Research Articles (Chemistry)

Permanent URI for this collectionhttps://hdl.handle.net/10566/387

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Efficient removal of mercury Ions stabilized by gold solution using chitosan–guar gum polymer blend in basic media
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Mishra, Ajay Kumar; Tshikovhi, Azwifunimunwe; Mishra, Shivani Bhardwaj
The highly efficient removal of mercury metal ions at a higher pH (basic media) is barely reported in the literature. In this study, we developed a novel adsorbent by blending chitosan with guar gum, designed to effectively remove mercury ions from basic media by stabilizing them with a gold (Au3⁺) solution. The FTIR confirmed the compatibility of chitosan and guar gum through hydrogen bonding. The morphology of the blend exhibited an amorphous and porous structure. A mesoporous structure with a surface area, volume, and diameter of 11.843 (m2/g), 0.184 (cm2/g), and 17.072 nm, respectively, was confirmed by BET. The adsorption behavior was analyzed using isotherms and kinetics models, which best fitted with the pseudo-second-order kinetic model and Freundlich adsorption isotherm model, respectively. The adsorbent was shown to be an excellent candidate for the removal of mercury ions in water, with an adsorption efficiency of 92% at pH 12 in 60 min and a maximum adsorption capacity of 370.37 (mg/g).
Simple, rapid, scalable confined synthesis of ultrafine Pt nanoclusters for fuel cells
(Elsevier B.V., 2026) Chidziva, Stanford; Bai, Yiming; Sang, Chengcheng
Small-sized nanoclusters exhibit catalytic activity in electrochemical reactions distinct from the bulk-like properties of nanoparticles 2 nm or larger, yet their surfactant-free synthesis remains a formidable challenge. A scalable microchannel-confined synthesis method enables rapid, controlled formation of 1.12 nm Pt nanoclusters without additional surfactants. Kinetic control achieves a nucleation and growth time of approximately 18.6 s, with heat transfer simulations confirming uniform temperature attainment within 0.5 s. Half-cell and single-cell tests, corroborated by density functional theory (DFT) calculations, demonstrate exceptional performance of these Pt nanoclusters in proton exchange membrane fuel cell (PEMFC), achieving a mass activity 1.9 times that of commercial samples and a rated power density of 1.55 W cm−2. This method can employ multiple capillaries assembled into a capillary bundle to enable parallel experiments, highlighting its scalability and potential to advance hydrogen-electricity conversion technologies.
Dual selective sensing of CH4 and ultra-low NO gas utilizing Ag-decorated CeO2-CuO nanorods: Role of humidity in p-n conductivity transition
(Elsevier B.V., 2026) Pholoana, Maphia G; Malgas, Gerald F.; Morulane, Katlego L.
Detecting hazardous gases like methane (CH4) and nitric oxide (NO) under real-world conditions is a significant challenge for gas sensors. Herein, pure and (0.5–2 wt%) Ag-decorated CeO2-CuO nanorods were prepared using a hydrothermal approach and tested as dual-gas sensors for NO and CH4, with controlled relative humidity (RH). The crystal structures, optical properties, surface adsorption states, and chemical states of the materials were probed using various analytical techniques. The sensors were tested at different temperatures for multiple gases, including benzene, acetone, xylene, carbon monoxide, and CH4. At 175 °C, a 2 wt% Ag-decorated CeO2-CuO nanorods demonstrated a superior response and selectivity towards 10,000 ppm CH4 gas. In comparison, at 200 °C, the 0.5 wt% Ag-decorated CeO2-CuO nanorods showed a remarkable selectivity towards a trace level of (5–100 ppb) NO gas. The sensor showed a notable p-n transition in its electrical response based on the gas and humidity levels. However, an opposite response emerged under humid conditions (RH >50 %), indicating a switch to n-type conductivity. This shift is due to humidity-driven surface hydroxylation, electron donation from Ag nanoparticles, and charge effects at the CeO2-CuO interface. Water molecules on the surface change band bending and increase electron accumulation, promoting n-type behaviour. The sensing mechanism associated with humidity-controlled conduction reversal is discussed in detail
