Solid-phase polarization matrixes for dynamic nuclear polarization from homogeneously distributed radicals in mesostructured hybrid silica materials.
J Am Chem Soc
; 135(41): 15459-66, 2013 Oct 16.
Article
em En
| MEDLINE
| ID: mdl-23978152
ABSTRACT
Mesoporous hybrid silica-organic materials containing homogeneously distributed stable mono- or dinitroxide radicals covalently bound to the silica surface were developed as polarization matrixes for solid-state dynamic nuclear polarization (DNP) NMR experiments. For TEMPO-containing materials impregnated with water or 1,1,2,2-tetrachloroethane, enhancement factors of up to 36 were obtained at â¼100 K and 9.4 T without the need for a glass-forming additive. We show that the homogeneous radical distribution and the subtle balance between the concentration of radical in the material and the fraction of radicals at a sufficient inter-radical distance to promote the cross-effect are the main determinants for the DNP enhancements we obtain. The material, as well as an analogue containing the poorly soluble biradical bTUrea, is used as a polarizing matrix for DNP NMR experiments of solutions containing alanine and pyruvic acid. The analyte is separated from the polarization matrix by simple filtration.
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MEDLINE
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En
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J Am Chem Soc
Ano de publicação:
2013
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Article
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