The perfect energy level overlap of ²H_11/2, ⁴S_3/2, and ⁴F_9/2 in Er³⁺ ions with those of ⁵F₃, ⁵F₄/⁵S₂, and ⁵F₅ in adjacently codoped Ho³⁺ ions allows efficient interenergy transfer. Therefore, in addition to routine activators, Er³⁺ or Ho³⁺ can further act as sensitizers to transfer the upconverted energy to nearby Ho³⁺ or Er³⁺, resulting in enhanced upconversion luminescence due to the emission overlap. Proper codoping of Er³⁺/Ho³⁺ or Ho³⁺/Er³⁺ obviously elevates the maximum doping concentration (thus producing additional upconverted photons) to a level higher than that causing luminescence quenching and significantly enhances upconversion emissions compared with those of singly Er³⁺ or Ho³⁺-doped host materials. Indeed, the so-far strongest red upconversion emission under 1532 nm excitation was obtained in LiYF₄:Er/[email protected]₄ nanoparticles and Ho³⁺-sensitized Er³⁺ upconversion emissions excited by 1150 nm laser was simultaneously discovered. With great enhancement compared with that of singly Ho³⁺ doped counterparts, this work demonstrates the generality and rationality of our design strategy.

中文翻译：

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通过镧系离子能级重叠实现更亮的光子上转换发射的设计

完美的能级重叠² ħ _11/2，⁴ š _3/2，和⁴ ˚F _9/2在铒³⁺离子与那些的⁵ ˚F ₃，⁵ ˚F ₄ / ⁵ š ₂，和⁵ ˚F ₅在相邻共掺杂的Ho ³⁺离子可实现高效的能量间转移。因此，除常规活化剂外，Er ³⁺或Ho ³⁺还可充当敏化剂，将上转换后的能量转移到附近的Ho ³⁺或Er ³⁺，由于发射重叠，导致上转换发光增强。与单独使用Er ³⁺ / Ho ³⁺或Ho ³⁺ / Er ^3+进行适当的共掺杂相比，最大掺杂浓度（从而产生额外的上转换光子）明显提高了引起发光猝灭的水平，并显着提高了上转换发射量。掺有Er ³⁺或Ho ^3+的基质材料。实际上，在LiYF ₄：Er / [受电子邮件保护的] ₄纳米粒子和Ho ³⁺致敏的Er ^3+中获得了1532 nm激发下迄今为止最强的红色上转换发射。同时发现了由1150 nm激光激发的上转换发射。与单独添加Ho ^3+的同行相比，这项工作有了很大的增强，证明了我们设计策略的普遍性和合理性。