Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments.
Thanks to instrumental and theoretical development, notably the access to high-power and high-frequency microwave sources, high-field dynamic nuclear polarization (DNP) on solid-state NMR currently appears as a promising solution to enhance nuclear magnetization in many different types of systems. In magic-angle-spinning DNP experiments, systems of interest are usually dissolved or suspended in glass-forming matrices doped with polarizing agents and measured at low temperature (down to ∼100K). In this work, we discuss the influence of sample conditions (radical concentration, sample temperature, etc.) on DNP enhancements and various nuclear relaxation times which affect the absolute sensitivity of DNP spectra, especially in multidimensional experiments. Furthermore, DNP-enhanced solid-state NMR experiments performed at 9.4 T are complemented by high-field CW EPR measurements performed at the same magnetic field. Microwave absorption by the DNP glassy matrix is observed even below the glass transition temperature caused by softening of the glass. Shortening of electron relaxation times due to glass softening and its impact in terms of DNP sensitivity is discussed.
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Hiroki
H
Takahashi
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Carlos
C
Fernández-de-Alba
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Daniel
D
Lee
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Vincent
V
Maurel
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Serge
S
Gambarelli
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Michel
M
Bardet
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
Sabine
S
Hediger
Laboratoire National des Champs Magnétiques Intenses, CNRS, F-38042 Grenoble, France.
Anne-Laure
AL
Barra
Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France. Electronic address: gael.depaepe@cea.fr.
Gaël
G
De Paëpe
Absolute sensitivity ratio; Dynamic nuclear polarization; Glassy solution; High-field EPR; Microwave absorption; Solid-state NMR