A Reversible Bis(Salamo)-Based Fluorescence Sensor for Selective Detection of Cd²⁺ in Water-Containing Systems and Food Samples

A novel, simple, highly selective, and sensitive fluorescence chemosensor for detecting Cd²⁺ that was constructed from a bis(salamo)-type compound (H₄L) with two N₂O₂ chelating moieties as ionophore was successfully developed. Sensor H₄L could show fluorescence turn-on response rapidly and significant selectivity to Cd²⁺ over many other metallic ions (Cu²⁺, Ba²⁺, Ca²⁺, K⁺, Cr³⁺, Mn²⁺, Sr²⁺, Co²⁺, Na⁺, Li⁺, Ni²⁺, Ag⁺, and Zn²⁺), and a clear change in color from colorless to yellow that can be very easily observed via the naked eyes in the existence of Cd²⁺, while other metallic ions do not induce such a change. Interestingly, its fluorescent intensity was increased sharply with the increased concentration of Cd²⁺. The detection limit of sensor H₄L towards Cd²⁺ was down to 8.61 × 10^-7 M.