Synthesis and luminescence properties of Eu(III)-doped nanoporous silica spheres

Europium (III) (Eu ³⁺)-doped nanoporous silica spheres were synthesized, and the states of Eu ³⁺ ions in the silica framework structure were investigated. The ordered nanopores were preserved with the doping at the Eu ³⁺ molar concentration to Si up to 10mol%, and the O-Si-O and Si-OH groups in the structures were clearly rearranged with the doping, indicating the interaction of Eu ³⁺ with the O atoms. The significant morphological changes in the spheres were observed with the doping. The photoluminescence spectral shapes due to the transitions of ⁵D ₀- ⁷F ₁ and ⁵D ₀- ⁷F ₂ were indicative of the presence of the Eu ³⁺ in an environment of a low symmetry. It was found that the Eu ³⁺ was located inside the silica framework to electrostatically interact with the environmental O atoms, which would prevent the aggregation among Eu ³⁺ ions to show the efficient luminescence. Therefore, the interactions between the Eu ³⁺ ions and silica framework structures in the spheres were successfully clarified.