Cr-Doped TiO_(2)Thin Films Prepared by Means of a Magnetron Co-Sputtering Process:Photocatalytic Application

This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite:Effect of etching parameters

Homogeneous and vertically aligned silicon nanowires(SiNWs)were successfully fabricated using silver assisted chemical etching technique.The prepared samples were characterized using scanning electron microscopy,transmission electron microscopy and atomic force microscopy.Photocatalytic degradation properties of graphene oxide(GO)modified SiNWs have been investigated.We found that the SiNWs morphology depends on etching time and etchant composition.The SiNWs length could be tuned from 1 to 42μm,respectively when varying the etching time from 5 to 30 min.The etchant concentration was found to accelerate the etching process;doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time.Changes in bundle morphology were also studied as function of etching parameters.The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration.The addition of GO was found to improve significantly the photocatalytic activity of SiNWs.A strong correlation between etching parameters and photocatalysis efficiency has been observed,mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8.A degradation of92%was obtained which further improved to 96%by addition of hydrogen peroxide.Only degradation efficiency of 16%and 31%has been observed for bare Si and GO/bare Si samples respectively.The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.