Change search
Refine search result
1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    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    KTH, Superseded Departments, Chemistry.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    KTH, Superseded Departments, Chemistry.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    KTH, Superseded Departments, Chemistry.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    KTH, Superseded Departments, Chemistry.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.

  • 2. Evertsson, H.
    et al.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Lindblom, G.
    Engstrom, S.
    NMR self diffusion measurements of the monooleoylglycerol/poly ethylene glycol/water L-3 phase2002In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 26, no 02-jan, p. 21-29Article in journal (Refereed)
    Abstract [en]

    The monooleoylglycerol (GMO)/poly ethylene oxide (PEG)/water sponge (L-3) phase has been investigated by pulsed-gradient spin-echo NMR self-diffusion. The data allow the L-3 phase to be modeled as a bicontinuous system with respect to the lipid and water domains. It is proposed by using the interconnected rod model that the solvent PEG mainly distributes to the water domain, but has a higher weight fraction partition to the lipid head groups of the local GMO bilayer than water. The data is put in relation to earlier self-diffusion measurements on the binary GMO/water cubic phase, as well as earlier conductivity and X-ray diffraction measurements on the very same L-3 phase.

  • 3.
    Furo, Istvan
    et al.
    KTH, Superseded Departments, Chemistry.
    Iliopoulos, I.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Structure and dynamics of associative water-soluble polymer aggregates as seen by F-19 NMR spectroscopy2000In: Journal of Physical Chemistry B, ISSN 1089-5647, Vol. 104, no 3, p. 485-494Article in journal (Refereed)
    Abstract [en]

    The microstructure and the molecular dynamics of aqueous solutions of an associative polymer (AP), consisting of a polyelectrolyte backbone and attached perfluorocarbon side chains, have been studied by F-19 NMR. The spectral shape and the distributions of the molecular self-diffusion coefficient and of the transverse and the longitudinal relaxation rates along the F-19 spectrum have been measured, together with the magnetic field dependence of the relaxation rates. A comprehensive analysis yields that the spectral lines are broadened by a chemical shift distribution that reflects the distribution of the average hydrophobicity of the environment within the aggregates in which the perfluorocarbon side chains reside. A fraction of the AP chains remain unaggregated with all their side chains immersed in water. As shown by the NMR data, the exchange time of the APs among different states of aggregation is long, > 1 s, while the exchange time of individual side chains among aqueous and hydrophobic environments within the same aggregate is fast, approximately microseconds. Among the aggregates, there is a considerable heterogeneity in the average hydrophobicity. Some implications of the F-19 NMR findings for H-1 NMR studies of APs with hydrocarbon side chains are discussed.

  • 4. Gavelin, P.
    et al.
    Jannasch, P.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry.
    Pettersson, E.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Topgaard, D.
    Soderman, O.
    Amphiphilic polymer gel electrolytes. 4. Ion transport and dynamics as studied by multinuclear pulsed field gradient spin-echo NMR2002In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 35, no 13, p. 5097-5104Article in journal (Refereed)
    Abstract [en]

