Showing papers on "Iron oxide published in 2014"
TL;DR: In this paper, the substitution of iron in an iron oxide with other transition metals as a mean to improve the properties of the iron oxide towards higher performance for contaminant degradation is discussed.
569 citations
TL;DR: This work presents a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and utilizes these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction.
Abstract: Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.
532 citations
TL;DR: In this article, the importance of proper structural and compositional engineering that leads to improved physical/chemical properties of iron oxides for efficient electrochemical energy storage is stressed and novel approaches to the construction of iron-oxide-based nanostructures are highlighted.
Abstract: Iron oxides, such as Fe2O3 and Fe3O4, have recently received increased attention as very promising anode materials for rechargeable lithium-ion batteries (LIBs) because of their high theoretical capacity, non-toxicity, low cost, and improved safety. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials. Here, recent research progress in the rational design and synthesis of diverse iron oxide-based nanomaterials and their lithium storage performance for LIBs, including 1D nanowires/rods, 2D nanosheets/flakes, 3D porous/hierarchical architectures, various hollow structures, and hybrid nanostructures of iron oxides and carbon (including amorphous carbon, carbon nanotubes, and graphene). By focusing on synthesis strategies for various iron-oxide-based nanostructures and the impacts of nanostructuring on their electrochemical performance, novel approaches to the construction of iron-oxide-based nanostructures are highlighted and the importance of proper structural and compositional engineering that leads to improved physical/chemical properties of iron oxides for efficient electrochemical energy storage is stressed. Iron-oxide-based nanomaterials stand a good chance as negative electrodes for next generation LIBs.
493 citations
TL;DR: It is suggested that the presence of organic acids (such oxalic or citric acids) plays an important role in the stabilization of iron nanoparticles, and that plants containing such constituents may be more efficacious for the green synthesis of Iron nanoparticles.
Abstract: We report the synthesis and characterization of amorphous iron oxide nanoparticles from iron salts in aqueous extracts of monocotyledonous (Hordeum vulgare) and dicotyledonous (Rumex acetosa) plants. The nanoparticles were characterized by TEM, absorbance spectroscopy, SAED, EELS, XPS, and DLS methods and were shown to contain mainly iron oxide and iron oxohydroxide. H. vulgare extracts produced amorphous iron oxide nanoparticles with diameters of up to 30 nm. These iron nanoparticles are intrinsically unstable and prone to aggregation; however, we rendered them stable in the long term by addition of 40 mM citrate buffer pH 3.0. In contrast, amorphous iron oxide nanoparticles (diameters of 10-40 nm) produced using R. acetosa extracts are highly stable. The total protein content and antioxidant capacity are similar for both extracts, but pH values differ (H. vulgare pH 5.8 vs R. acetosa pH 3.7). We suggest that the presence of organic acids (such oxalic or citric acids) plays an important role in the stabilization of iron nanoparticles, and that plants containing such constituents may be more efficacious for the green synthesis of iron nanoparticles.
243 citations
TL;DR: In this paper, surface modification strategy of iron oxide nanoparticles is also used for the remediation of water increases the efficiency of IR for the removal of the heavy metal ions from the aqueous system.
Abstract: In the 21st century water polluted by heavy metal is one of the environment problems. Various methods for removal of the heavy metal ions from the water have extensively been studied. Application of iron oxide nanaparticles based nanomaterials for removal of heavy metals is well-known adsorbents for remediation of water. Due to its important physiochemical property, inexpensive method and easy regeneration in the presence of external magnetic field make them more attractive toward water purification. Surface modification strategy of iron oxide nanoparticles is also used for the remediation of water increases the efficiency of iron oxide for the removal of the heavy metal ions from the aqueous system.
231 citations
TL;DR: Magnetic iron oxide nanoparticles (MION-Tea) successfully synthesized using tea waste template was used for removal of As(III) and As(V) from aqueous solution.
226 citations
TL;DR: In this paper, a review on different iron oxide phases and their magnetic properties along with various commonly used synthetic techniques are remarked and thoroughly described in this review. But despite the advantages of the electrochemical synthesis method, this technique has been poorly studied and requires deep investigations on effectual parameters such as current density, pH, electrolyte concentration etc.
223 citations
TL;DR: Activities of nano-iron metal and nano- iron oxides in ROS-related redox processes are summarized, addressing in detail the known homogeneous and heterogeneous redox mechanisms involved in these processes, intrinsic ROS- related properties of iron nanostructures (chemical composition, particle size, and crystalline phase), andros-related bio-microenvironmental factors.
