Fluorescent Nanodiamonds

A fluorescent nanodiamond (FND) refers to a type of nanodiamond (ND) that contains a high-density ensemble of fluorescent color centers. This chapter focuses on the properties of FND. The quantum sensing capabilities of FNDs are related to the magnetic states of the nitrogen-vacancy (NV) defect centers inside FND particles. The photoluminescent characteristics of FNDs are attributed to color centers, also known as local defects, present in ND crystals. These color centers act similarly to individual atoms or molecules within the solid host of the NDs. For cell biologists, Förster resonance energy transfer (FRET)–based sensors are important tools for gathering information about fluorescent proteins, interactions between proteins, and the conformational biology of components such as reporters. The FND can act as a permanent FRET donor, comparable with an organic dye or fluorescent protein, but without the low photostability or photoblinking that characterizes these other alternatives.