Tran N. Pham, Anne Lesage, Mingxue Tang, Staffan Schantz, Judith Schlagnitweit, Etienne Socie, Lyndon Emsley, Arthur C. Pinon, Aaron J. Rossini, Pierrick Berruyer, Moreno Lelli, Institut des sciences et ingénierie chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Solid-State NMR Methods for Materials - Méthodes de RMN à l'état solide pour les matériaux, Institut des Sciences Analytiques (ISA), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Karolinska Institutet [Stockholm], Dept Chem, Iowa State University (ISU), Center for Magnetic Resonance, Università degli Studi di Firenze = University of Florence (UniFI), GSK Med Res Ctr, GlaxoSmithKline SA, AstraZeneca, This work was supported by ERC Advanced Grant No. 320860., European Project: 320860,EC:FP7:ERC,ERC-2012-ADG_20120216,HI-SENS(2013), Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), and Università degli Studi di Firenze = University of Florence [Firenze] (UNIFI)
We are grateful to Matthew Conley and Christophe Coperet from ETH Zurich for providing the mesoporous silica materials. We are grateful to Prof. P. Tordo, Dr. O. Ouari, and Dr. G. Casano (Aix-Marseille Universite, France) for providing the biradicals used in the DNP NMR experiments.; International audience; We show how dynamic nuclear polarization (DNP) NMR can be used in combination with models for polarization dynamics to determine the domain sizes in complex materials. By selectively doping a source component with radicals and leaving the target undoped, we Can measure experimental polarization buildup curves which can be compared with simulations based on heterogeneous distributions of polarization-within the sample. The variation of the integrated DNP enhancement as a function of the polarization time is found to be characteristic of the geometry. We demonstrate the method experimentally on four different systems where we successfully determine domain sizes between 200 and 20 000 nm, specifically in powdered histidine hydrochloride monohydrate) pore lengths of mesoporous silica materials, and two domain sizes in two component polymer film coatings. Additionally, we find that even in the apparently homogeneous frozen solutions used as polarization sources in most DNP experiments, polarization is relayed from protons near the radicals to the bulk of the solution by spin diffusion, which explains the experimentally observed buildup times in these samples.