Utilisation of mango seed husk for the production of phenolic compounds and glucose with C1184 enzyme preparation reveals the role of glucuronoyl esters in lignin–carbohydrate linkages in biomass recalcitrance
(Springer, 2025) Alexander, Orbett; Mafa, Mpho Stephen; Mohotloane, Mamosela Marriam
This study assessed mango seed husk (MSH) fractions for producing glucose and phenolic compounds using commercial enzymes. We focused on cleaving lignin–carbohydrate linkages, specifically feruloyl and glucuronoyl esters, to decrease biomass recalcitrance and enhance product extraction. For saccharification studies, we used Sigma’s C1184 cellulase from Aspergillus niger. Characterisation results of ground MSH using phloroglucinol and scanning electron microscopy revealed that it could be separated into a fine fraction, containing less lignin and cellulose fibres with parallel orientation, and a coarse fraction, with higher lignin content and cellulose fibres at an angled orientation. Activity assays and zymogram analysis of the C1184 preparation prior to saccharification studies revealed diverse CAZyme activities associated with distinct proteins, with xylanolytic activity dominating. Saccharification studies with ground MSH found that the C1184 preparation supplemented with feruloyl or glucuronoyl esterases was suitable for extracting phenolic compounds (0.4–1.7% w/w) from MSH while converting up to 20% of the total biomass as glucose. Interestingly, when replacing 50% (w/w) of the C1184 preparation with glucuronoyl esterase, glucose release nearly doubled from both MSH fractions. Additionally, phenolics attached to carbohydrates may be less condensed in the fine fraction, as all three esterases released three-to-five times more phenolics from the fine fraction compared to the coarse fraction with higher lignin content. Saccharification trials with alkali-pretreated ground MSH showed that the C1184 preparation supplemented with β-glucosidase produced low glucose levels (170–250 mg/g dry biomass) from the substrate after 24 h, even at 50 mg/g biomass protein loading. Overall, this work advances our understanding of the importance of lignin–carbohydrate linkages formed via glucuronoyl esters in biomass recalcitrance. Furthermore, our study corroborates the potential of MSH as a valuable feedstock for producing value-added products in the biorefinery sector.
Novel antifouling and photocatalytic immobilized iron-doped cerium oxide@halloysite nanotubes decorated polyethersulfone membranes
(Elsevier B.V., 2025) Mishra, Ajay Kumar; Malatjie, Kgolofelo I.; Moutloali, Richard M.
Novel polyethersulfone (PES) ultrafiltration (UF) membranes were prepared by incorporating different contents of iron-doped cerium oxide-halloysite nanotubes (FC@NHT) nanocomposites onto the PES membranes. The properties of the prepared nanocomposite membranes were investigated using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), thermo-gravimetric analyzer (TGA) and scanning electron microscope (SEM). The results showed that iron dopped cerium oxide (FC) was indeed successfully loaded on the surface of halloysite nanotubes (HNTs). SEM characterization of FC@HNT/PES membranes showed an increase in pore sizes and microvoids which resulted in an increase in both hydrophilicity and flux due to the impact of FC@HNT. Pure water flux of 2% FC@HNT/PES (M4) was increased from 55.9 L.m−2.h−1 (0% FC@HNT/PES) to 320.4 L.m−2.h−1. The membranes also showed high antifouling properties towards humic acid (HA). This was attributed to the membranes becoming more hydrophilic upon modification. Subsequently, this reduced membrane-foulant hydrophobic interactions and made it difficult for hydrophobic contaminants to be attached onto the membranes surface. Photocatalytic ability of the modified membranes was tested against imidacloprid (IMD) insecticides. The membrane (M4) showed high photocatalytic activity of about 79% in 120 mins and 85.7% in 180 mins. The immobilization of FC onto the surface of the HNTs was for the homogenous dispersion of the nanoparticles and to mitigate the issue of agglomeration. Other remarkable functionalities are also provided by this integration. The membrane's ability to function as system for water filtration and for the degradation of imidacloprid pesticide with high antifouling propensity is by far its most intriguing aspect of this work.
