Band-gap sensitive adsorption of fluorine molecules on sidewalls of carbon nanotubes: an ab intio study

Woon Ih Choi, Sohee Park, Tae-Eun Kim, Noejung Park, Kwang-Ryeol Lee, Young Hee Lee, Jisoon Ihm and Seungwu Han
 

We report from ab initio calculations that the band-gap sensitive side-wall functionalization of a carbon nanotube is feasible with the fluorine molecule (F₂), which can provide a route to the extraction of semiconducting nanotubes by etching away metallic ones. In the small diameter cases like (11, 0) and (12, 0), the nanotubes are easily functionalized with F₂ regardless of their electronic properties. As the diameter becomes larger, however, the fluorination is favoured on metallic CNTs with smaller activation barriers than those of semiconducting ones. Our results suggest that low-temperature exposure to F₂ molecules in the gas phase can make a dominant portion of fluorinated metallic nanotubes and unfluorinated semiconducting ones. This is consistent with recent experimental reports.