Reversible diameter modulation of single-walled carbon nanotubes by acetonitrile-containing feedstock.

Changing the carbon feedstock from pure ethanol to a 5 vol % mixture of acetonitrile in ethanol during the growth of vertically aligned single-walled carbon nanotubes (SWNTs) reduces the mean diameter of the emerging SWNTs from approximately 2 to 1 nm. We show this feedstock-dependent change is reversible and repeatable, as demonstrated by multilayered vertically aligned SWNT structures. The reversibility of this process and lack of necessity for catalyst modification provides insight into the role of nitrogen in reducing the SWNT diameter.