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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BiOX(X=Cl, Br, I)-based S-scheme heterostructure photocatalysts for environmental remediation and energy conversion
Yusuf, Tunde Lewis; Orimolade, Benjamin O.; Masekela, Daniel; Adegoke, Kayode A.; Modibane, Kwena D.; Makgato, Seshibe S. (Elsevier, 2025-06)
Over the past decade, photocatalysis has gained recognition as a powerful tool for environmental remediation and sustainable energy production. Bismuth oxyhalides (BiOX, where X = Cl, Br, I) have attracted particular interest as efficient photocatalysts due to their excellent visible-light harvesting capabilities, straightforward-synthesis, and high photostability. S-scheme heterojunctions have been developed to further improve their performance, which enhances electron-hole separation and significantly increases photocatalytic efficiency. This review examines recent advancements in BiOX-based S-scheme heterostructures, focusing on their diverse applications in pollutant degradation, CO2 reduction, and H2 production. An evaluation of the effectiveness, benefits, and limitations of various synthesis methods has been carried out in this article in addition to various strategies to improve the photocatalytic activity of BiOX. This study also compares the suitability of the synthesized methods for removing emerging organic and inorganic pollutants, including dyes, pharmaceuticals, and other contaminants of environmental concern. The performances of various BiOX catalysts for H2 production and CO2 conversion to chemicals and fuels were discussed to point out the strengths, weaknesses, and the need for high-performance BiOX catalysts for energy conversion. Also, an analysis of the specific mechanisms driving the photocatalytic activity and strategies to address current challenges have been presented in the article. Finally, this review identifies key knowledge gaps and presents recommendations for scaling BiOX photocatalysts toward large-scale and industrial applications.
The detection of volatile organic compounds using a CNPs/polypyrrole-based solid-state sensor operating at room temperature
Malepe, Lesego; Ndinteh, Derek Tantoh; Ndungu, Patrick Gathura; Mamo, Messai Adenew (Elsevier, 2025-02)
In this work, we report the use of carbon nanoparticles (CNPs), commonly as carbon soot, as they are prepared from the pyrolysis of lighthouse candle, polypyrrole (PPy) and carbon nanoparticles@polypyrrole (CNPs@PPy) composite sensors to detect volatile organic compounds at room temperature. Five sensors were fabricated wherein the first sensor was made up of PPy only was named sensor 1, sensor 2 was made up of CNPs only; sensor 3 was made up of a 1:1 mass ratio of CNPs@PPy, sensor 4 was made up of a 2:1 mass ratio of CNPs@PPy, and sensor 5 was fabricated using a 3:1 mass ratio of CNPs@PPy respectively. The sensors were tested dynamically using acetone, 2-propanol, ethanol, and mesitylene vapours. Among all the tested sensors, sensor 5 showed improved sensitivity towards the analytes as compared to sensors; sensor 5 showed higher sensitivity towards acetone vapour than 2-propanol, ethanol, and mesitylene vapours because of a changed amount of CNPs within the composite. The response and recovery times of sensor 5 towards acetone vapour were 72 and 110 s, respectively and a limit of detection (LOD) of 1.212 ppm. Sensor 5 showed a slight increase in acetone vapour as humidity increased. The gas sensing mechanism on sensor 5 was studied using an in situ Fourier Transform infrared spectroscopy (FTIR) combined with an LCR meter; basically, the acetone vapour interacts with the solid-state gas sensor supplied with 0.5 V at 25 kHz. The setup confirmed that the acetone completely decomposes into carbon dioxide (CO2). It was also confirmed that the CO2 band intensity increases as the exposure time between the acetone vapour and the sensor increases.
