Lecture Topic:

What Leads to Aggregate-Induced Emission?

Lecturer:

Zheng Junrong

Time:

November 14, 2019 (Thursday) 15:00-16:00

Place:

Lecture Hall, North Campus, Liangxiang Campus

Organizer:

Graduate School, School of Chemistry and Chemical Engineering

Registration method:

Log-in to WeChat enterprise of Beijing Institute of Technology— 第二课堂（The Second Lecture）— Choose No.278 in the Lecture Registration

【Lecture Information】

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 molecular packing arrangement in solids. The mechanisms revealed can be general for tuning the properties of chromophores in different phases for various important applications.