Research Articles (Chemistry)

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

Browse

Now showing 1 - 20 of 369

The potential of hydrothermally synthesized MoO3 and Cr doped MoO3 nanoparticles for electrochemical energy storage applications
(Elsevier B.V., 2026) Iwuoha, Emmanuel Iheanyichukwu; Ogirima, Ibrahim Yakubu; Geremu, Tadele
Molybdenum trioxide (MoO3) based electrode materials have generated interest for electrochemical energy storage application due to their exceptional optical and chemical properties. However, MoO3 suffers from some drawbacks such as weak electrical conductivity and instability which have necessitated new and innovative approaches to overcome these challenges. In this work, we doped MoO3 with chromium (Cr) with the aim of enhancing its conductivity and further studied the effect of hydrothermal treatment time on its physicochemical and electrochemical properties. The x-ray diffraction results indicate that the materials exhibited an orthorhombic crystal structure. The electrochemical results show that the Cr doped MoO3 obtained after 12 h of hydrothermal treatment (Cr@MoO3-12h) gave the highest specific capacitance of 465 Fg−1, much higher than the other chromium doped MoO3 and the undoped MoO3 nanoparticles at all the hydrothermal treatment times considered. The Cr@MoO3-12h electrode also showed the highest stability retaining almost 89% of its initial specific capacitance over charge-discharge cycles 5000 cycles at 1 A g−1. This suggests that chromium doping and maximizing the hydrothermal treatment duration improved the electrochemical performance of the molybdenum trioxide nanoparticles.
Label-free novel platform for electrochemical detection of E. coli in tap water
(Elsevier B.V, 2026) Shahzad, Suniya; Iftikhar, Faiza Jan; Khan, Asad Ullah; Ullah, Riaz; Iwuoha, Emmanuel; Shah, Afza; Khan, Raees; Saqib, Ahmad Nauman Shah
Waterborne infections such as hepatitis, diarrhea, encephalitis etc., are caused by viruses and remain the main cause of fatality worldwide. Diarrhea alone has led to 2.2 million deaths per year worldwide. These viruses are mostly transferred by fecal-oral passage, causing waterborne diseases. The World Health Organization (WHO) estimates that waterborne pathogens contribute to 4% of the diseases worldwide which highlights a critical need to search for efficient methods to detect these pathogens in a robust and rapid manner. Thus, by employing a sensitive platform that can improve the limit of detection (LOD) by manifolds, the aim is to detect the virus timely and thus reduce disease prevalence. Here Zeolite imidazolate framework (ZIF) a type of MOFs with bimetallic transition elements, has been used to improve electrocatalytic performance and ability to detect pathogens without the need of using labels such as enzymes, fluorescent tags etc. We report an ultrasensitive electrochemical sensor based on NiCoZIF/CNTs to detect low concentrations of E.Coli in tap water where the LOD is reported as 0.37 CFU/mL. The sensing platform has also been morphologically and electrochemically studied. This sensor has clear practical applications such as public health, water quality monitoring and food safety.
