Fabrication and luminescence properties of YF_3:Eu~(3+) hollow nanofibers via coaxial electrospinning combined with fluorination technique

摘要

Polyvinyl pyrrolidone (PVP)-PVP/[Y(NO_3)_3 + Eu(NO_3)_3] core-sheath composite nanofibers were prepared by coaxial electrospinning, and then Y_2O_3:Eu~(3+) hollow nanofibers were synthesized by calcination of the as-prepared composite nanofibers. For the first time, YF_3:Eu~(3+) hollow nanofibers were successfully fabricated by fluorination of the Y_2O_3:Eu~(3+) hollow nanofibers via a double-crucible method using NH_4HF_2 as fluorinating agent. The morphology and properties of the products were investigated in detail by X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope (TEM), and fluorescence spectrometer. YF_3:Eu~(3+) hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with the mean diameter of 211 ± 29 nm. Fluorescence emission peaks of Eu~(3+) in the YF_3:Eu~(3+) hollow nanofibers were observed and assigned to the energy levels transitions of ~5D_0 → ~7F_1 (587 and 593 nm), ~5D_0 → ~7F_2 (615 and 620 nm), and the ~5D_0 → ~7F_1 hypersensitive transition at 593 nm was the dominant emission peak. Moreover, the emitting colors of YF_3:Eu~(3+) hollow nanofibers were located in the red region in CIE chromaticity coordinates diagram. The luminescent intensity of YF_3:Eu~(3+) hollow nanofibers was increased remarkably with the increasing doping concentration of Eu~(3+) ions and reached a maximum at 7 mol% of Eu~(3+). This preparation technique could be applied to prepare other rare earth fluoride hollow nanofibers.