XPS and XRD study of FeCl3-graphite intercalation compounds prepared by arc discharge in aqueous solution

A novel one-step synthesis method of FeCl₃–graphite intercalation compounds (FeCl₃–GICs) by an arc discharge in aqueous solution was reported for the first time. It presented a simply and controllable way to synthesize FeCl₃–GICs. The structure of the stage 7 GICs was examined and characterized by X-ray diffraction. X-ray photoelectron spectroscopic study of stage 7 of FeCl₃–GICs was also carried out. The change in the binding energy suggests the nature of charge transfer and lowering of Fermi level as has been reported previously for other acceptor intercalation compounds.     

Uptake and biological responses to nano-Fe versus soluble FeCl3 in excised mussel gills

Nano-Fe particle uptake was experimentally examined in vitro using excised gills and blood cells of the edible blue mussel Mytilus sp. Whole gills were exposed to both Fe₂O₃ nanoparticles and a solution of the hydrated FeCl₃ salt, for up to 12 h, and blood cells for 30 min. Equimolar Fe⁺³ in the nano- and the soluble form was estimated under the assumption of dense spherical particles accommodating the same number of Fe⁺³ as in the dissolved salt solution, namely: 1,000 μg L⁻¹ Fe₂O₃ equivalent to 100 μg L⁻¹ FeCl₃·6H₂O. Putative toxic impact of nano-Fe in gill epithelia and blood cells was assessed by an array of techniques including light- and electron microscopy, biomarkers for oxidative stress (lipid peroxidation levels), neurotoxic effects (acetylcholinesterase activity) and cytotoxicity (neutral red retention). Total and filtered fractions (20 and 200 nm, respectively) of Fe were analysed by ICP-OES. Our results provide evidence for the following: (1) much of both the soluble (95%) and the nano-Fe (90%) were removed from the water column within 12 h; (2) dissolved- and nano-Fe seemed to follow different routes of uptake within the gill epithelium; (3) both nano-Fe and soluble FeCl₃ caused similar impairment of lysosomal stability in circulating blood cells; (4) lipid peroxidation in gills exposed to the two distinct forms of Fe was increased, while acetylcholinesterase activity was unaffected. In these short-term in vitro studies, there appears to be little difference in toxic response between exposure to the Fe salt and the nano-Fe indicating that, in this case, the nanoparticles do not invoke special properties affecting biological function in gills. However, with the use of nano-Fe as a food additive, clearly longer-term in vivo studies are warranted.     

Thermal exfoliation of electrochemically synthesized graphite intercalation compound with perrhenic acid

In present work, we describe the synthesis of graphite intercalation compounds with perrhenic acid (HReO₄-GIC) through the anodic oxidation of graphite in aqueous perrhenic acid solution and their thermal exfoliation. Due to electrochemical treatment of graphite in perrhenic acid solution, ReO₄⁻ ions are intercalated into interlayer spaces of graphite. Anodic oxidation of graphite in HReO₄ solution leads to the formation of 3-stage GIC. Simultaneously, some amount of perrhenic acid becomes deposited on the graphite surface and edges. In the next step, thermal treatment of the previously synthesized GIC was performed, causing both the exfoliation of graphitic structure and transformation of perrhenic acid into rhenium oxides on the surface of graphene layers. The yielded product was exfoliated graphite-ReO₂/ReO₃ composite. The obtained composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Additionally, specific surface area of the exfoliated materials was measured.

     

The intercalation of transition metal salen complexes into layered MoS2

Exfoliation-restack method has been employed to synthesize the intercalation compounds based on the cationic complexes [M(Salen)]⁺ (M = Mn³⁺, Fe³⁺, Co³⁺; Salen = N, N′-ethylene-bis(salicylaldimine)) into the layered MoS₂. Their conductivity is in the range of 0.04–0.1 S/cm, which is much higher than the pristine MoS₂. Magnetic measurement indicated that the intercalation compounds [Mn(Salen)]_0.18MoS₂ · 0.25H₂O and [Fe(Salen)]_0.12MoS₂ · 0.3H₂O exhibit the temperature-dependent paramagnetism, which obviates from the Curie–Weiss law due to the temperature-independent paramagnetism of the exfoliated MoS₂ slabs, while [Co(Salen)]_0.14MoS₂ · 0.5H₂O exhibits the almost temperature-independent paramagnetism. All three intercalation compounds do not show magnetic spin crossover behavior.     

