The Role of Electrolytes in the Relaxation of Near-Surface Spin Defects in Diamond

Abstract

Quantum sensing with spin defects in diamond, such as the nitrogen-vacancy (NV) center, enables the detection of various chemical species on the nanoscale. Molecules or ions with unpaired electronic spins are typically probed by their influence on the NV center's spin relaxation. Whereas it is well-known that paramagnetic ions reduce the NV center's relaxation time ($T_1$), here we report on the opposite effect for diamagnetic ions. We demonstrate that millimolar concentrations of aqueous diamagnetic electrolyte solutions increase the $T_1$ time of near-surface NV center ensembles compared to pure water. To elucidate the underlying mechanism of this surprising effect, single and double quantum NV experiments are performed, which indicate a reduction of magnetic and electric noise in the presence of diamagnetic electrolytes. In combination with ab initio simulations, we propose that a change in the interfacial band bending due to the formation of an electric double layer leads to a stabilization of fluctuating charges at the interface of an oxidized diamond. This work not only helps to understand noise sources in quantum systems but could also broaden the application space of quantum sensors towards electrolyte sensing in cell biology, neuroscience and electrochemistry.

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Cited by in corpus (8)

• Quantum-grade nanodiamonds for ultrabright spin detection in live cells
• Optimal Sensing Protocol for Statistically Polarized Nano-NMR with NV Centers
• Photo-induced charge state dynamics of the neutral and negatively charged silicon vacancy centers in room-temperature diamond
• Magnetic Relaxometry of Methemoglobin by Widefield Nitrogen-Vacancy Microscopy
• Room temperature relaxometry of single nitrogen-vacancy centers in proximity to $\alpha$-RuCl${}_3$ nanoflakes
• Probing the fluctuating magnetic field of Fe-triazole spin-crossover thin-layers with nitrogen-vacancy centers in diamond
• Materials and Spin Characteristics of Nanodiamonds Partially Covered with Amino Groups and Embedded with Nitrogen-Vacancy Color Centers
• Engineering Nanodiamonds for Quantum Sensing: Material Constraints at the Nanoscale