Showing items 1 - 17 of 17

Your selections:

8th South African Conference on Computational and Applied Mechanics, 3-5 September 2012, Conference proceedings.

- Madyira, D., Janse van Rensburg, N., Nel, A.L.

Utilisation of targeted nanoparticle photosensitiser drug delivery systems for the enhancement of photodynamic therapy

- Kruger, Cherie Ann, Abrahamse, Heidi

  • Authors: Kruger, Cherie Ann , Abrahamse, Heidi
  • Date: 2018
  • Subjects: Photodynamic therapy , Cancer , Nanotechnology
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/279500 , uj:30016 , Citation: Kruger, C.A. & Abrahamse, H. 2018. Utilisation of targeted nanoparticle photosensitiser drug delivery systems for the enhancement of photodynamic therapy. Molecules 2018, 23, 2628; doi:10.3390/molecules23102628
  • Description: Abstract: The cancer incidence world-wide has caused an increase in the demand for effective forms of treatment. One unconventional form of treatment for cancer is photodynamic therapy (PDT). PDT has 3 fundamental factors, namely a photosensitiser (PS) drug, light and oxygen. When a PS drug is administered to a patient, it can either passively or actively accumulate within a tumour site and once exposed to a specific wavelength of light, it is excited to produce reactive oxygen species (ROS), resulting in tumour destruction. However, the efficacy of ROS generation for tumour damage is highly dependent on the uptake of the PS in tumour cells. Thus, PS selective/targeted uptake and delivery in tumour cells is a crucial factor in PDT cancer drug absorption studies. Generally, within non-targeted drug delivery mechanisms, only minor amounts of PS are able to passively accumulate in tumour sites (due to the enhanced permeability and retention (EPR) effect) and the remainder distributes into healthy tissues, causing unwanted side effects and poor treatment prognosis. Thus, to improve the efficacy of PDT cancer treatment, research is currently focused on the development of specific receptor-based PS-nanocarrier platform drugs, which promote the active uptake and absorption of PS drugs in tumour sites only, avoiding unwanted side effects, as well as treatment enhancement. Therefore, the aim of this review paper is to focus on current actively targeted or passively delivered PS nanoparticle drug delivery systems, that have been previously investigated for the PDT treatment of cancer and so to deduce their overall efficacy and recent advancements.
  • Full Text:

Development of electrochemical nano-biosensors for arsenic detection

- Mushiana, Talifhani

  • Authors: Mushiana, Talifhani
  • Date: 2018
  • Subjects: Nanochemistry , Nanotechnology , Electrochemical analysis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/292796 , uj:31825
  • Description: Abstract: Arsenic contamination in groundwater is a tenacious issue in various parts of the world. Owing to the toxicity of arsenic, its detection and analysis are important for national/global wellbeing of human and animals. This dissertation reports the development of two electrochemical aptamer biosensor on a nano-platform for selective detection of As(lll) in wastewater. In the process of fabricating the biosensor, different nanomaterials such as carbon nanoparticles (CNPs), gold nanoparticles (AuNPs) and iron oxide magnetic nanoparticles (MNPs) were used to facilitate electron transfer. A glassy carbon electrode was modified with CNPs by drop drying, then AuNPs were electrodeposited on the CNPs layer using cyclic voltammetry at 50 mV/s scan rate and a potential window of -400 mV to 1100 mV. The biosensor was prepared by immobilising a thiolated aptamer onto the nano-platform through the Au-S covalent linkage to form GCE/CNPs/AuNPs/Aptamer (aptasensor). The modified electrode (aptasensor) was characterised by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in phosphate buffer saline, ferrocyanide and ruthenium electrolytes. The performance of the aptasensor was evaluated in different standard solutions of As(lll) and also in real water samples using square wave voltammetry. The aptasensor effectively detected As(lll) to a detection limit of 0.092 ppb. The results obtained were validated with ICP-OES and the analytical T-test showed that the two methods were in agreement. The aptasensor was selective in the detection of As(III) in the presence of other metal ions such as cadmium, copper and mercury.The second biosensor was fabricated by incubating a mixture of the aptamer and MNPs on screen printed carbon electrode (SPCE/MNPs-Aptamer). This aptasensor was characterized in a similar way to the GCE/CNPs/AuNPs/Aptamer. It was found to be selective and detected As(III) to a limit of 0.19 ppb (SWV) and 0.24 ppb (EIS). The detection limits were lower when compared to other previously reported As(III) biosensors. The biosensor showed good stability, hence they can be applied in monitoring As(III) in environmental water. , M.Sc. (Chemistry)
  • Full Text:

