Intense ultraviolet upconversion luminescence from YF^sub 3^: Yb/Tm submicrorice

It is still a challenge to design and synthesize fluoride particles with novel morphology and superior ultraviolet (UV) upconversion (UC) emissions using simple strategy. Here, we report the preparation of water-soluble and morphology tunable YF3: Yb/Tm submicrorices (SMRs) with high UV UC efficiency. The morphology and size of the SMRs were controlled by tuning the added amount of fluorine source and organic modifier. All these SMRs presented excellent UV UC photoluminescence under 980-nm irradiation. Particularly, the intensities of the 5-photon UC emissions from the 1I6 level of Tm ions were much stronger than those of the 4-photon UC emissions from the 1D2 level and the 3-photon UC emissions from the 1G4 level. In addition, the UC mechanisms of these samples were investigated in detail.