Synthesis and upconversion luminescence properties of YF3:Yb3+/Tm3+ octahedral nanocrystals

YF3:Yb3+(20%)/Tm3+(2%) octahedral nanocrystals were synthesized by a microemulsion method with NH4HF2. Pumped with a 980-nm diode laser, the nanocrystals emitted weak blue and intense ultraviolet light. Especially, unusual 3P2 → 3H6 (∼265 nm) and 3P2 → 3F4 (∼309 nm) emissions, coming from a five-photon excitation process, were observed. The emissions from 1D2 and 1I6 were much stronger than those from 1G4 and 3H4. The upconversion mechanism was discussed in detail.

UC luminescence spectrum of YF3:Yb3+(20%)/Tm3+(2%) nanocrystals under 980-nm excitation. Inset: magnification of the spectrum in the range of 475–850 nm. Figure optionsDownload as PowerPoint slide