Carbon-coated Iron Nanoparticles Research Articles

Effect of carbon encapsulation on magnetic inter-particle interaction of iron nanoparticles

Carbon encapsulation of magnetic nanoparticles reduces agglomeration and makes the nanoparticles stable. In this work, as-prepared carbon-coated iron nanoparticles (CCFeNPs) are treated with hydrogen peroxide (H2O2) solution, and the effect of carbon coating on the interparticle interaction of iron nanoparticles is discussed. Morphological characterization and the magnetization data confirmed that the treatment removes some coating layers. Field cooled (FC) and zero-field cooled (ZFC) measurements on the two samples revealed that the blocking temperature (TB) of the treated sample is lowered post hydrogen peroxide treatment. Magnetic interaction is increased in the treated sample compared to the as-prepared one and follows the Morup–Tronc (MT) model of inter-particle interactions (IPI). MR/MS ratio decreases post-treatment, indicating an increase in IPI after treatment. Out-of-phase AC susceptibility data showed two slope changes; one at a higher temperature indicates the magnetic blocking of core Fe, and the other at a lower temperature with a broad peak that shifts with frequency due to spin-glass behavior in the system.

Electrical conductivity and electromagnetic interference shielding effectiveness of elastomer composites: Comparative study with various filler systems

This work presents a comparison study of Electrical conductivity and Electromagnetic Interference (EMI) shielding effectiveness (SE) of three different Polydimethylsiloxane (PDMS) composites with randomly embedded Multiwall carbon nanotubes (MWCNTs), Carbon coated iron nanoparticles (FeNPs) and Graphite. The incorporation of these fillers was found to appreciably enhance the electrical conductivity and EMI shielding performance of the composites. The analysis indicated that incorporation of fillers with high aspect ratio gives increased number of conducting pathways, which in turn improved the electrical conductivity and EMI shielding effectiveness of the composites. The 1 wt% MWCNT/PDMS composite displayed electrical conductivity nearly 4 orders of magnitude greater than that of pure PDMS. These composite structures are found to provide numerous interfaces to attenuate the electromagnetic waves, giving rise to an improved shielding mechanism. This work indicates that, creating conductive links within polymer composite structures is a favorable approach to create high-performance EMI shielding materials. The electrical conductivity above 10-6 S/m for all the composites reported here makes them suitable for antistatic coating applications. SEM, X-ray diffraction and Raman spectroscopy were used to analyze the effect of fillers on the PDMS composite structures. The higher filler content composites exhibited an EMI SE level of 20 dB necessary for commercial applications when the films were 1.5 mm thick.

Understanding the growth N–Fe3C from assembly of carbon-coated iron nanoparticles on rGO as efficient oxygen reduction electrocatalysts

The oxygen reduction reaction (ORR) is an essential reaction in metal-air battery systems. However, the traditional noble metal Pt-based catalysts for ORR limit the commercial applications of air battery systems due to their high price, low abundance and poor tolerance. In recent studies, nitrogen–doped transition metal carbides have shown promise as an alternative to traditional noble metal catalysts. In this paper, the thermal cracking and calcination method was used to successfully obtain the growth N-doped carbon coated iron carbide nanoparticles (Fe3C@NC/rGOx NP) from assembly of carbon-coated iron oxide Nano-crystals on rGO (Fe3O4@NC/rGOx NCs). Transmission electron and scanning electron microscopy of the fabricated specimens indicated the presence of many carbon shells and pores in the etched samples. The electrochemical test results of the fabricated specimens suggested that the Fe3C@NC/rGO 100 NP annealed at 800 °C exhibited a better ORR behavior than that of Pt/C in a basic electrolyte.

Effect of Chemically Modified Carbon-Coated Iron Nanoparticles on the Structure of Human Atherosclerotic Plaques Ex Vivo and on Adipose Tissue in Chronic Experiment In Vivo.

