Plasmonic metal decorated titanium dioxide thin films for enhanced photodegradation of organic contaminants

摘要

Photocatalysis using titanium dioxide as photocatalyst is an efficient way for the removal of organiccontaminants in water using solar energy. In this study, thinfilms of copper and silver were deposited onfused silica using the thermal evaporation technique. A 100 nmfilm of titanium dioxide (TiO2) was thendeposited on the plasmonic metalfilms using a sputter coating technique. The opposite order ofdeposition of thefilm was also explored. The prepared thinfilms were fully characterized using highresolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD), atomic force microscopy(AFM) and Rutherford backscattering spectrometry (RBS). The effect of plasmonic metalfilm thickness,order of deposition and the use of bimetallic layers on the photocatalytic activity of the TiO2photocatalyst was evaluated using methyl orange as a model pollutant. It was shown that, the increase inAgfilm thickness underneath the TiO2 film increased the photocatalytic activity of the TiO2 photocatalystuntil an optimumfilm thickness of 20 nm was attained. In the case of copper, the increase infilmthickness above 5 nm led to reduced photocatalytic activity. Silver was found to be a better plasmonicmetal than copper in enhancing the photocatalytic activity of TiO2 under UV light illumination. Cu wasfound to perform better when deposited underneath the TiO2 film whereas Ag performed better whendeposited on top of the TiO2 photocatalystfilm. The use of bimetallic layers was found to enhance TiO2photocatalytic activity more than monometallic layers.