Electrical conductivity of well-exfoliated single-walled carbon nanotubes

Aqueous suspensions of single-walled carbon nanotubes (SWCNTs) with controlled degree of exfoliation were used to prepare conductive thin films. Controlled exfoliation was achieved by physical separation of SWCNT bundles using our previously established nanoplatelet-dispersion method. Thin film networks of individual SWCNTs produced with this approach exhibit universal conduction behavior indicative of an isotropic network of random resistors with nearly monodisperse bond conductance distribution. Networks made of partially exfoliated SWCNTs experience a significant shift in percolation threshold because of effective local alignment of individual SWCNTs into bundles. Bundling increases the conductivity of the SWCNTs at higher concentration because of low contact resistance electron transport between metallic SWCNTs. The most significant impact of bundling is the development of non-universal electrical scaling. These findings suggest that while individually exfoliated SWCNTs should be of substantial importance for electrical devices requiring small increases in electrical conductivity at low concentration, adequate control of bundling may enable or enhance performance for applications requiring higher conductivity.