Review of the application of nanotechnology for sustainable construction materials

- Oke, Ayodeji, Aigbavboa, Clinton, Semenya, Kgothatso

Non-invasive diagnosis of diabete[s] mellitus using a nanostructured gas sensor

- Saasa, Raseputuka Valentine

  • Authors: Saasa, Raseputuka Valentine
  • Date: 2016
  • Subjects: Diabetes - Diagnosis , Breath tests , Nanostructured materials , Gas detectors , Nanotechnology
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/124784 , uj:20959
  • Description: Abstract: Breath analysis has attracted lots of interest in clinical and scientific research for its non-invasive diagnosis of various diseases. Over some decades, exhaled breath has become an important diagnostic method which can be used in the evaluation of health conditions. Volatile Organic Compounds (VOCs) such as acetone, toluene, isoprene and others have been regarded as biomarkers for different diseases (Xiao et al. 2014). Acetone which is generated by hepatocytes via decarboxylation of excess acetyl-coenzyme A, is considered a biomarker of type 1 and type 2 diabetes mellitus (Ueta et al. 2009). Furthermore, acetone has been considered as an indicator of poor diabetic control rather than glucose control (Mannolls, 1983). Current monitoring or diagnosis of diabetes mellitus is achieved through the use of glucose finger prick testing of blood several times daily. This is not only painful but can also be unsafe if proper handling is not undertaken and it is also expensive. Many studies have been done on the analysis of breath for detection of acetone using the Gas Chromatography Mass Spectrometry (GC-MS), Selected Ion-Flow Tube-Mass Spectrometry (SIFT-MS), and others. Although these techniques are accurate, sensitive and specific, they are not suitable for a daily diabetic monitoring for their demands in sample preparation, highly sophisticated laboratory equipment and they are expensive. In this study a portable gas sensor (chemio-resistance) device made of Vanadium dioxide (VO2) has been developed and tested for acetone detection in 30 diabetic and 30 non-diabetic patients. The chemio-resistance sensors are very easy to fabricate, has low limit of detection and are easy to use for non-invasive diagnosis of breath. Gas Chromatography-Mass Spectrometry coupled with Solid Phase Microextraction (SPME) offers a reliable determination of acetone concentration in breath as it is sensitive and specific. Thus breath acetone from 30 diabetic and 30 non diabetic were also analysed with the above mentioned instrumentation to verify and calibrate the result observed with the gas sensor device. The traditional method of diagnosing and monitoring diabetes which is currently used in clinics... , M.Sc. (Biochemistry)
  • Full Text:

Biosynthesis, characterization and antibacterial activity of silver and gold nanoparticles from the leaf and bark extracts of Zanthoxylum Capense

- Nephawe, Mbavhalelo Jade

  • 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.
  • Full Text:

