Browsing by Author "Duvenhage, Mart-Mari"

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    Plasmonic Au nanoparticles embedded in glass: Study of TOF-SIMS, XPS and its enhanced antimicrobial activities
    (2022) Kumar, Promod; Mathpal, Mohan Chandra; Ghosh, Soumya; Inwati, Gajendra Kumar; Maze, Jero R.; Duvenhage, Mart-Mari; Roos, W. D.; Swart, H. C.
    The Au nanoparticles (NPs) were formed near the surfaces of pre-synthesized sodium zinc -borate glass by an ion exchange process obtained by thermal heat treatment in an open air environment at various temperatures. The pre-heated Au doped glass samples were extensively tested by the different techniques such as optical absorption spectroscopy, Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), and these Au NPs were used for the antimicrobial applications. SEM confirmed the spherical shaped Au NPs with increasing thermal treatment up to 550 degrees C. The optical absorption findings showed that the as -synthesized Au NPs showed Localized Surface Plasmon Resonance behaviour, giving clear evidence of an Au NPs band formed in the glass matrix. The formation mechanism of the Au doped glass samples was studied theoretically from a thermodynamic point of view during heat treatment. XPS and TOF-SIMS were used to study the chemical state and the thermal stability of the pre-heated Au NPs doped glasses in an ultra-high vacuum. The effect of concentration changes in the line-shape and in binding energy as a function of thermal heat treatment suggests that the Au NPs formed near the glass surfaces and changes in the chemical composition as well as chemical structures of the Au doped glass samples occurred. Antimicrobial activity such as antibacterial as well as antifungal activity of pre-heated Au doped glass samples was tested against different strains by the disk diffusion method. The Au doped glass samples exhibited enhanced antibacterial as well as antifungal activities by the influence of thermal treatment at different temperatures. Thus, the Au doped glass sample could be efficiently explored as a medical tool in pharmaceutical industries, biotechnology industries and chemical laboratories based upon its antibacterial findings.
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    Study of Defect-Induced Chemical Modifications in Spinel Zinc-Ferrites Nanostructures by In-Depth XPS Investigation
    (2023) Kumar, Promod; Mathpal, Mohan Chandra; Inwati, Gajendra Kumar; Kumar, Sanjay; Duvenhage, Mart-Mari; Roos, Wiets Daniel; Swart, Hendrik C.
    Spinel zinc ferrite nanomaterials with exceptional physiochemical properties are potential candidates for various applications in the energy and environmental fields. Their properties can be tailored using several methods to widen their applications. The chemical combustion approach was followed to prepare the spinel zinc ferrite nanomaterials, which were then subjected to thermal treatment at a fixed temperature. Thermal heat treatment at a fixed temperature was used to evaluate the phase and morphological characteristics of the prepared spinel zinc-ferrite nanocomposites. Various techniques were employed to examine the samples, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS and X-ray-induced Auger electron spectroscopy were used to extensively examine the surface characteristics of the zinc-ferrite. To study the actual chemical states of the synthesized spinel zinc ferrite nanomaterials and the defects created during the thermal treatment, an extensive investigation of the kinetic energy of the X-ray-induced Zn L3M45M45 and Fe L3M45M45 was conducted. Finally, a detailed analysis of the Wagner plot using the modified Auger parameter was performed to verify the exact chemical states of Zn and Fe. Thus, the findings of the investigation show that XPS is a promising and powerful technique to study the composition and chemical states of spinel zinc ferrites, providing an understanding of changes in their properties for functional applications.