Fabrication and luminescence properties of YF3:Eu3+ hollow nanofibers via coaxial electrospinning combined with fluorination technique

Polyvinyl pyrrolidone (PVP)-PVP/[Y(NO3)(3) + Eu(NO3)(3)] core-sheath composite nanofibers were prepared by coaxial electrospinning, and then Y2O3:Eu3+ hollow nanofibers were synthesized by calcination of the as-prepared composite nanofibers. For the first time, YF3:Eu3+ hollow nanofibers were successfully fabricated by fluorination of the Y2O3:Eu3+ hollow nanofibers via a double-crucible method using NH4HF2 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. YF3:Eu3+ hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with the mean diameter of 211 +/- A 29 nm. Fluorescence emission peaks of Eu3+ in the YF3:Eu3+ hollow nanofibers were observed and assigned to the energy levels transitions of D-5(0) -> F-7(1) (587 and 593 nm), D-5(0) -> F-7(2) (615 and 620 nm), and the D-5(0) -> F-7(1) hypersensitive transition at 593 nm was the dominant emission peak. Moreover, the emitting colors of YF3:Eu3+ hollow nanofibers were located in the red region in CIE chromaticity coordinates diagram. The luminescent intensity of YF3:Eu3+ hollow nanofibers was increased remarkably with the increasing doping concentration of Eu3+ ions and reached a maximum at 7 mol% of Eu3+. This preparation technique could be applied to prepare other rare earth fluoride hollow nanofibers.