Production of nanosized (V,W)C powder by mechanical alloying

- Bolokang, Sylvester Amogelang

  • Authors: Bolokang, Sylvester Amogelang
  • Date: 2012-08-27
  • Subjects: Nanotechnology
  • Type: Thesis
  • Identifier: uj:3216 , http://hdl.handle.net/10210/6628
  • Description: M.Ing. , This work is an investigation into the production of nanosized vanadium-tungsten-carbide [V,W)C] powder by mechanical alloying (MA) starting from vanadium (V), tungsten (W) and amorphous carbon (C) powders. The milling conditions were optimized first for the production of tungsten carbide (WC) due to the high cost of V powder with variations of W/C ratios to determine the minimum time required (at a selected energy) to obtain a full synthesis, i.e. to obtain only carbide without primary powders left. Ball to powder ratio (BPR) of 11:1 at 300 revolutions per minute (rpm) was used with stoichiometric carbon for WC, and using the equilibrium formula (Vo.7,Wo.3)Ci_x ) for (V,W)C. The powder phase composition was monitored by X-ray diffraction (XRD), shape and morphology was monitored by scanning electron microscopy (SEM). The production of synthesized nanocrystallite (V,W)C and WC without residual elemental powders required different times. WC powder required 8 hours of MA, while (V,W)C required 40 hours. On account of the difficult choice of stoichiometry, in general WC was also formed together with (V,W)C but the WC formation will be useful in final WC-(V,W)C-Co alloy for toughness. Crystallite sizes of about 8 to 11 nm were obtained from synthesized (V,W)C, and WC powders respectively. The amount of free carbon was measured on both synthesized WC and (V,W)C by a Leco carbon analyzer. Free carbon was found to be 2.05 wt % for WC, and 5.83 wt % for (V,W)C. Oxygen content was also measured on both the synthesized powders, to check if oxidation had occurred. The amount of oxygen in (V,W)C was measured to be 9.2 wt % higher than that of WC which was measured to be 2.7 wt %.
  • Full Text:

An easy two-step microwave assisted synthesis of SnO2/CNT hybrids

- Motshekga, Sarah C, Pillai, Sreejarani K, Ray, Suprakas Sinha, Jalama, Kalala, Krause, Rui.W.M

Greener synthesis of biopolymer-inorganic nanocomposite beads and membranes for use in water purification

- Masheane, Monaheng Leonard

  • Authors: Masheane, Monaheng Leonard
  • Date: 2016
  • Subjects: Water - Purification - Membrane filtration , Water - Purification , Nanocomposites (Materials) , Nanotechnology , Biopolymers
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/84682 , uj:19251
  • Description: Abstract: In South Africa, the unavailability of clean drinking water is a life-threatening problem, especially in the rural areas. Millions of people living in rural areas rely on water directly from the source (surface and groundwater) for drinking, cooking and other domestic purposes without any prior treatment. These sources of water are known to be affected by contaminants from untreated wastewater, industrial effluent, agricultural runoffs and domestic waste. The exposure of humans to these polluted water bodies results in infection and waterborne diseases which sometimes result in death. This has a direct consequence to the productivity of the people living in these communities and has cost implications to the government. This study was aimed at determining the potential pollutants present in drinking water sources in Lochiel, a small community in the Mpumalanga province, eastern part of South Africa, and to develop efficient and cost effective materials (beads and membranes) that could be used in the rural communities to provide safe and clean water for consumption. The application of adsorption materials (e.g. in the form of beads) and filtration materials (e.g. membranes) has attracted great interest in water purification. This is because they have several advantages over the conventional methods. These advantages include but are not limited to low capital and operations costs, low energy requirements (especially when chemically modified) and ease of operation. In this study chitosan (CTs) was chosen to prepare novel and environmentally benign nanocomposite materials either in the form of beads or flat sheet using greener solvents. In an attempt to prepare biopolymer-ceramic nanofiltration composite membranes, small amounts of multiwalled carbon nanotubes (MWCNTs) (5 wt%) and alumina (Al) (20 wt%) were added to CTs in pH controlled aqueous media near room temperature. The resulting nanocomposite was found to readily form insoluble beads... , M.Sc. (Chemistry)
  • Full Text:

Synthesis of polyethersulfone and polyvinylidene fluoride based nanostructured membranes supported on non-woven fabrics for water purification

