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

Browse

Now showing 1 - 20 of 631

A conceptual framework for costing perovskite solar cells through material flow cost accounting
(MDPI, 2025-04) Van der Poll, Hendrik Johannes; Van der Poll, Huibrecht Margaretha; Van der Poll, John Andrew; hendrik.vanderpoll@up.ac.za
There is a global demand for alternative energy sources away from unsustainable fossil fuels. The Conference of Parties (COP) 26 agreed that fossil fuels should be phased down; at COP27, anxiety about the cost and availability of energy was raised, and COP28 reiterated the phasedown of coal power. Solar technology in the form of perovskite solar cells is one such alternative energy source. This article considers the fabrication of the perovskite layer in a solar cell and postulates the extent to which material flow cost accounting (MFCA) could be used as a feasible costing method, among other things, to address material flows and waste reduction. Through MFCA, the monetary and physical flows of materials are identified and can be applied throughout the supply chain to facilitate affordability, from the extraction of the ore to the transportation and fabrication of the chemicals, manufacturing and distribution of the solar cell and panels, and, finally, the recycling of the panel. Informed by these observations, a conceptual framework for applying MFCA in fabricating the perovskite layer in the supply chain is developed based on sets of qualitative propositions. Future work will involve researching the processes involved in manufacturing solar cells, costing raw materials, energy flows, and solar cell manufacturing emissions.
A comparative study of sol-gel synthesized ZnO/GO and ZnO/g-C3N4 nanocomposites in the photocatalytic degradation of acetaminophen
(Wiley, 2025-02) Chebwogen, Judith; Nyongesa, Francis W.; Mwabora, Julius M.; Ntshani, Gershom M.; Ndungu, Patrick Gathura; patrick.ndungu@up.ac.za
Please read abstract in the article.
Justicidin B and related lignans from two South African Monsonia species with potent activity against HeLa cervical cancer cells
(Elsevier, 2024-04) Tajuddeen, Nasir; Muyisa, Séverin; Maneenet, Juthamart; Nguyen, Hung Hong; Naidoo-Maharaj, Dashnie; Maharaj, Vinesh J.; Awale, Suresh; Bringmann, Gerhard
Please read abstract in the article.
Recent advances in Fe-based metal-organic frameworks : structural features, synthetic strategies and applications
(Elsevier, 2025-04) Mosupi, Keaoleboga; Masukume, Mike; Weng, Guoming; Musyoka, Nicholas M.; Langmi, Henrietta Wakuna; henrietta.Langmi@up.ac.za
Metal organic frameworks (MOFs) are very exciting porous materials owing to their unique properties such as high surface areas, high pore volume, tunable functionalities and great thermal stabilities. The properties of MOFs can be diversely constructed by precise control of synthesis conditions. Amongst the thousands of MOFs that have been discovered to date, Fe-MOFs make up a percentage of these MOFs. Fe-MOFs are increasingly gaining great interest due to their unique properties and chemical versatility. However, comprehensive reviews on their emerging architectural features and designs as well as strategies for tailoring their applications. Therefore, in this review, we present a panoptic summary of the recent developments of Fe-MOFs, which includes synthetic strategies, activation methods, functionalization, overview of selected applications, current challenges impeding their commercialization, and suggested remedial actions. A holistic view of the interconnectedness of Fe-MOFs structural features, synthetic strategies and applications provides greater insights that highlight challenges hindering their wide-scale industrial applications. Moreover, newer approaches such as utilization of machine learning technique that are providing an opportunity for out-of-sight insights for material design and prediction of material properties are briefly highlighted. Remedial actions for challenges of transitioning Fe-based MOFs towards commercialization and industrial applications are also explored, and suggestions for these aspects are presented.
Interfacial engineering of MoS2 and bimetallic MOF hybrid for superior piezo-photocatalytic hydrogen production and wastewater treatment
(Elsevier, 2025-03) Masekela, Daniel; Yusuf, Tunde Lewis; Balogun, Sheriff A.; Makhado, Edwin; Adeniran, Omolara I.; Modibane, Kwena D.
Please read abstract in the article.
