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 2H11/2/4S3/2 → 4I15/2 and 4F9/2 → 4Il5/2 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.