Title: Optical and AC conductivity studies of Co doped TiO₂ nanotubes

Authors: P. Pournami Vijayan; Marykutty Thomas; Lakshmi Nair; P. Poornima Vijayan; K.C. George

Addresses: Department of Physics, S.B. College, Changanacherry, Kerala 686101, India ' Department of Physics, B.C.M. College, Kottayam, Kerala 686001, India ' Department of Physics, M.G. College, Thiruvananthapuram, Kerala 695004, India ' School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala 686560, India ' Department of Physics, S.B. College, Changanacherry, Kerala 686101, India

Abstract: Cobalt doped TiO₂ nanotubes are prepared by the combination of sol-gel process with hydrothermal treatment. The morphology and crystalline structure of TiO₂ nanotubes are characterised by transmission electron microscopy (TEM) and X-ray diffraction respectively. Optical studies are done by UV-Vis reflectance spectra and photoluminescence spectra (PL). Co doping induces a structural transformation from anatase to rutile. PL spectrum shows the presence of surface oxygen vacancies and self trapped excitons in Co doped and undoped TiO₂ nanotubes. Co doped sample show a peak in PL spectrum at 526 nm, which is not in the undoped sample. An AC conductivity data analysis is carried out in the temperature range 303 to 423 K for the TiO₂ nanotubes and Co doped TiO₂ nanotubes. The temperature at which the transition to the positive temperature coefficient of resistance occurs differs in undoped and Co doped TiO₂ nanotubes.

Keywords: TiO2 nanotubes; cobalt doping; oxygen vacancies; AC conductivity; nanotechnology; titanium dioxide; titania; sol-gel; hydrothermal treatment; optical studies; reflectance spectra; photoluminescence.

DOI: 10.1504/IJMATEI.2014.064278

International Journal of Materials Engineering Innovation, 2014 Vol.5 No.3, pp.205 - 215

Received: 02 Feb 2013
Accepted: 31 Aug 2013
Published online: 30 Aug 2014 *

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