Electrochemical synthesis of Fe3O4-PB nanoparticles with core-shell structure and its electrocatalytic reduction toward H2O2

The Fe₃O₄-Prussian blue (PB) nanoparticles with core-shell structure have been in situ prepared directly on a nano-Fe₃O₄-modified glassy carbon electrode by cyclic voltammetry (CV). First, the magnetic nano-Fe₃O₄ particles were synthesized and characterized by X-ray diffraction. Then, the properties of the Fe₃O₄-PB nanoparticles were characterized by CV, electrochemical impedance spectroscopy, and superconducting quantum interference device. The resulting core-shell Fe₃O₄-PB-modified electrode displays a dramatic electrocatalytic ability toward H₂O₂ reduction, and the catalytic current was a linear function with the concentration of H₂O₂ in the range of 1 × 10⁻⁷~5 × 10⁻⁴ mol/l. A detection limit of 2 × 10⁻⁸ (s/n = 3) was determined. Moreover, it showed good reproducibility, enhanced long-term stability, and potential applications in fields of magnetite biosensors.     

Mathematical simulation of anodic intercalation of graphite in dilute nitric acid

The article suggests a mathematical model for the process of anodic intercalation of the dense graphite suspension in dilute nitric acid, where the spontaneous intercalation is absent. The model is based on the idea of electric neutrality of a graphite particle, due to which the anion current NO₃⁻ entering the particle is precisely equal to the quantity of electrons, which are diverted from a particle to a current lead according to the mechanism of electronic conductivity provided by the outer constriction of the suspension. The anodic polarization is conditioned by the mass transfer of anions NO₃⁻ inside the equipotential graphite particle. The computational solution of the problem showed that even at a small suspension layer height (2 cm), there is a significant nonuniformity of intercalation, which corresponds to the data provided in the literature. A method for the estimation of an intercalation nonuniformity and a method for its reduction by using a multistep process were suggested. The results of the computation can be used for an estimation of the technical characteristics of the final product.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

In situ synthesis of plate-like Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in porous cellulose films with obvious magnetic anisotropy

Nanocomposite cellulose films with obvious magnetic anisotropy have been prepared by in situ synthesis of plate-like Fe₂O₃ nanoparticles in the cellulose matrix. The influence of the concentrations of FeCl₂ and FeCl₃ solutions on the morphology and particle size of the synthesized Fe₂O₃ nanoparticles as well as on the properties of the composite films has been investigated. The Fe₂O₃ nanoparticles synthesized in the cellulose matrix was γ-Fe₂O₃, and its morphology was plate-like with size about 48 nm and thickness about 9 nm, which was totally different from those reported works. The concentration of FeCl₂ and FeCl₃ solution has little influence on the particle size and morphology of the Fe₂O₃ nanoparticles, while the content of Fe₂O₃ nanoparticles increased with the increase of the concentration of the precursor solution, indicating that porous structured cellulose matrix could modulate the growth of inorganic nanoparticles. The unique morphology of the Fe₂O₃ nanoparticles endowed the composite films with obvious magnetic anisotropy, which would expand the applications of the cellulose based nanomaterials.     

Photo-Fenton and photo-Fenton-like processes for the degradation of methyl orange in aqueous medium: Influence of oxidation states of iron

