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  • 1.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer mobilization and drug release during tablet swelling: A 1H NMR and NMR microimaging study2007In: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 122, p. 199-205Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to investigate the swelling characteristics of a hydroxypropyl methylcellulose (HPMC) matrix incorporating the hydrophilic drug antipyrine. We have used this matrix to introduce a novel analytical method, which allows us to obtain within one experimental setup information about the molecular processes of the polymer carrier and its impact on drug release. Nuclear magnetic resonance (NMR) imaging revealed in situ the swelling behavior of tablets when exposed to water. By using deuterated water, the spatial distribution and molecular dynamics of HPMC and their kinetics during swelling could be observed selectively. In parallel, NMR spectroscopy provided the concentration of the drug released into the aqueous phase. We find that both swelling and release are diffusion controlled. The ability of monitoring those two processes using the same experimental setup enables mapping their interconnection, which points on the importance and potential of this analytical technique for further application in other drug delivery forms.

  • 2.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Recrystallization of drug nanoparticles in solid dispersion tablets by multinuclear NMR spectroscopy and NMR microimagingManuscript (preprint) (Other academic)
  • 3.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Millqvist-Fureby, Anna
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer–drug interactions and wetting of solid dispersions2009In: European Journal of Pharmaceutical Sciences, ISSN 0928-0987, E-ISSN 1879-0720, Vol. 39, no 1-3, p. 125-133Article in journal (Refereed)
    Abstract [en]

    We demonstrate the ability of drugs to influence the wetting of solid dispersion tablets in unexpected ways. Five model drugs of different water solubility and ability to interact with the involved polymers were incorporated in hydrophilic polymer matrices, made of either hydroxypropyl methylcellulose (HPMC) or polyvinyl pyrrolidone (PVP). The physical mixtures of all combinations of drug and polymer presented surface hydrophobicities, as measured by the equilibrium advancing contact angle of water, which are expected for materials that do not influence the interactions of each other with water. However, the solid dispersions containing HPMC deviated from this regular behaviour and displayed contact angles below those of the pure compounds involved, either drug or polymer. This behaviour is explained by changed surface exposure of HPMC side groups, as a result of changes in intermolecular hydrogen bonds. In addition to water contact angle measurements, we employed NMR imaging to monitor the time course of water ingress and swelling.

  • 4.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Millqvist-Fureby, Anna
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Relationships between solid dispersion preparation process, particle size and drug release: an NMR and NMR microimaging study2010In: European journal of pharmaceutics and biopharmaceutics, ISSN 0939-6411, E-ISSN 1873-3441, Vol. 76, no 2, p. 311-319Article in journal (Refereed)
    Abstract [en]

    Solid dispersion tablets prepared by either spray drying or rotoevaporation and exhibiting different grain and pore sizes were investigated under the process of hydration-swelling-gelation. H-2 and H-1 NMR microimaging experiments were used to selectively follow water penetration and polymer mobilization kinetics, respectively, while the drug release kinetics was followed by H-1 NMR spectroscopy. The obtained data, in combination with morphological information by scanning electron microscopy (SEM), reveal a complex process that ultimately leads to release of the drug into the aqueous phase. We find that the rate of water ingress has no direct influence on release kinetics, which also renders air in the tablets a secondary factor. On the other hand, drug release is directly correlated with the polymer mobilization kinetics. Water diffusion into the originally dry polymer grains determines the rate of grain swelling and the hydration within the grains varies strongly with grain size. We propose that this sets the stage for creating homogeneous gels for small grain sizes and heterogeneous gels for large grain sizes. Fast diffusion through water-rich sections of the inhomogeneous gels that exhibit a large mesh size is the factor which yields a faster drug release from tablets prepared by rotoevaporation.

  • 5.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Estimating the size range of drug nanoparticles in solid dispersions by NMR spectroscopyManuscript (preprint) (Other academic)
  • 6.
    Dai, Jing
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden..
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.;Univ Porto, CIQUP, Dept Chem & Biochem, Fac Sci, P-4169007 Porto, Portugal..
    Regev, Oren
    Ben Gurion Univ Negev, Dept Chem Engn, IL-84105 Beer Sheva, Israel.;Ben Gurion Univ Negev, Ilse Katz Inst Nanotechnol, IL-84105 Beer Sheva, Israel..
    Marques, Eduardo F.
    Univ Porto, CIQUP, Dept Chem & Biochem, Fac Sci, P-4169007 Porto, Portugal..
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden..
    Dispersing Carbon Nanotubes in Water with Amphiphiles: Dispersant Adsorption, Kinetics, and Bundle Size Distribution as Defining Factors2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 42, p. 24386-24393Article in journal (Refereed)
    Abstract [en]

    Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, but the process is not well understood. In this work, aqueous SWNT dispersions were produced by sonicating pristine SWNT powder in the presence of an amphiphilic triblock copolymer (Pluronic F127) as dispersant. Upon centrifugation, one obtains a supernatant with suspended individual tubes and thin bundles and a precipitate with large bundles (and impurities). In the supernatant, that constitutes the final dispersion, we determined the dispersed SWNT concentration by thermogravi-metric analysis (TGA) and UV-vis spectroscopy, and the dispersant concentration by NMR The fraction of dispersant adsorbed at the SWNT surface was obtained by H-1 diffusion NMR Sigmoidal dispersion curves recording the concentration of dispersed SWNTs as a function of supernatant dispersant concentration were obtained at different SWNT loadings and sonication times. As SWNT bundles are debundled into smaller and smaller ones, the essential role of the dispersant is to sufficiently quickly cover the freshly exposed surfaces created by shear forces induced during sonication. Primarily kinetic reasons are behind the need for dispersant concentrations required to reach a substantial SWNT concentration. Centrifugation sets the size threshold below which SWNT particles are retained in the dispersion and consequently determines the SWNT concentration as a function of sonication time.

  • 7.
    Dvinskikh, Sergey
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Chapter 13: Characterization of Liquid-crystalline Materials by Separated Local Field Methods2018In: New Developments in NMR, Royal Society of Chemistry, 2018, no 15, p. 391-423Chapter in book (Refereed)
    Abstract [en]

    A unique feature of liquid crystals is a high degree of molecular mobility combined with orientational and positional order. Solid-state NMR contributes to fundamental understanding of diverse molecular organizations and complex dynamic processes in these exciting materials. The focus of this chapter is on the development and application of advanced solid-state NMR methodologies for liquid crystal studies, with emphasis on techniques for measuring anisotropic spin couplings. The discussion centers on applications of separated dipolar local field NMR spectroscopy, which is used in an increasing number of directions in studies of novel liquid-crystalline materials for emerging technological applications.

  • 8.
    Dvinskikh, Sergey
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Sandberg, Dick
    Linnæus University, School of Engineering.
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 3, p. 119-127Article in journal (Refereed)
    Abstract [en]

    This study evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low-field and low-resolution [1H]NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for in situ local moisture content measurements beneath a coating layer in the cladding, for example, and it is also possible to relate the moisture level to specific properties of the wood material.

  • 9.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Magnetic resonance imaging and nuclear magnetic resonance investigations of bentonite systems2009Report (Refereed)
  • 10.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A multinuclear magnetic resonance imaging (MRI) study of wood with adsorbed water: Estimating bound water concentration and local wood density2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 1, p. 103-107Article in journal (Refereed)
    Abstract [en]

    The interaction between moisture and the macromolecular wood tissue is of critical importance to wood properties. In this context, magnetic resonance imaging (MRI) is very promising as this method could deliver molecular information on the submillimeter scale (i.e., along concentration gradients) about both free and adsorbed water and the cell wall polymers. In the present study, it is demonstrated for the first time that wood containing adsorbed heavy water ((H2O)-H-2) can be studied by MRI based on separated images due to water (H-2 MRI) and cell wall polymers (H-1 MRI). Data confirm that in specimens equilibrated at controlled humidity there is a direct correlation between bound water content and relative density of the polymers in wood tissue; there is a strong variation across annual rings.

  • 11.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mendicino, Antonio Lorenzo
    Fortino, Stefania
    Toratti, Tomi
    NMR imaging study and multi-Fickian numerical simulation of moisture transfer in Norway spruce samples2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 11, p. 3079-3086Article in journal (Refereed)
    Abstract [en]

    Wood has potential as a renewable material for a large variety of applications that often call for improved properties such as dimensional stability, moisture insensitivity, and durability. Moisture migration in wood is a particularly important factor in determining the cost-effective service life of wooden construction. Within the present research, proton NMR imaging was applied for recording the moisture spatial distribution of various samples of Norway Spruce. Moisture distribution along the radial, tangential and longitudinal directions in wood was monitored at different times upon three consecutive changes of relative humidity: (1) from 65% to 94%; (2) from 94% to 33%; (3) from 33% to 65%. Uncoated samples and specimens treated with different types of surface coatings were studied. The experiments were numerically simulated by using the multi-Fickian model. The model describes the moisture transport process in wood which is characterized by three phenomena: (a) bound water diffusion, (b) water vapor diffusion and (c) coupling between the two phases through sorption. The model is implemented into the Abaqus FEM code. The numerical results are found to be in agreement with the experimental data.

