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

Abstract

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).