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  • 1.
    Abreu, Barbara
    et al.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Rocha, Jessica
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    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..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Marques, Eduardo F.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 547, p. 69-77Article in journal (Refereed)
    Abstract [en]

    Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.

  • 2.
    Ansari, Farhan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Erik, Lindh
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Mats, Johansson
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lars, Berglund
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Interface tailoring through covalent hydroxyl-epoxy bonds improves  hygromechanical stability in nanocellulose materialsManuscript (preprint) (Other academic)
    Abstract [en]

    Wide-spread use of cellulose nanofibril (CNF) biocomposites and nanomaterials is limited by CNF moisture sensitivity due to surface hydration. We report on a versatile and scalable interface tailoring route for CNF to address this, based on technically important epoxide chemistry. Bulk impregnation of epoxide-amine containing liquids is used to show that CNF hydroxyls can react with epoxides at high rates and high degree of conversion to form covalent bonds. Reactions take place inside nanostructured CNF networks under benign conditions, and are verified by solid state NMR. Epoxide modified CNF nanopaper shows significantly improved mechanical properties under moist and wet conditions. High resolution microscopy is used in fractography studies to relate the property differences to structural change. The cellulose-epoxide interface tailoring concept is versatile in that the functionality of molecules with epoxide end-groups can be varied over a wide range. Furthermore, epoxide reactions with nanocellulose can be readily implemented for processing of moisture-stable, tailored interface biocomposites in the form of coatings, adhesives and molded composites.

  • 3.
    Ansari, Farhan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Lindh, Erik L.
    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. Innventia AB, Sweden.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Johansson, Mats K.G.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    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.
    Interface tailoring through covalent hydroxyl-epoxy bonds improves hygromechanical stability in nanocellulose materials2016In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 134, p. 175-183Article in journal (Refereed)
    Abstract [en]

    Wide-spread use of cellulose nanofibril (CNF) biocomposites and nanomaterials is limited by CNF moisture sensitivity due to surface hydration. We report on a versatile and scalable interface tailoring route for CNF to address this, based on technically important epoxide chemistry. Bulk impregnation of epoxide-amine containing liquids is used to show that CNF hydroxyls can react with epoxides at high rates and high degree of conversion to form covalent bonds. Reactions take place inside nanostructured CNF networks under benign conditions, and are verified by solid state NMR. Epoxide modified CNF nanopaper shows significantly improved mechanical properties under moist and wet conditions. High resolution microscopy is used in fractography studies to relate the property differences to structural change. The cellulose-epoxide interface tailoring concept is versatile in that the functionality of molecules with epoxide end-groups can be varied over a wide range. Furthermore, epoxide reactions with nanocellulose can be readily implemented for processing of moisture-stable, tailored interface biocomposites in the form of coatings, adhesives and molded composites.

  • 4.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Vareikis, Aušvydas
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    van der Wal, Albert
    Lever Faberage Europe Global Technology Centre, Unilever R and D.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Garamus, Vasil M.
    GKSS Research Centre.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 1, p. 21-33Article in journal (Refereed)
    Abstract [en]

    A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PE045MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

  • 5.
    Bernin, Diana
    et al.
    Swedish NMR Ctr, Gothenburg, Sweden..
    Bialik, Erik
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    Stenqvist, Bjorn
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    Fang, Yuan
    KTH.
    Ostlund, Asa
    SP Tech Res Inst Sweden, Stockholm, Sweden..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Lindman, Bjorn
    Lund Univ, Chem, Lund, Sweden..
    Lund, Mikael
    Lund Univ, Div Theoret Chem, Lund, Sweden..
    On the ionization of cellulose in aqueous alkali2017In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Article in journal (Other academic)
  • 6. Bialik, Erik
    et al.
    Stenqvist, Bjorn
    Fang, Yuan
    Ostlund, Asa
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Lindman, Björn
    Lund, Mikael
    Bernin, Diana
    Ionization of Cellobiose in Aqueous Alkali and the Mechanism of Cellulose Dissolution2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 24, p. 5044-5048Article in journal (Refereed)
    Abstract [en]

    Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.