173 citations
TL;DR: In this article, a composite material made of graphene nanoribbons and iron oxide nanoparticles was used to provide a remarkable route to lithium-ion battery anode with high specific capacity and cycle stability.
Abstract: A composite material made of graphene nanoribbons and iron oxide nanoparticles provides a remarkable route to lithium-ion battery anode with high specific capacity and cycle stability. At a rate of 100 mA/g, the material exhibits a high discharge capacity of ~910 mAh/g after 134 cycles, which is >90% of the theoretical li-ion storage capacity of iron oxide. Carbon black, carbon nanotubes, and graphene flakes have been employed by researchers to achieve conductivity and stability in lithium-ion electrode materials. Herein, the use of graphene nanoribbons as a conductive platform on which iron oxide nanoparticles are formed combines the advantages of long carbon nanotubes and flat graphene surfaces. The high capacity over prolonged cycling achieved is due to the synergy between an electrically percolating networks of conductive graphene nanoribbons and the high lithium-ion storage capability of iron oxide nanoparticles.
157 citations
TL;DR: Advanced applications of iron-oxide-supported nanocarbon composites where iron oxides play a diverse role are reviewed, including hybrids of carbon nanotubes and rare forms (mesoporous carbon, nanofoam) with magnetic iron oxide carriers for advanced environmental technologies.
Abstract: Owing to the three different orbital hybridizations carbon can adopt, the existence of various carbon nanoallotropes differing also in dimensionality has been already affirmed with other structures predicted and expected to emerge in the future. Despite numerous unique features and applications of 2D graphene, 1D carbon nanotubes, or 0D fullerenes, nanodiamonds, and carbon quantum dots, which have been already heavily explored, any of the existing carbon allotropes do not offer competitive magnetic properties. For challenging applications, carbon nanoallotropes are functionalized with magnetic species, especially of iron oxide nature, due to their interesting magnetic properties (superparamagnetism and strong magnetic response under external magnetic fields), easy availability, biocompatibility, and low cost. In addition, combination of iron oxides (magnetite, maghemite, hematite) and carbon nanostructures brings enhanced electrochemical performance and (photo)catalytic capability due to synergetic and co...
155 citations
TL;DR: The data indicate that iron oxide nanoparticles induced cytotoxicity and genotoxicity in MCF-7 cells via oxidative stress, and warrants more careful assessment of ironoxide nanoparticles before their industrial applications.
Abstract: Broad applications of iron oxide nanoparticles re- quire an improved understanding of their potential effects on human health. In the present study, we explored the underly- ingmechanismthroughwhichironoxidenanoparticlesinduce toxicity in human breast cancer cells (MCF-7). MTT (3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) and lactate dehydrogenase assays were used to examine mecha- nisms of cytotoxicity. Concentration- and time-dependent cy- totoxicity was observed in MCF-7 cells. Iron oxide nanopar- ticles were found to induce oxidative stress evidenced by the elevation of reactive oxygen species generation, lipid peroxi- dation, and depletion of superoxide dismutase, glutathione, and catalase activities in MCF-7 cells. Nuclear staining was performed using 4', 6-diamidino-2-phenylindole (DAPI), and cells were analyzed with a fluorescence microscope. Iron oxide nanoparticles (60 μg/ml) induced substantial apoptosis that was identified by morphology, condensation, and frag- mentation of the nuclei of the MCF-7 cells. It was also observed that the iron oxide NPs induced caspase-3 activity. DNA strand breakage was detected by comet assay, and it occurred in a concentration- and time-dependent manner. Thus, the data indicate that iron oxide nanoparticles induced cytotoxicity and genotoxicity in MCF-7 cells via oxidative stress. This study warrants more careful assessment of iron oxide nanoparticles before their industrial applications.
TL;DR: In this paper, a mesoporous carbon/iron oxide composites were prepared by cooperative self-assembly of poly(t-butyl acrylate)-block-polyacrylonitrile (PtBA-b-PAN), which contains both a carbon precursor block and a porogen block, and phenol-functionalized iron oxide nanoparticles (NPs).
Abstract: Ordered mesoporous carbon/iron oxide composites were prepared by cooperative self-assembly of poly(t-butyl acrylate)-block-polyacrylonitrile (PtBA-b-PAN), which contains both a carbon precursor block and a porogen block, and phenol-functionalized iron oxide nanoparticles (NPs). Because of the selective hydrogen bonding between the phenol-functionalized iron oxide NPs and PAN, the NPs were preferentially dispersed in the PAN domain and subsequently within the mesoporous carbon framework. Ordered mesoporous carbon nanocomposites with Fe2O3 NPs mass loadings as high as 30 wt % were obtained upon carbonization at the block copolymer composites at 700 °C. The morphology of the mesoporous composites was studied using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption. The results confirmed high-fidelity preservation of morphology of the NP-doped block copolymer composites in the mesoporous carbon composites. The electrochemical performance of the mesoporous composite ...
