Synthesis and luminescence properties of Yb~(3+)-Er~(3+) co-doped LaOCl nanostructures

摘要

LaOCl:Yb~(3+), Er~(3+) nanofibers and hollow nanofibers were prepared by electrospinning combined with a double-crucible chlorination technique using NH_4Cl as chlorinating agent. X-ray powder diffraction analysis indicated that LaOCl:Yb~(3+), Er~(3+) nanostructures were tetragonal with space group P4mm. Scanning electron microscope analysis and histograms revealed that diameters of LaOCl: Yb~(3+), Er~(3+) nanofibers and hollow nanofibers, respectively, were 117.87 ± 15.48 and 141.09 ± 17.10 nm under the 95 % confidence level. Up-conversion (UC) emission spectra analysis manifested that LaOCl:Yb~(3+), Er~(3+) nanostructures exhibited strong green and red UC emission centering at 526, 548, and 671 nm, respectively, attributed to ~2H_(11/2) → ~4I_(15/2), ~4S_(3/2) → ~4I_(15/2), and ~4F_(9/2) → ~4I_(l5/2) transitions of Er~(3+) ions under the excitation of a 980-nm diode laser. It was found that the relative intensities of green and red emissions vary obviously with the addition of Yb~(3+) ions, and the optimized molar ratio of Yb~(3+) to Er~(3+) was 10:1 in the as-prepared nanofibers. Moreover, the near-infrared characteristic emissions of LaOCl:Yb~(3+), Er~(3+) nanostructures were achieved under the excitation of a 532-nm laser. CIE analysis demonstrated that color-tuned luminescence can be obtained by changing doping concentration of Yb~(3+) (and/or Er~(3+)) ions and morphologies of nanomaterials, which could be applied in the fields of optical telecommunication and optoelectronic devices. TheUC luminescent mechanism and the formation mechanisms of LaOCl:Yb~(3+), Er~(3+) nanofibers and hollow nanofibers were also proposed.