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排序方式: 共有319条查询结果,搜索用时 78 毫秒
311.
Eduardo R. Triboni Carla C. Schmitt Cavalheiro Mrio J. Politi Marcelo P. Bemquerer Magali A. Rodrigues 《Journal of photochemistry and photobiology. A, Chemistry》2009,208(1):36-41
Three novel hybrid organic/inorganic materials were synthesized from 4-substituted (NO2, Br, H) 1,8-naphthalene imide-N-propyltriethoxysilane by the sol–gel process. These materials were obtained as a xerogel and partially characterized. The ability to photosensitize the oxidation and degradation of tryptophan indole ring by these materials was studied through photophysical and photochemical techniques. Although the derivatives containing Br and NO2 as substituent do not cause efficient tryptophan photodamage, the hybrid material obtained from 1,8-naphthalic anhydride is very efficient to promote tryptophan photooxidation. By using laser flash photolysis it was possible to verify the presence of naphthalene imide transient radical species. The presence of oxygen causes an increase of the yield of radical formation. These results suggest that the mechanism of photodegradation of tryptophan occurs by type I, i.e. the transient radical (TrpH+) formed by the direct reaction of the triplet state of the naphthalene imide moiety with tryptophan. Thus a inorganic–organic hybrid material that can be used to promote the oxidation of biomolecules was obtained. 相似文献
312.
R. da Costa Lima Magali Silveira Pinho T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2009,97(1):131-136
The focus of this work is the use of thermal analyses and Fourier Transform Infrared Spectroscopy (FTIR) for characterization
of the gel decomposition, resulting from the formation of Y-barium hexaferrite substituted by Zn ions (Zn-Y-barium hexaferrite).
Samples with Ba2Zn2Fe12O22 composition were synthesized by the citrate auto-combustion method. During the TG experiments the highest mass loss was attributed
to citrate decomposition owing to the self-combustion reaction, confirmed by the disappearance of –OH band, and the drastic
decrease of –CO2
−and –NO3
− bands. Zn substitution resulted in an X-band microwave absorber material. 相似文献
313.
Michel Lamothe Magali Barré Sébastien Huot Stéphanie Ouimet 《Radiation measurements》2012,47(9):682-687
This study investigated the relationship between the natural luminescence intensity, the amplitude of anomalous fading and the apparent IRSL age of a suite of feldspar single grains. Correlating natural luminescence with fading may simplify the identification of weakly to non-fading feldspars grains in sediments. In our single grain experiments, the mean fading corrected IRSL age obtained from a small population of bright grains is close to the expected depositional age of the sediment investigated. It is proposed that in dating programs, more attention should be given to bright feldspar grains as they are the most stable grains in the population. 相似文献
314.
Laetitia Mespouille Magali Vachaudez Fabian Suriano Pascal Gerbaux Olivier Coulembier Philippe Dege Robert Flammang Philippe Dubois 《Macromolecular rapid communications》2007,28(22):2151-2158
Well‐defined amphiphilic PCL‐b‐PDMAEMA block copolymers were successfully synthesized by a combination of ATRP and “click” chemistry following either a commutative two‐step procedure or a straightforward one‐pot process using CuBr · 3Bpy as the sole catalyst. Compared to the traditional coupling method, combining ATRP and click chemistry even in a “one‐pot” process allows the preparation of PCL‐b‐PDMAEMA diblock copolymers characterized by a narrow molecular weight distribution and quantitative conversion of azides and alkynes into triazole functions. Moreover, the amphiphilic character of these copolymers was demonstrated by surface tension measurements and critical micellization concentration was calculated.
315.
316.
Fengycin interaction with lipid monolayers at the air-aqueous interface-implications for the effect of fengycin on biological membranes 总被引:10,自引:0,他引:10
In this study, we investigated the interaction of fengycin, a lipopeptide produced by Bacillus subtilis, with lipid monolayers using the Langmuir trough technique in combination with Brewster angle microscopy. Thermodynamic analyses were performed to get further information about the mixing behavior and the molecular interactions between the two components. The effect of fengycin on the structural and morphological characteristics of DPPC monolayers, as a simple model of biological membranes, depends on the fengycin molar ratio. With a small proportion of fengycin (X(f)0.1), the compressibility of the monolayer is modified but the morphological characteristics of the DPPC are not significantly affected. At an intermediate molar ratio (0.1相似文献
317.
Luka
orevi Cataldo Valentini Nicola Demitri Ccile Mzire Magali Allain Marc Sall Andrea Folli Damien Murphy Samuel Maas‐Valero Eugenio Coronado Davide Bonifazi 《Angewandte Chemie (International ed. in English)》2020,59(10):4106-4114
Herein we report an efficient synthesis to prepare O‐doped nanographenes derived from the π‐extension of pyrene. The derivatives are highly fluorescent and feature low oxidation potentials. Using electrooxidation, crystals of cationic mixed‐valence (MV) complexes were grown in which the organic salts organize into face‐to‐face π‐stacks, a favorable solid‐state arrangement for organic electronics. Variable‐temperature electron paramagnetic resonance (EPR) measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar π‐stacking architectures. Electric measurements of single crystals of the MV salts show a semiconducting behavior with a remarkably high conductivity at room temperature. These findings support the notion that π‐extension of heteroatom‐doped polycyclic aromatic hydrocarbons is an attractive approach to fabricate nanographenes with a broad spectrum of semiconducting properties and high charge mobilities. 相似文献
318.
319.
Jehovani M. Lázaro-Rangel Analilia Sánchez Dr. Motomichi Inoue Dr. José Luis Olivares-Romero Dr. Rocío Meza-Gordillo Dr. Magali Salas-Reyes Dr. Claudia Virués Dr. Zaira Domínguez 《European journal of organic chemistry》2023,26(5):e202201326
A eutectic mixture of L-menthol and malonic acid, Me / MA (4 : 1), was characterized by calorimetry and other physical measurements. The new deep eutectic solvent (m.p. 6 °C) solvates 338 mg of ibuprofen per mL, and the solution is stable in a wide temperature range. Strategies of NMR titration used in supramolecular chemistry were employed to explore binding forces between the eutectic constituents as well as solute-solvent interaction in ibuprofen solution. Even in acetonitrile, Me 4 MA is formed through a hydrogen-bonding network, where the constituents act as hydrogen donors and acceptors at the same time. The estimated association constant is around 30 M−1; the binding forces are enough to build the eutectic mixture at high concentrations. The aggregate Me 4 MA forms a molecular complex with ibuprofen in acetonitrile as a result of the cooperative effect of the constituents. In addition, van der Waals interactions are operative between ibuprofen and menthol in the saturated IB - Me / MA (4 : 1) solution. 相似文献