    The transport dynamics in gel electrolytes based on amphiphilic polymers was found to be faster than in gel electrolytes based on corresponding nonamphiphilic polymers. The amphiphilic polymer studied was a polymethacrylate grafted with fluorocarbon and (EO)(9) side chains, and the nonamphiphilic one was a polymethacrylate carrying only (EO)(9) side chains. Self-diffusion coefficients of gel electrolytes based on the two polymers with different contents of 1 M lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) salt in gamma-butyrolactone were determined by H-1, F-19, and Li-7 pulsed field gradient spin-echo NMR spectroscopy. The polymer self-diffusion coefficients showed that the amphiphilic polymer molecules diffused faster than the nonamphiphilic ones and seemed more intramolecularly aggregated than intermolecularly. At electrolyte contents above 43 wt %, the ion conductivity of the amphiphilic polymer gel electrolytes was higher than for the corresponding gel based on the nonamphiphilic polymer under identical conditions, as measured by impedance spectroscopy. Moreover, the lithium ion diffusion coefficient in the amphiphilic gel electrolytes was found to be significantly higher than that for corresponding gels based on the nonamphiphilic polymer, The higher ethylene oxide content of the nonamphiphilic polymer decreased the mobility of the lithium ions due to cooperative coordination of lithium ions by ether oxygens in comparison with gamma-BL. The TFSI anion diffusion was however approximately the same in the two gel systems. Consequently, the apparent lithium transference number (taudivided by) of the amphiphilic gels was higher by almost a factor of 3 as compared to that of the gels based on the nonamphiphilic polymer. A splitting of the TFSI signal in the F-19 NMR spectra suggested that the TFSI anions in the amphiphilic polymer gels were partly present in a solvent-rich environment and partly associated with the aggregates formed by the fluorinated side chains. This kind of splitting was not observed in the spectra of the gels based on the nonamphiphilic polymer. The association of TFSI anions to the aggregated fluorinated side chains may thus also play a role in increasing the value of taudivided by for the amphiphilic polymer gels.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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)
  • 8. Griffiths, P. C.
    et al.
    Cheung, A. Y. F.
    Farley, C.
    Paul, A.
    Heenan, R. K.
    King, S. M.
    Pettersson, Erik
    KTH, Superseded Departments, Chemistry.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Ranganathan, R.
    Small-angle neutron scattering, electron paramagnetic resonance, electrophoretic NMR, and time-resolved fluorescence quenching studies of sodium dodecyl sulfate and tetra(ethylene oxide) dodecyl ether mixed surfactant micelles2004In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, no 4, p. 1351-1356Article in journal (Refereed)
    Abstract [en]

    Small-angle neutron scattering (SANS), time-resolved fluorescence quenching (TRFQ), electrophoretic NMR (ENMR), and electron paramagnetic resonance (EPR) have been used to study mixed micelles formed from the two dodecyl tailed surfactants, sodium dodecyl sulfate (SDS) and tetra(ethylene oxide) dodecyl ether. By combining the TRFQ and EPR techniques, one is essentially able to calculate the SANS data, lending significant weight to the micelle characteristics thus obtained. EPR reports the degree of hydration of the surfactant headgroups; TRFQ, the micelle aggregation number and inter alia the volume of the hydrophobic core. Given the physical dimensions of the surfactant, i.e., alkyl chain length, headgroup volumes, etc., it is then possible to calculate the micelle ellipticity and shell thickness. The ENMR studies provide a rather different but complementary estimate of the ionic character of the micelle. With increasing nonionic content, the aggregation number increases, the micelle becomes more elliptical, and the headgroup region of the micelle becomes less hydrated and significantly more viscous. The degree of sodium counterion dissociation shows an initial small decrease with decreasing SDS micelle mole fraction but subsequently increases, reflecting the interplay between the electrostatic character of the micelle surface and the micelle curvature.

  • 9. Griffiths, P. C.
    et al.
    Paul, A.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Petterson, E.
    Charge on poly(ethylene imine): Comparing electrophoretic NMR measurements and pH Titrations2005In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 38, no 8, p. 3539-3542Article in journal (Refereed)
  • 10. Griffiths, P. C.
    et al.
    Paul, A.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Pettersson, E.
    Electrophoretic nuclear magnetic resonance (ENMR) - A new tool for studying counterion binding in mixed surfactant systems2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, no 20, p. 8605-8607Article in journal (Refereed)
  • 11. Griffiths, P. C.
    et al.
    Pettersson, E.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Cheung, A. Y. F.
    Howe, A. M.
    Pitt, A. R.
    Electrophoretic nuclear magnetic resonance studies of mixed anionic-nonionic surfactant micelles2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 22, p. 7178-7181Article in journal (Refereed)
  • 12. Griffiths, P.
    et al.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    NMR self-diffusion studies of polymeric surfactants2002In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 7, no 04-mar, p. 249-252Article, review/survey (Refereed)
    Abstract [en]

    The ability to visualise and quantify the mobility of particular components in multi-component solutions has had a profound impact on colloid science because the mobility of the species under investigation is determined not only by its chemical structure and size, but also by the physical environment in which it is located. These considerations are of course central to medical imaging (MRI) [1] and the MRI community has greatly benefited from the 'colloidal pioneers'. Thus, measurement and analysis of self-diffusion coefficients using the pulsed-gradient spin-echo nuclear magnetic resonance technique (PGSE-NMR, sometimes referred to as PFG-NMR) permits a non-perturbing in-situ probing of complex structure. This is especially true for colloid science since the characteristic structural dimensions are comparable to the displacements on the NMR timescale.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.
    Binding of Monovalent and Multivalent Metal Cations to Polyethylene Oxide in Methanol Probed by Electrophoretic and Diffusion NMRManuscript (preprint) (Other academic)
  • 16.
    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)
  • 17.
    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.

