Efficient room-temperature conversion of anatase to rutile TiO2 induced by high-spin ion doping

The surprising room-temperature phase conversion of anatase to rutile TiO2, a process that normally requires temperatures well in excess of 700 degrees C, is facilitated through the use of transition metal ions with highly unpaired electron spin. Raman spectroscopy is used to demonstrate this unexpected process, facilitated through the use of high-spin cobalt (Co-II) and nickel (Ni-II) transition metal ion seeding into a TiO2, or TiO2-xNx nanocolloid lattice. In distinct contrast, the effect is not manifest upon seeding with low-spin ions including Cull. The Raman spectra also demonstrate the concomitant incorporation of a spinel-like structure into the titania lattice, which is suggested to influence the high-spin cobalt interaction.