Bulk Nuclear Hyperpolarization of Inorganic Solids by Relay from the Surface

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
with
a general strategy using impregnation dynamic nuclear polarization
through homonuclear spin diffusion between low-γ 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 of 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, 113Cd spectra of CdTe,
and 29Si spectra of α-quartz.