Cd (II) coordination polymer as a strip based fluorescence sensor for sensing Fe3+ ions in aqueous system

Abstract

The design and construction of a sensor that can sensitively and conveniently recognize metal ions are essential for the treatment of industrial wastewater. In this work, {[Cd4(HL)2(pyp)2(H2O)2]·2H2O·1.5Diox}n (1) was synthesized under solvothermal condition and presented a 2D 3,5-connected layered network with the point symbol of {3.4.5} {32.4.5.62.74}, which was coated on the surface of polyvinylidene fluoride (PVDF) to construct a novel paper sensor (1@PVDF). Meanwhile, the stability of 1@PVDF was characterized by powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). In addition, fluorescence sensing experiments of 1@PVDF sensor for cations in aqueous system indicated that it has high sensitivity for sensing Fe3+ ions with the detection limit (DL) of 4.0 × 10−8 M. By the characterization of PXRD, UV–vis spectra, ICP, XPS, time-resolved excited-state decay measurements, the sensing mechanisms of 1@PVDF for Fe3+ ions were attributed to the competitive absorption and interaction between 1 and Fe3+. And the sensing process of 1@PVDF for Fe3+ ions was static in the Fe3+ concentration of 0 to 0.05 mM. In addition, the binding energies of Fe3+ and Zn2+ with the framework of 1 were calculated by density functional theory (DFT), which further proved that there was an obvious interaction between Fe3+ and the uncoordinated O atom in 1. Based on the thin film technology, a portable and convenient paper-based probe has been developed for practical applications.