Dependence of pH and surfactant effect in the synthesis of magnetite(Fe3O4) nanoparticles and its properties

Nanoparticles of Fe3O4 were synthesized by co-precipitation in an aqueous solution containing ferrous and ferric salts (1:2) at varying pH with ammonia as a base. It was found that the value of pH influences the reaction mechanism for the formation of Fe3O4. Furthermore, the addition of mercaptoethanol significantly reduced the crystalline size of Fe3O4 nanoparticles from 15.03 to 8.02 nm. X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles were epsilon-Fe2O3 or Fe3O4 phase. To further prove the composition of the product, as-prepared Fe3O4 were examined by X-rayphotoelectron spectroscopy (XPS). Magnetic properties of the obtained particles were determined by vibrating sample magnetometer (VSM). Further analysis of the X-ray studies shows that while maintaining a pH value of 6 and 9 in a solution containing iron salts II and III ions produces epsilon-Fe2O3. Whereas a pH value of 11 produces magnetite (Fe3O4) phase. All of these results show that the pH has a major role in the observed phase formation of (Fe3O4) nanoparticles.

Surfactant stabilized nanopetals morphology of α-MnO2 prepared by microemulsion method

α-Manganese dioxide is synthesized in a microemulsion medium by a redox reaction between KMnO4 and MnSO4 in presence of sodium dodecyl sulphate as a surface active agent. The morphology of MnO2 resembles nanopetals, which are spread parallel to the field. The material is further characterized by powder X-ray diffraction, energy dispersive analysis of X-ray, and Brunauer–Emmett–Teller surface area. Supercapacitance property of α-MnO2 nanopetals is studied by cyclic voltammetry and galvanostatic charge–discharge cycling. High values of specific capacitance are obtained.

Hydrothermal synthesis and characterization of CaSO4 pseudomicrorods

Calcium sulphate (CaSO4) pseudomicrorods have been synthesized by alow-temperature hydrothermal method using CaSO4 powder as a precursor and hexadecylamine as a surfactant at 180 degrees C for at different intervals of time. The powder X-ray diffraction pattern indicates that the as-formed pseudomicrorods are of orthorhombic phase with lattice parameters a = 7.0023(4) angstrom, b = 6.9939(5) angstrom and c = 6.2434(4) angstrom. Scanning electron microscopy images show that the pseudomicrorods have diameters of about 0.2-2.5 mm and lengths of about 2-10 mm. Fourier transform infrared spectroscopy shows a strong doublet near 609 and 681 cm(-1) arising from nu(4) (SO42) bending vibrations. The strongest band observed at 1132 cm(-1) is associated with nu(3) (SO42-) stretching vibrations. The band near 420-450 cm(-1) is attributed to nu(2) (SO42-) bending vibrations. The Raman spectrum exhibits an intense peak at 1008 cm(-1) associated with the SO42- mode. The photoluminescence spectrum exhibits UV bands (330, 350 nm), strong green bands (402, 436 nm) and weak blue bands (503 nm). A widening of the optical band gap was observed as the particle size decreased.

Activity of Ferric Oxide in Steelmaking Slag

Refining reactions in steelmaking primarily involve oxidation of impurity element(s). The oxidation potential of the slag and the activity of oxygen in the metal (h(O)) are the major factors controlling these chemical reactions. In turn, the oxidation potential of the slag is influenced strongly by the equilibrium distribution of oxygen between ferrous and ferric oxides. We recently investigated the activity coefficient of FeO in steelmaking slag and the effect of chemical composition thereon. This work is focused on estimation of theactivity coefficient of Fe2O3.

NMR study of internal motions in certain iron group fluosilicates

NMR study of ferrous fluosilicate hexahydrate indicated the presence of motion of both proton and fluorine nuclei. Only a single narrow line was observed for protons for any arbitrary orientation of a single crystal with respect to the applied magnetic field. This can be interpreted in terms of a phase-correlated flip motion of the interproton vectors between two disordered orientations or in terms of a hindered rotation of the Fe(H2O) 6 octahedron about the fourfold axes, together with the flip motion. The fluorine second moment indicated that the SiF6 octahedron also is undergoing reorientation. The temperature variation of the powder linewidth showed a transition around 195°K and led to rather low values for the potential barriers hindering the motions. No significant temperature variation of the linewidth was observed for hexahydrated cobalt fluosilicate in the temperature range between 90°K and room temperature. Similar observations in a powder sample of tetrahydrated copper fluosilicate also showed the presence of internal motions. The linewidth transition in this case took place at about 220°K and was found to be rather abrupt. The potential barrier for the motion was found to be relatively high.

