Multiplesite structure and photoluminescence properties of Eu3+ doped MgO nanocrystals

MgO:Eu3+ nanocrystals with average diameter around 15 nm were prepared via a facile combustion method under a weak reductive atmosphere at temperature as low as 300°C. The photoluminescence spectra showed that the MgO:Eu3+ nanocrystals emit white light, the hypersensitive transition (5D0→7Fj of Eu3+) emission was prominent in the emission spectra resulting from the noinversion symmetry local site at which Eu3+ ions were located. Two kinds of luminescence sites of Eu3+ are identified by means of the fluorescence decay and site-selective spectroscopy. The excitation and absorption spectra indicated that the absorption of surface state decreased with the increase of Eu3+ concentration, meaning that the surface defect decreased through Eu3+ doping for some of them located at the disordered sites near the surface or absorbed at the surface of MgO host. Meanwhile, absorptivity and CIE chromaticity coordinates of all samples were measured; the results were in accordance with the excitation and absorption spectra and photoluminescence spectra, respectively.