Oxidation state regulation of iron-based bimetallic nanoparticles for efficient and simultaneous electrochemical detection of Pb2+ and Cu2+

Abstract

In this work, bimetallic nanocomposites were synthesized by an emulsion hydrothermal method, and the electronic structure of the nanocomposite’s surface was adjusted to make it optimal by introducing different transition metal salts, providing more active adsorption sites for detecting heavy metal ions (HMIs). The results showed that different transition metal cations underwent redox reactions with Fe3+ at high temperature, resulting in generation of more Fe2+ as well as high valence transition metal ions. And this process formed more oxygen vacancies (OVs) on the material surface, enhancing the adsorption properties of HMIs. Among these nanocomposites, CoFe2O4 produced the most Fe2+ (Fe2+/Fe3+ = 1.29) and Co3+ (Co3+ = 44.0%) at a high temperature, suggesting the generation of the most active sites on the material surface. The corresponding modified electrode CoFe2O4 (CoFe2O4/GCE) also exhibited good electrochemical performance for simultaneously detecting Pb2+ and Cu2+, with the limit of detections of 3.94 and 8.27 nM, respectively. Compared with other nanocomposites, adsorption experiments showed that the CoFe2O4/GCE had the largest adsorption capacity of Pb2+ and Cu2+ (QPb2+=49.82 μC, QCu2+=48.88 μC). Therefore, this work showed that the interaction between metal ions in bimetallic nanomaterials can regulate the electronic structures of the material surface at high-temperature treatment, improve the adsorption capacity of nanomaterials, and lead to good electrochemical detection performance of HMIs.