Showing papers on "Iron oxide published in 2009"
TL;DR: In this article, the properties, applications, and syntheses of three magnetic iron oxides (hematite, magnetite, and maghemite) are discussed and methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles.
1,206 citations
TL;DR: The formation of small aggregates of about 170 nm and surface coating of several nanometers of SRHA on iron oxide NPs confirm the role of NOM in the disaggregation process and indicate that NPs might mimic the behavior of natural colloids.
514 citations
TL;DR: MWCNT/iron oxide magnetic composites may be a promising candidate for pre-concentration and solidification of heavy metal ions and radionuclides from large volumes of aqueous solution, as required for remediation purposes.
441 citations
TL;DR: Catechol-derivative anchor groups which possess irreversible binding affinity to iron oxide and thus can optimally disperse superparamagnetic nanoparticles under physiologic conditions are found, which leads to ultrastable iron oxide nanoparticles.
Abstract: We have found catechol-derivative anchor groups which possess irreversible binding affinity to iron oxide and thus can optimally disperse superparamagnetic nanoparticles under physiologic conditions. This not only leads to ultrastable iron oxide nanoparticles but also allows close control over the hydrodynamic diameter and interfacial chemistry. The latter is a crucial breakthrough to assemble functionalized magnetic nanoparticles, e.g., as targeted magnetic resonance contrast agents.
408 citations
TL;DR: A review on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized magnetic iron oxide NPs and their corresponding application is presented in this article.
Abstract: Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.
395 citations
TL;DR: A dense and optimized PEG coating provides high stability under physiological conditions together with low cytotoxicity and low nonspecific phagocytosis into macrophage cells as a part of the reticulo endothelial system at biologically relevant concentrations.
Abstract: In this study we systematically developed a potential MR T1 contrast agent based on very small PEGylated iron oxide nanoparticles. We adjusted the size of the crystalline core providing suitable relaxometric properties. In addition, a dense and optimized PEG coating provides high stability under physiological conditions together with low cytotoxicity and low nonspecific phagocytosis into macrophage cells as a part of the reticulo endothelial system at biologically relevant concentrations. The as developed contrast agent has the lowest r2/r1 ratio (2.4) at 1.41 T reported so far for PEGylated iron oxide nanoparticles as well as a r1 relaxivity (7.3 mM−1 s−1) that is two times higher compared to that of Magnevist as a typical T1 contrast agent based on gadolinium as a clinical standard.
369 citations
TL;DR: From the MTT assay results, it is observed that the biocompatibility of the nanoparticles, based on cell viabilities, can be enhanced by increasing the r-ratio, regardless of the stirring rate.
325 citations
TL;DR: In this article, a thin film photoelectrodes were fabricated by aerosol-assisted chemical vapor deposition (AACVD) using a new hexanuclear iron precursor [Fe6(PhCOO)10(acac)2(O)2 (OH)2]·3C7H8 (1) (where PhCOO = benzoate and acac = 2,4-pentanedionate).
Abstract: α-Fe2O3 thin film photoelectrodes were fabricated by aerosol-assisted chemical vapor deposition (AACVD) using a new hexanuclear iron precursor [Fe6(PhCOO)10(acac)2(O)2(OH)2]·3C7H8 (1) (where PhCOO = benzoate and acac = 2,4-pentanedionate). The precursor (1) designed for AACVD has a low decomposition temperature and sufficient solubility in organic solvents and was synthesized by simple chemical techniques in high yield. It was characterized by melting point, FT-IR, X-ray crystallography, and thermogravimetry (TGA). The TGA analysis proved that complex (1) undergoes facile thermal decomposition at 475 °C to give iron oxide residue. In-house designed AACVD equipment was used to deposit highly crystalline thin films of α-Fe2O3 on fluorine-doped SnO2 coated glass substrates at 475 °C in a single step. The material properties were characterized by XRD, XPS, and Raman spectroscopy, and the results confirmed that films were highly crystalline α-Fe2O3 and free from other phases of iron oxide. Further analysis of ...
321 citations
TL;DR: It is unambiguously demonstrated, for the first time, that at a given frequency, heating rates of superparamagnetic particles are dependent on particle size, in agreement with earlier theoretical predictions.
