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In this study, Fe3O4/Ag magnetite-silver (MSx) nanocomposites were investigated as catalysts for advanced oxidation processes by coupling the plasmonic effect of silver nanoparticles and the ferromagnetism of iron oxide species. A surfactant-free co-precipitation synthesis method yielded pure Fe3O4 magnetite and four types of MSx nanocomposites. Their characterisation included structural, compositional, morphological and optical analyses, revealing Fe3O4 magnetite and Ag silver phases with particle sizes ranging from 15 to 40 nm, increasing with the silver content. The heterostructures with silver reduced magnetite particle aggregation, as confirmed by dynamic light scattering. The UV–Vis spectra showed that the Fe:Ag ratio strongly influenced the absorbance, with a strong absorption band around 400 nm due to the silver phase. The oxidation kinetics of organic pollutants, monitored by in situ luminescence measurements using rhodamine B as a model system, demonstrated the higher performance of the developed catalysts with increasing Ag content. The specific surface area measurements highlighted the importance of active sites in the synergistic catalytic activity of Fe3O4/Ag nanocomposites in the photo-Fenton reaction. Finally, the straightforward fabrication of diverse Fe3O4/Ag heterostructures combining magnetism and plasmonic effects opens up promising possibilities for heterogeneous catalysis and environmental remediation. [ABSTRACT FROM AUTHOR]

The iron industry is the largest energy-consuming manufacturing sector in the world, emitting 4–5% of the total carbon dioxide (CO2). The development of iron-based systems for CO2 capture and storage could effectively contribute to reducing CO2 emissions. A wide set of different iron oxides, such as hematite (Fe2O3), magnetite (Fe3O4), and wüstite (Fe(1−y)O) could in fact be employed for CO2 capture at room temperature and pressure upon an investigation of their capturing properties. In order to achieve the most functional iron oxide form for CO2 capture, starting from Fe2O3, a reducing agent such as hydrogen (H2) or carbon monoxide (CO) can be employed. In this review, we present the state-of-the-art and recent advances on the different iron oxide materials employed, as well as on their reduction reactions with H2 and CO. [ABSTRACT FROM AUTHOR]

Iron oxide-based ferrite ceramics, widely applied in high-frequency applications, are conventionally produced through high-temperature sintering processes, often resulting in grain growth and phase transformation. In this study, we used a cold sintering process (CSP) with oxalic acid (OA) as a solvent to consolidate iron oxide (Fe 3 O 4) ceramics at a low temperature of 160 °C. The OA-assisted CSP technique has demonstrated a remarkable capacity to facilitate the dissolution and redeposition of iron oxide ions, leading to the interconnection of Fe 3 O 4 particles, forming densely packed ceramics even at low-temperature sintering. Importantly, CSP maintained particle sizes and hindered phase transitions of Fe 3 O 4. The OA concentrations in CSP had a minimal impact on crystal structure and magnetic properties, but it significantly enhanced microstructural features, density, hardness, and electrical resistance. Compared to reference samples prepared without an aqueous solution or with water alone, the CSP-prepared Fe 3 O 4 ceramics with OA exhibited substantially improved density (a relative density of ∼80 %), mechanical properties (Vickers hardness of 3.5–4.0 GPa), magnetic properties (saturation magnetization >70 emu/g), and electrical resistance (electrical conductivity ∼10−3 S/cm at 102–106 Hz). These findings demonstrate a novel approach to fabricating Fe 3 O 4 ceramics at significantly lower temperatures while still achieving properties comparable to those sintered at high temperatures. [ABSTRACT FROM AUTHOR]

The establishment of a new metallurgical complex in Bellara, located in El-Milia in the Jijel region, is geographically advantageous due to its proximity to the Sidi Maarouf deposit (Algeria). This proximity has been a fundamental motivation for the completion of the current study. The object of research is the quality of iron products from Sidi Maarouf. The research is aimed at developing a treatment process aimed at improving the quality of iron products from Sidi Maarouf, while reducing the impurities of quartz and clay present in this ore. This approach will be based on an approved technological treatment scheme, implemented through an experimental approach to ensure reliable results that meet the requirements of the steel industry. The problem issue revolves around the difficulties encountered in the production of steels due to the natural characteristics of the raw material. In the absence of a physico-chemical characterization of the Sidi Maarouf iron ore deposit, samples taken undergo a series of thorough analyses, including microscopic examinations, X-ray diffraction (XRD), as well as additional chemical analyses using X-ray fluorescence (XRF). The identified minerals are predominantly composed of hematite in terms of iron. As for the gangue, it is mainly composed of calcite and quartz. Through to the pretreatment process involving washing, we have successfully removed lightweight particles, resulting in a concentrate containing dense particles. This approach was crucial in achieving satisfactory results during the high-intensity dry magnetic separation. As a result of the research it is shown that the enrichment of the Sidi Maarouf iron ore through high-intensity dry magnetic separation, a final concentrate was obtained with a Fe2O3 content exceeding 67 %, along with a significant reduction in silica impurities to 0.92 % and alumina to 0.77 %. It was concluded that this concentrate, derived from the –1+0.5 mm fraction and obtained under a current intensity of 12 A, meets the requirements of the steel industry. Following the work carried out, it is found that the methods of valorization of iron ore through mineralogical processes consistently require a high level of efficiency and performance in terms of equipment and characterization of the products obtained. In the future, iron ore processing will be conducted using innovative methods, integrating advanced technologies to enhance its characteristics while adopting environmentally friendly practices. [ABSTRACT FROM AUTHOR]

Magnetite quantum dots were synthesized by solvothermal method in a conventional reflux setup, in an inert environment, at different reaction temperatures and times. Powder X-ray diffraction patterns of the as-prepared iron oxide confirmed magnetite crystalline phases irrespective of the reaction conditions. TEM micrographs revealed that the iron oxides obtained at 200, 180 and 165 °C are spherical in shapes with mean particle sizes of 3.25, 3.3 and 3.90 nm respectively, showing an increase in particle size with decreasing temperature. TEM micrographs revealed that particles obtained at 6 and 3 h have a mean particle size of 3.25 nm while particles obtained at 4.5-h has a bigger mean particle size of 7.5 nm. The results show that irrespective of the synthetic parameters, the average particle sizes of the magnetite are in the range 3–8 nm and could be described as quantum dots. Optical absorption spectra of the as-prepared magnetite quantum dots exhibited maximum absorption in the range of 200–210 nm. Fe3O4-1, Fe3O4-2 and Fe3O4-3 synthesized at 200, 180 and 165 °C have energy band gaps of 5.49, 5.13 and 5.01 eV respectively, showing a decrease in band gap with decreasing temperature. Fe3O4-4 and Fe3O4-6 synthesized at 6 and 3 h have optical band gap of 5.44 eV while Fe3O4-5 synthesized at 4.5 h has a band gap of 3.75 eV. FTIR spectra confirmed the passivation of the surface of the as-prepared magnetite quantum dots by oleate. [ABSTRACT FROM AUTHOR]

This study evaluated the spatial variability of magnetic minerals and the potential of mass-specific magnetic susceptibility (χlf) to recognize minimum areas of phosphorus adsorbed (Pads). In an area of 443 ha cultivated with sugar cane in the state of São Paulo, 84 soil samples were collected at a depth range of 0.0–0.20 m. Analysis of mass-specific magnetic susceptibility at low (χlf) and high (χhf) frequencies was performed in all soil samples. Characterization of ferrimagnetic minerals was carried out by X-ray diffraction (XRD) and the chemical distinction between lithogenic (magnetite-Mt) and pedogenic (maghemite-Mh) ferrimagnetic minerals was determined by χlf before and after chemical reduction by citrate-bicarbonate-dithionite (CBD), with subsequent determination of Pads. The analytical results were evaluated by descriptive analysis and the spatial pattern was assessed by applying the geostatistical technique. χlf differentiated soils from their respective parent material even under conditions of high weathering and lithologic complexity. Positive linear correlations between Pads and clay (R2 = 0.77; p < 0.01), Pads and χlf (R2 = 0.86; p < 0.01), and Pads and Mh (R2 = 0.84; p < 0.01) indicated the use of χlf as a component of pedotransfer functions (PTF) for indirect quantification of Pads in the soil. Quantification of Mh and Mt by χlf was more sensitive than by XRD. The spatial pattern of ferrimagnetic minerals indicated that Mh originated from the direct oxidation of Mt. Soil χlf was sensitive to the spatial variability of Pads and might have assisted with the identification of minimum areas of phosphate fertilization in soils under lithologic complexes. [ABSTRACT FROM AUTHOR]

