Ferromagnetic Fe3O4 Nanoparticles Research Articles

Acoustic Levitation-Assisted Contactless Printing of Microdroplets for Biomedical Applications

Abstract The cell is a microcapsule system wherein biological materials are encapsulated by a thin membrane, which provides valuable information on the metabolism, morphology, development, and signal transduction pathways of the studied cell. The cell-inspired microdroplet has the characteristics of efficient nanoscale substance transportation, self-organization, and morphological adaptation. However, it is extremely difficult to manufacture such systems. Mostly vesicles such as liposomes, polymersomes, and microcapsules are first produced by a high-pressure homogenizer and microfluidizer as an emulsion and then encapsulated microcapsules by the drop or emulsion method. Currently, acoustic levitation opens entirely new possibilities for creating bioinspired microdroplets because of its ability to suspend tiny droplets in an antigravity and noncontact manner. Herein, we propose contactless printing of single-core or multi-core cell-inspired microdroplets via acoustic levitation. First, the oscillation mode and microscopic morphology of the droplets under different ultrasonic vibration frequencies are shown by simulation, and the curing characteristics of the shell structure under different ultraviolet illumination conditions are quantitatively measured. The feasibility of manufacturing multi-core microdroplets and manufacturing submillimeter-scale particles based on oil trapping is extensively studied. To explore the morphological adaptability of microdroplets, ferromagnetic Fe3O4 nanoparticles are used to give magnetic-responsive properties to cells, and the microscopic deformation and motion in microfluidic channels under the magnetic field are characterized. Finally, the proposed printing method proves the versatility of in-space contactless printing of complex 3D beam structures and provides a powerful platform for developing biomedical devices and microrobots and studying morphogenesis and synthetic biological systems.

Ultra‐Small Ferromagnetic Fe3O4 Nanoparticles Modified Separator for High‐Rate and Long Cycling Lithium‐Sulfur Batteries

AbstractAs a promising energy storage system with high specific capacity, lithium‐sulfur (Li−S) battery is striving for a high‐rate and longer lifetime. Whereas the slow redox kinetics and the shuttle effect of polysulfides (PSs) still severely restrict the performance of Li−S batteries. Here, a rational designed ferromagnetic Fe3O4 nanoparticles (FM‐Fe3O4 NPs) modified separator is engineered for Li−S batteries. Moreover, the particle size of FM‐Fe3O4 NPs was tuned to enhance the energy storage performance. Consequently, the cells with FM‐Fe3O4 NPs modified separator achieved a high‐rate and long cycling performance, the specific capacity could reach 672.8 mAh g−1 and a low fading rate (0.028 % per cycle over 700 cycles) at a high rate of 5 C. Experimental results reveals that FM‐Fe3O4 NPs could mitigate shuttle effect, enable efficient redox reactions, and protect the Li anode from severe corrosion. The performance‐enhanced mechanism is further discovered by DFT calculations, the results show that FM‐Fe3O4 NPs act as mediators of redox reaction to block PSs shuttle and dynamically facilitate conversion via changing the molecular structure of PSs and reducing reaction barrier. This work provides a new pathway to improving Li−S batteries based on ferromagnetic materials, which may be generalized to other advanced batteries.

Isothermal models of Chromium (VI) adsorption by using Fe3O4 nanoparticles

The ferromagnetic Fe3O4 nanoparticles with the average particle size of about 10 nm were used to adsorb chromium (VI) in aqueous solution. The equilibrium of Cr(VI) adsorption can be achieved at the pH value of 2.5, in the contact time of 120 minutes. The mechanisms of Cr(VI) adsorption were evaluated by 4 isothermal adsorption models Langmuir, Freundlich, Redlich-Peterson, and Temkin. The results showed that all four models are satisfied; especially, Redlich-Peterson is the most suitable model to describe the adsorption kinetic of Cr(VI) on ferromagnetic Fe3O4 nanoparticles.

Pronounced and reversible modulation of the piezoelectric coefficients by a low magnetic field in a magnetoelectric PZT-5%Fe3O4 system

Composite magnetoelectric compounds that combine ferroelectricity/piezoelectricity and ferromagnetism/magnetostriction are investigated intensively for room-temperature applications. Here, we studied bulk composites of a magnetostrictive constituent, ferromagnetic Fe3O4 nanoparticles, homogeneously embedded in a ferroelectric/piezoelectric matrix, Pb(Zr0.52Ti0.48)O3 (PZT). Specifically, we focused on PZT-5%Fe3O4 samples which are strongly insulating and thus sustain a relatively high out-of-plane external electric field, Eex,z. The in-plane strain-electric field curve (S(Eex,z)) was carefully recorded upon successive application and removal of an out-of-plane external magnetic field, Hex,z. The obtained S(Eex,z) data exhibited two main features. First, the respective in-plane piezoelectric coefficients, d(Eex,z) = 200–250 pm/V, show a dramatic decrease, 50–60%, upon application of a relatively low Hex,z = 1 kOe. Second, the process is completely reversible since the initial value of d(Eex,z) is recovered upon removal of Hex,z. Polarization data, P(Eex,z), evidenced that the Fe3O4 nanoparticles introduced static structural disorder that made PZT harder. Taken together, these results prove that the Fe3O4 nanoparticles, except for static structural disorder, introduce reconfigurable magnetic disorder that modifies the in-plane S(Eex,z) curve and the accompanying d(Eex,z) of PZT when an external magnetic field is applied at will. The room-temperature feasibility of these findings renders the PZT-x%Fe3O4 system a solid basis for the development of magnetic-field-controlled PE devices.

