Fluolab【Adv.Mater.】突破极限！0.49微克戈瑞超低检测限，全向X射线探测迎来里程碑
文章标题：Molecularly Engineered Spherical Hybrid Glass Scintillator Enables Portable Omnidirectional X‐Ray Detection With High Sensitivity
通讯作者：Bing Chen, Qiang Zhao, Feng Wang
文章概要
引言
全向X射线探测技术在宇宙空间探索、核工业安全监控以及辐射防护等领域发挥着举足轻重的作用。例如在天体物理学中，全向探测器是捕捉超新星爆发或黑洞高能耀斑等突发宇宙事件的关键。然而，现有的气态、液态探测器或由多个平板探测器拼装而成的全向探测系统，普遍面临着结构极其复杂、体积庞大、成本高昂以及便携性差等瓶颈。虽然新兴的有机-无机杂化金属卤化物玻璃具有良好的加工性能，但它们往往在低熔点与高玻璃转变温度之间存在难以调和的矛盾，极易在工作环境中发生自发结晶而导致性能退化。为了突破这一两难困境，研究团队提出了一种崭新的分子工程策略，成功开发出兼具低熔点和高玻璃转变温度的优质全向X射线探测器。
Comparison between flat-panel X-ray detection with anisotropic response and spherical X-ray detection with isotropic response. (a) In anisotropic X-ray detection based on a flat-panel scintillator, the responsivity is highly dependent on the incidence direction of the X-ray. (b) In isotropic X-ray detection based on a spherical ODXD, the responsivity is largely independent of the incident direction of X-rays. S1 and S2 denote X-ray sources with different incidence directions, while _I_1 and _I_2 represent radioluminescence generated by S1 and S2, respectively.
主要实验及结论
研究人员通过巧妙的分子设计，在经典的 triphenylphosphine 阳离子中引入了小巧且刚性的环丙基，成功合成出一种新型杂化溴化锰单晶。晶体结构分析表明，该材料属于 空间群，展现出零维电子结构。由于环丙基带来的独特电荷分布和强大的位阻效应，这种材料的熔点被显著降低至170°C，使得团队能够利用温和的熔融淬火工艺将其轻松制备成均匀透明的非晶态玻璃。与此同时，该玻璃还拥有高达61°C的玻璃转变温度和107°C的结晶温度，在常温甚至较高温度下展现出优异的抗结晶能力和环境稳定性。
Characterizations of the (CPTP)2MnBr4 crystals. (a) Crystal structure of (CPTP)2MnBr4. (b) Powder XRD pattern of (CPTP)2MnBr4 crystals. (c) Attenuated total reflectance Fourier transform infrared spectra of (CPTP)2MnBr4 and CPTP-Br, respectively. The O─H stretching vibration at 3500 cm−1 originates from water molecules adsorbed on CPTP-Br. (d) Enlarged drawing of c in the range of 400–1000 cm−1. (e) Excitation (black line) and emission (green line) spectra of (CPTP)2MnBr4 crystals. (f) Thermogravimetric (gray line) and derivative thermogravimetric (blue line) curves of (CPTP)2MnBr4 crystals in an air atmosphere. (g) Distances between the positively charged unit (P+) and the negatively charged unit ([MnBr4]2− tetrahedron): d(1) = 5.61 Å and d(2) = 6.56 Å, respectively. The structure was visualized using the crystallographic visualization software Diamond (version 3.2).
Characterizations of (CPTP)2MnBr4 glass and mechanistic investigations of its glass formation process. (a) DSC curves of the crystalline (CPTP)2MnBr4 (top panel) and glassy (CPTP)2MnBr4 (bottom panel), respectively. (b) Powder XRD pattern of glassy (CPTP)2MnBr4. (c) Transmittance spectrum of glassy (CPTP)2MnBr4. Inset: a photograph of as-prepared (CPTP)2MnBr4 glass showing its high transparency. (d) Excitation (pink line) and emission (green line) spectra of (CPTP)2MnBr4 glass. (e) Contour plot of in situ temperature-dependent photoluminescence of (CPTP)2MnBr4 glass over the temperature range of 20°C–120°C. (f) Molecular structures (top panel) and electrostatic potential plots (bottom panel) of PTP, IPTP, and CPTP cations, respectively. (g) Comparison of _T_m values for (PTP)2MnBr4, (IPTP)2MnBr4, and (CPTP)2MnBr4, together with their corresponding viscosities measured at temperatures 2°C above their respective _T_m values. (h) Comparison of _T_g and _T_c values for (PTP)2MnBr4, (IPTP)2MnBr4, and (CPTP)2MnBr4.
