Lanthanide activator doped NaYb(1-x)Gd(x)F4 nanocrystals with tunable down-, up-conversion luminescence and paramagnetic properties

Novel NaYb1-xGdxF4 (0 <= x <= 1) nanocrystals were synthesized by a modified liquid-solid-solution solvothermal route for the first time. X-ray diffraction analyses and transmission electron microscope observations evidenced that the phase, size and shape of NaYb1-xGdxF4 nanocrystals were closely related to the Gd3+ content. Particularly, when the Gd3+ content reached 60 mol%, the final products were highly uniform and monodisperse hexagonal NaYb0.4Gd0.6F4 nanorods. By doping appropriate lanthanide activators, these nanorods exhibited efficient dual-sensitizing multicolor emissions, i.e., Gd3+ sensitizing down-conversion by an ultraviolet light excitation or Yb3+ sensitizing up-conversion by a near-infrared one. The lanthanide activator doped NaYb0.4Gd0.6F4 nanorods with tunable up-conversion luminescence and proper paramagnetism originating from Gd3+ ions may find potential applications in bio-probes and magnetic resonance imaging.