The NaYF₄:Yb/Er@NaLuF₄:Yb nanosphere were synthesized by a solvothermal method in a short time and low temperature, and applied to cell imaging.

NaYF₄:Yb³⁺/Er³⁺ nanocrystals were prepared using a hydrothermal method. The products were characterized by XRD, SEM, TEM, HRTEM, and photoluminescence (FL). The XRD results indicated that the sample’s phase transformed from cubic to hexagonal when EDTA was added at low reaction temperatures. The SEM results revealed that the products were transformed from granular to rod-shaped with an increase in temperature. TEM images revealed the diameter of sample prepared at 120°C is about 10-50nm. HRTEM showed that crystals prepared at 120°C grew along {111} surfaces. The PL results indicated that samples prepared at 180°C without EDTA have the strongest luminescence property.