  • 7.
    Bielejewski, Michal
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    On electrophoretic NMR. Exploring high conductivity samples2014In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 243, p. 17-24Article in journal (Refereed)
    Abstract [en]

    The performance of a new electrophoretic NMR (eNMR) method that uses a Carr-Purcell-Meiboom-Gill echo train with repeated electric field reversal is investigated. We show that this pulse sequence, with acronym CPMGER, yields strongly reduced artifacts from convective flow effects caused by the simultaneous presence of electroosmotic and thermal driving forces. We demonstrate the achieved improvements in various aqueous solutions. Ultimately, the method can be used for obtaining electrophoretic mobilities by eNMR without relying on uncharged reference molecules, otherwise a significant limitation for electrophoretic experiments performed with nuclei other than 1H.

  • 8. Callaghan, P. T.
    et al.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Diffusion-diffusion correlation and exchange as a signature for local order and dynamics2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, no 8, p. 4032-4038Article in journal (Refereed)
    Abstract [en]

    We demonstrate the use of new two-dimensional nuclear magnetic resonance experiments in the examination of local diffusional anisotropy under conditions of global isotropy. The methods, known as diffusion-diffusion correlation spectroscopy and diffusion exchange spectroscopy, employ successive pairs of magnetic field gradient pulses, with signal analysis using two-dimensional inverse Laplace transformation. Diffusional anisotropy is measured for water molecules in a polydomain lamellar phase lyotropic liquid crystal, 40 wt % nonionic surfactant C10E3 (C10H21O(CH2CH2O)(6)H) in H2O.

  • 9.
    Chaudhary, Himanshu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ferreira Fernandes, Ricardo M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, s/n, Porto, P-4169-007, Portugal.
    Gowda, Vasantha
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Claessens, Mirelle M. A. E.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Lendel, Christofer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 556, p. 172-179Article in journal (Refereed)
    Abstract [en]

    The rich pool of protein conformations combined with the dimensions and properties of carbon nanotubes create new possibilities in functional materials and nanomedicine. Here, the intrinsically disordered protein α-synuclein is explored as a dispersant of single-walled carbon nanotubes (SWNTs) in water. We use a range of spectroscopic methods to quantify the amount of dispersed SWNT and to elucidate the binding mode of α-synuclein to SWNT. The dispersion ability of α-synuclein is good even with mild sonication and the obtained dispersion is very stable over time. The whole polypeptide chain is involved in the interaction accompanied by a fraction of the chain changing into a helical structure upon binding. Similar to other dispersants, we observe that only a small fraction (15–20%) of α-synuclein is adsorbed on the SWNT surface with an average residence time below 10 ms

  • 10.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Terenzi, Camilla
    Wageningen Univ & Res, Wageningen, Netherlands..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Heterogeneous dynamics in cellulose from molecular dynamics simulations2019In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal (Other academic)
  • 11.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Terenzi, Camilla
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of C-13 NMR Relaxation Times and Their Distributions2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 7, p. 2567-2579Article in journal (Refereed)
    Abstract [en]

    Macromolecular dynamics in biological systems, which play a crucial role for biomolecular function and activity at ambient temperature, depend strongly on moisture content. Yet, a generally accepted quantitative model of hydration-dependent phenomena based on local relaxation and diffusive dynamics of both polymer and its adsorbed water is still missing. In this work, atomistic-scale spatial distributions of motional modes are calculated using molecular dynamics simulations of hydrated xyloglucan (XG). These are shown to reproduce experimental hydration-dependent C-13 NMR longitudinal relaxation times (T-1) at room temperature, and relevant features of their broad distributions, which are indicative of locally heterogeneous polymer reorientational dynamics. At low hydration, the self-diffusion behavior of water shows that water molecules are confined to particular locations in the randomly aggregated XG network while the average polymer segmental mobility remains low. Upon increasing water content, the hydration network becomes mobile and fully accessible for individual water molecules, and the motion of hydrated XG segments becomes faster. Yet, the polymer network retains a heterogeneous gel-like structure even at the highest level of hydration. We show that the observed distribution of relaxations times arises from the spatial heterogeneity of chain mobility that in turn is a result of heterogeneous distribution of water-chain and chain chain interactions. Our findings contribute to the picture of hydration-dependent dynamics in other macromolecules such as proteins, DNA, and synthetic polymers, and hold important implications for the mechanical properties of polysaccharide matrixes in plants and plant-based materials.

