SCIENCE CONCENTRATES

Metal patterns from polymer composites

Metal nanoparticles can be directed to grow into lines and 3-D structures with a new patterning technique developed by chemistry professors Joseph W. Perry and Seth R. Marder and coworkers at the University of Arizona [Adv. Mater., 14, 194 (2002)]. The method could find use in fabricating 3-D electronic, optical, and electromechanical devices, the researchers say. They designed polymer nanocomposites containing ligand-coated metal nanoparticles, a metal salt, and a photoreducing dye. Single- or two-photon excitation of the dye with a laser induces it to transfer an electron to a metal ion, which adds onto a seed nanoparticle. The "laser writing" results in continuous silver, copper, or gold microstructures. Alternatively, the Arizona chemists shaped patterns by using electron-beam irradiation of thin films containing a metal salt and a dye attached to a metal nanoparticle. The nanocomposites are photochemically stable and still photoactive after months of storage without special precautions, suggesting they might be used for optical data storage, the researchers write.