Liu Jun, Deng Huawei, Huang Zhanyun, Zhang Yueli, Chen Dihu, Shao Yuanzhi
State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, P. R. China.
Phys Chem Chem Phys. 2015 Jun 21;17(23):15412-8. doi: 10.1039/c5cp01632k.
Manipulation of upconversion (UC) emission is of particular importance for multiplexed bioimaging. Here, we precisely manipulate the UC color output by utilizing the phonon-assisted energy back transfer (EBT) process in ultra-small (sub-10 nm) Gd2O3:Yb(3+)/Er(3+) UC nanoparticles (UCNPs). We synthesized the Gd2O3:Yb(3+)/Er(3+) UCNPs by adopting the laser ablation in liquid (LAL) technique. The synthesized Gd2O3:Yb(3+)/Er(3+) UCNPs are small spherical and monoclinic structures. Continuous color-tunable (from green to red) UC fluorescence emission is achieved by increasing the concentration of Yb(3+) ions from 0 to 15 mol%. A phonon-assisted energy back transfer (EBT) process from Er(3+) ((4)S3/2 → (4)I13/2) to nearby Yb(3+) ((2)F7/2 → (2)F5/2), which can significantly enhance red emission at 672 nm and decrease green emission, is responsible for the color-tunable UC emission by increasing the Yb(3+) concentration in Gd2O3:Yb(3+)/Er(3+) UC nanoparticles.
上转换（UC）发射的调控对于多重生物成像尤为重要。在此，我们通过利用超小（小于10纳米）的Gd2O3:Yb(3+)/Er(3+)上转换纳米颗粒（UCNPs）中的声子辅助能量反向转移（EBT）过程，精确调控UC颜色输出。我们采用液体中的激光烧蚀（LAL）技术合成了Gd2O3:Yb(3+)/Er(3+) UCNPs。合成的Gd2O3:Yb(3+)/Er(3+) UCNPs为小球形单斜结构。通过将Yb(3+)离子浓度从0增加到15摩尔%，实现了连续的颜色可调（从绿色到红色）UC荧光发射。从Er(3+)（(4)S3/2 → (4)I13/2）到附近Yb(3+)（(2)F7/2 → (2)F5/2）的声子辅助能量反向转移（EBT）过程，可显著增强672纳米处的红色发射并降低绿色发射，该过程通过增加Gd2O3:Yb(3+)/Er(3+) UCNPs中Yb(3+)的浓度来实现颜色可调的UC发射。
