelling capacity of the synthesized nanofibres. Uniform non-beaded CS based nanofibres were obtained by electrospinning a CS polymer solution containing CS:PAA = 3.5:1, 5% PEG and 80% PIP relative to the CS. The optimum electrospinning conditions for the CS based nanofibres were: injection flow rate of 0.7 mL·h-1, a distance of 22 cm between the tip of the needle and the collector and a... , M.Sc. (Chemistry)
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- Authors: Nthunya, Lebea Nathnael
- Date: 2016
- Subjects: Water - Purification - Organic compounds removal , Nanostructured materials , Nanofibers , Electrospinning , Cyclodextrins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/85070 , uj:19298
- Description: Abstract: The quality of drinking water sources in a rural settlement within the Chief Albert Luthuli Local Municipality in Mpumalanga, South Africa was studied over a period of 8 months (from June 2014 – February 2015). Specifically the community that was used as a case study in this project is Lochiel, which has approximately 5000 residents. The community has no supply of purified water. It relies on open wells and boreholes as direct sources of drinking water and water for domestic purposes. At the inception of the study, no existing information could be found on the quality of these drinking water sources. The quality of these water sources was studied by determining the levels of toxic metals, organics, and bacteria using a range of analytical methods. The results obtained showed that the quality of the drinking water was generally acceptable and differed for each source and with change in seasons of the year. However, the study revealed that the concentrations of Co, Pb, Mn, Fe, chlorophenols, nitrophenols, E. coli and total coliforms were higher than the acceptable limits in some of the sources. In an attempt to develop materials to remove the detected pollutants in the water sources, antibacterial nanofibres based on chitosan (CS) and β-cyclodextrins (β- CDs) were synthesized for use in a point-of-use (POU) system. The CS and -CDs polymer powders were chosen due to their remarkable properties such as biodegradability, biocompatibility, low toxicity, gratifying design flexibility and cost effectiveness. The polymer powders were fabricated in the form of nanofibres using an electrospinning technique. Their ability to be electrospun was enhanced by the addition of other polymers prior to the preparation of the electrospinning solutions. Polyacrylamide (PAA), polyethylene glycol (PEG) and polyisoprene (PIP) were blended with CS to prevent its stream break-up, reduce its surface tension, improve its entanglement during electrospinning (polymers with high molecular weight assist in formation and entanglement of the jet, thereby resulting in fibre formation) and to reduce the swelling capacity of the synthesized nanofibres. Uniform non-beaded CS based nanofibres were obtained by electrospinning a CS polymer solution containing CS:PAA = 3.5:1, 5% PEG and 80% PIP relative to the CS. The optimum electrospinning conditions for the CS based nanofibres were: injection flow rate of 0.7 mL·h-1, a distance of 22 cm between the tip of the needle and the collector and a... , M.Sc. (Chemistry)
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Enhancing the antifungal effect of antimicrobials against opportunistic and mycotoxigenic fungi using copper nanoparticles
- Mofilikoane, Lerato Beatrice
- Authors: Mofilikoane, Lerato Beatrice
- Date: 2015
- Subjects: Antifungal agents , Nanostructured materials , Nanoparticles , Mycotoxins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124732 , uj:20952
- Description: Abstract: Various methods have been employed in controlling contamination of food and feed commodities by fungi and their toxins as well as in the management of associated diseases in various plant and animal species. However, one of the challenges in addressing these problems over the years has been the development of drug resistance by some fungal species. In addition, the lack of effectiveness of some of the drugs or antibiotics when utilized in isolation is another problem being faced. Therefore, incorporation of nanoparticles with antibiotics can be a breakthrough as the positive interactive activity between the two may enhance the effectiveness of the already existing antibiotics against opportunistic fungal species and associated diseases. The tenacity of this study was to enhance the antimicrobial effect of various antimicrobial agents against some mycotoxigenic and pathogenic fungi using CuNPs. In the present study, the synthesis of CuNPs was achieved by chemical reduction method using a reducing agent, ascorbic acid in the presence of polyethylene glycol (PEG-1000). Furthermore, ultraviolet-visible (UV-vis) light absorption spectra, scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques were utilized in characterizing the synthesized CuNPs. Individual antifungal activities of commercial antimicrobials, CuNPs and their conjugates were evaluated using the Kirby-Bauer disk diffusion assay. Initially, UV-vis spectroscopy was used to monitor the synthesis of CuNPs, which revealed a CuNP peak at 575 nm. FTIR further confirmed the coordination of PEG and CuNPs as expected and SEM micrographs confirmed the surface morphology of CuNPs even though agglomeration was observed. Antimicrobial study revealed the inhibition of fungal growth by some of the tested antimicrobial agents. Furthermore, the positive interactive effect of those active antibiotics and CuNPs resulted in an increase in 1.2 to 1.6 fold-area in antifungal activity, revealing that their conjugation enhanced their antimicrobial efficacy against the test pathogenic fungi. , M.Sc. (Nanoscience)
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- Authors: Mofilikoane, Lerato Beatrice
- Date: 2015
- Subjects: Antifungal agents , Nanostructured materials , Nanoparticles , Mycotoxins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124732 , uj:20952
- Description: Abstract: Various methods have been employed in controlling contamination of food and feed commodities by fungi and their toxins as well as in the management of associated diseases in various plant and animal species. However, one of the challenges in addressing these problems over the years has been the development of drug resistance by some fungal species. In addition, the lack of effectiveness of some of the drugs or antibiotics when utilized in isolation is another problem being faced. Therefore, incorporation of nanoparticles with antibiotics can be a breakthrough as the positive interactive activity between the two may enhance the effectiveness of the already existing antibiotics against opportunistic fungal species and associated diseases. The tenacity of this study was to enhance the antimicrobial effect of various antimicrobial agents against some mycotoxigenic and pathogenic fungi using CuNPs. In the present study, the synthesis of CuNPs was achieved by chemical reduction method using a reducing agent, ascorbic acid in the presence of polyethylene glycol (PEG-1000). Furthermore, ultraviolet-visible (UV-vis) light absorption spectra, scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques were utilized in characterizing the synthesized CuNPs. Individual antifungal activities of commercial antimicrobials, CuNPs and their conjugates were evaluated using the Kirby-Bauer disk diffusion assay. Initially, UV-vis spectroscopy was used to monitor the synthesis of CuNPs, which revealed a CuNP peak at 575 nm. FTIR further confirmed the coordination of PEG and CuNPs as expected and SEM micrographs confirmed the surface morphology of CuNPs even though agglomeration was observed. Antimicrobial study revealed the inhibition of fungal growth by some of the tested antimicrobial agents. Furthermore, the positive interactive effect of those active antibiotics and CuNPs resulted in an increase in 1.2 to 1.6 fold-area in antifungal activity, revealing that their conjugation enhanced their antimicrobial efficacy against the test pathogenic fungi. , M.Sc. (Nanoscience)
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Fabrication and characterization of nanocomposite membrane of polyethersulfone (PES) embedded with hyperbranched polyethyleneimine (HPEI) and bismuth vanadate (BiVO4) nanoparticles for the photocatalytic degradation of triclosan in solution
- Authors: Shaku, Koketjo Madielane
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polyethylene , Polyethylene - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401609 , uj:33572
- Description: Abstract : An increase in the production and usage of pharmaceutical and personal care products in various water bodies has attracted significant attention amongst the public and scientists. Classified as emerging pollutants, these pharmaceutical and personal care products ultimately accumulate and contaminate several water bodies through several pathways. Although reported to be found at very low concentrations, exposure to these emerging organic pollutants has adverse health effects to humans. Conventional methods are reported to partially degrade emerging pollutants. Therefore, it is of importance to explore effective and innovative methods for the complete degradation of these pollutants. In this study, a photocatalytic-membrane consisting of bismuth vanadate (BiVO4) nanoparticles, hyperbranched polyethyleneimine (HPEI) and polyethersulfone (PES) were used in the degradation of triclosan. BiVO4 is an n-type semiconductor with excellent properties such as lower band gap and visible light active. However, it has drawbacks such as agglomeration and having lower surface area. HPEI was used