Spin-strain coupling in nanodiamonds

TL;DR

This paper demonstrates that the spin-strain coupling in nanodiamonds can be used to generate unique, identifiable fingerprints for individual nanodiamonds, enabling tracking and anti-counterfeiting applications.

Contribution

It introduces a method to encode strain-induced spin variations as unique identifiers for nanodiamonds, enhancing their utility in biological and security applications.

Findings

Large variance in strain encodes unique RF fingerprints.

Single nanodiamonds can be tracked in real-time within cells.

Cluster nanodiamonds can serve as anti-counterfeiting markers.

Abstract

Fluorescent nanodiamonds have been used to a large extent in various biological systems due to their robust nature, inert properties and the relative ease of modifying their surface for attachment to different functional groups. Within a given batch, however, each nanodiamond is indistinguishable from its neighbors and so far one could only rely on fluorescence statistics for some global information about the ensemble. Here, we propose and measure the possibility of adding another layer of unique information, relying on the coupling between the strain in the nanodiamond and the spin degree-of-freedom in the nitrogen-vacancy center in diamond. We show that the large variance in axial and transverse strain can be encoded to an individual radio-frequency identity for a cluster of nanodiamonds. When using single nanodiamonds, this unique fingerprint can then be potentially tracked in real-time in, e.g., cells, as their size is compatible with metabolism intake. From a completely different aspect, in clusters of nanodiamonds, this can already now serve as a platform for anti-counterfeiting measures.