Charge-transfer interaction in single-walled carbon nanotubes with tetrathiafulvalene and their applications

We observed that single-walled carbon nanotube (SWNT) was aligned in the presence of TTF. This alignment was induced by a specific interaction between SWNT and tetrathiafulvalene (TTF), a well-known organic donor. The interaction between the two molecules can be explained by a charge-transfer, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The binding energies of S (2P _1/2) and S (2P _3/2) were shifted from 163.0 eV and 164.1 eV to 163.9 eV and 165.1 eV, respectively. In Raman spectra of the SWNT-TTF, three peaks of SWNT in radial breathing mode were also upshifted by 4-5 cm ^-1. The charge-transfer interaction also contributed in modifying the electronic structure of SWNT and furthermore enhanced the electrical conductivity of SWNT. A more conductive thin film was fabricated using the SWNT-TTF. Four-probe measurement revealed that the surface resistance of the SWNT-TTF film was reduced to 4.359 Ω at room temperature while that of SWNT film was 6.894 Ω. These results enable carbon nanotubes to be utilized more for practically for industrial applications in fabricating peculiar nano-sized building blocks.