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.
Novel PEI-modified NaBiF 4 :Yb 3+ /Er 3+ upconversion nanoparticles (UCNPs) with hollow structure were prepared by a surface modification free one-step solvothermal method and applied as a luminescent probe to determinate water content in organic solvents . XRD , SEM and HRTEM results demonstrate that the obtained PEI-NaBiF 4 :Yb 3+ /Er 3+ UCNPs are pure hexagonal phase with uniform size. The successful modification of PEI on the UCNPs surface was evidenced by ζ-potential test, XPS and TG analysis . These synthesized UCNPs are disintegrated into smaller nanoparticles in the presence of water and thus result in a surface quenching effect, which show the features of 0–100% wide range water response in various organic solvents. The sensing performance towards real samples was validated by the water content determination in beer, rum and white spirit. Furthermore, the luminescence intensity variation of the PEI-modified NaBiF 4 :Yb 3+ /Er 3+ enable the test visualization and ease of portability.
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