Mass Transport through Defects in Graphene Layers

The paper reports an experimental study of ZnTe and CuI transport through graphene wall of SWNTs by high resolution transmission electron microscopy. It is shown that encapsulated material evacuates the tube through the defects in the nanotube walls, while in-tube diffusion appears high enough to provide matter intake from the nanotube volume. Diffusion kinetics was studied by “atoms count” resulting in ZnTe and CuI diffusivities of 7.67 × 10^–21 and 1.99 × 10^–20 m²/s through single defects in SWNT wall. Semiempirical and DFT modeling of potential energy profiles for different types of defects was utilized to propose minimal structural disturbances in a graphene layer to make possible cross-plane transport of matter. The comparison of experimentally observed diffusivities with calculated activation barrier heights was carried out taking into account an effective temperature of substance under electron beam. Neither of the defects including framework disturbance with 5–7 defects or sp³-bound carbon atomic pairs give rise to valuable mass-transport efficiencies through graphene layer. Reasonable conformity of the results is only achieved with carbon vacancy pairs in sp²-carbon layer, thus, indicating effective transport of matter occurring through the “holes” in graphene