Octylamine (OTA), 1-dodecanethiol (DDT), and tri-n-octylphosphine (TOP) capped magnetite nanoparticles were prepared by co-precipitation method. Powder X-ray diffraction patterns confirmed inverse spinel crystalline phases for the as-prepared iron oxide nanoparticles. Transmission electron microscopic micrographs showed iron oxide nanoparticles with mean particle sizes of 2.1 nm for Fe3O4-OTA, 5.0 nm for Fe3O4-DDT, and 4.4 nm for Fe3O4-TOP. The energy bandgap of the iron oxide nanoparticles ranges from 2.25 eV to 2.76 eV. The iron oxide nanoparticles were used as photocatalysts for the degradation of methylene blue with an efficiency of 55.5%, 58.3%, and 66.7% for Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively, while for methyl orange the degradation efficiencies were 63.8%, 47.7%, and 74.1%, respectively. The results showed that tri-n-octylphosphine capped iron oxide nanoparticles are the most efficient iron oxide nano-photocatalysts for the degradation of both dyes. Scavenger studies show that electrons (e−) and hydroxy radicals (•OH) contribute significantly to the photocatalytic degradation reaction of both methylene blue and methyl orange using Fe3O4-TOP nanoparticles. The influence of the dye solution's pH on the photocatalytic reaction reveals that a pH of 10 is the optimum for methylene blue degradation, whereas a pH of 2 is best for methyl orange photocatalytic degradation using the as-prepared iron oxide nano-photocatalyst. Recyclability studies revealed that the iron oxide photocatalysts can be recycled three times without losing their photocatalytic activity. [ABSTRACT FROM AUTHOR]

The increased demand for the discovery of new conducting materials encourages the researchers for the development of advanced electronic technologies. In the present study, nanocomposites of poly (anthranilic acid- co -indole) / (PANA- C o -PIN) and magnetite nanoparticles (Fe3O4) were prepared via a one-step polymerization method and evaluated by various analytical techniques. The Fourier transform infrared spectroscopy (FT-IR) spectra proved the presence of Fe3O4 nanofillers in the copolymer at 507 cm−1. Optical characterization (UV-Vis) shows a clear blueshift indicating strong interactions between Fe3O4 and PANA- C o -PIN. The X-Ray diffraction (XRD) patterns revealed an increase in crystallinity due to the well dispersed nanoparticles. FESEM images evidenced the morphological changes caused by the uniform dispersion of nanoparticles in the copolymer matrix. The nano-dispersion of magnetite nanoparticles in the copolymer was confirmed by High-resolution transmission electron microscopy analysis. Magnetic properties of nanocomposites obtained from a vibrating sample magnetometer (VSM) showed an increase in the saturation of magnetism with the addition of nanoparticles and the composite exhibited superparamagnetic behaviour. The thermal stability and glass transition temperature of the nanocomposites were greatly enhanced with the addition of nanoparticles and were determined with the help of Thermogravimetric Analysis (TGA) and Differential scanning calorimetry (DSC) respectively. Filler-dependent electrical properties showed a linearly increased DC conductivity with the addition of nanoparticles. The impedance analysis showed that the AC conductivity and dielectric properties of the nanocomposites were higher than the copolymer and the maximum electrical properties were observed for 15 wt.% of composites. The ammonia gas sensing performance of copolymer composite indicates the easy access of gas molecules to the sensor surface through the metal oxide nanoparticles. The synthesized copolymer nanocomposites showed high sensitivity and fast response to ammonia gas. The prepared composite with good thermal properties, dielectric constant, ammonia gas sensing and magnetoelectric properties is a promising candidate for use in nanoelectronics devices. [ABSTRACT FROM AUTHOR]

Nanomaterials design, synthesis, and characterization are ever-expanding approaches toward developing biodevices or neural interfaces to treat neurological diseases. The ability of nanomaterials features to tune neuronal networks' morphology or functionality is still under study. In this work, we unveil how interfacing mammalian brain cultured neurons and iron oxide nanowires' (NWs) orientation affect neuronal and glial densities and network activity. Iron oxide NWs were synthesized by electrodeposition, fixing the diameter to 100 nm and the length to 1 µm. Scanning electron microscopy, Raman, and contact angle measurements were performed to characterize the NWs' morphology, chemical composition, and hydrophilicity. Hippocampal cultures were seeded on NWs devices, and after 14 days, the cell morphology was studied by immunocytochemistry and confocal microscopy. Live calcium imaging was performed to study neuronal activity. Using random nanowires (R-NWs), higher neuronal and glial cell densities were obtained compared with the control and vertical nanowires (V-NWs), while using V-NWs, more stellate glial cells were found. R-NWs produced a reduction in neuronal activity, while V-NWs increased the neuronal network activity, possibly due to a higher neuronal maturity and a lower number of GABAergic neurons, respectively. These results highlight the potential of NWs manipulations to design ad hoc regenerative interfaces. [ABSTRACT FROM AUTHOR]

Background: Persons with cosmetic tattoos occasionally experience severe pain and burning sensation on magnetic resonance imaging (MRI). Objective: To explore the culprit magnetic substances in commonly used permanent makeup inks. Material and methods: 20 inks used for cosmetic tattooing of eyebrows, eyeliners, and lips were selected. Ink bottles were tested for magnetic behavior with a neodymium magnet. Eight iron oxide inks qualified for the final study. Metals were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP‐MS). The magnetic fraction of inks was isolated and analyzed by X‐ray fluorescence (XRF). Magnetic iron compounds were characterized by Mössbauer spectroscopy and powder X‐ray diffraction (XRD). Results: ICP‐MS showed iron in all magnetic samples, and some nickel and chromium. Mössbauer spectroscopy and XRD detected ferromagnetic minerals, particularly magnetite, followed by goethite and hematite. Conclusion: This original study of cosmetic ink stock products made with iron oxide pigments reports magnetic impurities in inks for cosmetic tattooing, e.g., magnetite, goethite, and hematite. These may be the main cause of MRI burn sensation in cosmetic tattoos. The mechanism behind sensations is hypothesized to be induction of electrical stimuli of axons from periaxonal pigment/impurity activated by magnetic force. Magnetite is considered the lead culprit. [ABSTRACT FROM AUTHOR]

The chemical precipitation was used to obtain carbon fibers (CF) with surface modified by magnetite particles (Fe3O4). Processing was carried out by employing up to three subsequent coating stages of ultrasonic treatments. After each sonication stage, the coating was 17, 33, and 47 wt. % of the total weight of the modified fibers. Raman spectroscopy indicates the presence in the coating of a mixture of iron II and III states. As-decorated fibers were used to fabricate composites with an epoxy resin (ED-20) matrix cured with PEPA. The quantity of the carbon fiber filler was of 1, 3, and 6 wt %. At room temperature, the saturation magnetization of the soft magnetic samples was 0.37, 0.83, and 1.72 emu/g for the indicated compositions. Carbon fiber reinforced polymer materials with extra functions such as magnetic in this case, are expected to be useful in applications from the power and energy industries. [ABSTRACT FROM AUTHOR]

Controlled spatial arrangements of superparamagnetic iron oxide nanoparticles (SPIONs) in complex nanostructures determine fine tuning of physico-chemical properties which, in turn, may lead to new practical applications. We report here on newly observed properties of hierarchical SPIONs nanostructure with bundle-like morphology, also known as nanobundles. Colloidal chemical processes and sol-gel synthesis were used for the synthesis of nanobundles, i.e. i) self-assembly of SPIONs into magnetic nanoparticle clusters, ii) their magnetic assembly to the nanochains, and finally iii) formation of bundle-like hierarchical nanostructure. An XRPD measurements show spinel crystal structure of maghemite/magnetite nanoparticles, EDS analysis reveals Fe, Si and O as main elements whereas SEM/TEM analysis show silica-coated magnetic nanoclusters (∼100 nm) and their hierarchical assemblies with bundle-like morphology of ∼8 μm length and ∼1 μm width. TEM analysis revealed core-shell nature of iron oxide nanoparticle clusters with their size of around 80 nm that were coated by an amorphous silica shell with thickness of ∼15 nm. The nanoclusters in the core are constructed of maghemite/magnetite nanoparticle assembly with primary iron oxide nanoparticle size about 10 nm. The magnetization M data as a function of an applied external magnetic field H were successfully fitted by the Langevin function, whence the magnetic moment μ p = 19256 μ B , and the diameter d = 9.6 nm of nanoparticles were determined. Microsized bundle-like particles are superparamagnetic, magnetically guidable and possess high transverse relaxivity of r 2 = 397.8 mM−1s−1. Magnetic properties and such high value of transverse relaxivity holds promise for nanobundles application in MRI imaging (MRI contrast agent), as nanobundles may enhance the magnetic field in their surroundings and enhance proton relaxation processes. Our nanobundles can open new opportunities in the biomedical applications, magnetic separation, photonic crystals and magnetic liquid manipulation and can be inspiration for synthesizing novel self-assembled nanoparticle structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ iron oxide nanoparticles were synthesized into heavy crude oil. • Magnetite and akaganeite nanoparticles in situ presented sizes of 20–43 nm. • Reaction conditions were at 200 nm3/m3 of H 2 /heavy crude oil ratio, 380 °C and 1 h. • Residue conversion was approximately 20 %. • Spent catalyst showed the iron sulfide phase, although no presulfiding was realized. We proposed a direct in situ synthesis method for iron oxide nanoparticles (NPs) along with catalytic erformance upgrading of heavy crude oil (HCO). Our method compares the upgrading of a HCO where other iron oxide nanoparticles were synthesized by a traditional thermal decomposition method of organometallic compounds in the presence of stabilizing agents and solvents of high boiling points. Furthermore, the in situ nanoparticles were extensively characterized by XRD, Mössbauer spectroscopy and TEM microscopy which confirmed the presence of magnetite and akaganeite phases, with an average diameter of 20−43 nm. Nanoparticles by thermal decomposition method were investigated by XRD, UHR-FE-SEM and HRTEM and showed the formation of magnetite nanoparticles with an average diameter of 6.7 ± 1.4 nm. Subsequently, the nanoparticles were evaluated in a batch reactor using HCO from the Golden Lane of Mexico at 44.1 bar (initial H 2 pressure) and 380 °C, for 1 h at 500 rpm. It was observed that, even under hydrogen limited conditions, there are better physicochemical properties in terms of viscosity, API gravity and heavy fractions decrease, for example, the residue conversion was about 20 % and the kinetic model was adjusted to a five lump model. The formation of the iron sulfide phase (FeS) was detected during the analysis of the spent catalyst. [ABSTRACT FROM AUTHOR]

