(Invited) Substituted Aryl Structure Effects on Photoluminescence Properties of Locally Functionalized Single-Walled Carbon Nanotubes

Abstract

Sp3 defect doping to semiconducting single-walled carbon nanotubes (SWNTs) provides fascinating near infrared photoluminescence (NIR PL) properties, in which, compared to PL (E 11) of pristine SWNTs, redshifted PL with enhanced quantum yields (E 11*) 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 E 11* 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 E 11* 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 = E 11*-E 11 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 E 11* 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.