A tetraphenylethene-based Schiff base AIEgen with a large Stokes shift as probe for highly sensitive and selective detection of aqueous Cu2+ ions and its application in cell imaging.

In this work, an AIE-active tetraphenylethene-based Schiff base fluorescent probe 3 with a large Stokes shift (247 nm) was designed and synthesized. It was found that the aggregated probe 3 exhibited very high selectivity and anti-interference ability for Cu2+ in PBS buffer (70% fw) through a fluorescence "turn-off" strategy. Job's plot and NMR analysis indicated the two phenolic hydroxyl groups of the benzene ring and the N atom (-CH=N-) on probe 3 interacted with Cu2+ ions in a 1:1 stoichiometric ratio. A comprehensive analysis of the Stern-Volmer and binding constant indicated a rather strong interaction between probe 3 and Cu2+ ions. Probe 3 illustrated excellent sensitivity toward Cu2+ under ppb level (4.5 nM) and achieved more than 95% recovery in river, lake and tap water toward estimation of Cu2+ ions in the analytical applications. Moreover, probe 3 was able to realize bioimaging of HepG2 cells and be quenched by intracellular Cu2+ ions, making it promising as a sensitive Cu2+ sensor for organisms.