Impact of covalent functionalization of carbon nanotubes on their optical properties: Computational insights

Our simulations of covalently functionalized CNTs have complimented and advanced recent experimental efforts in spectroscopy and chemistry of CNTs. A covalent binding of molecular adduct to the CNT, introducing sp3-hybridized defects into the sp2-lattice of the nanotube, results in redshifted optically active transitions providing defect-originated emission at the near infrared (NIR) range. Also, the sp3-defect in CNTs creates a required condition for single photon emission tunable from NIR to telecom wavelengths and achievable at room temperature. We have compared calculated and experimental results from pump-dependent low-temperature photoluminescence spectroscopy and identified the role of tube’s chirality, tube’s mode, adduct polarity, and defect-defect interactions in selective control of defect-associated emission of CNTs. Our results demonstrate that manipulation of the tube chirality together with the polarity and bond character of molecular adducts is a practical strategy for precise tuning of light emission in functionalized CNTs. Overall, our research outcomes have established foundation for the novel material design for solar energy conversion, sensing, and quantum technologies.