NaYF_4:Er^(3+),Yb^(3+)纳米晶基于尺寸和激发功率的上转换荧光性能研究

Effect of Size and Excitation Power on Upconversion Fluorescence Properties of NaYF_4:Er^(3+),Yb^(3+) Nanocrystals

采用热分解法制备出纯β相的NaYF_4:Er^(3+),Yb^(3+)稀土上转换纳米晶,通过改变表面配体的种类和用量,合成出了两种不同尺寸和形貌的纳米颗粒。使用较少表面配体所合成的纳米颗粒具有更大的尺寸和更规则的形貌。比较了两种纳米颗粒的荧光性能,在980 nm激发光照射下,随着激发光功率的增加,纳米颗粒的荧光强度也逐渐增强,尺寸较大的纳米颗粒的荧光强度比尺寸较小的高了1个数量级。绿光与红光的比例也与纳米颗粒的尺寸和激发光功率密度相关,荧光性能较弱的小尺寸颗粒的绿光比例随激发光功率密度的增加而增大;荧光性能较好的大尺寸颗粒的绿光比例则在增大到一定程度后逐渐减小。此项工作可能在生物体荧光成像、荧光标记、光动力治疗以及生物传感等方面提供指导。

The NaYF4:Er3+,Yb3+ upconverting nanocrystals were prepared by thermal decomposition method. Two kinds of nanoparticles with different size and morphology were synthesized by changing the type and amount of surface ligands. Nanoparticles synthesized using less surface ligands had larger sizes and a more regular morphology. The fluorescence properties of the two nanoparticles were compared. Under the excitation of 980 nm, the fluorescence intensity of the nanoparticles increased with the increase of the excitation light power. The fluorescence intensity of the larger nanoparticles was higher than that of the smaller ones by 1 order of magnitude. The ratio of green light to red light was also related to the size of nano-particles and the power density of the excitation light. The green light proportion of the small-size particles with weaker fluorescence increases with the increase of the power density of the excitation light. The large-particles of the green ratio increased to a certain extent and then gradually decreased. This work may provide guidance in biological fluorescence imaging, fluorescent labeling, photodynamic therapy, and biosensing.