Research Articles (Chemistry)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1724

This collection contains some of the full text peer-reviewed/ refereed articles published by researchers from the Department of Chemistry

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Identifying skin surface chemicals as potential tuberculosis diagnostic biomarkers using ultra performance liquid chromatography-high resolution mass spectrometry
(Elsevier, 2025-05) Wooding, Madelien; Van Pletzen, Kornelis; Naude, Yvette; madelien.wooding@up.ac.za
Tuberculosis (TB) remains a significant cause of morbidity and mortality globally, despite its preventability and curability. Early and accurate diagnosis of active TB is essential for enhancing patient care, improving outcomes, and interrupting the transmission cycles of Mycobacterium tuberculosis (M.tb). Metabolomics proves to be an emerging area of study for the development of a non-invasive approach to TB diagnostics.. High-resolution mass spectrometry combined with ion mobility spectrometry enhances the confidence in identifying and annotating biological markers during metabolomic research. This study outlines an analytical workflow encompassing sample preparation through to multivariate analyses for detecting potential TB diagnostic biomarkers. A custom-designed wearable polydimethylsiloxane (PDMS) sampler was employed as a passive sampling device, effectively concentrating chemical compounds from the skin surface. The sampler was directly desorbed into solvent within an LC vial, streamlining the extraction-to-analysis process. Utilising accurate mass and collision cross sections (CCS), fourteen biomarkers were tentatively identified, demonstrating the ability to differentiate TB patients from control groups. Receiver operating characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.911. Among these, para-aminobenzoic acid (PABA) emerged as a promising biomarker for TB, achieving a specificity of 1, sensitivity of 0.9, and an AUC of 0.961. Method limits of detection for the 1-hour non-invasive skin sampling method ranged from 6 (PABA) to 172 ng (phenylalanine) for a calibration working range of 10 – 800 ng with a R2 of ≥ 0.99. These first results demonstrate the potential of using skin surface compounds in TB diagnostics.
Cutaneous volatile and semi-volatile organic compounds as markers of malaria-infection by wearable samplers and two-dimensional gas chromatography—time-of-flight-mass spectrometry
(Elsevier, 2025-11) Pretorius, Daniel Thomas; Rohwer, Egmont Richard; Naude, Yvette; yvette.naude@up.ac.za
Malaria has been found to alter normal cutaneous volatile organic compound (VOC) profiles, suggesting their potential application as markers of Plasmodium infection. The cutaneous VOCs and semi-VOCs (SVOCs) of malaria-negative and -positive individuals, who visited two local clinics in the Vhembe district of Limpopo Province, South Africa, were extracted into wearable silicone rubber (polydimethyl siloxane [PDMS]) sampling bands adhered to the surface of the epidermis. After sampling of epidermal VOCs from participants the samplers were analysed by thermal desorption-comprehensive two-dimensional gas chromatography-time-of-flight-mass spectrometry (TD-GC × GC-TOFMS). Individual cutaneous VOCs and SVOCs profiles were constructed from these complex chromatographic profiles in order to identify potential signatures of Plasmodium infection. Fatty acid compounds associated with rancid malodour, and previously reported as mosquito attractants, were found at an overall greater abundance in chemical profiles of malaria-positive cases. A targeted analysis was performed for compounds previously reported to be associated with Plasmodium infection, viz., heptanal, (E)-2-octenal, 2-octanone, octanal, nonanal and (E)-2-decenal. The linearity (R2) range was 0.93–0.99 for a matrix matched (simulated cutaneous sampling) calibration range of 2.5–60 ng. Limits of detection (LOD) ranged from 0.4 pg (2-octanone) to 6.3 pg ((E)-2-octenal), whilst limits of quantification (LOQ) ranged from 1.4 pg to 21.1 pg. The mean percentage recoveries (n = 2) ranged from 77.8 % ((E)-2-decenal) to 118.9 % (2-octanone). The percentage relative standard deviations ( %RSDs; n = 2) ranged from < 1 % for 2-octanone, octanal and nonanal to 27.1 % for (E)-2-octenal. We found that this particular suite of compounds, previously reported as indicators of malaria, was in fact non-specific for Plasmodium infection when compared to control subjects with comorbidities. A previously unreported (in a malaria-infection context) compound, (E)-2-octen-1-ol, correlated with malaria-positive participants, but was also observed for two malaria-negative participants, which could indicate latent malaria. In chronic cases, Plasmodium vivax can occur in reservoirs outside of the bloodstream, and thus blood-based diagnostic tests can miss latent infection. A key advantage of the epidermal sampler over blood tests is that the former collects whole-body organic compounds, and is therefore not limited to blood-borne markers of infection. As such it appears to be feasible for future investigations.
