Doped Fe3O4 Research Articles

In-situ growth of nanostructured catalytic coatings via one-step plasma electrolytic oxidation

In the present work, we reported the in-situ preparation of nanostructured PEO catalysts on Al substrate in a corrosive aluminate solution. The influence of treatment time on the structure, composition, and performance of the coatings was studied in detail, and the film formation mechanism was proposed with consideration of the PEO theoretical basis. The morphology study showed that the obtained samples were highly porous and evenly covered with spherical nanoparticles with diameters of 15–25 nm. The coating treated for 60 min showed a high porosity of 30.5 ± 1.3%, in addition, an oxide film with a unique branch-like structure was formed when the duration was 120 min. The composition analysis suggested that the nanostructured coatings mainly consisted of Al2O3, and the doped Fe3O4 and CuO were enriched on the upper surface of the layer. Owing to the superior structure and high-content of active component, the specimen treated for 120 min exhibited the highest activity during the catalytic test.

Decomposition of Nickel(Ⅱ)−Ethylenediaminetetraacetic acid by Fenton−Like reaction over oxygen vacancies-based Cu−Doped Fe3O4@γ−Al2O3 catalyst: A synergy of oxidation and adsorption

Nickel (Ⅱ)−ethylenediaminetetraacetic acid (Ni−EDTA) complexes are widely present in electroplating effluents. Owing to its chemical stability, Ni−EDTA is hardly removed in traditional Fenton/Fenton-like processes with conventional iron (Fe)−based catalyst. In this study, oxygen vacancies were introduced into our highly efficient and novel Fe3O4@γ−Al2O3 catalysts using Cu doping for Ni−EDTA decomposition in Fenton−like system. Without noble−metal cocatalyst, the introduction of oxygen vacancies in Cu−doped Fe3O4@γ−Al2O3 catalysts exhibit excellent Fenton−like activity even in neutral or alkaline conditions. Experimental results revealed that, without the aid of extra energy, Ni−EDTA complexes could be effectively decomposed over oxygen vacancies−based catalyst. Electron paramagnetic resonance (EPR), X−ray photoelectron spectroscopy (XPS), oxygen temperature−programmed desorption (O2−TPD), and hydrogen temperature−programmed reduction (H2−TPR) were used to get a deep insight into the decomposition mechanism. Additionally, by employing the Al−containing support, stable layered double−hydroxide phases of NiAl could be formed, indicating that a synergy of oxidation and adsorption could simultaneously take place, which led to the recovery of released Ni2+ ions and also reduction in secondary pollution. To investigate the decomposition process of Ni−EDTA over oxygen vacancies−based catalyst, liquid chromatography−quadrupole/electrostatic field orbitrap high resolution mass spectrometry (LC−MS/MS) was employed to identify the generated intermediates, and thus, a plausible decomposition pathway was successfully conceived.

Dopant segregation and CO adsorption on doped Fe3O4 (1 1 1) surfaces: A first-principle study

The water–gas shift reactions (WGS) used to produce hydrogen in industry are usually catalyzed by iron-based catalysts, in which the Fe3O4 was confirmed to be the catalytically active phase of iron oxide. In this work, based on the first-principle simulations, we theoretically study the relation between the dopant segregation and activities of the doped Fe3O4 for adsorbing CO. The surface electronic structure is proved to be a fundamental criterion for CO adsorption on doped Fe3O4 surfaces, which can be obtained by theoretical calculations. The surface segregation of dopants generally determine the effects of dopants on the surface properties, and the CO adsorption aims at the special reaction of WGS. It is worth emphasizing that, for a series of experiments on doped Fe3O4 catalyzed WGS, a unified explanation can be given based on the present results. Our theoretical calculations are well consistent with the recent experimental results at around 400 °C. Therefore, segregation could have decisive roles on the nature of WGS catalysis by iron oxides. This work is instructive for exactly depicting the catalytic activities of materials based on first-principle calculations, and is also helpful to search highly active catalysts.

Easy Synthesis and Characterization of Holmium-Doped SPIONs.

