Lanthanide-doped LiYF4 nanoparticles: Synthesis and multicolor upconversion tuning

We report the synthesis of tetragonal-phase LiYF4 nanoparticles doped with upconverting lanthanide ions. The nanoparticles have been characterized by XRD, TEM, and luminescence decay studies. The size of the as-synthesized LiYF4 nanoparticles can be tuned by varying the precursor ratio of F to lanthanide ions. Passivated by oleic acid ligands, the LiYF4 nanoparticles can be readily dispersed in a wide range of nonpolar solvents including hexane, cyclohexane, dichloromethane, and toluene. The lanthanide-doped (Yb3+, Er3+, Tm3+, Ho3+) LiYF4 nanoparticles show intense upconversion emissions upon near infrared excitation at 980 nm. By varying composition and concentration of the dopant ions, the color output can be precisely modulated under single wavelength excitation with a diode laser.