Electrospun Er3+–TiO2 nanofibrous films as visible light induced photocatalysts

Er3+ doped TiO2 nanofibrous films were prepared by a sol-gel derived electrospinning. The 0.5 mol% Er3+–TiO2 fibers with an average diameter of 160 nm exhibited porous and smooth surface. However, the fibers became disconnected when the Er concentration was above 1.0 mol%. The anatase peaks of TiO2 became broader and weaker with increasing Er concentration, indicative of reduced grain size and low extent of crystallinity. Crystallite size determined by the Scherrer formula decreased from 18 to 8 nm with increasing the amount of Er (0–1.5 mol%). The TiO2 had no absorption in the visible light region above 400 nm, while the Er3+–TiO2 nanofibers had typical absorption peaks located 490, 523 and 654 nm, corresponding to the transitions from 4I15/2 to 4F7/2, 2H11/2 and 4F9/2, respectively. Smaller crystallite size of the nanofibers may correspond to larger surface area, which is beneficial for the photocatalytic activity under visible light.