Ändra sökning
Avgränsa sökresultatet
123456 51 - 100 av 270
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51.
    Cunha, Gisera
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. INRA, Biopolymeres Interact & Assemblages, France.
    Mougel, Jean-Bruno
    Cathala, Bernard
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Capron, Isabelle
    Preparation of Double Pickering Emulsions Stabilized by Chemically Tailored Nanocelluloses2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 31, s. 9327-9335Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocelluloses are bio-based nanoparticles of interest as stabilizers for oil-in-water (o/w) Pickering emulsions. In this work, the surface chemistry of nanocelluloses of different length, nanofibrillated cellulose (NFC, long) and cellulose nanocrystals (CNC, short), was successfully tailored by chemical modification with lauroyl chloride (C12). The resulting nanofibers were less hydrophilic than the original and able to stabilize water-in-oil (w/o) emulsions. The combination of the two types of nanocelluloses (C12-modified and native) led to new surfactant-free oil-in-water-in-oil (o/w/o) double emulsions stabilized by nanocellulose at both interfaces. Characterization was performed with respect to droplet size distribution, droplet stability over time, and stability after centrifugation. Nanocellulose-based Pickering emulsions can be designed with a substantial degree of control, as demonstrated by the stability of the chemically tailored NFC double emulsions. Furthermore, it was demonstrated that increased nanofiber length leads to increased stability.

  • 52.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Campbell, B.
    Interactions between mica surfaces across triglyceride solution containing phospholipid and polyglycerol polyricinoleate2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 5, s. 2248-2253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results obtained by direct measurements of the forces acting between polar mica surfaces interacting across solutions of triolein containing phosphatidylethanolamine (PE), polyglycerol polyricinoleate (PGPR), and a PE/PGPR mixture are presented. It was shown that PE adsorbed on mica from anhydrous triolein and thus rendered the surface nonpolar. The change in ordering of the liquid triolein molecules induced by bringing two such surfaces together gives rise to a structural force with two force barriers. In contrast, the adsorption of PGPR from anhydrous triolein resulted in a steric force barrier with a range of 120 Angstrom. It was also found that from the mixture of PE and PGPR in triolein both additives adsorbed as a complex on mica surfaces. The presence of these aggregates on the surfaces gave rise to a very long-range strong repulsive force. We discuss the implication of the measured forces to colloidal stability of particle dispersion in nonpolar media and compare the efficiency of additives as dispersion stabilizers. We also show that the presence of water has an effect on the adsorbed layer structures. When PE is used as a dispersing agent, water induces formation of aggregates, which would provide strong repulsive barriers between the particles. In contrast, when PGPR is used as additive, water preferentially adsorbs on the polar mica surface and at water saturation gives rise to a capillary formation around the surface contact position. Finally, when a mixture of PE and PGPR is used, water is found to result in formation of a viscous, sticky, adsorbed layer that would flocculate the particles.

  • 53.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Claesson, Per M
    KTH, Tidigare Institutioner                               , Kemi.
    Interfacial properties of aggregates formed by cationic polyelectrolyte and anionic surfactant2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 4, s. 1951-1959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interactions between mica surfaces across aqueous solutions containing mixtures of a highly positively charged polyelectrolyte and an anionic surfactant were studied by use of a surface force apparatus. The investigation was carried out with a constant polyelectrolyte concentration (20 ppm) and a wide range of surfactant concentrations [0-1 times the critical micelle concentration (cmc)]. The chemical composition of the adsorbed polyelectrolyte-surfactant layers was analyzed by x-ray photoelectron spectroscopy (XPS). The properties of polyelectrolyte-surfactant aggregates formed in bulk were studied by measurements of turbidity and electrophoretic mobility. The aggregates formed at low surfactant concentrations (<0.04 times cmc) were positively charged, whereas at higher surfactant concentrations the aggregates carried a net negative charge. It was shown that polyelectrolyte-surfactant aggregates rapidly adsorb on negatively charged mica surfaces regardless of the sign of their charge. At surfactant concentrations up to 0.01 times cmc, the polyelectrolytes adsorb on mica surfaces with loops acid tails stretching out into solution and repulsive steric forces are generated. The thickness of the layer decreases with time and we suggest that this conformational change is accompanied by some expulsion of surfactant from the adsorbed layers. Thick adsorbed layers were formed in the surfactant concentration range 0.02-0.1 times cmc. In this concentration regime the measurement of equilibrium forces was inaccessible due to a very slow layer relaxation. During compression the forces were repulsive and during separation an attraction developed. We attribute this to formation of interlayer surfactant bridges. Finally, at high surfactant concentrations (greater than or equal to 0.4 times cmc) highly negatively charged aggregates adsorb on the surfaces in rather thin layers, resulting in purely repulsive forces of mixed electrostatic and steric origin.

  • 54.
    Dedinaite, Andra
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Claesson, Per M
    KTH, Tidigare Institutioner                               , Kemi.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner                               , Kemi.
    Polyelectrolyte-surfactant layers: Adsorption of preformed aggregates versus adsorption of surfactant to preadsorbed polyelectrolyte2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 12, s. 5257-5266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The character of adsorbed layers containing both polyelectrolyte and surfactant depends on the type of polyelectrolyte used and the surfactant concentrations, as demonstrated by several recent studies. However, the layer properties also depend on the experimental pathway. This shows that the adsorbed layers can be trapped in quasi-equilibrium states and that the true equilibrium is reached only after experimentally inaccessible time scales. This has to be kept in mind when comparing different results reported in the literature. The present article highlights these effects using a system consisting of a highly charged cationic polyelectrolyte, poly{(propionyloxy)ethyl}trimethylammonium chloride (PCMA), and an anionic surfactant, sodium dodecyl sulfate (SDS). The adsorbed layer properties were determined using mainly surface force measurements and atomic force microscope (AFM) imaging. We also present some small-angle neutron scattering data for bulk PCMA-SDS complexes formed between the polyelectrolyte and the surfactant. They demonstrate the presence of a characteristic correlation length of about 37-39 Angstrom. A similar characteristic length scale is also observed in some of the adsorbed layers, both employing the AFM and the surface force apparatus. It may be interpreted as the distance between surfactant loaded polyelectrolyte chains.

  • 55.
    Dobryden, Illia
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Ruiz, Maria Cortes
    CUNY City Coll, Dept Chem Engn, Grove Sch Engn, New York, NY 10031 USA..
    Zhang, Xuwei
    Univ Montreal, Dept Chem, CP 6128 Succursale Ctr Ville, Montreal, PQ H3C 3J7, Canada..
    Dédinaité, Andra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Div Biosci & Mat, SE-11486 Stockholm, Sweden..
    Wieland, D. C. Florian
    Helmholtz Zentrum Geesthacht, Inst Mat Res, Max Planck Str 1, D-21502 Geesthacht, Germany..
    Winnik, Francoise M.
    Univ Helsinki, Dept Chem, POB 55, FI-00014 Helsinki, Finland.;NIMS, Int Ctr Mat Nanoarchitecton MANA, 1-1 Namiki, Tsukuba, Ibaraki 3050044, Japan..
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, Div Biosci & Mat, SE-11486 Stockholm, Sweden..
    Thermoresponsive Pentablock Copolymer on Silica: Temperature Effects on Adsorption, Surface Forces, and Friction2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 3, s. 653-661Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of hydrophilic or amphiphilic multiblock copolymers provides a powerful means to produce well-defined "smart" surfaces, especially if one or several blocks are sensitive to external stimuli. We focus here on an A-B-A-B-A copolymer, where A is a cationic poly((3acrylamido-propyl)-trimethylammonium chloride) (PAMPTMA) block containing 15 (end blocks) or 30 (middle block) repeat units and B is a neutral thermosensitive water-soluble poly(2-isopropyl-2-oxazoline) (PIPOZ) block with 50 repeat units. X-ray reflectivity and quartz crystal microbalance with dissipation monitoring were employed to study the adsorption of PAMPTMA(15)-PAMPTMA(30)-PIPOZ(50)-PAMPTMA(15) on silica surfaces. The latter technique was employed at different temperatures up to 50 degrees C. Surface forces and friction between the two silica surfaces across aqueous pentablock copolymer solutions at different temperatures were determined with the atomic force microscopy colloidal probe force and friction measurements. The cationic pentablock copolymer was found to have a high affinity to the negatively charged silica surface, leading to a thin (2 nm) and rigid adsorbed layer. A steric force was encountered at a separation of around 3 nm from hard wall contact. A capillary condensation of a polymer-rich phase was observed at the cloud point of the solution. The friction forces were evaluated using Amontons' rule modified with an adhesion term.

