Semiconducting single-walled carbon nanotubes (SWNTs) show near infrared photoluminescence (NIR PL) based on the Van Hove singularity in the one-dimensional structures. Recently, PL enhancement with wavelength shifts of the SWNTs has been reported through a very limited amount of chemical modification by oxygen atom doping and sp³ defect doping on the sp²networks.[1-3] In this study, we have examined modulation of the PL properties from a view point of structural design of the modified sites on the local-f-SWNTs using designed molecules.[4,5]

Bisdiazonium compounds (2Dz) are newly synthesized and we find that the local-f-SWNTs using 2Dz (SWNT/2Dz) shows new red-shifted PL.[4] Namely, the emission peak appears at 1256 nm which is remarkably red-shifted than those of pristine SWNTs (985 nm) and mono-functionalized SWNTs (SWNT/1Dz, 1129 nm), as shown in Figure. It is considered that the chemical modification using 2Dz provides an emissive site with a narrower band gap on the SWNTs owing to local dissociation of a degenerate energy band through modification-induced symmetry breaking of the SWNT. Moreover, wavelengths of the new PL are changed with dependence of the methylene linker length of 2Dz.

Other structural factors for PL modulation of local-f-SWNTs will be presented at the meeting.

References: [1] Weisman, R. B. et al., Science 2010, 330, 1656-1659. [2] Wang, Y. et al., Nat. Chem. 2013, 5, 840-845. [3] Nakashima, N. et al., J. Phys. Chem. C 2016, 120, 15632-15639. [4] Nakashima, N. et al., Sci. Rep. 2016, 6, 28393. [5] Nakashima, N. et al., Chem. Commun. 2016, 52, 12972-12975.