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

Abstract

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 samples, with sensitivity sufficient to detect the magnetic field produced by a single protein. However, the best reported spectral resolution for NMR of molecules using nitrogen-vacancy centres is about 100 hertz. 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 hertz) 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 protocol 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.

NV−–N+ pair centre in 1b diamond

“…There are also applications that utilize ensembles of NV − centres. These includes detection of magnetic fields with the possibility over wide areas [5][6][7][8] and often for materials with biological [9,10] or geological interest [11,12]. In the case of these latter ensemble applications it is desirable that the NV − centres maintain the properties of the single centres.…”

Construction and operation of a tabletop system for nanoscale magnetometry with single nitrogen-vacancy centers in diamond

“…The use of the single-NV quantum sensor significantly reduces the required volume of analyte for nuclear magnetic resonance (NMR), ultimately down to the single molecular level. Recent demonstrations toward this ambitious goal include detection of single protons, 17 spectroscopy of single proteins, 18 sub-hertz spectral resolution, [19][20][21][22][23] spectroscopy and tracking of single nuclear spins via weak measurements, 24,25 determination of the positions of single nuclear spins, [26][27][28][29][30] and so forth. Remarkably, many of them have been realized at room temperature.…”

Probing phase transitions in a soft matter system using a single spin quantum sensor

“…Furthermore, NV based Nano-NMR methods could also be employed to study wetting and other interfacial phenomena in general. Particularly the finer details about molecular interactions at the solid(diamond)-liquid boundaries could be discerned non-invasively through the recently developed NV based nano-NMR methods with high spectral resolution [43][44][45]. The ultralong interrogation time scales offered by these methods could also enable observing the subtle molecular signatures like chemical shifts and J-coupling in ultra low sample volumes.…”