Ultrafast vibrational motion of carbon nanotubes in different pH environments

TL;DR

This study investigates how different pH environments affect the ultrafast vibrational dynamics of single-walled carbon nanotubes using femtosecond pump-probe Raman spectroscopy, revealing pH-dependent structural and electronic changes.

Contribution

It introduces a femtosecond pump-probe impulsive Raman method to analyze pH-dependent vibrational dynamics of SWNTs, highlighting protonation effects on their electronic properties.

Findings

pH influences the coherent phonon spectra of SWNTs

Protonation modifies the electronic properties of semiconductor SWNTs

A transient longitudinal breathing mode appears and vanishes after 1 ps

Abstract

We have used a femtosecond pump-probe impulsive Raman technique to explore the ultrafast dynamics of micelle suspended single walled carbon nanotubes (SWNTs) in various pH environments. The structures of coherent phonon spectra of the radial breathing modes (RBMs) exhibit significant pH dependence, to which we attribute the effect of the protonation at the surface of SWNTs, resulting in the modification of electronic properties of semiconductor SWNTs. Analysis of the time-domain data using a time-frequency transformation uncovers also a second transient longitudinal breathing mode, which vanishes after 1 ps of the photoexcitation.