Reversible metal-semiconductor transition of ssDNA-decorated single-walled carbon nanotubes.

A field effect transistor (FET) measurement of a single-walled carbon nanotube (SWNT) shows a transition from a metallic one to a p-type semiconductor after helical wrapping of DNA. Water is found to be critical to activate this metal-semiconductor transition in the ssDNA-SWNT hybrid. Raman spectroscopy confirms the same change in electrical behaviors. According to our ab initio calculations, a band gap can open up in a metallic SWNT with wrapped ssDNA in the presence of water molecules due to charge transfer.