  • 12.
    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.

  • 13.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Schuleit, Michael
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Polymer Swelling, Drug Mobilization and Drug Recrystallization in Hydrating Solid Dispersion Tablets Studied by Multinuclear NMR Microimaging and Spectroscopy2011In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 8, no 4, p. 1247-1256Article in journal (Refereed)
    Abstract [en]

    Despite the advantages offered by solid dispersions, the marketed products based on this technology are few. The most frequent concern is the stability of the amorphous drug. The state of the drug in solid dispersions is, in general, poorly characterized as the number of characterization techniques available to monitor nanometer-sized drug particles embedded in a matrix are limited. Here we present a combination of localized NMR spectroscopic and NMR imaging techniques which allow in situ monitoring of the state of the drug during tablet disintegration and dissolution. (19)F NMR relaxation is shown to be sensitive to both the crystalline/amorphous state and the size of the model nanoparticles made of the drug substance flutamide. The time course of drug mobilization and recrystallization is detected with spatial resolution within swelling solid dispersion tablets. Comparing results from spatially resolved (19)F, (2)H and (1)H NMR experiments, recrystallization is related to its enabling factors such as local hydration level and local mobility of the polymer matrix. The initially amorphous drug may recrystallize either by nanoparticle coalescence or by ripening of crystalline grains.

  • 14.
    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)
  • 15.
    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.

  • 16.
    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.

  • 17.
    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)
  • 18.
    Dai, Jing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Alaei, Zahra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Plazzotta, Beatrice
    Pedersen, Jan Skov
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Release of Solubilizate from Micelle upon Core Freezing2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 45, p. 10353-10363Article in journal (Refereed)
    Abstract [en]

    By combining NMR (yielding H-1 chemical shift, spin relaxation, and self-diffusion data) and small-angle X-ray scattering experiments, we investigate the complex temperature dependence of the molecular and aggregate states in aqueous solutions of the surfactant [CH3(CH2)(17)(OCH2CH2)(20)OH], abbreviated as C18E20, and.hexamethyldisiloxane, HMDSO. The latter molecule serves as a model for hydrophobic solubilizates. Previously, the pure micellar solution was demonstrated to exhibit core freezing at approximately 7-8 degrees C. At room temperature, we find that HMDSO solubilizes at a volume fraction of approximately 10% in the core of the C18E20 micelles, which consists of molten and thereby highly mobile alkyl chains. Upon lowering the temperature, core freezing is found, just like in pure micelles, but at a temperature shifted significantly to 3 degrees C. The frozen cores contain immobile alkyl chains and exhibit a higher density but are essentially devoid (volume fraction below 1%) of the solubilizate. The latter molecules are released, first gradually and then rather steeply, from the core in the temperature range that is roughly delimited by the two core freezing temperatures, one for pure micelles and one for micelles with solubilizates. The release behavior of systems with different initial HMDSO loading follows the same master curve. This feature is rationalized in terms of loading capacity being strongly temperature dependent: upon lowering the temperature, release commences once the loading capacity descends below the actual solubilizate content. The sharp release curves and the actual release mechanism with its molecular features shown in rich detail have some bearing on a diverse class of possible applications.

  • 19.
    Dai, Jing
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. 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 Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    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.

  • 20.
    Dai, Jing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Regev, Oren
    Marques, Eduardo
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    The dispersion process of carbon nanotubes sonicated in aqueous solutions of a dispersantManuscript (preprint) (Other academic)
    Abstract [en]

    Single-walled carbon nanotube (SWNT) dispersions are created by sonicating pristine SWNT powders added to aqueous solutions of the dispersant block copolymer Pluronic F127. In those dispersions, the amount of the dispersed SWNT is determined by the combination of TGA and UV-Vis methods, while the dispersant concentration is estimated by 1H NMR spectroscopy. In addition, the amount of dispersant adsorbed at the SWNT surface is obtained by 1H NMR diffusion experiments. A part of the dispersant is taken up by non-dispersed and precipitated particles. Dispersion curves recording the amount of the dispersed SWNT as a function of either the initial dispersant concentration or the final dispersant concentration are obtained at different initial SWNT loadings and sonication times. The results show in detail the way the original SWNT particles are divided into smaller and smaller sizes thereby increasing the available SWNT surface to be covered by dispersant. Centrifugation sets the size-threshold above which SWNT particles are retained in the dispersion which determined the SWNT content as a function of sonication time.