as a dispersing agent for the BiVO4 photocatalyst as this polymer has been found to be an excellent template/host for the production of monodispersed and uniform size particles. HPEI can also induce hydrophilic properties on the membrane thus alleviating fouling. BiVO4 was characterised using X-ray Diffraction (XRD) and Raman depicted that spectroscopy. These analyses revealed that there was successful synthesis of the monoclinic phase of BiVO4, as well as a phase transformation between the monoclinic phase and the tetragonal phase upon addition of HPEI within the nanoparticles. The modified membranes showed improved water flux and hydrophilicity (71°- 56°) as compared to the bare PES (75°) upon addition of HPEI and BiVO4. The modified membranes were effective in the photodegradation of triclosan (upto 86%) and this was accompanied by the generation of Cl- ions. , M.Sc. (Nanoscience)
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- Authors: Shaku, Koketjo Madielane
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polyethylene , Polyethylene - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401609 , uj:33572
- Description: Abstract : An increase in the production and usage of pharmaceutical and personal care products in various water bodies has attracted significant attention amongst the public and scientists. Classified as emerging pollutants, these pharmaceutical and personal care products ultimately accumulate and contaminate several water bodies through several pathways. Although reported to be found at very low concentrations, exposure to these emerging organic pollutants has adverse health effects to humans. Conventional methods are reported to partially degrade emerging pollutants. Therefore, it is of importance to explore effective and innovative methods for the complete degradation of these pollutants. In this study, a photocatalytic-membrane consisting of bismuth vanadate (BiVO4) nanoparticles, hyperbranched polyethyleneimine (HPEI) and polyethersulfone (PES) were used in the degradation of triclosan. BiVO4 is an n-type semiconductor with excellent properties such as lower band gap and visible light active. However, it has drawbacks such as agglomeration and having lower surface area. HPEI was used as a dispersing agent for the BiVO4 photocatalyst as this polymer has been found to be an excellent template/host for the production of monodispersed and uniform size particles. HPEI can also induce hydrophilic properties on the membrane thus alleviating fouling. BiVO4 was characterised using X-ray Diffraction (XRD) and Raman depicted that spectroscopy. These analyses revealed that there was successful synthesis of the monoclinic phase of BiVO4, as well as a phase transformation between the monoclinic phase and the tetragonal phase upon addition of HPEI within the nanoparticles. The modified membranes showed improved water flux and hydrophilicity (71°- 56°) as compared to the bare PES (75°) upon addition of HPEI and BiVO4. The modified membranes were effective in the photodegradation of triclosan (upto 86%) and this was accompanied by the generation of Cl- ions. , M.Sc. (Nanoscience)
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Graphene oxide and metal organic frameworks hybrids : synthesis, characterization and assessment in membrane application
- Authors: Masibi, Gaobodiwe Elizabeth
- Date: 2019
- Subjects: Graphene , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401277 , uj:33528
- Description: Abstract : Membrane technology has emerged as a viable means of water purification with advantages such as low cost, energy efficient, high removal efficiency and environmentally friendly production. The membrane that is considered ideal should provide improved stability, higher selectivity, higher flux, and resistance to chlorine and fouling. However fouling, low hydrophilicity and low flux remain challenges facing this technology. In this study Polyethersulfone (PES) membrane was used as a support for thin film composite membrane (TFC) and was adjusted by controlling fabrication processes, which are commonly recognized by adding additives that includes organic and inorganic materials and also by altering controlling fabrication parameters. Zeolitic imidazolate framework-8 @ graphene oxide (ZIF-8@GO) composites at different concentrations (0.1, 0.5, 0.9 and1):1 were synthesized and characterized using SEM, TEM, XRD, BET, TGA, FTIR and Raman instruments before they were embedded on top thin layer of polyamide-thin film composite (PA-TFC) membranes. PA-TFC membranes were prepared successfully using m-Phenylenediamine (MPD) and trimesoyl chloride (TMC) as monomers whereby composites (GO, ZIF-8, ZIF-8@GO) were dispersed into aqueous solution of MPD over PES support layer via interfacial polymerization process. Thereafter the surface morphology, cross section and surface roughness were characterized using SEM and AFM microscopes before reverse osmosis application. The membranes incorporated with composites resulted in lower surface roughness, higher fluxes, higher salt and dye rejection as compared to the pure PES. In addition membranes with lower surface roughness displayed a better fouling propensity than pristine PES and TFC membranes. , M.Sc. (Nanoscience)