  • 12.
    Elwinger, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Pourmand, Payam
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Diffusive Transport in Pores. Tortuosity and Molecular Interaction with the Pore Wall2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 25, p. 13757-13764Article in journal (Refereed)
    Abstract [en]

    The self-diffusion of neat water, dimethyl sulfoxide (DMSO), octanol, and the molecular components in a water-DMSO solution was measured by H-1 and H-2 NMR diffusion experiments for those fluids imbibed into controlled pore glasses (CPG). Their highly interconnected structure is scaled by pore size and shows invariant pore topology independent of the size. The nominal pore diameter of the explored CPGs varied from 7.5 to 72.9 nm. Hence, the about micrometer mean-square diffusional displacement during the explored diffusion tithes was much larger than the individual pore size, and the experiment yielded the average diffusion coefficient Great care was taken to establish the actual pore: volumes of the CPGs. Transverse relaxation experiments processed by inverse Laplace transformation were performed to verify that the liquids explored filled exactly the available pore volume. Relative to the respective diffusion coefficients obtained in bulk phases, we observe a reduction in the diffusion coefficient that is independent of pore size for the larger pores and becomes stronger toward the smaller pores. Geometric tortuosity governs the behavior at larger pore sizes, while the interaction with pore walls becomes the dominant factor at our smallest pore diameter. Deviation from the trends predicted by the Renkin equation indicates that the interaction with the pore wall is not a just simple steric one but is in part dependent on the specific features of the molecules explored here.

  • 13.
    Frise, Anton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    Ichikawa, Takahiro
    Yoshio, Masafumi
    Ohno, Hiroyuki
    Kato, Takashi
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Anisotropic Ion Mobility in an Ionic Liquid Crystal Complex of a Rodlike Mesogen Containing an Oxyethylene Moiety and Lithium TriflateManuscript (preprint) (Other academic)
    Abstract [en]

    A liquid-crystalline (LC) complex of a rodlike mesogen containing an oxyethylene moiety and lithium triflate has been synthesized and its mesophases have been characterized by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The ion conductive behaviour was investigated in isotropic and LC phases and related to the ionic mobility, as observed by 7Li and 19F NMR diffusometry. The observed two-dimensional ion mobilities show that planes conducting both lithium and triflate ions are formed in the smectic mesophases. The conductivity of the lithium ions is large in the smectic C phase where conductive planes rich in ethylene oxide chains exist.

  • 14.
    Frise, Anton E.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Ohno, Hiroyuki
    Kato, Takashi
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Ion Channels and Anisotropic Ion Mobility in a Liquid-Crystalline Columnar Phase As Observed by Multinuclear NMR Diffusometry2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 47, p. 15477-15482Article in journal (Refereed)
    Abstract [en]

    The anisotropic diffusion of anions and cations in the columnar and isotropic phases of a fan-shaped imidazolium hexafluorophosphate salt is measured by H-1 and F-19 diffusion NMR experiments. The macroscopic orientation of the columnar phase is investigated by H-2 NMR spectroscopy. We find that the anions, confined by the cations, diffuse faster than the cations along the columns but slowly across them, which exemplifies the ion channel model of these materials. The cations and anions are dissociated in the columnar phase but are paired or clustered in the isotropic phase.

  • 15.
    Frise, Anton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Nordstierna, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Hou, Yanbo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Adsorption isotherms of cationic surfactants on silica particles measured by NMR spectroscopyManuscript (preprint) (Other academic)
    Abstract [en]

    We present here a new method that employs NMR spectroscopy to quantify the adsorbed amount of surfactant on the surface of particles and thereby provide the adsorption isotherm. As demonstration, the adsorption isotherms for a series of cationic surfactants on silica particles are obtained. Those results are in general agreement with previous observations and the overall appearances of adsorption isotherms exemplify the interplay between electrostatic and hydrophobic interactions. Compared to other available methods, the experimental error is comparable or smaller in a very wide range of surfactant concentrations and there exist other potential advantages.

