Solid-state real-time colorimetric sensing of ultra-trace copper ions using aqueous compatible chromatic probe imbued porous polymer monolithic sensor

Abstract

In this work, we design an aqua-compatible and sustainable chromatic sensor for the selective detection of copper ions in aqueous solutions for application in industrial quality control and environmental analysis. The solid-state chromatic sensor is fabricated through the uniform decoration of an indigenously synthesized unique chromoionophoric probe (TMAP), i.e., (2,2′-(((1E,1′E)-thiophene-2,5-diylbis(methaneylylidene)) bis(azaneylylidene))diphenol) onto a bimodal macro-/meso‑porous polymer monolith, poly(2VP-co-DVB), i.e., poly(2vinylpyridine-co-divinylbenzene), to exploit the possibility of solid-state colorimetric ion sensing. The polymer monolith and sensor materials' topography and morphology are characterized through p-XRD, FE-SEM, XPS, EDX, TEM, SAED, TGA, FT-IR and BET/BJH analysis. The ion-sensing is accompanied by a discernible color transition from vivid yellow to subdued red, with a detection and quantification limit value of 0.20 and 0.51 μg/L for Cu2+, respectively. The sensor affirms a fast detection (≤60 s) for Cu2+, with a linear signal/colorimetric response in the concentration range of 3–100 μg/L. The parameters such as sensor dosage, chromatic receptor dose, pH, temperature, sensing kinetics and reusability are optimized for reliable and reproducible ion-sensing. The solid-state sensor reveals excellent selectivity and sensitivity for Cu2+, and its practical utility with environmental/industrial samples proves its utility as a portable sensor kit for real-time on-site analysis for ultra-trace Cu2+.