Advance in Synthesizing Carbon Nanotubes
The exciting new material that many hope will revolutionize electronics with amazing thermal, mechanical, and electronic properties is carbon nanotubes (CNTs). These are made from carbon atoms in a honeycomb arrangement, in a single-molecule sheet that can be rolled up into a tube. They promise a next generation of smaller, faster, and more efficient computers and electronics.
Mass production, however, has been challenging, specifically manufacturing CNTs in large amounts with sufficient purity. Even slight changes in structure may alter the electrical properties of CNTs, from conductors to semiconductors, for example.
Researchers at Empa and the Max Planck Institute for Solid State Research recently reported in Nature that they successfully tested a method for growing single-walled CNTs (SWCNTs) using a platinum based and a molecular seed. Depending on the starting molecule, they can control the formation of the SWCNTs, and grow long tubes of high purity with the desired electronic and other properties.
In the first step, in a manner reminiscent of origami, the flat starting molecule must be transformed into a three-dimensional object, the germling. This takes place on a hot platinum surface (Pt(111)) by means of a catalytic reaction in which hydrogen atoms are split off and new carbon-carbon bonds are formed at very specific locations. The “germ” – a small, dome-like entity with an open edge that sits on the platinum surface – is “folded” out of the flat molecule. This “end cap” forms the “lid” of the growing SWCNT. In a second chemical process, further carbon atoms are attached, which originate from the catalytic decomposition of ethylene (C2H4) on the platinum surface. They position themselves on the open edge between the platinum surface and the end cap and raise the cap higher and higher; the nanotube grows slowly upwards.
So far this process has only been tested under laboratory conditions. It’s not clear if this method, or some other method, will ultimately lead to commercial mass production of CNTs for specific applications. For now we have to drool over this promising future technology while the experts continue to make incremental advances.