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- Authors: Masibi, Gaobodiwe Elizabeth
- Date: 2019
- Subjects: Graphene , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401277 , uj:33528
- Description: Abstract : Membrane technology has emerged as a viable means of water purification with advantages such as low cost, energy efficient, high removal efficiency and environmentally friendly production. The membrane that is considered ideal should provide improved stability, higher selectivity, higher flux, and resistance to chlorine and fouling. However fouling, low hydrophilicity and low flux remain challenges facing this technology. In this study Polyethersulfone (PES) membrane was used as a support for thin film composite membrane (TFC) and was adjusted by controlling fabrication processes, which are commonly recognized by adding additives that includes organic and inorganic materials and also by altering controlling fabrication parameters. Zeolitic imidazolate framework-8 @ graphene oxide (ZIF-8@GO) composites at different concentrations (0.1, 0.5, 0.9 and1):1 were synthesized and characterized using SEM, TEM, XRD, BET, TGA, FTIR and Raman instruments before they were embedded on top thin layer of polyamide-thin film composite (PA-TFC) membranes. PA-TFC membranes were prepared successfully using m-Phenylenediamine (MPD) and trimesoyl chloride (TMC) as monomers whereby composites (GO, ZIF-8, ZIF-8@GO) were dispersed into aqueous solution of MPD over PES support layer via interfacial polymerization process. Thereafter the surface morphology, cross section and surface roughness were characterized using SEM and AFM microscopes before reverse osmosis application. The membranes incorporated with composites resulted in lower surface roughness, higher fluxes, higher salt and dye rejection as compared to the pure PES. In addition membranes with lower surface roughness displayed a better fouling propensity than pristine PES and TFC membranes. , M.Sc. (Nanoscience)
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Green synthesis of silver and platinum nanostructures using water hyacinth plant leave extract
- Authors: Anyik, John Leo
- Date: 2017
- Subjects: Nanostructured materials , Green chemistry , Metathesis (Chemistry) , Water-soluble organometallic compounds
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/244024 , uj:25231
- Description: M.Sc. (Chemistry) , Abstract: An eco-friendly synthesis of silver (Ag) and platinum (Pt) nanoparticles (NPs) using aqueous extracts from both fresh and dried leaves of water hyacinth plant as efficient reducing and stabilizing agents is presented. The optical properties of the as-synthesised material from both extracts were studied at different pH and reaction time and were characterized using UV-visible, transmission electron microscopy (TEM), Fourier Transform infra-red spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The colour changes from light yellow to brown with the presence of the silver surface plasmon resonance (SPR) band indicated the formation of Ag-NPs while the disappearance of the peak intensity at 260 nm confirmed the formation of Pt-NPs. TEM analysis showed that the as-synthesised materials from both extracts were of different sizes and spherical in shape while DLS analysis revealed their hydrodynamic sizes in the hydrated state. FTIR indicated that, the presence of polyphenols, alkaloids and polysaccharides groups present in both water hyacinth leaf extract were responsible for the reduction and capping of Ag-NPs and Pt-NPs. The presence of elemental silver as well as platinum and the purity of the as-synthesised sample were confirmed by EDS analysis. This study demonstrates the feasibility of using water hyacinth leaf extract from fresh and dried leaves for the synthesis of Ag-NPs and Pt-NPs. However, fresh leaves extract was more preferred than dried leaves extract as it retains most of the phytochemicals that could influence the formations of the nanoparticles. The as-synthesised materials were further used for colorimetric sensing of heavy metals in aqueous solution (Hg2+, Ca2+, Cr3+, Ba2+ Li+, K+, Ni2+, Co2+, Pb2+, Mn2+) and only Ag-NPs shows a sensitive response towards these metal ions as indicated by the shift in the position of the surface plasmon resonance (SPR) band with a more selective response to Hg2+. Pt-NPs on the other hand show no response towards these metal ions and hence cannot act as a colorimetric probe...
