A novel method to synthesize MFe2O4 (M2+=Fe2+ and Ni2+) nanoparticles based on M(AOT)2 surfactants

• Published in: Materials chemistry and physics Vol. 273; p. 125066
• Main Authors: Rubio, J.I. Martínez, Palomar-Padilla, M.A., Cano, M.E., Escalante, J.I., Casillas, N., Ceja, I., Gutiérrez-Becerra, A., Bárcena-Soto, M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.11.2021; Elsevier BV
• Subjects: AOT; Diffraction patterns; Ferrous ions; Iron oxides; Magnetic saturation; Magnetite; Nanoparticles; Nickel ferrite; Nickel ferrites; Photomicrographs; Precursors; Surfactants; Synthesis; Nanoparticles; Magnetite; Nickel ferrite; Surfactants; AOT
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2021.125066

The surfactants Fe(AOT)2 and Ni(AOT)2, prepared by replacing the Na+ ions of NaAOT with Fe2+ and Ni2+ respectively, were used as precursors in the synthesis of Fe3O4 and NiFe2O4 nanoparticles. FTIR and MS results confirmed the ionic substitution, having a molecular mass similar to the theoretical values of 898.98 and 901.30 g/mol for Fe(AOT)2 and Ni(AOT)2 respectively. When an aqueous surfactant solution is mixed with another containing Fe3+ (or Fe2+) maintaining a basic environment, magnetic nanoparticles with well-controlled size are obtained. The advantage of this approach is the availability of surfactant molecules (the dissociated ions form AOT– according to M(AOT)2 = M2+ + 2AOT–) immediately after the nanoparticles are formed. The interactions between the AOT– molecules and the negatively charged magnetic nanoparticles limit the nanoparticle growth, obtaining average sizes of 15.5 and 17.5 nm for Fe3O4 and NiFe2O4 respectively, according to TEM micrographs. The X-ray diffraction patterns of Fe3O4 and NiFe2O4 nanoparticles agree with those found in the literature. Employing TGA measurements, it was determined that 17 and 29% of the weight in the surfactant-nanoparticles mixtures were Fe3O4 and NiFe2O4, respectively. The magnetic saturation of these mixtures is in the same order as the typical values of saturation for coated magnetic nanoparticles. The respective blocking temperatures of 127 and 150 K for Fe3O4 and NiFe2O4 composites and the magnetic saturation values corroborate the superparamagnetic ordering. This work opens the possibility of using M(AOT)2 type surfactants as precursors in the synthesis of magnetic nanoparticles. [Display omitted] •The surfactants Fe(AOT)2 and Ni(AOT)2 were used as precursors in the synthesis of Fe3O4 and NiFe2O4 nanoparticles.•FTIR and mass spectroscopy confirmed the formation of the surfactants Fe(AOT)2 and Ni(AOT)2.•According to TEM, the average nanoparticle sizes were 15.5 and 17.5 nm for Fe3O4 and NiFe2O4 respectively.•The magnetic saturation agrees with that reported in the literature for nanoparticles with similar size.