Browsing by Author "Malima, Nyemaga Masanje"

Now showing 1 - 7 of 7
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    Alloying normal and inverse spinel (Zn–Co ferrite) nanostructures via direct precursor pyrolysis for enhanced supercapacitance and water splitting
    (Elsevier, 2023) Malima, Nyemaga Masanje; Khan, Malik Dilshad; Choi, Jonghyun; Gupta, Ram K.; Revaprasadu, Neerish
    The nanocrystals comprising of multiple redox-active cations are generally proficient electrocatalysts for renewable and sustainable energy applications. Ferrites have rich redox chemistry and crystallographically, they can be classified into normal spinel structures or inverse spinel structures, depending on the type of occupancy at tetrahedral and octahedral sites. Herein, taking advantage of the simplicity and environmental benignity of the solventless method, a series of mixed inverse and normal spinel nanocatalysts (Co1-xZnxFe2O4 (0 = x ≤ 1)) have been successfully synthesized and tested for supercapacitance and overall water splitting. The p-XRD and EDX analyses confirmed the successful nucleation of CoFe2O4 and ZnFe2O4 to form monophasic Co1-xZnxFe2O4 solid solutions over the entire composition range. The solid solutions with composition Co0·4Zn0·6Fe2O4 demonstrated higher discharge time, indicating higher specific capacitance of the material than other electrode compositions. The Co0·8Zn0·2Fe2O4 showed relatively low overpotentials of 317 mV to afford the current density of 10 mA/cm2 for oxygen evolution reaction (OER), while Co0·6Zn0·4Fe2O4 exhibited an overpotential of 169 mV for hydrogen evolution reaction (HER), outperforming most of the electrocatalysts reported in the literature. More impressively, such solid solutions demonstrated negligible deviation between the first and the 1 k cycles, suggesting high durability for the electrolysis of water.
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    Aquasomes: a novel nanocarrier system for drug delivery
    (Elsevier, 2023) Ayom, Gwaza Eric; Malima, Nyemaga Masanje; Owonubi, Shesan John; Revaprasadu, Neerish
    Aquasomes are three layered self-assembled nanoparticles that are emerging as drug carriers or systems for the delivery of drugs. They are composed of an inner core which is usually coated with a polyhydroxyl carbohydrate and a loaded drug. The solid nanocrystalline inner core provides the structural stability of the aquasomes while the carbohydrate coat shields the loaded drug against dehydration. These self-assembled particles maintain the conformational integrity of the loaded drugs and hence have been exploited as carriers of drugs including insulin, hemoglobin, oxygen, antigens, and antibodies. This system of drug delivery has also been shown to improve the solubility of poorly soluble drugs. This chapter presents aquasomes’ preparation, properties, applications, and potential as drug carriers.
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    Development of bacterial resistant acrylamide-polyvinylpyrrolidone-metal oxide hydrogel nanocomposites
    (Elsevier, 2021) Owonubi, Shesan John; Agwuncha, S.C.; Malima, Nyemaga Masanje; Sadiku, E.R.; Revaprasadu, Neerish
    Fabrication of polymer-based nanocomposites for numerous biomedical applications represents a predominant form of therapeutics for combating microbial and bacterial infections. Herein, we firstly synthesized metal oxide nanoparticles (MONPs) by previously reported precipitation methods. Hydrogel nanocomposites were then prepared by free radical polymerization of a combination of the synthesized MONPs, polyvinylpyrrolidone (PVP) and acrylamide. The hydrogel nanocomposites were characterized by FTIR, XRD and investigated for potential antibacterial protection. FTIR spectra of the prepared hydrogel nanocomposites revealed significant characteristic peaks of the distinctive MONPs within the polymer matrix. XRD micrographs revealed slight shifting of peak positions in nanocomposites; the change in peak intensity, coupled with the observed slight shift in the diffraction peaks of both CuO and ZnO nanoparticles confirmed the successful incorporation of the MONPs into the polymer matrix. The presence of the MONPs, in combination with PVP, displayed a synergistic antibacterial activity, with increasing concentration of the MONPs. The treatment against S.pneumoniae, revealed a zone of inhibition phenomenon which showed zones of PVP-5 > PVP-8 > PVP-6 > PVP-9 > PVP-7. PVP-1, PVP-2, PVP-3, PVP-4 did not show any significant zone of inhibition on treatment due to the quantity of MONPs present. The findings show that the hydrogel nanocomposites are potential topical wound dressing materials for the management of bacterial infections.
