Influence of the iron source on the solar photo-Fenton degradation of different classes of organic compounds

In this work the influence of two different iron sources, Fe(NO3)(3) and complexed ferrioxalate (FeOx), on the degradation efficiency of 4-chlorophenol (4CP), malachite green, formaldehyde, dichloroacetic acid (DCA) and the commercial products of the herbicides diuron and tebuthiuron was studied. The oxidation of 4CP, DCA, diuron and tebuthiuron shows a strong dependence on the iron source. While the 4CP degradation is favored by the use of Fe(NO3)(3), the degradation of DCA and the herbicides diuron and tebuthiuron is most efficient when ferrioxalate is used. on the other hand, the degradation of malachite green and formaldehyde is not very influenced by the iron source showing only a slight improvement when ferrioxalate is used. In the case of formaldehyde, DCA, diuron and tebuthiuron, despite of the additional carbon introduced by the use of ferrioxalate, higher mineralization percentages were observed, confirming the beneficial effect of ferrioxalate on the degradation of these compounds. The degradation of tebuthiuron was studied in detail using a shallow pond type solar flow reactor of 4.5 L capacity and 4.5 cm solution depth. Solar irradiation of tebuthiuron at a flow rate of 9 L h(-1), in the presence of 10.0 mmol L-1 H2O2 and 1.0 mmol L-1 ferrioxalate resulted in complete conversion of this herbicide and 70% total organic carbon removal. (c) 2005 Elsevier Ltd. All rights reserved.

Effect of iron on bovine enamel and on the composition of the dental biofilm formed in situ

Objectives: This study investigated in situ the effect of iron (Fe) on the reduction of demineralization of bovine enamel, as well as on the composition of dental biofilm.Design and methods: Twelve volunteers were included in this blind crossover study, which was conducted in two stages of 14 days each. For each stage, the volunteers received palatal appliances containing four blocks of bovine enamel (4 mm x 4 mm x 2.5 mm). Six volunteers dripped a solution of 15 mmol L-1 ferrous sulphate onto the fragments and the remaining six dripped deionized water (eight times per day). After five minutes, a fresh 20% (w/v) sucrose solution was dripped onto all enamel blocks. During the experimental period the volunteers brushed their teeth with non-fluoridated dentifrice. After each stage, the percentage of surface microhardness change (%SMHC) and area of mineral toss (Delta Z) were determined on enamel and the dental biofilm formed on the blocks was collected and analysed for F, P, Ca, Fe and alkali-soluble carbohydrates. The concentrations of F, Ca and Fe in enamel were also analysed after acid biopsies.Results: There was a statistically significant increase in the P and Fe concentrations in the biofilms treated with ferrous sulphate (p < 0.05), which was not observed for F, Ca and alkali-soluble carbohydrates. The group treated with ferrous sulphate had significantly lower %SMHC and Delta Z when compared to control (p < 0.05).Conclusions: These results showed that ferrous sulphate reduced the demineralization of enamel blocks and altered the ionic composition of the dental biofilm formed in situ. (c) 2005 Elsevier Ltd. All rights reserved.

Characterization of iron(III)porphyrin-hydroxo complexes in organic media through UV-Vis and EPR spectroscopies

The interaction of OH- with Fe(TPP)(+), Fe(TDCPP)(+), Fe(TMP)(+) and Fe(TFPP)(+) in 1,2-dichloroethane was studied by titrating FeP solutions with aliquots of a solution of tetrabutylammonium hydroxide in acetonitrile. The number of OH- ions (n) coordinated to the FeP and the stability constants (beta(n)) for the FeP-OH- complexes were calculated from UV-Vis absorbance data and iron spin states were determined through EPR spectroscopy, Fe(TMP) (+) forms a high-spin mono-hydroxo complex, while Fe(TPP)I and Fe(TDCPP)(+) form high-spin bis-hydroxo complexes. To our knowledge, this is the first time that the formation of bis-hydroxo complexes from Fe(TPP) (+) has been reported, and this was possible because the studies were carried out in basic organic media, In this same medium, Fe-III-Fe-II reduction upon OH- addition to Fe(TFPP) (+) was observed, without concomitant formation of the mu-oxo dimeric species [Fe(TFPP)](2)O. (C) 1999 Elsevier B.V., All rights reserved.