TL;DR: Iron oxide nanoparticles adsorb fluorescently labeled DNA oligonucleotides via the backbone phosphate and quench fluorescence, allowing detection of arsenate down to 300 nM.
TL;DR: In this paper, textural and compositional data of magnetite from the Chengchao iron deposit, Daye district, China to provide a better understanding in the formation mechanism and genesis of the deposit and shed light on analytical protocols for in-situ chemical analysis of hydrothermal magnetite.
TL;DR: A highly reproducible route to synthesize iron oxide nanoparticles (IONPs) with control over size and shape and with size dispersions around 10%, which uncovers the possibility of using large IONPs for magnetic hyperthermia in tumor therapy.
Abstract: We report a highly reproducible route to synthesize iron oxide nanoparticles (IONPs) with control over size and shape and with size dispersions around 10%. By tuning the relative ratio of squalane to dibenzyl ether, which were used as solvents in the synthesis, the size of the particles could be varied from 14 to around 100 nm, while their shape evolved from cubic (for size ranges up to 35 nm) to truncated octahedra and octahedra (for sizes from 40 nm up to 100 nm). Fine tuning of the size within each of these ranges could be achieved by varying the heating ramp and the iron precursor to decanoic acid ratio. We also demonstrate direct water transfer of the as-synthesized IONPs via in situ ligand exchange with gallol polyethylene glycol molecules, the latter simply added to the crude nanocrystal mixture at 70 °C. The specific absorption rate (SAR) values measured on the water transferred IONPs, at frequencies and applied magnetic fields that are considered safe for patients, confirmed their high heating performance. Finally, this method allows the transfer of 35 nm nanocubes as individually coated and stable particles to the water phase. For the first time, the heating performance of such large IONPs has been studied. This work uncovers the possibility of using large IONPs for magnetic hyperthermia in tumor therapy.
TL;DR: A previously unreported iron oxide/graphene oxide/chitosan (Fe3O4/GO/CS) composite was prepared by a simple solution mixing-evaporation method as discussed by the authors.
Abstract: A previously unreported iron oxide/graphene oxide/chitosan (Fe3O4/GO/CS) composite was prepared by a simple solution mixing-evaporation method. The structure, thermal stability, and mechanical properties of the composite were investigated by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetry analysis, and mechanical testing. The results obtained from these analyses revealed that chitosan, iron oxide and graphene oxide were able to form a homogeneous mixture. A great synergistic effect of iron oxide platelets and graphene oxide (GO) on reinforcing chitosan matrix has been observed. With incorporation of 0.5 wt.% Fe3O4 and 1 wt.% GO, the tensile strength and Young’s modulus of the composite have significantly improved by about 28% and 74%, respectively, compared with chitosan.
TL;DR: Sorption of reference MC252 oil with easy-to-synthesize and low-cost hydrophilic polyvinylpyrrolidone-coated iron oxide nanoparticles is reported for the first time, giving quantitative oil removal under optimized conditions.
Abstract: Catastrophic oil spills and oil from waste waters such as bilge and fracking waters pose major environmental concerns. The limitations of existing cleanup techniques for benign oil remediation has inspired a recent scientific impetus to develop oil-absorbing smart nanomaterials. Magnetic nanocomposites were here designed to allow easy recovery from various systems. In this study, sorption of reference MC252 oil with easy-to-synthesize and low-cost hydrophilic polyvinylpyrrolidone-coated iron oxide nanoparticles is reported for the first time. The one-step modified polyol synthesis in air directly generates water-soluble nanoparticles. Stable polyvinylpyrrolidone-coatings are known to minimize environmental alterations of nanoparticles from aggregation and other processes. Iron oxide provides effective magnetic actuation, while both PVP and iron oxide have low toxicity. These nanoparticles gave quantitative (near 100%) oil removal under optimized conditions. The facile synthesis and ease of use represents ...
TL;DR: In this article, the synthesis, characterization and chemical sensing properties of iron oxide (-Fe2O3) nanoparticles were reported and a high sensitivity of 57.88 Am M −1 cm −2 with an experimental detection limit of 97 M.
