Speakers
Description
Ensemble-averaged techniques for molecular structure determination, such as conventional nuclear magnetic resonance (NMR) spectroscopy, obscure heterogeneity and rare conformations, motivating approaches for imaging individual nuclear spins within single molecules. However, detecting and localizing dilute spin ensembles remains challenging, requiring nanoscale spatial resolution, chemical specificity, and exceptional magnetic sensitivity.
Here, we present nitrogen-vacancy (NV) center NMR measurements of 19F-labeled DNA in the few-molecule regime [1] using individual shallow (5-nm-deep) NV centers in diamond nanopillars [2]. Mixed nitrogen- and oxygen-terminated surface chemistries enable covalent DNA attachment [3], minimizing NV–target spin separation and maintaining molecular and sensor stability. Labeling density, DNA sequence, and surface environment are systematically varied to optimize sensing conditions and demonstrate stable detection. The observed NMR signals deviate from ensemble spin-density models, indicating a transition to the few-molecule regime and necessitating new modeling approaches. These results establish key practical considerations for achieving robust few-molecule measurements.
Extending these results to the single-molecule and single-spin limits remains constrained by NV magnetic sensitivity, which is limited by spin-readout fidelity. To address this, we investigate cryogenic quantum sensors based on shallow (3- to 20-nm-deep) single silicon-vacancy (SiV) centers in diamond nanostructures [4]. Using resonant optical excitation, we observe narrow optical transitions that remain stable over hours, supporting high-fidelity spin readout. Moreover, we routinely identify devices operating in the high-strain regime, with sufficient spin–orbit mixing to enable sensitive, directional magnetic detection. These results provide a pathway toward nuclear spin imaging in single molecules.
References
Manuscript in preparation. Work performed in the Degen Lab at ETH Zurich.
T Zhu, J Rhensius, K Herb, V Damle, G Puebla-Hellmann, C L Degen, and E Janitz. Multicone Diamond Waveguides for Nanoscale Quantum Sensing. Nano Letters 23 (2023).
JM Abendroth, K Herb, E Janitz, T Zhu, LA Völker, and CL Degen. Single-Nitrogen–Vacancy NMR of Amine-Functionalized Diamond Surfaces. Nano Letters 22 (2022).
Ongoing work in the Janitz Lab at the University of Calgary.