Structure of Ferroverdin

FERROVERDIN, a green iron-containing pigment, was isolated in 1955 by Chain, Tonolo and Carilli1 from an unidentified species of Streptomyces. It was at first assigned the formula C30H24O8N2Fe and the iron was shown by measurements of magnetic susceptibility to be in the ferrous state2. Later the ligand present was proved to be the p-vinyl phenyl ester of 3-nitroso-4-hydroxy-benzoic acid3,4. X-ray crystallographic measurements were undertaken to find the atomic arrangement in this unusual complex; they show, in two different crystal structures, that each iron atom is attached to three nitrosophenyl ligands and that the charge is balanced by sodium ions.

Purification and properties of uridine hydrolase from mung-bean (Phaseolus radiatus) seedlings

The occurrence in plants of an enzyme system catalyzing the cleavage of uridine has been demonstrated. The enzyme from Phaseolus radiatus was purified about 132-fold with 24% recovery by a combination of procedures involving mild acid treatment, ammonium sulphate fractionation, negative adsorption on calcium phosphate gel and DEAE-cellulose chromatography. The enzyme cleaves uridine to uracil and ribose in the absence of phosphate indicating that the mechanism of cleavage was hydrolytic rather than phosphorolytic. The enzyme is specific to uridine and does not act on other purine and pyrimidine compounds. The enzyme shows maximum activity at pH 7.4 and has a temperature optimum of 45 °. It does not require metal ions for activity. Inhibition of the enzyme by p-chloromercuribenzoate as well as N-ethylmaleimide and the reversal of p-chloromercuribenzoate inhibition by sulfhydryl agents indicate the probable involvement of readily oxidizable sulfhydryl groups in enzyme activity.

Influence of the hydrogen bond on the N-H stretching frequencies in amino-acids

The spectra of glycine, its addition compounds and other amino-acids exhibit Raman lines in the region from 3250 cm.−1 to 2500 cm.−1 It has been shown that these lines cannot be assigned to N-H...O stretching vibrations, where the N atom has the covalency of three, but to N+-H...O stretching vibration where the N atom has the covalency of four. Using the data obtained with triglycine sulphate which has the largest number of N+-H...O bonds and whose H bond lengths are known, the correlation curve giving the relation between the N+-H...O stretching frequencies and the corresponding H bond lengths has been drawn. Using this correlation curve, the N+-H...O stretching frequencies appearing inα-glycine,γ-glycine, diglycine hydrochloride, diglycine hydrobromide,l-asparagine monohydrate anddl-alanine have been satisfactorily accounted for on the basis of the known hydrogen bond lengths in these substances.

The proton magnetic resonance study of the structure of Na2Zn(SO4)2·4H2O

The proton magnetic resonance spectra of single crystals of Na2Zn(SO4)2·4H2O have been investigated and the orientations of the water molecules have been determined. Using the heavy atom structure determined by X-rays a system of hydrogen bonds between water and sulphate oxygens has been proposed.

Analysis of metal thiourea complexes by chloramine-T oxidation

A rapid method is described for the analysis of metal thiourea complexes of Zn, Cd, Hg and Cu by adding excess of chloramine-T and determining the excess iodometrically. Colloidal suspensions of metal sulphides (Cu, Hg, Zn, Cd) have been found to undergo rapid oxidation to sulphate quantitatively in acid medium by chloramine-T.

Raman spectrum of triglycine selenate (G3Se), [(NH2CH2COOH)3 H2SeO4]

The Raman spectrum of a single crystal of triglycine selenate G3Se which is ferroelectric below 22° C. has been photographed using λ 2537 excitation. 42 Raman lines have been recorded of which 6 belong to the lattice spectrum, 3 are due to NH...O oscillations and the remaining 33 are due to internal oscillations of the ions of glycine and SeO4--. There is a close similarity between the spectrum of triglycine selenate and the spectrum of its isomorph, triglycine sulphate, the frequency shifts due to the SO4-- ion being replaced by the frequency shifts due to the SeO4-- ion. The existence of glycine in the zwitterion form in the structure of G3Se is substantiated by the appearance in the Raman spectrum of lines which are attributable to NH3+ groups and COO- groups. The appearance of the additional C-H line at 2982 cm.-1 in the spectrum of triglycine selenate which is absent in the spectrum of α-glycine indicates the existence of planar monoprotonated glycine also in the structure, as indicated by X-ray studies.

