Tunable photoluminescence of NaYF4:Eu nanocrystals by Sr2+ codoping

NaYF4:Eu/Sr nanocrystals were synthesized by a hydrothermal method. Tunable photoluminescence of the NaYF4:Eu nanocrystals was successfully achieved by codoping with Sr2+ ions. With increasing Sr2+ concentration, not only the X-ray diffraction peaks of the nanocrystals become broader, but also the positions of them shift toward larger lattice parameters. Eu3+ and Eu2+ have been found to coexist in an NaYF4:Eu/Sr. The Eu3+/Eu2+ emission intensity ratio changed with the Sr2+ concentration and excitation wavelength. More interestingly, the spectral configurations of Eu2+ and Eu3+ also varied with the excitation wavelength, indicating that the nanocrystals have multiple luminescence centers or emitting states.

Graphical abstract(a) TEM and (b) HRTEM images of NaYF4:Sr(30%)/Eu(10%) nanocrystals. (c) TEM image of NaYF4:Sr(70%)/Eu(10%) nanocrystals. (d) EDXA pattern of NaYF4:Sr(30%)/Eu(10%) nanocrystals.Figure optionsDownload full-size imageDownload as PowerPoint slide