Research Articles (Chemistry)

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1D NiHPO4 nanotubes prepared using dissolution equilibrium as bifunctional electrocatalyst for high-efficiency water splitting
(Journal of Power Sources, 2021) Ji, Shan; Wang, Zining; Wu, Yutai
In this work, one-dimensional NiHPO4 nanotubes are successfully fabricated on nickel foam by hydrothermal reaction, in which a dissolution equilibrium between phosphates is controlled by tuning the proportion of the mixed solvent and amounts of KOH. As the dissolution equilibrium is broken, the morphology of NiHPO4 transfers from solid nanowires to hollow nanotubes. The resulting 1D NiHPO4 nanotubes exhibit good electrocatalytic activity and stability in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Notably, a water-splitting voltage of 1.62 V at a current density of 10 mA cm􀀀 2 is obtained in an electrolyzer setup assembled using 1D NiHPO4 nanotubes as cathode and anode, demonstrating NiHPO4 nanotubes are promising catalysts for overall water splitting. Moreover, the revealed mechanism of forming tube morphology can be extended to fabricate other metal phosphates with hollow structures.
2-Arylnaphthoquinone analogues: Potential anti-TB and pro-apoptotic agents
(Green, I. R. et al. (2011). 2-Arylnaphthoquinone analogues: Potential anti-TB and pro-apoptotic agents. ARKIVOC, (x), 192-212. https://doi.org/10.3998/ark.5550190.0012.a16, 2011) Green, Ivan R; Sagar, Sunil; Swigelaar, Wendell
A useful library of substituted 2-arylnaphthoquinones prepared by reaction between the corresponding bromonaphthoquinones and arylboronic acids via Suzuki-Miyaura protocols has been established. Conversion of some of the products into new analogues was effected. The bisnaphthoquinone disospyrin 1 comprises two 7-methyljuglone units linked between C2 and C6. 1,2 Antimycobacterial activity studies performed on diospyrin 1 alerted the scientific community to the potential importance of this natural product3 which was soon followed by its first published synthesis by Yoshida and Mori in the same year.4 Subsequent studies, which included the synthesis and evaluation of related analogues of diospyrin 1 demonstrated the potential of this basic scaffold to be considered as an integral aspect for good antimycrobacterial activity.
4-(Dimethylamino)pyridinium chlorosulfonate: A new ionic liquid exhibiting chlorosulfonic acid action as monoprotic Brönsted acid and no sulfonating reagent
(Journal of Molecular Liquids, 2021) Titinchi, Salam
Many papers considered chlorosulfonic acid as a sulfonating and sulfating agent, whereas our previous work and a few reports showed it acts as a monoprotic Brönsted acid. Therefore, in the present work, we decided to respond to this question by investigating the reaction between chlorosulfonic acid and DMAP. First, a new ionic liquid viz. 4-dimethylaminopyridinium chlorosulfonate was obtained, which its chemical structure was elucidated using different spectroscopic techniques. Another derivative, 4-dimethylaminopyridinium hydrogen sulfate, was also synthesized, which showed a similar NMR pattern. The NMR spectra analyses of reactants, the new ionic liquid, and 4 dimethylaminopyridinium hydrogen sulfate support the formation of 4-dimethylaminopyridinium chlorosulfonate. Therefore, the formation of N-sulfonic acid-4-dimethylaminopyridinium chloride or 4-dimethylaminopyridinium sulfate and the presence of an excess of chlorosulfonic acid and sulfuric acid were ruled out based on the spectroscopic results. Finally, the new ionic liquid's thermal behavior and thermal stability were investigated, and a possible mechanism was presented for its degradation based on a TGA/DTA analysis.