Synthesis of iron-based metal–organic frameworks and carbon derivatives via unconventional synthetic methods and waste precursors with potential for gas storage
Mosupi, Keaoleboga; Mthembu, Nqobile Themba; Masukume, Mike; Musyoka, Nicholas M.; Langmi, Henrietta Wakuna (Royal Society of Chemistry, 2025-12)
Metal–organic frameworks (MOFs) have remarkable characteristics including high porosity as well as large internal surface areas. However, these materials have found very limited use industrially due to their high cost of production. The use of waste materials and industrial by-products to generate cheaper and environmentally friendly precursors could potentially open doors for industrial production of MOFs. Two types of Fe-based MOFs (Fe-MIL-53 and Fe-MIL-88B) were prepared using acid mine drainage (AMD) waters as a metal precursor source and waste polyethylene terephthalate-derived terephthalic acid (PET-BDC) as a linker via microwave-assisted and sonochemical-assisted synthesis procedures. Additionally, a carbonization strategy was utilized to enhance the porosity and surface area of these MOF materials. Upon carbonization, surface areas were drastically improved to above 600 m2 g−1 for both MIL-53 and MIL-88B prepared using the two unconventional methods. The obtained carbons also exhibited reasonable gas uptake capacities, with MIL-53 derived carbons having a higher hydrogen capacity of 1.32 wt% (at 77 K and 1 bar) and a carbon dioxide capacity of 2.09 mmol g−1 (at 298 K and 1 bar). The gas uptake capacities of MIL-88B derived carbons were found to be relatively low.
Total synthesis of isoflavonoids
Selepe, Mamoalosi A.; Mthembu, Siyanda T.; Sonopo, Molahlehi S. (Royal Society of Chemistry, 2025-03)
Isoflavonoids are phenolic compounds with wide structural diversity and a plethora of biological activities. Owing to their structural variation and potential health-promoting and other benefits, they have been targeted for synthesis. Herein, we review the synthesis of natural isoflavonoids belonging to different classes that include isoflavones, isoflavanones, isoflavans, isoflavenes, pterocarpans, rotenoids, coumaronochromones, and coumestans. The synthetic methodologies employed and advancements in synthetic strategies are highlighted.
Unlocking reactivity : synthetic, structural and catalytic exploration of ruthenium(ii) complexes featuring pdc and NHC ligands
Awe, Babatunde; Swart, Glendin; Erasmus, Elizabeth; Landman, Marile; Malan, F.P. (Frederick) (Royal Society of Chemistry, 2026-01)
Eleven new ruthenium complexes (C2–C12), each incorporating the pyridine-2,6-dicarboxylate (pdc) pincer ligand and a tailored N-heterocyclic carbene (NHC) ligand, were synthesised in moderate to high yields. The feasibility of NHC coordination to the Ru(II) centre was found to depend on both the order of ligand addition to the precursor complex (C1) and the stepwise substitution of the 1,5-cyclooctadiene ligand with N-donor ancillary ligands. Characterisation techniques such as NMR spectroscopy, single-crystal X-ray diffraction (SCXRD), and cyclic voltammetry (CV) provided valuable insights into the synergistic roles of the pdc and NHC ligands in determining the structural, electronic, and catalytic properties of the complexes. The complexes exhibited moderate catalytic activity in both the transfer hydrogenation of ketones and the oxidation of alcohols. Among them, complex C2 showed the highest activity for the transfer hydrogenation of benzophenone to benzhydrol, achieving 99% conversion within 1 hour (TON = 99; TOF = 99 h−1). For the oxidation of benzyl alcohol to benzaldehyde, complex C6 reached 99% conversion within 4 hours (TON = 16; TOF = 8 h−1). Complementary density functional theory (DFT) studies supported the experimental results, particularly those relating to the structural and electronic characteristics of the complexes.