The exceptional magnetic properties of superparamagnetic iron oxide nanoparticles (SPIONs) make them promising materials for biomedical applications like hyperthermia, drug targeting and imaging. Easy preparation of SPIONs with the controllable, well-defined properties is a key factor of their practical application. In this work, we report a simple synthesis of Ho-doped SPIONs by the co-precipitation route, with controlled size, shape and magnetic properties. To investigate the influence of the ions ratio on the nanoparticles’ properties, multiple techniques were used. Powder X-ray diffraction (PXRD) confirmed the crystallographic structure, indicating formation of an Fe3O4 core doped with holmium. In addition, transmission electron microscopy (TEM) confirmed the correlation of the crystallites’ shape and size with the experimental conditions, pointing to critical holmium content around 5% for the preparation of uniformly shaped grains, while larger holmium content leads to uniaxial growth with a prism shape. Studies of the magnetic behaviour of nanoparticles show that magnetization varies with changes in the initial Ho3+ ions percentage during precipitation, while below 5% of Ho in doped Fe3O4 is relatively stable and sufficient for biomedicine applications. The characterization of prepared nanoparticles suggests that co-precipitation is a simple and efficient technique for the synthesis of superparamagnetic, Ho-doped SPIONs for hyperthermia application.

Synthesis and characterization of Fe3O4:Yb3+:Er3+ nanoparticles with magnetic and optical properties for hyperthermia applications

The synthesis and characterization of ytterbium (Yb3+) and erbium (Er3+) co–doped Fe3O4 nanoparticles (NPs) was reported for the first time in this work. A set of samples with fixed Er3+ (1 mol%) and different Yb3+concentrations (1, 10, 20 and 50 mol%) were prepared and systematically characterized to study their structural, magnetic, thermal and optical properties. The superparamagnetic behavior of Fe3O4 and Yb3+ and Er3+co–doped Fe3O4 NPs was verified by the hysteresis loop. The co–doped Fe3O4 NPs also presented an upconversion emission in the green and red region. The Fe3O4 and Fe3O4: Yb3+, Er3+ NPs showed hyperthermic behavior for an externally applied AC magnetic field, observing that the introduction of Yb3+ and Er3+ induced a temperature increase of 34.4% in optimal conditions with respect to the non–doped Fe3O4 with a reduction in saturation magnetization of 7.8%. These observations suggest that Fe3O4: Yb3+, Er3+ NPs turns out to be an important candidate in biomedical applications for simultaneous optical imaging and hyperthermic therapy.

PVP capped Mn2+ doped Fe3O4 nanoparticles: A novel preparation method, surface engineering and characterization

In this paper, we developed a novel and facile electrodeposition method for Mn2+ doped superparamagnetic iron oxide nanoparticles (Mn-SPIONs) in both bare and poly(vinylpyrrolidone) (PVP) capped forms (i.e. bare Mn-SPIONs and PVP capped Mn-SPIONs). The magnetite crystal structure, uniform spherical particle morphologies, nanometer size, Mn2+ cations incorporation and PVP surface coat were confirmed through XRD, IR, FE-SEM, DLS and DSC-TGA techniques. The superparamagnetic behavior of both Mn-SPIONs and PVP-Mn-SPIONs samples were indicated by vibrating sample magnetometer (VSM) data. Based on the obtained results, it was stated that the developed electrochemical route can be considered as a facile platform for preparation of novel biocompatible metal ion doped iron oxides for possible biomedical applications.

Gd3+ doped Fe3O4 nanoparticles with proper magnetic and supercapacitive characteristics: A novel synthesis platform and characterization

A novel electrochemical procedure was developed for the facile preparation of Gd-doped iron oxide nanoparticles (GdIO-NPs). A simple galvanostatic deposition (i=10 mA cm-2) was done in an additive-free aqueous solution containing FeCl2·4H2O, Fe(NO3)3·9H2O and GdCl3·6H2O. The XRD, FE-SEM, EDS and TEM characterizations showed that the product is composed of 15% GdIO-NPs with 10 nm in size. VSM analysis proved that the GdIO-NPs are superparamagnetic. The cyclic voltammetry and charge-discharge tests showed that the prepared GdIO-NPs are capable to deliver specific capacity as high as 190.1 F g-1 at 0.5A g-1 and capacity retention of 95.1% after 2000 cycling. Based on the results, it was concluded that the developed electrochemical strategy acts as an efficient procedure for the preparation of lanthanide doped MNPs with proper magnetic and supercapacitive characters.

