Mono-dispersed ultra-long single-walled carbon nanotubes as enabling components in transparent and electrically conductive thin films

We report on a simple and practical method for creation of transparent and electrically conductive films by using ultra-long single-walled carbon nanotubes (SWCNTs) as the functioning elements. The ultra-long SWCNTs were ultimately dispersed into tubular levels for dispersion (denoted as mono-dispersion) in aqueous solutions by using glycocholate mixed with cholate as the dispersant. The resulting colloids were cast uniformly over the surface of flexible polyethylene terephthalate film through a wire-bar coating process. After washing by diluted nitric acid, the dispersants have been largely eliminated while the carbon nanotubes have been firmly retained on the surface of the film. These carbon nanotubes were finally transferred and permanently immobilized onto the surface of another piece of film with cellulose as the binder. Serial film samples each having different densities of the carbon nanotubes on the surface were prepared for studying the conductive mechanism. Film samples having densities around 30-tubes per μm2 were found to be capable of creating continuously interconnected carbon nanotube networks with a 92% transparency and a 286 Ω/sq resistivity through the formation of approximately 160 tube-to-tube junctions per μm2. These highly conductive and transparent films transfer electrons by the carbon nanotube networks with a slightly deformed tube-to-tube junction feature.