Optimized upconversion emission of NaLuF4:Er,Yb nanocrystals codoped with Gd3+ ions and its mechanism

NaLu(Gd)F4:Yb,Er nanocrystals (NCs) with different Gd3+ concentrations were synthesized, and the luminescence enhancement mechanism under excitation at 980 nm is discussed. The optimized concentration of Gd3+ ions in NaLuF4:Yb,Er NCs is 20%, of which the upconversion emission is nearly 10 times stronger than that of the Gd3+-free sample. In addition, the optimized concentration indicates a good balance between phase-transition and concentration quenching.