The high mortality rate caused by atherosclerosis makes it necessary to constantly search for new and better treatments. In previous reports, chemically modified carbon-coated iron nanoparticles (Fe@C NPs) have been demonstrated a high biocompatibility and promising anti-plaque properties. To further investigate these effects, the interaction of these nanoparticles with the adipose tissue of Wistar rats (in vivo) and human atherosclerotic plaques (ex vivo) was studied. For the in vivo study, cobalt–chromium (CoCr) alloy tubes, which are used for coronary stent manufacturing, were prepared with a coating of polylactic acid (PLA) which contained either modified or non-modified Fe@C NPs in a 5% by weight concentration. The tubes were implanted into an area of subcutaneous fat in Wistar rats, where changes in the histological structure and functional properties of the surrounding tissue were observed in the case of coatings modified with Fe@C NPs. For the ex vivo study, freshly explanted human atherosclerotic plaques were treated in the physiological solution with doses of modified Fe@C NPs, with mass equal to 5% or 25% relative to the plaques. This treatment resulted in the release of cholesterol-like compounds from the surface of the plaques into the solution, thus proving a pronounced destructive effect on the plaque structure. Chemically modified Fe@C NPs, when used as an anti-atherosclerosis agent, were able to activate the activity of macrophages, which could lead to the destruction of atherosclerotic plaques structures. These findings could prove the fabrication of next-generation vascular stents with built-in anti-atherosclerotic agents.

Rechargeable Iron-Ion Battery Using a Pure Ionic Liquid Electrolyte.

A rechargeable iron-ion battery (Fe-ion battery) has been fabricated in our laboratory using a pure ionic liquid electrolyte. Magnetic ionic liquids of 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl4) and 1-methyl-3-octylimidazolium tetrachloroferrate (OmimFeCl4) are synthesized and utilized as electrolytes in this work. The chemical structure of the two ionic liquids (ILs) is investigated using Raman analysis. In addition, the physical and thermal stability properties of the ionic liquid (IL) BmimFeCl4, including density, viscosity, melting point, and decomposition temperature, are investigated using a density meter, viscosity meter, differential scanning calorimeter, and thermogravimetric analyzer. Moreover, the electrochemical properties, including electrochemical window, and ionic conductivity of the IL BmimFeCl4 are investigated using an electrochemical instrument and a conductivity meter. It is found that the magnetic IL BmimFeCl4 has good physical and electrochemical properties to be utilized as an electrolyte for iron-ion battery fabrication. Iron-containing materials, including pure iron foil, carbon-coated iron nanoparticles, and iron powder, are used as a cathode in the Fe-ion battery. The anode of the Fe-ion battery is graphite. Electrochemical properties of full cells are investigated, including cyclic voltammetry curves and specific charge–discharge capacity. The Fe-ion battery is a unique rechargeable ion battery with magnetic ions. In addition, pure IL BmimFeCl4 is utilized as an electrolyte in this Fe-ion battery. IL BmimFeCl4 is stable and almost nonvolatile. Therefore, an Fe-ion battery with a pure IL electrolyte is safer than that with an organic electrolyte. An Fe-ion battery using a pure IL electrolyte is a promising battery with many potential applications.

Chemically Modified Biomimetic Carbon-Coated Iron Nanoparticles for Stent Coatings: In Vitro Cytocompatibility and In Vivo Structural Changes in Human Atherosclerotic Plaques.

Atherosclerosis, a systematic degenerative disease related to the buildup of plaques in human vessels, remains the major cause of morbidity in the field of cardiovascular health problems, which are the number one cause of death globally. Novel atheroprotective HDL-mimicking chemically modified carbon-coated iron nanoparticles (Fe@C NPs) were produced by gas-phase synthesis and modified with organic functional groups of a lipophilic nature. Modified and non-modified Fe@C NPs, immobilized with polycaprolactone on stainless steel, showed high cytocompatibility in human endothelial cell culture. Furthermore, after ex vivo treatment of native atherosclerotic plaques obtained during open carotid endarterectomy surgery, Fe@C NPs penetrated the inner structures and caused structural changes of atherosclerotic plaques, depending on the period of implantation in Wistar rats, serving as a natural bioreactor. The high biocompatibility of the Fe@C NPs shows great potential in the treatment of atherosclerosis disease as an active substance of stent coatings to prevent restenosis and the formation of atherosclerotic plaques.