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- Authors: Anyik, John Leo
- Date: 2017
- Subjects: Nanostructured materials , Green chemistry , Metathesis (Chemistry) , Water-soluble organometallic compounds
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/244024 , uj:25231
- Description: M.Sc. (Chemistry) , Abstract: An eco-friendly synthesis of silver (Ag) and platinum (Pt) nanoparticles (NPs) using aqueous extracts from both fresh and dried leaves of water hyacinth plant as efficient reducing and stabilizing agents is presented. The optical properties of the as-synthesised material from both extracts were studied at different pH and reaction time and were characterized using UV-visible, transmission electron microscopy (TEM), Fourier Transform infra-red spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The colour changes from light yellow to brown with the presence of the silver surface plasmon resonance (SPR) band indicated the formation of Ag-NPs while the disappearance of the peak intensity at 260 nm confirmed the formation of Pt-NPs. TEM analysis showed that the as-synthesised materials from both extracts were of different sizes and spherical in shape while DLS analysis revealed their hydrodynamic sizes in the hydrated state. FTIR indicated that, the presence of polyphenols, alkaloids and polysaccharides groups present in both water hyacinth leaf extract were responsible for the reduction and capping of Ag-NPs and Pt-NPs. The presence of elemental silver as well as platinum and the purity of the as-synthesised sample were confirmed by EDS analysis. This study demonstrates the feasibility of using water hyacinth leaf extract from fresh and dried leaves for the synthesis of Ag-NPs and Pt-NPs. However, fresh leaves extract was more preferred than dried leaves extract as it retains most of the phytochemicals that could influence the formations of the nanoparticles. The as-synthesised materials were further used for colorimetric sensing of heavy metals in aqueous solution (Hg2+, Ca2+, Cr3+, Ba2+ Li+, K+, Ni2+, Co2+, Pb2+, Mn2+) and only Ag-NPs shows a sensitive response towards these metal ions as indicated by the shift in the position of the surface plasmon resonance (SPR) band with a more selective response to Hg2+. Pt-NPs on the other hand show no response towards these metal ions and hence cannot act as a colorimetric probe...
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Incorporation of zwitterion modified graphene oxide onto thin-film composite layer to enhance flix and solute rejection
- Authors: Xabela, Sinethemba Snezz
- Date: 2019
- Subjects: Nanostructured materials , Membrane separation , Graft copolymers , Nanofiltration , Membrane filters
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401694 , uj:33583
- Description: Abstract : In this work, surface Zwitterion functionalization of graphene oxide (GO) was carried out by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface by means of reverse atom transfer radical polymerization (RATRP) approach to generate GO-PSBMA nanoplates. GO-PSBMA was characterized by Fourier transforms infrared spectra (FT-IR), thermal gravimetric analysis (TGA), X-Ray Diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM) techniques. The influence of GO-PSBMA was investigated on different membrane polymers by incorporating different amounts of this additive into cellulose acetate (CA) and polyphenylsulfone (PPSU) casting solutions through phase inversion method, initially for the removal of both organic dyes and salts in water. Furthermore, GO-PSBMA was incorporated into the polyamide (PA) selective layer to develop a novel thin-film composite (TFC) membrane for desalination application. The effect of GO-PSBMA on the morphology and surface property of the CA, PPSU and TFC membranes was examined using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and ATR-FTIR. The contact angle (CA), pure water flux (PWF) and antifouling properties of modified membranes were also used to investigate the membranes performance. On cellulose acetate hybrid membranes, it was found that the water flux of the hybrid membrane was greatly enhanced from 100.71 L.m-2.h-1 to 258.39 L.m-2.h-1 when the GO-PSBMA content increased from 0 to 0.5 wt.%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (FRR) (93%) and a low total flux decline ratio (0.01%). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified CA membranes, the hybrid membranes had a higher retention of CR dye (99.01%), MO dye (84%) and MB dye (95%), and a lower rejection of salts at an operational pressure of 900 kPa, rendering the membranes... , M.Sc. (Chemistry)
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- Authors: Xabela, Sinethemba Snezz
- Date: 2019
- Subjects: Nanostructured materials , Membrane separation , Graft copolymers , Nanofiltration , Membrane filters
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401694 , uj:33583