Learning organic chemistry on the go : chemical engineering students’ perceptions of Chirality 2 app as a learning support
(American Chemical Society, 2025-04) Mosala, Tisetso; Mathabathe, Kgadi Clarrie; Tekane, Rethabile
Although the use of mobile-based learning applications in organic chemistry is rising, limited studies have evaluated their effectiveness as learning supports. This study presents a phenomenographic investigation into the evaluation of using the Chirality 2 app as a learning support in a first-year chemical engineering organic chemistry course in a South African University context. An open-ended questionnaire was used to probe students’ perceptions of the course and their suggestions regarding improving the Chirality 2 app. The findings revealed that students used the app to practice, revise, and test their understanding of organic chemistry concepts in preparation for class tests. Although the students liked the Chirality 2 app for providing immediate feedback, they also expressed dissatisfaction with the lack of detailed feedback for the incorrect answers, and the fact that they were restricted only to multiple-choice questions. The study offers valuable insights into the potential use of gaming apps as equitable learning tools to support organic chemistry students in diverse and resource-limited environments.
Copper(II) complexes derived from halogen-substituted Schiff base ligands : synthesis, crystal structures, antibacterial activity, and molecular docking studies
(American Chemical Society, 2025) Yusuf, Tunde Lewis; Waziri, Ibrahim; Oladipo, Segun D.; Abd El-Maksoud, Mostafa S.; Muller, Alfred J.; Vatsha, Banele; yusuf.tl@up.ac.za
In the face of escalating bacterial resistance to conventional antibiotics, the quest for novel antimicrobial strategies is urgenter than ever. Metal complexes, particularly those with biological activity, stand out as a promising alternative due to their unique mechanisms of action and potential for fewer side effects in comparison to standard organic antibiotics. This investigation focuses on the synthesis and characterization of six Cu(II) complexes, each formulated from halogen-substituted bidentate Schiff base ligands. Employing a suite of analytical methods, Fourier transform infrared, UV–vis, elemental analysis, and single-crystal X-ray diffraction, the structures of the complexes were fully established. All of the complexes were assigned to have square planar geometry, with the ligand acting as a bidentate and coordinate to the Cu(II) ion via nitrogen and oxygen atoms. The antibacterial efficacy of these complexes was rigorously tested against both Gram-positive bacteria Staphylococcus aureus and Streptococcus pyogenes and Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae, utilizing the broth microdilution technique. The results revealed a spectrum of activity, with minimum inhibitory concentrations (MICs) spanning from less than 15.63 to 125 μg/mL. Notably, Complex 2 demonstrated remarkable potency against S. aureus and S. pyogenes, registering an MIC of less than 15.63 μg/mL. To elucidate the underlying mechanism of action, molecular docking studies were performed targeting the topoisomerase IV receptor. The docking outcomes corroborated the empirical data, underscoring the strong affinity of the complexes for the bacterial targets.
