A simple polyethylenimine-salicylaldehyde fluorescence probe: sensitive and selective detection of Zn2+ and Cd2+ in aqueous solution by adding S2− ion

A novel polyethylenimine (PEI)-salicylaldehyde (SA) fluorescence probe, simply prepared by stirring procedure, can sensitively detect Zn 2+ (25   nM) and Cd 2+ (10   nM) in aqueous solution. Formation of metal-to-ligand complexes (Zn 2+ @PEI-SA and Cd 2+ @PEI-SA) between ions and Schiff base generate a new emission at 454   nm, which increase with the concentration of the ions (turn-on). Furthermore, after adding S 2− into the complexes, we can distinguish them due to the fluorescence quenching for Cd 2+ @PEI-SA (turn-off). Both response times for turning on and off the fluorescence are less than 1   min.