Research Articles (Chemistry)

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Crystal structure of dicarbonyl (μ2-indole-2-carboxylato κ2 O:O′)tris(triphenylarsine-κAs)dirhodium(I) acetone solvate, C68H56As3NO5Rh2
(De Gruyter, 2024) Alexander, Orbett T.; Elmakki, Mohammed A.; Venter, Johan A.
Background: The complex was synthesized starting with the reduction of hydrated RhCl3 in DMF which was refluxed for approxi mately 20 min to give a yellow solution of di-μ-chloro-tetra carbonyldirhodium(I), [RhCl(CO)2]2. 5–7 The addition of an equivalent amount of indol-2-carboxylic acid (indol(H2)) to the aforementioned yellow solution followed by addition of ice water yielded the dicarbonylrhodium(I) complex, [RhI(indol)(CO)2] by precipitation. The anion formed by double deprotonation of the indole-2-carboxylic acid (indol(H2)) ligand displays an unprecedented and unex pected mode of coordination with Rh(I) by forming bridging ligand to two rhodium centers; the ketonic oxygen atom coordinating (κO) to the Rh2 atom, while the N,O atoms bind to a second rhodium atom Rh1 atom in the more familiar bidentate (κN,O) fashion. The dinuclear title complex sim plifies as [Rh(indol)(CO)(AsPh3)Rh(CO)(AsPh3)2].8 [Rh(indol)(- CO)(AsPh3)Rh(CO)(AsPh3)2] was synthesized by dissolving [Rh(indol)(CO)2] (0.0412 g, 0.1291 mmol) in 5 cm3 of acetone. Triphenylarsine (AsPh3) (0.0396 g, 0.1291 mmol) was added to the solution with stirring, resulting in the immediate evolution of CO gas. After a few minutes the reaction was completed as determined by IR spectroscopy. Ice water was added drop-wise to the solution. A yellow precipitate was filtered off and dried.
Investigation of organic hydrotrioxide (roooh) formation from ro2 + oh reactions and their atmospheric impact using a chemical transport model, stochem-cri
(Royal Society of Chemistry, 2025) Shallcross, Dudley E; Khan, Md Anwar Hossain; Holland, Rayne
Incorporating the reactions of fifty peroxy radicals (RO2) with the hydroxyl radical (OH) into the global chemistry transport model, troposphere, affected the composition of the troposphere by changing the global burdens of NOx (−2.7 Gg, −0.5%), O3 (−2.3 Tg, −0.7%), CO (−3.2 Tg, −0.8%), HOx (+2.1 Gg, +7.7%), H2O2 (+0.5 Tg, +18.3%), RO2 (−8.0 Gg, −18.2%), RONO2 (−19.4 Gg, −4.7%), PAN (−0.1 Tg, −3.4%) HNO3 (−7.4 Gg, −1.3%) and ROOH (−96.9 Gg, −3.8%). The RO2 + OH addition reactions have a significant impact on HO2 mixing ratios in tropical regions with up to a 25% increase, resulting in increasing H2O2 mixing ratios by up to 50% over oceans. Globally, a significant amount of organic hydrotrioxides (ROOOH) (86.1 Tg per year) are produced from these reactions with CH3OOOH (67.5 Tg per year, 78%), isoprene-derived ROOOH (5.5 Tg per year, 6%) and monoterpene-derived ROOOH (4.2 Tg per year, 5%) being the most significant contributors. The tropospheric global burden of CH3OOOH is found to be 0.48 Gg. The highest mixing ratios of ROOOH, of up to 0.35 ppt, are found primarily in the oceans near the tropical land areas. The RO2 + OH reactions have a small, but noticeable, contribution to OH reactivity (∼5%) over tropical oceans. Additionally, these reactions have a significant impact on RO2 reactivity over tropical oceans where losses of the CH3O2 radical, isoprene derived peroxy radical (ISOPO2) and monoterpene derived peroxy radical (MONOTERPO2) by OH can contribute up to 25%, 15% and 50% to the total RO2 loss, respectively. The changes in RO2 reactivity influence the global abundances of organic alcohols (ROH) which are important species due to their crucial impact on air quality. The ROOOH generate secondary organic aerosol (SOA) of up to 0.05 μg m−3 which affects the Earth's radiation budget because of enhancing modelled organic aerosol by up to 5% and 2000% on land surfaces and the remote tropical oceans, respectively.
