High-sensitively fluorescent switch-type sensing for Ag⁺ and halide anions of 2D Cd-based network constructed with...

Effective detection of the concentration of Ag⁺ ions in bactericidal fluid is one of the necessary conditions for their effective utilization for sterilization. A novel 2D Cd(II) coordination polymer (CP1), named as [Cd(HDPN)(4,4'-bbpy)]·2H₂O, was hydrothermally synthesized using 5-(2',4'-dicarboxylphenyl) nicotic acid (H₃DPN) and 4,4'-bis(imidazolyl)biphenyl (4,4'-bbpy). The structure analysis discovered that CP1 possessed a 2D network structure of dinuclear inorganic building blocks. Fluorescence sensing discovered that CP1 could high-sensitively detect Ag⁺, tetracycline, nitrobenzene and pyrimethanil and the lowest limit of detection (LOD) were 1.44 × 10^-8M, 2.15 × 10^-8M, 8.09 × 10^-8M, and 2.54 × 10^-7M, respectively. It is worth noting that the quenching occurs after the addition of Ag⁺ to the aqueous solution of CP1, and then it gradually recovers when one of the halide anions (X^- = Cl^-, Br^- and I^-) is added, forming a unique "on-off-on" fluorescence sensor for Ag⁺ and constructing a simple logic gate. The fluorescence sensing mechanism of CP1 was investigated using ultraviolet-visible spectroscopy, PXRD, XPS, and DFT methods. The research indicates that CP1 is anticipated to serve as an excellent multifunctional fluorescence sensor, especially as a switch-type sensor for Ag⁺ and the halide anions.