Change search
Refine search result
1234567 1 - 50 of 874
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Abele, S
    et al.
    Sjöberg, M
    YKI – Ytkemiska institutet.
    Hamaide, T
    Zicmanis, A
    Guyot, A
    Reactive surfactants in heterophase polymerization. 10. Characterization of the surface activity of new polymerizable surfactants derived from maleic anhydride1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, p. 176-181Article in journal (Refereed)
    Abstract [en]

    Characterization of the surface activity of previously obtained polymerizable dialkyl maleates is performed to find out the relation between the structure of surfactants and their performances. The given polymerizable surfactants were synthesized for using in the emulsion polymerization. Three groups of dialkyl maleates-nonionic, cationic and zwitterionic-with different chain lengths of hydrophobic alkyl groups are investigated. Critical micelle concentration (cmc) values are determined for water soluble surfactants. It is found that cmc decreases with increasing chain length of the hydrophobic alkyl group. For nonionic and cationic surfactants interfacial tension at the interface between water and dodecane is measured. Droplet size in oil-in-water (O/W) emulsions is determined for all given surfactants. Cationic and zwitterionic dialkyl maleates with the longest investigated alkyl chain (R=C16H33, C17H35) provide good stability of O/W emulsions. In order to compare the obtained results, measurements with well-known surfactants-nonionic nonylphenol-poly(ethylene oxide) (NPEO10) and cationic hexadecyltrimethyl ammonium bromide (CTAB)-are performed.

  • 2.
    Abitbol, Tiffany
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. The Hebrew University of Jerusalem, Israel.
    Kam, Doron
    The Hebrew University of Jerusalem, Israel.
    Levi-Kalisman, Yael
    The Hebrew University of Jerusalem, Israel.
    Gray, Derek G
    McGill University, Canada.
    Shoseyov, Oded
    The Hebrew University of Jerusalem, Israel.
    Surface Charge Influence on the Phase Separation and Viscosity of Cellulose Nanocrystals2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 13, p. 3925-3933Article in journal (Refereed)
    Abstract [en]

    counterions in the suspensions. The results suggest that there is a threshold surface charge density (∼0.3%S) above which effective volume considerations are dominant across the concentration range relevant to liquid crystalline phase formation. Above this threshold value, phase separation occurs at the same effective volume fraction of CNCs (∼10 vol %), with a corresponding increase in critical concentration due to the decrease in effective diameter that occurs with increasing surface charge. Below or near this threshold value, the formation of end-to-end aggregates may favor gelation and interfere with ordered phase formation.

  • 3. Abraham, T
    et al.
    Kumpulainen, A
    Xu, Z
    Rutland, M
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Masliyah, J
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw ~ 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale RG of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Å due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH ~8.0-9.0, in contrast to the case of 3 mM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Å followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 4. Abraham, T.
    et al.
    Kumpulainen, A.
    Xu, Z.
    Rutland, Mark W
    KTH, Superseded Departments, Chemistry.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Masliyah, J.
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 26, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw similar to 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale R-G of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Angstrom due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH similar to8.0-9.0, in contrast to the case of 3 MM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Angstrom followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 5.
    Afifi, Hala
    et al.
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Heenan, Richard K
    ISIS-CCLRC, Rutherford Appleton Laboratory, U.K..
    Dreiss, Cécile A
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Solubilization of Oils or Addition of Monoglycerides Drives the Formation of Wormlike Micelles with an Elliptical Cross-Section in Cholesterol-Based Surfactants: A Study by Rheology, SANS, and Cryo-TEM2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 12, p. 7480-7492Article in journal (Refereed)
    Abstract [en]

    We report the formation of wormlike micelles (WLM) in poly(oxyethylene) cholesteryl ether (ChEO(10)) aqueous solutions by the addition of lipophilic monoglycerides at room temperature (monolaurin (ML), monocaprin (MC), and monocaprylin (MCL)) bearing 12-, 10-, and 8-carbon alkyl chains, respectively. A combination of rheology, small-angle neutron scattering (SANS), and cryo-TEM was used to study their viscoelastic properties and structure. With the successive addition of cosurfactant, a significant increase in viscosity and a clear solidlike behavior is obtained, suggesting the formation of a viscoelastic network of wormlike micelles. Only for MCL is typical Maxwellian behavior obtained. The onset of micellar growth, as detected by the occurrence of solidlike behavior and a significant increase in viscosity, is obtained for 0.30 (1 wt %), 0.34 (1 wt %), and 0.60 (1.5 wt %) cosurfactant/ChEO(10) molar ratios with ML, MC, and MCL, respectively. With ML and MC, extremely long relaxation times (exceeding 20 s) compared to those of MCL are obtained, and zero-shear viscosity values are more than 1 order of magnitude higher than with MCL. These results show that cosurfactants with longer alkyl chain lengths (ML and MC) induce the formation of longer wormlike micelles and do so at lower concentrations. SANS measurements on dilute solutions confirm that the viscoelastic behavior correlates with an increase in contour length and reveals an elliptical cross-section with an axial ratio of around 2. Cryo-TEM images provide visual evidence of the wormlike micelles and confirm the elliptical shape of the cross-section. The addition of small amounts of aliphatic oils (ethyl butyrate, EB, and ethyl caprylate, EC) and cyclic oils (peppermint, PP, and tea tree, TT, oils) to ChEO(10) solutions induces wormlike micelle formation at a lower cosurfactant concentration or even in its absence (for PP, TT, and EC) because of their probable localization in the palisade layer. The viscosity peak and height of the plateau modulus occur at increasing monoglyceride concentration following the order PP ≈ TT > EC > EB > no oil.

  • 6.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Intrinsic Heterogeneity in Liposome Suspensions Caused by the Dynamic Spontaneous Formation of Hydrophobic Active Sites in Lipid Membranes2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4873-4883Article in journal (Refereed)
    Abstract [en]

    The spontaneous, dynamic formation of hydrophobic active sites in lipid bilayer membranes is studied and characterized. It is shown that the rates of formation and consumption of these active sites control at least two important properties of liposomes: their affinity for hydrophobic surfaces and the rate by which they spontaneously release encapsulated molecules. The adhesion and spreading of liposomes onto hydrophobic polystyrene nanoparticles and the spontaneous leakage of an encapsulated fluorescent dye were monitored for different liposome compositions employing Cryo-TEM, DLS, and fluorescence measurements. It was observed that an apparently homogeneous, monodisperse liposome suspension behaves as if composed by two different populations: a fast leaking population that presents affinity for the hydrophobic substrate employed, and a slow leaking population that does not attach immediately to it. The results reported here suggest that the proportion of liposomes in each population changes over time until a dynamic equilibrium is reached. It is shown that this phenomenom can lead to irreproducibility in, for example, spontaneous leakage experiments, as extruded liposomes leak much faster just after preparation than 24 h afterward. Our findings account for discrepancies in several experimental results reported in the literature. To our knowledge, this is the first systematic study addressing the issue of an existing intrinsic heterogeneity of liposome suspensions.

  • 7.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Høydalsvik, Kristin
    Mayence, Arnaud
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Karvinen, Petri
    Liebi, Marianne
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nygård, Kim
    Controlling Orientational and Translational Order of Iron Oxide Nanocubes by Assembly in Nanofluidic Containers2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 45, p. 12537-12543Article in journal (Refereed)
    Abstract [en]

    We demonstrate that spatial confinement can be used to control the orientational and translational order of cubic nanoparticles. For this purpose we have combined X-ray scattering and scanning electron microscopy to study the ordering of iron oxide nanocubes that have self-assembled from toluene-based dispersions in nanofluidic channels. An analysis of scattering vector components with directions parallel and perpendicular to the slit walls shows that the confining walls induce a preferential parallel alignment of the nanocube (100) faces. Moreover, slit wall separations that are commensurate with an integer multiple of the edge length of the oleic acid-capped nanocubes result in a more pronounced translational order of the self-assembled arrays compared to incommensurate confinement. These results show that the confined assembly of anisotropic nanocrystals is a promising route to nanoscale devices with tunable anisotropic properties.

