Browsing by Author "Iwuoha, Emmanuel"
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Item Aluminium and gold functionalized graphene quantum dots as electron acceptors for inverted Schottky junction type rainbow solar cells(University of Western Cape, 2020) Mathumba, Penny; Iwuoha, EmmanuelThe main aim of this study was to prepare band gap-engineered graphene quantum dot (GQD) structures which match the different energies of the visible region in the solar spectrum. These band gap-engineered graphene quantum dot structures were used as donor materials in rainbow Schottky junction solar cells, targeting all the energies in the visible region of the solar spectrum for improved solar-to-electricity power conversion efficiency. Structural characterisation of the prepared nanomaterials under solid-state nuclear magnetic resonance spectroscopy (SS-NMR) showed appearance of bands at 40 ppm due to the presence of sp3 hybridised carbon atoms from the peripheral region of the GQD structures. Other bands were observed at 130 ppm due to the presence of polycyclic aromatic carbon atoms from the benzene rings of the GQD backbone, and around 180 ppm due to the presence of carboxylic acid carbons from oxidation due to moisture. Fourier-transform infrared resonance (FTIR) spectroscopy further confirmed the presence of aromatic carbon atoms and oxidised carbons due to the presence of C=O, C=C and -OH functional groups, concurrent with SS-NMR results.Item Amperometric biosensor systems prepared on poly (aniline-ferrocenium hexafluorophosphate) composites doped with poly(vinyl sulfonic acid sodium salt)(University of the Western Cape, 2008) Ndangili, Peter Munyao; Iwuoha, Emmanuel; Baker, Priscilla; Dept. of Chemistry; Faculty of ScienceThe main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media; shuttling electrons between HRP and GCE for biosensor applications.Item AtNOGC1 protein bioelectrode for the determination of stress signalling molecules - Nitric Oxide (NO), Carbon Monoxide (CO) and Calcium ion (Ca2+)(University of the Western Cape, 2018) Tshivhidzo, Tsumbedzo Tertius; Mulaudzi-Masuku, Takalani; Iwuoha, Emmanuel; Ajayi, FanelwaIt has been estimated that the world population will reach about 10 billion by the year 2050 and in order to accommodate the increased demand of food, the world agricultural production needs to rise by 70 % in the year 2030. However, the realisation of the goal in food production is hindered by limited arable land caused by urbanisation, salinisation, desertification and environmental degradation. Furthermore, abiotic and biotic stresses affect plant growth and development, which lead to major crop losses. The long term goal of this study is to improve food security by producing genetically engineered agricultural crops that will be tolerant to diverse stresses. This research aims at developing stress tolerant crops through the determination of important signalling molecules and second messengers, such as nitric oxide (NO), carbon monoxide (CO) and calcium ion (Ca2+), which can bind to plant proteins such as AtNOGC1 in order to induce stress tolerance in plants.Item Boron-doped Diamond Sensors for the Determination of Organic Compounds in Aqueous Media(University of the Western Cape, 2010) Hess, Euodia; Baker, Priscilla; Iwuoha, Emmanuel; Dept. of Chemistry; Faculty of ScienceIn electrochemical oxidation treatment of wastewater, the electrode material is an important parameter in optimizing oxidative electrochemical processes, since the mechanism and products of several anodic reactions are known to depend on the anode material. The electrochemical oxidation of benzaldehyde, nitrobenzene and m-cresol on bare boron-doped diamond (BDD) electrode was investigated. Cytochrome c was then electrochemically immobilsed onto the functionalized BDD electrode by cyclic voltammetry. Oxidation and reduction reaction mechanism of each flavonoid was studied. There was one oxidation and reduction peaks for quercitin and catechin respectively, and two oxidation and two reduction peaks for rutin. The cytochrome c modified BDD electrode showed good sensitivity for all three flavonoids and low detection limits i.e. 0.42 to 11.24 M