- Description: Abstract : In this work, surface Zwitterion functionalization of graphene oxide (GO) was carried out by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface by means of reverse atom transfer radical polymerization (RATRP) approach to generate GO-PSBMA nanoplates. GO-PSBMA was characterized by Fourier transforms infrared spectra (FT-IR), thermal gravimetric analysis (TGA), X-Ray Diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM) techniques. The influence of GO-PSBMA was investigated on different membrane polymers by incorporating different amounts of this additive into cellulose acetate (CA) and polyphenylsulfone (PPSU) casting solutions through phase inversion method, initially for the removal of both organic dyes and salts in water. Furthermore, GO-PSBMA was incorporated into the polyamide (PA) selective layer to develop a novel thin-film composite (TFC) membrane for desalination application. The effect of GO-PSBMA on the morphology and surface property of the CA, PPSU and TFC membranes was examined using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and ATR-FTIR. The contact angle (CA), pure water flux (PWF) and antifouling properties of modified membranes were also used to investigate the membranes performance. On cellulose acetate hybrid membranes, it was found that the water flux of the hybrid membrane was greatly enhanced from 100.71 L.m-2.h-1 to 258.39 L.m-2.h-1 when the GO-PSBMA content increased from 0 to 0.5 wt.%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (FRR) (93%) and a low total flux decline ratio (0.01%). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified CA membranes, the hybrid membranes had a higher retention of CR dye (99.01%), MO dye (84%) and MB dye (95%), and a lower rejection of salts at an operational pressure of 900 kPa, rendering the membranes... , M.Sc. (Chemistry)
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Mechanical and tribological properties of nanoceramics dispersion strengthened 2205 duplex stainless steel
- Mphahlele, Mahlatse Ramaesele
- Authors: Mphahlele, Mahlatse Ramaesele
- Date: 2018
- Subjects: Ceramic materials - Mechanical properties , Ceramic materials - Fatigue , Nanostructured materials , Tribology , Mechanical wear
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269167 , uj:28590
- Description: M.Tech. (Chemical Engineering) , Abstract: Conventional Duplex Stainless Steel used in industrial applications suffers degradation in wear and mechanical properties. A good approach to solve these problems is the dispersion of second phase nanoparticles into duplex stainless steel matrix to improve its strength and properties. Taking the advantage of the high hardness and high chemical stability of titanium nitride (TiN), efforts were made to disperse varying amounts of TiN nanoparticles into the matrices of SAF 2205 to enhance its properties. Hence the mechanical properties and tribological behaviour of the duplex stainless steel (SAF 2205 DSS) strengthened with varied amounts of titanium-based ceramics using nanoindentation system and tribometers were studied. The elastic and plastic deformation properties of the DSS composite materials were determined with a nanoindenter together with the wear behavior of the DSS samples using the strain-to-break (H/Er) and the plastic deformation (H3/Er2) parameters. Also the wear characteristics were estimated with a Tribometer, and Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was employed to evaluate the morphology and chemistry of the wear scar of the DSS composite. The TiN nanoceramics reinforced SAF 2205 composites were fabricated using spark plasma sintering using optimized process parameters: sintering pressure (50MPa), sintering temperature (1150 oC), heating rate (100 oC/min) and sintering holding time (15 minutes). The TiN dispersions into the SAF were varied between 0 - 8 wt% at an interval of 2 wt%. Nanoindentation technique was used to access the plastic (H) properties, elastic (E) properties, the strain-to-break parameter (H/Er) and the resistance to plastic deformation parameter (H3/Er2) behaviour of the composites under loading and unloading conditions. The wear properties of coefficient of friction, wear loss, wear and specific wear rates under dry sliding conditions and varying loads and worn surface were investigated. The microstructures and worn surfaces of the composites were then evaluated using JEOL Scanning Electron Microscopy (FESEM, JSM-7600F). The results show that the TiN is evenly dispersed in the duplex matrix with a general tendency to locate itself at the grain boundaries. The mechanical properties improved considerably as the TiN content increased, resulting from grain boundary refinements and better dispersion strengthening mechanisms. The grain boundaries have better hardness and reduced young modulus compared to the grains. Furthermore, the ratios H/Er and H3/Er2 increased as the TiN composition increases which demonstrates that the nanocomposites wear resistance is favourable and it was in good correlation with the wear test data. The worn mechanism was a mixed mode of adhesive-abrasive at lower TiN composition but at higher TiN content, the adhesive mechanism prevails. This study established that increasing the addition of nanosized titanium nitride confers better microstructural properties, nanoindentation properties and wear behaviour on spark plasma sintered SAF 2205. Nanocomposite with DSS–6 % TiN reinforcement is recommended for industrial applications.
