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291.
Silva JR de Souza NC Fernandes VC Homem-de-Mello P Oliveira ON 《Journal of colloid and interface science》2008,327(1):31-35
Langmuir-Blodgett (LB) films from diazobenzene Sudan III have been investigated using surface potential measurements as a function of number of layers and deposition pressures, with the surface potential data being related to molecular dipole moments obtained from theoretical electronic structure calculations. The surface potential increased with the number of layers for SIII LB films, and then tended to saturate. Results from density functional theory (DFT) and UV-vis spectroscopy indicated that the increase is due to addition of layers with oriented molecular dipoles, with the saturation tendency being attributed to a decrease in the amount of material deposited in each layer. The surface potential increased with the surface pressure used for deposition, probably owing to a higher contribution from the vertical component of the dipole moment as a closer molecular packing, which is associated with decreasing conformational entropy, was reached. 相似文献
292.
S.L. Pôrto P.S. Pizani L.G.P. Simões J.M. Ferreira L.E.B. Soledade M.R. Cássia-Santos C.A. Paskocimas A.G. Souza 《Journal of solid state chemistry》2008,181(8):1876-1881
In this work, a study was undertaken about the structural and photoluminescent properties, at room temperature, of powder samples from the CaxSr1−xWO4 (x=0-1.0) system, synthesized by a soft chemical method and heat treated between 400 and 700 °C. The material was characterized using Infrared, UV-vis and Raman spectroscopy and XRD. The most intense PL emission was obtained for the sample calcined at 600 °C, which is neither highly disordered (400-500 °C), nor completely ordered (700 °C). Corroborating the role of disorder in the PL phenomenon, the most intense PL response was not observed for pure CaWO4 or SrWO4, but for Ca0.6Sr0.4WO4. The PL emission spectra could be separated into two Gaussian curves. The lower wavelength peak is placed around 530 nm, and the higher wavelength peak at about 690 nm. Similar results were reported in the literature for both CaWO4 and SrWO4. 相似文献
293.
Coral J Karp SG Porto de Souza Vandenberghe L Parada JL Pandey A Soccol CR 《Applied biochemistry and biotechnology》2008,151(2-3):333-341
Propionic acid (PA) is widely used as additive in animal feed and also in the manufacturing of cellulose-based plastics, herbicides, and perfumes. Salts of propionic acid are used as preservative in food. PA is mainly produced by chemical synthesis. Nowadays, PA production by fermentation of low-cost industrial wastes or renewable sources has been an interesting alternative. In the present investigation, PA production by Propionibacterium acidipropionici ATCC 4965 was studied using a basal medium with sugarcane molasses (BMSM), glycerol or lactate (BML) in small batch fermentation at 30 and 36 degrees C. Bacterial growth was carried out under low dissolved oxygen concentration and without pH control. Results indicated that P. acidipropionici produced more biomass in BMSM than in other media at 30 degrees C (7.55 g l(-1)) as well as at 36 degrees C (3.71 g l(-1)). PA and biomass production were higher at 30 degrees C than at 36 degrees C in all cases studied. The best productivity was obtained by using BML (0.113 g l(-1) h(-1)), although the yielding of this metabolite was higher when using glycerol as carbon source (0.724 g g(-1)) because there was no detection of acetic acid. By the way, when using the other two carbon sources, acetic acid emerged as an undesirable by-product for further PA purification. 相似文献
294.
André Gustavo de A. Fernandes Pedro Ivo da S. Maia Elizeu J. de Souza Sebastião S. Lemos Alzir A. Batista Ulrich Abram Javier Ellena Eduardo E. Castellano Victor M. Deflon 《Polyhedron》2008
Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal)2] (1), [ReOCl2(mal)(PPh3)] (2), [ReOBr2(mal)(PPh3)] (3), [ReOCl2(koj)(PPh3)] (4) and [ReOBr2(koj)(PPh3)] (5). The products have been characterized by FTIR, 1H, 13C, and 31P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex 1 crystallizes monoclinic, space group C2/c, Z = 8. It contains two O,O′-bidentate maltolate ligands and one chloro ligand at the (ReO)3+ unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P21/n and Z = 4. In complexes 2–5, the (ReO)3+ unit is coordinated by a monoanionic O,O-bidentate unit of the maltolate (2 and 3) or kojate (4 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other. 相似文献
295.