4-Oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione derivatives as NMDA receptor- and VGCC blockers with neuroprotective potential
(MDPI, 2020) Egunlusi, Ayodeji O; Omoruyi, Sylvester I; Malan, Sarel F
The impact of excitotoxicity mediated by N-methyl-D-aspartate (NMDA) receptor overactivation and voltage gated calcium channel (VGCC) depolarization is prominent among the postulated processes involved in the development of neurodegenerative disorders. NGP1-01, a polycyclic amine, has been shown to be neuroprotective through modulation of the NMDA receptor and VGCC, and attenuation of MPP+-induced neurotoxicity. Recently, we reported on the calcium modulating effects of tricycloundecene derivatives, structurally similar to NGP1-01, on the NMDA receptor and VGCC of synaptoneurosomes. In the present study, we investigated novel 4-oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione derivatives for their cytotoxicity, neuroprotective effects via attenuation of MPP+-induced neurotoxicity and calcium influx inhibition abilities through the NMDA receptor and VGCC using neuroblastoma SH-SY5Y cells. All compounds, in general, showed low or no toxicity against neuroblastoma cells at 10–50 µM concentrations. At 10 µM, all compounds significantly attenuated MPP+-induced neurotoxicity as evident by the enhancement in cell viability between 23.05 ± 3.45% to 53.56 ± 9.29%. In comparison to known active compounds, the derivatives demonstrated mono or dual calcium modulating effect on the NMDA receptor and/or VGCC. Molecular docking studies using the NMDA receptor protein structure indicated that the compounds are able to bind in a comparable manner to the crystallographic pose of MK-801 inside the NMDA ion channel. The biological characteristics, together with results from in silico studies, suggest that these compounds could act as neuroprotective agents for the purpose of halting or slowing down the degenerative processes in neuronal cells.
Abundance of no3 derived organo-nitrates and their importance in the atmosphere
(MPDI, 2021) Foulds, Amy; Khan, M. Anwar H.; Shallcross, Dudley E.
The chemistry of the nitrate radical and its contribution to organo-nitrate formation in the troposphere has been investigated using a mesoscale 3-D chemistry and transport model, WRFChem-CRI. The model-measurement comparisons of NO2 , ozone and night-time N2O5 mixing ratios show good agreement supporting the model’s ability to represent nitrate (NO3 ) chemistry reasonably. Thirty-nine organo-nitrates in the model are formed exclusively either from the reaction of RO2 with NO or by the reaction of NO3 with alkenes. Temporal analysis highlighted a significant contribution of NO3 -derived organo-nitrates, even during daylight hours. Night-time NO3 -derived organo-nitrates were found to be 3-fold higher than that in the daytime. The reactivity of daytime NO3 could be more competitive than previously thought, with losses due to reaction with VOCs (and subsequent organo-nitrate formation) likely to be just as important as photolysis. This has highlighted the significance of NO3 in daytime organo-nitrate formation, with potential implications for air quality, climate and human health. Estimated atmospheric lifetimes of organo-nitrates showed that the organo-nitrates act as NOx reservoirs, with particularly short-lived species impacting on air quality as contributors to downwind ozone formation.
Actuation behaviour of a derivatized pyrrole accordion type polymer
(ESG, 2014) Ward, Meryck; Botha, Shanielle; Iwuoha, Emmanuel I.; Baker, Priscilla
A monomer (Phenazine-2,3-diimino(pyrrole-2-yl)–PDP) derived from the condensation reaction between 2,3-diaminophenazine and a pyrrole derivative has been synthesized as a hinge molecule in the design of a zig-zag polymer. The monomer was polymerized both chemically and electrochemically in order to produce the polymer material, phenazine-2,3-diimino(pyrrole-2-yl (PPDP). During electrochemical polymerization the system was doped using 1,4-napthaquinone sulphonic acid (NQSA) and polyvinylsulfonic acid (PVSA) respectively, to improve conductivity. Characterization of the materials by Fourier transform infrared spectroscopy (FTIR) confirmed the successful linking of the starting materials to produce the hinge molecule and nuclear magnetic resonance spectroscopy (NMR) supported the FTIR data. The electrochemistry of the polymer in the doped and undoped state was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).
