Magnetite Nanoparticle Composites Research Articles

Size-Dependent Elemental Composition in Individual Magnetite Nanoparticles Generated from Coal-Fired Power Plant Regulating Their Pulmonary Cytotoxicity.

High-resolution characterization of magnetite nanoparticles (MNPs) derived from coal combustion activities is crucial to better understand their health-related risks. In this study, size distribution and elemental composition of individual MNPs from various coal fly ashes (CFAs) collected from a representative coal-fired power plant were analyzed using a single-particle inductively coupled plasma time-of-flight mass spectrometry technique. Majority (61-80%) of MNPs were identified as multimetal (mm)-MNPs, while the contribution of single metal (sm)-MNPs to the total increased throughout all the CFAs, reaching the highest in fly ash escaped through the stack (EFA). Among Fe-rich MNPs, Fe-sole and Fe-Al matrices were predominant, and Fe-sole MNPs were identified as the important carrier for toxic metals, with the highest mass contributions of toxic metals therein. Toxic potency results showed that the oxidative stress induced by MNPs was 1.2-2.2 times greater than those of <1 μm fractions in CFAs, while the reduction in cell viability showed no significant difference, elucidating that these MNPs can induce more distinct oxidative stress compared to cell toxicity. Based on structural equation model, MNP size can both directly and indirectly regulate the toxic potency, and the indirect regulation is through a size-dependent elemental composition of MNPs, including toxic metals. sm-MNPs and Fe-rich MNPs with Fe-sole, Fe-Cr, and Fe-Zn matrices can regulate the oxidative stress, whereas Cr, Zn, and Pb associated with Fe-sole, Fe-Al, Si-Fe, and Al-Fe MNPs showed significant effects on cell viability.

Crystal-Chemical and Biological Controls of Elemental Incorporation into Magnetite Nanocrystals.

Magnetite nanoparticles possess numerous fundamental, biomedical, and industrial applications, many of which depend on tuning the magnetic properties. This is often achieved by the incorporation of trace and minor elements into the magnetite lattice. Such incorporation was shown to depend strongly on the magnetite formation pathway (i.e., abiotic vs biological), but the mechanisms controlling element partitioning between magnetite and its surrounding precipitation solution remain to be elucidated. Here, we used a combination of theoretical modeling (lattice and crystal field theories) and experimental evidence (high-resolution inductively coupled plasma-mass spectrometry and X-ray absorption spectroscopy) to demonstrate that element incorporation into abiotic magnetite nanoparticles is controlled principally by cation size and valence. Elements from the first series of transition metals (Cr to Zn) constituted exceptions to this finding, as their incorporation appeared to be also controlled by the energy levels of their unfilled 3d orbitals, in line with crystal field mechanisms. We finally show that element incorporation into biological magnetite nanoparticles produced by magnetotactic bacteria (MTB) cannot be explained by crystal-chemical parameters alone, which points to the biological control exerted by the bacteria over the element transfer between the MTB growth medium and the intracellular environment. This screening effect generates biological magnetite with a purer chemical composition in comparison to the abiotic materials formed in a solution of similar composition. Our work establishes a theoretical framework for understanding the crystal-chemical and biological controls of trace and minor cation incorporation into magnetite, thereby providing predictive methods to tailor the composition of magnetite nanoparticles for improved control over magnetic properties.

Impact of Silica-Modification and Oxidation on the Crystal Structure of Magnetite Nanoparticles

At present, the widespread use of iron oxide nanoparticles, including for commercial purposes, requires strict preservation of their phase composition during their application. The choice of nanoparticle modifier and modification conditions is decisive due to their high sensitivity to oxygen in the case of using real conditions (O2, pH change, etc.). In this work, we studied the change in the phase composition of magnetite nanoparticles after modification with 3-aminopropyltriethoxysilane (APTES) and oxidation with nitric acid in order to estimate the protective potential of the silica shell. After modification by APTES and oxidation with nitric acid, the nonstoichiometric nature of the magnetite nanoparticles according to XRD data increased, which indicates an increase in transition forms compared to the initial sample (magnetite content decreased to 27% and 24%, respectively). In contrast, Mössbauer spectroscopy data detected a decrease in the nonstoichiometric index due to APTES modification conditions, but strong oxidation after exposure to nitric acid. It also showed that by analyzing the data of the diffraction analysis and Mössbauer spectroscopy for the same sample, one can obtain information not only about the ionic composition of “magnetite”, but also about the distribution of iron ions of different charges over the crystalline and amorphous parts of the preparation.

