Individual Fe3O4 Nanoparticles Research Articles

Segregated Conductive Polymer Composite with Fe3O4-Decorated Graphite Nanoparticles for Microwave Shielding.

Graphite nanoplatelets (GNPs)-the segregated ultra-high molecular weight polyethylene (UHMWPE)-based composites with hybrid filler-decorated with Fe3O4 were developed. Using X-ray diffraction and scanning electron microscopy, it was shown that the decorated component has the shape of separate granules, or their clusters were distributed evenly over the GNPs surface. The individual Fe3O4 nanoparticles are predominantly rounded, with diameters of approximately 20-60 nm. The use of GNPs/Fe3O4 as a filler leads to significant decreases in the percolation limit φc, 0.97 vol% vs. 0.56 vol% for GNPs/UHMWPE- and (GNPs/Fe3O4)/UHMWPE segregated composite material (SCM), respectively. Modification of the GNP surface with Fe3O4 leads to an essential improvement in the electromagnetic interference shielding due to enhanced microwave absorption in the 26-37 GHz frequency range in its turn by abundant surface functional groups and lattice defects of GNPs/Fe3O4 nanoparticles.

Magnetic properties and hyperthermia behavior of iron oxide nanoparticle clusters

In this study, Iron Oxide nanoparticle clusters have been synthesized utilizing individual Fe3O4 nanoparticles with different sizes as building blocks. The synthesis was accomplished by encapsulation of the individual Fe3O4 nanoparticles in an oil in water emulsion via hydrophobic interactions between cetyltrimethylammonium bromide (CTAB) and the nanoparticle’s surface aliphatic capping agents. It has been observed that the time, temperature and CTAB concentration were three crucial factors for controlling the size, shape and collective behavior of the clusters. Powder X-Ray Diffraction study shows that both individual Fe3O4 and the corresponded nanoparticle clusters have the Fe3O4 cubic spinel structure. Dynamic Light Scattering (DLS) shows that the hydrodynamic diameter of cluster is in the range of 100 to 200 nm. Transmission electron microscopy (TEM) images illustrate that different sizes of clusters can be effectively synthesized by using different concentration of CTAB and the results are consistent with the DLS values. Magnetic measurements show that the saturation magnetization of clusters can be changed from 56.7 emu/g to 70.1 emu/g by just changing the size of primary individual nanoparticles from 7.1 nm to 11.5 nm. Also, the blocking temperatures for Fe3O4 clusters were increased to higher temperatures which confirms the stronger collective behavior in the case of larger nanoparticles. The magnetic hyperthermia behavior of the clusters has also been studied, and the data shows that the Specific Absorption Rate (SAR) values are increased by both the clustering and the size of the primary nanoparticles.

Sodium-copper hexacyanoferrate-functionalized magnetic nanoclusters for the highly efficient magnetic removal of radioactive caesium from seawater

Sodium-copper hexacyanoferrate (NaCuHCF)-functionalized magnetic nanoadsorbents were fabricated for the highly efficient magnetic removal of radioactive caesium from seawater. The magnetic nanoclusters (MNCs), composed of many individual Fe3O4 nanoparticles, were covalently coated with polyethyleneimine (PEI) to functionalize the MNC surfaces with NaCuHCF. After simple immobilization of Cu and Na ferrocyanide on the NC surface, the resulting NaCuHCF-functionalized MNCs showed good magnetic properties and a significant adsorption capacity for Cs+ with a high content of NaCuHCF (36.04%). The adsorption kinetics and isotherms were well fit to a pseudo-second-order model and Langmuir isotherm, respectively. The sorption of 97.35% Cs by the NaCuHCF-PEI-MNCs completed in less than 5 min, and the maximum adsorption capacity of the adsorbent was 166.67 mg/g. The NaCuHCF-PEI-MNCs selectively adsorbed Cs even in the presence of various competing ions, such as Na, K, Mg, and Ca, and the Cs removal mechanism was revealed as ion exchange between Cs in solution and Na in the NaCuHCF-PEI-MNCs. In radioactive tests, our adsorbent displayed excellent removal performance in real seawater with a high removal efficiency exceeding 99.73%, a decontamination factor exceeding 372, and a high stability in water over a wide pH range from 4 to 10 with negligible leaching of Fe.

