Showing papers by "Helena I. S. Nogueira published in 2008"

Photoluminescent 3D Lanthanide−Organic Frameworks with 2,5-Pyridinedicarboxylic and 1,4-Phenylenediacetic Acids

Abstract: Novel three-dimensional lanthanide−organic frameworks with 2,5-pyridinedicarboxylic (2,5-H2pdc) and 1,4-phenylenediacetic acids (1,4-H2pda) were synthesized by hydrothermal synthesis, and characterized structurally using single-crystal and powder X-ray diffraction, elemental and thermogravimetric analyses, FT-IR and photoluminescence spectroscopies, and diffuse reflectance. The structural details of [Ln2(2,5-pdc)2(1,4-pda)(H2O)2] [where Ln3+ = Eu3+, Tb3+, (Eu0.2Tb0.8)3+ and (Eu0.1Tb0.9)3+] and the dehydrated [Eu2(2,5-pdc)2(1,4-pda)] phase were unveiled by single-crystal X-ray diffraction. Photoluminescence measurements performed for the Eu3+ and Tb3+ compounds show emission at room temperature. Energy transfer from Tb3+ to Eu3+ has been observed for the Eu3+/Tb3+ mixed materials.

Silver-bacterial cellulosic sponges as active SERS substrates

Abstract: Synthetic Ag-bacterial cellulose nanocomposites are reported here and their performance as surface enhanced Raman scattering (SERS) substrates was investigated using thiosalicylic acid and 2,2 � dithiodipyridine as analytes. These nanocomposite materials act as natural sponges when immersed in aqueous or ethanolic solutions allowing capture and SERS detection of certain dissolved molecules. The detection limits for the above organic analytes reached concentrations as low as 10 −4 mol·dm −3 and are considerably lower than the conventional vegetable cellulose analogs. Furthermore, we anticipate that the use of these nanocomposites has a beneficial consequence for the development of handy and active cellulosic SERS substrates, in particular for bioanalysis, as we experimentally demonstrated by testing the amino acids L-phenylalanine, L-glutamin and L-histidine. Copyright  2008 John Wiley & Sons, Ltd. Supplementary electronic material for this paper is available in Wiley InterScience at http://www.interscience.wiley.com/ jpages//suppmat/

Catalytic Performance of Copper-Substituted Polyoxotungstate Materials and X-ray Structure of a New Sandwich-Type Compound

Abstract: Mono-substituted and sandwich-type copper substituted polyoxoanions ([PW11CuO39]5− and [Cu4(H2O)2(PW9O34)2]10−) were studied as catalysts for the epoxidation of cyclooctene and geraniol, using the green oxidant H2O2, with the results suggesting good efficiency at room temperature High selectivity and reasonable conversion data were found after the first minutes of reaction The copper centre may be responsible for this performance and our on-going research focuses in the preparation of new materials incorporating copper into polyoxometalates (POMs) In this context, we have also isolated a new crystalline dimeric sandwich-type polyoxocoppertungstate {H705[Cu3WO(H2O)(CuW9O34)(Cu06W9O34)]}775− This compound was isolated as potassium salt and structurally characterized by FTIR and single-crystal X-ray diffraction (XRD) The polyoxoanion is composed by the [CuW9O34]12− and [Cu06W9O34]128− anionic fragments, joined together by a rhomb-like arrangement of three Cu2+ and one W6+ metallic centres, all exhibiting octahedral coordination geometries

Poly[[aqua-μ3-picolinato-μ2-picolinato-dipicolinatopotassium(I)terbium(III)] 2.5-hydrate]

Abstract: In the title compound, [KTb(C6H4NO2)4(H2O)]·2.5H2O, each Tb3+ centre is coordinated by four N and five O atoms from five distinct picolinate ligands in a geometry resembling a highly distorted tricapped trigonal prism. One of the ligands establishes a skew bridge between neighbouring Tb3+ centres, leading to the formation of one-dimensional anionic polymeric chains, {[(C6H4NO2)4Tb]−}n, running along the direction [010]. Each K+ cation is seven-coordinated by six O atoms from one anionic polymeric chain and one water mol­ecule [K⋯O 2.676 (3)–3.208 (4) A]. The uncoordinated water mol­ecules are involved in O—H⋯O hydrogen bonding.

Comunidades sustentáveis: impacte do contexto social e material no aumento de peso e obesidade

Abstract: Este artigo insere-se na tematica das comunidades sustentaveis, procurando atribuir as caracteristicas(fisicas e imateriais) do ambiente local um papel explicativo na genese e manutencao dasvariacoes geograficas em saude publica. Considerando um dos maiores problemas de saude publicados paises desenvolvidos – obesidade e excesso de peso – e utilizando um modelo de regressaologistica binomial, procura-se avaliar o impacte dos atributos ambientais, para alem do impacte dosatributos individuais, no indice de massa corporal (IMC) de uma populacao urbana. Conclui-se quena Area Metropolitana de Lisboa, o risco de possuir excesso de peso/obesidade depende tanto decaracteristicas individuais – por exemplo, genero e idade – como de caracteristicas ambientais,nomeadamente das oportunidades dos lugares e do seu nivel de privacao social e material.