Last week’s post mentioned the work of Pittsburgh R.K. Mellon Professor of Chemistry and Physics John T. Yates Jr. He showed that water in carbon nanotube test tubes formed daisy chains connected by hydrogen and then stacked one upon the other as they went into the test tube nanotube.
This was a great puzzlement to me.
After all what did this have to do with the work of the LLNL scientists in May and the work of University of Kentucky scientists last November that showed super fast flow through rates for water passing through carbon nanotubes. (Certainly it seemed that LLNL & UK nanotubes were too wide to stop the Na & Cl atoms .)
What it looked like was that water actually takes on new properties spontaneously so as to conform appropriately to new space.
So I googled carbon nanotube +water and got one of those gee whiz duh wow moments that make science fun.
Consider this two year old post from the American Institute of Physics.
Nanotube water, a one-dimensional form of water consisting of a string of water molecules confined in a carbon nanotube, has been studied with neutron scattering by physicists at Argonne National Lab. Neutron scattering measurements, along with computer simulations of the molecular interactions between the water and the surrounding single-walled carbon nanotube, confirmed that water molecules had successfully been taken up into the nanotubes in the form of a “wire.” But this was not all; surrounding the water wire was another water structure, a sheath of water, a cylindrical square-ice- sheet formation (see figure).
The result of this novel architecture was that fluid-like behavior was observed at temperatures far below the freezing point of normal water. The hydrogen bonds along the water chain seem to be softened, allowing, for example, a freer movement of protons along the chain. The Argonne researchers (contact Alexander Kolesnikov, email@example.com, 630-252-3555) believe that this anomalous behavior might help to explain other phenomena featuring nm-scale confined water such as water migration from soil to plants via xylem vessels and the proton translocation in transmembrane proteins. (Kolesnikov et al., Physical Review Letters, 16 July 2004.)
Might also explain why water goes up a redwood tree. In any case, compare the picture presented by the American Institute of Physics with the picture presented by LLNL in their May 2006 presentation of their carbon nanotube and water experiments.
Proposed structure of nanotube-water, water confined with a single-wall carbon nanotube. The interior “chain” water molecules have been colored yellow to distinguish them from the exterior “shell” water molecules in red.
Reported by: Kolesnikov et al., Physical Review Letters, upcoming.
|Scott Dougherty, LLNL|
|Artist’s rendering of methane molecules flowing through a carbon nanotube less than two nanometers in diameter. (Click here to download a high-resolution image.)|
Of course, the LLNL picture shows methane passing through the nanotube and the American Institute of Physics picture shows water passing through the nanotube. But that’s not the point. The point here is that the American Institute of Physics picture may be the more accurate representation of what happened at the LLNL labs. So what? Well, the H20 molecule in Nanotube water has been strung out and shethed in more water. That configuration may be suffiently small & tight to exclude Na & Cl.