Metallic and semi-conducting separation of single-walled carbon nanotubes using amine functionalized surface

Abstract

Single-walled carbon nanotubes (SWNTs) are one layered carbon sheet rolled in cylindrical form with diameters on the order of one nanometer, lengths ranging from tens of nanometer to centimeters. The electrical properties depend on the direction (chiral vector) in which the carbon sheet is rolled up to form the nanotubes. Approximately 67% of SWNTs are semi-conducting and 33% metallic. Despite excellent thermal, mechanical and electrochemical properties of SWNTs, lack of uniformity in the samples is one of the primary reasons why they are rarely used in commercial applications today. Researchers have invested substantial effort toward the development of post-synthetic sorting schemes to overcome this limitation. Amine is widely used in the process for its selective and enhanced absorption toward semi-conducting SWNTs. In this work, SWNTs were deposited in sub-monolayer on aminosilane assembled surface by spin coating. SWNTs used in this study were dispersed in various solvents and surfactants to observe the effect on metallic and semi-conducting separation on aminosilane self-assembled surface. The solvents satisfying the following conditions were chosen: (1)SWNTs dispersion are individualized and remain stable (2)Solvents and surfactants are commonly used in industry. On the other hand, to observe the effect of SWNTs side wall defect, SWNTs were carefully treated in acids trying not to destroying the tube itself. After prepared SWNTs dispersions were deposited on the aminosilane treated substrates, the resulting substrates were characterized using Raman spectroscopy (633nm) for it metallic and semi-conducting selectivity. Next, a novel method for the separation of SWNTs is also described. The process involves simple filtration through the column packed with selective material coated glass beads. The selective beads are prepared by the same procedure used in preparing the aminosilane self-assembled substrate. The fraction which has affinity toward amine fu...