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Welcome to the NWU Repository, the open access Institutional Repository of the North-West University (NWU-IR). This is a digital archive that collects, preserves and distributes research material created by members of NWU. The aim of the NWU-IR is to increase the visibility, availability and impact of the research output of the North-West University through Open Access, search engine indexing and harvesting by several initiatives.

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Recent Submissions

Interfacial electron redistribution in 2D/3D MoS2/CuBi2O4 p-n heterojunction for visible light assisted reduction of Cr(VI) and oxidation of antibiotics.
(Elsevier Ltd., 2024) Olatunde, Olalekan C; Yusuf, Tunde L.; Mabuba, Nonhlangabezo; Onwudiwe, Damian C; Makgato, Seshibe
We report the successful design of a heterojunction comprising p-type CuBi2O4 (CBO) and n-type MoS2 semiconductors. This was achieved through a hydrothermal and calcination method, resulting in the uniform deposition of three-dimensional CBO nano-cubes onto the surface of two-dimensional MoS2 nanosheets. Under visible light, the best MoS2/CBO composite exhibited the maximum catalytic efficacy for both the reduction of Cr (VI) and the oxidation of tetracycline hydrochloride (TC) at a molar ratio of 10:1. For tetracycline degradation the heterostructure achieved 83 % efficiency and a rate constant of 0.00412 min−1 after 180 min, while complete reduction of Cr(VI) was achieved, with a rate constant of 0.11 min−1 after 40 min. The efficiency of MoS2/CBO was averagely 1.4 times higher than that of the pristine materials for TCE degradation, while the activity was almost 1.8 times of the pristine materials for Cr(VI) reduction. The remarkable catalytic activity can be ascribed to the combined effects of electron redistribution and charge transfer between 2D MoS2 and 3D CuBi2O4 leading to the formation of a heterostructure and thereby facilitating strong interfacial interactions among the components causing effective absorption of visible light and improved separation of photogenerated electron-hole pairs. It is important to note that MoS2/CBO demonstrated excellent stability and reusability after 6 cycles. The primary reactive species responsible for TC degradation were identified as photo-generated h+, and radical dotO2−. Additionally, e− was found to be mainly liable for Cr (VI) photoreduction. Furthermore, we propose a plausible photocatalytic reaction pathway for the elimination of both TC and Cr(VI). This research provides valuable inroads into the development of heterojunction photocatalysts for efficient water de-toxification.
X-ray diffraction profile analysis of green synthesized ZnO and TiO2 nanoparticles.
(IOP Publishing Ltd., 2024) Mathumba, Penny; Bilibana, Mawethu P; Olatunde, Olalekan C; Onwudiwe, Damian C
ZnO and TiO 2 nanoparticles were prepared through a plant-extract mediated hydrothermal synthesis. X-ray diffraction (XRD) study confirmed the crystalline nature and the phase characteristic of the obtained nanoparticles. X-ray diffraction profile analysis models such as Williamson–Hall analysis, size-strain plot and Rietveld analysis were further used in evaluating the microstructural parameters of the obtained materials. The calculated particle size for all the models was in great agreement, with values in the range of 55.46–87.6 nm recorded for ZnO, while for TiO 2, the crystallite size was in the range of 33.82–41.9 nm. The calculated crystal microstrain varied based on the model, while the stress in the ZnO and TiO 2 nanoparticles was evaluated at 3.8 and 13.7 MPa, respectively. Furthermore, TiO 2 nanoparticles had a higher energy density of 8.96× 10–8 KJ m− 3 compared to 7.12× 10–8 KJ m− 3 obtained for ZnO.
Antibacterial and antifungal activities of Platycladus orientalis leaf extract‑mediated Fe2O3 and Ce‑doped Fe2O3 nanoparticles.
