Nanoscale NMR Spectroscopy Using Nanodiamond Quantum Sensors

Abstract

Conventional nuclear magnetic resonance (NMR) spectroscopy relies on acquiring signal from a macroscopic ensemble of molecules to gain information about molecular structure and dynamics. Transferring this technique to nanoscale sample sizes would enable molecular analysis without the effects of averaging over spatial and temporal inhomogeneities and without the need for macroscopic volumes of analyte, both inherent to large ensemble measurements. Nanoscale NMR based on nitrogen vacancy (NV) centers inside bulk diamond chips achieves single nuclear spin sensitivity and the resolution required to determine chemical structure, but their detection volume is limited to a few nanometers above the diamond surface for the most sensitive devices. This precludes them from use for nuclear spin sensing with nanoscale resolution inside thicker structures, such as cells. Here, we demonstrate the detection of NMR signals from multiple nuclear species in a ~(19 nm) 3 volume using versatile NV-NMR devices inside nanodiamonds that have a typical ~30 nm diameter. The devices detect a signal generated by a small number of analyte molecules on the order of ~1000. To use these devices in situ, the detected signal must be corrected for the unknown geometry of each nanodiamond device. We show that such a calibration could be performed by exploiting the signal from a thin layer of nuclei on the diamond surface. These results, combined with nanodiamonds' low toxicity and amenability to surface functionalization, indicate that nanodiamond NV-NMR devices could become a useful tool for nanoscale NMR-based sensing inside living cells.

High-Field Magnetometry with Hyperpolarized Nuclear Spins

“…Here we contrast the key features of 13 C nuclear spins and NV centers focused on applications in magnetometry. We include in this comparison four representative papers from the literature for different regimes of NV center quantum sensors -(i) single NV electrons well-isolated in the lattice [71], (ii) sub-ensembles of NV centers (occupying <100 𝜇𝑚 3 ) in single crystal samples [12], (iii) ensembles of NVs in microdiamond [72], and (iv) dense NV centers in bulk single crystal samples [73]. For each, we elucidate values of key spin parameters, and in the last column in Fig.…”

Geometry dependence of micron-scale NMR signals on NV-diamond chips

“…This leads to a total cancellation of the thermally polarized NMR signal for an NV-center immersed in a sample, e.g. a nano-diamond in water [19]. However, for a diamond chip, some of this volume is occupied by the diamond itself, breaking the symmetry and leaving a nonzero signal -which is the strongest for γ = 45 • .…”

High Temperature Treatment of Diamond Particles Toward Enhancement of Their Quantum Properties

“…While a number of demonstrations using fluorescent diamond purely as a fluorescent label have been shown [4][5][6], diamond stands out against competing materials in sensing applications where the readout of fluorescence modulation is used to obtain information about the environment surrounding the optical center (e.g., biological sensing [7][8][9][10][11]) and can also be utilized for background-free imaging based on the magnetic modulation of the fluorescent signal [12,13]. While bulk (electronic grade single crystalline plates) diamond containing an engineered array of subsurface NV − centers has been demonstrated to advance quantum computing [14][15][16] and nano-NMR [17][18][19][20] applications, the use of diamond particles as nano-and microscale quantum probes holds the most promise for the future of high-tech particulate diamond applications. Fluorescent particulate diamond can enable substantial technological breakthroughs in the biological and medical disciplines, enabling analysis of local events in cells, tissue, and organisms in heterogeneous environments.…”