A simple, low-temperature route to synthesize aqueous-dispersible Yb3+–Er3+ co-doped hexagonal LaF3 nano-crystals for up-conversion fluorescence

Aqueous-dispersible Yb3+–Er3+ co-doped hexagonal LaF3 nano-crystals were synthesized by a low-temperature aqueous phase approach in the presence of d-glucose. These nano-crystals are about 15–20 nm in rectangular shape and are easily dispersed in water, producing a transparent colloidal solution; they can also be precipitated and separated by the addition of NaOH. The morphology, crystal structure, fluorescence properties of these nano-crystals were analyzed by TEM, XRD, and spectroscopy, respectively. Furthermore, these nano-crystals exhibit red and green fluorescence in the visible spectral region when they are excited at 980 nm. The nano-crystals can be coated by a silica shell and their shape is not changed, which will be useful in the application of biological labeling.