ABSTRACT
We present the first experimental vibrational spectroscopy study providing direct evidence of a water phase inside single-walled carbon nanotubes that exhibits an unusual form of hydrogen-bonding due to confinement. Water adopts a stacked-ring structure inside nanotubes, forming intra- and inter-ring hydrogen bonds. The intra-ring hydrogen bonds are bulk-like while the inter-ring hydrogen bonds are relatively weak, having a distorted geometry that gives rise to a distinct OH stretching mode. The experimentally observed infrared mode at 3507 cm(-1) is assigned to vibrations of the inter-ring OH-groups based on detailed atomic-level modeling. The direct observation of unusual hydrogen bonding in nanotubes has potential implications for water in other highly confined systems, such as biological channels and nanoporous media.
ABSTRACT
A new method to study the diffusion properties of molecules into porous materials using transmission IR spectroscopy is employed. A measurement of the diffusion of the 2-chloroethylethyl sulfide (2-CEES) molecule into two types of gamma-Al2O3 powder is performed, showing that the diffusion rate into subnanometer crystallite particle size gamma-Al2O3 powders (subnano-Al2O3) is higher than that into the larger crystallite particle size powder. It is shown that a surface diffusion mechanism can be used to model the diffusion process giving good agreement with the experimental results, where Dsubnano-Al2O3 is approximately 5 times larger than Dmultinano-Al2O3 at 170 K for the 2-CEES molecule.
