Fluorescence profile of a nitrogen-vacancy center in a nanodiamond

Abstract

Nanodiamonds containing luminescent point defects are widely explored for applications in quantum biosensing such as nanoscale magnetometry, thermometry, and electrometry. A key challenge in the development of such applications is the large variation in fluorescence properties observed between particles, even when obtained from the same batch or nominally identical fabrication processes. By theoretically modeling the emission of nitrogen-vacancy color centers 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 $a=200$ and 300 nm, with negligible effects below $a=100$ nm. These results show that the reproducible geometry of point defect position within a 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 optimized for biosensing applications.