Nuclear magnetic resonance immunoassay of tetanus antibodies based on the displacement of magnetic nanoparticles.

A nuclear magnetic resonance (NMR) immunoassay based on the application of carbon-coated iron nanoparticles conjugated with recognition molecules was designed. The principle of the assay is that ELISA plates are coated with a capture element, and then an analyte is added and detected by conjugating the magnetic nanoparticles with recognition molecules. Afterwards, the elution solution (0.1-M sodium hydroxide) is added to displace the magnetic nanoparticles from the well surfaces into the solution. The detached magnetic nanoparticles reduce transverse relaxation time (T2) values of protons from the surrounding solution. A portable NMR relaxometer is used to measure the T2. Magnetic nanoparticles conjugated with streptavidin, monoclonal antibodies, and protein G were applied for the detection of biotinylated albumin, prostate-specific antigen, and IgG specific to tetanus toxoid (TT). The limit of detection of anti-TT IgG was 0.08-0.12 mIU/mL. The reproducibility of the assay was within the acceptable range (CV < 7.4%). The key novelty of the immunoassay is that the displacement of the nanoparticles from the solid support by the elution solution allows the advantages of the solid phase assay to be combined with the sensitive detection of the T2 changes in a volume of liquid.

Understanding the Growth N-Fe &lt;sub&gt;3&lt;/sub&gt;C from Assembly of Carbon-Coated Iron Nanoparticles on rGO as Efficient Oxygen Reduction Electrocatalysts

Understanding the Growth N-Fe &lt;sub&gt;3&lt;/sub&gt;C from Assembly of Carbon-Coated Iron Nanoparticles on rGO as Efficient Oxygen Reduction Electrocatalysts

Flexible electrocatalysts: interfacial-assembly of iron nanoparticles for nitrate reduction.

We report a novel template-assisted epitaxial assembly strategy to assemble carbon-coated iron nanoparticles on a functionalized carbon cloth (CC/Fe@C). This delicate assembled architecture provides a useful guideline for designing flexible iron-based electrocatalysts.

Magnetic Nanoclusters Coated with Albumin, Casein, and Gelatin: Size Tuning, Relaxivity, Stability, Protein Corona, and Application in Nuclear Magnetic Resonance Immunoassay.

The surface functionalization of magnetic nanoparticles improves their physicochemical properties and applicability in biomedicine. Natural polymers, including proteins, are prospective coatings capable of increasing the stability, biocompatibility, and transverse relaxivity (r2) of magnetic nanoparticles. In this work, we functionalized the nanoclusters of carbon-coated iron nanoparticles with four proteins: bovine serum albumin, casein, and gelatins A and B, and we conducted a comprehensive comparative study of their properties essential to applications in biosensing. First, we examined the influence of environmental parameters on the size of prepared nanoclusters and synthesized protein-coated nanoclusters with a tunable size. Second, we showed that protein coating does not significantly influence the r2 relaxivity of clustered nanoparticles; however, the uniform distribution of individual nanoparticles inside the protein coating facilitates increased relaxivity. Third, we demonstrated the applicability of the obtained nanoclusters in biosensing by the development of a nuclear-magnetic-resonance-based immunoassay for the quantification of antibodies against tetanus toxoid. Fourth, the protein coronas of nanoclusters were studied using SDS-PAGE and Bradford protein assay. Finally, we compared the colloidal stability at various pH values and ionic strengths and in relevant complex media (i.e., blood serum, plasma, milk, juice, beer, and red wine), as well as the heat stability, resistance to proteolytic digestion, and shelf-life of protein-coated nanoclusters.

Conjugation of carbon coated-iron nanoparticles with biomolecules for NMR-based assay.

