Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Wetness-defying water?

17.10.2005


Pacific Northwest National Laboratory group discovers a paradox: hydrophobic H2O



Now you can extend that truism about oil and water to water and itself. Water and water don’t always mix, either.

The textbooks say that water readily comes together with other water, open arms of hydrogen clasping oxygen attached to other OH molecules. This is the very definition of “wetness.” But scientists at Pacific Northwest National Laboratory have observed a first: a single layer of water—ice grown on a platinum wafer—that gives the cold shoulder to subsequent layers of ice that come into contact with it.


“Water-surface interactions are ubiquitous in nature and play an important role in many technological applications such as catalysis and corrosion,” said Greg Kimmel, staff scientist at the Department of Energy lab and lead author of a paper to appear Oct. 15 in the advance online edition of Physical Review Letters. “It was assumed that one end of the water molecule would bind to metal, and at the other end would be these nice hydrogen attachment points for the atoms in next layer of water.”

A theory out of Cambridge University last year suggested that these attachment points, or “dangling OH’s,” did not exist, that instead of dangling, the OH’s were drawn by the geometry of hexagonal noble-metal surfaces and clung to that.

Kimmel and his co-authors, working at the PNNL-based W.R. Wiley Environmental Molecular Sciences Laboratory, tested the theory with a technique called rare gas physisorption that enlists krypton to probe metal surfaces and water layers on those surfaces. They found that the first single layer of water, or monolayer, wetted the platinum surface as they had expected but “that subsequent layers did not wet the first layer,” Kimmel said. “In other words, the first layer of water is hydrophobic.”

The results jibe with an earlier Stanford University study that used X-ray adsorption to show that rather than being fixed pointing outward in the dangling position, wet and ready to receive the next water layer, the arms of a water monolayer on a metal surface are double-jointed. They swivel back toward the surface of the metal to find a place to bind. To the water molecules approaching this bent-over-backward surface, the layer has all the attractiveness of a freshly waxed car’s hood.

The second layer beads up, but that’s not all: Additional water’s attraction to that first hydrophobic water monolayer is so weak that 50 or more ice-crystal layers can be piled atop the first until all the so-called non-wetting portions are covered—akin to “the coalescence of water drops on a waxed car in a torrential downpour,” said Bruce Kay, PNNL laboratory fellow and co-author with Kimmel and PNNL colleagues Nick Petrik and Zdenek Dohnálek.

Kimmel said that self-loathing water on metal is more than a curiosity and will come as a surprise to many in the field who assumed that water films uniformly cover surfaces. Hundreds of experiments have been done on thin water films grown on metal surfaces to learn such things as how these films affect molecules in which they come into contact and what role heat, light and high-energy radiation play in such interactions.

PNNL is a DOE Office of Science laboratory that solves complex problems in energy, national security, the environment and life sciences by advancing the understanding of physics, chemistry, biology and computation. PNNL employs 4,100 staff, has a $700 million annual budget, and has been managed by Ohio-based Battelle since the lab’s inception in 1965.

Bill Cannon | EurekAlert!
Further information:
http://www.pnl.gov

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>