Biomethane as a promising renewable carbon feedstock for the synthesis of zeolite templated carbons for hydrogen storage application
Mosupi, Keaoleboga; Dyosiba, Xoliswa Lindokuhle; Langmi, Henrietta Wakun; Musyoka, Nicholas M. (Springer, 2025-11-24)
Biogas, generated through the anaerobic digestion of organic matter, is an attractive renewable energy source due to its continuous production and utilisation cycle. Rising concerns about the environmental impact of fossil fuel-derived energy have sparked interest in developing sustainable energy alternatives. Consequently, considerable research efforts have been directed towards biogas valorisation, particularly its main component, methane (CH4). This is achieved by converting raw or upgraded biogas into high-value products, such as Zeolite-templated carbons (ZTCs), and concurrently producing cleaner hydrogen gas. ZTCs are highly ordered porous structures that exhibit high surface areas, uniform pore size distributions, and large pore volumes, rendering them attractive for various applications. These applications include gas storage, CO2 capture, supercapacitors and batteries. In this study, we focused on the utilisation of simulated biogas (CH4 and CO2 mixture) and pure CH4 (in this case, simulated ‘biomethane’) for the synthesis of zeolite-templated carbons (ZTCS). When CH4 was utilised on both the one-step and two-step processes, the obtained ZTCs had higher surface area and hydrogen (H2) adsorption. The highest surface area obtained was 2974 m2/g, while the best H2 storage capacity, at 1 bar, was 2.77 wt%. Structural (XRD) and morphological (SEM and TEM) characterisations were found to be indistinguishable from those of the samples obtained when fossil-derived ethylene was used as a carbon source. Unfortunately, ZTCs were not obtained when simulated biogas was used as a carbon source, due to the zeolite having a greater affinity towards CO2 than CH4, primarily because of the large quadrupole moment of CO2. This study has demonstrated that a sustainable source of carbonaceous feedstock, such as biogas-derived ‘biomethane’, can be converted into value-added products (ZTCs), thereby creating additional economic opportunities for industries within the biogas sector.
A comprehensive review on bismuth-based ternary heterojunctions in photocatalytic wastewater treatment
Orimolade, Benjamin O.; Peleyeju, Moses G.; Yusuf, Tunde Lewis (Elsevier, 2026-01)
Bismuth-based ternary heterostructured photocatalysts have emerged as one of the most promising classes of materials for wastewater treatment, owing to their narrow band gaps, high structural versatility, and capacity to facilitate efficient charge carrier separation under solar irradiation. Recent studies demonstrate that integrating Bi2WO6, BiVO4, BiOX, Bi2MoO6, Bi2O3, Bi2S3, or multi-bismuth phases into ternary configurations, particularly Z-scheme, S-scheme, and dual heterojunction architectures, substantially enhances photocatalytic performance by accelerating interfacial electron transport while preserving strong redox potentials. These systems consistently achieve high degradation efficiencies across dyes, pharmaceuticals, antibiotics, pesticides, and emerging contaminants, frequently outperforming binary and single-component counterparts. Key advances include the use of carbonaceous scaffolds to broaden visible-light absorption, magnetic and transition-metal components to strengthen redox cycling, and defect or vacancy engineering to intensify surface reaction kinetics. Comparative evaluation across recent reports reveals that the most efficient ternary systems often couple broad-spectrum light harvesting with strong built-in electric fields that drive directional charge migration. Despite these advances, persistent challenges remain regarding interfacial stability, secondary pollution risks, and scalability of synthesis routes. Overall, the rapidly evolving evidence indicates that bismuth-based ternary heterostructures represent a highly adaptable, high-performance platform for future solar-driven wastewater treatment, with clear opportunities for optimization through targeted band engineering, green synthesis strategies, and improved photonic utilization. HIGHLIGHTS • Advances in bismuth-based ternary photocatalysts for pollutant degradation. • Structural design strongly governs charge separation and photocatalytic activity. • Ternary S-scheme and Z-scheme systems show superior pollutant removal efficiency. • Morphology and interface engineering critically influence performance and stability. • Key challenges include scalability, leaching risks, and real-water applicability.
