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  • 101.
    Horvath, Andrew T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Horvath, A. Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Adsorption of Low Charge Density Polyelectrolytes to an Oppositely Charged Porous Substrate2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 13, s. 6585-6594Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption behavior of a low charge density cationic polyelectrolyte to cellulosic fibers has been studied. Cationic dextran served as a model polyelectrolyte, as it can be prepared over a range in molecular mass and charge density. The adsorption behavior of the cationic dextran was measured in electrolyte-free conditions using polyelectrolyte titration techniques. By fluorescent labeling the cationic dextran, the extent to which adsorption occurs inside the porous structure was further determined by fluorescent confocal laser scanning microscopy. Cationic dextran having a sufficiently low charge density adsorbed into the pores, although the extent the cationic dextran adsorbed was governed by the molecular mass. The adsorption behavior of the cationic dextran was also studied in various electrolyte concentrations. The adsorbed mass monotonically decreased with increasing electrolyte, as the electrostatic interaction with the substrate was more effectively screened. This behavior also suggests that the interactions between adsorbed polyelectrolyte chains, i.e. lateral correlation effects, are negligible for low charge density polyelectrolytes. Finally, the effect of having a preadsorbed layer of cationic dextran on the adsorption behavior was determined in electrolyte-free conditions using fluorescent double staining techniques. The preadsorbed cationic dextran had almost no effect on the adsorption of low molecular mass fractions. Low molecular mass fractions directly adsorbed into the pore structure, as opposed to adsorbing to a free surface and diffusing into the pores. It was also shown that cationic dextran can be selectively adsorbed to different locations, such that the surface of a porous substrate can be treated uniquely from the bulk.

  • 102.
    Horvath, Andrew T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Horvath, A. Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Diffusion of cationic polyelectrolytes into cellulosic fibers2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 19, s. 10797-10806Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The penetration of cationic polyelectrolytes into anionic cellulosic fibers was evaluated with fluorescent imaging techniques in order to clarify the mechanism and time scales for the diffusion process. The bulk charge of the cellulosic fibers indirectly creates a driving force for diffusion into the porous fiber wall, which is entropic in nature due to a release of counterions as the polyelectrolyte adsorbs. The individual bulk charges in the fiber cell wall also interact with the diffusing polyelectrolyte, Such that the polyelectrolyte diffuses to the first available charge and consequently adsorbs and remains fixed. Thus, Subsequent polyelectrolyte chains must first diffuse through the adsorbed polyelectrolyte layer before adsorbing to the next available bulk charges. This behavior differs from earlier suggested diffusion mechanisms, by which polyelectrolytes were assumed to first adsorb to the outermost surface and then reptate into the pore structure. The time scales for polyelectrolyte diffusion were highly dependent on the flexibility of the chain, which was estimated from calculations of the persistence length. The persistence length ultimately depended on the charge density and electrolyte concentration. The charge density of the polyelectrolyte had a greater influence on the time scales for diffusion. High charge density polyelectrolytes were observed to diffuse on a time scale of months, whereas the diffusion of low charge density polyelectrolytes was measured on the order of hours. An influence of the chain length, that is, steric interactions due the persistence length of the polyelectrolyte and to the tortuosity of the porous structure of the fiber wall, could only be noted for low charge density polyelectrolytes. Increasing the electrolyte concentration increased the chain flexibility by screening the electrostatic contribution to the persistence length, in turn inducing a faster diffusion process. However, a significant change in the diffusion behavior was observed at high electrolyte concentrations, at which the interaction between the polyelectrolyte charges and the fiber charges was almost completely screened.

  • 103.
    Horvath, Andrew T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Horvath, A. Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Polyelectrolyte Diffusion Into an Oppositely Charged Porous Substrate2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827Artikel i tidskrift (Refereegranskat)
  • 104.
    Höglund, Anders
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Surface Modification Changes the Degradation Process and Degradation Product Pattern of Polylactide2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 1, s. 378-383Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of surface modification on the degradation process and degradation product patterns of degradable polymers is still a basically unexplored area even though it significant effect can be expected. Polylactide (PLA) and PLA grafted with acrylic acid (PLA-AA) were, thus, subjected to hydrolytic degradation, and water-soluble degradation products were determined by electrospray ionization-mass spectrometry (ESI-MS) after different time periods. Low molar mass Compounds migrated from surface-grafted PLA already during the first 7 days at 37 degrees C, while it Look 133 days in the case of nongrafted PLA before any low molar mass compounds were detected in the aging water. In addition, the degradation product pattern of surface-grafted PLA showed significant variation as a function of hydrolysis time with the evolution of short and long AA-grafted lactic acid oligomers as well as plain lactic acid oligomers after different time periods, The degradation up to 13 lactic acid units. Surface grafting, thus, changed the degradation product patterns and accelerated the formation of water-soluble degradation products.

  • 105. Iliopoulos, I.
    et al.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    NMR study of the association of anionic surfactants with an anionic polyelectrolyte hydrophobically modified with perfluorinated side chains2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 26, s. 8049-8054Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mixtures of surfactants with a hydrophobically modified polyelectrolyte in aqueous solution are investigated by F-19 NMR spectroscopy performed on the fluorinated side chains of the polyelectrolyte component, The two added surfactants, one hydrogenated and one fluorinated, behave differently as manifested by the chemical shift effects in the obtained NMR spectra: the mixing of the hydrogenated one with the polyelectrolyte is clearly nonideal, while the mixing of the two fluorinated species is closer to ideal. The different aggregates dominated either by the polyelectrolyte or by the surfactant component share some dynamic features: the exchange of the polyelectrolyte molecules among them is slow, while that of the surfactant molecules is fast on the millisecond time scale.

  • 106. Imae, Toyoko
    et al.
    Kato, Motohisa
    Rutland, Mark W.
    KTH, Tidigare Institutioner, Kemi.
    Forces between two glass surfaces with adsorbed hexadecyltrimethylammonium salicylate2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 4, s. 1937-1942Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Forces have been measured for hexadecyltrimethylammonium salicylate (C(16)TASal) layers on glass beads. During the inward process, hydrophobic attraction occurred at lower adsorption of C(16)TASal and electrostatic repulsion interactions happened at higher adsorption. While the jump-in phenomenon was observed for solutions of concentrations below the critical micelle concentration (cmc = 0.15 mM), the step-in phenomenon was characteristic for solutions at the cme and above the cmc, suggesting the push-out of adsorbed C(16)TASal layers and/or inserted micelles. The remarkable pull-off phenomenon on the outward process occurred for all solutions, indicating a strong interaction between C(16)TASal molecules. For aqueous 0.15 mM C(16)TASal solutions of various NaSal concentrations, on the inward process, the electrostatic repulsive interaction decreased with adding NaSal. This is due to the electrostatic shielding by salt excess. The height of the force wall on the inward process reached a maximum at 0.01 M NaSal, but the interlocking between molecules on two surfaces during the outward process was minimized at 0.1 M NaSal. These tendencies, which are different from that of the electrostatic repulsion interaction, imply the strong cohesion between adsorbed C(16)TASal layers.

  • 107. Introzzi, Laura
    et al.
    Blomfeldt, Thomas O. J.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Trabattoni, Silvia
    Tavazzi, Silvia
    Santo, Nadia
    Schiraldi, Alberto
    Piergiovanni, Luciano
    Farris, Stefano
    Ultrasound-Assisted Pullulan/Montmorillonite Bionanocomposite Coating with High Oxygen Barrier Properties2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 30, s. 11206-11214Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the preparation and characterization of oxygen barrier pullulan sodium montmorillonite (Na+-MMT) nanocomposite coatings are presented for the first time. Full exfoliation of platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material even at high relative humidity (RH) conditions [oxygen permeability coefficients similar to 1.43 +/- 0.39 and 258.05 +/- 13.78 mL.mu m.m(-2).(24 h)(-1).atm(-1) at 23 degrees C and 0% RH and 70% RH, respectively]. At the micro- and nanoscale, the reasons are discussed. The final morphology of the coatings revealed that clay lamellae were stacked on top of one another, probably due to the forced confinement of the platelets within the coating thickness after solvent evaporation. This was also confirmed by modeling the experimental oxygen permeability data with the well-known Nielsen and Cussler permeation theoretical models, which suggested a reasonable aspect ratio (alpha) of similar to 100. Electron microscopic analyses also disclosed a peculiar cell-like arrangement of the platelets. The stacking of the clay lamellae and the cell-like arrangement create the excellent oxygen barrier properties. Finally, we demonstrated that the slight haze increase in the bionanocomposite coating materials arising from the addition of the clays depends on the clay concentration but not so much on the sonication time, due to the balance of opposite effects after sonication (an increase in the number of scattering centers but a reduction in their size).

