Resonance-inclined optical nuclear spin polarization of liquids in diamond structures

TL;DR

This paper introduces a novel method for dynamic nuclear polarization in liquids using resonance conditions with optically polarized NV centers in nanodiamonds, enabling enhanced NMR signals at room temperature for large molecules.

Contribution

It presents a new DNP mechanism applicable for large interaction correlation times, combining optical NV center polarization with resonance conditions for liquids.

Findings

Achieves 4700-fold polarization enhancement over thermal levels.

Effective in flow cells with nanodiamonds in hydrogel at 0.35 T.

Compatible with current NMR detection volumes.

Abstract

Dynamic nuclear polarization (DNP) of molecules in a solution at room temperature has potential to revolutionize nuclear magnetic resonance spectroscopy and imaging. The prevalent methods for achieving DNP in solutions are typically most effective in the regime of small interaction correlation times between the electron and nuclear spins, limiting the size of accessible molecules. To solve this limitation, we design a mechanism for DNP in the liquid phase that is applicable for large interaction correlation times. Importantly, while this mechanism makes use of a resonance condition similar to solid-state DNP, the polarization transfer is robust to a relatively large detuning from the resonance due to molecular motion. We combine this scheme with optically polarized nitrogen vacancy (NV) center spins in nanodiamonds to design a setup that employs optical pumping and is therefore not limited by room temperature electron thermal polarisation. We illustrate numerically the effectiveness of the model in a flow cell containing nanodiamonds immobilized in a hydrogel, polarising flowing water molecules 4700-fold above thermal polarisation in a magnetic field of 0.35 T, in volumes detectable by current NMR scanners.