Department of Advanced Materials Science, Graduate School of Frontier Sciences , The University of Tokyo , 5-1-5 Kashiwanoha , Kashiwa , Chiba 277-8561 , Japan.
ACS Appl Mater Interfaces. 2019 Mar 27;11(12):11893-11903. doi: 10.1021/acsami.8b22568. Epub 2019 Mar 13.
The coordination nanosheets (CONASHs) are emerging as a new class of functional two-dimensional materials, which are one of the most active research areas of chemistry and physics in this decade. Despite the success of various structural and functional CONASHs, the development of a new molecular structure to discover alluring functional CONASHs remains challenging. Herein, we report successful preparation of two novel CONASHs (NBP1 and NBP2) through coordination between one of the unexplored molecular frameworks of bis(2,2'-bipyridine)-based ligands (BP1 and BP2) and Fe ions. Using a liquid-liquid interface as a platform, large-scale thin films of multilayer CONASHs have been prepared without any support, which can be deposited onto any desired substrate. Detailed characterization of the CONASHs using various microscopic and spectroscopic techniques reveals homogeneous and flat morphology of nanometer thickness with the quantitative formation of tris(2,2'-bipyridine)-Fe complex motifs in the nanosheet frameworks. The color of the films has been tuned from blue to magenta by the suitable molecular design of the ligands. Owing to the insolubility of the CONASH films in any solvent and the presence of redox-active Fe, we explore the functionality of these nanostructured thin films deposited on indium tin oxide as electrochromic materials. The CONASHs exhibit color-to-colorless and color-to-color electrochromic transitions with attractive response times, switching stabilities, and coloration efficiencies. Finally, we demonstrate solid-state electrochromic devices of the CONASHs operated at a potential range of +2.5 to -2.5 V, which are electrochemically stable for several switching cycles, suggesting that these CONASHs are potential electrochromic materials for next-generation display applications.
协调纳米片 (CONASHs) 作为一类新兴的功能二维材料，是本十年化学和物理学最活跃的研究领域之一。尽管已经成功制备了各种结构和功能的 CONASHs，但开发新的分子结构以发现诱人的功能 CONASHs 仍然具有挑战性。在此，我们通过一个未探索的基于联吡啶的双齿配体（BP1 和 BP2）与 Fe 离子的配位，成功制备了两种新型 CONASHs（NBP1 和 NBP2）。利用液-液界面作为平台，在没有任何支撑的情况下制备了大面积多层 CONASHs 薄膜，这些薄膜可以沉积在任何所需的基底上。使用各种微观和光谱技术对 CONASHs 进行详细表征，揭示了纳米片框架中具有均匀和平坦形态的纳米级厚度，定量形成了三（2,2'-联吡啶）-Fe 配合物图案。通过配体的适当分子设计，薄膜的颜色可以从蓝色调谐到品红色。由于 CONASH 薄膜在任何溶剂中都不溶解，并且存在氧化还原活性的 Fe，我们探索了这些沉积在氧化铟锡上的纳米结构薄膜作为电致变色材料的功能。CONASHs 表现出从颜色到无色和从颜色到颜色的电致变色转变，具有吸引人的响应时间、开关稳定性和着色效率。最后，我们展示了 CONASHs 的固态电致变色器件，其工作电位范围为+2.5 至-2.5 V，在几个开关循环中具有电化学稳定性，这表明这些 CONASHs 是下一代显示应用的潜在电致变色材料。
