A novel ratiometric fluorescent probe through aggregation-induced emission and analyte-induced excimer dissociation

Ratiometric fluorescent sensing can minimize interfering effects and thus allow for more accurate and quantitative readouts. Ratiometric sensing can be achieved by adopting several mechanisms such as energy transfer and introduction of reference dye. Herein, we report a novel and facile approach for realizing fluorescent ratiometric sensing, which functions through aggregation-induced emission and analyte-induced excimer dissociation. For this sensing system, the fluorophore 9-anthraldehyde in its good solvent exhibits no monomer emission due to intramolecular charge transfer from anthracene moiety to aldehyde group; while in poor solvent such as water, 9-anthraldehyde molecules tend to aggregate and form excimers, which display yellow-green excimer emission. The presence of sulfite anions transforms the aldehyde groups into negatively charged ones in aqueous solution; this causes the excimers' dissociation, makes the fluorophores exhibit blue monomer emission, and thereby realizes the ratiometric sensing for sulfite ion. The system shows a large emission wavelength separation (∼100 nm) as well as highly selective and sensitive detection for sulfite with the detection limit of 3.19 μM. Moreover, it can be applied to real samples such as red wine, beer and rain water.