- Tshabalala, Tumelo Gladstone

  • Authors: Tshabalala, Tumelo Gladstone
  • Date: 2014-07-15
  • Subjects: Water - Purification , Water - Purification - Membrane filtration , Water - Fluoridation , Nanotechnology
  • Type: Thesis
  • Identifier: uj:11678 , http://hdl.handle.net/10210/11400
  • Description: M.Sc. (Chemistry) , Water purification technologies based on membranes are prone to fouling by natural organic matter (NOM) and other biological species in water. This leads to the short lifespan of the membranes and high demand in energy than normal due to high pressure needed to pump water across the fouled membrane. In a quest to address these challenges, polyethersulfone (PES) and polyvinylidene flouride (PVDF) membranes supported on 3 different types of non-woven fabrics NWF1(polyester), NWF2 (polyphenylene sulphide) and NWF3( thicker polyester) were fabricated using the phase inversion method. This enabled the modification the active top layer of PES and PVDF thin film while maintaining the high mechanical strength offered by the NWFs. FTIR spectroscopy, sessile drop contact angle measurements, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the membranes. The membrane flux and rejection were studied using the cross-flow membrane unit. The contact angle results revealed that the hydrophilicity of PES and PVDF membranes increased as the polyvinyl pyrrolidone (PVP) concentration was increased. TGA revealed that the PES and PVDF membranes were thermally stable up to 580ºC and 530ºC respectively. The cross-sectional SEM revealed that membrane pores become enlarged when PVP has been added. AFM showed that membrane roughness improved when PVP was added. A rejection of 98% humic acid was obtained for PES membranes supported on NWF1, compared to 94 % and 96 % for membranes supported on NWF2 and NWF3 respectively. The highest rejection of humic acid (HA) recorded for PVDF membranes supported on NWF1 was found to be 97 % compared to the 95% for membranes supported on NWF2 and NWF3 fabrics respectively. PES membranes supported on NWF2 exhibited low but best As(III) metal ions rejections whilst PVDF membranes supported on NWF3 exhibited low but best rejections for Cr(III) metal ions.
  • Full Text:

Organic-inorganic based nanocomposite for wastewater treatment

- Nduka, Peter Chijioke

  • Authors: Nduka, Peter Chijioke
  • Date: 2017
  • Subjects: Water - Purification , Nanocomposites (Materials) , Nanotechnology , Materials science , Environmental chemistry
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279331 , uj:29997
  • Description: M.Sc. (Chemistry) , Abstract: Improper treatment of wastewater from industries before disposal poses severe environmental and health hazards to the surrounding communities. Several treatment techniques have been developed and applied in making sure that these wastewaters are properly treated before being discharged into the environment. Photocatalysis is the most promising of all the techniques that have been employed. This is because its operation is simple and involves the use of readily available semiconductors and sunlight. However, the disadvantage of using these semiconductors as photocatalysts for photocatalytic degradation of organic pollutants are among others their wide band gap and the rate at which photogenerated electrons and holes recombine. These demerits make it difficult for the photocatalytic activities of these semiconductors to be extended into the more abundant visible light region of the solar spectrum. This research work focused on the synthesis of visible light active ZnO photocatalyst through its modification with nitrogen and graphene oxide followed by its application towards the degradation of Brilliant green (BG) dye. The GO and ZnO were synthesized using Hummers and co-precipitation methods respectively while N-ZnO and NZnO-GO composites were synthesized using solvent free method. The characterization of the synthesized photocatalysts was done using optical approaches such as X-Ray Diffraction (XRD), Fourier Transform Infra-red (FTIR), Transmission Electron Microscopy (TEM) and UV–Vis Absorption and Diffuse Reflectance Spectra (UV-Vis DRS). ZnO modified with nitrogen and graphene oxide (N-ZnO-GO) having different weight percentages of GO (0.1% wt-GO, 0.5% wt-GO, and 1% wt-GO) showed a higher photocatalytic activity in degrading BG dye in water compared to the bare ZnO and nitrogen-doped ZnO (N-ZnO) nanoparticles. The composite with 0.1% wt GO achieved 100% degradation and 80% mineralization of BG within 90 mins of irradiation. The results also showed that the degradation of BG using 0.1% wt-GO occurred faster in basic medium (pH 9) compared to acidic medium. Photostability test of 0.1% wt-GO analyzed after three cycles of exposure gave 94% degradation of BG which implied that the composite is also highly stable and can be recovered and reused. The results obtained highlighted that the modifications made on ZnO increased its light absorption capability into the visible region and thus drastically improved its photocatalytic activity under visible light...
  • Full Text:

