Selective and sensitive electrochemical sensors based on an ion imprinting polymer and graphene oxide for the detection of ultra-trace Cd(ii) in biological samples

Abstract

New selective and sensitive electrochemical sensors were designed based on the deposition of a promising ion imprinted polymer (IIP) on the surface of glassy carbon electrode (GCE) for the detection and monitoring of Cd(II) in different real samples. Herein, a highly selective Cd-imprinted polymer was successfully synthesized using a novel heterocyclic compound based on the benzo[f]chromene scaffold that acted as a complexing agent and a functional monomer in the presence of azobisisobutyronitrile (initiator) and ethylene glycol dimethacrylate (cross-linker). The characterization of the synthesized chelating agent and IIP was performed using FT-IR, SEM, ¹H-NMR, EIMS, and EDX analyses. After that, the voltammetric sensor was manufactured by introducing graphene oxide (GO) on the surface of GCE; then, the IIP was grown by a drop coating technique. The electrochemical characterization of the voltammetric sensor (IIP/GO@GCE) was performed by CV and EIS. For comparison, the potentiometric sensor was also prepared by embedding IIP in plasticized polyvinyl chloride and depositing it as one layer on the GCE surface. Anodic stripping voltammetry was used to construct the calibration graph; the IIP/GO@GCE exhibited a wider detection range (4.2 × 10⁻¹²–5.6 × 10⁻³ mol L⁻¹) and extremely low detection limit (7 × 10⁻¹⁴ mol L⁻¹) for Cd(II). Meanwhile, the potentiometric sensor showed a linear calibration curve for Cd(II) over a concentration range from 7.3 × 10⁻⁸ mol L⁻¹ to 2.4 × 10⁻³ mol L⁻¹ with a detection limit of 6.3 × 10⁻¹⁰ mol L⁻¹. Furthermore, both sensors offered outstanding selectivity for Cd(II) over a wide assortment of other common ions, high reproducibility, and excellent stability.