Aggregation-induced emission

Aggregation-induced emission (AIE) is a phenomenon in which certain organic luminophores (fluorescent dyes) exhibit stronger emission of light in their aggregated or solid state compared to when they are in solution.^[1][2][3] This counterintuitive behavior contrasts with most organic compounds, which typically show reduced photoemission in the solid state due to processes like aggregation-caused quenching. AIE is primarily attributed to restricted molecular motion in the aggregated state (decreased flexibility), which suppresses nonradiative energy dissipation and enhances fluorescence efficiency.^[4] The increase of fluorescence emission intensity was also observed upon restriction of molecular motion due to host-guest interactions and viscosity increase,^[5] which is not a common behavior of such host-guest complexes.^[6]

Aggregation-induced emission enhancement

The phenomenon in which organic luminophores show higher photoluminescence efficiency in the aggregated state than in solution is called aggregation-induced emission enhancement (AIEE). Some luminophores, e.g., diketopyrrolopyrrole-based and sulfonamide-based luminophores, only display enhanced emission upon entering the crystalline state. That is, these luminophores are said to exhibit crystallization-induced emission enhancement (CIEE).^[7][8] Luminophores such as noble metallic nanoclusters show higher photoluminescence efficiency in the aggregated state than homogenous dispersion in solution. This phenomenon is known as Aggregation-Induced Emission (AIE).^[9][10]

Aggregation-induced emission polymer

Fluorescence-emission Polymer is a kind of polymer which can absorb light of certain frequency and then give out light.^[11] These polymers can be applied in biomaterial area. Due to their high biocapacity and fluorescence, they can help researchers to find and mark the location of proteins. And polymers with property of aggregation-induced emission can also help to protect the healthy tissues from the harm of the medicines.^[12]