Rhodamine-based chemosensor for Hg(2+) in aqueous solution with a broad pH range and its application in live cell imaging

A new fluorescent probe, rhodamine B derivative (1) bearing an 8-hydroxyquinoline group, was synthesized and displayed highly selective and sensitive Hg(2+)-amplified absorbance and fluorescence emission above 500 nm in aqueous solution with a broad pH range 4-9. It was found that mercury ions coordinate reversibly to 1 and the spirolactam ring of 1 was opened, forming a 1 : 1 metal-ligand complex. Furthermore, this sensor was applied for in vivo imaging in HeLa cells to confirm that 1 can be used as a fluorescent probe for monitoring Hg(2+) in living cells.