Field-based assessment of selected pharmaceuticals, pesticides and sediment metals using macrofauna and nematode communities in False Bay, South Africa
(Elsevier Ltd, 2026) Mazeka, Buyani; Tshingana-Bali, Bomikazi; Murgatroyd, Olivia; Moser, Justin; Ojemaye, Cecilia Y.; Petrik, Leslie F; Karenyi, Natasha
False Bay supports high biodiversity but is increasingly subjected to anthropogenic pressures, including urbanisation and harbour activities. This study aimed to (1) quantify selected pharmaceuticals (e.g., acetaminophen, carbamazepine, diclofenac), herbicides (atrazine and metolachlor) and metals (Cu, Fe, Mn, Pb and Zn), (2) examine their spatial distribution, and (3) assess their potential effects on benthic assemblages. Sampling was conducted between 18 April and 14 June 2021 across 19 stations. Pharmaceuticals and herbicides were widely detected in seawater (LDL – 1.1 ng/L) and sediments (LDL – 54.6 ng/g), with higher concentrations in sediments, indicating their role as long-term contaminant reservoirs. Spatial patterns revealed localised enrichment near wastewater discharge zones and urbanised areas. Metal concentrations (1.6–7732 μg/g) were similarly elevated in anthropogenically influenced areas. However, risk quotient (RQ) remained <0.1 and metal concentrations were below ERL thresholds, suggesting a low potential of acute biological effects. Benthic assemblages were diverse and typical of coastal sandy environments, with no significant relationships detected between contaminant concentrations and community metrics. Nematode indices (MI and ITD) indicated good to high ecological quality. The single sampling design and family-level taxonomic resolution may have limited the detection of sub-lethal, chronic or species-specific responses. While contaminants are widespread and accumulate in sediments, their current concentrations are unlikely to cause acute ecological impacts benthos. However, chronic effects and the presence of unmonitored contaminants cannot be excluded. Long-term monitoring and higher taxonomic resolution are recommended to better understand and access cumulative ecological risks.
Towards regulatory readiness: evaluating frameworks for microplastic health risk assessment
(Springer Nature, 2026) Christopher, Emily A.; Bouwmeester, Hans; Christopher, Emily A.; Coffin, Scott; Haase, Andrea; Lane, Taylor; Legler, Juliette
Micro- and nanoplastic particles (MNPs) have emerged as pollutants of high public concern. Assessing and managing the risks of these particles remains challenging for several reasons. A long-term goal is to establish a comprehensive risk-governance framework that includes risk framing, scientifically sound risk assessment that accounts for human and environmental safety, evaluation, and risk management/decision making. A realistic short-term goal is to develop a comprehensive human health risk assessment framework (RAF). Very recently, RAFs for evaluating the human-health risks of MNPs have become available; however, comparative analyses of these frameworks are lacking. Here, we discuss six established frameworks to assess their technological and regulatory readiness. We begin by proposing nine technical criteria that a risk-assessment framework should meet to inform policy and action. These include the degree of quantifiability of outputs; the provision for systematic evaluation of the quality of input data; the consistency between exposure and effect data with respect to underlying mechanisms; the extent to which the complexity and diversity of environmentally realistic microplastics are addressed; readiness for integration into existing regulatory approaches; and the extent of real-world implementation to date. We discuss the specific strengths of each framework and recommend combining them into a single overarching framework that integrates these strengths.
Meroterpenoids and fucoxanthin from the brown seaweed sargassum incisifolium: solid lipid nanoparticle delivery, physicochemical characterization, and antimicrobial activity
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Witness, Sibiya; Samsodien, Mogammad L.; Vreulink, Jo-Marie; Le Roes-Hill, Marilize; Bolton, John J.; Beukes, Denzil R.; Antunes, Edith
Marine macroalgae are a rich source of bioactive natural products, although the application of many lipophilic compounds is limited by poor aqueous solubility and instability. This study investigated metabolites isolated from the South African brown seaweed Sargassum incisifolium and evaluated a solid lipid nanoparticle (SLN) system to improve their physicochemical properties and enable bioactivity studies. Five metabolites, including one previously unreported derivative and four known metabolites (including fucoxanthin), were isolated and characterized using standard chromatographic and spectroscopic techniques. SLNs composed of stearic acid and Poloxamer 188 were prepared via hot homogenization and characterized using dynamic light scattering, scanning electron microscopy, thermogravimetric analysis, and NMR, which confirmed the efficient encapsulation of the lipophilic compounds. Antimicrobial activity against clinically relevant bacterial and fungal pathogens was evaluated using a resazurin-based microdilution assay, with results expressed as percentage growth relative to untreated controls. The pure compounds exhibited moderate, concentration-dependent activity, while the SLN formulations improved dispersibility, and in several cases, reduced % growth or produced more consistent responses, particularly against Gram-positive bacteria and Candida auris. Although activity remained lower than that of conventional antimicrobials, these findings demonstrate that SLN-based delivery enables functional evaluation of hydrophobic marine metabolites and supports further development of Sargassum-derived natural products.
