A water-soluble naphthalimide fluorescent probe for Cr2O72- and Fe3+ based on inner filter effect

A probe 3 (2-ethoxy-N-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de] isoquinolin-6-yl)benzamide) that could selectively respond to Cr2O72- and Fe3+ was reported in this paper. The selectivity, pH titration, concentration titration, detection limit, time dependence, quenching constant and recognition mechanism of probe 3 for Cr2O72- and Fe3+ were studied in CH3CN/HEPES buffer solution. The results showed that Cr2O72- and Fe3+ could rapidly quench the fluorescence of probe 3 through the inner filter effect (IFE). The quenching kept constant after 30 s, and the quenching constants were 7.99 × 103 L.mol-1 and 4.13 × 103 L.mol-1, respectively. The detection limits of probe 3 for Cr2O72- and Fe3+ were 1.15 μmol.L-1 and 1.95 μmol.L-1, respectively, which were lower than the maximum allowable concentrations in drinking water stipulated by EPA. The determination results of Cr2O72- and Fe3+ in water samples indicated that probe 3 could be used as a potential detection tool in practical applications.