State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 430074, Wuhan, China.
Beijing National Laboratory for Molecular Science, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, 100190, Beijing, China.
Nat Commun. 2020 Mar 4;11(1):1174. doi: 10.1038/s41467-020-14879-9.
Photon upconversion in lanthanide-doped upconversion nanoparticles offers a wide variety of applications including deep-tissue biophotonics. However, the upconversion luminescence and efficiency, especially involving multiple photons, is still limited by the concentration quenching effect. Here, we demonstrate a multilayered core-shell-shell structure for lanthanide doped NaYF, where Er activators and Yb sensitizers are spatially separated, which can enhance the multiphoton emission from Er by 100-fold compared with the multiphoton emission from canonical core-shell nanocrystals. This difference is due to the excitation energy transfer at the interface between activator core and sensitizer shell being unexpectedly efficient, as revealed by the structural and temperature dependence of the multiphoton upconversion luminescence. Therefore, the concentration quenching is suppressed via alleviation of cross-relaxation between the activator and the sensitizer, resulting in a high quantum yield of up to 6.34% for this layered structure. These findings will enable versatile design of multiphoton upconverting nanoparticles overcoming the conventional limitation.
镧系掺杂上转换纳米粒子的光子上转换提供了广泛的应用，包括深层生物光子学。然而，上转换发光和效率，特别是涉及多光子，仍然受到浓度猝灭效应的限制。在这里，我们展示了一种镧系掺杂 NaYF 的多层核壳壳结构，其中 Er 激活剂和 Yb 敏化剂在空间上分离，这可以将 Er 的多光子发射增强 100 倍，与经典的核壳纳米晶体的多光子发射相比。这种差异是由于在激活剂核和敏化剂壳之间的界面处的激发能量转移出乎意料地高效，如通过多光子上转换发光的结构和温度依赖性所揭示的。因此，通过减轻激活剂和敏化剂之间的交叉弛豫，抑制了浓度猝灭，从而使这种分层结构的量子产率高达 6.34%。这些发现将使多光子上转换纳米粒子的设计具有多功能性，克服传统的限制。
