Green, Efficient Detection and Removal of Hg²⁺ by Water-Soluble Fluorescent Pillar[5]arene Supramolecular Self-Assembly

Abstract

Developing a water-soluble supramolecular system for the detection and removal of Hg2+ is extremely needed but remains challenging. Herein, we reported the facile construction of a fluorescent supramolecular system (H⊃G) in 100% water through the self-assembly of carboxylatopillar[5]arene sodium salts (H) and diketopyrrolopyrrole-bridged bis(quaternary ammonium) guest (G) by host–guest interaction. With the addition of Hg2+, the fluorescence of H⊃G could be efficiently quenched. Since Hg2+ showed synergistic interactions (coordination and Hg2+- cavity interactions with G and H, respectively), crosslinked networks of H⊃G@Hg2+ were formed. A sensitive response to Hg2+ with excellent selectivity and a low limit of detection (LOD) of 7.17 × 10−7 M was obtained. Significantly, the quenching fluorescence of H⊃G@Hg2+ can be recovered after a simple treatment with Na2S. The reusability of H⊃G for the detection of Hg2+ ions was retained for four cycles, indicating the H⊃G could be efficiently used in a reversible manner. In addition, the H⊃G could efficiently detect Hg2+ concentration in real samples (tap water and lake water). The developed supramolecular system in 100% water provides great potential in the treatment of Hg2+ detection and removal for environmental sustainability.

Keywords

• supramolecular self-assembly
• fluorescence sensing
• water-soluble pillar[5]arene
• mercury(II) detection
• diketopyrrolopyrrole