Chemical analysis of alliin-rich Allium sativum (Garlic) extract and its safety evaluation in Drosophila melanogaster
(Elsevier, 2024-12) Oyaluna, Zeniat Emike; Abolaji, Amos Olalekan; Bodede, Olusola; Olanlokun, John Oludele; Prinsloo, Gerhard; Steenkamp, Paul; Babalola, Chinedum Peace
Garlic (Allium sativum) has been traditionally valued for its medicinal properties attributed to the presence of organosulfur compounds. Despite its benefits, concerns about herbal extract toxicity have arisen, necessitating safety assessment. This study was designed to evaluate the chemical analysis and safety profile of Alliin-Rich Garlic Extract (ARGE) using Drosophila melanogaster as a model organism. The ARGE was extracted from garlic cloves (Allium sativum Linn: UIH-23262) using a microwave-assisted method and characterized using UPLC-ESI-MS, 1H NMR, HPLC and IR. Its safety evaluation was determined using D. melanogaster (Harwich strain), and various assays were conducted on 1–3-day-old flies. Toxicological markers and oxidative stress were assessed to understand the impact of ARGE on the flies. Chemical profiling of ARGE using UPLC-ESI-MS, confirmed the presence of alliin (S-ally-L-cysteine-S-oxide), L-arginine, γ-glutamylmethionine, S-(2-carboxypropyl) glutathione, N-γ-glutamyl-S-(1-propenyl) cysteine, N-γ-glutamyl-S-(2-propenyl) cysteine, N-γ-glutamylphenylalanine, S-(allylthio) cysteine, γ-glutamyl-S-allylthiocysteine and eruboside B. HPLC confirmed an alliin content of 0.073 mg/g. Toxicological assessment in D. melanogaster revealed that ARGE enhanced antioxidant defenses by increasing total thiol levels and GST activity, while reducing acetylcholinesterase activity. No significant alteration was observed in catalase activity and cellular metabolic rate. Histological examination revealed no alterations in the histoarchitecture of the brain, fat body or gut of D. melanogaster. The study demonstrated the safety of ARGE in D. melanogaster, supporting its potential as a safe herbal remedy.
Analytical application of carbon dot-based molecularly imprinted polymers in the fabrication of selective fluorescence and electrochemical sensors – a review
(Elsevier, 2026-01) Ng'andu, Clever; Nsibande, Sifiso Albert; sifiso.nsibande@up.ac.za
Carbon quantum dots (CQDs) offer unique chemical and optical properties which have led to their adoption in designing chemical sensors for environmental and biological applications. They have several advantages over heavy metal-based quantum dots, including low toxicity and biocompatibility, which have made them attractive for researchers. They can also be modified and incorporated with molecularly imprinted polymers (MIPs) to fabricate highly selective composite materials for the determination of target analytes. In this work, we first make a case for this specific review in the literature, considering other reviews that have been published on this subject. Then, we briefly introduce the reader to commonly used strategies for the synthesis of CDs and CD-MIPs for selective optical and electrochemical sensor fabrication. Subsequently, we discuss recent research advancements in the synthesis and application of these sensors across various matrices, with an emphasis on the determination of biologically relevant analytes, environmental monitoring, and food safety and quality assessment. Ultimately, key findings are highlighted, and future perspectives for this field are shared. HIGHLIGHTS • Preparation of carbon dots modified with molecularly imprinted polymers (CD-MIPs) for chemosensing. • Analytical performance of the fluorescence and electrochemical sensors with CD-MIP recognition units. • Applications of the CD-MIP sensors in food analysis, environmental monitoring, and sensing of biorelevant compounds. • Challenges and prospects of chemosensors with CD-MIP recognition units.
Techno-economic evaluation of retrofitting power-to-methanol : grid-connected energy arbitrage vs standalone renewable energy
(Elsevier, 2026-02) Mbatha, Siphesihle; Ghaebi Panah, Payam P.; Cui, Xiaoti; Debiagi, Paulo Eduardo Amaral; Louis, Benoît; M.Musyoka, Nicholas; Everson, Raymond C.; Parkhomenko, Ksenia; Langmi, Henrietta Wakuna
The power-to-methanol (PtMeOH) will play a crucial role as a form of renewable chemical energy storage. In this paper, PtMeOH techno-economics are assessed using the promising configuration from the previous work (Mbatha et al. [1]). This study evaluated the effect of parameters such as the CO2 emission tax, electricity price, and CAPEX reduction on the product methanol economic parity with respect to a reference case. Superior to previous economic studies, a scenario where an existing methanol synthesis infrastructure is 100 % retrofitted with the promising electrolyser is assessed in terms of its economics and the associated economic parity. The volatile South African electricity market is considered as a case study. The sensitivity of the PtMeOH and green H2 profitability are checked. Grid-connected and standalone renewable energy PtMeOH scenarios are assessed. Foremost, generalisable effect trends of these parameters on the net present value (NPV) and the levelized cost of methanol(LCOMeOH) and H2 (LCOH2) are discussed. The results show that economic parity of H2 (LCOH2 = current selling price = 4.06 €/kg) can be reached with an electricity price of 30 €/MWh and 70 % of the CAPEX. While the LCOMeOH will still be above 2 €/kg at 80 % of the CAPEX and electricity price of 20 €/MWh. This indicates that even if the CAPEX reduces to 20 % of its original in this study, and the electricity price reduces to about 20 €/MWh, the LCOMEOH will still not reach economic parity (LCOMeOH > current selling price = 0.44 €/kg). The results show that to make the retrofitted plant, with a minimum of 20 years of life span, profitable, a feasible reduction in the electricity price to below 10 €/MWh along with favourable incentives such as CO2 credit and reduction in CAPEX, particularly that of the electrolyser, and treatment of the PtMeOH as a multiproduct plant will be required. HIGHLIGHTS • Techno-economics of a 100kton/year retrofitted power-to-methanol are studied. • Grid-connected energy arbitrage and standalone scenarios are investigated. • Generalisable effect trends of key economic bearing parameters are discussed. • To be profitable, a reduction in electricity price to < 10 €/MWh is required. • Power-to-methanol should be treated as a multi-product plant to improve profit.
