Highly sensitive and selective Hg2+ chemosensor based on dithia cyclic fluorescein for optical and visual eye detections in aqueous buffer solution
Abstract A new fluorescent sensor FC4 based on fluorescein dithia cyclic skeleton was designed and prepared as a fluoroionophore for the optical and visual eye detections of Hg 2+ in aqueous buffer solution. FC4 was prepared via Kornblum oxidation, ester hydrolysis, alkylation, imine formation and imine reduction. The sensor provided highly sensitive and selective ON OFF fluorescence sensing toward Hg 2+ and was shown to discriminate various interfering metal ions, particularly Cu 2+ and Pb 2+ as well as Al 3+ Ba 2+ Ca 2+ Cd 2+ Fe 3+ K Mg 2+ Mn 2+ Na and Ni 2+ Sensor FC4 also exhibited chromogenic change upon binding to Hg 2+ which served as a "visual eye" indicator which could be observed as a noticeable change of the solution color from yellow to orange. The Hg 2+ detection limit of the sensor was 7.38 x 10 9 or 1.48 ppb which was lower than a permissible concentration of Hg 2+ in drinking water regulated by the United States Environmental Protection Agency (U.S. EPA)