Electrochemical Detection of Pb(II) by Glassy Carbon Electrode Modified with Amine-Functionalized Magnetite Nanoparticles

Advances in magnetic field-assisted electrolyte's physicochemical properties and electrokinetic parameters: A case study on the response ability of chloramphenicol on Fe3O4@carbon spheres-based electrochemical nanosensor

Despite the utilization of external magnetic field (MF) in promoting the intrinsic unique features of magnetic nanomaterials in many different applications has been reported, however the origin of MF-dependent electrochemical behaviors as well as the electrochemical response of analytes at the electrode in sensor applications is still not clear. In this report, the influence of MF on the electrolyte's physicochemical properties (polarization, mass transport, charge/electron transfer) and electrode's properties (conductivity, morphology, surface area, interaction, adsorption capability, electrocatalytic ability) was thoroughly investigated. Herein, the working electrode surface was modified with carbon spheres (CSs), magnetic nanoparticles (Fe₃O₄NPs), and their nanocomposites (Fe₃O₄@CSs), respectively. Then, they were directly used to enhance the electrochemical characteristics and response-ability of chloramphenicol (CAP). More interestingly, a series of various kinetic parameters related to the diffusion-controlled process of K₃[Fe(CN)₆]/K₄[Fe(CN)₆)] and the adsorption-controlled process of CAP were calculated at the bare electrode and the modified electrodes with and without the presence of MF. These parameters not only exhibit the crucial role of the modification of electrode surface with the proposed materials but also show positive impacts of the presence of external MF. Besides, the mechanism and hypothesis for the enhancements were proposed and discussed in detail, further demonstrating the development potential of using Fe₃O₄@CS nanocomposites with MF assistant for advanced energy, environmental, and sensor related-applications.

Magnetic nanoparticle modified electrodes for voltammetric determination of propellant stabiliser diphenylamine

The overall aim of the work was to advance electrochemical devices capable of analysis of forensically relevant residues using rapid electrochemical sensor technology. In order to achieve this, electrochemical detection of the propellant stabiliser diphenylamine (DPA) was achieved via voltammetry with signal enhancement realised in the presence of iron oxide nanoparticle modified transducers. This allowed both mechanistic and analytical evaluation with the aim to achieve the required selectivity and sensitivity for reliable detection. DPA electrochemistry was examined at glassy carbon electrodes in aqueous (3:7 methanol: sodium acetate pH 4.3) electrolyte via potential sweeping, with an irreversible wave at E_p = 0.67 V vs. Ag/AgCl. The diffusion coefficient (D) for the oxidation process was calculated as 1.43 × 10^-6 cm² s^-1 with αn_a = 0.7. DPA electrochemistry in a non aqueous methanol/acetonitrile electrolyte resulted in a D value of 5.47 × 10^-8 cm² s^-1 with αn_a = 0.5. Electrochemical preparation of magnetic iron oxide nanoparticles was achieved via electrooxidation of an iron anode in the presence of an amine surfactant followed by characterisation with SEM/EDX, XRD, FTIR and thermal analysis. A surface confined layer of these magnetic nanoparticles served to positively influence the response to DPA while impeding formation of surface confined oxidation products, with generation of an improved analytical signal - sensitivity 1.13× 10^-3 A cm^-2 mM^-1 relative to bare electrode response (9.80 × 10^-4 A cm^-2 mM^-1) over the range 0.5-50 μM DPA using differential pulse voltammetry, with LOD 3.51 × 10^-6 M and LOQ 1.17 × 10^-5 M. Real sample analysis involved recovery and differential pulse voltammetry of unburnt and burnt gunshot residue with DPA qualitative and quantitative analysis.