Ln³⁺-doped (Ln = lanthanide) nanocrystals are garnering strong interest for their potential as optical materials in various applications. For that reason, a thorough understanding of photophysical processes and ways to tune them in these materials is of great importance. This study, using Eu³⁺-doped Sr₂YF₇ as a well-suited model system, underscores the (not unexpected) significance of surface site occupation of Ln³⁺ and also challenges the prevailing views about their contribution to the luminescence of the system. High-temperature cation exchange and epitaxial shell growth allow nanocrystals to exclusively feature Eu³⁺ residing at the surface or in the interior, thereby separating their spectral responses. Meticulous experiments reveal that nanocrystals with high doping concentrations exhibit luminescence primarily from surface Eu³⁺, in contrast to the popular belief that luminescence from surface Ln³⁺ is largely negligible. The present study shows, on the one hand, the necessity to revise common ideas and also reveals the potential for manipulating the luminescence of such materials through an, until now, unperceived way of surface engineering.

中文翻译：

---

通过 Ln3+ 掺杂纳米晶体中的表面位点占据来操纵发光

Ln ³⁺掺杂（Ln = 镧系元素）纳米晶体因其在各种应用中作为光学材料的潜力而引起了人们的浓厚兴趣。因此，彻底了解光物理过程以及在这些材料中调整光物理过程的方法非常重要。这项研究使用Eu ³⁺掺杂的Sr ₂ YF ₇作为非常合适的模型系统，强调了Ln ³⁺表面位点占据的（并非意外的）重要性，并且还挑战了关于它们对发光的贡献的普遍观点。系统。高温阳离子交换和外延壳生长使纳米晶体能够仅以位于表面或内部的Eu ³⁺为特征，从而分离它们的光谱响应。细致的实验表明，具有高掺杂浓度的纳米晶体主要表现出来自表面Eu ³⁺的发光，这与普遍认为来自表面Ln ³⁺的发光在很大程度上可以忽略不计的看法相反。目前的研究一方面表明了修改常见想法的必要性，另一方面也揭示了通过迄今为止未被察觉的表面工程方式来操纵此类材料的发光的潜力。