Length characterization of DNA-wrapped carbon nanotubes using Raman spectroscopy

Abstract

A systematic resonance Raman study has been carried out on DNA-wrapped single walled carbon nanotubes (SWCNTs) of three different average lengths $⟨L_{\text{tube}}⟩$ using seven different values of laser excitation energy $E_{\text{laser}}$ . The dependence of the intensity ratio of the $D$ -band and $G$ -band Raman features $(I_D∕I_G)$ on $⟨L_{\text{tube}}⟩$ indicates that nanotube length can be used as an important structural parameter for Raman characterization. By systematically varying $E_{\text{laser}}$ , the ratio $I_D∕I_G$ is found to be much stronger for metallic than for semiconducting SWCNTs but appears to have the same functional dependence on $E_{\text{laser}}$ and $⟨L_{\text{tube}}⟩$ or crystallite size as does nanographite.