  • 8.
    Agthe, Michael
    et al.
    Stockholm Univ, Arrhenius Lab, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Wetterskog, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bergström, Lennart
    Stockholm Univ, Arrhenius Lab, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Following the Assembly of Iron Oxide Nanocubes by Video Microscopy and Quartz Crystal Microbalance with Dissipation Monitoring2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 1, p. 303-310Article in journal (Refereed)
    Abstract [en]

    We have studied the growth of ordered arrays by evaporation-induced self-assembly of iron oxide nanocubes with edge lengths of 6.8 and 10.1 nm using video microscopy (VM) and quartz crystal microbalance with dissipation monitoring (QCM-D). Ex situ electron diffraction of the ordered arrays demonstrates that the crystal axes of the nanocubes are coaligned and confirms that the ordered arrays are mesocrystals. Time-resolved video microscopy shows that growth of the highly ordered arrays at slow solvent evaporation is controlled by particle diffusion and can be described by a simple growth model. The growth of each mesocrystal depends only on the number of nanoparticles within the accessible region irrespective of the relative time of formation. The mass of the dried mesocrystals estimated from the analysis of the bandwidth-shift-to-frequency-shift ratio correlates well with the total mass of the oleate-coated nanoparticles in the deposited dispersion drop.

  • 9.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following the Assembly of Iron Oxide Nanocubes by Video Microscopy and Quartz Crystal Microbalance with Dissipation Monitoring2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 1, p. 303-310Article in journal (Refereed)
    Abstract [en]

    We have studied the growth of ordered arrays by evaporation-induced self-assembly of iron oxide nanocubes with edge lengths of 6.8 and 10.1 nm using video microscopy (VM) and quartz crystal microbalance with dissipation monitoring (QCM-D). Ex situ electron diffraction of the ordered arrays demonstrates that the crystal axes of the nanocubes are coaligned and confirms that the ordered arrays are mesocrystals. Time-resolved video microscopy shows that growth of the highly ordered arrays at slow solvent evaporation is controlled by particle diffusion and can be described by a simple growth model. The growth of each mesocrystal depends only on the number of nanoparticles within the accessible region irrespective of the relative time of formation. The mass of the dried mesocrystals estimated from the analysis of the bandwidth-shift-to-frequency-shift ratio correlates well with the total mass of the oleate-coated nanoparticles in the deposited dispersion drop.

  • 10.
    Ahren, Maria
    et al.
    Linkoping Univ, Linkoping, Sweden.
    Selegard, Linnea
    Linkoping Univ, Linkoping, Sweden.
    Klasson, Anna
    Linkoping Univ, Linkoping, Sweden.
    Soderlind, Fredrik
    Linkoping Univ, Linkoping, Sweden.
    Abrikossova, Natalia
    Linkoping Univ, Linkoping, Sweden.
    Skoglund, Caroline
    Linkoping Univ, Linkoping, Sweden.
    Bengtsson, Torbjörn
    Örebro University, School of Health and Medical Sciences. Linkoping Univ, Linkoping, Sweden.
    Engstrom, Maria
    Linkoping Univ, Linkoping, Sweden.
    Kall, Per-Olov
    Linkoping Univ, Linkoping, Sweden.
    Uvdal, Kajsa
    Linkoping Univ, Linkoping, Sweden.
    Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 8, p. 5753-5762Article in journal (Refereed)
    Abstract [en]

    Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study. We report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in NI RI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd2O3) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd2O3 nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd2O3 nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd2O3. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is. an extremely high MR signal at the cellular and molecular level.

  • 11.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Selegård, Linnéa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Klasson, Anna
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Abrikossova, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Skoglund, Caroline
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Bengtsson, Torbjörn
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, The Institute of Technology.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 8, p. 5753-5762Article in journal (Refereed)
    Abstract [en]

    Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3−5 nm) gadolinium oxide (DEG-Gd2O3) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd2O3 nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd2O3 nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r1 and r2 values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd2O3. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level.

  • 12.
    Ahualli, S.
    et al.
    Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
    Delgado, A.
    Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    White, L.R.
    Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA.
    Dynamic electrophoretic mobility of concentrated dispersions of spherical colloidal particles. On the consistent use of the cell model2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 16, p. 7041-7051Article in journal (Refereed)
    Abstract [en]

    This paper outlines a complete and self-consistent cell model theory of the electrokinetics of dense spherical colloidal suspensions for general electrolyte composition, frequency of applied field, ? potential, and particle size. The standard electrokinetic equations, first introduced for any given particle configuration, are made tractable to computation by averaging over particle configurations. The focus of this paper is on the systematic development of suitable boundary conditions at the outer cell boundary obtained from global constraints on the suspension. The approach is discussed in relation to previously published boundary conditions that have often been introduced in an ad hoc manner. Results of a robust numerical calculation of high-frequency colloidal transport properties, such as dynamic mobility, using the present model are presented and compared with some existing dense suspension models. © 2006 American Chemical Society.

  • 13. Al-Bataineh, Sameer A.
    et al.
    Luginbuehl, Reto
    Textor, Marcus
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Covalent Immobilization of Antibacterial Furanones via Photochemical Activation of Perfluorophenylazide2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 13, p. 7432-7437Article in journal (Refereed)
    Abstract [en]

    N-(3-Trimethoxysilylpropyl)-4-azido-2,3,5,6-tetrafluorobenzamide (PFPA-silane) was used as a photoactive crosslinker to immobilize antibacterial furanone molecules on silicon oxide surfaces. This immobilization strategy is useful, especially for substrates and molecules that lack reactive functional groups. To this end, cleaned wafers were initially incubated in solutions of different concentrations of PFPA-silane to form a monolayer presenting azido groups on the surface. The functionalized surfaces were then treated with a furanone solution followed by illumination with UV light and extensive rinsing with ethanol to remove noncovalently adhered molecules, In the presented study, we demonstrate the ability to control the surface density of the immobilized furanone molecules by adjusting the concentration of PFPA-silane solution used for surface functionalization using complementary surface analytical techniques. The fluorine in PFPA-silane and the bromine in furanone molecules were convenient markers for the XPS study. The ellipsometric layer thickness of the immobilized furanone molecules on the surface decreased with decreasing PFPA-silane concentration, which correlated with a decline of water contact angle as a sign of film collapse. The intensity of characteristic azide vibration in the MTR IR spectra was monitored as a function of PFPA-silane concentration, and the peak disappeared completely after furanone application followed by UV irradiation. As a complementary technique to XPS, TOF-SIMS provided valuable information on the chemical and molecular structure of the modified surfaces and spatial distribution of the immobilized furanone molecules. Finally, this report presents a convenient, reproducible, and robust strategy to design antibacterial coating based on furanone compounds for applications in human health care.

  • 14.
    Albet-Torres, Nuria
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Månsson, Alf
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Long-Term Storage of Surface-Adsorbed Protein Machines2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 11, p. 7108-7112Article in journal (Refereed)
    Abstract [en]

    The effective and simple long-term storage of complex functional proteins is critical in achieving commercially viable biosensors. This issue is particularly challenging in recently proposed types of nanobiosensors, where molecular-motor-driven transportation substitutes microfluidics and forms the basis for novel detection schemes. Importantly, therefore, we here describe that delicate heavy meromyosin (HMM)-based nanodevices (HMM motor fragments adsorbed to silanized surfaces and actin bound to HMM) fully maintain their function when stored at -20 degrees C for more than a month. The mechanisms for the excellent preservation of acto-HMM motor function upon repeated freeze thaw cycles are discussed. The results are important to the future commercial implementation of motor-based nanodevices and are of more general value to the long-term storage of any protein-based bionanodevice.