Shape-controlled fabrication of magnetite silver hybrid nanoparticles with high performance magnetic hyperthermia

Superparamagnetic Fe3O4 nanoparticles (NPs)-based hyperthermia is a promising non-invasive approach for cancer therapy. However, the heat transfer efficiency of Fe3O4 NPs is relative low, which hinders their practical clinical applications. Therefore, it is promising to improve the magnetic hyperthermia efficiency by exploring the higher performance magnetic NPs-based hybrid nanostructures. In the current study, it presents a straightforward in situ reduction method for the shape-controlled preparation of magnetite (Fe3O4) silver (Ag) hybrid NPs designed as magnetic hyperthermia heat mediators. The magnetite silver hybrid NPs with core-shell (Fe3O4@Ag) or heteromer (Fe3O4-Ag) structures exhibited a higher biocompatibility with SMMC-7721cells and L02cells than the individual Ag NPs. Importantly, in the magnetic hyperthermia, with the exposure to alternating current magnetic field, the Fe3O4@Ag and Fe3O4-Ag hybrid NPs indicated much better tumor suppression effect against SMMC-7721cells than the individual Fe3O4 NPs invitro and invivo. These results demonstrate that the hybridisation of Fe3O4 and Ag NPs could greatly enhance the magnetic hyperthermia efficiency of Fe3O4 NPs. Therefore, the Fe3O4@Ag and Fe3O4-Ag hybrid NPs can be used to be as high performance magnetic hyperthermia mediators based on a simple and effective preparation approach.

Single nanoparticles magnetization curves by controlled tip magnetization magnetic force microscopy.

The development of high spatial resolution and element sensitive magnetic characterization techniques to quantitatively measure magnetic parameters of individual nanoparticles (NPs) and deeply understand and tune their magnetic properties is a hot topic in nanomagnetism. Magnetic force microscopy (MFM), thanks to its high lateral resolution, appears as a promising technique for the magnetic characterization of single nano-sized materials although it is still limited by some drawbacks, especially by the presence of electrostatic artifacts. Recently, these limitations have been overcome by the development of a particular MFM based technique called controlled magnetization - MFM (CM-MFM) allowing, in principle, a quantifiable correlation between the measured magnetic signal and the magnetization of the object under investigation. Here we propose an experimental procedure, based on the use of CM-MFM technique, to measure the magnetization curve of single magnetic NPs individuating their saturation magnetization, magnetic field, and coercivity. We measured, for the first time, the magnetization curves of individual Fe3O4 nanoparticles with diameters in the range of 18-32 nm by using a MFM instrument. Results are in very good agreement with the quantitative data obtained by SQUID analysis on a macroscopic sample, showing the high potential of the technique in the field of nanomagnetometry.

Vector analysis of the magnetic polarity from individual magnetic nanoparticles

Vector analysis from individual Fe3O4 nanoparticles was achieved by magnetic force microscopy (MFM) technique with a micromagnetic modeling, which visualises the vector signals of the magnetic field from Fe3O4 nanoparticles. It is demonstrated that the MFM method combined with micromagnetics can effectively analyze the magnetic charge distribution with varying time. With this technique, the vector distribution of the magnetic field of the individual Fe3O4 magnetic nanoparticles was clearly presented, which will be of great importance for applications in nanobiological systems.

Magnetic nanoparticle clusters for photothermal therapy with near-infrared irradiation

In this study, the photothermal effect of magnetic nanoparticle clusters was firstly reported for the photothermal ablation of tumors both in vitro in cellular systems but also in vivo study. Compared with individual magnetic Fe3O4 nanoparticles (NPs), clustered Fe3O4 NPs can result in a significant increase in the near-infrared (NIR) absorption. Upon NIR irradiation at 808 nm, clustered Fe3O4 NPs inducing higher temperature were more cytotoxic against A549 cells than individual Fe3O4 NPs. We then performed in vivo photothermal therapy (PTT) studies and observed a promising tumor treatment. Compared with PBS and individual magnetic Fe3O4 NPs by NIR irradiation, the clustered Fe3O4 NPs treatment showed a higher therapeutic efficacy. The treatment effects of clustered Fe3O4 NPs with different time of NIR illumination were also evaluated. The result indicated that a sustained high temperature generated by NIR laser with long irradiation time was more effective in killing tumor cells. Furthermore, histological analysis of H&E staining and TUNEL immunohistological assay were further employed for antitumor efficacy assessment of PTT against A549 tumors.

