Abstract
Fluorescent nanodiamonds exhibiting outstanding optical and biocompatible properties are the subject of increased studies and attention in physics and biology. The nitrogen-vacancy center in diamonds with unique quantum properties at room temperature is sensitive to physical properties such as magnetic field, electric field, temperature, and pressure. By taking advantage of the NV center and high sensitivity that arises from the intrinsic quantum properties of spins in nanodiamonds, which are extensively employed in quantum sensing, bio-imaging, and bio-sensing. In this review, the selected topic mainly focuses on the surface functionalization of nanodiamonds and the recent progress in applying nanodiamonds as quantum sensors for intracellular orientation tracking, temperature sensing, and notably nuclear magnetic resonance and electron spin resonance applications.