Browsing by Author "Tichagwa, Lilian"

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    Plasmonic metal decorated titanium dioxide thin films for enhanced photodegradation of organic contaminants
    (Elsevier, 2017) Nyamukamba, Pardon; Tichagwa, Lilian; Ngila, Jane Catherine; Petrik, Leslie
    Photocatalysis using titanium dioxide as photocatalyst is an efficient way for the removal of organic contaminants in water using solar energy. In this study, thin films of copper and silver were deposited on fused silica using the thermal evaporation technique. A 100 nm film of titanium dioxide (TiO2) was then deposited on the plasmonic metal films using a sputter coating technique. The opposite order of deposition of the film was also explored. The prepared thin films were fully characterized using high resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS). The effect of plasmonic metal film thickness, order of deposition and the use of bimetallic layers on the photocatalytic activity of the TiO2 photocatalyst was evaluated using methyl orange as a model pollutant. It was shown that, the increase in Ag film thickness underneath the TiO2 film increased the photocatalytic activity of the TiO2 photocatalyst until an optimum film thickness of 20 nm was attained. In the case of copper, the increase in film thickness above 5 nm led to reduced photocatalytic activity. Silver was found to be a better plasmonic metal than copper in enhancing the photocatalytic activity of TiO2 under UV light illumination. Cu was found to perform better when deposited underneath the TiO2 film whereas Ag performed better when deposited on top of the TiO2 photocatalyst film. The use of bimetallic layers was found to enhance TiO2 photocatalytic activity more than monometallic layers.
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    Silver/carbon codoped titanium dioxide photocatalyst for improved dye degradation under visible light
    (Hindawi Publishing Corporation, 2017) Nyamukamba, Pardon; Tichagwa, Lilian; Mamphweli, S.; Petrik, Leslie
    Herein, we report the synthesis of quartz supported TiO2 photocatalysts codoped with carbon and silver through the hydrolysis of titanium tetrachloride followed by calcination at 500°C. The prepared samples were characterized by UV-Vis diffuse reflectance spectroscopy, high resolution scanning electron microscopy (HRSEM), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Codoping of TiO2 with Ag and carbon resulted in an increase in the surface area of the photocatalyst and altered the ratio of the anatase to rutile phase. The absorption edge of all the doped TiO2 photocatalysts redshifted and the band gap was reduced. The lowest band gap of 1.95 eV was achieved by doping with 0.5% Ag. Doping TiO2 using carbon as the only dopant resulted in a quartz supported photocatalyst that showed greater photocatalytic activity towards methyl orange than undoped TiO2 and also all codoped TiO2 photocatalysts under visible light irradiation.