Preparation of metallic single-wall carbon nanotubes by selective etching

We report the bulk synthesis of a sample with a high concentration of metallic single-wall carbon nanotubes (m-SWCNTs) using a modified floating catalyst chemical vapor deposition method with methane as the carbon precursor. By tuning experimental parameters, such as species and flux of carrier gases, catalyst concentration, growth temperature, etc., small-diameter semiconducting SWCNTs (s-SWCNTs) and large-diameter m-SWCNTs were obtained. Using identical growth conditions, at a temperature of 1000 °C, it was found that the addition of hydrogen as an etchant gas resulted in the preferential removal of the smaller diameter s-SWCNTs. As a result, a sample enriched with large-diameter metallic SWCNTs was obtained. The self-assembled fishnet-like m-SWCNT network showed excellent optical transparency and electrical conductivity.