Fabrication and characterization of MoO 3 clusters-coated TiO 2 nanotubes showing charge-transferred photoluminescenceM. R. Kim, S. J. Ahn and D.-J. JangEur. Phys. J. D, 52 1-3 (2009) 75-78DOI: https://doi.org/10.1140/epjd/e2008-00250-8