Coaxial electrospinning as a promising technique for fabricating advanced materials for energy storage applications
Alli, Yakubu Adekunle; Bamisaye, Abayomi; Ige, Akinsanmi S.; Elabor, Rabi; Ife-Adediran, Oluwatobi; Samson, Adanlawo Olayinka; Oni, Samuel Oluwadadepo; Yeboah, Alfred; Bankole, Owolabi Mutolib; Fapojuwo, Dele Peter; Ogunlaja, Adeniyi Sunday (Springer, 2026-01-12)
As the demand for efficient, high-performance energy storage systems intensifies, the need for innovative materials that can enhance energy density, power output, and cycle stability has become paramount. Coaxial electrospinning, a versatile nanofabrication technique, has emerged as a powerful method for producing advanced core-shell nanofibers with tailored properties specifically designed for energy storage applications. This review delves into the principles of coaxial electrospinning, highlighting its advantages over conventional fabrication techniques in creating multifunctional materials for batteries and supercapacitors. By manipulating the core and shell compositions, coaxial nanofibers offer superior ion/electron transport, mechanical stability, and electrochemical performance. The review discusses the latest breakthroughs in the field, including material selection, fiber design strategies, and the resulting improvements in energy storage capacity and durability. Challenges and future opportunities for scaling coaxial electrospinning to meet commercial demands are also explored, positioning this technique as a promising frontier for next-generation energy storage solutions.
Natural acids as catalysts for the continuous flow production of the green solvent 2,2,5,5-tetramethyltetrahydrofuran
Currie, Bernice Mercia; Van Vuuren, Estefan; Jugmohan, Jaimee; Panayides, Jenny Lee; Riley, Darren Lyall (Elsevier, 2026-06)
As the demand for chemists to adhere to green chemistry principles increases, so does the demand for green solvents. Unfortunately, many green solvents, such as 2,2,5,5-tetramethyltetrahydrofuran (TMTHF), are costly and difficult to source. Traditional synthesis of TMTHF from 2,5-dimethyl-2,5-hexanediol has been reported to be catalysed by acids such as phosphoric and sulfuric acid, or, more recently, by H-beta zeolite. Although H-beta zeolite catalysts are high-yielding and selective, the energy required for their regeneration is high, and their production has questionable environmental impacts. A new approach was developed using flow technologies and naturally occurring acids as catalysts for TMTHF synthesis. Flow technologies are scalable, safe, efficient, and reproducible for daily chemical reactions, aligning with principles of green chemistry. This study observed several key improvements, including i) the use of a natural acid as a catalyst, ii) the use of water as a solvent, and iii) a continuous process for multigram-scale synthesis of TMTHF using citric acid monohydrate, with a yield of 72 %, resulting in a throughput of 8.24 g h−1 (9.43 kg L −1 h−1 space-time yield).
Effect of the size of halide ligands on the crystal structures of halide-bibridged polymers of HgX2 with 4-ethylpyridine
Beebeejaun-Boodoo, B.M. Parveen (Wiley, 2025-12)
Halide-bridged polymers are a type of coordination polymer whereby halide ligands act as bridging ligands between the metal centres. The crystal structures of three halide-bibridged polymers of the formula [Hg(μ-X)2(4-Etpy)]n, namely, catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-halido], obtained through the combination of the organic ligand 4-ethylpyridine (4-Etpy, C7H9N) and HgX2 (X = Cl, Br or I), were determined. In these structures, abbreviated as 4epHgCl, 4epHgBr and 4epHgI, respectively, the HgII ion exhibits a coordination number of five. All three structures were found to display a similar one-dimensional scalloped polymeric chain with halide ligands bridging pairs of HgII ions in a bidentate fashion; however, 4epHgI differs from the other two structures in terms of the packing arrangement of the polymer. The change of the halide ligand to the larger iodide ligand disrupts the formation of the regular halide-bibridged polymeric chain observed in the chloride and bromide analogues, with 4epHgI displaying pseudo-bridging in the polymer chain.