Electro-photovoltaics of grignard metathesis-derived poly(propylene imine) tetra(salicylaldimine)-co-poly(3-hexylthiophene-2,5-diyl) copolymer
(Elsevier Ltd, 2025) Ramoroka, Morongwa E; Tesfay, Hayelom H; Ekwere, Precious; Mokwebo, Kefilwe V; John-Denk, Vivian S; Iwuoha, Emmanuel I.
End-functionalization of polymers and synthesis of copolymers has been reported to be an effective method in tuning intermolecular interactions and electronic energy levels, which is extremely vital for improving the power conversion efficiency (PCE) of organic photovoltaic cells (OPVs). In this work, in-situ synthesis of novel dendritic poly(propylene imine) tetra(salicylaldimine)-co-poly(3-hexylthiophene-2,5-diyl) (P3HT-PSL) copolymer by Grignard metathesis is reported. Prior to performing Grignard metathesis, the poly(propylene imine) tetra(salicylaldimine) (PPI-SL) dendritic core material was synthesized using Schiff base condensation. It is noteworthy that this Grignard metathesis has never been used to grow a linear polymer chain on the four branches of dendritic core material. The properties of synthesized PPI-SL and P3HT-PSL were studied by Fourier-transform infrared (FTIR), small angle X-rays scattering (SAXS), thermal gravimetric analysis (TGA), nuclear magnetic resonance (NMR), ultraviolet–visible spectroscopy (UV–Vis), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and cyclic voltammetry (CV). Effect of poly(3-hexylthiophene-2,5-diyl) (P3HT) chains on the PPI-SL branches were investigated. The formation of P3HT-PSL was confirmed by NMR, FTIR, TGA, and UV–Vis spectroscopy. Synthesized materials were used as donor materials for OPVs and champion PCE of 0.24 % was achieved for P3HT-PSL based OPV. This work uncovers a new avenue for synthesis of organic donor materials for use in OPVs.
Multiscale dual-network cellulose hydrogel electrolytes for dendrite-free Zn anode
(KeAi Communications Co., 2026) Iwuoha, Emmanuel; Lang, Aoxue; Liang, Zhiying
Aqueous zinc-ion batteries (AZIBs) have emerged as promising energy storage systems owing to their high safety, low cost, and environmental friendliness. However, their practical application faces critical challenges, including the formation of Zn dendrites and the occurrence of parasitic side reactions. These phenomena not only hinder ion transport kinetics but also cause rapid capacity decay and potential battery failure. To address these limitations, we developed a sustainable double-crosslinked cellulose hydrogel electrolyte by integrating micron-sized cellulose and cellulose nanofibers (CNFs). The hydrogel electrolyte, constructed from cellulose components with distinct size scales, exhibits a well-organized hierarchical porous network structure, which significantly facilitates the migration of zinc ions. Specifically, nanocellulose serves as a reinforcing filler that enhances the mechanical strength of the dual-network electrolyte, thereby inhibiting Zn dendrite growth. Additionally, abundant carboxyl polar functional groups were also introduced as high-affinity Zn2+ binding sites to mitigate side reactions. Consequently, the assembled Zn//Zn symmetric cells with this electrolyte demonstrate superior cycling stability exceeding 1100 h at current density of 0.5 mA/cm2, along with a high-capacity retention of 79.9% after 1000 cycles in the Zn//V2O5 battery. Furthermore, this cellulose hydrogel electrolyte is easily accessible and biodegradable, paving the way for the scalable production of high-performance and environmentally friendly energy storage devices.
