Synthesis and Photoluminescence Properties of Eu 3+ ‐Doped Silica@Coordination Polymer Core–Shell Structures and Their Calcinated Silica@Gd 2 O 3 :Eu and Hollow Gd 2 O 3 :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.