Controlling excited-state proton transfer dynamics using nanocavity engineering

控制分子的激发态特性对于开发新型光功能材料具有重要意义。随着新型多孔材料如金属有机骨架材料的快速发展，分子的封装成为一种很有前途的方法。然而，由于实验和理论上的困难，关于小腔体中的激发特性的信息很少。我们开发了各种纳米和微米腔中分子的处理方法，并结合我们的超快光谱技术。结果发现，当将二苯甲酮嵌入介孔材料MCM-41的纳米孔中时，其发光特性发生了显著的变化。针对这一新现象在发光器件中的应用，我们还研究了封装对有机发光二极管（OLED）发光材料的影响，发现封装大大提高了它们的热激活荧光（TADF）活性。近年来，TADF不仅在有机电致发光材料方面，而且在各种光功能材料中获得长寿命三重态方面的应用引起了人们的广泛关注。因此，这一新发现将有助于开发新型高效光功能器件。此外，我们发现光照射加速了某些类型的发光材料的封装过程。这一发现将打开一个新的世界，如光控制的封装和解封的光功能分子。

Controlling excited-state characters of molecules is of great importance for developing novel photofunctional materials. Encapsulation of a molecule is one of the promising methods by coupling with rapid development of novel porous materials such as metal organic frameworks. Nevertheless, there is little information on excited characters in a small cavity due to experimental and theoretical difficulties. We developed the handling methods of molecules in a various nano- and micro-cavities and combined with our ultrafast spectroscopic techniques. As a result, we found that the emissive character of a prototypical emissive molecule, benzophenone, is dramatically changed when it is encapsuled in a nanocavity of mesoporous material, MCM-41. Aiming at applications of this novel phenomenon to luminescent devices, we also investigated encapsulation effects on emissive materials for organic light emitting diode (OLED), and found that the encapsulation highly improves their thermally activated fluorescence (TADF) activities. Recently, TADF activities have attracted much attention for applications not only to the emissive materials for OLED but also to the harvesting of long-lived triplet-states in various photofunctional materials. Thus, this new finding would be contributed to developments of novel highly efficient photofunctional devices. Moreover, we discovered that light irradiation accelerates encapsulation process for a certain type of emissive materials. This finding would open a new world such as light control of encapsulation and decapsulation of photofunctional molecules.