  • 108.
    Jafarzadeh, Shadi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Direct measurement of colloidal interactions between polyaniline surfaces in a uv-curable coating formulation: The effect of surface hydrophilicity/ hydrophobicity and resin composition2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 4, s. 1045-1054Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interactions between polyaniline particles and polyaniline surfaces in polyester acrylate resin mixed with 1,6-hexanediol diacrylate monomer have been investigated using contact angle measurements and the atomic force microscopy colloidal probe technique. Polyaniline with different characteristics (hydrophilic and hydrophobic) were synthesized directly on spherical polystyrene particles of 10 μm in diameter. Surface forces were measured between core/shell structured polystyrene/polyaniline particles (and a pure polystyrene particle as reference) mounted on an atomic force microscope cantilever and a pressed pellet of either hydrophilic or hydrophobic polyaniline powders, in resins of various polymer:monomer ratios. A short-range purely repulsive interaction was observed between hydrophilic polyaniline (doped with phosphoric acid) surfaces in polyester acrylate resin. In contrast, interactions between hydrophobic polyaniline (doped with n-decyl phosphonic acid) were dominated by attractive forces, suggesting less compatibility and higher tendency for aggregation of these particles in liquid polyester acrylate compared to hydrophilic polyaniline. Both observations are in agreement with the conclusions from the interfacial energy studies performed by contact angle measurements.

  • 109.
    Joabsson, F.
    et al.
    Department of Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University.
    Thuresson, K.
    Department of Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Interfacial interaction between sodium dodecyl sulfate and hydrophobically modified ethyl(hydroxyethyl)cellulose. A surface force study2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 5, s. 1506-1510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of addition of sodium dodecyl sulfate (SDS) to a layer of hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC) preadsorbed on hydrophobized mica has been studied with an interferometric surface force apparatus (SFA). The force between the surfaces was always repulsive on both compression and separation. The range of this force, which is 1500 Angstrom for the HM-EHEC layers, undergoes a non-monotonic change on addition of SDS. Initially, at low SDS concentrations the layer expand, while at higher surfactant concentrations a contraction of the adsorbed layer is observed. At 1.5 mM SDS the range of the force is at maximum, while at 6 mM SDS the layer is significantly thinner than before addition of SDS. The results are discussed in terms of polymer-surfactant interfacial association and competitive adsorption. The data obtained by surface force measurements agree qualitatively with ellipsometry findings on the same system.

  • 110.
    Johansson, Emma
    et al.
    Department of Physical and Analytical Chemistry, Physical Chemistry, Uppsala University.
    Sandström, Maria C
    Department of Physical and Analytical Chemistry, Physical Chemistry, Uppsala University.
    Bergström, Lars Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Edwards, Katarina
    Department of Physical and Analytical Chemistry, Physical Chemistry, Uppsala University.
    On the Formation of Discoidal versus Threadlike Micelles in Dilute Aqueous Surfactant/Lipid Systems2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 5, s. 1731-1739Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a recent study, we showed that the surfactant 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000 (DSPE-PEG2000) induced mixed micelles of either threadlike or discoidal shape when mixed with different types of lipids. In this study, we have exchanged the PEG−lipid for the more conventional surfactants octaethylene glycol monododecyl ether (C12E8), hexadecyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Cryo-TEM investigations show that also these surfactants are able to induce the formation of long-lived discoidal micelles. Generally, the preference for either discoidal or threadlike micelles can be tuned by the choice of lipids and environmental conditions in much the same way as observed for the lipid/PEG−lipid system. Our investigation showed, furthermore, that the choice of surfactant may influence the type of mixed micelles formed. It is argued that the formation of discoidal rather than threadlike micelles may be rationalized as an effect of increasing bending rigidity. Our detailed theoretical model calculations show that the bending rigidity becomes significantly raised for aggregates formed by an ionic rather than a nonionic surfactant.

  • 111.
    Johansson, Erik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Lingström, Rikard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Adhesive Interaction between Polyelectrolyte Multilayers of Polyallylamine Hydrochloride and Polyacrylic Acid Studied Using Atomic Force Microscopy and Surface Force Apparatus2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 5, s. 2887-2894Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the adhesion between substrates treated with identical polyelectrolyte multilayers (PEM) from polyallylamine hydrochloride (PAR) and poly(acrylic acid) (PAA) was studied using atomic force microscopy (AFM) and the Surface force apparatus (SFA). The AFM measurements, conducted under wet conditions for PEMs formed at pH 7.5, showed a higher adhesion (pull-off force) when PAH was adsorbed in the outermost layers. There was also a difference depending on the Molecular mass of the polymers, demonstrating a greater adhesion for the low molecular mass combination of polyelectrolytes. Furthermore, die time in contact showed to be of importance, with increasing pull-off forces with contact time at maximum load. The SFA measurements were conducted under dry conditions, at 100% RH, and under wet conditions for PEMs adsorbed at pH 7.5/3.5. The SFA adhesion measurements showed that under dry conditions, the adhesive forces between two high energetic mica substrates were lowered when they were covered by PEMs before the measurements. The thickness of the adsorbed layers was also measured using SFA. This showed that there was a significant swelling when the dry layers were exposed to 100% RH or to wet conditions. The swelling was higher, indicating a less rigid layer, when PAH was adsorbed in the outermost layer than when the PEM was capped with PAA.

  • 112. Kadi, M.
    et al.
    Dvinskikh, Sergey V.
    KTH, Tidigare Institutioner                               , Kemi.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Almgren, M.
    Molecular mechanism of lateral diffusion of fluorosurfactants. A F-19 NMR study2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 12, s. 5015-5018Artikel i tidskrift (Refereegranskat)
  • 113. Kadi, M.
    et al.
    Hansson, P.
    Almgren, M.
    Bergström, Lars Magnus
    Garamus, V. M.
    Mixed micelles of fluorocarbon and hydrocarbon surfactants. A small angle neutron scattering study2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 10, s. 3933-3939Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mixtures of the partly fluorinated cationic surfactant HFDePC (N-(1, 1,2,2-tetrahydroperfluorodecanyl)pyridinium chloride and deuterated headgroup) with C(16)TAC, hexadecyl-trimethylammonium chloride, have been investigated using small angle neutron scattering with contrast matching. Earlier results from this system suggested that a demixing occurred, into two coexisting populations of micelles, hydrocarbon-rich and fluorocarbon-rich, respectively. The present results could be explained by one type of mixed micelles with an inhomogeneous distribution of fluorinated and hydrogenated surfactants within the micelles although a demixing cannot be definitely excluded.

  • 114. Kadi, M.
    et al.
    Hansson, P.
    Almgren, M.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Demixing of fluorinated and hydrogenated surfactants into distinct aggregates and into distinct regions within aggregates. A combined NMR, fluorescence quenching, and cryo-TEM study2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 24, s. 9243-9249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of two different kinds of micelles in the cationic surfactant mixture of HFDePC and CTAC as well as the increased mixing with increasing temperature has been investigated. A critical temperature of demixing was appreciated to 42 degreesC. NMR self-diffusion measurements reveal to us a coexistence of larger fluorocarbon-rich and smaller hydrocarbon-rich micelles, which is also observed using cryo-TEM. We also suggest, from F-19 line width data, that the two surfactant species constituting the demixed micelles are I'microphase-separated. The existence of such aggregates has earlier only been speculated upon. From time-resolved fluorescence quenching measurements, we have estimated the fraction of fluorocarbon surfactant in the hydrocarbon-rich micelles to larger than 0.1.

  • 115.
    Karlsson, Mattias E.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mamie, Yann C.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Calamida, Andrea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Gardner, James M.
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 17, s. 5079-5087Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.

  • 116.
    Kaufman, E. D.
    et al.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Belyea, J.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Johnson, M. C.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Nicholson, Z. M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Ricks, J. L.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Shah, P. K.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Bayless, M.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Feldötö, Zsombor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Franzen, S.
    Department of Chemistry, North Carolina State UniVersity, Raleigh, North Carolina.
    Probing Protein Adsorption onto Mercaptoundecanoic Acid Stabilized Gold Nanoparticles and Surfaces by Quartz Crystal Microbalance and ζ-Potential Measurements2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 11, s. 6053-6062Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption characteristics of three proteins [bovine serum albumin (BSA), myoglobin (Mb), and cytochrome c (CytC)] onto self-assembled monolayers of mercaptoundecanoic acid (MUA) on both gold nanoparticles (AuNP) and gold surfaces (Au) are described. The combination of quartz crystal microbalance measurements with dissipation (QCM-D) and pH titrations of the zeta-potential provide information on layer structure, surface coverage, and potential. All three proteins formed adsorption layers consisting of an irreversibly adsorbed fraction and a reversibly adsorbed fraction. BSA showed the highest affinity for the MUA/Au, forming an irreversibly adsorbed rigid monolayer with a side-down orientation and packing close to that expected in the jamming limit. In addition, BSA showed a large change in the adsorbed mass due to reversibly bound protein. The data indicate that the irreversibly adsorbed fraction of CytC is a monolayer structure, whereas the irreversibly adsorbed Mb is present in form of a bilayer. The observation of stable BSA complexes on MUA/AuNPs at the isoelectric point by zeta-potential measurements demonstrates that BSA can sterically stabilize MUA/AuNP. On the other hand, MUA/AuNP coated with either Mb or CytC formed a reversible flocculated state at the isoelectric point. The colloidal stability differences may be correlated with weaker binding in the reversibly bound overlayer in the case of Mb and CytC as compared to BSA.

