(Invited) Tube^2: Optical and Electrical Properties of Tube-in-a-Tube

Atomically-thick materials such as single-walled carbon nanotubes and graphene are prone to chemical attack because all of the constituent atoms are exposed. Conversely, at increased thicknesses, many of the remarkable properties of these materials are lost. In this talk, we will describe a novel tube-in-a-tube (Tube^2) structure with a unique combination of surface functionalities and interesting electronic and optical properties. Tube^2 is a synthetic semiconductor created from outer wall-selective functionalization of double-walled carbon nanotubes. Correlated Raman and optical absorption spectroscopy unambiguously confirm that the covalent modification is outer wall-selective. Nearly 50% of the electrical conductivity is retained in thin films of Tube^2 due to the intact inner-tube conducting channels. Lacking such channels, single-walled carbon nanotubes and graphene become insulators after similar functionalization. We further demonstrate that this chemically tailored functional structure allows simultaneous attainment of high sensitivity and selectivity in electrical detection of small molecules. These results highlight some of the structural advantages of this double-wall strategy for new materials and electronics.