Surprises in Nanoribbon Synthesis

CHEMISTRY In the world of nanoparticles, nanoribbons are a newcomer to the variety of shapes that have been synthesized. Starting from molecular precursors, they have been fabricated from a variety of semiconductor oxides through a vapor deposition process in the presence of oxygen. Although this technique is now well developed, there are still some occasional surprises in the products that form. For the synthesis of tin oxide (SnO2) nanowires and nanotubes, Dai et al. found that in addition to the normal rutile structure, they also formed an orthorhombic superlattice structure and that the two could coexist. This latter morphology only exists in bulk SnO2 at high pressures, and it may have been caused by a deficiency in oxygen during the wire growth. Extending the synthesis of these objects to non-oxide systems, Zhang et al. found that with the addition of lithium, they could form aluminum carbide nanowires and nanoribbons. While attempting to make a metal aluminum carbide solid, some of the lithium reacted to form gaseous CLix molecules, which subsequently reacted to form Al4C3. This serendipitous observation indicates that it may be possible to use Li as a catalyst to form other carbide and nitride nanowires and nanoribbons from materials that do not naturally have molecular precursors. — MSL J. Phys. Chem. B 10.1021/jp013214r; Nano Lett . 10.1021/nl015656k.