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    Development of cost-effective and eco-friendly adsorbent by direct physical activation of Tanzanian Malangali kaolinite for efficient removal of heavy metals
    (Elsevier, 2021) Malima, Nyemaga Masanje; Owonubi, Shesan John; Lugwisha, Esther Hellen; Mwakaboko, Alinanuswe Simon
    The occurrence, toxicity and hazardous nature of heavy metals have prompted researchers to search for affordable and efficient adsorbents for their removal from the environment. Malangali kaolin clay is an abundant and eco-friendly local adsorbent material which can offer sustainable and cost-effective solution towards heavy metal remediation. Raw kaolin clay has the ability to scavenge heavy metals by improvement to its surface chemistry and adsorption capacity through modification. In this study, the feasibility of physically activated Tanzanian Malangali kaolin clay to sequester cobalt and cadmium ions from simulated wastewater was examined under batch process. The physical activation of pristine kaolin clay was carried out by thermal treatment at 300 °C to influence its adsorption efficiency and physicochemical properties. The clay sample was characterized by Fourier Transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), Nitrogen adsorption–desorption and chemical analysis by atomic absorption spectrometer (AAS). After thermal treatment of the pristine kaolinite, the specific pore volume and surface area amplified significantly from 0.454 − 0.813 cc/g and 78.69–83.046 m2/g, respectively. The heavy metal removal efficiency of thermally activated Malangali kaolinite (TAMK) was evaluated by investigating cobalt (Co2+) and cadmium (Cd2+) ions as potential water pollutants. The results obtained from batch experiments showed the elimination of heavy metal ions is greatly influenced by the initial concentration, adsorbent amount, contact time and solution pH. Adsorption isotherm studies revealed that Langmuir isotherm (R2 = 0.988 for Cd2+ and 0.979 for Co2+) presented the best fit to the equilibrium data than Freundlich isotherm (R2 = 0.965 for Cd2+ and 0.953 for Co2+) with cadmium ions being favourably adsorbed on TAMK compared to cobalt ions. Owing to improved surface area and porosity characteristics, TAMK displayed higher removal efficiency for both Co2+ and Cd2+ ions in simulated polluted water.
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    Metal oxide nanoparticles: a welcome development for targeting bacteria
    (Elsevier, 2020) Fasiku, Victoria Oluwaseun; Owonubi, Shesan John; Malima, Nyemaga Masanje; Hassan, Daniel; Revaprasadu, Neerish
    Resistance to numerous antibiotics by a broad strain of microorganisms has become a global health concern. Conventional antibiotic agents and techniques have become inadequate to completely combat infectious diseases associated with this pathogen; thus, there is an increased rate of infectious disease mortality. In recent years, various scientific researchers have embarked on studies to explore alternate ways by which antibiotic resistance can be curbed. Nanotechnology has proven to be very promising, and a typical example of a nanotechnology strategy that has shown potential application in targeting different strains of resistant and nonresistant microbial strains is the treatment with metal oxide nanoparticles (MONPs). This chapter, therefore, focuses on different types of MONPs with antibacterial activities that have been studied, their method of synthesis, mechanisms of action, as well as the various fields that they can be potentially relevant in targeting pathogenic organisms.
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    Metal oxide–based nanocomposites as antimicrobial and biomedical agents
    (Elsevier, 2020) Owonubi, Shesan John; Malima, Nyemaga Masanje; Revaprasadu, Neerish
    Antibiotic and multidrug resistance are among the great challenges facing researchers in designing and developing effective antimicrobial and biomedical agents. Thus, various strategies are being explored for the design and development of novel and effective biomedical and antimicrobial agents, one of which involves the fabrication of metal oxide–based nanocomposites (MOBNCs). Inspired by remarkable advances in the synthesis and characterization techniques over the years, antimicrobial metal oxide nanocomposites have in recent times been explored as potential antibiotics to fight the rise of infectious diseases. In this chapter, we present a review of the synthesis and characterization techniques of MOBNCs. This is preceded by a brief account and classification of metal oxide nanocomposites. We also highlight key findings on the efficacy of various MOBNCs regarding their antimicrobial activities to the target organisms. Finally, we provide a brief account of the potential biomedical applications of MOBNCs.
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    Solventless synthesis of nanospinel Ni 1− x Co x Fe 2 O 4 (0≤ x≤ 1) solid solutions for efficient electrochemical water splitting and supercapacitance
    (The Royal Society of Chemistry, 2021) Malima, Nyemaga Masanje; Malik, Dilshad Khan; Choi, Jonghyun; Gupta, Ram K.; Mashazi, Philani; Nyokong, Tebello; Revaprasadu, Neerish
    The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites. However, solid solutions have been predominantly prepared via wet chemical routes, which involve the use of harmful and/or expensive chemicals. In the present study, a facile, inexpensive and environmentally benign solventless route is employed for the composition-controlled synthesis of nanoscopic Ni1−xCoxFe2O4 (0 ≤ x ≤ 1) solid solutions. The physicochemical characterization of the samples was performed by p-XRD, SEM, EDX, XPS, TEM, HRTEM and UV-Vis techniques. A systematic investigation was also carried out to elucidate the electrochemical performance of the prepared nanospinels towards energy generation and storage. Based on the results of CV, GCD, and stability tests, the Ni0.4Co0.6Fe2O4 electrode showed the highest performance for the supercapacitor electrode exhibiting a specific capacitance of 237 F g−1, superior energy density of 10.3 W h kg−1 and a high power density with a peak value of 4208 W kg−1, and 100% of its charge storage capacity was retained after 4000 cycles with 97% coulombic efficiency. For HER, the Ni0.6Co0.4Fe2O4 and CoFe2O4 electrodes showed low overpotentials of 168 and 169 mV, respectively, indicating better catalytic activity. For OER, the Ni0.8Co0.2Fe2O4 electrode exhibited a lower overpotential of 320 mV at a current density of 10 mA cm−2, with a Tafel slope of 79 mV dec−1, demonstrating a fast and efficient process. These results indicated that nanospinel ferrite solid solutions could be employed as promising electrode materials for supercapacitor and water splitting applications.