Quantitative Surface Characterization of As-Grown and Acid-Treated Single-Walled Carbon Nanotubes: Implications for Functional Materials

Characterizing surfaces of carbon nanotubes (CNTs) is indispensable for understanding the intrinsic properties and the applications to functional materials. We propose a quantitative approach based on comprehensive findings of the surfaces from 11 different analytical methods. To precisely analyze the surfaces, as-grown, single-walled CNTs were compared with acid-treated ones. Our approach clarified the kind of functional groups and furthermore quantitatively characterized the amounts and distributions on the surfaces, which have been unknown and elusive by one-sided analyses. These results interestingly revealed the increase of adsorbed water on the surfaces after acid treatment, and we successfully estimated the amounts of functional groups by removing them. The treated CNTs mainly possessed carboxylic acid (13 wt %) and hydroxy (6 wt %) groups in the total functional groups (41 wt %). Toward a full understanding of surfaces for nanocarbon materials, our method would make a key step.