NaYF4∶Er3＋, Yb3＋纳米晶的液相合成

采用丙三醇液相结晶法制备了NaYF4∶Er3＋, Yb3＋上转换纳米晶, 合成步骤被简化. 常温下, 用980 nm的红外激光激发可以观察到很强的绿光、红光发射, 用荧光光谱仪记录了该上转换光谱. X射线粉末衍射(XRD)结果表明, 该方法制备NaYF4∶Er3＋, Yb3＋纳米晶属于立方混合六方晶系. 研究了纳米晶的上转换发光机理, 根据晶体场理论对Er3＋的两个上转换能级进行了Stark分裂计算, 对两个能级之间的谱线进行了归属, 进一步证实了980 nm光子激发Er3＋离子的上转换机理, 一个是连续吸收两个980 nm光子的过程(激发态吸收), 另一个是吸收980 nm光子后, 电子转移到亚稳态能级, 然后再吸收980 nm光子过程(能量转移上转换).

Liquid Preparation of Soluble NaYF4 : Er3+, Yb3+ Nanocrystals

The NaYF4∶Er3＋, Yb3＋ nanocrystals have been prepared by liquid crystallization from glycerol. Red at 660 nm and green at 550 nm upconversion emissions were observed from NaYF4∶Er3＋, Yb3＋ nanocrystals under 980 nm excitation. The X-ray diffraction patterns confirm the nanocrystals are cubic and hexagonal. The mechanism of nanocrystal upconvertion has been studied. The Stark splits of two excitated states of Er3＋ have been calculated based on theory of crystallization fields. The results confirm the upconverted mechanisms in the NaYF4∶Er3＋, Yb3＋ nanocrystals are due to two processes, one is a consecutive absorption of two 980 nm photon process, and the other process is that electrons transfer to substeady states after absorption of 980 nm photons, then absorb 980 nm photons.