图文解析Nd@Yb@30%Nd@Y 纳米晶体的设计、表征与光学性质Figure 1. (a) Schematic illustration of the as-synthesized Nd@Yb@30%Nd@Y nanoparticles. (b) The dual-sensitization energy transfer pathway in the heterogeneous Nd@Yb@30%Nd@Y nanocrystal. (c) Transmission electron microscopy (TEM) image of the as-synthesized Nd@Yb@30%Nd@Y nanoparticles. Inset: high-resolution TEM image of the corresponding Nd@Yb@30%Nd@Y nanoparticles. (d) Energy-dispersive X-ray mapping of Nd@Yb@30%Nd@Y nanocrystals. (e) NIR-II emission spectra of Nd@Yb@30%Nd@Y and Nd@Y@1%Nd nanocrystals under 808 nm excitation. (f) NIR-II emission spectra of Nd@Yb@30%Nd@Y and 60%Nd@Y nanocrystals under 808 nm excitation. (g) NIR-II emission spectra of Nd@Yb@30%Nd@Y and 50%Nd@30%Nd@Y nanocrystals under 808 nm excitation. (h) Their enhancement factor of the emission at the range of 900-1400 nm by comparing the intensities of the corresponding nanocrystals in d, e, and f, respectively.纳米粒子设计的关键是在高掺杂浓度的异质纳米结构中构建双重敏化策略，以最大限度地利用激发能量并增强下转换发光。采用逐层生长法制备Nd@Yb@30%Nd@Y 纳米晶体，以100 mol%的Yb3+ 离子作为能量激活剂，可以从100 mol% Nd3+的敏化剂核心和高掺杂(30 mol% Nd3+)的外壳层中吸收激发光的能量促进Yb3+亚晶格中能量跳跃的发生。与传统得那么晶体相比，这种设计策略可使纳米晶体从入射光中捕获更多能量，容纳更高浓度的镧系元素，提供敏化剂和激活剂离子网络之间的最佳相互作用，并抑制有害的交叉松弛，从而获得显著的光学特性。 Nd@Yb@30%Nd@Y 纳米晶体的双敏化机制Figure 2 Schematic illustration (inset) and TEM images of Nd@Yb@30%Nd@Y (a), Y@Yb@30%Nd@Y (b), Nd@Y@30%Nd@Y (c), and Nd@Yb@Y@Y (d) nanoparticles. (e) Downshifting emission spectra of Nd@Yb@30%Nd@Y, Y@Yb@30%Nd@Y, Nd@Y@30%Nd@Y, and Nd@Yb@Y@Y nanoparticles under 808nm excitation. (f) Luminescence decay curves of Yb3+ emissions measured at 980 nm for Nd@Yb@30%Nd@Y, Y@Yb@30%Nd@Y, Nd@Y@30%Nd@Y, and Nd@Yb@Y@Y nanoparticles under 808nm pulsed excitation. (g) Luminescence decay curves of Nd3+ emissions measured at 893 nm for Nd@Yb@Y and Nd@Y@Y nanocrystals under 793 nm pulsed excitation. (h) Luminescence decay curves of Nd3+ emissions measured at 893 nm for Y@Yb@30%Nd@Y and Y@Y@30%Nd@Y nanocrystals under 793 nm pulsed excitation. (i) Schematic illustration of the dual-sensitization and energy transfer process. (j) Schematic energy diagram of the cascade energy transfer within Nd@Yb@30%Nd@Y nanocrystals. 荧光光谱和寿命的测试结果显示Nd@Yb@30%Nd@Y纳米晶体中Nd3+在核心和第二层外壳中发挥关键的作用，它促进了双敏化以及中间层中Nd3+到Yb3+的高效能量转移过程。量化纳米粒子中Nd3+到Yb3+的能量传递效率，结果显示第一个敏化通道中Nd3+到Yb3+的能量传递效率为69%。第二个敏化通道中Nd3+到Yb3+的能量传递效率为77%。这些结果再次证实了所设计的 Nd@Yb@30%Nd@Y 纳米晶体在 808 nm 脉冲激发下是双敏化能量转移过程。双敏化策略增强发光强度的通用性Figure 3. (a) Upconversion and dowshifting emission of A@Y, Yb@A@30%Yb@Y, and Y@A@Y@Y (A = 2% Ho, 2% Er and 1% Tm) nanocrystals. (b) Enhancement factor of the luminescence intensity of Yb@2%Ho@30%Yb@Y nanocrystals in the range of 250-750 nm 1120-1300 nm compared with 2%Ho@Y and Y@2%Ho@Y@Y nanocrystals, respectively. (c-d) Enhancement factor of luminescence of Yb@A@30%Yb@Y (A = 2%Ho, 2% Er and 1% Tm) nanocrystals at 250-750 nm 1300-1600 nm compared with A@Y and Y@A@Y@Y nanocrystals. 分别将发光离子Nd3+换成Ho3+、Er3+和Tm3+，结果显示与传统的单敏化纳米晶体相比，双敏化纳米晶体的上转换和下转换发射明显增强，说明了该双敏化策略具有普遍性。 染料敏化增强NIR - II发光的第三阶段能量收集的构建Figure 4. (a) Absorption spectrum of Nd@Yb@30%Nd@Y nanocrystals (red line) and fluorescence spectrum of ICG (brown line) under 730 nm excitation. (b) Absorption spectra of Nd@Yb@30%Nd@Y and ICG-coated Nd@Yb@30%Nd@Y nanocrystals. (c) Downshifting emission of Nd@Yb@30%Nd@Y and ICG-coated Nd@Yb@30%Nd@Y nanocrystals at an optimized concentration in DMF solution. Enhancement factor of luminescence of Nd@Yb@30%Nd@Y nanocrystals at 900-1100 nm after ICG coating (inset). (d) Fluorescence spectrum of ICG-coated Nd@Yb@30%Nd@Y and ICG-coated Y@Y@Y@Y nanocrystals under 808 nm excitation. (e) Luminescence decay curves of ICG fluorescence measured at 820 nm for Nd@Yb@30%Nd@Y and Y@Y@Y@Y nanocrystals with ICG coating by pulsed 270 nm excitation. (f) Downshifting emission of Nd@Yb@30%Nd@Y and ICG-coated Nd@Yb@30%Nd@Y nanocrystals at optimized concentration in aqueous solution. 为了进一步增强 Nd@Yb@30%Nd@Y 纳米晶体的近红外-II 发射，我们通过染料敏化技术引入了额外的外部能量收集。接下来，我们通过实验设计计算出从 ICG 到 Nd3+ 的能量转移效率为 63.2%。
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