A CHEF-based biocompatible turn ON ratiometric sensor for sensitive and selective probing of Cu2+

The newly synthesized 1-amino-2-naphthol functionalized fluorophoric ligand L1 specifically binds Cu2+ in presence of large excess of other competing ions with observable changes in their electronic and fluorescence spectral behavior. These spectral changes are significant enough in visible region of the spectrum and thus enable naked eye detection. As L1 displays Cu2+ ions dependent spectral changes at two different wavelengths of the emission spectra so it can be used as a ratiometric sensor for the analyte with minimal interference of environmental conditions and background disturbances. The coordination of Cu2+ with L1 force the molecule to attain a planar geometry with an increased opportunity of charge transfer throughout the π-system, leading to a highly conjugated geometry with sufficient enhancement of the fluorescence intensity, from which fluorogenic and ratiometric detection of Cu2+ ions are possible. Further, fluorescence microscopic studies confirmed that the reagent L1 could also be used as an imaging probe for detection and uptake of Cu2+ ions in HeLa cells.