Faculty of Science and Technology

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Browsing Faculty of Science and Technology by Author "Alotsi, Ntjamang Daniel"

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    Fast and complete degradation of Congo red under visible light with Er3+ and Nd3+ ions doped TiO2 nanocomposites
    (PAGEPress, 2012) Narayan, Himanshu; Alemu, Hailemichael; Alotsi, Ntjamang Daniel; Macheli, Lebohang; Thakurdesai, Madhavi; Jaybhaye, Sandesh; Singh, Arvind
    We report fast and complete destruction of the dye Congo red (CR) under visible light in the presence of Nd3+ and Er3+ doped TiO2 nanocomposites (NCs). TiO2 NCs with general composition TiO2[R2O3]x, {x=0.1, 0.2; R≡ Nd, Er} and particle size 12-16 nm were synthesized through co-precipitation/hydrolysis (CPH). A set of similar composites was also prepared through solid state reaction (SSR) route, which produced 31- 47 nm particles. After characterization, visible light photocatalytic activity of all the samples was recorded for the degradation of CR. NCs with molar concentration x=0.2 of both doping types produced close to 100% degradation in 180 min. The apparent rate constant (kobs) was found to be 2.91×10–2 min–1 and 2.36×10–2 min–1, for these Nd3+ and Er3+ doped NCs, respectively. The other NCs with x=0.1, also showed significant degradation of CR, but the samples prepared through SSR performed worse. The excellent degradation obtained with the NCs may be attributed to their small particle size. Moreover, the doping of Nd3+ and Er3+ ions further supported the photocatalysis through formation of intermediate energy levels within the band gap of TiO2. These new levels not only acted as electron traps for efficient suppression of the undesired e–/h+ recombination, but also facilitated to a certain extent the absorption of visible irradiation.
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    Synthesis and Characterization of Erbium and Neodymium Oxide doped Titanium Oxide Nanocomposites and their Application in Visible Light Photocatalysis of Congo red
    (National University of Lesotho, 2011-05) Alotsi, Ntjamang Daniel; Prof. Alemu, Hailmichael
    Nanocomposites (NCs) of Titanium dioxide doped with Erbium and Neodymium oxides, ( TiO2[Er2O3 ]x and TiO2[Er2O3 ]x, x=0.1,0.2) were prepared both by chemical co-precipitation followed by hydrolysis (CPH) as well as the solid-state reaction (SSR). The CPH synthesized NCs were obtained with particle sizes in the range (10nm-30nm). TiO2 was also synthesized using precipitation followed by hydrolysis method. All the NCs were investigated for their capability of degrading a dye, Congo Red (CR) using visible light and about 99.6% of CR was degraded. Throughout the entire research, all the chemically synthesized NCs showed high photocatalytic activity and this is attributed to smaller particle size of the NCs as compared to those NCs prepared by the SSR method. This directly reflects that photosensitization is major route of photocatalytic degradation mediated on TiO2 NCs. On comparison with the synthesized TiO2, the doped NCs revealed no greater photocatalytic activity than the synthesized TiO2, however this is apparent since TiO2 was synthesized with similar method to CPH method.