Search

The Co-doped titanate nanotubes, synthesized via a hydrothermal reaction, are calcined at 300, 400, and 500 °C for 2 h in an argon atmosphere to yield Co-doped TiO2(B) nanotubes and anatase nanotubes with a dark gray color. It is shown that all calcined titania nanotubes have a stronger absorption in visible region, attributed to the formation of oxygen vacancies. The saturation magnetization of all Co-doped titania nanotubes is stronger than that of as-prepared Co-doped titanate nanotubes. In particular, Co-doped TiO2(B) nanotubes calcined at 300 °C exhibit the strongest ferromagnetism due to the existence of oxygen vacancies, as confirmed further by electron paramagnetic resonance spectra. [ABSTRACT FROM AUTHOR]