  • 16.
    Frise, Anton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Pages, Guilhem
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Shtein, M.
    Pri Bar, I.
    Regev, O.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer binding to carbon nanotubes in aqueous dispersions: Residence time on the nanotube surface As Obtained by NMR diffusometry2012In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 9, p. 2635-2642Article in journal (Refereed)
    Abstract [en]

    The binding of block copolymer Pluronic F-127 in aqueous dispersions of single- (SWCNT) and multiwalled (MWCNT) carbon nanotubes has been studied by pulsed-field-gradient (PFG) 1H NMR spectroscopy. We show that a major fraction of polymers exist as a free species while a minor fraction is bound to the carbon nanotubes (CNT). The polymers exchange between these two states with residence times on the nanotube surface of 24 ± 5 ms for SWCNT and of 54 ± 11 ms for MWCNT. The CNT concentration in the solution was determined by improved thermal gravimetric analysis (TGA) indicating that the concentration of SWCNT dispersed by F-127 was significantly higher than that for MWCNT. For SWCNT, the area per adsorbed Pluronic F-127 molecule is estimated to be about 40 nm 2.

  • 17.
    Frise, Anton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Pages, Guilhem
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Shtein, Michael
    Pri-Bar, Ilan
    Regev, Oren
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer Binding to Carbon Nanotubes in Aqueous DispersionsStudied by NMR DiffusometryManuscript (preprint) (Other academic)
    Abstract [en]

    The diffusion behavior of block copolymer Pluronic F-127 in aqueous dispersions of single-walled (SW) and multi-walled (MW) carbon nanotubes (CNT) has been studied by pulsed-field-gradient (PFG) 1H NMR spectroscopy. We show that the polymers are either free monomers or bound to the CNT and exchange between these two states. The residence times and relative populations in those states could also be obtained. For both classes of CNT, the residence time in the bound state was found to be similar and in the order of 10-100 milliseconds. Thermal gravimetric analysis (TGA) showed that the SWCNT concentration dispersed by F-127 was higher than that for MWCNT.

  • 18.
    Giesecke, Marianne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Constant-time chemical-shift selective imaging2013In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 226, p. 19-21Article in journal (Refereed)
    Abstract [en]

    We demonstrate that chemical-shift-selective constant-time imaging (CTI) can be performed by simply inserting selective saturation into the original imaging pulse sequence. The performance of the proposed method is illustrated by 7Li CTI imaging in a battery model that contains both Li metal electrodes and an electrolyte containing a dissolved Li salt.

  • 19. Hagberg, Johan
    et al.
    Morozov, Evgeny
    Furo, Istvan
    KTH, Superseded Departments (pre-2005), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, Superseded Departments (pre-2005), Physics.
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Inequality of Axial and Radial Diffusion of Inserted Lithium Ions in Carbon Fibres as Revealed by Pulsed-Field Gradient NMRManuscript (preprint) (Other academic)
    Abstract [en]

    Nuclear Magnetic Resonance (NMR) studies has characterized lithiated polyacrylonitrile-based carbon fibres. The local dynamics has been probed by spin-lattice and spin-spin relaxation measurements and long range motion (diffusion) by pulsed field gradient NMR. Differences in fibre orientation was investigated by axially and radially aligned samples. One single peak related to lithium insertion was observed around 12-25 ppm, increasing with lithium load. A small effect of fibre orientation was observed on the relaxation behavior. The diffusion though was found to be around three times higher in axial compared to radial direction of the carbon fibres. This is believed to be due to the microstructure, with oriented crystallites along the carbon fibres contributing more in the axial direction to the average measured diffusion. The diffusion coefficients varied from around 10-12 m2/s to 4·10-12 m2/s, increasing with lithium load.

  • 20.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Ion Pairing in Ethanol/Water Solution Probed by Electrophoretic and Diffusion NMR2009In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 39, p. 13900-Article in journal (Refereed)
    Abstract [en]

    We demonstrate that a combination of electrophoretic NMR and diffusion NMR experiments can measure the average charge carried by ions in solution. This average charge is used as a quantitative indicator of ion pairing. Our results show that there is a Hofmeister relation in the ion pairing between monovalent anions and the tetramethylammonium cation in 95% ethanol/water solution. The ion pairing of the divalent sulfate ion was larger than that shown by any of the monovalent anions.

