Raman frequency shift in oxygen functionalized carbon nanotubes

TL;DR

This study investigates how oxygen functionalization affects the vibrational properties and Raman spectra of single-walled carbon nanotubes, revealing shifts dependent on coverage and configuration due to lattice interactions.

Contribution

It provides a theoretical analysis of vibrational mode splitting and Raman shifts in oxygen-functionalized nanotubes, highlighting the effects of oxygen coverage and adsorption configurations.

Findings

Degenerate phonon modes split due to oxygen interactions

Raman shifts depend on tube diameter, chirality, and oxygen coverage

Nonmonotonic G mode shifts observed with increasing oxygen coverage

Abstract

In terms of lattice dynamics theory, we study the vibrational properties of the oxygen-functionalized single wall carbon nanotubes (O-SWCNs). Due to the C-O and O-O interactions, many degenerate phonon modes are split and even some new phonon modes are obtained, different from the bare SWCNs. A distinct Raman shift is found in both the radial breathing mode and G modes, depending not only on the tube diameter and chirality but also on oxygen coverage and adsorption configurations. With the oxygen coverage increasing, interesting, a nonmonotonic up- and down-shift is observed in G modes, which is contributed to the competition between the bond expansion and contraction, there coexisting in the functionalized carbon nanotube.