Stimuli-Responsive Molecule Modification to Locally Functionalized Single-Walled Carbon Nanotubes for Wavelength Switching of Near Infrared Photoluminescence

Abstract

Single-walled carbon nanotubes (SWNTs) with semiconducting features show near infrared (NIR) photoluminescence (PL). Defect doping to the SWNTs has been found to enhance the PL properties, which is achieved by local chemical modification.[1-9] It allows us to functionalize various molecules on the doped sites and such locally functionalized SWNTs (lf-SWNTs) show PL property changes depending on the modified molecules. For example; electronic property difference in the modified aryl groups induced PL shifts.[3] Moreover, protonation of amine groups[6] and molecular recognition at the doped sites[7,8] can be used for wavelength tuning. Therefore, stimuli responsiveness in the NIR PL properties could be designed in the lf-SWNTs through molecular approaches. In this presentation, we report reversible wavelength modulation based on molecular structure changes occurring at the doped sites by external stimuli. Molecular binding through covalent bond formation and photo-induced structural changes are used for the wavelength switching processes.Imine chemistry is based on a condensation reaction of aldehyde and amine groups that occurs just by mixing the corresponding compounds. Owing to the reversibility of this reaction system, multistep wavelength switching of the NIR PL was conducted by imine bond formation, exchange or dissociation reactions of the imine bond, and Kabachnik-Fields reactions at the doped sites of the lf-SWNTs.[9] Photo-induced switching of the NIR PL was performed by creating the doped sites functionalized with photochromic molecules that showed color changes (= electronic property changes) by light irradiation. The photo-induced reversible structural changes of the modified molecules on the lf-SWNTs were observed by absorption spectroscopy, which accompanies spectral shifts of the NIR PL of the lf-SWNTs. Details including the relationship between PL shifts and molecular structure changes will be discussed at the meeting.[1] B. Weisman et al. Science, 330, 1656 (2010). [2] Y. Miyauchi et al. Nat. Photon., 7, 715 (2013). [3] Y. Wang et al. Nat. Chem., 5, 840 (2013). [4] S. Doorn et al. Nat. Photon., 11, 577 (2017). [5] T. Shiraki et al. Sci. Rep., 6, 28393 (2016). [6] Y. Wang et al. J. Phys. Chem. C, 119, 3733 (2015) [7] T. Shiraki et al. Chem. Commun., 52, 12972 (2016). [8] T. Shiraki et al. Chem. Eur. J., 24, 9393 (2018). [9] T. Shiraki et al. Chem. Eur. J., 24, 19162 (2018). Figure 1