  • 117. Kertmen, Ahmet
    et al.
    Torruella, Pau
    Coy, Emerson
    Yate, Luis
    Nowaczyk, Grzegorz
    Gapinski, Jacek
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Toprak, Muhammet
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Estrade, Sonia
    Peiro, Francesca
    Milewski, Slawomir
    Jurga, Stefan
    Andruszkiewicz, Ryszard
    Acetate-Induced Disassembly of Spherical Iron Oxide Nanoparticle Clusters into Monodispersed Core-Shell Structures upon Nanoemulsion Fusion2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 39, s. 10351-10365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has been long known that the physical encapsulation of oleic acid-capped iron oxide nanoparticles (OA-IONPs) with the cetyltrimethylammonium (CTA(+)) surfactant induces the formation of spherical iron oxide nanoparticle clusters (IONPCs). However, the behavior and functional properties of IONPCs in chemical reactions have been largely neglected and are still not well-understood. Herein, we report an unconventional ligand-exchange function of IONPCs activated when dispersed in an ethyl acetate/acetate buffer system. The ligand exchange can successfully transform hydrophobic OA-IONP building blocks of IONPCs into highly hydrophilic, acetate-capped iron oxide nanoparticles (Ac-IONPs). More importantly, we demonstrate that the addition of silica precursors (tetraethyl orthosilicate and 3-aminopropyltriethoxysilane) to the acetate/oleate ligand-exchange reaction of the IONPs induces the disassembly of the IONPCs into monodispersed iron oxide-acetate-silica core-shell-shell (IONPs@acetate@SiO2) nanoparticles. Our observations evidence that the formation of IONPs@acetate@SiO2 nanoparticles is initiated by a unique micellar fusion mechanism between the Pickering-type emulsions of IONPCs and nanoemulsions of silica precursors formed under ethyl acetate buffered conditions. A dynamic rearrangement of the CTA(+)-oleate bilayer on the IONPC surfaces is proposed to be responsible for the templating process of the silica shells around the individual IONPs. In comparison to previously reported methods in the literature, our work provides a much more detailed experimental evidence of the silica-coating mechanism in a nanoemulsion system. Overall, ethyl acetate is proven to be a very efficient agent for an effortless preparation of monodispersed IONPs@acetate@SiO2 and hydrophilic Ac-IONPs from IONPCs.

  • 118.
    Kharkov, Boris B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Corkery, Robert W.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Dvinskikh, Sergey V.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Phase Transitions and Chain Dynamics of Surfactants Intercalated into the Galleries of Naturally Occurring Clay Mineral Magadiite2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 26, s. 7859-7866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate conformational dynamics and phase transitions of surfactant molecules confined in the layered galleries of the organo-modified, natural polysilicate clay, magadiite. We have shown that our approach to studying this class of materials is capable of delivering detailed information on the molecular mobility of the confined molecules. From the analysis of the measured heteronuclear dipolar couplings, the orientational order parameters of the C-H bonds along the hydrocarbon chain have been determined. Three phases have been observed in the nanocomposite, characterized by distinct dynamical states of the surfactant. At room temperature, restricted mobility of the molecules led to the adoption of an essentially all-trans conformation by the chains. This behavior can be described by a model incorporating small-angle wobbling around the long molecular axes of the chains. Upon heating, dynamic transformation takes place, resulting in a rotator type solid phase where molecules in extended all-trans conformations undergo fast and unrestricted rotation about their respective symmetry axes. The second phase transition is associated with chain melting and the onset of translational dynamics and results in an essentially liquid-crystalline-like state of the organic component. The mobility of the surfactant is one of the key factors facilitating the efficient penetration of macromolecules in the process of preparing of polymer/organoclay nanocomposites. The exploration of dynamic properties of the fimctionalizing organic layer should provide important input into the improved design of new organic-inorganic hybrid materials.

  • 119. Kjellin, U. R. M.
    et al.
    Claesson, Per M.
    KTH, Tidigare Institutioner                               , Kemi.
    Surface properties of tetra(ethylene oxide) dodecyl amide compared with poly(ethylene oxide) surfactants. 2. Effect of the headgroup on surface forces2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 18, s. 6754-6763Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface interaction forces between layers of tetra(ethylene oxide) n-dodecyl amide, TEDAd, were compared with those of C12E5, C12E4, C10E5, and C10E4. It was found that adsorbed layers of TEDAd on a hydrophobic surface are thinner and less diffuse than layers Of C12E5. As the number of EO groups decreases, the short-range repulsion commences at shorter distances and at the same time the compressibility decreases. These results can be qualitatively explained with model mean-field lattice calculations, except for the fact that a higher attractive force was found between layers of TEDAd, whereas no adhesion was found in the case of the alcohol ethoxylates. The reason for this is proposed to be a smaller steric/protrusion force in the case of TEDAd caused by intralayer interactions between the amide groups inside the adsorbed layer. The force required to squeeze out the surfactant layers from the contact zone increased with concentration, and at the same time the adhesion decreased. Above the critical micelle concentration, no adhesion was found between the surfaces, and an outward jump from hydrophobic surface contact occurred on the repulsive side of the force curve as the compressive force was decreased. The force when this occurred was found to be highest for the largest hydrophilic headgroups, indicating that the surface pressure outside the contact region, and the pressure from surfactants remaining between the surfaces, was largest for these surfactants. In contrast to the ethoxylated surfactants, sugar surfactant layers are less compressible, show considerably larger adhesion, and are not possible to squeeze out at the compressive forces used in this study.

  • 120. Kjellin, U. R. M.
    et al.
    Claesson, Per M.
    KTH, Tidigare Institutioner                               , Kemi.
    Linse, P.
    Surface properties of tetra(ethylene oxide) dodecyl amide compared with poly(ethylene oxide) surfactants. 1. Effect of the headgroup on adsorption2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 18, s. 6745-6753Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surfactant tetra(ethylene oxide) n-dodecyl amide (TEDAd) was compared with the poly(ethylene oxide) n-alkyl ethers C12E5, C10E5, and C12E4. The adsorption to hydrophobic liquid-vapor and solid-liquid interfaces, as well as the wetting behavior on a hydrophobic surface, was investigated. The amide group is more hydrophilic than the ethylene oxide group, raising the cloud point and critical micelle concentration (cmc). The incorporation of an amide group decreases the adsorbed amount at a fixed surfactant concentration. For all studied surfactants the adsorbed amount was significantly lower on the solid-liquid interface than on the liquid-vapor interface at a fixed concentration below the cmc, but the maximum adsorbed amount was only slightly lower on the solid-liquid interface. The surface pressure vs area/molecule isotherms reveal attractive interactions between the amide groups in the adsorbed layer, which reduces the surface pressure at a fixed area/molecule. The advancing contact angles were only dependent on the surface tension at the liquid-vapor interface for C12E5 and TEDAd. The calculated adsorbed amount from the advancing contact angle agreed with the adsorbed amount on the liquid-vapor interface, while the adsorbed amount calculated from the receding contact angle was closer to the equilibrium value obtained with ellipsometry on the solid-liquid interface. The experimental results are supported by mean-field lattice model calculations, and due to the unfavorable interaction between the hydrocarbon region and the amide group in the adsorbed layer, the boundary between the hydrophobic and hydrophilic regions in the adsorbed layer becomes better defined in the presence of an amide group. This might be one of the explanations for the differences found in surface force measurements, and this will be described in part 2 of this investigation.

