Highly read on www.acs.org in February
A change in the orientation of molecular sheets in layered films may open up new uses for these materials.
Thin films are usually grown by stacking atoms horizontally, like sheets in a pad of paper. But Yi Cui and his colleagues at Stanford University in California have grown layers vertically, like dominoes balanced on their edges. The researchers started with strips of molybdenum and added sulphur or selenium atoms, which diffuse down through the molybdenum, carving nanometre-sized stripes.
The molybdenum atoms are sandwiched between sulphur or selenium atoms so that the top of the structure is made up of exposed edges. These sheet-edge structures are reactive, and so might make good catalysts, the authors say. As an example, they show that a reaction to produce hydrogen gas proceeds more rapidly with a higher concentration of sheet edges.