Browsing by Author "Nwanya, Assumpta Chinwe"
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Item Functional metal oxides synthesized using natural extracts from waste maize materials(Elsevier, 2021) Nwanya, Assumpta Chinwe; Botha, Subelia; Ezema, Fabian I.We show in this article the possibilities of employing an environmentally friendly, uncomplicated, economical and sustainable green synthesis technique effected by natural extracts from waste maize (zea mays lea) materials to synthesize some functional transition single metal oxide nanoparticles (NPs). Copper oxides (Cu2O and CuO), zinc oxide (ZnO), nickel oxide (NiO), chromium oxide (Cr2O3), iron oxide (Fe2O3) and cadmium oxide (CdO) were successfully synthesized using this facile method. Structural characterizations by X-ray diffraction (XRD) for the various oxides show the phases and space groups corresponding to their individual structures. Images from the high resolution transmission electron microscope (HRTEM) revealed various shapes and sizes of the obtained nanoparticles. Results from the attenuated total reflection-Fourier transform infrared (ATR-FTIR) revealed different kinds of functional groups present in the synthesized metal oxide nanoparticles. We showed that the phytochemicals in the natural extracts obtained from the waste materials from Zea mays lea plant is pivotal to the bio-reduction, stabilization and chelation of the metal oxide nanoparticles.Item Nanostructured Mn-doped CeO2 thin films with enhanced electrochemical properties for pseudocapacitive applications(Elsevier, 2021-06) Nwachukwu, Iheke Micheal; Nwanya, Assumpta Chinwe; Osuji, RoseCerium oxides with variable oxidation states, high interfacial charge transfer rate have demonstrated to be a potential pseudocapacitive material. In this paper, we present the structural and electrochemical properties of undoped and Mn-doped CeO2synthesized using successive ionic layer adsorption and reaction(SILAR) method. The structural results as obtained from x-ray diffraction (XRD) confirmed the cubic fluorite structure of CeO2 which was unaltered despite the doping concentration. However, a tensile strain of ~2.3% was observed due to ionic radii difference. The topography showed a porous network of nanograins, accounting for strong redox interfacial charge transfer. A specific capacitance of 690 Fg−1 was obtained for 5 wt% Mn-doped CeO2, from cyclic voltammetry curve at a scan rate of 10 mV/s. This value is considerably higher than what was obtained for the undoped ceria, indicating that doping with Mn improved the electrochemical performance of the ceria films.