  • 18. Hedin, Niklas
    et al.
    Ng, Jovice B. S.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Spectral deconvolution of NMR cross polarization data sets2009In: Solid State Nuclear Magnetic Resonance, ISSN 0926-2040, E-ISSN 1527-3326, Vol. 35, no 4, p. 208-213Article in journal (Refereed)
    Abstract [en]

    The COmponent-REsolved (CORE) strategy has been employed, for the first time to solid state NMR spectroscopy. CORE was used to extract two time-dependent spectral components in 24 Si-29(H-1) NMR spectra, recorded on a meso-structured silica material under conditions of cross polarization evolution. No prior assumptions were made about the component bandshapes, which were both found to be skewed to higher chemical shifts. For the silica fragments close to protons this skewness could be rationalized by a distribution of the degree of condensation in the silica network; however, for the other component the non-Gaussian shape was unexpected. We expect that the same strategy could be applied to a range of experiments in solid-state NMR spectroscopy, where spectral distributions or kinetic parameters need to be accurately extracted.

  • 19. Imberg, A.
    et al.
    Evertsson, H.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Kriechbaum, M.
    Engstrom, S.
    On the self-assembly of monoolein in mixtures of water and a polar aprotic solvent2003In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, no 10, p. 2311-2318Article in journal (Refereed)
    Abstract [en]

    Four different one-phase regions: two liquid phases (L and L-3) and two liquid crystalline phases (L-alpha and V-2) of the MO/NMP/water system, were studied by SAXS, PGSE-NMR, and rheology at 20 degreesC. The location of the dramatic increase in solubility of MO, in binary NMP/water mixtures, can be explained in terms of the presence or absence of free water, as a consequence of strong NMP(water)(2) complex formation in the binary NMP/water system. A direct effect of this complexation is aggregate formation at a certain region within the L, phase. The microstructure of the L-3 phase can be modeled as bicontinuous according to the theory of interconnected rods when formation of NMP(water)(2) complexes are taken into consideration. The swelling of the sponge phase correlates well to predicted swelling laws and characteristic lengths, as found in other sponge phases. The cubic phase region of the ternary system consists of at least two different cubic phases, with (Pn3m) over bar and (Ia3d) over bar symmetry of the space group, respectively. At higher NMP contents it seems as if the (Pn3m) over bar symmetry of the space group transforms into (Im3m) over bar.

  • 20.
    Lindh, Erik L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    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.
    Site-resolved H-2 relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra2016In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 268, p. 18-24Article in journal (Refereed)
    Abstract [en]

    We investigate a way one can achieve good spectral resolution in H-2 MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the H-2 MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two H-2 spin populations with similar chemical shifts but different quadrupole splittings. In H-2-exchanged cellulose containing two H-2 spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics.

  • 21. Lindman, Björn
    et al.
    Stilbs, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Molecular diffusion in microemulsions2018In: Microemulsions: Structure and Dynamics, CRC Press, 2018, p. 119-152Chapter in book (Other academic)
    Abstract [en]

    The interest in studies of diffusional processes in microemulsions has grown rapidly during the past few years. The reasons are an increased number of available techniques providing easily interpretable data and the realization that self-diffusion data give unique information on the molecular organization and structure of microemulsions. Furthermore, many current and potential applications of microemulsions are dependent on molecular transport over macroscopic distances.

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

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

  • 23.
    Nordstierna, Lars
    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.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Mixed Adsorption of Fluorinated and Hydrogenated Surfactants2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 19, p. 7969-7974Article in journal (Refereed)
    Abstract [en]

    The adsorption isotherms of sodium perfluorooctanoate and sodium decyl sulfate and their 1:1 mixture on gamma-alumina are recorded by depletion-type experiments with H-1 and F-19 NMR spectroscopy as the detection tool. The isotherms of the different surfactant species, obtained with and without added salt, closely resemble each other. Salt addition changes the isotherms from stepwise to the familiar S-shaped. After having reached saturation, a further increase of surfactant concentration in the mixed system leads to decyl sulfate desorption and increased perfluorooctanoate adsorption. The F-19 chemical shift of adsorbed perfluorooctanoate suggests that, for saturated surfaces, the two sorts of adsorbed surfactants form molecularly mixed surface aggregates.

