A new rhodamine B-based “off–on” fluorescent chemosensor for Cu2+ in aqueous media

A new fluorescent probe 1 (P1) for Cu2+ based on rhodamine B was designed and synthesized. P1 exhibits high sensitivity and selectivity for sensing Cu2+ and color changes from colorless to pink in aqueous media. Selective fluorescent enhancement of P1 was attributed to ring-opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent). A chemosensor based on rhodamine B has a good potential application to the determination of Cu2+ in environmental and biological systems.