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  • 251. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Swerin, Agne
    Ostlund, Catherine
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Influence of Surface Topography on Adhesive and Long-Range Capillary Forces between Hydrophobic Surfaces in Water2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 16, s. 9197-9207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report oil the interactions between a hydrophobic probe particle and surfaces with nanoscopic surface features, These surfaces have been prepared by spin-coating of nanoparticles and by polishing. The surface topography was characterized by AFM, using the methods of high-resolution imaging, low-resolution imaging using the probe particle, and by the rolling ball method. The spin-coated surfaces can be characterized as nanostructured due to the high density of nanoparticles that oil a short length scale provides a regular pattern of crevices and hills. Oil these surfaces a larger waviness is also distinguished. In contrast, the polished surfaces display sharp nanoscopic peaks and hardly any crevices. I n all cases the dominant force at short separations was found to be a capillary attraction due to the formation of an air/ vapor condensate. Our data show that the large-scale waviness of the surface does not significantly influence the range and magnitude of the capillary attraction, but large local variations in these quantities are found. The large variation in on force corresponds to a small variation in local contact angle of the capillary condensate It the surfaces. The adhesion report discusses how the nature of the surface topographical features influences the capillary attraction by influencing the local contact angle and by pinning of the three-phase contact line. The effect is clearly dependent on whether the surface features exist in the form of crevices or as extending ridges.

  • 252. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Swerin, Agne
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Influence of Wetting and Dispersing Agents on the Interaction between Talc and Hydrophobic Particles2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 12, s. 6909-6915Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interactions between a natural talc surface and a model hydrophobic particle have been investigated in aqueous solutions by employing the atomic force microscopy (AFM) colloidal probe technique. The results demonstrate the presence of long-range attractive forces due to bridging via preadsorbed or induced bubbles/cavities. Due to the natural heterogeneity of talc, and the stochastic nature of the bubble bridging process, the variability in the range and magnitude of the attraction is larger than that for cases when other interactions predominate or than that when only model surfaces are used. Addition of poly(acrylic acid), a common dispersing agent, did not affect the measured forces. Thus, we conclude that poly(acrylic acid) does not adsorb to the basal plane of talc. In sharp contrast, addition of Pluronic PE6400, a nonionic triblock polymer used as wetting agent, resulted in complete removal of the bubble-induced attractive force. Instead, a short-range steric repulsion is the dominating feature. Clearly, Pluronic PE6400 is able to displace air bubbles from the surface and prevent their formation when the particles come into contact. These are suggested to be important features of efficient wetting agents.

  • 253. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Swerin, Agne
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Interaction forces between talc and pitch probed by atomic force microscopy2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 8, s. 4248-4256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colloidal wood resin components present in pulp are collectively called pitch. The presence of pitch may cause severe problems due to deposits in and on the paper machine. There is thus a need for controlling pitch aggregation and adsorption. To be able to develop more efficient pitch control systems, one needs to develop the understanding of pitch-pitch interactions and of the interactions between pitch and other materials. With this general goal in mind, we present methods for preparing geometrically well-defined pitch particles attached to atomic force microscopy tips. This has enabled us to investigate the interactions between pitch and talc, an additive commonly used for pitch control. We have used model pitch particles consisting of one component only (abietic acid), a mixture of components (collophonium), and particles prepared from real pitch deposits. We show that the forces acting between pitch and talc are attractive and, once the initial approach is made, exert this attraction out to large distances of separation. We present evidence that the formation of bridging air bubbles or cavities is responsible for this interaction.

