Facile synthesis of cube-shaped Fe3O4 mesoporous nanoparticles and their application for electrochemical determination of Cu (II) in aqueous solutions through the mediating effect of indigo carmine

We developed an electrochemical copper sensor that was constructed by a modified carbon paste electrode with Fe3O4 mesoporous nanoparticles and multiwall carbon nanotubes. The Fe3O4 nanoparticles with sizes of 24–36 nm were synthesized by a hydrothermal method. The size and morphology of the nanoparticles were investigated by SEM, TEM images and X-ray diffraction patterns, and the results showed cubic shaped nanoparticles with porous structure. The Nitrogen adsorption − desorption isothermal measurements indicated that the prepared nanoparticles had two types of pore sizes of 4 nm and about 20 nm. The FT-IR spectroscopy revealed that the indigo carmine (IC) dye had a high tendency toward the as-synthesized nanoparticles through hydrogen bonding. The voltammetric techniques were employed to investigate the IC redox behavior and the complex formation between Cu2+ and IC. The decrease of IC oxidation peak, along with an obvious anodic shift potential, was observed because of the complex formation between IC and Cu2+.