Derivatives of pyrazole-based compounds as prospective cancer agents
(American Chemical Society, 2025-03) Ramoba, Lesetja V.; Nzondomyo, Wakopo J.; Serala, Karabo; Macharia, Lucy W.; Biswas, Supratim; Prince, Sharon; Malan, F.P. (Frederick); Alexander, Orbett T.; Manicum, Amanda-Lee E.
Please read abstract in the article.
Development of systems thinking in a large first-year Chemistry course using a group activity on detergents
(American Chemical Society, 2025-03) Reynders, Micke; Pilcher, Lynne A.; Potgieter, Marietjie; lynne.pilcher@up.ac.za
Systems Thinking is needed to address global sustainability challenges, yet opportunities to develop this skill set are not routinely included in chemistry curricula. Recurriculation is often a lengthy process, with many barriers slowing efforts to introduce Systems Thinking into chemistry education. Little is known concerning what systems thinking skills can be developed in a stand-alone intervention in a large-scale first-year chemistry course or if such an exercise would be valuable. We investigated student artifacts produced during a group activity on the chemistry and impacts of a surfactant commonly used in laundry detergent for evidence of engagement with Systems Thinking skills and a sustainable-action perspective. An adaptation of a virtual activity described elsewhere was introduced in a second-semester, first-year general chemistry course, coinciding with the introduction to organic chemistry. We used the characteristics of Systems Thinking from the ChEMIST table to explore students’ Systems-Oriented Concept Maps (SOCMEs) and reflections. Students displayed analytical, bridging, and holistic systems thinking skills, especially identifying the parts of a system and viewing it as a whole, organizing the relationships among these parts, identifying relevant system boundaries, and considering the role of humans. However, there was little evidence of engagement with the dynamic nature of systems. Students valued learning the molecular-level chemistry of surfactants, as the context-based approach highlighted the relevance of chemistry in their lives. They endorsed the role of chemistry in sustainability and were motivated to make a difference. The activity conformed to Talanquer’s chemical systems thinking framework and met the primary goal of introducing Systems Thinking in Chemistry Education, to orient Chemistry for sustainability.
Self-regulated learning strategies for success in an online first-year chemistry course
(Royal Society of Chemistry, 2025-01) Rakhunwana, Langanani; Kritzinger, Angelique; Pilcher, Lynne A.; lynne.pilcher@up.ac.za
During their first year of study at university, many students encounter challenges in developing learning strategies that align with success in the courses in which they are enrolled. The emergence of the COVID-19 pandemic heightened the challenges as universities were compelled to transition to online learning. Therefore, this study investigated the self-reported use of learning strategies in a first-year chemistry course delivered online due to the COVID-19 pandemic to identify learning strategies associated with success. Grounded in self-regulated learning (SRL) theory, a case study approach with an explanatory mixed methods design was adopted. Quantitative data were collected using a hybrid of the Motivated Strategies for Learning Questionnaire and the Online Self-regulated Learning Questionnaire. Follow-up open-ended questions were emailed to the students for the qualitative part of the study. Statistical analysis of the quantitative data was performed using SPSS and RUMM2030, while thematic analysis was applied to the qualitative data. Students reported more frequent use of SRL strategies of environment structuring, effort regulation, and elaboration. Conversely, critical thinking, task strategies, help-seeking, and peer learning were reportedly used less often. SRL strategies linked with success in the course were identified as effort regulation, goal setting, and time management. The findings from the qualitative data revealed an impact of online learning due to the pandemic on the use of peer learning and help-seeking strategies. The paper discusses the implications of these findings for educational practices, particularly in the context of hybrid learning in the post-pandemic era.
Piper betle extract inhibits ferroptosis by scavenging oxyradicals, hydroperoxides and inducing NRF2 regulated antioxidants
(Elsevier, 2025-04) Ranganathan, Veena; Deepashree, Vidyaranyapura S.; Gowda, Jadeppa; Dey, Sumit K.; Manjunath, Souparnika H.; Anantharaju, Preethi G.; Bidye, Durgesh Paresh; Pujar, Gurubasavaraj V.; Maharaj, Vinesh J.; Thimmulappa, Rajesh K.