Constructing pentagonal topological defects in carbon aerogels for flexible zinc-air batteries
(Wiley-VCH GmbH, 2025) Iwuoha, Emmanuel; Huang, Yongfa; Li, Tingzhen
In the context of energy conversion, the design and synthesis of high-performance metal-free carbon electrocatalysts for the oxygen reduction reaction (ORR) is crucial. Herein, a one-step nitrogen doping/extraction strategy is proposed to fabricate 3D nitrogen-doped carbon aerogels (NCA-Cl) with rich pentagonal carbon topological defects. The NCA-Cl electrocatalyst exhibits superb ORR activity, displaying a half-wave potential of 0.89 V vs RHE and 0.74 V vs RHE under alkaline (0.1 m KOH) and acidic (0.1 m HClO4) media, respectively, thanks to the balanced *OOH intermediate adsorption and desorption induced by the pentagonal carbon topological defects and nitrogen dopants. The aqueous zinc-air battery (ZAB) equipped with the NCA-Cl cathode delivers a peak power density of 206.6 mW cm−2, a specific capacity of 810.6 mAh g−1, and a durability of 400 h, and the flexible ZAB also performed convincingly. This work provides an effective strategy for the formation of topological carbon defects for the enhancement of the electrocatalytic activity of carbon-based catalysts.
Derivatives of pyrazole-based compounds as prospective cancer agents
(American Chemical Society, 2025) Alexander, Orbett T; Ramoba, Lesetja V.; Nzondomyo, Wakopo J.
Five pyrazole-based compounds, 3,5-dimethyl-1H-pyrazole, L1; 3,5-diphenyl-1H-pyrazole, L2; 3-(trifluoromethyl)-5-phenyl-1H-pyrazole, L3; 3-(trifluoromethyl)-5-methyl-1H-pyrazole, L4; and 3,5-ditert-butyl-1H-pyrazole, L5 were synthesized from a typical condensation reaction of β-diketone derivatives with hydrazine hydrate reagent and characterized using various spectroscopic techniques such as FT-IR, UV-vis, 1H and 13C NMR, and LC-MS spectroscopy. L1 was further analyzed by single-crystal X-ray diffraction, and the N1-N1′ bond distance was found to be 1.361(3) Å and correlated well with other pyrazole-based compounds. The short-term cytotoxicity of 10 μM pyrazole compounds (L1-L5) was evaluated against pancreatic (CFPAC-1 and PANC-1), breast (MDA-MB-231 and MCF-7), and cervical (CaSki and HeLa) cancer cell lines using the MTT cell viability assay. Cisplatin and gemcitabine were included as positive control drugs followed by the determination of the half-maximal effective concentrations of prospective compounds. L2 and L3, respectively, displayed moderate cytotoxicity against CFPAC-1 (61.7 ± 4.9 μM) and MCF-7 (81.48 ± 0.89 μM) cell lines.
