Synthesis and Upconversion Luminescence of LaF₃: Yb³⁺, Er³⁺/SiO₂ Core/Shell Microcrystals

LaF₃: Yb³⁺, Er³⁺ microcrystals were synthesized by a hydrothermal method, and then, the LaF₃: Yb³⁺, Er³⁺ microcrystals were coated with silica. Phase identification of LaF₃: Yb³⁺, Er³⁺ and LaF₃: Yb³⁺, Er³⁺/SiO₂ was performed via XRD. The TEM image showed that the size of LaF₃: Yb³⁺Er³⁺ was 150 nm and LaF₃: Yb³⁺, Er³⁺/SiO₂ presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF₃: Yb³⁺, Er³⁺ and LaF₃: Yb³⁺, Er³⁺/SiO₂ in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF₃: Yb³⁺, Er³⁺ microcrystals. At the same time, the green luminescence photo of LaF₃: Yb³⁺, Er³⁺/SiO₂ in the PBS buffer was obtained, which indicated that the LaF₃: Yb³⁺, Er³⁺/SiO₂ could be used in biological applications.