A Highly Selective Fluorescent Chemosensor for Cu2+

A new Zn²⁺ probe L2-Zn(L2=naphthofuran carbonylhydrazone derivant) was synthesized as a fluorescence chemosensor for Cu²⁺, by which Cu²⁺ ion could be detected with high selectivity and sensitivity in a wide pH range via a displacement “turn-off” signaling strategy. Whereas the coordination between Zn²⁺ and L2 resulted in a considerable enhancement of typical luminescence of a naphthalofuran group in complex L2-Zn, the addition of Cu²⁺ ion led to a dramatic decrease in the emission intensity of probe L2-Zn at about 503 nm(excitation at 423 nm). The competitive fluorescent experiments showed that other metal ions, such as Hg²⁺, Fe³⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Cr³⁺ and Mg²⁺ could not impact the detection of Cu²⁺. The detection limit of the novel probe L2-Zn for Cu²⁺ ion was as low as 2.3×10^-7 mol/L, which is far lower than the guideline value of 1.6×10^-5 mol/L of the United States Environmental Protection Agency.