Synthesis of BEA zeolite from coal fly ash nano-silica extract: application in CO2 adsorption
(Elsevier B.V., 2026) Ameh, Alechine; Mukaba, Jean-Luc; Pokpas, Keagan; Petrik, Leslie
This study demonstrates a circular economy approach to carbon dioxide sorption by re-purposing coal fly ash (CFA) into BEA zeolite using CFA-derived nano-silica and aluminum precursors via hydrothermal synthesis. The XRD patterns, with characteristic peaks at 15° and 37° 2θ, and SEM images both confirmed the complete transformation of the spherical-shaped CFA particles into amorphous nano-silica materials with particle sizes less than 100 nm. The absence of amorphous phases and the formation of high-intensity peaks at 7.8° and 22.8° 2θ further indicated the production of a highly crystalline BEA zeolite, obtained after hydrothermal synthesis durations between 10 and 72 h. The conversion of amorphous nano-silica into BEA zeolites significantly enhanced the surface area from 54 m2/g to 547 m2/g. The as-synthesized BEA zeolites exhibit a spheroidal shape with crystal dimensions ranging from 190 to 450 nm, solely controlled by the molar ratio of H2O/Si during hydrothermal synthesis. CO2 sorption capacity upon the transformation of nano-silica into BEA zeolites rose from 0.91 to 3.24 mmol/g for low-temperature evaluation (≈0 °C, 1.2 bar). The BEA zeolite adsorbent retained structural integrity with only ∼9% performance loss after ten adsorption–desorption cycles. These outcomes highlight CFA-derived BEA zeolite as a robust, scalable, and resource-efficient adsorbent for CO2 capture.
Silica derived from rice husk waste as anode material for lithium-ion battery: a comprehensive study
(Elsevier B.V., 2026) Iwuoha, Emmanuel Iheanyichukwu; Nzereogu, Paul; Omah, Augustine Dinobi
This research investigates the synthesis and characterization of silica extracted from rice husks sourced from Adani in Enugu State, Nigeria, and its application in lithium-ion batteries. In this work, two methodologies for extracting SiO2 from rice husk were explored: rice husk pre-treatment process (acid leaching) and rice husk post-treatment process (alkaline digestion). The rice husks underwent acid leaching with 10 % HCl, followed by calcination at temperatures ranging from 500°C to 800°C. The sample post-treatment involved alkaline digestion using a 1 N sodium hydroxide solution. Results from structural analysis showed a progressive increase in purity and amorphous properties of silica up to a calcination temperature of 700°C. At 800°C, crystalline forms of silica, such as cristobalite and tridymite, were observed. The post-treated samples, especially those calcined at 700°C (PT700), exhibited comparative higher purity. Electrochemical studies were carried out using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS), and the results show that the post treated rice husk that was calcined at 700 °C (PT700) had the highest specific capacity of 913 mAh g⁻¹ at a current density of 100 mA g−1 and retained ∼89 % of this capacity after 1000 charge-discharge cycles. The energy density of the PT700 sample was 302 Wh kg⁻¹, demonstrating its potential as a viable alternative to graphite in lithium-ion battery applications. The study concludes that silica extracted from rice husks is a sustainable and efficient material for use in energy storage devices, offering significant advantages in terms of reactivity, surface area, and electrochemical performance.
