On-Site Colorimetric Sensing of Ultra-trace Cu2+ Using Probe Anchored Porous Polymer Monolith as a Facile Solid-State Optical Sensor

Abstract

In this work, we have demonstrated a solid-state optical sensing methodology for Cu²⁺ using probe anchored porous polymer monolith. The indigenously designed polymer material offers a high surface area and enhanced porosity with a 3D network structure, that ensures greater immobilization of chromoionophoric probe, (E)-2-(2-hydroxy-1,2-diphenylethylidene) hydrazine-1-carbothioamide (HDHC) onto monolith matrix. It also provides greater accessibility for the Cu²⁺ ions towards the probe sites. The structural and surface features have been characterized using p-XRD, TEM, SEM, SAED, EDAX, XPS, and N₂ isotherm analysis. Moreover, the chromoionophoric probe selectively complexes with the Cu²⁺ producing a visible color transition from light yellow to greenish brown due to the metal to ligand charge transfer complexation process. Our study shows that the developed sensor can be used as an effective tool for monitoring the ultra-trace levels of Cu²⁺ in water samples and it renders excellent sensitivity, faster kinetics, and selectivity towards the target analyte amidst matrix constituents, which makes it the most promising candidate for real-time analysis. The polymeric sensor is reusable for several cycles and exhibited superior data reproducibility when tested with spiked real water samples.