Relaxation Dynamics of (6,5) Single-Walled Carbon Nanotube Under Xylyl Functionalization

Functionalization of single-walled carbon nanotubes (SWNTs) has been reported to tune the photoluminescence (PL) properties of SWNTs. In bioimaging applications, a PL signal excited by near-infrared (NIR) light is preferred because of the high transparency of biological tissues. Although it is missing in dispersed SWNT, chemical functionalization of SWNT using α,α′-dibromo-o-xylene (SWNT-xylyl) has been reported to have a new PL peak at 1231 nm, with intense emission upon NIR excitation. In this work, an ultrashort laser pulse was used to investigate the electronic and vibrational dynamics for two samples of SWNT and SWNT-xylyl. Global fitting analysis of the transient absorption spectroscopy data showed that electronic decay dynamics were comparable between the two samples. The transient absorption spectroscopy data measured with the ultrashort laser pulse whose duration is much shorter than the molecular vibration period enabled us to observe the vibration-induced modulation signal in the time domain. A difference between the two samples was found for the dynamics of the G-mode: alkylation by o-xylyl caused a frequency downshift that was not observed in the dispersed SWNTs. It is believed that the G-mode in SWNT-xylyl is initially localized on SWNT, followed by intramolecular vibrational energy redistribution with a time constant of 239±29 fs.