  • 254.
    Walter, Marie Valérie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Cheval, Nicolas
    Liszka, Olimpia
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Fahmi, Amir
    Hybrid One-Dimensional Nanostructures: One-Pot Preparation of Nanoparticle Chains via Directed Self-Assembly of in Situ Synthesized Discrete Au Nanoparticles2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 14, s. 5947-5955Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fabrication of well-defined one-dimensional (1D) arrays is becoming a challenge for the development of the next generation of advanced nanodevices. Herein, a simple concept is proposed for the in situ synthesis and self-assembly of gold nanoparticles (AuNPs) into ID arrays via a one-step process. The results demonstrated the formation of nanoparticle chains (NPC) with high aspect ratio based on discrete Au nanoparticles stabilized by short thiol ligands. A model was proposed to explain the self-assembly based on the investigation of several parameters such as pH, solvent, temperature, and nature of the ligand on the 1D assembly formation. Hydrogen bonding was identified as a key factor to direct the self-assembly of the hybrid organic inorganic nanomaterials into the well-defined 1D nanostructures. This simple and cost-effective concept could potentially be extended to the fabrication of a variety of hybrid 1D nanostructures possessing unique physical properties leading to a wide range of applications including catalysis, bionanotechnology, nanoelectronics, and photonics.

  • 255.
    Wang, Xin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Herting, Gunilla
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Swede.
    Adsorption of Lysozyme on Silver and Its Influence on Silver Release2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 46, s. 13877-13889Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silver is increasingly used in antimicrobial coatings of biomedical devices and implants to hinder infections. As proteins have been shown to largely influence the extent of released metals from various metal surfaces at biological conditions, silver may also be influenced in the same way. The aim of this study is to relate the structure of adsorbed lysozyme (LSZ) to the release of silver from metallic silver surfaces. Simultaneous adsorption measurements were performed in real time on the same surface using combined ellipsometry and quartz crystal microbalance with dissipation monitoring measurements to provide a more comprehensive understanding on the adsorption kinetics and the layer structures. The concentration of LSZ in 0.15 M NaNO3 solution (pH 7, 25 degrees C) influences the structure of the adsorbed layer. Monolayer coverage is obtained at concentrations =0.1 g/L, while a bilayer structure with a rigid inner layer and a relatively loosely adsorbed outer layer is formed at 1 g/L. The inner layer of LSZ is assumed to bind firmly to silver via disulfide bridges, which makes it irreversibly adsorbed with respect to dilution. The amount of released silver is further influenced by the structure of the LSZ layer. At low LSZ concentrations (=0.1 g/L) the amount of released silver is not significantly different compared with non-protein-containing NaNO3 solutions; however, noticeable reduction was observed at higher concentrations (1 g/L). This reduction in silver release has several possible explanations, including (i) surface complexation between LSZ and silver ions that may result in the incorporation of silver in the irreversible adsorbed layer and, hence, reduce the amount of released silver into solution, and (ii) net charge reversal at the protein/solution interface to slightly positive surface potentials. Any release of silver will therefore exhibit an electrostatic repulsion during transportation through the protein layer results in a reduced amount of silver in solution.

  • 256.
    Wang, Zhen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Ouyang, Liangqi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Tian, Weiqian
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Erlandsson, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Marais, Andrew
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Tybrandt, Klas
    Linkoping Univ, Dept Sci & Technol, Lab Organ Elect, S-60174 Norrkoping, Sweden.;Linkoping Univ, Dept Sci & Technol, Lab Organ Elect, Wallenberg Wood Sci Ctr, S-60174 Norrkoping, Sweden..
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Hamedi, Mahiar
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Layer-by-Layer Assembly of High-Performance Electroactive Composites Using a Multiple Charged Small Molecule2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 32, s. 10367-10373Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Layer-by-layer (LbL) assembly is a versatile tool for fabricating multilayers with tailorable nanostructures. LbL, however, generally relies on polyelectrolytes, which are mostly insulating and induce large interlayer distances. We demonstrate a method in which we replace polyelectrolytes with the smallest unit capable of LbL self-assembly: a molecule with multiple positive charges, tris(3-aminopropyl)amine (TAPA), to fabricate LbL films with negatively charged single-walled carbon nanotubes (CNTs). TAPA introduces less defects during the LbL build-up and results in more efficient assembly of films with denser micromorphology. Twenty bilayers of TAPA/CNT showed a low sheet resistance of 11 k Omega, a high transparency of 91% at 500 nm, and a high electronic conductivity of 1100 S/m on planar substrates. We also fabricated LbL films on porous foams with a conductivity of 69 mS/m and used them as electrodes for supercapacitors with a high specific capacitance of 43 F/g at a discharging current density of 1 A/g.

