Spherical Fe3O4 Nanoparticles Research Articles

High-frequency magnetic response of superparamagnetic composites of spherical Fe and Fe3O4 nanoparticles

The response of arrays of magnetic nanoparticles (MNPs) of cubic anisotropy materials (magnetite or iron) to high-frequency (sub-GHz) field is investigated utilizing micromagnetic simulations. Composites of MNPs embedded in dielectric media are of interest as core materials for high-frequency power microconverters with low eddy-current losses. Going beyond the macrospin approximation for MNPs (including internal spin structure), we simulate the magnetization dynamics of arrays of spherical and periodically arranged MNPs under periodic boundary conditions and in the presence of thermal fluctuations of the magnetization within the stochastic thermal field. Analyzing the dependence of the dynamical response on the size of the MNPs, we find the size to be crucial for exciting regular magnetization oscillations at room temperature and reducing hysteresis loss. The efficiency of the dynamical response of composites of high-magnetization-metal (iron) MNPs is compared to that of magnetite nanocomposites. We find the sub-GHz susceptibility of magnetite-containing nanocomposite to be comparable to that of the iron MNPs despite the lower saturation magnetization of Fe3O4, (at the volumetric ratio of the magnetic phase of 0.13, susceptibility is χ≈1.6 for 5 nm Fe and ≈1.4 for 12 nm Fe3O4 MNPs at T=300 K and frequency of 0.1 GHz).

Facile microwave-assisted preparation of Fe3O4 nanoparticles supported on carbonized cellulose nanocrystals derived from sugarcane bagasse

Microwave energy is an efficient form of energy used to speed up the synthesis of nanoparticles. Herein, we report the use of an unmodified domestic microwave oven to prepare magnetic spherical Fe3O4 (magnetite) nanoparticles (IONPs) supported on carbonized cellulose nanocrystals, forming a nanocomposite, in an expeditious and facile one-step reaction. This was achieved using the readily available precursors of FeCl3 as an iron source, and sugarcane bagasse, using activated charcoal as a microwave absorber. The nanocomposite was characterized using Raman spectroscopy which suggested a degree of crystallinity based on a G/D ratio of 1.25. The morphology of the Fe3O4/carbonized cellulose nanocrystal nanocomposite was characterized as spherical metallic nanoparticles supported on carbonized cellulose nanocrystals using Transmission electron microscopy (TEM), SEM, and EDX, while the identity of the Fe3O4 nanoparticles was confirmed with powder XRD.Graphical

High-frequency magnetic response of superparamagnetic composites of spherical Fe and Fe3O4 nanoparticles

High-frequency magnetic response of superparamagnetic composites of spherical Fe and Fe3O4 nanoparticles

Simulation and experimental study of cuboid and spherical magnetic Fe3O4 nanoparticles prepared with NaOH and NH4OH

A molecular dynamics study is done on cuboid and spherical Fe3O4 magnetic nanoparticles (NPs) to investigate qualitatively the influence of the molecules NH4OH and NaOH on their binding energy. This is done to determine the stability and therefore likely shape (morphology) and size of the synthesized NPs when these molecules are used as stabilizing agents. We show through molecular dynamics (MD) that small, spherical NPs synthesized with NH4OH, and large, cuboid NPs synthesized with NaOH, are the most stable NP systems and therefore the most likely outcome of a synthesis experiment. Furthermore, we synthesize these systems under similar conditions as predicted and find that when NaOH is used large (29 ± 2 nm), cuboid NPs are formed and when NH4OH is used, small (11 nm ± 2 nm), spherical NPs are formed. The role of pH is further investigated using the desorbed (and unadsorbed hydroxyl groups) as indicators of pH. The magnetic NPs are then synthesized via the co-precipitation method and the resulting NPs characterized for crystallinity, morphology, size and magnetic properties.