Degradation of methyl orange (MO) was carried out by the photo-Fenton process (Fe²⁺/H₂O₂/UV) and photo-Fenton-like processes (Fe³⁺/H₂O₂/UV, Fe²⁺/S₂O₈²⁻/UV, and Fe³⁺/S₂O₈²⁻/UV) at the acidic pH of 3 using hydrogen peroxide and ammonium persulfate (APS) as oxidants. Oxidation state of iron had a significant influence on the efficiency of photo-Fenton/photo-Fenton-like processes. It was found that a process with a source of Fe³⁺ ions as the catalyst showed higher efficiency compared to a process with the Fe²⁺ ion as the catalyst. H₂O₂ served as a better oxidant for both oxidation states of iron compared to APS. The lower efficiency of APS is attributed to the generation of excess protons which scavenges the hydroxyl radicals necessary for degradation. Further, the sulfate ions produced from S₂O₈²⁻ form a complex with Fe²⁺/Fe³⁺ ions thereby reducing the concentration of free iron ions in the solution. This process can also reduce the concentration of hydroxyl radicals in the solution. Efficiency of the various MO degradation processes follows the order: Fe³⁺/H₂O₂/UV, Fe³⁺/APS/UV, Fe²⁺/H₂O₂/UV, Fe²⁺/APS/UV.     

Microwave-assisted one-step hydrothermal synthesis of pure iron oxide nanoparticles: magnetite, maghemite and hematite

A simple, rapid, one-step synthesis way of pure iron oxide nanoparticles: magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃) and hematite (α-Fe₂O₃) was investigated. Nanoparticles were prepared by microwave synthesis, from ethanol/water solutions of chloride salts of iron (FeCl₂ and FeCl₃) in the presence of sodium hydroxide NaOH. X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize these nanoparticles.     

Facile preparation of graphite intercalation compounds in alkali solution

Graphite intercalation compounds are often prepared by flake graphite, oxidants, inorganic acids, organic acids and intercalated ions which are usually hydrogen protons between the graphene planes. They are also known as the acid-treated graphite intercalation compounds. In this work, alkaline graphite intercalation compounds were prepared by flake graphite, K₂Cr₂O₇, concentrated H₂SO₄ and NaOH, and the morphology and structure were characterized by Electron microscopy and X-ray techniques. The results display that the combination of neutralisation heat and oxidation capability produced by K₂Cr₂O₇ can break the bonds to produce the spaces between the graphene planes and hydroxyl ions also intercalate into the graphene planes to form alkaline graphite intercalation compounds in alkali solution. The morphology and structure of alkaline graphite intercalation compounds are analogous to the ones of the acid-treated graphite intercalation compounds, but the intercalated ions and the expansion volume are different. The results show that the method is an innovation.     

Studies on thermochemical properties of ionic liquids based on transition metal

A brown and transparent ionic liquid (IL), [C₄mim][FeCl₄], was prepared by mixing anhydrous FeCl₃ with 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]), with molar ratio 1/1 under stirring in a glove box filled with dry argon. The molar enthalpies of solution, Δ_s H _m, of [C₄mim][FeCl₄], in water with various molalities were determined by a solution-reaction isoperibol calorimeter at 298.15 K. Considering the hydrolyzation of anion [FeCl₄]⁻ in dissolution process of the IL, a new method of determining the standard molar enthalpy of solution, Δ_s H _m⁰, was put forward on the bases of Pitzer solution theory of mixed electrolytes. The values of Δ_s H _m⁰ and the sum of Pitzer parameters: and were obtained, respectively. In terms of thermodynamic cycle and the lattice energy of IL calculated by Glasser’s lattice energy theory of ILs, the dissociation enthalpy of anion [FeCl₄]⁻, ΔH _dis≈5650 kJ mol⁻¹, for the reaction: [FeCl₄]⁻(g)→Fe³⁺(g)+4Cl⁻(g), was estimated. It is shown that large hydration enthalpies of ions have been compensated by large the dissociation enthalpy of [FeCl₄]⁻ anion, Δ_d H _m, in dissolution process of the IL.     

