Aggregation Of Fe3O4 Nanoparticles Research Articles

Macroscopic Room-Temperature Magnetoelectricity in Piezoelectric (Core)-Ferrimagnetic (Shell) Nanocomposites.

The magnetoelectric (ME) effect, which involves the interaction of magnetic and electric fields within a material, has a significant potential for various applications. Our study addresses the limitations of conventional magnetostriction-based ME materials by demonstrating an alternative approach that achieves substantial ME effects in core-shell-type nanocomposites at room temperature. By synthesizing ferrimagnetic Fe3O4 nanoparticles onto piezoelectric poly(vinylidene fluoride) (PVDF) particles, we identified a distinct ME mechanism. In magnetorheological (MR) fluids, the magnetic-field-induced aggregation of Fe3O4 nanoparticles, combined with the piezoelectricity of PVDF, leads to a pronounced ME effect, significantly enhancing the performance and stability of MR fluids. This research highlights a crucial observation of distinct ME effects, which could suggest potential pathways for advancements in practical applications including microfluidics, vibration dampers, tactile technologies, and biomedical and bioengineering fields.

Increasing Light-Induced Forces with Magnetic Photonic Glasses

In this work, we theoretically and experimentally study the induction of electromagnetic forces in an opal-based magnetic photonic glass, where light normally impinges onto a disordered arrangement of SiO2 spheres by the aggregation of Fe3O4 nanoparticles. The working wavelength is 633 nm. Experimental evidence is presented for the force that results from forced oscillations of the photonic structure. Finite-element method simulations and a theoretical model estimate the magnetic force volumetric density value, peak displacement, and velocity of oscillations. The magnetic force is of the order of 56 microN, which is approximately 500-times higher than forces induced in dielectric optomechanical photonic crystal cavities.

Selective adsorption behavior of Cd2+ imprinted acrylamide-crosslinked-poly(alginic acid) magnetic polymers: fabrication, characterization, adsorption performance and mechanism.

Poly(acrylamide) grafted and glutaraldehyde-crosslinked alginic acid nano-magnetic adsorbent (AAMA) was prepared by selecting Cd2+ as a template ion. Scanning electron microscope (SEM), thermo-gravimetric analyzer (TGA), vibrating sample magnetometer (VSM) and infrared spectroscopy (IR) were used to characterize the morphology and structure of AAMA. The adsorption of AAMA for different metal ions was compared and the impact of various factors for adsorption of Cd2+ was systematically investigated. These results suggested that the AAMA was the aggregates of Fe3O4 nanoparticles with a diameter of about 50-100 nm and had selectivity for Cd2+ adsorption. The maximum adsorption capacity for Cd2+ is 175 mg/g at pH 5.0 and 303 K. The experimental data were well described by the Langmuir isotherm model and pseudo-second-order model. The parameters of adsorption thermodynamics concluded that the adsorption progress is spontaneous and endothermic in nature. The parameters of adsorption activation energy suggested that there is physical adsorption and chemisorption on the adsorption of metal ions. AAMA could be regenerated by EDTA and still keep 71% adsorption capacity in the fifth consecutive adsorption-regeneration cycle. Therefore, AAMA would be useful as a selective and high adsorption capacity nano-magnetic adsorbent in the removal of Cd2+ from wastewater.

An Oxidation-Enhanced Magnetic Resonance Imaging Probe for Visual and Specific Detection of Singlet Oxygen Generated in Photodynamic Cancer Therapy In Vivo.

Singlet oxygen is regarded as the primary cytotoxic agent in cancer photodynamic therapy (PDT). Despite the advances in optical methods to image singlet oxygen, it remains a challenge for in vivo application due to the limited tissue penetration depth of light. Up to date, no singlet oxygen-specific magnetic resonance imaging (MRI) probe has been reported. Herein, a T2 -weighted MRI probe is reported to visually detect singlet oxygen generated in PDT in vitro and in vivo. The MRI probe Ce6/Fe3 O4 -M is constructed by co-encapsulation of photosensitizer Ce6 and Fe3 O4 nanoparticles in mPEG2000 -TK-C16 micelles. Thioketal (TK) linker in the probe is highly sensitive to singlet oxygen, but lowly sensitive to other reactive oxygen species (ROS) existing in physiological and pathological environments. Singlet oxygen, generated with light irradiation, triggers the cleavage of TK, which leads to loss of surface polyethylene glycol, increment of the hydrophobicity, and aggregation of Fe3 O4 nanoparticles. Subsequently, negatively enhanced T2 -weighted MRI signal is obtained for visual detection of singlet oxygen in the solution, cancer cells, and in vivo. This oxidation responsive MRI probe is expected to hold great promise in evaluating the ability of photosensitizers to generate singlet oxygen and in predicting the therapeutic efficacies of PDT in vivo.