  • 121. Kjellin, U. R. M.
    et al.
    Claesson, Per M.
    KTH, Tidigare Institutioner                               , Kemi.
    Vulfson, E. N.
    Studies of N-dodecyllactobionamide, maltose 6'-O-dodecanoate, and octyl-beta-glucoside with surface tension, surface force, and wetting techniques2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 6, s. 1941-1949Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three different types of sugar surfactants, octyl-beta -glucoside, maltose 6'-O-dodecanoate, and N-dodecyllactobionamide have been investigated to examine the effect of the structure of the sugar headgroup on the adsorption to liquid/vapor and solid/liquid interfaces using a number of techniques (surface tension, surface force apparatus, MASIF, and wetting). It was found that all the surfactants form monolayers when adsorbed to a hydrophobic interface at high concentrations. Increased headgroup flexibility leads to the. adsorption of higher amounts on both the liquid/vapor and solid/liquid interfaces, resulting in a higher van der Waals attraction between two such monolayers. Increased hydrogen bonding within layers of more flexible surfactants is suggested to explain this difference. The most flexible surfactant, N-dodecyllactobionamide, is the least efficient wetting agent with the highest gamma (SL). The behavior of the receding contact angles indicates the importance of intralayer hydrogen bonds between larger and more flexible sugar headgroups.

  • 122.
    Knippenberg, S.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Hasselt Univ, Biomed Res Inst, Agoralaan Bldg C, B-3590 Diepenbeek, Belgium..
    Fabre, G.
    Limoges Univ, Fac Pharm, LCSN EA1069, 2 Rue Dr Marcland, F-87025 Limoges, France..
    Osella, S.
    Univ Warsaw, Ctr New Technol, Banacha 2C, PL-02097 Warsaw, Poland..
    Di Meo, F.
    Limoges Univ, Fac Pharm, INSERM UMR 1248, 2 Rue Docteur Marcland, F-87025 Limoges, France..
    Paloncyova, M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ameloot, M.
    Hasselt Univ, Biomed Res Inst, Agoralaan Bldg C, B-3590 Diepenbeek, Belgium..
    Trouillas, P.
    Limoges Univ, Fac Pharm, INSERM UMR 1248, 2 Rue Docteur Marcland, F-87025 Limoges, France.;Palacky Univ, Fac Sci, Ctr Adv Technol & Mat, Tr 17 Listopadu 12, Olomouc 77146, Czech Republic..
    Atomistic Picture of Fluorescent Probes with Hydrocarbon Tails in Lipid Bilayer Membranes: An Investigation of Selective Affinities and Fluorescent Anisotropies in Different Environmental Phases2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 30, s. 9072-9084Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By reverting to spectroscopy, changes in the biological environment of a fluorescent probe can be monitored and the presence of various phases of the surrounding lipid bilayer membranes can be detected. However, it is currently not always clear in which phase the probe resides. The well-known orange 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbo-cyanine perchlorate (DiI-C18(5)) fluorophore, for instance, and the new, blue BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) derivative were experimentally seen to target and highlight identical parts of giant unilamellar vesicles of various compositions, comprising mixtures of dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), sphingomyelin (SM), and cholesterol (Chol). However, it was not clear which of the coexisting membrane phases were visualized (Bacalum et al., Langmuir. 2016, 32, 3495). The present study addresses this issue by utilizing large-scale molecular dynamics simulations and the z-constraint method, which allows evaluating Gibbs free-energy profiles. The current calculations give an indication why, at room temperature, both BODIPY and DiI-C18(5) probes prefer the gel (S-o) phase in DOPC/DPPC (2:3 molar ratio) and the liquid-ordered (L-o) phase in DOPC/SM/Chol (1:2:1 molar ratio) mixtures. This study highlights the important differences in orientation and location and therefore in efficiency between the probes when they are used in fluorescence microscopy to screen various lipid bilayer membrane phases. Dependent on the lipid composition, the angle between the transition-state dipole moments of both probes and the normal to the membrane is found to deviate clearly from 90 degrees. It is seen that the DiI-C18(5) probe is located in the headgroup region of the SM/Chol mixture, in close contact with water molecules. A fluorescence anisotropy study also indicates that DiI-C18(5) gives rise to a distinctive behavior in the SM/Chol membrane compared to the other considered membranes. The latter behavior has not been seen for the studied BODIPY probe, which is located deeper in the membrane.

  • 123.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Linder, Markus B.
    Tilton, Robert D.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Kinetic and Equilibrium Aspects of Adsorption and Desorption of Class II Hydrophobins HFBI and HFBII at Silicon Oxynitride/Water and Air/Water Interfaces2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 8, s. 2683-2691Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrophobins are relatively small globular proteins produced by filamentous fungi. They display unusual high surface activity and are implied as mediators of attachment to surfaces, which has resulted in high scientific and technological interest. In this work we focus on kinetic and equilibrium aspects of adsorption and desorption properties of two representatives of class II hydrophobins, namely HFBI and HFBII, at a negatively charged hydrophilic solid/water interface and at the air/water interface. The layers formed at the air/liquid interface were examined in a Langmuir trough, whereas layers formed at the solid/liquid interface were studied using dual polarization interferometry (DPI) under different flow conditions. For comparison, another globular protein, lysozyme, was also investigated. It was found that both the adsorbed amount and the adsorption kinetics were different for HFBI and HFBII, and the adsorption behavior of both hydrophobins on the negatively charged surface displayed some unusual features. For instance, even though the adsorption rate for HFBI was slowed down with increasing adsorbed amount as expected from packing constraints at the interface, the adsorption kinetics curves for HFBII displayed a region indicating adsorption cooperativity. Further, it was found that hydrophobin layers formed under flow partly desorbed when the flow was stopped, and the desorption rate for HFBII was enhanced in the presence of hydrophobins in solution.

  • 124.
    Krivosheeva, Olga
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sababi, Majid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nanostructured Composite Layers of Mussel Adhesive Protein and Ceria Nanoparticles2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 30, s. 9551-9561Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive proteins are known for their high affinity to a range of different surfaces, and they therefore appear as ideal candidates for producing thin inorganic-organic composite films with high robustness. In this work we explore the possibility of making cohesive films utilizing layer-by-layer deposition of the highly positively charged mussel adhesive protein, Mefp-1, and negatively charged ceria nanoparticles. This particular material combination was chosen due to recent findings that such films provide good corrosion protection. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used for following the film formation process in situ on silica surfaces. A close to linear growth of the film with number of deposited layers was found for up to 18 deposition steps, the highest number of depositions investigated in this work. The Mefp-1 concentration during film deposition affected the film properties, where a higher protein concentration resulted in a stiffer film. It was also found that the added mass could be amplified by using a Mefp-1 solution containing small aggregates. The surface nanomechanical properties of dried multilayer films were investigated using peak force QNM (quantitative nanomechanical mapping) in air. Homogeneous surface coverage was found under all conditions explore, and the Young's modulus of the outer region of the coating increased when a higher Mefp-1 concentration was used during film deposition. The nature of the outermost surface layer was found to significantly affect the surface nanomechanical properties. The abrasion resistance of the coating was measured by using controlled-force contact mode AFM.

  • 125. Kubo, Takuya
    et al.
    Wang, Xin
    Tong, Qi
    Yan, Mingdi
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Polymer-based photocoupling agent for the efficient immobilization of nanomaterials and small molecules2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 15, s. 9372-9378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A highly efficient photocoupling agent, based on perfluorophenylazide (PFPA)-conjugated polyallylamine (PAAm), was developed for the efficient immobilization of polymers, nanoparticles, graphene, and small molecules. The conjugate, PAAm–PFPA, was synthesized, and the percentage of the photoactive moiety, PFPA, can be controlled by the ratio of the two components in the synthesis. By treating epoxy-functionalized wafers with PAAm–PFPA, photoactive surfaces were generated. Compared with the PFPA surface, these polymer-based photocoupling matrix resulted in significantly enhanced immobilization efficiencies, especially for nanomaterials and small molecules. Thus, polystyrene nanoparticles (PS NPs) and alkyl-functionalized silica nanoparticles (SNPs) were successfully immobilized on the PAAm–PFPA surface, resulting in a high material density. Graphene flakes patterned on the PAAm–PFPA surface showed improved feature resolution in addition to a higher material density compared to that of flakes immobilized on the PFPA surface. Furthermore, 2-O-α-d-mannopyranosyl-d-mannopyranose (Man2) immobilized on the PAAm–PFPA surface exhibited significantly enhanced signals when treated with lectin concanavalin A (Con A).