Abstract: This paper reports the simple and facile synthesis, characterization and chemical sensing properties of iron oxide (-Fe2O3) nanoparticles. Iron oxide nanoparticles were synthesized by a simple hydrothermal process and characterized in details of their morphological, structural and compositional properties. The iron oxide nanoparticles were found to be well-crystalline and grown in very high density which were used as efficient electron mediators for the fabrication of highsensitive phenyl hydrazine sensor. The fabricated hydrazine sensor demonstrated a high sensitivity of 57.88 Am M −1 cm −2 with an experimental detection limit of 97 M. The observed linear dynamic range (LDR) for the fabricated sensor was 97 m−1.56 mM. The presented work demonstrates that iron oxide nanoparticles can be used as a potential electron mediator for the fabrication of efficient chemical sensors.
01 Feb 2014
TL;DR: In this article, a cost effective co-precipitation method was used to synthesize nano-sized crystallites of iron oxide by using vibrating sample magnetometry (VSM).
Abstract: Nano-sized crystallites of iron oxide were synthesized by cost effective co-precipitation method. X-ray diffraction pattern indicated that the magnetic nanoparticles were pure Fe3O4 with a spinel structure. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared (FT-IR) spectra, Transmission electron microscope (TEM) and magnetization measurement of the nanoparticles were carried out using vibrating sample magnetometry (VSM). The cell thickness of fresh nanoparticle estimated from XRD lies in the range of 5.658.16 nm whereas the particle size in the TEM was 20-22 nm. This results indicated that few grains of ferrite were aggregated to form particles of about 20-50 nm in diameter. The thermogravimetric analysis of the nanoparticle was also carried out in temperature interval from room temperature to 700C. In the study, the particles having higher magnetization value in comparison to previously prepared ferrite were synthesized and the method used can also be a model for the synthesis of other nanoparticles in which Fe (II) is incorporated in the particle growth process.
TL;DR: Once amended, the 950 °C iron oxide amended rice husk char improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity.
TL;DR: In this paper, the cobalt-oxide/iron-oxide binary system was investigated and the results showed that the reaction enthalpy gradually decreases with increasing iron content, which is beneficial in terms of microstructural stability and related long-term reversibility of the chemical reaction.
TL;DR: In this paper, a facile method has been developed for the synthesis of nearly mono-dispersed iron oxide nanocrystals, which can be used as an electrode for supercapacitors.
Abstract: A facile method has been developed for the synthesis of nearly mono-dispersed iron oxide nanocrystals. The structural analysis of the synthesized iron oxide nanocrystals reveals the magnetite phase of Fe3O4. The average particle size of the iron oxide was estimated to be 8 ± 2 nm. The observed particle size is in good correlation with the particle size estimated by magnetic measurements. Furthermore, these nanocrystals showed bi-functional ferromagnetic and superparamagnetic behavior below and above the blocking temperature, respectively. The potential use of these nanocrystals as an electrode for supercapacitors was examined by investigating the electrochemical behavior of iron oxide using cyclic voltammetry (CV) and galvanostatic charge–discharge tests. The CV characteristics of the iron oxide electrode showed a typical pseudocapacitive behavior in 3 M KOH solution. Moreover, the specific capacitance of 185 F g−1 at the current of 1 mA was observed with excellent cyclic stability, which is much higher than the reported value for iron oxide. The higher specific capacitance is due to the uniform nano-size of iron oxide. This work provides an ultimate facile method to synthesize nanostructured iron oxide for application in next generation energy storage materials.
TL;DR: Comparisons with historical data show that while metal concentrations in mine drainage have decreased by more than an order of magnitude in recent decades, the chemical composition of mine waste pile runoff has remained relatively constant, indicating less attenuation and increased relative importance of pile runoff.
TL;DR: In this paper, the effect of heating duration and activated carbon (AC) oxidation on structural properties were studied using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), focused ion beam (FIB) microscopy, Brunauer, Emmett and Teller (BET), and porous texture analyses were utilized to characterize iron oxide/AC system.
TL;DR: It is demonstrated how monodisperse iron oxide nanocubes and nanospheres with average sizes between 5 and 27 nm can be synthesized by thermal decomposition.
TL;DR: Overall, the results suggest that nano-Fe(0) oxidized via the Fe( 0) - Fe(OH)2 - Fe3O4 - (γ-Fe2O3) route and the formation of superparamagnetic maghemite nanoparticles due to disruption of the surface oxide layer.
