Luminescent properties and lattice defects correlation on zinc oxide

The ZnO luminescent properties are strongly influenced by the preparation method and they are principally related to electronic and crystalline structures. This work reports about the correlation among luminescence properties of ZnO, obtained from zinc hydroxycarbonate, and crystalline lattice defects, microstrain, as function of thermal treatment. The crystallite size increase and the qualitative microstrain, obtained by Williamson-Hall plots, decrease as function of temperature. The evolution of electronic defects is analyzed by luminescence spectroscopy based on energy of the electronic transitions. From excitation spectrum, it is verified two bands around 377 nm and 405 nm attributed to the transitions between valence-conduction bands and valence band to interstitial zinc level, respectively. The emission spectra of sample treated at 600 degreesC shows large band at 670 nm. However, the green emission around 530 nm is observed for samples treated at 900 degreesC. The intensities of excitation and emission bands are associated with the increase of the electronic defects that depend on the strain lattice decrease. The lowest strain lattice results on the best green luminescent properties of zinc oxide. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Characterization of methylcellulose produced from sugar cane bagasse cellulose: Crystallinity and thermal properties

In the present work, methylcellulose produced from sugar cane bagasse was characterized by FTIR, WAXD, DTA and TGA techniques. Two samples were synthesized: methylcellulose A and rnethylcellulose B. The only difference in the process was the addition of fresh reactants during the preparation of methylcellulose B. The ratio between the absorption intensities of the C-H stretching band at around 2900 cm(-1) and C-H stretching at around 3400 cm(-1) for methylcellulose B is higher than for methylcellulose A, indicating that methylcellulose B showed an increase in the degree of substitution (DS). Methylcellulose A presents a more heterogeneous structure, which is similar to the original cellulose as seen through FTIR and DTA. Methylcellulose B showed thermal properties similar to commercial methylcellulose. The modification of rnethylcellulose preparation method allows the production of a material with higher DS, crystallinity and thermal stability in relation to the original cellulose and to methylcellulose A. (c) 2006 Elsevier Ltd. All rights reserved.

Ferritas 'MG IND. 1' - 'delta'ZN''delta''FE' IND. 2'O IND. 4' obtidas por síntese de reação de combustão: caracterização estrutural e nanoestrutural

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

Caracterização elétrica de cerâmicas à base de SnO2 dopadas com Mn, Nb e Cr

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

Complexos de európio e /ou de zinco com ácido 3-piridinocarboxílico

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nanopartículas de óxido de ítrio dopado com Eu3+ contendo prata

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Método de Taguchi aplicado a um processo de corte por fusão de um tecido sintético

A company must have full knowledge and control of its operations so as to meet the market requirements and meet their production goals. Thus this paper uses the Taguchi method to extend the operational control of a cutting process by fusion of a synthetic fabric in the longitudinal direction. For process analysis and tracking of possible causes of the problem techniques of Production Engineering as the cause and effect diagram, also known as Ishikawa diagram, and design of experiments were used, the last one was applied to the design techniques of Taguchi. Finally the preparation method of understanding and design of experiment was due to the use of the software MINITAB v15 ®, which showed that the speed of rolling the fabric after cutting is crucial for controlling the entire operation

Single precursor route to efficient cobalt sulphide counter electrodes for dye sensitized solar cells

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

The ultra-sonication of minerals in swine feed

A sample preparation method based on ultrasound assisted-extraction (UAE) of Ca, Mg and P from swine feed has been described. The experiment was performed to cover the variables influencing the sonication process and, the method validation using standard reference material. Final solutions obtained upon sonication were analyzed by flame atomic absorption spectrometry (for Ca and Mg) and by UV-vis spectrophotometry (for P). The best conditions for metal extraction were as follows: sample mass: 100 mg in 20 mL 0.10 mol/L HCl, a particle size: <60 μm, sonication time: 5 cycles of 10 s and ultrasound power: 102 W. The UAE method was applied in digestibility assays in different piglet feeds and their results showed that it is highly comparable (P > 0.05) to the other methods used for such purposes, as block digestion, and offered a Ca, Mg and P method of quantification limit of 10.6, 12.4 and 14 mg/kg, respectively. The major advantages of the UAE method compared to other methods are the high treatment rate, low reagent usage in the extracts and, it does not generate toxic residues that might negatively affect human health and the environment, accompanied by good precision and accuracy.

