Aqueous co-precipitation of iron oxide nanoparticle in presence of amino acids

Monodomain iron oxide nanoparticles with spinel structure (MNPs) are widely studied for many applications, from catalysis to biomedicine ​[1]​. The methodology to synthesize MNPs is well-established ​[2]​ but the co-precipitation mechanism in presence of ligands is not well-understood yet. The co-precipitation of magnetite nanoparticles occurs after the addition of a base to the solution of precursors, typically Fe(II) and Fe(III) chlorides. In this contribution, we titrate Fe(II)/Fe(III) solutions with sodium hydroxide in the presence of L-glutamic acid as a capping agent to explore the formation mechanism of magnetite nanoparticles in presence of the amino acid. In these titration/co-precipitation experiments, the base is injected at a constant temperature in the reaction batch containing the precursors and the capping agent. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) provide the morpho-structural features of the MNPs. The molecular coating on the surface of MNPs is investigated by coupling thermogravimetric analysis to Fourier-transform infra-red spectroscopy (TGA-FTIR). Colloidal stability of the dispersions and hydrodynamic diameter of the MNPs are evaluated by Dynamic Light Scattering (DLS). The magnetic properties (i.e. field and temperature-dependent magnetization) and Hyperfine structure of MNPs will be investigated by VSM magnetometry and Mössbauer spectroscopy, respectively.