Chemistry, Chirality, and Complexity as Concepts in Single-Walled Carbon Nanotube Research

More than 30 years have elapsed since the description of single-walled carbon nanotubes (SWCNTs). Thirty years of intense research effort initially focused on elucidating the outstanding physical properties of SWCNTs, which gave rise to hopes for an immediate technological revolution. In parallel, advancements in synthesis and purification procedures afforded ever better samples of SWCNTs. A deeper understanding of the difficulties in exploiting the extraordinary intrinsic properties of SWCNTs and the advent of graphene marked the end of the hype. SWCNTs have now stepped out of the valley of disillusionment and are firmly climbing the slope of enlightenment. In this review, we highlight three broad concepts that we believe will permeate research in SWCNTs for the next few years: chemistry, chirality, and complexity. The quality of commercially available SWCNT samples, coupled with advances in characterization techniques, particularly microscopy, facilitates complex chemical derivatization of SWCNTs with reliable structural characterization. The endohedral modification of SWCNTs, inclusion of quantum defects, and synthesis of mechanically interlocked derivatives are illustrative examples. We also overview how enantiomeric resolution of SWCNTs enables new fields of research such as chiral sensing, catalysis, and spin filtering. Complexity, once seen as an enemy, now shows promise in several fields, as exemplified by physically unclonable functions and neuromorphic computing. These three axes, controlled chemical modification, chiral discrimination, and system-level complexity, are increasingly interwoven, defining an emerging research landscape for SWCNTs. Taken together, they offer a framework for reimagining the roles of SWCNTs in both fundamental science and technology. We hope this review inspires innovative research lines and encourages young scientists to focus on SWCNTs.