title: Carbon nanotube doping mechanism in a salt solution and hygroscopic effect: density functional theory.
abstract: The mechanism of doping carbon nanotubes (CNTs) with a salt solution was investigated using the density functional theory. We propose that the anion-CNT complex is a key component in doping CNTs. Although the cations play an important role in ionizing CNTs as an intermediate precursor, the ionized CNTs are neutralized further by forming a stable anion-CNT complex as a final reactant. The anion-CNT bond has a strong ionic bonding character and clearly shows p-type behavior by shifting the Fermi level toward the valence band. The midgap state is introduced by the strong binding of carbon and anion atoms. These localized charged anion sites are highly hygroscopic and induce the adsorption of water molecules. This behavior provides a new possibility for using anion-functionalized CNTs as humidity sensors.
authors.affiliation: Sungkyunkwan Advanced Institute of Nanotechnology, Department of Energy Science, Center for Nanotubes and Nanostructured Composites, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Dinh Loc
authors.initials: DL
authors.lastname: Duong
authors.forename: Il Ha
authors.initials: IH
authors.lastname: Lee
authors.forename: Ki Kang
authors.initials: KK
authors.lastname: Kim
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
authors.forename: Seung Mi
authors.initials: SM
authors.lastname: Lee
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Lee