Acylation of anisole with benzoyl chloride over rapidly synthesized fly ash–based hbea zeolite
(Frontiers Media, 2021) Ameh, Alechine E.; Musyoka, Nicholas M.; Oyekola, Oluwaseun
Stable HBEA zeolite with high surface area and strong acid sites was synthesized from coal fly ash–based silica extract via indirect hydrothermal synthesis. The rapid HBEA hydrothermal crystallization times of 8, 10, and 12 h were achieved through a reduced molar water fraction in the synthesis composition. The HBEA zeolites prepared from fly ash silica extract exhibited well-defined spheroidal-shaped crystal morphology with uniform particle sizes of 192, 190, or 239 nm obtained after 8, 10, or 12 h of synthesis time, respectively. The high surface area and the microporous area of 702 and 722 m2 /g were achieved as a function of shorter hydrothermal synthesis durations (10 and 24 h, respectively) compared to 48 or 72 h, which resulted in HBEA zeolites with lower surface areas of 538 and 670 m2 /g. Likewise, temperature-programmed desorption measurements of fly ash–based HBEA zeolites revealed the presence of weak and strong acid sites in the zeolite.
Acylphloroglucinol derivatives from the South African helichrysum niveum and their biological activities
(MDPI, 2015) Popoola, Olugbenga K.; Marnewick, Jeanine L.; Rautenbach, Fanie; Iwuoha, Emmanuel I.; Hussein, Ahmed A.
Abstract: Phytochemical investigation of aerial parts of Helichrysum niveum (H. niveum) using different chromatographic methods including semi-preparative HPLC afforded three new (1–3) and six known (4–10) acylphloroglucinols alongside a known dialcohol triterpene (11). The structures of the isolated compounds were characterized accordingly as 1-benzoyl-3 (3-methylbut-2-enylacetate)-phloroglucinol (helinivene A, 1), 1-benzoyl-3 (2S-hydroxyl-3- methylbut-3-enyl)-phloroglucinol (helinivene B, 2), 8- (2-methylpropanone)-3S, 5, 7-trihydroxyl- 2,2-dimethoxychromane (helinivene C, 3), 1-(2-methylbutanone)-4-O-prenyl-phloroglucinol (4), 1-(2-methylpropanone)-4-O-prennyl-phloroglucinol (5), 1-(butanone)-3-prenyl-phloroglucinol (6), 1- (2-methylbutanone)-3-prenyl-phloroglucinol (7), 1-butanone-3- (3-methylbut-2-enylacetate)- phloroglucinol (8), 1-(2-methylpropanone)-3-prenylphloroglucinol (9), caespitate (10), and 3β-24-dihydroxyterexer-14-ene (11). Excellent total antioxidant capacities were demonstrated by helinivenes A and B (1 and 2) when measured as oxygen radicals absorbance capacity (ORAC), ferric-ion reducing antioxidant power (FRAP), trolox equivalent absorbance capacity (TEAC) and including the inhibition of Fe2+-induced lipid peroxidation (IC50 = 5.12 ± 0.90; 3.55 ± 1.92) µg/mL, while anti-tyrosinase activity at IC50 = 35.63 ± 4.67 and 26.72 ± 5.05 µg/mL were also observed for 1 and 2, respectively. This is the first chemical and in vitro biological study on H. niveum. These findings underpin new perspectives for the
Advancement in electrochemical sensing of chloramphenicol in varying matrixes: a review
(Elsevier B.V., 2025) Mulaudji, Kgwadu Percy; Mokwebo, Kefilwe Vanessa; De Bruin, Franklin Quelain; Pokpas, Keagan; Ross, Natasha
Chloramphenicol (CAP) have demonstrated its broad effectiveness against bacterial infections. However, its persistence in the environment and potential toxicity led to strict global regulations limiting its use. As a result, rapid and accurate detection methods for CAP are being developed to protect public health and maintain regulatory compliance regarding its presence in the environment. Conventional analytical methods such as High-Performance Liquid Chromatography, Gas Chromatography, and Liquid Chromatography–Mass Spectrometry were commonly used for CAP detection. However, these conventional methods suffer challenges such as time-consumption, fabrication complexity, reproducibility, and cost. With electrochemical sensing techniques presenting varying valuable benefits, such as instant detection, low power consumption, simultaneous analysis, and portability, making them essential for timely monitoring of various analytes. The performance of electrochemical sensor is further boosted by integrating materials such as spinels, metal oxides, and metallic nanoparticles. These materials are broadly investigated as electrode interface components thanks to their features that collectively boost electrochemical sensor such as providing excellent electrical conductivity, distinct catalytic behavior, and larger surface areas. Furthermore, this paper reviews the impact of traditional and standards analytical methods, as well as their recent advancement based on the detection of CAP in aqueous media.