Size engineering of Ni nanoparticles via dual templates to enhance zinc-Iodine batteries
(American Chemical Society, 2025) Iwuoha, Emmanuel I; Huang, Wei; Lian, Zheng
Zinc-iodine (Zn-I2) batteries have received widespread attention due to their higher safety, rich resources, and eco-friendly features and show a promising potential for large-scale energy storage. Nevertheless, challenges such as the shuttle effect of polyiodides and sluggish redox kinetics of iodine species during charge and discharge processes hinder their development. This work reports an effective strategy to improve the electrochemical performance of Zn-I2 batteries through the size engineering of nickel nanoparticles on biomass carbon. In situ UV and in situ Raman spectroscopies reveal that the dual-template size engineering strategy enables the catalyst to provide more active sites for adsorption and catalysis of iodine species, thereby enhancing the adsorption capacity of iodine species and accelerating the kinetics of I-/I2 redox conversion reaction. The shuttle effect of polyiodides is also significantly inhibited. Consequently, Zn-I2 batteries with the size-reduced catalyst as the iodine host cathode exhibit superior rate performance, low potential polarization, and long cycle life
Pt- and Ru-decorated metal organic framework as a trifunctional material for water electrolysis and hydrogen fuel cell applications
(Springer Science and Business Media B.V., 2026) Ramohlola, Kabelo E.; Monama, Gobeng R; Mothlathlo, Terrence
The development of efficient hydrogen fuel cell (HFC) and water-splitting electrocatalysts was considered critical for advancing clean energy technologies. In this study, platinum (Pt) and ruthenium (Ru) were incorporated into copper zeolitic imidazolate framework (CuZIF) using an electroless plating method. Comprehensive characterization through Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy confirmed the successful synthesis of pristine CuZIF and the metallic-incorporated Pt@CuZIF and Ru@CuZIF. Electrochemical measurements were carried out in 0.1 M potassium hydroxide (KOH) to evaluate the catalytic activity of the prepared materials in water electrolysis for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), as well as in HFC testing. Pt@CuZIF demonstrated enhanced catalytic activity for both HER and OER, with Tafel slopes of 118 and 118.5 mV dec−1, respectively, suggesting a Volmer–Heyrovsky mechanism, and overpotentials of 345 and 474 mV. Electrochemical impedance spectroscopy (EIS) further revealed that both HER and OER benefited from Pt@CuZIF due to its low charge transfer resistance and high capacitance value. HFC measurements showed that Pt@CuZIF exhibited excellent performance and stability, with a discharge voltage of 0.13 V, an energy density of 68.42 Wh kg−1, and a power density of 205.26 W kg−1. In comparison, Ru@CuZIF exhibited a discharge voltage of 0.17 V, an energy density of 90.91 Wh kg−1, and a power density of 272.73 W kg−1. Overall, Pt@CuZIF was considered the most promising material for application in both water electrolysis and HFCs.
Integration and characterization of synthetic biodegradable polymer (PVA) with graphite oxide (GO) for performance assessment in sustainable electrochemical devices
(Springer, 2025) Mishra, Ajay Kumar; Asthana, Nidhi; Khan, Ubaid Ahmad
In recent years, the demand for sustainable materials in electrochemical devices has driven the exploration of innovative composites. This study focuses on the integration and characterization of synthetic biodegradable polymer polyvinyl alcohol (PVA) with graphite oxide (GO) to evaluate their performance in sustainable electrochemical applications. PVA, known for its biodegradability and biocompatibility, was combined with GO to leverage its excellent electrical conductivity and large surface area. Microbial fuel cells (MFCs) represent a promising electrochemical biosynthesis technology that harnesses the enzymatic activities using microbes to produce energy from organic substrates. This renewable energy approach relies on the synergistic interaction between electrochemically active bacteria and electrode materials to facilitate electron transfer and power generation. Applications of MFCs range from wastewater treatment to sustainable power generation in remote or resource-limited settings. This study explores recent advances in MFC technology, challenges in scaling up for practical applications, and prospects for integrating MFCs into renewable energy strategies. The nano composite membrane was evaluated for structural, morphological, crystalline, and thermal properties by using Fourier Transform Infrared Spectroscopic (FTIR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and UV- visible spectroscopy. Additionally, the biodegradability of the composite was assessed, confirming that it maintains its environmental benefits while offering improved performance for potential applications in sustainable energy storage and conversion devices. This work provides a promising avenue for the development of eco-friendly electrochemical devices with optimized performance characteristics.
Aptamer-driven biosensor technology for the quantitative analysis of C-reactive protein
(John Wiley and Sons Inc, 2025) Oranzie, Marlon; January, Jaymi L; Sanga, Nelia A.; Leve, Zandile D; Mini, Sixolile; Cupido, Candice; Douman, Samantha F; Iwuoha, Emmanuel I.