Ferroptosis, an iron catalysed programmed cell death initiated by membrane lipid peroxidation (LPO), is implicated in various degenerative diseases. We screened medicinal/food plants and discovered leaf extract of Piper betle (PB), a popular mouth freshener, as a ferroptosis inhibitor. Compared to vehicle, PB suppressed LPO and inhibited ferroptosis triggered by rotenone or RSL3. Mechanistic studies revealed that PB extract is a powerful lipophilic radical trapping antioxidant and an inducer of Nuclear factor-erythroid 2-Related Factor 2 (NRF2) regulated antioxidant defenses (glutathione/glutathione peroxidase-4 axis). Utilizing diverse free radical systems (hydroxyl, peroxyl, hydroperoxides) and LPO models (serum, LDL), we found that PB extract effectively inhibits LPO by scavenging lipid oxyradicals. LC-HRMS analysis identified hydroxychavicol and polyphenols as the key bioactive constituents in PB extract. In a Drosophila model of rotenone-induced neurotoxicity, PB extract supplementation prevented locomotor deficits and mortality compared to the control diet. In conclusion, PB extract could be developed as a nutraceutical for mitigating ferroptosis-linked disorders.
All-body concept and quantified limits of cooperativity and related effects in homodromic cyclic water clusters from a molecular-wide and electron density-based approach
(Wiley, 2024-12) Cukrowski, Ignacy; Zaaiman, Stefan; Hussain, Shahnawaz; De Lange, Jurgens Hendrik; ignacy.cukrowski@up.ac.za
We strongly advocate distinguishing cooperativity from cooperativity-induced effects. From the MOWeD-based approach, the origin of all-body cooperativity is synonymous with physics- and quantum-based processes of electron (e) delocalization throughout water clusters. To this effect, over 10 atom-pairs contribute to the total e-density at a BCP(H,O) between water molecules in a tetramer. Intermolecular all-body e-delocalization, that is, cooperativity, is an energy-minimizing process that fully explains non-additive increase in stability of a water molecule in clusters with an increase in their size. A non-linear change in cooperativity and cooperativity-induced effects, such as (i) structural (e.g., a change in d(O,O)) or topological intra- and intermolecular properties in water clusters (e.g., electron density or potential energy density at bond critical points) is theoretically reproduced by the proposed expression. It predicted the limiting value of delocalized electrons by a H2O molecule in homodromic cyclic clusters to be 1.58e. O-atoms provide the vast majority of electrons that “travel throughout a cluster predominantly on a privileged exchange quantum density highway” ( O–H O–H O–H ) using Bader's classical bond paths as density bridges linking water molecules. There are, however, additional electron exchange channels that are not seen on molecular graphs as bond paths. A 3D visual representation of the “privileged” and “additional” exchange channels as well as detailed intra- and inter-molecular patterns of e-sharing and (de)localizing is presented. The energy stabilizing contribution made by three O-atoms of neighboring water molecules was found to be large ( 597 kcal/mol in cyclic hexamer) and 5 times more significant than that of a classical O–H O intermolecular H-bond.
Investigating the effects of a context-based laboratory exercise for meaningful learning
(American Chemical Society, 2024-08) Mundy, Christine Elizabeth; Nokeri, Boitumelo K.
We used the context of boot-legging of alcohol to support the concept of matter and separation in the laboratory components of a first-year general chemistry course. The bootlegging laboratory exercise was deployed over two years, Year 1 being online and Year 2 being in a traditional laboratory. Findings over both years indicated that students did significantly better in the context-based lab exercise compared to most traditional laboratory exercises. The use of the Meaningful Learning in the Laboratory Inventory (MLLI) revealed that students came in with high expectations and that cognitive and affective laboratory expectations were met or fell just short in both years. Blended questionnaire items, including both the cognitive and affective in one, showed that the students’ expectations were met in Year 1. In Year 2, most students had good cognitive/affective experiences compared to a wide range of incoming expectations. The majority of students enjoyed the laboratory exercise; reasons for this changed from cognitive in Year 1 to affective in Year 2, coinciding with the change to face to face laboratories, where students could enjoy the excitement of performing the experiments for themselves. The applicability of the context-based experiment resonated with many of the students and prompted a small portion of students to think metacognitively about their laboratory experience and the consequences of chemistry in health, society, and industry. Overall, the introduction of a context-based laboratory exercise provided a more meaningful laboratory experience for students, that is, a deeper learning experience relevant to their everyday lives.
