基于晶场调节和能量传递的β-Na(Gd_(1-x)Y_x)_(0.95)F_4:5%Eu^(3+)增强发光研究

The Enhanced Luminescence of β-Na(Gd_(1-x)Y_x)_(0.95)F_4:5%Eu^(3+) Nanocrystals Based on Crystal Field Adjustment and Energy Transfer

采用溶剂热法合成了固溶体纳米荧光粉β-Na(Gd_(1-x)Y_x)0.95F_4:5%Eu^(3+)。XRD衍射图样显示随着x由O逐渐增加到1,纳米荧光粉的晶相由纯六方β-NaGdF_4相变成纯六方β-NaYF_4相。在Gd^(3+)的~8S_(7/2)→~6I_J,激发峰激发下,当x=0.2时该固溶体具有最高的发射强度,且为纯六方相β-NaGdF_4的2.16倍。这种发光增强是因为共掺Y^(3+)离子会导致Eu^(3+)周围局域晶场畸变,但我们也发现x=0.4时依旧具有增强效果。纳米粒子表面包覆有机物均苯四甲酸(PMA)后,其激发带能够得到有效的加宽,相应地最强发射强度依旧为x=0.2时情形。文中最后详细讨论了能量传递的具体过程。

Solid-solution nanophosphors β-Na（Gd1-xYx）0.95F4 ： 5%Eu3＋ were synthesized via solvothermal method. The XRD diffraction profiles showed that the pure hexagonal phase β-NaGdF4 gradually transformed into the pure phase β-NaYF, with x increasing from 0 to 1. Under the excitation of 8Sv/2→ 6Ij of Gd3＋ ions, the highest emission intensity correspond to the case of x=0.2, which is of 116% stronger than that of the same fluoride without containing y3＋ ion. The enhancement mechanism of y3＋ co-doping is through crystal field tuning and energy transfer, which caused by the large difference in ion radius between the Gd3＋ and y3＋ ions. Surprisingly, we found that even x=0.4, the corresponding phosphor also have enhanced emission intensity. On coordinated with PMA ligands, the excitation band of the β-Na（Gd1-xYx）0.95F4 ： 5%Eu3＋-PMA hybrid structures was broadened, and the highest emission intensity was obtained also for the case of x=0.2. Detailed energy transfer process was discussed finally.