Besenbacher and his colleagues have one of the world's fastest scanning tunneling microscopes, which has atomic-scale resolution. With it, they could see how quickly hydrogen atoms diffused across iron oxide in the presence of water.
To explain the fundamental mechanisms of how that happened, Mavrikakis and his team used quantum mechanics, a branch of physics that explains the behavior of matter on the atomic scale; and massively parallel computing. Essentially, when water is present, hydrogen diffuses via a proton transfer, or proton "hopping," mechanism, in which hydrogen atoms from the oxide surface jump onto nearby water molecules and make hydronium ions, which then deliver their extra proton to the oxide surface and liberate a water molecule. That repeated process leads to rapid hydrogen atom diffusion on the oxide surface.
It's a process that doesn't happen willy-nilly, either. The researchers also showed that when they roll out the proverbial red carpeta nanoscale "path" templated with hydrogen atomson iron oxide, the water will find that path, stay on it, and keep moving. The discovery could be relevant in nanoscale precision applications mediated by water, such as nanofluidics, nanotube sensors, and transfer across biological membranes, among others.
|Contact: Manos Mavrikakis|
University of Wisconsin-Madison