Synthesis and photoluminescence properties of Eu3+-doped silica@coordination polymer core-shell structures and their calcinated silica@Gd2O3:Eu and hollow Gd2O3:Eu microsphere products.

The conjugation of Eu(3+)-doped coordination polymers constructed from Gd(3+) and isophthalic acid (H(2)IPA) with silica particles is investigated for the production of luminescent microspheres. A series of doping ratio-controlled silica@coordination polymer core-shell spheres is easily synthesized by altering the amounts of metal nodes used in the reactions, where the ratios of Gd(3+) and Eu(3+) are 10:0 (1a), 9:1 (1b), 8:2 (1c), 7:3 (1d), 5:5 (1e), and 0:10 (1f). The formation of monodisperse uniform core-shell structures is achieved throughout the entirety of a series. Investigations of the photoluminescence property of the resulting series of silica@coordination polymer core-shell spheres reveal that 20% Eu(3+)-doped product (1c) has the strongest emission intensity. The subsequent calcination process on the silica@coordination polymer core-shell structures (1a-f) results in the formation of a series of doping ratio-controlled silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) with uniform shell thickness. During the calcination step, the coordination polymers within silica@coordination polymer core-shells are transformed into metal oxides, resulting in silica@Gd(2)O(3):Eu core-shell structures. The final etching process on the silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) produces a series of hollow Gd(2)O(3):Eu microspheres (3a-f) as a result of the elimination of silica cores. The luminescence intensities of silica@Gd(2)O(3):Eu core-shell (2a-f) and hollow Gd(2) O(3):Eu microspheres (3a-f) also vary depending upon the doping ratio of Eu(3+) ions.