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arXiv · 2503.24341

Chemically Tuning Room Temperature Pulsed Optically Detected Magnetic Resonance

Sarah K. Mann·Angus Cowley-Semple·Emma Bryan·Ziqiu Huang·Sandrine Heutz·Max Attwood·Sam L. Bayliss
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Abstract

Optical detection of magnetic resonance enables spin-based quantum sensing with high spatial resolution and sensitivity-even at room temperature-as exemplified by solid-state defects. Molecular systems provide a complementary, chemically tunable, platform for room-temperature optically detected magnetic resonance (ODMR)-based quantum sensing. A critical parameter governing sensing sensitivity is the optical contrast-i.e., the difference in emission between two spin states. In state-of-the-art solid-state defects such as the nitrogen-vacancy center in diamond, this contrast is approximately 30%. Here, capitalizing on chemical tunability, we show that room-temperature ODMR contrasts of 40% can be achieved in molecules. Using a nitrogen-substituted analogue of pentacene (6,13-diazapentacene), we enhance contrast compared to pentacene and, by determining the triplet kinetics through time-dependent pulsed ODMR, show how this arises from accelerated anisotropic intersystem crossing. Furthermore, we translate high-contrast room-temperature pulsed ODMR to self-assembled nanocrystals. Overall, our findings highlight the synthetic handles available to optically readable molecular spins and the opportunities to capitalize on chemical tunability for room-temperature quantum sensing.

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Sarah K. Mann, Angus Cowley-Semple, Emma Bryan, Ziqiu Huang, Sandrine Heutz, Max Attwood, Sam L. Bayliss. 2025-03-31. Chemically Tuning Room Temperature Pulsed Optically Detected Magnetic Resonance. https://doi.org/10.1021/jacs.5c05505

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