Structural Investigation of MFe(2)O(4) (M = Fe, Co) Magnetic Fluids

Ferrites of the type M(II)Fe(2)O(4) (M = Fe and Co) have been prepared by the traditional coprecipitation method. These ferrites were modified by the adsorption of fatty acids derived from soybean and castor oil and were then dispersed in cyclohexane, providing very stable magnetic fluids, readily usable in nonpolar media. The structural properties of the ferrites and modified ferrites as well as the magnetic fluids were characterized by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), DRIFTS (diffusion reflectance infrared Fourier transform spectroscopy), FTMR (Fourier transform near-infrared), UV-vis, normal Raman spectroscopy, and surface-enhanced Raman scattering (SERS). XRD and TEM analysis have shown that the magnetic nanoparticles (nonmodified and modified) present diameters in the range of 10-15 nm. DRIFTS measurements have shown that the carboxylate groups of soybean and castor oil fatty acids adsorb on the ferrite surface, forming three different structures: a bridging bidentate, a bridging monodentate, and a bidentate chelate structure. The FTIR and Raman spectra of nonmodified Fe(3)O(4) and CoFe(2)O(4) nanoparticles have shown that the number of observed phonons is not compatible with the expected O(h)(7) symmetry, since IR-only active phonons were observed. in the Raman spectra and vice versa. SERS measurements of a CoFe(2)O(4) thin film on a SERS-active gold electrode at different applied potentials made possible the assignment of the signals near 550 and 630 cm(-1) to Co-O motions and the signals near 470 and 680 cm(-1) to Fe-O motions.

Investigation of Iron (III) desferrioxamine B oxalate ligand exchange by UV-vis spectroscopy: the next step in developing a quantitative analytical method for measuring bioavailable iron in marine ecosystems

To date there are no analytical techniques designed to exclusively measure bioavailable iron in marine environments. The goal of this research is to develop such a technique by isolating the bioavailable iron using the terrestrial siderophore desferrioxamine B (DFB). This project contained many challenging aspects, but the specific goal of this study was to develop a robust analytical technique for quantification of Fe(III)-DFB complexes at nanomolar concentrations. Past work showed that oxalate (Ox) promotes photodissociation of Fe(III)-DFB to Fe(Il), and we are specifically interested in the mechanism of this process. A model was developed using known thermodynamic constants for Fe(III)-DFB and Fe(III) oxalato complexes and adjusting for ionic strength. The model was confirmed by monitoring the UV-VIS absorbance of the system at a variety of oxalate concentrations and pH. The model did not include ternary complexes. Next., the rate of Fe(1I) production during UV irradiation was examined. The results showed that the rate of Fe(II) production was based entirely on the [Fe(Ox)?]3- speciation, and that reoxidation of Fe(II) occurred via reactive oxygen intermediates. This reoxidation could be avoided by either decreasing the oxygen concentration or by adding a Fe(II) stabilizing reagent, such as ferrozine. Further studies need to be done to confirm that these results apply at sub nanomolar concentrations, and the issue of Fe(II) reoxidation at lower Fe concentrations needs to be addressed.

Síntese e caracterização de espinélios a base de Cu, Fe e Cr para pigmentos cerâmicos

Inorganic pigment comprises a host lattice, which is part of the chromophore component (usually a transition metal cation) and possible components modifiers, which stabilize, add or restate the properties pigments. Among the materials with spinel, ferrites, and the chromite stand out, because they have broad technological importance in the area of materials, applicability, pigments, catalytic hydrogenation, thin film, ceramic tiles, among others. The present work, pigments containing CuFe2O4, CuCr2O4,e CuFeCrO4, were synthesized by a method that makes use of gelatin as organic precursor using their application to ceramic pigments. The pigments were characterized by X-ray diffraction (XRD), Infrared spectroscopy, scanning electron microscopy (SEM) spectroscopy in the UV-visible and Colorimetry. The results confirmed the feasibility of the synthetic route used, with respect to powders synthesized, there is the formation of spinel phase from 500°C, with an increase in crystallinity and the formation of other phases. The pigments were shown to be crystalline and the desired phases were obtained. The copper chromite have hues ranging from green to black according to the calcination temperature, while the copper chromite doped with iron had brownish. The ferrites showed copper color and darker brown to black, which may indicate an interesting factor because of the importance of black pigment

Síntese e impregnação de peneiras moleculares Fe MCM-41 derivada de sílica da casca do arroz

The mesoporous molecular sieves of the MCM-41 and FeMCM-41 type are considered promissory as support for metals used as catalysts in oil-based materials refine processes and as adsorbents for environmental protection proposes. In this work MCM-41 and FeMCM41 were synthesized using rice husk ash - RHA as alternative to the conventional silica source. Hydrothermal synthesis was the method chosen to prepare the materials. Pre-defined synthesis parameters were 100°C for 168 hours, later the precursor was calcinated at 550°C for 2 hours under nitrogen and air flow. The sieves containing different proportions of iron were produced by two routes: introduction of iron salt direct synthesis; and a modification post synthesis consisting in iron salt 1 % and 5% impregnation in the material followed by thermal decomposition. The molecular sieves were characterized by X ray diffraction XRD, Fourier transform infrared spectroscopy FT-IR, X ray fluorescence spectroscopy XFR, scanning electronic microscopy SEM, specific surface area using the BET method, Termogravimetry TG. The kinetic model of Flynn Wall was used with the aim of determining the apparent activation energy of the surfactant remove (CTMABr) in the MCM- 41 porous. The analysis made possible the morphology characterization, identifying the presence of hexagonal structure typical for mesoporous materials, as well as observation of the MCM41 and iron of characteristic bands.