Regularities of formation of iron(III) nanocrystalline oxides and oxyhydroxides during oxidation of iron(II) compounds in an alkaline medium

Regularities of formation of nanocrystalline iron(III) oxides and oxyhydroxides via oxidation of iron(II) compounds in an alkaline pH range (pH ≥ 12) were studied using pH and E _h measurements, chemical analysis, electron microscopy, and X-ray diffraction. When the molar ratio [OH⁻]/[Fe^II] ∼ 2 (pH ∼ 12–12.5), the oxidation process yields cube-shaped magnetite Fe₃O₄ particles. An excess of an alkaline agent with an overstoichiometric concentration equal to or higher than 0.5 mol/L (pH ≥ 13.5) induces the formation of anisotropic particles of nanocrystalline goethite α-FeOOH over the entire range of the synthesis parameters studied. Reaction products (Fe₃O₄ and/or α-FeOOH) are formed immediately as the initial Fe(OH)₂ starts oxidizing by the dissolution-oxidation-precipitation mechanism near the surface of Fe(OH)₂ precursor particles. Carbonate ions considerably change the structure and shape of newly formed α-FeOOH particles.     

Electronic structure of products of interaction between Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> cluster and water and its association with the corrosion behavior of magnetite

Electronic structure of Fe₃O₄ cluster and the products of its interaction with water molecule hydrates H₄O₂ and H₅O₂⁺ and H₃O₂⁻ ions is calculated by the quantum-chemical method DFT B3LYP/6-31G**. The expected behavior of magnetite in the acidic, neutral, and alkaline media is analyzed in the approximation of parameters of their electronic structure (the effective charges, binding and free valences of iron and oxygen atoms). In the interaction between Fe₃O₄ and H₅O₂⁺ (acidic medium), a hydride bond Fe-H forms, and the remainder of magnetite cluster becomes more susceptible to the attack of reagents. By contrast, the interaction of Fe₃O₄ with H₃O₂⁻ (alkaline medium) yields an oxide structure with low chemical activity of both iron and oxygen atoms. The calculated data are in agreement with the experimental data on the corrosion behavior of magnetite.     

Coprecipitation as a means for the determination of zirconium traces by isotope dilution analysis in the presence of substoichiometric amounts of complexones

The possibility of using coprecipitation on Cu(OH)₂·nH₂O and Fe₂O₃·nH₂O precipitates to separate a part of zirconium unreacted with complexone in the presence of a 100-fold amount of impurities has been examined. The reaction between ethylenedia-minetetraacetic acid (EDTA) and zirconium 10⁻³−10⁻⁵ M has been used as substoichiometric reaction. A zirconium determination in the concentration range of 10⁻⁴−10⁻⁶ g/ml in artificial mixtures and steel samples has been developed using the systems of EDTA-Zr−Cu(OH)₂·nH₂O and EDTA−Zr−Fe₂O₃·nH₂O.     

Sensitive fluorescent probes for determination of hydrogen peroxide and glucose based on enzyme-immobilized magnetite/silica nanoparticles

Sensitive fluorescent probes for the determination of hydrogen peroxide and glucose were developed by immobilizing enzyme horseradish peroxidase (HRP) on Fe₃O₄/SiO₂ magnetic core–shell nanoparticles in the presence of glutaraldehyde. Besides its excellent catalytic activity, the immobilized enzyme could be easily and completely recovered by a magnetic separation, and the recovered HRP-immobilized Fe₃O₄/SiO₂ nanoparticles were able to be used repeatedly as catalysts without deactivation. The HRP-immobilized nanoparticles were able to activate hydrogen peroxide (H₂O₂), which oxidized non-fluorescent 3-(4-hydroxyphenyl)propionic acid to a fluorescent product with an emission maximum at 409 nm. Under optimized conditions, a linear calibration curve was obtained over the H₂O₂ concentrations ranging from 5.0 × 10⁻⁹ to 1.0 × 10⁻⁵ mol L⁻¹, with a detection limit of 2.1 × 10⁻⁹ mol L⁻¹. By simultaneously using glucose oxidase and HRP-immobilized Fe₃O₄/SiO₂ nanoparticles, a sensitive and selective analytical method for the glucose detection was established. The fluorescence intensity of the product responded well linearly to glucose concentration in the range from 5.0 × 10⁻⁸ to 5.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 1.8 × 10⁻⁸ mol L⁻¹. The proposed method was successfully applied for the determination of glucose in human serum sample.     

