A novel “Off-On” fluorescent probe based on carbon nitride nanoribbons for the detection of citrate anion and live cell imaging

A novel fluorescent “off-on” probe based on carbon nitride (C₃ N₄) nanoribbons was developed for citrate anion (C₆ H₅ O₇³⁻) detection. The fluorescence of C₃ N₄ nanoribbons can be quenched by Cu²⁺ and then recovered by the addition of C₆ H₅ O₇³⁻, because the chelation between C₆ H₅ O₇³⁻ and Cu²⁺ blocks the electron transfer between Cu²⁺ and C₃ N₄ nanoribbons. The turn-on fluorescent sensor using this fluorescent “off-on” probe can detect C₆ H₅ O₇³⁻ rapidly and selectively, showing a wide detection linear range (1~400 µM) and a low detection limit (0.78 µM) in aqueous solutions. Importantly, this C₃ N₄ nanoribbon-based “off-on” probe exhibits good biocompatibility and can be used as fluorescent visualizer for exogenous C₆ H₅ O₇³⁻ in HeLa cells.