Study of ice leads to cool new research

Scientists at Pacific Northwest National Laboratory who studied how ice on comets can store large quantities of gas and release them as the comets near the sun are applying the same approach to new research. They're learning more about how nano-structures could be used to control and enhance chemical reactivity.

Stemming from the ice research funded by DOE's Office of Basic Energy Science, Zdenek Dohnálek, Bruce Kay, Greg Kimmel, Scott Smith and their colleagues in Pacific Northwest's Chemical Structure and Dynamics group began pursuing additional projects to determine how molecules enter pores, get captured and are eventually released.

New knowledge in this area could lead to the development of more efficient catalysts, which are materials that modify and increase the rate of chemical reactions.

Their current research is focused on creating porous films—not ice. They're building an understanding of the chemical and physical properties of these materials and characterizing their structure. The scientists are learning about the materials' surface areas and where gases and liquids accumulate on the surface. Soon they will begin studying how their catalytic properties may affect chemical reactions.

To create the films, researchers use a process called ballistic deposition to shoot a beam of molecules at a controlled angle toward the surface of a material. As these molecules condense at low temperatures, they form a porous film.

Similar to the way that a porous sponge can soak up large quantities of water, the porosity of the film results in a large surface area where more atoms are available for reactions.

"Virtually nothing is known about the fundamental chemistry of these nanoenvironments," said Dohnálek, a research scientist on the project. To date, most research in this area has been conducted by engineers who are interested in the dielectric and magnetic properties for potential uses in optics and electronics.

"We have the ability to create chemically tailored materials with various nonstructural features that can lead to enhanced selectivity and reactivity," said Kay, a senior chief scientist. "It takes specialized equipment to grow these kinds of materials and even more sophisticated instrumentation—like what we have available here—to study them," Kay said.

This work takes place at the William R. Wiley Environmental Molecular Sciences Laboratory, a DOE user facility operated by Pacific Northwest.•