Our knowledge of electromagnetic heating's effect on heavy oil upgrading is largely based on very limited data. The aim of the present research was thus to study in detail the effect of microwave exposure in the absence and presence of nanosized magnetite on the composition of heavy oil. The obtained data reveal that the use of nanosized magnetite improves not only microwave radiation application as a result of its absorption and release of thermal energy but also that these nanoparticles have a catalytic ability to break carbon–heteroatom bonds in the composition of resins and asphaltene molecules. In fact, the overall reduction in asphaltenes or resins does not always adequately describe very important changes in asphaltene composition. Even a small fraction of broken carbon–heteroatom bonds can lead to an increase in the mobility of asphaltenes. Moreover, this study has shed light on the important evidence for asphaltenes' transformation, which was found to be the formation of light aromatic compounds, such as alkylbenzenes, naphthalenes and phenanthrenes. These compounds were fixed in the composition of the aromatic fraction. We believe that these compounds could be the fragments obtained from asphaltenes' degradation. The evidence from this study points toward the idea that asphaltenes' destruction is crucial for increasing oil mobility in the reservoir rock during its thermal stimulation. [ABSTRACT FROM AUTHOR]

Nanostructured electrode materials for supercapacitors have attracted research interest due to their high power density and long cycle life. Herein, porous flower-like magnetite (Fe3O4) nanostructures have been synthesized using ethylene glycol mediated iron alkoxide as a precursor material. The magnetite nanostructures are prepared by heating an iron alkoxide at 450 °C for 3 h under N2 atmosphere. The prepared porous nanostructure is polycrystalline with a high surface area of 186 m2 g−1 and existence of pores with a pore volume 6.6 nm. The electrochemical capacitance performance of Fe3O4 nanostructures has been evaluated. The high discharge capacitance is 183 F g−1 at 1 A g-1 with high capacitance retention of about 65% upon charge–discharge cycling after 5000 cycles have been observed. The high discharge rate and cyclic stability are attributed to the porous nature of the Fe3O4 nanostructures. As Fe3O4 is inexpensive, relatively non-toxic, and environmental friendly nature has potential application for supercapacitors. [ABSTRACT FROM AUTHOR]

Every year, the steelmaking industry produces millions of tons of slags resulting in pollution to the environment. Among the waste, secondary metals and scales rich in iron oxides are also thrown away. There is a need to treat the steel waste in a reasonably way to protect the environment and proposing new cheap technologies for producing advanced materials. In this study we report the morphological and structural characterization of waste scales generated during roll milling steel process at JSC "Arcelor Mittal Temirtau". The raw slag and annealed at 1000 °C were measured by X-ray diffraction (XRD), scanning electron microscopy adapted with energy dispersive X-ray (SEM- EDX), magnetometry and Mössbauer Spectroscopy (MS). Fe and O were detected by EDX as main chemical elements and Si, S, Ca, Mg, C and Al as minimal elemental composition. XDR for the raw sample revealed α-Fe2O3 (hematite) and Fe3O4 (magnetite) as principal and secondary phase, respectively; whereas monophasic α-Fe2O3 is detected for the scales annealed at 1000 °C. Magnetometry measurements show the Verwey transition for the raw sample and the Morin transition for the annealed at 1000 °C; those are fingerprints for the presence of magnetite and hematite, respectively. MS measurements for the raw sample consist of 6 small peaks of absorption and a broad two-lines absorption peak in the central part. The doublets are associated to the hyperfine parameters belonging to wustite. Magnetite is related to the hyperfine parameters for two sextets in octahedral Fe2.5+ and tetrahedral Fe3+sites and a small sextet that resembles the Mössbauer parameters of α-Fe2O3. Only a well crystallized and weakly ferromagnetic sextet confirm the presence of α-Fe2O3 phase for the sample annealed at 1000 °C due to thermal oxidation. [ABSTRACT FROM AUTHOR]

The translation of nanoparticles to useful applications is often hindered by the reliability of synthetic methodologies to reproducibly generate larger particles of uniform size (diameter > 20 nm). The inability to precisely control nanoparticle crystallinity, size, and shape has significant implications on observed properties and therefore applications. A series of iron oxide particles have been synthesised and the impact of size as they agglomerate in aqueous media undergoing flow through a capillary tube has been studied. Reaction conditions for the production of large (side length > 40 nm) cubic magnetite (Fe3O4) have been optimised to produce particles with different diameters up to 150 nm. We have focussed on reproducibility in synthesis rather than dispersity of the size distribution. A simple oxidative cleavage of the as-synthesised particles surfactant coating transforms the hydrophobic oleic acid coated Fe3O4 to a hydrophilic system based on azelaic acid. The hydrophilic coating can be further functionalised, in this case we have used a simple biocompatible polyethylene glycol (PEG) coating. The ability of particles to either chain, flow, and fully/or partially aggregate in aqueous media has been tested in a simple in-house system made from commercial components. Fe3O4 nanoparticles (60–85 nm) with a simple PEG coating were found to freely flow at a 2 mm distance from a magnet over 3 min at a rate of 1 mL min−1. Larger particles with side lengths of ~150 nm, or those without a PEG coating were not able to fully block the tube. Simple calculations have been performed to support these observations of magnetic agglomeration. Polyethylene glycol coated magnetite nanoparticles have been optimised for aqueous flow experiments. Particles agglomerate in the capillary tube while under the influence of a rare earth magnet. [ABSTRACT FROM AUTHOR]

The aim of this work is to show how the magnetic properties of polyethyleneimine (PEI)-coated and naked magnetite (Fe3O4) nanoparticles are improved when the alternative in situ PEI microwave-assisted hydrothermal synthesis method is employed in contrast to the results obtained for nanoparticles synthesized from the same precursors by a conventional co-precipitation method. As far as we know, this is the first report on "in situ" PEI-coated Fe3O4 nanoparticles obtained by microwave-assisted hydrothermal synthesis. For this purpose, uncoated and PEI-coated Fe3O4 nanoparticles were synthesized by the co-precipitation method (CCPM) using ammoniac as precipitating agent after heating at 80 °C and by a microwave-assisted hydrothermal method (MWAM) using urea at 140 °C during 30 min. The obtained powders so were characterized by X-ray diffraction, scanning and transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Mössbauer spectroscopy and DC magnetization studies. It was seen that the magnetic properties of the nanoparticles strongly depend on the synthesis route and that they also vary if particles are coated by the nonmagnetic polymer (PEI). The morphology, size, surface and anisotropy effects play an important role in the magnetic behavior. In situ PEI-coated nanoparticles obtained by MWAM, with larger average size and better crystallinity, exhibited a higher coercive field and saturation magnetization values than PEI-coated nanoparticles synthesized by CCPM; the latter revealed a quasi-complete superparamagnetic behavior at room temperature. The synthesis by MWAM is a faster, simple and low-cost way to obtain in situ PEI-coated Fe3O4 nanoparticles with reasonable saturation magnetization, coercivity and suitable average particle size values to be tested for biomedical applications. [ABSTRACT FROM AUTHOR]