  • 21. Dvinskikh, S. V.
    et al.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid crystals2006In: Russian Chemical Reviews, ISSN 0036-021X, E-ISSN 1468-4837, Vol. 75, no 6, p. 497-506Article in journal (Refereed)
    Abstract [en]

    The experimental NMR techniques for studies of translational diffusion in anisotropic systems and the results of their applications to thermotropic liquid crystals arc reviewed. The main approaches to the theoretical description and computer simulations of diffusion are discussed. The experimental results are compared with computations. The bibliography includes 194 references.

  • 22.
    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.

  • 23.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Anisotropic self-diffusion in nematic, smectic-A, and reentrant nematic phases2012In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 86, no 3, p. 031704-Article in journal (Refereed)
    Abstract [en]

    The nature of the reentrant nematic phase has been actively investigated both experimentally and theoretically during the past few decades. Most studies concluded that, as concerning molecular dynamics, a reentrant nematic phase is essentially analogous to a conventional nematic one. Recent computer simulations [Mazza et al., Phys. Rev. Lett. 105, 227802 (2010)], however, predicted molecular translational self-diffusion along the phase director that was dominated by a collective transport mode and was, relative to that observed in a conventional nematic phase, enhanced by an order of magnitude. In the present work, the principal components of the diffusion tensor in a reentrant nematic phase are determined experimentally and compared to those in conventional nematic and smectic-A phases. We find that the temperature dependence of the translational diffusion in the two nematic phases, within experimental error, follows a uniform trend and can be adequately described in terms of available diffusion models in nematics. Hence, we find no evidence for enhanced diffusion but confirm instead the similarity of conventional and reentrant nematic phases with respect to molecular translational dynamics.

  • 24.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Anisotropic self-diffusion in the nematic phase of a thermotropic liquid crystal by H-1-spin-echo nuclear magnetic resonance2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, no 4, p. 1946-1950Article in journal (Refereed)
    Abstract [en]

    The orientation-dependent molecular diffusion in the nematic liquid crystal 4-pentyl-4'-cyanobiphenyl is measured to high accuracy. The applied nuclear magnetic resonance method combines multiple-pulse homonuclear dipolar decoupling with pulsed-field-gradient stimulated echo and slice selection. The obtained temperature dependencies of the principal diffusion coefficients are not described by a simple Arrhenius relationship but reflect the decrease of the molecular orientational order close to the nematic-to-isotropic phase transition. The geometric average of the principal diffusion coefficients is continuous with the diffusion coefficient in the isotropic phase. The results are best described in terms of the affine transformation model of diffusion in hard-ellipsoid nematics.

  • 25.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Combining PGSE NMR with homonuclear dipolar decoupling2000In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 144, no 1, p. 142-149Article in journal (Refereed)
    Abstract [en]

    A new robust approach for combining multiple-pulse homonuclear decoupling and ROSE NMR is introduced for accurately measuring molecular diffusion coefficients in systems with nonvanishing static homonuclear dipolar couplings. Homonuclear decoupling suppresses dipolar dephasing during the gradient pulses but its efficiency and scaling factor for the effective gradient vary across the sample because of the large variation of the frequency offset caused by the gradient. The resulting artifacts are reduced by introducing a slice selection scheme. The method is demonstrated by F-19 PGSE NMR experiments in a lyotropic liquid crystal.