  • 56.
    Dobryden, Illia
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Steponaviciute, Medeina
    Vilnius Univ, Inst Chem, Naugarduko 24, LT-03225 Vilnius, Lithuania..
    Klimkevicius, Vaidas
    Vilnius Univ, Inst Chem, Naugarduko 24, LT-03225 Vilnius, Lithuania..
    Makuska, Ricardas
    Vilnius Univ, Inst Chem, Naugarduko 24, LT-03225 Vilnius, Lithuania..
    Dedinaite, Andra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi. Division of Bioscience and Materials, RISE Research Institutes of Sweden, Stockholm, SE-114 86, Sweden.
    Liu, Xiaoyan
    Shaanxi Normal Univ, Sch Chem & Chem Engn, Xian 710062, Shaanxi, Peoples R China..
    Corkery, Robert
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Division of Bioscience and Materials, RISE Research Institutes of Sweden, Stockholm, SE-114 86, Sweden.
    Bioinspired Adhesion Polymers: Wear Resistance of Adsorption Layers2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 48, s. 15515-15525Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mussel adhesive polymers owe their ability to strongly bind to a large variety of surfaces under water to their high content of 3,4-dihydroxy-L-phenylalanine (DOPA) groups and high positive charge. In this work, we use a set of statistical copolymers that contain medium-length poly(ethylene oxide) side chains that are anchored to the surface in three different ways: by means of (i) electrostatic forces, (ii) catechol groups (as in DOPA), and (iii) the combination of electrostatic forces and catechol groups. A nanotribological scanning probe method was utilized to evaluate the wear resistance of the formed layers as a function of normal load. It was found that the combined measurement of surface topography and stiffness provided an accurate assessment of the wear resistance of such thin layers. In particular, surface stiffness maps allowed us to identify the initiation of wear before a clear topographical wear scar was developed. Our data demonstrate that the molecular and abrasive wear resistance on silica surfaces depends on the anchoring mode and follows the order catechol groups combined with electrostatic forces > catechol groups alone > electrostatic forces alone. The devised methodology should be generally applicable for evaluating wear resistance or "robustness" of thin adsorbed layers on a variety of surfaces.

  • 57.
    Dunér, Gunnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Anderson, Henrik
    Myrskog, Annica
    Hedlund, Maria
    Aastrup, Teodor
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Surface-confined photopolymerization of pH-responsive acrylamide/acrylate brushes on polymer thin films2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 14, s. 7559-7564Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic acrylamide/acrylate polymeric brushes were synthesized at gold-plated quartz crystal surfaces. The crystals were initially coated with polystyrene-type thin films, derivatized with photolabile iniferter groups, and subsequently subjected to photoinitiated polymerization in acrylamide/acrylate monomer feeds. This surface-confined polymerization method enabled direct photocontrol over the polymerization, as followed by increased frequency responses of the crystal oscillations in a quartz crystal microbalance (QCM). The produced polymer layers were also found to be highly sensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposed to buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and the extent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resulting responses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereas higher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfaces also proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansion and contraction. Using ellipsometry, copolymer layers were estimated to be similar to 220 nm in a collapsed state and similar to 340 nm in the expanded state, effectively increasing the thickness of the film by 55%.

  • 58.
    Dvinskikh, Sergey V.
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Domain structure in an unoriented lamellar lyotropic liquid crystal phase studied by H-2 NMR2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 21, s. 6455-6460Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spatial variation of the phase director in an unoriented lamellar lyotropic liquid crystal is investigated by H-2 two-dimensional and one-dimensional exchange and PGSE NMR. Exchange NMR probes the single-particle orientational correlation function of D2O molecules that diffuse among regions with different director orientations. The obtained correlation time and the water diffusion coefficient, measured by H-2 PGSE NMR, provide the persistence length of director orientation that is defined as domain size. The nature of spatial variation is revealed by the decay of the H-2 stimulated echo signal recorded with different evolution times. The persistence length of the director is found to be strongly dependent on the rate of cooling the sample from its isotropic phase.

  • 59.
    Dvinskikh, Sergey V.
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Order parameter profile of perfluorinated chains in a lamellar phase2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 6, s. 2962-2967Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cesium perfluorooctanoate molecules are investigated by NMR spectroscopy in the lamellar phase of their aqueous solution. The particular NMR method, C-13-detected, F-19-decoupled separated-local-field (SLF) spectroscopy, provides the dipolar splitting of each C-13 spin to its F-19 neighbors. These dipolar splittings are interpreted in terms of the molecular C-F bond order parameters of each difluoromethylene and trifluoromethyl group. The obtained variation of this order parameter along the fluoroalkyl chain strengthens the conclusion from an earlier, model-dependent study (Fur6, I.; Sitnikov, R. Langmuir 1999, 15, 2669): perfluorinated surfactant chains are significantly more rigid than their hydrogenated counterparts.

  • 60. Ellis-Gibbings, Lilian
    et al.
    Johansson, Viktor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Walsh, Rick B.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Quinton, Jamie S.
    Andersson, Gunther G.
    Formation of N719 Dye Multilayers on Dye Sensitized Solar Cell Photoelectrode Surfaces Investigated by Direct Determination of Element Concentration Depth Profiles2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 25, s. 9431-9439Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structure of the dye layer adsorbed on the titania substrate in a dye-sensitized solar cell is of fundamental importance for the function of the cell, since it strongly influences the injection of photoelectrons from the excited dye molecules into the titania substrate. The adsorption isotherms of the N719 ruthenium-based dye were determined both with a direct method using the depth profiling technique neutral impact collision ion scattering spectroscopy (NICISS) and with the standard indirect solution depletion method. It is found that the dye layer adsorbed on the titania surface is laterally inhomogeneous in thickness and there is a growth mechanism already from low coverage levels involving a combination of monolayers and multilayers. It is also found that the amount of N719 adsorbed on the substrate depends on the titania structure. The present results show that dye molecules in dye-sensitized solar cells are not necessarily, as presumed, adsorbed as a self-assembled monolayer on the substrate.

  • 61.
    Enarsson, Lars-Erik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Adsorption Kinetics of cationic Polyelectrolytes studied with Stagnation Point Adsorption Reflectometry and Quartz Crystal Microgravimetry2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 14, s. 7329-7337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of charge density, pH, and salt concentration on polyelectrolyte adsorption onto the oxidized surface of silicon wafers were studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry. Five different polyelectrolytes-cationic polyacrylamides of four charge densities and one cationic dextran-were examined. The adsorption kinetics was characterized using each technique, and the adsorption kinetics observed was in line with the impinging jet theory and the theory for one-dimensional diffusion, respectively. The polyelectrolyte adsorption increased with pH as an effect of the increased silica surface charge. A maximum in the saturation adsorption for both types of polyelectrolytes was found at 10 mM NaCl concentration. A significant adsorption also occurred at I M NaCl, which indicated a significant nonionic contribution to the adsorption mechanism. The fraction of solvent in the adsorbed layer was determined to be 70-80% by combining the two analysis techniques. This indicated a loose structure of the adsorbed layer and an extended conformation at the surface, favoring loops and tails. However, considering the solution structure with a hydrodynamic diameter larger than 100 nm for the CPAM and a thickness of the adsorbed layer on the order of 10 nm, the results showed that the adsorption is accompanied by a drastic change in polymer conformation. Furthermore, this conformation change takes place on a time scale far shorter than seconds.

