Lanthanide doped hexagonal phase (β) rare earth fluoride (NaREF₄) nanocrystals have considerable potential in laser and, especially, biological applications. However, their large size and extreme synthetic conditions have become unavoidable obstacles in their path to various applications. Herein, a core-mediated hetero-shell growth method was adopted to synthesize α-NaGdF₄@β-NaLuF₄:Nd³⁺ nanocrystals, in which cubic phase (α) NaGdF₄ was used as the core to induce the subsequent growth of a β-NaLuF₄:Nd³⁺ shell via a two-step solvothermal reaction. The resulting α-NaGdF₄@β-NaLuF₄:Nd³⁺ core–shell nanocrystals were characterized by structural analysis, photoluminescence spectroscopy and decay lifetime. Besides, a persuasive lattice-disordered heterointerface-induced mechanism was proposed to understand the core-mediated hetero-shell growth. Meanwhile, the influence of the heterointerface on the dynamic growth of the shell nanocrystals was also investigated in detail. Most importantly, the near-infrared luminescence intensity at 1.06 μm was enhanced by over two times via coating the lattice-matched homogeneous NaLuF₄ shell on the surface of α-NaGdF₄@β-NaLuF₄:Nd³⁺ nanocrystals. The high-performance α-NaGdF₄@β-NaLuF₄:Nd³⁺ nanocrystals thus obtained are expected to be used for laser output and depth detection of biological tissues.

中文翻译：

---

核介导的α-NaGdF4@β-NaLuF4：Nd3 +核壳纳米晶体的合成，生长机理和近红外发光增强

镧系元素掺杂的六方相（β）稀土氟化物（NaREF ₄）纳米晶体在激光尤其是生物应用中具有相当大的潜力。然而，它们的大尺寸和极端的合成条件已成为它们走向各种应用的不可避免的障碍。在此，芯介导的杂壳生长方法获得通过合成α-NaGdF ₄ @β-NaLuF ₄：钕³⁺纳米晶体，其中，立方相（α）NaGdF ₄用作芯诱导的随后的生长β-NaLuF ₄：钕³⁺壳经由两步溶剂热反应。将得到的α-NaGdF ₄ @β-NaLuF ₄：钕通过结构分析，光致发光光谱和衰变寿命来表征³⁺核壳纳米晶体。此外，提出了有说服力的晶格无序异质界面诱导机制，以了解核心介导的异壳生长。同时，还详细研究了异质界面对壳纳米晶体动态生长的影响。最重要的是，在1.06μm的近红外发光强度超过两次增强经由涂覆晶格匹配均匀NaLuF ₄ α-NaGdF的表面上壳₄ @β-NaLuF ₄的Nd： ³⁺纳米晶体。高性能的α-NaGdF ₄ @β-NaLuF ₄：钕由此获得的³⁺纳米晶体有望用于激光输出和生物组织的深度检测。