308 citations
TL;DR: In this paper, the effect of the fuel reactor temperature on gas composition of a 10 kWth reactor with iron oxide as an oxygen carrier was experimentally investigated with a total 30 h of test was achieved with the same batch of iron oxide oxygen carrier.
Abstract: Chemical-looping combustion of biomass was carried out in a 10 kWth reactor with iron oxide as an oxygen carrier A total 30 h of test was achieved with the same batch of iron oxide oxygen carrier The effect of the fuel reactor temperature on gas composition of the fuel reactor and the air reactor, the proportion of biomass carbon reacting in the fuel reactor, and the conversion of biomass carbon to CO2 in the fuel reactor was experimentally investigated The results showed that the CO production from biomass gasification with CO2 was more temperature dependent than the CO oxidation with iron oxide in the fuel reactor, and an increase in the fuel reactor temperature produced a higher increase for the CO production from biomass gasification than for the oxidation of CO by iron oxide Although the conversion of biomass carbon to CO2 in the fuel reactor decreased with the increase of the fuel reactor temperature, there was a substantial increase in the proportion of biomass carbon reacting in the fuel react
259 citations
TL;DR: A facile one-step hydrothermal approach to the synthesis of iron oxide (Fe(3)O(4)) nanoparticles (NPs) with controllable diameters, narrow size distribution, and tunable magnetic properties is reported.
Abstract: We report a facile one-step hydrothermal approach to the synthesis of iron oxide (Fe3O4) nanoparticles (NPs) with controllable diameters, narrow size distribution, and tunable magnetic properties. In this approach, the iron oxide NPs were synthesized by oxidation of FeCl2·4H2O in basic aqueous solution under an elevated temperature and pressure. Transmission electron microscopy and X-ray diffraction studies reveal that the particles are highly crystalline and that the diameters of the particles can be tuned from 15 to 31 nm through the variation of the reaction conditions. The NPs exhibit high saturation magnetization in the range of 53.3−97.4 emu/g and their magnetic behavior can be either ferromagnetic or superparamagnetic depending on the particle size. A superconducting quantum interference device magnetorelaxometry study shows that the size of the NPs significantly affects the detection sensitivity. The investigated iron oxide NPs may find many potential biological applications in cancer diagnosis an...
TL;DR: The drug delivery and the MRI properties of folate-mediated water-soluble iron oxide incorporated into micelles are investigated and it is demonstrated that the magnetic nanoparticles are superparamagnetic with insignificant hysteresis.
TL;DR: In this article, superparamagnetic iron oxide nanoparticles were synthesized by a simple and cost-effective gel-to-crystalline method by alkalizing ferrous chloride with ammonium hydroxide at 80-100 degrees.
TL;DR: N1s core electron binding energies (CEBEs) were calculated using DFT for a number of nitrogen-containing species in the gas phase and adsorbed on an Al(8)O(12) cluster and a range of CEBEs is calculated for various nitrogen species in different adsorption modes and oxidation states.
Abstract: The adsorption of nitrogen dioxide on gamma aluminium oxide (gamma-Al(2)O(3)) and alpha iron oxide (alpha-Fe(2)O(3)) particle surfaces under various conditions of relative humidity, presence of molecular oxygen and UV light has been investigated. X-Ray photoelectron spectroscopy (XPS) is used to monitor the different surface species that form under these environmental conditions. Adsorption of NO(2) on aluminum oxide particle surfaces results primarily in the formation of surface nitrate, NO(3)(-) with an oxidation state of +5, as indicated by a peak with binding energy of 407.3 eV in the N1s region. An additional minority species, sensitive to the presence of relative humidity and molecular oxygen, is also observed in the N1s region with lower binding energy of 405.9 eV. This peak is assigned to a surface species in the +4 oxidation state. When irradiated with UV light, other species form on the surface. These surface-bound photochemical products all have lower binding energy, between 400 and 402 eV, indicating reduced nitrogen species in the range of N oxidations states spanning +1 to -1. Co-adsorbed water decreases the amount of these reduced surface-bound products while the presence of molecular oxygen completely suppresses the formation of all reduced nitrogen species on aluminum oxide particle surfaces. For NO(2) on iron oxide particle surfaces, photoreduction is enhanced relative to gamma-Al(2)O(3) and surface bound photoreduced species are observed under all environmental conditions. Complementing the experimental data, N1s core electron binding energies (CEBEs) were calculated using DFT for a number of nitrogen-containing species in the gas phase and adsorbed on an Al(8)O(12) cluster. A range of CEBEs is calculated for various nitrogen species in different adsorption modes and oxidation states. These calculated values are discussed in light of the peaks observed in the XPS N1s region and the possible species that form following NO(2) adsorption and photoreaction on metal oxide particle surfaces under different conditions of relative humidity, presence of molecular oxygen and UV light.