  • 257.
    Werner, Oskar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Wetting of structured hydrophobic surfaces by water droplets2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 26, s. 12235-12243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Super-hydrophobic surfaces may arise due to an interplay between the intrinsic, relatively high, contact angle of the more or less hydrophobic solid surface employed and the geometric features of the solid surface. In the present work, this relationship was investigated for a range of different surface geometries, making use of surface free energy minimization. As a rule, the free energy minima (and maxima) occur when the Laplace and Young conditions are simultaneously fulfilled. Special effort has been devoted to investigating the free energy barriers present between the Cassie-Baxter (heterogeneous wetting) and Wenzel (homogeneous wetting) modes. The predictions made on the basis of the model calculations compare favorably with experimental results presented in the literature.

  • 258. With, Sebastian
    et al.
    Trebbin, Martin
    Bartz, Christian
    Dulle, Martin
    Yu, Shun
    Roth, Stephan V.
    Schmidt, Hans-Werner
    Förster, Stephan
    Fast Diffusion-Limited Lyotropic Phase Transitions Studied in-situ Using Continuous Flow Microfluidics / Microfocus-SAXS2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 42, s. 12494-12502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fast concentration-induced diffusion-limited lyotropic phase transitions can be studied in situ with millisecond time resolution using continuous flow microfluidics in combination with microfocus small-angle X-ray scattering. The method was applied to follow a classical self-assembly sequence where amphiphiles assemble into micelles, which subsequently assemble into an ordered lattice via a disorder/order transition. As a model system we selected the self-assembly of an amphiphilic block copolymer induced by the addition of a nonsolvent. Using microchannel hydrodynamic flow-focusing, large concentration gradients can be generated, leading to a deep quench from the miscible to the microphase-separated state. Within milliseconds the block copolymers assembly via a spinodal microphase separation into micelles, followed by a disorder/order transition into an FCC liquid-crystalline phase with late-stage domain growth and shear-induced domain orientation into a mesocrystal. A comparison with a slow macroscopic near-equilibrium kinetic experiment shows that the fast structural transitions follow a direct pathway to the equilibrium structure without the trapping of metastable states.

  • 259.
    Wågberg, Lars
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Decher, Gero
    Norgren, Magnus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Tom
    Ankerfors, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Axnäs, Karl
    The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 3, s. 784-795Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 mu m. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = similar to 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.

  • 260. Wågberg, Lars
    et al.
    Hagglund, R.
    Kinetics of polyelectrolyte adsorption on cellulosic fibers2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 4, s. 1096-1103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present investigation has been focused on studying the adsorption of three different molecular mass fractions of a polydimethyldiallylammonium chloride (DMDAAC) (8750 (LMw), 48 000 (MMw), and 1 200 000 (HMw)) on bleached chemical fibers. Both kinetics of adsorption and equilibrium adsorption measurements have been conducted, and the adsorption has been measured by polyelectrolyte titration. The results show that the LMw polymer can reach all the charges in the fiber wall whereas the MMw and HMw can only reach the charges on the external surfaces of the fibers. It is also shown that the kinetics of adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibers. Finally the results from the investigation show that it is possible to have a full coverage of the external surface of the fibers by a high molecular mass polymer and a full coverage of the internal surface of the fibers with a low molecular mass polymer provided that the high molecular mass polymer is adsorbed before addition of the low molecular mass polymer. This is true if the polymers are adsorbed to the same type of groups on the fibers. A simplistic model for describing ployelectrolyte adsorption in turbulent flow also shows good agreement with measured values for the low molecular mass polyelectrolyte whereas the agreement for the high molecular polyelectrolyte is not as good. For the high molecular mass polyelectrolyte a more sophisticated model is needed.