Understanding cholesterol-mycolic acid-phosphatidylcholine interactions : advancing electrochemical detection of tuberculosis
Mathebula, Nsovo Samuel; Ozoemena, Okoroike C.; Mwonga, Patrick V.; Haruna, Aderemi B.; Ozoemena, Kenneth I. (American Chemical Society, 2025-10-22)
Immunodetection of active tuberculosis (TB), including in human immnodeficiency virus (HIV)-positive patients, is crucial for effective treatment and disease elimination. Mycolic acid (MA) is a key antigen for detecting TB antibodies, although antimycolic acid antibodies (AMAAs) have not yet been isolated. However, AMAA levels are elevated in TB-infected patients and can interact with mycolic acid antigen (MAA). A significant challenge in TB detection arises from the cross-reactivity of cholesterol (Ch) and anticholesterol antibodies (AChAs) due to the cholesteroid nature of MAA. For the first time, the cholesteroidal nature of MAA has been established through electrochemical experiments and supported by theoretical density functional theory (DFT) calculations. An electrochemical TB immunosensor was developed by using a glassy carbon electrode modified with MAA-confined activated carbon (GCE–AC–MAA). Electrochemical analysis of TB-positive serum revealed activity similar to that of AChA in the presence of phosphatidylcholine (PC)/MAA, demonstrating cross-reactivity. The optimal detection protocol involved preincubating TB serum in liposomes to free AMAA, followed by electrochemical immunosensor detection. DFT calculations showed that cholesterol interacts with MAA (p-band center, εp = −11.3922 eV) but more strongly in the presence of PC/MAA (εp = −11.2695 eV). As the p-band center approaches the Fermi level, the bond length between cholesterol and the adsorbent shortens, increasing the interaction strength. The results indicate that the shorter the bond length between the adsorbate (Ch) and the adsorbent (PC, MA, or PC/MA), the stronger the p-band center (i.e., strong binding to the atomic nucleus). These findings provide valuable insights for improving TB immunodetection strategies.
A novel Co3Se4-CNFs hybrid system as a versatile enhancer for Pd NPs toward ethylene glycol electrooxidation
Matthews, Thabo; Dolla, Tarekegn Heliso; Mohamed, Rhiyaad; Yusuf, Tunde Lewis; Chabalala, Paulina; Agwamba, Ernest C.; Doyle, Bryan Patrick; Carleschi, Emanuela; Malepe, Lesego; Maxakato, Nobanathi Wendy (Wiley, 2025-11)
The commercialization of fuel cells requires electrocatalysts with improved electrocatalytic activity, stability, durability, and reduced cost. Pd nanoparticles supported on cobalt selenide-carbon nanofibers (Pd/Co3Se4-CNFs) are synthesized using a modified polyol-microwave sodium borohydride reduction method for the electrocatalytic oxidation of ethylene glycol. The electrochemical evaluation employs cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) for stability, while electrochemical impedance spectroscopy (EIS) assesses the electrocatalyst conductivity. Pd NPs on Co3Se4-CNFs are analyzed through X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), with morphology studied using transmission electron microscopy (TEM). The Pd/Co3Se4-CNFs exhibited excellent electrocatalytic properties in an alkaline medium due to strong metal-support interactions (SMSI), synergy, electronic interactions, and good dispersion. The electrochemically active surface area (ECSA) of Pd/Co3Se4-CNFs is 98.1 m2 g−1, mass activity of 2716.7 mA mgPd−1, which is 14.2 times more than Pd/Ccommercial electrocatalyst, which produced 191.2 mA mgPd−1. Also, Pd/Co3Se4-CNFs has high stability for 2.78 h and excellent durability after 500 cycles, retaining 65.7% current density. These findings reveal the Co3Se4-CNFs hybrid as a novel support that enhances the electronic interaction with Pd nanoparticles, significantly improves catalyst durability, and imparts strong resistance to poisoning during ethylene glycol electrooxidation, offering a robust platform for advanced alcohol fuel cell catalysis.
Immobilized tetrakis(triphenylphosphine)palladium(0) for Suzuki-Miyaura coupling reactions under flow conditions
Ramaotsoa, Gakanego Valerie; Strydom, Ian; Panayides, Jenny-Lee; Riley, Darren Lyall (Royal Society of Chemistry, 2025-06)
An immobilized triphenylphosphine scaffold was prepared by precipitation polymerization and functionalized to afford a cost-effective source of solid-supported tetrakis(triphenylphosphine)palladium(0). The catalyst was characterised and used to perform biphasic Suzuki–Miyaura cross-coupling reactions using a packed-bed reactor under flow conditions. The approach afforded comparable yields to those obtained under batch conditions with a single pass through the packed-bed reactor (1 h vs. 18 h). The use of a recycling system was investigated on a model reaction and found to afford close to quantitative conversion within 3 hours.
