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Quantitative Detection of Molecular Oxygen in the Gas Phase with Fluorescent Nanodiamonds
Authors:
Nicholas A. Nunn,
Antonin Marek,
Alex I. Smirnov,
Olga A. Shenderova,
Marco D. Torelli
Abstract:
The quantitative detection of paramagnetic molecular oxygen (O2) in gas mixtures using optically detected magnetic resonance (ODMR) from negatively charged nitrogen-vacancy (NV-) centers in fluorescent nanodiamonds is described. Fluorescent nanodiamonds approximately 70 nm in diameter were deposited on the glass surface of a microfluidic channel, and the oxygen concentration varied from 0 to 100%…
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The quantitative detection of paramagnetic molecular oxygen (O2) in gas mixtures using optically detected magnetic resonance (ODMR) from negatively charged nitrogen-vacancy (NV-) centers in fluorescent nanodiamonds is described. Fluorescent nanodiamonds approximately 70 nm in diameter were deposited on the glass surface of a microfluidic channel, and the oxygen concentration varied from 0 to 100% (0 to 760 mmHg O2 partial pressure) by mixing O2 and N2 gases at ambient pressure. Continuous-wave (CW) ODMR contrast was measured using a double-modulation (lock-in) detection scheme applied to both optical excitation and microwave drives. The ODMR contrast decreases linearly with oxygen partial pressure, with a sensitivity coefficient k of (-10.1 +/- 0.3) x 10^-4 % mmHg^-1. The oxygen detection limit of the experimental setup was estimated to be approximately 8 mmHg O2 partial pressure (corresponding to about 1% O2 in the gas mixture). Cycling of the content of O2 in the gas mixture in the range of 0-5% revealed slight hysteresis and corresponding repeatability of 0.006 in percent ODMR contrast. The observed fluorescence quenching and relatively slow response (ranging from several to tens of minutes) upon changes in oxygen concentration suggest that physisorption of gas molecules on the nanodiamond surfaces contributes to equilibration dynamics. The applicability of the nanodiamond-based oxygen quantum sensor was further demonstrated by detecting transient bursts of molecular oxygen generated by enzyme-catalyzed decomposition of hydrogen peroxide.
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Submitted 2 June, 2026;
originally announced June 2026.
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High-precision chemical quantum sensing in flowing monodisperse microdroplets
Authors:
Adrisha Sarkar,
Zachary Jones,
Madhur Parashar,
Emanuel Druga,
Amala Akkiraju,
Sophie Conti,
Pranav Krishnamoorthi,
Srisai Nachuri,
Parker Aman,
Mohammad Hashemi,
Nicholas Nunn,
Marco Torelli,
Benjamin Gilbert,
Kevin R. Wilson,
Olga Shenderova,
Deepti Tanjore,
Ashok Ajoy
Abstract:
We report on a novel flow-based method for high-precision chemical detection that integrates quantum sensing with droplet microfluidics. We deploy nanodiamond particles hosting fluorescent nitrogen vacancy defects as quantum sensors in flowing, monodisperse, picoliter-volume microdroplets containing analyte molecules. ND motion within these microcompartments facilitates close sensor-analyte intera…
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We report on a novel flow-based method for high-precision chemical detection that integrates quantum sensing with droplet microfluidics. We deploy nanodiamond particles hosting fluorescent nitrogen vacancy defects as quantum sensors in flowing, monodisperse, picoliter-volume microdroplets containing analyte molecules. ND motion within these microcompartments facilitates close sensor-analyte interaction and mitigates particle heterogeneity. Microdroplet flow rates are rapid (upto 4cm/s) and with minimal drift. Pairing this controlled flow with microwave control of NV electronic spins, we introduce a new noise-suppressed mode of Optically Detected Magnetic Resonance that is sensitive to chemical analytes while resilient against experimental variations, achieving detection of analyte-induced signals at an unprecedented level of a few hundredths of a percent of the ND fluorescence. We demonstrate its application to detecting paramagnetic ions in droplets with simultaneously low limit-of-detection and low analyte volumes, in a manner significantly better than existing technologies. This is combined with exceptional measurement stability over >103s and across hundreds of thousands of droplets, while utilizing minimal sensor volumes and incurring low ND costs (<$0.70 for an hour of operation). Additionally, we demonstrate using these droplets as micro-confinement chambers by co-encapsulating ND quantum sensors with analytes, including single cells. This versatility suggests wide-ranging applications, like single-cell metabolomics and real-time intracellular measurements in bioreactors. Our work paves the way for portable, high-sensitivity, amplification-free, chemical assays with high throughput; introduces a new chemical imaging tool for probing chemical reactions in microenvironments; and establishes the foundation for developing movable, arrayed quantum sensors through droplet microfluidics.
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Submitted 30 April, 2024;
originally announced April 2024.
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High temperature annealing enhanced diamond 13C hyperpolarization at room temperature
Authors:
M. Gierth,
V. Krespach,
A. I. Shames,
P. Raghavan,
E. Druga,
N. Nunn,
M. Torelli,
R. Nirodi,
S. Le,
R. Zhao,
A. Aguilar,
X. Lv,
M. Shen,
C. A. Meriles,
J. A. Reimer,
A. Zaitsev,
A. Pines,
O. Shenderova,
A. Ajoy
Abstract:
Methods of optical dynamic nuclear polarization (DNP) open the door to the replenishable hyperpolarization of nuclear spins, boosting their NMR/MRI signature by orders of magnitude. Nanodiamond powder rich in negatively charged Nitrogen Vacancy (NV) defect centers has recently emerged as one such promising platform, wherein 13C nuclei can be hyperpolarized through the optically pumped defects comp…
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Methods of optical dynamic nuclear polarization (DNP) open the door to the replenishable hyperpolarization of nuclear spins, boosting their NMR/MRI signature by orders of magnitude. Nanodiamond powder rich in negatively charged Nitrogen Vacancy (NV) defect centers has recently emerged as one such promising platform, wherein 13C nuclei can be hyperpolarized through the optically pumped defects completely at room temperature and at low magnetic fields. Given the compelling possibility of relaying this 13C polarization to nuclei in external liquids, there is an urgent need for the engineered production of highly "hyperpolarizable" diamond particles. In this paper, we report on a systematic study of various material dimensions affecting optical 13C hyperpolarization in diamond particles -- especially electron irradiation and annealing conditions that drive NV center formation. We discover surprisingly that diamond annealing at elevated temperatures close to 1720C have remarkable effects on the hyperpolarization levels, enhancing them by upto 36-fold over materials annealed through conventional means. We unravel the intriguing material origins of these gains, and demonstrate they arise from a simultaneous improvement in NV electron relaxation time and coherence time, as well as the reduction of paramagnetic content, and an increase in 13C relaxation lifetimes. Overall this points to significant recovery of the diamond lattice from radiation damage as a result of the high-temperature annealing. Our work suggests methods for the guided materials production of fluorescent, 13C hyperpolarized, nanodiamonds and pathways for their use as multi-modal (optical and MRI) imaging and hyperpolarization agents.
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Submitted 8 November, 2019;
originally announced November 2019.