  • 261. Xie, Fei
    et al.
    Lu, Hongduo
    Nylander, Tommy
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Forsman, Jan
    Theoretical and Experimental Investigations of Polyelectrolyte Adsorption Dependence on Molecular Weight2016Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, nr 23, s. 5721-5730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work focuses on adsorption of polyions onto oppositely charged surfaces and on responses to the addition of a simple monovalent salt as well as to the polyion length (degree of polymerization). We also discuss possible mechanisms underlying observed differences, of the adsorbed amount on silica surfaces at high pH, between seemingly similar polyions. This involves theoretical modeling, utilizing classical polymer density functional theory (DFT). We furthermore investigate; how long- and-short-chain Versions of the polymer adsorb onto carboxymethylatect cellulose, carrying a high negative charge. Interestingly enough, comparing results obtained for the two different surfaces, we observe an opposite qualitative response for the molecular weight. The large polymer adsorbs more strongly at a silica surface, but for cellulose at low salt levels, there are indications that the trend is opposite. Another difference is the very slow adsorption process observed for cellulose, particularly with short polymers; in fact, with short polymers, we were sometimes unable to establish any adsorption plateau at all. We speculate that the slow dynamics is due to a gradual diffusion of short polymers into the cellulose matrix. This phenomenon could also explain why short-chain polymers seem to adsorb more strongly than long-chain ones, at low salt concentrations, provided that the latter then are too large to enter the cellulose pores. Cellulose swelling at high salt concentrations might diminish these differences, leading to more similar adsorbed amounts or even a lower adsorption for short chains.

  • 262. Xie, Fei
    et al.
    Nylander, Tommy
    Piculell, Lennart
    Utsel, Simon
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Åkesson, Torbjörn
    Forsman, Jan
    Polyelectrolyte Adsorption on Solid Surfaces: Theoretical Predictions and Experimental Measurements2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 40, s. 12421-12431Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work utilizes a combination of theory and experiments to explore the adsorption of two different cationic polyelectrolytes onto oppositely charged silica surfaces at pH 9. Both polymers, poly(diallyldimethylammonium chloride), PDADMAC, and poly(4-vinyl N-methylpyridinium iodide), PVNP, are highly charged and highly soluble in water. Another important aspect is that a silica surface carries a relatively high surface charge density at this pH level. This means that we have specifically chosen to investigate adsorption under conditions where electrostatics can be expected to dominate the interactions. Of specific focus in this work is the response of the adsorption to the addition of simple salt (i.e., a process where electrostatics is gradually screened out). Theoretical predictions from a recently developed correlation-corrected classical density functional theory for polyelectrolytes are evaluated by direct quantitative comparisons with corresponding experimental data, as obtained by ellipsometry measurements. We find that, at low concentrations of simple salt, the adsorption increases with ionic strength, reaching a maximum at intermediate levels (about 200 mM). The adsorption then drops but retains a finite level even at very high salt concentrations, indicating the presence of nonelectrostatic contributions to the adsorption. In the theoretical treatment, the strength of this relatively modest but otherwise largely unknown nonelectrostatic surface affinity was estimated by matching predicted and experimental slopes of adsorption curves at high ionic strength. Given these estimates for the nonelectrostatic part, experimental adsorption data are essentially captured with quantitative accuracy by the classical density functional theory.

