Coumarin Xanthene Combined Probe for the Multi-Color Detection of Metal Ions and Electrospun Fibers Developed for...

A coumarin-rhodamine (RhBC)-fused colorimetric/fluorescent probe was designed and synthesized. The probe is effective in Cu²⁺/Hg²⁺ ion sensing. With the added Cu²⁺ to RhBC in water: N, N-dimethyl formamide (8:2, v/v), the cyclic form of RhBC, is converted into the open ring form and shows a clear color change from yellow to red. In the presence of additional participating cations, this moiety shows effectiveness for Cu²⁺ and Hg²⁺ ions. The RhBC's detection limit by the UV-visible spectral method was 8.81 × 10^-6 M for Cu²⁺ ions and 2.26 × 10^-5 M for Hg²⁺ ions. The detection limit in the fluorescence titration spectra was 2.02 × 10^-7 M for Cu²⁺ ions and 6.11 × 10^-8 M for Hg²⁺ ions. A 1:1 stoichiometric ratio was validated between the probe and copper/mercury ions by the method of the job plot. Moreover, RhBC-combined polyurethane electrospun nanofibers were synthesized. These nanofibers could detect Cu²⁺ in real samples with no complications, with an instinctive color difference from yellow to red and a weak orange color for mercury ions.