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In this study, the metallic-Ag@ferromagnetic-Fe3O4nanoparticles has been used as a promising spintronics material to gain deeper insights into spintronics-related electrochemical reactions under the influence of an applied external magnetic field (MF) including spin polarization, spin transport, and spin selectivity. Ferrocyanide/ferricyanide ([Fe(CN)6]3‒/4‒), paracetamol (PCM), and chloramphenicol (CAP) were chosen as the suitable reactants for one-electron transfer reversible redox reaction, two-electron transfer quasireversible redox reaction, and four-electron transfer irreversible reaction at Ag@Fe3O4modified electrodes, respectively. By using an external MF-assisted electrochemical platform and magneto-plasmonic Ag@Fe3O4electrode to trigger spin polarizing, spin transporting, and spin selectivity effects in electrode reactions, the selective enhancement of the electro-reduction reaction in comparison with electro-oxidation reaction has been elucidated. The obtained experimental data along with calculated electrochemical kinetic parameters indicate that an applied external MF affects the electrochemical kinetics (electron transfer kinetics, electrocatalytic activity, and adsorption/diffusion capacity) of the one-, two-, and four-electron transfer processes in different ways. Considering the pronounced effects of magnetic field on overall electrochemical performance and intrinsic advantages of spintronics enhanced the electro-reduction reaction, these developed techniques could provide innovative strategies for the development of novel spin-dependent electrochemical sensing approaches.

In this study, the preparation of core/shell Ag@Fe3O4nanoparticles (NPs) and its potential application toward highly sensitive electrochemical detection of furazolidone (FZD) have been reported. UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, and Zeta sizer are systematically carried out to confirm the formation, size distribution, and composition of Ag@Fe3O4NPs. By computing the electrochemical characteristic parameters such as electrochemically active surface area (ECSA), electron-transfer resistance (Rct), standard heterogeneous rate constant (k0), adsorption capacity (Γ), and electron transfer rate constant (ks), the Ag@Fe3O4-modified electrode possessed remarkably enhanced electrochemical sensing performance for FZD determination compared to the unmodified screen-printed electrode (SPE). This enhancement of electrochemical activity can be attributed to the fast electron transfer kinetics and great adsorption capacity that arise from the synergistic coupling between the good electrical conductivity of the core AgNPs and the porosity of the protective Fe3O4shell. Under optimum conditions, the Ag@Fe3O4-based electrochemical nanosensor exhibited not only high sensitivity toward FZD detection of 1.36 μA μM−1cm−2in the linear ranges from 0.5–15 μM and 15–100 μM, and low detection limit of 0.24 μM but also long-term stability, repeatability, and anti-interference ability. The applicability of the proposed sensing platform in honey and milk samples was also investigated.

The recent advancement in designing novel spinel nanostructures has opened virtually infinite possibilities for the development of high-performance electrochemical sensors to detect target species. The electrocatalytic activity of spinel structures can be enhanced by tuning the cation distribution; however, the role of cation distribution at tetrahedral ions on the electrochemical sensing responses has rarely been considered. Herein, the effect of cation distribution at tetrahedral sites (Td) in the spinel nanostructure ZnCo2O4on the electrochemical sensing performance toward carbaryl (CBR) was first investigated. The ZnCo2O4nanoflake samples with different cation ratios of Zn/Co at tetrahedral sites were designed by using a facile solvothermal method. We found that a higher Zn ion content at tetrahedral sites significantly enhanced the electron transfer ability through the electrolyte/electrode interface. More interestingly, a higher Co ion ratio between octahedral sites and tetrahedral (CoOh/CoTd) promoted the electrochemical oxidation process of CBR with a higher catalytic rate constant (kcat). Under optimized conditions, the ZnCo2O4-NF-based electrochemical nanosensor showed a linear response from 0.15 to 100 μM with a limit of detection of 0.05 μM and a high electrochemical sensitivity of 2.04 μA μM–1cm–2. The designed nanosensor also exhibited good repeatability, long-time stability, high anti-interference ability, and excellent recovery with fruit and vegetable samples. Furthermore, this study offers insights into the cation distribution-dependent electrocatalytic activities of spinel nanostructures, which is helpful to the design of advanced spinel nanostructure-based electrocatalysts for improving the electrochemical sensing performance.

In this work, we investigated the effect of morphology on the analytical performance of α-Fe2O3nanostructures-based electrochemical sensors toward chloramphenicol (CAP) antibiotic using three designed morphologies including α-Fe2O3nano-tube (α-Fe2O3-T), α-Fe2O3nano-rice (α-Fe2O3-R), and α-Fe2O3nano-plate (α-Fe2O3-P). Among these morphologies, α-Fe2O3-T displayed an outstanding electrochemical activity owing to the unique hollow structure and large specific surface area. However, due to the small pores size, α-Fe2O3-T showed the high steric hindrance (SD) effect towards an antibiotic with complex molecular structure, as CAP, leading to a significant decrease of their CAP electrochemical sensing performance. The CAP analytical performance of α-Fe2O3-R was highest in investigated morphologies owing to a high density of exposed Fe3+as well as less SD effect towards CAP molecules. Under optimized conditions, α-Fe2O3-R-based CAP electrochemical sensor reached an electrochemical sensitivity of 0.92 μA μM−1cm−2with a LOD of 0.11 μM in the detection range from 2.5–50 μM. In addition, all these α-Fe2O3nanostructures-based electrochemical sensors had excellent stability and high anti-interference ability for CAP analysis in a complex food matrix, as shrimp sample. This study provides valuable insights into the morphology-dependent sensing properties of α-Fe2O3nanostructures towards antibiotics, which is helpful to the design of novel α-Fe2O3-based electrochemical nanosensors.