The technique for making the nanocables was invented by UC Davis chemical engineers led by Pieter Stroeve, professor of chemical engineering and materials science. They manufacture the cables in the nano-sized pores of a template membrane. The insides of the pores are coated with gold. Layers of other semiconductors, such as tellurium, cadmium sulfide or zinc sulfide, are electrochemically deposited in the gold tube until a solid cable forms, then the membrane is dissolved, leaving finished cables behind.
Stroeve envisions many uses for these nanocables. For example, the cables' ability to conduct electricity changes when they are exposed to different chemicals or toxins. Earlier nano-devices could only detect whether a toxin was present, said Ruxandra Vidu, a postdoctoral scholar working with Stroeve. But nanocables will go further, measuring the quantity of toxins.
Stroeve's team can also construct arrays of nanocables. "You put a copper tape on the tops of the nanocables before the template is dissolved," Stroeve said. "You're left with nanocables sticking up at right angles from the tape."
These arrays have a very large surface area -- 1000 times greater than on a flat device of the same size. They could be used to efficiently capture sunlight in a tiny solar cell.
Nanocables could also be used to make computer chips more powerful by packing transistors closer together. Computers now contain silicon chips with metal transistors affixed to the surface. "With our new technique, we could embed transistors into the silicon chips to begin with," Stroeve said.
The work is published online in the Journal of the American Chemical Society.