  • 15. Alexandrova, L
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Grigorov, L
    Confirmation of the heterocoagulation theory of flotation1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, p. 7464-7471Article in journal (Refereed)
    Abstract [en]

    To model the flotation process, we have used the microscopic method developed by Scheludko to study the stability of an aqueous thin film containing tetradecyltrimethylammonium bromide ( C14TAB ) between an air bubble and a silica substrate. Experiments were performed at a range of C14TAB concentrations and pH values. Spontaneous rupture of the thin aqueous film was interpretated in terms of heterocoagulation resulting from the preferential adsorption of relatively low surfactant concentrations at the vapour/solution interface causing a net positive charge while the solution/silica interface remained negatively charged. In addition, during the the three-phase-contact (TPC) expansion or de-wetting step following film rupture, the movement of TPC across the silica substrate leads to transfer of amine from the vapour/solution interface to the vapour/silica. This process resembles a Langmuir-Blodgett deposition process and emphasized the importance of the solution/vapour interface in the de-wetting process.

  • 16. Alison, Lauriane
    et al.
    Demirörs, Ahmet F
    Tervoort, Elena
    Teleki, Alexandra
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Nutritional R&D Center Formulation and Application, DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland.
    Vermant, Jan
    Studart, Andre R
    Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: pH Control of Structure-Property Relations2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 21, p. 6147-6160Article in journal (Refereed)
    Abstract [en]

    In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil-water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.

  • 17.
    Alison, Lauriane
    et al.
    Swiss Fed Inst Technol, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Ruhs, Patrick A.
    Swiss Fed Inst Technol, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Tervoort, Elena
    Swiss Fed Inst Technol, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Teleki, Alexandra
    DSM Nutr Prod Ltd, Nutr R&D Ctr Formulat & Applicat, POB 2676, CH-4002 Basel, Switzerland..
    Zanini, Michele
    Swiss Fed Inst Technol, Interfaces Soft Matter & Assembly, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Isa, Lucio
    Swiss Fed Inst Technol, Interfaces Soft Matter & Assembly, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Studart, Andre R.
    Swiss Fed Inst Technol, Dept Mat, Complex Mat, CH-8093 Zurich, Switzerland..
    Pickering and Network Stabilization of Biocompatible Emulsions Using Chitosan-Modified Silica Nanoparticles2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 50, p. 13446-13457Article in journal (Refereed)
    Abstract [en]

    Edible solid particles constitute an attractive alternative to surfactants as stabilizers of food-grade emulsions for products requiring a long-term shelf life. Here, we report on a new approach to stabilize edible emulsions using silica nanoparticles modified by noncovalently bound chitosan oligomers. Electrostatic modification with chitosan increases the hydrophobicity of the silica nanoparticles and favors their adsorption at the oil water interface. The interfacial adsorption of the chitosan-modified silica particles enables the preparation of oil-in-water emulsions with small droplet sizes of a few micrometers through high-pressure homogenization. This approach enables the stabilization of food-grade emulsions for more than 3 months. The emulsion structure and stability can be effectively tuned by controlling the extent of chitosan adsorption on the silica particles. Bulk and interfacial rheology are used to highlight the two stabilization mechanisms involved. Low chitosan concentration (1 wt % with respect to silica) leads to the formation of a viscoelastic film of particles adsorbed at the oil water interface, enabling Pickering stabilization of the emulsion. By contrast, a network of agglomerated particles formed around the droplets is the predominant stabilization mechanism of the emulsions at higher chitosan content (5 wt % with respect to silica). These two pathways against droplet coalescence and coarsening open up different possibilities to engineer the long-term stabilization of emulsions for food applications.

  • 18. Allouche, Joachim
    et al.
    Tyrode, Eric
    Laboratorio FIRP, Ingeniería Química, Universidad de Los Andes, Avenida Don Tulio Febres, Mérida .
    Sadtler, Veronique
    Choplin, Lionel
    Salager, Jean-Louis
    Simultaneous Conductivity and Viscosity Measurements as a Technique To Track Emulsion Inversion by the Phase-Inversion-Temperature Method2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 6, p. 2134-2140Article in journal (Refereed)
    Abstract [en]

    Two kinds of transitions can occur when an emulsified water-oil-ethoxylated nonionic surfactant system is cooled under const. stirring. At a water-oil ratio close to unity, a transitional inversion takes place from a water-in-oil (W/O) to an oil-in-water (O/W) morphol. according to the so-called phase-inversion-temp. method. At a high water content, a multiple W/O/W emulsion changes to a simple O/W emulsion. The continuous monitoring of both the emulsion cond. and viscosity allows the identification of several phenomena that take place during the temp. decrease. In all cases, a viscosity max. is found on each side of the three-phase behavior temp. interval and correlates with the attainment of extremely fine emulsions, where the best compromise between a low-tension and a not-too-unstable emulsion is reached. The studied system contains Polysorbate 85, a light alkane cut oil, and a sodium chloride brine. All transitions are interpreted in the framework of the formulation-compn. bidimensional map.

  • 19.
    Almgren, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Borné, Johanna
    Feitosa, Eloi
    Khan, Ali
    Lindman, Björn
    Dispersed lipid liquid crystalline phases stabilized by a hydrophobically modified cellulose2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 5, p. 2768-2777Article in journal (Refereed)
    Abstract [en]

    Aqueous dispersions of monoolein (MO) with a commercial hydrophobically modified ethyl hydroxyethyl cellulose ether (HMEHEC) have been investigated with respect to the morphologies of the liquid crystalline nanoparticles. Only very low proportions of HMEHEC are accepted in the cubic and lamellar phases of the monoolein−water system. Due to the broad variation of composition and size of the commercial polymer, no other single-phase regions were found in the quasi-ternary system. Interactions of MO with different fractions of the HMEHEC sample induced the formation of lamellar and reversed hexagonal phases, identified from SAXD, polarization microscopy, and cryogenic TEM examinations. In excess water (more than 90 wt %) coarse dispersions are formed more or less spontaneously, containing particles of cubic phase from a size visible by the naked eye to small particles observed by cryoTEM. At high polymer/MO ratios, vesicles were frequently observed, often oligo-lamellar with inter-lamellar connections. After homogenization of the coarse dispersions in a microfluidizer, the large particles disappeared, apparently replaced by smaller cubic particles, often with vesicular attachments on the surfaces, and by vesicles or vesicular particles with a disordered interior. At the largest polymer contents no proper cubic particles were found directly after homogenization but mainly single-walled defected vesicles with a peculiar edgy appearance. During storage for 2 weeks, the dispersed particles changed toward more well-shaped cubic particles, even in dispersions with the highest polymer contents. In some of the samples with low polymer/MO ratio, dispersed particles of the reversed hexagonal type were found. A few of the homogenized samples were freeze-dried and rehydrated. Particles of essentially the same types, but with a less well-developed cubic character, were found after this treatment.