Efficient removal of selected neonicotinoids from single and combined systems using CuO/rGO modified musa parasidiaca biochar : insight into cost analysis
Bayode, Ajibola A.; Emmanuel, Stephen Sunday; Badamasi, Hamza; Sanni, Saheed O.; Ore, Odunayo T.; Dada, Adewumi Oluwasogo; Ilo, Obianuju Patience; Adesibikan, Ademidun Adeola (Royal Society of Chemistry, 2025)
The widespread use of neonicotinoid pesticides, particularly imidacloprid (IMI) and acetamiprid (ACE), has raised environmental concerns due to their persistence and toxicity in aquatic systems. This study investigates the efficacy of copper oxide-modified Musa Parasidiaca peel biochar-supported reduced graphene oxide (Cu/MPBC/rGO) as a novel adsorbent for removing IMI and ACE from aqueous solutions. The synthesized composite was characterized using scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) etc, to elucidate its morphology, surface chemistry, crystallinity, and porosity. Adsorption experiments were conducted to examine the influence of pH, contact time, adsorbent dose and adsorbate concentration. The adsorption kinetics followed the mixed order kinetic model, and the equilibrium data were best described by the Langmuir isotherm, indicating monolayer adsorption. Cu/MPBC/rGO exhibited high adsorption capacities of 62.19 mg g−1 for IMI and 32.78 mg g−1 for ACE. Reusability studies confirmed the material's stability and efficiency over multiple cycles. These findings proved the potential of Cu/MPBC/rGO as an efficient and sustainable adsorbent for the removal of neonicotinoid pesticides from contaminated water.
Surface engineered NiFe2O4/SnO2/CeO2 ternary heterojunction for dual applications in photocatalytic water treatment and supercapacitors
Oluwole, Adewunmi Olufemi; Sarr, Samba; Yusuf, Tunde Lewis; Tichapondwa, Shepherd Masimba; Daramola, Michael Olawale; Iwarere, Samuel Ayodele (Royal Society of Chemistry, 2025-11)
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Synthesis, characterization, biological evaluation, DFT calculations, and molecular docking study of transition metal complexes derived from a Schiff base ligand
Waziri, Ibrahim; Wahab, Olaide O.; Mala, Grema A.; Ismaila, Musa B.; Umaru, Usman; Abd El-Maksoud, Mostafa S.; Wakil, Ibrahim M.; Yusuf, Tunde Lewis (Wiley, 2025-11)
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Post-synthesis physical and hydrothermal mixing of MnO2, SnO2, and rGO influence on ultracapacitor electrode performance
Anito, Solomon E.; Saliu, Oluwaseyi D.; Mamo, Messai; Ramontja, James; Mombeshora, Edwin Tonderai; Ndungu, Patrick Gathura (Wiley, 2025-11)
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Construction of hierarchical S-scheme MgIn2S4/CeO2 heterojunction for boosted photocatalytic oxidation of tetracycline and reduction of Cr(VI)
Akintayo, Damilola Caleb; Yusuf, Tunde Lewis; Mabuba, Nonhlangabezo (Elsevier, 2025-09)
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Labdane diterpenoids from Leonotis ocymifolia with selective cytotoxic activity against HCC70 breast cancer cell line
Ncongwane, Jane Busisiwe; Tembu, Vuyelwa Jacqueline; Nkambule, Comfort Mduduzi; Kemboi, Douglas; Fouche, Gerda; Vukea, Nyeleti; De la Mare, Jo-Anne (MDPI, 2025-05-01)
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Sustainable Pb(II) remediation : efficacy and selectivity of Moringa Oleifera composite nanofibers
Ngulube, Ronald; Nombona, Nolwazi; Pillay, Letitia (Springer, 2025-10)
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