Surface, Density, and Temperature Effects on the Water Diffusion and Structure Inside Narrow Nanotubes

MH Kohler and JR Bordin, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 6684-6690 (2018).

DOI: 10.1021/acs.jpcc.8b00112

The nanoconfinement of water leads to outstanding anomalous behaviors. The interfacial interactions between water and surface is an important effect in the majority of these events. In this study, we have used the molecular dynamics simulations to investigate the diffusion characteristics of water molecules confined in narrow nanotubes with variable polarity. The nanotubes were built with hydrophilic or hydrophobic sites. Our results shows that there is a strong relation between density and surface properties for the water structuration inside the nanotubes. At low densities and narrower nanotubes, the surface characteristics play a major role, whereas for wider nanotubes, we observe distinct structuration at higher densities. The density is found to profoundly affect the water mobility in both nanotube species. This effect is accompanied by an organization in layers, resulting in structural transitions of water inside the nanotube as we increase the density. The temperature plays an important role in the transport of water inside small nanotubes. Our findings show that a small change in the nanotube diameter can lead to distinct dependence of diffusion with the temperature. The results indicate how density, temperature, and surface properties affect the dynamical and structural behavior of water inside narrow nanopores.

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