  • 20.
    Almgren, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Garamus, Vasil M
    Nordstierna, Lars
    Luc-Blin, Jean
    Stébé, Marie-José
    Nonideal mixed micelles of fluorinated and hydrogenous surfactants in aqueous solution: NMR and SANS studies of anionic and nonionic systems.2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 8, p. 5355-5363Article in journal (Refereed)
    Abstract [en]

    Contrast variation SANS and (19)F chemical shifts were measured for three mixed equimolar micelle systems: sodium perfluorooctanoate (SPFO) and sodiumdecylsulfate (SDeS) in 200 mM NaCl, lithium perfluorononanate (LiPFN) and lithium dodecylsulfate (LiDS) in 200 mM LiCl, and a nonionic system C(8)F(17)C(2)H(4)(OC(2)H(4))(9) and C(12)H(25)(OC(2)H(4))(8) in water, all at 25 degrees C. The chemical shift measurements allow the calculation of the average fraction of nearest neighbors of each kind around the reporter group (the trifluoromethyl group). A preference for like neighbors were found in all systems, smallest in the SDeS/SPFO system and largest in the nonionic system, but in all cases substantially smaller than expected at critical conditions. From the SANS measurements the width of the micelle composition distribution was obtained. For the ionic systems similar values were obtained, showing a broadening compared to ideal mixtures, but not broad enough for demixing or clearly bimodal distributions. In the nonionic system the width was estimated as sigma = 0.18 and 0.22 using two different evaluation methods. These values suggest that the system is close to critical conditions. The lower value refers to a direct modeling of the system, assuming an ellipsoidal shape and a Gaussian composition distribution. The modeling showed the nonionic mixed micelles to be prolate ellipsoids with axial ratio 2.2 and an aggregation number larger than 100, whereas the two ionic systems fitted best to oblate shapes (axial ratios 0.8 and 0.65 for SDeS/SPFO and LiDS/LiPFN, respectively) and aggregation numbers of 60 for both.

  • 21.
    An, Jungxue
    et al.
    KTH Royal Institute of Technology, Sweden.
    Jin, Chunsheng
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden.
    Dėdinaitė, Andra
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials. KTH Royal Institute of Technology, Sweden.
    Holgersson, Jan
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden.
    Karlsson, Niclas G.
    Sahlgrenska Academy, Sweden; University of Gothenburg, Sweden.
    Claesson, Per M.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials. KTH Royal Institute of Technology, Sweden.
    Influence of Glycosylation on Interfacial Properties of Recombinant Mucins: Adsorption, Surface Forces, and Friction2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 18, p. 4386-4395Article in journal (Refereed)
    Abstract [en]

    Interfacial properties of two brush-with-anchor mucins, C-P55 and C-PSLex, have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. Both are recombinant mucin-type fusion proteins, produced by fusing the glycosylated mucin part of P-selectin glycoprotein ligand-1 (PSLG-1) to the Fc part of a mouse immunoglobulin in two different cells. They are mainly expressed as dimers upon production. Analysis of the O-glycans shows that the C-PSLex mucin has the longer and more branched side chains, but C-P55 has slightly higher sialic acid content. The adsorption of the mucins to PMMA surfaces was studied by quartz crystal microbalance with dissipation. The sensed mass, including the adsorbed mucin and water trapped in the layer, was found to be similar for these two mucin layers. Atomic force microscopy with colloidal probe was employed to study surface and friction forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between mucin layers on compression, whereas a small adhesion was detected between both mucin layers on decompression. This was attributed to chain entanglement. The friction force between C-PSLex-coated PMMA is lower than that between C-P55-coated PMMA at low loads, but vice versa at high loads. We discuss our results in terms of the differences in the glycosylation composition of these two mucins.

  • 22.
    An, Junxue
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dèdinaitè, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Winnik, Francoise M.
    Qiu, Xing-Ping
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Temperature-Dependent Adsorption and Adsorption Hysteresis of a Thermoresponsive Diblock Copolymer2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 15, p. 4333-4341Article in journal (Refereed)
    Abstract [en]

    A nonionic-cationic diblock copolymer, poly(2-isopropyl-2-oxazoline)(60)-b-poly((3-acrylamidopropyl)- trimethylammonium chloride)(17), (PIPOZ(60)-b-PAMPTMA(17)), was utilized to electrostatically tether temperature-responsive PIPOZ chains to silica surfaces by physisorption. The effects of polymer concentration, pH, and temperature on adsorption were investigated using quartz crystal microbalance with dissipation monitoring and ellipsometry. The combination of these two techniques allows thorough characterization of the adsorbed layer in terms of surface excess, thickness, and water content. The high affinity of the cationic PAMPTMA(17) block to the negatively charged silica surface gives rise to a high affinity adsorption isotherm, leading to (nearly) irreversible adsorption with respect to dilution. An increase in solution pH lowers the affinity of PIPOZ to silica but enhances the adsorption of the cationic block due to increasing silica surface charge density, which leads to higher adsorption of the cationic diblock copolymer. Higher surface excess is also achieved at higher temperatures due to the worsening of the solvent quality of water for the PIPOZ block. Interestingly, a large hysteresis in adsorbed mass and other layer properties was observed when the temperature was cycled from 25 to 45 degrees C and then back to 25 degrees C. Possible causes for this temperature hysteresis are discussed.

  • 23.
    An, Junxue
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jin, Chunsheng
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Holgersson, Jan
    Karlsson, Niclas G.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Influence of Glycosylation on Interfacial Properties of Recombinant Mucins: Adsorption, Surface Forces, and Friction2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 18, p. 4386-4395Article in journal (Refereed)
    Abstract [en]

    Interfacial properties of two brush-with-anchor mucins, C-P55 and C-PSLex, have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. Both are recombinant mucin-type fusion proteins, produced by fusing the glycosylated mucin part of P-selectin glycoprotein ligand-1 (PSLG-1) to the Fc part of a mouse immunoglobulin in two different cells. They are mainly expressed as dimers upon production. Analysis of the O-glycans shows that the C-PSLex mucin has the longer and more branched side chains, but C-P55 has slightly higher sialic acid content. The adsorption of the mucins to PMMA surfaces was studied by quartz crystal microbalance with dissipation. The sensed mass, including the adsorbed mucin and water trapped in the layer, was found to be similar for these two mucin layers. Atomic force microscopy with colloidal probe was employed to study surface and friction forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between mucin layers on compression, whereas a small adhesion was detected between both mucin layers on decompression. This was attributed to chain entanglement. The friction force between C-PSLex-coated PMMA is lower than that between C-P55-coated PMMA. at low loads, but vice versa at high loads. We discuss our results in terms of the differences in the glycosylation composition of these two mucins.

  • 24.
    An, Junxue
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Liu, Xiaoyan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Linse, Per
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. SP Technical Research Institute of Sweden, Sweden .
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 10, p. 3039-3048Article in journal (Refereed)
    Abstract [en]

    Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic-nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 degrees C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

  • 25.
    An, Junxue
    et al.
    KTH Royal Institute of Technology, Sweden.
    Liu, Xiaoyan
    KTH Royal Institute of Technology, Sweden.
    Linse, Per
    Lund University, Sweden.
    Dedinaite, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Polymer och fiber. KTH Royal Institute of Technology, Sweden.
    Winnik, Françoise M.
    University of Montreal, Canada; National Institute for Materials Science, Japan.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 10, p. 3039-3048Article in journal (Refereed)
    Abstract [en]

    Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic–nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 °C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

  • 26.
    Andersson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Råsmark, Per Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Single microgel particle studies demonstrate the influence of hydrophobic interactions between charged micelles and oppositely charged polyions.2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 9, p. 3773-3781Article in journal (Refereed)
    Abstract [en]

    The binding of two cationic surfactants, dodecyltrimethylammonium bromide (DoTAB) and N-(1,1,2,2-tetrahydroperfluorodecanyl)pyridinium bromide (HFDePB), to covalently cross-linked sodium poly(styrenesulfonate) (PSS) microgels has been investigated by means of micromanipulator-assisted time-resolved light microscopy on single gels. It is demonstrated that repeated measurements on the same microgel under conditions of controlled liquid flow give highly reproducible results. The two surfactants are found to behave very differently with respect to degree of swelling, surfactant distribution in the gels, both during shrinking and at equilibrium, and kinetics of volume changes induced by them. The main difference is attributed to the presence of a hydrophobic interaction between PSS and the DoTAB micelles, absent in the case of HFDePB. Kinetic shrinking curves are recorded and analyzed using a model for steady-state transport of surfactant between the solution and the gels. Aggregation numbers for DoTAB in PSS solutions obtained from fluorescence quenching measurements are presented. A strong dependence on the surfactant-to-polyion concentration ratio is observed. Relations between surfactant binding isotherms, phase diagrams for linear polyelectrolyte/surfactant/water systems, and the binding to gels are discussed.

