We have measured photoluminescence (PL) excitation spectra of TiO2 powders with various rutile phase contents, and have found a correlation between the energy level of the PL excitation band (E-PLE) and the rutile phase content. The EPLE of the mixture and its band-gap energy were redshifted compared to those expected from its rutile phase content. We can explain this correlation by considering the charge transfer between the anatase and rutile TiO2 nanoparticles of the mixture. These results suggest that the extent of charge transfer can be estimated by PL spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.