Methods for Estimating Composition of Single Walled Carbon Nanotubes Based on Electronic Type

Abstract

— Synthesized single-walled carbon nanotubes (SWCNTs) consist of a mixture of chiralities and therefore a post-synthesis separation is essential to separate them based on electronic type i.e., metallic (m-SWCNT) or semiconducting (s-SWCNT) for device applications. A key parameter to measure the effectiveness of separation process is the enrichment composition percentage between m-SWCNT and s-SWCNT, which can be estimated via several methods based on optical characterizations. In this paper, we compare the composition percentage estimations from 3 different methods based on Raman spectroscopy and UV-Vis optical absorption spectroscopy. The estimation methods are radial breathing mode (RBM) peak analysis, optical absorption area under curve (OUA) and first derivative amplitude of the optical absorption curve (FDA). Four different SWCNT sources were used in this study, which were subjected to post-synthesis separation process via agarose gel chromatography. Raman and UV-Vis spectroscopy measurements were carried out on all samples, before and after separation. From the estimations, we observed firstly that there are some variations on the estimated enrichment compositions between different methods, although the values are comparable. Secondly, for some SWCNTs samples, only a certain estimation method showed reliable composition percentage. The results presented in this work may provide viable options for characterizations of SWCNTs as there is no direct method to quantify the absolute composition percentage of SWCNTs based on electronic type. Keywords—single-walledcarbon nanotube, separation, electronic type, optical characterization, purity percentage.