Non-Enzymatic Amperometric Sensor Based on Fe3O4@Ag Nanoparticles for Ascorbic Acid Detection: Production and Influence of Morphological and Magnetic Parameters

Non-enzymatic electrochemical sensors represent a promising alternative to enzyme-based systems, but still face challenges including nanoparticle aggregation, instability and high cost of noble metal catalysts. This work addresses these limitations through the development of Fe3O4@Ag core-shell nanoparticles synthesized via a polyol method. This structure utilizes the superparamagnetic properties of the magnetite core for stable electrode immobilization, while the tunable silver shell provides catalytic active sites. Comprehensive characterization confirmed core-shell formation with thicknesses of 1.3–2.4 nm depending on silver content. Mössbauer spectroscopy revealed that shell crystallinity directly influences the magnetite core structure and intermediate maghemite layer. Electrochemical testing demonstrated effective amperometric ascorbic acid detection, showing optimal performance: linear ranges of 1–500 µM, sensitivity of 2.4598 × 10–4 A/M and LOD of 5.4 µM. The results suggest a relationship between electrochemical response and nanoparticle characteristics (magnetic interactions and shell crystallinity), providing new insights for designing advanced non-enzymatic sensors with tunable properties for bioanalyte detection.