Noncovalent Functionalization of Carbon Nanotubes

Within the past decades extensive research has shed light into the structure, reactivity and properties of carbon nanotubes (CNTs) [1–3]. This new carbon allotrope is theoretically constructed by rolling up a graphene sheet into a cylinder with the hexagonal rings joining seamlessly. Commonly, carbon nanotubes are classified into single-walled carbon nanotubes (SWCNTs) which consist of one cylinder and multi-walled carbon nanotubes (MWCNTs) comprising an array of tubes being concentrically nested. Depending on the roll-up vector which defines the arrangement of the hexagonal rings along the tubular surface, single-walled carbon nanotubes exhibit different physical and electronic properties, e.g. they either possess metallic or semiconducting character. Apart from their outstanding electronic properties providing the foundation for multiple applications as nanowires, field-effect transistors and electronic devices [3–5], carbon nanotubes surmount any other substance class in their mechanical properties. The exceptionally high tensile modulus (640GPa) and tensile strength ( 100GPa) together with the high aspect ratio (300–1000) make nanotubes an ideal candidate for reinforcing fibers and polymers [6, 7]. However, in order to tap the full potential of nanotubes in electronics, photonics, as sensors or in composite materials, twomajor obstacles have to be overcome, e.g. separation