Chitosan-functionalized Ag–Cu-ferrite nanocomposite as a high-performance electrochemical sensor for ascorbic acid detection: experimental and theoretical exploration

Abstract

The present research introduces an electrochemical detection system constructed from chitosan-functionalized Ag–Cu-ferrite nanoparticles (Ag_0.02Cu_0.98Fe₂O₄@chitosan). This nanocomposite-based sensor provides an efficient approach for the targeted measurement of ascorbic acid (AA). Characterization using XRD and FTIR techniques confirmed the effective incorporation of chitosan into the Ag_0.02Cu_0.98Fe₂O₄ spinel framework. Using CV (cyclic voltammetry), the Ag₀.₀₂Cu₀.₉₈Fe₂O₄@chitosan-supported CPE electrode exhibited an oxidation peak at +0.28 V compared to +0.55 V for bare CPE in phosphate buffer (pH = 7), highlighting its superior electrocatalytic achievement. The current response exhibited a linear dependence with the square root of the scan rate (R² = 0.9895), suggesting that the process is governed by diffusion. Sensitivities of 411.59 µA mM⁻¹ cm² and 327.31 µA mM⁻¹ cm² were achieved by the sensor over two distinct linear ranges, 100–300 µM and 300 µM–13 mM. With a high degree of certainty, the limit of detection (LOD) was recorded at 89 µM. The fabricated electrode displayed high selectivity within the presence of commonly used interferents (glucose, fructose, sucrose, NaCl, and KCl), as well as impressive reproducibility (RSD = 1.96%) and repeatability (RSD = 1.15%).It also achieved a superior AA recovery rate of up to 98% in a real sample, demonstrating its consistency and reliability. DFT computations confirmed AA's chemical reactivity through a moderate energy gap (ΔE = 5.42 eV) and identified reactive sites on oxygen atoms using molecular electrostatic potential (MESP) and Fukui function analysis (FIs). Additionally, Monte Carlo simulations (MCS) revealed a highly favorable adsorption energy of −26.65 kcal mol⁻¹ for AA on the Ag₀.₀₂Cu₀.₉₈Fe₂O₄@chitosan-CPE surface, validating the strong affinity of the target analyte toward the modified electrode. Overall, the integration of chitosan into the Ag₀.₀₂Cu₀.₉₈Fe₂O₄ nanostructure significantly improved the electrocatalytic efficiency, selectivity, and stability of the sensor, making it an excellent option for practical applications in vitamin C detection.