Chromoionophore decorated renewable solid-state polymer monolithic naked eye sensor for the selective sensing and recovery of ultra-trace toxic cadmium ions in aqueous environment

In the present study, we report an intelligent solid-state chemosensor by embedding a chromo-ionophoric probe (MQP), i.e., (Z)− 4-methoxy-2-(quinolin-8-yldiazenyl)phenol) onto a bimodal meso-/macro-porous monolithic polymer template for the target-specific sensing of toxic cadmium(II) ions. The MQP probe anchored polymeric sensor material imposes rapid detection kinetics upon interaction with cadmium ions through concentration proportionate visual colour transitions from pale pink to red wine. The unique structural and surface properties of sensor material for the target-specific ion-sensing amidst matrix constituents have been analyzed using p-XRD, TEM-SAED, SEM-EDAX, XPS, FT-IR, and BET/BJH analysis. The analytical sensing performance of the MQP sensor material has been studied by optimizing various physicochemical parameters. For the efficient detection of ultra-trace Cd(II) ions, a solution pH range of 7.5–8.5, solution temperature of ≥ 30 °C, response kinetics of ≥ 25 s, and a linear response range of 0–300 µg/L, with excellent ion-selectivity/-sensitivity. The limit of detection and quantification for the MQP sensor material for Cd(II) ion-sensing is 0.32 and 1.10 µg/L, respectively. The proposed solid-state naked-eye sensor adopts a simple and low-cost fabrication procedure for continuously monitoring natural and industrial water samples. The sensor is reusable for up to eleven repeated cycles and exhibits excellent data reliability/reproducibility for the quantitative detection and recovery of ultra-trace Cd(II) ions.