Björgvinsdóttir, Snædís, Brennan J. Walder, Arthur C. Pinon, and Lyndon Emsley. “Bulk Nuclear Hyperpolarization of Inorganic Solids by Relay from the Surface.” Journal of the American Chemical Society 140, no. 25 (June 27, 2018): 7946–51.
NMR is a method of choice to determine structural and electronic features in inorganic materials, and has been widely used in the past, but its application is severely limited by its low relative sensitivity. We show how the bulk of proton-free inorganic solids can be hyperpolarized in a general strategy using impregnation dynamic nuclear polarization through homonuclear spin diffusion between low-g nuclei. This is achieved either through direct hyperpolarization or with a pulse-cooling cross-polarization method, transferring hyperpolarization from protons to heteronuclei at particle surfaces. We demonstrate a factor 50 gain in overall sensitivity for the 119Sn spectrum of powdered SnO2, corresponding to an acceleration of a factor >2500 in acquisition times. The method is also shown for 31P spectra of GaP, for 113Cd spectra of CdTe, and 29Si spectra of α-quartz.