Aggregation-Induced Emission Phenomena in Luminescent Materials

Aggregation-induced emission (AIE) describes the counter-intuitive enhancement of light emission that occurs when certain luminogenic molecules aggregate or crystallise. Unlike traditional fluorophores, which commonly suffer aggregation-caused quenching (ACQ) in the solid or aggregated state, AIE luminogens become highly emissive upon restriction of intramolecular motions. This restriction may involve rotations, vibrations or conformational changes being hindered in the aggregated phase, diverting excited-state energy into radiative decay. The discovery of AIE has opened pathways to robust solid-state emitters with high photoluminescence quantum yields (PLQYs), exceptional environmental stability and tunable optical properties. AIE materials now underpin applications in optoelectronic devices, mechanochromic sensors, bio-imaging probes and security printing. Their design leverages molecular engineering of propeller-like cores, supramolecular encapsulation and controlled packing motifs to achieve bespoke emission wavelengths and stimuli-responsive behaviour. Collectively, this field bridges fundamental photophysics with practical devices, offering a global platform for next-generation luminescent materials.

Research from Nature Portfolio

Recent studies have advanced AIE in three major directions. First, host–guest inclusion within macrocyclic frameworks has been shown to modulate mechanochromic emission: pyridinium-substituted luminogens form encapsulated complexes that exhibit sequential red shifts upon mechanical grinding, delivering finely tunable solid-state colours. Second, co-assembly strategies pairing planar polycyclic aromatic hydrocarbons with molecular barriers successfully suppress ACQ, boosting solid-state PLQYs by several hundred per cent and endowing nano-cocrystals with water dispersibility and excellent cell-imaging performance. Third, the introduction of nitrophenyl units into twisted AIE cores enables highly sensitive on–off luminescence switching via control of the intersystem crossing channel, yielding thin films capable of high-contrast optical data recording and haptic sensing. Together, these advances illustrate how supramolecular manipulation, co-assembly and photophysical control converge to enhance AIE-based emission and functionality.

Aggregation-Induced Emission Phenomena in Luminescent Materials publication trend

The graph below shows the total number of articles in aggregation-induced emission phenomena in luminescent materials across all publications each year (not limited to Nature Index journals).

Technical terms

Aggregation-induced emission (AIE): A photophysical phenomenon where emission intensifies upon molecular aggregation or crystallisation.

Aggregation-caused quenching (ACQ): Loss of fluorescence efficiency when planar chromophores aggregate, due to non-radiative decay.

Photoluminescence quantum yield (PLQY): The ratio of emitted to absorbed photons, indicating emission efficiency.

Host–guest inclusion: Supramolecular encapsulation of a guest molecule within a host framework, influencing photophysical properties.

Mechanochromism: Change in emission colour or intensity of a material in response to applied mechanical force.

Intersystem crossing (ISC): Non-radiative transition between electronic states of different spin multiplicity, affecting emission on–off behaviour.

References

1. The host–guest inclusion driven by host-stabilized charge transfer for construction of sequentially red-shifted mechanochromic system. Nature Communications (2023).
2. The Strong Light‐Emission Materials in the Aggregated State: What Happens from a Single Molecule to the Collective Group. Advanced Science (2017).
3. Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers. Nature Communications (2019).
4. Highly sensitive switching of solid-state luminescence by controlling intersystem crossing. Nature Communications (2018).
5. Exploration of biocompatible AIEgens from natural resources. Chemical Science (2018).
6. Soft Crystals: Flexible Response Systems with High Structural Order. Chemistry - A European Journal (2019).