  • 26.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Cross-relaxation effects in stimulated-echo-type PGSE NMR experiments by bipolar and monopolar gradient pulses2000In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 146, no 2, p. 283-289Article in journal (Refereed)
    Abstract [en]

    Exchange of longitudinal spin polarization by dipolar cross relaxation between nonequivalent spins results in a modulation of the stimulated echo signal on increasing the encoding/decoding delays and in a multiexponential decap on increasing the diffusion time. These artifacts are suppressed by 180 degrees pulses inserted in the middle of the gradient encoding/decoding periods. The efficiency of the gradient encoding is preserved if bipolar gradient pulses are used instead of monopolar pulses. The behavior of the different pulse sequences is demonstrated by F-19 PGSE NMR experiments in a lyotropic liquid crystal in both isotropic micellar and oriented nematic phases.

  • 27.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Domain structure in an unoriented lamellar lyotropic liquid crystal phase studied by H-2 NMR2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 21, p. 6455-6460Article in journal (Refereed)
    Abstract [en]

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

  • 28.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Measurement of the principal values of the anisotropic diffusion tensor in an unoriented sample by exploiting the chemical shift anisotropy: F-19 PGSE NMR with homonuclear decoupling2001In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 148, no 1, p. 73-77Article in journal (Refereed)
    Abstract [en]

    NMR methods (S. V. Dvinskikh et al. J. Magn. Reson. 142, 102-110 (2000) and S. V. Dvinskikh and I. Furo, J. Magn. Reson. 144, 142-149 (2000)) that combine PGSE with dipolar decoupling are extended to polycrystalline solids and unoriented liquid crystals. Decoupling suppresses dipolar dephasing not only during the gradient pulses but also under signal acquisition so that the detected spectral shape is dominated by the chemical shift tensor of the selected nucleus. The decay of the spectral intensity at different positions in the powder spectrum provides the diffusion coefficient in sample regions with their crystal axes oriented differently with respect to the direction of the field gradient. Hence, one can obtain the principal values of the diffusion tensor. The method is demonstrated by F-19 PGSE NMR with homonuclear decoupling in a lyotropic lamellar liquid crystal.

  • 29. Dvinskikh, Sergey V.
    et al.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid crystals2006In: Uspehi himii, ISSN 0042-1308, E-ISSN 1817-5651, Vol. 75, no 6, p. 557-568Article, review/survey (Refereed)
  • 30.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Order parameter profile of perfluorinated chains in a lamellar phase2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 6, p. 2962-2967Article in journal (Refereed)
    Abstract [en]

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

  • 31. Dvinskikh, Sergey V.
    et al.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Sandstrom, D.
    Maliniak, A.
    Zimmermann, H.
    Deuterium stimulated-echo-type PGSE NMR experiments for measuring diffusion: Application to a liquid crystal2001In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 153, no 1, p. 83-91Article in journal (Refereed)
    Abstract [en]

    The accessibility of molecular self-diffusion coefficients in anisotropic materials, such as liquid crystals or solids, by stimulated-echo-type H-2 PGSE NMR is examined. The amplitude and phase modulation of the signal in the stimulated-echo-type sequence by the static quadrupole coupling during the encoding/decoding delays is suppressed by adjusting the pulse flip angles and the phase cycle. For nuclei that experience both nonnegligible quadrupole and dipole couplings, the application of magic echoes during the evolution periods of stimulated echo is demonstrated as a helpful technique in the case of slow diffusion. These findings are demonstrated by experimental results in the thermotropic liquid crystal of partially deuterated 8CB. The obtained diffusion coefficients are also compared to data obtained by a H-1 homonuclear-decoupling-type PGSE NMR method in the same material.

  • 32. Dvinskikh, Sergey V.
    et al.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Zimmermann, H.
    Maliniak, A.
    Anisotropic self-diffusion in thermotropic liquid crystals studied by H-1 and H-2 pulse-field-gradient spin-echo NMR2002In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 65, no 6Article in journal (Refereed)
    Abstract [en]

    The molecular self-diffusion coefficients in nematic and smectic-A thermotropic liquid crystals are measured using stimulated-echo-type H-2 and H-1 pulse-field-gradient spin-echo nuclear magnetic resonance (PGSE NMR) combined with multiple-pulse dipolar decoupling and slice selection. The temperature dependence of the principal components of the diffusion tensor in the nematic phase follows a simple Arrhenius relationship except in the region of nematic-isotropic phase transition where it reflects, merely, the decrease of the molecular orientational order. The average of the principal diffusion coefficients in the isotropic-nematic phase transition region is close to the diffusion coefficient in the isotropic phase. At the nematic-smectic-A phase transition the diffusion coefficients change continuously. The results in nematic phase are best described in terms of the affine transformation model for diffusion in nematics formed by hard ellipsoids. In the smectic-A phase the data are interpreted using a modified model for diffusion in presence of a periodic potential along the director.

