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1.
Layered brucite was synthesized at room temperature and, after characterization, was reacted in a closed flask with either ethylene glycol or glycerol. Powder X-ray diffraction patterns have shown that new compounds with interlayer expansions were obtained. New bands attributed to grafting of ethylene glycol and glycerol into the interlayer surface of brucite were detected by FTIR. XPS spectroscopy and thermal analyses (TG/DSC) have shown that nearly all of the hydroxide groups of the layers were replaced by either ethylene glycol or glycerol through Mg-O-C bonds. 相似文献
2.
Background
Attending to a point in space in one modality may facilitate processing to information from the same region in another modality. The involvement of sensory-specific cortical areas in intramodal and crossmodal selective spatial attention can be assessed with event-related brain potentials (ERPs). 相似文献3.
Guilherme Fadel Picheth Maria Rita Sierakowski Marco Aurelio Woehl Cleverton Luiz Pirich Wido Herwig Schreiner Roberto Pontarolo Rilton Alves de Freitas 《Colloid and polymer science》2014,292(1):97-105
The process of catalytic oxidation of bacterial cellulose (BC) ultra-thin films with 2,2,6,6-tetramethyl-1-piperidinyloxy was investigated along with their capability to adsorb oppositely charged polyelectrolytes of chitosan and alginate. The time-dependent oxidation of BC films was analysed by X-ray photoelectron spectroscopy and quartz crystal microbalance (QCM) experiments. A negatively charged surface was achieved by inserting carboxylic groups, which was augmented by prolonged media exposure (17.9 %), compared with a fast oxidation process (9.1 %). Polyelectrolyte deposition was followed by QCM, which indicated that BC oxidation increased the first layer uptake of chitosan 17-fold (?105.0?±?1.5 Hz) in comparison with unoxidised BC (?6.0?±?0.2 Hz), confirming the capability of oxidised BC surfaces to exhibit strong electrostatic interactions and to support the build-up of a thicker multilayer system. These findings indicate that oxidised BC surfaces are capable of immobilising and detecting several charged species. 相似文献
4.
Couto GG Klein JJ Schreiner WH Mosca DH de Oliveira AJ Zarbin AJ 《Journal of colloid and interface science》2007,311(2):461-468
The synthesis of nickel nanoparticles using poly(N-vinilpyrrolidone) (PVP) as protective agent was studied. The nanoparticles were prepared in air according to a modified polyol route, using nickel chloride as precursor and sodium borohydride as reducing agent. Samples with different nickel/PVP ratio were obtained. The X-ray diffraction and transmission electron microscopy (TEM) measurements indicate the occurrence of face-centered cubic metallic nickel nanoparticles with a medium diameter of 3.8 nm and good size dispersion. Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) data show an effective interaction between the nickel nanoparticles surface and the carboxyl oxygen atoms of PVP. Magnetic measurements show single-domain nonideal superparamagnetism behavior due to dipolar magnetic coupling between particles. 相似文献
5.
We have carried out ab initio calculations in the frozen-core approximation for the metastable Rydberg states of H3 up to principal quantum numbers 相似文献
6.
Photoionization efficiency curves of ferrocene vapor have been recorded between 1900 and 590 A. The appearance potential of the patent ion Fe(C5H5)+2 was found at 6.747 eV. The fragments Fe(C5H5)+ and Fe+ appear at 13.162 and 13.506 eV respectively. We discuss a possible spin—orbit splitting and the thermochemistry of the reactions producting Fe+. 相似文献
7.
