Synthesis and characterization of monodisperse spherical SiO 2@ RE2O 3 ( RE=rare earth elements) and SiO 2@Gd 2O 3: Ln3+ ( Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

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Spherical SiO 2 particles have been coated with rare earth oxide layers by a Pechini sol–gel process, leading to the formation of core-shell structured SiO 2@ RE 2O 3 ( RE=rare earth elements) and SiO 2@Gd 2O 3: Ln 3+ ( Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO 2@ RE 2O 3 ( RE=rare earth elements) and SiO 2@Gd 2O 3: Ln 3+ (Eu 3+, Tb 3+, Dy 3+, Sm 3+, Er 3+, Ho 3+) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln 3+ ion mainly shows its characteristic emissions in the core-shell particles from Gd 2O 3: Ln 3+ (Eu 3+, Tb 3+, Sm 3+, Dy 3+, Er 3+, Ho 3+) shells.