Thermal quenching, in which light emission experiences a loss with increasing temperature, broadly limits luminescent efficiency at higher temperature in optical materials, such as lighting phosphors^1,2,3 and fluorescent probes^4,5,6. Thermal quenching is commonly caused by the increased activity of phonons that leverages the non-radiative relaxation pathways. Here, we report a kind of heat-favourable phonons existing at the surface of lanthanide-doped upconversion nanomaterials to combat thermal quenching. It favours energy transfer from sensitizers to activators to pump up the intermediate excited-state upconversion process. We identify that the oxygen moiety chelating Yb³⁺ ions, [Yb···O], is the key underpinning this enhancement. We demonstrate an approximately 2,000-fold enhancement in blue emission for 9.7 nm Yb³⁺-Tm³⁺ co-doped nanoparticles at 453 K. This strategy not only provides a powerful solution to illuminate the dark layer of ultra-small upconversion nanoparticles, but also suggests a new pathway to build high-efficiency upconversion systems.

热猝灭，其中光发射随着温度的升高而损失，广泛地限制了光学材料在较高温度下的发光效率，所述光学材料例如是发光荧光粉^1,2,3和荧光探针^4,5,6。热猝灭通常是由声子的活动增加引起的，该声子利用了非辐射弛豫途径。在这里，我们报告一种在镧系元素掺杂的上转换纳米材料表面存在的对热有利的声子，以对抗热猝灭。它有利于从敏化剂到活化剂的能量转移，以提高中间激发态上转换过程的效率。我们发现氧部分螯合Yb ³⁺离子[Yb···O]是增强此功能的关键。我们证明了在453 K下9.7 nm Yb ³⁺ -Tm ³⁺共掺杂纳米粒子的蓝色发射增强了约2,000倍。该策略不仅提供了一种强大的解决方案，可以照亮超小型上转换纳米粒子的暗层，而且还提出了构建高效上变频系统的新途径。