A forest of SiO2 nanowires covered by a TiO2 thin film for an efficient photocatalytic water treatment

We propose a highly disordered array (forest) of SiO2 nanowires (NWs) coated by a thin film of TiO2 as performing and scalable photocatalytic system for water treatment. The system consisted of a forest of SiO2 NWs, long tens of micron with diameter around few hundreds of nanometer, coated by a nanometric layer of TiO2. The SiO2 NWs were obtained via thermal oxidation of Si NWs grown by Plasma Enhanced Chemical Vapor and the TiO2 coverage (?10nm thick) was grown by Atomic Layer Deposition. The remarkable photocatalityc performance toghether with the stability of the TiO2/SiO2 composite NWs was demonstrated by degradation of the methylene blue dye in water. The morphology and optical properties imparted by the SiO2 NW forest to the resulting composite structure were the two key factors determing the enhancement of the photocatalytic activity of the overlaying TiO2 film. The fabrication methods based on the well-established Si technology and the material design not affected by problems of nanomaterial release in the environment make this strategy an effective approach for large-scale water treatment.