Polyelectrolyte Multilayering on a Charged Planar Surface

The adsorption of highly \textit{oppositely} charged flexible polyelectrolytes (PEs) on a charged planar substrate is investigated by means of Monte Carlo (MC) simulations. We study in detail the equilibrium structure of the first few PE layers. The influence of the chain length and of a (extra) non-electrostatic short range attraction between the polycations and the negatively charged substrate is considered. We show that the stability as well as the microstructure of the PE layers are especially sensitive to the strength of this latter interaction. Qualitative agreement is reached with some recent experiments.Comment: 28 pages; 11 (main) Figs - Revtex4 - Higher resolution Figs can be obtained upon request. To appear in Macromolecule

Silver nanoparticle embedded copper oxide as an efficient core–shell for the catalytic reduction of 4-nitrophenol and antibacterial activity improvement

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« Half dicht, half prose gheordineert » : vers et prose de moyen français en moyen néerlandais

In both French-speaking and Dutch-speaking literary cultures of the late Middle Ages, competition between poets produced a collective poetic expertise. To what extent, then, can such competition be identified across the two cultures, in translations of verse or prosimetrum compositions from Middle French into Middle Dutch? An examination of the Dutch translations reveals that verse is both a means to knowledge and an object of knowledge, in the target culture as well as the source culture. The diversity of translations shows that verse is not only a system that translators attempt to master, but also a formal supplement in ways that are unavailable to prose

Grafted ionomer complexes and their effect on protein adsorption on silica and polysulfone surfaces

We have studied the formation and the stability of ionomer complexes from grafted copolymers (GICs) in solution and the influence of GIC coatings on the adsorption of the proteins β-lactoglobulin (β-lac), bovine serum albumin (BSA), and lysozyme (Lsz) on silica and polysulfone. The GICs consist of the grafted copolymer PAA28-co-PAPEO22 {poly(acrylic acid)-co-poly[acrylate methoxy poly(ethylene oxide)]} with negatively charged AA and neutral APEO groups, and the positively charged homopolymers: P2MVPI43 [poly(N-methyl 2-vinyl pyridinium iodide)] and PAH∙HCl160 [poly(allylamine hydrochloride)]. In solution, these aggregates are characterized by means of dynamic and static light scattering. They appear to be assemblies with hydrodynamic radii of 8 nm (GIC-PAPEO22/P2MVPI43) and 22 nm (GIC-PAPEO22/PAH∙HCl160), respectively. The GICs partly disintegrate in solution at salt concentrations above 10 mM NaCl. Adsorption of GICs and proteins has been studied with fixed angle optical reflectometry at salt concentrations ranging from 1 to 50 mM NaCl. Adsorption of GICs results in high density PEO side chains on the surface. Higher densities were obtained for GICs consisting of PAH∙HCl160 (1.6 ÷ 1.9 chains/nm2) than of P2MVPI43 (0.6 ÷ 1.5 chains/nm2). Both GIC coatings strongly suppress adsorption of all proteins on silica (>90%); however, reduction of protein adsorption on polysulfone depends on the composition of the coating and the type of protein. We observed a moderate reduction of β-lac and Lsz adsorption (>60%). Adsorption of BSA on the GIC-PAPEO22/P2MVPI43 coating is moderately reduced, but on the GIC-PAPEO22/PAH∙HCl160 coating it is enhanced

Online monitoring of aluminium primary production gas composition by use of Fourier-transform infrared spectroscopy

Online monitoring of aluminium primary production raw gas is challenging due to the high concentration of HF in the presence of water. Tunable Diode Laser (TDL) analyzers retrofitted with sapphire optical windows allow for online monitoring of raw gas composistion. These systems are however limited to one or two gas constituents. In order to make use of multi-component analyzers like Fourier-Transform InfraRed Spectrometers (FTIR), HF must be selectively removed by filtration. This work presents some results from complete mapping of raw gas composition by comparing results from HF filtrated as well as non-filtrated measurements. The multivariate calibration models established for mapping of the raw gas is discussed. Open-path FTIR spectroscopy was applied in order to quantify fugitive emissions of HF and SO2. Quantitation showed good correlation with reported emissions. Monitoring of fugitive PFC emissions was also evaluated.acceptedVersio

Crystallographic and RMN structural study of 5' GCG-AGA-GC 3' and 5' CGC-GAG-AGC-G 3' oligonucleotid

9 - Conference paper; 43th Annual Meeting Argentine Society for Biochemistry and Molecular Biology Research (SAIB);NOV 17-20 2007 ;Buenos Aires (Argentine

Improvement in CO2 adsorption capacity of cocoa shell through functionalization with amino groups and immobilization of cobalt nanoparticles

International audienceThe aim of this research is to investigate how (3-aminopropyl)triethoxysilane (APTES) grafting and cobalt na-noparticles (Co-NPs) immobilization may improve the activity of cocoa shell (CS) towards the adsorption of CO 2 under ambient temperature. Pure CS are agricultural by-products which are inexpensive and abundantly available. CS powder was functionalized at 80°C by APTES grafting and modified through the subsequent im-mobilization of Co-NPs. Physical and thermal properties and stability of the adsorbents have been investigated. Thus, their composition, surface charge, and morphology were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), and zeta potential measurements. CO 2 adsorption capacity was remarkably increased from 0.015 mmol g −1 for the raw material to 0.24 mmol g −1 after surface modification, highlighting a promising synergistic effect. The adsorption behavior of CO 2 was investigated, which involves both physical and chemical adsorption. We hope that this work will open new prospects to develop high-performance biomass-derived adsorbents

Entrapment and stabilization of iron nanoparticles within APTES modified graphene oxide sheets for catalytic activity improvement

International audienceIn this work, for the first time, a grafting of 3-aminopropyltriethoxysilane (APTES) followed by incorporation of iron nanoparticles (Fe-NPs) was used for the functionalization of graphene oxide (GO). Changes in stability, structural, morphological, thermal and catalytic properties of the resulting GO/APTES/Fe material were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive X-Ray, Fourier transform infrared and UV–visible spectroscopies, zeta potential measurements, X-ray photoelectron spectroscopy and differential scanning calorimetry. The average crystallite size of GO/APTES/Fe was found to decrease significantly after the post treatment, producing slight structure compaction. Iron nanoparticles were immobilized by APTES on the GO sheets, with a particle size around 50 nm. Fe insertion and APTES grafting resulted in high thermal stability of GO. As an application, GO/APTES/Fe exhibited an excellent catalytic activity in the reduction of 4-nitrophenol into 4-aminophenol. The presence of both APTES and small amount of Fe nanoparticles in GO/APTES/Fe induced a significant improvement in catalytic activity. GO/APTES/Fe also showed appreciable recyclability after four repeated uses without noticeable loss in activity. This stability was higher to those of other GO-materials. The results obtained herein open new prospects for Fe-loaded organo-graphene oxide as efficient material in catalysis and industrial applications

Osteogenetic properties of electrospun nanofibrous PCL scaffolds equipped with chitosan-based nanoreservoirs of growth factors

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