  • 27. Andersson, N
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Corkery, R
    YKI – Ytkemiska institutet.
    Alberius, P
    YKI – Ytkemiska institutet.
    Combined emulsion and solvent evaporation (ESE) synthesis route to well-ordered mesoporous materials2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 3, p. 1459-1464Article in journal (Refereed)
    Abstract [en]

    Control over morphology and internal mesostructure of surfactant templated silicas remains a challenge, especially when considering scaling laboratory syntheses up to industrial volumes. Herewereport a method combining emulsification with the evaporation-induced self-assembly (EISA) method for preparing spherical, mesoporous silica particles. This emulsion and solvent evaporation (ESE) method has several potential advantages over classic precipitation routes: it is easily scaled while providing superior control over stoichiometric homogeneity of templating surfactants and inorganic precursors, and particle sizes and distributions are determined by principles developed for manipulating droplet sizes within water-in-oil emulsions. To demonstrate the method, triblock copolymer P104 is used as a templating amphiphile, generating unusually well-ordered 2D hexagonal (P6mm) mesoporous silica, while particle sizes and morphologies were controlled by varying the type of emulsifier and the method for emulsification

  • 28.
    Andersson, Nina
    et al.
    YKI, Institute for Surface Chemistry, Stockholm, Sweden.
    Kronberg, Bengt
    YKI, Institute for Surface Chemistry, Stockholm, Sweden.
    Corkery, Robert W.
    YKI, Institute for Surface Chemistry, Stockholm, Sweden.
    Alberius, Peter
    YKI, Institute for Surface Chemistry, Stockholm, Sweden.
    Combined Emulsion and Solvent Evaporation (ESE) Synthesis Route to Well-Ordered Mesoporous Materials2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 3, p. 1459-1464Article in journal (Refereed)
    Abstract [en]

    Control over morphol. and internal mesostructure of surfactant templated silicas remains a challenge, esp. when considering scaling lab. syntheses up to industrial vols. Here we report a method combining emulsification with the evapn.-induced self-assembly (EISA) method for prepg. spherical, mesoporous silica particles. This emulsion and solvent evapn. (ESE) method has several potential advantages over classic pptn. routes: it is easily scaled while providing superior control over stoichiometric homogeneity of templating surfactants and inorg. precursors, and particle sizes and distributions are detd. by principles developed for manipulating droplet sizes within water-in-oil emulsions. To demonstrate the method, triblock copolymer P104 is used as a templating amphiphile, generating unusually well-ordered 2D hexagonal (P6mm) mesoporous silica, while particle sizes and morphologies were controlled by varying the type of emulsifier and the method for emulsification. [on SciFinder(R)]

  • 29. Arleth, L.
    et al.
    Bergström, Lars Magnus
    KTH, Superseded Departments, Chemistry.
    Pedersen, J. S.
    Small-angle neutron scattering study of the growth behavior, flexibility, and intermicellar interactions of wormlike SDS micelles in NaBr aqueous solutions2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 14, p. 5343-5353Article in journal (Refereed)
    Abstract [en]

    SDS wormlike micelles in water with NaBr are studied using small-angle neutron scattering. SDS concentrations ranging from 0.08 to 8.6 % vol in NaBr aqueous solutions at salinities from 0.6 to 1.0 M are covered. The scattering data are analyzed using a novel approach based on polymer theory and the results of Monte Carlo simulations. The method makes it possible to give a full interpretation of the scattering data, even for the entangled micellar solutions occurring at high concentrations and high salinities. Analysis of the scattering data at zero scattering angle demonstrates that the length of the micelles increases according to a power law as a function of concentration in the studied interval. The analysis furthermore shows that the length of the micelles increases exponentially with increasing salinity. The scattering data in the full range of scattering angles are analyzed using a model for polydisperse wormlike micelles where excluded volume effects are taken into account via an expression based on the polymer reference interaction site model (PRISM). This part of the analysis show that the micelles become more flexible as the salinity increases, which is due to an increased screening of the ionic micelles.

  • 30.
    Arleth, L
    et al.
    YKI – Ytkemiska institutet.
    Bergström, M
    YKI – Ytkemiska institutet.
    Pedersen, JS
    Small-angle neutron scattering study of the growth behavior, flexibility, and intermicellar interactions of wormlike SDS micelles in NaBr aqueous solutions2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 5343-5353Article in journal (Refereed)
    Abstract [en]

    SDS wormlike micelles in water with NaBr are studied using small-angle neutron scattering. SDS concentrations ranging from 0.08 to 8.6 % vol in NaBr aqueous solutions at salinities from 0.6 to 1.0 M are covered. The scattering data are analyzed using a novel approach based on polymer theory and the results of Monte Carlo simulations. The method makes it possible to give a full interpretation of the scattering data, even for the entangled micellar solutions occurring at high concentrations and high salinities. Analysis of the scattering data at zero scattering angle demonstrates that the length of the micelles increases according to a power law as a function of concentration in the studied interval. The analysis furthermore shows that the length of the micelles increases exponentially with increasing salinity. The scattering data in the full range of scattering angles are analyzed using a model for polydisperse wormlike micelles where excluded volume effects are taken into account via an expression based on the polymer reference interaction site model (PRISM). This part of the analysis show that the micelles become more flexible as the salinity increases, which is due to an increased screening of the ionic micelles

  • 31. Asencio, RA
    et al.
    Cranston, ED
    Atkin, R
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ionic liquid nanotribology: Stiction suppression and surface induced shear thinning2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 26, p. 9967-9976Article in journal (Refereed)
    Abstract [en]

    The friction and adhesion between pairs of materials (silica, alumina, and polytetrafluoroethylene) have been studied and interpreted in terms of the long-ranged interactions present. In ambient laboratory air, the interactions are dominated by van der Waals attraction and strong adhesion leading to significant frictional forces. In the presence of the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waals interaction is suppressed and the attractive/adhesive interactions which lead to "stiction" are removed, resulting in an at least a 10-fold reduction in the friction force at large applied loads. The friction coefficient for each system was determined; coefficients obtained in air were significantly larger than those obtained in the presence of EAN (which ranged between 0.1 and 0.25), and variation in the friction coefficients between systems was correlated with changes in surface roughness. As the viscosity of ILs can be relatively high, which has implications for the lubricating properties, the hydrodynamic forces between the surfaces have therefore also been studied. The linear increase in repulsive force with speed, expected from hydrodynamic interactions, is clearly observed, and these forces further inhibit the potential for stiction. Remarkably, the viscosity extracted from the data is dramatically reduced compared to the bulk value, indicative of a surface ordering effect which significantly reduces viscous losses.