Green synthesis and application of biochar derived from alien vegetation wood for proton exchange membrane fuel cells
(John Wiley and Sons Inc, 2025) Sobekwa, Alunge Gift
Invasive alien vegetation brought about by various human activities has grown to be a significant threat to the ecosystem and its diversity; therefore, control strategies to combat this threat are being explored. This review aims to investigate the prospect of using biochar specifically from alien vegetation as a support material for the proton exchange membrane (PEM) fuel cell electrocatalyst, highlighting the need to move to green energy and invest in Eco conservation. The use of biochar derived from alien vegetation as carbon support for the platinum (Pt) electrocatalyst for PEM fuel cells is an interesting field that is slowly gaining momentum. Biochar has the potential to be used as a carbon support due to its high specific surface, area, and intrinsic property needed for an electrocatalyst support. The current widely used electrocatalyst, which is Pt supported on carbon black, has shown to suffer from corrosion which weakens the bond between the support and the Pt nanoparticles, leading to instability and resistance; therefore, alternative supports are needed also to decrease the Pt loading as it is expensive. The focus of this review is on the benefits and prospects of these cheap green resources in increasing efforts to conserve the environment.
Development of an efficient supercapacitor using hydrothermally synthesized nickel sulfide
(Springer, 2025) Sindhu, Sarita
The current research explores the hydrothermal synthesis of nickel sulfide over a temperature range of 120–180°C, with advanced characterization used to assess features influencing its electrochemical behavior in supercapacitor applications. The temperature variation in the synthesis process results in a pure β-NiS phase at lower temperatures, while at higher temperatures, up to 180°C, mixed phases were confirmed by XRD, with FTIR revealing the characteristic vibrational modes of nickel sulfide. FE-SEM micrographs show a morphological transition from nanoflakes to microflowers to agglomerated flakes, influencing the specific surface area (10.45 m2g⁻1), for the sample synthesized at 140 °C, as determined by BET analysis. The electrochemical analysis of the fabricated electrodes was conducted in different electrolytes, revealing that NiS synthesized at 140°C achieves the highest capacitance of 294 Fg⁻1 at 1 A g⁻1 in KOH, establishing it as a promising candidate for supercapacitor applications.
Electrochemical performance of ZnCo2O4: versatility in applications
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Sitole, Soyama; Ross, Natasha; Bilibana, Mawethu Pascoe
Zinc cobaltite (ZnCo2O4) is a ternary metal oxide found in spinel with promising properties for various applications. Optimizing its catalytic activity requires an understanding of its electrochemical behavior. The electrochemical properties of ZnCo2O4 have significantly improved due to recent developments in nanostructuring, doping, surface modification, hybridization, structural engineering, and electrochemical activation. These improvements have inspired and motivated researchers by presenting the latest developments in the field. The spinel structure, coupled with the redox properties of cobalt ions, semiconducting characteristics, and electrocatalytic potential, positions ZnCo2O4 as a versatile material for several electrochemical energy storage and conversion systems. This review explores these advancements; the notable properties of ZnCo2O4; and its applications in sensors, batteries, photovoltaics, and supercapacitors.
Green synthesis of crystalline silicon nanoparticles (SiNPs) via magnesiothermic reduction of mesoporous silica extracted from sugarcane bagasse ash (SCBA)
(Elsevier Ltd, 2026) September, Lyle; Seroka, Ntalane; Khotseng, Lindiwe
In this study, crystalline silicon nanoparticles (SiNPs) were successfully produced utilising a low-temperature magnesiothermic reduction method of mesoporous silica nanoparticles (SiO2NPs). Silicon nanoparticles (SiNPs) have gained attention in recent years due to their range of applications and specific properties. However, producing high-purity SiNPs necessitates high-energy production, such as carbothermic reduction at >2000 °C, in addition to the significant pollutants and CO2 emissions generated throughout the process. Thus, there has been an increase in research on extracting SiNPs from various agricultural wastes as a cost-effective source. This study investigates the extraction of SiO2NPs using sol-gel synthesis from sugarcane bagasse ash (SCBA) and resulted in a purity of 94.8% utilising XRF. After magnesiothermic reduction of SiO2NPs at 650 °C, XRD and Raman confirmed the resulting crystalline SiNPs. Furthermore, SEM and TEM were used to investigate the morphology along with BET to determine specific surface area, pore volume, and pore diameter, which resulted in 57.85 m2/g, 0.18 cm3/g, and 12.4 nm, respectively, for the produced SiNPs. Additionally, this study includes the use of a green-sustainable synthesis method to decrease energy usage and attempts to replace toxic counterparts with reagents such as the use of L-cysteine hydrochloride monohydrate and citric acid, while obtaining high-purity SiNPs. SiNPs have a variety of possible applications in new advancements, including energy production like solar photovoltaic cells and energy storage devices, which contribute towards the UN's sustainable development goals (SDG), particularly SDG 7 (Affordable and clean energy) and SDG 13 (Climate Action), as this study exhibits sustainability and increases the potential to reduce biomass waste production.
