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  • 1.
    Giesecke, Marianne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fang, Yuan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Stilbs, Peter
    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.
    Binding of monovalent and multivalent metal cations to polyethylene oxide in methanol probed by electrophoretic and diffusion NMR2016In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, no 39, p. 10358-10366Article in journal (Refereed)
    Abstract [en]

    Complex formation in methanol between monodisperse polyethylene oxide (PEO) and a large set of cations was studied by measuring the effective charge acquired by PEO upon complexation. Quantitative data were obtained at a low ionic strength of 2 mM (for some salts, also between 0.5 and 6 mM) by a combination of diffusion nuclear magnetic resonance (NMR) and electrophoretic NMR experiments. For strongly complexing cations, the magnitude of the acquired effective charge was on the order of 1 cation per 100 monomer units. For monovalent cations, the relative strength of binding varies as Na+ < K+ ≈ Rb+ ≈ Cs+, whereas Li+ exhibited no significant binding. All polyvalent cations bind very weakly, except for Ba2+ that exhibited strong binding. Anions do not bind, as is shown by the lack of response to the chemical nature of anionic species (perchlorate, iodide, or acetate). Diffusion experiments directly show that the acetate anion with monovalent cations does not associate with PEO. Considering all cations, we find that the observed binding does not follow any Hofmeister order. Instead, binding occurs below a critical surface charge density, which indicates that the degree of complexation is defined by the solvation shell. A large solvation shell prevents the binding of most multivalent ions.

  • 2.
    Giesecke, Marianne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Meriguet, Guillaume
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fang, Yuan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Stilbs, Peter
    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.
    Ion association in aqueous and non-aqueous solutions probed by diffusion and electrophoretic NMR2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 5, p. 3402-3408Article in journal (Refereed)
    Abstract [en]

    The results of diffusion and electrophoretic NMR (eNMR) measurements are reported for a series of tetramethylammonium (TMA) electrolytes (with sulphate, fluoride, acetate, chloride, bromide, nitrate, iodide and perchlorate as anions) in deuterated solvents such as water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol. In addition, similar data are presented for aqueous solutions of tetraalkylammonium salts with increasing alkyl chain length. The combination of diffusion NMR and eNMR yields the effective charge for the TMA cation. Relative to the nominal charge of z(nom) = 1 of TMA, the effective charge in the different solvents is found to be progressively smaller in the order water > DMSO > methanol > acetonitrile > ethanol. A part of this observed trend is ascribed to regular ion-ion interactions incorporated in the Onsager limiting law. Indeed, in solvents with high dielectric constants such as water, DMSO and methanol, the Onsager limiting law describes well the observations for all tetraalkylammonium ions. For ethanol and acetonitrile, there is a significant difference between the experimental data and the expected limiting-law behavior that is attributed to ion association (ion pairing) not taken into consideration by the Onsager limiting law.

  • 3.
    Giesecke, Marianne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Mériguet, Guillaume
    Sorbonne Universités, UPMC Université Pierre et Marie Curie Paris 06 and CNRS.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Stilbs, Peter
    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.
    Ion association in aqueous and non-aqueous solutions probed by diffusion and electrophoretic NMRManuscript (preprint) (Other academic)
  • 4.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Molecular Interactions Studied by Electrophoretic and Diffusion NMR2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Even though electrophoretic NMR (eNMR) experiments may provide unique chemical information and have been performed for three decades, the technique is still rarely applied, mainly because several experimental sources of artifacts have to be controlled to achieve accurate results. In this thesis, new experimental setups and protocols for accurate and precise eNMR experiments are presented. These include a novel eNMR sample cell, a radiofrequency filter and methods to suppress bulk flow effects. These developments improved the signal-to-noise ratio by roughly an order of magnitude compared to the U-tube setup previously used for eNMR. Convection-compensated pulse sequences in combination with a phase correction method were found to efficiently suppress bulk flow effects in the experiments and greatly increase experimental accuracy.

    These experimental setups and protocols were applied to probe association of ions and molecules in solution. It is particularly illustrated that the combination of diffusion and eNMR has great potential to provide quantitative results on ionic and molecular association in a variety of systems.

    The extent to which ionic surfactants associate with uncharged cyclodextrin probed by eNMR yielded very similar results to those obtained by diffusion NMR experiments. Complexation of a large set of small mono- and polyvalent metal cations to poly(ethylene oxide) was quantified by estimating the effective charge of the polymer through combined diffusion and eNMR information. Significant association was found for cations that have a surface charge density below a critical value.

