Nanocomposite based functionalized Polyethersulfone and conjugated ternary ZnYCdO nanomaterials for the fabrication of selective Cd²⁺ sensor probe

Carboxylated polyethersulfone (PES-COOH) was doped with various concentrations of ZnYCdO hybrid metal oxides on the surface of the polymer matrix to produce PES-COOH-ZnYCdO nanocomposites as a thin film. PES-COOH was fabricated by two-steps process: acetylating reaction followed by oxidation reaction, and its structure was investigated using proton nuclear magnetic resonance (¹H-NMR) and Fourier-transform infrared (FT-IR) spectroscopy. Then, the fabricated PES-COOH-ZnYCdO nanocomposites (NCs) were characterized using common characterization techniques which include: scanning electron microscope (SEM), X-ray powder diffraction (XRD), FT-IR, thermal analysis, SEM with energy dispersive X-Ray (EDX) spectroscopy and transmission electron microscopy (TEM). FT-IR and XRD analysis confirmed the interactions between carboxylate ions present on the polymer surface metric and the metals that were present as ZnYCdO nanoparticles. Based on values calculated from FT-IR spectra of the PES-COOH-ZnYCdO NCs, the metals and carboxylate ions formed bindentate complexes. Also, the signal peaks of the XRD for ZnYCdO were shifted to a lower degree which also confirmed the interactions between the nanoparticles and PES-COOH. A selective Cd²⁺ metal ion sensor was fabricated by coating of a glassy carbon electrode (GCE) with the slurry of PES-COOH-ZnYCdO NCs polymers. The NCs assembled film onto GCE was implemented to successive detection of Cd²⁺ metal ion in phosphate buffer medium. To evaluate the sensor analytical performances, a calibration curve has been plotted from current versus concentration of electrolyte (Cd²⁺ ion). It is found linear (r² = 0.9939) over linear dynamic range (LDR) of 0.1 nM~0.1 mM concentration of Cd²⁺ ion by electrochemical approach. The sensitivity and detection limit (DL) are 5.4589 μAμM⁻¹ cm⁻² and 17.39 ± 0.87 pM respectively were calculated from the slope of calibration plot. Therefore, the resultant Cd²⁺ sensor shows good sensitivity, reproducibility with high accuracy, wider dynamic range, short response time, very lower detection limit and long-term stability with similar performances.