Micron-Scale NV-NMR Spectroscopy with Signal Amplification by Reversible Exchange

Optically probed nitrogen-vacancy (NV)) quantum defects in diamond can detect nuclear magnetic resonance (NMR) signals with high-spectral resolution from micron-scale sample volumes of about 10 pl. However, a key challenge for NV-NMR spectroscopy is detecting samples at millimolar concentrations. Here we demonstrate an increase in NV-NMR proton concentration sensitivity by hyperpolarizing sample proton spins to about 0.5% through signal amplification by reversible exchange (SABRE), enabling micron-scale NMR spectroscopy of small-molecule sample concentrations as low as 1 mM in picoliter volumes. The SABRE-enhanced NV-NMR technique may enable detection and chemical analysis of low-concentration molecules and their dynamics in complex micron-scale systems such as single cells.