  • 32.
    Asencio, Rubén Alvarez
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Cranston, Emily D.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Atkin, Rob
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ionic Liquid Nanotribology: Stiction Suppression and Surface Induced Shear Thinning2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 26, p. 9967-9976Article in journal (Refereed)
    Abstract [en]

    The friction and adhesion between pairs of materials (silica, alumina, and polytetrafluoroethylene) have been studied and interpreted in terms of the long-ranged interactions present. In ambient laboratory air, the interactions are dominated by van der Waals attraction and strong adhesion leading to significant frictional forces. In the presence of the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waals interaction is suppressed and the attractive/adhesive interactions which lead to "stiction" are removed, resulting in an at least a 10-fold reduction in the friction force at large applied loads. The friction coefficient for each system was determined; coefficients obtained in air were significantly larger than those obtained in the presence of EAN (which ranged between 0.1 and 0.25), and variation in the friction coefficients between systems was correlated with changes in surface roughness. As the viscosity of ILs can be relatively high, which has implications for the lubricating properties, the hydrodynamic forces between the surfaces have therefore also been studied. The linear increase in repulsive force with speed, expected from hydrodynamic interactions, is clearly observed, and these forces further inhibit the potential for stiction. Remarkably, the viscosity extracted from the data is dramatically reduced compared to the bulk value, indicative of a surface ordering effect which significantly reduces viscous losses.

  • 33.
    Assarsson, Anna
    et al.
    Lund University.
    Linse, Sara
    Lund University.
    Cabaleiro-Lago, Celia
    Lund University.
    Effects of polyamino acids and polyelectrolytes on amyloid β fibril formation2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 29, p. 8812-8Article in journal (Refereed)
    Abstract [en]

    The fibril formation of the neurodegenerative peptide amyloid β (Aβ42) is sensitive to solution conditions, and several proteins and peptides have been found to retard the process. Aβ42 fibril formation was followed with ThT fluorescence in the presence of polyamino acids (poly-glutamic acid, poly-lysine, and poly-threonine) and other polymers (poly(acrylic acid), poly(ethylenimine), and poly(diallyldimethylammonium chloride). An accelerating effect on the Aβ42 aggregation process is observed from all positively charged polymers, while no effect is seen from the negative or neutral polymers. The accelerating effect is dependent on the concentration of positive polymer in a highly reproducible manner. Acceleration is observed from a 1:500 polymer to Aβ42 weight ratio and up. Polyamino acids and the other polymers exert quantitatively the same effect at the same concentrations based on weight. Fibrils are formed in all cases as verified by transmission electron microscopy. The concentrations of polymers required for acceleration are too low to affect the Aβ42 aggregation process through increased ionic strength or molecular crowding effects. Instead, the acceleration seems to arise from the locally increased Aβ42 concentration near the polymers, which favors association and affects the electrostatic environment of the peptide.

  • 34.
    Assarsson, Anna
    et al.
    Lund University.
    Pastoriza-Santos, Isabel
    Spain.
    Cabaleiro-Lago, Celia
    Lund University.
    Inactivation and adsorption of human carbonic anhydrase II by nanoparticles2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 31, p. 9448-56Article in journal (Refereed)
    Abstract [en]

    The enzymatic activity of human carbonic anhydrase II (HCAII) was studied in the presence of nanoparticles of different nature and charge. Negatively charged nanoparticles inhibit HCAII whereas no effect is seen for positively charged particles. The kinetic effects were correlated with the strength of binding of the enzyme to the particle surface as measured by ITC and adsorption assays. Moreover, conformational changes upon adsorption were observed by circular dichroism. The main initial driving force for the adsorption of HCAII to nanoparticles is of electrostatic nature whereas the hydrophobic effect is not strong enough to drive the initial binding. This is corroborated by the fact that HCAII do not adsorb on positively charged hydrophobic polystyrene nanoparticles. Furthermore, the dehydration of the particle and protein surface seems to play an important role in the inactivation of HCAII by carboxyl-modified polystyrene nanoparticles. On the other hand, the inactivation by unmodified polystyrene nanoparticles is mainly driven by intramolecular interactions established between the protein and the nanoparticle surface upon conformational changes in the protein.

  • 35.
    Atluri, Rambabu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Garcia-Bennett, Alfonso.E
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sakamoto, Yasuhiro
    Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 5, p. 3189-3195Article in journal (Refereed)
    Abstract [en]

    The synthesis of cubic Pmn mesocaged solid templated by cetyltrimethyl ammonium bromide (C16TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C16TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pmn symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 Å) and ellipsoidal cages (B-cages, 48 × 43 Å) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 Å. Finally, a mechanism is proposed, denoted S+NoI, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pmn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.

  • 36. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Hedin, Niklas
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Self-assembly mechanism of folate-templated mesoporous silica.2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 38, p. 12003-12Article in journal (Refereed)
    Abstract [en]

    A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic-inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30°. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.

  • 37. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 38, p. 12003-12012Article in journal (Refereed)
    Abstract [en]

    A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.

  • 38. Atluri, Rambabu
    et al.
    Sakamoto, Yasuhiro
    Stockholm University.
    Garcia-Bennettt, Alfonso E.
    Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 5, p. 3189-3195Article in journal (Refereed)
    Abstract [en]

    The synthesis of cubic Pm (3) over barn mesocaged solid templated by cetyltrimethyl ammonium bromide (C(16)TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C(16)TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pm3n symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 angstrom) and ellipsoidal cages (B-cages, 48 x 43 angstrom) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 angstrom. Finally, a mechanism is proposed, denoted S+similar to N degrees I-, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pm (3) over barn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.

  • 39. Attard, P
    et al.
    Carambassis, A
    Rutland, MW
    YKI – Ytkemiska institutet.
    Dynamic surface force measurement. 2. Friction and the atomic force microscope1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, p. 553-563Article in journal (Refereed)
    Abstract [en]

    The mechanism and geometry of force measurement with the atomic force microscope are analyzed in detail. The effective spring constant to be used in force measurement is given in terms of the cantilever spring constant. Particular attention is paid to possible dynamic effects. Theoretical calculations show that inertial effects may be neglected in most regimes, the exception being when relatively large colloidal probes are used. Model calculations of the effects of friction show that it can cause hysteresis in the constant compliance region and a shift in the zero of separation. Most surprising, friction can cause a significant diminution of the measured precontact force, and, if it actually pins the surfaces, it can change the sign of the calibration factor for the cantilever deflection, which would cause a precontact attraction to appear as a repulsion. Measurements are made of the van der Waals force between a silicon tip and a glass substrate in air. The evidence for friction and other dynamic effects is discussed. Interferometry is used to characterize the performance of the piezoelectric drive motor and position detector used in the atomic force microscope. It is shown that hysteresis in the former, and backlash in the latter, preclude a quantitative measurement of friction effects. The experimental data appear to underestimate the van der Waals attraction at high driving velocities, in qualitative agreement with the model friction calculations.

  • 40. Attard, P
    et al.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Effective spring constant of bubbles and droplets2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 26, p. 8217-8223Article in journal (Refereed)
    Abstract [en]

    It is shown that gas bubbles and liquid droplets respond as hookean springs to applied loads in the experimental weak force regime. An analytic expression is obtained for the spring constant that is identical for both, linear in the surface tension gamma, and logarithmically dependent on the lengths (the decay length of the interaction, the radius of the bubble or droplet, and the radius of the particle or probe). For acute interior contact angles greater than about 20 degrees, it is typically in the range 0.8-1.2 gamma, in agreement with published atomic force microscopy data, and it increases logarithmically for smaller contact angles. Analytic expressions are also obtained for the deformed profile, the extent of the dimple and of the interaction region, the wrapping radius, and the rupture force.

