Band Gap Opening in the Cycloaddition Functionalization of Carbon Nanotubes.

Covalent functionalization represents a promising avenue to tailor the electronic properties of carbon nanotubes. Recent experimental work has shown that cycloaddition of fluorinated olefins represents an effective approach to reduce the off-currents of mixed nanotube mats for transistor applications. We have studied the electronic structure characteristics of the corresponding [2 + 2] cycloaddition using dispersion-corrected density functional calculations. The band gap opening in chemically functionalized tubes is associated with the to rehybridization. Our calculation reveals that the experimentally observed suppression of metallic conductivity can be attributed to a symmetry aligned cycloaddition scheme that effectively transforms metallic tubes to semiconducting ones.