Ab initio study of OH-functionalized single-wall carbon nanotubes

The effects of the OH group on the electronic and optical properties of single-wall carbon nanotubes were investigated using first principles electronic structure calculations. Our results confirm band-gap reduction of semiconductor carbon nanotubes up on addition of the OH group. An additional energy level emerges near the Fermi level, which is due to coupling between one $p$ orbital of the oxygen with the big $\mathrm{\pi }$ bond of the nanotube. Analysis of loss function showed that the plasmon excitation shifts to lower frequency.

Figure 1

(a) Top and (b) side views of the SWCNT-OH supercell used in our calculation. One OH group is attached on the wall of the SWCNT with the oxygen atom onnected to the carbon atom.

Figure 2

(a) Band structure of the zigzag $(10\times 0)$ SWCNT. (b) shows its details near the Fermi level $(E_{\mathrm{F}}=0\mathrm{eV})$.

Figure 3

(a) Band structure of the SWCNT-OH system. (b)shows its details near the Fermi level $(E_{\mathrm{F}}=0\mathrm{eV})$.

Figure 4

Electron density corresponding to (a) the $E_0$ level in the pure tube, (b) the $E^{\prime }$ level crossing the Fermi level, (c) the $E_{01}$ level and, (d) the $E_{02}$ level in the tube-OH system, respectively.

Figure 5

Calculated (a) total DOS of the pure SWCNT, and (b) total DOS of SWCNT-OH. The Fermi level is at 0 eV.

Figure 6

Loss functions (a) of zigzag $(10\times 0)$ SWCNT and (b) the SWCNT-OH system. The dotted line (solid line) corresponds to the case when the polarization direction is perpendicular (parallel) to the axis of the tube, respectively.