Enhancement of upconversion luminescence intensity in NaMgF₃:2.5%Yb³⁺, 0.5%Er³⁺ nanocrystals with Eu³⁺ doping

NaMgF₃:2.5%Yb³⁺, 0.5%Er³⁺ nanocrystals with different Eu³⁺ concentration were synthesized via the hydrothermal method. The intensity of upconversion (UC) luminescence enhanced obviously, especially when Eu³⁺ concentration was 0.01 mol%. It could be comfirmed that both red and green emission were three photons UC processes according to the relationship between the excitation power and UC luminescence intensity. With the help of nanocrystal morphology, decay time and UC emission spectra analysis, the possible UC luminescence mechanism was discussed in detail. Er³⁺ played the important role of “bridging ion” in NaMgF₃:2.5%Yb³⁺, 0.5%Er³⁺, Eu³⁺ nanocrystals, which resulted in the effective energy transfer pocesses of Yb³⁺ → Er³⁺ → Eu³⁺.