Hydrolytic reactions of tetrasulphur tetranitride in a homogeneous medium

The hydrolytic reactions of tetrasulphur tetranitride are studied in a homogeneous medium. Alkaline hydrolysis gives sulphite, thiosulphate, sulphate and sulphide whereas the products in acid hydrolysis are mainly sulphur dioxide, elemental sulphur and hydrogen sulphide, with traces of polythionates. Under optimum conditions, tetrasulphur tetranitride reacts with sulphite consuming 2 moles of sulphite per mole of sulphur nitride to give 2 moles of trithionate. The reaction of sulphur nitride with thiosulphuric acid gives pentathionate and tetrathionate.

Mechanism of crystal structure transformations. Part 3. - Factors affecting the anatase-rutile transformation

The particle size and crystallite size of anatase increase markedly in the region of the crystal structure transformation. The unit cell of anatase seems to expand prior to the transformation to rutile. This expansion has been attributed to a displacive transformation of the type defined by Buerger. Smaller particle size and larger surface area seem to favour the transformation. The kinetics of the transformation of anatase prepared by the hydrolysis of titanium sulphate have been studied at different temperatures and are found to be considerably different from the kinetics of the transformation of pure anatase. The transformation becomes immeasurably slow below ∼695 ± 10°C compared to ∼610°C for pure anatase. An induction period is observed in the transformation of anatase obtained from sulphate hydrolysis and the duration decreases with increase in temperature. The activation energy is ∼120 kcal/mole, a value higher than that for the pure anatase-rutile transformation. The results have been interpreted in terms of the relative rates of nucleation and propagation processes. The activation energy for the nucleation process seems to be much larger than for the propagation process. The kinetics of the transformation of anatase samples doped with different amounts of sulphate ion impurity have also been studied and the transformation is found to be progressively decelerated with increase in the impurity concentration. The energy of activation for the transformation appears to increase progressively with increase in impurity concentration.

Indoleacetaldoxime hydro-lyase (4.2.1.29). III. Further studies on the nature and mode of action of the enzyme

Further purification of indoleacetaldoxime (IAOX) hydro-lyase from Gibberella fujikuroi by DEAE-cellulose chromatography is described. The purified enzyme was activated by dehydroascorbic acid (DHA), ascorbic acid (AA), and pyridoxal phosphate (PALP) and was inhibited by thiol compounds and thiol reagents including phenylthiocyanate. Ferrous ions but not ferric ions activated the purified enzyme. The enzyme was activated by dihydrofolic acid but inhibited by tetrahydrofolic acid. Phenylacetaldoxime, a competitive inhibitor, afforded partial protection of the enzyme from the action of N-ethylmaleimide suggesting the involvement of a thiol function at the active site or substrate-binding site. The inhibition of the enzyme by 2,3-dimercaptopropanol was reversed by DHA, PALP, or frozen storage. KCN inhibition of the enzyme was reversed by PALP. NaBH4 reduction of the purified enzyme in the presence of PALP gave an active enzyme which was further activated by PALP or DHA but not by ferrous ions. These results suggested a "structural" role for PALP in the activity of IAOX hydro-lyase. Dilute solutions of the purified enzyme, obtained during DEAE-cellulose chromatography and concentrated using sucrose, showed enhanced activity upon frozen storage and thawing. The increase in activity of the enzyme during certain culture conditions, the activation and inhibition of the enzyme by several unrelated compounds, and the effect of freezing indicate that IAOX hydro-lyase is probably a metabolically regulated enzyme with a structure composed of subunits.

Adhesion of Acidithiobacillus ferrooxidans to mineral surfaces

Direct contact mechanism in bioleaching implies prior mineral adhesion of Acidithiobacillus ferrooxidans and subsequent enzymatic attack.Prior bacterial adaptation to sulfide mineral substrates influences bacterial ferrous ion oxidation rates. It is highly beneficial to understand major biooxidation mechanisms with reference to solution- and mineral-grown cells in order to optimize bioleaching reactions. For A. ferrooxidans grown in the presence of solid substrates such as sulfur, pyrite and chalcopyrite, bacterial adhesion is required for its enzymatic machinery to come into close contact for mineral dissolution.But when grown in solution substrate such as ferrous ions and thiosulfate, such an adhesion machinery is not required for substrate utilization. Proteinaceous compounds were observed on the surface of sulfur-grown cells. Such an induction of relatively hydrophobic proteins and down regulation of exposed polysaccharides leads to changes in cell surface chemistry. Sulfur-grown and pyrite- and chalcopyrite-grown bacterial cells were found to be more efficient in the bioleaching of chalcopyrite than those grown in the presence of ferrous ions and thiosulfate. (C) 2010 Elsevier B.V. All rights reserved.