  • 24.
    Nordstierna, Lars
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Mixed Micelles of Fluorinated and Hydrogenated Surfactants2006In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 20, p. 6704-6712Article in journal (Refereed)
    Abstract [en]

    The model mixed surfactant system of sodium perfluorooctanoate and sodium decyl sulfate was carefully reexamined by a combination of nuclear magnetic resonance methods. Over a wide range of sample compositions, detailed F-19 and H-1 chemical shift data in combination with self-diffusion coefficients for the perfluorooctanoate and decyl sulfate ions are collected. All data are analyzed together in a framework that uses a minimal number of initial assumptions to extract the monomer concentrations of both surfactants and the micellar chemical shifts of F-19 and H-1 as a function of relative concentration. The main conclusion drawn from this analysis is that there exists neither complete demixing nor complete mixing on molecular or micellar levels. Instead, the experimental data favor a single type of micelles within which fluorinated surfactants are preferentially coordinated by fluorinated ones and hydrogenated surfactants by hydrogenated ones. The data are quantitatively interpreted in the framework of the first approximation of the regular solution theory (also called the quasi-chemical treatment) leading to an energy of mixing of omega = W/kT = 0.98 between the constituting surfactant types. These findings may help to resolve a long controversy about micellar mixing-demixing in this particular mixture and in its relatives.

  • 25. Paul, A.
    et al.
    Griffiths, P. C.
    Pettersson, E.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Bales, B. L.
    Zana, R.
    Heenan, R. K.
    Nuclear magnetic resonance and small-angle neutron scattering studies of anionic surfactants with macrocounterions: Tetramethylammonium dodecyl sulfate2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, p. 15775-15779Article in journal (Refereed)
    Abstract [en]

    Micellar solutions of tetramethylammonium dodecyl sulfate have been studied to determine the degree of counterion binding. Tetramethylammonium chloride was added over a wide range of surfactant concentrations such that the total concentration of tetramethylammonium ions in solution remained constant. Small angle neutron scattering experiments showed a constancy in aggregation number across this series, consistent with the constant C-aq concept of Bales et al. (J. Phys. Chent. B 2001, 105, 6798). Pulsed-field gradient and electrophoretic NMR experiments were used to determine the degree of counterion dissociation, alpha, which was found to be 0.33. This value is in contrast to the value from conductivity measurements (alpha = 0.2), but supports the concept of an aggregation number based definition of alpha.

  • 26.
    Pettersson, Erik
    et al.
    KTH, Superseded Departments, Chemistry.
    Topgaard, D.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Söderman, O.
    Surfactant/nonionic polymer interaction. a NMR diffusometry and NMR electrophoretic investigation2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 4, p. 1138-1143Article in journal (Refereed)
    Abstract [en]

    The interaction between the nonionic polymer poly(ethylene oxide) (PEO) of molecular weight 20 000 and surfactants of various types [sodium dodecyl sulfate (SDS), dodecyl trimethylammonium bromide, octyl beta-D-glucoside, and potassium laurate] has been investigated in an aqueous solution at 25 degreesC by H-1 NMR pulsed-gradient spin-echo self-diffusion techniques. The SDS/PEO study was further complemented by component-resolved H-1 NMR-based studies of the electrophoretic mobility of PEO and the alkyl part of SDS under the same measurement conditions. Through such combined studies, a much more complete picture of the binding and aggregation processes becomes accessible.

  • 27.
    Pettersson Thyboll, Erik
    et al.
    KTH, Superseded Departments, Chemistry.
    Furo, Istvan
    KTH, Superseded Departments, Chemistry. KTH, Superseded Departments, Physics.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    On experimental aspects of electrophoretic NMR2004In: Concepts in magnetic resonance. Bridging education and research, ISSN 1546-6086, E-ISSN 1552-5023, Vol. 22, no 2, p. 61-68Article in journal (Refereed)
    Abstract [en]

    Artefacts in electrophoretic NMR experiments are investigated in detail. We identify electroosmosis, sample heating, and gas development on the electrodes as main error sources and suggest experimental strategies and setups to suppress their influence on the monitored electrophoretic mobilities. We hereby demonstrate essentially artefact-free experiments up to currents and electric fields 3 mA and 70 V/cm, respectively.

