Local structural engineering is an endogenous approach to modulate upconversion luminescence (UCL) from upstream to meet the needs of specific application scenarios. Herein, high pressure is utilized as a means to modulate the local structure, and the designed LiErF₄:0.5%Tm³⁺@LiYF₄ (Er:Tm@Y) nanoparticles with fast energy transfer rates, abundant cross-relaxation processes, and multiple near-infrared wavelengths (808, 980, 1530 nm) excitation properties are tailored as local structure-sensitive hosts. A unique excitation wavelength-dependent UCL enhancement of Er:Tm@Y upconversion nanoparticles is observed by pressure-induced local structure distortions. When the pressure of ≈6 GPa is applied, the UCL is enhanced by a factor of 2.6 at 980 nm excitation only. After pressure release, the luminescence diminishes and recovers. Density functional theory calculations show that the symmetry distortion of the LiErF₄ crystal reaches a maximum at pressurization to 6 GPa, while a new Er-4f state emerges, greatly reducing the bandgap from 8.3 to 5.7 eV. Comparative experiments demonstrate that the local symmetry distortion caused by 0.5%Tm³⁺ doping and the different energy transfer patterns of Er³⁺ to Tm³⁺ at different excitations are responsible for this wavelength-dependent luminescence enhancement.

中文翻译：

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高压下 Tm3+ 掺杂 LiErF4@LiYF4 系统中激发波长相关的上转换发光增强

局部结构工程是一种从上游调制上转换发光（UCL）以满足特定应用场景需求的内源性方法。在此，利用高压作为调节局部结构的手段，设计的LiErF ₄ :0.5%Tm ³⁺ @LiYF ₄(Er:Tm@Y) 纳米粒子具有快速的能量传输速率、丰富的交叉弛豫过程和多个近红外波长（808、980、1530 nm）激发特性，被定制为局部结构敏感的主体。通过压力诱导的局部结构变形观察到 Er:Tm@Y 上转换纳米粒子独特的激发波长依赖性 UCL 增强。当施加 ≈6 GPa 的压力时，UCL 仅在 980 nm 激发下增强了 2.6 倍。压力释放后，发光减弱并恢复。密度泛函理论计算表明LiErF _{4的对称性畸变}晶体在加压至 6 GPa 时达到最大值，同时出现新的 Er-4f 态，将带隙从 8.3 大大降低到 5.7 eV。^{比较实验表明，由 0.5%Tm 3+}掺杂引起的局部对称畸变和不同激发下 Er ³⁺到 Tm ³⁺的不同能量转移模式是造成这种依赖于波长的发光增强的原因。