Cascade OFF–ON–OFF fluorescent probe: Dual detection of Fe3+ ions and thiols

• One dual-functional fluorescence probe based on Rhodamine B was designed.
• LDF shows a highly selective fluorescent response to trace amounts of Fe3+ ions.
• [LDF + Fe3+] ensemble is also further successfully utilized for detection of the thiols.
• This system can also be applied in Hela Cells.

A new novel Rhodamine B-based fluorescent probe was synthesized for the selective cascade signaling of Fe3+ and thiols (glutathione, homo-cysteine, cysteine). Non-fluorescent rhodamine derivatives can selectively detect Fe3+ over some other metal ions in ethanol-water (4/1, v/v, pH 7.0) media, leading to prominent fluorescence OFF–ON switching. The obtained LDF-Fe3+ ensemble can subsequently serve as a sensitive and selective chemosensor for thiols, exhibiting complete signal quenching (fluorescence ON–OFF switching). The practical use of its Fe3+ ions ensemble was demonstrated by its application to the detection of thiols in the living cells.