Oleic acid (OA)-modified LaF₃:Nd, NaYF₄:Nd and CaF₂:Nd nanocrystals (NCs) with the different Nd³⁺ ion concentration (2% and 5%) have been prepared. The structure and morphology of NCs were identified by XRD, TEM, FT-IR and TGA. The size of OA-modified NC is a mean diameter of 5–10 nm and can be dispersed in common organic solvents to form a transparent solution. The optical loss of NCs in organic solvent is the first time to discuss in this work. The luminescence properties of NCs were also characterized and studied by fluorescence spectrometer. The nanoparticles in solid and in the solution all exhibited the strong emission at the 1060 nm when the materials were excited around 800 nm. Compared with the LaF₃ and CaF₂ matrix, NaYF₄ as the host can protect the Nd³⁺ions more efficiently away from the nonradiative transitions. The longest luminescent lifetime of the solid NaYF₄:2%Nd NCs was up to 136 μs, and the little difference of the fluorescence lifetime existed between the NCs in solid state and in solution. The low optical loss in organic solvent indicated that the Nd³⁺ ions-doped fluoride NCs are promising materials for optical amplification fields.

Optical Materials,2015

High-resolution TEM (HRTEM) image of LaF₃:Nd (a), NaYF₄:Nd (b), and CaF₂:Nd (c) nanocrystals dispersed in CHCl₃, and the inset is a selected area electron diffraction pattern (SAED).