Density functional theory studies of OH-modified open-ended single-wall zigzag carbon nanotubes (SWCNTs)

Functionalized carbon nanotubes (CNTs) are often formed as result of oxidation and cleaning of raw product grown on metal catalyst. Structure and energy of ideal and OH-modified single-wall nanotubes (SWCNTs) of different length (2.8, 7.0 and 13.5 Å) were obtained at the DFT-B3LYP level. From one to nine OH groups were added at the end of the nanotube and a nonadditive dependence of attachment energy on the number of substituents was observed. The energetics of SWCNT end substitution with OH groups was supported by high level MP2 and CCSD(T) determination of reaction energy: R-H+1/2O2→R-OH+ΔE for methane, benzene and anthracene. In addition, a vibrational analysis of the shortest nanotube was carried out and characteristic Raman bands were identified.