A new "on-off-on" fluorescent probe containing triarylimidazole chromophore to sequentially detect copper and sulfide ions.

A novel compound TPI-H containing triphenylimidazole chromophore is synthesized and employed as fluorescent probe for sequential detection of Cu2+ and S2-. With three binding sites in its molecular structure, TPI-H exhibits highly selective binding towards Cu2+ and results in an apparent fluorescence "on-off" behavior. Fluorescence intensity is linear with the Cu2+ concentration, and the detection limit can be down to 8.7nM. Furthermore, the in-situ generated ensemble between TPI-H and Cu2+ (TPI-H-Cu(II)) can be used to detect S2- with a low detection limit of 15.6nM through Cu2+ displacement method. In addition, the potential utility of the probe for the detection of Cu2+ and further S2- in biological system is investigated by cell imaging.