  • 21.
    Jackalin, Lukas
    et al.
    KTH.
    Kharkov, B. B.
    Russia.
    Komolkin, A. V.
    Russia.
    Dvinskikh, Sergey
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Experimental strategies for 13C-15N dipolar NMR spectroscopy in liquid crystals at the natural isotopic abundance2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 34, p. 22187-22196Article in journal (Refereed)
    Abstract [en]

    Direct dipolar spin couplings are informative and sensitive probes for a wide range of dynamic processes and structural properties at atomic, molecular and supramolecular levels in liquid crystals and other anisotropic materials. Usually, heteronuclear 13C-1H dipolar couplings in liquid crystals with natural 13C abundance are measured. Recording 13C-15N NMR dipolar spectra in unlabeled materials is challenging because of the unfavorable combination of two rare isotopes. Here we design and compare various experimental strategies to measure short- and long-range heteronuclear 13C-15N dipolar couplings in liquid crystalline samples with high molecular orientational order. New techniques were developed to record 13C and 15N spectra of naturally occurring 13C-15N spin pairs with increased signal intensity and spectral resolution while suppressing the signals of the uncoupled isotopes. Highly resolved 13C-15N dipolar spectra were recorded within an experimental time of a few hours. Coupling constants in a broad range of 10-1000 Hz between spins separated by up to five chemical bonds and distances of up to 5 Å were measured. Because of their relatively low demands on radio-frequency power levels, the experiments were easy to implement using conventional high-resolution solution-state NMR hardware. Experimental data were compared to the results of density functional theory and molecular dynamics computational analyses. The presented experimental methods to characterize the dipolar couplings in unlabeled materials provide novel routes to investigate molecular structure and dynamics in mesophases.

  • 22.
    Macakova, Lubica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Nordstierna, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Karlsson, Göran
    Department of Physical Chemistry, Uppsala University.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Lack of association between a cationic protein and a cationic fluorosurfactant2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 2, p. 771-775Article in journal (Refereed)
    Abstract [en]

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

  • 23. Maeztu, Raquel
    et al.
    Gonzalez-Gaitano, Gustavo
    Tardajos, Gloria
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Chemiluminescence of phthalhydrazide derivatives in organized media: Interactions with surfactants and cyclodextrins2011In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 131, no 4, p. 662-668Article in journal (Refereed)
    Abstract [en]

    The chemiluminescent oxidation of some phthalhydrazide derivatives, luminol (LUM), isoluminol (ISOL), N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), has been carried out in micellar media and in the presence of natural cyclodextrins (CDs), using Co(II) as catalyst and H2O2 as oxidant. The cationic cetyltrimethylammonium bromide (CAB) and, in a lesser extent, the anionic sodium dodecyl sulfate (SDS) produce quenching in the chemiluminescence (CL) of all the luminophores at concentrations above the cmc, whereas slight enhancements are attained with the nonionic pentaethylene glycol monododecyl ether (C12E5). On the contrary, the incorporation of the CDs to the reaction produces a remarkable intensification of the CL. Binding of the luminophores to the macrocycles and the micelles has been studied by Pulsed-Gradient-Spin-Echo-NMR (PGSE-NMR) and fluorescence anisotropy. The cationic CTAB decreases the emission mainly due to charge compensation as a result of the association of the luminophores and the luminescent intermediates to the micelles. The presence of the alkyl substituents of ABEI and AHEI provides an additional hydrophobic contribution to the binding process. SDS quenches this reaction as the micelles retain Co(II) on their anionic layer. The protection and stabilization of these luminophores or their luminescent intermediates provided by the cavities of the CDs make this family of cyclic oligosaccharides much more suitable agents than the surfactants for enhancing the CL in aqueous media for this specific reaction.

  • 24. Ono, Yusuke
    et al.
    Mayama, Hiroyuki
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Sagidullin, Alexander I.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Matsushima, Keiichiro
    Ura, Hafuo
    Uchiyama, Tomoyuki
    Tsujii, Kaoru
    Characterization and structural investigation of fractal porous-silica over an extremely wide scale range of pore size2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 336, no 1, p. 215-225Article in journal (Refereed)
    Abstract [en]

    We have succeeded in creating Menger sponge-like fractal body, i.e., porous-silica samples with Menger sponge-like fractal geometries, by a novel template method utilizing template particles of alkylketene dimer (AKD) and a sol-gel synthesis of tetramethyl orthosilicate (TMOS). We report here the first experimental results on characterization and structural investigations of the fractal porous-silica samples prepared with various conditions such as calcination temperature and packing condition of the template particles. in order to characterize the fractal porous-silica samples, pore volume distribution, porosity and specific Surface area were measured over an extremely wide scale from*1 nm to 100 mu m by means of Mercury porosimetry, H-1 NMR cryoporometry, nitrogen gas adsorption experiments together with direct evaluations of cross-sectional fractal dimension D-cs, and size limits of D-cs. We have found that the pore volume distribution and specific surface area of the fractal porous-silica samples can be discussed in terms of different fractal porous Structures at different scale regions. Crown

