Fabrication of Y₂O₂S:Eu³⁺ hollow nanofibers by sulfurization of Y₂O₃:Eu³⁺ hollow nanofibers

Y₂O₃:Eu³⁺ hollow nanofibers were prepared by calcination of the electrospun PVP/[Y(NO₃)₃ + Eu(NO₃)₃] composite nanofibers, and then Y₂O₂S:Eu³⁺ hollow nanofibers were successfully synthesized by sulfurization of the as-obtained Y₂O₃:Eu³⁺ hollow nanofibers via a double-crucible method using sulfur powders as sulfur source. The samples were investigated in detail by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and fluorescence spectroscopy. XRD analysis shows that the Y₂O₂S:Eu³⁺ hollow nanofibers are pure hexagonal phase with the space group of P\( \bar{3} \) m1. SEM observation indicates that as-prepared Y₂O₂S:Eu³⁺ nanofibers are obvious hollow-centered structure with the mean outer diameter of 184 ± 26 nm. Under the excitation of 260-nm ultraviolet light, the Y₂O₂S:Eu³⁺ hollow nanofibers exhibit red emissions of predominant emission peaks at 628 and 618 nm originated from ⁵D₀ → ⁷F₂ energy levels transitions of Eu³⁺ ions. The luminescent intensity of Y₂O₂S:Eu³⁺ hollow nanofibers is remarkably increased with the increase of doping concentration of Eu³⁺ ions and reaches a maximum at 3 mol % of Eu³⁺ ions. The emitting colors of the samples are located in the red region in CIE chromaticity coordinates diagram. The possible formation mechanism of Y₂O₂S:Eu³⁺ hollow nanofibers is also proposed. This preparation technique could be applied to prepare other rare earth oxysulfide hollow nanofibers.