"The technique is dead simpleit's kind of remarkable that it works," Heath says. The method, he explains, "is sort of like how people sputter carbon or gold onto biological cells so they can image them. The carbon or gold fixes the cells. Here, the graphene perfectly templates the weakly adsorbed water molecules on the surface and holds them in place, for up to a couple of months at least."
Using the technique, the researchers revealed new details about how water coats surfaces. They found that the first layer of water on mica is actually two water molecules thick, and has the structure of ice. Once that layer is fully formed, a second, two-molecule-thick layer of ice forms. On top of that, "you get droplets," Heath says. "It's truly amazing that the first two adsorbed layers of water form ice-like microscopic islands at room temperature," says Xu. "These fascinating structures are likely important in determining the surface properties of solids, including, for example, lubrication, adhesion, and corrosion."
The researchers have since successfully tested other molecules on other types of atomically flat surfacessuch flatness is necessary so the molecules don't nestle into imperfections in the surface, distorting their structure as measured through the graphene layer. "We have yet to find a system for which this doesn
|Contact: Kathy Svitil|
California Institute of Technology