  • 25.
    Pagès, Guilhem
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salehi Movahed, Alireza
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Johansson, Mats K. G.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Vegetable oil reactions within wood studied by direct 13C excitation with 1H decoupling and magic-angle sample spinning (MAS) NMR2012In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 75, no 3, p. 259-263Article, review/survey (Refereed)
    Abstract [en]

    Despite having been used for ages to protect wood against the influence of outdoor elements, the chemistry of vegetable oils within wood is poorly known. We propose a method based on solid-state magic-angle sample spinning NMR to in situ characterize oil oxidation as well as its immobilization. To eliminate signal coming from wood molecules but to keep signal from the oil, direct 13C excitation is performed with low-power 1H decoupling during signal acquisition. To suppress the effect of anisotropic spin-interactions and magnetic field inhomogeneity, the sample is spun at the magic-angle. Mono- and polyunsaturated fatty acid derivatives show a difference in their oxidation process: the monounsaturated methyl oleate reacts with wood components and becomes immobilized while the polyunsaturated methyl linoleate becomes oxidized and form oligomers but does not seem to bind to wood. Linola ® oil behaves as would be expected on the basis of its composition by monounsaturated and polyunsaturated chains. This method can be generalized to all coating treatments to characterize chemical pathways and reactions. A better understanding of coating effects on wood is a crucial step to design more efficient protective mixtures.

  • 26.
    Petrov, Oleg
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A study of freezing-melting hysteresis of water in different porous materials: Part II: surfactant-templated silicas2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 36, p. 16358-16365Article in journal (Refereed)
    Abstract [en]

    The freezing-melting hysteresis of water in mesoporous silicas MCM-48, MCM-41 and SBA-16 has been studied by NMR cryoporometry. The hysteresis in MCM-48 was found to exhibit nearly parallel branches, matching type H1 hysteresis that had been observed earlier in controlled pore glass. The same type of hysteresis is observed in two of three different-sized MCM-41 under study (a pore diameter of 3.6 and 3 nm), superimposed with a secondary, extremely broad, type H3 hysteresis. No hysteresis was found in the smallest MCM-41 with a pore diameter < 3 nm. Finally, water in SBA-16 exhibits type H2 hysteresis with the freezing branch being essentially steeper than the melting one, which is attributed to a pore blockage upon freezing, similar to what we observed earlier in Vycor porous glass. The data were analyzed using the model of curvature-dependent metastability of a solid phase upon melting; the validity of this model has been discussed.

  • 27.
    Petrov, Oleg
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A study of freezing-melting hysteresis of water in different porous materials. Part I: Porous silica glasses2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 138, no 1-3, p. 221-227Article in journal (Refereed)
    Abstract [en]

    The freezing and melting temperature hysteresis of water in Vycor porous glass and controlled pore glass (CPG) with the nominal pore diameters 7.0 and 7.5 nm, respectively, has been explored by NMR cryoporometry and NMR relaxometry techniques. The freezing branch of the hysteresis in Vycor was found to be much steeper than the melting one, presumably due to the pore blocking on freezing. This is not observed in CPG, which exhibits parallel freezing and melting branches. Sub-loops recorded starting from partially frozen states are self-similar with respect to the amount of unfrozen water, in both CPG and Vycor. On the other hand, sub-loops starting from partially molten states are self-similar only in CPG, while in Vycor, their shape does depend on the amount of unfrozen water. T-2 relaxation measurements undertaken along the freezing branch reveal in both glasses a slow (on an NMR timescale) exchange of water molecules between frozen and unfrozen pore domains, indicating a good segregation of those domains on freezing. On melting, however, the regime of slow exchange persists only for CPG, while in Vycor, a quasi-exponential T-2 relaxation is observed, characteristic of fast exchange. This suggests that frozen and molten regions in Vycor are well dispersed on melting, while in CPG they present extended domains. We explain such a difference assuming a worse interconnection of a Vycor's pore space as compared to CPG, taking into account its essentially lower porosity (0.28 versus 0.51 in CPG).