Adsorption removal of methyl violet dye by α-fe2o3 and aminated α-fe2o3 metal oxide composites synthesized via solvothermal process
(Elsevier Ltd, 2026) Mouele, Emile Salomon Massima; Asemahle, Tupha; Petrik, Leslie F.; Bladergroen, Bernard; Okoh, Anthony Ifeanyi; Okoh, Omobola O.
The discharge of persistent artificial dyes, like the cationic methyl violet (MV) dye from textile industrial sewages, requires the development of efficient, cost-effective, and recyclable adsorbents. This work reports on the synthesis of hematite (α-Fe2O3) and amino-modified α-Fe2O3 via the solvothermal method. The effects of surface amination on the nanomaterials' physicochemical attributes were probed by the adsorption of MV wastewater. Successful amine functionalization was confirmed using FTIR and elemental analyses. SEM analysis revealed porous spherical morphologies with an enhanced surface texture following amination. XRD and TGA confirmed the structural stability and thermal resilience of the nanomaterials. Zeta potential showed that the aminated α-Fe2O3 carried a negative surface charge above pH 3, favoring the cationic dye adsorption. The aminated material exhibited a maximum MV adsorption capacity of 10.21 mg/g with equilibrium data conforming to the Langmuir isotherm (R2 = 0.978) as compared to the Freundlich (R2 = 0.662) and Temkin (R2 = 0.634) isotherms, while kinetics data fitted the pseudo-second-order model (R2 = 0.966). The regeneration of aminated α-Fe2O3 sorbent with 0.4 M HCl favoured reclaim for four successive cycles with a slight decrease in efficiency of about 19%. The study demonstrates that the solvothermally produced α-Fe2O3 is a promising low-cost adsorbent for the removal of organic dyes in wastewater treatment applications.
Non‐thermal plasma‐activated ammonia decomposition for hydrogen production: tuning CeO2 catalyst nanomorphology to enhance performance
(Wiley, 2026) Wu, Xuan; Xu, Shaojun; Bladergroen, Bernard Jan; Xiang, Nianwen; Bladergroen, Bernard Jan; Xiang, Nianwen; Zhang, Cheng; Shao, Tao; Chen, Weijiang; Ding, Lijian
Non‐thermal plasma coupled with catalysts offers a promising route to improve ammonia‐to‐hydrogen conversion efficiency.This study integrates plasma discharge with morphology‐controlled CeO2 nanocrystals (fiber, cuboids‐S, cuboids‐L, nano‐rod,and pyramid) to enhance ammonia decomposition. Among them, CeO2 fiber achieves outstanding ammonia conversionexceeding 99.9% (SIE = 19.8 kJ L−1) without metal additives or external heating, while also demonstrating remarkable long‐term stability. Through combined microscopic, electrical, and Mass Spectrometry‐based transient analysis, it is revealed that thefibrous CeO2 structure increases the surface Ce3+ and oxygen vacancy concentration and provides balanced NH3 adsorption,boosting catalytic activity. Additionally, its favorable dielectric properties enhance plasma discharge and plasma−catalystinteractions. These results demonstrate that tuning catalyst nanostructure is an effective alternative to noble metal doping forefficient plasma‐driven catalysis.
