Ab Initio Study on Electronic Sorting of Single-Wall Carbon Nanotubes Using Sodium Dodecyl Sulfate

Abstract

How differently sodium dodecyl sulfate (SDS) surfactants behave on metallic and semiconducting carbon nanotubes (CNTs) is one of the fundamental questions in the science and application of CNTs. In this study, we investigate the adsorption of SDS surfactants onto single-wall CNTs (SWCNTs) using ab initio methods to clarify the mechanism of metal/semiconductor separation of SWCNTs. We found that dodecyl sulfate (DS) ions are more likely to adsorb onto SWCNTs than sodium (Na) ions or SDS molecules, whereas the adsorption energy of SDS molecules becomes stronger as the diameter of the SWCNTs increases, the adsorption energy of DS ions for metallic (5, 5) CNTs is much stronger than those for semiconducting (6, 5) or (10, 3) CNTs, causing a larger aggregation number of DS ions on metallic SWCNTs and a separation of SWCNTs by electronic type. In actual multiple surfactant simulations, for a few DS ions, it is preferred that all DS ions adsorb on metallic (5, 5) CNTs; however, for more than eight DS ions, one or...