聚集诱导发光机理研究

Mechanism Study of Aggregation-Induced Emission

与传统荧光生色团聚集后导致荧光猝灭相反,有一类化合物在单分子状态下荧光微弱甚至观察不到荧光,而在聚集状态下荧光显著增强,这就是聚集诱导发光(AIE)现象。AIE现象独特的优越性使得众多研究组开发出越来越多的新AIE体系,其机理也被广泛而深入地研究。本文总结了目前为止已经提出的AIE机理,包括分子内旋转受限、分子内共平面、抑制光物理过程或光化学反应、非紧密堆积、形成J-聚集体以及形成特殊激基缔合物等;着重评述了目前研究最为全面、适用范围最广的分子内旋转受限机理。同时介绍了一些基于这些机理设计的新AIE体系。

Aggregation of classical fluorophores always quenches their light emission, which is notoriously known as aggregation-caused quenching （ACQ）. The ACQ effect prevents many fluorophores from finding aggregation-state applications. In contrast, a group of fluorophores is weakly luminescent or even nonluminescent in isolated state but highly emissive in aggregate state. Aggregatlon-induced emission （AIE） was coined for this novel phenomenon. Because of their unique advantages, more and more new AIE systems with emission colors covering the entire visible spectral region were developed by numerous research groups. Their applications as solid-state emitters and chemo/bio-sensors were explored widely and deeply. Deciphering the working principle of the AIE phenomenon is of great value in terms of helping gain new photophysical insights and guide further efforts in the development of new AIE materials with high luminescence efficiencies. However, whilst the mature theories to explain the ACQ effect had been written into textbooks, the ＂abnormal＂ AIE phenomenon still poses a challenge to our current understanding of solid-state luminescence. In this review, we summarize the accessible mechanisms for the AIE phenomenon, such as restricted intramolecular rotation （RIR） , intramolecular eoplanarization, inhibition of intramolecular photochemical or photophysical process, relatively loose molecular packing, J-aggregate formation, and special excimer formation. Particularly, we emphasize on the description of RIR mechanism, which is the most universal and best studied one among the proposed mechanisms. In addition, some new AIE systems based on these mechanisms are introduced briefly.