Nanostructured membranes embedded with hyperbranched polyethyleneimine (HPEI) hosts and titanium dioxide (TiO2) nanoparticles for water purification

- Mathumba, Penny

  • Authors: Mathumba, Penny
  • Date: 2016
  • Subjects: Water - Purification , Water - Purification - Membrane filtration , Titanium dioxide , Nanotechnology
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/84654 , uj:19247
  • Description: Abstract: Water scarcity is a huge challenge throughout the world. The capacity of water in South African water systems will decrease dramatically in the next 10 years. Moreover the removal of pollutants from industrial and municipal water has become a challenge for water treatment industries. In particular, the textile industry consumes large volumes of water during dyeing processes. Thus textile industries are regarded as major polluters in the world. Azo dyes (e.g. Methyl Orange and Methyl Blue) constitute about 70% of the dyes used in the textile industry. The water discharged from textile industries is highly coloured and contains compounds that are complex in nature. Coloured water prevents the penetration of light into rivers and lakes thus affecting the process of photosynthesis and this affects the natural flora and fauna. Moreover, the improper discharge of untreated coloured dye effluent into the environment has resulted in numerous public protests. Methyl orange has been reported to be toxic and mutagenic to animals. Moreover, most of these dyes are also not effectively removed by the use of conventional biological treatment processes since they are non-biodegradable... , M.Sc.
  • Full Text:

Nanotechnology and bamboo fibres as avenues to rejuvenate the Ghanaian Textile Industry

- Anane-Fenin, K., Akinlabi, Esther Titilayo

The fluid flow effect on the inlet injection of the thin film deposition in a square type atomic layer deposition reactor

- Coetzee, Rigardt Alfred Maarten, Lu, Hongliang, Jen, Tien-Chien

  • Authors: Coetzee, Rigardt Alfred Maarten , Lu, Hongliang , Jen, Tien-Chien
  • Date: 2019
  • Subjects: Nanotechnology , Atomic layer deposition , Computational fluid dynamics
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/400082 , uj:33374 , Citation: Coetzee, R.A.M., Lu, H., & Jen, T.C. 2019. The fluid flow effect on the inlet injection of the thin film deposition in a square type atomic layer deposition reactor.
  • Description: Abstract: In recent years, industry is ever striving to deposit optimal thin films on Nano devices. This strive led to interest in utilising advance Nano-manufacturing techniques that can fabricate ever-decreasing scale products along with films that provide highly uniform, conformal, and pin-hole free quality thin films. Atomic layer deposition provides a technique that fulfil these requirements. However, the understanding of the deposition process within the fabrication of these thin films are still greatly not well-known. The fluid flow patterns and distributions within the atomic layer deposition reactors are rarely investigated and lacks the fluid flow effect incorporated along with the deposition process near the substrate. Per se, these effects due to the geometrical effect of the inlet injection location from the deposited substrate of a square type Gemstar Reactor is investigated. The findings reveal the inlet flow effect, near substrate flow behaviour, and optimal selection for the deposition of aluminium oxide (Al2O3) thin film. The study simulates the fluid flow properties along with the chemical kinetics by utilizing computational fluid dynamics incorporated within ANSYS Fluent Software. The flow and surface reaction of Trimethylaluminium and Ozone as precursors, along with Argon as the purging substance, are incorporated within the atomic layer deposition sequence. The findings reveal close similarities to that of previous literature.
  • Full Text:

The use of ferrocene and camphor for the synthesis of carbon nanotubes using catalystic chemical vapor deposition

