title: Synthesis of TiO(2) nanocrystals controlled by means of the size of magnetic elements and the level of doping with them.
abstract: TiO(2) nanocrystals were synthesized by a hydrolysis method combined with a thermal treatment. TiO(2) nanocrystals with rutile and anatase structure were selectively synthesized by controlling the pH level in the precursor solution, and the crystallite size was controlled by changing the reaction temperature. Moreover, Co-doped TiO(2) nanocrystals with rutile structure were also synthesized by means of the addition of Co to the precursor solution. Secondary phases such as Co precipitates and Co oxide were not present in the sample tested, with [Co]<10 mol%. With an increase in the Co doping level, the E(g)-phonon signal at 447 cm(-1) was broadened and shifted to a lower frequency, indicating the incorporation of Co into the rutile TiO(2) host lattice and lattice expansion. Optical absorption spectra showed that the absorption edge at ∼3.0 eV corresponded to the band gap of rutile TiO(2) and shifted to the lower energy side upon Co doping. These results indicated the possibility of band gap engineering of rutile TiO(2) via Co doping. On the other hand, the charge transfer gap between O 2p and Co 3d orbitals was also observed for samples with Co, suggesting the possibility of photo-induced magnetism in rutile TiO(2) nanocrystals, obtained by visible light irradiation.
authors.affiliation: Department of Electronics, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.forename: N
authors.initials: N
authors.lastname: Hasuike
authors.forename: K
authors.initials: K
authors.lastname: Kisoda
authors.forename: K
authors.initials: K
authors.lastname: Nishio
authors.forename: T
authors.initials: T
authors.lastname: Isshiki
authors.forename: H
authors.initials: H
authors.lastname: Harima