Temperature Dependent ¹H NMR Spectroscopy on Confined Water via Nitrogen Vacancy Centers in Diamonds

Characterizing the nanoscale confinement of liquids via quantum sensing can overcome the sensitivity, spatial, and temporal limitations of other measurement techniques. Leveraging the unique spin state-dependent photoluminescence of the Nitrogen Vacancy (NV) center in diamond, we combined NV-based nanoscale nuclear magnetic resonance and molecular dynamics simulation to examine water entrapped within ∼5 nm-tall nanochannels engineered out of 2D material structures patterned on the diamond surface. Extending preceding room temperature measurements¹, we use a custom 3-d printed chamber and thermoelectric cooling to probe confined water dynamics at variable temperatures ranging from ambient to below freezing.We observe pronounced temperature sensitivity: apparent diffusion coefficients are strongly reduced well above the bulk freezing point, an effect we associate with illumination-induced (photogenerated) carriers accumulating at the interfaces and/or injected into the water. These results provide a quantitative framework for elucidating phase behavior and thermodynamic properties of liquids in nanometer-scale geometries.

References:

1.​Pagliero, D. et al. Slow Water in Engineered Nanochannels Revealed by Color-Center-Enabled Sensing. Nano Lett. 25, 9960–9966 (2025).