Exploiting Endogenous Surface Defects for Dynamic Nuclear Polarization of Silicon Micro- and Nanoparticles

Micro- and nanoparticles of elemental, crystalline silicon represent an attractive target for a wide range of applications spanning from quantum computing to contrast agents for biomedical imaging applications. To overcome the low sensitivity of the Si-29 nuclei in magnetic resonance, dynamic nuclear polarization (DNP), which exploits the endogenous surface defects as a source of polarization, can be used to temporarily boost nuclear polarization of the Si-29 spin bath. In the present work, we have assessed a number of commercially available silicon micro- and nanoparticles concerning properties and characteristics under DNP conditions. It has been found that optimal physical and chemical conditions, including surface-defect concentration adjusted to the particle size, are necessary to achieve a high level of polarization enhancement.