Synthesis and spectral properties of Eu3+-doped YF3 nanobundles

YF3:Eu3+ nanobundles were synthesized by a facile microemulsion method. Analysis of X-ray diffraction, scanning electron microscope, and transmission electron microscopy reveals that each nanobundle consists of numerous nanowhiskers with a mean length of ∼500 nm and a mean diameter of ∼2 nm. Under 393-nm excitation, the luminescence was dominated by 5D0 → 7F1 transition, indicating the inversion symmetry of Eu3+ site. The luminescence intensity increased with increasing Eu3+ concentration, up to about 30 mol%, and then decreased abruptly. The peak positions and spectral shapes of emissions were independent of Eu3+ concentration. Finally, the critical distance of energy transfer was calculated.