The intentional incorporation of impurities and defects can serve as a powerful tool for modification of the electronic and optical properties of host nanomaterials and enabling of new functionalities¹. Introduction of Sp³ defects by covalent functionalization to single-walled carbon nanotubes (SWCNTs) generates new emission states with energies lower than the optical bandgap (E₁₁) of SWCNTs by 100 to 300 meV². With controllable emission wavelengths and high quantum yield, these defect states open up new opportunities for the applications of SWCNTs in photonics such as lasing, photon upconversion and single photon emission³.

Recently, it has been shown that such doping sites are capable of emitting single photons at room-T, which opens the possibility of building room-T electrically-driven single photon emitters based on doped-SWCNTs. The realization of these devices needs the fine control of doping densities, to the point of introduction of solitary dopants on individual SWCNTs. It also requires the high emission quality from doping states, such as sharp linewidth of the emission spectra and non-blinking of the emission intensity.

In this work, we showed a chemical approach capable of creating solitary dopants on SWCNTs of different diameters. Our method was based on the fine control of the doping of surfactant-suspended and poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) wrapped SWCNTs by different diazonium salts. Quantum optical studies were performed on the diazonium doped-SWCNTs. We first investigated the photoluminescence (PL) spectra of doped-SWCNTs at room temperature and low temperature (4K). Individual, bright and stable emission peaks were observed from doped SWCNTs at room-T. The linewidth of the PL peaks decreased to 200 mirco-eV at 4K. Next, Hanbury Brown-Twiss (HBT) experiment was performed to explore the single photon nature of the emissions. Strong photon ant-bunching behavior with purity above 99% were observed on the doping emission peaks in the range of 1100-1400 nm at RT(295k).

[1] Piao, Yanmei. et al. Nature Chem. 2013, 5, 840.

[2] Hartmann, Nicolai F. et al. Nanoscale. 2015, 7,20521.

[3] Kim, Mijin. et al. J. Phys. Chem. C . 2016, 120, 11268.

[4] Ma, Xuedan. et al. Nature Nanotech. 2015, 10, 671.