e is single layer of carbon atoms arranged like a nanoscale chicken-wire fence. Graphene is known to have excellent mechanical properties. The material is strong and tough and because of its flexibility can evenly coat nearly any surface. Many researchers and technology leaders see graphene as an enabling material that could greatly advance the advent of flexible, paper-thin devices and displays. Used as a coating for such devices, the graphene would certainly come into contact with moisture. Understanding how graphene interacts with moisture was the impetus behind this new study.
The spreading of water on a solid surface is called wetting. Calculating wettability involves placing a drop of water on a surface, and then measuring the angle at which the droplet meets the surface. The droplet will ball up and have a high contact angle on a hydrophobic surface. Inversely, the droplet will spread out and have a low contact angle on a hydrophilic surface.
The contact angle of gold is about 77 degrees. Koratkar and Ajayan found that after coating a gold surface with a single layer of graphene, the contact angle became about 78 degrees. Similarly, the contact angle of silicon rose from roughly 32 degrees to roughly 33 degrees, and copper increased from around 85 degrees to around 86 degrees, after adding a layer of graphene.
These results surprised the researchers. Graphene is impermeable, as the tiny spaces between its linked carbon atoms are too small for water, or a single proton, or anything else to fit through. Because of this, one would expect that water would not act as if it were on gold, silicon, or copper, since the graphene coating prevents the water from directly contacting these surfaces. But the research findings clearly show how the water is able to sense the presence of the underlying surface, and spreads on those surfaces as if the graphene were not present at all.
As the researchers increased the number of layers of grPage: 1 2 3 4 Related biology technology :1
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