Low temperature annealing of amorphous gallium arsenide films

This work reports the changes in the optical properties produced by annealing of amorphous GaAs at temperatures smaller than or just sufficient to produce crystallization of the material. The films were grown by the flash evaporation technique on glass substrates at room temperature. Optical and structural changes of our samples were monitored through photothermal deflection spectroscopy, optical transmittance and reflectance and X-ray diffraction (XRD). The structural results from XRD detected no crystallization of the films for temperatures up to 240 degreesC. We have observed consistent changes in the optical gap and Urbach energy of the annealed film. The optical gap increases with increasing annealing temperature from 1.17 to 1.32 eV. The Urbach energy decrease from 120 meV (as-grown film) to 105 meV (anneal at 200 degreesC). We propose that these changes are due to a diminution of the tail state defects and/or the relaxation of strained bonds. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Photoluminescence in amorphous PLZ

Amorphous and crystalline powder of PLZ was prepared by using the polymeric precursor method. TGA-DSC (Thermal analysis and Differential Scanning Calorimetry) shows the decomposition of polymeric resin, an amorphous phase and the crystallization of powder. Raman scattering of powder shows an amorphous and semicrystalline phase at 450 and 550 degreesC, respectively. XRD (X-ray diffraction pattern) of powder shows high crystallinity at 700 degreesC/3 h. PL (Photoluminescence) analysis of powder at 300 degreesC/3 h shows a broad asymmetric peak at 585 nm and increases of calcining time led to intense peaks of PL at 300 degreesC/6 h. This emission could be attributed to Zr --> O from the oxygen-2p orbitals to the zirconate-3d orbitals. (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.

Synthesis, characterization and electropolymerization of a new polypyrrole iron(II) Schiff-base complex

This work presents the synthesis of the complex [Fe(L)(2)](PF6)(2) (.) H2O (L = 2,6-bis[1-(3-pyrrol-1-yl-propylimino)ethyl]pyridine (Fig. 1) and its characterization through elemental and thermal analysis, X-ray diffraction and UV-Vis, IR and H-1 NMR spectra. The use of this compound in the preparation of modified electrodes is also described. The best electrochemical parameters to achieve optimum film formation have been established and the effects of both the upper-limit of the applied scanning potential (E-aul) and the number of scans on the efficiency of film formation have been investigated. Film surface morphology has been characterized by atomic force microscopy. (C) 2004 Elsevier Ltd. All rights reserved.

Low-temperature, self-nucleated growth of indium-tin oxide nanostructures by pulsed laser deposition on amorphous substrates

Indium-tin oxide nanostructures were deposited by excimer laser ablation in a nitrogen atmosphere using catalyst-free oxidized silicon substrates at 500 degrees C. Up to 1 mbar, nanowires grew by the vapor-liquid-solid (VLS) mechanism, with the amount of liquid material decreasing as the deposition pressure increased. The nanowires present the single-crystalline cubic bixbyite structure, oriented < 100 >. For the highest pressure used, pyramids were formed and no sign of liquid material could be observed, indicating that these structures grew by a vapor-solid mechanism. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of an iron mouthrinse on enamel and dentine erosion subjected or not to abrasion: An in situ/ex vivo study

Objectives: This in situ/ex vivo study evaluated whether a rinse with an iron solution could reduce wear and the percentage of microhardness change of human enamel and dentine submitted to erosion followed by brushing after 1 or 30 min.Design: During 2 experimental 5-day crossover phases (wash-out period of 10 days), 10 volunteers wore intraoral palatal devices, with 12 specimens (6 of enamel and 6 of dentine) arranged in 3 horizontal rows (4 specimens each). In one phase, the volunteers immersed the device for 5 min in 150 mL of cola drink, 4 times a day. Immediately after immersion, no treatment was performed in one row. The other row was brushed after 1 min using a fluoride dentifrice and the device was replaced into mouth. After 30 min, the remaining row was brushed. In the other phase, the procedures were repeated, but after immersion the volunteers rinsed for 1 min with 10 mL of a 10 mM ferrous sulphate solution. Changes in surface microhardness (%SMH) and wear (profilometry) of enamel and dentine were measured. Data were tested using ANOVA and Tukey's tests (p < 0.05).Results: the enamel presented more wear than dentine, under all experimental conditions. The iron solution caused a significant reduction on the %SMH in enamel, and a significant reduction on the wear in dentine, regardless the other conditions.Conclusions: Rinsing with an iron solution after an erosive attack, followed or not by an abrasive episode, may be a viable alternative to reduce the loss of dental structure. (c) 2006 Elsevier Ltd. All rights reserved.

Preparation and properties of colloidal particles. Silica on yttrium iron garnet

Various properties of particles can be altered by coating them with a layer of different chemical composition. Yttrium iron garnet (YIG) particles has been coated with silica for control of their sintering, corrosion resistance, and stabilization of magnetic properties. This silica cover was obtained by hydrolysis of tetraethylorthosilicate (TEOS) in 2-propanol. This material was characterized by transmission (TEM) electron microscopy, (XEDS) X-ray energy-dispersive spectrometry, (XPS) X-ray photoemission spectroscopy and (VSM) vibrating sample magnetometry. YIG was heterocoagulated by silica as indicated by TEM micrographies. XPS measurements indicated that only binding energy for silicon and oxygen was found on the silica shell, which confirms that the YIG was covered. The values of the saturation magnetization differ from the heterocoagulated system to well-crystallized YIG.

