Synthesis, characterization and electrochemical study of layered double hydroxides intercalated with 2-thiophenecarboxylate anions

The synthesis, characterization, and electrochemical study of the Zn(II)-Al(III) and Zn(II)-Cr(III) Layered Double Hydroxides (LDHs) containing 2-thiopenecarboxylate as the interlayer anions are described. The LDHs were prepared by the constant pH coprecipitation technique followed by hydrothermal treatment for 72 h. The materials were analyzed by PXRD, FT-IR, C-13 CP-MAS, EDX, TEM, and CV. The presence of the organic heterocyclic anions was confirmed by FT-IR and the related solid-state C-13 NMR data strongly suggested that these were dimerised during coprecipitation. Accordingly, the basal spacing found by the X-ray technique was similar to 15.3 Angstrom, a distance coincident with the formation of bilayers of the intercalated anions. The structural organization of all the new materials was greatly enhanced by hydrothermal treatment, as shown by PXRD. The improved organization of the bilayered structures had a strong influence in the electrochemical behaviour of clay-modified electrodes produced with these materials, such as the diminished resistance to the ionic flow through the LDHs films. (C) 2003 Elsevier Ltd. All rights reserved.

Activity of Mo(II) allylic complexes supported in MCM-41 as oxidation catalysts precursors

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

NMR study of ion-conducting organic-inorganic nanocomposites poly(ethylene glycol) - Silica - LiClO4

Hybrid organic-inorganic ionic conductors, also called ormolytes, were obtained by dissolution of LiClO4 into silica/poly(ethylene glycol) matrices. Solid-state nuclear magnetic resonance (NMR) was used to probe the inorganic phase structure (Si-29) and the effects of the temperature and composition on the dynamic behavior of the ionic species (Li-7) and the polymer chains (H-1 and C-13). The NMR results between -100 and +90 degrees C show a strong correlation with ionic conductivity and differential scanning calorimetry experiments. The results also demonstrate that the cation mobility is assisted by segmental motion of the polymer, which is in agreement with the results previously reported for pure poly(ethylene oxide), PEG, electrolytes.

Electronic structure of polyacetylene with bonded oxygen

In this work we have studied the electronic structure of finite polyacetylene chains with structural oxygen-bonding models following data from 13C-NMR experiments. We have used a combination of Austin Method One and Hydrogenic Atoms in Molecules version 3 methods to perform geometric and spectroscopic calculations. Our results show that the electronically-active states are generally unaffected by the incorporation of oxygen. © 1992.

Study of adsorption and preconcentration by using a new silica organomodified with [3-(2,2′-dipyridylamine)propyl] groups

In this work, a silica surface chemically modified with [3-(2,2′-dipyridylamine)propyl] groups, named [3-(2,2′- dipyridylamine)propyl]silica (Si-Pr-DPA) was prepared, characterized, and evaluated for its heavy metal adsorption characteristics from aqueous solution. To our knowledge, we are the first authors who have reported the present modification. The material was characterized using infrared spectroscopy, SEM, and NMR 29Si and 13C solid state. Batch and column experiments were conducted to investigate for heavy metal removal from dilute aqueous solution by sorption onto Si-Pr-DPA. From a number of studies the affinity of various metal ions for the Si-Pr-DPA sorbent was determined to follow the order Fe(III) > Cr(III) >> Cu(II) > Cd(II) > Pb(II) > Ni(II). Two standard reference materials were used for checking the accuracy and precision of the method. The proposed method was successfully applied to the analysis of environmental samples. This ligand material has great advantage for adsorption of transition-metal ions from aqueous medium due to its high degree of organofunctionalization associated with the large adsorption capacity, reutilization possibility, and rapidity in reaching the equilibrium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preconcentration and determination of metal ions from fuel ethanol with a new 2,2'-dipyridylamine bonded silica

A silica surface chemically modified with [3-(2,2'-dipyridylamine) propyl] groups was prepared, characterized, and evaluated for its metal ion preconcentration in fuel ethanol. To our knowledge, we are the first authors who have reported the present modification on silica gel surface. The material was characterized using infrared spectra, scanning electronic microscopy, and 13C and 29Si solid-state NMR spectra. Batch and column experiments were conducted to investigate for metal ion removal from fuel ethanol. The results showed that the Langmuir model describes the sorption equilibrium data of the metal ions in a satisfactory way. From the Langmuir isotherms, the following maximum adsorption capacities (in mmolg -1) were determined: 1.81 for Fe(III), 1.75 for Cr(III), 1.30 for Cu(II), 1.25 for Co(II), 1.15 for Pb(II), 0.95 for Ni(II), and 0.87 for Zn(II). Thermodynamic functions, the change of free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) showed that the adsorption of metal ions onto Si-Pr-DPA was feasible, spontaneous, and endothermic. The sorption-desorption of the metal ions made possible the development of a preconcentration and quantification method of metal ions in fuel ethanol. © 2012 Elsevier Inc.

Bifunctional silica nanoparticles for the exploration of biofilms of Pseudomonas aeruginosa

Luminescent silica nanoparticles are frequently employed for biotechnology applications mainly because of their easy functionalization, photo-stability, and biocompatibility. Bifunctional silica nanoparticles (BSNPs) are described here as new efficient tools for investigating complex biological systems such as biofilms. Photoluminescence is brought about by the incorporation of a silylated ruthenium(II) complex. The surface properties of the silica particles were designed by reaction with amino-organosilanes, quaternary ammonium-organosilanes, carboxylate-organosilanes and hexamethyldisilazane. BSNPs were characterized extensively by DRIFT, 13C and 29Si solid state NMR, XPS, and photoluminescence. Zeta potential and contact angle measurements exhibited various surface properties (hydrophilic/hydrophobic balance and electric charge) according to the functional groups. Confocal laser scanning microscopy (CLSM) measurements showed that the spatial distribution of these nanoparticles inside a biofilm of Pseudomonas aeruginosa PAO1 depends more on their hydrophilic/hydrophobic characteristics than on their size. CLSM observations using two nanosized particles (25 and 68 nm) suggest that narrow diffusion paths exist through the extracellular polymeric substances matrix. © 2013 Copyright Taylor and Francis Group, LLC.

Preparação, caracterização e aplicações eletroanalíticas de silsesquioxanos e dendrímeros modificados suportados na superfície da sílica gel

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

Propriedades analíticas e eletroanalíticas de um silsesquioxano nanoestruturado organofuncionalizado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de híbridos inorgânico-orgânicos funcionalizados com tiouréia e 2,2’-dipiridilamina: aplicação em adsorção de íons metálicos, pré-concentração e catálise

Pós-graduação em Ciência dos Materiais - FEIS

Síntese e caracterização de silsesquioxanos organofuncionalizados: aplicações em adsorção, pré-concentração e catálise

Pós-graduação em Ciência dos Materiais - FEIS

Caracterização e estudo do comportamento térmico de ligninas extraídas de bagaço de cana-de-açúcar e resíduos sólidos urbanos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Compostos luminescentes em matrizes macroporosas de sílica obtidas por tratamento hidrotérmico a partir de vidro pyrex

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

Sínteses e caracterizações de materiais microporosos com estrutura cristalográfica mista e suas aplicações como catalisadores em reações de conversão de biomassa em produtos de química fina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)