Reversible "off-on" fluorescent chemosensor for Hg2+ based on rhodamine derivative

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg(2+) with high selectivity. The structure of chemosensor 1 was characterized by IR, (1)H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg(2+) in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg(2+) complex with the Hg(2+)-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg(2+) ions and TBAI (tetrabutylammonium iodide) titration experiments.