Keywords: single-walled carbon nanotubes, nanostructures, sidewall functionalisation, surface chemistry, electronic structure, scanning tunnelling microscopy, surface science, nanotube sidewalls, nanotechnology
Carbon nanotube surface science
This paper presents a surface science perspective on sidewall functionalisation of carbon nanotubes. Carbon nanotubes are varyingly described by physicists as extended solids or by organic chemists as molecules. As prototypical nanostructures, they are indeed a little bit of both. Their chemistry and resulting potential applications can only truly be appreciated by combining both perspectives. The emphasis of this review is on the interdependence of topography and electronic structure on one side and chemistry and reactivity of carbon nanotube sidewalls on the other side. A brief introduction to the structure of single-walled carbon nanotubes and related materials (graphite, multi-wall carbon nanotubes and fullerenes) is followed by a review of possible deviations from perfect order in nanotube sidewalls, such as defects, functional groups or non-covalent interactions with nearby entities. We then proceed to review the implications of these deviations on the sidewall local electronic structure and chemical reactivity. Site-dependent functionalisation and induced reactivity on carbon nanotube sidewalls have been proposed theoretically and we have found some initial experimental evidence that this is indeed the case. However, this is a young field and many theoretical and experimental challenges still lie ahead. Understanding site-selectivity of carbon nanotube sidewall functionalisation will allow us to tailor their properties and utilise them as components of more complex nanostructures in the future.