  Water, when confined at the nanoscale acquires extraordinary transport
properties. And yet there is no direct experimental evidence of these
properties at nanoscale resolution. Here, by using 2D NMR diffusion-relaxation
(D-T2) and spin-lattice - spin-spin relaxation (T1-T2) spectroscopy, we
succeeded to resolve at the nanoscale water diffusion in single and
double-walled carbon nanotubes (SWCNT/DWCNT). In SWCNTs, spectra display the
characteristic shape of uniform water diffusion restricted in one dimension.
Remarkably, in DWCNTs water is shown to split into two axial components with
the inner one acquiring unusual flow properties: high fragility, ultrafast
self-diffusion coefficient, and "rigid" molecular environment, revealing a
stratified cooperative motion mechanism to underlie fast diffusion in water
saturated CNTs.