Magnetite nanoparticles functionalized with citrate: A surface science study by XPS and ToF-SIMS

The surface composition of magnetite nanoparticles, bare and functionalized with citrate, was investigated by means of XPS and ToF-SIMS. Magnetite nanoparticles were prepared by co-precipitation and two different procedures were used to functionalize them with citrate ions. By means of XPS we found that the composition of the oxide is not modified, within the uncertainty of the analysis, by the functionalization swith citrate. Moreover, the amount of citrate ions adsorbed at the surface of the nanoparticles is the same, independently on the functionalization procedure. The thickness of the citrate shell is consistent with that of a single layer of citrate ions covering only partially the surface of the nanoparticles. XPS and ToF-SIMS analyses revealed the presence of ammonia molecules, resulting from the Fe(II) salt used to prepare the oxide nanoparticles, adsorbed at the surface of nanoparticles.

Magnetite Nanoparticle/Copper Phosphate Nanoflower Composites for Fenton-like Organic Dye Degradation

A fast and sustainable technique in catalytically degrading organic dyes under flow is reported. It involves the use of three different applications of the high-shear and intense micro-mixing vortex fluidic device (VFD), including material fabrication, reactor coating, and material “banding”. The active catalytic material is a composite of magnetite nanoparticles and Cu3(PO4)2 nanoflowers (MNPCuNFs), 8–10 μm in diameter, which are generated in the VFD within 30 min. MNPCuNFs magnetically and centrifugally held against the surface of the rapidly rotating tube in the VFD have enhanced catalytic activity in degrading four different organic dyes under real-time monitoring with at least a fivefold increase in the degradation efficiency compared to that in the batch processing. To further improve the platform performance, the VFD tube reactor was chemically modified, incorporating a thin layer of silica-activated carbon xerogel coating which behaves synergistically with the nanoflowers. This coated tube is highly stable and reusable, dramatically increasing the degradation efficiency by about 30-fold relative to using batch processing. Integrating an ultraviolet–visible spectroscopy-based probe allows real-time monitoring of the reaction and also provides a direct tool to evaluate the coating layer post reaction. This study provides a rational design of hybrid materials and the use of a modified VFD tube reactor toward efficient degradation of organic dyes in real time.

Study of the magnetic property of supermagnetic fluid

In this work, the magnetic fluids based on Fe3O4 have been obtained by the chemical co-precipitation method. Analysis of the size and morphology of the synthesized iron oxide nanoparticles of the magnetic fluid using transmission electron microscopy revealed that nanoparticles are of 25-38 nm in size and spherical in shape. The elemental composition of magnetite nanoparticles of the fluid was examined in energy-dispersive X-ray analysis and determined to contain only Iron and Oxygen. The magnetic property of the magnetic fluid was measured using vibrating sample magnetometer. The results showed that the magnetic fluid has a superparamagnetic character which of specific saturation magnetization of 3.4 emu/g

Optimization of Conditions for Obtaining Stable Hydrosols of Magnetite Nanoparticles

The work is devoted to the study of the influence of reaction parameters on the qualitative and quantitative composition of magnetite nanoparticles. The method of their synthesis is optimized using the method of mathematical planning and processing of experimental data. The mathematical model is obtained. It was established that the molar ratio of iron (II) and (III) ions, the time of preliminary boiling of distilled water for preparing solutions, the presence of an inert atmosphere of nitrogen, as well as an excess of alkali affect the formation of a stoichiometric product. Monophase magnetite nanoparticles with an average diameter of 8-12 nm were obtained under optimal conditions. The product is characterized by the methods of transmission electron microscopy and X-ray phase analysis. The effect of pretreatment of magnetite nanoparticles with solutions of strong mineral acids on the stability of its hydrosols has been studied by dynamic and electrophoretic light scattering. It was established that the best stabilization is achieved by pretreatment of magnetite with a solution of perchloric acid

Improvisation of diffusion coefficient in surface modified magnetite nanoparticles: A novel perspective.