Box-behnken design optimization of photocatalytic performance of znwo4 nanoparticles multiple doped with selected metals
(Elsevier B.V., 2025) Muya, Francis Ntumba; Ameh, Alechine Emmanuel; Abubakar, Hassana Ladio
Box-Behnken Design Optimization of the photocatalytic activity of the synthesized Na@Mg@Ti@ZnWO4 nanocomposite at different mixing ratios for the degradation of malachite green in wastewater was investigated. The synthesized ZnWO4-based nanomaterials were characterized using different analytical techniques. Optical analysis demonstrated a reduction in the band gap energy from 4.68 eV for ZnWO4 to 2.08 eV for the doped ZnWO4. HRTEM/HRSEM images revealed the formation of well-defined nanocrystals with distinct lattice fringes, while EDX confirmed the homogeneous distribution of dopants (Na, Mg, and Ti) on ZnWO4. The XRD analysis showed that the incorporation of the dopant did not change the phase of ZnWO4. In ZnWO4, XPS revealed electron sharing between 3 s (Na and Mg) and 3d (Ti) dopants. The host and doped ZnWO4 surface areas increased from 24.74 m2/g to 156.93 m2/g. Compared to the SPCE/ZnWO4/Na/Mg/Ti electrode, cyclic voltammetry analysis confirmed strong conductive properties. Maximum removal of 99.93 % malachite green (MG) from wastewater was achieved using catalyst load (0.7 g) (ZnWO4@NaMgTi), contact time (35 min), and pH 12. Even after five repeated cycles, ZnWO4 nanocomposite doped with 1 % Na, 1 % Mg, and 1 % Ti exhibited superior photocatalytic behavior than other ZnWO4 nanoparticles. A toxicity test demonstrated that dyeing wastewater treated with ZnWO4@NaMgTi nanocomposites supported aquatic life (juvenile fish) better than untreated dyeing wastewater, standard water of fish farming, and water treated with ZnWO4 nanoparticles alone. The immobilization of ZnWO4 with the dopants contributed to the enhanced photocatalytic and electrochemical performance.
Electrochemical detection of histamine in red wine using cb[7] modified electrodes
(John Wiley and Sons Inc, 2025) Ngwekazi, Andisiwe; Baker, Priscilla; Arendse, Christopher
In host-guest chemistry, cucurbiturils are macrocyclic molecules made of glycoluril monomers linked by methylene bridges. This macrocyclic compound was applied in the design of electrochemical sensors for the detection of biogenic amines. Biogenic amines (BAs) are organic bases, which can be present in food and can cause several adverse reactions in consumers. The most significant BAs occurring in food are histamine, serotonin, and dopamine. Limited studies have been reported on thin film cucurbituril-modified electrochemical sensors for solution-based studies. An electrochemical sensor for the detection of biogenic amines was developed by immobilizing CB[7] at the surface of a glassy carbon electrode (GCE). Initially, the L-lysine monomer was polymerized at the surface of GCE to introduce amine groups which will then form a peptide bond with CB[7]. Immobilization of CB[7] was performed through the electrodeposition method as well as physisorption with no applied potential to form GCE/PLL/CB[7]. Scanning electron microscopy and atomic force microscopy revealed morphological properties of CB[7] as reported in the literature. The response profile of the GCE/PLL/CB[7] sensor for histamine was studied using CV, SWV, and UV-vis. The linear response was obtained in the range of 1.66×10−9–8.30×10−9 M for HI with a sensitivity of 255.22±38.20 uA M−1 cm−2. The proposed sensor was successfully applied to the determination of histamine in commercial red wine samples, with good recoveries.
Computational evaluation of Khaya ivorensis against plasmodium falciparum aminopeptidase N (PfM1AP) enzyme: molecular docking, simulation and ADMET studies
(Elsevier B.V., 2025) Salubi, Christiana; Ugwah-Oguejiofor, Chinenye; Adegboyega, Abayomi
The extract obtained from the stem bark of Khaya ivorensis has been utilized for malaria treatment. Given the rising resistance of malaria parasites to current medications, exploring new pharmacological targets is essential. Metalloaminopeptidases, particularly PfM1AP, have been identified as promising targets due to their vital role in the survival of the parasite. This study employed computational modeling to evaluate the binding affinities and interaction characteristics of 165 compounds found in K. ivorensis with PfM1AP. The top five compounds showed binding affinities ranging from −18.306 to −13.073 kcal/mol, significantly higher than the standard ligand's − 7.97 kcal/mol. Among these, pentagalloylglucose displayed the strongest binding affinity and most stable interactions, suggesting its potential as a PfM1AP inhibitor. ADMET analysis revealed some limitations regarding oral bioavailability and permeability through the blood-brain barrier; however, these compounds exhibited favorable safety profiles with low predicted toxicity levels. Despite the pharmacokinetic challenges, their high binding affinities and stable interactions indicate their potential as effective antimalarial agents. These results highlight the need for further experimental validation and optimization to improve the drug-like properties of these compounds, particularly concerning bioavailability and pharmacokinetic issues. Ultimately, this research contributes to the growing body of work aimed at developing innovative antimalarial treatments and lays the groundwork for future studies focused on targeted approaches against malaria.
