Luminescence properties and energy transfer of Gd3+, Mn2+ co-doped cubic NaYF4 nanocrystals

NaYF4 co-doped with Gd3+ and Mn2+ nanocrystals were synthesized by a solvothermal route with PEI as the surfactant. X-ray diffraction analyses evidenced that the phases of synthesized NaYF4: Gd3+, Mn2+ nanocrystals were all pure cubic structure. The luminescence intensity of 20 mol% Gd3+ doped NaYF4 was stronger than that of any other concentration under the 272 nm excitation. The photoluminescence emission intensity of NaYF4: Gd3+, Mn2+ at 561 nm was increased with the increase of Gd3+ doping concentration. The energy transfer mechanisms between Gd3+ and Mn2+ were discussed. The results showed that the energy level of 6PJ of Gd3+ ions played a key role in the energy transfer process. Furthermore, the Mn2+ ions doped NaYF4: Gd3+ nanocrystals with a strong green emission and proper paramagnetism originated from Gd3+ and Mn2+ may find potential applications in bio-probes and magnetic resonance imaging.