Chemistry, Ames Laboratory
Journal or Book Title
Journal of Physical Chemistry C
We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated.
American Chemical Society
Lafon, Oliver; Thankamony, Aany S. Lilly; Kobayashi, Takeshi; Carnevale, Diego; Vitzhum, Veronika; Slowing, Igor I.; Kandel, Kapil; Vezin, Hervé; Amoureux, Jean-Paul; Bodenhausen, Geoffrey; and Pruski, Marek, "Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization" (2013). Ames Laboratory Publications. 309.