A “ diamond key ” opens the door to single-molecule magnetic resonance studies

The past half century has seen the emergence and rapid advance of single-molecule technology, which have deepened our understanding of the microworld and unprecedentedly improved our ability to control microsystems. Magnetic resonance (MR), a noninvasive technology extracting conformational and structural information from a sample, has been widely applied in physics, chemistry, materials science, biology and medicine. Conventional MR relies on accumulation and averaging of the signal from an ensemble of samples containing at least billions of molecules. Pushing the sensitivity to a single molecule is one of the most important subjects in MR research, although it faces numerous challenges. Most recent results show that nitrogen-vacancy centers in diamond could perform as a new type of sensor that would allow the detection of single molecules and improve the MR imaging resolution from millimeters to nanometers. We review the recent progress of this field and speculate on its future.