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首页> 外文期刊>Journal of Materials Chemistry, C. materials for optical and electronic devices >Selective synthesis, polymorphism, reversible phase transition and structure-dependent optical functionalities of gadolinium oxyfluorides
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Selective synthesis, polymorphism, reversible phase transition and structure-dependent optical functionalities of gadolinium oxyfluorides

机译：选择性合成，多态性，可逆相转变和钆氧化钆的依赖性光学函数

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摘要

Polymorphism in functional materials offers an excellent platform for comparative investigations of the structure-property relationship and thus the rational design of functional materials with enhanced performances. Here, we report a facile and selective fluorination route to phase-pure gadolinium oxyfluorides crystallizing in orthorhombic (O-GdOF) and rhombohedral (R-GdOF) structures. The phase selectivity can be achieved simply by controlling the reaction temperature and the amount of the fluoridizer (polytetrafluoroethylene). A reversible phase transition from R-GdOF to O-GdOF was observed around 600 degrees C upon heating and cooling, which was further confirmed by the in situ X-ray diffraction results. Trivalent rare-earth ion (RE3+) doping makes O- and R-GdOF potential bifunctional materials for optical imaging and magnetic resonance imaging (MRI) applications. Under near infrared (NIR) irradiation (980 nm), both RE3+-doped O- and R-GdOF exhibit intriguing visible upconversion (UC) emissions with a tunable G/R ratio (RE = Yb/Ho), near single-peak red emissions around 660 nm (RE = Yb/Er) and NIR emissions around 800 nm (RE = Yb/Tm). RE3+-doped O-and R-GdOF also show discrepant UC profiles in terms of emission intensity, peak shape and G/R ratios attributed to the subtle symmetry differences of the RE3+ doping sites. Besides, the ability of RE3+-doped O-and R-GdOF to serve as T-2 weighted MRI contrast agents was evaluated. The results show that R-GdOF performs better than O-GdOF in T-2 weighted MRI with higher r(2) relaxivity values and r(2)/r(1) ratio. The exploration of more RE oxyfluorides with multimorphism and the comparative studies of their optical performances will provide deep insight into their structure-property relationship and accelerate the rational design of better multifunctional materials.
机译：功能材料中的多态性提供了一个优异的结构性质关系的比较调查平台，因此具有增强性能的功能材料的合理设计。在这里，我们报告了在正交（O-Gdof）和菱形（R-Gdof）结构中结晶的相纯钆氧化载体的容易和选择性的氟化途径。通过控制反应温度和荧光剂（聚四氟乙烯）的量，可以简单地实现相选择性。在加热和冷却时，从R-GDOF到O-GdOF的可逆相转变在约600℃下观察到，通过原位X射线衍射结果进一步证实。三价稀土离子（RE3 +）掺杂使得用于光学成像和磁共振成像（MRI）应用的O-和R-GDOF潜在的双官能材料。在近红外（NIR）照射（980nm）下，RE3 +掺杂的O-和R-GDOF都表现出具有可调的G / R比（RE = YB / HO）的有趣的可见升高（UC）排放，在单峰值红色附近大约660nm（Re = Yb / ER）和NIR排放约为800nm（RE = YB / TM）的排放。 Re3 + -Doped O-and R-Gdof还在发射强度，峰值形状和G / R比归因于RE3 +掺杂位点的微妙对称差异而言。此外，评价RE3 + -DOPED O-o-和R-GDOF作为T-2加权MRI造影剂的能力。结果表明，R-GDOF在T-2加权MRI中比O-GDOF更好，具有较高的R（2）松弛率值和R（2）/ R（1）比率。具有多体形和其光学表现的更多Re氧化氧化物的探索将深入了解其结构性质关系，并加速了更好的多功能材料的合理设计。

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