Conductivity control of SWNT with organic compounds

Abstract

Chemical sensors using carbon nanotubes (CNTs) are examined to detect organic molecules such as sulfur-containg hydrocarbon molecules. First, organic molecules, here butanethiol (C4H9SH), heptanethiol (C7H15SH), nonanethiol (C9H19SH), and dodecanethiol (C12H25SH), are adsorbed on a carbon nanotube (CNT) film, and then we investigate the adsorption behavior of each molecule with spectroscopic method. Infra-red spectrum reveals CH2 symmetric and asymmetric stretching bands clearly 2700 ~ 3100 cm-1 region. Furthermore, the number of adsorbed molecules is increased substantially as the carbon numbers in a molecule are increased from 4 to 12, i.e., butanethiol to dodecanethiol, compared with the degree of increase onto the gold surface. It strongly suggests that the hydrophobic interaction between the CNT and hydrocarbon molecules plays the key role as the chain length is increased. X-ray photoelectron spectroscopy (XPS) also suggests strong interaction between sulfur-containing molecules and CNT surface.