  • 263.
    Yan, Hongji
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Chircov, Cristina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Zhong, Xueying
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    Winkeljann, Benjamin
    Tech Univ Munich, Dept Mech Engn, Boltzmannstr 11, D-85748 Garching, Germany.;Tech Univ Munich, Munich Sch Bioengn, Boltzmannstr 11, D-85748 Garching, Germany..
    Dobryden, Illia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Nilsson, Harriet Elisabeth
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). Karolinska Inst, Dept Biosci & Nutr, S-14183 Huddinge, Sweden..
    Lieleg, Oliver
    Tech Univ Munich, Dept Mech Engn, Boltzmannstr 11, D-85748 Garching, Germany.;Tech Univ Munich, Munich Sch Bioengn, Boltzmannstr 11, D-85748 Garching, Germany..
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Hedberg, Yolanda
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Crouzier, Thomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Reversible Condensation of Mucins into Nanoparticles2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 45, s. 13615-13625Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mucins are high molar mass glycoproteins that assume an extended conformation and can assemble into mucus hydrogels that protect our mucosal epithelium. In nature, the challenging task of generating a mucus layer, several hundreds of micrometers in thickness, from micrometer-sized cells is elegantly solved by the condensation of mucins inside vesicles and their on-demand release from the cells where they suddenly expand to form the extracellular mucus hydrogel. We aimed to recreate and control the process of compaction for mucins, the first step toward a better understanding of the process and creating biomimetic in vivo delivery strategies of macromolecules. We found that by adding glycerol to the aqueous solvent, we could induce drastic condensation of purified mucin molecules, reducing their size by an order of magnitude down to tens of nanometers in diameter. The condensation effect of glycerol was fully reversible and could be further enhanced and partially stabilized by cationic cross-linkers such as calcium and polylysine. The change of structure of mucins from extended molecules to nano-sized particles in the presence of glycerol translated into macroscopic rheological changes, as illustrated by a dampened shear-thinning effect with increasing glycerol concentration. This work provides new insight into mucin condensation, which could lead to new delivery strategies mimicking cell release of macromolecules condensed in vesicles such as mucins and heparin.

  • 264.
    Yushmanov, Pavel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Furó, István
    KTH, Skolan för kemivetenskap (CHE), Kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Stilbs, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Micellar kinetics of a fluorosurfactant through stopped-flow NMR2006Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 5, s. 2002-2004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     F-19 NMR chemical shifts and transverse relaxation times T, were measured as a function of time after quick stopped-flow dilution of aqueous solutions of sodium perfluorooctanoate (NaPFO) with water, Different initial concentrations of micellar solution and different proportions of mixing were tested. Previous stopped-flow studies by time-resolved small-angle X-ray scattering (TR-SAXS) detection indicated a slow (similar to 10 s) micellar relaxation kinetics in NaPFO solutions. In contrast, no evidence of any comparable slow (> 100 ms) relaxation process was found in our NMR studies. Possible artifacts of stopped-flow experiments are discussed as well as differences between NMR and SAXS detection methods. Upper bounds on the relative weight of a slow relaxation process are given within existing kinetic theories of micellar dissolution.

  • 265.
    Zhang, Fan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Xie, Guoxin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Tsinghua University, China.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 35, s. 8749-8756Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive proteins are of great interest in many applications because of their outstanding adhesive property and film forming ability. Understanding and controlling the film formation and its performance is crucial for the effective use of such proteins. In this study, we focus on the potential controlled film formation and compaction of one mussel adhesive protein, Mefp-1. The adsorption and film-forming behavior of Mefp-1 on a platinum (Pt) substrate under applied potentials were investigated by cyclic voltammetry, potential-controlled electro-chemical impedance spectroscopy (EIS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Moreover, microfriction measurements were performed to evaluate the mechanical properties of the Mefp-1 films formed at selected potentials. The results led to the conclusion that Mefp-1 adsorbs on the Pt substrate through both electrostatic and nonelectrostatic interactions and shows an effective blocking effect for the electroactive sites on the substrate. The properties of the adsorbed Mefp-1 film vary with the applied potential, and the compactness of the adsorbed Mefp-1 film can be reversibly tuned by the applied potential.

  • 266. Zhang, Peng
    et al.
    Santoro, Gonzalo
    Yu, Shun
    Vayalil, Sarathlal K.
    Bommel, Sebastian
    Roth, Stephan V.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Manipulating the Assembly of Spray-Deposited Nanocolloids: In Situ Study and Monolayer Film Preparation2016Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, nr 17, s. 4251-4258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fabrication of nanoparticle arrays on a substrate is one of the most concerned aspects for manipulating assembly of nanoparticles and preparing functional nanocomposites. Here, we studied in situ the assembly kinetics of polystyrene nanocolloids by using grazing incidence small-angle X-ray scattering. The structure formation of the nanoparticle film is monitored during air-brush spraying, which provides a rapid and scalable preparation. By optimizing the substrate temperature, the dispersion of the nanocolloids can be tailored to prepare monolayer film. The success of the monolayer preparations is attributed to the fast solvent evaporation which inhibits the aggregation of the nanocolloids. The present study may open a new avenue for the manufacture-friendly preparation of well-dispersed nanoparticle thin films.