C-reactive protein (CRP) is a widely recognized biomarker for early myocardial infarction (MI) detection, released into the bloodstream during heart inflammation. Traditional assays for CRP detection, like ELISA and immunoradiometric assays, are costly, time-consuming, and require large sample volumes. Aptasensors are becoming increasingly popular for MI diagnosis due to their affordability, simplicity, and potential for point-of-care use. In this study, an electrochemical aptasensor incorporating mercaptosuccinic acid-capped nickel selenide quantum dots (MSA-NiSe2 QD) were developed for CRP detection. The amine-modified aptamer was immobilized on the MSA-NiSe2 QD using EDC/NHS coupling chemistry. Chronocoulometric measurements showed high selectivity towards CRP in phosphate buffer, with a linear range of 10–110 pg/mL and a detection limit of 2.80 pg/mL. Cross-reactivity experiments confirmed the aptasensor's high selectivity for CRP. Testing in human serum samples demonstrated recovery rates of 94–100.5 %, indicating its suitability for clinical diagnostics. Validation studies with a commercial CRP ELISA kit showed the aptasensor's superior sensitivity in both physiological buffer and human serum.
Isoprene emissions, oxidation chemistry and environmental impacts
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Shallcross, Dudley; Khan, Md Anwar Hossain; Holland, Rayne
Isoprene emissions can affect the oxidizing capacity of the atmosphere and are likely to increase with an increase in the world’s biomass. The emission of isoprene is strongest in tropical forested regions, suggesting a major portion of tropospheric chemistry occurs in the tropics. As well as deforestation and reforestation having a direct impact on the world’s climate through land cover, there is also an indirect environmental impact (e.g., global warming, air pollution) through the resulting change in isoprene emissions. Previously, incomplete understanding of isoprene oxidation chemistry caused a model-measurement breakdown for concentrations of HOx radicals observed over certain low-NOx regions, such as the pristine Amazon rainforest. Over the last decade, however, understanding of isoprene oxidation chemistry has been vastly improved. Numerous research studies have provided evidence for the involvement of 1,6-H and 1,5-H shift reactions in the isoprene oxidation mechanism, which increases the level of HOx recycling that occurs. As well as helping to reduce the model-measurement breakdown observed, the updated isoprene oxidation mechanism affects the tropospheric burdens of other species, including carbon monoxide (CO), methane (CH4), ozone (O3), organic peroxides (ROOH), secondary organic aerosol (SOA), and organic nitrates (RONO2). There are still gaps in the understanding of the impacts and oxidation chemistry of isoprene emissions, which this literature review identifies and discusses. In the future, there is still much scope for further research, including modeling future reforestation scenarios with isoprene emissions and their impacts on both global and regional scales.
A Pollutant’s tale: an interactive talk on the chemistry of the earth’s climate and its response to pollutants
(American Chemical Society, 2025) Davies-Coleman, Michael T; Shallcross, Dudley E.; Harrison, Timothy G
A Pollutant’s Tale and its primary school version, Gases in the Air, are two talks that have been developed and modified over the last ca. 18 years, that provide audiences from approximately 4-90 years old with the background to the composition of the Earth’s lower atmosphere, the Earth’s climate, and the impact of air pollution. In this article, we describe the content of the talks and provide videos of each experiment individually as well as a recorded performance of both talks to an empty auditorium. In this article, we discuss ways that the talk can be further developed and its impact on audiences.
Constructing pentagonal topological defects in carbon aerogels for flexible zinc-air batteries
(John Wiley and Sons Inc, 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.
Inactivation of cyclotella meneghiniana to prepare biochar by in-liquid pulsed discharge plasma
(Elsevier Ltd, 2025) Massima Mouele, Emile Salomon; Petrik, Leslie Felicia; Bladergroen, Bernard Jan
The large-scale outbreaks of harmful algal blooms continue to impact river and lake ecosystems. Converting harmful algal blooms into algal biochar presents a novel approach. This work investigates the inactivation of Cyclotella meneghiniana (the dominant species in diatom blooms) to prepare biochar by in-liquid pulsed discharge plasma (LPDP). Under the conditions of a peak voltage of 30 kV and an electrode spacing of 7 mm, a 100 % inactivation ratio can be achieved within 20 min plasma treatment. The multiple physical and chemical effects generated by in-liquid pulsed discharge cause the cell structure destruction, chlorophyll-a content reduction, enzyme activity decrease, and malondialdehyde oxidative degradation leading to algal inactivation and biochar production. The obtained algal biochar has the advantages of a rich carbon content and a stable structure. This work provides a new technological option for resource utilization of algal blooms.
