利用溶剂热法合成了NaYF4∶20%Yb,0.5%Tm上转换发光纳米粒子(UCNPs), 用扫描电子显微镜、X射线衍射分析、发光光谱测量等手段对水溶性纳米颗粒进行了形貌和发光性质表征。结果表明, UCNPs是纯立方相的NaYF4, 尺寸均匀分布在30 nm左右。在980 nm红外光的激发下, UCNPs能够发出肉眼可见的明亮的蓝紫色光。发射光谱中最强发射峰在479 nm, 来源于Tm3+离子的1G4→3H6发射, 并且给出了UCNPs的上转换发光机制。利用聚乙烯吡咯烷酮(PVP)作为表面活性剂所制备的上转换发光纳米颗粒具有良好的水溶性, 尺寸较小, 在生物荧光标记领域具有潜在的应用价值。

Water soluble NaYF4∶20%Yb, 0.5%Tm upconversion nanoparticles(UCNPs) were prepared by a facile solvothermal approach using polyvinylpyrrolidone (PVP) as the surfactant. X-ray diffraction(XRD) analyses showed that the UCNPs were pure cubic phase NaYF4 nanocrystals. The size and morphology of the UCNPs were characterized by a scanning electron microscopy(SEM). The SEM　images proved that almost all the UCNPs were nanospheres with the size of ~40 nm. The UCNPs could be well dispersed in water to form a clearly transparent solution which could be kept for at least two days and there was no obvious precipitation. Pumped with 980-nm diode laser, the solution presented bright naked eye-visible violet/blue upconversion luminescence and the upconversion mechanism of the UCNPs was also given in this paper. These results showed that the UCNPs had potential applications in biological field as luminescence labeling probes.