8:00 PM - FF03.05.24
Theoretical Revelation and Experimental Confirmation of the Mechanism of Aggregation-Induced Emission in Organic Materials
Institution of Chemistry1
Better understanding of the mechanism of aggregation-induced emission can help develop novel AIE systems and exploit novel applications. Here, we have disclosed the microscopy mechanism of AIE by systematically investigating the excited-state electronic transition property, nuclear vibrational modes, the radiative and nonradiative decay rate constants, and the fluorescence quantum efficiency using the thermal vibration correlation function rate theory coupled with quantum chemistry calculations. For typical AIEgens with the nature of (π, π*), we have put forward that the block of the nonradiative decay channels recovered strong emission in aggregate. The nonradiative decay channels refer to the molecular vibration modes with large electron-vibration coupling value. We have found the rotational, twisting, bending and stretching vibration modes can be largely restricted in aggregate, resulting in the decrease of the nonradiative decay rate. For some hetero-AIEgens, we have proposed that the conversion from dipole-forbidden (n, π*) or (σ, π*) state to dipole-allowed (π, π*) state happen to induce strong emission when going from solution to aggregate.  Then, we have proposed some strategies to probe and verify the mechanism using the resonant Raman spectrum, isotopic effect, pressure effect, and the nanoparticle size effect and so on. Some of them have been fully confirmed by the experiments. Furthermore, the molecular design principles are raised and many unusual AIE fluophors are designed theoretically and synthesized experimentally. 
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