Synthesis and Characterisation of Ti 0 2 ( titanium dioxide) nanomaterials and Au I TiO2 (gold titanium dioxide) nanocomposites
Seoposengwe, Kelebile Pearl Maizie
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The Au I TiO2 nanocomposites were synthesized by the incipient wetness impregnation method. The TiO2 supports were first prepared and then Au was loaded on them. The TiO2 nanomaterials were synthesized by the hydrothermal method, using TiO2 (P-25 Degussa) containing 80 % anatase and 20 % rutile and NaOH, NH4OH, and KOH. TiO2 was treated with 18 M NaOH and then NH4OH was introduced as co -solvent, using different volumes. The materials were then characterized by SEM, TEM, XRD, BET, EDX and FTIR, to determine morphology and structure. 18 M NaOH concentration did not transform the spherical morphology of TiO2 but there was structural transformation. The samples treated with NH4OH were also found to be spherical in shape, but they were composed of clustered aggregates. NH4OH did not influence the morphology and the structure of the material, since it is considered to be a weak base. Then KOH and NaOH were used with three different mole ratios to check the influence of these bases on the structural and morphological transformation of the material. It was observed that the morphology transformation was dependent on the amount of KOH that was added. The morphology transformation decreased with a decrease in the amount of KOH. A mixture of nanotubes and nanorods were obtained, with average diameters of 4-11 nm and 3-18 nm for samples BI and B2 respectively. The variation in the amount of KOH resulted in nanobelts and nanorods. The samples were then calcined at 300 °C. It was found that the calcination temperature did not affect the crystallinity but it affected the morphology because no unreacted material was observed. Then the loading of Au followed. Incipient wetness impregnation was used. Samples B 1 and B2 and TiO2 P-25 Degussa were used as supports for Au particles, and they were later re-named samples C2, C3 and Cl respectively. HAuC'4.3H2O was used as the source of Au. The TEM results showed the presence of Au particles. The Au particles were found to be well dispersed on the spherical morphology than on the tubular morphology. EDX also confirmed the presence of Au on the materials. The surface areas of samples C2 and C3 increased due to the structural transformation.