Coumarin-based colorimetric-fluorescent sensors for the sequential detection of Zn2+ ion and phosphate anions and applications in cell imaging.

ABSTRACT

Two novel coumarin based fluorescent sensors CHP and CHS have been synthesized for the sequential detection of Zn2+ ion and phosphate anion (PA) in DMF/HEPES buffer medium (1/5 v/v, 10 mM, pH = 7.4). On the addition of Zn2+ ion to the solution of CHP or CHS resulted in a pronounced fluorescence enhancement, accompanying noticeable color change (under UV or daylight), while there was hardly obvious change with other competing metal ions co-existing. The detection limits (DL) of CHP and CHS toward Zn2+ were separately determined as 1.03 × 10-7 (R2 = 0.9886) and 1.87 × 10-7 (R2 = 0.9902). The PET binding processes were affirmed by spectroscopic techniques, HRMS experiments and theoretical calculations. Subsequently, the CHP-Zn2+ or CHS-Zn2+ complexes showed high selectivity fluorescence quenching toward PA by snatching Zn2+ ion from its complex and the binding processes were reversible. DLs were calculated as 2.07 × 10-7 M (R2 = 0.9928) and 2.63 × 10-7 M (R2 = 0.9954), respectively. Furthermore, the cell imaging experiments demonstrated that the sensors were capable of detecting of Zn2+ and PA in vitro cells.