An approach to widen the electromagnetic shielding efficiency in PDMS/ferrous ferric oxide decorated RGO–SWCNH composite through pressure induced tunability

In the present era, the advanced technology demands for the fabrication of light weight and compressible high performance electromagnetic interference (EMI) shielding materials for adaptable shielding application in the area of modern electronic gadgets and telecommunication devices. This study highlights facile fabrication of such lightweight compressible porous polydimethylsiloxane (PDMS)/FRS [Ferrous ferric oxide (Fe3O4) decorated reduced graphene oxide (RGO)/single wall carbon nanohorn (SWCNH)] composite for tunable EMI shielding applications. The Fe powder used to reduce GO, was decorated on the SWCNH and RGO as Fe3O4 during the in situ reaction. FRS dispersed PDMS was allowed to soak and cured in a sugar cube, followed by leaching out of the sugar to obtain highly porous network structure with lightweight and compressible PDMS/FRS composite. The composite possessed an absorption-dominated good comprehensive EMI shielding performance, possibly due to both conductive dissipation and multiple reflections and scattering of EM waves by the inside 3D conductive RGO-SWCNH network with ferromagnetic Fe3O4 nanoparticles. The measurement of attenuation constant and loss tangent describe the absorption property of the composite. The shielding performance of the composite could be simply adjusted owing to its’ pressure induced compressible property, applicable as smart tunable EMI shielding material.

Salt leached viable porous Fe3O4 decorated polyaniline – SWCNH/PVDF composite spectacles as an admirable electromagnetic shielding efficiency in extended Ku-band region

Abstract This study describes the preparation of porous poly(vinylidene fluoride) (PVDF)/(ferrosoferric oxide (Fe3O4) decorated polyaniline/single wall carbon nanohorn (SWCNH)) PFC composite through a simple solution blending process using pre-synthesized PFC composite prepared by the in-situ oxidative polymerization of aniline in the presence of SWCNH with FeCl3 as oxidant (also used as the Fe source in the synthesis of Fe3O4) for highly efficient electromagnetic shielding application with high absorption capability. PFC was homogeneously dispersed in the PVDF matrix as conductive nanofiller to develop the conducting network and the porous morphology in the composite was achieved by leaching out of the salt (NaCl) added during solution blending process. The composite shows an excellent EMI shielding effectiveness (EMI SE) due to its porous structure and presence of continuous conductive network (polyaniline-SWCNH) and ferromagnetic Fe3O4 nanoparticles. Moreover, the highly conductive (∼2.5 × 10−2 S cm−1) PVDF-PFC composite (2 mm thickness) has greater dielectric loss and permeability property with a high EMI SE value (≈−29.7 dB) at very low loading (10 wt %) of PFC and SWCNH (1 wt%) in extended Ku-band region. The microwave absorption value also exceeds the reflection as the incident microwaves reflected and scattered multiple times internally and dissipated by the conductive 3D network of SWCNH and polyaniline throughout the composite pore wall.

Diffusion and agglomeration of iron oxide nanoparticles in magnetic calcium alginate beads initiated by copper sorption

The contamination of aqueous solutions by heavy metals ions is an important environmental and social problem. During the last decade, cheap and environmentally friendly water treatment technologies based on the adsorption of ions by natural biosorbents were consequently proposed. Among them, magnetic biosorbents are of first interest due to their additional magnetic separation properties. The present study focuses on the bioadsorption of copper ions by magnetic alginate beads and on the associated modification of the beads. The Ferromagnetic behaviour was achieved by including ferromagnetic Fe3O4 nanoparticles in calcium alginate beads. The role of iron oxide on the biosorption process was investigated by kinetic studies and demonstrates the minor role of iron oxide during the adsorption process. Kinetic data are very well fitted by a second-order model and isotherms correspond to the Langmuir model. Morphological and chemical characterizations of the beads after adsorption were performed by Scanning Electron Microscopy (SEM), Fourier Transform InfraRed spectroscopy (FTIR) and X-Ray Photoelectron Spectroscopy (XPS). They demonstrate the presence of copper carboxylate complex in a unidentate form with or without Fe3O4 nanoparticles included in the beads. Moreover, they evidence the migration and the agglomeration of Fe3O4 nanoparticles toward the surface during copper adsorption. This phenomenon irremediably changes the nature of the beads and has to be considered within the context of reusability of the sorbents.