  • 28. Price, W. S.
    et al.
    Elwinger, F.
    Vigouroux, C.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    PGSE-WATERGATE, a new tool for NMR diffusion-based studies of ligand-macromolecule binding2002In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 40, no 6, p. 391-395Article in journal (Refereed)
    Abstract [en]

    A new pulsed gradient spin-echo NMR diffusion sequence, PGSE-WATERGATE, which is based on the extremely efficient WATERGATE solvent suppression sequence, is presented. The sequence is simple to set up and particularly suited to measuring the diffusion coefficients of small ligands in aqueous solution such as is commonly required in pharmaceutical and combinatorial applications. It also affords the possibility of measuring the diffusion of exchangeable resonances, which is often impossible in conjunction with other suppression schemes. Further, a trivial modification of the sequence affords the possibility of multiple solvent suppression, thereby increasing its suitability to LC-NMR applications. The utility of the sequence is demonstrated on the salicylate-bovine serum albumin system. The dissociation constant, K-d, and the number of binding sites were found to be 0.030 M and 33, respectively. Importantly, the extremely high degree of suppression provided by the new sequence allowed the salicylate diffusion coefficients to be measured over a very wide concentration range sufficient to show that the salicylate-bovine serum albumin system is not well described by a simple two-site model. Previous studies in the literature have been based on data from a smaller concentration range, for which this model gives an apparently good fit.

  • 29. Price, W. S.
    et al.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Jonsson, B.
    Soderman, O.
    Macroscopic background gradient and radiation damping effects on high-field PGSE NMR diffusion measurements2001In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 150, no 1, p. 49-56Article in journal (Refereed)
    Abstract [en]

    The effects of macroscopic background gradients due to susceptibility differences at the sample interfaces and of radiation damping on pulsed-gradient spin-echo (PGSE) experiments are examined. Both phenomena can lead to the seemingly strange effect of the echo signal growing as the gradient strength increases at low applied gradient strengths. For a freely diffusing species, background gradients manifest themselves as slight concave or convex inflections in the linearized PGSE attenuation curve, depending on the polarity of the applied gradient, The various means of overcoming macroscopic background gradient problems, including bipolar gradients, and their efficacy are examined experimentally and discussed. The effects of radiation damping can also result in the attenuation curve being nonlinear but, different from the effect of background gradients, the nonlinearity does not change with the polarity of the applied gradient. The vulnerability of the stimulated echo-based PGSE sequence and variations of Hahn-based PGSE sequences is investigated. Both background gradients and radiation damping have serious implications for accurate diffusion measurement determination.

  • 30. Price, W. S.
    et al.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Soderman, O.
    Determination of pore space shape and size in porous systems using NMR diffusometry. Beyond the short gradient pulse approximation2003In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 160, no 2, p. 139-143Article in journal (Refereed)
    Abstract [en]

    The influence of finite length gradient pulses on NMR diffusion experiments on liquids confined to diffuse between two parallel planes is investigated. It is experimentally verified that the pore size decreases when determined using finite gradient pulses if the results are analyzed within the short gradient pulse approximation. The results are analyzed using the matrix formulation. The observed minima in the echo decay profiles are considerably less sharp than theoretical analysis would indicate and we suggest that this is due to the presence of a distribution of pore sizes in the sample. In addition, effects due to the presence of background gradients are discussed. It is argued that effects due to the finite length gradient pulses are relatively minor and in realistic applications the effects due to inhomogeneities in pore sizes and effects due to background gradients will constitute more serious problems in pore size determinations by means of NMR diffusometry.

  • 31. 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.

  • 32. Soderman, O.
    et al.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Price, William S.
    KTH, Superseded Departments, Chemistry.
    NMR studies of surfactants2004In: Concepts in magnetic resonance. Bridging education and research, ISSN 1546-6086, E-ISSN 1552-5023, Vol. 23A, no 2, p. 121-135Article in journal (Refereed)
    Abstract [en]

    Surfactant molecules are amphipathic and posses complicated solution chemistry and self-assembly properties. In addition to being of enormous practical significance, the physical characterization of surfactant systems presents a rich area of condensed matter physics. This article focuses on the application and interpretation of the commonly used NMR approaches for probing these systems. In particular, the use of NMR relaxation, diffusometry and, more briefly, electrophoretic NMR to determine characteristics such as micellar size and structure, ion-binding and solubilization are considered. The application of these NMR techniques is illustrated by a number of pertinent examples.

