Early-warning and semi-quantitative colorimetric detection of Hg(II) with lysine-bis-Schiff base cellulose membranes designed by simple interfacial covalent bonding

It is of great significance to develop efficient platforms for the detection of hypertoxic Hg2+ in water. In previous decades, colorimetric sensors have received much attention for the early-warning detection of Hg2+. In this work, lysine-bis-Schiff base cellulose membranes (SCMs) were prepared by a simple interfacial covalent bonding method between lysine and high-purity cellulose membranes (CMs). SCMs, as immobilized probe colorimetric platforms, provides an efficient solution for Hg2+ early-warning detection, making it simple and convenient Hg2+ chemical colorimetric sensors. The morphology and structure were analyzed by SEM, EDS, FT-IR, and XPS. As per results, the unique high-loose interpenetrating porous morphology and easy chemically modified structure of CMs, not only improved the interface covalent bonding ability but also provided many channels and sites to chelate Hg2+. Selective Hg2+ chelation with N, O bidentate ligands formed on SCMs prompted the immediate colorimetric sensing. Further performance experiments were designed to study the Hg2+ colorimetric sensing ability of SCMs under real aqueous system. The results showed that SCMs had high selectivity, high sensitivity, robust reusability, and a wide response range without external interference. Qualitative and semi-quantitative detection of Hg2+ with a visual limit of detection (VLOD) of 5 × 10−8 mol/L was fast as 2 and 30 min, respectively. Notably, the capture-based dynamic colorimetry was first designed and used to detect the lower concentrations of Hg2+ (0.1 nM). All experimental results indicated that CM was an excellent material for the design of chemical colorimetric sensors, which held good promise for early-warning and semi-quantitative application.