  • 126. Kumpulainen, A. J.
    et al.
    Persson, C. M.
    Eriksson, J. C.
    Tyrode, E. C.
    Johnson, Claes Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Soluble monolayers of n-decyl glucopyranoside and n-decyl maltopyranoside. Phase changes in the gaseous to the liquid-expanded range2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 1, s. 305-315Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To examine the transition from the gaseous to the liquid-expanded monolayer state, surface tension data were recorded for n-decyl beta-D-glucopyranoside (Glu) and n-decyl beta-D-maltopyranoside (Mal) solutions at low concentrations and at different temperatures. Comparisons were also made with n-decyl beta-D-thiomaltopyranoside (S-Mal) solutions at room temperature. The transitions observed occur at very low concentrations and surface pressures, about 0.5% of the critical micelle concentration (cmc) and between 0.8 and 1 mN/m for Glu and Mal at 22 degreesC. For S-Mal the transition is recorded for a concentration of 0.5% of the cmc as well, but the surface pressure is lower, about 0.4 mN/m. The gradual change in molecular area about the transition is from about 500 to 200 Angstrom(2) and 400 to 150 Angstrom(2) for Mal and Glu, respectively, and from about 800 to 250 Angstrom(2) for S-Mal. The comparatively large molecular areas after the transitions are incompatible with the notion that a coherent hydrocarbon film would cover the entire surface already at this stage. Standard surface thermodynamics was applied to elucidate the nature of these transitions in combination with two model concepts: The formation of an infinite network of surfactant molecules and, second, the formation of surface micelles. Hard-disk simulation results were employed to quantify the additional surface pressure after the transition attributed to the formation of surface micelles. In conclusion the formation of surface micelles is plausible as the hard-disk model is capable of accounting for the additional surface pressure increase with acceptable accuracy. Further, vibrational sum frequency spectroscopy was used to investigate the transition for Mal. Using the distinct feature of the non-hydrogen-bonded OH (free OH) at 3700 cm(-1) for probing the surface water state, it could be determined that the surface holds a sizable fraction of unperturbed surface water even after the transition from the Henry range. The decrease in the free OH signal was found to correlate with the increase in surface density of surface micelles.

  • 127.
    Kumpulainen, Atte J.
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Persson, C M
    KTH, Tidigare Institutioner, Kemi.
    Eriksson, Jan Christer
    KTH, Tidigare Institutioner, Kemi.
    Headgroup and hydrocarbon tail effects on the surface tension of sugar-based surfactant solutions2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 25, s. 10935-10942Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements of surface tension isotherms were conducted for water solutions of pure and mixed n-decyl-beta-D-glucopyranoside (C-10-Glu) and n-deCyl-beta-D-maltopyranoside (C-10-Mal) surfactants. By applying the Gibbs surface tension equation, the surface densities of Glu and Mal were derived for different compositions and concentrations. The surface fractions were compared with theoretically calculated values where the headgroups were modeled as hard disks. Satisfactory agreement was found for hard-disk sizes of 22.9 and 11.3 Angstrom(2) in the case of a 1:1 mixture. The results of the hard-disk calculations were employed to estimate the configurational free energy of the n-decyl-hydrocarbon chain. The results obtained agree well with previous calculations for the n-dodecyl chain. Comparison with n-dodecyl beta-D-maltopyranoside (C-12-Mal) indicated a further contribution, with the longer hydrocarbon chain giving rise to a higher surface tension in good agreement with data for hydrocarbon liquids. Furthermore, the interpenetration of the headgroup into the hydrocarbon film was studied by means of comparing surface-tension data for n-decyl- and n-dodecyl-ethylene-oxide-based surfactants and n-decyl- and n-dodecyl-beta-D-thiomaltopyranosides (C-10-S-Mal and C-12-S-Mal, respectively) and -maltopyranosides. It was found that lengthening the tetra(etylene oxide) chain by one segment affects the surface tension only marginally, indicating little interpenetration of the additional ethylene-oxide group into the hydrocarbon film. For the thiomaltosides, however, the corresponding effect was found to be remarkably high.

  • 128.
    Kumpulainen, Atte
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Persson, Clas
    KTH, Tidigare Institutioner, Materialvetenskap.
    Eriksson, Jan Christer
    KTH, Tidigare Institutioner, Kemi.
    n-decyl-glucopyranoside and n-decyl-maltopyranoside Gibbs monolayers. Phase changes in the dilute liquid-expanded range2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 24, s. 10534-10541Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface tension isotherms were recorded for n-decyl-beta-(D)-glucopyranoside (Glu) and n-deCyl-beta-(D)-maltopyranoside (Mal) solutions at temperatures of 8,22, and 29degreesC. Comparison was made with isotherms of n-deCyl-beta-(D)-thiomaltopyranoside (S-Mal) at 22 degreesC. In addition to the transition from the gaseous to the liquid-expanded (LE) state, a second transition was observed in the early stages of the LE regime for Glu, Mal, and S-Mal at room temperature. The adsorption isotherm of Mal and Glu obtained at 22 degreesC shows the presence of an adsorption step at an average area/molecule of about 79 Angstrom(2) between, approximately, 0.02 and 0.1 mM (the critical micelle concentration (cmc) is 2 mM) and 0.015 and 0.03 mM (the cmc is 2 mM), respectively. Similarly, for S-Mal an adsorption plateau is observed at 70 Angstrom(2) between 0.01 and 0.03 mM (the cmc is 0.7 mM). From the temperature dependence of the surface tension, we have seen that there are considerable differences in the adsorption of Glu and Mal. For Mal, the adsorption plateau is also observed at 29 degreesC at around 79 Angstrom(2), whereas Glu exhibits no adsorption plateau at this temperature. At 8 degreesC, both Mal and Glu exhibit saturation behaviour in the dilute part of the liquid-expanded range, but at this temperature the average molecular areas are lower than at 22 degreesC: around 66 Angstrom(2) for Glu and 75 Angstrom(2) for Mal. Thus, the temperature sensitivity of Glu is considerably greater than for Mal in this range. The saturation regime coincides with a pronounced surface entropy minimum for Mal. The transition in the dilute liquid-expanded range supposedly occurs from a state with deformed surface micelles arranged in a hexagonal pattern, referred to as the granular range, to a true LE monolayer with a fluid hydrocarbon tail layer covering the entire surface.

  • 129.
    Lakshmanan, Ramnath
    et al.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Sanchez-Dominguez, Margarita
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Matutes-Aquino, Jose
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Wennmalm, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Kuttuva Rajarao, Gunaratna
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Removal of total organic carbon from sewage wastewater using poly(ethylenimine)-functionalized magnetic nanoparticles2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 4, s. 1036-1044Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increased levels of organic carbon in sewage wastewater during recent years impose a great challenge to the existing wastewater treatment process (WWTP). Technological innovations are therefore sought that can reduce the release of organic carbon into lakes and seas. In the present study, magnetic nanoparticles (NPs) were synthesized, functionalized with poly(ethylenimine) (PEI), and characterized using TEM (transmission electron microscopy), X-ray diffraction (XRD), FTIR (Fourier transform infrared spectroscopy), CCS (confocal correlation spectroscopy), SICS (scattering interference correlation spectroscopy), magnetism studies, and thermogravimetric analysis (TGA). The removal of total organic carbon (TOC) and other contaminants using PEI-coated magnetic nanoparticles (PEI-NPs) was tested in wastewater obtained from the Hammarby Sjöstadsverk sewage plant, Sweden. The synthesized NPs were about 12 nm in diameter and showed a homogeneous particle size distribution in dispersion by TEM and CCS analyses, respectively. The magnetization curve reveals superparamagnetic behavior, and the NPs do not reach saturation because of surface anisotropy effects. A 50% reduction in TOC was obtained in 60 min when using 20 mg/L PEI-NPs in 0.5 L of wastewater. Along with TOC, other contaminants such as turbidity (89%), color (86%), total nitrogen (24%), and microbial content (90%) were also removed without significant changes in the mineral ion composition of wastewater. We conclude that the application of PEI-NPs has the potential to reduce the processing time, complexity, sludge production, and use of additional chemicals in the WWTP.

  • 130.
    Le Berre, F.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Malmsten, M.
    YKI, Institute for Surface Chemistry, Stockholm.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Interfacial properties of a model polyampholyte studied by surface force measurements, ESCA, and ellipsometry2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 3, s. 699-704Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of a model polyampholyte, i.e., [acrylamide]-[sodium 2-(acrylamido)-2-methylpropanesulfonate]-[2-(methacryloyloxy)ethyltrimethylammonium chloride] ([AM]-[NaAMPS]-[MADQUAT]) at mica and silica surfaces was investigated by surface force measurements, electron spectroscopy for chemical analysis (ESCA), and ellipsometry. It was found that the adsorption isotherm of this polyampholyte on mica was of the high affinity type, yielding an adsorbed amount at saturation of 5.5 +/- 0.5 mg/m(2). By lowering the electron escape angle in the ESCA measurements (making the analysis more surface sensitive), it was found that the negatively charged groups in the polyampholyte are concentrated in the outer part of the adsorbed layer, i.e., away from the negatively charged mica surface. From ellipsometry studies with silica, it was found that the adsorption was relatively fast, reaching saturation after about 1000 s on adsorption from a 20 ppm solution. From both ellipsometry and ESCA it was found that the effect of electrolyte on the adsorbed amount of preadsorbed polyampholyte is relatively minor at concentrations up to 10 mM. At higher electrolyte concentrations, however, some desorption of the polyampholyte occurs. Surface force measurements showed that the extension of the polymer layer normal to the mica surface was small compared to the radius of gyration of the polymer in bulk. Upon addition of electrolyte the adsorbed layer was found to contract.

