Structure and Photoluminescence Study of TiO2 Nanoneedle Texture along Vertically Aligned Carbon Nanofiber Arrays

Abstract

A hybrid TiO2−carbon nanofiber hierarchical nanostructure has been fabricated by the metal−organic chemical vapor deposition of a TiO2 layer onto the vertically aligned carbon nanofiber array. As the deposition time increases from 10 to 60 min, the TiO2 coating changes from the particulated conformal ultrathin film to a nanoneedle-like texture along the sidewall of the carbon nanofibers. X-ray diffraction indicates that the TiO2 form anatase crystals with the coherent length over 50 nm, in good agreement with transmission electron microscopy images. Photoluminescence spectra are taken at both room temperature and 10 K. The absence of photoluminescence emission indicates that the electron−hole recombination in TiO2 is completely quenched in such core−shell hybrid structure. The charge separation may be much more effective at the TiO2−carbon nanofiber heterojunction. The nanoneedle-like texture drastically increases the effective surface area of the TiO2 while maintaining a much more effective electrical wiring through the highly conductive carbon nanofiber core. Such hierarchical architecture may be used as a novel anode material for dye-sensitized solar cells.