PICOLITER SCALE SOLUTION NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY USING NITROGEN-VACANCY CENTRES IN A DIAMOND CHIP

Janis Smits^{1, 2}, Joshua Damron¹, Pauli Kehayias^{1, 3}, Andrew McDowell⁴, Nazanin Mosavian¹, Ilja Fescenko¹, Nathaniel Ristoff¹, Abdelghani Laraoui¹, Andrey Jarmola^{5, 6}, Victor Acosta¹

¹ Center for High Technology Materials and Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, 87106, USA

² Laser Centre of the University of Latvia, Riga, LV-1586, Latvia

³ Sandia National Laboratories, Albuquerque, NM, 87123, USA

⁴ NuevoMR LLC, Albuquerque, NM, 87106, USA

⁵ Department of Physics, University of California, Berkeley, CA, 94720, USA

⁶ ODMR Technologies Inc., El Cerrito, CA, 94530, USA

[email protected]

Nuclear magnetic resonance spectroscopy is a powerful way of probing chemical composition and structure of matter. Typically implementations are based on inductive acquisition which scales poorly with small sample volumes (~nL). Quantum sensors based on nitrogen-vacancy (NV) centres in diamond are a promising alternative owing to their non-inductive detection method.

Most implementations up to now have relied on the stochastic polarization naturally emerging at small sensing volumes (~ 1 pL) to achieve reasonable sensitivity, however this puts a lower bound on the achievable spectral resolution due to spin diffusion of about ~ 100 Hz [2]. Glenn et. al. [3] addressed the resolution issue by substantially increasing the effective sensing volume and detecting the thermal equilibrium magnetization. This resulted in an order of magnitude improvement in resolution (~9±1 Hz) and a molar sensitivity of ~ 370 M (defined as the minimum proton spin concentration necessary to obtain a signal-to-noise ratio of 3:1 in 1 second of averaging time).

We report [1] a further order of magnitude improvement in resolution and sensitivity, realizing a spectral resolution of 0.65 ±0.05 Hz and a molar sensitivity of ~ 27 M, by spatially separating the pre-polarization and detection phases of the measurement. This is achieved by embedding a 35 × 1000 × 1000 μm thick diamond membrane into a microfluidic chip (see Figure 1(a)) and employing precise spatial and temporal magnetic field compensation. We use the developed

platform to measure the first (to the best of our knowledge) experimental 2D NMR spectra obtained using NVs (see Figure 1 (b,c)).

The results represent a significant step towards applications such as mass-limited spectroscopy and single-cell biology. A remaining challenge is the limited sensitivity of our technique which could be further improved using external polarizing agents [5] or polarization transfer from NVs themselves.

[1] Smits, J., Damron, J., Kehayias, P., McDowell, A.F., Mosavian, N., Fescenko, I., Ristoff, N., Laraoui, A., Jarmola, A. and Acosta, V.M., 2019. Two-dimensional nuclear magnetic resonance spectroscopy with a microfluidic diamond quantum sensor. arXiv:1901.02952 (2019).

[2] Aslam, Nabeel, Matthias Pfender, Philipp Neumann, Rolf Reuter, Andrea Zappe, Felipe Fvaro de Oliveira, Andrej Denisenko et al. "Nanoscale nuclear magnetic resonance with chemical resolution." Science 357(6346), 67-71, (2017).

[3] Glenn, David R., Dominik B. Bucher, Junghyun Lee, Mikhail D. Lukin, Hongkun Park, and Ronald L. Walsworth. "High-resolution magnetic resonance spectroscopy using a solid-state spin sensor." Nature 555(7696), 351, (2018).

[4] Hogben, H. J., M. Krzystyniak, G. T. P. Charnock, P. J. Hore, and Ilya Kuprov. "Spinach - a software library for simulation of spin dynamics in large spin systems." Journal of Magnetic Resonance 208(2), 179-194, (2011).

[5] Bucher, Dominik B., David R. Glenn, Hongkun Park, Mikhail D. Lukin, and Ronald L. Walsworth. "Hyperpolarization-enhanced NMR spectroscopy with femtomole sensitivity using quantum defects in diamond." arXiv:1810.02408 (2018).