  • 131.
    Li, Cui
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Monti, Susanna
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Carravetta, Vincenzo
    Cysteine on TiO2(110): A Theoretical Study by Reactive Dynamics and Photoemission Spectra Simulation2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 29, s. 8819-8828Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A coherent account of adsorption modes, dynamics, self aggregation, and spectroscopic properties of an indoline organic dye adsorbed on TiO2 anatase (101) substrates is reported. The study is performed by combining reactive molecular dynamics (reaxFF) simulations with time-dependent density functional theory calculations, and the reliability of the results is assessed through comparison with theoretical and experimental data available in the literature. The use of a theoretical multilevel approach has proven to be crucial to gain a deep understanding, at an atomistic level, of the morphology and electronic properties of dye-sensitized heterogeneous interfaces. A realistic description of the functionalized anatase (101) interface, where a variety of binding modes are present, has been achieved by means of extensive molecular dynamics simulations of the adsorption of dye clusters made of different molecular units on medium/large size TiO2 anatase slabs. Our results disclose that the main driving forces toward formation of ordered surface aggregates are pi stacking and T-shaped interactions between the aromatic rings of the donor moiety of the molecules, as well as the tendency to maximize the anchoring points with the surface. The dye aggregates were found to be organized in domains, characterized by a different orientation of the packing units, and, in the high coverage limit, presenting a certain degree of short-to-medium range order.

  • 132.
    Liu, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden.
    Tyrode, Eric
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Surface Grafted Chitosan Gels: Part I. Molecular Insight into the Formation of Chitosan and Poly(acrylic acid) Multi layers2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 29, s. 8866-8877Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Composite polyelectrolyte multilayers of chitosan and low molecular weight poly(acrylic acid) (PAA) have been assembled by sequential adsorption as a first step toward building a surface anchored chitosan gel. Si lane chemistry was used to graft the first chitosan layer to prevent film detachment and decomposition. The assembly process is characterized by nonlinear growth behavior, with different adsorption kinetics for chitosan and PAP.. In situ analysis of the multilayer by means of surface sensitive total internal reflection Raman (TIRR) spectroscopy, combined with target factor analysis of the spectra, provided information regarding composition, including water content, and ionization state of weak acidic and basic groups present in the thin composite film. Low molecular weight PAA, mainly in its protonated form, diffuses into and out of the composite film during adsorption and rinsing steps. The higher molecular weight chitosan shows a similar behavior, although to a much lower extent. Our data demonstrate that the charged monomeric units of chitosan are mainly compensated by carboxylate ions from PAP.. Furthermore, the morphology and mechanical properties of the multilayers were investigated in situ using atomic force microscopy operating in PeakForce tapping mode. The multilayer consists of islands that grow in lateral dimension and height during the build-up process, leading to close to exponentially increasing roughness with deposition number. Both diffusion in and out of at least one of the two components (PAA) and the island-like morphology contribute to the nonlinear growth of chitosan/PAA multilayers.

  • 133.
    Liu, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Tyrode, Eric
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Surface Grafted Chitosan Gels: Part II. Gel Formation and Characterization2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 29, s. 8878-8888Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Responsive biomaterial hydrogels attract significant attention due to their biocompatibility and degradability. In order to make chitosan based gels, we first graft one layer of chitosan to silica, and then build a chitosan/poly(acrylic acid) multilayer using the layer-by-layer approach. After cross-linking the chitosan present in the polyelectrolyte multilayer, poly(acrylic acid) is partly removed by exposing the multilayer structure to a concentrated carbonate buffer solution at a high pH, leaving a surface-grafted cross-linked gel. Chemical cross-linking enhances the gel stability against detachment and decomposition. The chemical reaction between gluteraldehyde, the cross-linking agent, and chitosan was followed in situ using total internal reflection Raman (TIRR) spectroscopy, which provided a molecular insight into the complex reaction mechanism, as well as the means to quantify the cross-linking density. The amount of poly(acrylic acid) trapped inside the surface grafted films was found to decrease with decreasing cross-linking density, as confirmed in situ using TIRR, and ex situ by Fourier transform infrared (FTIR) measurements on dried films. The responsiveness of the chitosan-based gels with respect to pH changes was probed by quartz crystal microbalance with dissipation (QCM-D) and TIRR. Highly cross-linked gels show a small and fully reversible behavior when the solution pH is switched between pH 2.7 and 5.7. In contrast, low cross-linked gels are more responsive to pH changes, but the response is fully reversible only after the first exposure to the acidic solution, once an internal restructuring of the gel has taken place. Two distinct plc's for both chitosan and poly(acrylic acid), were determined for the cross-linked structure using TIRR. They are associated with populations of chargeable groups displaying either a bulk like dissociation behavior or forming ionic complexes inside the hydrogel film.

  • 134.
    Liu, Longcheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    A Dynamic Force Balance Model for Colloidal Expansion and Its DLVO-Based Application2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 2, s. 679-687Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A force balance model that describes the dynamic expansion of colloidal bentonite gels/sols is presented. The colloidal particles are assumed to consist of one or several thin sheets with the other dimensions much larger than their thickness. The forces considered include van der Waals force, diffuse double layer force, thermal force giving rise to Brownian motion, gravity, as well as friction force. The model results in an expression resembling the instationary diffusion equation but with an immensely variable diffusivity. This diffusivity is strongly influenced by the concentration of counterions as well as by the particle concentration in the colloid gel/sol. The properties of the model are explored and discussed, exemplified by the upward expansion of an originally highly compacted bentonite tablet in a test tube. Examples are presented for a number of cases with ionic concentrations varying between very dilute waters up to several molar of counterions. The volume fraction of particles ranges from 40% to very dilute sols.

  • 135.
    Liu, Longcheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    A Novel Approach to Determine the Critical Coagulation Concentration of a Colloidal Dispersion with Plate-like Particles2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 2, s. 688-697Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The critical coagulation concentration (ccc) of counterions is commonly described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory on the basis of a static force balance. It can, however, also be estimated from a kinetic point of view by studying the process of colloidal coagulation, or from a dynamic point of view by considering colloidal transport in nonequilibrium systems where other processes such as diffusion and the influence of gravity come into play. In particular, in a test tube where colloidal expansion takes place, the ccc can be interpreted as the electrolyte concentration below which expansion of colloids would always lead to full access to the entire volume of the test tube and above which a sharp boundary is established between a colloidal gel and pure water. On the basis of this perception and the dynamic force balance model that we developed to describe colloidal expansion in a test tube, accounting for the effects of particle diffusion and gravity in contrast to the DLVO theory, we propose an alternative way to assess the ccc of counterions. We also derive an approximate expression for the case of homointeraction at constant charge for montmorillonite. The estimated ccc values agree quite well with those observed experimentally for both Na+ and Ca2+ counterions for montmorillonite dispersions, at pH similar to 6.5. This is in contrast to the DLVO theory, which overpredicts the ccc by about 2 orders of magnitude. In addition, the detailed analyses suggest that the ccc of counterions decreases with increasing surface area and with the thickness of the particles. For montmorillonite, the ccc is nearly independent of the surface charge density of the particles for the range of typical charge densities.

  • 136. Liu, Qingkun
    et al.
    Beier, Corinne
    Evans, Julian
    Lee, Taewoo
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Smalyukh, Ivan I.
    Self-Alignment of Dye Molecules in Micelles and Lamellae for Three-Dimensional Imaging of Lyotropic Liquid Crystals2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 12, s. 7446-7452Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report alignment of anisotropic amphiphilic dye molecules within oblate and prolate anisotropic micelles and lamellae, the basic building blocks of surfactant-based lyotropic liquid crystals. Absorption and fluorescence transition dipole moments of these dye molecules orient either parallel or orthogonal to the liquid crystal director. This alignment enables three-dimensional visualization of director structures and defects in different lyotropic mesophases by means of fluorescence confocal polarizing microscopy and two-photon excitation fluorescence polarizing microscopy. The studied structures include nematic tactoids, Schlieren texture with disclinations in the calamitic nematic phase, oily streaks in the lamellar phase, developable domains in the columnar hexagonal phase, and various types of line defects in the discotic cholesteric phase. Orientational three-dimensional imaging of structures in the lyotropic cholesterics reveals large Burgers vector dislocations in cholesteric layering with singular disclinations in the dislocation cores that are not common for their thermotropic counterparts.

