Rust on nanoparticle catalyst reversed by high-intensity light

Discovery : Propylene oxide, a chemical precursor to making plastics, is difficult to manufacture. Researchers are therefore looking for catalysts that will simplify and speed up the process. Marimuthu Andiappan of the University of Michigan and his colleagues were experimenting on the effects of metallic copper in the reaction. Although the copper did provide some improved reactions, much of the copper itself reacted with the oxygen, forming copper oxide rust. In an attempt to reduce the oxidation of the catalyst, they formed the copper into nanoparticles and coated them with silica. As a result, 20% of the propylene and oxygen reactants were converted into propylene oxide before the catalyst rusted. When they exposed the reaction to high-intensity light, 50% of the reactants were converted, meaning that the oxygen that had been trapped in the copper oxide had been released to react with the propylene. The successful catalyzation of the reaction is the more useful of the results, but the reversal of the rusting is the first known example of light changing the oxidization state of a metal.