Tin(II)-chloride (SnCl2) mediated reduction of α,(3-alkynyl carbonyl compounds
(Elsevier, 2025-02) Ralepelle, U.; Agbo, E.N.; Lekgau, K.; Chauke, H.; Cukrowski, Ignacy; Nxumalo, Winston
Please read abstract in the article.
Improving the electrocatalytic activity of Pd nanoparticles through electronic coupling interaction with a Ni2P-MoS2 hybrid support for ethanol electro-oxidation in an alkaline medium
(Royal Society of Chemistry, 2025-03) Matthews, Thabo; Chabalala, Makhaokane Paulina; Mbokazi, Siyabonga Patrick; Zikhali, Memory; Dolla, Tarekegn Heliso; Sarakovskis, Anatolijs; Vaivars, Guntars; Yusuf, Tunde Lewis; Mohamed, Rhiyaad; Maxakato, Nobanathi Wendy
Please read abstract in the article.
Processes regulating local community assembly of plants and spiders in high latitude mountains
(Wiley, 2024-11) Masviken, Johannes; Dalen, Love; Noren, Karin; Dalerum, Fredrik
AIM : Mountains are often used to study how environmental factors influence biodiversity. However, we have limited understanding of the processes causing biodiversity variation in mountains and whether such processes vary across trophic levels and spatial scales. The aim of this study was to evaluate (i) whether community assembly processes varied along elevational gradients, (ii) whether there were differences in such variation between primary producers (vascular plants) and secondary consumers (spiders) and (iii) whether there were scale dependencies in any elevational variation in community assembly. LOCATION : Fennoscandia, Northern Sweden. TAXON : Vascular plants, spiders. METHODS : We used phenotypic and phylogenetic dispersion to quantify how elevation influenced community assembly of vascular plants and spiders and whether there were any scale dependencies in such influences. Our original data of plant and spider communities came from our own field surveys, phenotypic dispersion was calculated based on matrices of ecological traits, and phylogenetic dispersion was calculated from phylogenetic trees for each organism group. Trait matrices were based on a combination of literature values and our own measurements. The phylogeny for vascular plants was based on a published plant super-tree, whereas the phylogeny for spiders was created by ourselves based on the DNA sequences at the mitochondrial cytochrome c oxidase subunit 1 (COI). RESULTS : Plants were environmentally filtered throughout all elevations and scales, but the importance of convergent evolution increased with elevation. For spiders, the importance of environmental filtering as well as niche conservatism increased with elevation. For both groups, communities at smaller scales were more influenced by biotic regulation and niche conservatism than at larger scales. MAIN CONCLUSIONS : Our study highlights both taxonomic differences and scale dependencies in how elevation influences community assembly. We argue that these results can have broad ramifications for our understanding of how spatial variation in biodiversity is generated and maintained. This may have particular relevance for our ability to predict the ecological consequences of climate change. Our results further highlight that high elevation specialists may suffer increased risks of climate driven extinctions due to a combination of increased competition and increased fragmentation of suitable habitats. Particularly for spiders, which had high elevation specialists clustered along specific lineages, such extinctions could lead to significant loss of phylogenetic variation.
Cyclic voltammetry study and solar light assisted photocatalytic activity of the CeFeO3/CeO2/Fe2O3 composite
(Wiley, 2024-11) Kanimozhi, M.; Harikrishnan, R.; Mani, M.; Kumaresan, S.; Rajasekar, A.; Devi, N. Saradha; Radhakrishnan, Shankara Gayathri; Sibali, L.; Kaviyarasu, K.
Please read abstract in article.