Surface properties are inevitable in determining the properties of any support involved in tethering biomolecular moieties. Porous carriers impose numerous diffusional limitations and make the need for surface modification significant. To best of our knowledge, this study would be a new perspective on diffusional limitations in nanoparticles for the first time. Chitosan was aimed to alter the porosity of solvo-thermally synthesized magnetite nanoparticles (MNs) through surface coating. Various instrumental techniques were performed on chitosan, MNs, chitosan coated MNs (MNβ) and urease tethered MNβ (U-MNβ) to reveal their behaviour. Maximum absorption with higher bandgap energy (2.76 eV) in visible spectrum, characteristic peaks in diffraction patterns and the presence of required peaks in Fourier transform infra-red (FT-IR) spectra suggested MNs synthesis and surface modification. Electron micrographs and Energy dispersive spectrum (EDS) showed surface variation and pure elemental composition of MNs respectively. Superparamagnetism and narrow size distribution were seen from magnetization curve with lower retentivity and Dynamic Light Scattering (DLS) respectively. Sorption profiles exhibited filling of pores on MNs and lower/higher diffusion co-efficient (De) were evaluated through respective conductivity measurements of free/tethered urease. The values of influencing parameters were optimized based on Box-Behnken design (BBD) matrix and the statistical analysis revealed that the optimum operating conditions for producing MNβ. Hence change in surface porosity that enhanced activity of tethered enzyme through improved diffusion was achieved via surface coating.

Ultrasound-assisted dispersive magnetic solid phase extraction based on metal–organic framework/1-(2-pyridylazo)-2-naphthol modified magnetite nanoparticle composites for speciation analysis of inorganic tin

A novel magnetic metal–organic framework (MMOF) consisting of MIL-101(Cr) and 1-(2-pyridylazo)-2-naphthol-modified magnetite nanoparticles was synthesized and utilized for the ultrasound-assisted magnetic solid phase extraction and speciation analysis of Sn(ii) and Sn(iv) at trace amounts.

Effect of iron oxide nanoparticle size on electromagnetic properties of composite nanofibers

Electrically conductive and magnetically permeable carbon nanofiber-based composites were developed using the electrospinning with subsequent heat treatment. The composite nanofiber contains a variable composition of magnetite nanoparticles with two different size regimes, ranging from superparamagnetic (10–20 nm) to ferromagnetic (20–30 nm). The composite nanofibers are then characterized using Scanning/Transmission Electron Microscopy, X-Ray Diffractometry, Raman Spectroscopy, four-point probe, and a Superconducting Quantum Interference Device. Electromagnetic Interference Shielding Effectiveness of pristine carbon nanofibers as well as electromagnetic composite nanofibers are examined in the X-band frequency region. Higher degree of graphitization, electrical conductivity, and magnetic strength are obtained for nanocomposites containing larger magnetite nanoparticles (20–30 nm). A transition from superpartamagnetic to ferromagnetic characteristics is observed during nanocomposite processing. Electromagnetic Interference Shielding Effectiveness of as high as 68 dB (in the working frequency of 10.4 GHz) is observed for composite nanofibers fabricated with larger magnetite nanoparticles carbonized at 900℃.

Superparamagnetic graphene oxide–magnetite nanoparticle composites for uptake of actinide ions from mildly acidic feeds

Super paramagnetic graphene oxide (GO) − Fe3O4 nanoparticle composites were prepared and characterized by conventional techniques such as XRD, SEM, EDX, FT-IR, Raman, XPS, DLS and zeta potential, etc. TEM studies have confirmed nanoparticle nature of the composites. The GO-magnetic nanoparticle composites can be dispersed in mildly acidic aqueous solutions and get concentrated in a small volume under application of an external magnetic field. The composites were evaluated for the uptake of actinide ions such as Am3+, UO22+, Th4+ and Pu4+ from mildly acidic aqueous solutions. Am3+ sorption sharply increased with pH as the Kd values increased from about 10 at pH 1 to 105 at pH 3 beyond which a plateau in the Kd values was seen. Eu3+ displayed nearly comparable uptake behaviour to that of Am3+ while the uptake of other metal ions followed the trend: Pu(IV)>Th(IV)>>UO22+. The adsorption behaviour of Am3+ onto the graphene oxide − Fe3O4 nanoparticle composites fitted very well to the Langmuir as well as Temkin isotherm models. The desorption rate (using 1M HNO3) was fast and reusability study results were highly encouraging. The very high uptake values suggest possible application of the magnetic nanoparticles in radioactive waste remediation in natural ground water.

