Luminescence quench is common in overdoped upconversion nanoparticles. Various methods have been proposed to counteract the adverse effects of concentration quenching on luminescence, but in upconversion nanoparticles that are highly doped with both sensitizers and activators, the factors that contribute to the diminishing of the emission cannot be summarized by a single cause. Herein, a core-shell design is used to spatially separate the sensitizer (Yb³⁺) and activator (Er³⁺) and to modulate the emission by changes in the distribution position as well as the concentration of the dopant ions in order to probe the factors affecting the luminescence. When the sensitizer ions are located in the core, the luminescence intensity of the nanoparticles is significantly weaker than that of the other distribution, which implies that the effect of sensitizer and activator on luminescence in the highly doped state has a different and more complex mechanism. The intensity of the emission is more affected by Yb³⁺ than Er³⁺, which includes not only the self-quenching of Yb³⁺, but also the dominance in the Yb³⁺–Er³⁺ cross-relaxation. In this finding may provide new ideas for revealing the reasons for the diminished luminescence of highly doped upconversion nanoparticles and thus for enhancing luminescence.

发光猝灭在过度掺杂的上转换纳米粒子中很常见。已经提出了各种方法来抵消浓度猝灭对发光的不利影响，但是在高度掺杂敏化剂和活化剂的上转换纳米颗粒中，导致发射减弱的因素不能用单一原因来概括。这里，核壳设计用于在空间上分离敏化剂（Yb ³⁺ ）和活化剂（Er ³⁺ ），并通过分布位置的变化来调节发射以及掺杂离子的浓度，以探究影响发光的因素。当敏化剂离子位于核心时，纳米粒子的发光强度明显弱于其他分布，这意味着在高掺杂状态下敏化剂和活化剂对发光的影响具有不同且更复杂的机制。发射强度受 Yb ³⁺ 的影响比 Er ³⁺ 的影响更大，这不仅包括 Yb ³⁺ 的自猝灭，还包括Yb ³⁺ –Er ³⁺ 交叉弛豫。这一发现可能为揭示高掺杂上转换纳米粒子发光减弱的原因从而增强发光提供新思路。