Rhodamine-based multianalyte colorimetric probe with potentialities as on-site assay kit and in biological systems

Abstract Herein, we report a new rhodamine-based multianalyte (Cu 2+ and Hg 2+ ) fluorescent sensor RH-FP . The synthesized probe acts as a dual chemosensor for recognition of Cu 2+ and Hg 2+ in acetonitrile-water (4:1 v/v, pH 7.2 with 10 mM, HEPES) in the presence of other miscellaneous metal cations i.e. Ag + , Al 3+ , Ba 2+ , Ca 2+ , Cd 2+ , Fe 3+ , Fe 2+ , K + , Li + , Mg 2+ , Mn 2+ , Cu +2 , Pb 2+ , Ni 2+ , Na + and Zn 2+ . A highly selective and sensitive colorimetric (colorless to pink) response accompanied by a significant increase in absorption and emission maxima (250-folds) was observed by the interaction of RH-FP and Cu 2+ or Hg 2+ . This makes RH-FP a suitable “bare-eye” detector. The Job’s plot and ESI–MS confirm 1:1 binding stoichiometry between sensor RH-FP and metal cations. The calculated binding constant for the complexes ( RH-FP-Cu 2+ and RH-FP-Hg 2+ ) are 3.37 × 10 5  mol −1 and 7.6 × 10 5  mol −1 , with a detection limit of 3.9 nm and 2.36 nm respectively. The binding mechanism was confirmed by Fourier transform infra-red spectroscopy (FT-IR) 1 H, 13 C NMR and density functional theory (DFT) calculations. Moreover, the fluorescent sensor RH-FP displayed potential in-field applications as detection kit and in fluorescent imaging of biological systems to detect Cu 2+ or Hg 2+ .