  • 137.
    Liu, Xiaoyan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Visnevskij, C.
    Makuska, R.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Electrostatically anchored branched brush layers2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 44, s. 15537-15547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel type of block copolymer has been synthesized. It consists of a linear cationic block and an uncharged bottle-brush block. The nonionic bottle-brush block contains 45 units long poly(ethylene oxide) side chains. This polymer was synthesized with the intention of creating branched brush layers firmly physisorbed to negatively charged surfaces via the cationic block, mimicking the architecture (but not the chemistry) of bottle-brush molecules suggested to be present on the cartilage surface, and contributing to the efficient lubrication of synovial joints. The adsorption properties of the diblock copolymer as well as of the two blocks separately were studied on silica surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and optical reflectometry. The adsorption kinetics data highlight that the diblock copolymers initially adsorb preferentially parallel to the surface with both the cationic block and the uncharged bottle-brush block in contact with the surface. However, as the adsorption proceeds, a structural change occurs within the layer, and the PEO bottle-brush block extends toward solution, forming a surface-anchored branched brush layer. As the adsorption plateau is reached, the diblock copolymer layer is 46-48 nm thick, and the water content in the layer is above 90 wt %. The combination of strong electrostatic anchoring and highly hydrated branched brush structures provide strong steric repulsion, low friction forces, and high load bearing capacity. The strong electrostatic anchoring also provides high stability of preadsorbed layers under different ionic strength conditions.

  • 138.
    Liu, Yingxin
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Schütz, Christina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Stockholm University, Stockholm.
    Salazar, German
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. Department of Materials and Environmental Chemistry, Stockholm University, Stockholm.
    Bergström, Lennart
    Assembly, Gelation, and Helicoidal Consolidation of Nanocellulose spersions2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 10, s. 3600-3606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability to probe the assembly, gelation, and helicoidal nsolidation of cellulose nanocrystal (CNC) dispersions at high ncentrations can provide unique insight into the assembly and can sist optimized manufacturing of CNC-based photonic and structural terials. In this Feature Article, we review and discuss the ncentration dependence of the structural features, characterized by e particle separation distance and the helical pitch, at CNC ncentrations (c) that range from the isotropic state, over the phasic range, to the fully liquid crystalline state. The structure olution of CNC dispersions probed by time resolved small-angle X-ray attering during evaporation-induced assembly highlighted the portance of gelation and consolidation at high concentrations. We iefly discuss how the homogeneity of helicoidal nanostructures in dry

  • 139. Lombardo, S.
    et al.
    Chen, Pan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Larsson, Per A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Thielemans, W.
    Wohlert, Jakob
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Svagan, Anna J.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Toward Improved Understanding of the Interactions between Poorly Soluble Drugs and Cellulose Nanofibers2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 19, s. 5464-5473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose nanofibers (CNFs) have interesting physicochemical and colloidal properties that have been recently exploited in novel drug-delivery systems for tailored release of poorly soluble drugs. The morphology and release kinetics of such drug-delivery systems heavily relied on the drug-CNF interactions; however, in-depth understanding of the interactions was lacking. Herein, the interactions between a poorly soluble model drug molecule, furosemide, and cationic cellulose nanofibers with two different degrees of substitution are studied by sorption experiments, Fourier transform infrared spectroscopy, and molecular dynamics (MD) simulation. Both MD simulations and experimental results confirmed the spontaneous sorption of drug onto CNF. Simulations further showed that adsorption occurred by the flat aryl ring of furosemide. The spontaneous sorption was commensurate with large entropy gains as a result of release of surface-bound water. Association between furosemide molecules furthermore enabled surface precipitation as indicated by both simulations and experiments. Finally, sorption was also found not to be driven by charge neutralization, between positive CNF surface charges and the furosemide negative charge, so that surface area is the single most important parameter determining the amount of sorbed drug. An optimized CNF-furosemide drug-delivery vehicle thus needs to have a maximized specific surface area irrespective of the surface charge with which it is achieved. The findings also provide important insights into the design principles of CNF-based filters suitable for removal of poorly soluble drugs from wastewater.

  • 140.
    Lundgren, Sarah M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Persson, Karin
    YKI, Institute for Surface Chemistry.
    Mueller, Gregor
    ThyssenKrupp Steel AG, Center of Materials Excellence, Surface Analysis.
    Kronberg, Bengt
    YKI, Institute for Surface Chemistry.
    Clarke, Jim
    Arizona Chemical B.V., European Technical Center.
    Chtaib, Mohammed
    Laboratories of LUXCONTROL SA.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Erratum: Unsaturated fatty acids in alkane solution: Adsorption to steel surfaces (Langmuir (2007) 23 (10598-10602))2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 17, s. 9922-9922Artikel i tidskrift (Refereegranskat)
  • 141.
    Lundgren, Sarah M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Persson, Karin
    YKI, Institute for Surface Chemistry.
    Mueller, Gregor
    ThyssenKrupp Steel AG, Center of Materials Excellence, Surface Analysis.
    Kronberg, Bengt
    YKI, Institute for Surface Chemistry.
    Clarke, Jim
    Arizona Chemical B.V., European Technical Center.
    Chtaib, Mohammed
    Laboratories of LUXCONTROL SA.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Unsaturated fatty acids in alkane solution: adsorption to steel surfaces2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 21, s. 10598-10602Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of the unsaturated fatty acids oleic, linoleic, and linolenic acid on steel surfaces has been investigated by means of a quartz crystal microbalance (QCM). Two different solvents were used, n-hexadecane and its highly branched isomer. viz.. 2.2,4,4,6,8,8-heptamethylnonane. The area occupied per molecule of oleic acid at 1 wt % corresponds to what is needed for adsorption parallel to the surface. At the same concentration, the adsorbed amount of linoleic acid and linolenic acid indicates that they adsorb in multilayers. The chemisorbed amount estimated from static secondary ion mass spectroscopy (SIMS) measurements was found to be similar for the three unsaturated fatty acids. In the case of linolenic acid, it was found that the presence of water significantly alters the adsorption, most likely because of the precipitation of fatty acid/water aggregates. Furthermore, static SIMS results indicate that the amount of water used here inhibits the chemisorption of linolenic acid.

  • 142.
    Lundin, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tilton, Robert D
    Carnegie Mellon University, Pittsburgh, USA.
    Polymer Dynamics in Layer-by-Layer Assemblies of Chitosan and Heparin2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 5, s. 3242-3251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The layer-by-layer deposition method has been used to build a multilayer thin film with two polysaccharides, chitosan CH (weak polycation) and heparin HEP (strong polyanion), on planar quartz surfaces. The film structure and dynamics in aqueous Solution were studied with fluorescence resonance energy transfer (FRET) and total internal reflection fluorescence (TIRF). Particular emphasis was placed on the effect of deposition conditions, i.e.. pH and salt concentration, on the out-of-plane (vertical) diffusion of fluorescence labeled chitosan in the chitosan/heparin (CH/HEP) film. FRET analysis showed that CH molecules diffused within the film with a diffusion coefficient that was not significantly sensitive to the deposition pH and Solution ionic strength. A pH-sensitive label bound to CH embedded within the CH/HEP Film wits sensitive to the charge of the outermost polymer layer even when buried under 14 alternate layers of CH and HER A consideration of the results obtained with both fluorescence techniques showed that the structure of the CH/HEP thin film wits highly interpenetrated without clear boundaries between each layer. These results are consistent with the hypothesis that the previously observed exponential-like film growth of CH and HEP in terms of, layer thickness and deposited amount versus deposition cycle can be attributed to out-of-plane diffusion of CH molecules in the multilayer.

  • 143.
    Lundin, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Macakova, Lubica
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Auletta, Tommaso
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Mucin−Chitosan Complexes at the Solid−Liquid Interface:  Multilayer Formation and Stability in Surfactant Solutions2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, s. 9502-9509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of a biologically important glycoprotein, mucin, and mucin-chitosan complex layer formation on negatively charged surfaces, silica and mica, have been investigated employing ellipsometry, the interferometric surface apparatus, and atomic force microscopy techniques. Particular attention has been paid to the effect of an anionic surfactant sodium, dodecyl sulfate (SDS), with respect to the stability of the adsorption layers. It has been shown that mucin adsorbs on negatively charged surfaces to form highly hydrated layers. Such mucin layers readily associate with surfactants and are easily removed from the surfaces by rinsing with solutions of SDS at concentrations >= 0.2 cmc (1 cmc SDS in 30 mM NaCl is equal to 3.3 mM). The mucin adsorption layer is negatively charged, and we show how a positively charged polyelectrolyte, chitosan, associates with the preadsorbed mucin to form mucin-chitosan complexes that resist desorption by SDS even at SDS concentrations as high as 1 cmc. Thus, a method of mucin layer protection against removal by surfactants is offered. Further, we show how mucin-chitosan multilayers can be formed.

