A visible light-responsive iodine-doped titanium dioxide nanosphere.

I-doped titanium dioxide nanospheres (I-TNSs) were synthesized via a two-step hydrothermal synthesis route, their potential for the efficient utilization of visible light was evaluated. The prepared anatase-phase I-TNSs had a bimodal porous size distribution with a Brunauer-Emmett-Teller surface area of 76 m2/g, a crystallite size of approximately 14 nm calculated from X-ray diffraction data, and a remarkable absorption in the visible light region at wavelengths > 400 nm. The photocatalytic activity of the samples was evaluated by decoloration of Methyl Orange in aqueous solution under visible light irradiation in comparison to the iodine-doped TiO2 (I-TiO2). The I-TNSs showed higher photocatalytic efficiency compared with I-TiO2 after irradiation for 180 min even though the latter had a much greater surface area (115 m2/g). It was concluded that the surface area was not the predominant factor determining photocatalytic activity, and that the good crystallization and bimodal porous nanosphere structure were favourable for photocatalysis.