Viscosity Variations and Tribological Performances of Oleylamine-Modified Fe3O4 Nanoparticles as Mineral Oil Additives

In order to improve the flowabilities and anti-friction and anti-wear properties of lubricants, the viscosity variations and tribological performances of oleylamine-modified Fe3O4 nanoparticles as mineral oil additives were systematically investigated via rotational parallel plate rheometer, ball–disc reciprocating tribometer, non-contact three-dimensional surface profiler, scanning electron microscope, energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. Spherical monodisperse Fe3O4 nanoparticles were synthesized and dispersed into mineral oils to obtain lubricants with mass fractions of 1%, 3%, 5%, 8%, 10% and 20%, respectively. These lubricants have excellent stabilities within 12 months. Interestingly, the dynamic viscosity and kinematic viscosity of the lubricants first decrease and then increase with the increase in Fe3O4 content, and the lubricants’ viscosity is at a minimum when the mass concentration is 5%. The tensile curves also show that with the mass fraction increase, the lubricants’ tackiness and adhesion have the same change law, and both reach the lowest point when the mass concentration is 5%. Meanwhile, Fe3O4 nanoparticles can improve the tribological properties of the base oils. It is worth noting that the maximum reduction in the wear volume at 25 °C is up to 93.8% compared with base oils when the additive concentration of the Fe3O4 nanoparticles is 5 wt%.

Ni-Pd-Incorporated Fe3O4 Yolk-Shelled Nanospheres as Efficient Magnetically Recyclable Catalysts for Reduction of N-Containing Unsaturated Compounds

The use of metal-based heterogeneous catalysts for the degradation of N-containing organic dyes has attracted much attention due to their excellent treatment efficiency and capability. Here, we report the synthesis of heterometals (Ni and Pd)-incorporated Fe3O4 (Ni-Pd/Fe3O4) yolk-shelled nanospheres for the catalytic reduction of N-containing organic dyes using a facile combination of solvothermal treatment and high-temperature annealing steps. Benefiting from the magnetic properties and the yolk-shelled structure of the Fe3O4 support, as well as the uniformly dispersed active heterometals incorporated in the shell and yolk of spherical Fe3O4 nanoparticles, the as-prepared Ni-Pd/Fe3O4 composite shows excellent recyclability and enhanced catalytic activity for three N-containing organic dyes (e.g., 4-nitrophenol, Congo red, and methyl orange) compared with its mono metal counterparts (e.g., Ni/Fe3O4 and Pd/Fe3O4). In the 4-nitrophenol reduction reaction, the catalytic activity of Ni-Pd/Fe3O4 was superior to many Fe3O4-supported nanocatalysts reported within the last five years. This work provides an effective strategy to boost the activity of iron oxide-based catalytic materials via dual or even multiple heterometallic incorporation strategy and sheds new light on environmental catalysis.

Ag NPs decorated on the magnetic Fe3O4@PDA as efficient catalyst for organic pollutants removal and as effective antimicrobial agent for microbial inhibition

In this paper, Ag NPs-decorated magnetic Fe3O4 @PDA nanocomposites have been successfully prepared. The spherical Fe3O4 nanoparticles with an average size approximately 340 nm were modified by dopamine under mild conditions. Dopamine was self-polymerized surrounding Fe3O4 nanoparticles and transformed into poly dopamine (PDA) layers. The PDA-encapsulated magnetic (Fe3O4 @PDA) nanoparticles could in-situ reduce silver ammonium ions by the catechol groups in PDA layers. The Ag NPs with an average size ranging from 20 nm to 36 nm were densely decorated on the thin PDA shell. The resultant Fe3O4 @PDA-Ag nanocomposites were employed as highly efficient catalysts for the reduction of different organic pollutants in the appearance of sodium borohydride. The Fe3O4 @PDA-Ag nanocomposites also demonstrated extraordinary cycling stability when the catalyst was recycled several times for the reduction of MB. The antimicrobial tests indicated Fe3O4 @PDA-Ag nanocomposites could efficiently prohibit the growth of microorganism, including various bacteria and fungi. The minimal inhibitory concentrations (MIC) for Fe3O4 @PDA-Ag nanocomposites against different bacteria and fungi were also determined. The excellent catalytic activity, magnetic recyclability, and antimicrobial performance make Fe3O4@PDA-Ag a feasible candidate for the remediation of wastewater which contains multiple water soluble organic pollutants and pathogenic microorganism.