- Parshotam, Heena

  • Authors: Parshotam, Heena
  • Date: 2008-07-08T13:14:49Z
  • Subjects: Nanotubes , Nanotechnology , Chemical vapor deposition
  • Type: Thesis
  • Identifier: uj:10413 , http://hdl.handle.net/10210/787
  • Description: The discovery of carbon nanotubes (CNTs) has sparked great interest in the scientific world because of their remarkable electrical and physical properties. Only a thorough understanding of these properties, however, will allow CNTs to be commercially viable. Essentially, CNTs are graphite-like surfaces of sp2 hybridized carbon atoms in the form of tubes. CNTs could range from single-walled carbon nanotubes (SWNTs), consisting of one cylindrical graphite sheet to multi-walled nanotubes (MWNTs) that have concentric sheets. Nanotubes can be synthesized using a number of techniques such as electric arc–discharge, laser ablation and catalytic chemical vapor deposition (CCVD). In this project the CCVD technique was used for the synthesis of CNTs because of it simplicity and availability. The source of carbon was not the conventional hydrocarbon gas, but was camphor, a botanical hydrocarbon that is a solid at room–temperature. Ferrocene was the catalyst, not only because it has been used before in the synthesis of nanotubes, but it appears to be one of the best catalysts during the CCVD synthesis of nanotubes. The presence of nitrogen gas is known to assist in the synthesis of CNTs that have a bamboo–like structure; hence the effect of carrier gases such as nitrogen, argon/hydrogen and argon on the quality of nanotubes synthesized was investigated. Initially, the optimal experimental method for the synthesis of CNTs was determined by varying the reaction path length, temperature, mixing the catalyst and carbon source together or keeping them separate and varying the %m/m of the catalyst to carbon source. It was found that either an increase in the reaction temperature or an increased path length resulted in an increase in the mass of product obtained, whereas mixing the catalyst and carbon source together as opposed to them being separated only caused a slight variation in the mass of product synthesized. The mass of product synthesized also increased as the catalyst concentration increased. The remainder of the project was aimed at investigating the role of different gases: nitrogen, argon and hydrogen (in argon) in the CCVD synthesis of CNTs. The resulting materials were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and laser Raman analysis. The results indicated that this method could be tailored to synthesize either carbon spheres or carbon nanotubes of specific diameters and quality. Finally, in an attempt to synthesize aligned carbon nanotubes, catalyst supports {characterized using Brunauer-Emmett-Teller analysis (BET)} namely; silica, alumina and magnesium oxide were used. Although this was not successful for the synthesis of aligned CNTs under the conditions used, alumina showed the most promise. , Mr. S. Durbach Dr. R. W. Krause
  • Full Text:

The effect of nitrogen on the synthesis of carbon nanotubes by nebulized spray pyrolysis

