"United we stand, divided we fall."--Aesop. Aggregation-induced emission (AIE) refers to a photophysical phenomenon shown by a group of luminogenic materials that are non-emissive when they are dissolved in good solvents as molecules but become highly luminescent when they are clustered in poor solvents or solid state as aggregates. In this Review we summarize the recent progresses made in the area of AIE research. We conduct mechanistic analyses of the AIE processes, unify the restriction of intramolecular motions (RIM) as the main cause for the AIE effects, and derive RIM-based molecular engineering strategies for the design of new AIE luminogens (AIEgens). Typical examples of the newly developed AIEgens and their high-tech applications as optoelectronic materials, chemical sensors and biomedical probes are presented and discussed.

CO(2) sensing is of great societal implications, as CO(2) is a component of gas mixtures from many natural and anthropogenic processes with huge impacts on globe climate and human well-being. Herein we report a CO(2) assay scheme over a wide concentration range, utilizing a fluorogen with an aggregation-induced emission feature and a liquid with tunable polarity and viscosity. The CO(2) sensing process is specific, quantitative, and interferent tolerant.