Small Leo J, Hill Ryan C, Krumhansl James L, Schindelholz Mara E, Chen Zhihengyu, Chapman Karena W, Zhang Xinran, Yang Sihai, Schröder Martin, Nenoff Tina M
Sandia National Laboratories , Albuquerque 87185 , New Mexico , United States.
Department of Chemistry , Stony Brook University , 100 Nicolls Road , New York 11794 , United States.
ACS Appl Mater Interfaces. 2019 Aug 7;11(31):27982-27988. doi: 10.1021/acsami.9b09938. Epub 2019 Jul 29.
Iodine detection is crucial for nuclear waste clean-up and first responder activities. For ease of use and durability of response, robust active materials that enable the direct electrical detection of I are needed. Herein, a large reversible electrical response is demonstrated as I is controllably and repeatedly adsorbed and desorbed from a series of metal-organic frameworks (MOFs) MFM-300(X), each possessing a different metal center (X = Al, Fe, In, or Sc) bridged by biphenyl-3,3',5,5'-tetracarboxylate linkers. Impedance spectroscopy is used to evaluate how the different metal centers influence the electrical response upon cycling of I gas, ranging from 10× to 10× decrease in resistance upon I adsorption in air. This large variation in electrical response is attributed not only to the differing structural characteristics of the MOFs but also to the differing MOF morphologies and how this influences the degree of reversibility of I adsorption. Interestingly, MFM-300(Al) and MFM-300(In) displayed the largest changes in resistance (up to 10×) yet lost much of their adsorption capacity after five I adsorption cycles in air. On the other hand, MFM-300(Fe) and MFM-300(Sc) revealed more moderate changes in resistance (10-100×), maintaining most of their original adsorption capacity after five cycles. This work demonstrates how changes in MOFs can profoundly affect the magnitude and reversibility of the electrical response of sensor materials. Tuning both the intrinsic (resistivity and adsorption capacity) and extrinsic (surface area and particle morphology) properties is necessary to develop highly reversible, large signal-generating MOF materials for direct electrical readout for I sensing.
碘检测对于核废料清理和应急响应活动至关重要。为便于使用并确保响应的耐久性，需要能够直接对碘进行电学检测的坚固活性材料。在此，当碘可控且反复地从一系列金属有机框架（MOF）MFM - 300(X)上吸附和解吸时，展示出了大的可逆电响应，每个MFM - 300(X)都具有由联苯 - 3,3',5,5'-四羧酸酯连接体桥接的不同金属中心（X = 铝、铁、铟或钪）。阻抗谱用于评估不同金属中心在碘气体循环过程中如何影响电响应，在空气中碘吸附时电阻下降幅度从10倍到10倍不等。这种电响应的巨大差异不仅归因于MOF不同的结构特征，还归因于不同的MOF形态以及这如何影响碘吸附的可逆程度。有趣的是，MFM - 300(Al)和MFM - 300(In)在空气中经过五次碘吸附循环后，电阻变化最大（高达10倍），但其吸附容量却损失了很多。另一方面，MFM - 300(Fe)和MFM - 300(Sc)的电阻变化较为适中（10 - 100倍），经过五次循环后仍保持大部分原始吸附容量。这项工作展示了MOF的变化如何深刻影响传感材料电响应的幅度和可逆性。为开发用于碘传感直接电学读出的高度可逆、大信号产生的MOF材料，调节内在（电阻率和吸附容量）和外在（表面积和颗粒形态）特性都是必要的。
