Aggregation-Induced Emission of Water-Soluble Tetraphenylethene Derivatives at Polarized Liquid|Liquid Interfaces

Aggregation-induced emission (AIE) behavior of water-soluble tetraphenylethene (TPE) derivatives bearing carboxy and sulfo groups was studied at polarized liquid|liquid interfaces. The aggregation behavior of TPE derivatives in solution and at the water|1,2-dichloroethane (DCE) interface was highly dependent on their ionizable functional groups. Spectroelectrochemical analysis elucidated that the TPE derivatives were transferred across the interface accompanied by the adsorption process at the interface. The ion transfer and interfacial AIE features of TPEs responded reversibly to the externally applied potential, indicating no rigid crystalline structure formation in the interfacial region. The red shift measured in intense interfacial emission spectra demonstrated that the carboxylate derivatives formed their J-aggregates specifically at the polarized water|DCE interface, while the aggregation processes with distinguishable emission properties took place in both the interfacial region and organic solution in the sulfonate derivative system. The AIE features were also investigated at a glycerophospholipid-adsorbed interface as a model of the biomembrane surface. The aggregation process of TPE derivatives was significantly modified through the interaction with phospholipid layers which stimulate the interfacial AIE process of tetra-anionic TPEs.