Nuclear Magnetic Resonance, or NMR is a powerful method to obtain information on structures of molecules and molecular motions. That is why NMR is used in various situations, such as organic chemistry, biological science, and materials science. In the conventional method of NMR, the magnetization of the thermal equilibrium polarization of the nuclear ensembles is measured. In the measurement, large amounts of samples and high magnetic field are required, which limits the measurement of microscopic samples. On the other hand, Magnetic resonance force microscopy is known for detecting nuclear spins and achieving nanoscale resolutions. However, it needs extremely low temperature and high vacuum. If the NMR measurement on nanoscale samples without any specific environment is achieved, it must be an innovative method in development of medicine in life science, two-dimensional materials in materials science, and so on.

The nitrogen vacancy center, or NV center, in diamond, which is a point defect in diamond lattice, is now considered as a highly promising quantum sensor to meet the demands above. It can detect signals with high spatial resolution from tiny amounts of samples at ambient conditions, which is essential for biological samples and life science.

In our laboratory, we are advancing the research related to NV centers. Firstly, we have built confocal fluorescence microscopy, or CFM, which is essential for make measurements, in our laboratory. Since then, we have succeeded in detecting nuclear spins in an organosilane monolayer on diamond surface with NV centers. The number of nuclear spins contributing to the signals is estimated to be less than 100, indicating that local information can be obtained with NV centers. We have also succeeded in the fabrication of nano structure on diamond surface to obtain clear spectrum, which enables to achieve higher frequency resolution.

Thus far, we have succeeded in sensing nuclear spins with NV centers and enhancing resolution of this quantum sensor. Currently, we are advancing in our research to obtain spectrum with high frequency resolution in the way of cooling down diamond with liquid nitrogen, implementing and improving new measurement systems in our CFM, and making electric circuits used in our systems better. Moreover, we are also researching on double electron-electron resonance measurements, which includes the manipulation of external electron spins as well as that of NV centers, to develop a new sensor system for a protein and a cell. In this way, we are exploring the possibility of NV centers.