Aggregation‐Induced Emission (AIE): A Historical Perspective

Abstract

Aggregation‐induced emission (AIE) has attracted considerable interest over the last twenty years. In contrast to the large number of available reviews focusing specifically on AIE, this Essay discusses the AIE phenomenon from a broader perspective, with an emphasis on early observations related to AIE made long before the term was coined. Illustrative examples are highlighted from the 20th century where fluorescence enhancement upon rigidification of dyes in viscous or solid environments or J‐aggregate formation was studied. It is shown that these examples already include typical AIE luminogens such as tetraphenylethylene (TPE) as well as stilbenes and oligo‐ or polyphenylenevinylenes and ‐ethynylenes, which became important fluorescent solid‐state materials in OLED research in the 1990s. Further examples include cyanine dyes such as thiazole orange (TO) or its dimers (TOTOs), which have been widely applied as molecular probes in nucleic acid research. The up to 10 000‐fold fluorescence enhancement of such dyes upon intercalation into double‐stranded DNA, attributable to the restricted intramolecular motion (RIM) concept, afforded commercial products for bioimaging and fluorescence sensing applications already in the early 1990s.

Supramolecular assemblies of a 1,8-naphthalimide conjugate and its aggregation-induced emission property

“…In the last two decades, aggregation-induced emission (AIE) [1][2][3][4][5][6][7] properties of different fluorophore-based systems have been explored extensively owing to their wide-range of applications in different research areas including sensing, imaging, and theranostic. Most of the common and conventional, organic aromatic fluorophores with planar structure undergo strong intermolecular H-type π-π stacking interaction and relax via a non-radiative pathway leading to aggregation-caused quenching (ACQ).…”

Phenylpyridyl‐Fused Boroles: A Unique Coordination Mode and Weak B−N Coordination‐Induced Dual Fluorescence

“…2 10 À5 M) at which the measurement was performed, we can rule out the formation of nanoparticleinduced emission (also termed aggregation-induced emission (AIE)). [34] To gain further insight into those processes,wemeasured the temperature dependence of the emission spectra and lifetime in 2-MeTHF (Figure 4, top). Thei ntensity of the emission decreases when the temperature is lowered and, at the same time,t he relative percentage of the short lifetime (% ST )i ncreases until the long lifetime (% LT )a t5 20 nm disappears completely at ca.…”

Potential of Microfluidics and Lab-on-Chip Platforms to Improve Understanding of “prion-like” Protein Assembly and Behavior

“…In addition, recent reports illustrate the relevance of the use of aggregation-induced emission (AIE) dyes as a preferential strategy to identify protein fibrillogenesis, particularly the light up characteristic associated with binding events during the aggregation process. These dyes feature high emission efficiency in the aggregate state, strong photo-stability, and excellent biocompatibility (Wurthner, 2020). Examples of their use can be found in the analysis of insulin (Hong et al, 2012;Huang Q. et al, 2017) and of β-amyloid aggregation (Zhang J. D. et al, 2016;Fu et al, 2019;Yang et al, 2019).…”

“…Examples of their use can be found in the analysis of insulin (Hong et al, 2012;Huang Q. et al, 2017) and of β-amyloid aggregation (Zhang J. D. et al, 2016;Fu et al, 2019;Yang et al, 2019). Readers may find a general survey of these techniques in Wurthner (2020).…”