Research Communications

Speedy Science 

New laser lab equipment to aid studies of next generation light-sensitive materials

May 31, 2011

For uses ranging from computer technology to green energy, scientists are seeking new materials that quickly react to light. How fast? With the aid of a new spectrometer, Ohio University researchers now can study changes on the time scale of femtoseconds, which are a millionth of a billionth of a second.

“Comparing femtoseconds to seconds is like comparing seconds to the age of the universe,” Greg Van Patten explains.

Van Patten and Jeff Rack, both associate professors of chemistry and biochemistry, now lead one of only 12 labs in North America with this particular spectrometer, which can track ultrafast processes in photosensitive materials. The equipment was funded with a $400,000 grant from the National Science Foundation.

Laser Lab
The spectrometer features a maze of delicate crystal lenses through which a laser passes before hitting its target.

Rack uses the spectrometer to study photochromic compounds, which can change color and structure when exposed to light, a useful quality for applications ranging from computer optics and military protection gear to commercial sunglasses.

Measurements from the new instrument will help Rack develop new types of these chameleon-like materials.

Rack opens the top of the machine to reveal a maze of delicate crystal lenses through which a laser passes before hitting its target. The process can yield clues to how well the particular photochromic material under study changes and responds to light, and how well it maintains those changes, which could point to candidates for new, stable materials.

Jeff Rack
Jeff Rack.

Ten years ago, this experiment took several days to complete rather than seconds, and would require pulling all-nighters in the lab, Rack recalls. Only certain wavelengths of light could be studied, due to technology limitations. The new spectrometer allows ready access to a broad range of wavelengths, from the ultraviolet, through the visible region, and into the mid-infrared.

Van Patten will take advantage of the new equipment’s attributes to further his research on quantum dots, nanometer-sized crystals of semiconductor material that could be a smaller, faster alternative to current materials used in solar energy applications.

Greg Van Patten
Greg Van Patten.

The spectrometer will allow scientists to observe a key event in solar energy conversion called photoinduced charge transfer in a matter of picoseconds, if not faster. Previously, the research group only could collect indirect evidence of the process, Van Patten says. Direct observation will help scientists learn how the size, shape, and composition of their quantum dots can be used to improve solar conversion efficiency in real devices, he notes.

The scientists’ laser lab also features equipment that makes measurements of light-induced changes on much longer time scales—nanoseconds, which is a million times slower than femtoseconds.  These existing instruments, coupled with the new spectrometer, can generate a complete understanding of photoinduced processes that occur in the materials under study.

The spectrometer also will be used for other lines of research on campus. Physicist Eric Stinaff plans to conduct additional nanoscience experiments, and chemist Jennifer Hines will pursue biomedical research on RNA.

By Andrea Gibson

This article appears in the Spring/Summer 2011 issue of Perspectives magazine.