A new route to fabricate LaOI:Yb3+/Er3+ nanostructures via inheriting the morphologies of the precursors

Abstract

LaOI:Yb³⁺/Er³⁺ nanostructures, including nanofibers and nanobelts, were successfully synthesized by electrospinning combined with a double-crucible iodination method using NH₄I as the iodine source. X-ray diffraction (XRD) analysis reveals that LaOI:Yb³⁺/Er³⁺ nanostructures are tetragonal in structure with a space group of P4/nmm. Scanning electron microscopy (SEM) analysis shows that the diameter of LaOI:Yb³⁺/Er³⁺ nanofibers and the width and thickness of LaOI:Yb³⁺/Er³⁺ nanobelts are 147.48 ± 17.50 nm, 1.95 ± 0.20 μm and 350 nm, respectively, under the 95% confidence level. Up-conversion (UC) emission spectroscopy analysis shows that LaOI:Yb³⁺/Er³⁺ nanostructures emit strong green and red up-conversion emission centered at 523 nm, 540 nm and 667 nm under the excitation of a 980 nm diode laser (DL), which are attributed to ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_l5/2 energy level transitions of Er³⁺, respectively. It is found that the relative intensities of green and red emission vary obviously by changing the molar concentration of Er³⁺ ions, and the optimum molar ratio of Yb³⁺ to Er³⁺ is 10 : 5 in the as-prepared LaOI:Yb³⁺/Er³⁺ nanofibers. The possible formation mechanisms of LaOI:Yb³⁺/Er³⁺ nanofibers and nanobelts are also proposed.