Peroxidase-mimetic, electrochemically active, Co₃O₄-decorated pectic acid-based polyacrylate derivatives for rapid...

In this work, a nanocomposite of a pectic acid (PcA)-based copolymer composed of acrylamide (Am) and acrylic acid (AcA) embedding cobalt oxide nanoparticles (Co₃O₄ NPs), PcA-g-poly(Am-co-AcA)/Co₃O₄, was fabricated as an enzyme-free electrochemical sensing platform for the sensitive detection of hydrogen peroxide (H₂O₂). This Co₃O₄ NP-based nanocomposite was developed through free radical-initiated grafting copolymerization and then characterized by Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). Pectic acid-based polyacrylate derivatives decorated with Co₃O₄ NPs formed a larger nanocomposite aggregate with an average size of approximately 67 nm, as observed by TEM. Electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed the superior charge-transfer capability and enlarged electrochemically active surface area of the nanocomposite-modified electrode compared with those of the bare electrode. Under the optimized experimental conditions, the fabricated sensor exhibited a rapid amperometric response, excellent sensitivity, a broad linear working range from 0.01 to 800 µM, an ultralow limit of detection (LOD) of 3 nM, a limit of quantification (LOQ) of 9 nM and high selectivity toward H₂O₂ in the presence of common interfering species. The Co₃O₄-based nanocomposite sensor demonstrated good repeatability with reproducibility besides long-term storage stability, highlighting its analytical reliability. The practical applicability of the sensing platform was successfully validated by determining H₂O₂ in commercial apple juice samples using the standard addition method, providing satisfactory recoveries and low relative standard deviations. The combination of a simple fabrication procedure, low-cost materials, and outstanding electrochemical performance makes the PcA-g-poly(Am-co-AcA)/Co₃O₄ nanocomposite a promising candidate for routine food safety monitoring and the development of advanced polymer-based nanozyme sensors, alongside its electroactivity exploitation in catalytic systems and other advanced bioelectronic technologies.