'Turn-on' Fluorescent and Colorimetric Determination of Cu2+ Ions in Aqueous Media Based on a Rhodamine-N-phenyl Semicarbazide Derivative

摘要

We report the design and synthesis of a novel chemosensor (RGPS) rhodamine-based indicator for selective detection of Cu2+ ion. Sensing behavior toward various metal ions (M=Hg2+, Cu2+, Co2+, K+, Cs+, Ag+, Pb2+, Zn2+, Mg2+,Fe3+, Ni2+, Li+ and Al3+) was investigated by UV-Vis and fluorescence spectroscopy in acetonitrile:water (CH3CN-H2O, v/v, 9:1) solution. The indicator exhibited highly selective and sensitive colorimetric and "turn-on" fluorescent responses toward Cu2+ ions based on the ring-opening mechanism of the rhodamine spirolactam in an CH3CN-H2O (v/v, 9:1) solution. The obvious change from colorless to pale pink upon the addition of Cu2+ could make it a suitable "naked eye" indicator for Cu2+. More significantly, the sensor displayed a remarkable colorless to yellowish green fluorescence switch in the presence of Cu2+ ions. The limit of detection is proved 1.405 x 10(-7) M from titration and 1:1 binding ratio is proved from jobs plot method. Finally, we proposed a reversible ring-opening mechanism (OFF-ON) of the rhodamine spirolactam induced by Cu2+ binding and forming a 1:1 stoichiometric complex of RGPS-Cu2+ which is supported by the material studio theory calculations.