(Springer Nature, 2024) Ogwuegbu, Mercy C; Olatunde, Olalekan C; Pfukwa, Trust M; Mthiyane, Doctor M. N; Fawole, Olaniyi A; Onwudiwe, Damian C
Green synthesis of nanomaterials harnesses naturally occurring materials, including plant extracts, to offer environmentally friendly alternatives to conventional biomedicine, agriculture, and other field applications. This study explores the green route to Fe2O3 and cerium-doped Fe2O3 (Ce-doped Fe2O3) nanoparticles synthesized for the first time using the leaf extract of Platycladus orientalis. The synthesized nanoparticles were characterized for their structural, morphological, chemical, and optical properties. The hematite phase of Fe2O3 nanoparticles with spherical morphology was obtained. The introduction of Ce as a dopant into Fe2O3 increased the lattice strain of Ce-doped Fe2O3 nanoparticles (0.51%) compared to pristine Fe2O3 (0.46%) even though the size of both nanomaterials was similar. Compared to pristine Fe2O3 nanoparticles, Ce-doped Fe2O3 nanoparticles also demonstrated enhanced antimicrobial and antifungal activities against Escherichia coli, Enterococcus faecalis, Listeria monocytogenes, Penicillium chrysogenum, Aspergillus niger, and Mucor mucedo. The green-synthesized Ce-doped Fe2O3 nanoparticles possess potential for application in biomedical and environmental fields based on their relevance to human health and food safety, diversity in microbial characteristics, and potential for resistance to conventional treatments.
Stephen R. MilfoBearing the weight: A qualitative study on expert views on integrating ethics in autonomous vehicles rd
(IGI Global Publishing, 2024) Stephen R. Milford et al
AVs are increasingly becoming present on public roads, the ethics of which have captured the publics attention. This study represents the first ever investigation into the opinion of AV development experts on the ethics of programming AVs in collision scenarios. The study makes use of a qualitative research model. A sample of 24 Swiss experts were interviewed using semi-structured interviews. The majority of experts were directly involved in the development of AVs and represented both research, private, and public sectors as well as national regulatory bodies. Three core themes emerged from the data. 1) Experts were keenly aware of the ethical challenges involved in AVs on public roads, including in collision situations. 2) Experts felt a moral responsibility for how AVs are programmed and developed. However, experts’ moral framework was not well developed with many experts stating that their own personal moral framework should not be used to program motion planning. 3) Experts saw a need for an ethical framework to guide the development of AVs. The paper concludes that it is clear experts are keenly aware of the ethics involved in AVs on public roads, and in particular collision scenarios. They feel a sense of responsibility for how AVs are programmed but do not feel ethically well-equipped themselves. Experts would, therefore, appreciate an ethical framework that would assist the development of these algorithms. This framework may be driven by either industry or government but should be clear and simple. We recommend countries like Switzerland develop such a framework.
Green-synthesis of CuO and Ce-doped CuO nanoparticles using aqueous extract of yam peel and their antimicrobial properties.
(Elsevier, 2024) Ogwuegbu, Mercy C.; Olatunde, Olalekan C.; Pfukwa, Trust M.; Mthiyane, Doctor M.N.; Fawole, Olaniyi A.; Onwudiwe, Damian C
The rise of drug-resistant microbes presents a critical global health challenge in the 21st century, necessitating the development of potent antimicrobial agents with broad-spectrum activity. Therefore, in this study, we explored the antimicrobial activity of copper oxide (CuO) and cerium-doped CuO (Ce-doped CuO) obtained through a facile green synthesis approach. The nanoparticles were synthesized using aqueous extract of Dioscorea spp (yam peel) and characterized for their physicochemical properties using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), electron microscopy, and UV–Vis spectroscopy. Their antimicrobial efficacy was tested against three bacterial strains—Enterococcus faecalis, Escherichia coli, and Listeria monocytogenes—and three fungal strains—Aspergillus niger, Mucor mucedo, and Penicillium chrysogenum. The results demonstrated that cerium doping significantly altered the physicochemical properties of CuO, leading to enhanced antimicrobial activity. The antibacterial zone of inhibition ranged from 7.50 to 16.55 mm for CuO and 11.80–19.50 mm for Ce-doped CuO. For antifungal activity, the minimum inhibitory concentration (MIC) ranged from 0.25 to 0.30 mg/mL for CuO and 0.025–0.03 mg/mL for Ce-doped CuO. Notably, the Ce-doped CuO nanoparticles exhibited antimicrobial effects comparable to standard antibiotics. These findings highlight the potential of green-synthesized Ce-doped CuO nanoparticles as effective antimicrobial agents. By leveraging green synthesis and elemental doping, this study offers a promising solution to combat a wide spectrum of infectious pathogens.