Facile fabrication of composite film modified electrodes based on vanadium-substituted tungstophosphate with Fe3O4@Au for electrochemical detection of sodium nitrite

Abstract

Sodium nitrite (NO₂⁻) is widely present in human daily life, so accurate, sensitive, and selective NO₂⁻ detection has implications for food safety. Novel composite films based on vanadium-substituted tungstophosphate (K₇P₂W₁₇VO₆₂·18H₂O, P₂W₁₇V) in polyoxometalate and the Au magnetic nanocomposites (Fe₃O₄@Au) have been successfully proposed. The electrodeposition method and the layer-by-layer (LBL) method can be utilized to self-assemble and produce composite films with modified electrodes, allowing for the creation of a highly sensitive electrochemical sensor for detecting NO₂⁻. The application of composite films on the GCE resulted in improved sensing for the detection of NO₂⁻ when compared to the use of P₂W₁₇V or Fe₃O₄ electrodes alone. The composite electrode has a linear range of 1–100 mM for sodium nitrite with a detection limit of 0.787 μM (S/N = 3). The effective combination of P₂W₁₇V with Fe₃O₄@Au not only overcame the defects of polyoxometalates but also had the advantages of fast charge transfer and multiple sensing sites in the electrochemical detection of NO₂⁻. Additionally, the composite films meet the demand for quickly and accurately detecting sodium nitrite concentration in real samples (red sausages, pickles, sauerkraut, and ham sausages).