Spectral resolution

Chemistry

Materials science

Physics

Nuclear magnetic resonance spectroscopy

Free induction decay

Organic chemistry

Vacancy defect

Astronomy

Diamond

Spectroscopy

Quantum mechanics

Magnetic resonance imaging

Nuclear magnetic resonance

Spectral line

Radiology

Spin echo

Solid-state nuclear magnetic resonance

Medicine

Nature

High-resolution nuclear magnetic resonance spectroscopy at the scale of single cells is achieved by combining a magnetometer consisting of an ensemble of nitrogen–vacancy centres with a narrowband synchronized readout protocol. The spin-hosting nitrogen–vacancy centres in diamond have the spatial sensitivity to detect the nuclear magnetic resonance (NMR) signals of single molecules. However, the spectral resolution of such schemes is not sufficient to unravel details of molecular structure. David Glenn et al. describe a sensitive magnetometer based on an ensemble of nitrogen–vacancy centres that, when combined with a customized pulsed readout protocol, can achieve a spectral resolution sufficient to resolve key chemical signatures at micrometre-scale spatial resolution. Such a scheme could enable NMR spectroscopy at the scale of single cells. Quantum systems that consist of solid-state electronic spins can be sensitive detectors of nuclear magnetic resonance (NMR) signals, particularly from very small samples. For example, nitrogen–vacancy centres in diamond have been used to record NMR signals from nanometre-scale samples1,2,3, with sensitivity sufficient to detect the magnetic field produced by a single protein4. However, the best reported spectral resolution for NMR of molecules using nitrogen–vacancy centres is about 100 hertz5. This is insufficient to resolve the key spectral identifiers of molecular structure that are critical to NMR applications in chemistry, structural biology and materials research, such as scalar couplings (which require a resolution of less than ten hertz6) and small chemical shifts (which require a resolution of around one part per million of the nuclear Larmor frequency). Conventional, inductively detected NMR can provide the necessary high spectral resolution, but its limited sensitivity typically requires millimetre-scale samples, precluding applications that involve smaller samples, such as picolitre-volume chemical analysis or correlated optical and NMR microscopy. Here we demonstrate a measurement technique that uses a solid-state spin sensor (a magnetometer) consisting of an ensemble of nitrogen–vacancy centres in combination with a narrowband synchronized readout protocol7,8,9 to obtain NMR spectral resolution of about one hertz. We use this technique to observe NMR scalar couplings in a micrometre-scale sample volume of approximately ten picolitres. We also use the ensemble of nitrogen–vacancy centres to apply NMR to thermally polarized nuclear spins and resolve chemical-shift spectra from small molecules. Our technique enables analytical NMR spectroscopy at the scale of single cells.

High-resolution magnetic resonance spectroscopy using a solid-state spin sensor