A Fluorescent Sensor for Cu2+ Ion with High Selectivity and Sensitivity Based on ICT and PET.

ABSTRACT

A novel fluorescent sensor (L) based on 1,8-naphthalic anhydride has been developed which can selectively detect Cu2+ in CH3CN medium over other metal ions at 408 nm in the fluorescence spectra. When Cu2+ was added into L, L showed fluorescent turn-off by coordinating with Cu2+. A fresh absorption band was found at the position of 290 nm as was a red-shifted absorption band from 356 nm to 376 nm in UV-vis spectra which might be attributed to the intramolecular charge transfer (ICT). Meanwhile, L-Cu2+ showed fluorescence quenching via photoinduced electron transfer (PET). The complexation ratio was proposed to be 11 which was determined by Job's plot, fluorescence titration and 1H NMR titration. The detection limit was 9.1 × 10-8 mol·L-1, a satisfying level to detect Cu2+ in the micromolar scale. Corresponding molecular geometries, orbital energies and electron contributions of sensor L were calculated by the DMol3 program package using the density functional theory.