A Schiff base luminescent chemosensor for selective detection of Zn2+ in aqueous medium

Luminescent chemosensors based on Schiff bases have drawn tremendous research interest owing to their easy synthesis, enriched photophysical properties, and potential applications in biology and materials science. A dinitrophenyl-based Schiff base molecular probe (L) was synthesized and characterized to estimate its selective detection of Zn2+. The probe L exhibits weak emission in the DMSO-H2O solvent mixture due to excited-state intramolecular proton transfer (ESIPT). Interestingly, fluorescence is enhanced with the addition of Zn2+ to the DMSO-H2O solution of L, whereas the emission remains unchanged with the addition of other ions. This specifies that probe L acts as a selective chemosensor for Zn2+. The binding stoichiometry for the L: Zn2+ complex is 1:1, which was calculated using the Benesi-Hildebrand plot from fluorescence data. Furthermore, the binding modes are also supported by density functional theory (DFT) calculation. The binding constant and detection limits are 6.35 × 107 M−1 and 1.1 × 10−8 M, respectively. The L-Zn2+ complex formation is reversible upon the addition of a strong chelating EDTA ligand. In addition, L is also used to detect Zn2+ in living Hela cells and selective sensing of Zn2+ in the solid phase.