Bio-based Fe₃O₄/chitosan nanocomposite sensor for response surface methodology and sensitive determination of gallic...

In this study, preparation of a novel bio-sensor based on Fe₃O₄/chitosan nanocomposites reported for electrochemical studies and determination of gallic acid (GA). Combination of chitosan with Fe₃O₄ nanoparticles causes to improve oxidation current of the GA. Characterization of the nanocomposite is carried out by different techniques such as X-ray diffraction, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, electrochemical impedance spectroscopy and cyclic voltammetry. Furthermore, multivariate optimization strategy is applied for simultaneous optimization of the chemical and instrumental parameters. Moreover, electrochemical behavior of GA at the surface of the nano-structured sensor is studied by various techniques such as chronoamperometry, chronocoulometry and linear sweep. Using these techniques, the diffusion coefficient (D = 5.05 × 10^-4 cm² s^-1 and or 4.86 × 10^-4 cm² s^-1), and the kinetic parameters containing the exchanging current density (j₀ = 0.23 μA cm^-2) and electron transfer coefficient (α = 0.1) are determined for GA, respectively. Then, the detection limit for GA is found to be 12.1 nM with a broad linear dynamic range 0.5-300.0 μM using differential pulse voltammetry DPV at the surface of the Fe₃O₄/chitosan sensor. Finally, the proposed method is successfully applied for the detection of the analyte in real samples.