Browsing by Author "Ngece-Ajayi, Rachel Fanelwa"

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    Green synthesis, XRD/SAXS modelling and electrochemistry of indium iron oxide nanocomposite
    (Springer Science and Business Media B.V., 2025) Ngema, Nokwanda Precious; Tshobeni, Ziyanda; January, Jaymi; Iwuoha, Emmanuel; Ngece-Ajayi, Rachel Fanelwa; Mulaudzi, Takalani
    A green synthesis approach was utilized to prepare indium iron oxide (InFeO 3 ) nanocomposites using coffee extract as a reducing and capping agent. The structural, morphological, optical, and electrochemical properties of the synthesized materials were systematically characterized through X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), high-resolution electron microscopy (HRTEM/HRSEM), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, photoluminescence (PL), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. XRD analysis confirmed the formation of a rhombohedral InFeO 3 structure with an average crystallite size of 27 nm, while HRTEM revealed spherical nanoparticles with partial agglomeration. SAXS and HRTEM data corroborated the nanoscale dimensions, with particle sizes ranging from 24 to 38 nm. Optical studies demonstrated a reduced bandgap (2.85 eV) for the composite compared to pure In 2 O 3 (3.3 eV) and Fe 2 O 3 (3.15 eV), attributed to charge transfer transitions between Fe 3+ and In 3+ . The nanocomposite exhibited enhanced magnetic properties, with a saturation magnetization (Ms) of 18.48 emu/g, and Mössbauer spectroscopy revealed disrupted super-exchange interactions due to In 3+ incorporation. Electrochemical analysis showed superior performance of the InFeO 3 -modified electrode, characterized by a higher diffusion coefficient (9.72 × 10 –5 cm 2 s −1 ) and surface concentration (4.62 × 10 –7 mol cm −2 ) compared to individual oxides, indicating improved charge transfer kinetics. These results highlight the potential of green-synthesized InFeO 3 as a promising material for electrochemical sensing applications, combining sustainability with enhanced functional properties.
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    UV–Vis detection of e. coli 0157:H7 using vitis vinifera and musa paradaisica modified au-nps
    (Elsevier B.V., 2024) Ngece-Ajayi, Rachel Fanelwa ; Nqunqa, Siphamandla ; Ngema, Nokwanda
    Herein, we demonstrate the simple one-pot novel green synthesis of gold nanoparticles (Au-NPs) functionalised with a combination of banana peel (Musa paradaisica) and grape (Vitis vinifera) fruit extracts. The reaction mixture of aqueous gold chloride, banana peel and grape extracts revealed a purple colour after a reaction time of one hour, an indication of the presence and the successful synthesis of gold nanoparticles. The optical and structural properties of the green synthesized nanoparticles were analysed using Ultraviolet-Visible spectroscopy (UV–Vis) and Fourier Transform Infrared Spectroscopy (FTIR) while their surface morphology was determined using X-Ray Diffraction (XRD), High-Resolution Transmission Microscopy (HRTEM) and Small Angle X-Ray (SAX). Furthermore, a quick and simple surface plasmon resonance (SPR) study in the form of an optical sensor for the detection of Escherichia coli 0157:H7 strain was also achieved using UV–Vis.