Y₂O₂S:Yb³⁺, Er³⁺ nanofibers: novel fabrication technique, structure and up-conversion luminescent characteristics

Y₂O₃:Yb³⁺, Er³⁺ nanofibers were prepared by calcination of the electrospun polyvinyl pyrrolidone (PVP)/[Y(NO₃)₃ + Yb(NO₃)₃ + Er(NO₃)₃] composite nanofibers. For the first time, Y₂O₂S:Yb³⁺, Er³⁺ up-conversion luminescent nanofibers were successfully synthesized via inheritance of the morphology and sulfurization of the above electrospinning-derived Y₂O₃:Yb³⁺, Er³⁺ nanofibers using sulfur powders as sulfur source by a double-crucible method we newly proposed. XRD analysis indicates that Y₂O₂S:Yb³⁺, Er³⁺ nanofibers are pure hexagonal in structure with space group \( {\text{P}}\overline{ 3} m 1 \). Observation results of FESEM and TEM reveal that the diameters of Y₂O₂S:Yb³⁺, Er³⁺ nanofibers are 105 ± 13 nm, and Y₂O₂S:Yb³⁺, Er³⁺ nanofibers are composed of nanoparticles with the diameter ranging from 40 to 70 nm. Up-conversion emission spectrum analysis manifests that Y₂O₂S:Yb³⁺, Er³⁺ nanofibers exhibit strong green and red upconversion emission centering at 526, 548 and 668 nm, respectively. The green emissions and the red emission are respectively assigned to ²H_11/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_l5/2 energy levels transitions of Er³⁺ ions. The formation mechanism of Y₂O₂S:Yb³⁺, Er³⁺ upconversion luminescence nanofibers is also proposed. More importantly, this new strategy and fabrication technique are of universal significance to prepare other rare earth oxysulfides with various morphologies.