Hyperpolarization and NMR dtection on a diamond quantum chip

• Applicant: Roberto Rizzato, Ph.D.
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Analytical Chemistry ; Inorganic Molecular Chemistry - Synthesis and Characterisation ; Solid State and Surface Chemistry, Material Synthesis ; Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451500848

Nuclear magnetic resonance (NMR) spectroscopy comprises many important techniques forchemical analysis and structure determination. A well-known problem of NMR is its poor sensitivitydue to low nuclear spin polarization that generates signal. Hyperpolarization methods are constantly being invented to overcome this limitation. Recently, a promising approach is emerging from the quantum sensing area based on utilizing nitrogen-vacancy (NV) defects in diamond as room temperature NMR sensors. The ability of these devices to optically read-out NMR signals allows for sample volumes several orders of magnitude smaller than what is necessary for conventional inductive detector. Furthermore, in such defects, the electrons exhibit spin states which can be highly polarized by laser pulses and their polarization transferred to the nuclei outside the diamond. A spectrometer based on such a technology will be utilized throughout the project where the core element is a tiny NV-diamond chip for high resolution NMR spectroscopy of picoliter sample volume placed above it. However, the concentration sensitivity can still be greatly improved, so far limited topure sample detection. This project introduces a method which for the first time fully exploits the dual role of the NVs to be used both as hyperpolarizers and NMR sensors. Since the approach to directly hyperpolarize the nuclear spins by the NVs seems to be challenging because of weak interaction energies, an indirect strategy with technical promise will be explored based on utilizing stable organic radicals, tethered to the diamond chip surface (spin-repeaters) which will be able to receive the polarization from the NVs and transfer it to the sample nuclei by means of Dynamic Nuclear Polarization (DNP) schemes. Such a strategy will improve the state-ofthe- art sensitivity by several orders of magnitudes, bringing this technology into real-world applications, e.g. drug discovery, catalysis research, and single cell studies.

• DFG Programme: WBP Position