Surface structure and electronic properties of Pt-Fe/C nanocatalysts and their relation with catalytic activity for oxygen reduction

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

Effects of Alloyed and Oxide Phases on Methanol Oxidation of Pt-Ru/C Nanocatalysts of the Same Particle Size

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

Alloys and oxides on carbon-supported Pt-Sn electrocatalysts for ethanol oxidation

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

Insight into Copper-Based Catalysts: Microwave-Assisted Morphosynthesis, In Situ Reduction Studies, and Dehydrogenation of Ethanol

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Copper determination in ethanol fuel samples by anodic stripping voltammetry at a gold microelectrode

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização do complexo sólido de estanho(II)-EDTA e influência do tratamento térmico sobre a morfologia do resíduo SnO2

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Redox Behavior of molybdenum and tungsten in phosphate glasses

In this work, vitreous samples were prepared in the binary system (100 - x)NaPO3-xMO(3) with M = Mo and W and x varying from 10 to 60. The transmittance properties in the UV, visible, and near-infrared were monitored as a function of MO3 concentration. In both cases, an increase in the amount of transition metal results in an intense and broad absorption band in the visible and near-infrared attributed to metal reduction under synthesis conditions. It was shown that this large absorption can be partially or totally removed using specific oxidizing agents or by improving synthesis parameters such as melting temperature or cooling rate of the melt. In addition, structural investigations by Raman and X-ray absorption spectroscopy suggest that reduction only occurs when the metal cation is in octahedral geometry and that the transmittance improvement is not related with any structural changes. These results were explained in terms of thermodynamic equilibrium of redox species in the melt and allowed to obtain for the first time transparent and chemically stable glasses containing high concentrations of MO3 with transition metals in octahedral geometry inside the glass network.

Influência da catálise ácida e básica na preparação da sílica funcionalizada pelo método sol-gel

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

Caracterização de cálculos renais por análise térmica

Dez amostras de cálculos renais foram estudadas por Análise Elementar de CHN (EA), Espectroscopia de Absorção no Infravermelho (IV) e Difração de raios X pelo método de Pó (XRD). O comportamento térmico das amostras foi estudado por Termogravimetria/Termogravimetria Derivada (TG/DTG) e por Calorimetria Exploratória Diferencial (DSC). Os resultados de EA, Espectroscopia de Absorção IV e XRD mostraram a presença de estruvita [NH4Mg(PO4).6H2O], apatita, oxalato de cálcio monohidratado e oxalato de cálcio dihidratado. As curvas TG e DSC permitiram classificar as amostras em dois grupos diferentes: Grupo I mostrando comportamento térmico típico de estruvita e Grupo II apresentando um perfil termoanalítico característico de mistura de oxalatos.

Synthesis and Structural Studies of Er3+ Containing Lead Cadmium Fluoroborate Glasses and Glass-Ceramics

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

The influence of soil and landfill leachate microorganisms in the degradation of PVC/PCL films cast from DMF

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

Influência da adição de níquel na síntese do SrSnO3

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural studies on lead-cadmium fluoride solid solutions

(1-x)PbF2-(x)CdF2 solid solutions (with 0.1 less than or equal to x less than or equal to 0.5) were obtained by hyper-quenching the melt. Structural characteristics have been studied by X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). A cubic solid solution was obtained in which the lattice parameter decreases with increasing CdF2 content. High anionic disorder was evidenced from EXAFS investigations, whereas cations remain in the FCC arrangement. Pb L-3-edge EXAFS results illustrate clearly the occurrence of CdxPb1-xF2 mixed crystals by the introduction of Cd atoms in the second Pb coordination shell. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Electroactive layer-by-layer films of iron tetrasulfonated phthalocyanine

Electroactive films of iron tetrasulfonated phthalocyanine (FeTsPc) were assembled via the electrostatic layer-by-layer technique (LBL), in which FeTsPc layers were alternated with the polycationic poly(allylamine hydrochloride) (PAN). The multilayer formation was monitored via UV-Vis spectroscopy by measuring the increase in the Q Band of FeTsPc at 676 nm. Film thickness was estimated by profilometry as ca. 10 Angstrom per bilayer. Fourier transform infrared and UV-Vis absorption spectroscopy suggested specific interactions between FeTsPc and PAR Cyclic voltammograms showed reproducible pairs of oxidation-reduction peaks at 0.92 mV and 0.70 mV, respectively, for a 50-bilayer PAH/FeTsPc film at 50 mV/s (vs Ag/AgNO3).

Structural and functional characterization of neuwiedase, a nonhemorrhagic fibrin(ogen)olytic metalloprotease from Bothrops neuwiedi snake venom

A fibrino(geno)lytic nonhemorrhagic metalloprotease (neuwiedase) was purified from Bothrops neuwiedi snake venom by a single chromatographic step procedure on a CM-Sepharose column, Neuwiedase represented 4.5% (w/w) of the crude desiccated venom, with an approximate Mr of 20,000 and pI 5.9, As regards the amino acid composition, neuwiedase showed similarities with other metalloproteases, with high proportions of Asx, Glx, Leu, and Ser, Atomic absorption spectroscopy showed that one mole of Zn2+ and one mole of Ca2+ were present per mole olf protein. The cDNA encoding neuwiedase was isolated by RT-PCR from venom gland RNA, using oligonucleotides based on the partially determined amino-acid sequences of this metalloprotease. The fall sequence contained approximately 594 bp, which codified the 198 amino acid residues with an estimated molecular weight of 22,375. Comparison of the nucleotide and amino acid sequences of neuwiedase with those of other snake venom metalloproteases showed a high level of sequential similarity, Neuwiedase has two highly conserved characteristics sequences H(142)E(143)XXH(146)XXG(140)XXH(152) and C164I165M166. The three-dimensional structure of neuwiedase was modeled based on the crystal structure of Crotalus adamanteus Adamalysin II. This model revealed that the zinc binding site region showed a I high structural similarity with other metalloproteases,, the proteolyitc specificity, using the B beta-chain of oxidized insulin as substrate, was shown to be directed to the Ala(14)-Leu(15) and Tyr(16)-Leu(17) peptide bonds which were preferentially hydrolyzed. Neuwiedase is a A alpha,B beta fibrinogenase, Its activity upon the A alpha chain of fibrinogen was detected within 15 min of incubation. The optimal temperature and pH for the degradation of both A alpha and B beta chains were 37 degrees C and 7.4-8.0, respectively. This activity was inhibited by EDTA and 1,10-phenantroline, Neuwiedase also showed proteolytic activity upon fibrin and some components of the extracellular matrix. However, it did not show TAME esterase activity and was not able to inhibit platelet aggregation. (C) 2000 Academic Press.