    Ion pairing between tetramethylammonium cations and a series of anions in several solvents was also probed by diffusion NMR and eNMR experiments. For the monovalent anions in ethanol and ethanol-water mixture a dependence on ionic size was demonstrated. In water, dimethylsulfoxide, and methanol no such trend and very little pairing was observed. In acetonitrile, a different pattern was seen that did not correlate well with any single ionic parameter.

    An experimental cell and procedures for electrokinetic studies of solvated proton-conducting polymer materials is also presented. Electro-osmotic flow and diffusion were studied for each molecular component in water-methanol mixtures that swell Nafion membranes.

  • 5.
    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.

  • 6.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Yushmanov, Pavel V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Sensitive and robust electrophoretic NMR: Instrumentation and experiments2008In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 192, no 1, p. 69-77Article in journal (Refereed)
    Abstract [en]

    Although simple as a concept, electrophoretic NMR (eNMR) has so far failed to find wider application. Problems encountered are mainly due to disturbing and partly irreproducible convection-like bulk flow effects from both electro-osmosis and thermal convection. Additionally, bubble formation at the electrodes and rf noise pickup has constrained the typical sample geometry to U-tube-like arrangements with a small filling factor and a low resulting NMR sensitivity. Furthermore, the sign of the electrophoretic mobility cancels out in U-tube geometries. We present here a new electrophoretic sample cell based on a vertically placed conventional NMR sample tube with bubble-suppressing palladium metal as electrode material. A suitable radiofrequency filter design prevents noise pickup by the NMR sample coil from the high-voltage leads which extend into the sensitive sample volume. Hence, the obtained signal-to-noise ratio of this cell is one order of magnitude higher than that of our previous U-tube cells. Permitted by the retention of the sign of the displacement-related signal phase in the new cell design, an experimental approach is described where bulk flow effects by electro-osmosis and/or thermal convection are compensated through parallel monitoring of a reference signal from a non-charged species in the sample. This approach, together with a CPMG-like pulse train scheme provides a superior first-order cancellation of non-electrophoretic bulk flow effects.

  • 7.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Ion Pairing in Various Solvents Probed by Electrophoretic and Diffusion NMRManuscript (preprint) (Other academic)
  • 8.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Vernersson, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Thyboll Pettersson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Dvinskikh, Sergey V.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Electrokinetic transport of water and methanol in Nafion membranes as observed by NMR spectroscopy2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 10, p. 3542-3549Article in journal (Refereed)
    Abstract [en]
    Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nation 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant. (C) 2010 Elsevier Ltd. All rights reserved.
  • 9.
    Hallberg, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Weise, Christoph F.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Yushmanov, Pavel V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Thyboll Pettersson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Molecular complexation and binding studied by electrophoretic NMR spectroscopy2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 24, p. 7550-+Article in journal (Refereed)
    Abstract [en]

    Electrophoretic mobilities obtained on a molecularly selective manner by electrophoretic NMR can be used to proved a quantitative characterization of the composition and stoichiometry of molecular complexes. This is demonstrated in complexes formed by uncharge cyclodextrins which attain an electrophoretic mobility upon inclusion of charged surfactants.

  • 10.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Nyman, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Quantifying mass transport during polarization in a Li Ion battery electrolyte by in situ 7Li NMR imaging2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 36, p. 14654-14657Article in journal (Refereed)
    Abstract [en]

    Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ 7Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li + transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.

  • 11.
    Mira, Isabel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Persson, Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Binding of surfactants to amylose in aqueous solution: Part II Sodium dodecyl and hexadecyl sulphateManuscript (Other academic)
  • 12. Price, William S.
    et al.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    A PGSE diffusion and electrophoretic NMR study of Cs+ and Na+ dynamics in aqueous crown ether systems2007In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 45, no 2, p. 152-156Article in journal (Refereed)
    Abstract [en]

    Multinuclear pulsed gradient spin-echo (PGSE) NMR diffusion and linewidth measurements were used to probe binding and transport in aqueous Na+-15-crown-5, Na+-18-crown-6, Cs+-15-crown-5 and Cs+-18-crown-6 systems. Since direct PGSE observation of many alkali cations is precluded by either low inherent sensitivity or rapid relaxation (or both), the feasibility of proton-detected electrophoretic NMR (ENMR) measurements to complement PGSE data was investigated. ENMR measurements were performed on aqueous Cs+-, Li+-, Na+-, K+-, and Rb+-18-crown-6 systems. The data analysis is based on a two-site binding model and its corresponding association constants. Cs+ was found to bind considerably more tightly to 18-crown-6 (K = 8 m(-1)) than to 15-crown-5 (K similar to 2 m(-1)), whereas Na+ had almost equal affinity (K similar to 4.5 m(-1)) for 15-crown-5 and 18-crown-6. The difficulties encountered in analysing the NMR parameters, methodological limitations and the implied need for more complicated binding models are discussed.

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