  • 62. Ericsson, C. A.
    et al.
    Soderman, O.
    Garamus, V. M.
    Bergström, Lars Magnus
    Ulvenlund, S.
    Effects of temperature, salt, and deuterium oxide on the self-aggregation of alkylglycosides in dilute solution. 2. n-Tetradecyl-beta-D-maltoside2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 4, s. 1507-1515Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of salt, temperature, and deuterium oxide on the self-aggregation of n-tetradecyl-beta-D-maltoside (C(14)G(2)) in dilute solution have been investigated by static light scattering, dynamic light scattering (DLS), small-angle neutron scattering (SANS), tensiometry, and capillary viscometry. SANS data show that the micelles can be described as relatively flexible polymer-like micelles with an elliptical cross section, at least at temperatures between 35 and 50 degreesC. The micelles grow in one dimension with increasing temperature and concentration. DLS and viscometry data suggest that the micelle size reaches a maximum at 60-70 degreesC. Comparison of DLS data in D2O and H2O shows that the micelles are larger in the former case. The effect of salt on the micelle size was found to follow the Hofmeister series. Thus, at constant salt concentration, the micelle size decreases according to the sequence SO42- > Cl (-)> NO3 > I- > SCN-, where I- and SCN- act as salting-in anions. From tensiometric data, it can be concluded that the temperature effects on micelle morphology do not correlate directly with those on unimer solubility. Rather, the temperature effect on the hydrocarbon chain conformation seems to be decisive for the micelle morphology. At constant temperature, on the other hand, the effect of salt and deuterium isotope is attributable to changes in effective headgroup area, including intermolecular interactions and water of hydration.

  • 63. Ericsson, C. A.
    et al.
    Söderman, O.
    Garamus, V. M.
    Bergström, Lars Magnus
    KTH, Tidigare Institutioner, Kemi.
    Ulvenlud, S.
    Effects of temperature, salt, and deuterium oxide on the self-aggregation of alkylglycosides in dilute solution. 1. n-nonyl-beta-D-glucoside2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 4, s. 1401-1408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of salt, temperature, and deuterium oxide on the self-aggregation of n-nonyl-beta-D-glucoside (beta-C(9)G(1)) in dilute solution has been investigated by static and dynamic light scattering, neutron scattering, and tensiometry. Scattering data show that the micelles can be described as relatively stiff, elongated structures with a circular cross section. With a decrease of temperature, the micelles grow in one dimension, which makes it surprising that the critical micelle concentration (cmc) shows a concomitant increase. On the other hand, substitution of D2O for H2O causes a large increase in micelle size at low temperatures, without any appreciable effect on cmc. With increasing temperature, the deuterium effect on the micelle size diminishes. The effects of salt on the micelle size and cmc were found to follow the Hofmeister series. Thus, at constant salt concentration, the micelle size decreased according to the sequence SO42- > Cl- > Br- > NO3- > I- > SCN-, whereas the effect on cmc displays the opposite trend. Here, I- and SCN- are salting-in anions. Similarly, the effects of cations decrease with increasing polarizability in the sequence Li-divided by > Na-divided by > K-divided by > Cs-divided by. At high ionic strength, the systems separate into two micellar phases. The results imply that the size of beta-C(9)G(1) micelles is extremely sensitive to changes in the headgroup size. More specifically, temperature and salt effects on effective headgroup size, including intermolecular interactions and water of hydration, are suggested to be more decisive for the micelle morphology than the corresponding effects on unimer solubility.

  • 64. Eriksson, Jan Christer
    et al.
    Henriksson, Ulf
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi (stängd 20110630).
    Bridging-cluster model for hydrophobic attraction2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 20, s. 10026-10033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new model is proposed to account for the long-range hydrophobic attraction repeatedly observed for thin water films between two stable (solid) hydrophobic surfaces. The model is based on the notion of structurally organized, elongated water clusters that span the gap between the hydrophobic surfaces. Two features are noted: (i) Mixing entropy due to the mixing of the clusters and the remainder of the water in the thin film is explicitly taken into account. (ii) A term is invoked that depends inversely on the film thickness, which accounts for the free-energy change associated with reorganizing the film as the film thickness varies. Fitting to experimental surface force data resulted in parameter values of reasonable magnitudes. The model developed covers film thicknesses from about 2 nm and above. On this basis, the amazingly long range of the hydrophobic attraction can be attributed to the formation of bridging, quasi-cylindrical clusters having a radius on the order of 1 to 2 nm.

  • 65.
    Eriksson, Jan Christer
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henriksson, Ulf
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Thermodynamic Properties of Bridging Clusters in Thin Films of Water between Hydrophobic Surfaces Assessed from Surface Force Isotherms2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 15, s. 4789-4795Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the course of a long-term effort to cope with surface force data for thin films of water between hydrophobic surfaces, we have applied the bridging-cluster model (Eriksson, J. C.; Henriksson, U. Bridging-cluster model for hydrophobic attraction. Langmuir 2007, 23, 10026-10033) to the recently published surface force isotherms for water films between hexadecylthiolated gold surfaces in the thickness range of 20-100 nm and temperature range of 10-40 degrees C (Wang, J.; Yoon, R.-H.; Eriksson, J. C. Excess thermodynamic properties of thin water films confined between hydrophobized gold surfaces. J. Colloid Interface Sci. 2011, 364, 257-263). We show that these isotherms can be faithfully reproduced on the basis of the bridging-cluster model. The thermodynamic excess properties (Delta G(c), Delta H-c, and T Delta S-c) of linear clusters that are assumed to bridge the core of the films were calculated from the experimental surface force isotherms. A crucial step taken was to infer two-dimensional ideal mixing of the clusters with the surrounding film water. We find that Delta H-c and T Delta S-c are both negative quantities, with the latter being larger than the former, which implies a positive excess Gibbs energy of a cluster, Delta G(c) = Delta H-c - T Delta S-c. Typically, for temperatures between 10 and 40 degrees C, these cluster properties are of the order of some k(B)T units, corresponding to 10(-4)-10(-3)k(B)T per water molecule entailed. Our analysis yields support of the notion that elongated aggregates can arise in thin films of water between hydrophobic surfaces driven by entropy of mixing.

  • 66.
    Eriksson, Mimmi
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, SE-11486 Stockholm, Sweden.
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. RISE Res Inst Sweden, SE-11486 Stockholm, Sweden.
    Jarn, Mikael
    RISE Res Inst Sweden, SE-11486 Stockholm, Sweden..
    Tuominen, Mikko
    RISE Res Inst Sweden, SE-11486 Stockholm, Sweden..
    Wallqvist, Viveca
    RISE Res Inst Sweden, SE-11486 Stockholm, Sweden..
    Schoelkopf, Joachim
    Omya Int AG, CH-4665 Oftringen, Switzerland..
    Gane, Patrick A. C.
    Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, FI-00076 Aalto, Finland..
    Swerin, Agne
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Wetting Transition on Liquid-Repellent Surfaces Probed by Surface Force Measurements and Confocal Imaging2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 41, s. 13275-13285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Superhydrophobic surfaces in the Cassie-Baxter wetting state retain an air layer at the surface which prevents liquid water from reaching into the porous surface structure. In this work we explore how addition of ethanol, which reduces the surface tension, influences the wetting properties of superhydrophobic and smooth hydrophobic surfaces. Wetting properties are measured by dynamic contact angles, and the air layer at the superhydrophobic surface is visualized by laser scanning confocal microscopy. Colloidal probe atomic force microscopy measurements between a hydrophobic microsphere and the macroscopic surfaces showed that the presence of ethanol strongly affects the interaction forces. When the macroscopic surface is superhydrophobic, attractive forces extending up to a few micrometers are observed on retraction in water and in 20 vol % ethanol, signifying the presence of a large and growing gas capillary. Submicrometer attractive forces are observed between the probe particle and a smooth hydrophobic surface, and in this case a smaller gas capillary is formed. Addition of ethanol results in markedly different effects between superhydrophobic and hydrophobic surfaces. In particular, we show that the receding contact angle on the superhydrophobic surface is of paramount importance for describing the interaction forces.