Enhanced catalytic performance on the thermal decomposition of TKX-50 by Fe3O4 nanoparticles highly dispersed on rGO

Fe3O4/reduced graphene oxide (Fe3O4/rGO) nanocomposite has been successfully fabricated using a modified interface solvothermal method and characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. In the preparation procedure, graphene oxide was reduced and ultrafine Fe3O4 nanoparticles (NPs) were uniformly loaded on reduced graphene oxide (rGO) carrier. Scanning electron microscope, transmission electron microscope images and Brunauer–Emmett–Teller specific surface area revealed that the aggregation of Fe3O4 NPs was greatly reduced by introducing rGO as a substrate. The average size of the Fe3O4 NPs anchored on the graphene sheets was 100 nm, which is much smaller than 1-μm bare Fe3O4. The DSC results showed that Fe3O4/rGO nanocomposite reduces the first decomposition temperature of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) by 44.9 °C and decreases the apparent activation energy of TKX-50 by 26.2 kJ mol−1, which exhibits higher catalytic performance than its individual components and their physical mixture (hybrid). Hence, Fe3O4/rGO nanocomposite can be a promising additive for insensitive solid propellants based on TKX-50.

Reduced graphene oxide-loaded-magnetite: A Fenton-like heterogeneous catalyst for photocatalytic degradation of 2-methylisoborneol

A reduced-graphene-oxide-loaded magnetite (rGOF) composite was successfully synthesized by co-precipitation method for photocatalytic degradation of an odorous water contaminant 2-methylisoborneol (MIB). This heterogeneous Fenton-like catalyst degraded the recalcitrant MIB under both UV and solar light irradiations at neutral pH without the addition of other chemicals. Bare magnetite (Fe3O4) degraded only 22.5% of MIB because of rapid charge recombination. In comparison, the degradation efficiency increased to 99% for 10% (by weight) reduced graphene oxide (rGO) loading in magnetite. The addition of the rGO not only increased the adsorption capacity by increasing surface area but also increased the photodegradation efficiency synergistically by separating the electron–hole pairs, indicated by the photoluminescence spectra. The reduction in aggregation of Fe3O4 nanoparticles was explained by the increase in d-spacing and with FE-SEM images. The impedance and photocurrent data also proved the transfer of electron in presence of light in the hybrid composite. The rGOF composite presented excellent ferromagnetism, which made its recovery very easy. The recycled composite showed significantly high photocatalytic activity even after the fifth cycle with increased adsorption capacity of the recycled composite. Degradation mechanism and degradation pathway have been proposed and intermediates were identified.

Tumor Microenvironment-Triggered Aggregation of Antiphagocytosis 99m Tc-Labeled Fe3 O4 Nanoprobes for Enhanced Tumor Imaging In Vivo.

A tumor microenvironment responsive nanoprobe is developed for enhanced tumor imaging through in situ crosslinking of the Fe3 O4 nanoparticles modified with a responsive peptide sequence in which a tumor-specific Arg-Gly-Asp peptide for tumor targeting and a self-peptide as a "mark of self" are linked through a disulfide bond. Positioning the self-peptide at the outmost layer is aimed at delaying the clearance of the nanoparticles from the bloodstream. After the self-peptide is cleaved by glutathione within tumor microenvironment, the exposed thiol groups react with the remaining maleimide moieties from adjacent particles to crosslink the particles in situ. Both in vitro and in vivo experiments demonstrate that the aggregation substantially improves the magnetic resonance imaging (MRI) contrast enhancement performance of Fe3 O4 particles. By labeling the responsive particle probe with 99m Tc, single-photon emission computed tomography is enabled not only for verifying the enhanced imaging capacity of the crosslinked Fe3 O4 particles, but also for achieving sensitive dual modality imaging of tumors in vivo. The novelty of the current probe lies in the combination of tumor microenvironment-triggered aggregation of Fe3 O4 nanoparticles for boosting the T2 MRI effect, with antiphagocytosis surface coating, active targeting, and dual-modality imaging, which is never reported before.

Facile Preparation of Fe3O4/Carbon Nanocomposite With High Lithium Storage Capacity

In the present work, Fe3O4/carbon nanocomposite was prepared using metal organic framework as a precursor. Meanwhile, the electrochemical performance of the Fe3O4/carbon nanocomposite, as an anode material, was evaluated by galvanostatic discharge-charge tests. The experimental results indicate that the as-prepared sample is a porous aggregation of Fe3O4 nanoparticles interconnected with amorphorous carbon layer, and the mean diameter of Fe3O4 nanoparticles is approximately 30 nm. Moreover, it is also observed that the Fe3O4/carbon nanocomposite possesses a high initial discharge capacity of 1586 mA h g−1.