• Ion bombardment transforms an epitaxial hematite thin film into an epitaxial magnetite/hematite bilayer. • The oxygen sublattice acts as a scaffold during the transformation between the two phases. • The resulting magnetite has a high density of twin and antiphase boundaries. • The magnetic contrast is diffuse and, apparently, does not correlate with the morphology. The search of new properties in novel oxide heterostructures requires the exploration of new fabrication methods and the study, at the microscopic level, of the processes involved during the synthesis. We present a synchrotron-based spectromicroscopic investigation of a magnetite/hematite bilayer on Pt(111) grown in a two-step process by thermal evaporation and Low Energy Ion Bombardment (LEIB). The characterization includes the study of structural, electronic, chemical, and magnetic properties using X-ray Absorption Spectroscopy (XAS), Low Energy Electron Microscopy (LEEM), Photoemission Electron Microscopy (PEEM), or X-ray Magnetic Circular Dichroism (XMCD). The aim is to obtain microscopic information of the thin film before, during, and after the ion bombardment. Ion bombardment gradually transforms the topmost layers of the hematite thin film into a defective sub-oxide, where magnetite nuclei grow and coalesce with increasing ion doses. Two rotational domains of magnetite coexist, which are typically a few tens of nanometres large and do not grow significantly with temperature annealings. The incoherent growth of the magnetite nuclei favours the formation of stable twin boundaries (TBs) and antiphase boundaries (APBs). Dichroic spectra show the characteristics of the ferrimagnetic (FiM) order of magnetite, and the spatial distribution of magnetic domains shows no apparent correlation with the structural image, displaying smooth domains separated by diffuse frontiers. These findings illustrate the importance of a spectromicroscopic characterization of novel oxide heterostructures for potential future applications. [ABSTRACT FROM AUTHOR]

In this study, green synthesis of iron oxide magnetite (Fe3O4-NPs) was successfully prepared from Artemisia leaves extract and Assessment of Their Antioxidant Activities. The effect of different ferric chloride concentrations 0.01-0.1 M on the nanoparticles' iron oxide formation was studied. The obtained Fe3O4 nanoparticles were characterized using various techniques, such as UV–Visible, FT-IR, XRD, SEM and EDAX are used for this purpose. The antioxidant activity of Fe3O4-NPs was determined by total antioxidant capacity (TAC), DPPH• (2, 2- diphenyl-1-picrylhydrazyl), FRAP (Ferric ion reducing antioxidant power assay) assays. In addition, UV–Vis spectra showed maximum absorption at range 275–301 nm related to the Fe3O4-NPs. FTIR spectra exhibit a two weak peak at 510 and 594 cm−1 attributed to Fe3O4-NPs vibration, confirming the formation nanoparticles XRD confirmed the crystalline nature of Fe3O4-NPs with average size ranged in 19–24 nm. SEM showed that the green synthesizing magnetite nanoparticles having in general as cubical shape. The purpose of this study, it highlights the high antioxidant activity of magnetite Fe3O4-NPs green synthesized, as a result, the use of Artemisia leaves extract offers its ease, fast, low-cost and friendly to the environment compared to other synthesis methods. [ABSTRACT FROM AUTHOR]

Chitosan (Chit) cross-linked via glutaraldehyde to graphene oxide (GO) was prepared as the basic nanocomposite support for further modification. The Chit/GO nanocomposite was modified with carbon nanotubes (CNT) and/or magnetite (Fe3O4), to separate the GO sheets even further and/or to render the nanocomposite magnetic. Palladium nanoparticles (Pd NPs) was embedded into the matrix of the nanocomposite using Pd(OAc)2 as the palladium source. SEM and TEM were used to visually investigated the sheet separation of GO, the entrapment of GO in chitosan and embedding of Pd NPs in the nanocomposite matrix. The properties of the GO nanocomposites were investigated by Attenuated Total Reflection Fourier transform infra-red spectroscopy (ATR FTIR), Thermo-Gravimetric Analysis (TGA), Inductively Coupled Plasma–Optical emission spectrometry (ICP-OES) and X-ray Photoelectron Spectroscopy (XPS). The applicability of these palladium-containing nanocomposites was investigated for the reduction of nitrophenol in the presence of NaBH4. The reduction reactions were followed by UV-Vis and their kinetic parameter were determined. All five Pd-containing nanocomposites displayed excellent catalytic activity towards the reduction of aromatic nitroarenes. The reduction of the nitrophenol compounds over all the nanocomposites showed pseudo first order kinetics with the estimate k′obs, between 2.0 × 10−3 and 2.5 × 10−2 s−1, and a possible mechanism for the reaction is proposed. Five Pd-containing nanocomposites, have been prepared by entrapping GO in chitosan and/or incorporating CNT and/or magnetite NP additives into the nanocomposites, followed by entrapment of Pd nanoparticles. The nanocomposites exhibited excellent catalytic activity towards the reduction of nitrophenol. ATR FTIR, SEM, TEM, TGA and XPS are effective characterisation tools of these surfaces. [ABSTRACT FROM AUTHOR]

In this work, we report a ultrahigh specific absorption rate (SAR) performance in Zn-substituted magnetite superparamagnetic (SPM) nanoparticles (NPs) for potential application in magnetic hyperthermia (MHT)-based cancer treatment. Although MHT shows promise in cancer therapy, challenges such as low heating performance, agglomeration of magnetic nanoparticles (MNPs) in blood veins, cytotoxicity, and hemocompatibility have hindered clinical uses. To overcome these challenges, we adopted a reverse-micelles based coprecipitation synthesis approach to prevent MNPs agglomeration and optimized the substitution of Zn ions in magnetite to enhance heating performance. Calorimetric measurements showed SAR values of 118 W/g and 181 W/g for magnetite NPs using the initial slope method (ISM) and Box Lucas method (BLM), respectively. Through our compositional optimizations, we achieved a significant increase in SAR value by consciously substituting Zn2+ ions in the magnetite lattice. Specifically, we obtained SAR values of 325 W/g and 579 W/g (>300% increase) for Zn 0.3 Fe 2.7 O 4 MNPs using ISM and BLM, respectively. This enhancement can be attributed to improved saturation magnetization (174–257 kA/m) and magneto-crystalline anisotropy (12–24 kJ/m3). The increase in saturation magnetization in the magnetite MNPs can be explained by the higher magnetic moment resulting from increased Zn concentration up to Zn x Fe 3-x O 4 (x = 0.3), strengthening the J AB interaction. However, further increases in Zn concentration lead to a decrease in saturation magnetization due to non-collinearity, as described by the Yafet-Kittle model. Our optimized MNPs exhibit improved heating performance, enabling the use of lower MNPs concentrations for cancer treatment, reducing potential toxicity effects. Biocompatibility investigations demonstrated a low hemolysis rate (<5%) in a hemolysis assay with red blood cells and high cytocompatibility (>92% cell viability) in MTT assays for all compositions, confirming their potential suitability for clinical applications. This study offers a promising approach to enhance SAR performance, addressing MHT-based cancer treatment challenges, and improving clinical suitability. • Achieved 300% increase in SAR, indicating enhanced heating performance for cancer treatment. • Optimized magnetic properties through the Zn ions substitution making it suitable for magnetic hyperthermia treatment. • Demonstrated low toxicity and high biocompatibility, ensuring their suitability for clinical treatment. [ABSTRACT FROM AUTHOR]

Zero-valent iron (Fe0) is restricted in phosphate removal due to the formation of a passive P–Fe layer on its surface. A micro-electric field (0.20 mA cm−2) was employed in Fe0 column to facilitate iron corrosion for enhanced phosphate removal with a Fe0 column as the control. The performance of two columns was compared by batch experiment at a Fe0 filling rate of 10 vol% with quartz sand as dispersing media. The stability and reusability of micro-electric field driven Fe0 (MFD-Fe0) column was estimated by cyclic test. Solid phase analysis showed promoted iron corrosion, iron ion generation, and secondary mineral production such as lepidocrocite and magnetite in the MFD-Fe0 column. Since iron ions tended to precipitate with phosphate, and iron minerals provided reaction sites for phosphate adsorption, the MFD-Fe0 column achieved an enhanced phosphate removal of 94.1%, 2.8 times higher than that of the Fe0 column. The increase of current density from 0 to 0.20 mA cm−2 significantly improved phosphate removal from 24.5% to 94.1%, further demonstrating the promoting effect of micro-electric field on iron corrosion. The MFD-Fe0 column also possessed excellent stability and reusability. It only showed a slight decrease of phosphate removal from 94.1% to 89.7% in eight cycles. It restored a phosphate removal capacity of 97.4% as compared to the initial MFD-Fe0 column by eluting iron (hydro)oxides on Fe0 and quartz sand surfaces with sulfuric acid. This study indicated that MFD-Fe0 is a promising method to remove phosphate from water and an alternative strategy for overcoming Fe0 passivation. [Display omitted] • Micro-electric field driven Fe0 (MFD-Fe0) column was established for enhanced phosphate removal. • MF promoted iron ion and reactive mineral generation for phosphate flocculation and adsorption. • Remarkably improved phosphate removal was achieved in MFD-Fe0 column. • MFD-Fe0 column also possessed excellent stability and reusability. [ABSTRACT FROM AUTHOR]

