MERCED, CA. — Visitors to the electron microscopy laboratory at UC Merced soon will be able to play Superman. No, they won't be able to fly, but they will be able to experience sight that is a million times more powerful than the human eye.
Recently hired as an Assistant Professor of Materials Engineering at UC Merced, Valerie Leppert, Ph.D., is currently overseeing installation of a transmission electron microscope that goes way beyond the famed Superhero's X-ray vision. By comparison, the new microscope, to be operational later this year, will be about 5,000 times more powerful than the typical light microscopes found in high school and undergraduate college classrooms.
The concept of such a powerful tool naturally invites a few questions, such as, “What is Leppert going to do with it?”
Leppert studies nanomaterials - particles about one billionth of a meter in diameter - including semiconductors and air particulates from the environment, in order to learn why the tiny particles behave the way they do. The semiconductor nanoparticles she examines are made of materials such as silicon and zinc selenide. The air particulates are made of iron oxides and soot, which are byproducts of combustion and are similar to diesel engine exhaust.
Focusing on light emission, her semiconductor research will someday let scientists engineer new and improved nanomaterials to benefit technology and the environment. Future uses for better nanomaterials could include more sensitive and environmentally friendly tests to detect hazards like chemical weapons in water and food supplies.
The research on air particulates, done in collaboration with colleagues at UC Davis, looks at why they make people sick when inhaled. She believes the answer lies in the chemistry of the particles' surfaces, and finding the answer could lead to better combustion processes that produce less harmful particulates, someday improving air quality and the respiratory health of San Joaquin Valley residents.
“It's an emerging science,” Leppert says. “If we're going to use these materials we need to understand them better. There's a lot we need to learn.”
She adds that there is a host of emerging uses for nanomaterials in technological applications, including use in airplane materials and electronic sensors.
“Dr. Leppert's extraordinary expertise in this exciting new field of nanomaterials, and her enthusiasm for scientific inquiry and discovery epitomize the academic excellence that is emerging at UC Merced,” says Jeff Wright, Dean of Engineering at the new campus. “Not only is she a gifted researcher, but she has assumed a leadership role among our faculty in developing innovative educational programs for our students. She has a passion for multidisciplinary scholarship that is contagious; we are so fortunate to have her on our team.”
Nanomaterials interest Leppert because at that extraordinarily reduced size, their properties are quite different from regular-sized particles, and can be size dependent. In addition, since they have proportionately more surface area than larger particles, their behavior is dominated by their surface properties, which can be very different from those of their interiors.
As a case in point, ordinary semiconductor materials of a particular composition emit light of one color only, while nanomaterials emit light that becomes a more intense blue as the size of the particle is reduced. Light emission also is key to the particles' various uses. For example, different-sized particles can be coded to react to different hazardous chemicals, and a water sample will then emit light of a particular color depending on what chemical is present.
Though other scientists have used the super-powerful microscopes, Leppert says the potential to study the properties of individual particles and their surfaces is just beginning to be realized - an area she views as important to human health research, since the surfaces are what people come into contact with when breathing polluted air.
“It is the only tool that is going to let you form an image of this really small thing and examine the structure and chemistry of the surface versus the interior at the same time. It is the only technique that allows you to do all of these on such a small scale,” Leppert says. “The tools have existed, but new advances being made in their capabilities are allowing us to use them to give us new information. Most research has looked at aggregates of many particles or at only one characteristic of a single particle, such as the wavelength of light emitted.”
Plans for the laboratory also include another microscope - a scanning electron microscope to study bulk materials - and an assortment of accessories and special “slicing and dicing” tools required to prepare samples for the transmission electron microscope. Leppert and her colleagues have submitted grant requests to the National Science Foundation seeking funding for these items and a staff member to run the lab. She is also quite pleased that she was able to buy the transmission electron microscope, which normally costs $650,000, for $350,000 by purchasing an almost-new demo model.
In 2002, Leppert received a prestigious $449,000 ADVANCE Fellows grant from the National Science Foundation for her studies on nanomaterials. The grant, in part, will fund graduate students who will assist in her research at UC Merced.
Before joining UC Merced, Leppert was an Adjunct Assistant Professor and Assistant Professional Researcher at UC Davis. She holds B.A. degrees in both biology and physics and chemistry from Sonoma State University, and a Ph.D. in materials science and engineering from Northwestern University.
She lives with her daughter Danielle, 6, and son Jonah, 3, in the Sierra foothills community of Mariposa.