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- Authors: Mphahlele, Mahlatse Ramaesele
- Date: 2018
- Subjects: Ceramic materials - Mechanical properties , Ceramic materials - Fatigue , Nanostructured materials , Tribology , Mechanical wear
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269167 , uj:28590
- Description: M.Tech. (Chemical Engineering) , Abstract: Conventional Duplex Stainless Steel used in industrial applications suffers degradation in wear and mechanical properties. A good approach to solve these problems is the dispersion of second phase nanoparticles into duplex stainless steel matrix to improve its strength and properties. Taking the advantage of the high hardness and high chemical stability of titanium nitride (TiN), efforts were made to disperse varying amounts of TiN nanoparticles into the matrices of SAF 2205 to enhance its properties. Hence the mechanical properties and tribological behaviour of the duplex stainless steel (SAF 2205 DSS) strengthened with varied amounts of titanium-based ceramics using nanoindentation system and tribometers were studied. The elastic and plastic deformation properties of the DSS composite materials were determined with a nanoindenter together with the wear behavior of the DSS samples using the strain-to-break (H/Er) and the plastic deformation (H3/Er2) parameters. Also the wear characteristics were estimated with a Tribometer, and Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was employed to evaluate the morphology and chemistry of the wear scar of the DSS composite. The TiN nanoceramics reinforced SAF 2205 composites were fabricated using spark plasma sintering using optimized process parameters: sintering pressure (50MPa), sintering temperature (1150 oC), heating rate (100 oC/min) and sintering holding time (15 minutes). The TiN dispersions into the SAF were varied between 0 - 8 wt% at an interval of 2 wt%. Nanoindentation technique was used to access the plastic (H) properties, elastic (E) properties, the strain-to-break parameter (H/Er) and the resistance to plastic deformation parameter (H3/Er2) behaviour of the composites under loading and unloading conditions. The wear properties of coefficient of friction, wear loss, wear and specific wear rates under dry sliding conditions and varying loads and worn surface were investigated. The microstructures and worn surfaces of the composites were then evaluated using JEOL Scanning Electron Microscopy (FESEM, JSM-7600F). The results show that the TiN is evenly dispersed in the duplex matrix with a general tendency to locate itself at the grain boundaries. The mechanical properties improved considerably as the TiN content increased, resulting from grain boundary refinements and better dispersion strengthening mechanisms. The grain boundaries have better hardness and reduced young modulus compared to the grains. Furthermore, the ratios H/Er and H3/Er2 increased as the TiN composition increases which demonstrates that the nanocomposites wear resistance is favourable and it was in good correlation with the wear test data. The worn mechanism was a mixed mode of adhesive-abrasive at lower TiN composition but at higher TiN content, the adhesive mechanism prevails. This study established that increasing the addition of nanosized titanium nitride confers better microstructural properties, nanoindentation properties and wear behaviour on spark plasma sintered SAF 2205. Nanocomposite with DSS–6 % TiN reinforcement is recommended for industrial applications.
