The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of... more
The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.
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Polyamide-based nanocomposites containing surface-modified SiO2 nanofillers with different morphologies were prepared by in situ polymerisation. The nanocomposites microstructure was investigated by scanning electron microscopy, which... more
Polyamide-based nanocomposites containing surface-modified SiO2 nanofillers with different morphologies were prepared by in situ polymerisation. The nanocomposites microstructure was investigated by scanning electron microscopy, which showed a high degree of dispersion of the fillers. The isothermal crystallization kinetics, recorded with a differential scanning calorimeter, has shown a strong influence of the nanofillers morphology on the poly(tetramethyleneterephthalamide) crystallization behaviour. The strong nucleating effect of the inorganic substrate is interpreted as the combined result of a lower activation energy for the primary nucleation and a higher activation energy for the transport of chain stems to the growing lamellae.
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The new erbium(III) complex of picolinic acid (Hpic), [nBu4N][Er(pic)4]·5.5H2O, was synthesized and the crystal structure determined by single-crystal X-ray diffraction. The compound was further characterized using IR, Raman, 1H NMR and... more
The new erbium(III) complex of picolinic acid (Hpic), [nBu4N][Er(pic)4]·5.5H2O, was synthesized and the crystal structure determined by single-crystal X-ray diffraction. The compound was further characterized using IR, Raman, 1H NMR and elemental analysis. The picolinate ligands (pic−) are coordinated through N,O-chelation to the erbium cations, as shown by X-ray diffraction and spectroscopic results, leading to an eight coordinate complex. Photoluminescence
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Page 1. Controlled Synthesis of Morphological Well-defined BiVO4 Pigment Particles supported on Glass Substrates Sandra G. Cruz, 1,a Penka I. Girginova, 1,b Márcia C. Neves, 1,c Petr Smolka, 2,d Robert Kusak, 2,e Madalena ...
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A process of TiO2 photosensitization by coupling it with a narrow band gap semiconductor has been investigated here. Distinct TiO2/Ag2S nanocomposites were prepared by a single-source decomposition method. After sensitization, the TiO2... more
A process of TiO2 photosensitization by coupling it with a narrow band gap semiconductor has been investigated here. Distinct TiO2/Ag2S nanocomposites were prepared by a single-source decomposition method. After sensitization, the TiO2 materials were evaluated as photocatalysts on the degradation of aqueous phenol solutions. The experimental results show that the nanocomposites photocatalytic activity is related with the existence of Ag2S
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We report a general method for the synthesis of metal oxide colloidal nanocrystals in sunflower oil using single-source precursors. In this research, iron oxide nanocrystals have been synthesized and characterized though this method can... more
We report a general method for the synthesis of metal oxide colloidal nanocrystals in sunflower oil using single-source precursors. In this research, iron oxide nanocrystals have been synthesized and characterized though this method can be extended to the synthesis of other common metal oxides such as ZnO and also to other types of vegetable oils as solvents. Using this method, nanoparticles with average diameters of 7 nm and 3 nm were obtained respectively for iron oxide and zinc oxide. The magnetic iron oxide phase was identified using powder XRD, surface enhanced Raman spectroscopy and magnetic measurements as maghemite as the main component. The magnetic measurements demonstrate the superparamagnetic behavior of the iron oxide nanoparticles. This synthetic approach is an interesting way to synthesize metal oxide nanocrystals in eco-friendly solvents of natural origin.
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Page 1. Synthesis of PbS nanocrystallites using a novel single molecule precursors approach: X-ray single-crystal structure of Pb(S 2 CNEtPri) 2 Tito Trindade,a, Paul O'Brien,*a Xiao-mei Zhangb and Majid Motevallic... more
Page 1. Synthesis of PbS nanocrystallites using a novel single molecule precursors approach: X-ray single-crystal structure of Pb(S 2 CNEtPri) 2 Tito Trindade,a, Paul O'Brien,*a Xiao-mei Zhangb and Majid Motevallic aDepartment ...
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The influence of magnetite (Fe(3)O(4)) nanoparticles on the rheological properties of kappa-, iota- and lambda-carrageenan gels has been investigated. Small amplitude oscillatory shear measurements were performed to study the effect of... more
The influence of magnetite (Fe(3)O(4)) nanoparticles on the rheological properties of kappa-, iota- and lambda-carrageenan gels has been investigated. Small amplitude oscillatory shear measurements were performed to study the effect of the presence of Fe(3)O(4) nanoparticles with particle sizes of ca. 10 nm on the gel properties, as a function of carrageenan type, carrageenan concentration and magnetite load. The formation of Fe(3)O(4) nanoparticles on the presence of biopolymer was observed to promote the gelation process and lead to stronger gels as indicated by an increase in the gel viscoelastic moduli and of the gelation temperature. This effect was more marked for kappa-carrageenan than for iota- and lambda-carrageenan and has been proposed to depend not only on Fe(3)O(4) concentration but also on the concentration of potassium ions. A mechanism based on the combined effect of Fe(3)O(4) nanoparticles and potassium ions was suggested, involving the adsorption of potassium ions on the negatively charged surface of the Fe(3)O(4) nanoparticles, thus leading to an increase of the potassium ion concentration within the "carrageenan cages" containing the magnetite. This would, therefore, promote more extensive biopolymer helical aggregation, thus resulting in the formation of a stronger kappa-carrageenan gel in the presence of Fe(3)O(4), as observed. Since iota- and lambda-carrageenan gels are known to be less sensitive to potassium ions concentration, the effect of precipitating Fe(3)O(4) within these biopolymers is reduced.
