Discovery of a highly selective turn-on fluorescent probe for Ag+

An ideal fluorescent probe should show the strongest affinity with the relevant target (binding-selectivity) by means of a selective fluorescence change (signal-selectivity). [15]aneNO(2)S(2) (1,4-dioxa-7,13-dithia-10-azacyclopentadecane) based probes usually show high binding selectivity for Ag+ but signal selectivity for Hg2+, because Ag+ can quench or silence the fluorescence. To amplify the Ag+ binding to the greatest extent, a carbonyl group was positioned between 1,8-naphthalimide and [15]aneNO(2)S(2) which played a key role of displaying selective fluorescence enhancements with Ag+ through increasing the oxidation potential of the fluorophore, blocking Ag+ from sterically interacting with the naphthalimide fluorophore, and by acting as a sacrificial donor. Probe 2 can detect Ag+ with a selective fluorescence enhancement (similar to 14 fold) and high affinity (K-a = 1.64 x 10(5) M-1).