Synthesis of Homogeneous Manganese-Doped Titanium Oxide Nanotubes from Titanate Precursors

We report a novel synthesis route of homogeneously manganese-doped TiO 2 nanotubes in a broad concentration range. The scroll-type trititanate (H 2 Ti 3 O 7 ) nanotubes prepared by hydrothermal synthesis were used as precursors. Mn 2+ ions were introduced by an ion exchange method resulting Mn x H 2– x Ti 3 O 7 . In a subsequent heat treatment, they were transformed into Mn y Ti 1– y O 2, where y = x /(3 + x ). The state and the local environment of the Mn 2+ ions in the precursor and final products were studied by the electron spin resonance (ESR) technique. It was found that the Mn 2+ ions occupy two positions: the first having an almost perfect cubic symmetry while the other is in a strongly distorted octahedral site. The ratio of the two Mn 2+ sites is independent of the doping level and amounts to 15:85 in Mn x H 2– x Ti 3 O 7 and to 5:95 in Mn y Ti 1– y O 2 . SQUID magnetometry does not show long-range magnetic order in the homogeneously Mn 2+ -doped nanotubes.