Electrochemical hydrogen evolution performance of molybdenum disulphide/HKUST-1 metal organic framework/polyaniline ternary nanocomposite in acidic medium
(Springer Science and Business Media B.V., 2025) Ramohlola, Kabelo; Ndipingwi, Miranda; Morudu, Tshaamano
A search for an abundant and cheap electrocatalyst to replace the expensive and scarce precious metal-based electrocatalysts for hydrogen evolution reaction (HER) is critical for realization of hydrogen as an energy carrier. Herein, molybdenum disulphide-copper-based metal organic framework/polyaniline (MoS2/HKUST-1/PANI) ternary composite was synthesized following a simple in situ chemical oxidative polymerization of aniline in the presence of already hydrothermally synthesized MoS2 and HKUST-1 pristine materials. Several analytical techniques were used to evaluation the formation and structure properties of the ternary composite. The X-ray photoelectron spectroscopy results were in agreement with the morphological and structural characterization techniques and further confirming the wrapping of MoS2 and HKUST-1 by PANI. Optical studies displayed an increase of direct and indirect band gaps the ternary composite but closer to the one of PANI homopolymer suggesting that the ternary composite exhibited good conductivity, which is an essential property for HER. The electrochemical characterization presented that the ternary composite possessed a diffusion-controlled nature with a 12-fold increase in the electrochemical surface area of as compared to PANI homopolymer. The prepared MoS2/HKUST-1/PANI composite exhibited excellent HER properties with a Tafel slope of 44.7 mV.dec−1 and low charge-transfer resistance as well as turnover frequency of 4.0 mol H2 per second at 750 mV potential versus reversible hydrogen electrode (RHE). Most importantly, it only needed 110 mV overpotential vs RHE to reach the current density of 10 mA.cm−2. In addition, MoS2/HKUST-1/PANI ternary composite achieved superior stability over other prepared electrocatalysts. For the first time, employing MoS2 and HKUST-1 to the backbone of polyaniline for the construction of the edge-rich integrative ternary nanocomposite has successfully achieved an outstanding HER performance.
Doping of iron transition metal onto cerium oxide lattice for enhanced photocatalytic degradation of acid violet 7 azo dye under solar irradiation
(Elsevier B.V., 2025) Mishra, Ajay Kumar; Malatjie, Kgolofelo; Ndlovu, Lloyd
Dye-contaminated water possess a severe environmental problem due to its adverse effects on ecosystems, human health, and water resources. In this study, cerium oxide (CeO2) was successfully produced and doped with different ratios of iron (5,10 and 15 mol%) via a facile co-precipitation method for use in photocatalytic degradation of acid violet 7 (AV7) from an aqueous solution. The physicochemical properties of the nanophotocatalysts were studied using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Ultraviolet–Visible spectrophotometer (UV–Vis), Raman spectroscopy, photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), and Brunauer-Emmett-Teller (BET). SEM-EDS confirmed the presence of Fe, O and Ce elements in the photocatalysts. The 5 mol% Fe-dopped CeO2 possess high photocatalytic activity with the removal efficiency of approximately 98 % of AV7 dye when compared to pristine CeO2 (38 %), 10 % Fe-doped CeO2 (85 %) and 15 % Fe-doped (86 %). The higher photodegradation of 5 mol% Fe-doped CeO2 was attributed to suppressed recombination of photogenerated charge carriers as displayed by PL, as well as the high surface area observed from BET analysis. In addition, the electrochemical characterization confirmed high migration of photogenerated electron-hole pairs for 5 mol% Fe-CeO2/FTO which substantiates the enhanced photocatalytic degradation of AV7.