Characterization of ornithobacterium hominis colonization dynamics and interaction with the nasopharyngeal microbiome in a South African birth cohort
(Microbiology Society, 2026) De Allende, Celine C.; Salter, Susannah J.; Brigg, Siobhan Ernan; Boardman, Micaela; Claassen-Weitz, Shantelle; Mwaikono, Kilaza Samson; Workman, Lesley J.; Zar, Heather J.; Nicol, Mark P.; Parkhill, Julian; Dube, Felix S.
Ornithobacterium hominis is a recently described Gram-negative bacterium that colonizes the human nasopharynx and may be associated with poor upper respiratory tract health. Here, we describe the isolation of O. hominis from samples collected from a South African birth cohort, creating the first archive of cultured strains of the species from Africa. Sequenced genomes from this archive reveal that South African O. hominis is more similar to Australian strains than those from Southeast Asia and that it may share genes with other members of the microbiome that are relevant for virulence, colonization and antibiotic resistance. Leveraging existing microbiome data from the cohort, O. hominis was found to be closely associated with bacterial co-colonizers that are rare in non-carrier individuals, including Suttonella, Rappaport, Helcococcus, Lwoffella, Moraxella and Gracilibacteria. Their collective acquisition has a significant impact on the diversity of nasopharyngeal communities that contain O. hominis. Individuals who have not yet acquired O. hominis have a higher abundance of Lwoffella lincolnii than individuals who never acquire O. hominis, suggesting that this could be a precursor state for successful colonization.
Investigation of Pd-Ti multilayer thin films for hydrogen storage applications
(Elsevier B.V, 2026) Rampai, Mojesi Monica; Nemukula, Enos; Mashiloane, Kamogelo Joseph
This study investigates the hydrogen storage properties of Pd/Ti/Pd/Ti multilayer thin films fabricated using an electron-beam evaporator. Rutherford backscattering spectrometry (RBS) was used for elemental composition and thickness analysis. The hydrogen profiling was performed using elastic recoil detection analysis (ERDA). The structural and morphological characterisations were performed using X-ray diffraction (XRD) and atomic force microscopy (AFM). The results revealed that the Pd layers were pure and free of any contamination, whereas the Ti layers were contaminated with oxygen, up to 63 at.%. Hydrogen absorption peaked at 200°C with a total concentration of 51.3 at.%.∼ 1.9 wt.%., but declined at higher temperatures. XRD confirmed the formation of TiH2 at elevated temperatures, while AFM showed a correlation between surface roughness and the hydrogen absorption
Adsorption of rees from aqueous solutions using modified polystyrene- di (2-ethylhexyl) phosphoric acid electrospun nanofibers
(Elsevier B.V., 2026) Mukaba, Jean-Luc; Mouele, Emile Salomon Massima; Ameh, Alechine Emmanuel; Eze, Chucks Paul; Petrik, Leslie; Tshentu, Zenixole R.
The recovery and separation of rare earth elements (REEs) is an emerging area of the current research due to their applications in modern technology and because both accessible and cost-effective approaches are required. In this study, polystyrene (PS) grafted with di(2-ethylhexyl) phosphoric acid (D2EHPA) ligand was fabricated via the electrospinning technique. The electrospun PS/DEHPA nanofiber mats were characterised using various techniques such as HR-SEM, TGA, FTIR, XRD, BET and ICP-OES. The fabricated electrospun nanofiber materials were then used for the recovery of Nd and Sm metal ions from the aqueous solutions. The supreme sorption uptake of Nd3+ and Sm3+was ˃ 100 mg/g at pH 4.0, reached at an equilibrium time of 70 min with the modified PS/DEHPA nanofiber mats. The recovery of Nd3+ and Sm3+was best described by the Langmuir isotherm and followed a pseudo second-order kinetic model. Thermodynamic data, ΔG°, Δ H° and ΔS° suggest that Nd3+ sorption onto PS/DEHPA was spontaneous and endothermic. The coordination of PS with the D2EHPA ligand occurred via hydrogen bonding while the binding of PS/DEHPA to the metal ion was likely bonded by ionic, covalent or electrostatic interactions. The reusability investigation indicates that the synthesized PS/DEHPA nanofiber mats can withstand up to four successive cycles, and the adsorption and desorption performances were over 60 %. Nd3+ sorption in the presence of interfering Ni2+ and Co2+ metals was 96.82 mg g−1(0.671 mmol g−1), closer to 101.46 mg g−1(0.703 mmolg−1) obtained in a single metal ion solution suggesting a good selectivity of PS/DEHPA fibres towards REEs (Nd3+).