Advancements in catalyst design for biomass-derived bio-oil upgrading to sustainable biojet fuel: a comprehensive review
(John Wiley and Sons Inc, 2025) Jideani, Thandiswa; Seroka, Ntalane Sello; Khotseng, Lindiwe
Biomass‐derived bio‐oil, produced through thermochemical methods such as pyrolysis and hydrothermal liquefaction, has immense potential as a renewable feedstock for aviation fuels because of its renewable nature and the potential to significantly reduce greenhouse gas emissions. The development of biojet fuel from renewable sources, such as biomass, is a critical step toward achieving global energy sustainability and reducing the carbon footprint of the aviation industry. This review aims to provide a comprehensive analysis of the advances in catalyst design to upgrade biomass‐derived oil to biojet fuel. The review will also explore the mechanisms by which these catalysts operate, the optimization of catalytic processes, and the performance metrics used to evaluate their efficiency. Recent case studies demonstrate the effectiveness of catalyst design in enabling efficient and sustainable conversion of biomass‐based bio‐oil into high‐quality fuels, advancing the viability of renewable energy sources in aviation and beyond.
Advances in nanotechnology towards development of silver nanoparticle-based wound-healing agents
(MPDI, 2021) Nqakala, Zimkhitha B.; Sibuyi, Nicole R. S.; Fadaka, Adewale O.
Since antiquity, silver-based therapies have been used in wound healing, wound care and management of infections to provide adequate healing. These therapies are associated with certain limitations, such as toxicity, skin discolouration and bacterial resistance, which have limited their use. As a result, new and innovative wound therapies, or strategies to improve the existing therapies, are sought after. Silver nanoparticles (AgNPs) have shown the potential to circumvent the limitations associated with conventional silver-based therapies as described above. AgNPs are effective against a broad spectrum of microorganisms and are less toxic, effective at lower concentrations and produce no skin discolouration. Furthermore, AgNPs can be decorated or coupled with other healingpromoting materials to provide optimum healing. This review details the history and impact of silver-based therapies leading up to AgNPs and AgNP-based nanoformulations in wound healing. It also highlights the properties of AgNPs that aid in wound healing and that make them superior to conventional silver-based wound treatment therapies.
Aerosol mass and size‑resolved metal content in urban Bangkok, Thailand
(Springer, 2022) Matthews, James C.; Navasumrit, Panida; Shallcross, Dudley E.
Inhalable particulate matter (PM) is a health concern, and people living in large cities such as Bangkok are exposed to high concentrations. This exposure has been linked to respiratory and cardiac diseases and cancers of the lung and brain. Throughout 2018, PM was measured in northern Bangkok near a toll road (13.87°N, 100.58°E) covering all three seasons (cool, hot and rainy). PM10 was measured in 24- and 72-h samples. On selected dates aerodynamic size and mass distribution were measured as 3-day samples from a fxed 5th foor inlet. Particle number concentration was measured from the 5th foor inlet and in roadside survey measurements. There was a large fraction of particle number concentration in the sub-micron range, which showed the greatest variability compared with larger fractions. Metals associated with combustion sources were most found on the smaller size fraction of particles, which may have implications for associated adverse health outcomes because of the likely location of aerosol deposition in the distal airways of the lung. PM10 samples varied between 30 and 100 μg m−3, with highest concentrations in the cool season.
Ag doped TiO2 anchored on metal free g-C3N4 for enhanced solar light activated photodegradation of a dye
(Elsevier, 2024) Ratshiedana, Rudzani; Mishra, Ajay Kumar; Mafa, Potlako John
Heterogeneous semiconductor photocatalysis has attracted researcher’s attention in wastewater treatment owing to the improved surface area, optical properties, and charge transfer rate for boosted degradation of organic pollutants. Thus, the g-C3N4/Ag/TiO2 was prepared following a hydrothermal route for the degradation of azo dye tartrazine (TA) used as a food colourant under solar light. Before application, the composite and pristine materials were interrogated for physicochemical and structural properties using SEM, TEM, EDS, XPS, XRD, UV–vis DRS, PL, BET, Raman, and FTIR spectroscopy. The PL and electrochemical analysis revealed that the CNAT composite had a high charge transfer rate that was coupled with low charge carrier complexation. The degradation efficiency of 91 % was realized in 180 min and the rate of pseudo-first-order kinetics of 0.01143 min− 1 was obtained. The CNAT catalyst also displayed high removal efficiency towards a cocktail of naproxen (NPX) and TA. The improved removal efficiencies stem from increased visible usage, reduced charge carrier compounding, and formation of Z-scheme heterojunction with high redox capabilities. The total organic carbon removal reached 95 % while CNAT showed high convincing stability even after four cycles. Given the above results, the hydrothermally prepared composite catalyst can be extended to other organic pollutants such as pharmaceuticals, pesticides, and reduction of inorganics.