Solid-phase microextraction combined with comprehensive two-dimensional gas chromatography for fatty acid profiling of cell wall phospholipids

The combination of solid-phase microextraction (SPME) with comprehensive two-dimensional gas chromatography is evaluated here for fatty acid (FA) profiling of the glycerophospholipid fraction from human buccal mucosal cells. A base-catalyzed derivatization reaction selective for polar lipids such as glycerophospholipid was adopted. SPME is compared to a miniaturized liquidliquid extraction procedure for the isolation of FA methyl esters produced in the derivatization step. The limits of detection and limits of quantitation were calculated for each sample preparation method. Because of its lower values of limits of detection and quantitation, SPME was adopted. The extracted analytes were separated, detected, and quantified by comprehensive two-dimensional gas chromatography with flame ionization detection (FID). The combination of SPME and comprehensive two-dimensional gas chromatography with FID, using a selective derivatization reaction in the preliminary steps, proved to be a simple and fast procedure for FA profiling, and was successfully applied to the analysis of adult human buccal mucosal cells.

Nonculture-based identification of bacteria in milk by protein fingerprinting

Traditional methods for bacterial identification include Gram staining, culturing, and biochemical assays for phenotypic characterization of the causative organism. These methods can be time-consuming because they require in vitro cultivation of the microorganisms. Recently, however, it has become possible to obtain chemical profiles for lipids, peptides, and proteins that are present in an intact organism, particularly now that new developments have been made for the efficient ionization of biomolecules. MS has therefore become the state-of-the-art technology for microorganism identification in microbiological clinical diagnosis. Here, we introduce an innovative sample preparation method for nonculture-based identification of bacteria in milk. The technique detects characteristic profiles of intact proteins (mostly ribosomal) with the recently introduced MALDI SepsityperTM Kit followed by MALDI-MS. In combination with a dedicated bioinformatics software tool for databank matching, the method allows for almost real-time and reliable genus and species identification. We demonstrate the sensitivity of this protocol by experimentally contaminating pasteurized and homogenized whole milk samples with bacterial loads of 10(3)-10(8) colony-forming units (cfu) of laboratory strains of Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus. For milk samples contaminated with a lower bacterial load (104 cfu mL-1), bacterial identification could be performed after initial incubation at 37 degrees C for 4 h. The sensitivity of the method may be influenced by the bacterial species and count, and therefore, it must be optimized for the specific application. The proposed use of protein markers for nonculture-based bacterial identification allows for high-throughput detection of pathogens present in milk samples. This method could therefore be useful in the veterinary practice and in the dairy industry, such as for the diagnosis of subclinical mastitis and for the sanitary monitoring of raw and processed milk products.

Study of CuO/CeO2 catalyst with for preferential CO oxidation reaction in hydrogen-rich feed (PROX-CO)

The CuO/CeO2 system was investigated as a catalyst for preferential CO oxidation reaction in hydrogen-rich feed (PROX-CO). The catalysts were prepared by deposition-precipitation (DEP) and co-precipitation (COP) methods and the catalytic performance reveals that the preparation method influences the properties of solids prepared, where a direct consequence is the difference in behavior of the catalysts in the PROX-CO reaction. A high specific area and a better dispersion of the metallic phase were obtained in the catalyst prepared by co-precipitation. The redox properties during the reaction were reported by measures of temperature programmed reduction (TPR), OSC measurements and X-ray absorption near edge structure (XANES-TPR) in situ showed the relationship between the preparation method, the physicochemical characteristics and redox properties in the PROX-CO reaction. By this means, the good dispersion of CuO and the best oxygen capacity are the response of the high performance of CuO/CeO2-COP catalysts for the PROX-CO reaction. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.

Optimización de un método basado en SPE-LC-MS/MS para la determinación de multiresiduos de compuestos farmacéuticos en aguas depuradas

Universidad de Las Palmas de Gran Canaria, Facultad de Ciencias del Mar, Doctorado en Gestión Costera.

Catalysts for H2 production

The research of new catalysts for the hydrogen production described in this thesis was inserted within a collaboration of Department of Industrial Chemistry and Materials of University of Bologna and Air Liquide (Centre de Recherche Claude-Delorme, Paris). The aim of the work was focused on the study of new materials, active and stable in the hydrogen production from methane, using either a new process, the catalytic partial oxidation (CPO), or a enhanced well-established process, the steam methane reforming (SMR). Two types of catalytic materials were examined: 1) Bulk catalysts, i.e. non-supported materials, in which the active metals (Ni and/or Rh) are stabilized inside oxidic matrix, obtained from perovskite type compounds (PVK) and from hydrotalcite type precursors (HT); 2) Structured catalysts, i.e. catalysts supported on materials having high thermal conductivity (SiC and metallic foams). As regards the catalytic partial oxidation, the effect of the metal (Ni and/or Rh), the role of the metal/matrix ratio and the matrix formulation of innovative catalysts obtained from hydrotalcite type precursors and from perovskites were examined. In addition, about steam reforming process, the study was carried out first on commercial type catalysts, examining the deactivation in industrial conditions, the role of the operating conditions and the activity of different type of catalysts. Then, innovative materials bulk (PVK and HT) and structured catalysts (SiC and metallic foam) were studied and a new preparation method was developed.