A novel naphthalimide-based “turn-on” fluorescent chemosensor for highly selective detection of Zn2+

Abstract

A novel Schiff base fluorescent probe (E)-N'-((2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-5-yl)methylene)furan-2-carbohydrazide (NFP) was prepared via a simple condensation strategy. NFP displayed high selectivity and rapid response (30 s) toward Zn2+ along with a remarkable fluorescence enhancement in DMSO/H2O solution (9/1, v/v, pH 7.4, HEPES buffer, 0.2 mM). Limit of detection (LOD) of NFP for Zinc ions was determined to be 39 nM, which was much lower than the WHO standard (76.0 μM). Binding ratio of NFP with Zn2+ ions was calculated to be 1:1 using job's plot analysis and the association constant (Ka) of NFP–Zn2+ was 1.18 × 105 M−1 on the basis of fluorometric titration. The plausible complexation mode of NFP with Zn2+ ions was demonstrated by the density functional theory (DFT), 1H NMR titration and IR spectrum. The good detection performance of NFP for Zn2+ was successfully reconfirmed by the detection of Zn2+ in real water samples. Furthermore, NFP-coated test strips were easily prepared and used for quickly and qualitatively monitoring Zn2+ ions in a visible manner.