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Modeling and simulation of nanostructured copper oxides solar cells for photovoltaic application
- Authors: Enebe, George Chukwuebuka
- Date: 2019
- Subjects: Photovoltaic power generation , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/424718 , uj:36333
- Description: Abstract: The increasing global population and demand for clean and sustainable energy has led to increased research on affordable and efficient energy materials. Solar energy materials are one of those promising options. There is increased research on nanostructured metal oxide solar cell as an option for inexpensive, clean and efficient solar cells material. Copper oxide based solar cells are among those attracting interest although the efficiency is still low. This study investigates the numerical modeling and simulation of nanostructured copper oxide (cuprous and cupric oxide) heterojunction solar cells for photovoltaic applications. This is with a view to providing an optimized cell efficiency to aid experimentation and the development of high-efficiency metal oxide solar cells. The inspiration for this investigation is to give premise for experimental design for affordable, non-harmful and efficient alternative material for silicon-based solar cells. This was performed using Solar cells capacitance simulator (SCAPS). The optimization was performed by varying the effect of film thickness and by varying the effect of annealing temperature on properties of the copper oxide solar cells using SCAPS for the numerical analysis. The simulation and optimization was modeled firstly by varying the thickness of both the absorber layer and the buffer layers of Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells. The input parameter for SCAPS, obtained from literatures includes; temperature of 300K for the film thickness, input power of 1000W/m2 using illumination of AM1.5 lamp, under varying thickness of 0.5 μm to 10.0 μm for the absorber layers (Cu2O and CuO) and 0.05 μm to 6.0 μm for the buffer layer (TiO2) respectively. The simulated solar cell displayed a short-circuit current (Jsc) of 24.0764 A and 26.0516 A, open-circuit voltage (Voc) of 1.0486 V and 0.0435 V, fill factor (FF) of 63.20 % and 71 % with an efficiency (η) of 1.6 % and 8.05 % respectively, at an absorber layer thickness of 500 nm and buffer layer thickness of 50nm. Furthermore, the defect density was obtained for each solar cell. Secondly, the Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells was numerically analysed under varied annealing condition. Three annealing conditions were considered i.e. the as-deposited (300K), air and nitrogen annealed (423.15 K). Other working conditions include; an illumination of AM 1.5G with a 500 W Xenon lamp representing the sunlight. For this simulation, silver was used as the electrode/contact. The absorber layer thickness was 2000 nm and buffer layer thickness was 200 nm. The simulation report showed that nitrogen... , M.Ing. (Mechanical Engineering Science)
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- Authors: Enebe, George Chukwuebuka
- Date: 2019
- Subjects: Photovoltaic power generation , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/424718 , uj:36333
- Description: Abstract: The increasing global population and demand for clean and sustainable energy has led to increased research on affordable and efficient energy materials. Solar energy materials are one of those promising options. There is increased research on nanostructured metal oxide solar cell as an option for inexpensive, clean and efficient solar cells material. Copper oxide based solar cells are among those attracting interest although the efficiency is still low. This study investigates the numerical modeling and simulation of nanostructured copper oxide (cuprous and cupric oxide) heterojunction solar cells for photovoltaic applications. This is with a view to providing an optimized cell efficiency to aid experimentation and the development of high-efficiency metal oxide solar cells. The inspiration for this investigation is to give premise for experimental design for affordable, non-harmful and efficient alternative material for silicon-based solar cells. This was performed using Solar cells capacitance simulator (SCAPS). The optimization was performed by varying the effect of film thickness and by varying the effect of annealing temperature on properties of the copper oxide solar cells using SCAPS for the numerical analysis. The simulation and optimization was modeled firstly by varying the thickness of both the absorber layer and the buffer layers of Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells. The input parameter for SCAPS, obtained from literatures includes; temperature of 300K for the film thickness, input power of 1000W/m2 using illumination of AM1.5 lamp, under varying thickness of 0.5 μm to 10.0 μm for the absorber layers (Cu2O and CuO) and 0.05 μm to 6.0 μm for the buffer layer (TiO2) respectively. The simulated solar cell displayed a short-circuit current (Jsc) of 24.0764 A and 26.0516 A, open-circuit voltage (Voc) of 1.0486 V and 0.0435 V, fill factor (FF) of 63.20 % and 71 % with an efficiency (η) of 1.6 % and 8.05 % respectively, at an absorber layer thickness of 500 nm and buffer layer thickness of 50nm. Furthermore, the defect density was obtained for each solar cell. Secondly, the Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells was numerically analysed under varied annealing condition. Three annealing conditions were considered i.e. the as-deposited (300K), air and nitrogen annealed (423.15 K). Other working conditions include; an illumination of AM 1.5G with a 500 W Xenon lamp representing the sunlight. For this simulation, silver was used as the electrode/contact. The absorber layer thickness was 2000 nm and buffer layer thickness was 200 nm. The simulation report showed that nitrogen... , M.Ing. (Mechanical Engineering Science)
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