Thin layers of length-sorted single wall carbon nanotubes (SWNT) were formed in to a buckypaper sample through vacuum filtration. These length sorted samples exhibit sharp changes in their optical and conductivity (S) properties with increasing SWNT surface coverage. At given surface concentrations, longer nanotubes are found to be more transparent and conducting. Changes of (S) with SWNT concentration can be quantitatively described by the generalized effective medium (GEM) theory which incorporates both effective medium and percolation theory concepts. The scaling exponents describing the conductivity percolation transition from an insulating to conducting state with increasing concentration are consistent with two-dimensional percolation theory, provided that the SWNTs are sufficiently long. The conductivity percolation threshold, xc, varies with particle aspect ratio L as, xc ~ 1 / L, which also accords with the expectations of conductivity percolation theory. Our results provide a framework for engineering the properties of thin SWNT layers for the numerous technological applications that are envisioned for buckypaper.
Proceedings Title: Influence of Single-Wall Carbon Nanotube Length on the Optical and Conductivity Properties of Thin Buckypaper Films
Conference Dates: December 1-5, 2008
Conference Location: Boston, MA
Pub Type: Conferences
Carbon nanotubes, percolation, thin film, 2D network, conductivity, optical properties