A highly sensitive and selective optical probe for detection of Hg2+ based on a 2,5-bis[2-(benzylthio)aniline]-croconaine

A highly sensitive and selective optical probe, 2,5-bis[2-(benzylthio)aniline]-croconaine (BAC) for sensing of Hg2+ was synthesized. The BAC can efficaciously recognize Hg2+ with the existence of competing cations (Ba2+, Fe3+, Na+, Ca2+, Co2+, K+, Mg2+, Ni2+, Cu2+, Pb2+, Al3+, Pb2+, Cr3+, Cd2+, Ag+) in DMSO. The binding constant (Ka) of BAC-Hg2+ was calculated to be about 1.6 × 105 M−1. Simultaneously, the chelating mode of BAC-Hg2+ was confirmed by Job's plot, FT-IR and 1H NMR. “Naked eye” detection has been performed, indicating the potential application of BAC on conveniently, selectively and fast detection of Hg2+. Moreover, Hg2+ and EDTA could be employed as inputs and the fluorescence emission intensity which was 480 nm as output so that a molecular logic gate could be realized.