Circularly polarized luminescence (CPL), the emission analogue to circular dichroism (CD), reflects the chirality of materials in the excited electronic state. CPL active materials with efficient performances are essentially suitable as emitters for optoelectronic devices for stereoscopic optical processing, display and storage, and sensors for chiral recognition in pharmaceutical industries and biological systems. However, compared to standard photoluminescence spectroscopy, CPL spectroscopy is less studied. Typically, CPL is generated when a luminophore experiences in a dissymmetric environment in the excited state and thus inevitably requires helical arrangement of the luminophoric molecules. The ordered assembly of the luminogens, however, results in reduced emission efficie...[ Read more ]

Circularly polarized luminescence (CPL), the emission analogue to circular dichroism (CD), reflects the chirality of materials in the excited electronic state. CPL active materials with efficient performances are essentially suitable as emitters for optoelectronic devices for stereoscopic optical processing, display and storage, and sensors for chiral recognition in pharmaceutical industries and biological systems. However, compared to standard photoluminescence spectroscopy, CPL spectroscopy is less studied. Typically, CPL is generated when a luminophore experiences in a dissymmetric environment in the excited state and thus inevitably requires helical arrangement of the luminophoric molecules. The ordered assembly of the luminogens, however, results in reduced emission efficiency owing to the notorious aggregation-caused quenching (ACQ) effect suffered by most conventional chromophores. Therefore, overcoming the ACQ effect is a key step towards the design and fabrication of efficient CPL emitters.

An excellent phenomenon opposite to ACQ was discovered in 2001 by our group: a series of nonluminescent molecules are induced to emit efficiently by aggregate formation [aggregation-induced emission (AIE)]. It is envisaged that AIE luminogens can possess improved CPL performance. Attracted by the intriguing phenomenon and its fascinating perspectives, I have launched a new program directed towards the development of new AIE materials with circularly polarized luminescence (CPL).

In order to induce the helical arrangement of the AIE luminogens, chiral peripheral groups including sugar and amino acid are used to functionalize the silole core. The resultant molecules are capable of self-assembling into helical structures which have high fluorescent quantum efficiency and remarkable CPL signals. Interestingly, different fabrication methods leading to different morphologies can change the preference of either left- or right-handed circular signals. One of the examples also shows that the preference can be tuned through the addition of enantio-pure mendalic acids.

In addition, facile oxidative coupling reactions are employed to construct new type of AIE luminogens with different functionalities.