An AIE triggered fluorescence probe with three-photon absorption and its biological applications

Three-photon absorption (3 PA) in the near IR region is among the most prominent nonlinear optical (NLO) effects and has attractive applications in chemical/biological sensing and imaging. Yet, rationally constructed molecules with small molecular weight and reasonable 3 PA cross-section has been rarely reported. Herein, we designed a novel three-photon absorption photostable luminogen (namely X1) with enhanced aggregation induced emission (AIE) and the ability to achieve multi-photon imaging with femtosecond laser excitation. X1 was constructed from diaminobenzene and diethylamino salicylaldehyde forming a novel di-Schiff base. It possesses a large conjugated delocalization which exhibits large three-photon absorption (3 PA) cross-section values. We also showed that by using a suitable delivery vector, X1 compound could applied as a live cell imaging probe thus providing a valuable tool to study lipid droplets/lysosome interaction in depth tissues.