Microwave Assisted Synthesis and Oxidation Resistance of Sm3+ Doped Fe3O4 Nanoparticles

In this study, pure and Sm3+ doped Fe3O4 nanoparticles were prepared via a microwave assisted synthesis in water solution. The samples were characterized by TEM, XRD, XANES, and VSM techniques. The structure and morphology, Fe and Sm oxidation states, the oxidation resistance and magnetic properties of pure and Sm doped Fe3O4 nanoparticles were studied. TEM and XRD results show that Sm doped Fe3O4 nanoparticles have a good dispersion and are smaller than pure Fe3O4 nanoparticles. The Fe and Sm oxidation states of pure and Sm doped Fe3O4 nanoparticles were studied by means of XANES analysis. The magnetic properties of Sm doped Fe3O4 nanoparticles determined by VSM exhibit superparamagnetic behavior with high saturation magnetization. It was found that Sm doping in a small amount makes it possible not only to reduce the sizes of magnetite nanoparticles but also to improve their oxidation resistance and increase their saturation magnetization value. These pure and Sm doped Fe3O4 magnetic nanoparticles are expected to be used in a number of biomedical applications.

Antimicrobial, electrochemical and photo catalytic activities of Zn doped Fe3O4 nanoparticles

In the present study, we report the synthesis of Fe3O4 and Zn-doped Fe3O4 (Zn/Fe3O4) nanoparticles by a simple co-precipitation method. The morphology, structure and optical properties of the samples are characterized by transmission electron microscopy, X-ray diffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, energy dispersive spectroscopy and UV–visible spectroscopy. The antibacterial, electrochemical energy storage and photocatalytic properties of the nanoparticles are studied in detail, and the results are discussed. Antibacterial activity of Fe3O4 and Zn/Fe3O4 nanoparticles are analyzed by disc diffusion method on Gram-negative pathogen Salmonella typhi and Gram-positive pathogen Staphylococcus aureus. Zn/Fe3O4 nanoparticles show a higher zone of inhibition because of having a larger specific surface area than the pure Fe3O4 nanoparticles. The electrochemical energy storage performances of the nanoparticles are tested in a symmetric two-electrode configuration, and the measurement demonstrated that Zn doping nearly doubles the energy storage properties of the Fe3O4 nanoparticles. The study of the photocatalytic degradation of methyl blue (MB) dye under UV irradiation in the presence of pure and doped Fe3O4 nanoparticles reveal that both nanoparticles act as ideal catalysts for degradation of MB dye.

Electrochemical fabrication of praseodymium cations doped iron oxide nanoparticles with enhanced charge storage and magnetic capabilities

Pr3+ doped iron oxide nanoparticles (Pr-IONPs) are fabricated through a facile one-pot electro-synthesis method. In this procedure, Pr-IONPs are electro-deposited from an additive-free mixed aqueous solution of iron(III) nitrate, iron(II) chloride and praseodymium chloride salts with applying direct current of 10 mA cm−2 for 30 min. The analysis results obtained from X-ray diffraction, field emission electron microscopy and energy-dispersive X-ray showed that the deposited Pr-IONPs sample is composed of magnetite nanoparticles with an average size of 20 nm, and had 15 wt% Pr3+ in its structure. The electrochemical data provided by galvanostatic charge–discharge tests showed that Pr3+ doped iron oxide working electrode is enable to exhibit specific capacitances (Cs) values as high as 221, 194, 171, 139, 112, 94 and 82 F g−1 at the scan rates of 2, 5, 10, 20, 50, 75 and 100 mV s−1, which are ~ 20% higher than those of undoped electrode with Cs values of 181, 159, 140, 112, 92, 83 and 68 F g−1 at the scan rates of 2, 5, 10, 20, 50 and 100 mV s−1, respectively. These results proved the suitability of the electro-synthesized Pr3+ doped Fe3O4 NPs for use in supercapacitors. Furthermore, the results of vibrating sample magnetometer measurements revealed that Pr-IONPs have better superparamagnetic and lower Mr and Hci values (i.e. Mr = 0.13 emu g−1 and H Ci = 2.37 G) as compared with pure IONPs (Mr = 0.95 emu g−1 and H Ci = 14.62 G). Based on the obtained data, the developed electro-synthesis method is introduced as a facile synthetic method for the fabrication of high performance metal ion doped magnetite nanoparticles.