  • 41. Aulin, C.
    et al.
    Varga, I.
    Claesson, P. M.
    Wågberg, L.
    Lindström, Tom
    RISE, STFI-Packforsk.
    Buildup of polyelectrolyte multilayers of polyethyleneimine and microfibrillated cellulose studied by in situ dual-polarization interferometry and quartz crystal microbalance with dissipation2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 6, p. 2509-2518Article in journal (Refereed)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concentrations of the components. Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements. The adsorption data obtained from both the techniques showed a steady buildup of multilayers. High pH and electrolyte concentration of the PEI solution was found to be beneficial for achieving a high adsorbed amount of PEI, and hence of MFC, during the buildup of the multilayer. On the other hand, an increase in the electrolyte concentration of the MFC dispersion was found to inhibit the adsorption of MFC onto PEL The adsorbed amount of MFC was independent of the bulk MFC concentration in the investigated concentration range (15-250 mg/L). Atomic force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements. The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC. The surface roughness expressed as the rms-roughness over 1 ÎŒm2 was calculated to be 4.6 nm (1 bilayer). The adsorbed amount of PEI and MFC and the amount of water entrapped by the individual layers in the multilayer structures were estimated by combining results from the two analytical techniques using the de Feijter formula. These results indicate a total water content of ca. 41% in the PEM.

  • 42. Aulin, C
    et al.
    Varga, I
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wågberg, L
    Lindström, T
    Buildup of polyelectrolyte multilayers of polyethyleneimine and microfibrillated cellulose studied by in situ dual-polarization interferometry and quartz crystal microbalance with dissipation2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 2509-2518Article in journal (Refereed)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concentrations of the components. Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements. The adsorption data obtained from both the techniques showed a steady buildup of multilayers. High pH and electrolyte concentration of the PEI solution was found to be beneficial for achieving a high adsorbed amount of PEI, and hence of MFC, during the buildup of the multilayer. On the other hand, an increase in the electrolyte concentration of the MFC dispersion was found to inhibit the adsorption of MFC onto PEI. The adsorbed amount of MFC was independent of the bulk MFC concentration in the investigated concentration range (15-250 mg/L). Atomic force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements. The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC. The surface roughness expressed as the rms-roughness over 1 m2 was calculated to be 4.6 nm (1 bilayer). The adsorbed amount of PEI and MFC and the amount of water entrapped by the individual layers in the multilayer structures were estimated by combining results from the two analytical techniques using the de Feijter formula. These results indicate a total water content of ca. 41% in the PEM.

  • 43.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Josefsson, Peter
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nanoscale Cellulose Films with Different Crystallinities and Mesostructures: Their Surface Properties and Interaction with Water2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 13, p. 7675-7685Article in journal (Refereed)
    Abstract [en]

    A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale Suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that Is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (similar to 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide(DMAc)/LiCl film possessed very low crystalline ordering (<15%). It was also established that the films ha different mesostructures, that is, structures around 10 nm, depending on the preparation conditions. The LS and LiCl/DMAc films are smooth without any clear mesostructure, whereas the other films have a clear mesostructure in which the dimensions are dependent oil the size of the nanocrystals, fibrillar cellulose, and electrostatic charge of the MFC. The swelling of the films was studied using a quartz crystal microbalance with dissipation. To understand the swelling properties of the films, it was necessary to consider both the difference in crystalline ordering and the difference in mesostructure of the films.

  • 44.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Tom
    STFI-Packforsk AB.
    Buildup of Polyelectrolyte Multilayers of Polyethyleneimine and Microfibrillated Cellulose Studied by in situ Dual Polarization Interferometry and Quartz Crystal Microbalance with Dissipation2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 6, p. 2509-2518Article in journal (Refereed)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concns. of the components.  Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements.  The adsorption data obtained from both the techniques showed a steady buildup of multilayers.  High pH and electrolyte concn. of the PEI soln. was found to be beneficial for achieving a high adsorbed amt. of PEI, and hence of MFC, during the buildup of the multilayer.  On the other hand, an increase in the electrolyte concn. of the MFC dispersion was found to inhibit the adsorption of MFC onto PEI.  The adsorbed amt. of MFC was independent of the bulk MFC concn. in the investigated concn. range (15-250 mg/L).  At. force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements.  The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC.  The surface roughness expressed as the rms-roughness over 1 μm2 was calcd. to be 4.6 nm (1 bilayer).  The adsorbed amt. of PEI and MFC and the amt. of water entrapped by the individual layers in the multilayer structures were estd. by combining results from the two anal. techniques using the de Feijter formula.  These results indicate a total water content of ca. 41% in the PEM.

  • 45.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhao, Guoying
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, p. 3822-3834Article in journal (Refereed)
    Abstract [en]

    Mesoporous silica particles (Davisil) were functionalized with aminopropyltriethoxysilane (APTES) in a fractional factorial design with 19 different synthesis and uptake experiments. The number of amino groups and the uptake of CO(2) were optimized in a 2(V)(5-1) design. Most important to functionalizationwas the amount of water present during synthesis, the reaction time, and pretreating the silica with a mineral acid; certain two-way interactions were shown to be statistically significant as well. Modifications performed at 110 or 80 degrees C showed no significant differences concerning amine content or uptake of CO(2). Properly choosing center points for the discrete variables is problematic and is somewhat related to the lack of fit with respect to CO(2) uptake; the regression was good. Solid-state (29)Si NMR showed that the APTES was mainly fully condensed. Specific surface areas did not correlate with the number of n-propylamine groups on the silica, which is indicative of differential levels of heterogeneity in the coverage of propylamines. The uptake of CO(2) and N(2) was measured from -20 to 70 degrees C and from 0 to 1 bar and parametrized by the Freundlich isotherm. Amine-modified silica adsorbed significant amounts of CO(2), especially at the low partial pressure, which is important for CO(2) capture from flue gas. At such pressures, samples with a high density of amine (4 amines/nm(2)) showed a much higher uptake of CO(2) than did those with densities of similar to 2-3 amines/nm(2), reflecting differential tendencies to form propylammonium-propylcarbamate ion pairs; these require close proximity among amine groups to form. Water affected the uptake of carbon dioxide in different ways. Certain samples took up more moist CO(2) gas than dry CO(2), and others took up less moist CO(2) than dry CO(2), which is indicative of differential tendencies toward water adsorption. We conclude that experimental design is a time-efficient approach to the functionalization of silica with propylamine groups.

  • 46. Bacalum, Mihaela
    et al.
    Wang, Lina
    Boodts, Stijn
    Yuan, Peijia
    Leen, Volker
    Smisdom, Nick
    Fron, Eduard
    Knippenberg, Stefan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Fabre, Gabin
    Trouillas, Patrick
    Beljonne, David
    Dehaen, Wim
    Boens, Noel
    Ameloot, Marcel
    A Blue-Light-Emitting BODIPY Probe for Lipid Membranes2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 14, p. 3495-3505Article in journal (Refereed)
    Abstract [en]

    Here we describe a new BODIPY-based membrane probe (1) that provides an alternative to dialkylcarbocyanine dyes, such as DiI-C,8, that can be excited in the blue spectral region. Compound 1 has unbranched octadecyl chains at the 3,5 -positions and a meso-amino function. In organic solvents, the absorption and emission maxima of 1 are determined mainly by solvent acidity and dipolarity. The fluorescence quantum yield is high and reaches 0.93 in 2-propanol. The fluorescence decays are well fitted with a single -exponential in pure solvents and in small and giant unilamellar vesicles (GUV) with a lifetime of ca. 4 ns. Probe 1 partitions in the same lipid phase as DiI-C-18(5) for lipid mixtures containing sphingomyelin and for binary mixtures of dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC). The lipid phase has no effect on the fluorescence lifetime but influences the fluorescence anisotropy. The translational diffusion coefficients of 1 in GUVs and OLN-93 cells are of the same order as those reported for DiI-C-18. The directions of the absorption and transition dipole moments of 1 are calculated to be parallel. This is reflected in the high steady-state fluorescence anisotropy of 1 in high ordered lipid phases. Molecular dynamic simulations of 1 in a model of the DOPC bilayer indicate that the average angle of the transition moments with respect to membrane normal is ca. 70 degrees, which is comparable with the value reported for al DiI-C-18.