TL;DR: In this paper, the reaction proceeds through the formation of a well-ordered, oxygen-rich FeO(1.1) film that reacts with CO through the redox mechanism.
TL;DR: In this article, an iron oxide-based particle can maintain good reactivity for more than 100 reduction−oxidation (redox) cycles in a thermogravimetric analyzer.
Abstract: The syngas chemical looping (SCL) process coproduces hydrogen and electricity. The process involves reducing metal oxides with syngas followed by regeneration of reduced metal oxides with steam and air in a cyclic manner. Iron oxide is determined to be a desired oxygen carrier for hydrogen production considering overall properties including oxygen carrying capacity, thermodynamic properties, reaction kinetics, physical strength, melting points, and environmental effects. An iron oxide based particle can maintain good reactivity for more than 100 reduction−oxidation (redox) cycles in a thermogravimetric analyzer (TGA). The particle exhibits a good crushing strength (>20 MPa) and low attrition rate. Fixed bed experiments are carried out which reaffirm its reactivity. More than 99.75% of syngas is converted during the reduction stage. During the regeneration stage, hydrogen with an average purity of 99.8% is produced.
TL;DR: In this article, the Vickers hardness, thermal expansion coefficient and thermal conductivity were measured at high-temperatures, and it was verified that the hardness of each synthesized oxide was identical with the naturally formed iron oxide, as observed in the cross-section of oxide scales on steels.
Abstract: The mechanical properties of oxide scales at high-temperature were studied in order to improve the surface quality of commercial Sicontaining high strength steels. Specific oxides of Fe2O3 ,F e 3O4, FeO and Fe2SiO4 were synthesized by powder metallurgy. The Vickers hardness, thermal expansion coefficient and thermal conductivity were measured at high-temperatures. A series of measurements confirmed that the physical properties of the synthesized oxides were different each other. From the Vickers hardness measurements, it was verified that the hardness of each synthesized oxide was identical with the naturally-formed iron oxide, as observed in the cross-section of oxide scales on steels. The influence of the Fe2SiO4 formed on Si-containing steels on the scale adhesion at high temperature and the surface property is discussed on the basis of the physical properties of the oxides. [doi:10.2320/matertrans.M2009097]
TL;DR: In this paper, a method was developed to control the position of the catalytic sites on either inner or outer surface of carbon nanotubes (CNTs) for Fischer-Tropsch (FT) reactions.
Abstract: In order to study the effects of catalytic site position on Fischer–Tropsch (FT) reactions, a method was developed to control the position of the catalytic sites on either inner or outer surface of carbon nanotubes (CNTs). TEM analyses revealed that more than 70–80% of iron oxide particles can be controlled to be positioned at inner or outer surface of the nanotubes. Based on H 2 -TPR analysis, deposition of iron oxide inside the nanotube pores resulted in easier reduction of the oxide at a lower temperature (from 418 to 381 °C). Catalytic performances of the catalysts in terms of FT experiment were tested in a fixed-bed reactor. According to the results of FT experiments, both catalysts showed similar initial %CO conversion (∼90%). However, the catalyst with catalytic sites inside the pores exhibited higher selectivity to heavier hydrocarbons. In addition, deposition of catalytic sites on interior surface of the nanotubes resulted in a more stable catalyst, while its counterpart experienced deactivation within a period of 125 h due to catalytic sites sintering. It is concluded that encapsulation of catalytic sites inside the nanotubes prevents the catalytic site agglomeration.
TL;DR: In this article, the sorption of As(V) on two commercial iron oxides (hematite and goethite) was studied as a function of different physico-chemical parameters such as pH and ionic strength.
