  Oxygen defects in semiconducting single-walled carbon nanotubes (SWCNTs) are
localized disruptions in the carbon lattice caused by the formation of epoxy or
ether groups, commonly through wet-chemical reactions. The associated
modifications of the electronic structure can result in luminescent states with
emission energies below those of pristine SWCNTs in the near-infrared range,
which makes them promising candidates for applications in biosensing and as
single-photon emitters. Here, we demonstrate the controlled introduction of
luminescent oxygen defects into networks of monochiral (6,5) SWCNTs using a
solid-state photocatalytic approach. UV irradiation of SWCNTs on the
photoreactive surfaces of the transition metal oxides TiOx and ZnOx in the
presence of trace amounts of water and oxygen results in the creation of
reactive oxygen species that initiate radical reactions with the carbon lattice
and the formation of oxygen defects. The created ether-d and epoxide-l defect
configurations give rise to two distinct red-shifted emissive features. The
chemical and dielectric properties of the photoactive oxides influence the
final defect emission properties, with oxygen-functionalized SWCNTs on TiOx
substrates being brighter than those on ZnOx or pristine SWCNTs on glass. The
photoinduced functionalization of nanotubes is further employed to create
lateral patterns of oxygen defects in (6,5) SWCNT networks with micrometer
resolution and thus spatially controlled defect emission.