在光学与辐射发光性能方面，由于零维结构有效抑制了锰离子之间的交叉弛豫，该杂化玻璃在X射线照射下表现出强烈的绿色荧光发射，中心波长位于528纳米。更令人振奋的是，该材料的绝对光产额高达12000 photons/MeV，这一数值足足是传统溶液法量子点闪烁体的四倍。基于这种材料高超的工艺可塑性，研究团队不仅成功制备出直径约60毫米的高质量平板闪烁体，更进一步打造出了直径仅为1.8厘米的球形全向X射线探测器。为了消除外界光线的干扰，探测器表面还致密包裹了一层40纳米厚的铝膜，这层极薄的铝膜在几乎不阻挡X射线穿透的同时，还将光收集效率提升了29%。实验结果表明，该球形探测器在全方位各角度下的X射线响应极其均匀，其最低响应极限达到了惊人的0.49微克戈瑞每秒，这一灵敏度比常规医疗诊断的剂量率标准还要低11倍。此外，团队还成功演示了该探测器在模拟生物组织放疗剂量监测，以及搭载无人机进行室内外全向核源追踪等复杂场景中的实际应用。
Design and performance evaluation of an ODXD based on spherical (CPTP)2MnBr4 glass scintillators. (a) X-ray absorption coefficient of (CPTP)2MnBr4 as a function of photon energy. LuAG:Ce and Eu(NTA)3DPEPO are plotted as references. (b) Absolute RL spectra of the (CPTP)2MnBr4 glass under the X-ray excitation (tube voltage/current: 50 kV/70 µA). LuAG:Ce and BGO are plotted as references. (c) photograph of the ODXD based on spherical (CPTP)2MnBr4 glass scintillator. Inset: photograph of spherical (CPTP)2MnBr4 scintillator under 365 nm excitation. (d) Schematic diagram of the ODXD under angle-dependent X-ray excitation. (e,f) Angle-dependence of the RL when the X-ray source moves along a circular path in the (e) xy plane (φ) and (f) yz plane (θ), respectively. (g) Thickness profile of the Al coating. Inset: scheme of thickness measurement of Al coating using a step profiler. (h) X-ray attenuation induced by the Al reflector as a function of Al thickness at a tube voltage of 50 kV. Inset: photograph of the ODXD with a 40 nm Al coating. (i) RL intensity of the ODXD with and without Al coating as a function of X-ray dose rate at a tube voltage of 50 kV. Inset: enlarged view of the response range from 0 to 3.5 µGyair s−1.
Applications of the ODXD for radiation source tracing and dosimetry. (a) Schematic diagram of the ODXD platform for monitoring a moving X-ray source and multiple X-ray sources. (b) Angle-dependent RL signal of the spherical (CPTP)2MnBr4 glass ODXD recorded under a moving X-ray source (Source 1). (c) Superimposed RL signals of the spherical (CPTP)2MnBr4 glass ODXD recorded under multiple X-ray sources. (d) Schematic diagram of a gastroscope-like X-ray dosimeter using an ODXD for radiotherapy monitoring. (e) Experimental setup for biological X-ray dosimetry. (f) RL intensity of spherical (CPTP)2MnBr4 glass ODXD as a function of X-ray dose rate in the presence of porcine skin, fat, and muscle tissues with a tube voltage of 50 kV. (g) Schematic diagram of indoor and outdoor X-ray tracing using an aerial vehicle equipped with the ODXD.
总结及展望
这项研究通过引入刚性环丙基的分子工程手段，成功打破了杂化玻璃在热力学稳定性与加工性之间的平衡限制，为构建高性能、高集成度的固态球形全向X射线探测器开辟了全新途径。这种新型探测器不仅体积小巧、便携性极佳，更在全向探测精度和灵敏度上取得了突破性进展。在未来的研究和产业化进程中，该技术有望在临床精准放射治疗实时监测、深空探测装备微型化以及智能化环境辐射安全预警等先进传感与光子学领域引发深远的变革。