Fluolab【Angew.Chem.】中科院福建物构所林启普、张健等|超稳异质簇MOF闪烁体面世：光产额突破37600，10 M碱液浸泡仍纹丝不动
文章标题：Ultrastable Heterocluster Metal-Organic Framework Scintillator via Reticular Armoring of Iodocuprate Modules for X-ray Imaging
通讯作者：Hui-Li Zheng, Jian Zhang, Qipu Lin
文章概要
引言
X射线闪烁体作为将高能射线转化为可见光的关键材料，在医学成像、安检监测及工业探伤等领域具有不可替代的作用。虽然传统的无机闪烁体性能优异，但其昂贵的制备成本、固有的脆性以及对复杂环境的敏感性限制了其在柔性设备和极端环境下的应用。近年来，金属有机框架（MOF） 因其结构可调控性成为闪烁体研究的热点，然而，如何在保持高发光效率的同时，赋予材料极强的化学抗性，一直是该领域难以攻克的瓶颈。
Synthetic route and crystal structures of CuSI-MPTZ. (a) Schematic illustration of the building units and assembly process. (b) Ball-and-stick representation of the 3D heterocluster framework. (c, d) Polyhedral view highlighting the 4,4-connected cds topology. Color code: Cu, bright-green/pink; I, orange; S, yellow; N, blue; C, gray; H atoms are omitted for clarity.
主要实验及结论
研究团队巧妙地采用原子精确的异质簇组装策略，将具有高效发光特性的碘化铜簇（{Cu2I2}） 嵌入到高度稳定的铜-巯基簇（{Cu6S6}） 构成的刚性骨架中，成功合成了名为CuSI-MPTZ的新型闪烁体。实验结果显示，该材料展现出了令人惊叹的稳定性：在1 M盐酸、10 M氢氧化钠溶液以及沸水中连续处理7天后，其晶体结构依然保持完整，甚至在空气中放置两年也未见降解。这种卓越的稳定性源于疏水性的叔丁基巯基壳层对金属配位键的精准屏蔽，有效阻断了水分子和腐蚀性离子的进攻。
Structural stability of CuSI-MPTZ. (a) PXRD patterns of CuSI-MPTZ after treatment with various acid–base solutions and boiling water for 7 days. (b) Comparison of the acid–base stability between CuSI-MPTZ with those of selected representative MOFs. (c) pH-dependent contact angles of CuSI-MPTZ; insets show photographs of droplets on compressed CuSI-MPTZ tablets.
Photophysical properties of CuSI-MPTZ. (a) Photographs of CuSI-MPTZ powder (top) and composite film (bottom) under daylight (left) and 365 nm UV irradiation (right). (b) Normalized PL excitation and emission spectra. (c) CIE 1931 chromaticity coordinates (0.55, 0.45) corresponding to the yellow emission. (d) 3D excitation–emission correlation map. (e) Temperature-dependent 3D PL emission spectra. (f) Integrated PL intensity as a function of reciprocal temperature, fitted to the Arrhenius model. (g) Temperature-dependent PL decay curves. (h) Power-density-dependent 3D PL emission spectra. (i) PL intensity as a function of excitation power density.
Electronic structure and photophysical mechanism of CuSI-MPTZ. (a) Band structure. (b) projected density of states (PDOS). (c) Spatial distributions of the frontier orbitals (HOMO and LUMO). (d) Schematic energy-level diagram illustrating the key photophysical processes.
在光物理性能方面，CuSI-MPTZ的表现同样亮眼。其光致发光量子产率达到38.7%，呈现出宽带黄光发射。在X射线激发下，该材料的光产额高达37,600 photons/MeV，大幅超越了BGO、LYSO:Ce等商用无机闪烁体。同时，它的最低检测限仅为81.84 nGy/s，仅为医学诊断标准阈值的几十分之一。更具实用价值的是，研究者利用该材料制备了大面积、高透明且柔性的PDMS复合闪烁屏，其空间分辨率达到11.82 lp/mm，能够清晰捕捉到金属钥匙、圆珠笔弹簧以及生物组织内部微细针头的影像，且余辉时间短至3毫秒以内，有效避免了动态成像中的鬼影现象。
Water stability of CuSI-MPTZ. (a) Time-dependent photographs of CuSI-MPTZ immersed in water under 365 nm UV irradiation. (b) Time-dependent 3D PL emission spectra during water immersion. (c) Time-dependent PXRD patterns of CuSI-MPTZ upon prolonged exposure to water.
Radioluminescence performance of CuSI-MPTZ. (a) RL spectra of CuSI-MPTZ and LuAG:Ce under X-ray irradiation. (b) Comparison of light yields for CuSI-MPTZ and selected commercial scintillators. (c) X-ray absorption coefficients of CuSI-MPTZ and LuAG:Ce as a function of photon energy. (d) Dose-dependent RL spectra of CuSI-MPTZ. (e) RL intensity versus X-ray dose rate for CuSI-MPTZ with the detection limit. (f) RL stability of CuSI-MPTZ under continuous X-ray irradiation. (g) Comparison of the scintillation performance of CuSI-MPTZ and representative X-ray scintillators. (h) Schematic illustration of the proposed RL mechanism in CuSI-MPTZ under X-ray excitation.
Flexible X-ray imaging using CuSI-MPTZ-PDMS composite screens. (a) Schematic representation of the indirect X-ray imaging system. (b) Photographs illustrating the uniformity, transparency, and mechanical flexibility of the CuSI-MPTZ-PDMS composite film. (c) MTF curve for the CuSI-MPTZ-PDMS scintillation screen. (d) Bright-field (left) and X-ray transmission (right) images of selected objects: a metal key enclosed in a box, a ballpoint pen with its internal spring, a light-emitting diode (LED) lamp, and duck wings with an inserted needle. (e) Afterglow intensity decay profile following X-ray cutoff; the inset highlights the detailed intensity decay.
总结及展望
这项研究通过创新的异质簇网格铠甲化策略，成功解决了杂化闪烁体效率与稳定性不可兼得的长期矛盾。CuSI-MPTZ不仅刷新了低毒、低成本MOF闪烁体的性能上限，更通过柔性大面积成像展示了其在低剂量医学影像和 harsh-environment（恶劣环境）辐射监测中的巨大潜力。这一成果为开发下一代高性能、长寿命的晶态杂化闪烁体开辟了新的结构设计范式，有望推动X射线探测技术向更安全、更精准、更灵活的方向迈进。