In this work, we developed and optimized conjugates of carbon-coated iron nanoparticles (Fe@C) with streptavidin and monoclonal antibodies. The conjugation procedure included two stages. First, amino groups were grafted onto the carbon shell to facilitate noncovalent sorption of bovine serum albumin (BSA). Further, the covalent attachment of proteins to the BSA layer via glutaraldehyde coupling was performed. It was established and confirmed that the synthesis procedure is reproducible and allows preparation of stable conjugates. The resulting nanoparticles are clusters of Fe@C particles coated by proteins. The size of the clusters is in the range of 100-190 nm and can be controlled via the tuning of conjugation conditions, including pH, BSA-to-Fe@C ratio, etc. Conjugates of Fe@C with streptavidin and monoclonal antibodies (sizes of approximately 140-150 nm) were synthesized. Proton T2 relaxometry was used to detect these conjugates with very high sensitivity due to the magnetic markers, Fe@C. The relaxivity (r2) of different conjugates varied within the range of 290-450 1/s*mM. Conjugate applicability for relaxometry-based assay was confirmed by direct detection of streptococcal protein G and biotinylated BSA in a dot immunoassay.

Three-Dimensional Visualization of Conductive Domains in Battery Electrodes with Contrast-Enhancing Nanoparticles

Replacing conductive carbon black with commercial carbon-coated iron nanoparticles yields an effective contrast-enhancing agent to differentiate between active material, conductive additive, and binder in lithium-ion battery electrodes. Nano-XCT resolved the carbon–binder domain with 126 nm voxel resolution, showing partial coatings around the active material particles and interparticle bridges. In a complementary analysis, SEM/EDS determined individual distributions of conductive additives and binder. Surprisingly, the contrast-enhancing agents showed that the effect of preparation parameters on the heterogeneity of conductive additives was weaker than on the binder. Incorporation of such contrast-enhancing additives can improve understanding of processing–structure–function relationships in a multitude of devices for energy conversion and storage.

Shock-tube study of the formation of iron, carbon, and iron–carbon binary nanoparticles: experiment and detailed kinetic simulations

ABSTRACTAn experimental and computational study of the formation of pure iron nanoparticles, carbon nanoparticles (soot), and binary carbon-coated iron nanoparticles during the pyrolysis of iron pentacarbonyl–argon, ethylene–argon, and iron pentacarbonyl–ethylene–argon mixtures, respectively, behind reflected shock waves is carried out. The shape and size distribution of these nanoparticles are examined on a Zeiss Ultra plus ultrahigh-resolution field-emission scanning electron microscope. The binary iron–carbon particles were also investigated by high-resolution transmission electron microscopy and high-angle annular dark-field imaging (HAADF STEM) on a FEI Osiris transmission electron microscope equipped with a Bruker SuperX detector. Detailed kinetic simulations of the formation of these three types of particles are performed, which predict the concentration, average size, and size distribution of particles.

Determination of magnetic domain state of carbon coated iron nanoparticles via 57Fe zero-external-field NMR

The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57Fe-IFNMR.

Multifunctional carbon-coated magnetic sensing graphene oxide-cyclodextrin nanohybrid for potential cancer theranosis

We functionalized graphene oxide (GO) with cyclodextrin (CD) to increase the drug loading and cellular uptake of GO, and bound the GO-CD to carbon-coated iron nanoparticles (Fe@C) with superparamagnetic properties for potential magnetic-directed drug delivery and as a diagnostic agent. The GO-CD/Fe@C was loaded with an anticancer drug, doxorubicin (DOX), to form a multifunctional GO-CD/Fe@C/DOX nanohybrid. A cumulative increase in DOX loading was observed probably due to DOX adsorption to the graphitic domains in Fe@C and also to the GO-CD. In acidic pH that resembles the pH of the tumor environment, a higher amount of DOX was released from the GO-CD/Fe@C/DOX nanohybrid when compared to the amount released at physiological pH. The signal intensity and the contrast enhancement in magnetic resonance imaging of Fe@C decreased with its concentration. Besides, the cellular uptake of GO-CD/Fe@C/DOX nanohybrid was significantly higher by 2.5-fold than that of Fe@C/DOX in MDA-MB-231 human breast cancer model. The nanohybrids were internalized into the tumor cells via an energy-dependent process and localized mainly in the nuclei, where it exerts its cytotoxic effect, and some in the lysosomes and mitochondria. This has resulted in significant cytotoxicity in tumor cells treated with GO-CD/Fe@C/DOX. These findings highlight the potential use of multifunctional GO-CD/Fe@C nanohybrid for magnetic sensing anticancer drug delivery to tumor cells.

