Controlling excited-state proton transfer dynamics using nanocavity engineering

控制分子的激发态性质对于开发新型光功能材料具有重要意义。分子的包覆与金属有机骨架等新型多孔材料的快速发展相结合，是一种很有前途的方法。然而，由于实验和理论上的困难，关于小腔中激发特征的信息很少。我们开发了在各种纳米和微腔中处理分子的方法，并与我们的超快光谱技术相结合。结果，我们发现，当一个典型的发射分子二苯甲酮被包裹在介孔材料MCM-41的纳米腔中时，它的发射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，发现这种封装大大提高了它们的热激活荧光(TADF)活性。近年来，TADF在有机电致发光材料以及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极大关注。因此，这一新的发现将有助于新型高效光功能器件的开发。此外，我们还发现，光照射加速了某类发光材料的封装过程。这一发现将开辟一个新的领域，如光控制光功能分子的封装和解封。

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.