Functionalities of electrochemical fluoroquinolone sensors and biosensors
(Sringer, 2023) Ajayi, Rachel F.; Nepfumbada, Collen; Mthombeni, Nomcebo H.
Fluoroquinolones (FQs) are a class of broad-spectrum antimicrobial agents that are used to treat variety of infectious diseases. This class of antibiotics was being used for patients exhibiting early symptoms of a human respiratory disease known as the COVID-19 virus. As a result, this outbreak causes an increase in drug-resistant strains and environmental pollution, both of which pose serious threats to biota and human health. Thus, to ensure public health and prevent antimicrobial resistance, it is crucial to develop efective detection methods for FQs determination in water bodies even at trace levels. Due to their characteristics like specifcity, selectivity, sensitivity, and low detection limits, electrochemical biosensors are promising future platforms for quick and on-site monitoring of FQs residues in a variety of samples when compared to conventional detection techniques. Despite their excellent properties, biosensor stability continues to be a problem even today. However, the integration of nanomaterials (NMs) could improve biocompatibility, stability, sensitivity, and speed of response in biosen sors. This review concentrated on recent developments and contemporary methods in FQs biosensors. Furthermore, a variety of modifcation materials on the electrode surface are discussed. We also pay more attention to the practical applications of electrochemical biosensors for FQs detection. In addition, the existing challenges, outlook, and promising future perspec tives in this feld have been proposed. We hope that this review can serve as a bedrock for future researchers and provide new ideas for the development of electrochemical biosensors for antibiotics detection in the future.
Evaluating the therapeutic potential of curcumin and synthetic derivatives: a computational approach to anti-obesity treatments
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Moetlediwa, Marakiya T.; Titinchi, Salam J. J.; Jack, Babalwa Unice
Natural compounds such as curcumin, a polyphenolic compound derived from the rhizome of turmeric, have gathered remarkable scientific interest due to their diverse metabolic benefits including anti-obesity potential. However, curcumin faces challenges stemming from its unfavorable pharmacokinetic profile. To address this issue, synthetic curcumin derivatives aimed at enhancing the biological efficacy of curcumin have previously been developed. In silico modelling techniques have gained significant recognition in screening synthetic compounds as drug candidates. Therefore, the primary objective of this study was to assess the pharmacokinetic and pharmacodynamic characteristics of three synthetic derivatives of curcumin. This evaluation was conducted in comparison to curcumin, with a specific emphasis on examining their impact on adipogenesis, inflammation, and lipid metabolism as potential therapeutic targets of obesity mechanisms. In this study, predictive toxicity screening confirmed the safety of curcumin, with the curcumin derivatives demonstrating a safe profile based on their LD50 values. The synthetic curcumin derivative 1A8 exhibited inactivity across all selected toxicity endpoints. Furthermore, these compounds were deemed viable candidate drugs as they adhered to Lipinski’s rules and exhibited favorable metabolic profiles.
Smart worksheets and their positive Impact on a second-year chemical kinetics course
(American Chemical Society, 2024) Shallcross, Dudley E.; Davies-Coleman, Michael T.; Lloyd, Chris
Smart worksheets were introduced in 2017 into a second-year undergraduate chemical kinetics course (UK) and were available to students from the start of the course until the summer examination (ca. 3 months in duration). Several metrics strongly suggest that the introduction of the smart worksheets has a very positive impact on student understanding. For example, students who attended workshops completed twice as many questions as in previous years, with some completing them all. Students who attended workshops were much better prepared for these workshop activities, and because students had used the Smart Worksheets before the workshops, the tutor had information on what students understood and did not understand. Therefore, workshop tutors were able to prepare workshops that targeted specific needs. Questions asked in workshops and in an online forum showed more higher-order thinking than in previous years. Student feedback highlighted the usefulness of the smart worksheets (e.g., the instant feedback), and examination scores showed a statistically significant difference (95% confidence level) between the mean score for those who used the smart worksheets (larger than) compared with those who did not. This study suggests that smart worksheets can have a significant positive impact on student cognition, assessment (here examination) performance, enjoyment, and enthusiasm for a highly quantitative course.
