Effective colour modulation of upconversion emissions in lanthanide-doped nanomaterials becomes even more important for fundamental and applied research. Herein, on the one hand, by raising the content of doped Yb³⁺ from 10 mol% to 50 mol%, a significant increase of the red/green emission ratio from 4.0 to 68.2 is observed in K₂NaScF₆:Yb/Er nanocrystals. This yellow to red colour change is attributed to the increased cross relaxation between Er³⁺ and Yb³⁺ caused by the increased Yb³⁺ amount, ⁴S_3/2 (Er³⁺) + ²F_7/2 (Yb³⁺) → ⁴I_13/2 (Er³⁺) + ²F_5/2 (Yb³⁺). On the other hand, the upconversion green and red emission of K₂NaScF₆:Yb/Er (20/2 mol%) nanocrystals are intensified 10.6 and 8.8 folds, respectively, after an active shell (K₂NaScF₆:Yb) is epitaxially grown, which are more effective than the 7.4- and 6.4-fold enhancement from an inert shell (K₂NaScF₆) growth. Moreover, the shell thickness from 2.85 to 9.5 nm through controlling the molar ratio of shell-precursor to core from 1:2 to 3:1 can be easily realized. This study will provide more opportunities for the application of K₂NaScF₆:Yb/Ln nanoparticles in varied fields such as theranostics, photovoltaics, and photocatalysis.

镧系元素掺杂纳米材料中上转换发射的有效颜色调制对于基础和应用研究变得更加重要。在此，一方面，通过将掺杂 Yb ³⁺的含量从 10 mol% 提高到 50 mol%，在 K ₂ NaScF ₆ :Yb/Er 中观察到红/绿发射比从 4.0 显着增加到 68.2纳米晶体。这种黄色到红色的变化归因于 Er ³⁺和 Yb ³⁺之间的交叉弛豫增加，这是由增加的 Yb ³⁺量引起的，⁴ S _3/2 (Er ³⁺ ) +  ² F _7/2 (Yb ³⁺ ) →⁴ I _13/2 (Er ³⁺ ) +  ² F _5/2 (Yb ³⁺ )。另一方面，K ₂ NaScF ₆ :Yb/Er (20/2 mol%) 纳米晶体的上转换绿色和红色发射分别增强了 10.6 和 8.8 倍，在活性壳 (K ₂ NaScF ₆ :Yb) 被外延生长，这比惰性壳 (K ₂ NaScF ₆） 生长。此外，通过控制壳前体与核的摩尔比从 1:2 到 3:1，可以很容易地实现壳厚度从 2.85 到 9.5 nm。这项研究将为 K ₂ NaScF ₆ :Yb/Ln 纳米粒子在治疗诊断学、光伏和光催化等不同领域的应用提供更多机会。