Huang Xiaoyong
Opt Lett. 2015 Aug 1;40(15):3599-602. doi: 10.1364/OL.40.003599.
In this work, colloidal hexagonal-phase (NaYF4:Nd3+/Yb3+/Ho3+)/(NaYF4:Nd3+/Yb3+) core/shell nanoparticles with intense visible upconversion emissions under 808-nm laser excitation were prepared. Compared with the core-only nanoparticles, a maximum 990-fold overall enhancement in the emission intensity of Ho3+ ions was achieved with the help of active-shell coating design, due to the significant increase in the near-infrared absorption and efficient energy transfer from Nd3+ primary-sensitizers to Ho3+ activators via Yb3+ bridging sensitizers. The luminescence-enhancement effect exhibited a strong dependence on the doping concentrations of NaYF4:Nd3+/Yb3+ active-shell. The optimal concentrations of Nd3+ and Yb3+ ions in the active-shell layer were found to be 30 and 5 mol. %, respectively. Moreover, the upconversion emission intensity of NaYF4:Nd3+/Yb3+-coated nanoparticles was about 2.5 times higher than the one coated with a NaYF4:Nd3+ active-shell.
在这项工作中，制备了在808 nm激光激发下具有强烈可见上转换发射的胶体六方相（NaYF4:Nd3+/Yb3+/Ho3+）/（NaYF4:Nd3+/Yb3+）核壳纳米粒子。与仅含核的纳米粒子相比，通过活性壳层包覆设计，Ho3+离子的发射强度总体上最大提高了990倍，这是由于近红外吸收显著增加，以及通过Yb3+桥连敏化剂实现了从Nd3+主敏化剂到Ho3+激活剂的高效能量转移。发光增强效应强烈依赖于NaYF4:Nd3+/Yb3+活性壳层的掺杂浓度。发现活性壳层中Nd3+和Yb3+离子的最佳浓度分别为30和5 mol.%。此外，涂覆有NaYF4:Nd3+/Yb3+的纳米粒子的上转换发射强度比涂覆有NaYF4:Nd3+活性壳层的纳米粒子高约2.5倍。
