Multiwall carbon nanotubes decorated with FeCr₂O₄, a new selective electrochemical sensor for amoxicillin determination

FeCr₂O₄ nanoparticles were synthesized and then multiwall carbon nanotubes (MWCNTs) were decorated with FeCr₂O₄ nanoparticles. The new nanoparticles were characterized with different techniques such as vibrating sample magnetometer, Fourier transform infrared spectroscopy, scanning surface microscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy. The results of the study confirm that the particles are pure FeCr₂O₄–MWCNTs with a cubic structure. No diffraction peaks of other impurities such as FeO or Cr₂O₃ were observed. The diffractive peaks of FeCr₂O₄–MWCNTs are broadened, implying that the crystalline size of FeCr₂O₄–MWCNTs particles is quite small. The mean particle size of FeCr₂O₄–MWCNTs calculated by Scherrer equation is about 25 nm, whereas the existence of particles with less than 30 nm size at FeCr₂O₄–MWCNTs is clearly reflected in 2D and 3D AFM images. The TEM image confirms that the spaghetti-like FeCr₂O₄–MWCNTs formed a porous structure. The synthesized FeCr₂O₄–MWCNTs nanoparticles could be used as a new electrocatalysis for voltammetric determination of amoxicillin (AMC). Under the optimized conditions at pH 7.5 and in differential pulse voltammetry, the oxidation peak current of AMC at the surface of the mediator has two linear dynamic ranges including 0.1–10.0 and 10.0–70.0 μmol L⁻¹. The detection limit of 0.05 μmol L⁻¹ was achieved. The influence of potential interfering compounds on the selectivity was studied. Finally, the modified electrode showed good sensitivity, selectivity, and stability for the determination of AMC in real samples.