Abstract: Oxidation behavior of nano-Fe-0 particles in an anoxic environment was determined using different state-of-the-art analytical approaches, including high resolution transmission electron microscopy (HR-TEM) combined with energy filtered transmission electron microscopy (EFTEM), X-ray absorption spectroscopy (XAS), and magnetic measurements. Oxidation in controlled experiments was compared in standard double distilled (DD) water, DD water spiked with trichloroethene (TCE), and TCE contaminated site water. Using HR-TEM and EFTEM, we observed a surface oxide layer (similar to 3 nm) formed immediately after the particles were exposed to water. XAS analysis followed the dynamic change in total metallic iron concentration and iron oxide concentration for the experimental duration of 35 days. The metallic iron concentration in nano-Fe-0 particles exposed to water, was similar to 40% after 35 days; in contrast, the samples containing TCE were reduced to similar to 15% and even to nil in the case of TCE contaminated site water, suggesting that the contaminants enhance the oxidation of nano-Fe0. Frequency dependence measurements confirmed the formation of superparamagnetic particles in the system. Overall, our results suggest that nano-Fe0 oxidized via the Fe-0 - Fe(OH)(2) - Fe3O4 - (gamma-Fe2O3) route and the formation of superparamagnetic maghemite nanoparticles due to disruption of the surface oxide layer.
TL;DR: In this article, a new type of tantalum and aluminum co-doped iron oxide (Ta/Al-Fe2O3) material was fabricated by a simple drop coating method.
Abstract: Efficient and stable photocatalysts for water oxidation are highly sought after in the field of photoelectrochemical (PEC) water splitting. Herein, a new type of tantalum and aluminum co-doped iron oxide (Ta/Al-Fe2O3) material was fabricated by a simple drop coating method. XPS analysis suggests that Ta and Al were successfully co-doped into Fe2O3 and Ta can greatly influence the chemical environment of Al and O on the surface of catalyst. The resultant optimum (0.25%)Ta/(10%)Al-Fe2O3 film presented excellent enhanced PEC activity and photostability. A 15 times higher photocurrent density as well as two times higher incident-photon-to-current efficiency (IPCE, 430 nm) can be clearly observed relative to (10%)Al-Fe2O3 at 0.35 V vs. Ag/AgCl. The dramatic enhanced PEC and IPCE performance are attributed to mixed effects induced by tantalum doping, such as positive shift of flat band potential (ca. 50 mV), a reduction in anodic overpotential for water oxidation and greatly reduced charge transfer resistance, which eventually facilitate more efficient separation and easier transfer of photogenerated electron–hole pairs. The highly improved visible light activity and film stability indicate that tantalum and aluminum co-doped iron oxide will be a promising semiconductor for water oxidation.
TL;DR: In this paper, single atoms and small clusters were dispersed on iron oxides by a facile coprecipitation method, and these catalysts, with or without calcination at elevated temperatures, show excellent activity a...
Abstract: Pt single atoms and small clusters were dispersed on iron oxides by a facile coprecipitation method. These catalysts, with or without calcination at elevated temperatures, show excellent activity a...
TL;DR: In this paper, the performance of cobalt oxide-based composites for energy storage in future concentrated solar power plants was evaluated in the form of small structured perforated monolithic bodies (flow-through pellets).
TL;DR: In this paper, a series of MoOx-modified Fe2O3 catalysts have been prepared in an attempt to make core-shell oxidic materials of the type MoOx/FeO3.
Abstract: A series of MoOx-modified Fe2O3 catalysts have been prepared in an attempt to make core–shell oxidic materials of the type MoOx/Fe2O3. It is conclusively shown that for three monolayers of Mo dosed, the Mo stays in the surface region, even after annealing to high temperature. It is only when the material is annealed above 400 °C that it reacts with the iron oxide. We show by a combination of methods, and especially by XAFS, that at temperatures above 400 °C, most of the Mo converts to Fe2(MoO4)3, with Mo in a tetrahedral structure, whereas below that temperature, nanocrystalline MoO3 is present in the sample; however, the active catalysts have an octahedral MoOx layer at the surface even after calcination to 600 °C. This surface layer appears to be present at all temperatures between 300 and 600 °C, and it is the nanoparticles of MoO3 that are present at the lower temperature that react to form ferric molybdate, which underlies this surface layer. It is the MoOx layer on the Fe2(MoO4)3 underlayer that makes the surface active and selective for formaldehyde synthesis, whereas the iron oxide surface itself is a combustor. The material is both activated and improved in selectivity due to the dominance of the methoxy species on the Mo-doped material, as opposed to the much more stable formate, which is the main intermediate on Fe2O3.