Fluorescence profile of a nitrogen-vacancy center in a nanodiamond

TL;DR

This paper models how the fluorescence spectrum of nitrogen-vacancy centers in nanodiamonds varies with the emitter’s position and particle size, impacting the reproducibility of bio-sensing applications.

Contribution

It provides a theoretical model linking emitter position within nanodiamonds to fluorescence variation, highlighting the importance of controlled defect placement.

Findings

Fluorescence spectrum varies with emitter position in particles larger than 100 nm.

Significant fluorescence profile changes occur at particle sizes of 200-300 nm.

Negligible effects on fluorescence for particles smaller than 100 nm.

Abstract

Nanodiamonds containing luminescent point defects are widely explored for applications in quantum bio-sensing such as nanoscale magnetometry, thermometry, and electrometry. A key challenge in the development of such applications is a large variation in fluorescence properties observed between particles, even when obtained from the same batch or nominally identical fabrication processes. By theoretically modelling the emission of nitrogen-vacancy colour centres in spherical nanoparticles, we are able to show that the fluorescence spectrum varies with the exact position of the emitter within the nanoparticle, with noticeable effects seen when the diamond radius, $a$, is larger than around 100 nm, and significantly modified fluorescence profiles found for larger particles when $a=200$ nm and $a=300$ nm, while negligible effects below $a=100$ nm. These results show that the reproducible geometry of point defect position within narrowly sized batch of diamond crystals is necessary for controlling the emission properties. Our results are useful for understanding the extent to which nanodiamonds can be optimised for bio-sensing applications.