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Per M. Claesson - One of the best experts on this subject based on the ideXlab platform.

  • the structures of complexes between Polyethylene Imine and sodium dodecyl sulfate in d2o a scattering study
    Journal of Physical Chemistry B, 2005
    Co-Authors: Luis A Bastardo, Vasil M Garamus, Magnus Bergstrom, Per M. Claesson
    Abstract:

    The association between a highly branched polyelectrolyte with ionizable groups, Polyethylene Imine (PEI), and an anionic surfactant, sodium dodecyl sulfate (SDS), has been investigated at two pH v ...

  • Effect of sodium dodecyl sulfate on adsorbed layers of branched Polyethylene Imine
    Journal of Physical Chemistry B, 2004
    Co-Authors: Andra Dedinaite, Róbert Mészáros, Per M. Claesson
    Abstract:

    The effect of an anionic surfactant, sodium dodecyl sulfate, SDS, on the properties of adsorbed layers of a cationic highly branched polyelectrolyte, Polyethylene,Imine, PEI, has been investigated using surface force measurements, atomic force microscopy, and ESCA. The strategy used was to preadsorb PEI on negatively charged muscovite mica surfaces from a 20 ppm polyelectrolyte solution in 10 mM NaCl. The adsorption of PEI under these conditions gives rise to a strong recharging of the surface, i.e. after adsorption of PEI the surface carries a net positive charge. This conclusion was supported by ESCA measurements. Despite the high molecular weight of PEI (1.8 x 10(5) g/mol), the adsorbed layer is found to be very flat, and a repulsive double-layer force dominates at large separations. At smaller separation a strong attractive force is the main feature. Addition of SDS to a concentration of 0.01 cmc results in a nearly complete removal of the double-layer force, an increase in compressed layer thickness, and an increase in the magnitude of the adhesion force. Hence, significant SDS incorporation in the adsorbed layer occurs already at this low surfactant concentration. A recharging of the layer occurs at higher surfactant concentrations. At 0.5 cmc, the compressed thickness of the adsorbed layer is increased significantly and the adhesion between the surfaces has disappeared. We argue that each layer now is coated with an outer SDS layer oriented with the polar groups toward solution. In fact, there are striking similarities between the interfacial association between SDS and PEI and the adsorption of an ionic surfactant to an oppositely charged mineral surface. AFM imaging reveals that the adsorbed PEI layer is somewhat nonhomogeneous and contains polyelectrolyte patches. These surface features are smoothed out by addition of SDS to a concentration of 6 mM (1 cmc in 10 mM NaCl). ESCA measurements showed that exposure of the preadsorbed PEI layer to SDS concentrations around the cmc resulted in a limited desorption; about 15% of the initially adsorbed polyelectrolyte was removed after 16 h.

Luis A Bastardo - One of the best experts on this subject based on the ideXlab platform.

Imre Dekany - One of the best experts on this subject based on the ideXlab platform.

  • size dependent photoluminescence properties of bare zno and Polyethylene Imine stabilized zno nanoparticles and their langmuir blodgett films
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010
    Co-Authors: Nora Abraham, Imre Dekany
    Abstract:

    Abstract Zinc oxide nanocrystals (∼3 nm) were prepared by colloid chemical method adapted from Meulenkamp [7] . The aging of the sol (particle size increase and aggregation) was investigated by UV–vis absorbance, dynamic light scattering and XRD measurement, particle growth was hindered by surface stabilization with PEI (Polyethylene Imine). Photoluminescence measurement of ZnO nanoparticles revealed the size-dependent emission properties of ZnO nanocrystals: larger particles show visible emission band at higher wavelengths and weaker intensity. Langmuir–Blodgett (LB) technique was used for the preparation of multilayered films of ZnO and PEI-modified ZnO. Films were characterized with UV–vis absorbance measurements and AFM images. Photoluminescence study of LB films demonstrated that particles preserve their emission properties which makes possible to tune the emission properties of films using ZnO nanoparticles of different sizes.

Róbert Mészáros - One of the best experts on this subject based on the ideXlab platform.

  • deuterium isotope effects on the interaction between hyperbranched Polyethylene Imine and an anionic surfactant
    Journal of Physical Chemistry B, 2005
    Co-Authors: Luis A Bastardo, Róbert Mészáros, Imre Varga, Tibor Gilanyi, P M Cleasson
    Abstract:

    Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, Polyethylene Imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated ...

  • Effect of sodium dodecyl sulfate on adsorbed layers of branched Polyethylene Imine
    Journal of Physical Chemistry B, 2004
    Co-Authors: Andra Dedinaite, Róbert Mészáros, Per M. Claesson
    Abstract:

