Dynamic Nuclear Polarization in Silicon Microparticles

TL;DR

This paper demonstrates high Si-29 nuclear spin polarization in silicon microparticles using dynamic nuclear polarization, with potential applications in magnetic resonance imaging due to their long relaxation times.

Contribution

It reports the first high Si-29 polarization in silicon microparticles achieved through DNP, highlighting the role of amorphous regions and spin diffusion.

Findings

Achieved record high Si-29 polarization levels.

Long T1 relaxation times in hyperpolarized microparticles.

Potential use as MRI tracers.

Abstract

We report record high Si-29 spin polarization obtained using dynamic nuclear polarization in microcrystalline silicon powder. Unpaired electrons in this silicon powder are due to dangling bonds in the amorphous region of this intrinsically heterogeneous sample. Si-29 nuclei in the amorphous region become polarized by forced electron-nuclear spin flips driven by off-resonant microwave radiation while nuclei in the crystalline region are polarized by spin diffusion across crystalline boundaries. Hyperpolarized silicon microparticles have long T1 relaxation times and could be used as tracers for magnetic resonance imaging.