  • 67.
    Evenäs, L.
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Stilbs, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Valiullin, Rustem
    KTH, Tidigare Institutioner                               , Kemi.
    Adsorption Isotherm and Aggregate Properties of Fluorosurfactants on Alumina Measured by 19F NMR2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 21, s. 8096-8101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption and self-assembly of ammonium perfluorooctanoate (APFO) at surfaces of porous alumina immersed in solution at pH similar to 4 have been studied using F-19 NMR. From the intensity of the APFO NMR signals, the amount of adsorbed surfactant, and thereby the adsorption isotherm, was determined. The adsorption isotherm indicates that APFO forms bilayers on alumina. This result is supported by finding the CF3 signal of adsorbed APFO shifted upfield compared to the signal in aqueous solution with an amount that corresponds to a change from aqueous to fluorocarbon environment. Additionally, faster transverse relaxation of the fluorine nuclei adjacent to the head group compared to that of the CF3 group adds a further argument for the formation of a bilayer. The exchange pattern of surfactants between the adsorbed layer and the aqueous bulk was studied through the CF3 group F-19 signals and their time-averaged behavior. Inside the pores of the alumina particles, the exchange time was found to be fast (much less than1 ms) between adsorbed and dissolved APFO. The presented NMR method to determine the adsorption isotherm could be a powerful new tool when studying systems of mixed surfactants, since the adsorbed amount of chemically different surfactants and their formation in aggregates would become separately quantifiable. The method is readily applicable to any NMR nuclei and thereby to many adsorption problems.

  • 68.
    Fall, Andreas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Biofibermaterial, BiMaC.
    Lindström, Stefan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Sundman, Ola
    Department of Forest Products Technology, Aalto, Finland.
    Ödberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Colloidal Stability of Aqueous Nanofibrillated Cellulose Dispersions2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 18, s. 11332-11338Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aqueous suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Experiments support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concentration. It is shown that the primary mechanism for aggregation upon the addition of salt is the surface charge reduction through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.

  • 69. Falt, S.
    et al.
    Wågberg, Lars
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Vesterlind, E. L.
    Swelling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers2003Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, nr 19, s. 7895-7903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose model films with different charge densities were prepared by spin-coating dissolved cellulose in N-methylmorpholine-N-oxide onto SiO2 surfaces. The swelling of the model cellulose films due to exposure to solutions of different electrolytes and at different ionic strengths and pH values were studied using QCM-D (quartz crystal microbalance with dissipation monitoring). Results show that at pH 5, there is a swelling of the film at a low electrolyte concentration (10(-4)-10(-2) M), whereas the deswelling of the film was observed at a high electrolyte concentration (10(-1)-1 M). A considerable swelling of the films is seen when they are treated with deionized water with an increasing pH. The swelling of the films is accompanied by an increase in dissipation, that is, a softening of the material, and the deswelling by a decrease in dissipation, that is, a stiffening of the material. Furthermore, exposure of the films to solutions of different electrolytes affected the swelling of the layer. In this respect, the swelling response of Na2SO4 differs from that of NaCl and CaC1(2) by showing simultaneously high swelling and low dissipation values. The results also show that the rate of swelling reaches its lowest value as the electrolyte concentration reaches the detected limit for the deswelling. The QCM-D results are compared to the swelling of the corresponding carboxymethylated fibers, where a similar behavior was found. However, for the fibers a marked deswelling occurred at a high electrolyte concentration, but only a minor deswelling of the cellulose film was observed. This difference between the materials can be ascribed to noncovalent bonds within the film that will not reform when the swelling forces are decreased at high electrolyte concentrations. A direct measurement of the thickness changes was performed using atomic force microscopy, which shows that the change in frequency measured with QCM-D for the films treated with different NaCl electrolyte concentrations corresponds to changes of 1-2%.

  • 70. Feiler, A.
    et al.
    Plunkett, M. A.
    Rutland, Mark W
    KTH, Tidigare Institutioner                               , Kemi.
    Atomic force microscopy measurements of adsorbed polyelectrolyte layers. 1. Dynamics of forces and friction2003Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, nr 10, s. 4173-4179Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The measurement of surface forces and friction between silica substrates bearing adsorbed layers acrylamide-1% [3-(2-methylpropionamide)propyl]trimethyl ammonium chloride (AM-MAPTAC) was examined using atomic force microscopy. The cationic polymer had a large molecular weight (900 000) and a very low charge density (1% MAPTAC units). The force curves in the presence of adsorbed polyelectrolyte showed a very long range repulsive interaction and large deformation on compression typical of electrosteric interactions and consistent with the expected adsorption profile. There was also a strong dependence on the scan rate with increased repulsion during approach and increased attraction during separation as the scan rate increased. The hysteresis was attributed entirely to a hydrodynamic interaction induced by the polyelectrolyte. At slow enough scan rates, the hysteresis between approach and retract curves was absent. The friction force measurements were sensitive to both applied load and scan rate. With increasing applied load, a critical load was apparent, above which the friction force increased. Upon decrease of the load, the friction force remained higher than that before the yield point, suggesting a metastable deformation of the polymer layer. In addition, the friction coefficient increased with increasing scan rate. At low scan rates the friction coefficient was lower than the bare surfaces, whereas at high scan rates the friction coefficient was significantly larger that obtained than for the bare surfaces. Subsequent force curves taken after friction measurements confirm that a permanent change in the polyelectrolyte layer had occurred. The magnitude of the repulsive interaction was reduced to about half of its original force.

  • 71. Feiler, Adam A.
    et al.
    Bergstrom, Lennart
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Superlubricity using repulsive van der Waals forces2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 6, s. 2274-2276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using colloid probe atomic force microscopy, we show that if repulsive van der Waals forces exist between two surfaces prior to their contact then friction is essentially precluded and supersliding is achieved. The friction measurements presented here are of the same order as the lowest ever recorded friction coefficients in liquid, though they are achieved by a completely different approach. A gold sphere attached to an AFM cantilever is forced to interact with a smooth Teflon surface (templated on mica). In cyclohexane, a repulsive van der Waals force is observed that diverges at short separations. The friction coefficient associated with this system is on the order of 0.0003. When the refractive index of the liquid is changed, the force can be tuned from repulsive to attractive and adhesive. The friction coefficient increases as the Hamaker constant becomes more positive and the divergent repulsive force, which prevents solid-solid contact, gets switched off.

  • 72.
    Feiler, Adam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Stiernstedt, Johanna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Theander, Katarina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Jenkins, Paul
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Effect of capillary condensation on friction force and adhesion2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 2, s. 517-522Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction - load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

  • 73.
    Feldötö, Zsombor
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Mucin-electrolyte interactions at the solid-liquid interface probed by QCM-D2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 7, s. 3348-3357Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction between mucin and ions has been investigated by employing the quartz crystal microbalance technique with measurement of energy dissipation. The study was partially aimed at understanding the adsorption of mucin on surfaces with different chemistry, and for this purpose, surfaces exposing COOH, OH, and CH3 groups were prepared. Mucin adsorbed to all three types of functionalized gold surfaces. Adsorption to the hydrophobic surface and to the charged hydrophilic surface (COOH) occured with high affinity despite the fact that in the latter case both mucin and the surface were negatively charged. On the uncharged hydrophilic surface exposing OH groups, the adsorption of mucin was very low. Another aim was to elucidate conformational changes induced by electrolytes on mucin layers adsorbed on hydrophobic surfaces from 30 mM NaNO3. To this end, we investigated the effect of three electrolytes with increasing cation valance: NaCl, CaCl2, and LaCl3. At low NaCl concentrations, the preadsorbed layer expands, whereas at higher concentrations of NaCl the layer becomes more compact. This swelling/compacting of the mucin layer is fully reversible for NaCl. When the mucin layer instead is exposed to CaCl2 or LaCl3, compaction is observed at I mM. For CaCl2, this process is only partially reversible, and for LaCl3, the changes are irreversible within the time frame of the experiment. Finally, mucin interaction with the DTAB cationic surfactant in an aqueous solution of different electrolytes was evaluated with turbidimetry measurements. It is concluded that the electrolytes used in this work screen the association between mucin and DTAB and that the effect increases with increasing cation valency.

