A new fluorescent chemosensor for Zn2+ with facile synthesis: “Turn-on” response in water at neutral pH and its application for live cell imaging

A series of salicylaldehyde-2-pyridinehydrazone derivatives were found to exhibit interesting “turn-on” fluorescence response toward Zn2+ in water at neutral pH, which could be prepared readily from commercially available materials through a one-step reaction in ethanol at room temperature. Among these compounds, 1 showed a 22-fold fluorescence enhancement in 99% water/DMSO (v/v) at pH 7.0 with a linear range of 0.10–1.00 μmol/L and detection limit of 30 nmol/L Zn2+. Especially, 1 was not affected by Cd2+ which usually induced a comparable fluorescence response to that of Zn2+ in other reported works. Moreover, live cell imaging showed that 1 could be useful for monitoring Zn2+ within biological samples.