Evaluation of antioxidant & antidiabetic activities of iridoid glycoside isolated from Stachytarpheta cayennensis (Rich) Vahl leaf extract : in vitro combined with molecular docking approach
(Elsevier, 2025-01) Ajayi, O.S.; Balogun, O.S.; Fakola, E.G.; Olawuni, I.J.; October, Natasha; Adewole, Adetola Henry
BACKGROUND : Stachytarpheta cayennensis is a medicinal plant widely used in the treatment of inflammations, ulcer, fever, pain, hepatic, renal disorders, syphilis, gonorrhoea, pain, diabetes, and hypertension. PURPOSE : This study aimed at investigating the antioxidant and antidiabetic potentials of the chemical constituents of Stachytarpheta cayennensis leaf and its solvent extracts using both in vitro and in silico methods METHODS : The crude methanolic extract of S. cayennensis and its solvents fractions were tested for the presence of secondary metabolites using standard methods while the total phenolic content (TPC) and total flavonoid content (TFC) were determined by colorimetric assays using the Folin-Ciocalteu's and aluminum chloride reagents respectively. Thereafter, the aqueous methanolic fraction was purified on column chromatography to give compound 1 which was characterised using spectroscopic techniques. The pure isolate and solvents fractions of the extract were then evaluated for antioxidant and antidiabetic properties. Furthermore, in silico antidiabetic activity of the isolated compound was established using Autodock. RESULTS : The phytochemical screening of the crude methanolic extract and the solvent fractions revealed the presence of terpenoids, flavonoids, tannins, alkaloids, glycosides, sterols and phenols. The highest TPC and TFC were observed in ethyl acetate fraction (117.88 ± 9.83 GAE mg/g and 869.16 ± 7.26 QUE mg/g) while n-hexane fraction had the lowest (69.73 ± 1.47 GAE mg/g and 139.19 ± 2.69 QUE mg/g). The aqueous methanolic fraction, fractionated on column chromatography led to the isolation of compound 1, an iridoid glycoside known as ipolamiide. The ethyl acetate fraction demonstrated the highest DPPH free radical scavenging antioxidant activity (IC50 of 25.78 ± 0.05 µg/mL) while n-hexane fraction exhibited the least (4.67 ± 0.06 µg/mL) respectively, while the isolated ipolamiide had IC50 value of 49.4 ± 2.18 µg/mL. The in vitro α-amylase and α-glucosidase inhibitory activity of ipolamiide expressed in IC50 were 0.041 ± 0.021 mg/mL and 0.129 ± 0.030 mg/mL respectively compared to the standard drug acarbose (0.0163 ± 0.001 mg/mL and 0.0735 ± 0.0223 mg/mL) for α-amylase and α-glucosidase respectively. The docking analysis showed that ipolamiide exhibited docking scores that were comparable to those of established antidiabetic drugs (rosiglitazone, acarbose, gliclazide, and metformin) when interacting with the selected protein targets. Remarkably, ipolamiide displayed the most favourable docking score of -7.1 when bound to the insulin-like growth factor 1 kinase target. The docking results were visualized using Discovery Studio, which unveiled key molecular interactions contributing to the docking scores. These interactions comprised hydrogen bonding, pi-alkyl interactions, alkyl interactions, charge attraction, salt bridge interactions, and halogen interactions. These findings highlight the promising potential of ipolamiide as a prospective antidiabetic drug candidate. CONCLUSION : The antioxidant and antidiabetic activities of extract and solvent fractions of S. cayennensis give credence to their traditional use as food and medicine. In addition, the in silico and in vitro antidiabetic assessment of ipolamiide obtained from the plant indicated that it may provide a lead for development of a new antidiabetic drugs in the near future.
