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What Leads to Aggregation-Induced Emission? 为什么会聚集诱导发光?
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主讲人: 郑俊荣 北京大学化学学院 教授
地点: 物理楼西楼464
时间: 2020年12月16日(周三)下午 13:30-15:30
主持 联系人: 肖立新(62767290)
主讲人简介: Prof. Junrong Zheng completed his PhD and postdoctoral studies from Stanford University. He is professor of chemistry at Peking University. Prior to joining PKU, he was a faculty member at Rice University in Houston. He is a recipient of numerous prestigious awards including the Sloan Fellowship and the Packard Fellowship. 

The mechanism of aggregation-induced emission (AIE), which overcomes the common aggregation-caused quenching (ACQ) problem in organic optoelectronics, is revealed by monitoring the real time structural evolution and dynamics of electronic excited state with frequency and polarization resolved ultrafast ultraviolet/infrared spectroscopy and theoretical calculations. The formation of Woodward-Hoffmann cyclic intermediates upon ultraviolet excitation is observed within picoseconds in dilute solutions of AIE moleculetetraphenylethylene(TPE) and its derivatives but not in their respective solid. The ultrafast excited state cyclization by crossing a conical intersection (CI) provides an efficient nonradiative relaxation pathway in solutions. Without such a reaction mechanism, the electronic excitation is preserved in the molecular solids and the molecule fluoresces efficiently, aided by the very slow intermolecular charge and energy transfers due to the well separated nonplanar molecular packing arrangement in solids. The mechanisms revealed can be general for tuning the properties of chromophores in different phases for various important applications.