A highly selective and sensitive “turn-on” fluorescent probe of Cu2+ by p-dimethylaminobenzamide-based derivative and its bioimaging in living cells

A novel p-dimethylaminobenzamide-based Schiff base derivative DTBL was synthesized via a simple reaction and utilized as a “turn-on” fluorescent indicator for copper ion (Cu2+). It showed extraordinary high selectivity toward Cu2+ in MeCN-H2O (v/v = 3:2, pH = 5) HOAc-NaOAc buffer solution, and the fluorescence intensity change were noticeable for the Cu2+ detection even in the presence of different kinds of foreign ions and compounds at very high concentrations. The 2:1 stoichiometry of DTBL-Cu2+ complex was calculated from Job's plot based on fluorescence titrations. The good linear relationship easily exhibited a dynamic response range for Cu2+ from 0 to 3.4 μM and the detection limit (0.32 nM) of DTBL for Cu2+ was far lower than the maximum allowable level of the WHO limit (30 μM) for drinking water. Moreover, the adaptability of DTBL for biological applications was also demonstrated by fluorescence imaging of intracellular Cu2+ in living cells. The results indicate that DTBL should be available for the research on the biological and environmental applications associated with Cu2+.