Structure of Rat Lungs after Administration of Magnetomicelles Based on the Carbon-Coated Iron Nanoparticles.

We studied the effects of single administration of a suspension of magnetomicelles based on carbon-coated iron nanoparticles on the structure of rat lungs within 40 days. Histological analysis revealed a complex of hemodynamic alterations in the lungs. Described changes persisted in the lung stroma from day 1 until day 40, but their intensity decreased by the end of the experiment. Using immunohistochemical Perls reaction we identified cells morphologically corresponding to alveolar and interstitial lung macrophages. The number of Perls+ cells decreased by day 40 of the experiment. Ultrastructural analysis showed endocytosis of modified iron nanoparticles and their accumulation in intracellular digestionorganelles (endo- and lysosomes) of mononuclear phagocyte system cells. Accumulation of magnetomicelles in the lungs was not associated with damage to pneumocytes, macrophages, and blood-air barrier.

Conformational control of human transferrin covalently anchored to carbon-coated iron nanoparticles in presence of a magnetic field.

To our best knowledge this is the first paper that reports on covalent anchoring of human transferrin (Tf) to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field, which results in its conformational integrity and electroactivity. We showed that it is possible to attach, without changing pH, more than one single layer of transferrin to the Fe@C-COOH Nps. This is a very rare phenomenon in the case of proteins. We proved, using various experimental techniques, that the proposed methodology does not lead to release of iron from Tf molecules, what was the major problem so far. We believe that this finding opens new possibilities in targeting drug delivery systems and medical diagnostics.

Excellent improvement in the static and dynamic magnetic properties of carbon coated iron nanoparticles for microwave absorption

Carbon coated iron nanoparticles were synthesized, using a simple arc-discharge method. The morphology and the internal structure of the core/shell nanoparticles were studied, using field emission scanning electron microscopy and transmission electron microscopy. X-ray diffraction analysis showed that both magnetic α-Fe and nonmagnetic γ-Fe phases existed in the as-prepared particles. In order to improve the static and dynamic magnetic properties of the core/shell nanoparticles, the produced nanocapsules were annealed in argon atmosphere at two different temperatures. Hysteresis loops revealed that the value of the saturation magnetization (MS) increased more than 4.1 times of its original value by annealing and this led to 70% increase in the imaginary part of the permeability. Phase analysis showed that heat treatment eliminated the nonmagnetic γ-Fe phase completely. The reflection loss plots were studied for composite layers containing 20vol% of the annealed and not annealed nanocapsules. One of the absorber layers which contained annealed nanocapsules showed at least −10dB loss in the whole G, C, X and Ku frequency bands and the optimal absorption exceeded −37dB at 5.8GHz for the as-prepared sample with a thickness of 3.2mm. The results revealed that the magnetic properties of the arc-made Fe/C core/shell nanoparticle can be improved significantly by annealing in argon.

Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

Core–shell structure carbon coated ferric oxide (Fe2O3@C) nanoparticles for supercapacitors with superior electrochemical performance

Core–shell structure carbon coated ferric oxide nanoparticles (Fe2O3@C) were fabricated by the oxidation of carbon coated iron nanoparticles (Fe@C) prepared by a direct current carbon arc discharge method. Porous activated-Fe2O3@C was prepared by KOH activation of Fe2O3@C at the temperature of 750°C. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the structure and morphology of the Fe2O3@C and activated-Fe2O3@C. The specific surface area and pore size distribution of the samples were also tested. The activated-Fe2O3@C electrodes exhibited good electrochemical performance with a maximum specific capacitance of 612Fg−1 at the charge/discharge current density of 0.5Ag−1 with 5M NaOH electrolyte. After 10,000 cycling DC tests at the charge/discharge current density of 4Ag−1, a high level specific capacitance of 518Fg−1 was obtained (90.6% retention of the initial capacity), suggesting excellent long-term cycling stability.