Hydrogen production via potassium formate hydrolysis on metal-organic framework supported Pd-based catalysts
(Wiley, 2025) Li, Ke; Cai, Tianyi; Li, Jiaye; Dlamini, Mbongiseni William; Sun, Zhiqiang; Sun, Zhao
Please read abstract in the article.
Preliminary characterisation of the Thaumatococcus daniellii fruit as a potential biomass source for biorefinery
(Springer, 2025) Elango, Lena Yoh Ekaney; Langmi, Henrietta Wakuna; Beckley, Victorine Namondo; Etape, Ekane Peter; Akoachere, Jane-Francis; Foba-Tendo, Josepha
The inherent variability of biomass composition and structure, as well as the increased trends towards blending of biomass feedstock for energy, chemicals and materials, requires the systematic characterisation of biomass from both established and new sources. The high-value sweet protein thaumatin is produced from Thaumatococcus daniellii (T.d) fruit, native to West Africa, leaving about 90% of the fruit as waste. In this study, the proximate, ultimate, compositional and thermochemical characterisation of T.d fruit pulp and seeds, are determined, with a view to establishing the potential for a T.d biorefinery platform. Extractives content was determined through ethanol soxhlet extraction; cellulose, lignin and pectin contents by alkali hydrolysis, Klason method and acid hydrolysis respectively; while the thermochemical properties were determined by FTIR, EA, EDS and TGA. The proximate composition for pulp and seed biomass, respectively were; ash 17.47%/11.64%, moisture 16.29%/9.56%, fixed carbon 12.5/14.2%, extractives 15.7/3.4%, cellulose 25.34/26.82%, hemicellulose 21.61/15.89%, lignin 10.75/18.20%, pectin14.78/20.85%; elemental composition; C 34.27%/43.09%, H 4.7%/5.72%, N 1.08%/2.16% S 0.33%/ 0.15%, O 59.62%/48.88%. Analyses of the Thaumatococcus daniellii pulp and seed biomass samples revealed a relatively low lignin content, and high pectin and ash content. These characteristics indicate their potential as feedstock for low to medium value products such as pectin, cellulose and mineral-rich biochar. The potential for the recovery of a wide range of low to high value products from this biomass merits its consideration for a biorefinery platform. This should increase the economic value of this local plant while simultaneously alleviating pollution problems.
Tungsten-based nano-architecture for the photocatalytic degradation of recalcitrant pharmaceutical pollutants : a review
(Elsevier, 2025-09) Adesibikan, Ademidun Adeola; Saliu, Oluwaseyi Oluwadamilare; Ndungu, Patrick Gathura; patrick.ndungu@up.ac.za
The growing occurrence of pharmaceutical contaminants in aquatic environments presents a significant challenge to water security, a critical component of sustainable development. These emerging pollutants, often resistant to conventional treatment methods, pose risks to human health and disrupt aquatic ecosystems, highlighting the urgent need for advanced water purification strategies. As a result, there is a need for the development of innovative and environmentally sustainable techniques and advanced oxidation processes (AOPs), including photocatalysis using tungsten-based nanomaterials (TBNPs), have shown a promising approach. This review critically focuses on the application of TBNPs as eco-effective photocatalysts, exploring the potential synergistic effects of combining tungsten (W) nanoparticles with other materials, leading to enhanced photocatalytic performance. It discusses the principal mechanism of photodegradation, focusing on the interaction between TBNPs and pharmaceutical pollutants. It also presents an overview of recyclability (>80 % degradation efficiency by the 5th cycle), advantages, and limitations. This review shows that TBNPs exhibit promising photocatalytic efficiency compared to other materials, based on reported studies. HIGHLIGHTS • Degradation of pharmaceuticals using W-based materials for was reviewed. • W-nanomaterials exhibit >60 % degradation efficiency for pharmaceuticals. • Maintained stability and structural integrity over 2–15 cycles • Performance stems from oxygen vacancies that boosts radical generation. • Superoxide radicals (O2−) dominate degradation over OH/h+ in W-systems.
