Review—Progress toward Applications of Carbon Nanotube Photoluminescence

Abstract

In the fifteen years following the discovery of single-walled carbon nanotube (SWCNT) photoluminescence, investigators have made significant progress in their understanding of the phenomenon and toward the development of applications. The intrinsic potential of semiconducting carbon nanotubes – a family of bright, photostable near infrared (NIR) fluorophores (900–2100 nm) with tunable properties, has motivated their use as optical probes and sensors. In this perspective, we highlight the advances made in the synthesis, processing, modification, separation, and metrology of carbon nanotubes in the context of applications of their photoluminescence. Single-walled carbon nanotubes are hollow cylinders of graphene, with diameters of approximately 1 nm and lengths that typically range from ∼ 10 nm to 10 μm 1 . The hexagonal graphene lattice, composed entirely of sp 2 -bonded carbon, can be rolled at varying angles to create seamless cylinders representing different nanotube structures. 2 Each distinct nanotube structure, or helicity, is uniquely identifiable by a pair of (n,m) integers, known as its chiral indices. Additionally, nanotubes exist as enantiomers, with (n,m) and (m,n) corresponding to the same chirality but different handedness. 3 The electronic bandgap between valence and conducting bands in the density of states determines whether a SWCNT is metallic (0 meV bandgap), semi-metallic (<100 meV bandgap) or semiconduct-ing (> 500 meV). 3 One-third of nanotube chiralities are metallic.