A highly sensitive and selective phthalazine derivative based fluorescent organic nanosheets for simultaneous detection of Cr6+ and Mn7+ in aqueous media

Abstract A phthalazine derivative 13-(4-bromophenyl)-3,3-dimethyl-3,4-dihydro-1H-indazolo [1,2-b] phthalazine-1,6,11(2H,13H)-trione based fluorescent organic nanosheets (IDP NS) were prepared by a simple reprecipitation method in an aqueous medium. It can display turn-off type fluorescence with high selectivity and sensitivity for simultaneous recognition of Cr6+ and Mn7+ among other biologically important cations and anions. Under the selected optimized conditions, the fluorescent intensity of IDP NS studied at an excitation wavelength of λex = 360 nm was quenched gradually by the continuous addition of concentrations of Cr6+ and Mn7+ ions. Moreover, the fluorescence quenching experimental data found to fit the Stern–Volmer relationship in the concentration range of 0–50 μg.mL−1 and 0–80 μg.mL−1 with a limit of detection (LOD) 0.0715 µM and 0.0739 µM towards Cr6+ and Mn7+ respectively. This method based on fluorescence quenching was successfully used for the quantitative determination of Cr6+ and Mn7+ in different environmental water samples.