as evaluated at oxidation and reduction peaks, respectively.Item Chemical isolation and electro-chemical characterization of antidiabetic compounds from selected South African lamiaceae plant species(University of the Western Cape, 2020) Etsassala, Ninon Geornest Eudes Ronauld; Iwuoha, EmmanuelDiabetes mellitus (DM), being one of the most common metabolic disorders with an elevated morbidity and mortality rate around the world. It is characterised by deficiency in insulin secretion or degradation of secreted insulin. Many internal and external factors such as oxidative stress, obesity and sedentary lifestyle among others have been suggested as the major causes of these cell alterations. Diabetes I and II are the most common types of diabetes. Treatment of type I requires insulin injection, while type II can be managed using different synthetic antidiabetic agents. However, their effectiveness is limited as a result of low bioavailability, high cost of drug production, and unfavourable side effects. There is a great need to develop alternative and more active antidiabetic drugs from natural sources. Natural products are a well-known source for the discovery of new scaffold for drugs discovery, and South Africa is one of the most important megaflora with high percentage of endemism.Item Chromium and Titanium based Stannum Nanocomposites materials as electron acceptors for next generation bulk Heterojunction photovoltaic cells(University of the Western Cape, 2018) Raleie, Naledi; Iwuoha, EmmanuelRenewable energy has become the centrepiece of research in resolving the energy crisis. One of the forms of renewable energy is solar energy. This form of energy is costly to develop. Organic molecules are promising materials for the construction of next generation photovoltaic cells considering their advantage of lower cost compared to crystalline silicon that is currently used in solar cells. This forms the basis of this research, which focused on the synthesis and characterisation of poly(3- hexylthiophene) P3HT, stannum (Sn) nanoparticles and stannum-based bimetallic stannum-titanium (SnTi), stannum-chromium (SnCr) and stannum-vanadium (SnV) nanoparticles for the application in the construction of heterojunction photovoltaic cells (PVCs).Item Composite poly(dimethoxyaniline) electrochemical nanobiosensor for glufosinate and glyphosate herbicides(University of the Western Cape, 2008) Songa, Everlyne Apiyo; Iwuoha, Emmanuel; Baker, Priscilla G.L.; Dept. of Chemistry; Faculty of ScienceIn this thesis, I present a simple, sensitive and low cost electrochemical nanobiosensor for quantitative determination of the herbicides glufosinate, glyphosate and its metabolite aminomethylphosphonic acid (AMPA). Firstly, the nanostructured poly(2,5-dimethoxyaniline) (PDMA) materials were synthesized on gold electrode by the electrochemical "template"method using poly(4-styrenesulfonic acid) (PSS) as the dopant and structure-directing molecule. Fourier transform infrared (FTIR) spectroscopy, UV-Vis Spectroscopy, Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) studies inferred successful doping of the nanostructured PDMA film by PSS and that the template PSS directed the synthesis of both nanotubes and nanoparticles of PDMA with diameters less than 100 nm.Item Cytochrome C biosensor for the determination of trace level arsenic and cyanide compounds(University of the Western Cape, 2011) Fuku, Xolile Godfrey; Baker, Priscilla G.L.; Iwuoha, Emmanuel; Dept. of Chemistry; Faculty of ScienceIn this work, an electrochemical method based on a cyt c biosensor has been developed, for the detection of selected arsenic and cyanide compounds. Boron Doped Diamond (BDD) electrode was used as a transducer, onto which cyt c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide by inhibition mechanism. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH= 7) was found to be (1.087- 4.488 ×10-9 M) and the detection limits ranging from 0.0043- 9.1 μM. These values represent a big improvement over the current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines.Item Cytochrome P450 2E1/Nickel-Poly(propylene imine) dendrimeric nanobiosensor for pyrazinamide - A first line TB Drug(University of the Western Cape, 2015) Zosiwe, Mlandeli Siphelele Ernest; Iwuoha, EmmanuelThe tuberculosis (TB) disease to this day remains one of the world’s prominent killerdiseases. Pyrazinamide (PZA) is one of the most commonly prescribed anti- tuberculosis (anti-TB) drugs due to its ability to significantly shorten the TB treatment period from the former nine months to the current six months duration. However, excess PZA in the body causes hepatotoxicity and damages the liver. This hepatotoxicity, together with the resistance of the bacteria to treatment drugs, poor medication and inappropriate dosing, greatly contribute to the high incidents of TB deaths and diseases that are due to side effects (such as liver damage). This brings about the calls for alternative methods for ensuring reliable dosing of the drug, which will be specific from person to person due to inter-individual differences in drug metabolism. A novel biosensor system for monitoring the metabolism of PZA was prepared with a Ni-PPI-PPy star copolymer and cytochrome P450 2E1 (CYP2E1) deposited onto a platinum electrode. The nanobiosensor system exhibited enhanced electro-activity that is attributed to the catalytic effect of the incorporated star copolymer. The biosensor had a sensitivity of 0.142 µA.nM-1, and a dynamic linear range (DLR) of 0.01 nM-0.12 nM (1.231 – 7.386 ng/L PZA). The limit of detection of the biosensor was found to be 0.00114 nM (0.14 ng/L) PZA. From the HPLC peakconcentration (Cmax) of PZA determined 2 h after drug intake is 2.79 – 3.22 ng.L-1,which is very detectable with the nanobiosensor as it falls within the dynamic linear range.Item Dendritic poly(3-hexylthiophene) star copolymer systems for next generation bulk heterojunction organic photovoltaic cells(University of the Western Cape, 2018) Yonkeu, Anne Lutgarde Djoumessi; Iwuoha, Emmanuel; Cimrova, VeraThe continuous increase in energy consumption and decrease in fossil fuels reserves are a primary concern worldwide; especially for South Africa. Therefore, there is an urgent need for alternative energy resources that will be sustainable, and environmentally friendly in order to tackle the ecological degradation generated by the use of fossil fuels. Among many energy ‘niches’, solar energy appears to be one of the most promising and reliable for the African continent because of the constant availability of sun light. Organic conjugated polymers have been identified as suitable materials to ensure proper design and fabrication of flexible, easy to process and cost-effective solar cells. Their tendency to exhibit good semiconducting properties and their capability to absorb photons from the sunlight and convert it into electrical energy are important features that justify their use in organic photovoltaic cells. Many different polymers have been investigated as either electron donating or electron accepting materials. Among them, poly(3-hexylthiophene) is one of the best electron donor materials that have been used in organic photovoltaic cells. It is a good light absorber and its Highest Occupied Molecular Orbital (HOMO) energy level is suitable to allow electron transfer into an appropriate electron acceptor. On the other hand, the molecular ordering found in dendrimers attracted some interest in the field of photovoltaics as this feature can ensure a constant flow of charges. In this work, I hereby report for the first time, the chemical synthesis of a highly crystalline dendritic star copolymer generation 1 poly(propylene thiophenoimine)-co-poly(3-hexylthiophene) (G1PPT-co-P3HT) with high molecular weight and investigate its application as donating material in bulk heterojunction organic photovoltaics.Item The design of ultrasensitive immunosensors based on a new multi-signal amplification gold nanoparticles-dotted 4-nitrophenylazo functionalised graphene sensing platform for the determination of deoxynivalenol(University of Western Cape, 2014) Sunday, Christopher Edozie; Iwuoha, Emmanuel; Baker, Priscilla G. L.A highly dispersive gold nanoparticle-dotted 4-nitrophenylazo functionalised graphene nanocomposite (AuNp/G/PhNO2) was successfully synthesised and applied in enhancing sensing