aggregationinduced

Aggregationinduced is a descriptor used in chemistry and materials science to refer to phenomena that arise when molecules aggregate. The most widely studied instance is aggregation-induced emission (AIE), where compounds emit more strongly in the aggregated or solid state than in dilute solution. The term captures the idea that certain properties emerge or change as molecular assemblies form.

Aggregation-induced emission was first demonstrated in the early 2000s with silole-based fluorophores. In solution, intramolecular motions can dissipate excited-state energy nonradiatively, quenched by flexible bonds. Upon aggregation, these motions become restricted, reducing nonradiative decay and increasing radiative emission. This mechanism is often described as a restriction of intramolecular rotation (RIR) or restriction of intramolecular motion (RIM). The effect has been observed in a wide range of organic and inorganic systems and can be tuned by molecular design and aggregation conditions.

Applications of aggregation-induced phenomena are broad. AIE luminogens are used in organic light-emitting diodes, displays, chemical and biological sensing, and bioimaging, where solid-like environments or aggregates enhance performance. Related concepts include aggregation-induced quenching (AIQ), where aggregation diminishes emission for some dyes, highlighting that aggregation can have opposite photophysical outcomes depending on molecular structure. Beyond emissions, aggregation can also influence crystallization, phase behavior, and catalytic or sensing performance, making aggregation-induced effects a central consideration in materials design.