Advancements in piezo-photocatalysts for sustainable hydrogen generation and pollutant degradation : a comprehensive overview of piezo-photocatalysis
(Elsevier, 2025-03) Masekela, Daniel; Balogun, Sheriff A.; Yusuf, Tunde Lewis; Makgato, Seshibe; Modibane, Kwena D.
Photocatalysis and piezocatalysis have been extensively employed in energy production and environmental restoration applications. However, the photocatalysis process suffers from rapid recombination of photogenerated electrons (e−) and holes (h+), limiting its practical application. Recently, the piezoelectric effect, which relies on the conversion of mechanical energy to trigger chemical reactions, has shown promise. It can produce an internal piezoelectric field under mechanical vibration, promoting the separation and migration of photogenerated charge carriers. This enhancement leads to significantly improved photocatalytic performance. However, there are still limited reports on other strategies to improve the performance of piezo-photocatalysts. Therefore, a comprehensive review was conducted to categorize the development of piezo-photocatalysts, detailing their classifications, synthetic methods and construction strategies, as well as their applications in energy production and wastewater treatment. This review aims to address the present challenges and future prospects of piezo-photocatalysis, providing clarity on its developmental trajectory. HIGHLIGHTS • Overview of classification and synthesis of piezo-photocatalyst, including hydrothermal and solvothermal methods. • Strategies for modifying piezo-photocatalys to improve catalytic perfomance. • Structural properties and bandgap engineering for improved charge separation. • Analysis of piezo-photocatalytic performance in hydrogen production and wastewater treatment. • Challenges and future directions for optimizing perfomance and scalability of piezo-photocatalyst.
Preparation of polydimethylsiloxane thin films containing immobilized CdSeTe/ZnS quantum dots for water sensing applications
(South African Chemical Institute, 2024-01) Putter, Wilme; Nsibande, Sifiso Albert ; Forbes, Patricia B.C.; patricia.forbes@up.ac.za
Pollutants in water systems are a significant environmental problem, as they can have harmful effects on both human health and the ecosystem. Here we developed a robust method for preparing CdSeTe/ZnS core/shell (C/S) quantum dots (QDs) immobilized into polydimethylsiloxane (PDMS) thin films for pollutant sensing applications. Highly fluorescent hydrophobic QDs were first synthesized using the hot-injection organometallic approach with the use of hydrophobic trioctylphosphine oxide and oleic acid ligands as capping agents. The C/S QDs had an average particle diameter of 4.0 nm and had broad absorbance in the ultraviolet-visible region. Their maximum fluorescence was at 594 nm and the photoluminescence quantum yield of the C/S QDs relative to rhodamine 6G was 47%. The C/S QDs were then immobilized into PDMS (to form QD@PDMS) by means of an optimized spin coating procedure onto glass slides at a speed of500 rpm and acceleration of 300 rpm/s for 10 s, followed by curing at 80 ºC for 15 min. This thin film format enabled direct use and analysis of the thin films by submersion into water samples followed by fluorescence spectroscopy. The homogeneity of the QD@PDMS thin films thus produced was excellent, as determined by visual inspection under an ultraviolet lamp and by fluorescence spectroscopy. An excitation wavelength of 400 nm led to the highest fluorescence intensity of the thin films and repeated exposure to this excitation wavelength did not have a major negative impact on the fluorescence emission of the QD@PDMS thin films, as the difference between the maximum and minimum fluorescence emission intensity was 8% over 60 repeated measurements. A mixture of water and ethanol (2:1) had the smallest effect on the fluorescence of the films and was thus the most effective matrix for sensing of organic pollutants. The interaction of the QD@PDMS films with individual organic pollutants (polar atrazine pesticide and non-polar phenanthrene) and with real water samples, resulted in a change in fluorescence of the thin films indicating that they are a promising candidate for sensing pollutants in water. The relative uptake and interaction of organic compounds by the thin films would need to be determined and their selectivity towards target analytes investigated for a particular application, in order to assess the viability of use of the QD@PDMS thin films to screen for the presence of the analytes and to semi-quantify them using fluorescence.
