Water-sensitive ratiometric fluorescent probes and application to test strip for rapid and reversible detection of water

Naphthalimide-decorated fluorinated acetamides 1 and 2 were developed as solvent-sensitive dual emissive fluorescence probes. Particularly, 1 exhibited dual emission with a large Stokes shift for water, DMF, and DMSO solvents over other various organic solvents. The dual emission might be due to the increase of intramolecular charge transfer (ICT) of the naphthalimide moiety through the association of the difluorinated acetamide group with the solvent molecules. The 1 can give rise to a ratiometric change in the dual emission and a visual fluorescent color change depending on the water contents in organic solvents, including ethanol, methanol, acetonitrile and DMF solvents. Moreover, the 1-impregnated paper strips showed a rapid and easy-to-visualize fluorescent color change enabling water detection in organic solvents. These simple-to-use paper strips were also found to be reusable over 20 times.