  Semiconducting single-walled carbon nanotubes show extraordinary electronic
and optical properties, such as high charge carrier mobilities and
diameter-dependent near-infrared photoluminescence. The introduction of sp3
defects in the carbon lattice of these nanotubes creates new electronic states
that result in even further red-shifted photoluminescence with longer lifetimes
and higher photoluminescence yield. These luminescent defects or organic color
centers can be tuned chemically by controlling the precise binding
configuration and the electrostatic properties of the attached substituents.
This review covers the basic photophysics of luminescent sp3 defects, synthetic
methods for their controlled formation and discusses their application as
near-infrared single-photon emitters at room temperature, in electroluminescent
devices, as versatile optical sensors, and as fluorophores for bioimaging and
potential super-resolution microscopy.
