Cascade OFF-ON-OFF fluorescent probe: dual detection of trivalent ions and phosphate ions

A new rhodamine B-based fluorescent probe was developed for the selective cascade signaling of trivalent cations (Fe3+, Al3+, Cr3+) and phosphate anion (PO43-). Non-fluorescent rhodamine derivatives can selectively detect trivalent cations over some other metal ions in CH3CN-Tris buffer (1/1, v/v, pH 7.0) solutions, leading to prominent fluorescence OFF-ON switching. The obtained probe-cation complex can subsequently serve as a sensitive and selective chemosensor for PO43-, exhibiting complete signal quenching (fluorescence ON-OFF switching).