Ag induced plasmonic tio2 for photocatalytic degradation of pharmaceutical under visible light: insights into mechanism, antimicrobial and cytotoxicity studies
(Elsevier, 2024) Ratshiedana, Rudzani; Mishra, Ajay Kumar; Malefane, Mope Edwin
Global concerns include water scarcity and shortage, which are escalated by organic pollutants such as naproxen (NPX) that deteriorate drinking water and taint access to safe drinking water by humans. Moreover, NPX may cause gastrointestinal difficulties, cardiovascular risks, kidney damage, allergic reactions, liver toxicity, bleeding issues and pregnancy risks, hence it is essential to remove it in water. Ag-TiO2 was synthesized by hydrothermal method for NPX degradation. Ag on TiO2 reduced the band gap and surface area of TiO2 and resulted in a plasmonic Ag-TiO2 composite of 0.2 % Ag. The photocatalytic degradation of 0.2 % Ag-TiO2 was 80 % in 180 minutes using a solar simulator during NPX degradation with a first order reaction rate that was 3.6 times faster than that of pure TiO2 and the catalyst showed good stability for four cycles. The dual activity of Ag0 surface plasmon resonance improved light absorption capability and enhanced charge transfer for increased photodegradation rate and stability. The antibacterial studies demonstrated that 0.2 % Ag-TiO2 posted strong antibacterial properties under light irradiation and less in the dark, with a greater effect on gram-negative than gram-positive bacteria. The minimum inhibitory concentration (MIC) values of 620, 1250, 2500, 2500 µg/mL were attained against B. subtilis, S. aureus, E. coli and S. typhimurium bacteria, respectively. The low cell toxicity of 0.2 % Ag-TiO2 was determined using human embryonic kidney (HEK293) cells with an inhibitory concentration (IC50) of 61.09 ± 0.24 µg/mL under light irradiation. Radical trapping experiments demonstrated that hydroxyl radicals (OH• ) played a vital role during the degradation and bactericidal activity of NPX under light irradiation. This work advances new insights on the synthesis of less toxic nanoparticles with high photocatalytic and bactericidal activity for possible applications at industrial scale.
Air mass flow and pressure optimization of a pem fuel cell hybrid system for a forklift application
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Radica, Gojmir; Lototskyy, Mykhaylo V.; Pasupathi, Sivakumar
The air compressor holds paramount importance due to its significant energy consumption when compared to other balance of plant components of polymer electrolyte membrane (PEM) fuel cells. The air supply system, in turn, plays a critical role in ensuring the stable and efficient operation of the entire fuel cell system. To enhance system efficiency, the impact of varying the stoichiometric ratio of air and air pressure was observed. This investigation was carried out under real loading conditions, replicating the conditions experienced by the power module when fuel cells are in use within a forklift. The air compressor can be operated at different pressure and excess air ratios, which in turn influence both the fuel cell’s performance and the overall efficiency of the power module system. Our research focused on assessing the performance of PEM fuel cells under different load cycles, adhering to the VDI60 requirements for forklift applications. This comprehensive examination encompassed the system’s minimum and maximum load scenarios, with the primary goal of optimizing excess air and pressure ratio parameters, especially under dynamic load conditions. The results revealed that higher air pressures and lower excess air ratios were conducive to increasing system efficiency, shedding light on potential avenues for enhancing the performance of PEM fuel cell systems in forklift applications.