Balancing yields and sustainability: an eco-friendly approach to losartan synthesis using green palladium nanoparticles
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Antunes, Edith M.; Adegoke, Yusuf Adeyemi; Mgwigwi, Sinazo; Malan, Sarel F.; Beukes, Denzil R.
This study presents a sustainable, environmentally friendly synthetic route for the production of key intermediates in losartan using palladium nanoparticles (PdNPs) derived from a brown seaweed, Sargassum incisifolium, as a recyclable nanocatalyst. A key intermediate, biaryl, was synthesized with an excellent yield (98%) via Suzuki–Miyaura coupling between 2-bromobenzonitrile and 4-methylphenylboronic acid, catalyzed using bio-derived PdNPs under mild conditions. Subsequent bromination using N-bromosuccinimide (NBS) under LED light, followed by imidazole coupling and tetrazole ring formation, allowed for the production of losartan with an overall yield of 27%. The PdNP catalyst exhibited high stability and recyclability, as well as strong catalytic activity, even at lower loadings, and nitrosamine formation was not detected. While the overall yield was lower than that of traditional industrial methods, this was due to the deliberate avoidance of the use of toxic reagents, hazardous solvents, and protection/deprotection steps commonly used in conventional routes. This trade-off marks a shift in pharmaceutical process development, where environmental and safety considerations are increasingly prioritized in line with green chemistry and regulatory frameworks. This study provides a foundation for green scaling up strategies, incorporating sustainability principles into drug synthesis.
Inactivation of Cyclotella meneghiniana to prepare biochar by in-liquid pulsed discharge plasma
(Elsevier Ltd, 2025) Massima Mouele, Emile Salomon; Petrik, Leslie Felicia; Bladergroen, Bernard Jan
The large-scale outbreaks of harmful algal blooms continue to impact river and lake ecosystems. Converting harmful algal blooms into algal biochar presents a novel approach. This work investigates the inactivation of Cyclotella meneghiniana (the dominant species in diatom blooms) to prepare biochar by in-liquid pulsed discharge plasma (LPDP). Under the conditions of a peak voltage of 30 kV and an electrode spacing of 7 mm, a 100 % inactivation ratio can be achieved within 20 min plasma treatment. The multiple physical and chemical effects generated by in-liquid pulsed discharge cause the cell structure destruction, chlorophyll-a content reduction, enzyme activity decrease, and malondialdehyde oxidative degradation leading to algal inactivation and biochar production. The obtained algal biochar has the advantages of a rich carbon content and a stable structure. This work provides a new technological option for resource utilization of algal blooms.
Multifunctional metal oxides synthesized via a solvo-hydrothermal process for photocatalytic degradation of organic dye and bacteria in wastewater
(Elsevier B.V, 2025) Mouele, Emile Salomon Massima; Mukaba, Jean-Luc; Petrik, Leslie; Ameh, Alechine Emmanuel; Bladergroen, Bernard; Muya, Francis
The persistent occurrence of textile industrial dyestuff in water bodies has continuously threatened aquatic life and public health, requiring effective remediation. This study explores the solvo-hydrothermal synthesis of Ag2O, Fe2O3, AgFe2O3, TiO2, Ag-TiO2, Fe-TiO2, and AgFe-TiO2 catalysts. Various techniques, including SEM-EDS, FTIR, XRD, BET, TGA, and XPS characterized the as-prepared metal oxide (MO) catalysts. The multi-functionality of the catalysts was assessed on the degradation of Congo red dye and the inhibition of gram-positive B. subtilis in simulated wastewater. SEM analysis shows that MOs mostly appeared in granular morphologies except for Fe₂O₃, which comprised elongated grains, and showed that both Ag and Fe were successfully doped into the TiO₂ framework. The XRD survey revealed that Fe₂O₃ and TiO₂ were abundant in hematite and anatase phases. The BET findings indicated that the MOs are fine mesoporous particles, with TiO₂ showing the highest surface area of 83 m²/g, followed by 63, 28.27, and 24.03 m²/g for AgFe-TiO₂, AgFe₂O₃, and Ag-TiO₂, respectively. The antibacterial assays showed that Ag-TiO₂ and AgFe₂O₃ inhibited 58 % and 64 % of B. subtilis, correspondingly. The highest removals 98 and 99.99 % of Congo red (CR) dye were achieved with AgFe₂O₃ and TiO₂ after 5 h of irradiation time. At optimum conditions, AgFe₂O₃ and TiO₂ performed well and reached complete degradation up to 3 cycles. The outcomes of this study show that the multifunctional metal oxides produced via the solvohydrothermal method are thermally stable and can effectively be used for the simultaneous degradation of organic dye and disinfection of bacterial-polluted water
