Synthesis of high-purity and high-crystallinity single-walled carbon nanotubes homogeneously dispersed by wet process

Abstract

• The highly crystalline single-walled carbon nanotubes are basic electronic elements. • It is necessary to remove contaminants in hc-SWCNTs to disperse them homogeneously. • Carbon contaminants in hc-SWCNTs disperse the shear force of hc-SWCNT bundles. • The shear force to disperse hc-SWCNTs is required to break up their aggregates. • Highly purified hc-SWCNTs could be dispersed without deteriorated chemical stability. Field emission (FE) electron sources based on high-purity and high-crystallinity single-walled carbon nanotubes (hc-SWCNTs) are promising electronic devices from the viewpoint of industrial application. However, to utilize high-purity hc-SWCNTs as a component of electronic devices, it is necessary to homogeneously disperse hc-SWCNTs using a wet process. Shear force is required to break up aggregates of hc-SWCNTs to produce a film with uniformly dispersed hc-SWCNTs, but contaminants such as fine graphite in the aggregates disperse the shear force of hc-SWCNT bundles. Therefore, it is necessary to remove these contaminants to achieve the uniform dispersion of hc-SWCNTs. In this study, we have succeeded in the highly efficient synthesis of hc-SWCNTs with few contaminants by the arc discharge method using glass-like carbon as a raw material to produce SWCNTs. It was demonstrated that hc-SWCNTs with low foreign matter contamination can be uniformly dispersed without the need for wet dispersion tools such as a homogenizer and a jet mill. Moreover, the long-term stability of the current emitted by FE devices fabricated using the dispersed solution can be obtained.