  • 28.
    Petrov, Oleg V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A joint use of melting and freezing data in NMR cryoporometry2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 136, no 1-3, p. 83-91Article in journal (Refereed)
    Abstract [en]

    Freezing and melting behaviour of water, benzene, cyclooctane and cyclohexane confined in different-sized controlled pore glasses (CPG's) has been studied by NMR cryoporometry technique. It was found that the freezing (Delta Tf) and melting (Delta Tm) temperature shifts correlate linearly, giving a constant ratio AT, Delta Tm/Delta Tf over different fluids. This suggests that the ratio is a measure of pore morphology rather than fluid's properties. The suggestion is supported by the theoretical treatment that predicts for Delta Tf to be controlled by the surface-to-volume ratio (S/V) and Delta Tm, by the pore curvature (dS/dV). Therefore, the ratio Delta Tm/Delta Tf provides one with the information on the pore shape, unavailable from Delta Tf or AT, measurements alone. For CPG samples under study, this ratio decreases from 0.67 in 7.5 nm pores, which is expected for spherical geometry, to 0.57 in 27.3 and 72.9 nm pores, which is closer to what is expected for cylindrical, or tubular, pores. The pore size distribution functions obtained from the freezing and melting data were found to be similar in shape and width, which indicates that melting and freezing processes occur in CPG on the same length scale of the pore structure.

  • 29.
    Petrov, Oleg V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Vargas-Florencia, Dulce
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    The surface melting of octamethylcyclotetrasiloxane confined in controlled pore glasses as studied by 1H-NMR2007In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 7, p. 1574-1581Article in journal (Refereed)
    Abstract [en]

    We have measured the thickness of the pre-molten surface layer that appears at the interface of octamethylcyclotetrasiloxane (OMCTS) to the matrix in controlled pore glasses with pore diameters ranging 7.5-73 nm. Except for the glass with the largest pores, the layer thickness data for different pore diameters fall on a single master curve when plotted versus T-m - T, where T-m is the size-dependent volume melting point of the pore-confined OMCTS. Hence, at a single temperature, the surface layer thickness depends strongly on the curvature of the pore wall and therefore that of the solid-liquid interface. For temperatures where it exceeds two monolayers, the layer thickness depends logarithmically on T-m - T; for the glass with the largest pores, this turns into a power law with the exponent -1/2. The results are interpreted in terms of a continuous model of the solid-liquid interface with an arbitrary curvature. Because OMCTS is a weakly polar molecule with close to spherical shape, our data also lend themselves to Lennard-Jones type simulations.

  • 30.
    Pourmand, Payam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Wang, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Assessment of moisture protective properties of wood coatings by a portable NMR sensor2011In: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, Vol. 8, no 5, p. 649-654Article in journal (Refereed)
    Abstract [en]

    We have evaluated the potential of nuclear magnetic resonance (NMR) spectroscopy based on small portable magnets for in situ assessment of moisture protective properties of wood coatings. Low field (1)H NMR with a unilateral permanent magnet was used to monitor and map the local moisture content (MC) of wood specimens uncoated or coated with various types of commercial paint systems. The MC beneath a coating layer was measured with a penetration depth up to 5 mm and with a depth resolution of 0.2 mm. The method is quick, noninvasive, simple to perform, and does not require removing wooden parts from the structure.

  • 31.
    Prakobna, Kasinee
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Terenzi, Camilla
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Core-shell cellulose nanofibers for biocomposites: Nanostructural effects in hydrated state2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 125, p. 92-102Article in journal (Refereed)
    Abstract [en]

    Core-shell wood cellulose nanofibers (CNF) coated by an XG hemicellulose polymer are prepared and used to make biocomposites. CNF/XG biocomposites have interest as packaging materials and as hydrated CNF/XG plant cell wall analogues. Structure and properties are compared between Core-shell CNF/XG and more inhomogeneous CNF/XG. Experiments include XG sorption, dynamic light scattering of CNF nanoparticle suspensions, FE-SEM of nanostructure, moisture sorption, tensile testing in moist conditions and dynamic mechanical analysis. (2)H NMR relaxometry is performed on materials containing sorbed (2)H2O2 in order to assess water molecular dynamics in different materials. The results clarify the roles of CNF, XG and the CNF/XG interface in the biocomposites, both in terms of moisture sorption mechanisms and mechanical properties in moist state. The concept of core-shell nanofiber network biocomposites, prepared by filtering of colloids, provides improved control of polymer matrix distribution and interface structure. Also, present mechanical properties are much superior to comparable plant fiber biocomposites.

  • 32.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    RECORD processing: A robust pathway to component-resolved HR-PGSE NMR diffusometry2010In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 207, no 2, p. 332-336Article in journal (Refereed)
    Abstract [en]

    It is demonstrated that very robust spectral component separation can be achieved through global least-squares CORE data analysis of automatically or manually selected spectral regions in complex NMR spectra in a high-resolution situation. This procedure (acronym RECORD) only takes a few seconds and quite significantly improves the effective signal/noise of the experiment as compared to individual frequency channel fitting, like in the generic HR-DOSY approach or when using basic peak height or integral fitting. Results from RECORD processing can be further used as starting value estimates for subsequent CORE analysis of spectral data with higher degree of spectral overlap.

