X-ray photoelectron spectra were obtained for a series of M-TiO 2 samples in which transition metal ions are directly attached to the surface of anatase TiO 2 nanocrystals. The samples were prepared using CrCl 3 .nH 2 O, MnCl 2 .nH 2 O, FeCl 2 .nH 2 O, CoCl 2 .nH 2 O, NiCl 2 .nH 2 O, and CuCl 2 .nH 2 O as metal sources. We observed spontaneous air oxidation of the metal for the Mn-TiO 2 and Fe-TiO 2 samples as indicated by rapid color changes. X-ray photoelectron spectroscopy (XPS) data confirms the oxidation states of the metals Cr, Co, and Ni are unchanged from the precursor, Mn and Fe are oxidized, and Cu is in a more reduced state. The reduction of Cu likely arises during the XPS experimenta phenomenon well-documented in the literature; whereas UV-visible data of the Cu-TiO 2 dispersions are consistent with Cu 2+ .