Facile and Controllable Synthesis of Monodisperse CaF2 and CaF2:Ce3+/Tb3+ Hollow Spheres as Efficient Luminescent Materials and Smart Drug Carriers

Highly uniform and well‐dispersed CaF₂ hollow spheres with tunable particle size (300–930 nm) have been synthesized by a facile hydrothermal process. Their shells are composed of numerous nanocrystals (about 40 nm in diameter). The morphology and size of the CaF₂ products are strongly dependent on experimental parameters such as reaction time, pH value, and organic additives. The size of the CaF₂ hollow spheres can be controlled from 300 to 930 nm by adjusting the pH value. Nitrogen adsorption–desorption measurements suggest that mesopores (av 24.6 nm) exist in these hollow spheres. In addition, Ce³⁺/Tb³⁺‐codoped CaF₂ hollow spheres can be prepared similarly, and show efficient energy transfer from Ce³⁺ to Tb³⁺ and strong green photoluminescence of Tb³⁺ (541 nm, ⁵D₄→⁷F₅ transition of Tb³⁺, the highest quantum efficiency reaches 77 %). The monodisperse CaF₂:Ce³⁺/Tb³⁺ hollow spheres also have desirable properties as drug carriers. Ibuprofen‐loaded CaF₂:Ce³⁺/Tb³⁺ samples still show green luminescence of Tb³⁺ under UV irradiation, and the emission intensity of Tb³⁺ in the drug‐carrier system varies with the released amount of ibuprofen, so that drug release can be easily tracked and monitored by means of the change in luminescence intensity. The formation mechanism and luminescent and drug‐release properties were studied in detail.