One-pot ultrasonic-assisted synthesis of magnetic hydroxyapatite nanoparticles using mussel shell biowaste with the aid of trisodium citrate

The studies on hydroxyapatite (HAp) nanoparticles have prompted prospects for superior biomaterials in orthopedics and dentistry. In this work, one-pot ultrasonic-assisted synthesis of magnetic HAp nanoparticles was carried out using a mussel shell calcium source by incorporating Fe2+/Fe3+ ions during Ca-citrate complex formation. Characterization of prepared specimens revealed that Fe2+/Fe3+ ions integration at low concentrations (0.01:0.02 ratio) does not affect the phase purity of HAp nanoparticles while at high concentrations (0.1:0.2 ratio) produced HAp/Fe3O4 nanocomposite. The developed HAp/Fe3O4 nanocomposite was composed of spherical Fe3O4 nanoparticles (10 nm size) and rod-like HAp nanoparticles (5–10 nm width and 20–30 nm length), and it revealed soft ferromagnetic properties with coercivity (Hc) and saturation magnetization (Ms) values of 750 G and 7.05 emu/g, respectively. Furthermore, the developed HAp/Fe3O4 nanocomposite exhibited good bone-forming ability in SBF and accomplished hyperthermia temperature within 8 min at 400 A applied current. Hence, it can be a potential bone repair material with magnetic induction heating ability. Also, this study utilized mussel shell calcium precursor which is a cost-effective and ecologically friendly method.

Cytotoxicity of Fe3O4 Nanoparticles with Different Morphologies In Vitro

Fe3O4 nanoparticles have been widely used as drug carriers, but their toxicity is rarely reported. Herein, we compared the toxicity of novel Fe3O4 nanorings, nanotubes and conventional Fe3O4 nanospheres. The structure, morphology and magnetic properties of Fe3O4 nanoparticles were characterized via X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. Scanning electron microscope images revealed that the morphologies of Fe3O4 particles were annular, tubular or spherical. The magnetic property measurements demonstrated that saturation magnetization values of nanorings, nanotubes and nanospheres were 85.3, 90.1 and 74.8[Formula: see text]emu/g, respectively. In addition, the cytotoxic effects on the 264.7 mouse macrophages cells of Fe3O4 nanorings, nanotubes and nanospheres were determined by cck-8 test and TUNEL staining assay. Cell viability was slightly decreased on spherical Fe3O4 nanoparticles compared to annular and tubular Fe3O4 nanoparticles.

Green fabrication of ZnO/magnetite-based nanocomposite - using Salvia officinalis extract with antibacterial properties enhanced infected full-thickness wound

The present study was conducted to develop a simple and novel synthesis process, one-step Salvia officinalis extract-assisted biosynthesis route to synthesize ZnO/Magnetite-based nanocomposites (ZnO/Mgt-NCs). Characterization of the physicochemical properties of the ZnO/Mgt-NCs was performed using XRD, FESEM, EDX, TEM, FT-IR, and DLS techniques. Furthermore, their biomedical properties for antibacterial properties and wound healing activity were assessed. According to the TEM and FESEM image, the synthesized spherical Fe3O4 nanoparticles on the surface of quartz were formed ranging from about 13–14 nm. In addition, based on the EDX spectra, the elemental analysis showed the presence of Zinc, Oxygen, and Iron elements in the as-synthesized ZnO/Mgt-NCs. Biomedical studies confirmed that ZnO/Mgt-NCs had antibacterial properties and demonstrated antibacterial activity against Streptococcus pyogenes and Pseudomonas aeruginosa. It also revealed infected wound healing activity by decreasing the total bacterial tissue on top of improving granulation tissue, collagen density and epithelization. Therefore, the new Magnetite-based ZnO/Mgt-NCs has greater potential to cure wounds efficiently.

Multiscale simulations of the hydration shells surrounding spherical Fe3O4 nanoparticles and effect on magnetic properties.

Iron oxide magnetic nanoparticles (NPs) are excellent systems in catalysis and in nanomedicine, where they are mostly immersed in aqueous media. Even though the NP solvation by water is expected to play an active role, the detailed structural insight at the nanostructure oxide/water interface is still missing. Here, based on our previous efforts to obtain accurate models of dehydrated Fe3O4 NPs and of their magnetic properties and through multiscale molecular dynamics simulations combining the density functional tight binding method and force field, we unravel the atomistic details of the short range (chemical) and long range (physical) interfacial effects when magnetite nanoparticles are immersed in water. The influence of the first hydration shell on the structural, electronic and magnetic properties of Fe3O4 NPs is revealed by high-level hybrid density functional calculations. Hydrated Fe3O4 NPs possess larger magnetic moment than dehydrated ones. This work bridges the large gap between experimental studies on solvated Fe3O4 NPs and theoretical investigations on flat Fe3O4 surfaces covered with water and paves the way for further study of Fe3O4 NPs in biological environments.

