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 Hg(2+), 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 (∼14 fold) and high affinity (K(a) = 1.64 × 10(5) M(-1)).