  • 47.
    Bacsik, Zoltan
    et al.
    Department of Materials and Environmental Chemistry , Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Ahlsten, Nanna
    Department of Organic Chemistry, Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Ziadi, Asraa
    Department of Organic Chemistry, Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Zhao, Guoying
    Department of Materials and Environmental Chemistry , Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Garcia-Bennett, Alfonso E.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Martin-Matute, Belen
    Department of Organic Chemistry, Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry , Berzelii Center EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University.
    Mechanisms and Kinetics for Sorption of CO(2) on Bicontinuous Mesoporous Silica Modified with n-Propylamine2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 17, p. 11118-11128Article in journal (Refereed)
    Abstract [en]

    We studied equilibrium adsorption and uptake kinetics and identified molecular species that formed during sorption of carbon dioxide on amine-modified silica. Bicontinuous silicas (AMS-6 and MCM-48) were postsynthetically modified with (3-aminopropyl)triethoxysilane or (3-aminopropyl)methyldiethoxysilane, and amine-modified AMS-6 adsorbed more CO(2) than did amine-modified MCM-48. By in situ FTIR spectroscopy, we showed that the amine groups reacted with CO(2) and formed ammonium carbamate ion pairs as well as carbamic acids under both dry and moist conditions. The carbamic acid was stabilized by hydrogen bonds, and ammonium carbamate ion pairs formed preferably on sorbents with high densities of amine groups. Under dry conditions, silylpropylcarbamate formed, slowly, by condensing carbamic acid and silanol groups. The ratio of ammonium carbamate ion pairs to silylpropylcarbamate was higher for samples with high amine contents than samples with low amine contents. Bicarbonates or carbonates did not form under dry or moist conditions. The uptake of CO(2) was enhanced in the presence of water, which was rationalized by the observed release of additional amine groups under these conditions and related formation of ammonium carbamate ion pairs. Distinct evidence for a fourth and irreversibly formed moiety was observed under sorption of CO(2) under dry conditions. Significant amounts of physisorbed, linear CO(2) were detected at relatively high partial pressures of CO(2), such that they could adsorb only after the reactive amine groups were consumed.

  • 48.
    Bacsik, Zoltan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ahlsten, Nanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ziadi, Asraa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Guoying
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mechanisms and Kinetics for Sorption of CO(2) on Bicontinuous Mesoporous Silica Modified with n-Propylamine2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 17, p. 11118-11128Article in journal (Refereed)
    Abstract [en]

    We studied equilibrium adsorption and uptake kinetics and identified molecular species that formed during sorption of carbon dioxide on amine-modified silica. Bicontinuous silicas (AMS-6 and MCM-48) were postsynthetically modified with (3-aminopropyl)triethoxysilane or (3-aminopropyl)methyldiethoxysilane, and amine-modified AMS-6 adsorbed more CO(2) than did amine-modified MCM-48. By in situ FTIR spectroscopy, we showed that the amine groups reacted with CO(2) and formed ammonium carbamate ion pairs as well as carbamic acids under both dry and moist conditions. The carbamic acid was stabilized by hydrogen bonds, and ammonium carbamate ion pairs formed preferably on sorbents with high densities of amine groups. Under dry conditions, silylpropylcarbamate formed, slowly, by condensing carbamic acid and silanol groups. The ratio of ammonium carbamate ion pairs to silylpropylcarbamate was higher for samples with high amine contents than samples with low amine contents. Bicarbonates or carbonates did not form under dry or moist conditions. The uptake of CO(2) was enhanced in the presence of water, which was rationalized by the observed release of additional amine groups under these conditions and related formation of ammonium carbamate ion pairs. Distinct evidence for a fourth and irreversibly formed moiety was observed under sorption of CO(2) under dry conditions. Significant amounts of physisorbed, linear CO(2) were detected at relatively high partial pressures of CO(2), such that they could adsorb only after the reactive amine groups were consumed.

  • 49.
    Bacsik, Zoltan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Atluri, Rambabu
    Uppsala universitet.
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 12, p. 10013-10024Article in journal (Refereed)
    Abstract [en]

    Adsorption-mediated CO2 separation can reduce the cost of carbon capture and storage. The reduction in cost requires adsorbents with high capacities for CO2 sorption and high CO2-over-N2 selectivity. Amine-modified sorbents are promising candidates for carbon capture. To investigate the details of CO2 adsorption in such materials, we studied mesocaged (cubic, Pmn symmetry) silica adsorbents with tethered propylamines using Fourier transform infrared (FTIR) spectroscopy and volumetric uptake experiments. The degree of heterogeneity in these coatings was varied by either cosynthesizing or postsynthetically introducing the propylamine modification. In situ FTIR spectroscopy revealed the presence of both physisorbed and chemisorbed CO2 in the materials. We present direct molecular evidence for physisorption using FTIR spectroscopy in mesoporous silica sorbents modified with propylamines. Physisorption reduced the CO2-over-N2 selectivity in amine-rich sorbents. Samples with homogeneous coatings showed typical CO2 adsorption trends and large quantities of IR-observable physisorbed CO2. The uptake of CO2 in mesocaged materials with heterogeneous propylamine coatings was higher at high temperatures than at low temperatures. At higher temperatures and low pressures, the postsynthetically modified materials adsorbed more CO2 than did the extracted ones, even though the surface area after modification was clearly reduced and the coverage of primary amine groups was lower. The principal mode of CO2 uptake in postsynthetically modified mesoporous silica was chemisorption. The chemisorbed moieties were present mainly as carbamate−ammonium ion pairs, resulting from the quantitative transformation of primary amine groups during CO2 adsorption as established by NIR spectroscopy. The heterogeneity in the coatings promoted the formation of these ion pairs. The average propylamine−propylamine distance must be small to allow the formation of carbamate−propylammonium ion pairs.

  • 50.
    Bacsik, Zoltán
    et al.
    Stockholm University.
    Atluri, Rambabu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Garcia-Bennett, Alfonso E.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Hedin, Niklas
    Stockholm University.
    Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 12, p. 10013-10024Article in journal (Refereed)
    Abstract [en]

    Adsorption-mediated CO2 separation can reduce the costs of carbon capture and storage. The reduction in cost requires adsorbents with high capacities for CO2 sorption and high CO2-over-N2 selectivity. Amine-modified sorbents are promising candidates for carbon capture. To investigate the details of CO2 adsorption in such materials, we studied mesocaged (cubic, Pm3n symmetry) silica adsorbents with tethered propylamines using Fourier transform infrared (FTIR) spectroscopy and volumetric uptake experiments. The degree of heterogeneity in these coatings was varied by either co-synthesizing or post-synthetically introducing the propylamine modification. In situ FTIR spectroscopy revealed the presence of both physisorbed and chemisorbed CO2 in the materials. We present the first direct molecular evidence for physisorption using FTIR spectroscopy in mesoporous silica sorbents modified with propylamines. Physisorption reduced the CO2-over-N2 selectivity in amine-rich sorbents. Samples with homogenous coatings showed typical CO2 adsorption trends and large quantities of IR-observable physisorbed CO2. The uptake of CO2 in mesocaged materials with heterogeneous propylamine coatings was higher at high temperatures than at low temperatures. At higher temperatures and low pressures, the post-synthetically modified materials adsorbed more CO2 than did the extracted ones, even though the surface area after modification was clearly reduced and the coverage of primary amine groups was lower. The principal mode of CO2 uptake in post-synthetically modified mesoporous silica was chemisorption. The chemisorbed moieties were present mainly as carbamate–ammonium ion pairs, resulting from the quantitative transformation of primary amine groups during CO2 adsorption as established by NIR spectroscopy. The heterogeneity in the coatings promoted the formation of these ion pairs. The average propylamine–propylamine distance must be small to allow the formation of carbamate–propylammonium ion pairs.

1234567 1 - 50 of 874
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf