Nanoporous TiO2/SiO2 prepared by atomic layer deposition as adsorbents of methylene blue in aqueous solutions

TiO2 films supported by porous SiO2 with high surface area were synthesized by atomic layer deposition (ALD). Porous structure of SiO2 could be maintained even after deposition of TiO2 using 500 ALD cycles. All the TiO2-covered SiO2 samples showed comparable methylene blue (MB) adsorption abilities to that of bare ones. Moreover, MB adsorption capability of TiO2/SiO2 was almost fully recovered by simple re-annealing process, whereas MB adsorption capacity of bare SiO2 was not fully recovered by the same treatment. FT-IR study demonstrated that thermal decomposition of adsorbed MB molecules was much facilitated in the presence of TiO2 films, hence preventing deposition of surface-bound species created on the adsorbents surface during the thermal treatment process. Photocatalytic activity of TiO2/SiO2 samples was also investigated as a function of TiO2 film thickness, and the result will be discussed. (C) 2012 Elsevier B.V. All rights reserved.