# Edges of graphite

I've been asked this question a few times, and while I think I know the answer, I'd like to know more.

Graphite, as we know, is a sheet polymer. Since polymers are bound to be finite by physical considerations, graphite must have "edges". My question is, what happens at these edges?

I can cook up these possibilities:

• A graphene sheet "folds back" on itself, thus forming a tube and taking care of most of the edge carbons. But this would make graphite less slippery, so I doubt this is the case.

• Random elements/compounds from the environment at time of synthesis latch on to the edges, taking care of the valency of Carbon

• The edge carbons form double/triple bonds amongst themselves

I'd like to know more about this. I'm also curious what happens to the resonance of graphene at the edges.

• Are you sure "folding back" would make it significantly less slippery? After all, those bonds would only be present along lines of length of order $\mathcal{O}(\sqrt{n})$, while the forces between sheets act on a whole area: $\mathcal{O}(n)$, where $n$ is the number of atoms per sheet. Of course these forces are much weaker than valence bonds, but only by some 2-4 orders of magnitude. What is the size of graphene sheets in graphite? I would have thought it's more than $10^8$ atoms, so $\sqrt{n} > \eta$ and the forces between sheets would still dominate. – leftaroundabout May 17 '12 at 12:41
• @leftaroundabout: No, I'm not sure ;-) Yeah, that sort of makes sense. The slipperyness would decrease if the tubes had small diameter but large length. – ManishEarth May 17 '12 at 13:02

Defects in graphite result from oxidation. They are $\ce{ OH, COOH}$ and epoxy groups, as in this image: