Nanosized clusters of germanium that can be reacted chemically to make useful materials, such as plastics, have been made by chemists at the University of Wisconsin-Stevens Point and UC Davis.

Nanoparticles, just a few atoms in size, can have different properties from bulk materials because of their small size. Germanium nanoparticles can have luminescent properties and could be used, for example, to make highly efficient lasers or other light-emitting devices. But these nanoparticles are difficult to work with without a chemical "handle."

Robin Tanke, an assistant professor of chemistry at UWSP, worked with UC Davis chemistry professors Susan Kauzlarich and Tim Patten to put useful coatings on germanium nanoclusters. Kauzlarich's laboratory has developed methods for making germanium and silicon nanoclusters, while Patten's research focuses on attaching polymer coatings to different kinds of nanoparticles.

Using this approach, the researchers grew chains of polymers from the nanoparticle surfaces. These materials could be made into plastics that could be cast as thin films for displays or other uses.

The strength of the chemical bonds between the nanoparticle and the coating makes the materials much more stable, Tanke said.

"You can process them as polymers, without losing the nanoparticles," she said.

The ability to put different types of chemical groups on the surface vastly expanded the possible uses of these semiconductor nanoparticles, Patten said. For example, one could connect a magnetic nanoparticle to a luminescent one to make a tiny building block that could be precisely moved or positioned on a surface, he said.

Katherine Pettigrew from UC Davis, Drew Murphy and Mark Thompson from the University of Southern California and Howard Lee from UltraDots Inc., Fremont, Calif. also contributed to the work, which was published in the journal Chemistry of Materials.