One-step electro-synthesis of Ni2+ doped magnetite nanoparticles and study of their supercapacitive and superparamagnetic behaviors

Application of a novel electrochemical based procedure for the preparation of the Fe3O4 nanoparticles doped with Ni2+ cations led to improvement of the magnetic and capacitive performances of the doped iron oxides in comparison with its undoped form. Electro-synthesis was employed for the preparation of both undoped and Ni2+ doped Fe3O4 nanoparticles on a stainless steel cathode under simple electrochemical conditions (i = 10 mA cm−2 and T = 25 °C and t = 30 min). Analysis of electrosynthesized samples by XRD and TEM revealed the formation of pure crystalline magnetite phase and uniform particles with size of 10 nm, and doped/undoped states were distinguished by FE-SEM and EDS analyses. The measurement of superparamagnetic characteristics of undoped Fe3O4 (Ms = 72.96 emu g−1, Mr = 0.95 emu g−1 and H Ci = 2.39 Oe) and Ni2+ doped Fe3O4 (Ms = 47.25 emu g−1, Mr = 0.22 emu g−1 and H ci = 0.78 Oe) were done using vibrating sample magnetometer. Accordingly, the doped oxide form demonstrates improved magnetic ability in comparison with the undoped state. The evaluation of charge storage capability of both doped and undoped oxide forms by cyclic voltammetry and galvanostatic charge–discharge confirmed a significant improvement in the supercapacitive performance of the iron oxide electrode doped with Ni2+ cation compared to corresponding undoped electrode.

One-pot electrochemical synthesis and assessment of super-capacitive and super-paramagnetic performances of Co2+ doped Fe3O4 ultra-fine particles

Here, we report a facile and one-step fabrication of Co2+ doped iron oxide nanoparticles (Co-IONPs). In this procedure, Co-IONPs are galvanostatically deposited from an additive-free aqueous solution of mixed iron(III) nitrate, iron(II) chloride and cobalt chloride salts. The obtained data from XRD, FE-SEM and energy-dispersive X-ray revealed that the deposited Co-IONPs sample has composition of Co2+ doped magnetite crystal structure with fine particles (size ≈ 15 nm) morphology. The obtained electrochemical data showed that Co-IONPs are capable to deliver specific capacitances as high as 214.1 and 166.8 F g−1 at the discharge loads of 0.25 and 1 A g−1, respectively, and capacity retentions of 95.1 and 88.6% after 2000 galvanostatic charging/discharging cycling. And about 20% enhanced in the charge storage ability of iron oxide electrode was obtained through 15 wt% Co2+ doping. Furthermore, the results of vibrating sample magnetometer measurements confirmed an improvement in the superparamagnetic behavior of IONPs via Co2+ doping. Based on the obtained results, our developed one-step electrochemical preparation platform is introduced as a facile procedure for the preparation of metal ion doped magnetite nanoparticles.

