Fluorometric sensing, Mechanism and Extraction of Cu (II) ions on a single platform using benzene sulfonyl appended Thiacalix [4]arene

Supramolecular-based fluorescent probes have attracted the attention of researchers for selective sensing of toxic metal ions for environmental remediation. But the increasing concentration of such toxic ions in water reservoirs is a serious concern and complete dependence on only sensing them is not enough. Thus, we introduced a novel approach i.e.; selective sensing and extraction/removal of such toxic analytes directly from the aqueous phase on a single platform. We have synthesized and characterized Benzene sulfonyl allied tetrasubstituted Thiacalix[4] arene based fluorescent probes named P1 and P2, which show exclusive selectivity for Cu (II) from the pool of other cations. The detection limit (LOD) for receptors P1 and P2 were obtained as 0.098 ppm and 0.19 ppm respectively which are well below the maximum permissible limit demarcated by WHO. The high association constant obtained from spectrometric titration data of P1 and P2, ranging (1.61-3.12) X 104 M-1 and (1.56-3.04) X 104 M-1, respectively, and their recyclable nature leads us to the extraction of Cu (II) ions directly from the aqueous phase. Under SLE (Solid-liquid extraction), the receptors P1 and P2 show %Loading of 90.13% and 88.75%, respectively, whereas under LLE (Liquid-liquid extraction), the %Extraction of 34.38% and 40.58% were obtained, respectively. After multistage extraction, we obtained a total extraction efficiency of 41.33% from the real sample. This new method demonstrates the effectiveness of a supramolecular ligand system for the removal of metal ions and can inspire further research to modify for even higher extraction efficiency, which is currently rare in the reported literature.