Na+ Triggered Fluorescence Sensors for Mg2+ Detection Based on a Coumarin Salen Moiety

Two coumarin salen-based sensors CS1 and CS2 can exhibit a pronounced fluorescence enhancement response toward Mg2+ as high as 36-fold (CS1) and 111-fold (CS2) in the presence of Na+ as a synergic trigger. More importantly, the fluorescent color of CS1 was bright green instead of weak yellow after the addition of Mg2+ and Na+ together, which can be easily detected by the naked eye.