Improvement of supercapacitive and superparamagnetic capabilities of iron oxide through electrochemically grown La3+ doped Fe3O4 nanoparticles

In this paper, undoped and La3+ doped iron oxide nanoparticles (IONPs and La-IONPs) are prepared through a one-step electrosynthesis process. The prepared La-IONPs are characterized by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) and vibrating sample magnetometer (VSM) analyses. Furthermore, the electrochemical performance of IONPs and La-IONPs are evaluated using cyclic voltammetry (CV) and galvanostat charge–discharge (GCD) tests. The analyses results showed that both electrosynthesized samples have magnetite (Fe3O4) crystal structure. The doped IONPs exhibited composition of 15% wt La3+ cations incorporated into Fe3O4. Also, both IONPs and La-IONPs samples have nano-particle morphologies with particle size of 15 and 20 nm, respectively. The VSM data indicated that an improvement in the superparamagnetic behavior of Fe3O4 is obtained as a result of La3+ doping, where La-IONPs sample exhibited smaller remanent magnetization (Mr) and coercivity (Ci) values as compared with undoped IONPs. Furthermore, GCD showed that La-IONPs are capable to deliver specific capacity value of 187 F g−1 and 84.8% after 2000 discharging cycles at 1 A g−1, where undoped IONPs electrode exhibited specific capacity and cycle life of 145 F g−1 and 78.7%, respectively, at the same discharging conditions. The obtained results well established the improvement of capacitive characters for La3+ iron oxide electrode.

Al3+ doped Fe3O4 Nanoparticles: A Novel Preparation Method, Structural, Magnetic and Electrochemical Characterizations

Al3+ doped Fe3O4 Nanoparticles: A Novel Preparation Method, Structural, Magnetic and Electrochemical Characterizations

Evaluation of zinc-doped magnetite nanoparticle toxicity in the liver and kidney of mice after sub-chronic intragastric administration.

Super-paramagnetic iron oxide nanoparticles (SPIONs) have been approved for clinical use due to their salient super-paramagnetic properties and low toxicity. Zn2+ doped SPIONs possess significantly higher magnetic susceptibility than that of conventional SPIONs. Here we evaluated the potential toxicity of Zn2+ doped Fe3O4 nanoparticles (Zn0.4Fe2.6O4 NPs) in the liver and kidney of mice after repeated intragastric administration for 30 days. Zn0.4Fe2.6O4 NPs did not cause significant changes in their body weights and the coefficients of the liver and kidney, but increased the levels of Fe and Zn in the two organs. Zn0.4Fe2.6O4 NP induced slight oxidative stress in the liver and kidney, which could be successfully counteracted by their intrinsic antioxidant systems and had no observable hazardous effects on the histopathology, ultrastructure and functions of the two organs. These results demonstrated that high-performance magnetic Zn0.4Fe2.6O4 NPs did not produce apparent toxicity in the liver and kidney of mice even after sub-chronic intragastric administration. In addition, Zn2+ doping not only markedly enhanced magnetic susceptibility of Zn0.4Fe2.6O4 NPs but also significantly increased the stability of Zn0.4Fe2.6O4 NPs in biological conditions, making them appropriate for use in magnetic resonance imaging and drug delivery by the oral route.

Preparation, Characterization of High-Luminescent and Magnetic Eu3+, Dy3+ Doped Superparamagnetic Nano-Fe3O4.

Pure superparamagnetic nano-Fe3O4 (SPMNPs) and Ln3+ (Eu3+, Dy3+) doped SPMNPs are successfully synthesized by reverse micelle method. The structure, morphology, magnetic properties and PL properties of the samples were characterized by XRD, FT-IR, TEM, PPMS, EDS and luminescence spectrometer respectively. The influences of Ln3+ doping amount on magnetic properties and PL properties were investigated in detail. The results show, with increasing of the Lna+ doping amount increasing, the morphologies and particle sizes of the doped Fe304 nanoparticles change, leading to saturation magnetization and coercivity changing accordingly. The change of lattice parameter and particle size was discussed based on Rietveld analysis of XRD pattern of the doped Fe3O4 nanoparticles. The coincidence of the ZFC and FC magnetization curves within the temperature range from 120.6 to 300 K, indicating that Fe3O4 nanoparticles are single domain super-paramagnetic.

