  The temperature dependence (10-290 K) of the low-frequency (20-150 cm-1)
Raman-active phonon modes of supercooled confined water in L,L-diphenylalanine
micro/nanotubes was analysed. The isolated dynamics of a specific geometry of
water cluster (pentamer) in supercooled confined regime was studied in detail.
A particular mode concerning water-nanotube interaction was also probed. A
fragile-to-strong transition at 204 K was observed and related to the crossing
of the Widom line. The critical exponent analyses of the relaxation rate data
based on mode-coupling theory indicated perfect agreement among experimental
data and theory. Our results are consistent with the existence of a second
critical point of water.
