PH-dependent morphology and its effect on the optical properties of LaF3:Nd nanocrystals

• PH-dependent shape and optical properties for the LaF3:Nd nanocrystals were observed.
• The samples with hollow structures and hexagon-shape were obtained at low and high pH respectively.
• The fluorescence lifetime were decreased with the pH increasing and exhibit the maximum at pH 2.

Nd3+-doped LaF3 nanocrystals with different morphologies have been produced via solvothermal method at various pH values (1–6). Their morphologies and optical properties were characterized by TEM, fluorescence spectra and decay curves. A possible formation mechanism including burst-nucleation and growth process was proposed. The results reveal that when the pH increases from 1 to 2 to 4–6, the nanocrystals' mean size reduces slightly and the morphologies transform from the hollow sphere to the packed hexagon. The fluorescence lifetime and quantum efficiency achieved maximum for the samples synthesized at pH = 2. These nanocrystals with small size (<30 nm) and bright photoluminescence are promising phosphors in the applications of biological, optical amplifiers and liquid laser fields.