Particle Size, Morphology, and Chemical Composition Controlled CoFe₂O₄ Nanoparticles with Tunable Magnetic Properties via Oleic Acid Based Solvothermal Synthesis for Application in Electronic Devices

Abstract

We report on the realization of particle size, morphology, and chemical composition controlled cobalt ferrite nanoparticles (CFO NPs) with tunable magnetic properties for application in electronic and electromagnetic devices. The effect of oleic acid concentration (0.0–0.1 M) on the structural, physical, chemical, electronic, and magnetic properties of solvothermally synthesized CFO NPs is investigated in detail by using the oleic acid (OA) based chemical method for synthesis. Crystalline, cubic, and chemically homogeneous CFO NPs (5–15 nm) can be obtained by controlling the OA concentration. Spectroscopic analyses revealed that the OA molecules form covalent bonds with CFO NPs. The particle-size control was achieved by bridging bidentate interactions between the OA molecules and CFO NPs. Detailed magnetic measurements revealed that the OA concentration helps to effectively control the magnetic behavior of particle-size-controlled CFO NPs. The interfacing between OA molecules and CFO surface atoms leads to modified magnetism which is the key to understand the underlying mechanisms and utilize magnetic nanoparticles in practical applications. The anisotropy constant variation directly with nanoparticle size indicates that the magnetocrystalline component governs the magnetic anisotropy in OA coated CFO. Removal of OA (after thermal treatment) induces enhanced magnetic anisotropy and exchange bias as consequence of surface component. The results and analyses suggest that the molecular coating of nanoparticles offers the most important and critical step to design novel nanostructured magnetic materials for current and emerging electronic device technologies.

Improvements in the Organic-Phase Hydrothermal Synthesis of Monodisperse MxFe3–xO4 (M = Fe, Mg, Zn) Spinel Nanoferrites for Magnetic Fluid Hyperthermia Application

“…All nanoferrite NPs presented very strong signals corresponding to C atoms which were ascribed to the carbon chains of the surfactants/capping agents on the NP surface and the coated carbon to increase the conductivity of samples before imaging. 48 The characteristic peaks for Fe and O were detected in the EDS spectra of Fe1 and Fe2 NPs. The EDS spectra of MgFe1 and MgFe2 exhibit the signals for Fe, Mg, and O atoms.…”

“…The C 1s XPS spectra of all nanoferrites revealed a single peak centered at 285 eV arising from C–C bonds from organic molecules adsorbed on the surface 52 and adventitious carbon from exposure of the samples to the air. 48 The O 1s core-level spectra of all nanoferrites exhibit a main peak at ∼532 eV corresponding to −COO– carboxylate groups 48 and a second signal centered at ∼530 eV corresponding to the lattice oxygen of metal–oxygen bonds (M–O) of M x Fe 3– x O 4 . 53 , 54 …”

“…Typically, Fe 3+ ions at the O h site of Fe 3 O 4 exhibit the spin–orbit split doublet of Fe 2p 1/2 and Fe 2p 3/2 at 724 and 711 eV, 48 whereas the Fe 2p 3/2 peak at ∼707 and ∼709 eV verifies the existence of Fe in either 0 and +2 oxidation states. 55 Additionally, γ-Fe 2 O 3 will exhibit a small satellite peak at 718–719 eV between the 2p 1/2 and 2p 3/2 peaks, which is ascribed to the Fe 2p XPS spectrum of Fe 3+ ions.…”

“… 12 , 13 Metal nanoferrites of various shapes and size configurations have been synthesized by the hydrothermal synthesis route via either aqueous phase or organic-phase reactions of metal precursors with or without surfactants for potential technological applications. 14 Typically, the decomposition of iron precursors in an aqueous solution with or without surfactants results in aggregated clusters of larger size distribution. For example, a polyethylene glycol (PEG)–Fe 3 O 4 nanodisc, 15 ethylene glycol (EG)–Fe 3 O 4 nanoflowers, 10 dodecyltrimethylammonium bromide–Fe 3 O 4 NPs, 16 Fe 3 O 4 /C core–shell nanorings with EG/PEG, 17 and PEG–Mn 0.2 Ni 0.8 Fe 2 O 4 18 have all been synthesized utilizing this method.…”

Enhanced Performance of Reagent-Less Carbon Nanodots Based Enzyme Electrochemical Biosensors

“…The high sensitivity and selectivity of nanomaterials-based biosensors have led to great advances in the development of new methodologies for the early detection and diagnosis of disease associated biomarkers. Currently, the new synthetic methods available, allow preparation of a wide range of nanomaterials with tunable size, shape, surface functional groups, and physicochemical features [3,4]. In particular, a wide range of carbon nanomaterials have been explored as potential base platforms for the development of biosensing systems [5].…”