By grabbing various types of atoms and putting them together LEGO-style, the new technique could potentially be used to build tiny wires for a wide range of applications, including optoelectronic devices that employ both electricity and light and superconducting materials that conduct electricity without any loss.
“What we have shown here is that we can make tiny, conductive wires of the smallest possible size that essentially assemble themselves,” said Hao Yan, postdoctoral researcher at Stanford University in the US.
“The process is a simple, one-pot synthesis. You dump the ingredients together and you can get results in half an hour. It’s almost as if the diamondoids know where they want to go,” said Yan.
This animation shows molecular building blocks joining the tip of a growing nanowire.
Each block consists of a diamondoid, the smallest bit of diamond, attached to sulphur and copper atoms.
Like LEGO blocks, they only fit together in certain ways that are determined by their size and shape.
The copper and sulphur atoms form a conductive wire in the middle, and the diamondoids form an insulating outer shell.
Although there are other ways to get materials to self-assemble, this is the first one shown to make a nanowire with a solid, crystalline core that has good electronic properties, said Nicholas Melosh, from the US Department of Energy’s SLAC National Accelerator Laboratory.
The needle-like wires have a semiconducting core, a combination of copper and sulphur known as a chalcogenide surrounded by the attached diamondoids, which form an insulating shell.
Their size is important because a material that exists in just one or two dimensions as atomic-scale dots, wires or sheets – can have very different, extraordinary properties compared to the same material made in bulk, Melosh said.
The new method allows researchers to assemble those materials with atom-by-atom precision and control.
The diamondoids they used as assembly tools are tiny, interlocking cages of carbon and hydrogen.
Found naturally in petroleum fluids, they are extracted and separated by size and geometry in a SLAC laboratory.
For this study, the research team took advantage of the fact that diamondoids are strongly attracted to each other, through what are known as van der Waals forces.
They started with the smallest possible diamondoids, single cages that contain just 10 carbon atoms and attached a sulphur atom to each.
Floating in a solution, each sulphur atom bonded with a copper ion. This created the basic nanowire building block.
The building blocks then drifted toward each other, due to van der Waals attraction and attached to the tip of the wire.
The research was published in the journal Nature Materials.