Structural Investigation of MFe₂O₄ (M = Fe, Co) Magnetic Fluids

Abstract

Ferrites of the type M II Fe 2 O 4 (M ) Fe and Co) have been prepared by the traditional coprecipitation method. These ferrites were modified by the adsorption of fatty acids derived from soybean and castor oil and were then dispersed in cyclohexane, providing very stable magnetic fluids, readily usable in nonpolar media. The structural properties of the ferrites and modified ferrites as well as the magnetic fluids were characterized by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), DRIFTS (diffusion reflectance infrared Fourier transform spectroscopy), FTNIR (Fourier transform near-infrared), UV-vis, normal Raman spectroscopy, and surface-enhanced Raman scattering (SERS). XRD and TEM analysis have shown that the magnetic nanoparticles (nonmodified and modified) present diameters in the range of 10-15 nm. DRIFTS measurements have shown that the carboxylate groups of soybean and castor oil fatty acids adsorb on the ferrite surface, forming three different structures: a bridging bidentate, a bridging monodentate, and a bidentate chelate structure. The FTIR and Raman spectra of nonmodified Fe 3 O 4 and CoFe 2 O 4 nanoparticles have shown that the number of observed phonons is not compatible with the expected O h 7 symmetry, since IR-only active phonons were observed in the Raman spectra and vice versa. SERS measurements of a CoFe 2 O 4 thin film on a SERS-active gold electrode at different applied potentials made possible the assignment of the signals near 550 and 630 cm -1 to Co-O motions and the signals near 470 and 680 cm -1 to Fe-O motions.

Ferrofluids: Synthetic Strategies, Stabilization, Physicochemical Features, Characterization, and Applications

“…This has been demonstrated by Jacintho et al from the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements of Fe 3 O 4 and Co 3 O 4 MNPs in cyclohexane, modified by fatty acids derived from soybean and castor oil. [121] Colloidal stabilization in a biocompatible magnetic fluid can be achieved by using biologically active polyelectrolyte molecules with two or more polyfunctional chemical groups. Other than these types, Tourinho et al proposed a new type of particle peptization in polar media without using surfactants or an electrical double layer.…”

Sonohydrothermal synthesis of MFe2O4 magnetic nanoparticles for adsorptive removal of tetracyclines from water

“…The absorption peaks with a wavenumber larger than 1300 cm À1 were generally attributed to the vibrations of -OH (i.e., the -OH stretching vibration (m OH ) and bending vibration (d OH )) and hydrogen bond (or H-bridge (Fig. 4b), implying the formation of nanoscale particles [25]. The peaks of these NPs observed in the 450-400 cm À1 region (e.g., 420 cm À1 for CoFe 2 O 4 ) were assigned to the T 1u phonon of the Fe-O bond.…”

Controllable Synthesis of Single‐Crystalline Fe3O4 Nanorice by a One‐Pot, Surfactant‐Assisted Hydrothermal Method and Its Properties

“…The predominant peak seen at 670 cm -1 in all the spectra represents the A 1g vibration mode of Fe 3 O 4 , which is consistent with the reported value for single-crystalline and nanophase Fe 3 O 4 . [29,30] Figure 6 (d) corresponds to the spectrum of the Fe 3 O 4 nanorice and shows the predominant peak at 670 cm -1 in addition to peaks at 474 and 538 cm -1 , which are assigned to the T 2g (2) and T 2g (3) modes of Fe 3 O 4 , respectively. [31] The peaks at 832 cm -1 and in the range 1115-1130 cm -1 are not related to iron oxide and represent DTAB bound to the surface.…”

“…[29,30] Figure 6 (d) corresponds to the spectrum of the Fe 3 O 4 nanorice and shows the predominant peak at 670 cm -1 in addition to peaks at 474 and 538 cm -1 , which are assigned to the T 2g (2) and T 2g (3) modes of Fe 3 O 4 , respectively. [31] The peaks at 832 cm -1 and in the range 1115-1130 cm -1 are not related to iron oxide and represent DTAB bound to the surface. The intensity of these bands increased with the increasing amount of DTAB.…”