Elidiane C. Rangel Nazir M. dos Santos José Roberto R. Bortoleto Steven F. Durrant Wido H. Schreiner Roberto Y. Honda Rita de Cássia C. Rangel Nilson C. Cruz 《Applied Surface Science》2011,258(5):1854-1861
In many applications, polymers have progressively substituted traditional materials such as ceramics, glasses, and metals. Nevertheless, the use of polymeric materials is still limited by their surface properties. Frequently, selective modifications are necessary to suit the surface to a given application. Amongst the most common treatments, plasma immersion ion implantation (PIII) has attracted the attention of many researchers owing to its versatility and practicality. This method, however, requires a power supply to provide high voltage (tens of kV) negative pulses, with a controlled duty cycle, width and frequency. Owing to this, the implementation of PIII on the industrial scale can become economically inviable. In this work, an alternative plasma treatment that enables low energy ion bombardment without the need of a high voltage pulse generator is presented. To evaluate the efficiency of the treatment of polymers, polyvinylchloride, PVC, specimens were exposed to 5 Pa argon plasmas for 3600 s, at excitation powers, P, of between 10 and 125 W. Through contact angle and atomic force microscopy data, the influence of P on the wettability, surface free energy and roughness of the samples was studied. Surface chemical composition was measured by X-ray photoelectron spectroscopy, XPS. To evaluate the effect of aging under atmospheric conditions, contact angle and XPS measurements were performed one and 1334 days after the treatment. The plasma potential and ion density around the driven electrode were determined from Langmuir probe measurements while the self-bias potential was derived with the aid of an oscilloscope. From these data it was possible to estimate the mean energy of ions bombarding the PVC surface. Chlorine, carbon and oxygen contamination were detected on the surface of the as-received PVC. Upon exposure to the plasma, the proportion of chlorine was observed to decrease while that of oxygen increased. Consequently, the wettability and surface energy increased after the treatment but such modifications were not stable after aging: the contact angle increased for all the samples, modifying the initially hydrophilic surface into a highly hydrophobic one. Consistently, the surface composition also changed after aging: there was carbon enrichment due to further losses of oxygen and chlorine. Another relevant factor for the elevation of θ was the change in morphology induced by the treatment. At greater powers, the uniform matrix of the PVC was transformed into a columnar structure containing randomly distributed sharp pillars. Interpretation of such results is proposed in terms of the total energy deposited in the solid by ionic collisions. 相似文献
8.
Jul Nager S. J. 《Monatshefte für Mathematik》1896,7(1):325-331
Ohne Zusammenfassung 相似文献
9.
Adriana F. Lubambo Neoli Lucyszyn Joo J. Klein Wido H. Schreiner Paulo C. de Camargo Maria -R. Sierakowski 《Colloids and surfaces. B, Biointerfaces》2009,70(2):174-180
Thin polysaccharide films prepared with xyloglucan (XG), a neutral polysaccharide extracted from the seeds of Guibourtia hymenifolia were prepared by spin-coating and drop deposition under pH3, pH5 and pH12, on silicon and mica substrates. Atomic force microscopy (AFM) images show flat nanoporous matrices with additional grain-like structures on both mica and silicon for pH 3 and pH 5. However, X-ray photoelectron spectroscopy (XPS) and Auger spectra of these adsorbed biopolymers prepared under alkaline condition (pH 12) reveal that Na+ ions from the solution interact with the mica substrate surface and with XG forming chemical bonds. Both XPS and Auger results suggest XG depolymerisation during adsorption, caused by an alkaline ß-base catalyzed degradation mechanism, which is consistent with the more basic character of the mica surface under these conditions. Thus, the polysaccharide diffusion is inhibited during dewetting due to the surface bonding. On the other hand, the interaction of Na+ in solution with the silicon surface is weaker, favoring its interaction with the polysaccharide, conserving the overall polymer structure of XG and allowing the biopolymer to slip and diffuse during dewetting, forming the final branched fractal structure. 相似文献
10.
Rodrigues PC Berlim LS Azevedo D Saavedra NC Prasad PN Schreiner WH Atvars TD Akcelrud L 《The journal of physical chemistry. A》2012,116(14):3681-3690
The donor-acceptor copolymer containing benzothiadiazole (electron acceptor), linked to functionalized fluorene (electron donor), [poly[9,9-bis(3'-(tert-butyl propanoate))fluorene-co-4,7-(2,1,3-benzothiadiazole)] (LaPPS40), was synthesized through the Suzuki route. The polymer was characterized by scanning electron microscopy, gel permeation chromatography, NMR, thermal analysis, cyclic voltammetry, X-ray photoelectron spectroscopy, UV-vis spectrometry, and photophysical measurements. Theoretical calculations (density functional theory and semiempirical methodologies) used to simulate the geometry of some oligomers and the dipole moments of molecular orbitals involved were in excellent agreement with experimental results. Using such data, the higher energy absorption band was attributed to the π-π* (S(0) → S(4)) transition of the fluorene units and the lower lying band was attributed to the intramolecular (ICT) (S(0) → S(1)) charge transfer between acceptor (benzothiadiazole) and donor groups (fluorene) (D-A structure). The ICT character of this band was confirmed by its solvatochromic properties using solvents with different dielectric properties, and this behavior could be well described by the Lippert-Mataga equation. To explain the solvatochromic behavior, both the magnitude and orientation of the dipole moments in the electronic ground state and in the excited state were analyzed using the theoretical data. According to these data, the change in magnitude of the dipole moments was very small for both transitions but the spatial orientation changed remarkably for the lower energy band ascribed to the ICT band. 相似文献