A Novel Strategy to Obtain Hollow NaBiF4:Yb3+/Er3+ Upconversion Nanospheres by One Step Coprecipitation

Hollow upconversion luminescence nanomaterials have widespread applications in drug delivery, high efficiency catalysis, as well as energy storage owes to super-large specific surface area, cavity volume, and fluorescence properties. However, a series of complex processes and high temperature is required for the synthesis of these materials. Herein, a facile template-free coprecipitation route based on the Kirkendall diffusion process at room temperature had been developed to synthesize hollow NaBiF4:Yb3+/Er3+ nanospheres with upconversion luminescence. X-ray diffraction (XRD), nitrogen adsoption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and upconversion emission spectra demonstrated the successful preparation of NaBiF4:Yb3+/Er3+ nanospheres with pervasive hollow morphology, relatively high specific surface area, and excellent upconversion luminescence properties. Moreover, the influence of some reaction parameters on the morphology and structure of the obtained samples were systematically explored. Additionally, the evolution mechanism of the hollow structure nanospheres was analyzed on account of the Kirkendall diffusion process related to the solid–liquid interfacial ion migration. It is expected that these hollow upconversion NaBiF4:Yb3+/Er3+ nanospheres with upconversion luminescence prepared by this type of synthetic strategy will have widespread medical, environmental, and energy applications.