  • 144.
    Lundin, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Macakova, L.ubica
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Interactions between Chitosan and SDS at a Low-Charged Silica Substrate Compared to Interactions in the Bulk: The Effect of Ionic Strength2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 8, s. 3814-3827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of ionic strength on association between the cationic polysaccharide chitosan and the anionic surfactant sodium dodecyl sulfate, SDS, has been studied in bulk solution and at the solid/liquid interface. Bulk association was probed by turbidity, clectrophoretic mobility, and surface tension measurements. The critical aggregation concentration, cac, and the saturation binding of surfactants were estimated from surface tension data. The number of associated SDS molecules per chitosan segment exceeded one at both salt concentrations. As a result, a net charge reversal of the polymer-surfactant complexes was observed, between 1.0 and 1.5 mM SDS, independent of ionic strength. Phase separation occurs in the SDS concentration region where low charge density complexes form, whereas at high surfactant concentrations (up to several multiples of cmc SDS) soluble aggregates are formed. Ellipsometry and QCM-D were employed to follow adsorption of chitosan onto low-charged silica substrates, and the interactions between SDS and preadsorbed chitosan layers. A thin (0.5 nm) and rigid chitosan layer was formed when adsorbed from a 0.1 mM NaNO3 solution, whereas thicker (2 nm) chitosan layers with higher dissipation/unit mass were formed from solutions at and above 30 mM NaNO3. The fraction of solvent in the chitosan layers was high independent of the layer thickness and rigidity and ionic strength. In 30 mM NaNO3 Solution, addition of SDS induced a collapse at low concentrations, while at higher SDS concentrations the viscoelastic character of the layer was recovered. Maximum adsorbed mass (chitosan + SDS) was reached at 0.8 times the cmc of SDS, after which surfactant-induced polymer desorption occurred. In 0.1 mM NaNO3. the initial collapse was negligible and further addition of surfactant lead to the formation of a nonrigid, viscoelastic polymer layer until desorption began above a surfactant concentration of 0.4 times the cmc of SDS.

  • 145.
    Lundin, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Solaqa, Faten
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Macakova, Lubica
    Institute for Surface Chemistry, Sweden.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Institute for Surface Chemistry, Sweden.
    Layer-by-layer assemblies of chitosan and heparin: effect of solution ionic strength and pH2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 12, s. 7537-7548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The growth of polysaccharide multilayers consisting of positively charged chitosan (CH) and negatively charged heparin (HEP) was monitored in situ by employing a quartz crystal microbalance (QCM-D) and dual-polarization interferometry (DPI). The main focus was on how the physicochemical properties of the solution affect the growth and structure of the resulting multilayer film These results showed that when increasing the ionic strength of the polysaccharide solutions at a fixed pH, both the "dry" (optical) (DPI) mass and wet (QCM) mass of the adsorbed multilayer film increased. The same effect was found when increasing the pH while keeping the ionic strength constant. Furthermore, the growth of multilayers showed an exponential-like behavior independent of the solution conditions that were used in this study. It was also established that chitosan was the predominant species present in the chitosan heparin multilayer film. We discuss the viscoelastic properties of the adsorbed layers and their variation during the multilayer buildup. Interestingly and contrary to common interpretation of the QCM-D results, we found that under one particular solution condition (pH 4.2 and 30 mM NaCl) the increase in the dissipation of oscillation energy from the adsorbed layer was a consequence of layer stiffening rather than indicating a more hydrated and viscous film. On the basis of the widely used Voigt viscoelastic model for an adsorbed layer, we show that it is the film viscosity and shear that define the layer viscoelasticity (structure) of the film and not the absolute value of energy dissipation, which in fact can be very misleading.

  • 146.
    Macakova, Lubica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    The effect of adsorbed layer surface roughness on the QCM-D response: focus on trapped water2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 24, s. 12436-12444Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of surface roughness on the quartz crystal microbalance with dissipation monitoring (QCM-D) response was investigated with emphasis on determining the amount of trapped water. Surfaces with different nanoroughnesses Were prepared on silica by self-assembly of cationic surfactants with different packing parameters. We used surfactants with quaternary ammonium bromide headgroups: the double-chained didodecyltrimethylammonium bromide (C-12)(2)-DAB (DDAB), the single-chained hexadecyltrimethylammonium bromide C(16)TAB (CTAB), and dodecyltrimethylammonium bromide C(12)TAB (DTAB). The amount of trapped water was obtained from the difference between the mass sensed by QCM-D and the adsorbed amount detected by optical reflectometry. The amount of water, which is sensed by QCM-D, was found to increase with the nanoroughness of the adsorbed layer. The water sensed by QCM-D cannot be assigned primarily to hydration water, because it differs substantially for adsorbed surfactant layers with similar headgroups but with different nanoscale topographies

  • 147.
    Macakova, Lubica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Nordstierna, Lars
    KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Karlsson, Göran
    Department of Physical Chemistry, Uppsala University.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Lack of association between a cationic protein and a cationic fluorosurfactant2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 2, s. 771-775Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface tension, F-19 and H-1 NMR spectroscopy, and cryotransmission electron microscopy are used to characterize the state of association in aqueous solutions of a fluorosurfactant CF3(CF2)(n)SO2NH(CH2)(3-4)N(CH3)(3)(+) I- (n = 8, 6) with and without lysozyme added. In the absence of lysozyme, we find monomers, small aggregates, and large vesicles to coexist, with the individual fluorosurfactant molecules exchanging slowly (> 1 ms) among those states. When both lysozyme and fluorosurfactant are present in the solution, they have no measurable influence on the physical state of the other. In contrast, a hydrogenated cationic surfactant with the same headgroup, hexadecyltrimethylammonium bromide, is shown to associate to lysozyme.

  • 148. Madwar, Carolin
    et al.
    Kwan, William Chu
    Deng, Lingquan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Schmidt, Rolf
    Zou, Shan
    Cuccia, Louis A.
    Perfluorophenyl Azide Immobilization Chemistry for Single Molecule Force Spectroscopy of the Concanavalin A/Mannose Interaction2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 22, s. 16677-16680Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The versatility of perfluorophenyl azide (PFPA) derivatives makes them useful for attaching a wide variety of biomoleculcs and polymers to surfaces. Herein, it single molecule force spectroscopy (SMFS) study of the concanavalin A/mannose interaction was carried out using PFPA immobilization chemistry. SMFS of the concanavalin A/mannose interaction yielded in average unbinding force of 70-80 pN for loading rates between 8000 and 40 000 pN/s for mannose surfaces on aminated glass. and an unbinding force of 57 +/- 20 pN at 6960 pN/s for mannose surfaces on gold-coated glass. Dynamic force spectroscopy was used to determine the dissociation rate constant, k(off), for this interaction to be 0.16 s(-1).

  • 149.
    Marinado, Tannia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Nonomura, Kazuteru
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Nissfolk, Jarl
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Karlsson, Martin K
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Hagberg, Daniel P
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Mori, Shogo
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    How the Nature of Triphenylamine-Polyene Dyes in Dye-Sensitized Solar Cells Affects the Open-Circuit Voltage and Electron Lifetimes2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 4, s. 2592-2598Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three donor-linker-acceptor triphenylamine-based cyanoacrylic acid organic dyes used For dye-sensitized solar cells (DSCs) have been examined with respect to their effect on the open-circuit voltage (V-oc). Our previous study showed a decrease in V-oc for DSCs based oil dyes with increased molecular size (increased linker conjugation). In the present study, we investigate the origin of V-oc with respect to (i) conduction band (E-CB) positions of TiO2 and (ii) degree of recombination between electrons in TiO2 and electrolyte acceptor species at the interface. These parameters were Studied its it function of dye structure, dye load, and I-2 concentration. Two types of behavior were identified: the smaller polyene dyes show a surface-protecting effect preventing recombination upon increased dye loading, whereas the larger dyes enhance the recombination. How the different dye structures affect the recombination is discussed in terms of dye surface blocking and intermolecular interactions between dyes and electrolyte acceptor species.

  • 150. Marquet, Philip
    et al.
    Andersson, Gunther
    Snedden, Alan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Atkin, Rob
    Molecular Scale Characterization of the Titania-Dye-Solvent Interface in Dye-Sensitized Solar Cells2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 12, s. 9612-9616Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Charge separation at the dye/titania interface in dye sensitized solar cells is strongly influenced by the thickness and homogeneity of the sensitizing dye layer, as this controls the potential drop across the interface, and the probability of an excited electron being transferred from the dye to the titania. In this study we use atomic force microscopy and the depth profiling method neutral impact collision ion scattering spectroscopy (NICISS) to investigate the thickness and homogeneity of N719 dye adsorbed to titania before and after rinsing with pure acetonitrile. Both experimental methods show that the dye layers are closed but inhomogencous. Inhomogeneity is more pronounced for unrinsed samples.

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