Observation of an ultraviolet emission band in TiO2 nanocrystals doped with Eu3+

The photoluminescence spectra of titanium dioxide (TiO2) nanocrystals doped with Eu3+ (molar ratio Eu3+/TiO2 = 0, 1, 2, 4%) are investigated under different excitation wavelengths. An ultraviolet band of emission energy higher than the energy gap is found for excitation wavelengths larger than 315 nm when the Eu3+ content is higher than 2%. The new emission band redshifts and its emission intensity is intensified with the increase of excitation wavelength. The emission mechanism for the new ultraviolet emission band is analyzed.