Shape Of Fe3O4 Nanoparticles Research Articles

Shape-Controllable Synthesis of Peroxidase-Like Fe3O4 Nanoparticles for Catalytic Removal of Organic Pollutants

The shape of Fe3O4 nanoparticles is controlled using a simple oxidation-precipitation method without any surfactant. The morphology and structure of the obtained Fe3O4 nanoparticles were characterized by using x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, N2 physisorption and vibrating sample magnetometer. As-prepared Fe3O4 samples showed octahedron, cube, hexagonal plate and sphere morphologies. Peroxidase-like activity of the four nanostructures was evaluated for catalytic removal of organic pollutants in the presence of H2O2, using rhodamine B as a model compound. The results showed that the H2O2-activating ability of the Fe3O4 nanocrystals was structure dependent and followed the order sphere > cube > octahedron > hexagonal plate, which was closely related to their surface FeII/FeIII ratios or crystal planes. The reusability of Fe3O4 spheres was also investigated after five successive runs, which demonstrated the promising application of the catalyst in the degradation of organic pollutants. This investigation is of great significance for the heterogeneous catalysts with enhanced activity and practical application.

Hydrophilic Magnetochromatic Nanoparticles with Controllable Sizes and Super-high Magnetization for Visualization of Magnetic Field Intensity.

Hydrophilic Fe3O4 nanoparticles with controllable size and shape have been fabricated using a facile solvothermal approach followed by surface modification with polyacrylic acid (PAA). The nanoparticles form one-dimension photonic crystal structure under external magnetic field ranging from 29.6 to 459 G. The reflection peaks of formed photonic crystals cover the entire visible spectrum, which indicates a good magnetochromatic property and prospect of wide applications. The size and shape of Fe3O4 nanoparticles are controlled by changing the ratio between ethylene glycol and diethylene glycol. In the process of surface modification, PAA synthesized by free radical polymerization was chemisorbed onto the surface of Fe3O4 particles with the aid of Fe3+ cations, which renders the particles well dispersed in aqueous solution with high thermo-stability. The Fe3O4 particles exhibit ferrimagnetism with a high saturation magnetization value of 88.0 emu/g. Both the high magnetization and the wide reflection spectrum under magnetic field make the magnetochromatic nanoparticles a promising material for visualization of the distribution of magnetic field intensity on microfluidic chips.

Influencing factors on the synthesis of magnetically responsive lipases

Magnetic Fe3O4 nanoparticles decorated with native carboxyl groups (Fe3O4COOH) were prepared and used as magnetic carriers. These carriers were different from traditional solid supports, because they were free-standing and no aggregation in solution. Lipases were covalently bonded to these Fe3O4 nanoparticles through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (Sulfo-NHS) activated coupling to synthesize magnetically responsive lipases (MRLs). The analyses of transmission electron microscope (TEM) showed no significant change on the size and shape of Fe3O4 nanoparticles after being conjugated with lipases. The conjugation of Fe3O4 nanoparticles and lipases was confirmed by electrophoresis and zeta potential analyses. Furthermore, the factors that affected the enzyme activity and specific activity of the MRLs were discussed. The optimized conjugation conditions were found to be that the dosages of the lipase solution and the EDC solution were 200μL and 10μL for 1mL Fe3O4 respectively, the molar ratio of EDC and Sulfo-NHS was 1:2.5, and the conjugation time was 2h. The prepared MRLs exhibited higher thermal stability and reusability.

Shape-Controlled Growth and Shape-Dependent Cation Site Occupancy of Monodisperse Fe3O4 Nanoparticles

The shape control and formation mechanism of Fe3O4 nanoparticles (NPs) synthesized by a modified hot-injection method were investigated. Monodisperse Fe3O4 nanocubes terminated at {100} planes with the average size of 16.1 ± 0.9 nm were synthesized by injecting Fe precursor into reaction solution at 290 °C with a slow injection rate of 10 mL/h. When we increased the monomer concentration in solution by increasing the injection rate to 20 mL/h or doubling the precursor concentration with the same reaction time, the main terminated planes of Fe3O4 NPs became {100} and {110} planes leading to a rhombicuboctahedral shape. The shape of NPs was strongly affected by the monomer concentration and the intrinsic surface energy of Fe3O4. The shape-induced crystallographic orientation-ordered superlattices were obtained in both cubic and rhombicuboctahedral Fe3O4 NPs. On the other hand, the shape-dependent occupancy of the cation sites was clearly observed, measured by using X-ray magnetic circular dichroism (XMCD) spectra. The octahedral sites were occupied by more ferric ions, Fe3+, when the shape of Fe3O4 NPs became cubic.