Fluorescence is a gift from nature and plays an important role in our colorful world. Inspired by nature, humanity started to study this “interesting phenomenon” in the early 19th century. Deeper cognition on the fluorescence process can not only reveal some natural laws but also better utilize and reform the natural world. With the rapid development of science and technology, fluorescence-based techniques have been well applied in the fields of biology, medicine, optoelectronics, mechanical engineering, and so forth, as evidence by the Nobel prize in Chemistry in 2008 and 2014 for the discovery of green fluorescent protein and super-resolved fluorescence microscopy, respectively.

However, most of the conventional luminophores show strong emission in solution but almost no emission in...[ Read more ]

Fluorescence is a gift from nature and plays an important role in our colorful world. Inspired by nature, humanity started to study this “interesting phenomenon” in the early 19th century. Deeper cognition on the fluorescence process can not only reveal some natural laws but also better utilize and reform the natural world. With the rapid development of science and technology, fluorescence-based techniques have been well applied in the fields of biology, medicine, optoelectronics, mechanical engineering, and so forth, as evidence by the Nobel prize in Chemistry in 2008 and 2014 for the discovery of green fluorescent protein and super-resolved fluorescence microscopy, respectively.

However, most of the conventional luminophores show strong emission in solution but almost no emission in the aggregate state. This phenomenon was defined as aggregation-caused quenching (ACQ) and had been documented for more than 50 years. The AIE luminogens (AIEgens) exhibit exact opposite photophysical properties of ACQ molecules and generally show weak or no emission in solution but strong emission upon aggregate formation. Such discovery is not only of academic importance but also shows wide application prospects. Based on the previous research of AIE, several mechanistic works were carried out during my PhD research.

Through systematic molecular design, we have developed a new kind of AIEgens. Further experimental and theoretical study suggested that the excited-state phenyl-ring twisting, bond stretching and double-bond torsion contributed majorly to the nonradiative pathway of AIEgens in solution. These motions were restricted by molecular aggregation to result in strong emission of the molecules in the aggregate state.

After that, we have well studied another special AIE system – clusteroluminogens. Several non-conjugated systems were designed and synthesized. Then, with the help of theoretical calculation, we proved that several types of interaction contributed to the clusteroluminescence. Such as intramolecular through-space π conjugation, intermolecular through-space π conjugation and intermolecular through-space n-electron conjugation.

At last, inspired by the restriction of intramolecular rotation (RIR) mechanism. We have synthesized a series of diphenylethylene and p-terphenyl derivatives and unexpected chiroptical signals were observed in their aggregate state. Theoretical calculation was used to explain the mechanism of spontaneous resolution. Finally, we proposed that the spontaneous resolution was caused by the difference of resolution rate of two enantiomers, K₁ > K₂.