  • 74.
    Feldötö, Zsombor
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Varga, Imre
    Eotvos Lorand University, Institute of Chemistry, Budapest, Hungary.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Influence of Salt and Rinsing Protocol on the Structure of PAH/PSS Polyelectrolyte Multilayers2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 22, s. 17048-17057Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A quartz crystal microbalance (QCM) and dual polarization interferometry (DPI) have been utilized to study how the structure of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) multilayers is affected by the rinsing method (i.e., the termination of polyelectrolyte adsorption). The effect of the type of counterions used in the deposition solution was also investigated, and the polyelectrolyte multilayers were formed in a 0.5 M electrolyte solution (NaCl and KBr). From the measurements, it was observed that thicker layers were obtained when using KBr in the deposition solution than when using NaCl. There different rinsing protocols have been studied: (i) the same electrolyte solution as used during multilayer formation. (ii) pure water, and (iii) first a salt solution (0.5 M) and then pure water. When the multilayer with PAH as the outermost layer was exposed to pure water, an interesting phenomenon was discovered: a large change in the energy dissipation was measured with the QCM. This could be attributed to the swelling of the layer, and from both QCM and DPI it is obvious that only the outermost PAH layer swells (to a thickness of 25-30 nm) because of a decrease in ionic strength and hence an increase in intra- and interchain repulsion. whereas the underlying layers retain a very rigid and compact structure with a low water content. Interestingly, the outermost PAH layer seems to obtain very similar thicknesses in water independent of the electrolyte used for the multilayer buildup. Another interesting aspect was that the measured thickness with the DPI evaluated by a single-layer model did not correlate with the estimated thickness from the model calculations performed on the QCM-D data. Thus, we applied a two-layer model to evaluate the DPI data and the results were in excellent agreement with the QCM-D results. To our knowledge. this evaluation of DPI data has not been done previously.

  • 75.
    Fernandes, Ricardo M.F.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, s/n, Porto, Portugal.
    Abreu, Bárbara
    Claro, Bárbara
    Buzaglo, Matat
    Regev, Oren
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Marques, Eduardo
    Dispersing Carbon Nanotubes with Ionic Surfactants under Controlled Conditions: Comparisons and Insight2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 40, s. 10955-10965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fundamental understanding of the mechanisms involved in the surfactant-assisted exfoliation and dispersion of carbon nanotubes (CNTs) in water calls for well-controlled experimental methodologies and reliable comparative metrics. We have assessed the ability of several ionic surfactants to disperse single and multiwalled carbon nanotubes, resorting to a stringently controlled sonication-centrifugation method for the preparation of the dispersions. The CNT concentration was accurately measured for a wide range of surfactant concentration, using combined thermogravimetric analysis and UV–vis spectroscopy. The obtained dispersibility curves yield several quantitative parameters, which in turn allow for the effects of nanotube morphology and surfactant properties (aromatic rings, chain length, headgroup charge, andcmc) to be assessed and rationalized, both in terms of dispersed nanotube mass and surface area. The data also indicate that the CNT-surfactant association follows patterns that are markedly different from other equilibrium processes governed by hydrophobicity (such as micellization); in particular, the surfactant concentration needed for maximum dispersibility,cs,max, and the number of surfactant molecules per unit CNT area at cs,max are shown to depend linearly on chain length. The results further suggest that the presence of micelles in the exfoliation process is not a key factor either for starting CNT dispersibility or attaining its saturation value.

  • 76.
    Ferreira Fernandes, Ricardo Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi. Univ Porto, Dept Chem & Biochem, CIQUP, Fac Sci, P-4169007 Porto, Portugal..
    Dai, Jing
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Regev, Oren
    Ben Gurion Univ Negev, Dept Chem Engn, IL-84105 Beer Sheva, Israel.;Ben Gurion Univ Negev, Ilse Katz Inst Nanotechnol, IL-84105 Beer Sheva, Israel..
    Marques, Eduardo F.
    Univ Porto, Dept Chem & Biochem, CIQUP, Fac Sci, P-4169007 Porto, Portugal..
    Furo, Istvan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 45, s. 13672-13679Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When using amphiphilic polymers to exfoliate and disperse carbon nanotubes in water, the balance between the hydrophobic and hydrophilic moieties is critical and nontrivial. Here, we investigate the mode of surface attachment of a triblock copolymer, Pluronics F127, composed of a central hydrophobic polypropylene oxide block flanked by hydrophilic polyethylene oxide blocks, onto single-walled carbon nanotubes (SWNTs). Crucially, we analyze the composition in dispersant of both the as-obtained dispersion (the supernatant) and the precipitate-containing undispersed materials. For this, we combine the carefully obtained data from H-1 NMR peak intensities and self-diffusion and thermogravimetric analysis. The molecular motions behind the observed NMR features are clarified. We find that the hydrophobic blocks attach to the dispersed SWNT surface and remain significantly immobilized leading to H-1 NMR signal loss. On the other hand, the hydrophilic blocks remain highly mobile and thus readily detectable by NMR. The dispersant is shown to possess significant block polydispersity that has a large effect on dispersibility. Polymers with large hydrophobic blocks adsorb on the surface of the carbonaceous particles that precipitate, indicating that although a larger hydrophobic block is good for enhancing adsorption, it may be less effective in dispersing the tubes. A model is also proposed that consistently explains our observations in SWNT dispersions and some contradicting findings obtained previously in carbon nanohorn dispersions. Overall, our findings help elucidating the molecular picture of the dispersion process for SWNTs and are of interest when looking for more effective (i.e., well-balanced) polymeric dispersants.

  • 77.
    Ghalgaoui, Ahmed
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Shimizu, Ryosuke
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Hosseinpour, Saman
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Alvarez-Asencio, Rubén
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    McKee, Clayton
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Monolayer Study by VSFS: In Situ Response to Compression and Shear in a Contact2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 11, s. 3075-3085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assembled octadecyltrichlorosilane ((OTS), CH3(CH2)(17)SiCl3) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared. The monolayers were characterized with atomic force microscopy (AFM) and contact angle measurements; their conformation was studied before, during, and after contact with a polymer (either PDMS or PTFE) surface using the vibrational sum frequency spectroscopy (VSFS) technique. During contact, the effect of pressure was studied for both polymer surfaces, but in the case of PTFE, the effect of shear rate on the contact was simultaneously studied. The VSFS response of the monolayers with pressure was almost entirely due to changes in the real area of contact with the polymer and therefore the Fresnel factors, whereas sliding caused disorder in the previously all-trans monolayer, as evidenced by a significant increase in the population of gauche defects.

  • 78.
    Ghorbani, Morteza
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning. Sabanci Univ, Fac Engn & Nat Sci, Mechatron Engn Program, TR-34956 Istanbul, Turkey.
    Olofsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Benjamins, Jan-Willem
    Research Institute of Sweden (RISE), Chemistry, Materials and Surfaces, Box 5607, SE-114 86 Stockholm, Sweden.
    Loskutova, Ksenia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Paulraj, Thomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Grishenkov, Dmitry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Medicinsk avbildning.
    Svagan, Anna Justina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Unravelling the Acoustic and Thermal Responses of Perfluorocarbon Liquid Droplets Stabilized with Cellulose Nanofibers2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 40, s. 13090-13099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The attractive colloidal and physicochemical properties of cellulose nanofibers (CNFs) at interfaces have recently been exploited in the facile production of a number of environmentally benign materials, e.g. foams, emulsions, and capsules. Herein, these unique properties are exploited in a new type of CNF-stabilized perfluoropentane droplets produced via a straightforward and simple mixing protocol. Droplets with a comparatively narrow size distribution (ca. 1–5 μm in diameter) were fabricated, and their potential in the acoustic droplet vaporization process was evaluated. For this, the particle-stabilized droplets were assessed in three independent experimental examinations, namely temperature, acoustic, and ultrasonic standing wave tests. During the acoustic droplet vaporization (ADV) process, droplets were converted to gas-filled microbubbles, offering enhanced visualization by ultrasound. The acoustic pressure threshold of about 0.62 MPa was identified for the cellulose-stabilized droplets. A phase transition temperature of about 22 °C was observed, at which a significant fraction of larger droplets (above ca. 3 μm in diameter) were converted into bubbles, whereas a large part of the population of smaller droplets were stable up to higher temperatures (temperatures up to 45 °C tested). Moreover, under ultrasound standing wave conditions, droplets were relocated to antinodes demonstrating the behavior associated with the negative contrast particles. The combined results make the CNF-stabilized droplets interesting in cell-droplet interaction experiments and ultrasound imaging.

