A smart optical probe for detection and discrimination of Zn2+, Cd2+ and Hg2+ at nano-molar level in real samples.

• Report on discrimination of group 12 metal ions using a rhodamine derived smart optical probe (L). • The L detects as low as 1.2 × 10−9 M Zn2+, 9.6 × 10−9 M Cd2+ and 1.5 × 10-10 M Hg2+. • L determines Cd2+ and Hg2+ in sea fishes. • Binary logic gate has been constructed. • TD-DFT studies support experimental spectral properties of L and its cation adduct. A multi-signaling optical probe (L) having rhodamine B spacer has been developed for rapid detection and discrimination of Zn2+, Cd2+ and Hg2+ at nano-molar level. L recognizes them through bare eye, absorption and emission spectroscopy. The probe detects as low as 1.2 × 10−9 M Zn2+, 9.6×10−9 M Cd2+ and 1.5×10-10 M Hg2+ with corresponding binding constants, 2.1 × 104 M-1, 6.5 ×105 M−1 and 3.4×106 M−1 respectively. The recognition mechanism involves PET-CHEF-FRET processes. TD-DFT studies reveal minimum energy optimized geometries of L and its' adduct with the said cations. Theoretical calculations also support experimental spectral properties. Interference free new method allows determination of said cations in sea fish and water samples. [ABSTRACT FROM AUTHOR]