Stropko: Nanoscale sensing of dynamics and pH with nitrogen-vacancy centers

Nitrogen-vacancy (NV) centers are highly sensitive microscopic sensors in diamond with the potential to probe many interesting physical systems. For one, NV centers can perform nuclear magnetic resonance on extremely small volumes of liquids to study microscopic dynamics. However, the interplay between the surface of diamond and liquid samples is complicated, and its effect on NV sensing is not well understood. We have designed and built a novel variable-temperature NV experiment to study the dependence of temperature and NV surface depth on NMR signals for the study of molecular diffusion. The results show how microscopic diffusion studies may be extended to low temperatures to measure unknown diffusion coefficients. We also outline a plan for a future experiment to test a theory of glasses using the same NMR techniques and variable-temperature setup. Separately, we show how NV-enriched nanodiamonds can be electrically induced to detect local pH, with applications to cell biology and surface chemistry.