Identification of hypoxia-immune-related signatures for predicting immune efficacy in triple-negative breast cancer
(De Gruyter, 2024-02-28) Wang, Luping; Han, Haote; Ma, Jiahui; Feng, Yue; Han, Zhuo; Maharaj, Vinesh J.; Tian, Jingkui; Zhu, Wei; Li, Shouxin; Shao, Xiying
OBJECTIVES: The therapeutic effect against triple-negative breast cancer (TNBC) varies among individuals. Finding signatures to predict immune efficacy is particularly urgent. Considering the connection between the microenvironment and hypoxia, hypoxia-related signatures could be more effective. Therefore, in this study, we aimed sought to construct a hypoxia-immune-related prediction model for breast cancer and identify therapeutic targets. METHODS: Immune and hypoxia status in the TNBC microenvironment were investigated using single-sample Gene Set Enrichment Analysis (ssGSEA) and Uniform Manifold Approximation and Projection (UMAP). The least absolute shrinkage and selection operator (LASSO) and multivariate Cox regression analysis were employed to build a prognostic model based on hypoxia-immunerelated differentially expressed genes. The Cancer Genome Atlas (TCGA) cohort, real-time quantitative polymerase chain reaction (qRT-PCR), and immunofluorescence staining were utilized to analyze the expression differences. Tumor immune dysfunction and exclusion indexes were used to indicate the effect of immunotherapy. RESULTS: We identified 11 signatures related to hypoxia and immunity. Among these genes, C-X-C motif chemokine ligand (CXCL) 9, 10, and 11 were up-regulated in TNBC tissues compared to normal tissues. Furthermore, CXCL9, 10, 11, and 13 were found to enhance the effect of immunotherapy. CONCLUSIONS: These findings suggest the value of the hypoxia-immune-related prognostic model for estimating the risk in patients with TNBC, and CXCL9, 10, 11, and 13 are potential targets to overcome immune resistance in TNBC.
Uncovering thermally activated purple-to-blue luminescence in co-modified MgAl-layered double hydroxide
(Royal Society of Chemistry, 2024-04) Gevers, Bianca R.; Roduner, Emil; Leuteritz, Andreas; Labuschagne, F.J.W.J. (Frederick Johannes Willem Jacobus)
Thermally activated blue-to-purple luminescence of Co-modified nano-sandrose MgAl-layered double hydroxides (LDHs) is concentration dependent, occurring only for MgCoAl-LDH with a molar metal cation concentration of 15% Co. Temperature sweep luminescence spectroscopy between 83 K and 298 K shows that the luminescence is strongest at room temperature, increasing with an activation energy of 1 kJ mol−1 between these temperatures. The luminescence occurs in a broad, but fine-structured band below the conduction band (CB) edge at 3.0 eV after excitation at 5.0 eV.
Capacity building in porous materials research for sustainable energy applications
(The Royal Society, 2024-08) Langmi, Henrietta Wakuna; Musyoka, Nicholas M.; Kemmegne-Mbouguen, Justin Claude; Kowenje, Chrispin; Kengara, Fredrick; Mokaya, Robert
The project aimed to develop porous materials for sustainable energy applications, namely, hydrogen storage, and valorization of biomass to renewable fuels. At the core of the project was a training programme for Africa-based researchers in (i) the exploitation of renewable locally available raw materials; (ii) the use of advanced state-of-the-art techniques for the design and synthesis of porous materials (zeolites and metalorganic frameworks (MOFs)) for energy storage; and (iii) the valorization of sustainable low-value feedstock to renewable fuels. We found that compaction of the UiO-66 MOF at high pressure improves volumetric hydrogen storage capacity without any loss in gravimetric uptake, and experimentally demonstrated the temperature-dependent dynamic behaviour of UiO-66, which allowed us to propose an activation temperature of ≤ 150°C for UiO-66. Co-pelletization was used to fabricate UiO-66/nanofibre monoliths as hierarchical porous materials with enhanced usable (i.e. deliverable) hydrogen storage capacity. We clarified the use of naturally occurring kaolin as a source of silica and alumina species for zeolite synthesis. The kaolin-derived zeolite X was successfully used as a catalyst for the transesterification of Jatropha curcas oil (from non-edible biomass) to biodiesel. We also prepared porous composites (i.e. carbon/UiO-66, organoclay/UiO-66 and zeolite/carbon) that were successfully applied in electrochemical sensing.
Unexpected XPS binding energy observations further highlighted by DFT calculations of ruthenocene-containing [IrIII(ppy)2(RCOCHCORc)] complexes : cytotoxicity and crystal structure of [Ir(ppy)2(FcCOCHCORc)]
(MDPI, 2024-11-15) Buitendach, Blenerhassitt E.; Erasmus, Elizabeth; Fourie, Eleanor; Malan, F.P. (Frederick); Conradie, Jeanet; Niemantsverdriet, J.W. (Hans); Swarts, Jannie C.
Please read abstract in the article.

Browse

Recent Submissions