- Letsoalo, Phatu Jack

  • Authors: Letsoalo, Phatu Jack
  • Date: 2008-06-12T05:35:15Z
  • Subjects: Nanotubes , Nanotechnology
  • Type: Thesis
  • Identifier: uj:2644 , http://hdl.handle.net/10210/608
  • Description: The discovery of carbon nanotubes has stimulated intensive research on the synthesis, modification and physical properties of these novel carbon materials due to their unique and one dimensional pore structure, rolled graphitic layers as well as their potential application in sensors, separations, electronic devices, gas storage and quantum dots. Research has suggested that the role of nitrogen in the synthesis of carbon nanotubes could be either to enhance the formation of graphitic layers on the catalyst or to increase the separation of the graphitic layers from the catalyst. The studies further suggested that if nitrogen is incorporated into the structure then the presence of nitrogen in the pentagonal defects would induce the bending and distortion of the carbon nanotubes, whilst nitrogen in substitutional sites would not produce major distortion of the nanotubes. Well-aligned carbon nanotubes were grown from the pyrolysis of ferrocene, toluene and small fractions of various amines, aromatic amines, diamines and amides by nebulized spray pyrolysis at temperature of 8500C. Transmission electron microscopy and scanning electron microscopy reveal that the carbon nanotubes possess bamboo-like-structures and that the nanotubes are well-aligned. The nanotubes ranged from 36 nm to 121 nm in diameter and 65 μm to 625 μm in length depending on the specific growth conditions such as concentration of various nitrogen containing hydrocarbons, growth time and flow rates of the carrier gasses. Raman spectra show the characteristics bands at 1336 cm-1 (D-band) and 1583 cm-1 (G-band). The G-band modes are larger than the D-band modes, suggesting that the carbon nanotubes synthesized In the presence of nitrogen additives are more graphitic than those synthesized without nitrogen addition. TGA analysis under static air environment, showed that the carbon nanotubes are stable within a temperature range of 40 – 5600C and in the at temperature range of 590 – 8000C, the mass loss of carbon nanotubes is constant. The residual metal content in the carbon nanotubes was found to be approximately 20%, when nanotubes were synthesized by the pyrolysis of toluene and ferrocene and about 7% after addition of nitrogen containing hydrocarbons to the catalyst. Selected carbon nanotubes were purified using a microwave purification method. The mass loss between unpurified carbon nanotubes and purified nanotubes were found to be insignificant. The diameters of the carbon nanotubes were found to have been reduced drastically, which suggest that defects were removed during the purification process. The data generated in this study revealed that nitrogen containing hydrocarbons acted as co-promoters of CNTs during the synthesis of carbon nanotubes. , Mr. L.M. Cele Prof. N. Coville
  • Full Text:

Preparation/synthesis of electrospun polymer/metal oxide nanocomposite fibers and their application in treatment of brines

- Ramutshatsha-Makhwedzha, Denga

  • Authors: Ramutshatsha-Makhwedzha, Denga
  • Date: 2019
  • Subjects: Polymers - Materials , Polymeric composites , Nanocomposites (Materials) , Nanotechnology , Materials science
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/401548 , uj:33565
  • Description: Abstract : Many developing countries around the world still lack access to clean fresh water. This refers to water that is free from contaminants as it is highly essential for human livelihood and environment. In countries along the coast, ocean water is the most available water resource; however, it comes at a salt concentration that is very high for human consumption. Most of available water has a salinity of up to 10 000 ppm and seawater consists of dissolved salt concentrations of about 35 000-45 000 ppm. This lead to desalination process being used as an option to treat seawater and this has become one of the most important processes of providing fresh water in developing countries. Therefore, the aim of this study was to investigate the practicability of using nanometer metal oxides and polymer/NMO composite as the potential adsorbents for adsorption desalination of seawater. The quantification of analytes in sample solutions was done using the inductively-coupled plasma atomic emission spectroscopy (ICP-OES). Nanometal oxide composites such as Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3, Fe2O3-SiO2-PAN and zeolite/Fe3O4 adsorbents were used for the adsorptive desalination of saline water. Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3 and zeolite/Fe3O4 adsorbents were prepared using a sol gel method whereas Fe2O3-SiO2-PAN nanocomposite was obtained using in-situ preparation method. The adsorbents were characterized using different techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). SEM image of Fe2O3-SiO2 nano composite showed the porous morphological structure. The Fe2O3-SiO2 showed partial crystalline pattern due to silica oxide that has pure amorphous structure, whereas the SiO2/Nb2O5/Fe2O3 has an amorphous structure. TEM structure of α-Fe2O3 has dominant shapes of spherical and some few cubic and hexagonal shapes, the hexagonal shape were also observed on Fe2O3-SiO2 nanocomposite material. SiO2/Nb2O5/Fe2O3 adsorbent resembled a core-like structure. The TEM result of Fe2O3-SiO2-PAN revealed that the crystalline Fe3O4 nanoparticles were encapsulated with PAN polymer that suggests the core-shell structure. EDX-mapping analysis showed the uniform elemental distribution which suggests the successful preparation of the in-situ method... , Ph.D. (Chemistry)
  • Full Text:
  • 1
  • Disclaimer
  • Privacy
  • Copyright
  • Contact