UV–Vis detection of e. coli 0157:H7 using vitis vinifera and musa paradaisica modified au-nps
(Elsevier B.V., 2024) Ngece-Ajayi, Rachel Fanelwa ; Nqunqa, Siphamandla ; Ngema, Nokwanda
Herein, we demonstrate the simple one-pot novel green synthesis of gold nanoparticles (Au-NPs) functionalised with a combination of banana peel (Musa paradaisica) and grape (Vitis vinifera) fruit extracts. The reaction mixture of aqueous gold chloride, banana peel and grape extracts revealed a purple colour after a reaction time of one hour, an indication of the presence and the successful synthesis of gold nanoparticles. The optical and structural properties of the green synthesized nanoparticles were analysed using Ultraviolet-Visible spectroscopy (UV–Vis) and Fourier Transform Infrared Spectroscopy (FTIR) while their surface morphology was determined using X-Ray Diffraction (XRD), High-Resolution Transmission Microscopy (HRTEM) and Small Angle X-Ray (SAX). Furthermore, a quick and simple surface plasmon resonance (SPR) study in the form of an optical sensor for the detection of Escherichia coli 0157:H7 strain was also achieved using UV–Vis.
Phytochemistry, anti-tyrosinase, and anti-diabetes studies of extracts and chemical constituents of dicerothamnus rhinocerotis leaves
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Watti, Olusola Ifedolapo; Mabusela, Wilfred T.; Yalo, Masande
Dicerothamnus rhinocerotis (L.f.) Koekemoer, also known as rhinoceros bush and previously called Elytropappus rhinocerotis (L.f.) Less., is from the Asteraceae plant family. The plant is traditionally used to treat indigestion, stomach ulcers, influenza, and diarrhea. This study was aimed at investigating the phytochemistry, anti-glucosidase, anti-amylase, and anti-tyrosinase effects of D. rhinocerotis as research in this area is limited. The air-dried plant materials were macerated in 80% methanol (MeOH) and fractionated between hexane, dichloromethane (DCM), ethyl acetate (EtOAc), and butanol (BuOH). Column chromatography on silica gel was employed for the isolation of the compounds. A total of six compounds (1–6) were isolated from the fractions viz. acacetin (1), 15-hydroxy-cis-clerodan-3-ene-18-oic-acid (2), acacetin-7-glucoside (3), pinitol (4), apigenin (5), and β-sitosterol-3-O-glycoside (6). Compounds 2–4 and 6 are reported for the first time from this plant. Among the different fractions, the BuOH and EtOAc fractions had strong tyrosinase inhibitory activities with IC50 values of 13.7 ± 1.71 and 11.6 ± 2.68 µg/mL, respectively, while among the isolated compounds, apigenin (5) had the strongest inhibitory activity, with an IC50 of 14.58 µM, which competes favorably with Kojic acid (17.26 µM). The anti-glucosidase assay showed good activity in three of the fractions and compound 5, while the anti-amylase assays did not show significant inhibition activity.