  • 79. Gibson, Elizabeth A.
    et al.
    Le Pleux, Loic
    Fortage, Jerome
    Pellegrin, Yann
    Blart, Errol
    Odobel, Fabrice
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Boschloo, Gerrit
    Uppsala University.
    Role of the Triiodide/Iodide Redox Couple in Dye Regeneration in p-Type Dye-Sensitized Solar Cells2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 15, s. 6485-6493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of perylene dyes with different optical and electronic properties have been used as photosensitizers in NiO-based p-type dye-sensitized solar cells. A key target is to develop dyes that absorb light in the red to near-infrared region of the solar spectrum in order to match photoanodes optically in tandem devices; however, the photocurrent produced was found to decrease dramatically as the absorption maxima of the dye used was varied from 517 to 565 nm and varied strongly with the electrolyte solvent (acetonitrile, propionitrile, or propylene carbonate). To determine the limitations of the energy properties of the dye molecules and to provide guidelines for future sensitizer design, we have determined the redox potentials of the duodide radical intermediate involved in the charge-transfer reactions in different solvents using photomodulated voltammetry. E degrees(I-3(-)/I-2(center dot-)) (V vs Fe(Cp)(2)(+/0)) = -0.64 for propylene carbonate, -0.82 for acetonitrile, and -0.87 for propionitrile. Inefficient regeneration of the sensitizer appears to be the efficiency-limiting step in the device, and the values presented here will be used to design more efficient dyes, with more cathodic reduction potentials, for photocathodes in tandem dye-sensitized solar cells.

  • 80. Graupner, R K
    et al.
    Yan, Mingdi
    Department of Chemistry, Portland State University.
    Theoretical model for photochemical or thermally activated immobilization of macromolecules2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 20, s. 8675-8680Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The covalent immobilization of macromolecules on surfaces and within 3-dimensional networks is quantitatively described using a model based on Poisson statistics. This model determines the immobilized density or layer thickness as a function of molecular weight of the macromolecule or radiant exposure prior to and following the surface deposition of the macromolecule. Measurements of immobilized layer thickness provide first-order rate constants for decomposition of the surface-bound linker molecules and an estimate of the surface-bound linker density. The model predicts the relative density of immunocomplexed antibodies as a function of the irradiation time used to immobilize antigens. By providing the average number of bonds to the immobilized molecule, the model enables studies of the effect of multiple bonds on the activity of biomolecules. Experimental data by the authors and from the literature validate the model.

  • 81. Griffiths, P. C.
    et al.
    Paul, A.
    Stilbs, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Pettersson, E.
    Electrophoretic nuclear magnetic resonance (ENMR) - A new tool for studying counterion binding in mixed surfactant systems2003Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, nr 20, s. 8605-8607Artikel i tidskrift (Refereegranskat)
  • 82. Griffiths, P. C.
    et al.
    Pettersson, E.
    Stilbs, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Cheung, A. Y. F.
    Howe, A. M.
    Pitt, A. R.
    Electrophoretic nuclear magnetic resonance studies of mixed anionic-nonionic surfactant micelles2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 22, s. 7178-7181Artikel i tidskrift (Refereegranskat)
  • 83.
    Guo, Weijin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Hansson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    van der Wijngaart, Wouter
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Capillary Pumping Independent Of Liquid Sample Viscosity2016Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Capillary flow is a dominating liquid transport phenomenon on the micro- and nanoscale. As described at the beginning of the 20th century, the flow rate during imbibition of a horizontal capillary tube follows the Washburn equation, i.e. decreases over time and depends on the viscosity of the sample. This poses a problem for capillary driven systems that rely on a predictable flow rate and where the liquid viscosity is not precisely known. Here we introduce and successfully experimentally verify the first compact capillary pump design with a flow rate constant in time and independent of the liquid viscosity that can operate over an extended period of time. We also present a detailed theoretical model for gravitation independent capillary filling, which predicts the novel pump performance to within measurement error margins, and in which we, for the first time, explicitly identify gas inertia dominated flow as a fourth distinct flow regime in capillary pumping. These results are of potential interest for a multitude of applications and we expect our results to find most immediate applications within lab-on-a-chip systems and diagnostic devices.

  • 84.
    Gustafsson, Emil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hedberg, Jonas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Larsson, Per A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Vibrational sum frequency spectroscopy on polyelectrolyte multilayers: Effect of molecular surface structure on macroscopic wetting properties2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 15, s. 4435-4442Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption of a single layer of molecules on a surface, or even a reorientation of already present molecules, can significantly affect the surface properties of a material. In this study, vibrational sum frequency spectroscopy (VSFS) has been used to study the change in molecular structure at the solid-air interface following thermal curing of polyelectrolyte multilayers of poly(allylamine hydrochloride) and poly(acrylic acid). Significant changes in the VSF spectra were observed after curing. These changes were accompanied by a distinct increase in the static water contact angle, showing how the properties of the layer-by-layer molecular structure are controlled not just by the polyelectrolyte in the outermost layer but ultimately by the orientation of the chemical constituents in the outermost layers.

  • 85.
    Halthur, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Björklund, Anna
    YKI, Institute for Surface Chemistry.
    Elofsson, Ulla
    YKI, Institute for Surface Chemistry.
    Self-assembly/aggregation behavior and adsorption of enamel matrix derivate protein to silica surfaces2006Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 5, s. 2227-2234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption of the amelogein protein mixture enamel matrix derivate (EMD) to silica surfaces has been studied by in situ ellipsometry and quartz crystal microbalance with dissipation (QCM-D). The protein was found to adsorb as nanospheres in mono- or multilayers, depending on the concentration of "free" nanospheres available in solution. The concentration of free nanospheres is determined by the competitive processes of adsorption and rapid aggregation into microscopic particles, measured by dynamic light scattering (DLS). Multilayers could also be formed by sequential injections of fresh EMD solution. At higher temperature, an up to 6 times thicker gel-like film was formed on the substrate surface, and decreasing the pH lead to disruption of the multi layer/aggregate formation and a decreased amount adsorbed.

  • 86.
    Halthur, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Elofsson, Ulla
    Immobilization of Enamel Matrix Derivate Protein onto Polypeptide Multilayers: Comparative in Situ Measurements using Ellipsometry, Quartz Crystal Microbalance with Dissipation, and Dual Polarization Interferometry2006Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 26, s. 11065-11071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.

  • 87.
    Halthur, Tobias
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Elofsson, Ulla
    YKI, Institute for Surface Chemistry.
    Multilayers of Charged Polypeptides As Studied by in Situ Ellipsometry and Quartz Crystal Microbalance with Dissipation2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 5, s. 1739-1745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces, with and without an initial layer of polyethyleneimine (PEI), was investigated and characterized by means of in situ ellipsometry and quartz crystal microbalance with dissipation. A two-regime buildup was found in all systems, where the length of the first slow-growing regime is dependent on the structure of the initial layers. In the second fast-growing regime, the film thickness grows linearly while the mass increases more than linearly (close to exponentially) with the number of deposited layers. The film refractive indices as well as the water contents indicate that the film density changes as the multilayer film builds up. The change in film density was proposed to be due to polypeptides diffusing into the multilayer film as they attach. Furthermore, the use of PEI as the initial layer was found to induce a difference in the thickness increments for PGA and PLL.

