Mulder Jence T, Jenkinson Kellie, Toso Stefano, Prato Mirko, Evers Wiel H, Bals Sara, Manna Liberato, Houtepen Arjan J
Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands.
Electron Microscopy for Materials Science (EMAT), Department of Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Chem Mater. 2023 Jul 3;35(14):5311-5321. doi: 10.1021/acs.chemmater.3c00502. eCollection 2023 Jul 25.
Lanthanide-doped LiYF (Ln:YLF) is commonly used for a broad variety of optical applications, such as lasing, photon upconversion and optical refrigeration. When synthesized as nanocrystals (NCs), this material is also of interest for biological applications and fundamental physical studies. Until now, it was unclear how Ln:YLF NCs grow from their ionic precursors into tetragonal NCs with a well-defined, bipyramidal shape and uniform dopant distribution. Here, we study the nucleation and growth of ytterbium-doped LiYF (Yb:YLF), as a template for general Ln:YLF NC syntheses. We show that the formation of bipyramidal Yb:YLF NCs is a multistep process starting with the formation of amorphous Yb:YLF spheres. Over time, these spheres grow via Ostwald ripening and crystallize, resulting in bipyramidal Yb:YLF NCs. We further show that prolonged heating of the NCs results in the degradation of the NCs, observed by the presence of large LiF cubes and small, irregular Yb:YLF NCs. Due to the similarity in chemical nature of all lanthanide ions our work sheds light on the formation stages of Ln:YLF NCs in general.
镧系元素掺杂的LiYF（Ln:YLF）通常用于广泛的光学应用，如激光发射、光子上转换和光制冷。当合成纳米晶体（NCs）时，这种材料在生物应用和基础物理研究方面也备受关注。到目前为止，尚不清楚Ln:YLF NCs是如何从其离子前驱体生长成具有明确双锥体形状和均匀掺杂剂分布的四方NCs的。在这里，我们研究了镱掺杂的LiYF（Yb:YLF）的成核和生长，作为一般Ln:YLF NCs合成的模板。我们表明，双锥体Yb:YLF NCs的形成是一个多步骤过程，始于无定形Yb:YLF球体的形成。随着时间的推移，这些球体通过奥斯特瓦尔德熟化生长并结晶，形成双锥体Yb:YLF NCs。我们进一步表明，NCs的长时间加热会导致NCs降解，这可通过大的LiF立方体和小的、不规则的Yb:YLF NCs的存在观察到。由于所有镧系离子在化学性质上的相似性，我们的工作总体上揭示了Ln:YLF NCs的形成阶段。
