Anomalously Immobilized Water:  A New Water Phase Induced by Confinement in Nanotubes

Abstract

Confinement can induce unusual behavior in the properties of matter. Using molecular dynamics simulations, we show here that water confined to carbon nanotubes of a critical size under ambient conditions (1 bar, 300 K) can undergo a transition into a state having icelike mobility with an amount of hydrogen bonding similar to that in liquid water. The onset of this behavior occurs rapidly, raising the possibility that confinement inside nanotubes, and perhaps even buckyballs, can provide an environment in which the dynamics of phase changes may be studied directly by simulation. Moreover, because of a variety of evidence suggesting that water ordering may modulate proton conductance via a "proton wire" hydrogen bonding network, the ability to modulate water ordering with geometry suggests a possible mechanism for a switchable nanoscale semiconductor.

Structural and dynamical properties of water confined in carbon nanotubes

“…It can be seen that the water density is strongly dependent on the CNT diameter in narrower nanotubes, what can be attributed to the different arrangements observed for water molecules inside these nanotubes. In (6,6) CNT water forms a single chain of molecules and, as diameter increases, tubular structures are observed, which is in agreement with previous reports [14][15][16][17][18][19]. These differences on the structural ordering is a direct consequence of the changing in the effective volume of nanotube, in the sense that not all the inner volume is available to water due to the repulsion (scaling to r À12 ) between these molecules and CNT wall.…”

Effect of Cross-Linking on the Diffusion of Water, Ions, and Small Molecules in Hydrogels

“…where a is the equivalent bond length of the monomer, ϕ is the polymer volume fraction, r s is the radius of solute, r f is the radius of polymer chain, C ∞ is the characteristic ratio of polymer, χ is the Flory-Huggins polymer/solvent interaction parameter, D g is the diffusion coefficient of solute in gel, and D 0 is the diffusion coefficient of solute in water calculated from MD simulation and verified by literature [38,102,72,73,74].…”

Formation of ice nanotube with hydrophobic guests inside carbon nanotube

“…Then the isobaric partition function, i.e., the Laplace transform of Eq. (7), is given by Y (P T) = e ;N = y N+1 a N (8) with y = Z 1 0 e ; Pz e ; (z) dz and a = e ; f 1 =l: (9) In the thermodynamic limit N ! 1 , = ;kTln(ya) (10) and = ; @ ln y @ P !…”