采用溶剂热法合成了超小尺寸三氟化镧（LaF₃）纳米晶. 利用XRD、TEM等对其进行结构与形貌表征，结果显示制得的纳米颗粒为LaF₃纳米晶，且具有高度均一的尺寸分布和良好的结晶度，颗粒尺寸为6±0.4 nm. 通过共掺杂镱铒两种稀土元素，所得材料在近红外光激发下（980 nm）可发射出明亮的绿光；发光光谱显示，在524，544，655 nm等位置有较强的发射峰. 利用聚琥珀酰亚胺高分子（PSI）对油溶性的纳米颗粒表面进行功能化修饰，将其成功转移水相. 利用叶酸对其进行进一步生物标记，可与肝癌细胞表面叶酸受体特异性识别，成功地实现了肝癌细胞上转换绿色发光成像研究.

Rare earth doped lanthanum fluoride nanocrystals (LaF₃:5% Yb, 2% Er) with ultra-small particle size and uniform shape were successfully synthesized via a solvothermal method in octadecylene. In this synthetic system, oleic acid and octadecylene was used as surfactant and solvent, respectively. After the surfactant oleic acid, the precursor of rare earth ions and HF-oleylamine solution were added in octadecylene orderly, the mixture solution was then heated to 310 ℃ and maintained at this temperature for 1 h under a protective nitrogen flow throughout. The morphology, crystal structures and average size of the LaF₃: 5% Yb, 2% Er nanocrystals were characterized by transmission electron microscope (TEM), powder X-ray diffraction (XRD), and dynamic light scattering (DLS). The XRD patterns show a representative refiection of hexagonal phase LaF₃ nanocrystals, which was also confirmed by high-resolution TEM (HRTEM) analysis. Based on over 100 nanoparticles from the TEM image, the average size of the monodispersible nanoparticles was 6 nm with a standard deviation of 0.4 nm. Under the irradiation of 980-nm diode laser, these small nanocrystals emit strong green upconversion luminescence. The green emissions at 524 and 544 nm can be assigned to the energy level transition of Er³⁺ ions from ²H_11/2 to ⁴I_15/2 and ⁴S_3/2 to ⁴I_15/2, respectively. Another obvious emission bands at 655 nm is the result of transition from ⁴F_9/2 to ⁴I_15/2 (red) of Er³⁺ ions. Before the biomedical applications as biomarkers, these hydrophobic nanocrystals were successfully functionalized with poly(amino acid) to render them water-dispersible, bioconjugatable and biocompatible by means of a novel and facile encapsulation strategy. The TEM imaging shows the hydrophobic nanocrystals were successfully transferred into water with one particle per micelle without aggregation and the DLS characterization show the average hydrate particle size was 14.1 nm. The above results indicate that these water soluble materials were well monodispersible. Due to their ultrasmall particle size and novel upconversion luminescence, these nanocrystals were bioconjugated with folic acid and successfully utilized as biomarkers for targeted cancer cell imaging.