Preparation of Fe-Cr-P-Co amorphous alloys by electrodeposition

The effects of bath composition and electroplating conditions on structure, morphology, and composition of amorphous Fe-Cr-P-Co deposits on AISI 1020 steel substrate, priorly plated with a thin Cu deposit, were investigated. The increase of charge density activates the inclusion of Cr in the deposit. However, above specific values of the charge density, which depend on the deposition current density, the Cr content in the deposit decreases. This Cr content decreasing is probably due to the significant hydrogen evolution with the increasing of deposition cur-rent and charge density. The effect of charge density on the content of Fe and Co is not clear. However, there is a tendency of increasing of Fe content and decreasing of Co content with the raising of current density. The Co is more easily deposited than the P, and its presence results in a more intense inhibition effect on the Cr deposition than the inhibition effect caused by P presence. Scanning electron microscope (SEM) analysis showed that Co increasing in the Fe-Cr-P-Co alloys analyzed does not promote the susceptibility to microcracks, which led to a good quality deposit. The passive film of the Fe-Cr-P-Co alloy shows a high ability formation and high protective capacity, and the results obtained by current density of corrosion, j(cor), show that the deposit with addition of Co, Fe31Cr11P28Co30, presents a higher corrosion resistance than the deposit with addition of Ni, Fe54Cr21P20Ni5. (C) 2004 Published by Elsevier B.V.

Development and Evaluation of a Nanoporous Iron (Hydr)oxide Electrode for Phosphate Sensing

Nanoporous iron (hydr) oxide electrodes are evaluated as phosphate sensors using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The intensity of the reduction peak current (I-cp) of the ferrihydrite working electrode is tied to phosphate concentration at low pH; however, a hematite electrode combined with the use of EIS provided reliable sensing data at multiple pH values. Nanoporous hematite working electrodes produced an impedance phase component (theta) that shifts with increasing phosphate, and, at chosen frequencies, theta values were fitted for the range 1 nM to 0.1 mM phosphate at pH 4 and pH 7 in 5 mM NaClO4.

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb1-XLaXTiO3 thin films, (X = 0.0; 13 and 0.27 mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO2/Si (1 1 1), Si (1 0 0) and glass substrates by spin coating, and annealed in the 200-300degreesC range in an O-2 atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO3. The films deposited on Pt/Ti/SiO2/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Transplacental Transfer of Iron in the Water Buffalo (Bubalus bubalis): Uteroferrin and Erythrophagocytosis

The objectives of this investigation were to understand transplacental transport of iron by secreted uteroferrin (UF) and haemophagous areas of water buffalo placenta and clarify the role(s) of blood extravasation at the placental-maternal interface. Placentomes and interplacentomal region of 51 placentae at various stages of gestation were fixed, processed for light and transmission electron microscopy, histochemistry and immunohistochemistry. Haemophagous areas were present in placentomes collected between 4 and 10 months of pregnancy. Perl's reaction for ferric iron was negative in placentomes, but positive in endometrial glands. Positive staining for UF indicated areas in which it was being taken up by phagocytosis and/or fluid phase pinocytosis in areolae of the interplacentomal mesenchyme, with little staining in endometrial stroma. Imunohistochemistry detected UF in trophectoderm of haemophagous regions of placentomes and in other parts of the foetal villous tree, but the strongest immunostaining was in the epithelial cells and lumen of uterine glands. Ultrastructural analyses indicated that erythrophagocytosis was occurring and that erythrocytes were present inside cells of the chorion that also contained endocytic vesicles and caveolae. Results of this study indicate that both the haemophagous areas of placentomes and the areolae at the interface between chorion and endometrial glands are important sites for iron transfer from mother to foetal-placental tissues in buffalo throughout pregnancy.

Organic complexation and translocation of ferric iron in podzols of the Negro River watershed. Separation of secondary Fe species from Al species

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Construction and application of an electrochemical sensor for paracetamol determination based on iron tetrapyridinoporphyrazine as a biomimetic catalyst of P450 enzyme

This work describes the construction and application of a biomimetic sensor for paracetamol determination in different samples. The sensor was prepared by modifying a glassy carbon electrode surface with a Nafion (R) membrane doped with FeTPyPz. The best performance of the sensor in 0.1 mol L-1 acetate buffer was at pH 3.6. Under these conditions, an oxidation potential of paracetamol was observed at 445 mV vs. Ag vertical bar AgCl. The sensor presented a linear response range between 4.0 and 420 mu mol L-1, a sensitivity of 46.015 mA L mol(-1) cm(-2), quantification and detection limits of 4.0 mu mol L-1 and 1.2 mu mol L-1, respectively. A detailed investigation about its electrochemical behavior and selectivity was carried out. The results suggested that FeTPyPz presents catalytic properties similar to P450 enzyme for paracetamol oxidation. Finally, the sensor was applied for paracetamol determination in commercial drugs and for the monitoring of its degradation in an electrochemical batch reactor effluent.