Dual charge transfer mechanisms in intimately bonded S-scheme heterojunction photocatalyst with expeditious activity toward environmental remediation
(Wiley, 2025-05) Mafa, Potlako J.; Malefane, Mope E.; Opoku, Francis; Oladipo, Adewale O.; Mamba, Gcina; Yusuf, Tunde Lewis; Nure, Jemal Fito; Lebelo, Sogolo L.; Liu, Dan; Gui, Jianzhou; Mamba, Bhekie B.; Kuvarega, Alex T.
Please read abstract in the article.
Pristine graphene oxide treatment of wastewater from a typical sub-tropical mine in Chegutu, Zimbabwe
(Springer, 2025-08) Kalitsilo, F.R.; Hashemi, H.; Mombeshora, Edwin Tonderai; et.mombeshora@up.ac.za
Mining activities in sub-tropical regions are one of the major contributors to environmental contamination and therefore require monitoring and mitigation methodologies. The study investigated the composition of the real-world wastewater from mine explosions and explored the potential of graphene oxide as an adsorbent. Heavy metals, namely, Fe (12.10 ppm), Cu (40.70 ppm), Cr (148 ppm) and Pb (0.03 ppm) were present. The optimal pH, adsorbent dose, temperature, and contact time for heavy metal removal were 12.08, 0.5 g, 25 °C and 0.5 h, respectively. The basic conditions were favourable for efficient removal through the adsorption method. Kinetic modelling indicated adsorption via pseudo-second-order kinetics, insinuating the influence of oxygen moieties of graphene oxide. Furthermore, the Langmuir isotherm revealed favourable removal of Fe, Cu, and Cr. The study indicated potential hazards of current mining activities, especially unmonitored illegal mines in sub-tropical regions. These findings highlight the prospects of graphene oxide as a practical and effective adsorbent for water resource recovery facilities. Therefore, the study demonstrated the capability to adopt pristine graphene oxide in a simple protocol using simple setups for wastewater recovery in the sub-tropical regions in a natural matrix.
Investigations into the impact of storage conditions and filtration on the analysis of natural organic matter in water
(South African Chemical Institute, 2025) Marais, Savia S.; Nokeri, Boitumelo K.; Forbes, Patricia B.C.; patricia.forbes@up.ac.za
When treating water for drinking water purposes, it is crucial to consider the composition of natural organic matter (NOM). NOM is a complex mixture of organic compounds influencing water quality and treatment processes. To ensure accurate reporting of analytical results, suitable sample storage and preparation are essential for maintaining sample integrity. This study investigated the effects of different storage conditions on water samples collected from Africa's largest bulk water provider, which sources its water from the Upper Vaal Catchment area. Samples were stored for varying durations under different temperature and light conditions to assess their impact on dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254). The results showed that storing water samples for 34 days in the dark, at room temperature or at 5 oC did not significantly alter the DOC and UV254 measurements compared to the initial sample measurements. The pre-washing of filters from different brands with ultrapure water indicated that there were retained UV-active contaminants in the filter materials, of which 81% to 91% were removed after washing with 25 mL of ultrapure water. Furthermore, the portable, battery-operated UV254 Go! analyser is a cost-effective tool for direct field measurements of NOM aromaticity.
(1R,2S,4aR,6S,8R,8aS)-1-(3-Hydroxypropanoyl)- 1,3,6,8-tetramethyl-1,2,4a,5,6,7,8,8a-octahydronaphthalene- 2-carboxylic acid
(International Union of Crystallography, 2024) Botha, C.J. (Christoffel Jacobus); Fouche, Gerda; Malan, F.P. (Frederick); frikkie.malan@up.ac.za
The molecular structure of C18H28O4, (+)-diplodiatoxin, is described, whereby the absolute configuration of the structure of diplodiatoxin has been confirmed by single-crystal X-ray diffraction. Diplodiatoxin crystallizes in the chiral P43212 space group with one molecule in the asymmetric unit.
Enhanced photocatalytic efficiency of a novel GO/Bi2SO5/AgBr ternary heterojunction for the degradation of tetracycline and rhodamine B
(Elsevier, 2025-06) Oluwole, Adewunmi Olufemi; Yusuf, Tunde Lewis; Tichapondwa, Shepherd Masimba; Daramola, Michael Olawale; Iwarere, Samuel Ayodele; samuel.iwarere@up.ac.za
Please read abstract in the article.
Enhanced piezo-induced photocatalytic activity of BaTiO3/Cd0.5Zn0.5S S-scheme heterojunction for water pollution remediation : performance, degradation pathway, and toxicity evaluation
(Elsevier, 2025-06) Mohlala, Tshepo T.; Yusuf, Tunde Lewis; Masukume, Mike; Ojijo, Vincent; Mabuba, Nonhlangabezo
Please read abstract in the article.
Mesoporous Mn-substituted MnxZn1-xCo2O4 ternary spinel microspheres with enhanced electrochemical performance for supercapacitor applications
(Nature Research, 2024-05-19) Dolla, Tarekegn Heliso; Lawal, Isiaka Ayobamidele; Kifle , Gizachew Wendimu; Jikamo , Samuel Chufamo; Matthews , Thabo; Maxakato , Nobanathi Wendy; Liu , Xinying; Mathe , Mkhulu; Billing, David Gordon; Ndungu, Patrick Gathura
Extensive investigations have been carried out on spinel mixed transition metal oxide-based materials for high-performance electrochemical energy storage applications. In this study, mesoporous Mn-substituted MnxZn1−xCo2O4 (ZMC) ternary oxide microspheres (x = 0, 0.3, 0.5, 0.7, and 1) were fabricated as electrode materials for supercapacitors through a facile coprecipitation method. Electron microscopy analysis revealed the formation of microspheres comprising interconnected aggregates of nanoparticles. Furthermore, the substitution of Mn into ZnCo2O4 significantly improved the surface area of the synthesized samples. The electrochemical test results demonstrate that the ZMC3 oxide microspheres with an optimal Mn substitution exhibited enhanced performance, displaying the largest specific capacitance of 589.9 F g−1 at 1 A g−1. Additionally, the ZMC3 electrode maintained a capacitance retention of 92.1% after 1000 cycles and exhibited a significant rate capability at a current density of 10 A g−1. This improved performance can be ascribed to the synergistic effects of multiple metals resulting from Mn substitution, along with an increase in the surface area, which tailors the redox behavior of ZnCo2O4 (ZC) and facilitates charge transfer. These findings indicate that the incorporation of Mn into mixed transition metal oxides holds promise as an effective strategy for designing high-performance electrodes for energy storage applications.
Electrocapacitive removal of Na and Cd ions from contaminated aqueous solution using Fe3O4-poly (3,4-ethylenedioxythiophene) poly(styrene sulfonate) modified chitosan nanosheets
(Nature Research, 2024-11-15) Saliu, Oluwaseyi D.; Leping, Omphemetse; Yusuf, Tunde Lewis; Adeniyi, Adewale G.; Ramontja, James
Chitosan nanosheets (NS) stabilized on poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) was functionalized using Fe3O4 to capacitively remove chloride ions and toxic cadmium ions at optimized pH, concentration, and number of charging cycles. The synthesis procedure was investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope – Energy Dispersive X-ray Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The analyses confirms increase in surface area of the nanocomposite from 41 to 132 m2/g and a decrease in crystallinity from 75.3 to 66.9% after nanosheet formation. The highest sorption exchange capacity (SEC) for this work, 93% CdCO3 removal is achieved at 100 CDI cycles while 82% NaCl removal was achieved at 80 cycles. The SEC% increased with pH during Na ion deionization and decreased with pH during Cd removal. The works shows that chitosan is able to impart advanced structural properties to Fe3O4 and PEDOT and is able to reduce reverse migration of ions from electrodes to bulk solution, leading to higher SEC performance.

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