Anion Recognition Triggered Nanoribbon-Like Self-Assembly: A Fluorescent Chemosensor for Nitrate in Acidic Aqueous Solution and Living Cells

A water-soluble π-conjugated bispyridinium phenylenevinylene-based fluorogenic probe has been developed as a novel fluorescent chemosensor for highly selective, sensitive, and rapid detection of NO₃^– anion in acidic aqueous media. This system self-assembles to a nanoribbon as a result of ionic interaction. The positively charged chemosensor generates a nearly instantaneous significant fluorescence signal (475 vs 605 nm) in response to NO₃^– in the green/yellow spectral region, with a large Stokes shift (130 nm). The fluorescence changes can be attributed to the self-aggregation of the sensor triggered by ionic interaction, which occurs as a consequence of the subtle cooperation of electrostatic ionic bonding, van der Waals forces, and π-stacking of the π-conjugated aromatic moieties. Importantly, this chemosensor has been employed for the first time for the fluorescence detection of intracellular NO₃^– anion in cultured cells.