Sp3 defect doping to semiconducting single-walled carbon nanotubes (SWNTs) provides fascinating near infrared photoluminescence (NIR PL) properties, in which, compared to PL (E₁₁) of pristine SWNTs, redshifted PL with enhanced quantum yields (E₁₁*) is observed by local functionalization through the doping.[1-6] In the locally functionalized SWNTs (lf-SWNTs), chemical structures of the modified molecules on the doped sites play an important role to determine and control the E₁₁* PL wavelengths. For example, we have succeeded in generation of remarkably redshifted PL on the basis of a proximal modification approach [5] and development of dynamic wavelength shift systems driven by molecular recognition at the doped sites [6].

Here, we report recent findings of the chemical structure factors that modulate the E₁₁* PL properties of aryl functionalized lf-SWNTs. When positional isomeric structures of the substituted aryl groups are introduced for the doped sites of lf-SWNTs (Figure), significantly different PL is observed from that of typical para-aryl modified lf-SWNTs.[3] Namely, the meta-aryl modified lf-SWNTs show deviation from the reported liner relationship between the Hammett substituent constants and ΔE = E₁₁*-E₁₁ of the para-aryl modified lf-SWNTs. For the ortho-aryl modified lf-SWNTs, two PL peaks generate by the functionalization and one of them appears in the largely redshifted region compared to typically observed E₁₁* PL. The present findings, therefore, are expected to provide new designs for the molecule-based PL modulation of lf-SWNTs. In this presentation, more details about the structural factors will be discussed.

References: [1] Schatz, G. C. and Wang, Y. et al., J. Am. Chem. Soc. 2016, 138, 6878-6885. [2] Htoon, H. and Doorn, S. K. et al., Nat. Photon. 2017, 11, 577-582. [3] Shiraki, T. and Nakashima, N. et al., Chem. Commun. 2017, in press, DOI:10.1039/C7CC06663E. [4] Shiraki, T. and Nakashima, N. et al., Nanoscale. 2017, in press, DOI:10.1039/C7NR05480G. [5] Shiraki, T. and Nakashima, N. et al., Sci. Rep. 2016, 6, 28393. [6] Shiraki, T. and Nakashima, N. et al., Chem. Commun. 2016, 52, 12972-12975.