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SnO2 nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sol-gel synthesis and characterization of Fe(2)O(3) center dot CeO(2) doped with Pr ceramic pigments

Undoped x center dot alpha-Fe(2)O(3) y center dot CeO(2) and doped with praseodymium ceramic pigments were obtained by the sol-gel method after heat treatment at 800 degrees C for 2 h. These pigments were characterized by XRD, nitrogen adsorption, scanning electron microscopy, ultraviolet-visible absorption spectroscopy and colorimetrical measurements. Red and brown colors with several tonalities were observed after changes with Ce and Pr concentration.

Piezoresponse behavior of niobium doped bismuth ferrite thin films grown by chemical method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn for foliar diagnosis using high-resolution continuum source flame atomic absorption spectrometry: Feasibility of secondary lines, side pixel registration and least-squares background correction

The fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry is proposed. For this, the main lines for Cu (324.754 nm), Fe (248.327 nm), Mn (279.482 nm) and Zn (213.857 nm) were selected, and the secondary lines for Ca (239.856 nm), Mg (202.582 nm) and K (404.414 nm) were evaluated. The side pixel registration approach was studied to reduce sensitivity and extend the linear working range for Mg by measuring at wings (202.576 nm; 202.577 nm; 202.578 nm; 202.580 nm: 202.585 nm; 202.586 nm: 202.587 nm; 202.588 nm) of the secondary line. The interference caused by NO bands on Zn at 213.857 nm was removed using the least-squares background correction. Using the main lines for Cu, Fe, Mn and Zn, secondary lines for Ca and K, and line wing at 202.588 nm for Mg, and 5 mL min(-1) sample flow-rate, calibration curves in the 0.1-0.5 mg L-1 Cu, 0.5-4.0 mg L-1 Fe, 0.5-4.0 mg L-1 Mn, 0.2-1.0 mg L-1 Zn, 10.0-100.0 mg L-1 Ca, 5.0-40.0 mg L-1 Mg and 50.0-250.0 mg L-1 K ranges were consistently obtained. Accuracy and precision were evaluated after analysis of five plant standard reference materials. Results were in agreement at a 95% confidence level (paired t-test) with certified values. The proposed method was applied to digests of sugar-cane leaves and results were close to those obtained by line-source flame atomic absorption spectrometry. Recoveries of Ca, Mg, K, Cu, Fe, Mn and Zn in the 89-103%, 84-107%, 87-103%, 85-105%, 92-106%, 91-114%, 96-114% intervals, respectively, were obtained. The limits of detection were 0.6 mg L-1 Ca, 0.4 mg L-1 Mg, 0.4 mg L-1 K, 7.7 mu g L-1 Cu, 7.7 mu g L-1 Fe, 1.5 mu g L-1 Mn and 5.9 mu g L-1 Zn. (C) 2009 Elsevier B.V. All rights reserved.

Evaluation of alternate lines of Fe for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determinação direta e simultânea de Al, As, Fe, Mn e Ni em cachaça por espectrometria de absorção atômica em forno de grafite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of metal - SiO2 nanocomposites in a single-step process by the polymerizable complex method

This work presents the synthesis and characterization of SiO2:metal (Ni, Co, Ag, and Fe) nanocomposites processed by the polymerizable complex method. The polymeric precursor solutions obtained were characterized by means of FT-Raman and C-13 NMR spectroscopy. The results show the formation of a hybrid polymer with carbon and silicon in the macromolecule chain and the transition metal cation arrested within this polymeric chain. The nanocomposites are formed during the controlled polymeric precursor pyrolysis. The reduction of the metal cation is promoted by the CO/CO2 atmosphere resulting from the pyrolysis of the organic material. Microstructural characterization, performed by TEM and X-ray diffraction (XRD), showed that the nanocomposites are formed by metal nanoparticles embedded in a amorphous matrix formed by SiO2 and carbon. In the SiO2:Fe system, Fe3C was also detected by XRD.

Correlation of reactivity with structural factors in a series of Fe(II) substituted cobalt ferrites

A series of powdered cobalt ferrites, CoxFe3-xO4 with 0.66 <= x< 1.00 containing different amounts of Fe-II, were synthesized by a mild procedure, and their Fe and Co site occupancies and structural characteristics were explored using X-ray anomalous scattering and the Rietveld refinement method. The dissolution kinetics, measured in 0.1 M oxalic acid aqueous solution at 70 degrees C, indicate in all cases the operation of a contracting volume rate law. The specific rates increased with the Fell content following approximately a second-order polynomial expression. This result suggests that the transfer of Fe-III controls the dissolution rate, and that the leaching of a first layer of ions Co-II and Fe-II leaves exposed a surface enriched in slower dissolving octahedral Fe-III ions. Within this model, inner vicinal lattice Fe-II accelerates the rate of Fe-III transfer via internal electron hopping. A chain mechanism, involving successive electron transfers, fits the data very well. (C) 2006 Elsevier B.V. All rights reserved.

Simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by GFAAS

A method has been developed for the simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by graphite furnace atomic absorption spectrometry (GFAAS) using a transversely heated graphite atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of analytes during the pyrolysis and atomization stages using the mixture Pd(NO3)(2) + Mg(NO3)(2) as the chemical modifier was investigated in 0.028 mol L-1 HNO3, 0.14 mol L-1 HNO3, and diluted ethanol (1 + 1, v/v) containing different nitric acid concentrations. With 5 rhog Pd + 3 mug Mg as the modifiers, pyrolysis and atomization temperatures of the heating program of the atomizer were fixed at 1200 C and 2200degreesC respectively. For 20 muL of diluted sample (10 muL ethanol + 10 muL of 0.28 mol L-1 HNO3) dispensed into the graphite tube, analytical curves in the 2.0 - 50 mug L-1 Al, As, Cu, Fe, Mn, Ni ranges were established. The calculated characteristic masses were - 37 pg Al, 73 pg As, 31 pg Cu, 16 pg Fe, 9 pg Mn, and 44 pg Ni, and the lifetime of the tube was around 2 50 firings. The limits of detection (LOD) based on integrated absorbance were 1.2 mug L-1 Al, 2.5 mug L-1 As. 0.22 mug L-1 Cu, 1.6 L-1 Fe 0.20 mug L-1 Mn 1.1 mug L-1 Ni. The relatively standard deviations (n = 12) were less than or equal to 3%, less than or equal to 6%, less than or equal to 2%, less than or equal to 3.4%, less than or equal to 1.3%, and less than or equal to 2% for Al, As, Cu, Fe, Mn, and Ni, respectively, the recoveries of Al, As, Cu, Fe, Mn and Ni added to fuel ethanol samples varied from 77% to 112%, 92% to 114%, 104% to 113%, 73% to 116%, 91% to 122% and 93% to 116%, respectively. Accuracy was checked for Al, As, Cu, Fe, Mn, and Ni determination in 20 samples purchased at local gas stations in Araraquara city, Brazil. A paired t-test showed that the results were in agreement at the 95% confidence level with those obtained by single-element GFAAS.

Direct determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by simultaneous GFAAS using integrated platforms pretreated with W-Rh permanent modifier together with Pd plus Mg modifier

A method is proposed for the simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by electrothermal atomic absorption spectrometry (ETAAS) using W-Rh permanent modifier together with Pd(NO3)(2) + Mg(NO3)(2) conventional modifier. The integrated platform of a transversely heated graphite atomizer (THGA) was treated with tungsten, followed by rhodium, forming a deposit containing 250 mug W + 200 mug Rh. A 500-muL, volume of fuel ethanol was diluted with 500 muL, of 0.14 mol L-1 HNO3 in an autosampler cup of the spectrometer. Then, 20 muL, of the diluted ethanol was introduced into the pretreated graphite platform followed by the introduction of 5 mug Pd(NO3)(2) + 3 mug Mg(NO3)(2). The injection of this modifier was required to improve arsenic and iron recoveries in fuel ethanol. Calibrations were carried out using multi-element reference solutions prepared in diluted ethanol (1 + 1, v/v) acidified to 0. 14 mol L-1 HNO3. The pyrolysis and atomization temperatures of the heating program were 1200degreesC and 2200degreesC, respectively, which were obtained with multielement reference solutions in acidic diluted ethanol (1 + 1, v/v; 0. 14 mol L-1 HNO3). The characteristic masses for the simultaneous determination in ethanol fuel were 78 pg Al, 33 pg As, 10 pg Cu, 14 pg Fe, 7 pg Mn, and 24 pg Ni. The lifetime of the pretreated tube was about 700 firings. The detection limits (D.L.) were 1.9 mug L-1 Al, 2.9 mug L-1 As, 0.57 mug L-1.Cu, 1.3 mug L-1 Fe, 0.40 mug L-1 Mn, and 1.3 mug L-1 Ni. The relative standard deviations (n = 12) were 4%, 4%, 3%, 1.5%, 1.2%, and 2.2% for Al, As, Cu, Fe, Mn, and Ni, respectively. The recoveries of Al, As, Cu, Fe, Mn, and Ni added to the fuel ethanol samples varied from 81% to 95%, 80% to 98%, 97% to 109%, 85% to 107%, 98% to 106% and 97% to 103%, respectively. Accuracy was checked for the Al, As, Cu, Fe, Mn, and Ni determination in 10 samples purchased at a local gas station in Araraquara-SP City, Brazil. A paired t-test showed that at the 95% confidence level the results were in agreement with those obtained by single-element ETAAS.