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 (C₃N₄) nanoribbons was developed for citrate anion (C₆H₅O₇3-) detection. The fluorescence of C₃N₄ nanoribbons can be quenched by Cu2+ and then recovered by the addition of C₆H₅O₇3-, because the chelation between C₆H₅O₇3- and Cu2+ blocks the electron transfer between Cu2+ and C₃N₄ nanoribbons. The turn-on fluorescent sensor using this fluorescent "off-on" probe can detect C₆H₅O₇3- 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 C₃N₄ nanoribbon-based "off-on" probe exhibits good biocompatibility and can be used as fluorescent visualizer for exogenous C₆H₅O₇3- in HeLa cells.