Synergistic mechanism of U(VI) sequestration by magnetite-graphene oxide composites: Evidence from spectroscopic and theoretical calculation

Graphene oxide (GO) supported uniform magnetite nanoparticle composites (M-GO) were prepared via in situ chemical precipitation method. The reaction mechanisms between M-GO and U(VI) under anoxic conditions were clarified based on macroscopic, spectroscopic, and theoretical techniques. Incorporation of magnetite nanoparticle into GO matrix facilitated removal rate and reduction of U(VI) to U(IV), as indicated by the kinetics model. According to XPS and XANES analysis, high efficient removal of U(VI) by M-GO was attributed to the abundant oxygen-containing groups of GO and reduction potential of magnetite dispersed on the GO surface uniformly. Based on DFT calculation, the high binding energy of [GO-O…UO2]+ (23.5kcal/mol) and [GO-COO…UO2]+ (51.1kcal/mol) (51.1kcal/mol) revealed that the hydroxyl and carboxyl groups were responsible for the high removal of U(VI) on M-GO, which further facilitated the reduction of U(VI) to U(IV) due to the vicinity of structural Fe(II) of M-GO.

Lanthanide sorbent based on magnetite nanoparticles functionalized with organophosphorus extractants

In this work, an adsorbent was prepared based on the attachment of organophosphorus acid extractants, namely, D2EHPA, CYANEX 272, and CYANEX 301, to the surface of superparamagnetic magnetite (Fe3O4) nanoparticles. The synthesized nanoparticles were coated with oleic acid, first by a chemisorption mechanism and later by the respective extractant via physical adsorption. The obtained core–shell functionalized magnetite nanoparticle composites were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, thermogravimetry, infrared absorption and vibrating sample magnetometry. All the prepared nanoparticles exhibited a high saturation magnetization capacity that varied between 72 and 46 emu g−1 and decreased as the magnetite nanoparticle was coated with oleic acid and functionalized. The scope of this study also included adsorption tests for lanthanum, cerium, praseodymium, and neodymium and the corresponding analysis of their results. Sorption tests indicated that the functionalized nanoparticles were able to extract the four studied lanthanide metal ions, although the best extraction performance was observed when the sorbent was functionalized with CYANEX 272, which resulted in a loading capacity of approximately 12–14 mgLa/gMNP. The magnetization of the synthesized nanoparticles was verified during the separation of the lanthanide-loaded sorbent from the raffinate by using a conventional magnet.

Synthesis and Evaluation of Poly(Sodium 2-Acrylamido-2-Methylpropane Sulfonate-co-Styrene)/Magnetite Nanoparticle Composites as Corrosion Inhibitors for Steel

Self-stabilized magnetic polymeric composite nanoparticles of coated poly-(sodium 2-acrylamido-2-methylpropane sulfonate-co-styrene)/magnetite (PAMPS-Na-co-St/Fe3O4) were prepared by emulsifier-free miniemulsion polymerization using styrene (St) as a monomer, 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na) as an ionic comonomer, N,N-methylenebisacrylamide (MBA) as crosslinker, hexadecane (HD) as a hydrophobic solvent, and 2,2-azodiisobutyronitrile (AIBN) as an initiator in the presence of hydrophobic oleic acid coated magnetite particles. Hydrophobic oleic acid coated magnetite particles with an average size of about 7-10 nm were prepared with the new modified water-based magnetite ferrofluid, synthesized by a chemical modified coprecipitation method. The morphology and the particle size distributions of the crosslinked PAMPS-Na-co-St/Fe3O4 composite were observed and analyzed by transmission electron microscopy (TEM). The average Fe3O4 content of PAMPS-Na-co-St/Fe3O4 was determined by thermogravimetric analysis (TGA). The inhibitory action of PAMPS-Na-co-St/Fe3O4 towards steel corrosion in 1 M HCl solutions has been investigated by polarization and electrochemical impedance spectroscopy (EIS) methods. Polarization measurements indicate that PAMPS-Na-co-St/Fe3O4 acts as a mixed type-inhibitor and the inhibition efficiency increases with inhibitor concentration. The results of potentiodynamic polarization and EIS measurements clearly showed that the inhibition mechanism involves blocking of the steel surface by inhibitor molecules via adsorption.

Synthesis of magnetite hydrosols in inert atmosphere

A setup is described for magnetite hydrosol synthesis in inert atmosphere via coprecipitation of bi� and trivalent iron salts in the presence of a base with the formation of nanoparticles having desired sizes and chemical composition. The size of nanoparticles is estimated based on analysis of lightscattering and trans� missionelectronmicroscopy data. The chemical comp osition of magnetite nanoparticles is monitored by Raman spectroscopy.