Alpha-glucosidase and alpha-amylase inhibitory activities, molecular docking, and antioxidant capacities of plectranthus ecklonii constituents
(MDPI, 2022) Etsassala, Ninon G. E. R.; Badmus, Jelili A.; Iwuoha, Emmanuel. I.
Shortage in insulin secretion or degradation of produced insulin is the principal characteristic of the metabolic disorder of diabetes mellitus (DM). However, because the current medications for the treatment of DM have many detrimental side effects, it is necessary to develop more effective antidiabetic drugs with minimal side effects. Alpha-glucosidase and alpha-amylase inhibitors are directly implicated in the delay of carbohydrate digestion. Pharmacologically, these inhibitors could be targeted for the reduction in glucose absorption rate and, subsequently, decreasing the postprandial rise in plasma glucose and the risk for long-term diabetes complications. The main objectives of this research study were to isolate different phytochemical constituents present in the methanolic extract of Plectranthus ecklonii and evaluate their alpha-glucosidase and alpha-amylase inhibitory activities and antioxidant capacity.
Alpha-glucosidase and alpha-amylase inhibitory activities, molecular docking, and antioxidant capacities of salvia aurita constituents
(MPDI, 2020) Etsassala, Ninon G.E.R.; Badmus, Jelili A.; Marnewick, Jeanine L.
Diabetes mellitus (DM) is one of the most dangerous metabolic diseases with a high rate of mortality worldwide. It is well known that insulin resistance and deficiency in insulin production from pancreatic β-cells are the main characteristics of DM. Due to the detrimental side effects of the current treatment, there is a considerable need to develop new effective antidiabetic drugs, especially alpha-glucosidase and alpha-amylase inhibitors with lesser adverse effects. These inhibitors are known to be directly involved in the delay of carbohydrate digestion, resulting in a reduction of glucose absorption rate and, consequently, reducing the postprandial rise of plasma glucose, which can reduce the risk of long-term diabetes complications. Furthermore, natural products are well-known sources for the discovery of new bioactive compounds that can serve as scaffolds for drug discovery, including that of new antidiabetic drugs. The phytochemical investigation of Salvia aurita collected from Hogobach Pass, Eastern Cape Province, South Africa (SA), yielded four known abietane diterpenes namely carnosol (1), rosmanol (2), 7-methoxyrosmanol (3), 12-methoxycarnosic acid (4), and one flavonoid named 4,7-dimethylapigenin (5)
Amorphous Pt@dCu/CNT catalyst for methanol elextrooxidation
(South African Chemical Institute (SACI), 2013) Wang, Hui; Ji, Shan; Wang, Wei; Wang, Rongfang
A multi-walled carbon nanotube-supported, Pt decorated nano-sized amorphous PdCu alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a galvanic displacement reaction. The structure is examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical activity of the Pt@PdCu/CNT catalyst is tested by cyclic voltammogrametry (CV) and compared to that of PtRu/CNT catalysts. The results show that amorphous Pt@PdCu/CNT catalyst exhibits better electro-catalytic performances for methanol oxidation than its crystalline counterpart.
Analyzing chemical data in more than two dimensions: A tutorial on factor and cluster analysis
(Journal of chemical education, 1990) Auf der Heyde, Thomas P. E
This tutorial is intended to introduce factor and cluster analysis at a level that will afford a senior student-and the practicing chemist, for that matter-some insights into the workings of the computer packages employing these methods, without overwhelming him or her with mathematical detail in the process.
Anode materials for lithium-ion batteries: A review
(Elsevier, 2022) Iwuoha, E.I
The need for eco-friendly and portable energy sources for application in electrical, electronic, automobile and even aerospace industries has led to an ever-increasing research and innovation in lithium-ion battery technology. Owing to the research and discoveries in recent years, lithium-ion batteries (LIBs) have stood out as the most suitable device for the storage of electrical power for application in mobile appliances and electric vehicles. This is as a result of the very attractive properties inherent in LIBs, which include lightweight, high energy density, small-scale size, few memory effects, long cycle life and low pollution. In this review article, recent advances in the development of anode materials for LIBs will be discussed, along with their advantages and disadvantages. New approaches for alleviating the drawbacks associated with LIB anode materials will also be highlighted.

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