Various functionalization methods for carbon nanotubes have been proposed over several years now and some applications have come to reality using multi-walled structures. However, single-walled carbon nanotubes (SWCNTs) offer a rich and exciting scope of physical properties that cannot be overseen and there is still a vast playground for research. In this context, using functionalization methods to access the properties of SWCNTs in a controllable manner is of enormous interest. Among those methods, substitutional doping and intercalation will be the focus of this talk as examples since they offer a rich scope of potential applications. The heteroatoms responsible for the functionalization of the tubular structures can induce changes in the physical properties of the tubes, but the greatest challenge in this field is the proper understanding of the heteroatom content and distribution, which should be controlled for the next research phase towards applications. We will discuss the progress towards understanding how the energies of charge carriers and lattice vibrations are modified, among other effects due to the presence of heteroatoms and defects. I will give particular emphasis on establishing the prerequisites for studying the rich low-dimensional physics of substitutionally doped SWCNTs as an example. Furthermore, we will discuss the changes in the site selective electronic structure of other various examples of functionalized SWCNTs.
