Models of liquid samples confinement for nanoscale NMR

Diffusion is a prominent source of noise affecting nuclear magnetic resonance at the nanometer scale (nano-NMR), preventing high resolution studies of unpolarized liquid samples. Actively managing diffusion noise through, for example, sample confinement, is likely to unveil alternative noise sources which so far have been disregarded, as they occur in longer time-scales and are, consequently, masked by diffusion. These secondary noise sources could diminish the advantages provided by sample confinement but, on the other hand, they can provide with valuable information about the behavior of the sample and its interactions. In this article, we study for the first time and in detail two noise models for confined nano-NMR, namely, surface interactions and porosity, and discuss their implications for typical nano-NMR experiments.