  • 88.
    Hansson, Petra M.
    et al.
    YKI, Ytkemiska Institutet AB.
    Hormozan, Yashar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Brandner, B. D.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Swerin, Agne
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Schoelkopf, J.
    Gane, P. A. C.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Effect of surface depressions on wetting and interactions between hydrophobic pore array surfaces2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 30, s. 11121-11130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface structure is known to significantly affect the long-range capillary forces between hydrophobic surfaces in aqueous solutions. It is, however, not clear how small depressions in the surface will affect the interaction. To clarify this, we have used the AFM colloidal probe technique to measure interactions between hydrophobic microstructured pore array surfaces and a hydrophobic colloidal probe. The pore array surfaces were designed to display two different pore spacings, 1.4 and 4.0 ÎŒm, each with four different pore depths ranging from 0.2 to 12.0 ÎŒm. Water contact angles measured on the pore array surfaces are lower than expected from the Cassie-Baxter and Wenzel models and not affected by the pore depth. This suggests that the position of the three-phase contact line, and not the interactions underneath the droplet, determines the contact angle. Confocal Raman microscopy was used to investigate whether water penetrates into the pores. This is of importance for capillary forces where both the movement of the three-phase contact line and the situation at the solid/liquid interface influence the stability of bridging cavities. By analyzing the shape of the force curves, we distinguish whether the cavity between the probe and the surfaces was formed on a flat part of the surface or in close proximity to a pore. The pore depth and pore spacing were both found to statistically influence the distance at which cavities form as surfaces approach each other and the distance at which cavities rupture during retraction.

  • 89. Hansson, Petra M.
    et al.
    Skedung, Lisa
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Swerin, Agne
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Robust Hydrophobic Surfaces Displaying Different Surface Roughness Scales While Maintaining the Same Wettability2011Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, nr 13, s. 8153-8159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A range of surfaces coated with spherical silica particles, covering the size range from nanometer to micrometer, have been produced using Langmuir-Blodgett (LB) deposition. The particles were characterized both in suspension and in the Langmuir trough to optimize the surface preparation procedure. By limiting the particle aggregation and surface layer failures during the preparation steps, well-defined monolayers with a close-packed structure have been obtained for all particle sizes. Thus, this procedure led to structured surfaces with a characteristic variation in the amplitude and spatial roughness parameters. In order to obtain robust surfaces, a sintering protocol and an AFM-based wear test to determine the stability of the deposited surface layer were employed. Hydrophobization of the LB films followed by water contact angle measurements showed, for all tested particle sizes, the same increase in contact angle compared to the contact angle of a flat hydrophobic surface. This indicates nearly hexagonal packing and gives evidence for nearly, complete surface wetting of the surface features.

  • 90. Hansson, Petra M.
    et al.
    Swerin, Agne
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Influence of Surface Topography on the Interactions between Nanostructured Hydrophobic Surfaces2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 21, s. 8026-8034Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanostructured particle coated surfaces, with hydrophobized particles arranged in close to hexagonal order and of specific diameters ranging from 30 nm up to 800 nm, were prepared by Langmuir-Blodgett deposition followed by silanization. These surfaces have been used to study interactions between hydrophobic surfaces and a hydrophobic probe using the AFM colloidal probe technique. The different particle coated surfaces exhibit similar water contact angles, independent of particle size, which facilitates studies of how the roughness length scale affects capillary forces (previously often referred to as "hydrophobic interactions") in aqueous solutions. For surfaces with smaller particles (diameter < 200 nm), an increase in roughness length scale is accompanied by a decrease in adhesion force and bubble rupture distance. It is suggested that this is caused by energy barriers that prevent the motion of the three-phase (vapor/liquid/solid) line over the surface features, which counteracts capillary growth. Some of the measured force curves display extremely long-range interaction behavior with rupture distances of several micrometers and capillary growth with an increase in volume during retraction. This is thought to be a consequence of nanobubbles resting on top of the surface features and an influx of air from the crevices between the particles on the surface.

  • 91. He, J. J.
    et al.
    Hagfeldt, A.
    Lindquist, S. E.
    Grennberg, H.
    Korodi, F.
    Sun, Licheng C.
    Akermark, B.
    Phthalocyanine-sensitized nanostructured TiO2 electrodes prepared by a novel anchoring method2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 9, s. 2743-2747Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel method for anchoring phthalocyanines substituted with ester groups onto nanostructured TiO2 films is described. Such phthalocyanines did not adsorb on nanostructured TiO2 film by the ordinary methods. In our new method, the TiO2 film is pretreated with (CH3)(3)COLi to change the surface hydroxyl groups (-OH) into oxygen anions (-O-), thus making the surface more reactive toward the ester functionalities of the dye. The dye can then be anchored onto the semiconductor surface through the produced carboxylate group(s). The amount of anchored dye on the semiconductor shows a dependence on both the time of base treatment and the time of dye treatment. Electrodes treated with the free base phthalocyanine and zinc phthalocyanine were characterized by absorption spectroscopy, photocurrent action spectroscopy, and photocurrent-photovoltage measurements. The homogeneous blue-green color and the absorption bands in the far-red region are indicative of an attachment of the dye on TiO2 film. A monochromatic incident photo-to-current conversion efficiency of 4.3 % was achieved at 690 nm for a cell where the base-treated electrode was treated with ZnPcBu.

  • 92.
    Hedberg, Yolanda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Killian, Manuela S.
    Department of Materials Science and Engineering 4, Chair for Surface Science and Corrosion, Friedrich-Alexander-University of Erlangen-Nuremberg, Martensstr.7, 91058 Erlangen, Germany.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Virtanen, Sannakaisa
    Department of Materials Science and Engineering 4, Chair for Surface Science and Corrosion, Friedrich-Alexander-University of Erlangen-Nuremberg, Martensstr.7, 91058 Erlangen, Germany.
    Schmuki, Patrik
    Department of Materials Science and Engineering 4, Chair for Surface Science and Corrosion, Friedrich-Alexander-University of Erlangen-Nuremberg, Martensstr.7, 91058 Erlangen, Germany.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Interaction of bovine serum albumin and lysozyme with stainless steel studied by time of flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 47, s. 16306-16317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An in-depth mechanistic understanding of the interaction between stainless steel surfaces and proteins is essential from a corrosion and protein-induced metal release perspective when stainless steel is used in surgical implants and in food applications. The interaction between lysozyme (LSZ) from chicken egg white and bovine serum albumin (BSA) and AISI 316L stainless steel surfaces was studied ex situ by means of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) after different adsorption time periods (0.5, 24, and 168 h). The effect of XPS measurements, storage (aging), sodium dodecyl sulfate (SDS), and elevated temperature (up to 200 °C) on the protein layers, as well as changes in surface oxide composition, were investigated. Both BSA and LSZ adsorption induced an enrichment of chromium in the oxide layer. BSA induced significant changes to the entire oxide, while LSZ only induced a depletion of iron at the utmost layer. SDS was not able to remove preadsorbed proteins completely, despite its high concentration and relatively long treatment time (up to 36.5 h), but induced partial denaturation of the protein coatings. High-temperature treatment (200 °C) and XPS exposure (X-ray irradiation and/or photoelectron emission) induced significant denaturation of both proteins. The heating treatment up to 200 °C removed some proteins, far from all. Amino acid fragment intensities determined from ToF-SIMS are discussed in terms of significant differences with adsorption time, between the proteins, and between freshly adsorbed and aged samples. Stainless steel–protein interactions were shown to be strong and protein-dependent. The findings assist in the understanding of previous studies of metal release and surface changes upon exposure to similar protein solutions.