One-pot high temperature hydrothermal synthesis of Fe3O4@C/graphene nanocomposite as anode for high rate lithium ion battery

This study develops a facile and effective methodology to synthesize carbon-coated Fe3O4/graphene composite in one-pot high temperature hydrothermal processing, which not only simplifies the synthesis procedure, but also partly avoids graphene re-stacking and aggregation of Fe3O4 nanoparticles. Fe3O4@C nanoparticles of about 50nm are uniformly dispersed on the graphene nanosheets. The electrochemical test of the Fe3O4@C/graphene nanocomposite demonstrates high rate capacity. The first reversible specific capacity is 1016.6mAhg−1 and increases to 1199.8mAhg−1 after 500 cycles at 1.0Ag−1, and the reversible specific capacity at 20.0Ag−1 remains 52.8% of that at 0.2 Ag−1. The excellent electrochemical performance can be attributed to high extrinsic conductivity where carbon layer and graphene can provide rapid transfer channels for electrons and small particles size that can accommodate volumetric changes of Fe3O4 due to their elastic feature. In addition, the winkle structure representing a curled and corrugated morphology that the graphene owns intrinsically may also act as lithium ion rapid transfer channels. Full batteries using the Fe3O4@C/graphene nanocomposite as the anode and lithium nickel cobalt manganese oxide as the cathode show excellent cycle performance.

In Situ Chemical Synthesis of Fe3O4 Nanoparticles on Reduced Graphene Oxide Sheets in Polyol Medium and Magnetic Properties.

This letter reports the one-pot synthesis of reduced graphene oxide/Fe3O4 composites. By the electrostatic interaction of exfoliated graphene oxide and Fe3+ ions, graphene oxide/Fe3+ ions were prepared in a diethylene glycol. In situ formation of Fe3O4 nanoparticles on graphene oxide sheets and reduction of graphene oxide were then achieved simultaneously by the thermal decomposition reaction of Fe(acac)3 at high temperature. This synthetic method enables control over the phase of Fe3O4 nanoparticles on graphene sheets, further preventing restacking of the graphene sheets and aggregation of Fe3O4 nanoparticles. By controlling the mass ratio of Fe(acac)3 and graphene oxide, a series of reduced graphene oxide/Fe3O4 composites were prepared. Magnetic properties of the reduced graphene oxide/Fe3O4 composites are investigated.

Synthesis of Magnetic Ferriferrous Oxide/Halloysite Composite

Nanometer ferriferrous oxide (Fe3O4) with about 10–30 nm diameter were deposited on the inner and outer surfaces of natural halloysite nanotubes (HNTs) via the reduction co-precipitation process. The aggregation of Fe3O4 nanoparticles will be significantly reduced as they are distributed on the surfaces of HNTs with higher specific surface areas. Powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectrometer showed that Fe3O4/HTNs composites had a good thermal stability at 373 K and 523 K. Furthermore, Vibrating-sample magnetometer (VSM) confirmed the superparamagnetism of Fe3O4/HTNs composites could be preserved at different heat treatment of 373 K and 523 K.

Nanostructured Materials with Conducting and Magnetic Properties: Preparation of Magnetite/Conducting Copolymer Hybrid Nanocomposites by Ultrasonic Irradiation

Conducting copolymer poly(aniline-co-p-phenylenediamine) [poly(Ani-co-pPD)] and surface-modified magnetite (Fe3O4) composites were synthesized by ultrasonically-assisted chemical oxidative polymerization. Fe3O4 nanoparticles were surface-modified with silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS) in order that they would be well dispersed for the reaction process. It was also found that the aggregation of Fe3O4 nanoparticles could be reduced under ultrasonic irradiation. TEM analysis confirmed that the resulting poly(Ani-co-pPD)/Fe3O4 nanocomposite showed core–shell morphology, in which Fe3O4 nanoparticles were well dispersed. The incorporation of Fe3O4 in the nanocomposites was endorsed by FT-IR. The nanocomposites were also confirmed by UV-visible, TGA and XRD. Conductivity of the nanocomposites was found to be in the range of 7.02 × 10−4–6.54 × 10−6 S/cm. Higher saturated magnetization of 12 emu/g was observed for composite with 20% Fe3O4.

Studies on the synthesis and microwave absorption properties of Fe3 O4/polyaniline FGM

Electrically conducting polyaniline (PANI)–magnetic oxide (Fe3 O4) composites were synthesized by emulsion polymerization in the presence of dodecyl benzene sulfonic acid (DBSA) as the surfactant and dopant and ammonium persulfate (APS) as the oxidant. Transmission electron microscopy (TEM) indicates that the composite has a magnetic core and an electric shell and the modification has prevented the aggregation of Fe3 O4 nanoparticles effectively. The electromagnetic parameter measurements (ε″, ε′, μ″ and μ′) in the range of 2–18 GHz prove that Fe3 O4 in the Fe3 O4/PANI/DBSA is responsible for the electric and ferromagnetic behavior of the composites. As a result, the electromagnetic parameters can be designed by adjusting the content of the Fe3 O4. The microwave absorption of functionally graded material (FGM) was simulated by the computer according to the principle of impedance match and the calculated results agreed quite well with the experimentally measured data (R<−20 dB, Δf>4 GHz).