Generation of photoluminescent ultrashort carbon nanotubes through nanoscale exciton localization at sp3 -defect sites

The intrinsic near-infrared photoluminescence observed in long single walled carbon nanotubes is systematically quenched in ultrashort single-walled carbon nanotubes (usCNTs, below 100 nm length) due to their short dimension as compared to the exciton diffusion length. It would however be key for number of applications to have such tiny nanostructure displaying photoluminescence emission to complement their unique physical, chemical and biological properties. Here we demonstrate that intense photoluminescence can be created in usCNTs (~40 nm length) upon incorporation of emissive sp3-defect sites in order to trap excitons. Using super-resolution imaging at <25 nm resolution, we directly reveal the localization of excitons at the defect sites on individual usCNTs. They are found preferentially localized at nanotube ends which can be separated by less than 40 nm and behave as independent emitters. The demonstration and control of bright near-infrared photoluminescence in usCNTs through exciton trapping opens the possibility to engineering tiny carbon nanotubes for applications in various domains of research including quantum optics and bioimaging.