Low-Temperature Preparation of Superparamagnetic CoFe2O4 Microspheres with High Saturation Magnetization

Abstract

Based on a low-temperature route, monodispersed CoFe2O4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe2O4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe2O4 MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role.

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) copolymer micromicelles: surface RAFT synthesis, self-assembly and drug release applications

“…Thus, the vinylferrocene moieties are verified to remain stable upon preparation of the micromicelles. Only after oxidation, the BE of the above spin–orbit-coupled doublet is shifted into 705.7 and 718.5 eV, respectively, and a new peak emerges at around 709.2 eV, indicative of the presence of Fe 3+ cations [ 48 ]. These findings provide the support for the interpretation of TEM, SEM and DLS results.…”

FeCo2O4/hollow graphene spheres hybrid with enhanced electrocatalytic activities for oxygen reduction and oxygen evolution reaction

“…3c) shows two peaks centered at 710.86 and 724.11 eV, corresponding to Fe 2p 3/2 and Fe 2p 1/2 , respectively, suggesting the existence of Fe 3+ cation [34][35][36]. A shift of 0.98 and 1.31 eV toward a low binding energy also exists in the peak of Fe 2p 3/2 and Fe 2p 1/ 2 , respectively, for FCO/HrGOS, as compared to free FCO (Fig.…”

“…3b) be further fitted to two peaks, respectively. The two fitted peaks at 780.76 and 796.86 eV are ascribed to Co 2+ , another two fitted two peaks at 779.52 and 794.71 eV are ascribed to Co 3+ [23,[32][33][34][35][36], and the Co 2+ :Co 3+ atomic ratio is calculated to be very close to 1:1. As compared to free FCO, a shift of 1.65 and 1.77 eV toward a low binding energy exists in the peak of Co 2p 3/2 and Co 2p 1/2 , respectively, for FCO/HrGOS hybrid.…”

Influence of PVP on the Morphologies of Bi2S3 Nanostructures Synthesized by Solvothermal Method

“…The results supported very well with the preferential orientation growth along the axis in building up of 1D nanostructured orthorhombic Bi 2 S 3 . For the synthesis of superparamagnetic Fe 3 O 4 and CoFe 2 O 4 with high saturation magnetization by solvothermal processing of the solution containing PVP, these products were in the shape of microspheres [19,20].…”