Magnetic iron oxide nanoparticles synthesized by coprecipitation and thermal decomposition yield largely monodisperse size distributions. The diameters of the coprecipitated particles measured by X-ray diffraction and transmission electron microscopy are between approximately 9 and 15 nm, whereas the diameters of thermally decomposed particles are in the range of 8 to 10 nm. Coprecipitated particles are indexed as magnetite-rich and thermally decomposed particles as maghemite-rich; however, both methods produce a mixture of magnetite and maghemite. Fourier transform IR spectra reveal that the nanoparticles are coated with at least two layers of oleic acid (OA) surfactant. The inner layer is postulated to be chemically adsorbed on the nanoparticle surface whereas the rest of the OA is physically adsorbed, as indicated by carboxyl O-H stretching modes above 3400 cm(-1). Differential thermal analysis (DTA) results indicate a double-stepped weight loss process, the lower-temperature step of which is assigned to condensation due to physically adsorbed or low-energy bonded OA moieties. Density functional calculations of Fe-O clusters, the inverse spinel cell, and isolated OA, as well as OA in bidentate linkage with ferrous and ferric atoms, suggest that the higher-temperature DTA stage could be further broken down into two regions: one in which condensation is due ferrous/ferrous- and/or ferrous/ferric-OA and the other due to condensation from ferrous/ferric- and ferric/ferric-OA complexes. The latter appear to form bonds with the OA carbonyl group of energy up to fivefold that of the bond formed by the ferrous/ferrous pairs. Molecular orbital populations indicate that such increased stability of the ferric/ferric pair is due to the contribution of the low-lying Fe(3+) t(2g) states into four bonding orbitals between -0.623 and -0.410 a.u.
PEGylated, monodispersed, superparamagnetic, iron oxide nanoparticles (Fe3O4 / γ-Fe2O3) were synthesized by using a novel metal-organic approach in three steps. Ferric nitrate nonahydrate, Fe (NO3)3.9H2O, was used as iron source, which was sterically hindered among the interstices and / or in the cavities of β-Cyclodextrin (β-CD) molecules, following a modified complexation procedure. Via a polyol process the obtained complex system was first dispersed in polyethylene glycol (PEG) and under mild thermal treatment and in the presence of 1,12 dodecanediol, a new complex system of carboxylate type was formed, between ferric nitrate and PEG, denoted Fe (NO3)3.9H2O-PEG. This metal-organic precursor was thermally decomposed, forming the iron oxide nanoparticles. The obtained particles were characterized by X-ray diffraction spectroscopy (XRD), Fourier Transform Infrared spectroscopy (FTIR) and transmission electron microscopy (TEM).
Monodispersed magnetite (Fe3O4) nanoparticles were obtained via an innovative three step synthetic approach. First, the formation of iron enneacarbonyl, Fe2(CO)9, a stable, solid organometallic complex compound, took place in a hexane solution, by the decomposition reaction of the unstable, liquid iron pentacarbonyl, Fe (CO)5, in the presence of sunlight and mild heating. In a second step, the dry compound Fe2(CO)9 was complexed with β-Cyclodextrin (β-CD) molecules, according to a combination of two modified complexation procedures. Steric hindrance of the organometallic molecules was achieved, among the interstices of the formed CD molecular network, which poses a novel, very crucial size control factor and stabilizing agent for the synthesized nanoparticles.
Magnetic iron oxide nanoparticles synthesized via co precipitation and thermal decomposition yielded largely monodisperse size distributions. Both methods produced a mixture of magnetite and maghemite. However CP NPs were indexed as magnetite-rich while TD yielded largely maghemite NPs. XRD-and TEM-measured diameters of the co-precipitated particles were approximately between 9 to 15 nm, while thermally decomposed diameters were in the range of 8 to 10 nm. FTIR spectra revealed no distinct differences in the bulk structure of the two systems. Based on the Density functional theory calculations and on HOMO-LUMO gap energies, we propose that ferric Fe is the state of preference by the surfactant in bidentate linkage.
In the course of this work, two iron oxide nanopowder samples (a mixture of FeO / γ-Fe2Ο3-Fe3O4) were composed, implementing the methodology. The synthesis used is a simple thermal decomposition route of organometallic precursors. The organometallic precursor used was the iron acetylacetonate (Fe (acac)3) which underwent reductive thermal degradation. The shape of the nanoparticles was examined and determined by the reaction time and the ratio of the used surfactants, oleic acid (OA) and oleylamine (OAm). The first sample underwent controlled oxidation in the air to transform the non-magnetic FeO phase to a mixture of magnetic phases, while the second sample underwent thermal reduction in a hydrogen atmosphere to produce a composite nanomaterial, with α-Fe, Fe3O4, γ-Fe2Ο3, being the dominant phases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.