This study aims to identify the content and particle shape, and to determine the type, of iron oxide in the magnetic material from Aceh iron sand. The samples were taken from four seacoast locations, namely Mon Klayu, Mantak Tari, Lam Panah and Syiah Kuala beaches. The magnetic materials are separated from the iron sand using an external magnet, washed out with distilled water and dried at 80 °C. The materials were characterized by XRD and SEM. The results show that the magnetic materials sampled from Aceh iron sand contain 88.93, 96.3, 92 and 85% of Fe, respectively. The iron oxide found in Aceh iron sand was predominantly magnetite (Fe3O4) or ilmenite (Fe, Ti3)O4; however, there are also other oxide impurities, such as silica and chromium oxides. The identified minerals were classified as lithogenous sedimentary volcanic minerals, which have a black colour and spherical shape. Related to that, the sampling locations of these minerals were types of volcanic minerals and lithogenous sediments, since the position of the coast locations is adjacent to Burni Telong, Peut Sago and Seulawah volcanos, and the minerals are carried by the stream to the beaches through the river flow, which further supports the assumption of their volcanic origins. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of FexOy nanoparticles were carried out in order to study reaction parameters influence in a spray flame reactor. FexOy powders were prepared with three different precursors aiming to understand how the reactor conditions, dispersion gas flow, and precursor solution flow affect morphology, shape, particle size distribution, crystalline phases, and residue content of the obtained materials. Thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman spectroscopy were employed to characterize the materials. In addition, magnetic behavior of the obtained samples was evaluated. It was found that the evaluated parameters influenced the residue contents obtaining weight changes from 10 to 35%. Particle size distribution centers also showed differences between 17 and 24 nm. By XRD, Raman, and TEM, the presence of hematite (a-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) was evidenced and explained based on the gas and liquid content in the flame. Additionally, the saturation magnetization was measured for selected samples, obtaining values between 26 and 32 emu g−1. These magnetic measurements were correlated with the crystalline phase composition and particle size distributions. [ABSTRACT FROM AUTHOR]

Magnetite iron oxide nanoparticles synthesized using the co-precipitation methods were further functionalized with activated carbon. The magnetite-activated carbon nanoparticles were characterized by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. X-ray diffraction and Fourier transform infrared confirmed the functionalization of the Fe3O4 nanoparticles with the activated carbon. The X-ray diffraction studies demonstrate that magnetite-activated carbon nanoparticles were indexed into the spinel cubic lattice with a lattice parameter of 0.833 nm and an average particle size of about 14 nm. Various parameters such as dislocation density, microstrain, and surface morphological studies were calculated. However, this work implicated the use of magnetite-activated carbon nanoparticles in antibacterial studies. Further, the antibacterial effect of magnetite-activated carbon nanoparticles was evaluated against three pathogenic bacteria, which showed that the nanoparticles have moderate antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Proteus mirabilis and Pseudomonas aureginosa) pathogenic bacterial strains in the presence of different magnetite-activated carbon nanoparticle concentrations at room temperature. [ABSTRACT FROM AUTHOR]

Purpose: Acoustic coupling baths, nominally composed of degassed water, play important roles during transcranial focused ultrasound surgery. However, this large water bolus also degrades the quality of intraoperative magnetic resonance (MR) guidance imaging. In this study, we test the feasibility of using dilute, aqueous magnetite nanoparticle suspensions to suppress these image degradations while preserving acoustic compatibility. We examine the effects of these suspensions on metrics of image quality and acoustic compatibility for two types of transcranial focused ultrasound insonation regimes: low‐duty cycle histotripsy procedures and high‐duty cycle thermal ablation procedures. Methods: Magnetic resonance guidance imaging was used to monitor thermal ablations of in vitro gel targets using a coupling bath composed of various concentrations of aqueous, suspended, magnetite nanoparticles in a clinical transcranial transducer under stationary and flowing conditions. Thermal deposition was monitored using MR thermometry simultaneous to insonation. Then, using normal degassed water as a coupling bath, various concentrations of aqueous, suspended, magnetite nanoparticles were placed at the center of this same transducer and insonated using high‐duty cycle pulsing parameters. Passive cavitation detectors recorded cavitation emissions, which were then used to estimate the relative number of cavitation events per insonation (cavitation duty cycle) and the cavitation dose estimates of each nanoparticle concentration. Finally, the nanoparticle mixtures were exposed to low‐duty cycle, histotripsy pulses. Passive cavitation detectors monitored cavitation emissions, which were used to estimate cavitation threshold pressures. Results: The nanoparticles reduced the MR signal of the coupling bath by 90% in T2‐ and T2*‐weighted images and also removed almost all imaging artifacts caused by coupling bath motion. The coupling baths caused <5% changes in peak temperature change achieved during sonication, as observed via MR thermometry. At low duty cycle insonations, the nanoparticles decreased the cavitation threshold pressure by about 15 ± 7% in a manner uncorrelated with nanoparticle concentration. At high duty cycle insonations, the 0.5 cavitation duty cycle acoustic power threshold varied linearly with nanoparticle concentration. Conclusions: Dilute aqueous magnetite nanoparticle suspensions effectively reduced MR imaging artifacts caused by the acoustic coupling bath. They also attenuated acoustic power deposition by <5%. For low duty cycle insonation regimes, the nanoparticles decreased the cavitation threshold by 15 ± 7%. However, for high‐duty cycle regimes, the nanoparticles decreased the threshold for cavitation in proportion to nanoparticle concentration. [ABSTRACT FROM AUTHOR]

In this paper, we present a simple and inexpensive method for synthesizing conductive polyaniline and magnetite composites. Firstly, the magnetite was synthesized by precipitation in basic medium from FeCl3, and the Rietveld refinement confirmed the spinel structure. Different amounts of magnetite were used in the in situ synthesis of Pani- Fe3O4 composites to determine the influence, resulting in the following materials: Pani-Fe3O4 (1) with 0.06 g and Pani-Fe3O4 (2) with 0.24 g. The x-ray diffractogram demonstrates that interaction occurs between the polyaniline chains and the magnetite particles in the composites. Infrared and ultraviolet-visible vibrational spectra indicate that the composites are in the state of oxidation polyaniline salt emerald, which is the conductive form of greatest interest. Scanning electron microscopy images show that composites have particles with no definite geometry in the form of clusters, and the best homogeneity was achieved in the composite with the highest amount of magnetite. Evidence indicates that Pani-Fe3O4 (2) material with 0.24 g of magnetite to be incorporated in polyaniline synthesis may have more technologically interesting properties, but further studies will be needed for confirmation. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility (χ lf) is a sensitive, fast, and accurate technique to detect soil pedogenic processes and features, and can improve understanding of soil-forming factors. The aim of this study was to determine catenary groupings of geochemical segments by identifying the relationship between magnetic susceptibility and the soil-forming factors within and along the landscape. Soil physical and chemical properties, as well as soil mineralogy were evaluated in twenty-two topsoil samples from three different landscapes in southern Brazil. The bulk χ lf and frequency-dependent susceptibility (χ fd) were also measured, represented by i) air-dried fine earth (< n μm, χ lf ADFE) ii) after dithionite-citrate-bicarbonate treatment (χ lf CBD), and iii) the parent material (χ lf ROCK). Geochemical segments were grouped using multivariate analysis. Our results indicate that soil parent material and climate, are first order factors for the pedogenic enhancement of magnetic minerals. Magnetic susceptibility of air-dried fine earth (χ lf ADFE) is widely variable, from 11.00 to 2.075 × 10−8 m3 kg−1. χ lf was higher in soils developed on basalt, and much lower for soils developed on sandstone. χ lf ADFE also reveals a strong positive linear correlation with χ lf CBD (r = 0.96) and a moderate positive linear correlation with "free" and total Fe content (r = 0.49 and 0.69, respectively). The χ fd (< 2%) indicates samples in which either non-SP grains dominate the assemblage or where the SP fraction is <0.03 nm. After CBD dissolution there is an increase in χ lf values. The rate of iron weathering and iron release, driven by hydrolysis and oxidation, and reductive dissolution of magnetite affect the formation and/or persistence of secondary iron oxides in some of the soil transects. Both principal component analysis (PCA) and cluster analysis group soils from a) crest and upper slope locations, b) down slope and sandstone areas, and c) valley floors, indicating that magnetic susceptibility is an effective proxy for soil properties for grouping and identifying pedogenic/geochemical segments along a landscape of 360 km2. • Lithology, relief and climate conditions affect magnetic properties. • Magnetite did not dissolve completely under gleying conditions. • Magnetic measurements were effective to group and identify soil transects of different landscapes • Magnetic susceptibility can be used as a fast, cost-effective proxy for soil classification. [ABSTRACT FROM AUTHOR]

