Oct. 24, 2002
Vol. 22 No. 3

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    Scientists to further explore nanohybrid structures

    By Steve Koppes
    News Office

    The distances between the polymer-based structures in this image are only 50 nanometers in diameter. With further modifications, such structures could possibly be used to create next-generation electronics or ultrahigh density data storage devices. The image above was obtained by graduate student Deepak Sundrani, working in the laboratory of Professor Steven Sibener, who will speak at the Nanohybrid Structures Workshop Friday, Nov. 15, and Saturday, Nov. 16.

    A select group of 60 scientists from across the country will convene at the University Friday, Nov. 15 and Saturday, Nov. 16, to discuss the emerging field of nanohybrid structures. Nanoscientists build these structures to develop smaller, faster computers, accelerate drug discovery and development, and spur a variety of other potential applications.

    Only in the last few years have scientists attempted to make nanohybrid structures, which involves combining organic and inorganic building blocks at the scale of atoms and molecules. “Now we realize that there are insights to be gained,” said Thomas Witten, Professor in Physics and workshop co-organizer. “We wanted to get the people together who are excited about this field, see where we stand and where we could take the field.”

    Scientists find it difficult to produce hybrid structures measuring between 10 and 20 nanometers, or the width of 100 to 200 atoms, Witten said. Nature is quite capable of producing structure at this scale, but rarely does. Workshop participants will discuss how to technologically influence nature to produce structure at the desired scale for them. The workshop is sponsored by the Materials Research Science and Engineering Center, and the Argonne National Laboratory/University of Chicago Consortium for Nanoscience Research.

    “We are especially interested in not-too-small sizes,” Witten said. “If structures or patterns are much smaller than 10 nanometers, the discrete size of the atoms starts to influence the structure.”

    Instead, nanoscientists are interested in developing new types of structure that arise from the collective effects of an indefinite number of atoms. “These collective effects require the size of the structure to be large enough so that each piece has many atoms. In practice, this sets a lower limit in the range of 10 nanometers,” Witten said.

    The processes and materials to be examined are nanoscale self-assembly, a process which guides the formation of materials following the inherent tendencies of their properties; colloidal materials–particles that are suspended in liquids; and self-structuring polymers–large, chainlike molecules that can be similarly coaxed into new configurations.

    One class of technologically promising polymers are amphiphilic, meaning they consist of two mutually repulsive parts. Nevertheless, scientists have found that they can forge new structures by forcing connections between these opposing polymers. Likewise, mixing polymers with colloids also can result in the synthesis of new structures. “You get structures that are not foreseeable, or at least not obvious, from the things that you put in,” Witten said.

    Workshop speakers who will address polymer structures include Steven Sibener, the Carl Eisendrath Professor in Chemistry at Chicago, and Princeton University’s Paul Chaikin.

    Several workshop speakers will make presentations on tiny particles called soluble quantum dots that have applications ranging from computation and magnetic memory, to drug testing and development. Quantum dots are tiny pieces of semiconductor material, which can both resist or pass the flow of electric current.

    “One of the neat features of those things is that they not only absorb light, but they also emit light,” said workshop co-organizer Philippe Guyot-Sionnest, Professor in Chemistry and Physics and Physics. This permits them to be used as molecular beacons for identifying specific enzymes and proteins in biological tests.

    “There’s a lot of interest in developing these particles for biological imaging,” Guyot-Sionnest said.

    Speakers on quantum dots will include Victor Klimov of Los Alamos National Laboratory and Chris Murray of IBM. Klimov helped develop the first lasers made of quantum dots. “Murray is one of the leaders in making these types of nanoparticles, controlling their size and their chemical composition,” Guyot-Sionnest said.

    Controlling the composition of quantum dots enables researchers to tune their properties for use as either semiconductors or magnetic materials. By controlling semiconductor size, researchers also can control the wavelengths–and therefore the colors–of the dots, permitting a variety of tests to be conducted simultaneously.

    For magnetic materials, controlling dot size defines a bit’s storage density and its magnetic properties.

    Quantum-dot technology already has entered the marketplace for pharmaceutical and diagnostic applications via companies such as Evident Technologies of Troy, N.Y., and Quantum Dot Corporation of Hayward, Calif. Representatives of both companies are planning to attend the workshop.

    Although the workshop organizers expect no breakthroughs to be announced at the meeting, “people are going to make connections that maybe will lead to a discovery later on,” Witten said.