Peroxidase application reduces microcrystalline cellulose recalcitrance towards cellulase hydrolysis in model cellulose substrates and rooibos biomass
(Elsevier Ltd, 2024) Alexander, Orbett; Mohotloane, Mamosela Marriam; Adoons, Vanthini Nelson; Pletschke, Brett Ivan
We have identified a HRP enzyme with microcrystalline cellulose activity, which has not yet been explored. The current study investigated the effect of HRP pretreatment on the microcrystalline cellulose substrates, Avicel and filter paper. SEM findings showed that HRP pretreatment catalysed the para-microcrystalline regions of Avicel, cracking and opening the pores on the surface. On filter paper, HRP removed the para-microcrystalline regions exposing fibres. Crystallinity index (CrI) analysis confirmed that HRP increased the CrI of Avicel from 49 % to 54.19 % and filter paper from 42 % to 47 %. The cellulose crystallite sizes increased from 45 to 47 nm at the 002 lattices in Avicel, suggesting a reduction of crystalline cellulose. In addition, endoglucanase displayed 1.15-fold increased activity on HRP-pretreated Avicel, confirming reduced crystalline cellulose. These findings showed that HRP pretreatment changed the structural and chemical properties of Avicel, i.e., loosening crystalline cellulose to make the substrate accessible to enzymes during hydrolysis. Finally, these findings were supported by rooibos microcrystalline cellulose modification post-HRP pretreatment, resulting in a 95 % yield of soluble sugars at 25 mg enzyme cocktail/g biomass.
Sutherlandiosides e−k: further cycloartane glycosides from sutherlandia frutescens
(Elsevier Ltd, 2024) Tchegnitegni, Billy Toussie; Lerata, Mookho S.; Beukes, Denzil R.; Antunes, Edith M.
A further chemical investigation of the butanol extract of leaves from the South African medicinal plant Sutherlandia frutescens led to the isolation of eight previously unreported saponins (1−8), together with the known sutherlandio sides A−D. Their structures were established by spectroscopic (1D and 2D NMR) analyses, CD, optical rotation, mass spectrometry, as well as chemical conversions. The isolates were screened for their cytotoxic activity against the MCF-7 human breast cancer cell line, although no significant activity was observed. In addition to the chemophenetic markers for this genus, i.e. the cycloartane glycosides, the present work also reports on the first isolation of an oleanan-type saponin from the Sutherlandia genus, forming an important fingerprint for the chemical composition of the plant.
Sunlight-driven charge separation for a heterojunction of nano-pyramidal CuWO4-MOF modified TiO2 nanoflakes for photocatalytic degradation of ciprofloxacin
(Springer Science and Business Media Deutschland GmbH, 2024) Mishra, Ajay Kumar; Mabape, Kgaugelo S.; Mishra, Shivani Bhardwaj; Moloto, Makwena Justice
The study presents a breakthrough of a balanced charge separation for heterojunction CuWO4-TiO2 cocatalyst to efficiently enhance visible light photocatalytic degradation of ciprofloxacin (CIP). A solvothermal-synthesized nanopyramid-like CuWO4 semiconductor was assembled before sol–gel treatment with TiO2 precursors to generate CuWO4-TiO2 nanocomposites. The optical, structural, and morphological properties of CuWO4-TiO2 were elucidated using UV–Vis DRS, XRD, FTIR, Raman spectroscopy, and TEM/SEM techniques. The UV–Vis DRS spectroscopy of as-synthesized CuWO4-TiO2 cocatalyst demonstrated enhanced visible light absorbance. The XRD patterns of CuWO4-TiO2 revealed a triclinic phase nanocrystal. The O-Ti–O functionality was confirmed by FTIR spectroscopy. The photoactive bands corresponding to anatase redshift were observed from Raman spectroscopy of CuWO4-TiO2 nanocomposite. The PL studies attributed this redshift to the elevated extra energy bands that aid electron/hole pair charge separation in a co-catalyst heterojunction CuWO4-TiO2 nanocomposite afforded by embedding CuWO4-MOF within TiO2 crystalline.