Magnetite, Fe3O4 exhibits the strongest magnetism of transition metal oxides. Hematite, α-Fe2O3 being the most stable oxide and semiconductor type n under environmental conditions, can be widely used in catalysts, pigments and gas sensors. Iron oxide nanoparticles (Fe3O4 and γ-Fe2O3) with superparamagnetic properties and low toxicity, are particularly useful for catalytic applications especially in the medical field. For these applications, the Fe3O4 and γ-Fe2O3 nanoparticles are usually smaller than 20 nm, where they have superparamagnetic properties, i.e. a high magnetic saturation moment and almost zero coercivity. This review presents the theoretical concepts of the structure properties of this oxide and the elaboration methods that make iron oxide the ideal candidate for catalytic applications. [ABSTRACT FROM AUTHOR]

Anaerobic batch tests with a 22 full-factorial design of ammonia (1.5, 6.5 g N/L) and magnetite concentrations (0, 20 mmol/L) were conducted separately for methanogenic degradation of acetate, propionate, and butyrate (volatile fatty acids (VFAs)) to 1) quantify the effect of magnetite as an enhancer in methanogenic degradation of each of the VFAs in conditions without ammonia stress (1.5 g N/L) and with ammonia stress (6.5 g N/L), and 2) identify methanogenic consortia that are related to such enhancement. Among the three VFAs, methanogenic degradation of propionate was the least feasible (57% lower specific methanogenic activity R CH4 and three times longer lag time λ than acetate degradation). At low ammonia concentration, only propionate showed improvement in R CH4 (46%) with supplementation of magnetite. In the ammonia-stressed condition without magnetite, R CH4 decreased by 38–58% and λ increased 2.2–8.8 times for all VFAs; magnetite supplementation significantly alleviated these effects. These results demonstrate that magnetite supplementation effectively increases methanogenic degradation of the VFAs even under ammonia-stressed conditions. 16S metagenomic sequencing revealed that distinctive methanogenic consortia were active in the different combinations of substrate, ammonia and magnetite. Alkaliphilus , Hyphomonadaceae SWB02 and Clostridia DTU014 , Clostridia D8A-2 , Christensenellaceae R-7 group and Rikenellaceae DMER64 were identified as potential syntrophic bacteria that can establish magnetite-mediated direct electron transfer with methanogens (Methanosaeta concilii , Methanosaeta harundinacea , Methanolinea tarda , Methanoculleus bourgensis and Methanosarcina spp.) during methanogenic degradation of VFAs. The results may be useful as a reference to develop effective strategies using magnetite supplementation to remediate anaerobic digestion processes that have been afflicted by VFA accumulation and ammonia inhibition. • Magnetite effect on AD of VFAs under NH 3 -stressed condition was tested. • Methanogenic degradation of propionate was improved by magnetite addition. • Magnetite alleviated NH 3 inhibition of methanogenic degradation of VFAs. • Distinctive syntrophic consortia were responsible for such enhancement effect. [ABSTRACT FROM AUTHOR]

In the given paper, we evaluate the efficiency of iron oxide (magnetite in the form of water suspension) nanoparticles (50-120 nm) in intensification of cracking reactions of heavy components of biodegradated oil. The physical simulation of thermal influence on heavy oil in the presence of synthesized catalyst (concentration = 0.3%) was carried out in autoclave at temperature ranges of 150-300°С and reaction period of 24 hours. According to the results of SARA-analysis and dynamic viscosity measurements, the destructive hydrogenation processes that were catalyzed by iron oxide were conducted already at 200°С. However, the significant effect was achieved at 300°С (the degree of viscosity reduction was higher than 67%). [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A three-component nano-electrocatalyst, magnetite coated molybdenum disulfide hybridized with reduced graphene oxide (Fe 3 O 4 @MoS 2 /RGO), is synthesized by a two-step hydrothermal method. This catalyst is applied as an effective substitution for the platinum catalyst in methanol oxidation and hydrogen evolution reactions. Cyclic voltammetry, chronoamperometry, and linear sweep voltammetry are used to evaluate the performance of the electrocatalyst in acidic and basic media. The results of methanol oxidation reaction on the hybridized nano-electrocatalyst showed good electrocatalytic properties with considerable diffusion currents. This fact is confirmed by the Tafel plots and the calculated kinetic parameters of electron transfer. Fe 3 O 4 @MoS 2 /RGO showed an anodic transfer coefficient and exchange current of 0.464 and 4.80 × 10−8, respectively that are higher than Fe 3 O 4 /RGO. The presence of the porous MoS 2 in catalyst has a key effect on supplying electroactive sites for electron transfer. Also, the high actual surface area obtained for the hybridized nano-electrocatalyst (A = 0.0295 cm2). The maximum power density of 35.03 mW cm−2 obtained for a single cell containing the prepared hybridized catalyst as the anode which shows a competitive feature of the synthetic catalyst compared to other reports. Furthermore, the synthetic catalyst shows the low-value overpotential of 108 mV and Tafel slope of 48 mV dec−1 during the hydrogen evolution process in acidic media. This is attributed to the synergistic effect between Fe 3 O 4 and MoS 2 and also increase the electron transfer rate due to adding conductive RGO to the catalyst. The results show that the synthetic nanocatalyst can have promising applications for hydrogen evolution and methanol oxidation reactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnetic nanomaterials were formed by pulsed laser ablation of iron in water and air. • Material ablated in water contained spherical particles of Fe 3 O 4 , Fe 2 O 3 , FeO and Fe. • Material ablated in air contained more Fe 3 O 4 and nitrogen (N-O, N-H or FeN x) • The surface composition and electrokinetic properties of the materials differed. • Material obtained in air is more stable in colloids due to its surface composition. Abstract Magnetic nanomaterials were synthesized using a method of pulsed laser ablation of an iron target in water (PLAL) and in air (PLAG). The microstructure and composition of the obtained materials differed. Spherical nanoparticles (NPs) of 2–80 nm containing Fe 3 O 4 , α-Fe 2 O 3 , γ-Fe 2 O 3 , FeO and Fe were obtained using PLAL. According to the XPS and FTIR data, the surfaces of these particles contained both Fe 3 O 4 and Fe 2 O 3. PLAG led to the formation of NPs of 2–120 nm and 2-D lamellar structures up to 1 μm. This material contained more magnetite and nitrogen species, presumably iron nitrides. This material's surface contained FeOOH; the OH-group content was very high. It exhibited the greatest sedimentation stability and zeta potential value, while magnetic NPs (MNPs) obtained in water were less stable in colloids. The difference in the magnetic parameters of the two materials can be connected to not only the different composition (different magnetite content and nitrogen species presence) but also their structural features. Thus, PLAL and PLAG methods allowed for obtaining magnetic nanostructured materials with different characteristics suitable for application in different fields. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide nanoparticles (Fe3O4) provide multiple advantages for drug delivery application due to their inertness, non-toxicity, biocompatibility, and ease of detection as the diagnostic tool for contrast imaging in the human body. To protect against oxidation, preferably covalently bonded a surfactant for coating Fe3O4 is required. For this purpose, in the present study, oleic acid (OA) was applied to stabilize Fe3O4 magnetic nanoparticles via onepot-three-component reaction. Mild conditions as a well as simple reaction could be attributed to this method in producing Fe3O4-OA nanoparticles. The amount of oleic acid (OA) was studied to explore properties of the resulted nanoparticles. Infrared spectroscopy revealed that OA is chemisorbed via a carboxyl group onto the surface of the iron oxide nanoparticle and is coordinated symmetrically to the oxide atoms. Furthermore, there is a ligand exchange between -OH groups and -COO groups on the Fe3O4 nanoparticle surfaces. X-ray diffraction (XRD) spectra indicated that Fe3O4 phase was predominantly obtained beside small amount of γ-Fe2O3 phase. The average crystallite size of the synthesized Fe3O4 nanoparticles at different amount of OA was found in the range of 6.60 nm to 9.48 nm. Magnetic properties of the nanoparticles were determined by electron spin resonance (ESR). The gradient curve of ESR spectra revealed that Fe3O4 and OA-coated Fe3O4 nanoparticles possess significantly different magnetic properties. [ABSTRACT FROM AUTHOR]