Single-atom-anchored hierarchically nanopores hard carbon toward high-performance sodium storage
(Elsevier B.V., 2026) Iwuoha, Emmanuel; Wang, Q; Zou, Ren
Hard carbon anodes for sodium-ion batteries (SIBs) face a critical challenge in simultaneously achieving high capacity and rapid reaction kinetics, particularly in the low-voltage plateau region, due to the ambiguous storage mechanism and sluggish ion transport. Herein, we demonstrate a one-step metal salt-catalyzed strategy that enables the concurrent construction of hierarchical nanopores and the immobilization of single-atom Zn-N4 sites within hard carbon derived from lignosulfonate biomass. The resulting material achieves a remarkable reversible capacity of 354 mAh/g at 0.02 A/g and outstanding rate capability (238 mAh/g at 3.0 A/g). In situ X-ray diffraction (XRD) and Raman spectroscopy (Raman) spectroscopy elucidate a cooperative layer-insertion/nanopore-filling mechanism governing sodium storage in the plateau region. Furthermore, theoretical simulations reveal that Zn-N4 sites do not dominate the Na-storage behavior alone, but cooperate with the hierarchical pore structure by optimizing the local sodium ions (Na+) adsorption strength and facilitating ion transport. Compared with pure carbon nanopores, Zn-N4 modified nanopores show moderated Na+ binding over the whole pore-size range, indicating a more balanced interaction between Na+ and the carbon framework. This work highlights the advantages of integrating an ordered hard carbon framework with single-atom sites and provides new insights into high-performance sodium storage. The synergistic combination of hierarchical nanopores with single-atom sodium-affinity sites offer a general design paradigm for next-generation sodium-ion battery anodes.
Potential use of metal organic framework composites by recycling 4-nitrophenol in wastewater for electrocatalytic hydrogen production: A waste-to-profit approach
(Elsevier Ltd, 2026) Iwuoha, Emmanuel I.; Maake, Tumisang J.; Ramohlola, Kabelo E.
Development of efficient and sustainable hydrogen evolution reaction (HER) electrocatalyst is crucial for advancing green hydrogen technology. Herein, a waste-to-profit strategy is proposed wherein metal–organic frameworks (Cu-BTC and Cu-BDC) are employed for the removal of 4-nitrophenol (4NP) from wastewater and use the resultant adsorbent–adsorbate composites (Cu-BTC4NP and Cu-BDC4NP) for HER. MOFs were synthesised hydrothermally, and their effective adsorption of 4NP was confirmed through equilibrium and kinetic studies, revealing high adsorption capacities exceeding 500 mg g−1. Linear sweep voltammetry (LSV) revealed that Cu-BDC required low overpotential of 133.99 mV to reach a current density of 10 mA cm−2 compared to the 4NP-loaded composites which exhibited higher overpotentials of 175.54 mV (Cu-BTC4NP) and 203.88 Mv (Cu-BDC4NP). This decline suggests that 4NP adsorption modifies the electronic environment of Cu active sites and may induce framework instability in aqueous media, where hydrolysis of metal–carboxylate bonds is a concern.
