Aggregation- and crystallization-induced light emission

A group of organic chromophoric molecules including siloles, pyrans, tetraphenylethylenes and fulvenes, are designed and synthesized. Light emissions of conventional luminescent materials are often quenched by aggregate formation. These molecules, however, become stronger luminophors when aggregated although they are practically nonemissive in their dilute solutions. By varying their packing structures in the aggregation states, emission color ranging from blue to red can be achieved. The emission of fulvenes can also be controlled by changing their morphology. While they emit a faint light in the amorphous state, their crystal forms are strongly luminescent. Intermolecular interaction or restriction of intramolecular rotation in different states may be responsible for such behaviors. Thanks to such effects, the molecules can be employed as sensors for the detection of explosives, organic solvent vapors, solution pH, and biomacromolecules. Further modification of their structures by molecular engineering endeavors may generate materials that can find an array of applications in optical display systems and as biological probes.