Phase transition and luminescent properties of the Eu3+ ions-doped NaYF4:Yb, Er nanoparticles

Monodisperse cubic NaYF 4 : 20%Yb, 2%Er nanoparticles (NPs) were successfully synthesized using the high-temperature thermal decomposition method. It is found that the crystal structure of NaYF 4 : 20%Yb, 2%Er, [Formula: see text]%Eu ([Formula: see text] 0, 2, 4) NPs changes from cubic to hexagonal phase with the increase in Eu[Formula: see text] concentration, and the upconversion (UC) luminescent intensities of green and red emissions were decreasing. The emission peaks of Eu[Formula: see text] ([Formula: see text] ([Formula: see text] 1, 2)) ions and the extra peaks of Er[Formula: see text] ([Formula: see text] ions at 450 nm are found, which suggests that the energy transfer between Er[Formula: see text] ions and Eu[Formula: see text] ions occurred with the near infrared light excitation. The probable mechanism related to the cubic-to-hexagonal phase transition of NaYF 4 and energy transfer between Eu[Formula: see text] and Er[Formula: see text] ions or Yb[Formula: see text] ions are discussed.