  • 33. Dvinskikh, Sergey V.
    et al.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Zimmermann, H.
    Maliniak, A.
    Molecular self-diffusion in a columnar liquid crystalline phase determined by deuterium NMR2002In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 65, no 5Article in journal (Refereed)
    Abstract [en]

    We report translational-diffusion coefficients in a columnar phase of a discotic liquid crystal formed by a triphenylpne-based compound. The experiments were performed using H-2 stimulated-echo-type pulsed-field-gradient spin-echo NMR applied to a chain-deuterated sample. The diffusion coefficients were found in the range of 1 x 10(-14)-4 x 10(-14) m(2)/s, three orders of magnitude lower than in the isotopic phase of the same compound. This, together with the high activation energy obtained in, columnar phase, indicates that the diffusion is dominated by solidlike jump processes.

  • 34.
    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)
  • 35.
    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.

  • 36.
    Dvinskikh, Sergey V.
    et al.
    KTH, Superseded Departments, Chemistry.
    Sitnikov, R.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    C-13 PGSE NMR experiment with heteronuclear dipolar decoupling to measure diffusion in liquid crystals and solids2000In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 142, no 1, p. 102-110Article in journal (Refereed)
    Abstract [en]

    A new PGSE NMR experiment, designed to measure molecular diffusion coefficients in systems with nonvanishing static dipolar coupling, is described. The fast static dipolar dephasing of the single-quantum C-13 coherences is removed by multiple-pulse heteronuclear decoupling. The resulting slow dephasing of the C-13 coherences allows for inserting appropriate gradient pulses into the pulse sequence. The presence of the large magnetic field gradient reduces the efficiency of the decoupling sequences which is compensated for by introducing a scheme of sequential slice selection across the sample. The method is demonstrated by F-19-decoupled C-13 PGSE NMR experiments in a lyotropic nematic and lamellar liquid crystal,

  • 37.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Szutkowski, Kosma
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    MRI profiles over very wide concentration ranges: Application to swelling of a bentonite clay2009In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 198, no 2, p. 146-150Article in journal (Refereed)
    Abstract [en]

    In MRI investigation of soils, clays, and rocks, mainly mobile water is detected, similarly to that in biological and medical samples. However, the spin relaxation properties of water in these materials and/or low water concentration may make it difficult to use standard MRI approaches. Despite these limitations, one can combine MRI techniques developed for solid and liquid states and use independent information on relaxation properties of water, interacting with the material of interest, to obtain true images of both water and material content. We present procedures for obtaining such true density maps and demonstrate their use for studying the swelling of bentonite clay by water. A constant time imaging protocol provides 1D mapping of the clay distribution in regions with clay concentration above 10 vol%. T-1 relaxation time imaging is employed to monitor the clay content down to 10(-3) vol%. Data provided by those two approaches are in good agreement in the overlapping range of concentrations. Covering five orders of magnitude of clay concentration, swelling of sodium-exchanged bentonite clays from pre-compacted pellets into a gel phase is followed in detail.

  • 38.
    Elwinger, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. GE Healthcare Biosci AB.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    C-13 SPE MAS measurement of ligand concentration in compressible chromatographic beads2015In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 53, no 8, p. 572-577Article in journal (Refereed)
    Abstract [en]

    A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, C-13 single pulse excitation magic angle spinning NMR experiment with broadband H-1 decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed. Copyright (C) 2015 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.

  • 39.
    Elwinger, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. GE Healthcare Biosci AB, Sweden.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    High-resolution magic angle spinning H-1 NMR measurement of ligand concentration in solvent-saturated chromatographic beads2016In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 54, no 4, p. 291-297Article in journal (Refereed)
    Abstract [en]

    A method based on H-1 high-resolution magic angle spinning NMR has been developed for measuring concentration accurately in heterogeneous materials like that of ligands in chromatography media. Ligand concentration is obtained by relating the peak integrals for a butyl ligand in the spectrum of a water-saturated chromatography medium to the integral of the added internal reference. The method is fast, with capacity of 10min total sample preparation and analysis time per sample; precise, with a reproducibility expressed as 1.7% relative standard deviation; and accurate, as indicated by the excellent agreement of derived concentration with that obtained previously by C-13 single-pulse excitation MAS NMR. The effects of radiofrequency field inhomogeneity, spin rate, temperature increase due to spinning, and distribution and re-distribution of medium and reference solvent both inside the rotor during spinning and between bulk solvent and pore space are discussed in detail.

  • 40.
    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.

  • 41.
    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), Chemistry, Applied Physical Chemistry.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Diffusive transport in pores. Tortuosity and molecular interaction with the pore wallManuscript (preprint) (Other academic)
    Abstract [en]

    The self-diffusion of neat water, dimethylsulfoxide (DMSO), octanol and the molecular components in a water-DMSO solution were measured by 1H and 2H NMR diffusion experiments for those fluids imbibed into Controlled Pore Glasses (CPG). Their highly interconnected structure is scaled by pore size and shows the some pore topology independently of the size. The nominal pore diameter of the explored CPGs varied from 7.5 nm to 72.9 nm. Hence, the ∼μm mean-square diffusional displacement during the explored diffusion times was much larger than the individual pore size. Great care was taken to establish the actual pore volumes of the CPGs. In addition, 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 sizes for the larger pores and becomes larger towards 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. The interaction with the pore wall is not just simple steric one but must in part be dependent on the specific features of the molecules explored here.

  • 42.
    Elwinger, Fredrik
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. GE Healthcare Biosci AB, Bjorkgatan 31, SE-75184 Uppsala, Sweden..
    Wernersson, Jonny
    GE Healthcare Biosci AB, Bjorkgatan 31, SE-75184 Uppsala, Sweden..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. GE Healthcare Biosci AB, Bjorkgatan 31, SE-75184 Uppsala, Sweden..
    Quantifying Size Exclusion by Diffusion NMR: A Versatile Method to Measure Pore Access and Pore Size2018In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 19, p. 11431-11438Article in journal (Refereed)
    Abstract [en]

    Size-exclusion quantification NMR spectroscopy (SEQNMR) is introduced for measuring equilibrium distribution coefficients, K-eq, in porous media. The porous medium is equilibrated with a polydisperse polymer solution. The original bulk polymer solution and the polymer solution after equilibration but in the absence of the porous medium are analyzed by NMR diffusion experiments. The joint evaluation of the two diffusion attenuation curves under suitable constraints provides the extent by which polymer fractions of particular size were depleted from the solution by pore access. This procedure yields K-eq versus polymer probe size, the selectivity curve that in turn can provide the pore size and its distribution. Simulations probe the performance of the method that is demonstrated experimentally in chromatographic media using dextran polymers. SEQ-NMR and inverse size- exclusion chromatography (ISEC) yield selectivity curves that virtually coincide. Crucial advantages with SEQ-NMR, such as versatility with regard to both the polymer used and porous system explored, high speed, potential for automation, and small required sample volume, are discussed.

  • 43.
    Elwinger, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wernersson, Jonny
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    SEQ-NMR: A new tool for measuring distribution coefficients and pore size in chromatography mediaManuscript (preprint) (Other academic)
    Abstract [en]

    We present a new method, SEQ-NMR (size-exclusion quantification NMR spectroscopy) for measuring equilibrium distribution coefficients, Keq, in chromatography media. The same method is also generally applicable to measure pore sizes in any porous media. Keq versus probe size, the selectivity curve, is obtained by equilibrating a chromatographic medium with a solution of polymers with a broad size distribution. The solution before and after equilibration is analyzed with NMR diffusion experiments. The joint least-squares analysis of the two diffusion attenuation curves under suitable constraints provides the extent by which the different polymer fractions are diluted upon equilibration that in turn yields the selectivity curve. The relation of the applied procedure to Inverse Laplace transformation is clarified. Simulations probe the performance of the method, in particular with respect to signal-to-noise ratio (SNR) and other parameters used in the data inversion process. The method is demonstrated experimentally using dextran polymers and the chromatographic medium Sephacryl™ S-200 High Resolution for which it yields, within a cylindrical pore model, 6.9 nm for the average hydrated pore size. Comparison is made to the analysis of the same system with inverse size-exclusion chromatography (ISEC). Advantages of the method, primarily that in speed, potential for automation, and small sample size, are discussed.

  • 44.
    Evenäs, L.
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Valiullin, Rustem
    KTH, Superseded Departments, Chemistry.
    Adsorption Isotherm and Aggregate Properties of Fluorosurfactants on Alumina Measured by 19F NMR2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 21, p. 8096-8101Article in journal (Refereed)
    Abstract [en]

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

  • 45.
    Fang, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Different Binding Mechanisms of Cations and Anions to Proteins: Electrophoretic NMR Studies in Bovine Serum AlbuminManuscript (preprint) (Other academic)
  • 46.
    Fang, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Weak Anion Binding to Poly(N-isopropylacrylamide): A Quantitative Study by Electrophoretic NMRManuscript (preprint) (Other academic)
  • 47.
    Fang, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Complexing Cations by Poly(ethylene oxide): Binding Site and Binding Mode2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 9, p. 2179-2188Article in journal (Refereed)
    Abstract [en]

    The binding of K+ and Ba2+ cations to short poly(ethylene oxide) (PEO) chains with ca. 4-25 monomeric units in methanol was studied by determining the effective charge of the polymer through a combination of electrophoretic NMR and diffusion NMR experiments. These cations were previously found to bind to long PEO chains in a similar strong manner. In addition, H-1 chemical shift and longitudinal spin relaxation rate changes upon binding were quantified. For both systems, binding was stronger for the short chains than that for the longer chains, which is attributed mainly to interactions between bound ions. For K+ ions, the equilibrium binding constant of a cation to a binding site was measured. For both cations, the binding site was estimated to consist of ca. six monomeric units that coordinated with the respective ions. For the systems with barium, a significant fraction of the bound ions are (BaAnion)(+) ion pairs. This leads to a strong anion effect in the effective charge of the oligomers acquired upon barium ion binding. For K+, the coordinating oligomer segment remains rather mobile and individual oligomers exchange rapidly (<<s) between their free and ion-complexing states. In contrast, segmental dynamics slows significantly for the oligomer section that coordinates with the barium species, and for individual oligomers, binding and nonbinding sections do not exchange on the time scale of seconds. Hence, oligomers also exchange slowly (>s) between their free and barium complexing states.

  • 48.
    Fang, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Complexing Cations by Polyethylene Oxide. Binding Site and Binding Mode2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207Article in journal (Refereed)
  • 49.
    Fang, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Yushmanov, Pavel V.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Assessing the potential of 2D electrophoretic mobility spectroscopy (2D MOSY) for analytical applications2017In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 55, no 6, p. 584-588Article in journal (Refereed)
    Abstract [en]

    Electrophoretic displacement of charged entity phase modulates the spectrum acquired in electrophoretic NMR experiments, and this modulation can be presented via 2D FT as 2D mobility spectroscopy (MOSY) spectra. We compare in various mixed solutions the chemical selectivity provided by 2D MOSY spectra with that provided by 2D diffusion-ordered spectroscopy (DOSY) spectra and demonstrate, under the conditions explored, a superior performance of the former method. 2D MOSY compares also favourably with closely related LC-NMR methods. The shape of 2D MOSY spectra in complex mixtures is strongly modulated by the pH of the sample, a feature that has potential for areas such as in drug discovery and metabolomics.

  • 50.
    Fernandes, Ricardo M.F.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, s/n, Porto, Portugal.
    Abreu, Bárbara
    Claro, Bárbara
    Buzaglo, Matat
    Regev, Oren
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Marques, Eduardo
    Dispersing Carbon Nanotubes with Ionic Surfactants under Controlled Conditions: Comparisons and Insight2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 40, p. 10955-10965Article in journal (Refereed)
    Abstract [en]

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

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