platform signals. Three label-free electrochemical immunosensors for the detection of deoxynivalenol mycotoxin (DON) based on the systematic modification of glassy carbon electrodes (GCE) with AuNp/G/PhNO2 was effectively achieved. General electrochemical impedance method was employed for the sensitive and selective detection of DON in standard solutions and reference material samples. A significant increase in charge transfer resistance (Rct) of the sensing interface was observed due to the formation of insulating immune-complexes by the binding of deoxynivalenol antibody (DONab) and deoxynivalenol antigen (DONag). Further attachments of DONab and DONag resulted in increases in the obtained Rct values, and the increases were linearly proportional to the concentration of DONag. The three immunosensors denoted as GCE/PDMA/AuNp/G/PhNH2/DONab, GCE/Nafion/[Ru(bpy)3]2+/AuNp/G/PhNH2/DONab and GCE/Nafion/[Ru(bpy)3]2+/G/PhNH2/DONab have detection range of 6 – 30 ng/mL for DONag in standard samples. Their sensitivity and detection limits were 43.45 ΩL/ng and 1.1 pg/L; 32.14ΩL/ng and 0.3 pg/L; 9.412 ΩL/ng and 1.1 pg/L respectively. This result was better than those reported in the literature and compares reasonably with Enzyme Linked Immunosorbent Assay (ELISA) results. The present sensing methodology represents an attractive alternative to the existing methods for the detection of deoxynivalenol mycotoxin and other big biomolecules of interest due to its simplicity, stability, sensitivity, reproducibility, selectivity, and inexpensive instrumentation. And they could be used to develop high-performance, ultra-sensitive electrochemiluminescence, voltammetric or amperometric sensors as well.Item Designing next generation high energy density lithium-ion battery with manganese orthosilicate-capped alumina nanofilm(University of the Western Cape, 2015) Ndipingwi, Miranda Mengwi; Iwuoha, Emmanuel; Ikpo, ChinweIn the wide search for advanced materials for next generation lithium-ion batteries, lithium manganese orthosilicate, Li₂MnSiO₄ is increasingly gaining attention as a potential cathode material by virtue of its ability to facilitate the extraction of two lithium ions per formula unit, resulting in a two-electron redox process involving Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. This property confers on it, a higher theoretical specific capacity of 333 mAhg⁻¹ which is superior to the conventional layered LiCoO₂ at 274 mAhg⁻¹ and the commercially available olivine LiFePO₄ at 170 mAhg⁻¹. Its iron analogue, Li₂FeSiO₄ has only 166 mAhg⁻¹ capacity as the Fe⁴⁺ oxidation state is difficult to access. However, the capacity of Li₂MnSiO₄ is not fully exploited in practical galvanostatic charge-discharge tests due to the instability of the delithiated material which causes excessive polarization during cycling and its low intrinsic electronic conductivity. By reducing the particle size, the electrochemical performance of this material can be enhanced since it increases the surface contact between the electrode and electrolyte and further reduces the diffusion pathway of lithium ions. In this study, a versatile hydrothermal synthetic pathway was employed to produce nanoparticles of Li₂MnSiO₄, by carefully tuning the reaction temperature and the concentration of the metal precursors. The nanostructured cathode material was further coated with a thin film of aluminium oxide in order to modify its structural and electronic properties. The synthesized materials were characterized by microscopic (HRSEM and HRTEM), spectroscopic (FTIR, XRD, SS-NMR, XPS) and electrochemical techniques (CV, SWV and EIS). Microscopic techniques revealed spherical morphologies with particle sizes in the range of 21-90 nm. Elemental distribution maps obtained from HRSEM for the novel cathode material showed an even distribution of elements which will facilitate the removal/insertion of Li-ions and electrons out/into the cathode material. Spectroscopic results (FTIR) revealed the vibration of the Si-Mn-O linkage, ascertaining the complete insertion of Mn ions into the SiO₄⁴⁻ tetrahedra. XRD and ⁷Li MAS NMR studies confirmed a Pmn21 orthorhombic crystal pattern for the pristine Li₂MnSiO₄ and novel Li₂MnSiO₄/Al₂O₃ which is reported to provide the simplest migratory pathway for Li-ions due to the high symmetrical equivalence of all Li sites in the unit cell, thus leading to high electrochemical reversibility and an enhancement in the overall performance of the cathode materials. The divalent state of manganese present in Li₂Mn²⁺SiO₄ was confirmed by XPS surface analysis. Scan rate studies performed on the novel cathode material showed a quasi-reversible electron transfer process. The novel cathode material demonstrated superior electrochemical performance over the pristine material. Charge/discharge capacity values calculated from the cyclic voltammograms of the novel and pristine cathode materials showed a higher charge and discharge capacity of 209 mAh/g and 107 mAh/g for the novel cathode material compared to 159 mAh/g and 68 mAh/g for the pristine material. The diffusion coefficient was one order of magnitude higher for the novel cathode material (3.06 x10⁻⁶ cm2s⁻¹) than that of the pristine material (6.79 x 10⁻⁷ cm2s⁻¹), with a charge transfer resistance of 1389 Ω and time constant (τ) of 1414.4 s rad⁻¹ for the novel cathode material compared to 1549 Ω and 1584.4 s rad-1 for the pristine material. The higher electrochemical performance of the novel Li₂MnSiO₄/All₂O₃ cathode material over the pristine Li₂MnSiO₄ material can be attributed to the alumina nanoparticle surface coating which considerably reduced the structural instability intrinsic to the pristine Li₂MnSiO₄ cathode material and improved the charge transfer kinetics.Item Determination of paracetamol at the electrochemically reduced graphene oxide-metal nanocomposite modified pencil graphite (ERGO-MC-PGE) electrode using adsorptive stripping differential pulse voltammetry(University of Western Cape, 2020) Leve, Zandile Dennis; Jahed, Nazeem; Iwuoha, EmmanuelThis project focuses on the development of simple, highly sensitive, accurate, and low cost electrochemical sensors based on the modification of pencil graphite electrodes by the electrochemical reduction of graphene oxide-metal salts as nanocomposites (ERGO-MC-PGE; MC = Sb or Au nanocomposite). The electrochemical sensors ERGO-Sb-PGE and ERGO-Au-PGE were used in the determination of paracetamol (PC) in pharmaceutical formulations using adsorptive stripping differential pulse voltammetry. The GO was prepared from graphite via a modified Hummers’ method and characterized by FTIR and Raman spectroscopy to confirm the presence of oxygen functional groups in the conjugated carbon-based structure whilst, changes in crystalline structure was observed after XRD analysis of graphite and GO.Item Determination of Thallium and Indium with an Electrochemically-reduced Graphene Oxide-Carbon Paste Electrode by Anodic Stripping Voltammetry(University of the Western Cape, 2018) Martin, Tayla; Iwuoha, EmmanuelIn this study, graphene oxide was synthesized by oxidizing graphite using the modified Hummer's method. The graphene oxide was characterized by Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, High Resolution Transmission Electron Microscopy, Scanning Electron Microscopy and X-Ray Diffraction for structural and morphological properties. The graphene oxide was electrochemically reduced on a carbon paste electrode followed by the in situ deposition of mercury thin films to achieve electrochemically reduced graphene oxide modified carbon paste metal film electrodes (ERGO-CP-MEs). The experimental parameters (amplitude, deposition time, deposition potential, frequency and rotation speed) were optimized, and the applicability of the modified electrode was investigated towards the simultaneous and individual determination of TI1+ and In3+ at the low concentration levels (?g L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limit values for individual analysis at electrochemically reduced graphene oxide modified carbon paste mercury film electrode (ERGO-CP-HgE ) was 2.4 and 1.1 ?g L-1 for TI1+ and In3+, respectively. The detection limit values for simultaneous analysis at ERGO-CPE was 1.32 and 1.33 ?g L-1 and individual analysis was 0.975 and 1.04 ?g L-1 for TI1+ and In3+, respectively.Item Development of amperometric biosensor with cyclopentadienylruthenium (II) thiolato schiff base self-assembled monolayer (SAM) on gold(University of the Western Cape, 2007) Ticha, Lawrence Awa; Baker, Priscilla; Iwuoha, Emmanuel; Dept. of Chemistry; Faculty of ScienceA novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(η5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, Γ, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 M, 6.92 M and 7.01 M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.Item Development of Copper Selenide Quantum Dots-Based Therapeutic Drug Monitoring Biosensors for Toremifene - A Breast Cancer Drug(University of the Western Cape, 2017) Pacoste, Laura Gabriella Calmanovici; Iwuoha, EmmanuelWith rising knowledge of the effects on plasma concentration caused by allelic variations in the cytochrome P450 genes and other metabolic factors such as drug-drug or drug-food interactions, more attention is paid to the possibility of therapeutic drug monitoring (TDM). Thus, there is a rising demand for quick, low-cost and efficient equipment for drug targeting. For such devices, electrochemical biosensing techniques serve as a promising alternative. Toremifene is the chlorinated analogue of tamoxifen and is used for adjuvant antiestrogenic treatment for breast cancer and could serve as a candidate for TDM treatments. In this work, a proof of concept enzymatic electrochemical biosensor is developed for the detection of toremifene in aqueous solution. The biosensor uses water-soluble 6-mercaptopropinoic acid capped copper selenide quantum dots (6MHACuSe QDs) conjugated to a cysteamine selfassembled monolayer on a gold electrode. The 6MHACuSe QDs where further conjugated with CYP2C9 enzyme, which has shown to have a major part in the hydroxylation of toremifene (TOR) to form 4-hydroxytoremifene (4OH-TOR). The 6MHACuSe QDs where synthesized using a facile and rapid aqueous route. Results from synthesis of 3-mercaptiorproionic acid (3MPA) and mercaptosuccinic acid (MSA) capped copper selenide QDs, are also presented in the study and compared to the results of the 6MHA capped copper selenide QDs. X-ray diffraction analysis (XRD) confirmed formation of copper selenide species of nonstoichiometric form Cu2-xSe (for the 6MHA and 3MPA capped CuSe QDs) and ?-CuSe stoichiometric form (for the MSA capped CuSe QDs).Item Development of electrochemical sensors containing bimerallic silver and gold nanoparticles(University of the Western Cape, 2010) Mailu, Stephen Nzioki; Iwuoha, Emmanuel; Baker, Priscilla G.L.; Dept. of Chemistry; Faculty of SciencePolyaromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants that have been shown to be teratogenic, mutagenic and carcinogenic and pose serious threats to the health of aquatic and human life. Several methods have been developed for their determination such as immunoassay, gas chromatography and high performance liquid chromatography (HPLC) in combination with fluorescence or absorbance detection. However, these methods are known to manifest underlying disadvantages such as complicated pretreatment, high costs and time consuming processes. In this work, a simple, less time consuming electrochemical method in the form of an electrochemical sensor has been developed for the detection of PAHs. The sensor was fabricated by the deposition of silver-gold (1:3) alloy nanoparticles (Ag-AuNPs) on ultrathin overoxidized polypyrrole (PPyox) film which formed a PPyox/Ag-AuNPs composite on glassy carbon electrode (PPyox/Ag-AuNPs/GCE). The silver-gold alloy nanoparticles deposited to form the composite were chemically prepared by simultaneous reduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4) using sodium citrate and characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the alloy nanoparticles. Transmission electron microscopy showed that the synthesized nanoparticles were in the range of 20-50 nm. The properties of the composite formed upon deposition of the nanoparticles on the PPyox film were investigated by electrochemical methods. The PPyox/Ag-AuNPs/GCE sensor showed strong catalytic activity towards the oxidation of anthracene, phenanthrene and pyrene, and was able to simultaneously