Time-resolved fluorescence study of aggregation-induced emission enhancement by restriction of intramolecular charge transfer state.
Cyano-substituted oligo (alpha-phenylenevinylene)-1,4-bis(R-cyano-4-diphenylaminostyryl)-2,5-diphenylbenzene (CNDPASDB) molecules are studied in solution and aggregate state by time-resolved fluorescence techniques. CNDPASDB exhibits a strong solvent polarity dependent characteristic of aggregation-induced emission (AIE). By time-dependent spectra, the gradual transition from local excited state to intramolecular charge transfer state with the increasing solvent polarity is clearly resolved. The transition time in high polarity solvent DMF is very fast, around 0.5 ps, resulting in a low fluorescence quantum yield. While in aggregate state, the intramolecular torsion is restricted and the local environment becomes less polar. Thus, the intramolecular charge transfer state is eliminated and efficient AIE occurs.
Gao
Bing-Rong
BR
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China.
Wang
Hai-Yu
HY
Hao
Ya-Wei
YW
Fu
Li-Min
LM
Fang
Hong-Hua
HH
Jiang
Ying
Y
Wang
Lei
L
Chen
Qi-Dai
QD
Xia
Hong
H
Pan
Ling-Yun
LY
Ma
Yu-Guang
YG
Sun
Hong-Bo
HB