Sensing of single nuclear spins in random thermal motion with proximate nitrogen-vacancy centers

TL;DR

This paper demonstrates that nitrogen-vacancy centers in diamond can detect single nuclear spins even when they are in thermal motion, enabling applications in chemistry and biology.

Contribution

The authors develop an effective model for NV-based sensing of moving spins and validate it with realistic experimental scenarios involving diffusive motion.

Findings

Detection of single nuclear spins in thermal motion is feasible.

Time-resolved monitoring of fluorine spin detachment is possible within seconds.

NV centers can sense spins attached to vibrating biological molecules.

Abstract

Nitrogen-vacancy (NV) centers in diamond have emerged as valuable tools for sensing and polarizing spins. Motivated by potential applications in chemistry, biology, and medicine, we show that NV-based sensors are capable of detecting single spin targets even if they undergo diffusive motion in an ambient thermal environment. Focusing on experimentally relevant diffusion regimes, we derive an effective model for the NV-target interaction, where parameters entering the model are obtained from numerical simulations of the target motion. The practicality of our approach is demonstrated by analyzing two realistic experimental scenarios: (i) time-resolved sensing of a fluorine nuclear spin bound to an N-heterocyclic carbene-ruthenium (NHC-Ru) catalyst that is immobilized on the diamond surface and (ii) detection of an electron spin label by an NV center in a nanodiamond, both attached to a vibrating chemokine receptor in thermal motion. We find in particular that the detachment of a fluorine target from the NHC-Ru carrier molecule can be monitored with a time resolution of a few seconds.