In this work, microwave-shielding behavior of epoxy thermosetting plastic reinforced with silanized Cu and Cu-Fe3O4 compound particles were studied in frequency bands E, F, I, and J. The principal aim of this work is to evaluate the significant advantage of surface-modified magnetic and conductive fillers over as-received fillers in microwave shielding. The conductive and magnetic properties of epoxy resin were improved by additions of Cu and Fe3O4 particles. Compound particles of Cu-Fe3O4 were produced by mechanical alloying process (ball milling). The compound particles were surface treated by 3-Aminopropyltrimethoxysilane (APTMS) for better dispersion in epoxy resin matrix. Functional groups on particle’s surface after silane surface treatment were confirmed by FT-IR spectra analysis. The TEM images revealed that effective Cu-Fe3O4 particle compounding was formed at 1 h milling time. The maximum dielectric constant of 6.8 and magnetization of 675E−6 were observed for surface-modified compound particle-reinforced epoxy composite designation RCF2. Similarly, maximum microwave attenuation of 35% (44 dB) was observed for surface-modified compound particle-reinforced composite designation RCF2 in ‘J’-band frequency. [ABSTRACT FROM AUTHOR]

This work reports the synthesis, characterization, and electrochemical properties of magnetite nanoparticles (MNPs). MNPs were prepared by a simple solvothermal method at 200 °C for 8 h using three different concentrations of poly(vinyl)pyrrolidone (PVP). Transmission electron microscopy (TEM) images of the prepared samples reveal agglomerated like-sphere shape with mean particle sizes of ∼ 50–90 nm. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) from TEM confirm the formation of pure phase Fe 3 O 4 nanoparticles. The existence of PVP on the surface of the prepared samples is confirmed by high resolution X-ray photoemission spectroscopy (XPS). Consequently, the electrochemical performances of MNPs prepared using different PVP concentrations were evaluated by using the three-electrode cell system within 6.0M KOH. The results show that the specific capacitances was determined to be 396, 344, and 327 F/g at a scan rate of 2 mV/s and 197, 95, and 75 F/g at a current density of 3.0 A/g for MNPs samples prepared using 0.5 g, 1.0 g, and, 1.5 g of PVP, respectively. MNPs electrode showed the high power density of 777.65 W/kg with 7.36 Wh/kg of energy density addressing in high power density SC region. The cycle stability after 1000 cycles was also tested at 3 A/g and demonstrated the improvement of stability as increasing the amount of PVP. This indicates that the addition of surface element polymer plays a role in the cycle stability of supercapacitor devices. [ABSTRACT FROM AUTHOR]

In this work, the electrochemical response of Vanadium(V) species on magnetite film electrodes is investigated. Magnetite is deposited electrochemically on glassy carbon electrodes, with an intermediate layer of poly(thiophene) to avoid water infiltration. These electrodes show good reproducibility and stability up to pH = 2.0. Mononuclear V(V) species show low electroactivity on this surface. Cyclic voltammetry at low V(V) concentration shows that it is electroactive only at pH < 3. i.e. as VO 2 + . A single reduction peak is observed at ~− 0.7 V vs SCE (at 50 mV s − 1 ), and an oxidation one at ~ 0.5 V vs SCE, indicating high irreversibility of the V(V)/V(IV) couple; these peaks are found to be solution phase reactions. These features are interpreted in terms of mononuclear V species. At higher V concentrations, where polymeric V(V) species are dominant, a somewhat higher electroactivity is observed, with two reduction peaks and two/three oxidation peaks. [ABSTRACT FROM AUTHOR]

Hypothesis Ligand exchange is a widely-used method of controlling the surface chemistry of nanomaterials. Exchange is dependent on many factors including the age of the core particle being modified. Aging of the particles can impact surface structure and composition, which in turn can affect ligand binding. Experiments To quantify the effects of aging on ligand exchange, we employed a technique to track the exchange of radiolabeled 14 C-oleic acid with unlabeled, oleic acid bound to iron oxide nanoparticles. Liquid scintillation counting (LSC) was used to determine the amount of 14 C-oleic acid adsorbing to the particles throughout the duration of the exchange for particles aged for 2 days, 7 days, and 30 days. Findings Results revealed an increase in the total amount of ligands exchanged with aging up to 30 days. Kinetic analysis of these results revealed a significant decrease in the overall rate of ligand exchange between 2 and 30 days. The change in extent of adsorption with age could suggest increased availability of free binding sites. A follow-up study comparing exchange with oxidized and unoxidized particles suggested this increase in ligand adsorption may be due to changes in the Fe 2+ /Fe 3+ ratio on the surface as the particles aged. [ABSTRACT FROM AUTHOR]

Iron oxide nanostructures (IONs) in combination with graphene or its derivatives-e.g., graphene oxide and reduced graphene oxide-hold great promise toward engineering of efficient nanocomposites for enhancing the performance of advanced devices in many applicative fields. Due to the peculiar electrical and electrocatalytic properties displayed by composite structures in nanoscale dimensions, increasing efforts have been directed in recent years toward tailoring the properties of IONs-graphene based nanocomposites for developing more efficient electrochemical sensors. In the present feature paper, we first reviewed the various routes for synthesizing IONs-graphene nanostructures, highlighting advantages, disadvantages and the key synthesis parameters for each method. Then, a comprehensive discussion is presented in the case of application of IONs-graphene based composites in electrochemical sensors for the determination of various kinds of (bio)chemical substances. [ABSTRACT FROM AUTHOR]

A facile strategy developed for the fabrication of composite material comprising mesopores and representing an iron oxide core/encapsulated in carbon nanodisk shell using Fe-based MOF as precursor. Catalytic carbonization of Fe 2+ coordinated 1,4,5,8 -naphthaleneteracarboxylic dianhydride MOF at 725 °C under N 2 atmosphere followed by air treatment at 300 °C yielded Fe 3 O 4 nanoparticles encapsulated in mesoporous carbon matrix (FeMCNA-300). The XRD and N 2 adsorption studies confirm the presence of Fe 3 O 4 nanoparticles and mesopores in the carbon matrix, respectively. MOF precursor generates mesopores of narrow pore size distribution without aid of structure directing agent in the carbon shell through straightforward catalytic reduction of core iron oxide. FeMCNA-300 demonstrated outstanding catalytic activity towards the degradation of 150 ppm of methylene blue (MB) dye in water with 84% TOC conversion in 15 min at room temperature. MB and oxidant H 2 O 2 interact with iron oxide nanoparticles through confined mesoporous channel in the FeMCNA-300 carbon nanodisk. This permits the generated OH at the surface of magnetite nanoparticles to instantly oxidize the MB molecules adsorbed in the close proximity. FeMCNA-300 under ultra-sonication decolourise MB completely with high TOC conversion of about 84% at maximum iron leaching of 2% up to five successive recycles. [ABSTRACT FROM AUTHOR]

Acetate is a key intermediate in anaerobic crude oil biodegradation and also a precursor for methanogenesis in petroleum reservoirs. The impact of iron oxides, viz. β-FeOOH (akaganéite) and magnetite (FeO), on the methanogenic acetate metabolism in production water of a high-temperature petroleum reservoir was investigated. Methane production was observed in all the treatments amended with acetate. In the microcosms amended with acetate solely about 30% of the acetate utilized was converted to methane, whereas methane production was stimulated in the presence of magnetite (FeO) resulting in a 48.34% conversion to methane. Methane production in acetate-amended, β-FeOOH (akaganéite)-supplemented microcosms was much faster and acetate consumption was greatly improved compared to the other conditions in which the stoichiometric expected amounts of methane were not produced. Microbial community analysis showed that Thermacetogenium spp. (known syntrophic acetate oxidizers) and hydrogenotrophic methanogens closely related to Methanothermobacter spp. were enriched in acetate and acetate/magnetite (FeO) microcosms suggesting that methanogenic acetate metabolism was through hydrogenotrophic methanogenesis fueled by syntrophic acetate oxidizers. The acetate/β-FeOOH (akaganéite) microcosms, however, differed by the dominance of archaea closely related to the acetoclastic Methanosaeta thermophila. These observations suggest that supplementation of β-FeOOH (akaganéite) accelerated the production of methane further, driven the alteration of the methanogenic community, and changed the pathway of acetate methanogenesis from hydrogenotrophic methanogenesis fueled by syntrophic acetate oxidizers to acetoclastic. [ABSTRACT FROM AUTHOR]

