In Roman mythology, Janus was the god of change and transition, often portrayed with two faces gazing in opposite directions. At the University of Illinois at Urbana-Champaign, Janus particles are providing insight into the movement of molecules, and serving as the basis for new materials and sensors.
"By modifying the surface of colloidal particles into a Janus chemical compound, we can measure the rotational dynamics of single colloidal particles in suspension as well as at interfaces," said Steve Granick, a professor of materials science and engineering, chemistry and physics. "We can also take advantage of the particles two very dissimilar sides to create families of microsensors."
Using a metal-deposition technique, Granick and his research team -- graduate students Liang Hong and Steven Anthony, and postdoctoral research associate Huilin Tu -- make particles half-covered by metal, and generate geometrically symmetric but chemically asymmetric materials. Trapped inside the micron-size particles are fluorescent dyes, which can only be seen through the uncoated hemisphere, not through the metal-coated hemisphere.
James E. Kloeppel | EurekAlert!
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