Composite of graphene quantum dots and Fe3O4nanoparticles: peroxidase activity and application in phenolic compound removal

Graphene quantum dots (GQDs) are graphene sheets with lateral sizes less than 100 nm, and have a higher electron conjugate state and a better dispersion ability in aqueous solution compared to micrometer-sized graphene oxide (GO) sheets. Therefore they can overcome the drawbacks of GO and are an ideal candidate for nano-composites. In this work, composites of GQDs and Fe3O4 nanoparticles (NPs) (GQDs/Fe3O4) were prepared via a one-step co-precipitation approach. The as-prepared GQDs/Fe3O4 composites showed superb peroxidase-like activities, which were much higher than composites of micrometer sized GO and Fe3O4 NPs (GO/Fe3O4), individual GQDs, and individual Fe3O4 NPs. The excellent peroxidase activities of the GQDs/Fe3O4 composites can be attributed to the unique properties of GQDs and the synergistic interactions between the GQDs and Fe3O4 NPs. The GQDs/Fe3O4 composites also exhibited a higher stability and reusability than natural peroxidases. The application of a GQDs/Fe3O4 composite as a catalyst for the removal of phenolic compounds from aqueous solutions was explored with nine phenolic compounds, and showed better or comparable removal efficiencies for some phenolic compounds compared to native horseradish peroxidase (HRP) under the same conditions. The extraordinary catalytic performance and physical properties of the as-prepared GQDs/Fe3O4 composite render it practically useful for industrial wastewater treatment.

Improvement of microwave absorption for PAni/HA/TiO2 /Fe3 O4 nanocomposite after chemical treatment

In order to obtain efficient microwave absorbers that possess high conductivity, dielectric and magnetic properties, hexanoic acid doped polyaniline (PAni) nanocomposites which contain different ratios of ferum (II) oxide (Fe3O4) and titanium dioxide (TiO2) nanoparticles were successfully prepared by in situ chemical polymerization through template free method. Chemical structure, conductivity, morphology, thermal stability, magnetic properties, and amorphous/ crystalline behavior of PAni nanocomposites were characterized by Fourier transform infrared spectrometer (FTIR), four point probe, field emission scanning electron microscope (FESEM), thermal gravimetric analysis (TGA), vibrating samples magnetometer (VSM), and X-ray diffractometer (XRD), respectively. From this study, conductivity was significantly improved from 8.48 3 10 24 21.23 3 10 22 S/cm for PAni nanocomposites without any chemical treatment (during addition of Fe3O4) to 3.58 3 10 22 24.77 3 10 22 S/ cm for those with chemical treatment. PAni nanocomposites with chemical treatment show a narrow sharp reflection loss (RL) peak with high absorption (248.9 dB) at lower frequency due to the limited individual Fe3O4 nanoparticles outside the nanorods/nanotubes as proved by the new proposed mechanism (Fig. 5), while it shows a broad RL peak with poor absorption (213 dB) at higher frequency for those without chemical treatment. The novelty of this research has been focused on PAni with chemical treatment which yield better microwave absorption property (99.999% absorption), combination of high conductivity (3.58 3 10 22 24.77 3 10 22 S/cm), high heterogeneity and moderate magnetization (Ms 58.87–28.49 emu/g) compare to the PAni without chemical treatment. POLYM. COMPOS., 34:1186–1194, 2013. V C 2013 Society of Plastics Engineers

Aggregation of dextran coated magnetic nanoparticles in aqueous medium: Experiments and Monte Carlo simulation

Number density distribution of aggregates of dextran coated superparamagnetic iron oxide (Fe3O4) nanoparticles in an aqueous medium has been predicted using Monte Carlo simulation, and compared with our and others’ experimental data on aggregates. In addition to van der Waals and magnetic attraction between particles, the simulation included both bridging attraction and steric repulsion due to the presence of dextran on the nanoparticle surface. The simulation methodology is system independent and gave very good agreement with experimentally observed extensive aggregation in dextran coated particles – both for a wide range of molecular weight of dextran and different diameter and volume percentage of individual Fe3O4 nanoparticles.