  • 93. Hedin, N.
    et al.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Ostwald ripening of an emulsion monitored by PGSE NMR2001Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 16, s. 4746-4752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coarsening of surfactant-stabilized oil-in-water emulsions (C12E5-decane-D2O) induced by a fast temperature drop from their microemulsion phase is studied by H-1 stimulated-echo-type pulsed-field-gradient spin-echo (PGSE) NMR spectroscopy. The data obtained on a small amount of hexamethyldisilane dissolved in the oil phase display two distinct diffusion coefficients. The slower diffusion is interpreted in terms of large droplets containing the oil that had been expelled from the original microemulsion droplets. The faster diffusion belongs to smaller microemulsion droplets that coexist with the large oil droplets. The results show that the investigated emulsions exhibit regular Ostwald ripening. Both the actual amounts of the expelled oil and the obtained coarsening rates agree well with theoretical estimates. As a consequence of fast surfactant exchange among the different droplets, the diffusion of the surfactant molecules is described by a single diffusion coefficient.

  • 94. Hedin, N.
    et al.
    Yu, T. Y.
    Furo, Istvan
    KTH, Tidigare Institutioner                               , Kemi.
    Growth of C12E8 micelles with increasing temperature. A convection-compensated PGSE NMR study2000Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, nr 19, s. 7548-7550Artikel i tidskrift (Refereegranskat)
  • 95. Herzog, Gerd
    et al.
    Benecke, Gunthard
    Buffet, Adeline
    Heidmann, Berit
    Perlich, Jan
    Risch, Johannes F.H.
    Santoro, Gonzalo
    Schwartzkopf, Matthias
    Yu, Shun
    Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85c, D-22607 Hamburg, Germany.
    Wurth, Wilfried
    Roth, Stephan V.
    In-situ GISAXS investigation of polystyrene nanoparticle spray deposition onto a silicon substrate2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 36, s. 11260-11266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the spray deposition and subsequent self-assembly during drying of a polystyrene nanoparticle dispersion with in situ grazing incidence small-angle X-ray scattering at high time resolution. During the fast deposition of the dispersion and the subsequent evaporation of the solvent, different transient stages of nanoparticle assembly can be identified. In the first stage, the solvent starts to evaporate without ordering of the nanoparticles. During the second stage, large-scale structures imposed by the breakup of the liquid film are observable. In this stage, the solvent evaporates further and nanoparticle ordering starts. In the late third drying stage, the nanoparticles self-assemble into the final layer structure.

  • 96.
    Heydari, Golrokh
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tyrode, Eric
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Visnevskij, Ceslav
    Makuska, Ricardas
    Claesson, Per
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Temperature-Dependent Deicing Properties of ElectrostaticallyAnchored Branched Brush Layers of Poly(ethylene oxide)2016Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, nr 17, s. 4194-4202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydration water of hydrophilic polymersfreezes at subzero temperatures. The adsorption of suchpolymers will result in a hydrophilic surface layer that stronglybinds water. Provided this interfacial hydration water remainsliquidlike at subzero temperatures, its presence could possiblyreduce ice adhesion, in particular, if the liquidlike layer isthicker than or comparable to the surface roughness. Toexplore this idea, a diblock copolymer, having one branchedbottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. Theshear ice adhesion strength on such polymer-coated surfaces was investigated down to −25 °C using a homebuilt device. Inaddition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branchedbottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, attemperatures above −15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer.Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of waterinteracting with branched and linear poly(ethylene oxide) (with hydration water melting points of about −18 and −10 °C,respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branchedbottle-brush structured poly(ethylene oxide) at −10 °C, whereas no significant adhesion reduction was obtained with linearpoly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottlebrushstructured poly(ethylene oxide), which, in the bulk, does not freeze until −18 °C.

  • 97.
    Hjalmarsson, Nicklas
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Attana AB, Stockholm, SE-11419, Sweden.
    Bergendal, Erik
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Attana AB, Stockholm, SE-11419, Sweden.
    Wang, Yong-Lei
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Munavirov, Bulat
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi. KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Wallinder, Daniel
    Attana AB, SE-11419 Stockholm, Sweden..
    Glavatskih, Sergei
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.). Department of Electrical Energy, Metals, Mechanical Constructions and Systems, Ghent University, Ghent, B-9000, Belgium.
    Aastrup, Teodor
    Attana AB, SE-11419 Stockholm, Sweden..
    Atkin, Rob
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia..
    Furo, Istvan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Rutland, Mark W.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Surfaces, Processes and Formulation, RISE Research Institutes of Sweden, Stockholm, SE-50115, Sweden.
    Electro-Responsive Surface Composition and Kinetics of an Ionic Liquid in a Polar Oil2019Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, nr 48, s. 15692-15700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence. The measured mass changes cannot be explained only in terms of simple ion exchange; the relative molecular volumes of the ions and the density changes in response to ion exclusion must be considered. The relaxation behavior of the potential between the electrodes upon disconnecting the applied potential is more complex than that observed for pure ionic liquids, but a measure of the surface charge can be extracted from the exponential decay when the rapid initial potential drop is accounted for. The adsorbed film at the gold surface consists predominantly of ionic liquid despite the low concentration, which is unsurprising given the surtactant-like structures of (some of) the ionic liquid ions. Changes in response to potential correspond to changes in the relative numbers of cations and anions, rather than a change in the oil composition. No evidence for an electric field induced change in viscosity is observed. This work shows conclusively that electric potentials can be used to control the surface composition, even in an oil-based system, and paves the way for other ion solvent studies.

  • 98. Hodgkins, Robert P.
    et al.
    Ahniyaz, Anwar
    Parekh, Kinnari
    Belova, Lyubov M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Bergstroem, Lennart
    Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica2007Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 17, s. 8838-8844Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-control led decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.

  • 99. Holten-Andersen, Niels
    et al.
    Mates, Thomas E
    Toprak,, M.S.
    University of California at Santa Barbara, Chemistry Department.
    Stucky, Galen D
    Zok, Frank W.
    Waite, J. Herbert
    Metals and the integrity of a biological coating: The cuticle of mussel byssus2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 6, s. 3323-3326Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cuticle of mussel byssal threads is a robust natural coating that combines high extensibility with high stiffness and hardness. In this study, fluorescence microscopy and elemental analysis were exploited to show that the 3,4-dihydroxyphenyl-L-alanine (dopa) residues of mussel foot protein-1 colocalize with Fe and Ca distributions in the cuticle of Mytilus galloprovincialis mussel byssal threads. Chelated removal of Fe and Ca from the cuticle of intact threads resulted in a 50% reduction in cuticle hardness, and thin sections subjected to the same treatment showed a disruption of cuticle integrity. Dopa-metal complexes may provide significant interactions for the integrity of composite cuticles deformed under tension.

  • 100.
    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 Highly Charged Polyelectrolytes onto an Oppositely Charged Porous Substrate2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 15, s. 7857-7866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption behavior of highly charged cationic polyelectrolytes onto porous substrates is electrostatic in nature and has been shown to be highly dependent on the polyelectrolyte properties. Copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) were synthesized to have a range of macromolecular properties (i.e., charge density and molecular mass). Traditional titration methods have been complemented by fluorescence labeling techniques that were developed to directly observe the extent that fluorescently labeled poly(AM-co-DADMAC) adsorbs into the pore structure of a cellulosic Substrate. Although contributing to the electrostatic driving force, the charge density acts to limit adsorption to the outermost surface under electrolyte-free conditions. However, adsorption into the pores call occur if both the molecular mass and charge density of poly(AM-co-DADMAC) are Sufficiently low. Adsorption initially increases as the electrolyte concentration is increased. However, the electrostatic persistence length of poly(AM-co-DADMAC) restricts the polyelectrolyte from entering the pores. Therefore, changes ill the adsorption behavior at moderate electrolyte concentrations have been attributed to swelling of the polyelectrolyte layer at the fiber exterior. The adsorption behavior changes again at high electrolyte concentrations Such that poly(AM-co-DADMAC) could adsorb into the pore Structure. This occurred when the electrolyte concentration was sufficient to screen the electrostatic persistence length of poly(AM-co-DADMAC), provided that the entropic driving force for adsorption still existed. It is suggested that adsorption into the pore structure is a kinetic process that is governed by localized electrostatic interactions between poly(AM-co-DADMAC) and the charges located within the pores.

123456 51 - 100 av 270
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf