http://hdl.handle.net/10386/33 2026-04-05T19:24:27Z http://hdl.handle.net/10386/5408 The design, synthesis, and antitubercular properties of the tri-substituted benzofuran derivatives Mojapelo, Semola Kabelo Tri-Substituted benzofuran derivatives exhibit greater biological activities influenced by natural compounds with highest potency, selectivity, and multifunctionality. Naturally occurring benzofuran with hydroxyl, methoxy, phenyl modification in different position showed antimicrobial, anticancer, antitubercular, and neuroprotective activities. These modification groups can influence lipophilicity, binding affinity and membrane permeability of mycobacterium tuberculosis which impact bioactivity. The aim of the study was to design, synthesise, and evaluate the anti-tubercular properties of the tri-substituted benzofuran derivatives. 5-iodovanillin 1B was made by iodinating commercially available vanillin 1A in a 92% yield. 2-(substituted)-7-methoxybenzofuran-5-carbaldehydes 2A-2E were produced by a Sonogashira cross-coupling reaction with palladium using a variety of acetylenes in a 60–80% yield. 2-(substituted)-7-methoxybenzofuran-5-carbaldehydes (2A-2E) were reduced with sodium borohydride in ethanol at room temperature, producing 2-substituted-7-methoxybenzofuran-5-ylmethanols (3A-3E) in a 60–82% yield. The esterification of the 2-substituted-7-methoxybenzofuran-5-carbaldehydes 3A-3E was catalysed by a Mukaiyama catalyst with several carboxylic acids in dichloromethane at room temperature, producing esters 3A1-3E5 in 40–80% yields. FTIR and NMR spectroscopy were used to characterise each of the synthesised substances. The online platform ADMET3.0 was used to perform the ADMET characteristics of esters 3A1-3E5. The antimycobacterial, cytotoxic, and solubility properties of every synthesised compound were assessed biologically. Several trisubstituted benzofuran derivatives that were synthesised demonstrated antimycobacterium tuberculosis (Mtb H37Rv) activity. For example, compound 3B3 showed good activity in all three media used with less toxicity. Additionally, six compounds (2A, 3A, 3A2, 2B, 3B, and 3B1) showed solubility results ranging between 5-195 μM. Compound 3B showed the best solubility of 195 μM but poor antitubercular activity in all three media used. On the contrary, compound 2A showed promising antimycobacterial activity of 2.02-18.08 μM in two media but had poor solubility of less than 5 μM. Additionally, compound 3A2 demonstrated activity in one medium (7H9/CAS/Glu/Tx), whereas compound 3B1 demonstrated activity in two media (7H9/ADC/Glu/Tw and 7H9/ADC/Glu/Tx). Both compounds displayed comparable outcomes, including good solubility at 50 μM and cytotoxicity at or above 50 μM, respectively. Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2025 2025-01-01T00:00:00Z http://hdl.handle.net/10386/5398 Mineralogical characterisation of brittleness indices of platinum-bearing reefs (UG 2), located in the eastern limb of the Bushveld Igneous Complex Matukane, Ncedo Matricia The brittleness of rocks has traditionally been measured utilizing mechanical properties, however, it has been established that the mechanical properties of rock masses strongly depend on their petrographic properties, and mineralogical composition plays a critical role in determining the property of rocks to fail. Despite the existence of established brittleness indices based on the mineralogical composition of rocks, the selection of brittle components in rocks remains subjective and can be contradictory. The effects of porosity, stress state, cement type and strength, pre-consolidation factor, grain size, and external mechanical conditions are also not considered in the existing brittleness indices. This study aims to characterize the brittleness indices of platinum-bearing (UG2) reefs on the eastern limb of the Bushveld Igneous Complex using mineralogical analysis. To this aim, microscopic examinations identified different mineralogical characteristics, laboratory analysis of UG2 samples was performed to obtain the mechanical parameters, and additional parameters were obtained from numerical simulations. Innovative brittleness indexes (B1, B2, B3, B4, and B5) are developed utilizing parameters such as textural variables, contact type, contact nature, and packing density. The brittleness indexes are additionally compared with previous important brittleness indices utilizing fieldwork, laboratory analysis, numerical simulation, and predictions (multivariate linear models). Additionally, a similar approach was applied to the mechanical parameters, developing innovative brittleness indexes B1, B2, B4 and B6 using traditional mechanical parameters. The results revealed that contact type and contact nature were the most significant mineralogical predictors of brittleness, with models B2 and B6 demonstrating strong predictive accuracy (R² values of 0.778 and 0.727, respectively) and near-perfect precision (SE = 0.000). Texture and packing variables had a lesser impact on brittleness prediction. While tensile (σt) and compressive strength (σc) emerged as key predictors with high accuracy. Models B2 and B6 were the most reliable, showing near-perfect precision with SE values of 0.000. In contrast, models B1 and B4 were less precise, and B3 lacked statistical significance. The high statistical significance and low SE values of B2 and B6 confirmed their reliability for brittleness prediction. It is recommended that more sophisticated methods be applied as well. Thesis (M.Sc. (Geology)) -- University of Limpopo, 2025 2025-01-01T00:00:00Z http://hdl.handle.net/10386/5091 Fabrication of functionalised-MWCNTS/metal chalcogenides composite non-enzymatic electrochemical sensor for the the detection of glucose Maphake, Precious One of the most significant analysis in medical diagnosis is blood glucose measurement. In other scientific and industrial domains, such as environmental monitoring, pharmaceuticals, and the food sector, they are equally indispensable, however commercial glucometers that are sold on the market frequently have a lot of flaws and limits. These can be caused by a variety of challenges, such as poor material design, incorrect storage, coding mistakes, issues with device calibration, manufacturing processes, and the substantial influence of ambient elements like pH and temperature. Some of these issues might be resolved by creating brand-new hybrid materials with enhanced characteristics (such stability and adsorption capabilities). The metal sulfide-decorated-functionalised-multi-walled carbon nanotube modified non-enzymatic glucose detecting sensor was studied. Many physicochemical and structural investigations, such as Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy, were performed to characterize the synthesized nanocomposites. Electrochemical methods such as square wave voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy were used to comprehensively test the produced sensors. The p-MWCNTs were purified and functionalised by acid treatment into COOH-MWCNTs. Amine functionalise MWCNTs (NH2-MWCNTs) were donated by Mintek. Metal sulfides nanoparticles (FeS2 and ZnS) were synthesised using hydrothermal method under the same experimental conditions as the metal sulfides/f-MWCNTs nanocomposites for comparison in the electrochemical studies. Fourier transform infrared spectroscopy (FTIR) verified that carboxyl (COOH) and amine (NH2) functional groups were detected on the surface of the f-MWCNTs, which appeared at lower wavenumbers, i.e., below the fingerprint due to the presence of metal sulfides. Transmission electron microscopy (TEM) was used to confirm that FeS2 and ZnS nanoparticles successfully decorated MWCNTs in situ. The functionalized MWCNTs surface exhibited a well-dispersed distribution of metal sulfides, as demonstrated by TEM pictures. X-ray diffraction (XRD) was used to confirm the chemical composition of the as-prepared MWCNTs, indicating the existence of MWCNTs and metal sulfides. The XRD pattern of FeS2/COOH-MWCNTs nanocomposites represented crystal planes of pyrite FeS2. The ZnS/COOH-MWCNTs nanocomposites' XRD pattern agrees with published data and confirms that ZnS forms in the cubic (sphalerite) phase with acceptable crystallinity. The Raman spectra of pristine MWCNTs, COOH-MWCNTs, FeS2/COOH-MWCNTs, FeS2/NH2-MWCNTs ZnS/COOH-MWCNTs and ZnS/NH2-MWCNTs all showed three vibration bands namely, D, G, and G’, further confirming the presence of the carbonous nature of the MWCNTs. The electrochemical characteristics of the nanocomposites formed by metal sulfides/functionalized-MWCNTs were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). These analyses were performed in a solution containing 5 mM K3Fe(CN)6 /K4Fe(CN)6 as the redox probe and 0.1 M KCl as the supporting electrolyte. The resultant nanomaterials had redox active groups that produced a signal on the electrode surface, and these groups could be used to build electrochemical sensors and biosensors. The cyclic voltammograms illustrate the comparative current in this decreasing order: ZnS/COOH-MWCNTs-GCE> FeS2-GCE> p-MWCNTs-GCE> BARE-GCE> ZnS/NH2-MWCNTs-GCE> FeS2/NH2-MWCNTs-GCE> GCE-ZnS-GCE˃ GCE-COOH-MWCNTs-GCE> FeS2/COOH-MWCNTs-GCE˃ NH2-MWCNTs-GCE. The fitted impedance data reveals that the GCE-ZnS/COOH-MWCNTs electrode has the lowest Rct value of 33 Ω, proposing a swift electron transfer of the GCE-ZnS/COOH-MWCNTs electrode as in comparison to the remaining electrodes, consistent with the findings from cyclic voltammetry. Consequently, the ZnS/COOH-MWCNTs nanocomposite showed better electroactivity and great potential to be employed for glucose detection. Square wave voltammetry (SWV) was used for the electroanalysis of the analyte (glucose) at the GCE-ZnS/COOH-MWCNTs. The results showed that the GCE-ZnS/COOH-MWCNTs had better electrocatalytic behaviour resulting from the higher oxidation peak currents (Ipa) and faster electron transport. The results from scan rate studies demonstrate that the scan rate (v) correlates directly with the glucose anodic current responses (Ipa) at GCE-ZnS/COOH-MWCNTs. The glucose oxidation mechanism at GCE-ZnS/COOH-MWCNTs was diffusion-controlled, indicated by the linear relationship observed between oxidation peak currents (Ipa) and the square root of the scan rate (v1/2). Employing square wave voltammetry, a limit of detection (LoD) of 0.83 mM was achieved for GCE-ZnS/COOH-MWCNTs within alinear dynamic range (LDR) of 1-9 mM. The sensitivity of the sensor was measured at 7.2 x 106 A.mM-1. Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2024 2024-01-01T00:00:00Z http://hdl.handle.net/10386/5023 Detection of chromium and mercury in water using rGO incorporated Cu-based nanomaterials Moremi, Harold Heavy metal ions can build up for years or even decades in a number of body organs. Heavy metal poisoning symptoms have the potential to be fatal and to cause permanent harm. According to the United States Environmental Protection Agency (EPA), heavy metals such as chromium, nickel, cadmium, copper, lead, mercury, and arsenic are classified as the most toxic, hence it is important to be able to find simple, rapid methods to detect them in either wastewater or drinking water. In this research study, Cu-based nanomaterials on reduced graphene oxide (RGO) are prepared and then used as an electrocatalyst for the detection of chromium(III) and mercury(II). Copper oxide (CuO) and copper sulfide (CuS) nanoparticles (NPs) were prepared using co-precipitation method and chemical reduction method, respectively. Copper chloride dihydrate (CuCl2.2H2O) was employed as a metal source in both methods. In the case of copper sulfide nanoparticles, thioacetamide (TAA) was employed as the sulfur source in the presence of GSH (Glutathione), which was employed as a capping agent. Both CuONPs and CuSNPs were also coated with Gold (Au) to form polyhedral hetero-structure composed of both gold nanoparticles and CuO nanoparticles. The prepared CuO, CuS, CuO-Au and CuS-Au were then incorporated on RGO using different chemical processes in order to produce CuO/RGO, CuS/RGO, CuO-Au/RGO and CUS-Au/RGO nanocomposites. All prepared nanoparticles and nanocomposites were characterized with ultraviolet visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), fourier-transform infrared (FTIR) microscopy and Raman spectroscopy. In addition, glassy carbon electrodes (GCEs) modified with CuO, CuS, CuO-Au, CuS-Au CuO/RGO, CuS/RGO, CuO-Au/RGO and CUS-Au/RGO were prepared, and the electrochemical activities of each modified electrode were investigated using the [Fe(CN)6]3-/4- probe via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CuS-Au/RGO exhibited high electron transfer with low resistance charge transfer (Rct) by EIS analysis. Therefore, was chosen as the material of interest during the development of the electrochemical sensor for both Cr(III) and Hg (II) heavy metal ions. The sensor parameters such as scan rate, pH and deposition potential and time were optimized. The CUS-Au/RGO showed good stability and reactivity at pH of 6.17. The fabricated sensor exhibited very low detection limits of 2 ppb for Hg(II) and 2 ppb for Cr(III). However, the CuS-Au/RGO nanocomposite based electrochemical sensor evidently demonstrated to have a strong binding affinity and preference for Hg(II) than Cr(III) Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2024 2024-01-01T00:00:00Z