Engineering titanium dioxide-reduced graphene oxide nanocomposite for electrooxidation of nitrite as a surrogate for electrochemical sensing of NO2
(Elsevier Ltd, 2026) Leve, Zandile Dennis; Januarie, Kaylin Cleo; January, Jaymi Leigh; Oranzie, Marlon; Sanga, Nelia Abraham; Uhuo, Onyinyechi Vivian; Ross, Natasha; Pokpas, Keagan; Iwuoha, Emmanuel Iheanyichukwu
Nitrogen dioxide (NO2) is a reddish-brown irritating gas characterised by sharp and biting odour. Its detection is imperative as it is harmful to the respiratory system and contributes to the acid rain formation. Aqueous NO2 gas is converted into nitrite (NO2−) ion in solution, which is considered an environmental pollutant with consequential health effects. Oxidation of NO2− has been reported to provide provisional insights for that of NO2 gas in electrolyte. However, detection of NO2− at electrode surface is encountered by difficulty due to high overpotentials. This study presents electrochemical behaviour of a titanium dioxide/reduced graphene oxide-palladium/silver nanocomposite-modified screen-printed carbon electrode (TiO2/rGO-PdAg/SPCE) for the detection of NO2− as a surrogate for NO2 oxidation mechanism in aqueous NaClO4 as electrolyte. Comparative analysis demonstrated superior performance of TiO2/rGO-PdAg/SPCE over bare, TiO2, and TiO2/rGO modified SPCEs due to the synergistic effect of its components. The sensor exhibited a broad detection range of 0.1 – 10 mM and a linear response at 0.1 – 1.4 mM with a limit of detection (LOD) = 1.07 µM NO2− and a sensitivity of 44.38 µA/mM. Simultaneous detection of NO2−and S2O32−demonstrated that the oxidation peak of the former was favoured while the latter was not observed in the investigated potential range. However, adsorption of S2O32− exhibited interference with a decrease in sensitivity to 24.15 µA/mM, which limits the selectivity of the sensor for oxidation of NO2−. Reproducibility exhibited an RSD of 4.18 % at five different electrodes, and stability tests with 74.02 % of peak current retained from initial response for a 12-day period. The recovery of NO2 gas in aqueous medium was studied using calibration curve of NO2−, with average of the triplicate experiments corresponding to 0.4 mM NO2−. These observations present TiO2/rGO-PdAg/SPCE sensor as a potential for reproducible, sensitive, and selective detection of NO2 in environmental monitoring.
Sustained release and efficacy of Kn2-7-loaded chitosan nanoparticles under low pH conditions
(Nature Research, 2026) Phathekile, Bonke; Sibuyi, Nicole Remaliah Samantha; Meyer, Samantha; Madiehe, Madimabe Abram; Okuthe, Emily Grace; Onani, Martin Opiyo; Meyer, Mervin E.
Delivery of antimicrobial peptides to low-pH sites is a significant challenge, and results in reduced treatment efficacy for vaginal infections. Chitosan nanoparticles (CNPs) could be ideal vehicles for drugs to acidic pH environments and sustain their therapeutic effects. CNPs were synthesized using the ionic gelation technique and loaded with Kn2-7 peptide. The CNPs were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, high-resolution transmission and scanning electron microscopes. The stability and antibacterial effects of Kn2-7-loaded CNPs were evaluated at low and normal pH levels. The CNPs had a size distribution of 327–416 nm and a zeta potential of 9.61–23.9 mV. The size distribution (340.2–753.7 nm) and Zeta potential (15.9–67.7 mV) of CNPs changed after loading Kn2-7. The CNPs loading capacity and Kn2-7 entrapment efficiency were 35.6% and 78.3%, respectively. The Kn2-7-CNPs were not stable at low-pH and released Kn2-7 instantly; however, stabilization of Kn2-7-CNPs with poly (acrylic acid) (PAA) and tripolyphosphate (TPP) increased their stability and sustained Kn2-7 release at acidic pH. The Kn2-7-CNPs_1 mg/mL TPP-PAA inhibited the growth of Staphylococcus aureus at pH 3.8 better than the Kn2-7 alone. Therefore, the Kn2-7-CNPs_1mg/mL TPP-PAA could serve as a promising candidate for protecting and delivering drugs in low-pH environments.

Browse

Recent Submissions