Sacrificial Template Method for Fabrication of Submicrometer-Sized YPO₄:Eu³⁺ Hierarchical Hollow Spheres

Large-scale good-quality submicrometer-sized YPO₄:Eu³⁺ hollow spheres were synthesized by utilizing the colloidal spheres of Y(OH)CO₃:Eu³⁺ as a sacrificial template and NH₄H₂PO₄ as a phosphorus source, for the first time. The whole process mainly consists of the hydrothermal reaction and acid erosion. The YPO₄:Eu³⁺@Y(OH)CO₃:Eu³⁺ core−shell structures were first obtained after the hydrothermal process. Then, the remaining Y(OH)CO₃:Eu³⁺ was removed by selective dissolution in a dilute nitric acid solution. The YPO₄:Eu³⁺ hollow spheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL). The formation mechanism was also investigated. The obtained YPO₄:Eu³⁺ hollow spheres may have potential applications in cell biology, drug release, and diagnosis, due to high chemical stability and luminescence functionality.