  • 33.
    Terenzi, Camilla
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Wood Microstructure Explored by Anisotropic H-1 NMR Line Broadening: Experiments and Numerical Simulations2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 28, p. 8620-8632Article in journal (Refereed)
    Abstract [en]

    The cellular structure of wood, which is highly anisotropic along its main growth directions, is responsible for the observed anisotropy in its physical and mechanical properties that depend in a complex manner on the moisture content. Here, we demonstrate that the H-1 NMR spectra of wood from Norway spruce exhibit a strong and characteristic dependence on the direction of the sample relative to the applied magnetic field. By comparing spectra recorded at different magnetic-field strengths, we show that this variation is caused by the magnetic-field distribution created by the anisotropic and inhomogeneous distribution of matter and thereby magnetic susceptibility. On the basis of the observations that (i) the recorded spectral peak predominantly arises from translationally mobile water molecules and (ii) the spectral broadening is large if the long axis of the wood tracheid cells is perpendicular to the magnetic field, we set out to test the hypothesis that it is the susceptibility variation on the tracheid length scale that is responsible for the observed spectral features. To verify this, we numerically calculate in a discrete grid approximation the NMR line shapes obtained in realistic tracheid models, and we find that the calculated NMR line shapes are in good agreement with the corresponding experimental ones. We envisage the application of these findings for revealing the inhomogeneous distribution of water and its molecular properties in wood and wood-based materials at varying degrees of humidity.

  • 34.
    Vargas-Florencia, Dulce
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Petrov, Oleg
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    NMR cryoporometry with octamethylcyclotetrasiloxane as a probe liquid. Accessing large pores2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 305, no 2, p. 280-285Article in journal (Refereed)
    Abstract [en]

    Octamethylcyclotetrasiloxane is presented and investigated as probe liquid for NMR cryoporometry or DSC-based thermoporometry. This compound which may imbibe into both hydrophilic and hydrophobic pores is shown to exhibit a melting point depression that is larger than that for other cryoporometric probe materials such as cyclohexane. The transverse relaxation time differs by more than three orders of magnitude between the solid and liquid states, separated by a sharp phase transition. Hence, as demonstrated in controlled pore glasses, octamethylcyclotetrasiloxane can provide pore size distributions for materials with pore sizes up to the micrometer range.

  • 35.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A temperature-jump design for conventional NMR probes2006In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 181, no 1, p. 148-153Article in journal (Refereed)
    Abstract [en]

     The design and performance of a simple probe insert for temperature-jump experiments in conventional NMR probes is described. The insert uses the output from conventional NMR amplifiers for heating conductive aqueous samples with a rate of 30-80 K/s for 200 W radiofrequency power. The observed dependence of the heating rate on sample conductivity is explained by the dominance of dielectric heating. Factors governing the temperature gradient within the sample are discussed.

  • 36.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Iliopoulos, Ilias
    Kinetics of demixing and remixing transitions in aqueous solutions of poly(N-isopropylacrylamide):  A temperature-jump H-1 NMR study2006In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 207, no 21, p. 1972-1979Article in journal (Refereed)
    Abstract [en]

    The time course of the coil-to-globule collapse and intermolecular aggregation of poly(N-isopropylacrylamide) in aqueous solution upon exceeding the lower critical solution temperature (LCST) are investigated by temperature-jump 1H NMR spectroscopy. After the temperature jump, we record the time dependences of (i) the mobile fraction of the polymer chain as revealed by the intensity of the liquid-like NMR signal, (ii) the local mobility of those chains as revealed by the transverse relaxation time T2, and (iii) their self-diffusion coefficient D. The same data are also reported at their temperature-dependent long-time limits. The results suggest a sudden, faster than one second, collapse and intermolecular aggregation into globules and a slower reorganization/redistribution of the individual chains among and within the globular and mobile states. We found that all molecular changes are reversible if the temperature remains less than ca. 6-8 K above the LCST for less than a few minutes; under those conditions, experiments upon sudden temperature quench below the LCST show that the aggregates disintegrate and swell into coils in less than a few seconds.

  • 37.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Micellar kinetics of a fluorosurfactant through stopped-flow NMR2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, p. 2002-2004Article in journal (Refereed)
    Abstract [en]

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

1 - 37 of 37
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