  • 33.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Automated CORE, RECORD, and GRECORD processing of multi-component PGSE NMR diffusometry data2013In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 42, no 1, p. 25-32Article in journal (Refereed)
    Abstract [en]

    Pulsed gradient spin-echo (PGSE) NMR techniques have found growing and widespread use for investigation of a variety of physicochemical phenomena in solution, because of their effect on molecular self-diffusion, and for primarily analytical purposes, for example separation of overlapping NMR bandshapes obtained from multi-component samples. A multi-component spectral separation approach previously introduced by the author (named CORE) is founded on the fact that each part of a molecule diffuses at the same rate, and thus PGSE NMR signals from each functional group will attenuate in a fully concerted fashion throughout a PGSE experiment. Numerical separation and analysis of component NMR spectra by CORE processing is therefore stabilized and steered by this prior knowledge constraint. However, even with two components and with similar self-diffusion rates, numerical instability and cross-talk between similar component self-diffusion may appear even with good experimental signal-to-noise ratio and only minor or no component spectral overlap. So-called RECORD processing was recently introduced to accompany the CORE method. In this more robust variant, spectra are divided into several sub-regions that are treated separately and combined in a later stage. The rationale for and advantages of the generic RECORD-based approach are further discussed and illustrated. A further hybrid CORE processing variant named GRECORD is suggested and briefly tested.

  • 34.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Diffusion and Electrophoretic Studies Using Nuclear Magnetic Resonance2011In: Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation, Supplementary Volumes S1 - S3 / [ed] Robert A. Meyers, John Wiley & Sons, 2011, p. 1439-1461Chapter in book (Refereed)
    Abstract [en]

    The NMR diffusometry methodology and instrumentation currently available is routinely capable of quite fast multicomponent self-diffusion mapping in solution, providing a quantitative pathway to many analytical applications as well as physicochemical information. A measurement time span of approximately 10 min may suffice, and an accuracy of a few percent or better is normally routinely achievable. Relating the behavior of self-diffusion coefficients of solution components to, e.g. solution composition changes adds another dimension to the field and a path to quantitative methods for elucidation of, e.g. molecular association or conformational changes even in complex systems. In routine form, the techniques are primarily applicable to liquid systems and use proton (1H) NMR detection. A limited number of nuclei other than protons (primarily 2H, 7Li, 13C, 19F, 31P) are also amenable for monitoring. Electrophoretic NMR (eNMR) is a related, less exploited technique, which has a more limited applicability than NMR diffusometry, but which can be uniquely useful. Instrumental and methodological advances have lately also opened up the application field to proton-detected diffusion studies in semisolid systems.

  • 35.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Diffusion Studied Using NMR Spectroscopy2010In: Encyclopedia of Spectroscopy and Spectrometry, Elsevier, 2010, p. 423-428Chapter in book (Refereed)
    Abstract [en]

    The use of NMR spectroscopy for the study of molecular diffusion is described. The pulse sequences used and the data processing methods employed are both explained. Some illustrative examples are given.

  • 36.
    Stilbs, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Diffusion Studied Using NMR Spectroscopy2016In: Encyclopedia of Spectroscopy and Spectrometry, Elsevier Inc. , 2016, p. 409-414Chapter in book (Other academic)
    Abstract [en]

    The use of NMR spectroscopy for the study of molecular diffusion is described. The pulse sequences used and the data processing methods employed are both explained. Some illustrative examples are given. 

  • 37.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Historical: early multi-component FT-PGSE NMR self-diffusion measurements-some personal reflections2017In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 55, no 5, p. 386-394Article in journal (Refereed)
  • 38.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    RECORD processing: A robust pathway to component-resolved HR-PGSE NMR diffusometry2010In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 207, no 2, p. 332-336Article in journal (Refereed)
    Abstract [en]

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

  • 39.
    Stilbs, Peter
    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.
    Electrophoretic NMR2006In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 11, no 1, p. 3-6Article, review/survey (Refereed)
    Abstract [en]

    The current status of the title subject and its applications in the fields of colloid and surfactant science are reviewed.

  • 40. Szutkowski, Kosma
    et al.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Jurga, Stefan
    Proton chemical exchange in aqueous solutions of dodecylammonium chloride: Effects of micellar aggregation2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 43, p. 15613-15619Article in journal (Refereed)
    Abstract [en]

    Proton chemical exchange was studied in aqueous solutions of dodecylammonium chloride (DDAC1) for two selected concentrations, 18 and 33 wt %. The Fourier transform Carr-Pureell-Meiboom-Gill (CPMG) NMR method combined with the Carver and Richards model for T-2 dispersion curve analysis were employed to evaluate the temperature dependence of the proton exchange rates k(ex). An increase of the energy barrier height Delta G double dagger for the proton chemical exchange between water and ammonium cation (-NH3+) was observed as the DDAC1 concentration was increased. Results are complementary to previous studies of aggregation phenomena for various n-alkylammonium chlorides.

  • 41. Valstar, A.
    et al.
    Vasilescu, M.
    Vigouroux, C.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Almgren, M.
    Heat-set bovine serum albumin-sodium dodecyl sulfate gels studied by fluorescence probe methods, NMR, and light scattering2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 11, p. 3208-3215Article in journal (Refereed)
    Abstract [en]

    In this work, concentrated protein-surfactant solutions and their corresponding heat-set gels; were studied by fluorescence probe methods, NMR, and light scattering. Bovine serum albumin (BSA) was used as the protein, and sodium dodecyl sulfate (SDS) as the surfactant. Heating concentrated BSA solutions gives turbid gels. Heat-setBSA-SDS gels are transparent. From fluorescence measurements it was concluded that SDS forms micelle-like clusters on BSA, both in solution and in the corresponding heat-set gel. Aggregation numbers were found to be similar in solution and gel. Also, I-1/I-3 values in solution and gel were similar. H-2 NMR relaxation measurements of specifically deuterated SDS at the ct-carbon position next to the headgroup were performed, and the longitudinal relaxation rates R-1 were found to be the same in solution and gel. High values for the transverse relaxation rate R-2 (indicating slow motions of SDS bound to large aggregates) were obtained, and the largest R-2 value was found for the gel. Dynamic light scattering on BSA-SDS gels was used to obtain the correlation length xi, which defines a mean distance between two points of entanglements. The decrease of xi with increasing [SDS]/[BSA] molar ratio was explained by the size of the BSA-SDS complex and the possibility that micelle-like structures might form cross-links between different BSA molecules. With static light scattering the extent of inhomogeneities in BSA and BSA-SDS gels was found to decrease with increasing SDS concentration. Also, the gel region in the ternary phase diagram BSA-SDS-3.1 mM NaN3 at room temperature and constant pressure (1 atm) was determined.

  • 42. Xia, Yang
    et al.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    The First Study of Cartilage by Magnetic Resonance: A Historical Account2016In: Cartilage, ISSN 1947-6035, E-ISSN 1947-6043, Vol. 7, no 4, p. 293-297Article in journal (Refereed)
    Abstract [en]

    Objective. To recap the historical journey leading to the first cartilage research article using nuclear magnetic resonance (NMR), published in 1955 by 2 Swedish researchers, Erik Odeblad and Gunnar Lindstrom. Design. Extensive Internet search utilizing both English and Swedish websites, and reading the dissertations available at the Royal Institute of Technology (Stockholm, Sweden) and via interlibrary loans at Oakland University (Michigan, USA). Results. Using a primitive NMR instrument that Lindstrom built for his graduate research at the Nobel Institute for Physics (Stockholm, Sweden), Odeblad and Lindstrom studied the characteristics of the NMR signal in calf cartilage. The authors wrote, "In cartilage and fibrous tissue, in which the proton signals probably arise from highly viscous water with short spin-lattice relaxation time, the signals were also larger than would correspond to the water content." The authors speculated the signal differences between water and biological tissues could be attributed to the absorption and organization of the water molecules to the proteins in the tissue, which was remarkably accurate. Conclusions. It is quite certain that Odeblad and Lindstrom published the first biomedical study using NMR in 1955. In this article, cartilage and a number of other biological tissues were examined for the first time using NMR.

