A highly selective fluorescent chemosensor for Hg2+ based on rhodamine B and its application as a molecular logic gate

A novel and simple fluorescent chemosensor based on rhodamine (R-2) is designed and synthesized to detect Hg2+. Probe R-2 exhibits high selectivity and sensitivity for sensing Hg2+ with a detection limit at 10−8 M level, and displays a significant color change from colorless to pink color in the presence of Hg2+. About a 400-fold increase in fluorescence emission intensity is observed upon binding excess Hg2+ in 50% H2O/CH3CN HEPES buffer at pH 7.00. The titration results show a 1:1 complex formation between R-2 and Hg2+. The reversibility of chemosensor R-2 is verified through its spectral response toward Hg2+ and I− titration experiments. Using Hg2+ and I− as chemical inputs and the fluorescence intensity signal as outputs, R-2 can be utilized as an INHIBIT logic gate at molecular level.

► A Hg2+ sensor (R-2) has been developed based on rhodamine B.
► The sensor has high fluorescent selectivity for Hg2+ over various competitive cations.
► R-2 is recyclable when adding I− to the solution of Hg2+/R-2.
► Using Hg2+ and I− as inputs, R-2 could be used as an INHIBIT logic gate.