Relay recognition of Cu2+ and S2- in water by a simple 2-(2'-aminophenyl)benzimidazole derivatized fluorescent sensor through modulating ESIPT.

A new 2-(2'-aminophenyl)benzimidazole (2-APBI) derivatized fluorescent sensor (L) that behaves relay recognition of Cu(2+) and S(2-) in water solution (pH 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu(2+) through two emissions simultaneous quenching. The on-site formed L-Cu(2+) complex exhibits excellent selectivity to S(2-) with fluorescence "off-on" response via Cu(2+) displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu(2+) and S(2-) in water has been achieved.