Structurally engineered ion-receptor probe immobilized porous polymer platform as reusable solid-state chromogenic sensor for the ultra-trace sensing and recovery of mercury ions

Abstract

This study reports an efficacious solid-state optical sensor through the synergistic coalescences of an original chromoionophoric probe and a structurally engineered porous polymer monolith for the selective and sensitive colorimetric spotting of ultra-trace toxic mercury ions. The unique properties of the bimodal macro-/meso-pore structured polymer, i.e., poly(AAm-co-EGDMA) monolith, offer voluminous and uniform anchoring of probe molecules, i.e., (Z)-N-phenyl-2-(quinoline-4-yl-methylene)hydrazine-1-carbothioamide (PQMHC). The structure/surface features of the sensory system, i.e., surface area, pore dimensions, monolith framework, elemental mapping, and phase composition, were examined by p-XRD, XPS, FT-IR, HR-TEM-SAED, FE-SEM-EDAX, and BET/BJH analysis. The sensor's ion-capturing ability was established through naked eye color transition and UV-Vis-DRS response. The sensor exhibits a strong binding affinity for Hg2+, with a linear signal response in the concentration range of 0–200 μg/L (r2 >0.999), with a detection limit of 0.33 μg/L. The analytical parameters were optimized to facilitate pH-dependent visual sensing of ultra-trace Hg2+ in ≤ 30 s. The sensor exhibits high chemical/physical stability characteristics, with reliable data reproducibility (RSD ≤1.94 %), while testing with natural/synthetic water and cigarette samples. The proposed work offers a cost-effective and reusable naked-eye sensory system for the selective sensing of ultra-trace Hg2+, with potential prospects of commercialization considering their simplicity, viability, and reliability.