A Mechanistic Understanding of Nonclassical Crystal Growth in Hydrothermally Synthesized Sodium Yttrium Fluoride Nanowires,Chemistry of Materials

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A Mechanistic Understanding of Nonclassical Crystal Growth in Hydrothermally Synthesized Sodium Yttrium Fluoride Nanowires
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-02-26 , DOI: 10.1021/acs.chemmater.9b04076
Alexander B. Bard ₁ , Xuezhe Zhou ₂ , Xiaojing Xia ₃ , Guomin Zhu _{2,

4} , Matthew B. Lim ₂ , Seung Min Kim ₅ , Matthew C. Johnson ₆ , Justin M. Kollman ₆ , Matthew A. Marcus ₇ , Steven R. Spurgeon ₈ , Daniel E. Perea ₉ , Arun Devaraj ₄ , Jaehun Chun ₄ , James J. De Yoreo _{1,

2,

4} , Peter J. Pauzauskie _{1,

2,

4}

Affiliation

Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
Department of Molecular Engineering and Science, University of Washington, Seattle, Washington 98195, United States
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk 55324, Republic of Korea
Department of Biochemistry, University of Washington, Seattle, Washington 98195, United States
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
Environmental Molecular Sciences Laboratory, Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

Sodium yttrium fluoride (NaYF₄) is an important upconverting material with many potential uses in chemistry, materials science, and biology, which can be synthesized hydrothermally in both cubic (α) and hexagonal (β) crystallographic polymorphs. Understanding the mechanisms underlying the phase conversion between the cubic and hexagonal polymorphs is of great interest to help inform future synthetic efforts, for example in the design of atomically precise quantum materials with well-defined sizes and morphologies. In this work, we use a combination of analytical transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), powder X-ray diffraction (XRD), in situ liquid cell TEM, atom probe tomography (APT), and extended X-ray absorption fine structure (EXAFS) measurements to show that the hexagonal NaYF₄ nanowires form through a nonclassical crystal growth mechanism involving the formation and subsequent oriented attachment of mesocrystals consisting of cubic (α) phase units. EXAFS measurements also suggest that substitutional Yb³⁺ point defects within NaYF₄ are distributed evenly throughout the crystal lattice without clustering and also that they may exhibit selective substitution into one of the two possible trivalent yttrium sites in the unit cell for hydrothermally synthesized β-NaYF₄.

中文翻译：

水热合成氟化钇钇纳米线中非经典晶体生长的机理理解。

氟化钇钇（NaYF ₄）是一种重要的上转换材料，在化学，材料科学和生物学中具有许多潜在用途，可以水热合成立方（α）和六角形（β）晶体多晶型物。理解立方和六边形多晶型物之间的相变机理很重要，有助于为将来的合成工作提供信息，例如在设计具有明确定义的尺寸和形貌的原子精确量子材料时。在这项工作中，我们结合使用了分析透射电子显微镜（TEM），扫描透射电子显微镜（STEM），粉末X射线衍射（XRD），原位液池TEM，原子探针层析成像（APT）和扩展X射线吸收精细结构（EXAFS）测量显示六角形的NaYF ₄纳米线是通过非经典的晶体生长机制形成的，该机制涉及由立方（α）相单元组成的介晶的形成和随后的定向附着。EXAFS测量还表明，NaYF ₄中的取代Yb ³⁺点缺陷均匀分布在整个晶格中，而没有聚集，并且对于水热合成的β-NaYF，它们可能表现出选择性取代进入晶胞中两个可能的三价钇位点之一的可能性。₄。

更新日期：2020-02-26

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