Controllable synthesis and upconversion luminescence of NaYF4:Yb3+, Er3+ nanocrystals

NaYF4 nanorods, and nanoparticles co-doping with Yb3+ and Er3+ were synthesized by hydrothermal method. The effects of doped ion concentration, the ratio of NaF to Ln (NO3)(3) and the reactant content on the luminescence properties of the nanocrystals were investigated in detail in this paper. The materials were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectra. The results indicate that a doping level of 20 mol% Yb3+ and 2 mol% Er3+ gives the strongest luminescence, and concentration quenching occurs, when Er3+ concentration exceeds 5 mol%. Besides, the reaction of temperature and time were also investigated and the results showed that they have an effect on the shape, size, and crystal phase purity of the nanoparticles. The luminescence mechanism for the NaYF4: Yb3+, Er3+ was discussed. Under 980 nm excitation, the Er3+ ions doped into NaYF4 samples emitted green fluorescence 520 nm (H-4(11/2)-> H-4(15/2)), 550 nm (S-4(3/2)-> H-4(15/2)) and red fluorescence 650 nm(F-4(9/2)-> I-4(15/2)), which were modified and enhanced by Yb3+ ions. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.