Fluorescence Variation in Selective Sensing of Hg2+and Cu2+ Ions By Coumarin-xanthene Fused Optical Probe.

The fluorescent moieties coumarin and xanthene (R6GCP) combined in a single molecule was designed and synthesized. The colorimetric and fluorescent variation of the probe towards the copper and mercury ions sensing is examined. With the added copper/mercury ions to the solution of R6GCP in DMF:H2O (2:8, v/v), the probe showed deep red color from yellow color. The probe showed turn-off and turn-on fluorescence for copper and mercury ion respectively. In the presence of other competing metal ions, the probe showed better sensitivity towards copper and mercury ions. The probe's detection limit found to be 5.29 × 10-6 M and 1.24 × 10-5 M for Cu2+ and Hg2+ ion respectively by the UV-visible spectral measurement. Fluorescence measurement, the detection limit for the Cu2+ and Hg2+ ions detection by this probe is 1.91 × 10-7 M, and 1.32 × 10-8 M respectively. 1:1 binding stoichiometry was confirmed between the probe and Cu2+/Hg2+ ions from jobs plot by UV-visible spectral technique. Moreover, R6GCP combined filter paper were prepared. These test paper containing probe could detect Cu2+/Hg2+ ions in real-time with a spontaneous color change.