981 resultados para State-derivative signals


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conjugated polymers have been subject of great interest in the recent literature from both fundamental point of view and applied science perspective. Among the several types of conjugated polymers used in recent investigations, polythiophene and its derivatives have attracted considerable attention over the past 20 years due to their high mobility and other remarkable solid-state properties. They have potential applications in many fields, such as microelectronic devices, catalysts, organic field-effect transistors, chemical sensors, and biosensors. They have been studied as gas and volatile organic compounds (VOCs) sensors using different principles or transduction techniques, such as optical absorption, conductivity, and capacitance measurements. In this work, we report on the fabrication of gas sensors based on a conducting polymer on an interdigitated gold electrode. We use as active layer of the sensor a polythiophene derivative: poly (3-hexylthiophene) (P3HT) and analyzed its conductivity as response for exposure to dynamic flow of saturated vapors of six VOCs [n-hexane, toluene, chloroform, dichloromethane, methanol, and tetrahydrofuran (THE)]. Different responses were obtained upon exposure to all VOCs, THF gave the higher response while methanol the lower response. The influence of moisture on the measurements was also evaluated. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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

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Solid-state M-2-Cl-BP, where M stands for Mn, Fe, Co, Ni, Cu, Zn and Pb and 2-Cl-BP is 2-chlorobenzylidenepyruvate, have been synthesized. Thermogravimetry and derivative thermogravimetry (TG/DTG), simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.

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Solid compounds of general formula ML(2) . nH(2)O [where M is Mg, Ca, Sr or Ba; L=4 methoxybenzylidenepyruvate (4-MeO-BP); n = 4, 1 or 0] have been synthetized. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), x-ray diffraction powder patterns and elemental analysis have been used to characterize the compounds. The thermal stability of these compounds as well as that of the decomposition products were studied using Pt or Al2O3 crucibles in an air or a CO2 atmosphere.

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Solid state compounds M-4-DMCP, where 4-DMCP is 4-dimethylaminocynnamylidenepyruvate and M represents Mn (II), Co (II), Ni (II), Cu (II), Zn (II) and Pb (II) were prepared. These compounds were studied by thermoanalytical techniques: thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and complexometric titration with EDTA. From the results obtained by the complexometric titration with EDTA, TG, DTG and DSC curves, was possible to establish the hydration degree, stoichiometry and thermal stability of the prepared compounds.

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Solid-state M-EDTA chelates, where M represents the divalent ions Mg(II), Ca(II), Sr(II) or Ba(II) and EDTA is ethylenediaminetetraacetate anion, were synthesized. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC) and X-ray diffraction powder patterns have been used to characterize and to study the thermal behaviour of these chelates. The results provided information concerning the stoichiometry, crystallinity, thermal stability and thermal decomposition.

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Solid Ln-OKCO3-DMCP compounds, where Ln represents lanthanides (III) and yttrium (III) ions and DMCP is the anion 4-dimethyiaminocinnamylidenepyruvate, have been prepared. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and elemental analysis have been used to characterize the compounds. The thermal stability as well as the thermal decomposition of these compounds were studied using an alumina crucible in an air atmosphere.

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