Physicists from Umeå University and Humboldt University in
Berlin have solved a mystery that has puzzled scientists for half a century.
They show with the help of powerful microscopes that the distance between graphite
oxide layers gradually increases when water molecules are added. That is
because the surface of graphite oxide is not flat, but varies in thickness with
"hills" and "valleys" of nanosize. The new findings are
published in the scientific journal Nano Letters.