Nanocrystalline gold and gold palladium alloy catalysts for chemical synthesis.

Catalysis by gold has become one of the most studied new topics in chemistry in recent years, and yet for many gold acting as a catalyst is, perhaps, a most unlikely possibility since bulk gold is a relatively non-reactive, immutable, ductile metal that is prized for its great beauty and value rather than for the depth of its chemistry. However, when prepared in nanocrystalline form, as a collection of a few hundreds of atoms, it displays remarkable activity as a heterogeneous catalyst for a broad range of redox reactions. Of particular note is the ability of gold, either alone or alloyed with palladium, to catalyse selective oxidation reactions, e.g. alkene epoxidation, alcohol oxidation, and the direct synthesis of hydrogen peroxide by the hydrogenation of molecular oxygen. In this article the recent advances in this exciting new field are explored.