Development of Methanol Sensor Based on Sol-Gel Drop-Coating Co3O4·CdO·ZnO Nanoparticles Modified Gold-Coated µ-Chip by Electro-Oxidation Process

Herein, novel Co₃O₄·CdO·ZnO-based tri-metallic oxide nanoparticles (CCZ) were synthesized by a simple solution method in basic phase. We have used Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscope (FESEM), Dynamic Light Scattering (DLS), Tunneling Electron Microscopy (TEM), and Energy-Dispersive Spectroscopy (EDS) techniques to characterize the CCZ nanoparticles. XRD, TEM, DLS, and FESEM investigations have confirmed the tri-metallic nanoparticles' structure, while XPS and EDS analyses have shown the elemental compositions of the CCZ nanoparticles. Later, a Au/μ-Chip was modified with the CCZ nanoparticles using a conducting binder, PEDOT: PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) in a sol-gel system, and dried completely in air. Then, the CCZ/Au/μ-Chip sensor was used to detect methanol (MeOH) in phosphate buffer solution (PBS). Outstanding sensing performance was achieved for the CCZ/Au/μ-Chip sensor, such as excellent sensitivity (1.3842 µAµM^-1cm^-2), a wide linear dynamic range of 1.0 nM-2.0 mM (R² = 0.9992), an ultra-low detection limit (32.8 ± 0.1 pM at S/N = 3), a fast response time (~11 s), and excellent reproducibility and repeatability. This CCZ/Au/μ-Chip sensor was further applied with appropriate quantification results in real environmental sample analyses.