The composite ceramics of (YBa2Cu3O7−δ)1−x(Fe3O4)x

The effect of sintering temperatures on the superconducting properties of the composites of (YBCO)0.975(Fe3O4)0.025 (2.5wt.%) has been studied. The field-cooled measurement finds that with the sintering temperature increasing the superconducting fraction is increased first and then decreased. The optimum sintering temperature is found. The Raman vibration modes (out-of-phase bond-buckling mode and in-plane bond-stretching mode) are recorded at room temperature. The extended X-ray absorption fine structure proves that no further lattice distortion occurs on YBCO after the addition of Fe3O4, but the local structure disorder of YBCO has altered as the sintering temperatures changed. Compared the shift of the Raman phonon modes with the magnitude of oscillations of extended X-ray absorption fine structure in R space it can be concluded that the local disorder has relation with superconducting properties. Scanning electron microscopy images show that the doped Fe3O4 are diffused into the inter-grain sites. With sintering temperature increasing the small-size grains get fused to form larger grains. The strain produced by grain interaction leads to the change of local structure disorder. Whereas, further increase of the sintering temperatures, some Fe ions at the grain boundaries are incorporated into the unit cell of YBCO, which leads to the decrease of superconducting fractions. By X-ray absorption near edge structure, it is found that the white lines occurring near K edge of Cu2+ show an energy shift toward high energy side. It can be considered that as the sintering temperature increases more holes are formed and the screening effect around the Cu2+ weakens. The screening behavior is also conducive to the formation of superconducting fractions.

An approach to reduce the antiferromagnetic coupling of antiphase boundaries in half-metallic magnetite films

Highly conductive (∼105 μΩ cm) Mn doped epitaxial Fe3O4 films were fabricated by reactive sputtering. The larger size of magnetic domains compared to grain size with the increasing Mn content indicates that the partial antiferromagnetic coupling across the antiphase boundaries has been weakened, which was further demonstrated by the smaller exchange bias, faster saturated magnetization, and decreasing exchange interaction JAF. The decrease of antiferromagnetic strength originates from the larger Mn-O bond length than that of Fe-O bond. The first-principle calculation shows that the half-metallic feature (100% spin polarization) of Fe3O4 was unchanged with the incorporation of Mn atoms.

Structural origin for low-temperature relaxation features in magnetic nanoparticles

In addition to superparamagnetic relaxation associated with coherent spin reversal, magnetic nanoparticles often also exhibit additional relaxation features in the magnetic dissipation at low temperatures. Our studies show that the incorporation of boron, gadolinium and lanthanum into iron oxide (Fe3O4) nanoparticles substantially enhances these low-temperature magnetic relaxation properties. The structural and morphological studies of these nanoparticles were conducted using x-ray diffraction, transmission electron microscopy and Raman spectroscopy. The doped samples have retained the crystal structure of the parent Fe3O4 nanoparticles, although the shape and size of some of the nanoparticle samples have changed. Using ac magnetic susceptibility measurements, we parameterized the low-temperature magnetic features, with the amplitude of the associated magnetic relaxation showing a dramatic increase for certain dopants. The enhanced frequency-dependent magnetic relaxation features can be attributed to structural, rather than magnetic, defects in these doped Fe3O4 nanoparticles. These results strongly suggest that the low-temperature magnetic relaxation typically observed in magnetic nanoparticles is a single-particle effect produced by structural defects and is not significantly influenced by interparticle interactions.

Tungsten doping magnetic iron oxide and their enhanced lithium ion storage properties

This work presents a hydrothermal synthesis of W-doped Fe3O4 nanoparticles. The results indicate that Fe2+ but not Fe3+ is substituted with W6+. Both undoped and doped Fe3O4 show ferromagnetic behaviors. The magnetism of Fe3O4 decreases from 7.2emug−1 to 5.0emug−1 after doping, because the superexchange interactions between Fe2+ and Fe3+ are hindered by W. Interestingly, W-doped Fe3O4 exhibits improved reversible capacity of 629mAhg−1 in comparison with 341.3mAhg−1 of pure Fe3O4 for their first charge/discharge cycle, and shows higher initial Coulombic efficiency of 86.1%. Moreover, better cyclic stability has been obtained for W-doped Fe3O4. The W-doped Fe3O4 would be a candidate in applications of lithium ion batteries, magnetic materials, and other areas.