TL;DR: The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was examined by employing Rhodamine B (RhB) as a model compound at neutral pH and results indicated that surface complexation reaction may take place in the system.
TL;DR: In this article, the authors report on the Si-isotopic fractionation during H4SiO40 adsorption on synthesized ferrihydrite and goethite in batch experiment series designed as function of time (0-504 h) and initial concentration (ic) of Si in solution (0.21-1.80 mM).
TL;DR: In this article, L-lysine coated iron oxide (LCIO) nanoparticles were synthesized by a co-precipitation method in the presence of amino acid.
TL;DR: Adsorption features of activated carbon and the oxidation properties of iron oxides were combined in a composite to produce new materials for atrazine removal from aqueous medium, indicating that the efficiency of the oxidation reaction is related with the iron content and not with the pre-concentration of the contaminant on the carbon surface through adsorption process.
TL;DR: In this article, the authors measured the reduction rate of Fe(III) oxyhydroxides by the bacterium Shewanella putrefaciens as a function of the bacterial density and the substrate concentration.
TL;DR: In this paper, the structure, thermal properties, chemical durability and redox state of modified iron phosphate glasses have been characterized, and it has been shown that the addition of divalent cations has a less deleterious effect on glass stability than alkali additions.
Abstract: Modified iron phosphate glasses have been prepared with nominal molar compositions [(1−x)·(0.6P2O5–0.4Fe2O3)]·xRySO4, where x = 0–0.5 in increments of 0.1 and R = Li, Na, K, Mg, Ca, Ba, or Pb and y = 1 or 2. In most cases the vast majority or all of the sulfate volatalizes and quarternary P2O5–Fe2O3–FeO–RyOz glasses or partially crystalline materials are formed. Here we have characterized the structure, thermal properties, chemical durability and redox state of these materials. Raman spectroscopy indicates that increasing modifier oxide additions result in depolymerization of the phosphate network such that the average value of i, the number of bridging oxygens per –(PO4)– tetrahedron, and expressed as Qi, decreases. Differences have been observed between the structural effects of different modifier types but these are secondary to the amount of modifier added. Alkali additions have little effect on density; slightly increasing Tg and Td; increasing α and Tliq; and promoting bulk crystallization at temperatures of 600–700 °C. Additions of divalent cations increase density, α, Tg, Td, Tliq and promote bulk crystallization at temperatures of 700–800 °C. Overall the addition of divalent cations has a less deleterious effect on glass stability than alkali additions. 57Fe Mossbauer spectroscopy confirms that iron is present as Fe2+ and Fe3+ ions which primarily occupy distorted octahedral sites. This is consistent with accepted structural models for iron phosphate glasses. The iron redox ratio, Fe2+/ΣFe, has a value of 0.13–0.29 for the glasses studied. The base glass exhibits a very low aqueous leach rate when measured by Product Consistency Test B, a standard durability test for nuclear waste glasses. The addition of high quantities of alkali oxide (30–40 mol% R2O) to the base glass increases leach rates, but only to levels comparable with those measured for a commercial soda-lime-silica glass and for a surrogate nuclear waste-loaded borosilicate glass. Divalent cation additions decrease aqueous leach rates and large additions (30–50 mol% RO) provide exceptionally low leach rates that are 2–3 orders of magnitude lower than have been measured for the surrogate waste-loaded borosilicate glass. The P2O5–Fe2O3–FeO–BaO glasses reported here show particular promise as they are ultra-durable, thermally stable, low-melting glasses with a large glass-forming compositional range.
TL;DR: In this article, the effect of iron oxide nanoparticle addition on the physicochemical properties of polypyrrole (PPy) was investigated, where PPy was observed in the form of discrete nanoparticles, not the usual network structure.
