Synthesis and photoluminescence behavior of the Eu3+ ions as a nanocoating over a silica Stöber matrix.

In this work, a SiO(2) spherical were prepared by the Stöber Method and then recovered with a single layer of Eu(2)O(3) oxide (SiO(2)@Eu(2)O(3)) obtained by the Polymeric Precursor Method. The SiO(2)@Eu(2)O(3) powder was heated treated at 100, 300, 400, 500 and 800 °C. The samples were characterized by the Scanning Electonic Microscopy (SEM), Thermal Analysis (TGA/DTA), and the luminescent properties of the SiO(2)@Eu(2)O(3) powders were studied by their emission and excitation spectra as well as by the lifetime measurements of the Eu(3+) (5)D(0) → (7)F(2) transition. The SEM analysis shows that the silica prepared by the Stöber Method is spherical with a particle size of 460 nm. The emission spectra of the SiO(2)@Eu(2)O(3) powders presented the Eu(3+) characteristics bands related to the (5)D(0) → (7)F(J) (J = 0, 1, 2, 3, 4) transitions at 577, 591, 616, 649 and 695 nm, respectively. The band related to the (5)D(0) → (7)F(2) transition is the most intense in the spectra, and its intensity decreases with the temperature enhancement. The decay curves of the SiO(2)@Eu(2)O(3) samples presented monoexponential features, and the obtained lifetime values were higher than the Eu(2)O(3) oxide. It was possible to conclude that the (5)D(0) → (7)F(2) hypersensitive transition is strongly dependent on the Eu(3+) surrounding.