Posted in | Nanoanalysis

Understanding the Secrets of Water on a Surface

It may seem a harmless question to ask how molecules of water arrange themselves to cover a surface, but the answer has big consequences. For instance, the drag experienced by water flowing past a surface affects the transport of pollutants in the environment. And the initial growth of ice crystals on dust is essential to the formation of raindrops.

Sandia National Laboratories researcher Peter J. Feibelman studies unexpected behavior at the liquid-solid interface (Photo by Randy Montoya)

In 2001, senior scientist Peter Feibelman proposed an unexpected solution to a long-standing experimental mystery concerning a one-molecule thick layer of water on ruthenium: By giving up a hydrogen atom, half the layer's water molecules find themselves more attracted to the surface. They therefore move closer to it, just as was seen, but not understood, in a 1994 diffraction experiment.

Feibelman's technical paper on this work, published in Science, has subsequently been referenced more than 200 times - an average of once every two weeks.

Now Feibelman has written, in his usual lucid style, the cover-story article of the current issue of Physics Today, the widely distributed publication of the American Institute of Physics. The article describes research leading up to his seminal paper and the papers following it.

Said Feibelman, "I had offered an explanation for the odd results of essentially the only quantitative measurement of atom positions on a wetting layer. As I recount in my review, this explanation stirred up a lot of interest, controversy, and further work, including several papers of my own."

Thereafter, Feibelman did other work on water-solid interactions, developing theoretical tools to help interpret data from (recently retired Sandian) Jack Houston's interfacial force microscope, and interpreting atomic-resolution, scanning-tunneling-microscope pictures of water on metals.

The editors of Physics Today emailed to ask Feibelman whom he would recommend to write a review of what was going on.

"I gave them several names, but also said I'd be happy to give it a try," said Feibelman. "They asked for an outline. I gave them a 2500 word stream-of-consciousness sample of what I had on my mind. They liked that enough to ask me to write the article."

The subject might seem abstract. But, as Feibelman wrote in the opening paragraph of his review, "The first layer of water molecules at a surface is the structural template that guides the growth of ice, embodies the boundary condition for water transport, and mediates aqueous interfacial chemistry. It thus determines if rain will fall, how fast pollutants migrate in rock and soil, and governs corrosion, catalysis, and countless other processes."

The article can be found at

Source: Sandia National Laboratories

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