The peptides are made of 20 or so amino acids, so changing the sequence of amino acids allows the researchers to "tune the peptides and recognize different compounds," Tao said. "We developed a simple way to attach different peptides to different nanotubes."
Erica Forzani, an ASU assistant research professor in electrical engineering, said the peptides are selective to specific compounds. In the heavy metal tests, the researchers developed a peptide to detect nickel and one to detect copper. If the nickel peptide were used, it would only detect the presence of nickel and be "blind" to any other heavy metal ion (copper, lead or zinc) passing over the carbon nanotubes.
"The nanotubes basically are a sheet of interconnected atoms rolled into a tube," Tao said. "Every single atom in the tube is exposed to the environment and can interact with chemicals and molecules. That is why it is so sensitive. But without the peptides, it would not recognize specific compounds."
"The potential for the carbon nanotubes is extraordinary," Forzani added, "because with a very simple device that does not require sophisticated electronic circuitry, you can detect very low concentrations of analytes."
The researchers now will investigate the use of the sensors on biological molecules, like RNA sequence detection, Tao and Forzani said.