Fabrication and characterization of TiO₂/Sepiolite nanocomposites doped with rare earth ions

Several rare earth (RE)-doped TiO₂/Sepiolite (RE-TiO₂/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using six different types of RE ions: La, Ce, Pr, Nd, Eu or Gd. The obtained nanocomposites were characterized by using XRD, SEM and TEM techniques. The results revealed that the structures of the nanocomposites were significantly dependent on the radius of the RE³⁺. Since the radius of RE³⁺ is much larger than that of Ti⁴⁺, the doped RE species were not incorporated into the matrix of TiO₂ but rather lie in the grain junctions and boundaries of titania. By forming the Ti-O-RE bonds, the crystallite growth of titania can be inhibited owing to the relatively larger radii of RE³⁺ ions.