Fig 2. Cation selectivity of CT51.

(A) Fluorescence emission spectra of CT51 (20 μM) recorded before and after addition of several different chloride salts of Hg²⁺, Fe³⁺, Fe²⁺, Co²⁺, Cu²⁺, Ca²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Ni²⁺, Pb²⁺ or Cd²⁺; all salt solutions (200 μM) were prepared in 20 mM HEPES buffer, pH 7.4. (B) Emission spectra of CT51 (20 μM) were recorded (λ_ex = 330 nm) upon addition of increasing concentrations (up to 200 μM) of Fe(NH₄)₂(SO₄₎₂·6H₂O prepared in 20 mM HEPES buffer, pH 7.4. (C) Cyclic voltammetric analysis. The voltammograms represent the behavior of solutions containing 0.58 mM Fe²⁺ without CT51 (black line), or in the presence of 0.96 mM CT51 (red line). The voltammograms were performed at a scan rate of 100 mV s^-1, using a potentiostat DropSens μStat 400.