Photoluminescence-structure relationships in ormosils for integrated optical devices

Planar waveguides with low losses in the infrared (from 0.6-1.1 dB/cm) were prepared with sol-gel derived poly(oxyethylene)/siloxane hybrid doped with zirconium(IV) n-propoxide (ZPO) and methacryloxypropyltrimethoxysilane (MAPTMS). The doped nanohybrids were characterized by small angle X-ray scattering, 29Si nuclear magnetic resonance and photoluminescence spectroscopy and compared with the undoped hybrid material. The results indicate an effective interaction between the zirconium particles and the siliceous nanodomains. © 2005 Materials Research Socicty.

Flavonóides de Calotropis procera R. Br. (Asclepiadaceae)

In this work we report the identification of two flavonol glycosides isolated from the leaves of Calotropis procera R. Br. (Asclepiadaceae), a plant species with large occurrence in Northwest of Brazil with some applications in folk medicine. Some proved pharmacological activities in this species could be attributed to the presence of flavonol glycosides. The extraction and isolation of flavonol glycosides was carried out firstly by a liquid-liquid partition, and then by elution of n-BuOH fraction with MeOH over a Sephadex LH-20 column. The identification of flavonol glycosides isorhamnetin-3-O-rutinoside (1), and isorhamnetin-3-O-robinobioside (2), was obtained by 1H and 13C NMR, one- and two-dimensional techniques.

Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier, increasing the total impedance by 4 orders of magnitude and reducing the current densities by more than 3 orders of magnitude, compared to the bare steel electrode. © 2013 Elsevier B.V. All rights reserved.

Determination of copper in different ethanolic matrices using a chloropropyl silica gel modified with a nanostructured cubic octa(3-aminopropyl)octasilsesquioxane

The chloropropyl silica gel was modified with octa(3-aminopropyl) octasilsesquioxane and characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), spectroscopies, and surface and area porosity. The specific sorption capacity of metallic ions (Cu2+ and Ni2+) increases in the following solvent order: water < ethanol 42% < ethanol < ketone. The high values of the constant (K) in the order of 103 L mol-1 suggested the high adsorbent capacity of the modified silica (SGAPC) for Cu2+ and Ni2+. SGAPC was applied to a separation column and shows recoveries of around 100% of copper in samples of sugar cane spirit, vodka, ginger brandy, and ethanol fuel. © 2013 Devaney Ribeiro Do Carmo et al.

Synthesis and characterization of melanin in DMSO

Recently soluble melanin derivatives have been obtained by a synthetic procedure carried out in DMSO (D-melanin). In this work a comparative study of the structural characteristics of synthetic melanin derivatives obtained by oxidation of L-DOPA in H2O and DMSO are presented. To this end, Fourier-transform infrared spectroscopy as well as proton and carbon nuclear magnetic resonance techniques has been employed. In addition, aging effects have been investigated for D-melanin. The results suggest that sulfonate groups (-SO2CH3) from the oxidation of DMSO, are incorporated into melanin, which confers protection to the phenolic hydroxyl group present in its structure. The solubility of D-melanin in DMSO is attributed to the presence of these groups. When D-melanin is left in air for long time periods, the sulfonate groups leave the structure, and an insoluble compound is obtained. NaOH and water have been used, in order to accelerate the release of the sulfonate groups attached to D-melanin, thereby corroborating the proposed structure and the synthesis mechanism. © 2013.

Pesquisa e desenvovimento de novos materiais microporosos e mesoporosos para uso em ressonância magnética nuclear por imagem como agentes de contraste

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Micro-extração em fase sólida de Cu(II) e Cd(II) em meio aquoso utilizando sílica organicamente modificada para quantificação por espectrometria de absorção atômica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Constituintes micromoleculares de Aristolochia melastoma Manso: compostos nitrados

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo químico de Jatropha curcas e de Jatropha gossypifolia nativas e cultivadas: avaliação de ciclopeptídeos em função de habitat e hábito : prospecção e atividade biológica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese, caracterização e atividade antifúngica de derivados anfifílicos de dietilaminoetil-quitosana contra Aspergillus flavus e Aspergillus parasiticus

Pós-graduação em Química - IBILCE

Caracterização e estudo do comportamento térmico dos adutos flunixina-meglumina e diclofenaco-meglumina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanopartículas de sílica e ácido p-amino benzóico: um estudo de associação para protetores solares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação das potencialidades de complexos pirazólicos de Pd (II) no desenvolvimento de novas metalo-drogas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigação estrutural e atividade tuberculostática de complexos mononucleares e binucleares de paládio (II)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese, caracterização e investigação das atividades biológicas de compostos ciclopalados

Pós-graduação em Química - IQ