detect anthracene and phenanthrene in a binary mixture of the two. The catalytic peak currents obtained from square wave voltammetry increased linearly with anthracene, phenanthrene and pyrene concentrations in the range of 3.0 x 10-6 to 3.56 x 10-4 M,3.3 x 10-5 to 2.83 x 10-4 M, 3.3 x 10-5 to 1.66 x 10-4 M and with detection limits of 0.169 μM, 1.59 μM and 2.70 μM, respectively. The PPyox/Ag-AuNPs/GCE sensor is simple, has antifouling properties and is less time consuming with a response time of 4 s.Item Development of electrochemical ZnSe Quantam dots biosensors for low-level detection of 17β-Estradiol estrogenic endocrine disrupting compound(University of the Western Cape, 2010) Jijana, Abongile Nwabisa; Iwuoha, Emmanuel; Dept. of Chemistry; Faculty of ScienceThe main thesis hub was on development of two electrochemical biosensors for the determination of 17β-estradiol-estradiol: an estrogenic endocrine disrupting compound. Endocronology have significantly shown that the endocrine disruptors contribute tremendously to health problems encountered by living species today, problems such as breast cancer, reproductive abnormalities, a decline in male population most significant to aquatic vertebrates, reduced fertility and other infinite abnormalities recurring in the reproductive system of mostly male species. The first biosensor developed for the detection of 17β-estradiol-estradiol endocrine disrupting compound; consisted of an electro-active polymeric 3-mercaptoprorionic acid capped zinc selenide quantum dots cross linked to horseradish peroxidase (HRP) enzyme as a bio-recognition element. The second biosensor developed was comprised of cysteamine self assembled to gold electrode, with 3-mercaptopropionic acid capped zinc selenide quantum dots cross linked to cytochrome P450-3A4 (CYP3A4) enzyme in the presence of 1-ethyl-3-(3- dimethylaminopropyl)carbodiimide hydrochloride and succinimide.Item The development of graphene oxide sheet- and polyanilino-immunosensor systems for lipoarabinomannan (LAM) tuberculosis biomarker(University of the Western Cape, 2017) Wilson, Lindsay Robin; Iwuoha, Emmanuel; Waryo, Tesfaye T.Tuberculosis (TB) is an infectious disease with adverse effect on a global scale. The disease is one of the major causes of death in sub-Saharan Africa. Nearly 70% of TB-infected persons are co-infected by the human immunodeficiency virus (HIV). About 50% of TB/HIV patients are smear negative and up to 28% are sputum scarce, which is a significant problem in South Africa since sputum smear microscopy is the most widely used diagnostic test for TB. The detection of Mycobacterium tuberculosis (MTB) and resistance to the TB drug rifampicin (RIF) are the basis of the GeneXpert MTB/RIF protocol. The GeneXpert MTB/RIF is an automated nucleic acid amplification technique for detecting the DNA that originates from MTB. However, low sensitivity and low concentrations of MTB for DNA amplification are a serious issue associated with the protocol. Therefore, other TB diagnostic methods, such as the ones involving biochemical markers of TB, are becoming very important.Item Development of high performance composite lithium ion battery cathode systems with carbon nanotubes functionalised with bimetallic inorganic nanocrystal alloys(University of Western Cape, 2011) Ikpo, Chinwe Oluchi; Iwuoha, Emmanuel; Ozeomena, Kenneth I.Lithium ion cathode systems based on composites of lithium iron phosphate (LiFePO₄), iron-cobalt-derivatised carbon nanotubes (FeCo-CNT) and polyaniline (PA) nanomaterials were developed. The FeCo-functionalised CNTs were obtained through in-situ reductive precipitation of iron (II) sulfate heptahydrate (FeSO₄.7H₂O) and cobalt (II) chloride hexahydrate (CoCl₂.6H₂O) within a CNT suspension via sodium borohydrate (NaBH₄) reduction protocol. Results from high Resolution Transmission Electron Microscopy (HRTEM) and Scanning Electron Microscopy (SEM) showed the successful attachment FeCo nanoclusters at the ends and walls of the CNTs. The nanoclusters provided viable routes for the facile transfer of electrons during lithium ion deinsertion/insertion in the 3-D nanonetwork formed between the CNTs and adjacent LiFePO₄ particles.