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

A novel Schiff base fluorescent probe ( E )- N '-((2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1 H -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 Zn 2+ along with a remarkable fluorescence enhancement in DMSO/H 2 O 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 Zn 2+ ions was calculated to be 1:1 using job's plot analysis and the association constant (Ka) of NFP –Zn 2+ was 1.18 × 10 5 M −1 on the basis of fluorometric titration. The plausible complexation mode of NFP with Zn 2+ ions was demonstrated by the density functional theory (DFT), 1 H NMR titration and IR spectrum. The good detection performance of NFP for Zn 2+ was successfully reconfirmed by the detection of Zn 2+ in real water samples. Furthermore, NFP -coated test strips were easily prepared and used for quickly and qualitatively monitoring Zn 2+ ions in a visible manner. • A novel naphthalimide based optical chemosensor NFP is presented for Zn 2+ . • NFP possessed high specificity toward Zn 2+ via a distinct fluorescence light-up response. • Limit of detection (LOD) of NFP for Zn 2+ was as low as 39 nM. • NFP was successfully applied in the determination of Zn 2+ in real water samples. • The dramatic color changes in test paper were observed by naked eyes upon exposing in different concentrations of Zn 2+ .