De Souza EJ Brinkmann M Mohrdieck C Arzt E 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):8813-8820
Capillary forces can significantly contribute to the adhesion of biological and artificial micro- and nanoscale objects. In this paper, we study numerically the effect of meniscus size on the force between two homogeneous flat plates for different contact angles. The force distance curves show excellent quantitative agreement with previous investigations. The results for n menisci of equal total liquid volume reveal interesting scaling properties and an unexpected maximum force for moderately hydrophilic surfaces (i.e., contact angles around 70 degrees ). Further, we calculate the minimum solid-liquid area for multiple bridges, the cohesive stress (i.e., force per area) between the plates, and the work required to separate them. The results are presented in two-dimensional maps, which may be useful in the understanding of biological attachment structures and in the design of artificial contact systems. 相似文献
296.
Derogis PB Martins FT de Souza TC de C Moreira ME Souza Filho JD Doriguetto AC de Souza KR Veloso MP Dos Santos MH 《Magnetic resonance in chemistry : MRC》2008,46(3):278-282
This article reports the structural elucidation by IR, UV and MS spectroscopic data along with 1H and 13C NMR chemical shift assignments of two benzophenones isolated from the fruit pericarp of Garcinia brasiliensis Mart. (Clusiaceae): garciniaphenone, (1R,5S,7S)-3-benzoyl-4-hydroxy-6,6-dimethyl-5,7-di(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione, a novel triprenylated benzophenone; and 7-epi-clusianone, a tetraprenylated benzophenone that has already been extracted from another species of the same family. Furthermore, the keto-enol tautomeric equilibrium at solution-state was described for these compounds by 1D and 2D NMR spectral methods and one attempt to rationalize the different ratios between the noted tautomers was based on stereochemical features. 相似文献
297.
Costa EV Pinheiro ML de Souza AD Dos Santos AG Campos FR Ferreira AG Barison A 《Magnetic resonance in chemistry : MRC》2008,46(1):69-74
Using modern NMR techniques, including 1H--13C and 1H--15N heteronuclear correlation experiments, the complete and unambiguous 1H, 13C, and 15N NMR chemical shift assignments of annomontine, methoxyannomontine, and N-hydroxyannomontine pyrimidine-beta-carboline alkaloids were performed. All 1H--1H scalar coupling constants and signal multiplicities were determined, and all nOe observations were also included. 相似文献
298.
da Silva Júnior EN de Souza MC Pinto AV Pinto Mdo C Nogueira CM Ferreira VF Azeredo RB 《Magnetic resonance in chemistry : MRC》2008,46(12):1158-1162
Six new nor-beta-lapachones have been synthesized from reaction of 3-bromo-nor-beta-lapachone with arylamines. These derivatives have potent anticancer properties against several cell lines. Here, we report complete unambiguous assignments of (1)H and (13)C chemical shifts of the new compounds. The assignments were made using a combination of one- and two-dimensional NMR techniques ((1)H, (13)C, (1)H-(1)H COSY, (1)H-(13)C HSQC, and (1)H-(13)C HMBC). 相似文献
299.
Polyanilines doped with different acids (HCl, H2SO4 and dodecylbenzenesulfonic acid, DBSA) were prepared and their surface electrical conductivities were characterized in a four-probe device, connected to a real-time data acquisition board. Collected data were synchronized and conductivity calculations were performed. The conductive behavior of the polyanilines was investigated along the electrification time. This allowed for introduction of a non-Gaussian technique for determination of the confidence intervals of surface resistivity data. It is shown that the distribution of experimental surface resistivity data does not follow a normal probability distribution function (PDF). Thus, ordinary assumptions related to normal distribution of the experimental errors are wrong and must be corrected for proper determination of the confidence limits of measured resistivity values. It is shown here that confidence limits of resistivity values are asymmetrical and that distribution of experimental values can follow multimodal distributions. 相似文献
300.
J. C. Maciel A. A. D. Mercês M. Cabrera W. T. Shigeyosi S. D. de Souza M. Olzon-Dionysio J. D. Fabris C. A. Cardoso D. F. M. Neri M. P. C. Silva L. B. CarvalhoJr. 《Hyperfine Interactions》2016,237(1):3
It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe 3+ ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ~15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and 57Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite (γFe2O3). The coated magnetic nanoparticles (sample labeled “mPANI”) presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample “mPANIG-Trypsin”). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 °C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused. 相似文献