Magnetic-field-assisted synthesis of anisotropic iron oxide particles: Effect of pH.

The synthesis of magnetite (Fe3O4) nanorods using reverse co-precipitation of Fe3+ and Fe2+ ions in the presence of a static magnetic field is reported in this work. The phase composition and crystal structure of the synthesized material were investigated using electron diffraction, Raman spectroscopy, and transmission electron microscopy. It was shown that the morphology of the reaction product strongly depends on the amount of OH− ions in the reaction mixture, varying from Fe3O4 nanorods to spherical Fe3O4 nanoparticles. Fe3O4 nanorods were examined using high-resolution transmission electron microscopy proving that they are single-crystalline and do not have any preferred crystallographic orientation along the axis of the rods. According to the data obtained a growth mechanism was proposed for the rods that consists of the dipole–dipole interaction between their building blocks (small hexagonal faceted magnetite nanocrystals), which are formed during the first step of the reaction. The study suggests a facile, green and controllable method for synthesizing anisotropic magnetic nanoparticles in the absence of stabilizers, which is important for further modification of their surfaces and/or incorporation of the nanoparticles into different media.

Influence on the Magnetic Properties of Nd Doped in Fe3O4 Nanoparticles

Spherical magnetic Fe3O4 nanoparticles with different Nd doping amounts were successfully prepared using a simple hydrothermal method. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser scattering particle size (DLS), and vibrating sample magnetometer (VSM) analysis. Results showed that the spherical nanoparticles of pure Fe3O4, pure Nd2O3, and Nd-Fe3O4 were confirmed by XRD and TEM. The size of the prepared nanoparticles decreased first and then increased with increasing Nd doping amount by dynamic laser scattering. In addition, magnetic parameters, including saturation magnetization, remanent magnetization, and coercivity of Fe3O4 nanoparticles with different doping ratios of Nd, were analyzed by VSM.

Molecular dynamics simulation of ferronanofluid behavior in a nanochannel in the presence of constant and time-dependent magnetic fields

In this work, the molecular dynamics method is implemented to study the time evolution of water/Fe3O4 nanofluid dynamics with constant and time-dependent magnetic fields. The nanochannel with four walls is simulated to carrier water base-fluid and spherical Fe3O4 nanoparticles in a nanochannel. Simulations reveal that the density, velocity, and temperature profiles of nanofluid inside copper nanochannel are increased by increasing the nanoparticle numbers. Our results show that the simulated nanofluids with magnetic forces agglomerate faster. Furthermore, the effects of nanoparticles’ number on the aggregation process are examined. Also, when the magnetic fields are subjected to nanofluid atomic structure, this external parameter prevents the aggregation of Fe3O4 nanoparticles, and so the assembly rate decreases and needed longer time for this phenomenon to occur. Physically, our results show that the magnetic field with normal direction to the nanofluid flow affects to the simulation process. This external parameter avoids the movement of nanoparticles along the fluid flow direction, and aggregation of these nanostructures occurs at a long time.

The activation energy and antibacterial investigation of spherical Fe3O4 nanoparticles prepared by Crocus sativus (Saffron) flowers

We proposed a simple and environmental-friendly method to prepare magnetite nanoparticles and their application as antibacterial material. We successfully prepared Fe3O4 nanoparticles using Crocus Sativus (Saffron) flowers followed by calcination at 400 ˚C for 15 minutes. The UV–Visible spectroscopy was used to study the bandgap energy of the prepared Fe3O4 nanoparticles and the value was found to be 3.23 eV. The scanning electron microscopy (SEM) was used to study the structure and morphology and X-ray diffraction was used to study the phase and crystallite size of the magnetite nanoparticles. The percentage weight loss, the enthalpy change and activation energy of Fe3O4 nanoparticles were calculated by using the thermogravimetric (TG) and differential thermal analysis (DTA) respectively. The DTA curve at a heating rate of 6, 8 and 10˚C/min shows endothermic peaks at 586, 594 and 600˚C respectively. The activation energy of Fe3O4 nanoparticles was calculated by the Kissinger method and was found to be 8.09 kJ/moles. The antibacterial activity of Fe3O4 nanoparticles was carried out against 3 gram-positive and 3 gram-negative bacteria by using a minimum inhibition concentration (MIC) assay method and they showed excellent antibacterial activity against gram-negative bacterial strains only.

Enhanced Microwave Absorption and Electromagnetic Properties of Si-Modified rGO@Fe3O4/PVDF-co-HFP Composites.

Graphene has been regarded as one of the most promising two-dimensional nanomaterials. Even so, graphene was still faced with several key issues such as impedance mismatching and narrow bandwidth, which have hindered the practical applications of graphene-based nanocomposites in the field of microwave absorption materials. Herein, a series of Si-modified rGO@Fe3O4 composites were investigated and fabricated by a simple method. On one hand, the degree of defects in graphene carbon could be tuned by different silane coupling reagents, which were beneficial to enhancing the dielectric loss. On the other hand, the spherical Fe3O4 nanoparticles provided the magnetic loss resonance, which contributed to controlling the impedance matching. Subsequently, the electromagnetic absorption (EMA) properties of Si-modified rGO@Fe3O4 composites with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) were investigated in this work. As a result, the Si(2)-rGO@Fe3O4/PVDF-co-HFP composite exhibited the excellent EMA performance in the range of 2–18 GHz. The maximum reflection loss (RLmax) reached −32.1 dB at 3.68 GHz at the thickness of 7 mm and the effective absorption frequency bandwidth for reflection loss (RL) below −10 dB was 4.8 GHz at the thickness of 2 mm. Furthermore, the enhanced absorption mechanism revealed that the high-efficiency absorption performance of Si(2)-rGO@Fe3O4/PVDF-co-HFP composite was attributed to the interference absorption (quarter-wave matching model) and the synergistic effects between Si(2)-rGO@Fe3O4 and PVDF-co-HFP. This work provides a potential strategy for the fabrication of the high-performance EMA materials.

Necklace-like Fe3O4 nanoparticle beads on carbon nanotube threads for microwave absorption and supercapacitors

Commonly, one typical performance of the materials can be fully utilized in a certain field due to the particular physical or chemical properties. In this work, a multifunctional novel necklace-like three-dimension (3D) Fe3O4/CNTs nanocomposite with carbon nanotubes (CNTs) threading into homogeneous spherical Fe3O4 nanoparticles have been fabricated by a one-pot hydrothermal method. The good intrinsic magnetic and dielectric properties for the 3D Fe3O4/CNTs nanocomposites lead to their outstanding microwave absorption performances (minimum RL value of −59.2 dB with a thin thickness of 1.68 mm). Furthermore, high electrical conductivity and fast surface redox are also observed in these Fe3O4/CNTs nanocomposites resulting in their excellent electrochemical properties (specific capacitance of 361.1 F g−1 at 0.5 A g−1). This work indicates that the distinct physical and chemical properties can be realized in the same composite structure by the suitable composite technology, which can not only improve the material utilization but also enable the preparation of multifunctional devices.

Shape-Dependent Fenton-Like Catalytic Activity of Fe3O4 Nanoparticles

AbstractOctahedral and spherical Fe3O4 nanoparticles (NPs) were synthesized and used as heterogeneous Fenton-like catalysts to degrade methylene blue (MB). Their catalytic activities were investiga...

Selective and Recyclable Congo Red Dye Adsorption by Spherical Fe3O4 Nanoparticles Functionalized with 1,2,4,5-Benzenetetracarboxylic Acid

In this study, the new material Fe3O4@BTCA has been synthesized by immobilization of 1,2,4,5-Benzenetetracarboxylic acid (BTCA) on the surface of Fe3O4 NPs, obtained by co-precipitation of FeCl3.6H2O and FeCl2.4H2O in the basic conditions. Characterization by P-XRD, FE-SEM, and TEM confirm Fe3O4 has a spherical crystalline structure with an average diameter of 15 nm, which after functionalization with BTCA, increases to 20 nm. Functionalization also enhances the surface area and surface charge of the material, confirmed by BET and zeta potential analyses, respectively. The dye adsorption capacity of Fe3O4@BTCA has been investigated for three common dyes; Congo red (C.R), Methylene blue (M.B), and Crystal violet (C.V). The adsorption studies show that the material rapidly and selectively adsorbs C.R dye with very high adsorption capacity (630 mg/g), which is attributed to strong H-bonding ability of BTCA with C.R dye as indicated by adsorption mechanism study. The material also shows excellent recyclability without any considerable loss of adsorption capacity. Adsorption isotherm and kinetic studies suggest that the adsorption occurs by the Langmuir adsorption model following pseudo-second-order adsorption kinetics.

Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.