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The rheological behavior of silica/kappa-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as... more
The rheological behavior of silica/kappa-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.
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In order to evaluate the environmental impact resulting from co-combustion of oily sludges, a detailed characterisation of the ashes produced was carried out.The main bulk composition and the trace elements were determined, thus allowing... more
In order to evaluate the environmental impact resulting from co-combustion of oily sludges, a detailed characterisation of the ashes produced was carried out.The main bulk composition and the trace elements were determined, thus allowing a comparison of the ashes produced from coal to those from co-combustion of the residue with and without limestone.The leachability was evaluated with two different standards,
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ABSTRACT The homoleptic, square pyramidal organochromium(III) compound [NBu(4)](2)[Cr(C(6)F(5))(5)] (1) reacts with excess organic isocyanides, CNR [R = (t)Bu, 2,6-dimethylphenyl (Xy)], under dissociation of the apical C(6)F(5) ligand to... more
ABSTRACT The homoleptic, square pyramidal organochromium(III) compound [NBu(4)](2)[Cr(C(6)F(5))(5)] (1) reacts with excess organic isocyanides, CNR [R = (t)Bu, 2,6-dimethylphenyl (Xy)], under dissociation of the apical C(6)F(5) ligand to give the more saturated, singly charged complexes [NBu(4)][trans-Cr(C(6)F(5))(4)(CNR)(2)] [R = (t)Bu (2), Xy (3)], containing six monodentate C-donor ligands. These compounds exhibit an axially distorted octahedral structure (single-crystal X-ray diffraction) with the four C(6)F(5) groups defining the equatorial positions and the CNR ligands occupying the axial ones. Compounds 2 and 3 both behave as spin quartet species (S = 3/2) at microscopic level (EPR spectroscopy), their macroscopic magnetic properties depending upon the nature of the terminal R group, as established by magnetisation measurements. When the R substituent is the saturated alkyl group (t)Bu, the compound (2) behaves as a simple paramagnet, with no magnetic interaction between individual Cr(III) centres along the whole temperature range measured (1.8-265 K). By contrast, a weak antiferromagnetic interaction is detected for compound 3 at low temperature with T(N) = 0.19(1) K. Since the closest intermetallic distances are similar in the crystals of 2·CH(2)Cl(2) and 3·1.75CH(2)Cl(2) (ca. 1.1 nm), we conclude that the insaturation of the aromatic Xy group together with the extended intermolecular π-π stacking interactions between Xy rings observed in the crystal lattice of 3·1.75CH(2)Cl(2) (centroid-to-centroid distance: 0.35 nm) favour magnetic interaction between the individual magnetic centres.
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ABSTRACT
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Research Interests: Nanoparticles, Biological Sciences, Environmental Sciences, Mercury, Animals, and 11 moreGlutathione, Glutathione Peroxidase, Lipid peroxidation, CHEMICAL SCIENCES, Hepatocytes, Glutathione Transferase, Physiological Stress Markers, Glutathione Reductase, Silicon Dioxide, Anguilla, and Ferric Compounds
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This in vitro study investigates the impact of silica-coated magnetite particles (Fe3O4@SiO2/SiDTC, hereafter called IONP; 2.5 mg L(-1)) and its interference with co-exposure to persistent contaminant (mercury, Hg; 50 μg L(-1)) during 0,... more
This in vitro study investigates the impact of silica-coated magnetite particles (Fe3O4@SiO2/SiDTC, hereafter called IONP; 2.5 mg L(-1)) and its interference with co-exposure to persistent contaminant (mercury, Hg; 50 μg L(-1)) during 0, 2, 4, 8, 16, 24, 48, and 72 h on European eel (Anguilla anguilla) brain and evaluates the significance of the glutathione (GSH) redox system in this context. The extent of damage (membrane lipid peroxidation, measured as thiobarbituric acid reactive substances, TBARS; protein oxidation, measured as reactive carbonyls, RCs) decreased with increasing period of exposure to IONP or IONP + Hg which was accompanied with differential responses of glutathione redox system major components (glutathione reductase, GR; glutathione peroxidase, GPX; total GSH, TGSH). The occurrence of antagonism between IONP and Hg impacts was evident at late hour (72 h), where significantly decreased TBARS and RC levels and GR and glutathione sulfo-transferase (GST) activity imply the positive effect of IONP + Hg concomitant exposure against Hg-accrued negative impacts [vs. early (2 h) hour of exposure]. A period of exposure-dependent IONP alone and IONP + Hg joint exposure-accrued impact was perceptible. Additionally, increased susceptibility of the GSH redox system to increased period of exposure to Hg was depicted, where insufficiency of elevated GR for the maintenance of TGSH required for membrane lipid and cellular protein protection was displayed. Overall, a fine-tuning among brain glutathione redox system components was revealed controlling IONP + Hg interactive impacts successfully.