Magnetic Silicone Composites with Uniform Nanoparticle Dispersion as a Biomedical Stent Coating for Hyperthermia

Magnetic nanoparticles (NPs) offer some attractive possibilities in the field of medicine such as magnetic separation for purification and immunoassay and hyperthermia treatment of cancer. Hyperthermia uses the thermal energy adsorbed by magnetite NPs to kill cancer cells. Concerns regarding esophageal cancer treatment by hyperthermia are related to the development of an advanced film as a polymeric stent cover for hyperthermia. In this paper, we tried to confer the hyperthermia function to the stent cover by the composition of magnetite NPs with a silicone rubber film. Herein, we fabricated the hybrid composite of magnetite NPs and a silicone matrix with a uniform particle dispersion. Forty percent of magnetite NPs could be dispersed in silicone matrices, which was confirmed in the scale of hundreds of nanometers by transmission electron microscopy. The composition could be possible via the surface modification of magnetite NPs with oleic acid in the silicone rubber, which was identified by the analysis of FT-IR. Plasma treatment of the composite film transforms the hydrophobicity of the film to the hydrophlicity. The hyperthermia effect of the composite film increased temperature from 36 to 42°C. Moreover, our manufacturing strategy could readily control the thickness of the smooth composite film, facilitate large-scale synthesis, and enable multifunctionalization. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E714–E723, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21314

Magnetic field dependence of the diffusion of single dextran molecules within a hydrogel containing magnetite nanoparticles

We consider the effect of applied magnetic fields on the diffusion of single dextran molecules labeled with fluorescein isothiocyanate within a ferrogel [a composite of magnetite nanoparticles in a poly(methacrylic acid) hydrogel] using fluorescence correlation spectroscopy. We show that the mesh size of the ferrogel is controlled by the applied magnetic field, B, and scales as exp(-(4)√ξ(3)B(2)/2μ(0)k(B)T), where ξ is a correlation length, μ(0) the magnetic constant, k(B) the Boltzmann constant, and T is the absolute temperature. The diffusion coefficient of the dextran can be modeled with a simple Stokes-Einstein law, containing the same scaling behavior with magnetic field as the swelling of the hydrogel. Furthermore, the magnetic field-dependent release of dextran from the hydrogel is also controlled by the same relationship. The samples were characterized by small angle x-ray scattering (SAXS) and magnetometry experiments. Magnetic hysteresis loops from these ferrogels and zero field cooled∕field cooled measurements reveal single domain ferromagnetic behavior at room temperature with a similar coercivity for both as-prepared and fully swollen ferrogels, and for increasing magnetic nanoparticle concentration. SAXS experiments, such as the hysteresis loops, show that magnetite does not aggregate in these gels.

Synthesis and Electrochemical Behavior of Single-Crystal Magnetite Nanoparticles

Water-dispersed magnetite nanoparticle synthesis from iron(II) chloride in dimethyl sulfoxide (DMSO)−water solution at different DMSO−water ratios in alkaline medium was reported. TEM and XRD results suggest a single-crystal formation with mean particle size in the range 4−27 nm. Magnetic nanoparticles are formed by the oxidative hydrolysis reaction from green rust species that leads to FeOOH formation, followed by autocatalysis of the adsorbed available Fe(II) on the FeOOH surfaces. The available hydroxyl groups seem to be dependent on the DMSO−water ratio due to strong molecular interactions presented by the solvent mixture. Goethite phase on the magnetite surface was observed by XRD data only for sample synthesized in the absence of DMSO. In addition, cyclic voltammetry with carbon paste electroactive electrode (CV-CPEE) results reveal two reduction peaks near 0 and +400 mV associated with the presence of iron(III) in different chemical environments related to the surface composition of magnetite nanoparticles. The peak near +400 mV is related to a passivate thin layer surface such as goethite on the magnetite nanoparticle, assigned to the intensive hydrolysis reaction due to strong interactions between DMSO−water molecules in the initial solvent mixture that result in a hydroxyl group excess in the medium. Pure magnetite phase was only observed in the samples prepared at 30% (30W) and 80% (80W) water in DMSO in agreement with the structured molecular solvent cluster formation. The goethite phase present on the magnetite nanoparticle surface like a thin passivate layer only was detectable using CV-CPEE, which is a very efficient, cheap, and powerful tool for surface characterization, and it is able to determine the passivate oxyhydroxide or oxide thin layer presence on the nanoparticle surface.