Organic heterostructures with dendrimer based mixed layer for electronic applications
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Rasoga, Oana; Yonkeu, Anne Lutgarde Djoumessi; Iwuoha, Emmanuel
Recently, much research has focused on the search for new mixed donor–acceptor layers for applications in organic electronics. Organic heterostructures with layers based on the generation 1 poly(propylene thiophenoimine) (G1PPT) dendrimer, N,N′ -diisopropylnaphthalene diimide (MNDI), and a combination of the two were prepared and their electrical properties were investigated. Single layers of G1PPT and MNDI and a mixed layer (G1PPT:MNDI) were obtained via spin coating on quartz glass, silicon, and glass/ITO substrates, using chloroform as a solvent. The absorption mecha nism was investigated, the degree of disorder was estimated, and the emission properties of the layers were highlighted using spectroscopic methods (UV–Vis transmission and photoluminescence). The effects of the concentration and surface topographical particularities on the properties of the layers were analyzed via atomic force microscopy. All of the heterostructures realized with ITO and Au elec trodes showed good conduction, with currents of the order of mA. Additionally, the heterostructure with a mixed layer exhibited asymmetry in the current–voltage curve between forward and reverse polarization in the lower range of the applied voltages, which was more significant at increased concentrations and could be correlated with rectifier diode behavior. Consequently, the mixed-layer generation 1 poly(propylene thiophenoimine) dendrimer with N,N′ -diisopropylnaphthalene diimide can be considered promising for electronic applications.
Elucidating the effects of covid-19 lockdowns in the UK on the o3-nox-voc relationship
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Shallcross, Dudley; Holland, Rayne; Seifert, Katya
The unprecedented reductions in anthropogenic emissions over the COVID-19 lockdowns were utilised to investigate the response of ozone (O3) concentrations to changes in its precursors across various UK sites. Ozone, volatile organic compounds (VOCs) and NOx (NO+NO2) data were obtained for a 3-year period encompassing the pandemic period (January 2019–December 2021), as well as a pre-pandemic year (2017), to better understand the contribution of precursor emissions to O3 fluctuations. Compared with pre-lockdown levels, NO and NO2 declined by up to 63% and 42%, respectively, over the lockdown periods, with the most significant changes in pollutant concentrations recorded across the urban traffic sites. O3 levels correspondingly increased by up to 30%, consistent with decreases in the [NO]/[NO2] ratio for O3 concentration response. Analysis of the response of O3 concentrations to the NOx reductions suggested that urban traffic, suburban background and suburban industrial sites operate under VOC-limited regimes, while urban background, urban industrial and rural background sites are NOx-limited. This was in agreement with the [VOC]/[NOx] ratios determined for the London Marylebone Road (LMR; urban traffic) site and the Chilbolton Observatory (CO; rural background) site, which produced values below and above 8, respectively. Conversely, [VOC]/[NOx] ratios for the London Eltham (LE; suburban background) site indicated NOx-sensitivity, which may suggest the [VOC]/[NOx] ratio for O3 concentration response may have had a slight NOx-sensitive bias. Furthermore, O3 concentration response with [NO]/[NO2] and [VOC]/[NOx] were also investigated to determine their relevance and accuracy in identifying O3-NOx-VOC relationships across UK sites. While the results obtained via utilisation of these metrics would suggest a shift in photochemical regime, it is likely that variation in O3 during this period was primarily driven by shifts in oxidant (OX; NO2 + O3) equilibrium as a result of decreasing NO2, with increased O3 transported from Europe likely having some influence.
Particle number concentration measurements on public transport in Bangkok, Thailand
(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Shallcross, Dudley E; Matthews, James C; Chalida, Chompoobut; Navasumrit, Panida
Traffic is a major source of particulate pollution in large cities, and particulate matter (PM) level in Bangkok often exceeds the World Health Organisation limits. While PM2.5 and PM10 are both measured in Bangkok regularly, the sub-micron range of PM, of specific interest in regard to possible adverse health effects, is very limited. In the study, particle number concentration (PNC) was measured on public transport in Bangkok. A travel route through Bangkok using the state railway, the mass rapid transport underground system, the Bangkok Mass Transit System (BTS) Skytrain and public buses on the road network, with walking routes between, was taken whilst measuring particle levels with a hand-held concentration particle counter. The route was repeated 19 times covering different seasons during either morning or evening rush hours.

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