    The effect of an anionic surfactant, sodium dodecyl sulfate, SDS, on the properties of adsorbed layers of a cationic highly branched polyelectrolyte, Polyethylene,Imine, PEI, has been investigated using surface force measurements, atomic force microscopy, and ESCA. The strategy used was to preadsorb PEI on negatively charged muscovite mica surfaces from a 20 ppm polyelectrolyte solution in 10 mM NaCl. The adsorption of PEI under these conditions gives rise to a strong recharging of the surface, i.e. after adsorption of PEI the surface carries a net positive charge. This conclusion was supported by ESCA measurements. Despite the high molecular weight of PEI (1.8 x 10(5) g/mol), the adsorbed layer is found to be very flat, and a repulsive double-layer force dominates at large separations. At smaller separation a strong attractive force is the main feature. Addition of SDS to a concentration of 0.01 cmc results in a nearly complete removal of the double-layer force, an increase in compressed layer thickness, and an increase in the magnitude of the adhesion force. Hence, significant SDS incorporation in the adsorbed layer occurs already at this low surfactant concentration. A recharging of the layer occurs at higher surfactant concentrations. At 0.5 cmc, the compressed thickness of the adsorbed layer is increased significantly and the adhesion between the surfaces has disappeared. We argue that each layer now is coated with an outer SDS layer oriented with the polar groups toward solution. In fact, there are striking similarities between the interfacial association between SDS and PEI and the adsorption of an ionic surfactant to an oppositely charged mineral surface. AFM imaging reveals that the adsorbed PEI layer is somewhat nonhomogeneous and contains polyelectrolyte patches. These surface features are smoothed out by addition of SDS to a concentration of 6 mM (1 cmc in 10 mM NaCl). ESCA measurements showed that exposure of the preadsorbed PEI layer to SDS concentrations around the cmc resulted in a limited desorption; about 15% of the initially adsorbed polyelectrolyte was removed after 16 h.

Josiel B Domingos - One of the best experts on this subject based on the ideXlab platform.

  • association of branched Polyethylene Imine with surfactants in aqueous solution
    Química Nova, 2015
    Co-Authors: Ismael C Bellettini, Josiel B Domingos, Renato Eising, Arlindo C Felippe, Edson Minatti, Vanderlei G Machado
    Abstract:

    Three polymer-surfactant systems comprised of branched Polyethylene Imine (PEI) with an anionic surfactant (sodium dodecylsulfate; SDS), a cationic surfactant (tetradecyltrimethylammonium bromide; TTAB), and a zwitterionic surfactant (N-tetradecyl-N,N-dimethyl3-ammonio-1-propanesulfonate; SB3-14) were studied based on the properties of surface tension, pyrene fluorescence emission, dynamic light scattering, pH, and zeta potential measurements. The critical aggregation concentration (cac) and polymer saturation point (psp) were determined for all three systems. The effect of these surfactants on the physico-chemical characteristics (diameter and surface charge) of the complexes formed was determined. Polymer-surfactant interactions occurred in all of the systems studied, with the strongest interactions, electrostatic in nature, occurring in the SDS-PEI system. After the neutralization of the polymer charges with the addition of the surfactant, the hydrophobic effect started to control the interlacing of the polymer chains. For the PEI-TTAB system, a very dense film was formed at surfactant concentrations above 2.0 mmol L −1. In this case, the bromide counterion interacted with both the positively-charged PEI and the head of the surfactant, which is responsible for the formation of double layer coordination complexes. For the system composed of PEI and the zwitterionic surfactant, less cooperative associations occurred in comparison with the other systems.

  • synthesis and catalytic properties of silver nanoparticle linear Polyethylene Imine colloidal systems
    Journal of Physical Chemistry C, 2012
    Co-Authors: Kelly De O Santos, Welman C Elias, Aline M Signori, Fernando Carlos Giacomelli, Hong Yang, Josiel B Domingos
    Abstract:

    The excellent catalytic properties of colloidal metal nanoparticles (M-NPs), such as good selectivity, efficiency, and recyclability, have attracted great interest in academic and industrial research. However, new M-NP stabilizers/supports still need to be developed and their performance needs to be better understood. Herein, we report an approach for effectively combining a high-throughput method using linear Polyethylene Imine (LPEI) with in situ screening and multivariate optimization of the synthesis conditions to produce highly catalytically stable Ag-NPs. Selected Ag-NP/stabilizers were able to efficiently catalyze the p-nitrophenol (Nip) reduction by NaBH4 in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k1) up to 1.66 s–1 m–2 L. A full kinetic analysis based on the Langmuir model indicates that the Nip molecules have a much stronger adsorption affinity than BH4– ions for the Ag-NP surface and all species are likely adsorbed and accommodated on the ...

  • Polyethylene Imine derivatives synzymes accelerate phosphate transfer in the absence of metal
    Journal of the American Chemical Society, 2007
    Co-Authors: Frederic Avenier, Josiel B Domingos, Liisa D Van Vliet, Florian Hollfelder
    Abstract:

    The efficient integration of binding, catalysis, and multiple turnovers remains a challenge in building enzyme models. We report that systematic derivatization of Polyethylene Imine (PEI) with alkyl (C2-C12), benzyl, and guanidinium groups gives rise to catalysts (‘synzymes') with rate accelerations (kcat/kuncat) of up to 104 for the intramolecular transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate, HPNP, in the absence of metal. The synzymes exhibit saturation kinetics (KM ≈ 250 μM, kcat ≈ 0.5 min-1) and up to 2340 turnovers per polymer molecule. Catalysis can be specifically and competitively inhibited by anionic and hydrophobic small molecules. The efficacy of catalysis is determined by the PEI derivatization pattern. The derivatization reagents exert a synergistic effect, i.e., their combinations increase catalysis by more than the sum of each single modification. The pH−rate profile for kcat/KM is bell shaped with a maximum at pH 7.85 and can be explained as a combination of two effects t...