  • 43.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Micellar kinetics of a fluorosurfactant through stopped-flow NMR2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, p. 2002-2004Article in journal (Refereed)
    Abstract [en]

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

  • 44.
    Yushmanov, Pavel V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furó, 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.
    Stopped-flow F-19 NMR studies of surfactant precipitation2006In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 291, no 1-3, p. 59-62Article in journal (Refereed)
    Abstract [en]

    The kinetics of the phase change in surfactant solutions is studied by F-19 stopped-flow NMR. In the aqueous solution of sodium perfluooctanoate, we observe precipitation and crystal growth induced by the addition of NaCl solution to the system. The time dependences of the NMR signal intensity and chemical shift, evaluated in the framework of a single model, narrow the range of possible scenarios, the most plausible of which is monomer incorporation into the growing crystals. In accordance to existing models of crystallization, both the nucleation rates and the crystal growth rates are strongly dependent on the magnitude of supersaturation.

  • 45. Zubkov, M.
    et al.
    Stait-Gardner, T.
    Price, W. S.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Steady state effects in a two-pulse diffusion-weighted sequence2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, no 15, article id 154201Article in journal (Refereed)
    Abstract [en]

    In conventional nuclear magnetic resonance (NMR) diffusion measurements a significant amount of experimental time is used up by magnetization recovery, serving to prevent the formation of the steady state, as in the latter case the manifestation of diffusion is modulated by multiple applications of the pulse sequence and conventional diffusion coefficient inference procedures are generally not applicable. Here, an analytical expression for diffusion-related effects in a two-pulse NMR experiment (e.g., pulsed-gradient spin echo) in the steady state mode (with repetition times less than the longitudinal relaxation time of the sample) is derived by employing a Fourier series expansion within the solution of the Bloch-Torrey equations. Considerations are given for the transition conditions between the full relaxation and the steady state experiment description. The diffusion coefficient of a polymer solution (polyethylene glycol) is measured by a two-pulse sequence in the full relaxation mode and for a range of repetition times, approaching the rapid steady state experiment. The precision of the fitting employing the presented steady state solution by far exceeds that of the conventional fitting. Additionally, numerical simulations are performed yielding results strongly supporting the proposed description of the NMR diffusion measurements in the steady state.

  • 46.
    Östlund, Jenny A.
    et al.
    KTH, Superseded Departments, Chemistry.
    Nydén, M.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Component-resolved diffusion in multicomponent mixtures. A case study of high-field PGSE-NMR self-diffusion measurements in asphaltene/naphthenic acid/solvent systems2004In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, no 2, p. 531-538Article in journal (Refereed)
    Abstract [en]

    The diffusion of a multitude of different-sized molecules in various asphaltene mixtures has been measured by means of the pulsed gradient spin-echo nuclear magnetic resonance (PGSE-NMR) self-diffusion technique. The multicomponent mixtures studied contained mixtures of polydisperse asphaltenes and monodisperse naphthenic acid in solvent. Spectra obtained from a high-field PGSE-NMR self-diffusion experiment on these systems showed that the peaks from all components were almost completely overlapping, making a standard least-squares fit approach for evaluating individual self-diffusion coefficients from the decrease in signal intensity quite difficult. However, to study the details of the molecular interactions that occur between asphaltenes and naphthenic acids, the experimental data must be such that component-resolved information is obtained. Hence, with the purpose to obtain a robust evaluation procedure, with regard to obtaining component-resolved diffusion coefficients, a standard least-squares fit approach was tested against a global least-squares approach. The global least-squares evaluation was performed using a program called CORE (component-resolved spectroscopy). CORE not only fits predetermined functions to specific peak intensities or areas obtained from the diffusion experiments, but also considers the full information in the spectra. That is, the intensity at each frequency in the spectra is considered and the band shapes for all components in the mixture can be calculated. The calculated band shapes are thus a good test of the validity of the results for the diffusion coefficients. In this work, the band shapes were calculated and the diffusion for each individual component in the samples was extracted. The band shapes were observed to be in close agreement with the spectra obtained for the pure components. In addition, the diffusion coefficients, as obtained from CORE and from the least-squares fit method, were in close agreement, although some discrepancies were noted.

1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf