Browsing by Author "Ghosh, Soumya"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Defects induced enhancement of antifungal activities of Zn doped CuO nanostructures
    (2021) Kumar, Promod; Inwati, Gajendra Kumar; Chandra Mathpal, Mohan; Ghosh, Soumya; Roos, W. D.; Swart, H. C.
    CuO nanostructures doped with different concentration of Zn have been synthesized by a simple low-cost combustion method. The prepared samples have been tested by the various techniques such as X-ray diffraction (XRD), Transmission Electron Microscope (TEM), Optical absorption spectroscopy, Photoluminescence, and X-ray photoelectron spectroscopy (XPS). XRD confirmed the presence of the monoclinic phase of CuO along with an extra ZnO phase in the CuO:Zn. TEM results confirmed almost spherical - shaped nanoparticles as well as some irregular shaped NPs for pure CuO and Zn doped CuO with the average size from 24 to 55 nm. The change in morphology revealed a structural change in the CuO:Zn crystal due to different concentration of the Zn. The chemical study was done by XPS and the results were also correlated with XRD based results. The role of localized defects was compared and interpreted for the change in the luminescence spectral bands, micro-stains and oxidation states of the CuO:Zn for the different concentrations. CuO:Zn nanostructures demonstrated significant antifungal activities against two South African plant pathogens, Alternaria alternata CGJM3078 and Alternaria alternate CGJM3006, in comparison to pure CuO samples. The result showed that the pure and Zn doped CuO samples could be used as a good antifungal agent that could have an extensive applications in the agricultural and biotechnological industries.
  • No Thumbnail Available
    Item
    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.