Abstract: The effect of iron oxide nanoparticle addition on the physicochemical properties of the polypyrrole (PPy) was investigated. In the presence of iron oxide nanoparticles, PPy was observed in the form of discrete nanoparticles, not the usual network structure. PPy showed crystalline structure in the nanocomposites and pure PPy formed without iron oxide nanoparticles. PPy exhibited amorphous structure and nanoparticles were completely etched away in the nanocomposites formed with mechanical stirring over a 7-h reaction. The thermal stability of the PPy in the nanocomposites was enhanced under the thermo-gravimetric analysis (TGA). The electrical conductivity of the nanocomposites increased greatly upon the initial addition (20 wt%) of iron oxide nanoparticles. However, a higher nanoparticle loading (50 wt%) decreased the conductivity as a result of the dominance of the insulating iron oxide nanoparticles. Standard four-probe measurements indicated a three-dimensional variable-range-hopping conductivity mechanism. The magnetic properties of the fabricated nanocomposites were dependent on the particle loading. Ultrasonic stirring was observed to have a favorable effect on the protection of iron oxide nanoparticles from dissolution in acid. A tight polymer structure surrounds the magnetic nanoparticles, as compared to a complete loss of the magnetic iron oxide nanoparticles during conventional mechanical stirring for the micron-sized iron oxide particles filled PPy composite fabrication.
TL;DR: In this article, the authors used FTIR spectroscopy of adsorbed N2O, NO, and NO2 to investigate the structure and environment of the iron active species of the Fe-MFI catalysts before and after atomic oxygen deposition.
TL;DR: In this paper, the equations of state and volume difference between the metal-oxide pairs Fe-FeO and Ni-NiO were measured using synchrotron X-ray diffraction in a multi-anvil press and laser heated diamond anvil cells.
TL;DR: In this article, the authors demonstrate the production of iron-based nanoparticles, ranging from iron oxide to iron and iron carbide, by systematically modifying the degree of reduction during flame spray synthesis under a controlled atmosphere.
Abstract: The rapidly growing applications of nanomagnets require acid/base stable, oxidation-resistant shells with chemically controlled surface structure. An ideal core should be metallic and highly magnetic. We demonstrate the production of iron-based nanoparticles, ranging from iron oxide to iron and iron carbide, by systematically modifying the degree of reduction during flame spray synthesis under a controlled atmosphere. At a laboratory scale, continuous production yields iron-based particles of 20−50 nm at a production rate of >10 g h−1. Carbon-encapsulated iron carbide (C/Fe3C) combines exceptionally high saturation magnetization (140 emu g−1), air stability (up to 200 °C), and resistance against acidic dissolution (1 week in 24% HCl). The top graphene-like carbon layer could be covalently functionalized with various linkers, thus allowing us to chemically design the particle surface. Activity was demonstrated by reacting 2-phenyl ethyl amine functionalized nanomagnets with carboxylic acid chlorides as a m...
TL;DR: In this paper, three kinds of mixed oxides were investigated in a thermogravimetric analyzer and a fixed-bed reactor using methane as fuel and air as oxidizing gas and it was revealed that the addition of transition-metal oxides into cerium oxide can improve the reactivity of the Ce-based oxygen carrier.
Abstract: Chemical-looping reforming (CLR) is a technology that can be used for partial oxidation and steam reforming of hydrocarbon fuels. It involves the use of a metal oxide as an oxygen carrier, which transfers oxygen from combustion air to the fuel. Composite oxygen carriers of cerium oxide added with Fe, Cu, and Mn oxides were prepared by co-precipitation and investigated in a thermogravimetric analyzer and a fixed-bed reactor using methane as fuel and air as oxidizing gas. It was revealed that the addition of transition-metal oxides into cerium oxide can improve the reactivity of the Ce-based oxygen carrier. The three kinds of mixed oxides showed high CO and H-2 selectivity at above 800 degrees C. As for the Ce-Fe-O oxygen carrier, methane was converted to synthesis gas at a H-2/CO molar ratio close to 2:1 at a temperature of 800-900 degrees C; however, the methane thermolysis reaction was found on Ce-Cu-O and Ce-Mn-O oxygen carriers at 850-900 degrees C. Among the three kinds of oxygen carriers, Ce-Fe-O presented the best performance for methane CLR. On Ce-Fe-O oxygen carriers, the CO and H-2 selectivity decreased as the Fe content increased in the carrier particles. An optimal range of the Ce/Fe molar ratio is Ce/Fe > 1 for Ce-Fe-O oxygen carriers. Scanning electron microscopy (SEM) analysis revealed that the microstructure of the Ce-Fe-O oxides was not dramatically changed before and after 20 cyclic reactions. A small amount of Fe3C was found in the reacted Ce-Fe-O oxides by X-ray diffraction (XRD) analysis.