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 Hg 2+ . Probe R-2 exhibits high selectivity and sensitivity for sensing Hg 2+ with a detection limit at 10 −8  M level, and displays a significant color change from colorless to pink color in the presence of Hg 2+ . About a 400-fold increase in fluorescence emission intensity is observed upon binding excess Hg 2+ in 50% H 2 O/CH 3 CN HEPES buffer at pH 7.00. The titration results show a 1:1 complex formation between R-2 and Hg 2+ . The reversibility of chemosensor R-2 is verified through its spectral response toward Hg 2+ and I − titration experiments. Using Hg 2+ 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.