Benefiting from the hydrophilicity and modifiability, aminated iron oxide nanoparticles play significant roles in the construction of magnetically responsive functional materials, and are then widely used in the field of biomedicine and water purification. Using the deep eutectic solvent (DES) composed of urea and choline chloride as an electrolyte, amino-grafted water-soluble maghemite (γ -Fe 2 O 3) nanocrystals have been synthesized by organic electrolysis (DES-electrolysis). In the present work, the DES containing ferrous ions is used as the electrolyte to verify whether magnetite (Fe 3 O 4) can be prepared by that organic electrolysis strategy. The results show that, regardless of the presence or absence of ferrous ions in the DES-based electrolyte, the resulting nanocrystals are maghemite rather than magnetite. The synthesized amino-grafted γ -Fe 2 O 3 nanoparticles can also be highly and stably dispersed in water. The present work deepens the understanding of the formation mechanism of amino-grafted water-soluble maghemite nanocrystals synthesized by DES-electrolysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• An innovative galvanic cell simulated electrochemical reactions in pipe scale. • Electrochemical evidence verified the reduction of iron oxides in anoxic conditions. • Kinetics plays most important role in the reduction of iron oxide scale. • Goethite was transformed into magnetite as a result of the reduction of pipe scale. Iron release from pipe scale is an important reason for water quality deterioration in drinking water distribution systems (DWDS) globally. Disruption of pipe scale, release and transformation of iron compounds are hot topics in the field of water supply. The aim of this study is to determine whether and how ferric components in pipe scale be reduced under anoxic condition. In this study, new investigation approaches were applied, which include simplifying the complex scale into electrode pairs, developing novel simulating reactors and conducting tailored electrochemical assays. A galvanic cell reactor with anode of metallic iron (Fe0) and various cathode made of certain iron oxide (FeO x) was firstly developed to simulate the complex niche and components of pipe scale. Electrochemical methods were used to study the reduction characteristics of scale. The results proved that reduction of iron oxide scale did occur under anoxic condition. Electromotive forces between various electrodes match the Nernst Equation quite well. As main components in pipe scale, lepidocrocite (γ-FeOOH) was found to be the most reducible iron oxide but at low rate, while goethite (α-FeOOH) has weak reducibility but can be quickly reduced. As a result of electrochemical reactions, goethite in pipe scale was transformed into magnetite (Fe 3 O 4). By these means, electrochemical reaction mechanisms of pipe scale disruption were revealed, which is helpful to restrain pipe corrosion and water deterioration in DWDS. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, an integrated system of Fe0 and hydrogenotrophic microbes mediated by nitrate (nitrate-mediated bio-Fe0, NMB-Fe0) was established to remediate Cd(II)-contaminated sediment. Solid phase characterization confirmed that aqueous Cd(II) (Cd(II) aq) was successfully immobilized and enriched on iron surface due to promoted iron corrosion driven by hydrogenotrophic denitrification and subsequent greater biomineral production such as magnetite, lepidocrocite and green rust. Compared to a Cd(II) aq removal of 21.1% in overlying water of the nitrate-mediated Fe0 (NM-Fe0) system, the NMB-Fe0 system obtained a much higher Cd(II) aq removal of 83.1% after 7 d remediation. The leaching test and sequential extraction results also showed that the leachability of Cd(II) decreased by 75.9% while the residual fraction of Cd(II) increased by 185.7% in comparison with untreated sediment. Besides, the Cd(II) aq removal raised with the increase of nitrate concentration and Fe0 dosage, further revealing the promotion effect of nitrate on Cd(II) removal by bio-Fe0. This study highlighted the involvement of bio-denitrification in the remediation of Cd(II)-contaminated sediment by Fe0 and provided a new insight to enhance its reactivity and applicability for Cd(II) immobilization. [Display omitted] • Hydrogenotrophic denitrification promoted Fe0 corrosion and biomineral formation. • Nitrate-mediated biological iron corrosion enhanced Cd(II) immobilization. • Leachability and bioavailability of Cd(II) in sediment remarkably decreased. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide nanosheets (GO) are dual functionalized with Fe 3 O 4 nanoparticles and hydroxypropyl cellulose (CLS) for chemo/phototherapy. The TEM, XRD, FTIR, Raman, UV, TG, DLS, and VSM analyses were used to confirm the CLS and Fe 3 O 4 incorporated GO (CLS@mGO) nanobiocomposite structure. Functionalization of magnetite graphene oxide surface by CLS not only improved biocompatibility, colloidal stability, and entrapment efficiency for paclitaxel (PTX) but also accelerated PTX release. Under 808 nm laser light, the CLS@mGO-PTX nanobiocomposite displayed good photothermal features. The CLS@mGO-PTX nanobiocomposite exhibited high photothermal conversion efficiency (47.85%) and photo stability. The notable synergistic chemo/photothermal impacts have also been determined by the in vitro experiments in killing MCF-7 cancer cells. The results of these experiments exhibited that compared to single phototherapy and chemotherapy, chemo/phototherapy could more effectively kill cancer cells by synergetic anticancer impact. Therefore, the CLS@mGO-PTX nanobiocomposite has great potential for chemo/phototherapy. [Display omitted] • CLS-functionalized magnetite mGO nanobiocomposite was developed for chemo/PTT. • CLS@mGO showed enhanced biocompatibility, thermal, colloidal and photo stability. • It displayed superparamagnetic behavior and high entrapment efficiency for PTX. • A synergetic therapeutic effect was noticed when utilizing 808 nm laser and PTX. • CLS@mGO-PTX nanobiocomposite showed pH-sensitive PTX release. [ABSTRACT FROM AUTHOR]

The present study describes a novel and very sensitive electrochemical assay for determination of hydrogen peroxide (H2O2) based on synergistic effects of reduced graphene oxide- magnetic iron oxide nanocomposite (rGO-Fe3O4) and celestine blue (CB) for electrochemical reduction of H2O2. rGO-Fe3O4 nanocomposite was synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy and cyclic voltammetry. Chitosan (Chit) was used for immobilization of amino-terminated single-stranded DNA (ss-DNA) molecules via a glutaraldehyde (GA) to the surface of rGO-Fe3O4. The MTT (3-(4,5-Di methyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide) results confirmed the biocompatibility of nanocomposite. Experimental parameters affecting the ss-DNA molecules immobilization were optimized. Finally, by accumulation of the CB on the surface of the rGO-Fe3O4-Chit/ssDNA, very sensitive amperometric H2O2 sensor was fabricated. The electrocatalytic activity of the rGO-Fe3O4-Chit/DNA-CB electrode toward H2O2 reduction was found to be very efficient, yielding very low detection limit (DL) of 42 nM and a sensitivity of 8.51 μA/μM. Result shows that complex matrices of the human serum samples did not interfere with the fabricated sensor. The developed sensor provided significant advantages in terms of low detection limit, high stability and good reproducibility for detection of H2O2 in comparison with recently reported electrochemical H2O2 sensors. [ABSTRACT FROM AUTHOR]

The wet chemical route of co-precipitation method is used to synthesize ultrafine magnetite for study. Using XRD, the estimated average size was ~24nm and confirmed the phase Fe3O4 with inverse spinal structure. The M-H loop of the Fe3O4 has investigated the magnetic entities and has confirmed the single domain nature. The paper has reported the magnetization saturation of Iron Oxide nanoparticles (IONs) increases with wetting. The effect of wetting has been discussed from the theoretical point of view. Dependency of magnetic property on the K, a and size for an effect was considerably analyzed in this study. [ABSTRACT FROM AUTHOR]

Bulk magnetite (Fe3O4), the loadstone used in magnetic compasses, has been known to exhibit magnetoelectric (ME) properties below -10 K; however, corresponding ME effects in Fe3O4 nanoparticles have been enigmatic. We investigate quantitatively the ME coupling of spherical Fe3O4 nanoparticles with uniform diameters (d) from 3 to 15 nm embedded in an insulating host, using a sensitive ME susceptometer. The intrinsic ME susceptibility (MES) of the Fe3O4 nanoparticles is measured, exhibiting a maximum value of -0.6 ps/m at 5 K for d = 15 nm. We found that the MES is reduced with reduced d but remains finite until d = -5 nm, which is close to the critical thickness for observing the Verwey transition. Moreover, with reduced diameter the critical temperature below which the MES becomes conspicuous increased systematically from 9.8 K in the bulk to 19.7 K in the nanoparticles with d = 7 nm, reflecting the core-shell effect on the ME properties. These results point to a new pathway for investigating ME effect in various nanomaterials. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 nanoparticles have been obtained by ageing method under controlling such conditions as follows: temperature, oxidation time, ageing time. Fe 3 O 4 nanopowders have been examined by a transmission electron microscopy (TEM) and by X-ray diffractometry (XRD). XRD results showed that under time of the oxidant addition up to 30 min only a crystalline phase of magnetite had been formed and also under such condition but time of the oxidant addition more then 30 min an γ-FeOOH phase had been revealed. It has been established that size of Fe 3 O 4 nanoparticles increased in the range of 42 nm to 81 nm with the increasing time of the ageing process. In order to obtain Fe 3 O 4 nanoparticles with a narrow range of size distribution, optimal parameters have been determined. Nanoparticles with the standard deviation equal to 10 nm have been obtained with an ambient temperature during the deposition process (deposition temperature) of 10 °С and with an ambient temperature during the ageing process (ageing temperature) of 40 °С. [ABSTRACT FROM AUTHOR]