Aggregation-Induced Emission for Visualization in Materials Science

Fluorescent imaging techniques have attracted much attention as a powerful tool to realize the visualization of structural and morphological evolution of various materials. However, the traditional fluorescent dyes usually suffered from aggregation-caused quenching, which severely limits the visualization results. In contrast, aggregation-induced emission (AIE) molecules with high quantum yields in the condensed state showed great opportunities for imaging techniques. In this feature article, recent progresses in visualization with AIE molecules are discussed. Assembly processes including crystallization, gelation process, and dissipative assembly have been observed. To better study information obtained regarding the processes, visualization during reactions, phase transitions, and molecular motions are successfully presented. Based on these successes, AIE molecules were further applied for phase recognition, macro-dispersion evaluation, and damage detection. Finally, we also present the outlook and perspectives, in our opinion, for the development of visualization by AIE molecules.

Multi-Stimuli-Responsive Fluorescence Switching from a Pyridine-Functionalized Tetraphenylethene AIEgen

The discovery of the striking aggregation-induced emission (AIE) phenomenon has opened a new avenue for smart light-emitting materials. Herein, a new AIE luminogen (AIEgen), 1,1,2,2-tetrakis(4-((E)-2-(pyridin-2-yl)vinyl)phenyl)ethene (TP2VPE), has been designed and synthesized by introducing the vinylpyridine motifs into the tetraphenylethene backbone. The emission spectrum of the new obtained AIEgen crystalline material can be switched in response to not only mechanical grinding and hydrostatic compression but also the protonation effect with excellent reversibility and reproducibility. Single-crystal X-ray structural analysis disclosed the supramolecular porous channel structure, which provides a shrinkable volume to maintain the fluorescence emission upon high pressure. Furthermore, protonation-deprotonation of the pyridine moieties in TP2VPE has a significant effect on the frontier molecular orbitals as well as very distinctive emission characteristics upon acid and base stimuli. The dual-response performance and the ease of its preparation and renewal endow the material with potential applications in pressure and acid/alkali fluorescence sensing.

Two novel AIEE-active imidazole/ α-cyanostilbene derivatives: photophysical properties, reversible fluorescence switching, and detection of explosives

Novel imidazole derivatives containing the α-cyanostilbene unit can act as reversible acid/base stimulated fluorescence switches in the solid state, as chemosensors for explosives detection in aqueous systems, and as test strip detectors.

A novel carbazole derivative containing fluorobenzene unit: aggregation-induced fluorescence emission, polymorphism, mechanochromism and non-reversible thermo-stimulus fluorescence

Different conformations and packing modes induce the compound with unique stimuli-responsive properties.

Tunable solid state emission of novel V-shaped fluorophores by subtle structure modification: polymorphism, mechanofluoro-chromism and micro-fabrication

A largely wide and nearly successive range of solid-state emission wavelengths can be achievedviapolymorphism, mechanofluorochromism and micro-fabrication on rationally designed V-shaped fluorophores with subtle structure modification.