N-doped activated carbon derived from water hyacinth for ultra-stable metal-free bifunctional electrode for zinc-air battery
(Chemical Society of Ethiopia, 2025) Iwuoha, Emmanuel Iheanyichukwu; Ergete, Assegid; Huang, Yongfa
Activated N-doped carbon derived from water hyacinth leaves (WHL) was prepared and investigated as metal-free bi-functional catalyst for oxygen reduction and evolution (ORR/OER) in zinc-air batteries (ZABs). Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) methods were used to examine the morphology, elemental composition and the specific surface area of the samples, respectively. Linear sweep voltammetry (LSV) at rotating disk electrodes (RDEs) and rotating ring-disk electrodes (RRDEs) were employed to characterize the electrocatalytic activities. The electrochemical studies reveal that N-doped porous carbon from N-WHLs exhibited remarkable electrocatalytic activity for ORR, with an onset potential of 0.95 V and half-wave potential of 0.88 V comparable to commercial Pt/C catalyst. It also displays promising activity towards OER, with an overall potential of 1.86 V versus RHE to reach a current density of 10 mAcm, resulting in an oxygen electrode activity (OEA) value of 0.98 V. The percentage of hydrogen peroxide produced was significantly low, with average electron transfer number value of 3.94 at 0.8 V for N-WHL. Furthermore, the ZAB using N-WHL catalysts as an air cathode displayed a power density of 84 mW cm−2 and superior stability over 450 hours.
Characterization and cytotoxicity of nanoceria phytosynthesized using Eucalyptus camaldulensis bark extract
(Elsevier B.V., 2025) Aucamp, Marique; Abedi Tameh, Fatemeh; Ahmed Mohamed, Hamza Elsayed
Cancer, a complex group of diseases characterized by uncontrolled cell growth, poses a significant global health risk. In the context of the high occurrence of breast cancer (BC) in women, conventional chemotherapeutic agents, although effective, frequently bring about challenges such as resistance and recurrence. Nanotechnology is emerging as a promising approach, with attention focused on cerium oxide nanoparticles (CNPs). CNPs possess distinctive characteristics such as antioxidant activity, the ability to transition between Ce3+ and Ce4+ oxidation states, and biocompatibility with living systems. This study introduces a novel phytosynthesis method using Eucalyptus camaldulensis bark extract to synthesize CNPs, emphasizing environmentally friendly methods. Characterization techniques including Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), Diffuse Reflectance (DR) were used to elemental, structural, and morphological properties of synthesized CNPs. Results have shown the successful synthesis of CNPs having cubic fluorite structure with a space group of Fm3m (225) and a crystallite size of 11.2 nm based on XRD characterization. FTIR and EDX have confirmed the elemental analysis of CNPs and the presence of extracted biomolecules during the synthesis process. SEM and TEM images revealed the morphology of the phytosynthesized CNPs as sphere-like, with a size of 2 to 10 nm. Finally, cytotoxicity by MTT assay and uptake of these CNPs on MCF-7 cells demonstrates successful uptake and their potential to inhibit these cancerous cells. The protective effect of CNPs on normal cells was further investigated using a ROS assay on the MCF10A cell line. Furthermore, the catalase-mimic (CAT-mimic) activity of phytosynthesized CNPs was assessed by a commercial CAT-mimic kit assay.

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