Seminar: What Leads to Aggregation-Induced Emission?

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Title:What Leads to Aggregation-Induced Emission?
Speaker:Prof.Junrong Zheng from Peking University
Time:May 12  10:00am
Venue:Third floor conference room, Scientific Building
Host:Prof. Xiaohui Qiu

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 molecule tetraphenylethylene (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.


Junrong Zheng, Professor of Chemistry.
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.

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