By Marlene Cimons, National Science Foundation
Mildred Dresselhaus started studying carbon nearly 50 years ago, early in her research career, when few scientists had any interest in this important element, the strongest material known and the sixth most abundant in nature.
Often dubbed the “Queen of Carbon Science,” Dresselhaus, 81, a longtime Massachusetts Institute of Technology professor, is regarded as a leader in the field of condensed matter and materials physics, and an expert on all the multi-faceted forms of carbon from its largest sizes to its tiniest.
“Carbon is a very important material in our planet,’’ she says. “The world has a huge amount of carbon in it. Lots of things have to do with carbon. Carbon atoms, all by themselves, make interesting material in nature. If you go walking in the woods, you can find flakes of carbon in the soil. My first ten years were spent studying the electronic structure of carbon, and getting to understand how it works.’’
Her research into superconductivity, the electronic properties of carbon, thermoelectricity and the new physics at the nanometer scale have led to numerous scientific discoveries, with the potential for more.
Dresselhaus, MIT’s institute professor emerita of electrical engineering and physics, recently won the prestigious Kavli Prize for nanoscience, “for her pioneering contributions to the study of phonons, electron-phonon interactions, and thermal transport in nanostructures,” an honor that also brings $1 million award. She also is a longtime grantee of the National Science Foundation (NSF), dating back to the 1960s, when NSF first began supporting her materials research.
The Kavli committee lauded her multiple advances explaining how the nanoscale properties of materials can vary from those of the same materials at larger dimensions, as well as her early work on carbon fibers and on intercalation compounds for laying the groundwork for later discoveries concerning carbon nanotubes, graphene and buckeyballs. (The latter are large molecules of carbon, each one composed of 60 or 70 carbon atoms linked together in a structure that resembles a soccer ball. Buckeyballs can trap other atoms, appear capable of withstanding great pressures and have magnetic and superconductive properties.)
“Nowadays, circuits are based on nanotubes and graphene combinations,’’ she says. “I’m not going to tell you that they will replace silicon, but carbon electronics will have a role in electronics in the future, particularly in high frequency communications. There is a big limit to what silicon can go up to, and in that regime, carbon will take over.’’
The first concept she worked on involved creating atomic sized “intercalation’’ compounds made up of “super lattices,’’ layers of different chemical species sandwiched between layers of graphite, the foundation of lithium-ion batteries, such as those used in automobiles and cell phones.
Later, she sought to learn more about carbon at the nanoscale, a size so incredibly small it must be magnified ten million times to be seen by the naked eye. In 1992, she was among the first to propose that carbon nanotubes--tubes with the thickness of a single atom--could be metallic or semi-conducting, depending on their structure. Later, she made them.
“Nowadays, we’ve gone beyond the nanotubes and we’re back to graphene, which is where we started in 1960,’’ she says. “You take a single nanotube, split it open and you get a little ribbon of graphene. You flatten it out and make a sheet out of it. A nanotube is a rolled up graphene sheet.’’
Graphene is a single atomic layer of carbon molecules, and currently the focus of considerable research. It shows great promise for use in electronics and other fields as a fast, efficient substance from which to make computer chips, sensors, and ultracapacitors, devices that supply energy but differ from batteries in that they can be charged and discharged quickly, although, unlike batteries, cannot store energy very well.