A new tactic to achieve Y2O2S:Yb3+/Er3+ up-conversion luminescent hollow nanofibers

Abstract

Y₂O₃:Yb³⁺/Er³⁺ hollow nanofibers were prepared by calcination of monoaxial electrospinning-made PVP/[Y(NO₃)₃ + Yb(NO₃)₃ + Er(NO₃)₃] composite nanofibers, and then Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers were synthesized by sulfurization of the as-obtained Y₂O₃:Yb³⁺/Er³⁺ hollow nanofibers via a double crucible method using sulfur powder as the sulfur source. X-ray diffraction (XRD) analysis shows that Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers are pure hexagonal phase with the space group Pm1. Scanning electron microscope (SEM) observation indicates that Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers are obviously hollow-centered with a mean outer diameter of 226 ± 21 nm. Up-conversion emission spectrum analysis manifests that Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers emit strong green and weak red up-conversion emission bands centered at 526, 546 and 667 nm. The green emission and the red emission bands respectively originated from ²H_11/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_l5/2 energy level transitions of Er³⁺ ions. The optimum molar ratio of Yb³⁺ to Er³⁺ in Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers is 5 : 1. The emitting colors of Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers are located in the green region of the CIE chromaticity coordinate diagram. The formation mechanism of Y₂O₂S:Yb³⁺/Er³⁺ hollow nanofibers is also studied. This preparation technique can be applied to prepare other rare earth oxysulfide hollow nanofibers.