Synthesis and characterization of La<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>Co<Subscript>0.5</Subscript>Fe<Subscript>0.5</Subscript>O<Subscript>3±δ</Subscript> nanopowders by microwave assisted sol–gel route

Nano-crystalline La_0.8Sr_0.2Co_0.5Fe_0.5O_3±δ powder has been successfully synthesized by microwave assisted sol–gel (MWSG) method. The decomposition and crystallization behavior of the gel-precursor was studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis. From the result of FT-IR and X-ray diffraction patterns, it is found that a perovskite La_0.8Sr_0.2Co_0.5Fe_0.5O_3±δ was formed by irradiating the precursor at 700 W for 3 min, but the well-crystalline perovskite La_0.8Sr_0.2Co_0.5Fe_0.5O_3±δ was obtained at 700 W for 35 min. Morphological and specific area analysis of the powder were done by transmission electron microscopy (TEM), scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET). The surface areas measured was 38.9 m²/g and the grain size was ∼23 nm. Electrochemical properties of pure LSCF cathode on YSZ electrolyte at intermediate temperatures were investigated by using AC impedance analyzer, which shows a low area specific resistance (0.077 Ω cm² at 1073 K and 0.672 Ω cm² at 953 K). Moreover, the synthesis period of 20 h usually observed for conventional heating mode is reduced to a few minutes. Thus, the MWSG method is proved to be a novel, extremely facile, time-saving and energy-efficient route to synthesize LSCF powders.     

FeCl3 solutions in isopropanol-water

Summary This paper is devoted to the characterization of FeCl₃ solutions in isopropanol containing water. For this goal optical absorption and e.p.r. techniques have been used in conjunction with magnetization and M?ssbauer data reported very recently. It is shown that in a 10⁻² M solution of FeCl₃ containing 0.4 M of water the main iron(III) species present in the solution are [FeCl₄]⁻ (55%) and [FeCl₂(H₂O)₄]⁺ (20%) while the remainding 25% is due to dihydroxo dimers, . When the water concentration increases the [FeCl₄]⁻ anions are progressively destroyed, the main iron(III) species present in the solution being the dihydroxodimers and [FeCl₂(H₂O)₄]⁺. The variation of the concentration of the three species mentioned with the water content and FeCl₃ concentration is presented in this paper.     

Thermal Decompositions of the Molybdotellurates of Nickel(II) and Cobalt(II)

Molybdotellurates [M(H₂O)₆]₃·[TeMo₆O₂₄], with M=Ni(II) and Co(II), were synthesized and characterized by single-crystal X-ray diffraction for compound 1 and X-ray powder diffraction for compound 2, EDAX, IR, electronic spectra in the solid phase and in solution, and magnetic properties. Thermogravimetry and differential scanning calorimetry of both compounds revealed a loss of 11 water molecules through an endothermal process with ΔH=800 kJ mol⁻¹ for the nickel compound and ΔH=833 kJ mol⁻¹ for the cobalt compound. The residual compounds were characterized by chemical analysis, IR and XPS spectroscopy This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetic and thermodynamic sorption study of radiocobalt by magnetic hydroxyapatite nanoparticles

A novel composite adsorbent, magnetite/hydroxyapatite (Fe₃O₄/HAP) composites, was prepared by biowaste chicken eggshell for the purpose of removing radiocobalt from aqueous solutions. It highlighted that more than 92% Co(II) could be removed by using the developed composites under the experimental conditions. The maximum sorption capacity of Co(II) on Fe₃O₄/HAP composites was 6.9 × 10⁻⁴ mol/g. The coexisted foreign ions, e.g., ClO₄ ⁻, NO₃ ⁻, Cl⁻, Na⁺ and K⁺, did not interfere the elimination of Co(II) from aqueous solutions, while Mg²⁺ did. The sorption process was found to be controlled well by pseudo-second-order and intra-particle diffusion models, and the equilibrium data were simulated by Langmuir model very well with high correlation coefficients. The thermodynamic parameters confirmed the spontaneity and endothermic nature of Co(II) sorption processes. After sorption, the Fe₃O₄/HAP composites could be effectively and fleetly separated from aqueous solutions by magnetic separation technique in large scale. The Fe₃O₄/HAP composites are suitable materials in the preconcentration of Co(II) from large volumes of aqueous solutions.