  • 267. Zhu, Liang-Liang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Ji, Feng-Yuan
    Ma, Xiang
    Wang, Qiao-Chun
    Tian, He
    Photolockable Ratiometric Viscosity Sensitivity of Cyclodextrin Polypseudorotaxane with Light-Active Rotor Graft2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 6, s. 3482-3486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A prototype, based on light-active fluorescent rotor grafted to beta-cyclodextrin, shows a good solvent viscosity-sensitive behavior due to the environment-dependent nonradiative decay. With the reversible photoisomerization of the cyanostilbene unit, the viscosity sensitivity of the molecular rotor could be locked and activated, and the two switchable states can be distinguished by fluorescent signals. This cyclodextrin derivative was threaded to form a novel polypseudorotaxane. Such supramolecular assembly displays a lockable ratiometric fluorescent viscosity sensitivity with two emission channels: one aroused by fluorophore's intramolecular excimer without influenced by viscosity is used to gauge the concentration of the compound, while the other corresponding to the monomer's rotor fluorescence acts as a viscosity-sensitive signal and it can be shut off by UV irradiation.

  • 268.
    Zuleta, Marcelo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Yu, Shun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Hagfeldt, Anders
    Monitoring N719 Dye Configurations on (1 x n)-Reconstructed Anatase (100) by Means of STM: Reversible Configurational Changes upon Illumination2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 16, s. 13236-13244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report experimental results concerning the STM imaging of cis-bis (isothiocyanate)-bis-(2,2'-bipyridyl-4,4'dicarboxylate)ruthenium(II)bis( tetrabutylammonium) dye (known as N719) adsorbed on a single crystal of anatase TiO2(100). The cleaning pretreatment, by sputtering and annealing, of TiO2(100) yields a reproducible (1 x n) surface reconstruction. Previous to dye deposition, TiO2 was covered with one monolayer of 4-tert-butylpyridine (4-TBP) in ultrahigh vacuum (UHV) in order to protect the surface against air contamination. N719 was subsequently deposited by dipping the crystal into the dye solution. 4-TBP was removed partially in the solution and totally by heating the sample to around 285-300 degrees C in UHV. The images of the deposited 4-TBP on TiO2(100) revealed a complete surface coverage showing three modes of adsorption on TiO2. The relatively uncomplicated desorption of 4-TBP enables the accommodation and chemisorption of most N719 molecules directly onto the TiO2 surface. The STM imaging of N719 was affected, in a reversible way, by illumination, because the quality of the image changed after a few hours in the dark or under illumination conditions. The results presented herein are discussed in terms of changes in molecular configurations and in open circuit potentials.

  • 269.
    Öberg, Kim
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Ropponen, Jarmo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Kelly, Jonathan
    Löwenhielm, Peter
    Berglin, Mattias
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Templating Gold Surfaces with Function: A Self-Assembled Dendritic Monolayer Methodology Based on Monodisperse Polyester Scaffolds2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 1, s. 456-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 angstrom), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules.nm(-2) and functional availability of 0.95-5.5 groups.nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  • 270.
    Östmark, Emma
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Macakova, Lubica
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Auletta, Tommaso
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dendritic Structures Based on Bis(hydroxymethyl)propionic Acid as Platforms for Surface Reactions2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 10, s. 4512-4519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we present results related to the self-assembly of different generations of disulfide-cored 2,2-bis(hydroxymethyl)propionic acid-based dendritic structures onto gold surfaces. These molecular architectures, ranging from generation 1 to generation 3, contain removable acetonide protecting groups at their periphery that are accessible for hydrolysis with subsequent formation of OH-terminated surface-attached dendrons. The deprotection has been investigated in detail as a versatile approach to accomplish reactive surface platforms. A special focus has been devoted to the comparison of the properties of the layers formed by hydrolysis of the acetonide moieties directly on the surface and in solution, prior to the layer formation.

3456 251 - 270 av 270
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