Nanoscale nuclear magnetic resonance with chemical structure resolution

The nitrogen-vacancy (NV) center in diamond has recently proven its capability as a nanoscale nuclear magnetic resonance (NMR) sensor. Compared to the required number of nuclear spins in conventional NMR, NV nanoscale NMR has been able to detect a sample containing a 12 orders of magnitude smaller number of nuclear spins. For chemical structure analysis however the spectral resolution is the crucial parameter and so far it has been challenging to achieve the required resolution.

In the measurement protocol the NV electron spin sensor is entangled with the intrinsic nuclear spin acting as the quantum memory. This novel sensor-memory system operates at a high magnetic field and enables a measurement time in the minutes-scale. As a result, for liquid samples a chemical shift resolution of ~1 part per million is achieved in ¹H and ¹⁹F NMR spectroscopy of 20-zeptoliter sample volumes. Furthermore the tracking of sensor-to-sample spin interaction allows the measurement and analysis of spatial diffusion. In addition high-resolution solid-state NMR is performed by applying homonuclear decoupling and achieving a 20-fold narrowing of the NMR linewidth. The technique also allows spin diffusion measurement in solids. Finally possible improvements of NV nanoscale NMR are discussed.