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Low rf power high resolution H-1-C-13-N-14 separated local field spectroscopy in lyotropic mesophases
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0002-6524-1441
2012 (English)In: Journal of magnetic resonance (San Diego, Calif. 1997: Print), ISSN 1090-7807, E-ISSN 1096-0856, Vol. 223, 73-79 p.Article in journal (Refereed) Published
Abstract [en]

Efficiency of the proton detected (encoded) H-1-C-13-N-14 local field spectroscopy technique at low radiofrequency power is examined when applied to concentrated ionic lyotropic mesophases exhibiting heteronuclear and homonuclear dipolar couplings in kHz range. We demonstrate that highly resolved heteronuclear dipolar spectra can be obtained with limited radiofrequency power corresponding to decoupling B-1 field of 20 kHz and with superior spectral resolution and sensitivity provided by standard solution state probes. To maintain sufficiently large spectral window in indirect dimension, power level alternation scheme for homonuclear decoupling was introduced. In anisotropic mesophases of an ionic surfactant, pair-wise coupling constants in the three-spin system H-1-C-13-N-14 were accurately determined. Relative signs of heteronuclear dipolar couplings to nitrogen were obtained employing frequency selective decoupling.

Place, publisher, year, edition, pages
2012. Vol. 223, 73-79 p.
Keyword [en]
Separated local field spectroscopy, PDLF, Heteronuclear dipolar coupling, Liquid crystal
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-105666DOI: 10.1016/j.jmr.2012.07.012ISI: 000309570600013ScopusID: 2-s2.0-84865824129OAI: diva2:572827
Swedish Research Council

QC 20121129

Available from: 2012-11-29 Created: 2012-11-23 Last updated: 2015-02-25Bibliographically approved
In thesis
1. Molecular Order and Dynamics in Nanostructured Materials by Solid-State NMR
Open this publication in new window or tab >>Molecular Order and Dynamics in Nanostructured Materials by Solid-State NMR
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies.

In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs.

Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found.

The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 54 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:7
mesoporous materials, organic-inorganic nanocomposites, surfactants, liquid crystals, MCM-41, clays, conformational dynamics, solid-state NMR, local field spectroscopy, dipolar coupling, dipolar recoupling, spin decoupling.
National Category
Physical Chemistry
Research subject
urn:nbn:se:kth:diva-160636 (URN)978-91-7595-424-0 (ISBN)
Public defence
2015-03-20, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20150225

Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2015-02-25Bibliographically approved

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Kharkov, Boris B.Dvinskikh, Sergey V.
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