Highly sensitive and selective Hg~(2+)-chemosensor based on dithia-cyclic fluorescein for optical and visual-eye detections in aqueous buffer solution

摘要

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 × 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).