In their paper, titled "Wet electrons at the H2O/TiO2(110) Surface," Hrvoje Petek, Pitt professor of physics and codirector of Pitt's Institute of NanoScience and Engineering, and Kenneth Jordan, professor and chair of Pitt's Department of Chemistry, extend Jordan's previous work on the structure of electrons in small water clusters, which was named one of the top 10 breakthroughs of 2004 by Science.
Wet electrons, which occur on metal oxide surfaces, represent a transition point for electrons between solid and liquid states of matter. A tiny amount of water from the atmosphere sticks to the surfaces of the oxides and forms hydroxide molecules, which then act like "molecular-scale Velcro," said Petek. In the presence of energy, their positively charged hydrogen atoms attract negatively charged electrons. Those so-called "wet" electrons then determine how other molecules interact with the surfaces of metal oxides.
The researchers gave the electrons sufficient energy to achieve the wet state by directing short bursts of laser light at titanium dioxide. Titanium dioxide was used because it is a photocatalyst: Exposure to light excites its electrons, which split water molecules into hydrogen and oxygen. Because of this potential for making hydrogen from water, it is possible that titanium dioxide could be used to make a clean fuel--but the process remains inefficient, said Petek. "If we could find out how to make it more efficient by observing how electrons interact with hydrogen atoms, it would have a huge economic impact," he added.