Rotating ferro-nanofluid over stretching plate under the effect of hall current and joule heating

The behavior of boundary layer over a stretching plate filled with ferromagnetic Fe3O4 nanoparticles and subjected to magnetic field with hall current, joule heating and nonlinear thermal radiation has been investigated. The modeling based on nonlinear partial differential equations due to continuity, momentum and heat equations, these equations transformed to a system of nonlinear ordinary differential equations using similarity transformation technique then solved numerically. The effect of hall current, joule heating and thermal radiation on the physical quantities such as surface shear stress and heat flux have been investigated and discussed. Moreover, the velocities and temperature profiles of the boundary layer under the influence of the presented external forces plotted and discussed.

Magnetization reversal of ferromagnetic nanoparticles induced by a stream of polarized electrons

The remagnetization of ferromagnetic Fe3O4 nanoparticles of several thousand cubic nanometers by spin-polarized current is investigated. For this purpose, magnetite nanoparticles are synthesized and deposited on a conductive nonmagnetic substrate. The remagnetization is conducted in high-vacuum scanning tunneling microscope (STM). The STM tip from magnetized iron wire constitutes one electrode while the ferromagnetic nanoparticle on the graphite surface represents the second electrode. The measured threshold value of remagnetization current (Ithresh=9nA) is the lowest value of current at which remagnetization occurs. The change in nanoparticle magnetization is detected by the effect of giant magnetic resistance, specifically, the dependence of the weak polarized current (I<Ithresh) on the mutual directions of magnetization of the electrodes. The results indicate essential difference with available literature data on the influence of polarized current on magnetic moment of small ferromagnetic nanoclusters. The peculiarities of size dependence of the observed effects are explained.

Osteogenic differentiation of MC3T3-E1 cells on poly(L-lactide)/Fe3O4 nanofibers with static magnetic field exposure.

Proliferation and differentiation of bone-related cells are modulated by many factors such as scaffold design, growth factor, dynamic culture system, and physical simulation. Nanofibrous structure and moderate-intensity (1 mT-1 T) static magnetic field (SMF) have been identified as capable of stimulating proliferation and differentiation of osteoblasts. Herein, magnetic nanofibers were prepared by electrospinning mixture solutions of poly(L-lactide) (PLLA) and ferromagnetic Fe3O4 nanoparticles (NPs). The PLLA/Fe3O4 composite nanofibers demonstrated homogeneous dispersion of Fe3O4 NPs, and their magnetism depended on the contents of Fe3O4 NPs. SMF of 100 mT was applied in the culture of MC3T3-E1 osteoblasts on pure PLLA and PLLA/Fe3O4 composite nanofibers for the purpose of studying the effect of SMF on osteogenic differentiation of osteoblastic cells on magnetic nanofibrous scaffolds. On non-magnetic PLLA nanofibers, the application of external SMF could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells. In comparison with pure PLLA nanofibers, the incorporation of Fe3O4 NPs could also promote the proliferation and osteogenic differentiation of MC3T3-E1 cells in the absence or presence of external SMF. The marriage of magnetic nanofibers and external SMF was found most effective in accelerating every aspect of biological behaviors of MC3T3-E1 osteoblasts. The findings demonstrated that the magnetic feature of substrate and microenvironment were applicable ways in regulating osteogenesis in bone tissue engineering.

Magnetite Nanoparticles Synthesized Using Pulsed Plasma in Liquid

Iron oxide nanoparticles have attracted much attention over the last few years owing to their fundamental importance and technological applications. In this work, spherical ferromagnetic Fe3O4 nanoparticles with an average diameter of 19 nm were synthesized by a simple and one-step method, pulsed plasma in liquid. Pulsed plasma, induced by a low-voltage spark discharge, was submerged in a dielectric liquid at a voltage of 200 V, a current of 6 A, a frequency of 60 Hz, and a single discharge duration of 10 µs. Water with different concentrations of 1-hexadecylpyridinium bromide (CPyB) was applied as a liquid, and several experiments made evident that the surfactant concentration affects the phase compositions of the produced materials. The purity of the magnetite phase in the sample increased (from 65 to 98%) with increasing CPyB concentration (from 0.10 to 0.84 g) in 200 ml of water. The crystal structure of magnetite (Fe3O4) nanoparticles with the Fd3̄m space group and a lattice parameter of a = 0.8393 nm was evident from X-ray diffraction results. Magnetite nanoparticles were investigated further by high-resolution transmission electron microscopy/energy-dispersive spectroscopy and thermogravimetrical analysis, and using a vibrating sample magnetometer.