The structural and electronic properties of monovalent sidewall functionalized double-walled carbon nanotubes

The structural and electronic properties of (6,0)@(13,0) double-walled carbon nanotubes (DWCNTs) and monovalent sidewall functionalized DWCNTs with -NH2 and -COOH groups were studied using density functional theory. The results show that pure (6,0)@(13,0) DWCNTs are metallic. However, by functionalizing a DWCNT, local distortions are induced in the outer tube sidewall along the radial direction. The resulting structures, NH2/(6,0)@(13,0) and COOH/(6,0)@(13,0) DWCNTs, exhibit significant structural changes, and are semimetal with no energy gap and semiconducting with a small energy gap, respectively. In NH2/(6,0)@(13,0) DWCNTs, new electronic states are created and distributed on the outer wall and NH2 group by electron transfer from the inner tube to the NH2 group. In COOH/(6,0)@(13,0) DWCNTs, new states are created and distributed on the inner wall, but there is insignificant charge transfer between the inner tube and the COOH group. These results confirm that local atomic structural distortion on DWCNTs caused by sidewall functionalization can modify the electronic structures of DWCNTs. (C) 2012 Elsevier B. V. All rights reserved.