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Past Winner
2007 E.W.R. Steacie Memorial Fellowship

Gregory D. Scholes

Chemistry

University of Toronto


Gregory D. Scholes
Gregory D. Scholes

Plants have it all figured out. They simply stick out their leaves into the nearest available ray of sunshine and turn solar energy into chemical energy that fuels their growth. The energy supply is free, abundant and available almost everywhere. University of Toronto chemist Gregory Scholes understands that process better than most, and is using his expertise to generate new materials that react to light in similar ways.

Dr. Scholes has spent his whole career studying how light initiates physical processes at the molecular scale and pondering how to help humans take better advantage of this fact. His diverse research program spans physics, physical chemistry, materials chemistry and biology. The results of his work, which include helping develop two major new theories about photosynthesis, have earned him a 2007 NSERC E.W.R. Steacie Memorial Fellowship.

His discoveries have led not only to an increased understanding of how molecules react to light, but to a wide range of applications including a potential source of new materials for use in semiconductors and other devices. Many of these devices exist already, of course, but there is a lot of room for improvement.

Taking his inspiration from the way naturally occurring molecules use light for their own purposes, Dr. Scholes focuses his research on nanocrystals – microscopic bits of material that can measure as little as two nanometres (billionths of a metre) across. Despite their tiny size, these are actually large and complex structures as molecules go, containing 1,000 or more atoms apiece.

One of the basic facts of chemistry is that the composition of molecules determines their properties, and even tiny differences in their chemical formula can lead to substantially different characteristics. In the case of nanocrystals, however, it turns out that the physical size of the molecule, although not necessarily the precise arrangement of every atom, has an effect on their properties. For example, when fashioned into “quantum dots” for use in a laser or a light-emitting diode, changing the size of the nanocrystal results in the colour of light being emitted by the device shifting from blue to green to red. Greater control over the size of these nanocrystals means a greater ability to fine tune the devices.

Even more intriguing, and one of the subjects of Dr. Scholes’ research during his Steacie Fellowship, is the possibility that changing the shape of a nanocrystal will also affect how it behaves. The possibilities include basic shapes such as cubes and rods, as well as more complex three-dimensional shapes. Testing this hypothesis is tricky business, since the nanocrystals greatly prefer to be spherical in shape. The growth of the crystal must be tightly controlled, then stopped at a certain point and the resulting material stabilized.

Dr. Scholes already knows which experiments he wants to conduct to test his ideas about the shape of nanocrystals, but is working on designing them carefully so they will work on more than one material. “Developing a way of seeing why shape might be special is a tricky thing,” he says. “The challenge is to create materials that have function.”

Those functions includes not just ensuring that a material has a certain property, but that it can be controlled, whether it’s transmitting energy, storing information or emitting light. And traditional semiconductor materials such as silicon are by no means the only ones under investigation, so are “conjugated polymers” – plastics that are among the leading candidates for building organically-based electronics.

The potential applications are numerous. One long-term dream, for example, would be to create solar cells that have the ability to rebuild themselves similar to the way components of the plant solar energy conversion machinery constantly regenerate themselves as sunlight breaks down their structure. Electronics manufacturers have their sights set on plastic TV screens that are flexible, lightweight and easy to manufacture. On the medical front, the ability to control the properties of nanocrystals has implications that include increasing the precision of imaging techniques and even developing completely new imaging methods.

Dr. Scholes is on sabbatical during the 2006-07 academic year, which has allowed him to study a few areas that have been simmering on the back burner. He spent last summer learning about new materials for solar cells at the National Renewable Energy Laboratory in Colorado and is currently working on problems related to the photosynthetic antennae built from chlorophyll at the Università di Pisa in Italy.

As testimony to the practical, real-world nature of much of his research, Dr. Scholes is named on three patent applications. Still, he also places great emphasis on the importance of understanding the theoretical underpinnings of his results. “The systems we are looking at are very complex and what they do is complex,” he explains. “You can do measurements on them, but it’s not a simple process of doing a measurement and getting an answer. You need a strong theoretical basis to guide you. The experiment provides the window, and the theory provides the means to look through the window.”