Molecular Probe Embedded Porous Polymer Scaffold as Solid-State Visual Sensor for Selective and Sequential Sensing of Ultra-Trace Toxic Heavy Metal Ions in Environmental/Commercial Samples

The article reports on the tailor-made solid-state optical sensor through controlled imbuement of an amphiphilic probe onto a dual interwoven macro-/meso-porous polymer monolithic scaffold for the selective ocular sensing of ultra-trace toxic heavy metal ions. The structural/surface morphology of the poly(LMC-co-TMP) monolith is customized through the stochiometric inclusion of lauryl methacrylate (LMC), trimethyl propanetrimethacrylate (TMP) and porogenic solvents. The riveting sensing performance of the poly(LMC-co-TMP) scaffolds for the target ions arises from the built-in twofold intermingled porous architects that render voluminous surface area and porosity for the embedding of 2-((1H-benzoimidazol-2-yl)-4-butan-2-yl)phenol (HBBP), a chromoionophoric probe. The sensor's unique structural and surface properties endure stable ion-complexation through color transitions from yellow (blank) to a leafy green, peanut brown, and dark blue for Pb2+, Hg2+, and Cd2+, respectively. The sensor imposes high binding affinity for the target ions, with a linear response range of 0-200 ppb for Pb2+/Hg2+ and 0-300 ppb for Cd2+. The detection limit values are 0.46, 0.52, and 0.41 ppb for Pb2+, Hg2+, and Cd2+, respectively. The sensor's hassle-free on-field testing in environmental and synthetic samples reveals excellent data reproducibility (Relative Standard Deviation (RSD) <= 1.97%), with pH-assisted reliable color transitions for eight regenerative trials, with a response time of 45 s. The proposed solid-state colorimetric sensor using porous polymer monolith, i.e., poly(LMC-co-TMP) imbuement with a chromoionophoric HBBP probe, is a simple/eco-benign approach for trapping ultra-trace toxins. The spatial orientation constraints of the HBBP molecules within the bimodal porous monolith offer exclusive selectivity for Pb2+/Hg2+/Cd2+, with brilliant color transitions. The parameter fine-tuning offers rapid and reliable ion-sensing, essential for on-site/real-time toxicity monitoring.image